Учебники / Otolaryngology - Basic Science and Clinical Review

Ha P and Califano J. The molecular biology of laryngeal cancer. Otolaryngol Clin N Am 2002;35:993–1012

HongW, Endicott J, Itri LM, et al. 13 Cis-retinoic acid in the treatment of oral leukoplakia. N Engl J Med. 1986;315:1501–1505

Hu Y, Sidransky D, Ahrendt S. Molecular detection approaches for smoking associated tumors. Oncogene 2002;21:7289–7297 Induction chemotherapy plus radiation compared with surgery plus radiation in patients with advanced laryngeal cancer. The Department of Veterans Affairs Laryngeal Cancer Study

Group. N Engl J Med. 1991;324:1685–1690

Kim E and HongW.An apple a day . . . Does it really keep the doctor away? The current state of cancer chemoprevention. J Natl Cancer Inst 2005;97:468–469

Kirchner J and Carter D. Intralarygeal barriers to the spread of cancer. Acta Otolaryngol (Stockh) 1987;103:503–513

Mohan S and Epstein J. Carcinogenesis and cyclooxygenase: the potential role of COX-2 inhibition in upper aerodigestive tract cancer. Oral Oncology 2003;39:537–546

SELF-TEST QUESTIONS

For each question select the correct answer from the lettered alternatives that follow.To check your answers, see Answers to Self-Tests on page 715.

1.A patient with a right 3.5 cm oral tongue squamous cell carcinoma with normal tongue mobility, no mandibular involvement, no distant metastases, and two 2 cm lymph nodes on the right side is classified as

A.T2N1MO, stage II

B.T3N2bMO, stage III

C.T2N2aMO, stage III

D.T2N2bMO, stage IV

E.T2N2bM0, stage III

2.Squamous cell dysplasia

A.is a clinical diagnosis

B.is equivalent to leukoplakia

C.transforms to invasive squamous cell carcinoma 36 to 61% of the time

D.is one of the best known predictors of invasive squamous cell carcinoma

E.most often occurs after the sixth decade of life

3.In an otherwise healthy patient with advanced laryngeal cancer, the treatment regimen that is most likely to result in preservation of the larynx at 2 years is

A.concurrent chemotherapy and radiation therapy

B.induction chemotherapy followed by radiation.

Morton R and Izzard M. Quality-of-life outcomes in head and neck cancer patients.World J Surg 2003;27:884–889

Napgal J, Das B. Oral cancer: reviewing the present understanding of its molecular mechanism and exploring the future directions of its effective management. Oral Oncol 2003;39: 213–221

National Cancer Institute, National Institutes of Health, Public Health Service, Department of Health and Human Services. Oral cancers: research report. (NIH publication no. 92-2876). Bethesda, MD;1991

Parsons J, MendenhallW, Stringer S, et al.Twice-a-day radiotherapy for squamous cell carcinoma of the head and neck: the University of Florida experience. Head Neck 1993;15: 87–96

Spafford MF, Koch WM, Reed AL, et al. Detection of head and neck squamous cell carcinoma among exfoliated oral mucosal cells by microsatellite analysis. Clin Cancer Res 2001;7: 607-612

C.radiation followed by adjuvant chemotherapy

D.total laryngectomy followed by radiation

E.radiation alone

4.Examples of tumor suppressor genes include all of the following except

A.p53

B.p16

C.cyclin D1

D.erbB2

E.c and d

5.COX-2

A.is involved in prostaglandin synthesis

B.is usually active under normal conditions

C.is not expressed in head and neck squamous cell carcinoma

D.all of the above

E.a and c

HISTORICAL PERSPECTIVE

IMMUNOBIOLOGY OF HEAD AND NECK

SQUAMOUS CELL CARCINOMA

DEFICIENT IMMUNE RESPONSES IN HNSCC

FAILURE OF IMMUNOSURVEILLANCE IN HNSCC

THE ROLE OF CELL-MEDIATED IMMUNITY IN

HNSCC

HISTORICAL PERSPECTIVE

The immunology of head and neck squamous cell carcinoma (HNSCC) of the upper aerodigestive tract occupies a special place in tumor biology. It is therefore important to define what cancers are being discussed. The term HNSCC usually excludes squamous cell carcinomas of the skin, which seem to have a somewhat different biology from mucosal-derived cancers even though the head and neck surgeon usually will provide care for both. Similarly, the biology of cancers that arise from the paranasal sinuses, nose, and nasopharynx have a different induction from other upper aerodigestive tract carcinomas. Other tumors that appear to have a separate biology are melanomas that occur in the head and neck and glandularbased (adeno-) carcinomas.These tumors have different patterns of induction, spread, and response to therapy. Although there are some similar fundamental concepts shared in all cancers, this chapter will focus on the

IMMUNOTHERAPY OF HNSCC

ALTERING CYTOKINE PRODUCTION

MODIFYING ANTIGEN PRESENTATION

TRANSFERRING IMMUNE CELLS

SUGGESTED READINGS

SELF-TEST QUESTIONS

immunobiology of squamous cell carcinoma of the upper aerodigestive tract arising in the oral cavity, oropharynx, hypopharynx, and larynx.

The identification of normal cells and tissues by the body is a complex and complicated phenomenon. For years, it was thought that a unique activity occurred during the newborn period in mammals that allowed maturation of the immune system, whereby a cell learns to distinguish self from nonself. It was known that identical twins of various species could receive transplants from one to another if the immune exposure (i.e., shared circulation via the placenta) occurred during gestation or in the early newborn period. Once the observation that dizygotic cattle twins who share common placentas could receive organ transplants from one another (even though they were separate genetic individuals), the advance of transplantation biology leaped ahead. By this time, the concept of surface antigens of major blood groups had been identified. Whereas

under normal circumstances individuals with major blood group incompatibilities would immediately reject organs from one another, dizygotic twin cattle would accept organ transplants later in life from each other, but not from siblings from other pregnancies.

A series of experiments attributed to Medawar and colleagues investigated transplanted hematologic stem cells from one group of mice to another. Newborn mice of one species who were given stem cells from a second species would later on in life accept skin transplants from the second species, whereas the control animals not receiving stem cells would reject them in the normal way.These experiments from the 1950s became the basis for the concepts of immunologic development that would predominate for the next 45 years.

Over the past several years, the concept of antigenprocessing cell control of these activities has become more important. The term professional antigen-processing cells specifically refers to dendritic cells and a few other cells that are largely responsible for these phenomena. Matzinger and others have been able to show that both tolerance and immunity can be induced in the newborn period as well as later in life. Matzinger’s experiments use inbred mice that are immunologically identical from one individual to the other. Mice, however, are different from humans, in that male mice express a unique antigen, Hy, on the surface of all cells. Male mice have one more antigen than female mice.This difference allows experiments in which all but one antigen can be controlled in an experiment. What Matzinger observed was that spleen cells from male mice given to female mice in the newborn period would induce tolerance similar to the experiments observed by Medawar et al. If, however, dendritic cells from male mice were purified and used as the material to be injected, specific anti-male cellmediated immunity was induced. This immunity could be induced either in the newborn period or in immunologically mature life; in a corresponding fashion, large numbers of hemopoietic cells that contained few, if any, dendritic cells and,even given later in life, induced tolerance similar to that which was observed in the newborn period.

Conclusions from these experiments are that the dendritic cells are responsible for inducing immunity either in the newborn period or later in life.The explanation of Medawar et al’s experiments is that the inocula of “stem cells” into the newborn mice included mostly B cells and T cells but did not contain a critical number of professional antigen-processing cells, which are the only cells that can activate a virginT cell. Because the inocula of “stem cells” contains large numbers of immunologically important cells that can induce tolerance such as B cells

and cells that are immunologically neutral, such as nonnaive T cells, the end result is to induce tolerance.

The interaction between dendritic cells and T cells has been studied in great detail, and although there is still a great deal left to be uncovered, it appears that dendritic cells must present the antigen in combination with a major histocompatibility antigen complex. This presentation is not a selective process, and many antigens can be expressed in this situation, which are pinocytosed by dendritic cells or by chance manufactured within the dendritic cells themselves. For the T cell to become activated, the dendritic cell must be in an activated state. Dendritic cells expressing normal antigens on their surface when not in an activated state–induced tolerance.

Dendritic cell activation primarily occurs in what is commonly known as “infection.” At least one mediator of this danger signal appears to be heat shock protein, a substance liberated early in the infectious process. Early cancers have no reason to call attention to themselves and initiate an infectious response. It is known that some tumors can produce substances rendering the dendritic cell inactive. Hence dendritic cells presenting tumor antigens on their surface are seen as presenting antigens to which the host should not respond; and when a dendritic cell presents an antigen in a nonactivated state, tolerance is induced. There is speculation that thymic T cells can never respond to the second signal; therefore, the process of thymic maturation is a statistical game of the likelihood that an antigen will be exposed to a nonreacting dendritic/T-cell complex, thus inducing tolerance.

The observations of the 1960s that demonstrated profound systemic and regional immunosuppression in head and neck cancer patients point to more than subtle disturbance in the immune system. It is likely that there are multiple ways in which the immune system is affected by cancer and that one single therapy affecting the immune system will not completely reactivate an immune system that has become tolerant in a patient with advanced cancer. Future experiments will need to involve patients with relatively early tumors who still have intact immune systems that can be activated, with the hope that, once the immunologic mechanisms are understood, immunologic manipulation can be used to treat postsurgical patients.

IMMUNOBIOLOGY OF HEAD AND NECK SQUAMOUS CELL CARCINOMA

HNSCC of the upper aerodigestive tract is a devastating disease that affects both communication and survival. HNSCC represents 4% of all cancers, with an estimated

37,000 new cases and 12,000 expected deaths in the United States in 2003.Approximately half of all patients have advanced-stage disease at the time of diagnosis, with an expected 5-year survival rate between 10 and 40%. Despite treatments that may consist of mutilating surgery, radiotherapy, and/or chemotherapy, overall long-term survival remains low due to uncontrollable persistent or recurrent disease.The low rate of survival of patients with local and distant recurrence has highlighted the need for new approaches for diagnosis and treatment. Stimulating the immune system to recognize and destroy tumor cells is a promising treatment modality for HNSCC patients, who have been shown to have significant immunologic dysfunction. However, the intricate cross-talk between cancer and cells of the immune system is still poorly understood in HNSCC.

Recent breakthroughs in the field of tumor immunology have provided tools to better understand the complex interactions between squamous cancer cells and their tumor environment. Dendritic cells have been recognized as one of the key players necessary for induction of immune responses to cancer and immunosurveillance. Genes encoding tumor-associated antigens (TAAs) have been identified, and strategies for immunizing against these antigens have been investigated. Indeed, immunotherapeutic strategies have shown that immune manipulation can induce the regression of established cancer in humans. This chapter will summarize our knowledge of tumor immunology in HNSCC and will discuss recent advances in immunotherapy that hold promise for eliciting and sustaining antitumor immune responses in these patients.

DEFICIENT IMMUNE RESPONSES IN HNSCC

Like many cancers, the interrelations between transformed epithelium and the tissue microenvironment play a critical role in tumorigenesis of squamous cell carcinoma (SCC). In particular, experimental and clinical evidence supports the concept that deficiencies in the immune system play an important role in the initiation and propagation of HNSCC. First, patients who are immunosuppressed due to heart or kidney transplant treatments show increased frequencies of SCC of the skin. Moreover, precancerous lesions in transplant patients progress more rapidly into SCC and show an increased tendency to metastasize, suggesting a failure of immunosurveillance. Second, increased antitumor immune responses in patients with HNSCC have been demonstrated in draining lymph nodes and tissues harboring HNSCC after treatment with immunostimulatory agents such as

bacille Calmette-Guérin or levamisole, suggesting that it is feasible to elicit immune responses in these patients. Third, the presence of tumor-infiltrating lymphocytes (TILs) in tumor specimens of patients with HNSCC has been shown to collaborate with better clinical outcomes in these patients, suggesting that TILs may play a significant role in HNSCC tumor regression. This evidence suggests that the immune system plays an important role in surveillance and tumor growth of HNSCC, and also suggests that growth of these tumors may be prevented or modified by interventions that target immune responses. Further basic scientific research is required before we completely understand how HNSCC evades immune elimination and use this information to devise successful methodologies to increase immune killing.

FAILURE OF IMMUNOSURVEILLANCE

IN HNSCC

The role of immunosurveillance is to protect the host from tumor formation. In order for the immune system to accomplish this task, several criteria must be met. First, the host should have a competent immune system with a strong cytotoxic response. Second, the abnormal/ tumor cells must express unique antigens that can be recognized by the immune system. Third, there should be no suppressive influences to dampen the immune response. Lastly, the number of abnormal/tumor cells should be small enough for the tumor to be eliminated entirely.

Several mechanisms may account for failure to elicit an effective antitumor immune response against developing HNSCC.

Malignant transformation of epithelial cells may involve loss or changes of normal surface antigens. Downregulation of immune recognition antigens on the surface of tumor cells is a potential mechanism used by HNSCC to escape from immunosurveillance and killing by cytotoxicT cells. Changes in the immune recognition antigens major histocompatibility complex (MHC) class I [human leukocyte antigens, (HLAs), in humans], and/or costimulatory molecules may block recognition and allow for tolerance of the immune system to tumor cells. A majority of tumors from patients with HNSCC show no expressions of HLA-class I, and a small percentage of these tumors show extensive downregulation of this molecule. Inadequate expression of costimulatory molecules on the surface of tumor cells may also contribute to immune tolerance. Costimulatory molecules are important forT-cell activation. CD80 and CD86 molecules provide the most potent costimulatory

signals found to date. Many cell lines and established HNSCC lack expression of costimulatory molecules on the surface of tumor cells. In addition, decreased or lack of CD80 costimulatory molecule expression has been associated with increased tumorigenesis of HNSCC.

The absence of an effective cell-mediated antitumor immune response may be due to poor immunogenicity of TAAs. These are antigens expressed by tumors that distinguish them from normal cells. Although TAAs are found on tumor cells and also on some normal cells, qualitative and quantitative differences in their antigen expression may permit the immune system to distinguish between the two. Integrins, mucins, cadherins, growth factor receptors, and glycoproteins are types of TAAs overexpressed on the cell surface that may play an important role in carcinogenesis and progression of HNSCC. Despite their expression, these antigens may evoke an immune response that is successfully evaded or no response at all. Methods to elicit therapeutic responses to these antigens in patients whose tumors express the protein are being investigated.

Soluble factors secreted during the progressive growth of HNSCC have been shown to restrict cell-mediated immune functions resulting in immunosuppression of the host. Autocrine cytokines secreted by HNSCC such as granulocyte-macrophage colony–stimulating factor (GM-CSF) have been shown to have direct immunosuppressive effects on host immune responses. In addition, cytokines secreted by precancerous or HNSCC lesions may lead to increased expression of COX-2 enzyme in tumor-associated macrophages and, subsequently, increased synthesis of prostaglandins. Prostaglandins have been shown to decrease T-cell proliferation and natural killer (NK) cell cytotoxicity and to inhibit the production of immune regulatory lymphokines.

THE ROLE OF CELL-MEDIATED

IMMUNITY IN HNSCC

Tumor-specific immune responses have been demonstrated during the growth of established HNSCC, despite the failure of the immune system in preventing its emergence. Immune responses to these tumors, however, generally are ineffective in inducing regression of established HNSCC. Several immunologic abnormalities in cell-mediated immune responses in patients with HNSCC have been observed. These include decreased T-cell proliferation, migration, and cytotoxicity responses, depressed NK cell activity, significant dysfunction of T helper immunity, and depressed lymphokine-activated killer cell activity.

The T-cell immune response is the most important host response for the control of growth of HNSCC.T-cell immunity involves two T-cell subsets: CD4 T helper cells, which are class II MHC restricted, and CD8 T cytolytic cells, which are class I MHC restricted. CD4 T cells mediate their effect by the generation of lymphokines/cytokines to activate other effector cells. CD8 T cells also can secrete cytokines, but they are involved in direct lysis of tumor cells by disrupting the target membrane and nucleus. Perturbations in the numbers and function of T lymphocyte subsets in patients with HNSCC have been associated with decreased survival. Recent evidence suggests that a significant proportion of circulating T cells (especially CD8 T cells) in patients with HNSCC is eliminated by apoptosis (programmed cell death). The reasons for this are still not fully understood. However, inadequate stimulation of T cells by lack of CD80 costimulatory pathway signals on antigen-presenting cells (APCs) at the time of T-cell stimulation is a possible mechanism that may cause apoptosis of T cells.

Dendritic cells are important in the induction of immunity against HNSCC.They are the most potent of the APCs, whose function is to process and present antigens to T cells in the context of MHC.T cells must receive two signals to become activated. One signal is mediated by the interaction between T cell and peptide bound to MHC molecules on the surface of APCs. The second signal is provided by costimulatory molecules on the APCs interacting with their receptors on the surface of T cells. Increased infiltration of dendritic cells into tumors has been shown to correlate with tissue differentiation, prolonged survival rates, and reduced incidence of metastasis in patients with HNSCC of the nasopharynx, oral cavity, and larynx. Furthermore, tumor dendritic cells in patients with HNSCC have been shown to lack adequate antigen-presenting function. These studies suggest that T cell–mediated immunity to HNSCC may depend on the satisfactory activation of dendritic cells.

NK cells are large lymphocytes that play a critical role in the early host defense against cancer. In contrast to T cells, NK cells do not require prior sensitization to antigen to effect killing of tumor cells. NK cells produce large amounts of immunoregulatory cytokines in response to various activation stimuli and can therefore regulateT-cell immune responses. Suppression of NK cell function has been observed in draining lymph nodes of patients with HNSCC. Deficient NK cell activity has been correlated to nodal metastases in patients with laryngeal carcinoma. Thus low pretreatment NK cell activity in peripheral blood of patients with HNSCC

may serve as a prognostic indicator for survival. In patients with poorly differentiated, low HLA class I–expressing molecules, the NK cell is an important defense mechanism against metastatic disease.

In summary, host–immune system interactions in HNSCC comprise an intricate molecular network still poorly understood. Immunosuppression and tumor progression in these patients may be the net result of a complex cascade of events that begins with failure of immunosurveillance. Successful immunotherapeutic approaches in the treatment of HNSCC will need to repair host immunoincompetence in the function of T and NK cells, circumvent immunosuppressive factors generated in the tumor microenvironment, optimize target tumor antigen presentation, and sustain a persistent long-term effective antitumor immune response.

IMMUNOTHERAPY OF HNSCC

The major goal of immunotherapy of cancer is to manipulate and amplify the immune system to promote tumor eradication.As the field of tumor immunology of HNSCC advances and pathways of immune dysfunction in HNSCC are delineated, considerable emphasis is being placed on identifying specific immunologic abnormalities that may prove to be useful prognostic markers and targets for immune therapy. The objectives to achieve successful immunotherapy in HNSCC are to activate local defense factors, induce lymphocyte release of mediators such as cytokines, and increase direct lymphocyte and macrophage killing of tumors.

The strategies employed by immunotherapy can be classified as (1) altering cytokine production, (2) optimizing the presentation of antigens to the immune system, and (3) transferring immune cells.

ALTERING CYTOKINE PRODUCTION

Cytokines are a diverse group of intercellular signaling proteins that regulate local and systemic immune responses. When cytokines are secreted by tumor cells or by tumor-infiltrating lymphocytes, they appear to regulate tumor cell growth and the cytotoxicity ofTILs. However, patients with HNSCC have a deficit of immune stimulatory cytokines present in the tumor milieu. Increasing immune stimulatory cytokine levels has been a potential target because it is thought to increase the local production and activation of CD8 T cells and NK cells. Interleukin-2 (IL-2), IL-12, and interferon are polypeptides that have been studied in this context.

Amplification of cell-mediated immune responses requires an optimal supply of these cytokines.

IL-2 is a polypeptide secreted by CD4 T cells that induces lymphokine-activated killer (LAK) activity and activates neutrophils and macrophages. As a result, it enhances the immune responses by increasing production of secondary cytokines. Despite achieving modest success in the treatment of renal cell carcinoma and metastatic melanoma (15–20% antitumor response rate), IL-2 by itself has not been particularly effective in inducing significant tumor regression in HNSCC. Initial studies using IL-2 therapy in the late 1980s and early 1990s showed disappointing results with minimal (6–10%) partial response rates observed that lasted less than 6 months.Toxicity from systemic administration of IL-2 also limits its clinical use. However, new studies show some promise using IL-2 (intratumoral or perinodal) in combination therapy with other known chemotherapeutic agents or cytokines. Potentially, this will allow for reductions in IL-2 dosages and, consequently, a decrease in systemic toxicities. Combination of external beam radiation or chemotherapy (e.g., cisplatin) with IL-2 has shown potent antitumor effects in preclinical models. When cisplatin is used in combination with IL-2, an increase in apoptosis and decrease in tumor growth are observed and may be due to IL-2’s effect on activating CD8 T cells and NK cells. IL-2 in combination with IL-12 has been shown to have synergistic effects on tumor control. Although these preclinical studies are encouraging, a phase III study failed to show a difference in the addition of IL-2 to cisplatin and 5-Fluorouracil (5-Fu) therapy in patients with HNSCC stages III and IV. Clinical trials using IL-2 with a combination of other cytokines such as interferon and tumor necrosis factor in patients with stage II HNSCC have resulted in clinical and histological tumor responses and appear promising, although these trials are still in the early phases of testing.

IL-12 is a protein produced by B cells, monocytes, and macrophages that augments the cytolytic activity of NK cells, synergizes with IL-2 to generate LAK cells, and facilitates the development of cellular immune responses. In preclinical models, use of IL-12 has shown significant antitumor responses and complete tumor regression. However, earlier clinical trials using systemic IL-12 in patients with advanced, unresectable solid tumors including HNSCC has been limited by its toxicity. A recent phase I clinical trial effectively limited toxicity of this cytokine by using peritumoral IL-12 gene transfer (IL-12-transduced autologous fibroblasts). This method has made IL-12 treatment feasible and has paved the way for future clinical studies to evaluate its potential.

Interferon is a polypeptide secreted by CD8 T cells, some CD4 cells, and NK cells. It increases surface expression of MHC molecules and activates many immune cells, including NK cells, neutrophils, vascular endothelial cells, and macrophages to secrete cytokines. Small-scale studies using interferon in patients with HNSCC showed disappointingly minimal clinical responses to systemic therapy. Further preclinical studies and large-scale clinical trials are required to determine whether increasing levels of cytokines IL-2, IL-12, and interferon have significant effects on tumor responses and clinical outcome.

In contrast to the cytokines already mentioned, some proinflammatory and proangiogenic cytokines such as IL-6, IL-8, and granulocyte-macrophage colony–stimulating factor (GM-CSF) are expressed at high levels by HNSCC and have been associated with potentially deleterious effects, including increased proliferation, angiogenesis, metastasis, and decreased immune responsiveness. Designing the optimal host milieu for tumor regression not only will need to replace deficient antitumor cytokines such as IL-2, IL-12, and interferon but will also need to decrease expression of these proinflammatory cytokines.A potential target that regulates cytokine expression is the transcription factor nuclear factor kappa B (NF- B). NF- B acts on the promoter site for many of these proinflammatory and proangiogenic cytokines to increase their expression.As a result, inhibiting NF- B may be a promising immunotherapeutic modality for patients with HNSCC. A proteosome inhibitor of NF- B (PS-341) was shown in preclinical studies to decrease production of these cytokines.This is expected to result in decreases in tumor growth, cell survival, and angiogenesis of HNSCC. Although, phase I clinical trials in patients with HNSCC have just begun, proteosome inhibitor–based therapy has shown potent antitumor results in phase I/II studies in other tumors.

MODIFYING ANTIGEN PRESENTATION

Optimizing the presentation of tumor antigens to the immune system can reduce their tumorigenicity and promote immune recognition and destruction of tumors. This objective can be accomplished in two ways: increasing the expression of MHC molecules and of costimulatory molecules on the surface of tumor cells, and improving antigen presentation by dendritic cells. Because T-cell activation requires two signals, one from interaction between MHC with the T-cell receptor and the other between costimulatory molecules with their counterreceptors on the T cell, providing these two key signals to tumor cells may augment T-cell proliferation and cytotoxicity.

Gene therapy has been used to transfect the alloantigen HLA-B7 (an MHC class I molecule) to tumors in patients with HNSCC who failed conventional therapy and whose tumors did not express this MHC antigen. Partial responses or stable disease was obtained in these patients after gene therapy. Biopsy results showed evidence that HLA-B7 expression had been achieved in these tumors.This study demonstrated the feasibility of enhancing tumor antigen presentation in patients with HNSCC. A phase II multicenter study is under way to investigate the efficacy of this treatment in a more adequate sample size.

An inhibitory signal for T-cell activation is generated when costimulatory molecules (CD80, CD86) on the APC interact with the CTLA-4 receptor onT cells. Unlike signals generated from CD80/CD28 interactions, signaling through CTLA-4 leads to decreased production of IL-2, cyclins, and cyclin-dependent kinases and restricts T-cell proliferation. The dynamic interaction between T-cell receptor, CD28, and CTLA-4 signals determines the outcome of T-cell activation. Phase I–II trials using antibodies against human CTLA-4 in prostate cancer and melanoma are ongoing, and research in patients with HNSCC will soon follow.

Another immunotherapeutic strategy that has received much attention is the use of dendritic cells to enhance tumor antigen presentation to the immune system. Recent evidence suggests that dendritic cells primed with tumor antigens can stimulate the regression of solid tumors such as renal cell carcinoma and melanoma. Generating sufficient numbers of dendritic cells to drive large clinical-scale expansions of lymphocyte cultures remains a significant challenge for dendritic cell–based therapies. Priming dendritic cells to generate tumor-specific T lymphocytes has also been a challenge in the development of dendritic cell–based therapies for HNSCC, because HNSCC–specific peptide antigens are largely unknown. Because it has been demonstrated that dendritic cells can efficiently acquire antigens from apoptotic tumor cells and crossprime cytotoxic T cells, research on dendritic cell–based therapy in HNSCC is showing better outcomes in preclinical studies. Encouraging results from these studies have warranted two phase I clinical trials that are under way. In these trials, dendritic cells are derived from patients and are pulsed with irradiated tumor cells.

TRANSFERRING IMMUNE CELLS

Adoptive immunotherapy or adoptive cell transfer refers to the isolation of antigen-specific cells, their expansion

and activation ex vivo, and their autologous administration to the host. Several cell types have been used for adoptive immunotherapy: T cells (peripheral or TIL), LAK cells, and dendritic cells. Preclinical studies on adoptive immunotherapy have provided the earliest evidence that established tumors can be induced to regress. However, several factors have delayed successful clinical studies using adoptive immunotherapy. Although it has been shown that CD8 T cells are essential for antitumor effects in many models, the number and effectiveness of cells transferred during adoptive immunotherapy are directly correlated with treatment efficacy. The addition of T-cell growth factors such as IL-2 has significantly increased the effectiveness of transferred cells. Moreover, circumventing the immunosuppressive effects of regulatory T cells may improve immune responses to cancer cells.The feasibility of systemic adoptiveT-cell immunotherapy in 15 patients with unresectable HNSCC was demonstrated in a phase I trial using autologous irradiated tumor cells and T cells. However, only two patients showed clinical responses. Although adoptive T-cell immunotherapy continues to be an active area of interest for other cancers, it is not thought to be an ideal target in HNSCC. This is largely because these cells have been found to be defective (decreased killing and decreased proliferation) in HNSCC. Clearly, this obstacle must be overcome to generate effective responses to adoptive transfer of T cells.

LAK cells are NK cells orT lymphocytes that have not been exposed previously to antigen and subsequently are activated using IL-2. Use of these cells in murine models has shown significant tumor regression.Autologous LAK cells have been administered to patients with HNSCC in multiple phase I studies with or without IL-2 or GM-CSF. The infusions were well tolerated; however, partial or minimal responses were observed at the primary tumor sites. The limited clinical benefit evidenced in these clinical trials emphasizes the need for continued research into strategies to improve tumor antigen–specific therapies against HNSCC.

In summary, no specific immunotherapeutic intervention has shown great promise in clinical studies of patients with HNSCC. Although tumor antigens on HNSCC have been recognized and tumor antigen– specific immune responses have been demonstrated, these immune responses have been ineffective in rejecting newly appearing and established tumor cells. The field of tumor immunology of HNSCC has advanced significantly in the past 30 years, although many obstacles remain that impede successful immune treatment

of these cancers. A better understanding of the basis of immunosurveillance and tumor escape, antigen presentation to cytotoxic cells, mechanisms of host immunosuppression, and the complex cytokine network between tumor and host is needed. Deciphering the ideal strategy for immune treatment in these patients remains a significant challenge as well and may ultimately require a cohesive approach involving surgical debulking to reduce the immunosuppressive cytokine release by tumor and systemic or local immune therapy to augment antigen presentation and provide cytokines and other necessary signals for effective immune killing. As the effectiveness of promising new immune agents and strategies is established in clinical trials in patients with HNSCC, antigen-specific immunotherapy may be considered as an alternative modality for adjuvant treatment of patients with this disease.

SUGGESTED READINGS

Medawar PB. The use of antigenic tissue extracts to weaken the immunological reaction against skin homografts in mice. Transplantation. 1963 Jan;1:21–38

Ridge JP, Fuchs EJ, Matzinger P. Neonatal tolerance revisited: turning on newborn T cells with dendritic cells. Science. 1996 Mar 22;271(5256):1723–1736

IMMUNOBIOLOGY OF HEAD AND

NECK SQUAMOUS CARCINOMA

Dunn GP, Bruce AT, Ikeda H, Old LJ, Schreiber RD. Cancer immunoediting: from immunosurveillance to tumor escape. Nat Immunol 2002;3(11):991–998

HoffmannTK, Muller-Berghaus J, Ferris RL, Johnson JT, StorkusWJ, Whiteside TL. Alterations in the frequency of dendritic cell subsets in the peripheral circulation of patients with squamous cell carcinomas of the head and neck. Cancer Res 2002; 8(6):1787–1793

Reichert TE, Strauss L, Wagner EM, Gooding W, Whiteside TL. Signaling abnormalities, apoptosis, and reduced proliferation of circulating and tumor-infiltrating lymphocytes in patients with oral carcinoma. Clin Cancer Res 2002; 8(10):3137–3145

Whiteside TL. Immune cells in the tumor microenvironment: mechanisms responsible for functional and signaling defects. Adv Exp Med Biol 1998;451:167–171

Wustrow T, Issing W. Immune defects in patients with head and neck cancer. Anticancer Res 1993;13:2507–2519

IMMUNOTHERAPY OF HEAD AND

NECK SQUAMOUS CARCINOMA

Gleich LL, Gluckman JL, Armstrong S, Biddinger PW et al. Alloantigen gene therapy for squamous cell carcinoma of the

head and neck: results of a phase-1 trial. Arch Otolaryngol Head Neck Surg. 1998 Oct;124(10):1097–1104.

Hoffmann TK, Bier H, Whiteside TL. Targeting the immune system: novel therapeutic approaches in squamous cell carcinoma of the head and neck. Cancer Immunol Immunother 2004 Dec;53(12):1055–1067

SELF-TEST QUESTIONS

For each question select the correct answer from the lettered alternatives that follow.To check your answers, see Answers to Self-Tests on page 715.

1.The following are tumor-induced mechanisms to subvert host anticancer immune responses:

A.Alterations of major histocompatibility complex class I and tumor antigen expression

B.Increased surface expression of costimulatory molecules

C.Secretion of soluble immunosuppressive factors

D.All of the above

E.A and C only

2.Which of the following is involved in cell-mediated immunity in HNSCC?

A.Cytokines

B.Antibodies

C.NK cells

D.Macrophages

E.A, C, and D only

3.Which immunologic abnormality in cell-mediated immunity is not seen in patients with HNSCC?

A.Dysfunction of CD4 T cells

B.Increased NK cell activity

Resser JR, Carbone DP. Immunotherapy of head and neck cancer. Curr Opin Oncol 1998;10(3):226–232

Van Waes C, Chen Z, Callister M, et al. Cytokines in the immune pathogenesis and therapy of head and neck cancer. In:Veldman JE, Passali D, Lim JD, eds. New Frontiers in Immunobiology. Kugler Publications,The Netherlands; 2000:233–243

C.Decreased proliferation and cytotoxicity of CD8 T cells

D.Dendritic cell dysfunction

E.All of the above

4.Which of the following cytokines is being investigated as an immunotherapeutic agent in HNSCC?

A.IL-2

B.IL-12

C.IL-1

D.A and B

E.All of the above

5.Which cells have been used in immunotherapy because of their ability to present antigens to the immune system?

A.CD8 T cells

B.CD4 T cells

C.Dendritic cells

D.NK cells

E.All of the above

CLINICAL APPLICATIONS OF RADIATION THERAPY

Radiation therapy may be integrated into the management of head and neck cancer in a variety of ways.The manner in which it is applied depends on many factors, including the stage of disease, extent of primary and nodal involvement, presence of clinical and pathological prognostic factors, opportunity for organ preservation, desire to preserve form and function, overall patient condition, and the skill and experience of the specialists involved.

The combination of surgery plus radiation should be considered under certain circumstances, which include the following:

1.Close or positive surgical margins at the primary site

2.Large ( T3) primary lesions or lesions at sites where complete resection is problematic (skull base, infratemporal fossa, brachial plexus, internal carotid artery)

3.Cervical node metastasis beyond primary lymphatic drainage area or multiple positive nodes, multiple levels of positive nodes, or extracapsular nodal disease

PREOPERATIVE RADIATION

The planned use of preoperative radiation therapy takes advantage of several theoretical circumstances.The blood supply to a tumor preoperatively may be significantly better than after surgery.This makes the clonogens more responsive to radiation. Lesions felt to be unresectable or at high risk for positive or uncertain margins may be converted to a more resectable status.Also, the possibility of tumor embolization during surgery resulting in distant metastasis may be decreased.

Disadvantages of preoperative radiation include the fact that the dose of radiation must be limited ( 50 Gy) to avoid complications.Also, there is the decreased benefit of surgical staging. Finally, the patient may have an unfounded belief that no further treatment (surgery) is necessary if there is a complete response. Preoperative radiation should be considered if the neck has been violated (previous incisional biopsy), if a delay in surgical recovery is anticipated, or, in the case of large cervical metastases, if the primary site can be treated with irradiation.

Surgery following planned preoperative radiation is relatively safe, in sharp contrast to surgical salvage following failed, full-course irradiation with intent to cure. In the case of planned preoperative radiation, the