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Table8.2 Summary ofmost important genetic alterations inT- cell lymphomas
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Important cytogenetic/
Entity
Molecular findings Testing methodology Other
Lymphoma genetics 123
Anaplastic large cell lymphoma,
ALK-
positive
Anaplastic large cell lymphoma,
ALK- negative
T- follicular helper lymphomas
(angioimmunoblastic type;
nodal type; NOS)
Peripheral T- cell lymphoma, NOS • Multiple gene mutations and
Abbreviations: FISH=fluorescence insequencing; PCR=polymerase chain reaction.
ALK rearrangements:
• t(2;5)(p23;q35) NPM1::ALK–
most common
• DUSP22- IRF4 (6p25.3)
rearrangement
• TP63 (3q28) rearrangement
• TET2, DNMT3A, IDH2, RHOA
mutations
CNVs
situ hybridization; GEP=Gene expression profiling; IHC=immunohistochemistry; HTS: high- throughput
PTCL- TBX21lymphomas. In particular, deletions of 17p13
(TP53) and 9p (CDKN2A) are common in GATA3 cases,
while mutations in TET2 and DNMT3A are more common
in TBX21 types. While TBX21 cases generally have a more
favorable prognosis, a subset shows cytotoxic T- cell differentiation with more aggressive behavior. While GEP is not
commonly used in clinical settings, immunohistochemical
stains can be used as a substitute to classify PTCL- NOS cases
into the GATA3 and TBX21 subtypes: TBX21 and/or CXCR3
positivity is seen in PTCL- TBX21 cases, while GATA3 and/
or CCR4 positivity indicates the PTCL- GATA3 subtype.
Unfortunately, many PTCL- NOS cases remain unclassifiable; as more cases are molecularly characterized, new diagnostic subgroups are likely to emerge.
Table8.2 summarizes the most important genetic altera-
tions in T- cell lymphomas.
Conclusions
Genetics plays an integral role in the classification, prognosis, and treatment of lymphoma. Novel NGS- based techniques are rapidly transitioning from research to the clinical
setting, paving the way for a more comprehensive understanding of the distinct biology underlying each patient’s illness. A deeper comprehension of the biological pathways
implicated in lymphoma, derived from the abundance of
genetic and gene expression data at hand has yielded
advancements in therapeutic alternatives. This progress is
expected to further augment the array of targeted therapies
and, ideally, enhance clinical outcomes for individuals
affected by these diseases.
IHC
FISH
Cytogenetics
FISH
PCR- based (point mutations
like RHOA
HTS
HTS GEP subtypes described. May
G17V
and IDH2
R172
Mandatory for diagnosis
)
be useful for risk stratification
and trial patient selection
Further reading
Introduction
Alizadeh, A.A., Eisen, M.B., Davis, R.E. etal. (2000). Distinct types of
diffuse large B- cell lymphoma identified by gene expression profiling. Nature 403 (6769): 503–511.
Rosenwald, A., Bens, S., Advani, R. etal. (2019). Prognostic significance
of MYC rearrangement and translocation partner in diffuse large
B- cell lymphoma: a study by the Lunenburg lymphoma biomarker
consortium. J. Clin. Oncol. 37 (35): 3359–3368.
Techniques
Gibson, S.E., Luo, J., Sathanoori, M. etal. (2014). Whole- genome single
nucleotide polymorphism array analysis is complementary to classical cytogenetic analysis in the evaluation of lymphoid proliferations.
Am. J. Clin. Pathol. 141 (2): 247–255.
Hans, C.P., Weisenburger, D.D., Greiner, T.C. etal. (2004). C onfirmation
of the molecular classification of diffuse large B- cell lymphoma by
immunohistochemistry using a tissue microarray. Blood 103 (1):
275–282.
Mullis, K., Faloona, F., Scharf, S. etal. (1986). Specific enzymatic ampli-
fication of DNA invitro: the polymerase chain reaction. Cold Spring
Harb. Symp. Quant. Biol. 51 (Pt 1): 263–273.
Reddy, A., Zhang, J., Davis, N.S. etal. (2017). Genetic and functional
drivers of diffuse large B cell lymphoma. Cell 171 (2): 481–94 e15.
Rothberg, J.M., Hinz, W., Rearick, T.M. et al. (2011). An integrated
semiconductor device enabling non- optical genome sequencing.
Nature 475 (7356): 348–352.
Zech, L., Haglund, U., Nilsson, K. etal. (1976). Characteristic chromo-
somal abnormalities in biopsies and lymphoid- cell lines from
patients with Burkitt and non- Burkitt lymphomas. Int. J. Cancer 17
(1): 47–56.
本书版权归John Wiley & Sons Inc.所有
124 Molecular Hematology
https://t.me/med1917
Burkitt lymphoma
Pasqualucci, L. (2019). Molecular pathogenesis of germinal center-
derived B cell lymphomas. Immunol. Rev. 288 (1): 240–261.
Thomas, N., Dreval, K., Gerhard, D.S. etal. (2023). Genetic subgroups
inform on pathobiology in adult and pediatric Burkitt lymphoma.
Blood 141 (8): 904–916.
Zayac, A.S. and Olszewski, A.J. (2020). Burkitt lymphoma: bridging the
gap between advances in molecular biology and therapy. Leuk.
Lymphoma 61 (8): 1784–1796.
Diffuse large B- cell lymphoma
Chapuy, B., Stewart, C., Dunford, A.J. etal. (2018). Molecular subtypes
of diffuse large B cell lymphoma are associated with distinct pathogenic mechanisms and outcomes. Nat. Med. 24 (5): 679–690.
Davies, A.J., Barrans, S., Stanton, L. et al. (2023). Differential
efficacy from the addition of bortezomib to R- CHOP in diffuse
large B- cell lymphoma according to the molecular subgroup in the
REMoDL- B study with a 5- year follow- up. J. Clin. Oncol. 41 (15):
2718–2723.
Morin, R.D., Arthur, S.E., and Hodson, D.J. (2022). Molecular profiling
in diffuse large BBr. J. Haematol. 196 (4): 814–829.
Schmitz, R., Wright, G.W., Huang, D.W. et al. (2018). Genetics and
pathogenesis of diffuse large B(15): 1396–1407.
Ta, R., Yang, D., Hirt, C. etal. (2022). Molecular diagnostic review of
diffuse large BDiagnostics (Basel) 12 (5): 1087.
cell lymphoma: why so many types of subtypes?
cell lymphoma. N. Engl. J. Med. 378
cell lymphoma and its tumor microenvironment.
Mantle cell lymphoma
Eskelund, C.W., Dahl, C., Hansen, J.W. et al. (2017). TP53 muta-
tionsidentify younger mantle cell lymphoma patients who do not
benefit from intensive chemoimmunotherapy. Blood 130 (17):
1903–1910.
Hill, H.A., Qi, X., Jain, P. etal. (2020). Genetic mutations and features of
mantle cell lymphoma: a systematic review and meta- analysis. Blood
Adv. 4 (13): 2927–2938.
Nadeu, F., Martin-
epigenomic insights into the origin, pathogenesis, and clinical
behavior of mantle cell lymphoma subtypes. Blood 136 (12):
1419–1432.
Sander, B., Quintanilla- Martinez, L., Ott, G. et al. (2016). Mantle cell
lymphomaArch. 468 (3): 245–257.
Garcia, D., Clot, G. et al. (2020). Genomic and
- a spectrum from indolent to aggressive disease. Virchows
Follicular lymphoma
Carbone, A., Roulland, S., Gloghini, A. et al. (2019). Follicular lym-
phoma. Nat. Rev. Dis. Primers. 5 (1): 83. Published 2019 Dec 12.
Xerri, L., Dirnhofer, S., Quintanilla- Martinez, L. et al. (2016). The
heterogeneity of follicular lymphomas: from early development to
transformation. Virchows Arch. 468 (2): 127–139.
Lymphoplasmacytic lymphoma
Treon, S.P., Xu, L., Guerrera, M.L. etal. (2020). Genomic landscape of
Waldenström macroglobulinemia and its impact on treatment strategies. J. Clin. Oncol. 38 (11): 1198–1208.
Wang, Y., Gali, V.L., Xu-
genetic biomarkers implemented from nextprovide treatment insights in clinical practice for Waldenström macroglobulinemia. Neoplasia 23 (4): 361–374.
Monette, Z.Y. et al. (2021). Molecular and
generation sequencing
Marginal zone lymphomas
Rossi, D., Bertoni, F., and Zucca, E. (2022). Marginal- zone lymphomas.
N. Engl. J. Med. 386 (6): 568–581.
Vela, V., Juskevicius, D., Dirnhofer, S. et al. (2022). Mutational land-
scape of marginal zone Btypic alterations and diagnostic potential for assignment of organ
origin. Virchows Arch. 480 (2): 403–413. https://doi.org/10.1007/
021- 03186- 3.
s00428-
cell lymphomas of various origin: organo-
CLL/SLL
Döhner, H., Stilgenbauer, S., Benner, A. etal. (2000). Genomic aberra-
tions and survival in chronic lymphocytic leukemia. N. Engl. J. Med.
343 (26): 1910–1916.
Nadeu, F., Diaz-
genomic alterations in chronic lymphocytic leukemia. Annu. Rev.
Pathol. 15: 149–177.
Navarro, A., Delgado, J. etal. (2020). Genomic and epi-
Anaplastic large cell lymphoma
Parrilla Castellar, E.R., Jaffe, E.S., Said, J.W. etal. (2014). ALK- negative
anaplastic large cell lymphoma is a genetically heterogeneous disease
with widely disparate clinical outcomes. Blood 124 (9): 1473–1480.
Zhang, X.R., Chien, P.N., Nam, S.Y. etal. (2022). Anaplastic large cell
lymphoma: molecular pathogenesis and treatment. Cancers (Basel).
14 (7): 1650.
Nodal T- follicular helper (TFH) cell
lymphoma
Huang, Y., Moreau, A., Dupuis, J. etal. (2009). Peripheral T- cell lympho-
mas with a follicular growth pattern are derived from follicular helper
T cells (TFH) and may show overlapping features with angioimmunoblastic T-
de Leval, L., Parrens, M., Le Bras, F. et al. (2015). Angioimmunoblastic
T- cell lymphoma is the most common T- cell lymphoma in two distinct French information data sets. Haematologica 100 (9): e361–e364.
Mourad, N., Mounier, N., Briere, J. etal. (2008). Clinical, biologic, and
pathologic features in 157 patients with angioimmunoblastic T- cell
lymphoma treated within the Groupe d’Etude des Lymphomes de
l’Adulte (GELA) trials. Blood 111 (9): 4463–4470.
Petrich, A.M., Helenowski, I.B., Bryan, L.J. etal. (2015). Factors predict-
ing survival in peripheral T- cell lymphoma in the USA: a populationbased analysis of 8802 patients in the modern era. Br. J. Haematol.
168 (5): 708–718.
cell lymphomas. Am. J. Surg. Pathol. 33 (5): 682–690.
本书版权归John Wiley & Sons Inc.所有
Lymphoma genetics 125
https://t.me/med1917
Xie, Y. and Jaffe, E.S. (2021). How I diagnose angioimmunoblastic
T-
cell lymphoma. Am. J. Clin. Pathol. 156 (1): 1–14.
Peripheral T- cell lymphoma, not otherwise
specified
Amador, C., Bouska, A., Wright, G. et al. (2022). Gene expression
signatures for the accurate diagnosis of peripheral T- cell lymphoma
entities in the routine clinical practice. J. Clin. Oncol. 40 (36):
4261–4275.
Iqbal, J., Amador, C., McKeithan, T.W. et al. (2019). Molecular and
genomic landscape of peripheral T176: 31–68.
Nelson, M., Horsman, D.E., Weisenburger, D.D. et al. (2008).
Cytogenetic abnormalities and clinical correlations in peripheral
cell lymphoma. Br. J. Haematol. 141 (4): 461–469.
T-
cell lymphoma. Cancer Treat. Res.
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Chapter9
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Molecular basis ofchronic
lymphocytic leukemia
Bita Fakhri1 and Alexey Danilov
1
Division of Hematology, Department of Medicine, Stanford University, Palo Alto, CA, USA
2
Department of Hematology and Hematopoietic Stem Cell Transplant, City of Hope National Medical Center, Duarte, CA, USA
Introduction and definition, 127
Epidemiology, 128
Genetic factors, 128
Environmental factors, 128
Molecular biology of CLL, 128
B- cell receptor signaling pathway, 130
Introduction anddefinition
2
BCL2 family, 131
CLL microenvironment, 132
Impaired immunity in CLL, 133
Richter transformation, 134
Conclusion, 135
Further reading, 135
involvement, or any other characteristic of B- cell lymphoproliferative disorders. It is important to differentiate between
Chronic lymphocytic leukemia/small lymphocytic
lymphoma (CLL/SLL) is a neoplasm of mature B- lymphocytes
involving peripheral blood, bone marrow, and secondary
lymphoid tissues (spleen, lymph nodes). Although the terms
are mostly used almost interchangeably, SLL is referred to
the population of mature B-
lymphocyte with CLL- like
immunophenotype residing in lymphoid tissues. The diagnosis is established by blood count, lymph node biopsy in
cases of SLL, morphology, and immunophenotyping by flow
cytometry (FC) of circulating B- lymphocytes.
Diagnosis of CLL requires ≥5 × 10
3
/μL circulating monoclonal B- lymphocytes with a CLL immunophenotype in the
peripheral blood. The term SLL describes the cases with a
3
circulating CLL cell count <5
× 10
/μL and known lymph
node, splenic, or other extranodal and extramedullary
involvement. FC is an essential part of diagnosis. CLL typically displays a characteristic immunophenotype, expressing
CD5, CD19, dim CD20, dim CD22, CD23, bright CD43, dim
CD45, dim- to- negative CD79b, dim CD81, CD200, and
dim monoclonal surface immunoglobulin (Ig). The CLL
clone is known to be negative for CD10, CD103, and CD123
as well as other T-
cell and myeloid antigens.
The immediate differential diagnosis for CLL/SLL primarily
includes monoclonal Bcell lymphoma (MCL). MBL is the presence of <5 × 10
cell lymphocytosis (MBL) and mantle
3
/μL circulating monoclonal B- lymphocytes in the absence of any associated lymphadenopathy, hepatosplenomegaly, extramedullary
CLL- like MBL, which has CD5 and CD23 co- expression along
with weak CD20, CD79b, and surface immunoglobulin, and
other (non- CLL) sub- types of MBL. The two most common
−
non-
CLL types are CD5
MBL”) and CD5
+
MBL (labeled as “non- CLL phenotype
MBL with a phenotype that is not characteristic for CLL, i.e. strong CD20, CD79b or immunoglobulin
expression (labeled as “atypical- CLL phenotype MBL”).
+
Individuals with a CD5
, CD23 negative phenotype must be
ruled out for the diagnosis of MCL by FISH evaluation for the
t(11;14)– which is pathognomonic for MCL, or overexpression
of Cyclin D1 by immunohistochemistry – before being
inaccurately labeled as carrying a diagnosis of atypical- CLL
phenotype MBL.
The CLL pathogenesis is driven by constant proliferation
through the B- cell receptor (BCR) pathway and ongoing cell
death managed through the expression of both proand anti- apoptotic members of the BCL2 family proteins. In
the recent decade, the advances leading to the approval of
novel targeted agents resulted in a dramatic paradigm shift
in the treatment options for CLL/SLL. These include inhibitors of BCR- associated kinases, which target Bruton tyrosine
kinase (BTK; i.e. ibrutinib, acalabrutinib, and zanubrutinib),
phosphointiside- 3kinase (PI3K; i.e. idelalisib and duvelisib),
as well as and inhibitors of BCL2, e.g. venetoclax. The
outstanding outcomes associated with these novel agents
highlight and call for the need for a more instanding of the molecular biology of this disease.
apoptotic
depth under-
Molecular Hematology, Fifth Edition. Edited by Drew Provan and Hillard M. Lazarus.
© 2024 John Wiley & Sons Ltd. Published 2024 by John Wiley & Sons Ltd.
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127
128 Molecular Hematology
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Epidemiology
CLL is the most common leukemia in the Western world
comprising 25–30% of total leukemias in the United States.
CLL accounts for approximately 11% of all hematologic
malignancies. CLL affects approximately 3–5 out of every
100 000 individuals in the United States and currently is
considered a treatable but incurable hematologic malignancy with conventional therapies [4]. CLL can affect
adults as young as 30 and 40 years of age. However, it is
mostly seen in adults with an average age of 70 years. CLL
is extremely rare in children. CLL has a slightly higher incidence in male populations compared to female populations
(1.3–1.7/1 ratio) [4, 5].
The incidence of CLL varies by geographic location and
race. CLL is most commonly seen in adults of the Western
population. It is more common in nonpopulations compared to the Asian Pacific Islanders or the
African American population. The incidence in African
Americans is in between the Caucasian and the Asian racial
groups [6]. Both genetic and environmental factors have
been extensively studied and associated with the development of CLL. In brief, the exact reasons for differences in
CLL incidences between the different ethnic groups remain
unclear.1 However, a number of studies point that genetic
factors likely carry more weight compared with environmental factors. For example, analysis of the Los Angeles Countybased cancer registry demonstrated that the incidence of
CLL was significantly lower among the individuals of Asian
descent compared to non- Hispanic whites, both residing in
the county. With the advancement of gene sequencing techniques, ongoing studies aim to determine the genetic underpinnings of this distinction.
Hispanic Caucasian
of these risk loci are mapped to regulatory genes. Some of
these loci have been identified at sites of genes involved in
CLL pathogenesis. For example, CLL- associated loci have
been found mainly targeting genes encoding transcription
factors, BCL- 2 family proteins (BCL2L11 and PMAIP1), or
cyclin- dependent kinase inhibitors (CDKN2A/CDKN2B)
that play roles in promoting oncogenesis or apoptosis. Other
CLL- associated SNPs have been found at interferon regulatory factor 4 (IRF4), leading to its reduced expression, implicated in NOTCH signaling. Furthermore, An SNP associated
with reduced expression of microRNAs, particularly miR15a and miR16- 1, is linked with familial CLL. Decreased
expression of these microRNA results in increased expression of BCL2 and ZAP70, proteins that have been attributed
to increased resistance to cell death or enhanced BCRmediated signaling and CLL cell proliferation.
Environmental factors
Multiple case- control and cohort studies have investigated
the effects of environmental risk factors in CLL. Some studies
have found that farming exposures (pesticides, herbicides,
exposure to animals) are significant. The evidence of
increased risk of CLL due to exposure to rubber industry
chemicals and benzene among different studies is not consistent. In studies of atomic bomb survivors, the incidence of
CLL was not found to be increased. Studies of other occupational radiation–exposed cohorts have not found an
increased risk, but several methodologic limitations relevant
to CLL, including the long latency of this tumor, make drawing solid conclusions challenging. Finally, the US Department
of Veteran Affairs has acknowledged exposure to Agent
Orange as a risk factor for developing CLL.
Genetic factors
CLL is reported to have a genetic basis and is known to run
in families (familial CLL). The finding that the wide geographical variability does not impact the incidence of CLL in
patients of Asian origin indicates a strong genetic susceptibility. The age at diagnosis of the second- generation offspring is nearly two decades younger as compared to the
parent. First- degree relatives (siblings, children, or parents)
of CLL patients have double the risk for CLL. Moreover,
about 20% of first- degree family members of CLL patients
had monoclonal B- cell lymphocytosis, which is a precursor
of CLL. Ultimately, only a small percentage of patients with
monoclonal MBL will progress to CLL.
Genome- wide association studies in familial CLL have
shown that the increased hereditary risk is polygenic. Singlenucleotide polymorphisms (SNPs) have been identified in
more than 40loci associated with familial CLL and over 90%
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Molecular biology of CLL
CLL is a heterogenous disease with a constellation of IGHV
mutation status, chromosome alterations, somatic mutations,
microRNA changes, and epigenetic factors contributing to
the heterogeneity of the disease. In this section, we will
review the major alterations in each category.
IGHV mutations status
The acquired immune system is responsible for protecting
against a wide range of potential pathogens. During the normal B- cell maturation process, chromosomal recombination
of the V (variable), D (diversity), and J (junctional) segments
form the variable (V) region of the heavy and light immunoglobulin chains. These recombination events create the
immunologic diversity that is central to the humoral immune
response.
Molecular basis ofchronic lymphocytic leukemia 129
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When a mature B- cell encounters an antigen, further
diversification occurs through a process of somatic hypermutation, typically within the germinal center. Somatic
hypermutation introduces random nucleotide changes into
the V genes, selecting for B- cells that produce immunoglobulins with the highest level of selectivity, a process known as
affinity maturation. Cells that fail to go through the affinity
maturation process subsequently undergo apoptosis. As germline genes encoding the V region have been mapped, it is
possible to determine whether the malignant B- cell clone has
undergone somatic hypermutation.
CLL can be divided into two major subsets, determined by
whether CLL cells express immunoglobulin heavy chain variable (IGHV) genes that have undergone somatic hypermutation in their variable regions. Those cases that have less than
98% homology with germline are specified as IGHV- mutated
CLL, and those that have 98% or higher are specified as unmutated CLL. IGHV- mutated CLL cells that are known to be more
differentiated since their proliferation is halted at a later stage of
development, whereas CLL cells with unmutated IGHV status
are less differentiated as their proliferation is halted at an earlier
stage of B- cell maturation process. As expected, CLL cells with
mutated IGHV status (more differentiated CLL cells) have
shown to have better outcomes in terms of time to initiation of
the first line of therapy, progression- free survival following
chemotherapy and certain targeted therapies (i.e. venetoclax in
combination with an anti- CD20 antibody), as well as overall
survival compared to CLL cells with unmutated IGHV status.
Interestingly, IGHV mutational status does not seem to be predictive of outcomes with BTK inhibitor therapy, with both
disease subtypes responding equally well in terms of
progression- free survival. Nevertheless, IGHV mutational status is a strong prognostic marker in patients with CLL with
mutated IGHV established as a favorable prognostic feature.
At least a third of CLL patients express stereotyped BCR
immunoglobulins and can be assigned to distinct subsets,
each with a particular immunoglobulin.2 The most important examples are stereotyped subsets #2 and #8, which are
associated with aggressive CLL course. Subset #2 includes
patients whose immunoglobulin gene encodes IGHV3-
21/IG LV 3- 21 genes with restricted VH and VL CDR3
sequences. It is postulated that the presence of these genes
allowed for BCR- BCR interactions, triggering BCR signaling. Meanwhile, subset #8 includes patients with CLL
expressing IGHV4- 39/IGKV1(D)- 39 genes, which is thought
to increase the risk of Richter transformation (RT).
Chromosome abnormalities
Several chromosome abnormalities have been identified in
CLL cells. The most common chromosome alterations recognized through fluorescence in situ hybridization include:
del(13q) (55%), trisomy 12 (16%), del(11q) (18%), and
del(17p) (7%). Among these chromosome abnormalities,
del(13q) is associated with a favorable prognosis with the
longest time to initiation of therapy, progressionoverall survival. Trisomy 12 is known to be an intermediate
risk feature. Del(11q) and del(17p) resulting in the deletion of
ATM and TP53, respectively, portend an unfavorable prognosis. It is important to note that the advent of targeted therapies
replacing chemotherapy for patients with CLL has largely
counteracted the negative impact of del(11q). But del(17p)
and/or TP53 gene mutation remains an ongoing challenge in
the field calling for more creative combinations of targeted
therapies and novel therapies. The FISH studies for CLL
should ideally investigate translocations involving chromosomal band 14q32including the t(11;14)(q13;32), which is
typically seen in MCL– another CD5+ B- cell clonal disease
that needs to be distinguished from CLL at the time of
diagnosis.
Although FISH is essential in determining chromosome
abnormalities in CLL, it can be further complemented by
classical cytogenetics. A broader spectrum of aberrations
can be detected through classical cytogenetics, which makes
it indispensable at present. Complex karyotype, which is
typically defined as 3 chromosome abnormalities, is identified as another adverse prognostic feature in patients with
CLL. While patients with 3 chromosomal abnormalities
who do not have a TP53 aberration may still have a relatively favorable clinical course, the presence of 5 cytogenetic
abnormalities is independently associated with inferior outcomes in CLL.
Somatic mutations
Whole genome sequencing and whole exome sequencing
helped elucidate the genomic landscape of CLL. CLL is
known to be a genetically heterogeneous disease. The most
frequently identified mutations have been found in SF3B1
(21%), AT M (15%), TP53 (7%), NOTCH1 (6%), and BIRC3
(4%). Recurrent somatic mutations have been observed in
genes that have a role in mRNA processing (SF3B1 and
XPO1), DNA damage (TP53 and ATM), Notch signaling
(NOTCH1), B-
cell signaling (EGR2 or BRAF), chromatin
modification (HIST1H1E, CHD2, and ZMYM3), Wnt signaling, and inflammatory pathways (MYD88).
Sequencing has also helped illuminate the timing of
somatic mutations and copy number alterations. The timing of genetic aberrations might suggest whether the
changes happened at the clonal level or subclonal level.
Subclonal level changes are suggested to happen later in the
course of disease and thought to cause more aggressive disease. Some somatic mutations, such as MYD88, or copy
number alterations, such as trisomy 12 or del(13q), are usually found in almost all CLL cells in a patient, indicating
that these genetic aberrations occurred early in disease
free, and
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130 Molecular Hematology
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evolution. Some other mutations, such as SF3B1 or
NOTCH1, TP53, or the chromosomal abnormality del(17p),
are found in only a number of the CLL cells in a patient and
must therefore signify subclonal events that occur later in
disease development. One of the interesting areas of
ongoing research is to determine how different treatment
modalities– chemoimmunotherapy (CIT) or various targeted therapies– might affect the enrichment or eradication of these somatic mutations and copy number
alterations, respectively.
MicroRNA changes
MicroRNAs are small, single- stranded, non- coding RNA
molecules containing 21–23nucleotides. MicroRNAs regulate gene expression, and their dysregulation can affect
expression of genes involved in onset and progression of
tumors including CLL. In CLL, microRNAs can function as
oncogenes or tumor suppressors.
Del(13q) is the most frequent chromosome abnormality
found in CLL and is associated with the longest time to initiation of therapy in patients with CLL, corroborating its
positive prognostic feature. A cluster of two microRNA
genes, miR- 15a and miR- 16- 1, are located within the 13q14.3
deleted region. The expression of miR- 15a/16- 1 is found to
be downregulated in ~66% of CLL cases. The mouse model
studies have shown that the downregulation of miR- 15a/16- 1
results in increased expression of BCL2, an antiapoptotic
protein, which will promote survival of CLL cells by inhibiting apoptosis.
Del(11q) region includes the miR- 34b/c cluster locus.
Downregulation of miR- 34b/c will result in higher levels of
ZAP- 70. Higher levels of ZAP70 are mostly associated with
unmutated IGHV status and portend an unfavorable prognosis. Correspondingly, Patients with CLL with del(11q)
show lower levels of miR- 34b/c and higher levels of ZAP- 70.
Other noteworthy microRNAs involved in the pathogenesis of CLL include, but are not limited to, miR- 181b, miR- 29,
miR-
17/92, and miR- 155. Downregulation of miR- 29 and
miR- 181b is correlated with TCL1 ((T cell leukemia/
lymphoma 1) overexpression. Activation of TCL1 oncogene
(T cell leukemia/lymphoma 1) is an essential step in the initiation of aggressive phenotype.
MiR- 17/92 cluster is overexpressed in several lymphoid
malignancies. MiR- 17/92 inhibits the expression of the
tumor suppressor PTEN and the pro- apoptotic protein
BIM. MiR- 155 have been reported to accumulate in human
B- cell lymphomas, particularly diffuse large B- cell lymphomas, classic Hodgkin lymphoma, and Burkitt lymphoma.
Mouse studies indicate that miR- 155 can induce polyclonal
expansion suggesting that miR- 155 is directly implicated in
the onset and/or progression of these lymphoproliferative
disorders.
Epigenetic factors
Genome- wide methylation studies have shown substantial
heterogeneity of intratumoral methylation in CLL– with a
constellation global hypomethylation and local hypermethylation. Methylation profiling has identified 3 epigenetic
CLL subtypes. These subtypes, which correlate for the most
part with IGHV mutational status and patient outcomes, are
called memory- like CLL (m- CLL; mainly mutated IGHV,
with good prognosis), intermediate CLL (i- CLL; mixed
between mutated and unmutated IGHV, with intermediate
prognosis), and naïve- like CLL (n- CLL; mainly unmutated
IGHV, with poor prognosis). Increasing methylation heterogeneity is associated with increased genetic complexity, likely
in the setting of acquiring subclonal mutations with disease
evolution.
B- cell receptor signaling pathway
In CLL, unlike diffuse large B- cell lymphomas, the activation
of BCR pathway does not require activating pathway mutation and is considered antigen- dependent, resulting from
BCR ligation via antigens (auto- antigens and/or microbial
antigens) that are probably present in the microenvironment; however tonic BCR signaling may also occur. The
gene expression profiling studies have revealed BCR signaling as the most prominent pathway activated in CLL cells
isolated from proliferation centers of the lymphatic tissues.
The BCR comprises of the two antigen- binding heavy
chains (IgH) and their two accompanying light chains (IgL)
that form a non- covalent bind with the CD79A (Ig- α) and
CD79B (Ig- β) subunits. Engagement of the BCR by antigen
results in aggregation of BCR components leading to phosphorylation of immunoreceptor tyrosine- based activation
motif (ITAMs) in the cytoplasmic tails of CD79A and CD79B
by Src family kinases (LYN, FYN, and BLK). Phosphorylated
ITAMs then recruit spleen tyrosine kinase (SYK). SYK activation initiates activation of a signaling cascade that engages
Bruton’s tyrosine kinase (BTK), and phosphoinositide kinase
(PI3Ks), as well as promotes activity of nuclear factor kappa
kB) and nuclear factor of activated T cells (NF- AT)
B (NFtranscription factors, as well as MAP kinase and RAS signaling pathways. Collectively, these signaling events promote
B- cell survival and proliferation.
The in- depth understanding of the BCR signaling pathway has led to some of the breakthrough advances in drug
development in CLL. The currently FDA- approved treatment options inspired by the BCR signaling pathway that
have revolutionized the treatment landscape of CLL include:
covalent BTK inhibitors (BTKi) such as the first in- class
agent ibrutinib and newer generation drugs including acalabrutinib and zanubrutinib. Unlike CIT, covalent BTKi’s have
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CD79A (ITAM)
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Molecular basis ofchronic lymphocytic leukemia 131
BCR
CD79B (ITAM)
CD19
P
P
lbrutinib
Acalabrutinib
Zabubruthinid
SyK
BTK
PLCG
PKCB
NFκB
MS-553
PIK3
Idelalisib
Duvelisib
AKT
CDK 7, 9
MCL1
Cyclin T, H
Cell cycle and
proliferation
Figure9.1 A schematic review of the BCR signaling pathway and BCL2 family proteins.
proved to be effective even in patient with CLL harboring
high- risk features such as patients with TP53- aberrant disease, del(11q), unmutated IGHV status and complex karyotype. Mutational analysis following acquired resistance to
ibrutinib in patients who eventually progress on ibrutinib
(and other covalent BTK inhibitors), has shown mutations at
the BTK C481S amino acid residue, which impairs drug
binding and reinstitute the catalytic activity of BTK. Under
these circumstances the noncovalent BTK inhibitor, pirtobrutinib, becomes effective. Since the drug forms a
non- covalent bond with BTK, it does not require the pristine
BTK to be able to exert its function. As expected, response to
pirtobrutinib has been shown to be independent of C481S
mutation status. In addition, activating mutations in phospholipase C gamma 2 (PLCγ2), a direct substrate of BTK,
render malignant cells less reliant on BTK. The efficacy of
non- covalent BTK inhibitors in this setting has not been
reported, but these drugs will not be anticipated to be active
in this particular setting.
In addition to covalent and non- covalent BTK inhibitors
which have improved the outcomes for patients with CLL in
both the upfront and relapsed/refractory settings, PI3K
inhibitors have also emerged as another treatment option for
patients with CLL. The currently two FDA- approved agents
in this category for patients with relapsed/refractory CLL
include duvelisib and idelalisib. Other potential targeted
which target BCR- associated kinases which have or are being
investigated include SYK inhibitors (entospletinib) and
PKCβ inhibitors (MS-
BCL2 family
Programmed cell death, or apoptosis, is a distinct biochemical pathway that is essential for normal embryonic development and maintenance of homeostasis within the normal
tissues. The intrinsic apoptosis pathway is dependent on
orchestrated interaction between the BCL2 family proteins
and is deregulated in CLL.
Bcl- 2was the first identified endogenous inhibitor of cell
death. The BCL2 gene, along with the immunoglobulin
heavy chain locus, was cloned as a partner in t(14;18)
BBC3
PMAIP1
Cytochrome C
APAF1
Caspase 9, 3, 6, 7
Apoptosis
553).
BAX
BCL2L1
BAK
BCL2
Venetoclax
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132 Molecular Hematology
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Pro-apoptotic BH3-only proteins
BIM
BID
NOXA
BAD
HRK
BMF
BIK
Figure9.2 The intrinsic apoptotic pathway is regulated by three major groups of proteins: 1. Pro- apoptotic BH3- only proteins.
2. Pro- survival BCL2- like proteins. 3. Death effectors.
BCL2
MCL1
BCL-xL
BCLW
BCLB
A1
Death mediators
BAK BIM
chromosomal translocation in follicular lymphoma, and
Bcl- 2 protein overexpression was shown to prevent cell death
in response to either physiological or pathological stimuli. It
is now understood that a family of proteins, comprised
members antagonistic or similar in function to Bcl- 2:
pro- apoptotic “initiators” (BH3- only proteins, e.g. Noxa,
Bim, Bid, Puma, and others), anti- apoptotic “guardians”
(e.g.Bcl- 2, Mcl- 1, Bcl- xL, A1, and Bcl- w), and pro- apoptotic
effectors (Bax and Bak), regulates the intrinsic mitochondrial apoptotic pathway Interactions between these proteins
at the mitochondrial outer membrane determine if proapoptotic proteins BAX or BAK will create pores in the outer
mitochondrial membrane, resulting in the release of
cytochrome c followed by caspase activation and apoptosis
(Figure9.2).
Enhancing the pro- apoptotic or inhibiting the antiapoptotic apparatus of cancer cells is a promising treatment
strategy that has inspired the development of an important
class of compounds termed “BH3mimetics.” Venetoclax, an
oral BCL2inhibitor agent, was initially approved for patients
with CLL harboring del(17p). Its use has rapidly expanded as
a single agent or in combination with anti- CD20monoclonal antibodies and/or BTK inhibitors in both frontline and
relapsed/refractory settings. In patients who progress on
venetoclax, in addition to mutations in BCL2, resistance to
venetoclax may be mediated by upregulation of the alternative pro- survival BCL2- like proteins, such as MCL1, BCL- xL,
and others.
Multiple investigational agents are currently being studied
in this family: AZD5991 is a highly selective BH3- mimetic
that demonstrates high potency in MCL1- dependent cell
lines. AZD5991 binds directly to MCL1 and induces rapid
apoptosis in cancer cells, most notably myeloma and acute
myeloid leukemia, by activating the BAK- dependent
mitochondrial apoptotic pathway. The preclinical activity of
AZD5991has shown that selective targeting of MCL1induced
metabolic dysfunction and abrogated survival of diffuse
large B- cell lymphoma and ibrutinib- resistant MCL cell lines
in vivo and in vitro. Other BH3- mimetics targeting
MCL1 include AMG- 176 and S63845. In an experimental
design testing the effects of AMG- 176 on CLL and normal
hematopoietic cell death, it was demonstrated that AMG176 is an active agent in inducing CLL cell death while sparing normal blood cells. However, MCL1 targeting agents
may be associated with toxicities, including suppression of
hematopoietic stem and progenitor cells, potentially leading
to cytopenias in the clinic. The clinical trials investigating
MCL1inhibitors should help define the therapeutic window
for these agents.
BH3- mimetics that target BCL- xL, such as navitoclax, are
not being developed in CLL due to concerns of thrombocytopenia. However, AZD4320, an alternative dual inhibitor of
BCL2 and BCL- xL, is being studied in lymphoid malignancies as an intravenous formulation, with hope to mitigate its
effect on platelets and resultant thrombocytopenia.
CLL microenvironment
CLL is often characterized by a highly complicated
microenvironment that promotes proliferation, progression,
and survival of the leukemia cells.
The CLL microenvironment includes various types of cells
including, but not limited to, T lymphocytes, natural
killer cells (NK cells), macrophages, endothelial cells, and
stromal cells. Immune cells such as T- cells and NK cells
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