molecular of lymphoma new.pptx MBBS PG STUDENT

Lymphoma is a cancer that affects the lymphatic system, a part of the immune system that produces white blood cells and removes excess fluids from the body. It occurs when lymphocytes, a type of white blood cell, mutate and become cancerous cells that multiply and collect in the lymph nodes.
Lymphoma is a cancer that affects the lymphatic system, a part of the immune system that produces white blood cells and removes excess fluids from the body. It occurs when lymphocytes, a type of white blood cell, mutate and become cancerous cells that multiply and collect in the lymph A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland and bone marrow. The main types of lymphoma are Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Symptoms include enlarged lymph nodes, fatigue, significant weight loss and fever.
Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.
nodes. A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland and bone marrow. The main types of lymphoma are Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Symptoms include enlarged lymph nodes, fatigue, significant weight loss and fever.
Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.
A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland and bone marrow. The main types of lymphoma are Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Symptoms include enlarged lymph nodes, fatigue, significant weight loss and fever.
Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.
A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland and bone marrow. The main types of lymphoma are Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Symptoms include enlarged lymph nodes, fatigue, significant weight loss and fever.
Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.
A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland and bone marrow. The main types of lymphoma are Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Symptoms include enlarged lymph nodes, fatigue, significant weight loss and fever.
Treatment may involve chemotherapy, medication, radiation therapy and rarely stem-cell transplant.
A cancer of the lymphatic system.
This cancer impacts the lymphatic system which is the body's disease-fighting network. It includes the lymph nodes, spleen, thymus gland an

1. Molecular Biology of Lymphoma Presented by Dr Hemant K Mittal DM Resident Dept of Medical Oncology

2. INTRODUCTION A heterogeneous group of biologically and clinically distinct neoplasms O riginate from cells in the lymphoid organs Historically divided into two categories: NHL and HL Molecular pathogenesis of lymphoid malignancies : C lonal expansion of B cells or T cells The molecular characterization of the most frequent genetic abnormalities included the role of multiple proto- oncogenes and tumor suppressor genes whose abnormal functioning contributes to neoplastic transformation.

3. THE CELL OF ORIGIN OF LYMPHOMA

4. B-Cell Development and the Dynamics of the Germinal Center Reaction B lymphocytes are generated from a common pluripotent stem cell in the bone marrow Precursor B cells first assemble their immunoglobulin heavy chain locus (IGH) followed by the light chain loci (IGL) through a site-specific process of cleavage and rejoining, known as V(D)J recombination . Cells fail to express a functional (and non- autoreactive ) antigen receptor eliminated within the bone marrow, whereas S uccessfully rearranged their antibody genes positively selected to migrate into peripheral lymphoid organs as mature, naive B cells . In most cells, the subsequent maturation steps are linked to the histologic structure of the germinal center (GC)

5. Germinal center A specialized microenvironment that forms after encounter of naive B cells with a foreign antigen, in the context of signals delivered by CD4+ T cells and antigen-presenting cells. H ighly dynamic structure in which B cells transit back and forth between two zones : Dark zone (DZ), which consists of rapidly proliferating centroblasts (CBs) (doubling time, 6 to 12 hours), and L ight zone (LZ), which consists of more quiescent cells termed centrocytes , amid a network of resident accessory cells (follicular dendritic cells [FDCs] and Tfh cells).

6. DZ is the site where GC B cells modify the variable region of their IG genes by the process of somatic hypermutation (SHM), which introduces mostly single nucleotide substitutions, with few deletions and duplications, to change the affinity of the antibody for the antigen. CBs are then believed to cease proliferation and shuttle to the LZ, where they are rechallenged by the antigen through the interaction with CD4+ T cells and FDCs . LZ B cells expressing a B-cell receptor (BCR) with reduced affinity for the antigen will be eliminated by apoptosis, whereas a few cells with greater affinity will be selected for survival and differentiation into memory cells and plasma cells or re-enter the DZ following stimulation by a variety of signals. Iterative rounds of mutations and selection lead to affinity maturation at the population level.

7. The LZ is also the site where B cells undergo class-switch recombination (CSR), a DNA remodeling event that confers distinct effector functions to antibodies with identical specificities. SHM and CSR represent B-cell–specific functions that modify the genome of B cells via mechanisms involving single- or double-strand breaks and depend on the activity of the activation-induced cytidine deaminase (AID) enzyme.

8. BCL6 A critical regulator of the GC reaction A transcriptional repressor that negatively modulates the expression of a broad set of genes involved in BCR and CD40 signaling T-cell–mediated B-cell activation Induction of apoptosis Response to DNA damage Various cytokine and chemokine signalling pathways Plasma cell differentiation, via suppression of BLIMP1

9. Establish the proliferative status of CBs Allow the execution of antigen-specific DNA modification processes (SHM and CSR) without eliciting responses to DNA damage Keep in check a variety of signaling pathways that lead to premature activation and differentiation prior to the selection for the survival of cells by producing high-affinity antibodies Once these processes are completed , two critical signals for licensing GC exit are represented by engagement of the BCR by the antigen and activation of the CD40 receptor by the CD40 ligand present on CD4+ T cells. These signals induce down-regulation of BCL6 at the translational and transcriptional level, respectively, thus restoring DNA damage responses, as well as activation and differentiation capabilities.

10. Basic concepts of B-NHL pathogenesis Majority of B-NHLs (exception of most MCLs), derive from GC-experienced B cells M alignant clones harbor hypermutated IgV sequences, an irreversible marker of SHM activity Common mechanisms of oncogenic lesions in B-NHL Chromosomal translocations Aberrant SHM (ASHM ) These result from mistakes in the machinery that normally diversifies the IG genes during B-lymphocyte differentiation

11. Model for the generation of genetic lesions in lymphoma

12. Normal B-cell development and lymphomagenesis

13. T-Cell Development The process of T-cell development proceeds through sequential stages defined according to the expression of CD4 and CD8 Committed lymphoid progenitors exit the bone marrow and migrate to the thymus as early T-cell progenitors or double-negative 1 (DN1) cells , which lack expression of both CD4 and CD8 and harbor unrearranged T-cell receptor (TCR) genes In the thymic cortex, T cells advance through the double negative stages DN2 , DN3 , and DN4 while undergoing specific rearrangements at the TCRβ locus in order to acquire expression of the pre-TCR These thymocytes further differentiate into double-positive cells (CD4+CD8+), which express a complete surface TCR

14. Then enter a process of positive and negative selection in the medulla before exiting the thymus as single positive T cells The end result of this process is a pool of mature T cells that exhibit coordinated TCR and co-receptor specificities, as required for effective immune responses to foreign antigens Most mature T-NHLs arise from post- thymic T cells in the lymphoid organs.

15. GENERAL MECHANISMS OF GENETIC ALTERATIONS IN LYMPHOMA

16. Chromosomal Translocations G enetic hallmark of hematopoietic malignancies Reciprocal and balanced recombination of two chromosomes Recurrently associated with a given tumor type C hromosomal translocations occur as a consequence of mistakes during IG and TCR gene rearrangements in B and T cells, respectively .

17. Translocations derived from mistakes of the RAG-mediated V(D)J recombination process , as translocations involving IGH and CCND1 in MCL or IGH and BCL2 in FL Translocations mediated by errors in the AID-dependent CSR process , such as those involving the IG genes and MYC in sporadic Burkitt lymphoma (BL) Based on the characteristics of the chromosomal breakpoint, can be broadly divided into the following three groups Translocations occurring as by-products of the AID-mediated SHM mechanism , which also generates DNA breaks, such as those joining the IG and MYC loci in endemic BL ( eBL )

18. The common feature of all NHL-associated chromosomal translocations is the presence of a proto-oncogene in the proximity of the chromosomal recombination sites T he coding domain of the oncogene is not affected by the translocation, but pattern of expression is altered ( proto-oncogene deregulation ) M ost NHL-associated translocations: Heterotopic Less commonly, B-NHL–associated chromosomal translocations juxtapose the coding regions of the two involved genes to form a chimeric unit that encodes for a novel fusion protein, an outcome typically observed in acute leukemia . Examples: the t(11;18) of MALT lymphoma and the t(2;5) of ALCL.

19. Molecular consequences of chromosomal translocations in lymphoma

20. Aberrant Somatic Hypermutation (ASHM) Malfunction in the physiologic SHM process, leading to the mutation of multiple non-IG genes. This phenomenon is uniquely associated with B-NHL and particularly with DLBCL In GC B cells, SHM is tightly regulated both spatially and temporally to introduce mutations only in the rearranged IGV genes as well as in the 5′ region of a few other genes, including BCL6. Target loci include several well-known proto- oncogenes such as PIM1, PAX5, and MYC (one of the most frequently altered human oncogenes ).

21. Copy Number Gains and Amplifications Lead to overexpression of an intact protein Examples are exemplified by REL and BCL2 in DLBCL and by the genes encoding for programmed cell death 1 (PD-1) ligands in primary mediastinal B-cell lymphoma .

22. Activating Point Mutations Somatic point mutations in the coding sequence of a target proto-oncogene may alter the biologic properties of its protein product, leading to its stabilization or constitutive activation. Very rare. F or example, mutations of the RAS genes, a very frequent proto-oncogene alteration in human neoplasia , are rare in lymphoma.

23. Inactivating Mutations and Deletions The TP53 gene , the most common target of genetic alterations in human cancer, is involved at generally low frequencies, with the exception of BL and DLBCL derived from the transformation of FL and CLL. T he mechanism of TP53 inactivation in NHL : point mutation of one allele and chromosomal deletion or mutation of the second allele. S everal additional tumor suppressor genes that are lost through chromosomal deletions and/or mutations, including genes that function as haplo -insufficient tumor suppressors (e.g., the histone modifiers CREBBP and KMT2D).

24. Infectious agents Viral and bacterial infections have both been implicated in the pathogenesis of lymphoma. At least three viruses are associated with specific NHL subtypes: EBV, HHV- 8/KSHV, and HTLV-1. Other infectious agents, including HIV, HCV, H . pylori, and Chlamydia psittaci have an indirect role either impairing the immune system and/or providing chronic antigenic stimulation.

25. EBV (γ- herpesvirus 4): initially identified in endemic African BL and subsequently a fraction of sporadic BLs ( sBLs ), HIV-related lymphomas, and primary effusion lymphomas. Alter the growth of B cells Upon infection, the EBV genome is transported into the nucleus of the B lymphocyte, where it exists predominantly as an extrachromosomal circular molecule ( episome ). The formation of circular episomes is mediated by the cohesive terminal repeats, which are represented by a variable number of tandem repeats sequence. EBV-infected lymphomas usually display a single form of fused EBV termini, suggesting that the lymphoma cell population represents the clonally expanded progeny of a single infected cell .

26. HHV-8 (γ- herpesvirus 8): initially identified in HIV-related Kaposi sarcoma and subsequently in primary effusion lymphoma and multicentric Castleman disease. Like other γ- herpesviruses , HHV-8 is also lymphotropic . Lymphoma cells naturally infected by HHV-8 harbor the viral genome in its episomal configuration D isplay a marked restriction of viral gene expression, suggesting a pattern of latent infection. HTLV-1 ( ssRNA retrovirus): first discovered oncogenic human retrovirus Isolated in T-cell leukemia /lymphoma (ATLL ) The pathogenetic effect of HTLV-1: viral production of a transregulatory protein (HTLV-1 tax) that can activate the transcription of several host genes

27. HCV ( ssRNA Flavivirus ) : increase s risk of developing lymphoproliferative disorders among HCV-positive patients and eradication of HCV with antiviral treatment could directly induce lymphoma regression in seropositive patients affected by indolent NHL. C hronic B-cell stimulation by antigens associated with HCV infection induce nonmalignant B-cell expansion, which subsequently evolves into B-NHL through the accumulation of additional genetic lesions. More recently, a few large epidemiologic studies also revealed a higher risk of developing NHL in patients with chronic HBV infection .

28. H. Pylori: In MALT lymphoma of the stomach Antigen stimulation Eradication of infection with antibiotics leads to long-term complete regression in 70% of cases. Patients with t(11;18)(q21;21) respond poorly to antibiotic eradication C. Psittaci : An obligate intracellular bacterium Linked to ocular adnexal marginal zone B-cell lymphoma (MZL) Causes both local and systemic persistent infection, contributing to lymphomagenesis through its mitogenic activity and its ability to promote polyclonal cell proliferation and resistance to apoptosis Bacterial eradication with antibiotic therapy is often followed by lymphoma regression.

29. MOLECULAR PATHOGENESIS OF B-CELL NON-HODGKIN LYMPHOMA

30. Mantle Cell Lymphoma Cell of Origin Aggressive disease representing a pprox 5% of all NHL diagnoses and generally regarded as incurable. T wo variants of MCL : C lassical MCL , characterized by unmutated or minimally mutated IGV genes and derive from naive, pre-GC peripheral B cells located in the inner mantle zone of secondary follicles; and L eukemic non-nodal MCL , characterized by IGV-mutated cells thought to derive from antigen-experienced B ce lls ( indolent behavior , can be transformed into a more aggressive disease through the acquisition of additional genetic lesions ).

31. Genetic Lesions Associated with the t(11;14)(q13;q32), which juxtaposes the IGH gene at 14q32 to a region containing the CCND1 gene on chromosome 11q13. It leads to deregulation and overexpression of cyclin D1 ( a member of the D-type G1 cyclins that regulates the early phases of the cell cycle, and is normally not expressed in resting B cells). Perturb the G1-S phase transition of the cell cycle I ncrease the mRNA half-life The frequency and specificity of this genetic lesion, together with the expression of cyclin D1 in the tumor cells, provide an excellent marker for MCL diagnosis . In cases resembling conventional MCL both morphologically and phenotypically but lacking the t(11;14) (10% of diagnoses), overexpression of CCND2 and CCND3 is often detected.

32. Burkitt Lymphoma Cell of Origin BL is an aggressive lymphoma comprising three clinical variants, namely, sBL , eBL , and immunodeficiency associated BL (often diagnosed as the initial manifestation of AIDS). sBL and eBL differ in their geographical distribution, with eBL being present in equatorial areas endemic for malaria and sBL occurring throughout the world. These two subtypes also differ in their association with EBV, which is present in the tumor cells of all eBL cases but only in 10-20% of sBL cases. Derive from DZ GC B cells

33. Genetic Lesions All BL cases share a virtually obligatory genetic lesion (i.e., chromosomal translocations involving the MYC gene on region 8q24 and one of the IG loci on the partner chromosome). In 80% cases , IGH locus is involved, leading to t(8;14) (q24;q32), whereas in remaining 20 % cases, either IGk (2p12) or IGλ (22q11) is involved. Display a high degree of molecular heterogeneity: the breakpoints being located 5′ and centromeric to MYC in t(8;14) but mapping 3′ to MYC in t(2;8) and t(8;22). The common consequence of t(8;14), t(2;8), and t(8;22) is overexpression of the MYC proto-oncogene , which is normally absent in the majority of proliferating GC B cells, in part due to BCL6-mediated transcriptional repression.

34. MYC ( a nuclear phospho -protein), functions as a sequence-specific DNA-binding transcriptional regulator controlling proliferation, cell growth, differentiation, and apoptosis In addition, MYC controls DNA replication independent of its transcriptional activity: promote genomic instability by inducing replication stress. D eregulation cause genomic instability and tumor progression by facilitating the occurrence of additional genetic lesions. L eads to the development of aggressive B-cell lymphomas with high penetrance and short latency . Mutations of the transcription factor TCF3 (10-25%) and its negative regulator ID3 (35-58%) are highly recurrent in all three subtypes, promote tonic (antigen-independent) BCR signaling and sustain survival by engaging the PI3 kinase pathway.

35. One contributing factor is monoclonal EBV infection , which is present in all cases of eBL and in approx 30% of sBLs . The consistent expression of EBER, a class of small RNA molecules, mediates the transforming potential of EBV in BL. EBV infection in BL displays a peculiar latent infection phenotype characterized by negativity of both EBV transforming antigens LMP1 and EBNA2.

36. Follicular Lymphoma Cell of Origin 2 nd most common type of B-NHL (20 % of diagnoses) M ost common low-grade B-NHL A n indolent but largely incurable disease C ontinuous pattern of progression and relapses that often transformed to an aggressive lymphoma with a diffuse large-cell architecture and dismal prognosis ( 20- 30% cases). The ontogeny of FL from a GC B cell is supported by the expression of specific GC B-cell markers such as BCL6 and CD10, together with the presence of somatically mutated IG variable region genes showing evidence of ongoing SHM activity.

37. Genetic Lesions The genetic hallmark of FL: chromosomal translocations of the BCL2 gene on chromosome band 18q21, in 80% to 90% of cases. These rearrangements join the 3′ untranslated region of BCL2 to an IG JH segment, resulting in the ectopic expression of BCL2 in GC B cells (normally repressed by BCL6). Rare rearrangements involving the 5′ flanking region of BCL2. BCL2 gene: encodes a 26-kD integral membrane protein that controls the cell apoptotic threshold by preventing programmed cell death and thus contributes to lymphomagenesis independent of antigen selection . A dditional genetic aberrations are required: Mutations in multiple epigenetic modifiers, including the methyltransferase KMT2D (70-80%), the Polycomb group oncogene EZH2 (20%), the acetyltransferases CREBBP (55%) and EP300 (10% ).

38. A major role is also played by chronic antigen stimulation . Approx 45% of patients harbor mutations affecting the BCR signaling pathway, and its blockade by selective PI3K α/δ inhibitors showed promising results in clinical trials. tFL -specific lesions include inactivation of CDKN2A/B by deletion, mutation, and hypermethylation (one-third of patients); rearrangements and amplifications of MYC ; TP53 mutations or deletions (25% to 30% of cases); loss of chromosome 6 (20%); chromosomal translocations of BCL6 (in 5% to 14% cases); ASHM ; and, biallelic loss of the immune regulator B2M .

39. Diffuse Large B-Cell Lymphoma M ost common form of B-NHL 40% diagnosed cases, including that arise de novo and that derive from the clinical evolution of various, less aggressive B-NHL types (i.e., FL and CLL).

40. Cell of Origin A molecularly, phenotypically , and clinically heterogeneous malignancy C lassified, into two molecular subtypes, reflecting the derivation from B cells at various developmental stages: Germinal center B-cell–like (GCB) DLBCL, and A ctivated B-cell–like (ABC) DLBCL GCB-DLBCL derives from cells recirculating toward the DZ ABC-DLBCL resembles a small subset of LZ B cells committed to plasmablastic differentiation or of in vitro BCR-activated B cells GCB-DLBCL display better overall survival compared to ABC-DLBCL.

41. Genetic Lesions Most prominent program disrupted in DLBCL: epigenetic remodeling This is largely due to loss-of-function mutations in the genes encoding for the CREBBP/EP300 acetyltransferases (30% of cases) and the KMT2D H3K4 methyltransferase (35% of cases). Deletion of KMT2D before GC formation leads to a significant increase in the percentage of GC B cells (i.e., the target cell of lymphoma transformation) CREBBP/EP300 inactivation alters the balance between the BCL6 oncogene and the tumor suppressor p53 Finally , CREBBP modulates the expression of MHC-II, suggesting a link between epigenetics and immune surveillance.

42. Chromosomal rearrangements of the BCL6 gene are observed in up to 35% of cases DLBCL cells have also acquired the ability to escape both arms of immune surveillance, including cytotoxic T lymphocyte– mediated cytotoxicity (through genetic or epigenetic loss of the B2M/HLA-I genes; approximately 60% of cases) and natural killer cell–mediated death (through genetic loss of the CD58 molecule). Half of all DLBCLs are associated with ASHM M utations of MYC and BCL2 being found at significantly higher frequencies in GCB-DLBCL and mutations of PIM1 almost exclusively observed in ABC-DLBCL. Mutations and deletions of TP53 (in 20% cases) and more often associated with chromosomal translocations involving BCL2.

43. GCB-DLBCL Genetic lesions specific to GCB-DLBCL include the t(14;18) and t(8;14) translocations, which deregulate the BCL2 and MYC oncogenes in 34% and 10% of cases, respectively. Also exquisitely restricted to this subtype are mutations of the EZH2 gene (22% of cases), which encodes a histone methyltransferase responsible for trimethylating Lys27 of histone H3 (H3K27). EZH2 mutations leading to increased H3K27 trimethylation . TNFRSF14 (a frequent target of CN losses affecting chromosome 1p36), encoding for a tumor necrosis factor (TNF) receptor superfamily member, is another commonly mutated and deleted gene in GCB-DLBCL.

44. ABC-DLBCL A predominant feature of ABC-DLBCL is the presence of multiple genetic alterations lead to activation of the NF- κB transcription complex . Amplifications of the BCL2 locus, inactivating mutations or deletions of BLIMP1, and deletion or lack of expression of the CDKN2A/B tumor suppressor are almost exclusively seen In a significant fraction of cases, this is associated with the presence of a “chronic active” BCR signaling that is sustained by somatic gain-of-function mutations affecting proximal members of the pathway. Kinase inhibitors that interfere with the Bruton tyrosine kinase (BTK) , a molecule linking BCR to NF- κB , are emerging as a new treatment paradigm for ABC-DLBCL

45. Approximately 30% of ABC-DLBCL patients harbor a recurrent change in the intracellular Toll/interleukin-1 receptor domain of the MYD88 adaptor molecule, which has the potential to activate NF- κB as well as JAK/STAT3 transcriptional responses. MYD88 is required for the survival of ABC-DLBCLs ABC-DLBCLs harboring the MYD88 mutant isoform did not respond to BTK inhibition, but tumors with concurrent MYD88 and CD79A/B mutations showed exceptional responses. Up to 30% of ABC-DLBCL patients carry biallelic mutations and/or deletions inactivating TNFAIP3 , (a negative regulator of NF- κB ). TNFAIP3-mutated DLBCL do not respond to BTK inhibitors. A second important program disrupted by genetic lesions in ABC-DLBCL includes terminal B-cell Differentiation. In 25% of ABC-DLBCL, the PRDM1/BLIMP1 gene is inactivated (it blocks post-GC B-cell differentiation)

46. DLBCL Derived from CLL and FL Transformation : CDKN2A/B loss, TP53 loss, and MYC translocations (in both conditions), along with ASHM and B2M inactivation in tFL or NOTCH1 mutations in RS. M utations of epigenetic modifiers are acquired early during tumor clonal evolution, suggesting a facilitator role in the initial phases of malignant transformation.

47. Most common genetic lesions identified in PMBCL and DLBCL

48. Primary Mediastinal B-Cell Lymphoma Cell of Origin An aggressive B-cell neoplasia , accounting for 2% to 4% of NHL Most commonly observed in young female adults Involves the mediastinum Post-GC thymic B cells origin Displays a distinct gene expression profile, largely similar to HL

49. Genetic Lesions A genetic hallmark of both PMBCL and HL is the amplification of chromosomal region 9q24 , detected in nearly 50% of patients. Lesions affecting regulators of immune responses in PMBCL: Mutation in the gene encoding for the JAK2 tyrosine kinase and the PDL1/PDL2 genes Genomic breakpoints and mutations of the MHC class II trans-activator gene CIITA (down-regulates surface HLA class II expression) PMBCL also shares with HL the presence of genetic lesions affecting the NF- κB pathway and the deregulated expression of receptor tyrosine kinases JAK-STAT signalling pathway : a major disease contributor

50. Marginal Zone Lymphoma Cell of Origin A group of indolent lymphomas Derived from marginal zone memory B cells Post-GC origin Three groups according to the involved sites and to the underlying molecular pathogenesis: extranodal MZL or MALT lymphoma , splenic MZL (SMZL) , and nodal MZL (NMZL) . A critical role of antigen stimulation

51. MALToma : M.C. MZL (70%) and the 3rd M.C. NHL. Associated with chronic infection of the gastric mucosa by H. Pylori Eradication of H. pylori by antibiotic treatment can lead to tumor regression in 70% cases Salivary gland and thyroid MALT lymphoma are generally a sequela of autoimmune processes, namely, Sjögren syndrome and Hashimoto thyroiditis , respectively.

52. Genetic Lesions Target: NF- Κ b signaling pathway t(11;18 )(2;33), most common lesion, which involves the BIRC3 gene on 11q21 and the MALT1 gene on 18q21 (in 25-40 % cases). BIRC3 plays an role in regulating programmed cell death, whereas MALT1 together with BCL10 and CARD11, is a component of the CBM ternary complex and plays a central role in BCR and NF- κB signaling activation. Translocation confers a survival advantage to the tumor by i nhibition of apoptosis and constitutive NF- κB activation. Other translocations: t(14;18)(q32;q21): 15-20% cases, MALT1 with IGH locus t(1;14)(p22;q32): 5% cases, MALT1 with 1p22 These translocations provide both antiapoptotic and proliferative signals mediated via NF- κ B transcriptional targets.

53. Similar genetic landscape is seen in SMZL and NMZL with the activator IKBKB and the inhibitor TNFAIP3 being the most commonly affected genes. Other recurrently mutated genes are including in the NOTCH pathway (mutations in the NOTCH2 receptor; in 10-25% of patients)

54. Chronic Lymphocytic Leukemia Cell of Origin A malignancy of mature, resting B lymphocytes that accumulate in the blood, bone marrow, and other lymphoid tissues. Two main subtypes, defined by the presence or absence of mutations affecting the IGV genes ( IGV-mutated CLL and un-mutated CLL ). O riginate from the oncogenic transformation of an antigen experienced B cell (IGV-mutated CLL from CD5+CD27+ memory B cells and IGV un-mutated CLL from pre-GC CD5+ naive B cells ) IGV-mutated CLL shows longer survival 6% of normal elderly population develops a monoclonal B-cell lymphocytosis (MBL): precursor to CLL in 1% to 2% of cases.

55. Genetic Lesions Devoid of balanced, reciprocal chromosomal translocations Several numerical abnormalities, including trisomy 12 and monoallelic or biallelic deletion/inactivation of chromosomal regions 17p, 11q, and 13q14(most common) Trisomy 12 (16% of cases) and correlates with poor survival. Deletions of 11q22-23 (18% of cases) almost invariably encompass the ATM gene and promote genomic instability . Gain-of-function mutations of NOTCH1 (10% cases): poor prognosis Mutations in splicing factor 3b subunit 1 ( SF3B1 ): components of the spliceosome ; in 5-10% cases; poor prognosis NF- κB is one of the main pathways activated after BCR activation, and pharmacologic inhibition of BCR signaling through BTK or PI3K inhibition is effective in CLL patients

56. MOLECULAR PATHOGENESIS OF T-CELL NON-HODGKIN LYMPHOMA

57. Adult T-Cell Leukemia /Lymphoma (HTLV-1 Positive) Cell of Origin Associated with HTLV-1 infection Mainly restricted to Southwestern Japan and the Caribbean basin US and Europe are considered low-risk areas because <1% of the population are HTLV-1 carriers and only 2% to 4% of seropositive individuals eventually develop ATLL Clonal rearrangement of the TCR with integration of the virus

58. Genetic Lesions HTLV-1: production of a transregulatory protein (HTLV-1 tax) that markedly increases expression of all viral gene products and transcriptionally activates the expression of certain host genes, including IL-2, CD25, c-sis, c- fos , and GCSF. These genes have central role in normal T-cell activation and growth In addition, tax interferes with DNA damage repair functions and with mitotic checkpoints, consistent with the high frequency of karyotypic abnormalities in ATLL cells. The long period of clinical latency that precedes the development of ATLL (usually 10 to 30 years), the small percentage of infected patients who develop this malignancy, and the observation that leukemic cells from ATLL are monoclonal suggest that HTLV-1 is not sufficient to cause the full malignant phenotype.

59. A recurrent genetic lesion in ATLL is represented by mutations of the TP53 gene , inactivated in 40% of cases. Multiple alterations leading to the activation of the TCR and NF- κB signaling pathways (most commonly, PLCG1, PRKCB, CARD11, and STAT3, all mutated in 20% to 30% of samples). > 50% of cases harbor mutations and CN aberrations in genes responsible for immune recognition (HLA-A and HLA-B, B2M, CD58, FAS). These mutations provide a mechanism to escape immune surveillance : high immunogenicity of HLTV-1–derived proteins.

60. Angioimmunoblastic T-Cell Lymphoma Cell of Origin An aggressive disease of the elderly Accounts for about one third of all PTCLs in Western countries. The tumor cells display a mature CD4+CD8- T-cell phenotype, with frequent aberrant loss of one or several T-cell markers and coexpression of BCL6 and CD10 in at least a fraction of cells. Derived from follicular helper T cells

61. Genetic Lesions Recurrent mutations in the small GTPase protein RHOA (67% cases) In most of these cases, a recurrent amino acid substitution (Gly17Val) impairs the RHO signaling pathway most likely by sequestering activated guanine-exchange factor (GEF) proteins. Activating mutations or gene fusions involving the VAV1 gene have also been detected in some patients. VAV1 encodes for a GEF that mediates multiple signalling cascades triggered by the TCR, and its mutations result in the increased activation of VAV1 effector pathways (NFAT, MAPK, JNK ).

62. Anaplastic Large-Cell Lymphoma Cell of Origin ALCL is a distinct subset of T-NHL (approx 12% cases) Composed of large pleomorphic cells that characterized by CD30 +ve and loss of most T-cell markers. Based on the expression of a chimeric protein containing the cytoplasmic portion of anaplastic lymphoma kinase (ALK), ALCL subdivided into two groups : ALK-positive ALCL (most common and curable ) ALK-negative ALCL (more aggressive) These two subgroups are closely related and may derive from a common precursor.

63. Genetic Lesions The genetic hallmark of ALK-positive ALCL is a chromosomal translocation involving band 2p23 and a variety of chromosomal partners t(2;5)(p23;q35) ; 70-80% cases: ALK gene on 2p23 and the nucleophosmin (NPM) gene ( NPM1 ) on 5q35. ALK gene , which is not expressed in normal T lymphocytes, becomes inappropriately expressed in lymphoma cells ALK, activates several downstream signaling cascades, among which JAK-STAT and PI3K-AKT play central roles. Constitutive JAK-STAT activation (20% cases) has also been shown in ALK-negative ALCL due to multiple genetic lesions including activating mutations in JAK1 and/or STAT3 .

64. Cutaneous T-Cell Lymphoma Mycosis fungoides and Sézary syndrome are primary cutaneous T-cell malignancies derived from skin-homing CD4+ T cells. Presence of recurrent and focal CN losses affecting tumor suppressor genes (e.g., TP53, RB1, CDKN1A, PTEN) and oncogenes (e.g., MYC) in these malignancies, particularly in Sézary syndrome . More recently, NGS studies revealed an important role for epigenetic modifiers in the pathogenesis of these tumors , which commonly harbor inactivating point mutations of TET2, CREBBP, KMT2D, and KMT2C (15-20% of cases ).

65. Peripheral T-Cell Lymphoma Not Otherwise Specified The largest and most heterogeneous group of PTCLs , lack specific features allowing them to classified within other entities . Cell of Origin Majority cases derive from CD4+ T cells D efective expression of one or more T-cell–associated antigens Closely related to activated T cells Genetic Lesions Clonal numerical and structural aberrations are found in most cases Candidate genes include CDK6, MYC, and the NF- κB regulator CARD11, whereas losses of 9p21 associate with reduced expression of CDKN2A/B

66. Hepatosplenic T-Cell Lymphoma A rare type of PTCL, characterized by an early age at onset and dismal prognosis. Associated with chronic immunosuppressive treatments and immune dysregulation . Derives from the malignant transformation of γδ T cells in 80% of cases. Chromosomal abnormalities, including isochromosome 7 (47%), trisomy 8 or amplification of 8q (31%), chromosome 10 losses (19%) and gains in chromosome 1 (13%). One-third of HTCL cases carry mutations in the histone -lysine Nmethyltransferase SETD2 ( tumor suppressor gene) Other mutated genes: STAT5B (31%), STAT3 (9%), and PIK3CD (9%).

67. MOLECULAR PATHOGENESIS OF HODGKIN LYMPHOMA B lymphoid malignancy Presence of scattered large atypical cells—the mononucleated Hodgkin cells and the multinucleated Reed-Sternberg cells (HRS)—residing in a complex admixture of inflammatory cells. Based on the morphology and phenotype of the neoplastic cells, as well as on the composition of the infiltrate, HL is classified into two major subgroups: Nodular lymphocyte-predominant HL (NLPHL) (~5% of cases) Classical HL ( cHL )

68. Cell of Origin Despite the HRS cells of cHL cells have lost expression of nearly all B-cell–specific genes, both HL types represent clonal populations of B cells, as revealed by the presence of clonally rearranged and somatically mutated IG genes. In approximately 25% of cHL cases, nonsense mutations disrupt originally in-frame VH gene rearrangements (crippling mutations), thereby preventing antigen selection and suggesting that HRS cells have escaped apoptosis through a mechanism not linked to antigen stimulation.

69. Genetic Lesions A number of structural alterations lead to the constitutive activation of NF- κB in cHL. 50% cases display amplification of REL , coupled with inactivating mutations in a number of genes coding for negative NF- κB regulators, including NFKBIA (20%), NFKBIE (15%), and TNFAIP3 (40%; EBV - ve ). EBV : An important pathogenic cofactor in cHL (in 40% cases) Amplification of JAK2, mutations of STAT6, and inactivating mutations of SOCS1 and PTPN1 are frequent in NLPHL BCL6 translocations have been reported in the lymphocytic and histiocytic (L&H) cells of NLPHL, but only rarely in cHL. Translocations of BCL2 or mutations in positive or negative regulators of apoptosis (e.g., TP53, FAS, BAD, and ATM) are virtually absent.

70. Thank you