Clinical Relevance of BCL2, BCL6, and MYC Rearrangements in Diffuse Large B-Cell Lymphoma

Increased MYC expression without MYC gene translocation in patients with the diffuse large B-cell-lymphoma subtype of iatrogenic immunodeficiency-associated lymphoproliferative disorders

Post-transplant lymphoproliferative disorder (PTLD) and other iatrogenic immunodeficiency-associated lymphoproliferative disorders (OIIA-LPD) are iatrogenic lymphoproliferative disorders (LPD) that develop in association with immunosuppressive treatment in the setting of organ transplantation and autoimmune disease, respectively. Each has a spectrum of pathologies ranging from lymphoid hyperplasia to lymphoma. To clarify the characteristics of the diffuse large B-cell lymphoma (DLBCL) subtype in a cohort of 25 patients with PTLD or OIIA-LPD from our institute, we selected 13 with a histological subtype of DLBCL, including 2 cases of PTLD and 11 of OIIA-LPD. The median patient age at diagnosis was 70 years, with a female predominance. Both PTLD cases developed after kidney transplant. Of the patients with OIIA-LPD, 10 had rheumatoid arthritis, 1 had mixed connective tissue disease, and 8 were treated using methotrexate. Both of the PTLD patients and 6 of the OIIA-LPD patients had extranodal manifestations. All patients except for one were classified as having the non-germinal center B-cell (non-GCB) subtype according to the Hans algorithm. Tissue samples from 8 patients were positive for CD30 and 8 were positive for Epstein–Barr virus (EBV)-encoded small RNA. Seven patients had MYC-positive tissue samples, but none had MYC translocation. Our study suggests that extranodal manifestations and the non-GCB subtype are common, that EBV is associated with the DLBCL subtype of PTLD and OIIA-LPD, and that anti-CD30 therapy is applicable. In addition, our patients with the DLBCL subtype of PTLD and OIIA-LPD exhibited MYC overexpression without MYC translocation, suggesting an alternative mechanism of MYC upregulation.

Clinical and Molecular Properties of Human Immunodeficiency Virus-Related Diffuse Large B-Cell Lymphoma

Non-Hodgkin lymphoma is the most common malignancy affecting people living with HIV (PLWH). Among its several subtypes, diffuse large B-cell lymphoma (DLBCL) is an important manifestation within the HIV-infected compartment of the population. Since HIV is able to modulate B cells and promote lymphomagenesis through direct and indirect mechanisms, HIV-related DLBCL has specific characteristics. In this review, we address the clinical and molecular properties of DLBCL disease in the context of HIV infection, as well as the mechanisms by which HIV is able to modulate B lymphocytes and induce their transformation into lymphoma.

Disease site as a determinant of survival outcome in patients with systemic anaplastic lymphoma kinase positive anaplastic large cell lymphoma with extranodal involvement: an analysis of 1306 cases from the US National Cancer Database

Systemic anaplastic lymphoma kinase positive (ALK+) anaplastic large cell lymphoma with extranodal involvement (ALCL-E) is a rare form of non-Hodgkin lymphoma. No large study in the literature has compared the survival outcomes among different primary extranodal sites of involvement in ALK+ ALCL-E. We identified 1306 patients with ALK+ ALCL-E diagnosed between 2004 and 2014 in the US National Cancer Database, among whom 387 had primary extranodal site in the chest/abdomen/pelvis, 103 in the bone, 62 in the central nervous system, 134 in the head and neck and 620 in the cutaneous/soft tissue. Younger age, lower Charlson-Deyo score, lower clinical stage, receipt of chemotherapy and receipt of radiotherapy were predictors of longer overall survival. Patients with extranodal involvement of central nervous system and chest/abdomen/pelvis had shorter overall survival than those with involvement of head and neck, bone, and cutaneous/subcutaneous tissue after adjusting for confounding variables. We recommend treating these patients upfront with more aggressive therapy.

Prognostication of diffuse large B-cell lymphoma in the molecular era: moving beyond the IPI

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with variable outcomes. Despite the majority of patients being cured with combination chemoimmunotherapy, up to 30% eventually succumb to the disease. Until recently, baseline prognostic assessment has centred on the International Prognostic Index (IPI), although this index is yet to impact strongly on treatment choice. Molecular features such as cell of origin, MYC and BCL-2 genetic alterations and protein overexpression were identified over a decade ago, yet their prognostic value is still not fully elucidated. Adding complexity are the plethora of new clinical, biological and molecular prognostic markers described in the recent literature, most of which lack independent validation, likely act as surrogate markers for those already in common use and have yet to substantially impact on therapeutic decision making. This review comprehensively assesses the value of individual prognostic markers in the clinical setting and their potential to predict response to novel agents, and ways to optimise their use in future research.

Venetoclax: A new wave in hematooncology

Inhibitors of antiapoptotic proteins of the BCL2 family can successfully restart the deregulated process of apoptosis in malignant cells. Whereas nonselective agents have been limited by their affinity to different BCL2 members, thus inducing excessive toxicity, the highly selective BCL2 inhibitor venetoclax (ABT-199, Venclexta™) has an acceptable safety profile. To date, it has been approved in monotherapy for the treatment of relapsed or refractory chronic lymphocytic leukemia (CLL) with 17p deletion. Extension of indications can be expected in monotherapy and in combination regimens. Sensitivity to venetoclax is not common in lymphomas, but promising outcomes have been achieved in the mantle cell lymphoma group. Venetoclax is also active in multiple myeloma patients, especially in those with translocation t(11;14), even if high-risk features such as del17p are also present. Surprisingly, positive results are being obtained in elderly acute myeloid leukemia patients, in whom inhibition of BCL2 is able to substantially increase the efficacy of low-dose cytarabine or hypomethylating agents. Here, we provide a summary of available results from clinical trials and describe a specific mechanism of action that stands behind the efficacy of venetoclax in hematological malignancies.

BCL2 expression in DLBCL: reappraisal of immunohistochemistry with new criteria for therapeutic biomarker evaluation

A BCL2 IHC score is a strong prognostic factor independent of the IPI and MYC protein/rearrangement status in DLBCL treated with R-CHOP. The BCL2 scoring system we propose is a simple, at-a-glance, and highly reliable system, which was confirmed by an image analysis.

Immunohistochemical double-hit score is a strong predictor of outcome in patients with diffuse large B-cell lymphoma treated with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone

PURPOSE

Approximately 5% of diffuse large B-cell lymphomas (DLBCLs) are double-hit lymphomas (DHLs) with translocations of both MYC and BCL2. DHLs are characterized by poor outcome. We tested whether DLBCLs with high expression of MYC protein and BCL2 protein share the clinical features and poor prognosis of DHLs.

PATIENTS AND METHODS

Paraffin-embedded lymphoma samples from 193 patients with de novo DLBCL who were uniformly treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) were studied using immunohistochemistry for MYC, BCL2, CD10, BCL6, and MUM1/interferon regulatory factor 4, and fluorescent in situ hybridization (FISH) for MYC and BCL2.

RESULTS

FISH analysis identified DHL in 6% of patients, who showed the expected poor overall survival (OS; P = .002). On the basis of immunohistochemical MYC and BCL2 expression, a double-hit score (DHS) was assigned to all patients with DLBCL. The DHS-2 group, defined by high expression of both MYC and BCL2 protein, comprised 29% of the patients. DHS 2 was significantly associated with lower complete response rate (P = .004), shorter OS (P < .001), and shorter progression-free survival (PFS; P < .001). The highly significant correlation with OS and PFS was maintained in multivariate models that controlled for the International Prognostic Index and the cell-of-origin subtype (OS, P < .001; PFS, P < .001). DHS was validated in an independent cohort of 116 patients who were treated with R-CHOP.

CONCLUSION

The immunohistochemical DHS defined a large subset of DLBCLs with double-hit biology and was strongly associated with poor outcome in patients treated with R-CHOP.

Expression of LMO2 is associated with t(14;18)/IGH-BCL2 fusion but not BCL6 translocations in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) can be separated for prognostic purposes using gene expression profiling (GEP) into 2 subgroups: germinal center B-cell (GCB) and activated B-cell phenotypes. However, GEP is impractical for routine clinical use, and immunophenotyping is an imperfect surrogate. Therefore, we studied the relationship between expression of the purported germinal center marker LMO2 and the presence of IGH-BCL2 fusions, BCL6 translocations, and LMO2 translocations. In addition, we investigated the usefulness of LMO2 expression as a marker of GCB subtype in DLBCL. Immunohistochemical and fluorescence in situ hybridization studies were successfully performed on 101 cases of de novo DLBCL that had been incorporated into a tissue microarray. There was a statistically significant association between IGH-BCL2 fusion and LMO2 protein expression (P = .02) but not between BCL6 translocations and LMO2 expression. LMO2 translocations were not identified. Although uncommon, all cases that had both IGH-BCL2 fusion and BCL6 translocations expressed LMO2. The findings suggest LMO2 as a potential marker for the GCB phenotype.

Rearrangement of MYC Is Associated With Poor Prognosis in Patients With Diffuse Large B-Cell Lymphoma Treated in the Era of Rituximab

Purpose

Rearrangement of MYC occurs in a proportion of diffuse large B-cell lymphomas (DLBCL), where they may be associated with an adverse clinical outcome. The aim of this study was to determine the frequency of MYC translocations in DLBCL and their prognostic impact in the era of cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab (CHOP-R) therapy.

Patients and Methods

Three hundred three patients with previously untreated DLBCL, with no evidence of underlying follicular lymphoma, were investigated using immunohistochemistry and interphase fluorescent in situ hybridization for MYC, BCL6, and t(14;18)/BCL2 rearrangements. All patients (median age, 71.1 years; range, 23 to 96 years) were treated when CHOP-R was standard therapy for DLBCL and observed for a maximum of 4 years. Overall survival (OS) at 3 years was 49% (95% CI, 42% to 56%).

Results

MYC rearrangements were demonstrated in 35 (14%) of 245 biopsies with data available. Of these, 26 (74%) also had a t(14;18), 10 (26%) were BCL6 and MYC rearranged, and seven had all three abnormalities. Only age, International Prognostic Index, and MYC rearrangement retained prognostic significance in the final model. OS was significantly worse for patients with rearrangement of MYC (survival probability at 2 years = 0.35 in v 0.61 in the nonrearranged group).

Conclusion

The presence of a MYC rearrangement is a strongly adverse prognostic factor in CHOP-R–treated patients and can be used in combination with patients' age and IPI to accurately predict clinical outcome. In DLBCL, rearrangement of MYC is rarely found as the sole genetic abnormality and the poor prognosis of these patients is likely to reflect a synergistic effect alongside deregulation of BCL6 or BCL2.

MYC gene rearrangements are associated with a poor prognosis in diffuse large B-cell lymphoma patients treated with R-CHOP chemotherapy

Approximately 5% to 10% of diffuse large B-cell lymphomas (DLBCLs) harbor an MYC oncogene rearrangement (MYC+). The prognostic significance of MYC+ DLBCL was determined in an unselected population of patients with newly diagnosed DLBCL treated with rituximab in combination with cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy (R-CHOP). Using a Vysis break-apart fluorescence in situ hybridization probe, 12 of 135 (8.8%) cases of MYC+ DLBCL were identified that had no defining high-risk features. MYC+ DLBCL was associated with an inferior 5-year progression-free survival (66% vs 31%, P = .006) and overall survival (72% vs 33%, P = .016). Multivariate analysis confirmed the prognostic importance of MYC for both progression-free survival (hazard ratio = 3.28; 95% confidence interval, 1.49-7.21, P = .003) and overall survival (hazard ratio = 2.98; 95% confidence interval, 1.28-6.95, P = .011). Cases of MYC+ DLBCL also had a higher risk of central nervous system relapse (P = .023), independent of other risk factors. The diagnosis of MYC+ DLBCL is likely underappreciated; and given the lack of defining risk factors, fluorescence in situ hybridization for MYC rearrangements should be performed in all patients with DLBCL. In the R-CHOP treatment era, MYC+ DLBCLs have an inferior prognosis. Treatment regimens similar to those used in Burkitt lymphoma may be more appropriate in this patient population and need to be prospectively tested.

Lymphomas with concurrent BCL2 and MYC translocations: the critical factors associated with survival

BCL2 and MYC are oncogenes commonly deregulated in lymphomas. Concurrent BCL2 and MYC translocations (BCL2(+)/MYC(+)) were identified in 54 samples by karyotype and/or fluorescence in situ hybridization with the aim of correlating clinical and cytogenetic characteristics to overall survival. BCL2(+)/MYC(+) lymphomas were diagnosed as B-cell lymphoma unclassifiable (BCLU; n = 36) with features intermediate between Burkitt lymphoma and diffuse large B-cell lymphoma (DLBCL); DLBCL (n = 17), or follicular lymphoma (n = 1). Despite the presence of a t(14;18), 5 cases were BCL2 protein-negative. Nonimmunoglobulin gene/MYC (non-IG/MYC) translocations occurred in 24 of 54 cases (44%) and were highly associated with DLBCL morphology (P < .001). Over a median follow-up of 5.3 years, 6 patients remained in remission and 32 died within 6 months of the MYC(+) rearrangement, irrespective of whether MYC(+) occurred at diagnosis (31 of 54) or transformation (23 of 54; P = .53). A non-IG/MYC translocation partner, absent BCL2 protein expression and treatment with rituximab-based chemotherapy, were associated with a more favorable outcome, but a low International Prognostic Index score and DLBCL morphology were independent predictors of overall survival. A comprehensive cytogenetic analysis of BCL2 and MYC status on all aggressive lymphomas may identify a group of high-risk patients who may benefit from chemotherapeutic regimens that include rituximab and/or BCL2-targeted therapy.

Small-molecule XIAP antagonist restores caspase-9 mediated apoptosis in XIAP-positive diffuse large B-cell lymphoma cells

Clinical outcome in patients with primary nodal diffuse large B-cell lymphomas (DLBCLs) is correlated with expression of inhibitors of the intrinsic apoptosis pathway, including X-linked inhibitor of apoptosis protein (XIAP). XIAP suppresses apoptosis through inhibiting active caspase-3, caspase-7, and caspase-9. In this study, we investigated to see if the small-molecule XIAP antagonist 1396-12 induces cell death in cultured lymphoma cells of patients with DLBCL. Treatment with this XIAP antagonist resulted in relief of caspase-3 inhibition and in induction of apoptosis in 16 of 20 tested DLBCL samples. Sensitivity to the XIAP antagonist was observed in both chemotherapy-refractory and -responsive DLBCL, but did not affect peripheral blood mononuclear cells and tonsil germinal-center B cells from healthy donors. XIAP antagonist-sensitive samples were characterized by high expression levels of XIAP, relatively low expression levels of Bcl-2, and by constitutive caspase-9 activation. These data indicate that the small-molecule XIAP antagonist can induce apoptosis in cultured DLBCL cells and therefore should be considered for possible development as a therapy for these patients. In vitro sensitivity to the XIAP antagonist can be predicted based on biological markers, suggesting the possibility of predefining patients most likely to benefit from XIAP antagonist therapy.

Preclinical studies of TW-37, a new nonpeptidic small-molecule inhibitor of Bcl-2, in diffuse large cell lymphoma xenograft model reveal drug action on both Bcl-2 and Mcl-1

PURPOSE

Overexpression of Bcl-2 protein has been observed in more than 80% of B-cell lymphomas, including diffuse large cell lymphoma (DLCL), the most common subtype of non-Hodgkin's lymphoma. We have previously employed the natural product (-)-gossypol to test its therapeutic potential as a small-molecule inhibitor of Bcl-2 for the treatment of B-cell lymphomas.

EXPERIMENTAL DESIGN

Recently, we have used a structure-based strategy to design a new class of potent small-molecule inhibitor acting on Bcl-2. One such lead compound is the benzenesulfonyl derivative TW-37, which was designed to target the BH3-binding groove in Bcl-2 where proapoptotic Bcl-2 proteins, such as Bak, Bax, Bid, and Bim bind.

RESULTS

In our fluorescence polarization-based binding assays using recombinant Bcl-2, Bcl-X(L), and Mcl-1 proteins, TW-37 binds to Bcl-2, Bcl-X(L), and Mcl-1 with K(i) values of 290, 1,110 and 260 nmol/L, respectively. Hence, TW-37 is a potent inhibitor of Bcl-2 and has >3-fold selectivity over Bcl-X(L). In vitro, TW-37 showed significant antiproliferative effect in a de novo chemoresistant WSU-DLCL(2) lymphoma cell line and primary cells obtained from a lymphoma patient with no effect on normal peripheral blood lymphocytes. Coimmunoprecipitation experiments showed that TW-37 disrupted heterodimer formation between Bax or truncated-Bid and antiapoptotic proteins in the order Mcl-1 > Bcl-2 >> Bcl-X(L). As expected, TW-37 caused apoptotic death. Pre-exposure of lymphoma cells to TW-37 significantly enhanced the killing effect of cyclophosphamide-doxorubicin-vincristine-prednisone (CHOP) regimen. The maximum tolerated dose of TW-37 in severe combined immunodeficient (SCID) mice was 40 mg/kg for three i.v. injections when given alone and 20 mg/kg, x3 when given in combination with CHOP. Using WSU-DLCL(2)-SCID mouse xenograft model, the addition of TW-37 to CHOP resulted in more complete tumor inhibition compared with either CHOP or TW-37 alone.

CONCLUSIONS

We conclude that the administration of TW-37, as a potent Bcl-2 and Mcl-1 inhibitor, to standard chemotherapy may prove an effective strategy in the treatment of B-cell lymphoma.

Diffuse large B-cell lymphoma in pediatric patients belongs predominantly to the germinal-center type B-cell lymphomas: a clinicopathologic analysis of cases included in the German BFM (Berlin-Frankfurt-Münster) Multicenter Trial

Diffuse large B-cell lymphoma (DLBCL) in adults is a heterogeneous disease. Biologic subgroups of DLBCL with a favorable prognosis (germinal center B-cell–like, GCB) and with a poor prognosis (activated B-cell–like, ABC) have been defined by gene expression profiling and can be distinguished by immunohistochemistry. In contrast to their adult counterparts, children with DLBCL have an excellent prognosis. We analyzed 63 cases of DLBCL in pediatric patients by immunohistochemistry and fluorescence in situ hybridization (FISH) and found a striking predominance of a GCB subtype, which might explain the good clinical outcome in these lymphomas. Interestingly, FISH applied to 50 of these cases, as well as conventional cytogenetics available in 3 cases, revealed absence of the translocation t(14;18) involving the BCL2 gene, which is present in about 15% of adult GCB subtype DLBCL. Our data indicate that pediatric DLBCL differs from adult DLBCL and might comprise a biologically unique subgroup of DLBCL from which important insights into the pathogenesis and biology of this disease might be gained.

Pathogenetic and Clinical Implications of Non-Immunoglobulin; BCL6 Translocations in B-Cell Non-Hodgkin's Lymphoma

Chromosomal translocations affecting band 3q27, where BCL6 gene is located, are among the most common genetic abnormalities in non-Hodgkin's lymphoma of B-cell type (B-NHL). The BCL6 gene encodes a BTB/POZ zinc finger transcription factor, which exerts repressive activity by recruiting corepressor molecules. The 3q27/BCL6 translocation is unique in that it can involve not only immunoglobulin (Ig) genes but also non-Ig chromosomal loci as a partner. To date, around 20 non-Ig partner genes have been identified. As a result of non-Ig ; BCL6 translocations, many types of regulatory sequences of each partner gene substitute for the 5' untranslated region of BCL6, and the rearranged BCL6 comes under the control of the replaced promoter. The introduction of non-Ig ; BCL6 constructs into transformed cells led to high-level Bcl-6 protein expression in the nucleus, while BCL6 mRNA levels in clinical materials of diffuse large B-cell lymphoma (DLBCL) with non-Ig ; BCL6 translocations were unexpectedly low. A comparative study suggested that non-Ig ; BCL6 translocation and a low level of BCL6 mRNA expression are concordant indicators of a poor clinical outcome in cases of DLBCL. The coexistence of a non-Ig ; BCL6 translocation with t(14 ; 18)(q32 ; q21) in a single clone did not significantly affect the clinical features of follicular lymphoma. The pathogenetic and clinical implications of non-Ig ; BCL6 translocations in B-NHL subtypes may not be identical to those of Ig ; BCL6.

Targeted somatic mutation of the BCL6 proto-oncogene and its impact on lymphomagenesis

Cloning translocation breakpoints which cluster suspiciously to specific chromosomal loci has proved fruitful, leading to the identification of genes implicated in the onset of hematological malignancy. One of the most notable is BCL6, located on chromosome 3q27. The BCL6 is now known to encode a nuclear transcriptional repressor, with pivotal roles in germinal center (GC) formation and regulation of lymphocyte function, differentiation and survival. Unusually, the BCL6 gene locus is also actively targeted by the somatic mutation (SM) mechanism, at a rate indicative of specific, regulated events in both normal and malignant B-cells. These mutations occur in approximately 30% of normal centrocytes and centroblasts, but not in naive or pre-GC B-cells. They are also observed in approximately 70% of diffuse large B-cells lymphomas, approximately 30% of follicular lymphomas (FL) and at various frequencies in many lymphoma subtypes. Mutations are generated in the 5' proximity of the BCL6 promoter, including the first intron and are mainly single nucleotide substitutions, but with insertions and deletions also observed. Mutations in BCL6 occur independently of translocations, although mutational levels can be dramatically influenced by aberrantly translocated chromosomal elements, which map in the vicinity of the gene. Indeed, SMs are directly implicated in the generation of chromosomal translocations, as suggested by the overlap of the breakpoint cluster region and the mutational cluster domain. The prognostic value of the overall level of BCL6 mutations in specific lymphoma populations is, in the main, not as yet fully resolved. The accumulation of mutations in BCL6 during high grade transformation of FL, a mutational clustering and specific recurrent mutations suggest that some mutations may be selected for by their effect on the survival of the tumoral clone. In fact, it is now clear that SM can target and disrupt regulatory motifs in BCL6 to result in upregulated gene expression. Exogenous factors can also perturbate SM in BCL6. Viral infection elevates BCL6 mutational activity, suggesting a potential link with onset of virus-associated lymphoma. These findings to date reveal several mechanisms which can influence specific mutations targeting BCL6, and which may contribute to lymphomagenesis by dysregulating control of BCL6 expression.

Contig array CGH at 3p14.2 points to the FRA3B/FHIT common fragile region as the target gene in diffuse large B-cell lymphoma

Deletions of the 3p arm have been detected in various solid tumors, but no study to date has investigated this deletion in diffuse large B-cell lymphoma (DLBCL). Recently, we demonstrated that 3p14.2 was deleted in approximately 30% of DLBCL cases by use of a genome-wide array-comparative genomic hybridization (CGH). For a more detailed examination of the genomic losses at 3p14.2, here we made use of contig BAC array for 3p14.2, and found that 12 DLBCL samples displayed losses. All of the deleted regions were located within the fragile histidine triad (FHIT) gene, and the most frequent region of loss was mapped to 0.4 Mbp of the region encompassing the introns 4 and 5 and exon 5 of the FHIT gene. Concomitant analysis of transcripts showed that the FHIT gene was aberrantly transcribed in 31% of the DLBCL samples examined and that the lost exons of the aberrant transcripts were correlated with genomic deletions. These findings indicate that (1) loss of genomic material at 3q14.2 is responsible for exon losses of the FHIT gene, and (2) genomic loss of the FHIT gene is one of the causes of the generation of aberrant transcripts.

Cell cycle deregulation in B-cell lymphomas

Disruption of the physiologic balance between cell proliferation and death is a universal feature of all cancers. In general terms, human B-cell lymphomas can be subdivided into 2 main groups, low- and high-growth fraction lymphomas, according to the mechanisms through which this imbalance is achieved. Most types of low-growth fraction lymphomas are initiated by molecular events resulting in the inhibition of apoptosis, such as translocations affecting BCL2, in follicular lymphoma, or BCL10 and API2/MLT1, in mucosa-associated lymphoid tissue (MALT) lymphomas. This results in cell accumulation as a consequence of prolonged cell survival. In contrast, high-growth fraction lymphomas are characterized by an enhanced proliferative activity, as a result of the deregulation of oncogenes with cell cycle regulatory functions, such as BCL6, in large B-cell lymphoma, or c-myc, in Burkitt lymphoma. Low- and high-growth fraction lymphomas are both able to accumulate other alterations in cell cycle regulation, most frequently involving tumor suppressor genes such as p16(INK4a), p53, and p27(KIP1). As a consequence, these tumors behave as highly aggressive lymphomas. The simultaneous inactivation of several of these regulators confers increased aggressivity and proliferative advantage to tumoral cells. In this review we discuss our current knowledge of the alterations in each of these pathways, with special emphasis on the deregulation of cell cycle progression, in an attempt to integrate the available information within a global model that describes the contribution of these molecular changes to the genesis and progression of B-cell lymphomas.

HGAL is a novel interleukin-4-inducible gene that strongly predicts survival in diffuse large B-cell lymphoma

We have cloned and characterized a novel human gene, HGAL (human germinal center-associated lymphoma), which predicts outcome in patients with diffuse large B-cell lymphoma (DLBCL). The HGAL gene comprises 6 exons and encodes a cytoplasmic protein of 178 amino acids that contains an immunoreceptor tyrosine-based activation motif (ITAM). It is highly expressed in germinal center (GC) lymphocytes and GC-derived lymphomas and is homologous to the mouse GC-specific gene M17. Expression of the HGAL gene is specifically induced in B cells by interleukin-4 (IL-4). Patients with DLBCL expressing high levels of HGAL mRNA demonstrate significantly longer overall survival than do patients with low HGAL expression. This association was independent of the clinical international prognostic index. High HGAL mRNA expression should be used as a prognostic factor in DLBCL.

Nonimmunoglobulin (non-Ig)/BCL6gene fusion in diffuse large B-cell lymphoma results in worse prognosis than Ig/BCL6

Chromosomal translocation involving the BCL6 gene affects not only immunoglobulin (Ig) genes but also a number of non-Ig genes as partners. The molecular anatomy of the BCL6 gene rearrangements in 39 cases with diffuse large B-cell lymphoma (DLBCL) by long-distance polymerase chain reaction–based assays was determined. The results showed that Iggenes were affected in 21 cases; non-Ig genes, 15 cases; a deletion of more than a 1-kb segment, 2 cases; and a point mutation, 1 case. Comparative studies between the 21 cases withIg gene partners and the 17 cases with non-Iggene partners, including 2 cases with the deletion, showed that the overall survival of the latter group of patients was significantly inferior to that of the former (P = .0440), and the estimated 2-year overall survival rates were 58.3% vs 17.6% (P = .005). Non-Ig/BCL6 fusion is a poor prognostic indicator of DLBCL, and DLBCL with BCL6translocation could be subclassified according to the individual partner locus and/or gene.