Rituximab plus CHOP (R-CHOP) overcomes PRDM1-associated resistance to chemotherapy in patients with diffuse large B-cell lymphoma

Clinical Features and Outcomes of Primary Breast Diffuse Large B-Cell Lymphoma: A Matched-Pair Study

Background

The influence of the breast as the primary site on the outcome of diffuse large B-cell lymphoma (DLBCL) and further changes in therapeutic strategies remain unclear. We aimed to compare the outcomes between primary breast and non-breast DLBCL and analyze the genetic profiles of some of the study cohorts using next-generation sequencing.

Methods

This matched-pair study reviewed the medical records of 19 patients with stage I and II primary breast DLBCL diagnosed between January 2005 and December 2021 on the basis of the Wiseman and Liao criteria, and we used 1:4 propensity score matching to identify patients with non-breast DLBCL as the control group. The overall response rate, progression-free survival (PFS), and overall survival (OS) were the outcome measures.

Results

Patients with primary breast and non-breast DLBCL had a 5-year PFS of 72.6% and 86.9%, respectively (P = .206). These 2 groups also had comparable 5-year OS (86.9% vs 87.8%; P = .772). The breast as the primary site was not associated with inferior PFS (hazard ratio [HR]: 2.14; 95% CI: 0.66-6.96; P = .206) and OS (HR: 1.26; 95% CI: 0.27-5.93; P = .772).

Conclusion

Patients with primary breast DLBCL and those with non-breast DLBCL had comparable PFS and OS under rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or R-CHOP-like regimens. Further investigations of the mutation profile, its clinical impact, potential central nervous system relapse, and prognosis of primary breast DLBCL are required.

Intracellular osteopontin protects from autoimmunity-driven lymphoma development inhibiting TLR9-MYD88-STAT3 signaling

BACKGROUND

Autoimmune disorders, including Systemic Lupus Erythematosus (SLE), are associated with increased incidence of hematological malignancies. The matricellular protein osteopontin (OPN) has been linked to SLE pathogenesis, as SLE patients show increased serum levels of OPN and often polymorphisms in its gene. Although widely studied for its pro-tumorigenic role in different solid tumours, the role of OPN in autoimmunity-driven lymphomagenesis has not been investigated yet.

METHODS

To test the role of OPN in the SLE-associated lymphomagenesis, the SLE-like prone Fas^lpr/lpr mutation was transferred onto an OPN-deficient background. Spleen from Fas^lpr/lpr and OPN-/-Fas^lpr/lpr mice, as well as purified B cells, were analysed by histopathology, flow cytometry, Western Blot, immunohistochemistry, immunofluorescence and gene expression profile to define lymphoma characteristics and investigate the molecular mechanisms behind the observed phenotype. OPN cellular localization in primary splenic B cells and mouse and human DLBCL cell lines was assessed by confocal microscopy. Finally, gain of function experiments, by stable over-expression of the secreted (sOPN) and intracellular OPN (iOPN) in OPN-/-Fas^lpr/lpr -derived DLBCL cell lines, were performed for further validation experiments.

RESULTS

Despite reduced autoimmunity signs, OPN-/-Fas^lpr/lpr mice developed splenic lymphomas with higher incidence than Fas^lpr/lpr counterparts. In situ and ex vivo analysis featured such tumours as activated type of diffuse large B cell lymphoma (ABC-DLBCL), expressing BCL2 and c-MYC, but not BCL6, with activated STAT3 signaling. OPN-/-Fas^lpr/lpr B lymphocytes showed an enhanced TLR9-MYD88 signaling pathway, either at baseline or after stimulation with CpG oligonucleotides, which mimic dsDNA circulating in autoimmune conditions. B cells from Fas^lpr/lpr mice were found to express the intracellular form of OPN. Accordingly, gene transfer-mediated re-expression of iOPN, but not of its secreted isoform, into ABC-DLBCL cell lines established from OPN-/-Fas^lpr/lpr mice, prevented CpG-mediated activation of STAT3, suggesting that the intracellular form of OPN may represent a brake to TLR9 signaling pathway activation.

CONCLUSION

These data indicate that, in the setting of SLE-like syndrome in which double strand-DNA chronically circulates and activates TLRs, B cell intracellular OPN exerts a protective role in autoimmunity-driven DLBCL development, mainly acting as a brake in the TLR9-MYD88-STAT3 signaling pathway.

PRDM1/BLIMP1 induces cancer immune evasion by modulating the USP22-SPI1-PD-L1 axis in hepatocellular carcinoma cells

Programmed death receptor-1 (PD-1) blockade have achieved some efficacy but only in a fraction of patients with hepatocellular carcinoma (HCC). Programmed cell death 1 ligand 1 (PD-L1) binds to its receptor PD1 on T cells to dampen antigen-tumor immune responses. However, the mechanisms underlying PD-L1 regulation are not fully elucidated. Herein, we identify that tumoral Prdm1 overexpression inhibits cell growth in immune-deficient mouse models. Further, tumoral Prdm1 overexpression upregulates PD-L1 levels, dampening anti-tumor immunity in vivo, and neutralizes the anti-tumor efficacy of Prdm1 overexpression in immune-competent mouse models. Mechanistically, PRDM1 enhances USP22 transcription, thus reducing SPI1 protein degradation through deubiquitination, which enhances PD-L1 transcription. Functionally, PD-1 mAb treatment reinforces the efficacy of Prdm1-overexpressing HCC immune-competent mouse models. Collectively, we demonstrate that the PRDM1-USP22-SPI1 axis regulates PD-L1 levels, resulting in infiltrated CD8⁺ T cell exhaustion. Furthermore, PRDM1 overexpression combined with PD-(L)1 mAb treatment provides a therapeutic strategy for HCC treatment.

Dysregulated MDR1 by PRDM1/Blimp1 Is Involved in the Doxorubicin Resistance of Non-Germinal Center B-Cell-Like Diffuse Large B-Cell Lymphoma

INTRODUCTION

The chemoresistance mechanism of diffuse large B-cell lymphoma (DLBCL) is still poorly understood, and patient prognosis remains unsatisfactory. This study aimed to investigate drug resistance mechanisms in non-germinal center B-cell-like (non-GCB) DLBCL.

METHODS

Doxorubicin (DOX)-resistant OCI-Ly3 cells were generated through long-term incubation of cells in a medium with gradually increasing DOX concentrations. The expression levels of genes related to drug metabolism were determined using a functional gene grouping polymerase chain reaction (PCR) array. Drug-resistant proteins were identified using bioinformatics, and molecular association networks were subsequently generated. The association and mechanism of key genes were determined using a dual-luciferase reporter assay System and chromatin immunoprecipitation (ChIP). The expression of drug-resistant genes and target genes was then measured using Western blotting and immunohistochemistry. The correlation between gene expressions was analyzed using Spearman's rank correlation coefficient.

RESULTS

Using the PCR array, MDR1 was identified as the key gene that regulates DOX resistance in OCI-Ly3/DOX-A100, a non-GCB DLBCL cell line. The dual-luciferase reporter assay system demonstrated that MDR1 transcription could be inhibited by PRDM1. ChIP results showed that PRDM1 had the ability to bind to the promoter region (-1,132 to -996) of MDR1. In OCI-Ly3/DOX cells, NF-κB activity and PRDM1 expression decreased with an increase in drug-resistant index, whereas MDR1 expression increased with enhanced drug resistance. Immunohistochemical analysis revealed that relative MDR1 expression was higher than that of PRDM1 in human DLBCL tissue samples. A negative correlation was observed between MDR1 and PRDM1.

CONCLUSION

In non-GCB DLBCL cells, NF-κB downregulates PRDM1 and thereby promotes MDR1 transcription by terminating PRDM1-induced transcriptional inhibition of MDR1. Such a mechanism may explain the reason for disease recurrence in non-GCB DLBCL after R-CHOP or combined CHOP with bortezomib treatment. Our findings may provide a potential therapeutic strategy for reducing drug resistance in patients with DLBCL.

Genetic alterations in B cell lymphoma subtypes as potential biomarkers for noninvasive diagnosis, prognosis, therapy, and disease monitoring

Neoplastic transformation of germinal center B (GCB) cells may give rise to a variety of different B cell lymphoma subtypes, most of which show substantial heterogeneity in terms of genetic alterations and clinical features. The mutations observed in cancer-related genes in GCB cells are related to abnormalities in the immunogenetic mechanisms associated with germinal center reaction. Recent studies have rapidly identified genomic alterations in B cell lymphomas that may be useful for better subclassification, noninvasive diagnosis, and prediction of response to therapy. The WHO recognizes different lymphoma subsets classified within 2 major categories of B cell lymphoma: Hodgkin’s lymphoma (HL) and B cell non-Hodgkin’s lymphoma (NHL), each with distinct genetic aberrations, including chromosomal translocations, copy number abnormalities, or point mutations. Next-generation sequencing-based technologies have allowed cancer researchers to identify somatic mutations and gene expression signatures at a rapid pace so that novel diagnostic or prognostic biomarkers, as well as therapeutic targets, can be discovered much faster than before. Indeed, deep sequencing studies have recently revealed that lymphoma-specific somatic mutations may be detected in cell-free circulating DNA obtained from the peripheral blood of B cell lymphoma patients, suggesting the possibility of minimally invasive diagnosis, monitoring, and predicting response to therapy of B cell lymphoma patients. In this study, the current status of the recurrent genetic aberrations observed during diagnosis and/or relapse in HL and the major subtypes of B cell NHL (i.e. diffuse large B cell lymphoma, follicular lymphoma, mantle cell lymphoma, and Burkitt lymphoma) are discussed to shed light on their potential use as noninvasive diagnostic or prognostic biomarkers and to reveal their role in lymphomagenesis as a target in therapy for newly diagnosed and chemotherapy-resistant cases.

Rituximab-Based Therapy in Newly Diagnosed Diffuse Large B-Cell Lymphoma Patients: Individualized Risk-Adapted Therapy Approach Using Molecular Subtypes

Rituximab (R) with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) is the current standard of care as first-line treatment for diffuse large B-cell lymphoma (DLBCL), the most common lymphoma subtype. Patients who fail R-CHOP have a poor outcome with relapse or refractory disease resulting in fatality in majority of patients. This review focuses on novel therapies which are currently being assessed as first-line treatment in combination with R-CHOP in patients with DLBCL. Targeted drug development is a possibility with recent developments like gene expression profiling, RNA interference screening, DNA sequencing, identification of new biomarkers and signaling pathways. Newer drugs such as bortezomib, lenalidomide, and ibrutinib are being investigated as first-line therapy in combination with R-CHOP (XR-CHOP) in the activated B-cell (ABC) subtype of DLBCL. Additionally, inhibitors of BCL6, EZH2, and PI3K/Akt/mTOR are being considered for treatment of germinal center B-cell (GCB) subtype of DLBCL in patients with probable survival of less than 5 years. Double- or triple-hit lymphomas and double-expressor lymphomas also have poor prognosis and research to identify effective first-line therapy in these patients remains an unmet need. Presently, individualized approach that includes effective therapeutic combinations with acceptable safety profiles for use in routine practice, especially in patients likely to have poor outcomes such as relapsed/refractory DLBCL remains a distant possibility. Current evidence shows that untreated high risk patients do not have the greater benefit with use of newer drugs compared with R-CHOP. Therefore, R-CHOP remains the first-line treatment for newly diagnosed DLBCL patients.

Loss of PRDM1/BLIMP-1 function contributes to poor prognosis of activated B-cell-like diffuse large B-cell lymphoma

PRDM1/BLIMP-1, a master regulator of plasma-cell differentiation, is frequently inactivated in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) patients. Little is known about its genetic aberrations and relevant clinical implications. A large series of patients with de novo DLBCL was effectively evaluated for PRDM1/BLIMP-1 deletion, mutation, and protein expression. BLIMP-1 expression was frequently associated with the ABC phenotype and plasmablastic morphologic subtype of DLBCL, yet 63% of the ABC-DLBCL patients were negative for BLIMP-1 protein expression. In these patients, loss of BLIMP-1 was associated with Myc overexpression and decreased expression of p53 pathway molecules. In addition, homozygous PRDM1 deletions and PRDM1 mutations within exons 1 and 2, which encode for domains crucial for transcriptional repression, were found to show a poor prognostic impact in patients with ABC-DLBCL but not in those with germinal center B-cell-like DLBCL (GCB-DLBCL). Gene expression profiling revealed that loss of PRDM1/BLIMP-1 expression correlated with a decreased plasma-cell differentiation signature and upregulation of genes involved in B-cell receptor signaling and tumor-cell proliferation. In conclusion, these results provide novel clinical and biological insight into the tumor-suppressive role of PRDM1/BLIMP-1 in ABC-DLBCL patients and suggest that loss of PRDM1/BLIMP-1 function contributes to the overall poor prognosis of ABC-DLBCL patients.

Factors That Regulate the Generation of Antibody-Secreting Plasma Cells

The generation of antigen-specific neutralizing antibodies and memory B cells is one of the most important immune protections of the host and is the basis for successful vaccination strategies. The protective antibodies, secreted by preexisting long-lived plasma cells and reactivated antigen-experienced memory B cells, constitute the main humoral immune defense. Distinct from the primary antibody response, the humoral memory response is generated much faster and with greater magnitude, and it produces antibodies with higher affinity and variable isotypes. Humoral immunity is critically dependent on the germinal center where high-affinity memory B cells and plasma cells are generated. In this chapter, we focus on recent advances in our understanding of the molecular mechanisms that govern fate decision for memory B cells and plasma cells and the mechanisms that maintain the long-lived plasma-cell pool, with emphasis on how the transcription factor Blimp-1 (B lymphocyte-induced maturation protein-1) helps regulate the above-mentioned immunoregulatory steps to ensure the production and maintenance of antibody-secreting plasma cells as well as how it directs memory cell vs plasma-cell fate. We also discuss the molecular basis of Blimp-1 action and how its expression is regulated.

Methylation contributes to imbalance of PRDM1α/PRDM1bβ expression in diffuse large B-cell lymphoma

The positive regulatory domain 1 (PRDM1) exists as two isoforms: PRDM1α and PRDM1β. The former is frequently inactivated, while the latter is overexpressed in a subset of diffuse large B-cell lymphoma (DLBCL). To investigate the possible epigenetic alteration of PRDM1α and PRDM1β expression, the methylation of these two promoter isoforms was assessed in B lymphoma cell lines and DLBCL samples. Hypomethylation of PRDM1β CpG islands was preferentially detected in lymphoma cells. However, both high and low methylation of PRDM1α CpG islands was simultaneously observed in cases of DLBCL compared with the moderate methylation of non-tumor cases. CpG 16-21-specific high methylation was correlated with low expression of PRDM1α in PRDM1β-positive DLBCL samples. Three increased and one decreased miRNAs were significantly different between cases of DLBCL and non-tumor reactive hyperplasia. Thus, our results indicate that aberrant methylation silencing of PRDM1α and hypomethylation activation of PRDM1β are frequent events in DLBCL.

FOXO1 repression contributes to block of plasma cell differentiation in classical Hodgkin lymphoma

FOXO1 directly activates PRDM1α, the master regulator of PC differentiation, and it enriches a PC signature in cHL cell lines. PRDM1α is a tumor suppressor in cHL.

MicroRNA-21 regulates the sensitivity of diffuse large B-cell lymphoma cells to the CHOP chemotherapy regimen

Numerous studies have demonstrated that microRNA-21 (miR-21), as an oncogene, is involved in the occurrence of many types of tumor and the sensitivity of tumor cells to chemotherapeutic drugs. In the present study, we investigated whether miR-21 is involved in regulating the sensitivity of the diffuse large B-cell lymphoma (DLBCL) cell line CRL2631 to the cyclophosphamide, vincristine, Adriamycin, and prednisone (CHOP) chemotherapeutic regimen. Knockdown of miR-21 with antisense oligonucleotides significantly increased the cytotoxic effects of the CHOP regimen in CRL2631 cells. A luciferase reporter assay showed that PTEN is a target gene of miR-21 in CRL2631 cells, and subsequent experiments demonstrated that miR-21 impacts the PI3K/AKT signaling pathway through the regulation of PTEN, thereby affecting cellular sensitivity to the CHOP chemotherapeutic regimen. Furthermore, knockdown of NF-κB decreased miR-21 expression and sensitized CRL2631 cells to CHOP treatment. These results provide evidence that it may be possible to overcome microRNA-based DLBCL drug resistance.

BLIMP1α, the master regulator of plasma cell differentiation is a tumor supressor gene in B cell lymphomas

AIMS

The aim of this review was to summarize recent knowledge of the structure and function of a transcriptional repressor, B lymphocyte induced maturation protein 1 (BLIMP1) and its participation in the pathogenesis of B lymphomas.

METHODS AND RESULTS

This review summarizes the structure and function of BLIMP1, its major target genes and its role as a tumour suppressor in B cell lymphomas. We review our recent data implicating the loss of BLIMP1α as an important step in the pathogenesis of the Epstein-Barr virus (EBV) associated B cell lymphomas.

CONCLUSIONS

BLIMP1 is a transcriptional repressor essential for the differentiation of germinal centre (GC) B cells to plasma cells. The loss of BLIMP1 in GC B cells could contribute to the pathogenesis of EBV-associated lymphomas by preventing plasma cell differentiation and viral replication.

Hypomethylation and Over-Expression of the Beta Isoform of BLIMP1 is Induced by Epstein-Barr Virus Infection of B Cells; Potential Implications for the Pathogenesis of EBV-Associated Lymphomas

B-lymphocyte-induced maturation protein 1 (BLIMP1) exists as two major isoforms, α and β, which arise from alternate promoters. Inactivation of the full length BLIMP1α isoform is thought to contribute to B cell lymphomagenesis by blocking post-germinal centre (GC) B cell differentiation. In contrast, the shorter β isoform is functionally impaired and over-expressed in several haematological malignancies, including diffuse large B cell lymphomas (DLBCL). We have studied the influence on BLIMP1β expression of the Epstein-Barr virus (EBV), a human herpesvirus that is implicated in the pathogenesis of several GC-derived lymphomas, including a subset of DLBCL and Hodgkin’s lymphoma (HL). We show that BLIMP1β expression is increased following the EBV infection of normal human tonsillar GC B cells. We also show that this change in expression is accompanied by hypomethylation of the BLIMP1β-specific promoter. Furthermore, we confirmed previous reports that the BLIMP1β promoter is hypomethylated in DLBCL cell lines and show for the first time that BLIMP1β is hypomethylated in the Hodgkin/Reed-Sternberg (HRS) cells of HL. Our results provide evidence in support of a role for BLIMP1β in the pathogenesis of EBV-associated B cell lymphomas.

Tyrosine kinase inhibitors as potential drugs for B-cell lymphoid malignancies and autoimmune disorders

INTRODUCTION

In the last few years, several tyrosine kinase inhibitors (TKIs) have been synthesized and become available for preclinical studies and clinical trials. This article summarizes recent achievements in the mechanism of action, pharmacological properties, and clinical activity and toxicity, as well as the emerging role of TKIs in lymphoid malignancies, allergic diseases, and autoimmune disorders.

AREAS COVERED

A literature review was conducted of the MEDLINE database PubMed for articles in English. Publications from 2000 through January 2012 were scrutinized. The search terms used were Bruton's tyrosine kinase (Btk) inhibitors, PCI-32765, GDC-0834, LFM-A13, AVL-101, AVL-292, spleen tyrosine kinase (Syk) inhibitors, R343, R406, R112, R788, fostamatinib, BAY-61-3606, C-61, piceatannol, Lyn, imatinib, nilotinib, bafetinib, dasatinib, GDC-0834, PP2, SU6656 in conjunction with lymphoid malignancy, NHL, CLL, autoimmune disease, allergic disease, asthma, and rheumatoid arthritis. Conference proceedings from the previous 5 years of the American Society of Hematology, European Hematology Association, American Society of Clinical Oncology, and ACR/ARHP Annual Scientific Meetings were searched manually. Additional relevant publications were obtained by reviewing the references from the chosen articles.

EXPERT OPINION

The use of TKIs, especially inhibitors of Btk, Syk, and Lyn, is a promising new strategy for targeted treatment of B-cell lymphoid malignancies, autoimmune disorders and allergic diseases. However, definitive data from ongoing and future clinical trials will aid in better defining the status of TKIs in the treatment of these disorders.

Large B-cell lymphomas with plasmablastic differentiation: a biological and therapeutic challenge

Plasmablastic differentiation can be found in a variety of large B-cell lymphomas, including plasmablastic lymphoma, ALK-positive large B-cell lymphoma, primary effusion lymphoma, large B-cell lymphoma arising in human herpesvirus-8 (HHV-8)-associated multicentric Castleman disease and diffuse large B-cell lymphoma (DLBCL) with partial plasmablastic phenotype. These tumors are characterized by acquisition of the transcriptional profile of plasma cells (with overexpression of PRDM1/Blimp1 and XBP1s, in concert with extinction of the B-cell differentiation program) by proliferating immunoblasts. This particular biological entity, i.e. large B-cell lymphoma with plasmablastic differentiation, is almost always associated with an aggressive clinical behavior. This review summarizes the current knowledge of the biological basis of plasmablastic differentiation in large B-cell lymphomas, the diagnostic borders with DLBCL and multiple myeloma, the associated adverse molecular events (with concomitant MYC, p53 and ALK alterations) and the potential therapeutic targets so far identified (including the unfolded protein response pathway). The highly aggressive nature of these lymphomas and the relative paucity of molecular data available highlight the need for deeper insights into the molecular pathogenesis of large B-cell lymphomas with plasmablastic differentiation in order to identify new and effective alternative treatments.

Targeting cell surface β2 -microglobulin by pentameric IgM antibodies

Monoclonal antibodies (mAbs) specific for human β(2) -microglobulin (β(2) M) have been shown to induce tumour cell apoptosis in haematological and solid tumours via recruiting major histocompatibility complex (MHC) class I molecules into and excluding cytokine receptors from the lipid rafts. Based on these findings, we hypothesized that IgM anti-β(2) M mAbs might have stronger apoptotic effects because of their pentameric structure. Our results showed that, compared with IgG mAbs, IgM anti-β(2) M mAbs exhibited stronger tumouricidal activity in vitro against different tumour cells, including myeloma, mantle cell lymphoma, and prostate cancer, and in vivo in a human-like xenografted myeloma mouse model without damaging normal tissues. IgM mAb-induced apoptosis is dependent on the pentameric structure of the mAbs. Disrupting pentameric IgM into monomeric IgM significantly reduced their ability to induce cell apoptosis. Monomeric IgM mAbs were less efficient at recruiting MHC class I molecules into and exclusion of cytokine receptors from lipid rafts, and at activating the intrinsic apoptosis cascade. Thus, we developed and validated the efficacy of anti-β(2) M IgM mAbs that may be utilized in the clinical setting and showed that IgM anti-β(2) M mAbs may be more potent than IgG mAbs at inducing tumour apoptosis.

Prognostic markers in diffuse large B-cell lymphoma: Keys to the underlying biology

Prognostic markers identify subgroups of patients with similar risk profiles, helping to guide clinical care. The addition of rituximab to conventional anthracycline-based chemotherapy has improved clinical outcomes for patients with diffuse large B-cell lymphoma (DLBCL). Studies suggest that rituximab eliminates or modulates the significance of some markers (eg, BCL6 or BCL2), whereas other previously unimportant markers may emerge as significant prognostic indicators in the setting of treatment that now includes rituximab. These changes in the prognostic profile are likely to reflect the impact of rituximab on survival pathways important to some groups of patients with DLBCL but not to other groups, and thereby may provide clues to the underlying biology of the disease. They also identify subgroups of patients likely to benefit most from rituximab therapy and those who seem to garner no advantage from its inclusion in their treatment. Studies of prognostic indicators in the context of modern therapy have the potential to identify new, rational therapeutic targets for this biologically diverse disease.

PRDM1 is required for mantle cell lymphoma response to bortezomib

Mantle cell lymphoma (MCL) is an aggressive form of B-cell lymphoma with a poor disease-free survival rate. The proteasome inhibitor bortezomib is approved for the treatment of relapsed and refractory MCL and has efficacy in about 30% of patients. However, the precise mechanism of action of bortezomib is not well understood. This report establishes a requirement for the transcription repressor PR domain zinc finger protein 1 (PRDM1, Blimp1) in the response to bortezomib. Bortezomib rapidly induces transcription of PRDM1 as part of the apoptotic response in both cell lines and primary MCL tumor cells. Knockdown of PRDM1 blocks activation of NOXA and inhibits apoptosis, whereas ectopic expression of PRDM1 alone leads to apoptosis in MCL. Two novel direct targets of PRDM1 were identified in MCL cells: MKI67 (Ki67) and proliferating cell nuclear antigen (PCNA). Both MKI67 and PCNA are required for proliferation and survival. Chromatin immunoprecipitation and knockdown studies reveal that specific repression of MKI67 and PCNA is mediated by PRDM1 in response to bortezomib. Furthermore, promoter studies and mutation/deletion analysis show that PRDM1 functions through specific sites in the PCNA proximal promoter and an MKI67 distal upstream repression domain. Together, these findings establish PRDM1 as a key mediator of bortezomib activity in MCL.

Expression of p21 protein predicts clinical outcome in DLBCL patients older than 60 years treated with R-CHOP but not CHOP: a prospective ECOG and Southwest Oncology Group correlative study on E4494

PURPOSE

To prospectively investigate the prognostic significance of p21 and p53 expression in diffuse large B-cell lymphoma in the context of the U.S. Intergroup trial comparing conventional cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy to rituximab-CHOP (R-CHOP) induction, with or without maintenance rituximab.

EXPERIMENTAL DESIGN

Immunohistochemical staining of 197 paraffin-embedded biopsy specimens was scored by an independent panel of experts.

RESULTS

The cyclin-dependent kinase inhibitor, p21, was expressed in 55% of cases examined. In a multivariable analysis adjusting for International Prognostic Index score and BCL2 status, p21 expression was a significant, independent, favorable predictive factor for failure-free survival (relative risk, 0.3; P = 0.001) and overall survival (relative risk, 0.3; P = 0.003) for patients treated with R-CHOP. Expression of p21 was not predictive of outcome for CHOP-treated patients. Only p21-positive cases benefited from the addition of rituximab to CHOP. Among p21-positive patients, treatment with R-CHOP was associated with a higher failure-free survival rate at 5 years compared with CHOP (61% versus 24%; P = 0.01). In contrast, no significant differences were detected in failure-free survival according to treatment arm for p21-negative patients. Expression of p53, alone or in combination with p21, did not predict for outcome in univariable or multivariable analyses.

CONCLUSIONS

In this study, p21 protein expression emerged as an important independent predictor of a favorable clinical outcome when rituximab was added to CHOP therapy. These data suggest that rituximab-related effects on lymphoma survival pathways may be functionally linked to p21 activity.

[Molecular diagnosis of malignant lymphomas]

BACKGROUND

Malignant lymphomas comprise a heterogeneous group of non-solid tumors originating in lymphocytes at different maturation stages. The diagnosis is based on a traditional histopathological diagnostic procedure supplemented with immunophenotyping, cytogenetics, molecular genetic analyses and clinical information. This article describes experimental molecular diagnostics, mainly based on microarray-based gene expression technology.

MATERIAL AND METHODS

Results achieved through an international multicentre project (headed by the National Cancer Institute in the USA), in which the Norwegian Radium Hospital has taken part as the only Nordic institution, are summarized. The findings are discussed in light of other relevant studies identified through a non-systematic search in PubMed.

RESULTS

New clinically relevant subgroups of malignant B-cell lymphomas have been characterized. Retrospective survival analyses have shown correlations between gene expression profiles and patient outcome and have provided important biological knowledge, which has led to new targeted treatments (currently being tested in clinical studies).

INTERPRETATION

As a supplement to today's diagnostics, molecular diagnostics yields an improved diagnostic precision and opens up for new treatment possibilities for patients with malignant lymphomas.

The prognostic value of immunohistochemical subtyping in Chinese patients with de novo diffuse large B-cell lymphoma undergoing CHOP or R-CHOP treatment

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with recognised variability in molecular aetiology and clinical outcome. Though the use of agents such as rituximab significantly improves outcome, intrinsic genetic and morphological factors greatly affect the response to treatment. The objective of this study was to evaluate the prognostic value of immunohistochemical subtyping and the International Prognostic Index (IPI) for predicting treatment outcome in Chinese DLBCL patients. We followed 108 cases of DLBCL and performed prognostic analyses based on molecular subtyping of the disease through immunostaining of tissue samples. The use of rituximab conferred a clinical benefit to DLBCL patients regardless of disease subtype. Importantly, this treatment regimen also improved outcomes in patients with the non-germinal centre B-cell-like (GCB) DLBCL subtype, frequently associated with poorer prognosis. Our results suggest that IPI was the best tool for the prediction of treatment outcome in our patient cohort, regardless of treatment regimen. Furthermore, the use of rituximab alongside classical chemotherapy regimens can improve the outcomes for DLBCL patients who exhibit both GCB and non-GCB subtypes of the disease.

Recent prognostic factors in diffuse large B-cell lymphoma indicate NF-kappaB pathway as a target for new therapeutic strategies

The diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoid cancer. The classical chemotherapy regimen given to these patients was the CHOP (Cyclophosphamide, Hydroxydaunorubicin or Adriamycin, Oncovin or Vincristine, Prednisone or Prednisolone), but recently rituximab with CHOP (R-CHOP) increased the number of cases responding to first line therapy. DLBCL classification identified three principle subgroups. The first one, named germinal centre B cell-like (GCB), responds to both CHOP and R-CHOP treatment and it is mainly characterised by the expression of markers like Bcl-6 and CD10. The second, the activated B-cell like (ABC), has a worse prognosis in comparison with GCB, and is mainly characterised by the expression of IRF-4, PRDM1 and NF-kappaB. It is interesting to notice that IRF-4 and PRDM1 are under the transcriptional control of NF-kappaB, whose high activation level is associated with a worse prognosis. The third one, mediastinal large B-cell lymphoma (PMBCL) is an uncommon subtype characteristically found in young females. Gene expression profiling suggests that this disease resembles Hodgkin lymphoma more than other types of DLBCL. The impact of rituximab on the outcome of patients with PMBCL has still not been fully assessed. It was seen that rituximab inhibits NF-kappaB pathway in vitro. However, the clinical significance of this finding is still unknown, because both ABC and GCB DLBCL show a significant improvement of overall survival after R-CHOP treatment. In this review, the NF-kappaB pathway is suggested as a target for new chemotherapy strategies based on the association of CHOP with molecules more effective than rituximab in this pathway inhibition.

Phase II study of dose-adjusted EPOCH and rituximab in untreated diffuse large B-cell lymphoma with analysis of germinal center and post-germinal center biomarkers

PURPOSE

To assess the clinical outcome and the influence of biomarkers associated with apoptosis inhibition (Bcl-2), tumor proliferation (MIB-1), and cellular differentiation on the outcome with dose-adjusted (DA) EPOCH (etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin) plus rituximab (R) infusional therapy in diffuse large B-cell lymphoma (DLBCL) with analysis of germinal center B-cell (GCB) and post-GCB subtypes by immunohistochemistry.

PATIENTS AND METHODS

Phase II study of 72 patients with untreated de novo DLBCL who were at least 18 years of age and stage II or higher. Radiation consolidation was not permitted.

RESULTS

Patients had a median age of 50 years (range, 19 to 85) and 40% had a high-intermediate or high International Prognostic Index (IPI). At 5 years, progression-free survival (PFS) and overall survival (OS) were 79% and 80%, respectively, with a median potential follow-up of 54 months. PFS was 91%, 90%, 67%, and 47%, and OS was 100%, 90%, 74%, and 37%, for 0 to 1, 2, 3, and 4 to 5 IPI factors, respectively, at 5 years. The Bcl-2 and MIB-1 biomarkers were not associated with PFS or OS. Based on DA-EPOCH historical controls, rituximab only benefited Bcl-2 positive tumors. Bcl-6 expression was associated with higher PFS whereas GCB exhibited a marginally significant higher PFS compared with post-GCB DLBCL.

CONCLUSION

DA-EPOCH-R outcome was not affected by tumor proliferation and rituximab appeared to overcome the adverse effect of Bcl-2. Bcl-6 may identify a biologic program associated with a superior outcome. Overall, DA-EPOCH-R shows promising outcome in low and intermediate IPI groups. A molecular model of treatment outcome with rituximab and chemotherapy is presented.

PRDM1 is involved in chemoresistance of T-cell lymphoma and down-regulated by the proteasome inhibitor

The positive regulatory domain I (PRDM1) is a master regulator of terminal B-cell differentiation. However, PRDM1 is not B-cell specific. To determine its role in T-cell lymphoma, PRDM1 expression was investigated in 60 patients. PRDM1alpha and PRDM1beta transcripts were detected in laser-microdissected T-lymphoma cells in 27 and 14 patients, respectively, mostly in cases with IRF4 expression. PRDM1beta was associated with increased c-MYC expression. PRDM1beta-positive patients displayed advanced Ann Arbor stage and high-risk International Prognostic Index and were linked to short survival times. In vitro, PRDM1beta was related to resistance to chemotherapeutic agents and could be down-regulated by the proteasome inhibitor bortezomib. Kinetic studies showed that bortezomib down-regulation of PRDM1beta preceded decreased IRF4 and c-MYC expression. An earlier retaining of cytoplasmic IkappaBalpha in bortezomib-treated cells was revealed, concomitant with blockade of NF-kappaB nuclear translocation. These results demonstrate the involvement of PRDM1beta in T-cell lymphoma, with possible therapeutic interference by the proteasome inhibitor.

BLIMP1 guides the fate of effector B and T cells

B-lymphocyte-induced maturation protein 1 (BLIMP1) is a transcriptional repressor, and its importance in controlling the terminal differentiation of antibody-secreting cells (ASCs) is well established. However, as we discuss in this Progress article, it has now become evident that the ASC programme consists of a discrete BLIMP1-independent initiation phase, followed by a second step in which BLIMP1 is absolutely required for the differentiation of fully mature ASCs. In addition, an important role for BLIMP1 in maintaining the homeostasis of effector T cells is emerging, suggesting intriguing parallels between the control of effector-cell fates in both B and T cells.

Human BSAP and BLIMP1 conform an autoregulatory feedback loop

B-lymphocyte-induced maturation protein-1 (BLIMP1), encoded by the PRDM1 gene, is a transcriptional repressor considered a master regulator that is required and sufficient for plasma cell (PC) differentiation. BLIMP1 represses the PAX5 gene, coding for the B-cell lineage-specific activator protein (BSAP), which is required for B-cell identity and survival. Mutations in PAX5 gene as well as in PRDM1 gene have been recently implicated in lymphomas. In the present study, sequence analysis of PRDM1 gene revealed a binding site for BSAP transcription factor. By analyzing different human cell lines, we have found that a specific nuclear factor for B-cell lines binds to a site on the PRDM1 promoter. Electrophoretic mobility shift assays identified this factor as BSAP, and chromatin immunoprecipitation assays confirmed its binding in vivo to the human PRDM1 promoter. Moreover, by ectopically expressing BSAP, and using a PRDM1 promoter with the BSAP-binding site mutated, we demonstrated that this factor represses the expression of BLIMP1. Therefore, repression of PRDM1 by BSAP reveals an autoregulatory negative-feedback loop that could play a relevant role in controlling human PC differentiation.