MiR-17∼92 is involved in NF-κB activation via targeting the ubiquitin-editing proteins to mediate RIP1 complex polyubiquitinations in ABC-DLBCL.

Activated B-cell-like diffuse large B-cell lymphoma (ABC-DLBCL) is an aggressive lymphoma characterized by constitutive NF-κB activation, but whether miR-17∼92 contributes to this activation remains unclear. Herein, we sought to evaluate the role of miR-17∼92 in the process of NF-κB activation in ABC-DLBCL. We found that the expression of miR-17∼92 primary transcript was positively correlated with NF-κB activity, miR-17∼92 activated the NF-κB signaling in ABC-DLBCL, and its over-expression promoted ABC-DLBCL cell growth, accelerated cell G1 to S phase transition and enhanced cell resistance to NF-κB inhibitor. Importantly, miR-17∼92 promoted NF-κB activation through directly targeting multiple ubiquitin-editing regulators to lead to increase the K63-linked polyubiquitination and decrease the K48-linked polyubiquitination of RIP1 complex in ABC-DLBCL. We further found that miR-17∼92 selectively activated IκB-α and NF-κB p65 but not NF-κB p52/p100, and high miR-17∼92 expression was also associated with poorer outcome in ABC-DLBCL patients. Overall, our results showed that miR-17∼92 selectively activated the canonical NF-κB signaling via targeting ubiquitin-editing regulators to lead to constitutively NF-κB activation and poorer outcome in ABC-DLBCL. These findings uncovered an innovative function of miR-17∼92 and previously unappreciated regulatory mechanism of NF-κB activation in ABC-DLBCL. Targeting miR-17∼92 may thus provide a novel bio-therapeutic strategy for ABC-DLBCL patients.

MYC overexpression in natural killer cell lymphoma: prognostic and therapeutic implications.

The current clinical management of Extranodal NK/T-cell lymphoma (ENKTL) primarily depends on conventional chemotherapy and radiotherapy, underscoring the need for innovative therapeutic strategies. This study explores the clinical significance and therapeutic implication of c-MYC (MYC) in ENKTL. Initially, we identified MYC protein overexpression in approximately 75% of cases within a large cohort of 111 patients. MYC overexpression was strongly correlated with lymphoma cell proliferation and poor clinical outcomes. Intriguingly, integrating MYC expression into the PINK-E prognostic model significantly enhanced its predictive power. Subsequently, we implemented MYC knockdown (KD) in NK malignancy cell lines with MYC overexpression, resulting in significant viability reduction. RNA-sequencing (RNA-seq) used to determine MYC function revealed a high overlap with canonical MYC-regulated genes and enrichment in metabolism and cell cycle regulation. Integrative analysis of the RNA-seq data upon MYC KD with gene expression profiles of primary ENKTL cases identified a subset of genes closely associated with MYC overexpression. Among these, CDK4 emerged as a potential therapeutic target, and its inhibition not only abrogated MYC function but also decreased MYC expression in NK malignancy cells. Furthermore, the clinical-grade CDK4/6 inhibitor palbociclib exhibited a potent anti-tumor effect in xenograft mouse models, especially when combined with gemcitabine. In summary, our study firmly establishes MYC as an oncogene with prognostic significance in ENKTL and highlights CDK4 inhibition as a promising therapeutic strategy for treating ENKTL with MYC overexpression.

OX40 shapes an inflamed tumor immune microenvironment and predicts response to immunochemotherapy in diffuse large B-cell lymphoma.

OX40 enhances the T-cell activation via costimulatory signaling. However, its molecular characteristics and value in predicting response to immunochemotherapy in DLBCL remain largely unexplored. Here, we performed an integrative analysis of sequencing and multiplex immunofluorescence staining, and discovered abnormally higher expression of OX40 in DLBCL patients. Elevated OX40 could activate T cells leading to a higher immune score for tumor immune microenvironment (TiME). OX40 upregulation simultaneously happened with immune-related genes including PD-1, CTLA4 and TIGIT et,al. Patients with high OX40 expression exhibited a lower Ann Arbor stage and IPI score and more easily achieved a complete response/partial response. The analysis of infiltrated T-cell subset revealed that patients with a greater number of CD4+/OX40+ or CD8+/OX40+ T cells had a longer OS. Our findings indicated that OX40 shapes an inflamed tumor immune microenvironment and predicts response to immunochemotherapy, providing insights for the application of OX40 agonist in DLBCL patients.

Adult high-grade B-cell lymphoma with Burkitt lymphoma signature: genomic features and potential therapeutic targets.

The adult high-grade B-cell lymphomas sharing molecular features with Burkitt lymphoma (BL) are highly aggressive lymphomas with poor clinical outcome. High-resolution structural and functional genomic analysis of adult Burkitt lymphoma (BL) and high-grade B-cell lymphoma with BL gene signature (adult-molecularly defined BL [mBL]) revealed the MYC-ARF-p53 axis as the primary deregulated pathway. Adult-mBL had either unique or more frequent genomic aberrations (del13q14, del17p, gain8q24, and gain18q21) compared with pediatric-mBL, but shared commonly mutated genes. Mutations in genes promoting the tonic B-cell receptor (BCR)→PI3K pathway (TCF3 and ID3) did not differ by age, whereas effectors of chronic BCR→NF-κB signaling were associated with adult-mBL. A subset of adult-mBL had BCL2 translocation and mutation and elevated BCL2 mRNA and protein expression, but had a mutation profile similar to mBL. These double-hit lymphomas may have arisen from a tumor precursor that acquired both BCL2 and MYC translocations and/or KMT2D (MLL2) mutation. Gain/amplification of MIR17HG and its paralogue loci was observed in 50% of adult-mBL. In vitro studies suggested miR-17∼92's role in constitutive activation of BCR signaling and sensitivity to ibrutinib. Overall integrative analysis identified an interrelated gene network affected by copy number and mutation, leading to disruption of the p53 pathway and the BCR→PI3K or NF-κB activation, which can be further exploited in vivo by small-molecule inhibitors for effective therapy in adult-mBL.

Inhibition of 4EBP phosphorylation mediates the cytotoxic effect of mechanistic target of rapamycin kinase inhibitors in aggressive B-cell lymphomas.

Mechanistic target of rapamycin (mTOR) complex 1 is a central integrator of nutrient and growth factor inputs that controls cell growth in eukaryotes. The second generation of mTOR kinase inhibitors (TORKi), directly targeting the mTOR catalytic site, are more effective than rapamycin and its analogs in cancer treatment, particularly in inducing apoptosis. However, the mechanism underlying the cytotoxic effect of TORKi remains elusive. Herein, we demonstrate that TORKi-induced apoptosis is predominantly dependent on the loss of mTOR complex 1-mediated 4EBP activation. Knocking out RICTOR, a key component of mTOR complex 2, or inhibiting p70S6K has little effect on TORKi-induced apoptosis. Conversely, increasing the eIF4E:4EBP ratio by either overexpressing eIF4E or knocking out 4EBP1/2 protects lymphoma cells from TORKi-induced cytotoxicity. Furthermore, downregulation of MCL1 expression plays an important role in TORKi-induced apoptosis, whereas BCL-2 overexpression confers resistance to TORKi treatment. We further show that the therapeutic effect of TORKi in aggressive B-cell lymphomas can be predicted by BH3 profiling, and improved by combining it with pro-apoptotic drugs, especially BCL-2 inhibitors, both in vitro and in vivo Taken together, the study herein provides mechanistic insight into TORKi cytotoxicity and identified a potential way to optimize its efficacy in the clinical treatment of aggressive B-cell lymphoma.

Quantitative proteomics reveals that miR-155 regulates the PI3K-AKT pathway in diffuse large B-cell lymphoma.

The aberrant expression of microRNA-155 (miR-155), which has emerged as having a significant impact on the biological characteristics of lymphocytes, plays important roles in B-cell malignancies, such as diffuse large B-cell lymphoma (DLBCL). DLBCL is the most common non-Hodgkin's lymphoma in the adult population, accounting for approximately 40% of newly diagnosed non-Hodgkin's lymphoma cases globally. To determine the specific function of miR-155, a quantitative proteomics approach was applied to examine the inhibitory effects of miR-155 on protein synthesis in DLBCL cells. PIK3R1 (p85α), a negative regulator of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway, was identified as a direct target of miR-155. A luciferase reporter was repressed through the direct interaction of miR-155 and the p85α 3'-untranslated region, and overexpression of miR-155 down-regulated both the transcription and translation of p85α. The PI3K-AKT signaling pathway was highly activated by the sustained overexpression of miR-155 in DHL16 cells, whereas knockdown of miR-155 in OCI-Ly3 cells diminished AKT activity. Taken together, our results reveal a novel target involved in miR-155 biological characteristics and provide a molecular link between the overexpression of miR-155 and the activation of PI3K-AKT in DLBCL.

[Diffuse large B-cell lymphoma of testis: a clinicopathologic and immunophenotypic study of 58 cases].

OBJECTIVE: To investigate the clinicopathologic features, immunophenotype, diagnosis and differential diagnosis, and prognostic factors of testicular diffuse large B-cell lymphoma (DLBCL). METHODS: The clinical and pathologic profiles of 58 cases of testicular DLBCL were investigated.Immunohistochemical stainings and EBER1/2 in situ hybridization were performed on formalin fixed tissues. RESULTS: The average age of the patients was 62.1 years, and the median age was 65 years. The course of disease was short in most of the cases. Clinical stages at diagnosis were mainly stage I or II (87.9%, 51/58). Forty eight patients (82.8%) had unilateral testis involvement. Inguinal lymphadenopathy was observed in 12 (20.7%) patients and the other organs were seldom involved. Morphologically, centroblast-like neoplastic cells infiltrated interstitial tissue of testis diffusely and invaded into seminiferous tubules. Tunica albuginea and vessels were involved in 14 (24.1%) and 10 (17.2%) patients, respectively. Immunophenotype analysis showed predominant non-GCB type of DLBCL (48/58, 82.8%) by Hans classification. No EBV infection was detected. Follow-up data were available in 48 (82.8%) patients. Twenty eight patients (58.3%) died of the disease. One-year, 3-year, and 5-year overall survivals were 55.7%, 31.6% and 27.6%, respectively. Age (older than 60 years), B-symptoms, high serum level of LDH, advanced Ann Arbor stage as well as lack of combination of therapy were associated with a poor prognosis. CONCLUSIONS: This large series of testicular DLBCL mainly present with local disease at diagnosis. Most cases show non-GCB immunophenotype. Despite early clinical stage at presentation, the prognosis is poor. Combined chemotherapy postoperation may prolong survival of the patients.

Integrative analysis of clinicopathological features defines novel prognostic models for mantle cell lymphoma in the immunochemotherapy era: a report from The North American Mantle Cell Lymphoma Consortium.

BACKGROUND: Patients with mantle cell lymphoma (MCL) exhibit a wide variation in clinical presentation and outcome. However, the commonly used prognostic models are outdated and inadequate to address the needs of the current multidisciplinary management of this disease. This study aims to investigate the clinical and pathological features of MCL in the immunochemotherapy era and improve the prognostic models for a more accurate prediction of patient outcomes. METHODS: The North American Mantle Cell Lymphoma Project is a multi-institutional collaboration of 23 institutions across North America to evaluate and refine prognosticators for front-line therapy. A total of 586 MCL cases diagnosed between 2000 and 2012 are included in this study. A comprehensive retrospective analysis was performed on the clinicopathological features, treatment approaches, and outcomes of these cases. The establishment of novel prognostic models was based on in-depth examination of baseline parameters, and subsequent validation in an independent cohort of MCL cases. RESULTS: In front-line strategies, the use of hematopoietic stem cell transplantation was the most significant parameter affecting outcomes, for both overall survival (OS, p < 0.0001) and progression-free survival (PFS, p < 0.0001). P53 positive expression was the most significant pathological parameter correlating with inferior outcomes (p < 0.0001 for OS and p = 0.0021 for PFS). Based on the baseline risk factor profile, we developed a set of prognostic models incorporating clinical, laboratory, and pathological parameters that are specifically tailored for various applications. These models, when tested in the validation cohort, exhibited strong predictive power for survival and showed a stratification resembling the training cohort. CONCLUSIONS: The outcome of patients with MCL has markedly improved over the past two decades, and further enhancement is anticipated with the evolution of clinical management. The innovative prognostic models developed in this study would serve as a valuable tool to guide the selection of more suitable treatment strategies for patients with MCL.

[Analysis of the immunohistochemical subtypes and prognosis of primary diffuse large B cell lymphoma of the central nervous system].

OBJECTIVE: To analyze the subtypes of primary diffuse large B cell lymphoma of the central nervous system (CNS DLBCL) and to explore the relationship between the subtype classification and prognosis. METHODS: Immunohistochemical staining was used to determine the expression of CD20, CD3, CD10, Bcl-6, Mum-1, CD5, Bcl-2, Ki-67, FOXP-1, GCET-1, BLIMP-1 and LMO-2 antigens on paraffin-embedded sections of 47 cases. Hans, Choi and Tally subtypes were classified, and univariate and multivariate analyses were used to elucidate the relationship between the subtypes and prognosis. RESULTS: In the 47 cases, the expression of Bcl-2 in the tumor cells was 46.8%, CD10 4.3%, Bcl-6 70.2%, Mum-1 53.2%, GCET-1 36.2%, BLIMP-1 4.3%, FOXP-1 63.8% and LMO-2 19.2%. The positive rate of Ki-67 was 30% to 95%, with a median of 80%, of which 12 cases (25.5%) was > or = 90%. The Hans subtype classification showed 16 cases (34.0%) were of GCB type and 31 cases (66.0%) of non-GCB type. The Choi subtype classification showed 16 cases (34.0%) were of GCB type and 31 cases (66.0%) of ABC type. The Tally subtype classification showed 6 cases (12.8%) were of GCB type and 41 cases (87.2%) of non-GCB type. CONCLUSIONS: The results of this study show that there is no significant correlation between the three subtypes and prognosis. The prognosis is correated with post-operative radiotherapy, chemotherapy and MTX therapy.

[Langerhans cell histiocytosis: a clinicopathologic and immunohistochemical analysis of 258 cases].

OBJECTIVES: To observe the clinicopathologic features of Langerhans cell histiocytosis (LCH), and to evaluate the values of langerin, CD1a and S-100 protein expression in diagnosis of the tumor. METHODS: Total 258 cases of Langerhans cell histiocytosis in the past 18 years (from 1992 to 2008) were collected, morphologic review and immunohistochemical staining were performed. RESULTS: In all 258 cases, the ages of patients older than 16 years or younger than 2 years were 126 (48.8%) and 37 (14.3%), respectively, in the remaining 95 (36.8%) of the cases, the age of the patients ranged from 2 to 16 years. For all of 258 cases, there were 364 diseased sites. Bony lesions accounted for 77.2% (281 cases), especially the skull (112 cases, 39.9%), followed by lymph node (25 cases, 6.9%) and skin (14 cases, 3.8%). Clinically, unisystem or unifocal disease was predominant (201 cases, 77.9%), followed by unisystem and multifocal disease (21 cases, 8.1%), multi-system disease (26 cases, 10.1%), isolated pulmonary LCH (2 cases, 0.8%), and unclassified (8 cases, 3.1%). Histologically, variable number of Langerhans cells was present in 265 samples of 258 cases. Multinucleated giant cells were found in 166 (62.6%) of the samples. Eosinophils were the major infiltrating non-neoplastic cells, and eosinophilic abscess was seen in 57 cases (21.5%). Coagulative necrosis and dead bone were detected in 29 (10.9%) and 124 (46.8%) of the cases, respectively. Immunohistochemically, the expression of S-100 protein, CD1a and langerin was 99.1% (209/211), 100% (206/206) and 98.5% (193/196), respectively, and the sensitivity of them had no statistical difference. CONCLUSIONS: In this group of LCH cases, the ratio of adult patients is high, but the proportion of multi-organ lesion is low. No significant difference of the sensitivity is found among langerin, CD1a and S-100 expression in diagnosis of LCH.

[Primary gastrointestinal diffuse large B-cell lymphoma: an immunohistochemical and prognostic study of 90 cases].

OBJECTIVE: To study the immunophenotype and prognostic significance of primary gastrointestinal diffuse large B-cell lymphoma, with reference to Hans, Choi and Tally algorithms. METHODS: The clinicopathologic features and follow-up data in 90 cases of primary gastrointestinal diffuse large B-cell lymphoma were analyzed by Kaplan-Meier method, Log-rank test and Cox regression model. Immunohistochemistry was carried out using EliVision and EnVision methods for CD20, CD3ε, CD10, bcl-6, MUM-1, CD5, bcl-2, GCET1, FOXP1, LMO2, BLIMP1 and Ki-67. RESULTS: The age of patients ranged from 27 to 83 years (mean = 58 years). The male-to-female ratio was 1.31:1. Amongst the 90 cases studied, 64.4% (58/90) involved the stomach and 35.6% (32/90) involved the intestine. The immunohistochemical findings were as follows: 100% positivity for CD20, 0% for CD3ε and CD5, 17.8% (16/90) for CD10, 75.6% (68/90) for bcl-6, 52.2% (47/90) for MUM-1 (cut off was 30%), 43.3% (39/90) for MUM-1 (cut off was 80%), 50.0% (45/90) for GCET1, 45.6% (41/90) for FOXP1, 23.3% (21/90) for LMO2, 42.2% (38/90) for bcl-2 and 8.9% (8/90) for BLIMP1. The Ki-67 index ranged from 20% to 95% (median = 80%). According to Hans algorithm, 51.1% of the cases belonged to germinal center B-cell (GCB) subtype and 48.9% belonged to non-GCB subtype. In contrast, Choi algorithm classified 55.6% cases as GCB subtype and 44.4% as activated B-cell (ABC) subtype. According to Tally algorithm, 34.4% were of GCB subtype and 65.6% of non-GCB subtype. Most of the patients (67.8%, 61/90) received chemotherapy and 68.9% (62/90) underwent surgical resection. The overall 2, 3 and 5-year survival rates were 58.5%, 52.8% and 49.8%, respectively. The overall 2, 3 and 5-year survival rates in the CHOP therapy group were 68.5%, 61.2% and 52.9%, respectively. CONCLUSIONS: There is no significant difference in ratio between the GCB and non-GCB/ABC subtypes by Hans and Choi algorithms. The non-GCB subtype seems to be more prevalent according to Tally algorithm. Although there is no significant difference in survival between GCB and non-GCB/ABC subtypes by the 3 algorithms, GCB subtype tends to show a better survival. In univariate analysis, LDH level, international prognostic index, chemotherapy, surgical resection, B symptoms, number of involved sites and clinical stage are found to have prognostic significance. In multivariate analysis, Choi algorithm, Tally algorithm, chemotherapy, surgical resection, LDH level and clinical stage are independent prognostic factors.

Programmed Cell Death Protein 1/Programmed Cell Death Ligand-1 Axis activates Intracellular ERK Signaling in Tumor Cells to Mediate Poor Prognosis in T-cell Lymphoma.

Purpose: To investigate the prognostic significance of programmed cell death ligand-1 (PD-L1) and phosphorylated ERK (p-ERK) and their interactions in T-cell lymphoma (TCL). Methods: The mRNA levels of PD-L1 and ERK in TCL samples were analyzed. Formalin-fixed paraffin-embedded tissues from 69 TCL patients were collected to detect the expression of PD-L1 and p-ERK by multiplexed immunofluorescence staining. The total PD-L1 and p-ERK was measured by western blotting, and membrane PD-L1 was determined using flow cytometry. Results: PD-L1 and ERK mRNA levels were significantly upregulated in TCL. The expression rates of PD-L1 and p-ERK were 52.2% and 27.5%, respectively. PD-L1 expression correlated with stage (R=0.304, P=0.011) and IPI score (R=0.313, P=0.009), and p-ERK expression correlated with stage (R=0.330, P=0.006) and IPI score (R=0.376, P=0.002). PD-L1 expression positively correlated with p-ERK expression (R=0.355, P=0.003). Patients with co-expression of PD-L1 and p-ERK had the worst overall survival (P=0.007). In three TCL cell lines with PD-L1 expression, we demonstrated that the expression of p-ERK was upregulated after stimulation with PD-1, suggesting that ERK signaling was activated. Conclusions: The PD-1/PD-L1 axis activates intracellular ERK signaling in tumor cells and that PD-L1, p-ERK or their combination are potential biomarkers for predicting the prognosis in TCL patients.

[Primary lymphoma of breast: a clinicopathologic, immunophenotypic and prognostic study of 21 cases].

OBJECTIVE: To investigate the clinicopathologic and immunophenotypic features of primary breast lymphoma (PBL) and to discuss the diagnosis of the tumor. METHODS: Twenty-one cases of PBL with follow up data were clinically reviewed. The histologic diagnosis of the tumor was based on the updated WHO Classification of tumors of hematopoietic and lymphoid tissues (2008). Immunohistochemistry was performed by SP method and antibodies selected were as follows: CD20, CD3epsilon, CD10, Bcl-6, MUM-1, CD5, Bcl-2, CD23, CD10, cyclin D1, CD43 and Ki67. RESULTS: (1) All 21 patients were female and the median age of patients was 48 years. The right and the left breasts were involved in 11 (52.4%) and 10 patients (47.6%), respectively. According to Ann Arbor staging system, 20 cases were stage I-II (95.2%), and the remaining case was stage IV (4.8%). For the international prognostic index (IPI), 19 cases were score 0-1, and 2 cases were score 2-3. For ECOG score, 19 cases were 0, and the remaining 2 cases were 1. (2) Histologically, all 21 cases (100%) were DLBCL. Immunohistochemically, the frequency of antigen expression was as follows: CD20 (100%), MUM-1 (14/21, 66.7%), bcl-6 (5/21, 23.8%), CD10 (0), bcl-2 (13/21, 61.9%), CD5 (1/21, 4.8%); Ki-67 index: 10 cases (47.6%) were less than 59%, with the expression of seven cases (33.3%) being 60% - 89%, and more than 90% in the remaining four cases (19.1%). The median Ki-67 index was 60%. All the cases were considered non germinal center B-cell-like type of DLBCL. (3) Follow-up data was available in 64% of the cases. One, two and five-year survival rates were 11 cases, 7 cases and 3 cases, respectively. CONCLUSION: All the cases of PBL in the current study were DLBCL, non germinal center B-cell-like type, and a diagnosis of PBL can only be established after excluding breast involvement in systemic lymphoma.

[Solitary plasmacytoma of bone: a clinicopathologic, immunohistochemical and immunoglobulin gene rearrangement study].

OBJECTIVE: To investigate clinicopathologic features of solitary plasmacytoma of bone (SPB) and the role of immuno-phenotype and immunoglobulin gene rearrangement detection in the diagnosis and differential diagnosis of SPB. METHODS: A total of 21 cases of SPB were selected during a period from 1990 to 2008. A retrospective clinicopathologic study and immunohistochemistry (EnVision or EliVision methods) of 17 antigens were performed. In addition, universal IgH (FR3A/LJH/VLJH) primers and BIOMED-2 PCR multiplex tubes were used for IgK and IgL rearrangement analysis. RESULTS: The age of patients ranged from 36 to 72 years with a media of 50 years. Axial skeleton was the most common site of involvement, accounting for 66.7% of the cases (14 of 21), followed by the extremities of 33.3% (7 cases). Low serum level of M-components was found in 5 cases, including two of IgG type (21.4 g/L) and three of IgA type. Clinical manifestations were closely related to the anatomic sites involved, such as pain due to bone destruction, symptoms and signs caused by compression of spinal cord or nerve root, and pathological fracture. All cases presented as a solitary osteolytic lesion. According to the histological grading criteria, grade I tumor was seen in 12 of 21 cases (57.1%). The remaining were grade II (5 cases, 23.8%) and grade III (4 cases, 19.0%). Immunohistochemically, the neoplastic cells expressed two or more plasma cell antigens, including CD138, CD38 and PC, but no CD19 and CD20. CD79a expression detected in 23.8%(5/21) of the cases. Expression of CD56, CD27 and CD44v6 were 57.1% (12/21), 15.0% (3/20) and 23.8% (5/21), respectively. Follow-up data were available in 12 of the 21 patients (57.1%). Five patients were alive and 7 died. Three patients developed multiple myeloma (MM) and died of the tumor. CONCLUSIONS: SPB is a rare tumor with bone pain as the most common presenting symptom due to bone destruction. The diagnosis of EMP can only be established after exclusion of an extramedullay invasion by MM. Immunophenotype and IgH gene rearrangement analysis play important roles in the diagnosis of SPB.

Targeting translation initiation by synthetic rocaglates for treating MYC-driven lymphomas.

MYC-driven lymphomas, especially those with concurrent MYC and BCL2 dysregulation, are currently a challenge in clinical practice due to rapid disease progression, resistance to standard chemotherapy, and high risk of refractory disease. MYC plays a central role by coordinating hyperactive protein synthesis with upregulated transcription in order to support rapid proliferation of tumor cells. Translation initiation inhibitor rocaglates have been identified as the most potent drugs in MYC-driven lymphomas as they efficiently inhibit MYC expression and tumor cell viability. We found that this class of compounds can overcome eIF4A abundance by stabilizing target mRNA-eIF4A interaction that directly prevents translation. Proteome-wide quantification demonstrated selective repression of multiple critical oncoproteins in addition to MYC in B-cell lymphoma including NEK2, MCL1, AURKA, PLK1, and several transcription factors that are generally considered undruggable. Finally, (-)-SDS-1-021, the most promising synthetic rocaglate, was confirmed to be highly potent as a single agent, and displayed significant synergy with the BCL2 inhibitor ABT199 in inhibiting tumor growth and survival in primary lymphoma cells in vitro and in patient-derived xenograft mouse models. Overall, our findings support the strategy of using rocaglates to target oncoprotein synthesis in MYC-driven lymphomas.

Targeting EZH1/2 induces cell cycle arrest and inhibits cell proliferation through reactivation of p57CDKN1C and TP53INP1 in mantle cell lymphoma.

OBJECTIVE: To explore the effect of dysregulation of epigenetic regulator EZH1 and EZH2 on the proliferation in MCL and the underlying mechanisms. METHODS: In this study, we elucidated the role of EZH1 and EZH2 overexpression by immunohistochemistry and correlated them to clinical outcome in 41 MCL patients. Quantitative real-time PCR and Western blot were applied to confirm the level of EZH1 and EZH2 in well-characterized MCL cell lines which were compared to those of naïve B cells. Then we manipulated the expression of EZH1 and EZH2 in MCL cells using CRISPR/Cas9 system to directly investigate their functional roles in MCL. We also evaluated the effect of two small molecule selective inhibitors, EPZ005687 and UNC1999, on MCL cell proliferation, cell cycle distribution and apoptosis in vitro. Finally, we performed RNA-sequencing (RNA-Seq) and Chromatin immunoprecipitation (ChIP) assay to further gain insight into the underlying molecular mechanisms. RESULTS: We found that EZH2 protein is overexpressed in approximately half of this cohort of MCL cases. More importantly, the overexpression of EZH2 is associated with poor OS in the patients. Nevertheless, simple EZH2 depletion in vitro has little impact on the viability of MCL cells, predominantly because of the consequent up-regulation of EZH1. Consistently, UNC1999, a dual EZH1/2 inhibitor, unlike the EZH2 selective inhibitor EPZ005687, exerts a potent inhibitory effect on MCL cells. Furthermore, we discover CDKN1C and TP53INP1 as the two important cell cycle regulators, the expression of which are repressed by EZH1/2 mediated epigenetic regulation and are restored by EZH1/2 dual inhibition. CONCLUSIONS: Our study suggests that EZH2 participates in the pathogenesis of MCL which may serve as a potential biomarker for prognosis prediction. The dual inhibition of EZH1/2 is a promising therapeutic strategy for MCL.

BCL2 Amplicon Loss and Transcriptional Remodeling Drives ABT-199 Resistance in B Cell Lymphoma Models.

Drug-tolerant "persister" tumor cells underlie emergence of drug-resistant clones and contribute to relapse and disease progression. Here we report that resistance to the BCL-2 targeting drug ABT-199 in models of mantle cell lymphoma and double-hit lymphoma evolves from outgrowth of persister clones displaying loss of 18q21 amplicons that harbor BCL2. Further, persister status is generated via adaptive super-enhancer remodeling that reprograms transcription and offers opportunities for overcoming ABT-199 resistance. Notably, pharmacoproteomic and pharmacogenomic screens revealed that persisters are vulnerable to inhibition of the transcriptional machinery and especially to inhibition of cyclin-dependent kinase 7 (CDK7), which is essential for the transcriptional reprogramming that drives and sustains ABT-199 resistance. Thus, transcription-targeting agents offer new approaches to disable drug resistance in B-cell lymphomas.