In the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), NF-κB activity is essential for viability of the malignant cells and is sustained by constitutive activity of IκB kinase (IKK) in the cytoplasm. Here, we report an unexpected role for the bromodomain and extraterminal domain (BET) proteins BRD2 and BRD4 in maintaining oncogenic IKK activity in ABC DLBCL. IKK activity was reduced by small molecules targeting BET proteins as well as by genetic knockdown of BRD2 and BRD4 expression, thereby inhibiting downstream NF-κB-driven transcriptional programs and killing ABC DLBCL cells. Using a high-throughput platform to screen for drug-drug synergy, we observed that the BET inhibitor JQ1 combined favorably with multiple drugs targeting B-cell receptor signaling, one pathway that activates IKK in ABC DLBCL. The BTK kinase inhibitor ibrutinib, which is in clinical development for the treatment of ABC DLBCL, synergized strongly with BET inhibitors in killing ABC DLBCL cells in vitro and in a xenograft mouse model. These findings provide a mechanistic basis for the clinical development of BET protein inhibitors in ABC DLBCL, particularly in combination with other modulators of oncogenic IKK signaling.cancer therapy | drug synergism T he activated B-cell like subtype (ABC) of diffuse large B-cell lymphoma (DLBCL) has an aggressive clinical course compared with other DLBCL subtypes, with an overall survival of only 40% with current multidrug chemotherapies (1, 2). In recent years, detailed genetic and functional genomic analyses unveiled the key oncogenic mechanisms that sustain the aggressiveness of this subtype. Notably, all ABC DLBCLs rely on constitutive NF-κB activation for survival (3). Various oncogenic events converge on NF-κB to promote lymphomagenesis. About 10% of ABC DLBCL tumors have activating mutations affecting CARD11, a scaffolding protein required for the assembly of the CARD11-BCL10-MALT1 (CBM) complex. Mutant CARD11 proteins spontaneously generate cytoplasmic CBM aggregates that drive constitutive NF-κB activity (4). ABC DLBCL tumors with wild-type CARD11 use other mechanisms to activate NF-κB. In 20% of cases, signals emanating from the B-cell receptor (BCR) are augmented by somatically acquired mutations targeting the BCR subunits CD79A and CD79B (5). In 39% of ABC DLBCLs, NF-κB is activated by somatic mutations targeting MyD88, an adaptor protein in the Toll-like receptor (TLR) pathway (6). In normal B cells, stimulus-dependent engagement of the BCR and MyD88 pathways activates IκB kinase (IKK), which phosphorylates ΙκBα, thereby promoting its degradation and allowing NF-κB transcription factors to enter the nucleus and activate a distinctive set of target genes. By contrast, ABC DLBCL cells become addicted to constitutive activity of IKK such that its inhibition is lethal (7). Recent therapeutic efforts to target oncogenic signaling in ABC DLBCL have focused on ibrutinib, a selective inhibitor of the kinase BTK that transmits signals from the BCR to the NF-κB pathway (5)...

Despite effective and widely available suppressive anti-HIV therapy, the prevalence of mild neurocognitive dysfunction continues to increase. HIV-associated neurocognitive disorder (HAND) is a multifactorial disease with sustained central nervous system inflammation and immune activation as prominent features. Inflammatory macrophages, HIV-infected and uninfected, play a central role in the development of HIV dementia. There is a critical need to identify biomarkers and to better understand the molecular mechanisms leading to cognitive dysfunction in HAND. In this regard, we identified through a subtractive hybridization strategy osteopontin (OPN, SPP1, gene) an inflammatory marker, as an upregulated gene in HIV-infected primary human monocyte-derived macrophages. Knockdown of OPN in primary macrophages resulted in a threefold decrease in HIV-1 replication. Ectopic expression of OPN in the TZM-bl cell line significantly enhanced HIV infectivity and replication. A significant increase in the degradation of the NF-κB inhibitor, IκBα and an increase in the nuclear-to-cytoplasmic ratio of NF-κB were found in HIV-infected cells expressing OPN compared to controls. Moreover, mutation of the NF-κB binding domain in the HIV-LTR abrogated enhanced promoter activity stimulated by OPN. Interestingly, compared to cerebrospinal fluid from normal and multiple sclerosis controls, OPN levels were significantly higher in HIV-infected individuals both with and without neurocognitive disorder. OPN levels were highest in HIV-infected individuals with moderate to severe cognitive impairment. Moreover, OPN was significantly elevated in brain tissue from HIV-infected individuals with cognitive disorder versus those without impairment. Collectively, these data suggest that OPN stimulates HIV-1 replication and that high levels of OPN are present in the CNS compartment of HIV-infected individuals, reflecting ongoing inflammatory processes at this site despite anti-HIV therapy.

Although targeted therapies have revolutionized cancer treatment, overcoming acquired resistance remains a major clinical challenge. EZH2 inhibitors (EZH2i), EPZ-6438 and GSK126, are currently in the early stages of clinical evaluation and the first encouraging signs of efficacy have recently emerged in the clinic. To anticipate mechanisms of resistance to EZH2i, we used a forward genetic platform combining a mutagenesis screen with next generation sequencing technology and identified a hotspot of secondary mutations in the EZH2 D1 domain (Y111 and I109). Y111D mutation within the WT or A677G EZH2 allele conferred robust resistance to both EPZ-6438 and GSK126, but it only drove a partial resistance within the Y641F allele. EZH2 mutants required histone methyltransferase (HMT) catalytic activity and the polycomb repressive complex 2 (PRC2) components, SUZ12 and EED, to drive drug resistance. Furthermore, D1 domain mutations not only blocked the ability of EZH2i to bind to WT and A677G mutant, but also abrogated drug binding to the Y641F mutant. These data provide the first cellular validation of the mechanistic model underpinning the oncogenic function of WT and mutant EZH2. Importantly, our findings suggest that acquired-resistance to EZH2i may arise in WT and mutant EZH2 patients through a single mutation that remains targetable by second generation EZH2i.

BackgroundSialoglycans, a type of glycans with a terminal sialic acid, have emerged as a critical glyco-immune checkpoint that impairs antitumor response by inhibiting innate and adaptive immunity. Upregulation of sialoglycans on tumors has been observed for decades and correlates with poor clinical outcomes across many tumor types. We previously showed that targeted desialylation of tumors using a bifunctional sialidase x antibody molecule, consisting of sialidase and a tumor-associated antigen (TAA)-targeting antibody, has led to robust single-agent efficacy in mouse tumor models. In addition to tumor cells, most immune cells present substantially more abundant sialoglycans than non-hematological healthy cells, which may also contribute to immunosuppression. Therefore, we studied the impact of immune cell desialylation and evaluated the therapeutic potential of a newly developed sialidase-Fc fusion (Bi-Sialidase), which lacks a TAA-targeting moiety and consists of engineered human neuraminidase 2 (Neu2) and human IgG1 Fc region, in preclinical mouse tumor models.MethodsThe first generation Neu2 variant was further optimized to improve titers and stability to constructed Bi-Sialidase. Bi-Sialidase’s desialylation potency and impact on immune responses were studied in vitro using various human immune functional assays, including T-cell activation, allogeneic mixed lymphocyte reaction, antibody-dependent cellular cytotoxicity, macrophages polarization/activation, neutrophil activation, and peripheral blood mononuclear cell (PBMC) cytokine release assays. We evaluated its antitumor efficacy in mouse tumor models. Bi-Sialidase’s safety profile was characterized by conducting rat and non-human primate (NHP) toxicology studies.ResultsThe optimized Bi-Sialidase achieved a titer of 2.5 g/L from a 15-day fed-batch Chinese hamster ovary cell culture; in contrast, the wild-type and first-generation Neu2 had no production or a low titer (<0.1 g/L) under similar conditions, respectively. We demonstrated that Bi-Sialidase led to dose-dependent desialylation of immune cells and potentiated T-cell immunity, without impacting NK, macrophage, or neutrophil activation by desialylating immune cells. Activated and exhausted T cells upregulated surface sialoglycans and Bi-Sialidase-mediated desialylation reinvigorated exhausted-like T cells as measured by IFNg production. Bi-Sialidase treatment also enhanced DC priming and activation of naïve T cells by desialylating both T cells and DCs. Furthermore, Bi-Sialidase showed single-agent antitumor activity in multiple mouse tumor models, including MC38, CT26, A20, and B16F10. Importantly, Bi-Sialidase did not cause cytokine release in human PBMC assays and was tolerated to up to 100 mg/kg in rats and NHPs, demonstrating a wide safety margin.ConclusionsBi-Sialidase with an optimized Neu2 offers a novel immunomodulatory approach to enhancing T-cell immunity by desialylating immunosuppressive sialoglycans for cancer treatment.