Patrizia Mondello

T cells. The regulation of MHC-I by kinases is largely unstudied, even though many patients with cancer are receiving therapeutic kinase inhibitors. Regulators of cell-surface HLA amounts were discovered using a pooled human kinome shRNA interference-based approach. Hits scoring highly were subsequently validated by additional RNAi and pharmacologic inhibitors. MAP2K1 (MEK), EGFR, and RET were validated as negative regulators of MHC-I expression and antigen presentation machinery in multiple cancer types, acting through an ERK output-dependent mechanism; the pathways responsible for increased MHC-I upon kinase inhibition were mapped. Activated MAPK signaling in mouse tumors in vivo suppressed components of MHC-I and the antigen presentation machinery. Pharmacologic inhibition of MAPK signaling also led to improved peptide/MHC target recognition and killing by T cells and TCR-mimic antibodies. Druggable kinases may thus serve as immediately applicable targets for modulating immunotherapy for many diseases. Cancer Immunol Res; 4(11); 936-47. ©2016 AACR.

Abstract CREBBP mutations are highly recurrent in B-cell lymphomas and either inactivate its histone acetyltransferase (HAT) domain or truncate the protein. Herein, we show that these two classes of mutations yield different degrees of disruption of the epigenome, with HAT mutations being more severe and associated with inferior clinical outcome. Genes perturbed by CREBBP mutation are direct targets of the BCL6–HDAC3 onco-repressor complex. Accordingly, we show that HDAC3-selective inhibitors reverse CREBBP-mutant aberrant epigenetic programming, resulting in: (i) growth inhibition of lymphoma cells through induction of BCL6 target genes such as CDKN1A and (ii) restoration of immune surveillance due to induction of BCL6-repressed IFN pathway and antigen-presenting genes. By reactivating these genes, exposure to HDAC3 inhibitors restored the ability of tumor-infiltrating lymphocytes to kill DLBCL cells in an MHC class I and II–dependent manner, and synergized with PD-L1 blockade in a syngeneic model in vivo. Hence, HDAC3 inhibition represents a novel mechanism-based immune epigenetic therapy for CREBBP-mutant lymphomas. Significance: We have leveraged the molecular characterization of different types of CREBBP mutations to define a rational approach for targeting these mutations through selective inhibition of HDAC3. This represents an attractive therapeutic avenue for targeting synthetic vulnerabilities in CREBBP-mutant cells in tandem with promoting antitumor immunity. This article is highlighted in the In This Issue feature, p. 327

The proviral insertion in murine (PIM) lymphoma proteins are a serine/threonine kinase family composed of three isoformes: Pim-1, Pim-2 and Pim-3. They play a critical role in the control of cell proliferation, survival, homing and migration. Recently, overexpression of Pim kinases has been reported in human tumors, mainly in hematologic malignancies. In vitro and in vivo studies have confirmed their oncogenic potential. Indeed, PIM kinases have shown to be involved in tumorgenesis, to enhance tumor growth and to induce chemo-resistance, which is why they have become an attractive therapeutic target for cancer therapy. Novel molecules inhibiting Pim kinases have been evaluated in preclinical studies, demonstrating to be effective and with a favorable toxicity profile. Given the promising results, some of these compounds are currently under investigation in clinical trials. Herein, we provide an overview of the biological activity of PIM-kinases, their role in hematologic malignancies and future therapeutic opportunities.

// Patrizia Mondello 1 , Enrico Derenzini 1 , Zahra Asgari 1 , John Philip 2 , Elliott J. Brea 3 , Venkatraman Seshan 4 , Ronald C. Hendrickson 2 , Elisa de Stanchina 5 , David A. Scheinberg 3 , Anas Younes 1 1 Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA 2 Proteomics Core Facility, Memorial Sloan Kettering Cancer Center, New York, NY, USA 3 Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA 4 Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA 5 Antitumor Assessment Core, Memorial Sloan Kettering Cancer Center, New York, NY, USA Correspondence to: Anas Younes, email: younesa@mskcc.org Keywords: MYC, PI3K, DLBCL, BCR pathway Received: September 28, 2016      Accepted: January 02, 2017      Published: January 28, 2017 ABSTRACT Phosphoinositide 3-kinase (PI3K) and Myc are known to cooperate in promoting the survival and growth of a variety of B-cell lymphomas. While currently there are no small molecule inhibitors of Myc protein, histone deacetylase (HDAC) inhibitors have been shown to reduce levels of Myc protein by suppressing its transcription. We assessed the efficacy of CUDC-907, a new rationally designed dual inhibitor of PI3K and HDACs, in a panel of lymphoma cell lines. CUDC-907 treatment resulted in a dose- and time-dependent growth inhibition and cell death of DLBCL cell lines, irrespective of the cell of origin. CUDC-907 treatment down-regulated the phosphorylation of PI3K downstream targets, including AKT, PRAS40, S6, and 4EBP1, increased histone 3 acetylation, and decreased Myc protein levels. SILAC-based quantitative mass spectrometry demonstrated that CUDC-907 treatment decreased the protein levels of several components of the B cell receptor (BCR) and Toll like receptor (TLR) pathways, including BTK, SYK, and MyD88 proteins. These cellular changes were associated with an inhibition of NF-kB activation. CUDC-907 demonstrated in vivo efficacy with no significant toxicity in a human DLBCL xenograft mouse model. Collectively, these data provide a mechanistic rationale for evaluating CUDC-907 for the treatment of patients with Myc and PI3K-dependent lymphomas.

Although methotrexate (MTX) is the most widely used therapy for central nervous system (CNS) prophylaxis in patients with diffuse large B-cell lymphoma (DLBCL), the optimal regimen remains unclear. We examined the efficacy of different prophylactic regimens in 585 patients with newly diagnosed DLBCL and high-risk for CNS relapse, treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) or R-CHOP-like regimens from 2001 to 2017, of whom 295 (50%) received prophylaxis. Intrathecal (IT) MTX was given to 253 (86%) and high-dose MTX (HD-MTX) to 42 (14%). After a median follow-up of 6.8 years, 36 of 585 patients relapsed in the CNS, of whom 14 had received prophylaxis. The CNS relapse risk at 1 year was lower for patients who received prophylaxis than patients who did not: 2% vs. 7.1%. However, the difference became less significant over time (5-year risk 5.6% vs. 7.5%), indicating prophylaxis tended to delay CNS relapse rather than prevent it. Furthermore, the CNS relapse risk was similar in patients who received IT and HD-MTX (5-year risk 5.6% vs. 5.2%). Collectively, our data indicate the benefit of MTX for CNS prophylaxis is transient, highlighting the need for more effective prophylactic regimens. In addition, our results failed to demonstrate a clinical advantage for the HD-MTX regimen.