The combination of histone deacetylase inhibitors with immune-stimulating antibodies has potent anti-cancer effects

The use of immunotherapy to treat cancer is rapidly gaining momentum. Using pre-clinical mouse models, we have recently demonstrated potent and long lasting tumor regression can be elicited by immune-stimulating monoclonal antibodies (mAbs) when combined with histone deacetylase inhibitors (HDACi) and believe this therapy will have broad application in humans

The mTORC1 inhibitor everolimus prevents and treats Eμ-Myc lymphoma by restoring oncogene-induced senescence

MYC deregulation is common in human cancer. IG-MYC translocations that are modeled in EμMyc mice occur in almost all cases of Burkitt lymphoma as well as in other B-cell lymphoproliferative disorders. Deregulated expression of MYC results in increased mTOR complex 1 (mTORC1) signaling. As tumors with mTORC1 activation are sensitive to mTORC1 inhibition, we used everolimus, a potent and specific mTORC1 inhibitor, to test the requirement for mTORC1 in the initiation and maintenance of EμMyc lymphoma. Everolimus selectively cleared premalignant B cells from the bone marrow and spleen, restored a normal pattern of B-cell differentiation, and strongly protected against lymphoma development. Established EμMyc lymphoma also regressed after everolimus therapy. Therapeutic response correlated with a cellular senescence phenotype and induction of p53 activity. Therefore, mTORC1-dependent evasion of senescence is critical for cellular transformation and tumor maintenance by MYC in B lymphocytes

Genomic characterisation of Eμ-Myc mouse lymphomas identifies Bcor as a Myc co-operative tumour-suppressor gene

The Eμ-Myc mouse is an extensively used model of MYC driven malignancy; however to date there has only been partial characterization of MYC co-operative mutations leading to spontaneous lymphomagenesis. Here we sequence spontaneously arising Eμ-Myc lymphomas to define transgene architecture, somatic mutations, and structural alterations. We identify frequent disruptive mutations in the PRC1-like component and BCL6-corepressor gene Bcor. Moreover, we find unexpected concomitant multigenic lesions involving Cdkn2a loss and other cancer genes including Nras, Kras and Bcor. These findings challenge the assumed two-hit model of Eμ-Myc lymphoma and demonstrate a functional in vivo role for Bcor in suppressing tumorigenesis.We acknowledge the following funding agencies: Leukaemia Foundation of Australia, Arrow Bone Marrow Transplant Foundation, National Health and Medical Research Council Australia, Cancer Council Victoria, Victorian Cancer Agency, Australian Cancer Research Foundation, Peter MacCallum Cancer Centre Foundation, National Institutes of Health

Functional Crosstalk between Type I and II Interferon through the Regulated Expression of STAT1

Small "priming" quantities of type I interferon enhance cellular responses to type II interferon by maintaining basal levels of STAT1, explaining the observed crosstalk between these two cytokines

Dual-specific chimeric antigen receptor T cells and an indirect vaccine eradicate a variety of large solid tumors in an immunocompetent, self-antigen setting

Purpose: While adoptive transfer of T cells bearing a chimeric antigen receptor (CAR) can eliminate substantial burdens of some leukemias, the ultimate challenge remains the eradication of large solid tumors for most cancers. We aimed to develop an immunotherapy approach effective against large tumors in an immunocompetent, self-antigen preclinical mouse model. Experimental Design: In this study, we generated dual-specific T cells expressing both a CAR specific for Her2 and a TCR specific for the melanocyte protein (gp100). We used a regimen of adoptive cell transfer incorporating vaccination (ACTIV), with recombinant vaccinia virus expressing gp100, to treat a range of tumors including orthotopic breast tumors and large liver tumors. Results: ACTIV therapy induced durable complete remission of a variety of Her2+ tumors, some in excess of 150 mm2, in immunocompetent mice expressing Her2 in normal tissues, including the breast and brain. Vaccinia virus induced extensive proliferation of T cells, leading to massive infiltration of T cells into tumors. Durable tumor responses required the chemokine receptor CXCR3 and exogenous IL-2, but were independent of IFN-gamma. Mice were resistant to tumor rechallenge, indicating immune memory involving epitope spreading. Evidence of limited neurologic toxicity was observed, associated with infiltration of cerebellum by T cells, but was only transient. Conclusions: This study supports a view that it is possible to design a highly effective combination immunotherapy for solid cancers, with acceptable transient toxicity, even when the target antigen is also expressed in vital tissuesThis work was supported by grants from the Cancer Council of Victoria, Australia (1066554), The Peter MacCallum Cancer Center Foundation, and the National Health and Medical Research Council (NHMRC) of Australia (1103352). C.Y. Slaney and P. Beavis were supported by Postdoctoral Fellowships from the National Breast Cancer Foundation of Australia. A.J. Davenport and S. Mardiana received Postgraduate Scholarships from the Fight Cancer Foundation and University of Melbourne respectively. R.W. Johnstone and M.J. Smyth were supported by Senior Principal Research Fellowships from the NHMRC. M.H. Kershaw and P.K. Darcy were supported by Senior Research Fellowships from the NHMRC. S. Ellis was supported by a New Investigator Grant from the NHMR

Imprinted CDKN1C Is a Tumor Suppressor in Rhabdoid Tumor and Activated by Restoration of SMARCB1 and Histone Deacetylase Inhibitors

SMARCB1 is deleted in rhabdoid tumor, an aggressive paediatric malignancy affecting the kidney and CNS. We hypothesized that the oncogenic pathway in rhabdoid tumors involved epigenetic silencing of key cell cycle regulators as a consequence of altered chromatin-remodelling, attributable to loss of SMARCB1, and that this hypothesis if proven could provide a biological rationale for testing epigenetic therapies in this disease. We used an inducible expression system to show that the imprinted cell cycle inhibitor CDKN1C is a downstream target for SMARCB1 and is transcriptionally activated by increased histone H3 and H4 acetylation at the promoter. We also show that CDKN1C expression induces cell cycle arrest, CDKN1C knockdown with siRNA is associated with increased proliferation, and is able to compete against the anti-proliferative effect of restored SMARCB1 expression. The histone deacetylase inhibitor (HDACi), Romidepsin, specifically restored CDKN1C expression in rhabdoid tumor cells through promoter histone H3 and H4 acetylation, recapitulating the effect of SMARCB1 on CDKNIC allelic expression, and induced cell cycle arrest in G401 and STM91-01 rhabdoid tumor cell lines. CDKN1C expression was also shown to be generally absent in clinical specimens of rhabdoid tumor, however CDKN1A and CDKN1B expression persisted. Our observations suggest that maintenance of CDKN1C expression plays a critical role in preventing rhabdoid tumor growth. Significantly, we report for the first time, parallels between the molecular pathways of SMARCB1 restoration and Romidepsin treatment, and demonstrate a biological basis for the further exploration of histone deacetylase inhibitors as relevant therapeutic reagents in the treatment of rhabdoid tumor

Histone deacetylase inhibitors: potential targets responsible for their anti-cancer effect

The histone deacetylase inhibitors (HDACi) have demonstrated anticancer efficacy across a range of malignancies, most impressively in the hematological cancers. It is uncertain whether this clinical efficacy is attributable predominantly to their ability to induce apoptosis and differentiation in the cancer cell, or to their ability to prime the cell to other pro-death stimuli such as those from the immune system. HDACi-induced apoptosis occurs through altered expression of genes encoding proteins in both intrinsic and extrinsic apoptotic pathways; through effects on the proteasome/aggresome systems; through the production of reactive oxygen species, possibly by directly inducing DNA damage; and through alterations in the tumor microenvironment. In addition HDACi increase the immunogenicity of tumor cells and modulate cytokine signaling and potentially T-cell polarization in ways that may contribute the anti-cancer effect in vivo. Here, we provide an overview of current thinking on the mechanisms of HDACi activity, with attention given to the hematological malignancies as well as scientific observations arising from the clinical trials. We also focus on the immune effects of these agents