Multifactoral immune modulation potentiates durable remission in multiple models of aggressive malignancy.

Tumors typically lack canonical danger signals required to activate adaptive immunity and also frequently employ substantial immunomodulatory mechanisms that downregulate adaptive responses and contribute to escape from immune surveillance. Given the variety of mechanisms involved in shielding tumors from immune recognition, it is not surprising that single-agent immunomodulatory approaches have been largely unsuccessful in generating durable antitumor responses. Here we report a unique combination of immunomodulatory and cytostatic agents that recondition the tumor microenvironment and eliminate complex and/or poor-prognosis tumor types including the non-immunogenic 4T-1 model of TNBC, the aggressive MOC-2 model of HNSCC, and the high-risk MYCN-amplified model of neuroblastoma. A course of therapy optimized for TNBC cured a majority of tumors in both ectopic and orthotopic settings and eliminated metastatic spread in all animals tested at the highest doses. Immune responses were transferable between therapeutic donor and naïve recipient through adoptive transfer, and a sizeable abscopal effect on distant, untreated lesions could be demonstrated experimentally. Similar results were observed in HNSCC and neuroblastoma models, with characteristic remodeling of the tumor microenvironment documented in all model systems. scRNA-seq analysis implicated upregulation of innate immune responses and antigen presentation in tumor cells and the myeloid cell compartment as critical early events. This analysis also highlighted the potential importance of the autonomic nervous system in the governance of inflammatory processes. The data indicate that the targeting of multiple pathways and mechanisms of action can result in substantial synergistic antitumor effects and suggest follow-up in the neoadjuvant setting may be warranted.

Adenoviral delivery of an immunomodulatory protein to the tumor microenvironment controls tumor growth.

Targeted modulation of the immune system against tumors can achieve responses in otherwise refractory cancers, which has spurred efforts aimed at optimizing such strategies. To this end, we have previously investigated cancer immunotherapy approaches using recombinant adenovirus vectors, as well as via modulation of the self-ligand receptor SLAMF7. Here, we present a gene transfer-based immunotherapy approach using targeted expression of a SLAMF7-Fc fusion construct directly into tumors at high concentrations via a recombinant adenoviral vector (Ad-SF7-Fc). Using multiple murine cancer models, we show that Ad-SF7-Fc can induce tumor control via augmentation of innate immunity; specifically, induction of type I interferons and activation of dendritic cells (DCs) and macrophages. Analogously, we find that modulating SLAMF7 signaling via an adenoviral vector expressing its intracellular adaptor, EAT-2, is also capable of inducing tumor control. Finally, we employ a novel in vivo prediction approach and dataset integration with machine learning to dissect how Ad-SF7-Fc modulates cell-type-specific responses in the tumor microenvironment to achieve tumor control. Thus, our novel combinatorial cancer immunotherapy highlights the benefit of multimodal immune modulation and lays a framework for combination with complementary approaches capable of inducing adaptive immune responses.

SLAMF7 Signaling Reprograms T Cells toward Exhaustion in the Tumor Microenvironment.

T cell exhaustion represents one of the most pervasive strategies tumors employ to circumvent the immune system. Although repetitive, cognate TCR signaling is recognized as the primary driving force behind this phenomenon, and it remains unknown what other forces drive T cell exhaustion in the tumor microenvironment (TME). In this study, we show that activation of the self-ligand SLAMF7 immune receptor on T cells induced STAT1 and STAT3 phosphorylation, expression of multiple inhibitory receptors, and transcription factors associated with T cell exhaustion. Analysis of The Cancer Genome Atlas revealed that SLAMF7 transcript levels were strongly correlated with various inhibitory receptors and that high SLAMF7 expression was indicative of poor survival in clear cell renal cell carcinoma (ccRCC). Targeted reanalysis of a CyTOF dataset, which profiled the TME in 73 ccRCC patients, revealed cell-type-specific SLAMF7 expression patterns, strong correlations between exhausted T cells and SLAMF7+ tumor-associated macrophages (TAMs), and a unique subset of SLAMF7highCD38high TAMs. These SLAMF7highCD38high TAMs showed the strongest correlations with exhausted T cells and were an independent prognostic factor in ccRCC. Confirmatory ex vivo coculture studies validated that SLAMF7-SLAMF7 interactions between murine TAMs and CD8+ T cells induce expression of multiple inhibitory receptors. Finally, mice lacking SLAMF7 show restricted growth of B16-F10 tumors, and CD8+ T cells from these mice express less PD-1 and TOX and exhibited an impaired ability to progress through the exhaustion developmental trajectory to terminal exhaustion. These findings suggest that SLAMF7 might play an important role in modulating T cell function in the TME.

SLAMF7 Is a Critical Negative Regulator of IFN-α-Mediated CXCL10 Production in Chronic HIV Infection.

Current advances in combined antiretroviral therapy have rendered HIV infection a chronic, manageable disease; however, the problem of persistent immune activation still remains despite treatment. The immune cell receptor SLAMF7 has been shown to be upregulated in diseases characterized by chronic immune activation. In this study, we studied the function of the SLAMF7 receptor in immune cells of HIV patients and the impacts of SLAMF7 signaling on peripheral immune activation. We observed increased frequencies of SLAMF7+ PBMCs in HIV+ individuals in a clinical phenotype-dependent manner, with discordant and long-term nonprogressor patients showing elevated SLAMF7 levels, and elite controllers showing levels comparable to healthy controls. We also noted that SLAMF7 was sensitive to IFN-⍺ stimulation, a factor elevated during HIV infection. Further studies revealed SLAMF7 to be a potent inhibitor of the monocyte-derived proinflammatory chemokine CXCL10 (IP-10) and other CXCR3 ligands, except in a subset of HIV+ patients termed SLAMF7 silent (SF7S). Studies utilizing small molecule inhibitors revealed that the mechanism of CXCL10 inhibition is independent of known SLAMF7 binding partners. Furthermore, we determined that SLAMF7 activation on monocytes is able to decrease their susceptibility to HIV-1 infection in vitro via downregulation of CCR5 and upregulation of the CCL3L1 chemokine. Finally, we discovered that neutrophils do not express SLAMF7, are CXCL10+ at baseline, are able to secrete CXCL10 in response to IFN-⍺ and LPS, and are nonresponsive to SLAMF7 signaling. These findings implicate the SLAMF7 receptor as an important regulator of IFN-⍺-driven innate immune responses during HIV infection.