Matthew C. Dallos

PURPOSE: Intratumoral immunosuppression mediated by myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) represents a potential mechanism of immune checkpoint inhibitor (ICI) resistance in solid tumors. By promoting TAM and MDSC infiltration, IL1β may drive adaptive and innate immune resistance in renal cell carcinoma (RCC) and in other tumor types. EXPERIMENTAL DESIGN: Using the RENCA model of RCC, we evaluated clinically relevant combinations of anti-IL1β plus either anti-PD-1 or the multitargeted tyrosine kinase inhibitor (TKI), cabozantinib. We performed comprehensive immune profiling of established RENCA tumors via multiparameter flow cytometry, tumor cytokine profiling, and single-cell RNA sequencing (RNA-seq). Similar analyses were extended to the MC38 tumor model. RESULTS: Analyses via multiparameter flow cytometry, tumor cytokine profiling, and single-cell RNA-seq showed that anti-IL1β reduces infiltration of polymorphonuclear MDSCs and TAMs. Combination treatment with anti-IL1β plus anti-PD-1 or cabozantinib showed increased antitumor activity that was associated with decreases in immunosuppressive MDSCs and increases in M1-like TAMs. CONCLUSIONS: Single-cell RNA-seq analyses show that IL1β blockade and ICI or TKI remodel the myeloid compartment through nonredundant, relatively T-cell-independent mechanisms. IL1β is an upstream mediator of adaptive myeloid resistance and represents a potential target for kidney cancer immunotherapy.

Abstract Purpose: Previous studies suggest that androgen deprivation therapy (ADT) promotes antitumor immunity in prostate cancer. Whether a vaccine-based approach can augment this effect remains unknown. Patients and Methods: We conducted a neoadjuvant, randomized study to quantify the immunologic effects of a GM-CSF–secreting allogeneic cellular vaccine in combination with low-dose cyclophosphamide (Cy/GVAX) followed by degarelix versus degarelix alone in patients with high-risk localized prostate adenocarcinoma who were planned for radical prostatectomy. Results: Both Cy/GVAX plus degarelix and degarelix alone led to significant increases in intratumoral CD8+ T-cell infiltration and PD-L1 expression as compared with a cohort of untreated, matched controls. However, the CD8+ T-cell infiltrate was accompanied by a proportional increase in regulatory T cells (Treg), suggesting that adaptive Treg resistance may dampen the immunogenicity of ADT. Although Cy/GVAX followed by degarelix was associated with a modest improvement in time-to-PSA progression and time-to-next treatment, as well as an increase in PD-L1, there was no difference in the CD8+ T-cell infiltrate as compared with degarelix alone. Gene expression profiling demonstrated that CHIT1, a macrophage marker, was differentially upregulated with Cy/GVAX plus degarelix compared with degarelix alone. Conclusions: Our results highlight that ADT with or without Cy/GVAX induces a complex immune response within the prostate tumor microenvironment. These data have important implications for combining ADT with immunotherapy. In particular, our finding that ADT increases both CD8+ T cells and Tregs supports the development of regimens combining ADT with Treg-depleting agents in the treatment of prostate cancer.

Metformin is the most commonly prescribed drug for type II diabetes and is associated with decreased cancer risk. Previously, we showed that metformin prevented tobacco carcinogen (NNK)-induced lung tumorigenesis in a non-diabetic mouse model, which was associated with decreased IGF-I/insulin receptor signaling but not activation of AMPK in lung tissues, as well as decreased circulating levels of IGF-I and insulin. Here, we used liver IGF-I-deficient (LID) mice to determine the importance of IGF-I in NNK-induced lung tumorigenesis and chemoprevention by metformin. LID mice had decreased lung tumor multiplicity and burden compared with wild-type (WT) mice. Metformin further decreased lung tumorigenesis in LID mice without affecting IGF-I levels, suggesting that metformin can act through IGF-I-independent mechanisms. In lung tissues, metformin decreased phosphorylation of multiple receptor tyrosine kinases (RTK) as well as levels of GTP-bound Ras independently of AMPK. Metformin also diminished plasma levels of several cognate ligands for these RTKs. Tissue distribution studies using [(14)C]-metformin showed that uptake of metformin was high in liver but four-fold lower in lungs, suggesting that the suppression of RTK activation by metformin occurs predominantly via systemic, indirect effects. Systemic inhibition of circulating growth factors and local RTK signaling are new AMPK-independent mechanisms of action of metformin that could underlie its ability to prevent tobacco carcinogen-induced lung tumorigenesis.

cells when compared with patients who do not develop irAEs. These data support the hypothesis that different populations of T cells are associated with different irAEs and that characterization of these cells' pre-treatment has the potential to serve as a toxicity-specific predictive biomarker.