Vaccine Targeting of RCC Blood Vessels to Promote TME Normalization and Enhance TIL Recruitment

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ABSTRACT Although RCC is typically classified as an immunogenic tumor, recent profiling studies instead suggest that presence of CD8+ TIL in this form of cancer is an indicator of poor prognosis. These findings emphasize the importance of appreciating immune context/immune cell networking in the tumor microenvironment when interpreting the operational status of tumor immunity and its likely impact on disease progression and response to interventional therapy. Indeed, if one instead considers organized clusters of CD8+ T cells and mature DC- LAMP+ dendritic cells (DC) within tertiary lymphoid structures (TLS) in tumors, these lymphoid “organs” are positive prognostic indicators for overall survival/PFS in RCC patients. Tumor-associated TLS have been suggested to serve as an immune “oasis” for infiltrating lymphocytes exhibiting less-exhausted phenotypes, and as sites for in situ DC-mediated cross-priming of a diversified therapeutic CD8+ T cell repertoire. We have recently shown that vaccination against tumor-associated blood vessel antigens (TBVA) results in vascular normalization (VN; i.e. vascular trimming, reduced vascular leak/hypoxia/interstitial fluid pressure) and the de novo development of TLS within tumors in mice and humans responding to interventional vaccine-based immunotherapy. Remarkably, we have also observed that the anti-tumor efficacy of these vaccines exhibits profound gender/sexual dimorphism, with higher response rates in females (or castrated males) vs. intact males, suggesting a regulatory role for sex steroids and their receptors. Our central hypotheses are that: i.) combination immunotherapy promoting VN in RCC will enhance TLS development and the generation of a broadly-reactive therapeutic CD8+ T cell repertoire exhibiting superior “fitness” and anti-tumor efficacy, and ii.) gender dimorphic response to vaccination can be circumvented by co-administration of androgen synthesis/AR antagonists. Given a 2:1 male:female incidence of ccRCC, these latter studies are expected to dramatically expand the therapeutic utility of TBVA-targeted vaccines against RCC. We will initially perform an exploratory clinical trial to determine the impact of an autologous αDC1/peptide vaccine targeting TBVA + oral low-dose cabozantinib on VN, TLS formation and tumor-infiltrating T cell fitness in patients with recently-diagnosed primary ccRCC prior to planned surgical resection (Aim 1), before then pursuing animal models to test the hypotheses that i.) agents capable of promoting VN in murine RCC (RENCA, RENCA.VHL-/-) tumors will synergize with vaccines targeting RCC and/or TBVA antigens +/- checkpoint blockade in promoting the development of TLS, improved tumor-infiltrating T cell (TIL) fitness, an expanded TIL repertoire and superior therapeutic benefit (Aim 2) and ii.) agents capable of interrupting androgen synthesis/androgen receptor-signaling will improve therapeutic efficacy of VN-inducing immunotherapies in male/female BALB/c mice bearing RCC tumors (Aim 3).