Introduction/Rationale: Clear cell renal carcinoma (ccRCC) is known to carry a hypoxic tumor microenvironment (TME). Hypoxia-associated tumor associated macrophages (TAMs) are considered drivers of therapy resistance in ccRCC. We discovered nuclear protein 1 (NUPR1), a known pro-tumor factor in ccRCC, is highly expressed in hypoxic TAMs across multiple transcriptomics datasets. This study aims to assess whether inhibiting NUPR1 can drive hypoxic TAMs to downregulate pro-tumor markers, improving treatment outcomes for immune checkpoint blockade (ICB) in ccRCC.
Methods: We used a novel in-vivo model of kidney cancer -- LVRCC647 – which transcriptionally carried genes detected in patients resistant to ICB. Mice were given PD-1 and CTLA-4 blockade combination therapy with or without ZZW-115 -- an NUPR1 inhibitor -- then monitored for survival and tumor growth. We used bone marrow derived macrophages (BMDMs) ex vivo cultures polarized to become either naïve macrophage (M0) or TAMs with tumor conditioned media (TCM) in 2% oxygen condition to mimic hypoxia, with or without ZZW-115 treatment to assess the TAMs specific effects of NUPR1 inhibition.
Results: NUPR1 inhibition exhibited synergistic effects with ICB in vivo by increasing survival of B6 mice injected with LVRCC647 tumors, and tumor volumes also decreased compared to untreated groups and ICB alone. Inhibiting NUPR1 in an in-vitro setting could also ablate hypoxic TAMs Arg1 expression, suggesting that NUPR1 plays a key role in driving TAM immunosuppression particularly in hypoxic tumor regions. A novel BMDMs culture protocol was also discovered to be effective, with pro-tumor phenotypes shown the combination of tumor conditioned media and hypoxia (2% O2), without the conventional supplementation of anti-inflammatory cytokines such as IL-4 and IL-10.
Conclusion: Our findings revealed the potentials for NUPR1 inhibition to drive TAMs towards anti-tumor responses, promoting immunotherapy response in ccRCC.
