7P - ACOX2 disturbs the stability of MRE11-RAD50-NBS1 complex and shapes activated immune tumor microenvironment in clear cell renal cell carcinoma

Background

Clear cell renal cell carcinoma (ccRCC), accounting for 80% of renal cell carcinoma (RCC) cases, is a common and deadly urological cancer. Only a small proportion of ccRCC patients obtain durable benefits from immunotherapy. Therefore, exploring novel predictive biomarkers for immunotherapy would be beneficial in guiding personalized clinical management for ccRCC patients.

Methods

The mass spectrum (MS) analyzation, co-immunoprecipitation (Co-IP), immunocytochemistry (ICC) are conducted to identify and confirm the interaction of ACOX2 and MRE11. The protein markers are detected by western blot (WB) and ICC to evaluate the effects of ACOX2 on homologous recombination repair (HRR) and double-strand break (DSB). Picogreen dyeing, WB, ELISA, and immunohistochemistry (IHC) are applied to test the role of ACOX2 in cGAS-STING pathway. Multiple immunohistochemistry (mIHC) and multiple immunofluorescence (mIF) are conducted to assess the association of ACOX2 expression and tertiary lymphoid structures (TLS) maturity. IC50 and clone formation assay are carried out to detected the sensitivity of PARPi to ccRCC cells with different expression level of ACOX2. Patient-derived organoids (PDOs), patient-derived xenografts (PDXs), and immunocompetent mouse models are applied to investigate the predictive value of ACOX2 to the therapeutic effect of PARPi plus anti-PD-1 antibody combination therapy in ccRCC.

Results

ACOX2 interacts with MRE11 and inhibits the binding of MRE11 and RAD50, thereby disturbing the stability of MRE11-RAD50-NBS1 (MRN) complex. Over-expressed of ACOX2 inhibits the HRR efficiency and causes the accumulation of DSBs in ccRCC cells. Furthermore, ACOX2 activates the cGAS-STING pathway and induces the formation of more mature TLS, contributing to immune-activated tumor microenvironment in ccRCC. Therapeutically, ACOX2 augments the efficacy of PARPi plus anti-PD-1 antibody combination therapy in vivo.

Conclusions

Our findings reveal a key inhibiting role of ACOX2 in HRR and suggest that the combination therapy of PARPi plus ICI could be a promising treatment strategy for ccRCC patients with elevated ACOX2 expression.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.