S-nitrosylation of CSF1 receptor increases the efficacy of CSF1R blockage against prostate cancer

Abstract

Sustained oxidative stress in castration-resistant prostate cancer (CRPC) cells potentiates the overall tumor microenvironment (TME). Targeting the TME using colony-stimulating factor 1 receptor (CSF1R) inhibition is a promising therapy for CRPC. However, the therapeutic response to sustained CSF1R inhibition (CSF1Ri) is limited as a monotherapy. We hypothesized that one of the underlying causes for the reduced efficacy of CSF1Ri and increased oxidation in CRPC is the upregulation and uncoupling of endothelial nitric oxide synthase (NOS3). Here we show that in high-grade PCa human specimens, NOS3 abundance positively correlates with CSF1-CSF1R signaling and remains uncoupled. The uncoupling diminishes NOS3 generation of sufficient nitric oxide (NO) required for S-nitrosylation of CSF1R at specific cysteine sites (Cys 224, Cys 278, and Cys 830). Exogenous S-nitrosothiol administration (with S-nitrosoglutathione (GSNO)) induces S-nitrosylation of CSF1R and rescues the excess oxidation in tumor regions, in turn suppressing the tumor-promoting cytokines which are ineffectively suppressed by CSF1R blockade. Together these results suggest that NO administration could act as an effective combinatorial partner with CSF1R blockade against CRPC. In this context, we further show that exogenous NO treatment with GSNOR successfully augments the anti-tumor ability of CSF1Ri to effectively reduce the overall tumor burden, decreases the intratumoral percentage of anti-inflammatory macrophages, myeloid-derived progenitor cells and increases the percentage of pro-inflammatory macrophages, cytotoxic T lymphocytes, and effector T cells, respectively. Together, these findings support the concept that the NO-CSF1Ri combination has the potential to act as a therapeutic agent that restores control over TME, which in turn could improve the outcomes of PCa patients.

The Dual Roles of S-Nitrosylation of Proteins in Cancer: Molecular Mechanisms and Recent Advancements

“…Nitric oxide S-nitrosylates CSF1R to induce tumor inhibitory functions. The study proves that GSNO promoted the nitrosylation of the three sites (Cys224, Cys278, and Cys830) on CSF1R, and then it effectively suppressed the tumor of prostatic cancer [36,37]. Increased NO levels augment the action of CSF1R inhibition in the suppression of prostatic cancer (Figure 2).…”

“…CSF1/CSF1R signaling mediates tumorassociated macrophages recruitment and M2 polarization [36]. CSF1R signaling via CSF1 regulates the production and differentiation of most circulating and tissue resident macrophages, where S-nitrosylation of CSF1R mediated by nitric oxide can induce tumor-suppressive functions [37].…”

“…Blocking the interaction between immune receptors and ligands has emerged as an effective paradigm for cancer immunotherapy [38]. CSF1R blockade restrain the progression of some tumours [37]. Uncoupled NOS3 could negatively influence the anti-tumor effectiveness of CSF1R blockade therapy against CRPC [37].…”

“…CSF1R blockade restrain the progression of some tumours [37]. Uncoupled NOS3 could negatively influence the anti-tumor effectiveness of CSF1R blockade therapy against CRPC [37].…”

“…Cells treated with GSNO suggesting that an exogenous increase in NO could inhibit macrophage polarization in-vitro, increased the percentage of M1 macrophages, reduced the percentage of M2 macrophages, rescue increased oxidation, inhibit macrophage polarization and have tumor inhibitory effects against CRPC [37].…”