D-mannose augments targeted radioligand-immunotherapy of prostate cancer by enhancing radiosensitivity and reshaping immune microenvironment.

Targeted radioligand therapy (TRT) is an emerging therapeutic modality for advanced tumors like metastatic castration-resistant prostate cancer. The patients bare, however, varying degrees of resistance to TRT, which would greatly lessen the treatment efficacy and response rate. Here, we find that oral medication of D-mannose effectively enhances the radiosensitivity of PSMA-positive murine RM1-hPSMA prostate cancer cells to TRT by suppressing glucose metabolism. This metabolic disruption not only impeded the proliferation of RM1-hPSMA cells but also augmented DNA damage within tumor cells subjected to TRT, co-promoting cell apoptosis. Interestingly, TRT-D-mannose combination strongly boosted the anti-tumor immune responses by inducing immunogenic cell death, disrupting the immune evasion mechanisms employed by tumor cells, and reducing immunosuppressive cells in the tumor. D-mannose significantly improved the TRT efficacy for highly aggressive murine RM1-hPSMA and human LNCaP Clone FGC models, without causing adverse effects. Hence, D-mannose is potentially a safe radio-sensitizer and a potent immune activator for TRT.