Background: Emergence of hormone-refractory PrCa (HRPC) after the anti-androgen therapy, cancer metastasis and chemo-resistance are the major hurdle for the treatment of prostate cancer (PrCa) patients. Accumulative evidence suggests that altered glucose metabolism is one of the mechanisms for metastatic PrCa cell survival and chemo-resistance. Therefore, identification and generation of natural/or synthetic pharmacological agents that can limit altered glucose metabolism might be highly useful for the treatment of metastatic and chemo-resistant PrCa. Cucurbitacins have shown potent anti-cancer and glucagonostic activities along with severe liver toxicity. Thus, a focus on developing different analogues of cucurbitacin is being pursued by scientific community. Herein, we report that Cucurbitacin D, an analogue of cucurbitacin, suppresses the growth of metastatic PrCa cells in vitro and in vivo via targeting glucose metabolism and its associated molecular targets.

Methods: HRPC cells (PC3 and DU145) was used as a model system. Effect of Cucurbitacin D on PrCa cell proliferation and apoptosis was performed by MTS, xCELLigence and Annexin V assays. Effect of Cucurbitacin D on clonogenic potential of PrCa cells was examined by colony formation assay. In silico analysis was performed to study if Cucurbitacin D interacts with GLUT1 receptor. Effect of Cucurbitacin D on glucose metabolism of PrCa cells was performed by metabolic shift, glucose and lactate uptake assays. Effect of Cucurbitacin D treatment on key molecules of cell survival and glucose metabolism signaling pathways in PrCa cells was analyzed by Western blot and qRT-PCR analyses. Therapeutic efficacy of Cucurbitacin D against PrCa was evaluated in an ectopic PrCa xenograft mouse model.

Results: Cucurbitacin D (0.1 to 1 µM) treatment significantly (P<0.01) inhibited the growth and metastatic potential of PrCa cells in a dose-dependent manner. Cucurbitacin D effectively induced apoptosis in PrCa cells as shown by enhanced Annexin V staining and PARP protein cleavage and arrested cells in G2/M phase via modulation of cell cycle regulatory proteins (inhibition of cyclin D1/E and Mcl-1 and induction of p21 and p27). Cucurbitacin D treatment dose-dependently decreased the lactate production, glucose uptake in PrCa cells which was correlated by suppressed expression of GLUT1 and its proficient docking with GLUT1 (with binding energy for this complex is -8.5 kcal mol-1). It has been reported that miR-132 targets the GLUT1, interestingly, Cucurbitacin D replenished the expression of miR-132 in PrCa cells. These growth inhibitory effects of Cucurbitacin D were confirmed in PrCa xenograft mouse model while administered intra-tumorally (1 mg/kg body weight thrice/week).

Conclusion: Our results suggest that Cucurbitacin D is a novel modulator of glucose metabolism which could be a promising therapeutic modality alone or in combination of conventional chemotherapeutic agents for PrCa.

Citation Format: Mohammed Sikander, Bilal Bin Hafeez, Shabnam Malik, Aditya Ganju, Fathi T. Halaweish, Murali Mohan Yallapu, Subhash C. Chauhan, Meena Jaggi. Cucurbitacin D inhibits prostate tumor growth via targeting glucose metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3224. doi:10.1158/1538-7445.AM2017-3224