Synergistic antitumor interaction of valproic acid and simvastatin sensitizes prostate cancer to docetaxel by targeting CSCs compartment via YAP inhibition

Abstract

Background Despite the introduction of several novel therapeutic approaches that improved survival, metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease. Herein we report the synergistic antitumor interaction between two well-known drugs used for years in clinical practice, the antiepileptic agent with histone deacetylase inhibitory activity valproic acid and the cholesterol lowering agent simvastatin, in mCRPC models. Methods Synergistic anti-tumor effect was assessed on PC3, 22Rv1, DU145, DU145R80, LNCaP prostate cancer cell lines and EPN normal prostate epithelial cells, by calculating combination index (CI), caspase 3/7 activation and colony formation assays as well as on tumor spheroids and microtissues scored with luminescence 3D-cell viability assay. Cancer stem cells (CSC) compartment was studied evaluating specific markers by RT-PCR, western blotting and flow cytometry as well as by limiting dilution assay. Cholesterol content was evaluated by 1H-NMR. Overexpression of wild-type YAP and constitutively active YAP5SA were obtained by lipofectamine-based transfection and evaluated by immunofluorescence, western blotting and RT-PCR. 22Rv1 R_39 docetaxel resistant cells were selected by stepwise exposure to increasing drug concentrations. In vivo experiments were performed on xenograft models of DU145R80, 22Rv1 parental and docetaxel resistant cells, in athymic mice. Results We demonstrated the capacity of the combined approach to target CSC compartment by a novel molecular mechanism based on the inhibition of YAP oncogene via concurrent modulation of mevalonate pathway and AMPK. Because both CSCs and YAP activation have been associated with chemo-resistance, we tested if the combined approach can potentiate docetaxel, a standard of care in mCRCP treatment. Indeed, we demonstrated, both in vitro and in vivo models, the ability of valproic acid/simvastatin combination to sensitize mCRPC cells to docetaxel and to revert docetaxel-resistance, by mevalonate pathway/YAP axis modulation. Conclusion Overall, mCRPC progression and therapeutic resistance driven by CSCs via YAP, can be tackled by the combined repurposing of two generic and safe drugs, an approach that warrants further clinical development in this disease.

Statins: a repurposed drug to fight cancer

“…Taccioli et al identified that dasatinib and statins are an effective combined strategy for inhibiting YAP/TAZ in cancer cells by interrogating the Mutations and Drugs Portal (MDP) [ 298 ]. Iannelli et al demonstrated the ability of the valproic acid/simvastatin combination to sensitize metastatic castration-resistant prostate cancer cells to docetaxel and to revert docetaxel-resistance through mevalonate pathway/YAP axis modulation using both in vitro and in vivo models [ 299 ]. Adriamycin-based chemotherapy is the first-line treatment for osteosarcoma, but most patients will experience tumor recurrence and metastasis.…”

Valproic Acid: A Promising Therapeutic Agent in Glioma Treatment

“…Gathering evidence demonstrated that synergistic antitumor effects of VPA and other therapeutic agents have been explored. The combination therapy of VPA and simvastatin sensitized prostate cancer cells via YAP inhibition (6). VPA and Arsenic Trioxide were verified to induce cell-cycle arrest at the G2/M phase and apoptotic cell death in lung cancer (88).…”

“…Valproic acid (VPA), one of the most common histone deacetylase inhibitors (HDACIs), is known as an anticonvulsant and mood-stabilizing drug clinically (5). Gathering evidence have manifested that VPA directly or synergistically exerted anti-tumor effects on various solid tumors (6,7). For instance, VPA suppressed gastric cancer cell proliferation and induced autophagy through HDAC1/PTEN/Akt signaling (8).…”

“…For instance, VPA suppressed gastric cancer cell proliferation and induced autophagy through HDAC1/PTEN/Akt signaling (8). Similarly in breast cancer, the inhibitory role of VPA is mainly reflected in cellular Abbreviations: VPA, valproic acid; OS, overall survival; PFS, progression-free survival; HDACIs, histone deacetylase inhibitors; GSCs, glioma stem cells; EMT, epithelial-mesenchymal transition; MMPs, matrix metalloproteinases; AIF, apoptosis-inducing factor; PARP, poly ADP-ribose polymerase; EM, electron microscopy; VEGF, vascular endothelial growth factor; HDAC, histone deacetylase; MT1, melatonin 1; MeCP2, methyl CpG binding protein 2; H3, histone 3; BDNF, brain-derived neurotrophic factor; GDNF, glial cell line-derived neurotrophic factor; TMZ, temozolomide; MGMT, O 6 -methylguanine-DNA methyltransferase; EGFR, epidermal growth factor receptor; LC3-II, light chain 3-II; LKB1, liver kinase-B1; AMPK, AMP-activated protein kinase; ICIs, immune checkpoint inhibitors; EHV-1, equine herpesvirus type 1; DNMTi, DNA-methyltransferase inhibitors; HSV-TK, herpes simplex virus type I thymidine kinase; DIPG, diffuse intrinsic pontine glioma; AED, anti-epilepsy drug; BTE, brain tumor-related epilepsy; FGR, fluorescence-guided resection; AR, amphiregulin. proliferation, cell cycle, and apoptosis via Hsp70 acetylation (9), while in most cancers, VPA tended to serve as an adjuvant drug for chemotherapy, radiotherapy, and other therapies.…”

Overcoming Drug Resistance in Advanced Prostate Cancer by Drug Repurposing

“…Ianelli et al demonstrated the synergistic effects of simvastatin and valproic acid in sensitizing PCa to docletaxel and decreasing resistance rates. This combination method targets the CSCs by inhibiting the action of the Yes-associated protein (YAP) oncogene, a transcriptional regulator implicated in many cancers, including PCa [ 143 , 144 ]. Zhuang et al demonstrated that simvastatin acts to promote apoptosis via cholesterol depletion.…”