Combined metformin-salicylate treatment provides improved anti-tumor activity and enhanced radiotherapy response in prostate cancer; drug synergy at clinically relevant doses.

Abstract

BACKGROUND:

There is need for well-tolerated therapies for prostate cancer (PrCa) secondary prevention and to improve response to radiotherapy (RT). The anti-diabetic agent metformin (MET) and the aspirin metabolite salicylate (SAL) are shown to activate AMP-activated protein kinase (AMPK), suppress de novo lipogenesis (DNL), the mammalian target of rapamycin (mTOR) pathway and reduce PrCa proliferation in-vitro. The purpose of this study was to examine whether combined MET+SAL treatment could provide enhanced PrCa tumor suppression and improve response to RT.

METHODS:

Androgen-sensitive (22RV1) and resistant (PC3, DU-145) PrCa cells and PC3 xenografts were used to examine whether combined treatment with MET+SAL can provide improved anti-tumor activity compared to each agent alone in non-irradiated and irradiated PrCa cells and tumors. Mechanisms of action were investigated with analysis of signaling events, mitochondria respiration and DNL activity assays.

RESULTS:

We observed that PrCa cells are resistant to clinically relevant doses of MET. Combined MET + SAL treatment provides synergistic anti-proliferative activity at clinically relevant doses and enhances the anti-proliferative effects of RT. This was associated with suppression of oxygen consumption rate (OCR), activation of AMPK, suppression of acetyl-CoA carboxylase (ACC)-DNL and mTOR-p70s6k/4EBP1 and HIF1α pathways. MET + SAL reduced tumor growth in non-irradiated tumors and enhanced the effects of RT.

CONCLUSION:

MET+SAL treatment suppresses PrCa cell proliferation and tumor growth and enhances responses to RT at clinically relevant doses. Since MET and SAL are safe, widely-used and inexpensive agents, these data support the investigation of MET+SAL in PrCa clinical trials alone and in combination with RT.

• Authors: Evangelia E Tsakiridis, Lindsay Broadfield, Katarina Marcinko, Olga-Demetra Biziotis, Amr Ali, Bassem Mekhaeil, Elham Ahmadi, Kanwaldeep Singh, Aruz Mesci, Panayiotis G Zacharidis, Alexander E Anagnostopoulos, Tobias Berg, Paola Muti, Gregory R Steinberg, Theodoros Tsakiridis
• Journal: Translational oncology (Transl Oncol) Vol. 14 Issue 11 Pg. 101209 (Nov 2021) ISSN: 1936-5233 [Print] United States
• PMID: 34479029 (Publication Type: Journal Article)
• Copyright: Copyright © 2021. Published by Elsevier Inc.