Abstract 121: Differential resistance to hypoxia is linked to increased lipid accumulation in treatment resistant prostate cancer cells
Authors: Siltari Aino , Bläuer Merja , Syvälä Heimo , Tammela Teuvo L. , Murtola Teemu J. 
Published: June 2022

Introduction: Solid tumors typically favor non-oxygen related pathways on utilizing energy for cell metabolism. This helps tumor cells to survive in hypoxic microenvironment which is common in solid tumors such as prostate cancer (PCa). PCa cells characteristically store lipids, especially cholesterol. Furthermore, hypoxia and lipid metabolism are both associated with decreased responses to immune system and resistance to cancer treatments. Aim of this study was to investigate the impact of hypoxia on cell proliferation and lipid metabolism in advanced PCa cells at various stages of treatment resistance.

Material and Methods: PCa cells, VCaPs, were cultured for months to form several unique, treatment resistant advanced PCa cell lines as follows: first, cells were cultured with high (10 nM) testosterone level until they required testosterone for growth to form testosterone sensitive cell line (VCaP-T, demonstrating metastatic hormone sensitive PCa); second, VCaP-T cells were cultured further under low testosterone (0.1 nM) until they gained ability to grow at low androgen level, forming castration resistant cell line (VCaP-CT); third, VCaP-CT cells were further cultured with bicalutamide and/or enzalutamide, androgen signaling inhibitors, until they again gained ability to grow despite the treatment, forming cell lines resistant to these drugs (VCaP-CT-BR, VCap-CT-ER, and VCaP-CT-BR-ER, demonstrating bicalutamide-, enzalutamide-, or mutually resistant cell lines, respectively).All cell lines were exposed to hypoxia (3% O2) with or without simvastatin (1 and 2.5 μM) for 3 days and compared to the cells growing in normoxia. Changes in proliferation was measured using crystal violet staining and amount of intracellular lipids were evaluated using Oil Red O staining.

Results: Hypoxia decreased cell proliferation compared to normoxia by 20-25% in VCaP-T, VCaP-CT, and VCaP-CT-BR cells, but had no impact in enzalutamide-resistant cells VCaP-CT-ER or VCaP-CT-BR-ER. Simvastatin treatment decreased cell proliferation in all cell lines equally in hypoxia and normoxia.Compared to androgen-sensitive VCaP-T cells, all treatment resistant cell lines displayed greater intracellular lipid accumulation. Further analyses will address whether hypoxia and/or simvastatin treatment impacts amount of intracellular lipids and whether inhibition of lipid accumulation leads to less tolerance to hypoxia.

Conclusion: Enzalutamide resistant cell lines displayed greater hypoxia tolerance compared to androgen sensitive or treatment naïve castration resistant cells. This indicates these cells are adopted to hypoxic microenvironment. All treatment resistant cell lines had greater intracellular lipid accumulation compared to testosterone-sensitive cells, suggesting importance of lipid metabolism in treatment resistance and hypoxia tolerance.

Citation Format: Aino Siltari, Merja Bläuer, Heimo Syvälä, Teuvo L. Tammela, Teemu J. Murtola. Differential resistance to hypoxia is linked to increased lipid accumulation in treatment resistant prostate cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 121.