Cholesterol-driven enhancement of the androgenic axis and the suppressive role of miR-137 in p160 coactivators on prostate cancer

Author(s)

Ruan Cesar Aparecido Pimenta

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2023-08-25

Examining board members

Sabrina Thalita dos Reis Faria; Katia Ramos Moreira Leite

• Advisor: Sabrina Thalita dos Reis Faria

Abstract

INTRODUCTION: Elevated cholesterol levels can influence prostate cancer (PCa), which leads to alterations in the intratumoral androgen signaling pathway. In addition to being a precursor molecule for synthesizing steroid hormones, cholesterol can accumulate and interact with the androgen receptor (AR), further enhancing its activity. Understanding these molecular mechanisms in castration-resistant prostate cancer is not fully elucidated. Some coactivators of AR, such as those belonging to the p160 family, SRC-1, SRC-2, and SRC-3, are involved in modulating cholesterol metabolism in prostate cancer cells and can affect AR transactivation activity. Moreover, the interaction between coactivators and AR can be influenced by microRNAs, small RNA molecules that regulate gene expression. Recent studies have suggested that certain microRNAs are involved in AR regulation and may play a role in modulating cholesterol metabolism in cancer cells. Specifically, miR-137 has binding regions for all three components of the p160 family and exhibits antiproliferative activity in PCa. Therefore, investigating the effect of cholesterol and miR-137 on p160 coactivators and AR may provide essential insights for understanding and treating castration-resistant prostate cancer. OBJECTIVES: This study aimed to investigate the impact of cholesterol on AR coactivators and explore the potential suppressive effect of miR-137 in PCa, including an animal model with diet-induced hypercholesterolemia. METHODS: The effect of cholesterol on AR coactivators (SRC-1, SRC-2, SRC-3) was studied in PC-3 cells. Coactivator gene expression was analyzed using qPCR after exposure to 2 g/mL of cholesterol for 8 hours. Cell migration, viability, apoptosis, and cell cycle were assessed through flow cytometry assays. Protein expression of AR coactivators was evaluated by immunofluorescence and Western blot. In vivo experiments were conducted using male NOD/SCID mice fed a standard diet (SD) or a hypercholesterolemic diet (HCOL). Tumor growth, serum lipid profile, intratumoral lipid profile, and expression of p160 coactivators and AR were assessed at the end of the experiment, along with the effect of miR-137 on the HCOL-induced CPRC model administered intratumorally. RESULTS: Cholesterol supplementation positively induced gene expression of SRC-1, SRC-2, and SRC-3 coactivators, leading to increased AR expression in PC-3 cells. Cholesterol-supplemented cells showed enhanced migration, altered cell cycle phases, increased proliferation, and reduced apoptosis. Data related to PC-3 cell treatment with miR-137 indicated that this miRNA could inhibit gene and protein expression of p160 coactivators and AR. Following these findings, we demonstrated that miR-137 induction inhibits cell migration and invasion, has a negative impact on proliferation rate, and induces increased levels of apoptosis. In the in vivo model, the HCOL group exhibited higher serum and intratumoral cholesterol levels, increased concentrations of testosterone and dihydrotestosterone, and increased expression of p160 coactivators and AR. Tumor volume was significantly more significant in the HCOL group when compared to the SD group. In the miR-treated models, the SD and HCOL groups displayed reduced tumor growth rates after the intratumoral restoration of miR-137 and decreased proliferation levels. CONCLUSIONS: Overall, cholesterol supplementation of PC-3 cells led to increased gene and protein expression of p160 coactivators and AR, significantly impacting cell proliferation, reducing apoptosis levels, and increasing tumor volume in the in vivo model. Treatment with miR-137 was able to suppress the expression of p160 (AU)

• FAPESP's process: 19/00156-7 - In vivo study of co-activators and co-repressors of androgen receptor in Prostate Câncer
• Grantee: Ruan César Aparecido Pimenta
• Support Opportunities: Scholarships in Brazil - Doctorate