Abstract 5414: RNA sequencing reveals that CYP3A5 siRNA treatment induces cell cycle blockade and senescence in MDAPCa2b human prostate cancer cells
Authors: Tillett Richard L. , Shen Shirley , Oh Edwin C. , Goodman Oscar B. , Mitra Ranjana 
Published: June 2022

Background: Previously we have demonstrated that CYP3A5 inhibition blocks prostate cancer (PC) cell growth partly by attenuating androgen receptor (AR) activation and downstream signaling. We further investigated whether CYP3A5 inhibition blocks PC cell growth independently of AR signaling. Initially, most PCs respond to androgen deprivation therapy (ADT), but eventually PC becomes castration resistant and does not respond to ADT. With very limited options available for patients with castration resistant prostate cancer (CRPC), there is an urgent need for the development of novel targeted therapies for this subtype of PC. Additionally, understanding the role of CYP3A5 as promoter of PC growth in African Americans (AA) is very relevant as AAs preferentially carry wild type CYP3A5 gene, often present with aggressive disease, and have higher mortality rate versus Caucasian (CA) patients, who typically express the mutant CYP3A5.

Method: We used MDAPCa2b PC cell line of AA origin carrying one copy of wild type CYP3A5 for our study. After inhibiting the CYP3A5 using siRNA pool of 3 siRNAs, we performed Illumina RNA sequencing. Differentially expressed genes (DEGs) between non-target and CYP3A5 siRNA triplicate samples were identified using DESeq2, at a false discovery rate of adjusted p &lt; 0.05. Furthermore, KEGG pathway analysis was performed to identify the roles of the differentially expressed genes in regulating prostate cancer growth.

Results: We identified 1814 DEGs after inhibiting CYP3A5 using siRNA pool in MDAPCa2b cells, 825 of which increased or decreased expression greater than two-fold. The differentially down-regulated genes associate with several growth regulatory pathways: cell cycle progression (39), cellular senescence (16) DNA replication (18) and base excision repair (9). Additionally, we identified that CYP3A5 siRNA downregulates several genes which are dysregulated (including oncogenes and tumor suppressors) in different cancer type including RAS, c-Met, ERBB2, FGFR2, cyclin E, p53, Myc, PTEN, RARβ and CDK2. The upregulated genes correspond to two pathways, retinol metabolism pathway (arrests proliferation) and steroid hormone biosynthesis. We also identified several unique genes which are down regulated with CYP3A5 siRNA treatment like Glo1, FoxM1 (often upregulated in several cancers) and Tk1 (marker for chemotherapy sensitivity).

Conclusion: CYP3A5 siRNA inhibits several genes involved in cell growth and proliferation. Targeting CYP3A5 represents a potential novel therapeutic approach, especially for AAs expressing wild type CYP3A5.

Citation Format: Richard L. Tillett, Shirley Shen, Edwin C. Oh, Oscar B. Goodman Jr., Ranjana Mitra. RNA sequencing reveals that CYP3A5 siRNA treatment induces cell cycle blockade and senescence in MDAPCa2b human 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 5414.