Exploring STEAP1 Expression in Prostate Cancer Cells in Response to Androgen Deprivation and in Small Extracellular...

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Six-transmembrane epithelial antigen of the prostate (STEAP) metalloreductases (STEAP1, STEAP2) are therapeutic targets in advanced prostate cancer.
• STEAP expression is linked to androgen receptor (AR) signaling, but regulatory mechanisms and functions in prostate cancer progression are unclear.

Purpose of the Study:

• To investigate the influence of androgen modulation and AR inhibition on STEAP family member expression in prostate cancer cells.
• To examine STEAP1 and STEAP2 expression in small extracellular vesicles (sEVs) derived from prostate cancer cells and in circulation.

Main Methods:

• In vitro androgen modulation and AR inhibition experiments on prostate cancer cell lines.
• Analysis of STEAP family member transcript levels in response to androgen deprivation.
• Evaluation of STEAP1 and STEAP2 expression in cell-derived and circulating sEVs.
• Ex vivo analysis of circulating sEVs from genetically engineered mouse models of prostate cancer.

Main Results:

• Androgen deprivation elevated STEAP1 and STEAP2 transcript levels, while reducing STEAP4, mirroring KLK3 expression.
• STEAP1, but not STEAP2, was upregulated in sEVs from both AR-negative and AR-positive cells.
• Selective packaging of STEAP1 into sEVs occurred irrespective of cellular STEAP1 levels and AR status.
• Circulating sEVs in mice with prostate cancer contained STEAP1, independent of prostatic β1 integrin expression.

Conclusions:

• STEAP1 exhibits selective packaging into extracellular vesicles in prostate cancer.
• STEAP1 levels in circulating sEVs are independent of AR status and β1 integrin expression.
• Understanding androgen dependence of STEAP1 in tumor cells and sEVs may guide combinatorial therapies.