Generation 2.5 antisense oligonucleotides targeting the androgen receptor and its splice variants suppress...

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Enzalutamide (ENZ) is effective against castration-resistant prostate cancer (CRPC).
• Resistance to ENZ often involves the androgen receptor (AR), specifically its full-length (ARFL) and variant (AR-V) forms.
• Understanding the roles of ARFL and AR-Vs in ENZ-resistant CRPC (ENZ-R CRPC) is critical for developing new therapies.

Purpose of the Study:

• To investigate the functional significance of ARFL and AR-Vs in the progression of ENZ-R CRPC.
• To evaluate the efficacy of targeting ARFL and AR-Vs using antisense oligonucleotides (ASOs).

Main Methods:

• Designed three ASOs targeting different regions of AR pre-mRNA (exon-1, intron-1, exon-8) to achieve selective or combined knockdown of ARFL and AR-Vs.
• Assessed the effects of ASO treatment on CRPC cell lines (LNCaP, 22Rv1) and patient-derived xenografts (PDX).
• Measured cell growth, apoptosis, AR transcriptional activity, and tumor growth in vivo.

Main Results:

• ENZ-R LNCaP cells exhibit significantly higher levels of ARFL than AR-V7, with both predominantly nuclear.
• Knockdown of ARFL alone, or ARFL plus AR-Vs, in ENZ-R LNCaP cells induced apoptosis, suppressed growth, and reduced AR-regulated gene expression.
• In 22Rv1 cells, combined knockdown of ARFL and AR-Vs was more potent in suppressing growth and AR activity than ARFL knockdown alone.
• Exon-1 AR-ASO treatment inhibited tumor growth in a patient-derived CRPC xenograft model.

Conclusions:

• The androgen receptor (AR) is a key driver of enzalutamide resistance in CRPC.
• While ARFL and AR-V contributions vary, ARFL plays a critical role in the ENZ-R LNCaP model.
• Targeting both ARFL and AR-Vs represents a rational therapeutic strategy for AR-dependent CRPC.