Grade Group 1 Prostate Cancers Exhibit Tumor-defining Androgen Receptor-driven Programs

Area of Science:

• Oncology
• Molecular Biology
• Epigenetics

Background:

• Grade group 1 (GG1) prostate cancers (Gleason score 6) are indolent with low metastatic risk, prompting debate on their cancer classification.
• The molecular drivers, particularly the androgen receptor (AR), in these low-grade tumors are not fully understood.
• Characterizing AR activity is crucial to distinguish low-grade cancers from benign prostate tissue.

Purpose of the Study:

• To delineate the androgen receptor (AR) chromatin-binding landscape in GG1 prostate cancers.
• To investigate if AR-driven molecular programs in GG1 tumors are tumor-specific or resemble normal prostate epithelium.
• To provide epigenetic insights into the classification of low-grade prostate cancers.

Main Methods:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to map AR binding sites.
• Analysis of cis-regulatory elements and enhancer activity.
• Gene expression profiling of AR target genes.

Main Results:

• GG1 tumors do not exhibit a distinct AR cistrome compared to higher-grade cancers.
• AR preferentially binds to tumor-defining cis-regulatory elements in GG1 tumors.
• Enhancer activity and target gene expression remain similar to higher-grade cancers, distinguishing them from benign tissue.

Conclusions:

• Epigenetic profiles support the cancer designation for GG1 prostate tumors.
• AR-driven molecular activity in GG1 tumors is tumor-specific and distinct from benign prostate epithelium.
• These findings clarify the biological nature of low-grade prostate cancers.