Abstract 5219: Kaiso as a novel therapeutic target in castration-resistant prostate cancer (CRPC)

Androgen receptor (AR) is a critical driver in the progression of prostate cancer (PCa). Androgen deprivation therapy(ADT) has been a standard treatment of PCa. However, the PCa develops to castration resistant prostate cancer (CRPC) in almost 53% of patients after 18-32 month’s therapy. Metastatic CRPC has poor prognosis and mean survival time is fewer than 2 years. Kaiso belongs to a BTB/POZ zinc finger protein family and is known as a transcriptional repressor. Kaiso expression and localization have been reported to correlate with the prognosis and metastatic potential in several human malignancies. Previous works from our lab have demonstrated that transcription factor Kaiso was upregulated in the progression of PCa. Therefore, our objective is to explore the interrelationship between Kaiso and AR, further to clarify Kaiso as a potential therapeutic target in PCa progression and CRPC. To investigate molecular mechanisms underlying how aberrant expression of Kaiso contributes to CRPC, the androgen sensitive human prostate cancer LNCaP cells were treated with 10µM anti-androgen Enzalutamide (MDV3100). Kaiso expression levels were increased as detected by RT-PCR and immunofluorescence. To systematically investigate Kaiso targets in PCas, we performed Kaiso ChIP-Seq assay using prostate cancer cell lines LNCaP, C4-2B and PC3. The Kaiso ChIP-Seq peaks indicate androgen receptor motif enrichment in AR expressing LNCaP and C4-2B cells but not in AR-negative PC3 cells, indicating Kaiso could cooperate with AR as co-regulator and potentially control transcription of a subset of its target genes. The interaction of them was confirmed by co-immunoprecipitation of AR using Kaiso antibody in LNCaP cells. To identify Kaiso target genes that interacted with AR pathway, Kaiso knockdown and overexpression stable cell lines were established in LNCaP cells and C42B cells. RT2 Profiler PCR array of AR pathway were performed using LNCaP scramble (LNCaP-Scr) cells and shKaiso cells. The results showed multiple genes were upregulated and downregulated, such as FOLH1, PTEN, RAC3 and IGF1. More importantly, LNCaP Kaiso overexpression cells were more resistant to MDV3100 treatment compared to resistance observed in LNCaP-Scr cells. There were significant negative correlations between Kaiso expression levels and castration-sensitivity. Our results suggest that Kaiso is a novel AR-interacting protein. Kaiso regulates the genes in AR pathway. Targeting Kaiso presents a potential therapeutic strategy for disrupting AR signaling in CRPC and may prevent CRPC development. These studies were supported by grants U54MD007585, (NIH/RCMI) [CY], U54CA118623-01 (NIH/NCI) [CY] Citation Format: Hui-Xian Lin, Honghe Wang, Jason White, Balasubramanyam Karanam, Anghesom Ghebremedhin, Benjamin Adu Addai, William E. Grizzle, Clayton Yates. Kaiso as a novel therapeutic target in castration-resistant prostate cancer (CRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5219.