Abstract 1779: PCDH7 and SET are overexpressed in prostate cancer and promote aberrant MEK and AKT signaling
Authors: Shishodia Gauri , Koul Sweaty , Koul Hari K. 
Published: August 2019

Introduction: Most of prostate cancer (PCa) deaths are a result of distant metastasis. Aberrant activation of AKT and MEK play an important role in PCa progression. PCDH7, a cadherin superfamily transmembrane protein, is involved in cell-cell recognition and adhesion. Recent reports suggest overexpression of PCDH7 promotes metastasis in lung and breast cancer and PCDH7 was shown to interact with SET in lung cancer. Overexpression of SET promoted cell proliferation, survival, drug resistance, invasion and metastasis in different cancers. We evaluated expression and function of PCDH7 and SET in PCa.

Materials and Methods: PCDH7 and SET expression in clinical samples was extracted from publically available data sets (CRPC/NEPC-Trento et al 2016; TCGA, Cell 2015; adenocarcinoma- MSKCC, Cancer Cell 2010 using cBioPortal and UALCAN). PCa cells- LNCaP, C4-2B, DU145, PC3, 22Rv1 and RWPE1 were used in this study. Protein expression was measured by Western blotting in cell lines and immunohistochemistry in FFPE TRAMP and human prostate tissue sections. Gene expression was monitored by quantitative real time PCR. Gene knock down was performed by shRNA using lentiviral expression. Colony formation was assessed by staining with 0.4% crystal violet after 3 weeks of cell seeding. Co-IP studies were performed to check interactions of PCDH7 with SET and PP2A.

Results: Our results show that PCDH7 mRNA is overexpressed in 43% patients in CRPC as compared to 4% of patients in TCGA data set. SET was amplified in 23% of NEPC patients (Trento, 2016), mRNA upregulation in more than 5% adenocarcinoma patients (TCGA, 2015 and MSKCC, 2010). TCGA dataset showed that SET expression is high in tumor samples of adenocarcinoma patients as compared to normal prostate and increase in SET expression was observed with increase in Gleason score (UALCAN). PCDH7 mRNA and protein is overexpressed in CRPC (C4-2B, 22Rv1, DU145 and PC3) cells as compared to castrations sensitive (LNCaP) cells and normal prostate (RWPE1) cells. We also observed increased expression of PCDH7 in prostate tissues of TRAMP mice during PCa progression as well as human PCa as compared to normal tissues. We observed that knocking down PCDH7 and SET decreased colony formation. Co-IP studies revealed that PCDH7 interacts with SET and PP2A. We observed that knocking down PCDH7 reduced ERK and AKT activities, decreased cell migration, reduced cell invasion, and decreased colony formation. Co-IP studies revealed that PCDH7 interacts with SET and PP2A suggesting that PCDH7 could be promoting aberrant ERK and AKT activities upon interaction with SET and PP2A. Collectively, these data suggest PCDH7 and SET are overexpressed in PCa and promotes aberrant activation of ERK/AKT signaling in CRPC.

Conclusion: Our results, for the first time, show overexpression of PCDH7 and SET promotes PCa progression, as such PCDH7 may be an attractive target for therapeutic intervention in subsets of CRPC patients.

Citation Format: Gauri Shishodia, Sweaty Koul, Hari K. Koul. PCDH7 and SET are overexpressed in prostate cancer and promote aberrant MEK and AKT signaling [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 1779.