Abstract 4960: ERp46 (thioredoxin domain-containing protein 5, TXND5) promotes prostate cancer growth in vitro and in vivo
Authors: Pinthus Jehonathan H. , Hopmans Sarah N. , Federov Stephanie , Duivenvoorden Wilhelmina C. 
Published: August 2015

We have recently demonstrated that endoplasmic reticulum protein ERp46, a member of the protein disulfide isomerase family of oxidoreductases, TXND5, is overexpressed in human metastatic renal cell carcinoma. The expression and function of ERp46 in prostate cancer has not been studied. Using both in vitro and in vivo approaches, we explore the suitability of ERp46 as a potential therapeutic target in prostate cancer.

Tissue microarray containing normal prostate epithelium (n = 9) and prostate cancer specimens from 57 patients was stained for ERp46 and the staining intensity (H-score) was determined. Human prostate adenocarcinoma 22Rv1 cells were used to generate gain- and loss-of-function models by stable ERp46 shRNA knockdown and ERp46 overexpression, respectively. In vitro, the doubling time and PSA production were determined. In vivo, xenografts of each subclone were established in nude mice (n = 10/group) to determine the longitudinal tumor growth and serum PSA values. Gene expression profiling of RNA isolated from 22Rv1 xenografts was performed using human whole genome HT-12 V4 BeadChip array (Illumina).

Our results demonstrated that human prostate carcinoma samples of Gleason scores ≥7 showed strong cytoplasmic ERp46 staining which was significantly increased compared to normal prostatic tissue (p = 0.02). ERp46 staining in prostate tumors of Gleason scores ≤6, however, was not different compared to normal prostate tissue. The stably transfected human prostate carcinoma 22Rv1 cells expressed 89% knockdown of ERp46 protein expression (shERp46) or a 4-fold increase in ERp46 protein expression (ERp46+) compared to the respective control cells. In vitro, shERp46 cells proliferated slower, whereas ERp46+ cells exhibited accelerated growth compared to corresponding control cells (p&lt;0.05). Similarly, the tumor volume of subcutaneously growing shERp46 cells in nude mice led to significantly slower tumor growth (p&lt;0.0005, ANOVA). Vice versa, tumors from ERp46+ cells were significantly larger than the tumor volume of shControl-cell injected mice (p = 0.02, ANOVA). Gene expression analysis confirmed the downregulation and upregulation of ERp46 in the corresponding xenografts and also showed several candidate genes, including NAAA, SH3BP4 and ID1 that were reciprocally up-and downregulated. In conclusion, this is the first report to suggest a role for ERp46 as an oncogenic protein and potential therapeutic target in prostate cancer given its expression profile in human prostate cancer samples and its effect on prostate cancer cell growth.

Funding was provided by Prostate Cancer Canada and McMaster Surgical Associates (JHP and WCMD)

Citation Format: Jehonathan H. Pinthus, Sarah N. Hopmans, Stephanie Federov, Wilhelmina C. Duivenvoorden. ERp46 (thioredoxin domain-containing protein 5, TXND5) promotes prostate cancer growth in vitro and in vivo. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4960. doi:10.1158/1538-7445.AM2015-4960