Investigating PSMA differential expression in canine uroepithelial carcinomas to aid disease-based stratification and guide therapeutic selection

Abstract

Background: In male dogs, uroepithelial cancers include invasive urothelial carcinoma (iUC) and prostate carcinoma (PCA). The inability to distinguish iUC involving the prostate from PCA results in indiscriminate clinical management strategies that could be suboptimal as first-line chemotherapy for iUC (cisplatin) and PCA (docetaxel) differ in people. Prostate specific membrane antigen (PSMA) is a transmembrane protein, and its overexpression has been identified in human prostate carcinoma and neovasculature associated with solid tumor growth. This study investigates whether differential PSMA expression exists between presumptive canine iUC and PCA among cell lines and archived patient samples, which might allow for improved accuracy in disease-based stratification and optimal chemotherapy selection. Additionally, in vitro sensitivities of reported canine iUC and PCA cell lines to uroepithelial directed chemotherapeutic agents were characterized.

Results: Normalized PSMA gene and protein expressions were not significantly different between 5 iUC and 4 PCA cell lines. PSMA protein expression was uniformly observed in uroepithelial cancers regardless of anatomic origin from archived patient samples, further confirming that PSMA cannot differentiate iUC from PCA. In vitro sensitivity of cell lines to uroepithelial directed chemotherapeutics revealed that vinblastine exerted the broadest cytotoxic activity.

Conclusions: Differential expression of PSMA was not identified between canine iUC and PCA cell lines or archived patient samples, and PSMA alone cannot be used for disease stratification. Nonetheless given its conserved overexpression, PSMA may be a targetable surface marker for both canine iUC and PCA. Lastly, in uroepithelial carcinomas, vinblastine might exert the broadest anticancer activity regardless of cellular origin.

Keywords: Canine; Chemotherapy; Comparative oncology; Prostate-specific membrane antigen; Urothelial carcinoma, prostate carcinoma, druggable target.

Fig. 1

PSMA gene & protein expression among canine uroepithelial carcinoma cell lines. (A) PSMA gene expression patterns among canine uroepithelial carcinoma cell lines. Error bars represent RQ min and max values from a representative biologic replicate. (B) PSMA western blot image with known human control cell lines (LNCaP +, PC3-), and (C) PSMA protein expression normalized to β-actin loading control. Within bar graphs, grey represents canine PCA cell lines and red represents canine iUC cell lines

Fig. 2

Immunohistochemical detection of PSMA among canine uroepithelial carcinoma cell lines and representative patient samples. (A) PSMA IHC of known human reference control cell lines (LNCaP+, PC3-). (B) PSMA IHC among canine uroepithelial cell lines with grey labeled (top row) representing PCA cell lines and red labelled (bottom row) representing iUC cell lines. (C) PSMA IHC of archived iUC patient sample (red labelled, left) and carcinomas of the prostate (grey labelled, right)

Fig. 3

Dose-response line graphs of canine uroepithelial carcinoma cell lines to each urothelial directed chemotherapeutic agent. In each of four panels of different chemotherapeutic agents, 5 canine iUC (left) and 4 canine PCA (right) cell lines were incubated with varying concentrations of drug for 72 hours, then processed using Sulforhodamine B assay. Dot size indicates SEM