Virginia Commonwealth University Health System, Richmond, VA
Prashant J. Joshi , Ayesha Chawla , Patrick Memari , John Stansfield , Michael Idowu , Adam Sima , Steven R. Grossman
Background: Overexpression of the oncogenic transcription factors CtBP1 and 2 is common and associated with poor prognosis in ovarian, breast and prostate cancer. CtBP2 drives tumor progression through promotion of epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) activity. Frequent early metastasis observed in PDAC may depend on EMT and CSC activity, prompting us to investigate the prognostic significance of CtBP1/2 in PDAC. In parallel, we determined the oncogenic contribution of CtBP2 to PDAC utilizing a transgenic KRAS mutant mouse PDAC model (CKP) that incorporated heterozygous loss of the Ctbp2 gene (CKP2). Methods: Immunohistochemistry (IHC) using CtBP1/2 antibodies was performed on 69 cases of resected PDAC from VCU Health for the period 2005-16. Clinical data included stage (84% stage 1/2; 16% stage 3/4), initial CA19-9 level, and overall survival. IHC stains were assigned an Allred score (sum of intensity and proportion) by two independent pathologists with a scale from 0-8. Cox Proportional Hazard survival models were fit for CtBP1/2 staining vs. survival. CtBP1/2 correlation with stage and CA19-9 level was tested by ANOVA. CKP mice were bred to Ctbp2 +/- mice, and survival of cohorts (n = 10 each) of CKP vs. CKP2 mice was analyzed by log-rank analysis of Kaplan-Meier survival curves. Results: CtBP1 and 2 expression was uniformly high (7-8) across all cases, including stage 1/2. Thus, no statistically significant survival difference could be derived based on CtBP1/2 expression [CtBP1 HR 1.03 (0.67-1.41) p 0.92, CtBP2 HR 0.75 (0.39-1.43) p 0.31], and no significant association of CtBP1/2 was seen with stage or CA19-9. Suggesting a possible contribution of CtBP2 in human PDAC, Ctbp2 knockout in CKP2 mice improved median survival (9.5 vs. 8.1 weeks, p < 0.05), decreased mean tumor weight (750 mg vs. 400 mg, p < 0.05), and also abrogated peritoneal metastases and ascites normally seen in 100% of CKP mice. Conclusions: While uniformly high CtBP expression in PDAC subverts prognostic use, CtBP may play a pathogenic role, as CKP2 mice exhibited improved survival, lower tumor burden and no peritoneal spread. Our data supports further study of CtBP inhibition as a potential therapeutic strategy in PDAC.
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