Abstract 4093: The impact of the prostate cancer microenvironment on the expression and regulation of aldehyde dehydrogenases

Abstract

Abstract Introduction: Aldehyde dehydrogenase (ALDH) enzymes are involved in the detoxification of specific endogenous and exogenous aldehyde substrates. High ALDH activity is used to identify stem cells and has also been associated with poor prognosis in cancer. In prostate cancer (PCa) high ALDH activity has been associated with elevated clonogenicity, migratory behaviour, tumor progression and metastasis. Despite these observations there exists a poor understanding of the role of selected ALDH isoforms in PCa. In an attempt to understand if the tumor microenvironment impacts on ALDH function, we investigated their expression under hypoxia. Methods: Gene and protein expression analysis of ALDH isoforms -1A1, -1A2, -1A3, -1B1, -2, -3A1 and -7A1 in normal prostate cell line PNT2C2, and a panel of PCa cell lines with different stages of cancer was carried out by quantitative PCR and western blot under normoxic and hypoxic conditions at 24 and 48 hours. Gene expression of the ALDHs in primary prostate cultures was assessed following retinoic acid treatment. siRNA knockdown technology was used to study functional roles of selected ALDH isoforms. Results: Gene expression of ALDH1A3 was increased in Bob cells at 24h under hypoxia, at 48h this was less apparent but the expression of most ALDHs in Bob cells including ALDH1A2, -2, -3A1 and -7A1 was reduced at 48h. In SerBob cells, the gene expression of ALDH1A1 and -1B1 was reduced at both time points, whereas the expression of ALDH1A2, -2, and -7A1 was increased under hypoxia. At protein level, the expression of ALDH1A3 appeared low under hypoxia at both time points in SerBob cells while the expression of ALDH3A1 also appeared low after 24h exposure to hypoxia. In DU145 cells, there was an increase in ALDH1A1, -1A2, 1A3, -2, and -3A1 gene expression under hypoxia at 48h. In LNCAP cells, the gene expression of ALDH2 was increased at 48h under hypoxia whereas the expression of ALDH7A1 was reduced at 48h. The protein expression of ALDH7A1 was higher in PC3 cells under hypoxia at 24h. A significant increase was observed in ALDH1A3 and ALDH3A1 expression in response to retinoic acid. ALDH1A3 knockdown showed a significant reduction of cell viability in PC3 cells. Other investigations underway that will be reported at the conference are focused on how prostate cancer stem-like cells expressing ALDHs are responding to hypoxia. Conclusion: Our data suggests that the expression of certain ALDHs is affected by hypoxia and ALDH1A3 potentially is involved in cell survival in PCa. Future work will investigate if any of these isoforms can be used as biomarkers to distinguish indolent from malignant PCa. Citation Format: Maria Sadiq, Simon J. Allison, Fiona Frame, Mark Sutherland, Roger M. Phillips, Norman J. Maitland, Klaus Pors. The impact of the prostate cancer microenvironment on the expression and regulation of aldehyde dehydrogenases. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4093.