ALDH9A1 and prostate carcinoma: Furthermore, it has been demonstrated that ALDH4A1 and ALDH9A1 are the primary enzyme isoforms responsible for ALDEFLUOR activity in prostate cancer tissues, whereas ALDH3A2 and ALDH18A1 are the predominant enzyme isoforms in non-tumor tissues and high-grade prostate intraepithelial neoplasia [160].