ALDH1a3 inhibitor effects on Breast cancer Cells Transcriptome

Aldehyde dehydrogenase (ALDH1) activity has long been established as a pro-tumorigenic feature of many cancers, yet the identification of specific isoforms that are enriched in cancer, the mechanism of action of this isoform(s), and viable therapeutic strategies to target this pathway have long remained absent. Whereas one of the well-established functions of the ALDH1a family is the conversion of retinaldehyde into retinoic acid to activate nuclear retinoid signaling, the retinoid pathway is paradoxically hypothesized as a cell-intrinsic tumor suppressor pathway. Here we resolve this long-standing conflict by showing that while ALDH1a3 is broadly overexpressed across diverse cancer types, ALDH1a3 expressing tumor cells often lose the sensitivity to retinoid signaling. Instead, all-trans retinoic acid produced by ALDH1a3 acts in a paracrine fashion to suppress anti-tumor immunity and promote tumor growth. We further used structure-based high throughput screening to develop a series of first-in-class, therapeutically viable antagonists of ALDH1a3 with potent anti-tumor immunotherapeutic activity, an excellent pharmacological profile and no evidence of toxicity. Findings of this study resolve prior contradictions in the retinoid pathway through the development of highly specific and potent ALDH1a3 inhibitors. Overall design: To determine the effects of ALDH1a3 inhibitor MBE1.5 on gene expression regulation in breast cancer cells, 4 breast cancer cell lines including 3 ALDH1a3 positive cells and 1 ALDH1a3 negative cells are treated with MBE1.5 vs DMSO control for 9 hours. Total RNA were harvested from the cells and whole transcriptome expression were determined by RNAseq.