Uracil‐ and Pyridine‐Containing HDAC Inhibitors Displayed Cytotoxicity in Colorectal and Glioblastoma Cancer Stem Cells

Abstract

Cancer stem cells (CSCs) are a niche of highly tumorigenic cells featuring self‐renewal, activation of pluripotency genes, multidrug resistance, and ability to cause cancer relapse. Seven HDACi (1‐7), showing either hydroxamate or 2'‐aminoanilide function, were tested in colorectal cancer (CRC) and glioblastoma multiforme (GBM) CSCs to determine their effects on cell proliferation, H3 acetylation levels and in‐cell HDAC activity. Two uracil‐based hydroxamates, 5 and 6, which differ in substitution at C5 and C6 positions of the pyrimidine ring, exhibited the greatest cytotoxicity in GBM (5) and CRC (6) CSCs, followed by the pyridine‐hydroxamate 2, with 2‐ to 6‐fold higher potency than the positive control SAHA. Finally, increased H3 acetylation as well as HDAC inhibition directly in cells by selected 2'‐aminoanilide 4 and hydroxamate 5 confirmed target engagement. Further investigation will be conducted into the broad‐spectrum anticancer properties of the most potent derivatives and their effects in combination with approved, conventional anticancer drugs.