Aza-PBHA, a potent histone deacetylase inhibitor, inhibits human gastric-cancer cell migration via PKCα-mediated AHR-HDAC interactions

Recently, histone deacetylase inhibitors (HDACi) have become widely used in anti-cancer treatment; however, due to acquired drug resistance and their relatively low specificity, they are largely ineffective against late-stage cancer. Thus, it is critical to elucidate the molecular mechanisms underlying these issues, so as to identify novel therapeutic targets to prevent late-stage cancer progression and resistance acquisition. The present study investigated the Aryl hydrocarbon receptor (AHR), that has been shown to mediate histone acetylation by regulating histone deacetylase (HDAC) activity during HDACi treatment in human gastric-cancer cell lines (i.e. AGS and NCI-N87 cells). The potent HDACi, Aza-PBHA, was thus shown to upregulate AHR expression in both AGS and NCI-N87 cell lines, and to increase histone acetylation levels by facilitating AHR/HDAC interactions. Conversely, AHR knockdown increased HDAC activity. Aza-PBHA also increased PKCα phosphorylation and membrane translocation; however, interestingly, PKCα inhibition reduced the Aza-PBHA-increased AHR and histone acetylation levels, and inhibited the formation of the AHR/HDAC complex, likely upregulating Aza-PBHA-inhibited cell migration. Thus, our results suggest that Aza-PBHA treatment increased AHR levels to suppress HDAC activity, and inhibited cell migration by activating PKCα activation. These findings support the use of drugs to control AHR-related epigenetic regulation as a promising potential method to prevent acquired resistance to cancer treatments.