Hyaluronan-mediated CD44 interaction with p300 and SIRT1 regulates β-catenin signaling and NFκB-specific transcription activity leading to MDR1 and Bcl-xL gene expression and chemoresistance in breast tumor cells

Abstract

In this study we have investigated hyaluronan (HA)-mediated CD44 (an HA receptor) interactions with p300 (a histone acetyltransferase) and SIRT1 (a histone deacetylase) in human breast tumor cells (MCF-7 cells). Specifically, our results indicate that HA binding to CD44 up-regulates p300 expression and its acetyltransferase activity that, in turn, promotes acetylation of β-catenin and NFκB-p65 leading to activation of β-catenin- associated T-cell factor/lymphocyte enhancer factor transcriptional co-activation and NFκB-specific transcriptional up-regulation, respectively. These changes then cause the expression of the MDR1 (P-glycoprotein/P-gp) gene and the anti-apoptotic gene Bcl-xL resulting in chemoresistance in MCF-7 cells. Our data also show that down-regulation of p300, β-catenin, or NFκB-p65 in MCF-7 cells (by transfecting cells with p300-, β-catenin-, or NFκB-p65-specific small interfering RNA) inhibits the HA/CD44-mediated β-catenin/NFκB-p65 acetylation and abrogates the aforementioned transcriptional activities. Subsequently, there is a significant decrease in both MDR1 and Bcl-xL gene expression and an enhancement in caspase-3 activity and chemosensitivity in the breast tumor cells. Further analyses indicate that activation of SIRT1 (deacetylase) by resveratrol (a natural antioxidant) induces SIRT1-p300 association and acetyltransferase inactivation, leading to deacetylation of HA/CD44-induced β-catenin and NFκB-p65, inhibition of β-catenin-T-cell factor/lymphocyte enhancer factor and NFκB-specific transcriptional activation, and the impairment of MDR1 and Bcl-xL gene expression. All these multiple effects lead to an activation of caspase-3 and a reduction of chemoresistance. Together, these findings suggest that the interactions between HA/CD44-stimulated p300 (acetyltransferase) and resveratrol-activated SIRT1 (deacetylase) play pivotal roles in regulating the balance between cell survival versus apoptosis, and multidrug resistance versus sensitivity in breast tumor cells.