Combination of Pan-Histone Deacetylase Inhibitor and Autophagy Inhibitor Exerts Superior Efficacy against Triple-Negative Human Breast Cancer Cells

Abstract

Histone deacetylase (HDAC) inhibitors (HDI) induce endoplasmic reticulum (ER) stress and apoptosis, while promoting autophagy, which promotes cancer cell survival when apoptosis is compromised. Here, we determined the in vitro and in vivo activity of the combination of the pan-HDI panobinostat and the autophagy inhibitor chloroquine against human estrogen/progesterone receptor and HER2 (triple)-negative breast cancer (TNBC) cells. Treatment of MB-231 and SUM159PT cells with panobinostat disrupted the hsp90/histone deacetylase 6/HSF1/p97 complex, resulting in the upregulation of hsp. This was accompanied by the induction of enhanced autophagic flux as evidenced by increased expression of LC3B-II and the degradation of the autophagic substrate p62. Treatment with panobinostat also induced the accumulation and colocalization of p62 with LC3B-II in cytosolic foci as evidenced by immunofluorescent confocal microscopy. Inhibition of panobinostat-induced autophagic flux by chloroquine markedly induced the accumulation of polyubiquitylated proteins and p62, caused synergistic cell death of MB-231 and SUM159PT cells, and inhibited mammosphere formation in MB-231 cells, compared with treatment with each agent alone. Finally, in mouse mammary fat pad xenografts of MB-231 cells, a tumor size-dependent induction of heat shock response, ER stress and autophagy were observed. Cotreatment with panobinostat and chloroquine resulted in reduced tumor burden and increased the survival of MB-231 breast cancer xenografts. Collectively, our findings show that cotreatment with an autophagy inhibitor and pan-HDI, for example, chloroquine and panobinostat results in accumulation of toxic polyubiquitylated proteins, exerts superior inhibitory effects on TNBC cell growth, and increases the survival of TNBC xenografts. Mol Cancer Ther; 11(4); 973-83. Ó2012 AACR.

Histone Deacetylases as New Therapeutic Targets in Triple-negative Breast Cancer: Progress and Promises

“…This abruption of the HSF1 from the multiprotein comlex is reported to lead to HSF1 phosphorylation, trimerization and nuclear translocation (125,126). Moreover, panobinostat treatment induced endoplasmic reticulum stress response and autophagy (123), evidence also supported by previous research (127)(128)(129). Combinational treatment of panobinostat with chloroquine was found to significantly enhance both the in vivo and the in vitro effect of panobinostat, given the fact that it inhibited tumor growth and increased viability of MDA-MB-231 xenografts (123).…”

“…A study on MDA-MB-231cells investigated the in vitro and in vivo effect of co-treatment of panobinostat with the autophagy inhibitor chloroquine (123). First of all, panobinostat treatment disrupted the hsp90/HDAC6/HSF1/p97 complex (124,125) and induced a heat shock response mediated by heat shock factor protein 1 (HSF1).…”

Combined autophagy and HDAC inhibition

“…We and others have demonstrated that inhibition of autophagy leads to synergistic enhancement of the anticancer activity of HDAC inhibitors. 8,9,15,16,[19][20][21] These studies provided the foundation for the clinical evaluation of the autophagy inhibitor HCQ in combination with VOR as a potential novel therapy for advanced solid tumors. We selected 400 mg daily dosing for VOR in this study, which is frequently used for VOR administration.…”

Cytotoxic Effects of Jay Amin Hydroxamic Acid (JAHA), a Ferrocene-Based Class I Histone Deacetylase Inhibitor, on Triple-Negative MDA-MB231 Breast Cancer Cells

“…In light of such evidence, we cannot exclude the occurrence of an interplay between the early ROS increase, MMP collapse, and autophagy down-regulation in JAHA-treated MDA-MB231 cells, although further studies will be required to confirm this hypothesis. Importantly, Rao et al 51 reported the superior anticancer activity of cotreating triple-negative breast cancer cells and xenografts with the pan-HDACi panobinostat and the autophagy inhibitor chloroquine; therefore, the possible clinical utilization of the sole JAHA, an HDACi possessing an intrinsic autophagy-inhibiting activity, appears to be worth investigating. Noteworthy, the time−course study of JAHA effect on the control of the autophagic flux revealed a biphasic trend of the biological progress, whose molecular basis will deserve further and more detailed investigation.…”