Curcumin Reverses Resistance to Histone Deacetylase Inhibitors In Cutaneous T-Cell Lymphoma Cells: a Potential Role for NF-κB Signaling

Abstract 3973

Histone deacetylase inhibitors (HDACi), including vorinostat (SAHA), depsipeptide (FK228), panobinostat (LBH589), belinostat (PXD101), and entinostat (SNDX275), show in-vitro and clinical activity against cutaneous T-cell lymphoma (CTCL) cell lines and patients' skin lesions [Zhang & Duvic, Expert Rev Dermatol 5: 393–401, 2010]. Vorinostat and depsipeptide were recently approved [Duvic et al, Blood 109: 31-9, 2007; Olsen et al, J Clin Oncol 25: 3109-15, 2007; Piekarz et al, J Clin Oncol 27: 5410-7, 2009], at response rates of 29% and 42%, respectively, but development of resistance remains an important clinical problem. Because we have shown that curcumin, the active ingredient of turmeric, exhibits anti-cancer activity through selective induction of tumor T-cell apoptosis and inhibition of NF-κB signaling in CTCL [Zhang et al, J Invest Dermatol 130: 2110-9, 2010], we now investigated whether curcumin combined with HDACi has synergistic anti-tumor effects in CTCL. HDACi-resistant MJ, HDACi-sensitive HH and HDACi cross-resistant HH/VOR CTCL cells were treated with HDACi (panobinostat, vorinostat, or enlinostat) plus or minus curcumin for up to 48 hrs. Cell viability was examined by the MTS assay and apoptosis by FACS analysis of annexin V/PI binding populations and/or cell cycle distribution. The NF-κB signaling pathway was analyzed by electrophoretic mobility gel shift assay and Western blotting. In MJ and HH cell lines, 5 nM panobinostat induced 1.4% and 11.4% apoptosis and 10 μM curcumin induced 24.5% and 29% apoptosis compared to vehicle controls. Panobinostat combined with curcumin induced 46.9% and 83.4% apoptosis in MJ and HH cell lines, respectively. Of interest, the HDACi cross-resistant HH/VOR CTCL cells were sensitive to curcumin alone and curcumin further enhanced panobinostat-induced apoptosis by 30% in the HH/VOR CTCL cells. Moreover, panobinostat combined with curcumin synergistically suppressed the DNA binding of NF-κB and decreased protein expression of the NF-κB activator RANK and NF-κBp65. Synergism was associated with down-regulation of NF-κB-regulated anti-apoptotic proteins (bcl-2, bcl-xL, and survivin), anti-proliferative proteins (c-myc and cyclooxygenase-2), and pro-invasive protein matrix metalloproteinase-9. Similar synergism was also seen when vorinostat or entinostat was combined with curcumin. These results suggest that HDACi could be combined with curcumin to enhance apoptosis of malignant T-cells through inhibition of NF-κB signaling in CTCL. Curcumin alone and in combination with HDACi may be an attractive strategy for the treatment of HDACi-refractory CTCL patients.