Antitumor action of curcumin in human papillomavirus associated cells involves downregulation of viral oncogenes, prevention of NFκB and AP-1 translocation, and modulation of apoptosis

Abstract

Curcumin (diferuloyl methane), the major yellow pigment from the rhizomes of turmeric (Curcumalonga Linn), has anticancer properties. Infection with high-risk human papillomaviruses (HPV) leads to development of cervical carcinoma, predominantly through the action of viral oncoproteins E6 and E7. The present study aims at analyzing the antitumor and antiviral properties of curcumin, on HPV associated cervical cancer cells. Our findings indicate curcumin to be cytotoxic to cervical cancer cells in a concentration-dependent and time-dependent manner. The cytotoxic activity was selectively more in HPV16 and HPV18 infected cells compared to non-HPV infected cells. Balance between tumor cell proliferation and spontaneous cell death via apoptosis had an important role in regulation of tumor cell growth. Curcumin-induced apoptosis in cervical cancer cells. Morphological hallmarks of apoptosis such as nuclear fragmentation and internucleosomal fragmentation of DNA were observed. Curcumin also selectively inhibited expression of viral oncogenes E6 and E7, evident from RT-PCR and Western blotting data. Electrophoretic mobility shift assay revealed that activation of NFκB-induced by TNFα is downregulated by curcumin. Curcumin blocked IkBα phosphorylation and degradation, leading to abrogation of NFκB activation. Curcumin also downregulated the expression of COX-2, a gene regulated by NFκB. Binding of AP-1, an indispensable component for efficient epithelial tissue-specific gene expression of HPV was also selectively downregulated by curcumin. These results provide attractive data for the possible use of curcumin in the management of HPV associated tumors.