Abstract Title:

Curcumin modulates the radiosensitivity of colorectal cancer cells by suppressing constitutive and inducible NF-kappaB activity.

Abstract Source:

Int J Radiat Oncol Biol Phys. 2009 Oct 1;75(2):534-42. PMID: 19735878

Abstract Author(s):

Santosh K Sandur, Amit Deorukhkar, Manoj K Pandey, Ana María Pabón, Shujun Shentu, Sushovan Guha, Bharat B Aggarwal, Sunil Krishnan

Article Affiliation:

Department of Experimental Therapeutics, The University of Texas M D Anderson Cancer Center, Houston, TX 77030, USA.


PURPOSE: Radiation therapy is an integral part of the preoperative treatment of rectal cancers. However, only a minority of patients achieve a complete pathologic response to therapy because of resistance of these tumors to radiation therapy. This resistance may be mediated by constitutively active pro-survival signaling pathways or by inducible/acquired mechanisms in response to radiation therapy. Simultaneous inhibition of these pathways can sensitize these tumors to radiation therapy. METHODS AND MATERIALS: Human colorectal cancer cells were exposed to clinically relevant doses of gamma rays, and the mechanism of their radioresistance was investigated. We characterized the transcription factor nuclear factor-kappaB (NF-kappaB) activation as a mechanism of inducible radioresistance in colorectal cancer and used curcumin, the active ingredient in the yellow spice turmeric, to overcome this resistance. RESULTS: Curcumin inhibited the proliferation and the post-irradiation clonogenic survival of multiple colorectal cancer cell lines. Radiation stimulated NF-kappaB activity in a dose- and time-dependent manner, whereas curcumin suppressed this radiation-induced NF-kappaB activation via inhibition of radiation-induced phosphorylation and degradation of inhibitor of kappaB alpha, inhibition of inhibitor of kappaB kinase activity, and inhibition of Akt phosphorylation. Curcumin also suppressed NF-kappaB-regulated gene products (Bcl-2, Bcl-x(L), inhibitor of apoptosis protein-2, cyclooxygenase-2, and cyclin D1). CONCLUSIONS: Our results suggest that transient inducible NF-kappaB activation provides a prosurvival response to radiation that may account for development of radioresistance. Curcumin blocks this signaling pathway and potentiates the antitumor effects of radiation therapy.

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