title: Targeting constitutive and interleukin-6-inducible signal transducers and activators of transcription 3 pathway in head and neck squamous cell carcinoma cells by curcumin (diferuloylmethane).
abstract: Numerous reports suggest that interleukin-6 (IL-6) promotes survival and proliferation of tumor cells through the phosphorylation of a cell-signaling protein, signal-transducer-and-activator-of-transcription-3 (STAT3). Constitutive activation of STAT3 in head and neck squamous cell carcinoma (HNSCC) and its role in proliferation of this tumor has been demonstrated. Thus, agents that can suppress STAT3 activation have potential for the treatment of HNSCC. In the present report, we demonstrate that most HNSCC cell lines had constitutively active STAT3 and that curcumin (diferuloylmethane), a pharmacologically safe agent in humans, inhibited STAT3 phosphorylation in a dose- and time-dependent manner. Nuclear translocation of STAT3 was also inhibited by curcumin. The inhibition of STAT3 activation by curcumin was reversible, although even 24 hr after curcumin removal, only partial reversal occurred. Besides inhibiting constitutive expression, curcumin also abrogated the IL-6-induced activation of STAT3 in HNSCC cells. When compared with AG490, a well-characterized JAK2 inhibitor, curcumin was more rapid (30 min vs. 4 hr) and more potent (25 microM vs. 100 microM) inhibitor of STAT3 phosphorylation. Curcumin was also a more potent inhibitor of HNSCC cell proliferation than AG490. Overall, our results demonstrated that curcumin is a potent inhibitor of constitutive and IL-6-induced STAT3 phosphorylation. This mechanism may be at least partially responsible for curcumin's ability to suppress proliferation of HNSCC cells.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Nitin
authors.initials: N
authors.lastname: Chakravarti
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Myers
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Aggarwal
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism* / Q000556:secondary; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D053614:Janus Kinase 2; D008207:Lymphatic Metastasis / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014062:Tongue Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D015850:Interleukin-6; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D003474:Curcumin