Curcumin mediated down-regulation of α V β 3 integrin and up-regulation of pyruvate dehydrogenase kinase 4 (PDK4) in Erlotinib resistant SW480 colon cancer cells.

Erlotinib is a potent, selective, and orally active inhibitor of the epidermal growth factor receptor, but the development of erlotinib resistance during chemotherapy can lead to treatment failure. To shed light on the erlotinib-resistant pathway, this study investigated the effect of combination therapy using curcumin- and erlotinib-loaded nanoparticles on the expression of alpha(V)beta(3) integrin and pyruvate dehydrogenase kinase 4 (PDK4) in an erlotinib-resistant SW480 colon cancer cell line. An erlotinib-resistant SW480 colon cancer cell line was produced by long-term exposure to erlotinib. Curcumin-loaded Methoxy poly ethylene glycol Poly caprolactone (cur/mPEG-PCL) and erlotinib-loaded mPEG-PCL (erl/mPEG-PCL) micelles were provided using a single step nanoprecipitation method and used as combination therapy of resistant SW480 cancer cells. After that, gene expression levels of PDK4, alpha v, and beta 3 mRNA were determined by the semiquantitative reverse transcription-polymerase chain reaction. Protein levels of whole alpha(V)beta(3) integrin were evaluated using the enzyme-linked immunosorbent assay method. In SW480 cell line, the IC50 of nonresistant and resistant cells was 87.6 +/- 1.2 nM and 19.1 +/- 0.14 mu M, for erlotinib and it was about 21.8 and 30 mu M for curcumin, respectively. Although PDK4 expression was not significantly different in resistant and nonresistant cells, its expression was up regulated (1.4 fold) in resistant cells by a combination therapy of cur/mPEG-PCL at a dose of 3 mu M and erl/mPEG-PCL at a dose of 5 mu M.beta(3) mRNA and the protein level of whole alpha(V)beta(3) integrin was significantly higher in resistant SW480 cells as compared with those in nonresistant cells. In terms of treatment, a combination of 6-mu M cur/mPEG-PCL and 5-mu M erl/mPEG-PCL down regulated beta(3) gene expression 6.6-fold in resistant cells as compared with nonresistant cells. At the protein level, a combination of 3-mu M-cur/mPEG-PCL and 10-mu M erl/mPEG-PCL reduced alpha(V)beta(3) protein in resistant cells. The results indicated that combination therapy using cur/mPEG-PCL and erl/mPEG-PCL could decrease alpha(V)beta(3) integrin expression and increase PDK4 gene expression in resistant colon cancer cells, which may have effects on drug resistance signaling pathways.