Elucidating the Role of TGF and#946;2 Signaling in Doxorubicin Induced Chemoresistance in Colon Cancer Cells

Abstract

Colorectal cancer is now the third most common and second leading cause of newlinecancer related mortality worldwide. With ever-increasing cancer rates due to rapid changes newlinein the food habit, dependency on chemotherapy for cancer treatment is high especially when newlinethe cancer is detected at a latter stages. Doxorubicin (dox) is a well-known chemotherapeutic newlinedrug that is clinically used to combat a wide range of cancers alone or in combination with newlineother drugs. Dox has multiple intracellular targets and can also promote immune cell newlineinfiltration and tumor clearance. However, development of resistance to chemotherapy has newlinebeen the main hinderance in cancer therapy. More than 90% of chemotherapy failure is newlineattributed to resistance development. Multidrug resistance protein, MDR1, belonging to a newlinefamily of ATP dependent transporter, effectively pumps dox out of the cells. Many signaling newlinepathways, cytokines, and growth factors have been implicated in the development of newlinechemoresistance. Increase in the serum level of TGF-and#946; is noted in colon cancer patients and newlinethis level was reversed with curative surgery. In the early stages of colorectal cancers, TGF- newlineand#946;1 secretion is observed and there is a shift to TGF-and#946;2 cytokine as the cancer progress. TGF- newlineand#946;2 cytokine is associated with evading infiltration of immune cells. In this study, we tried to newlineevaluate the important role played by TGF-and#946;2 in development of chemoresistance in benign newlineand metastatic colon cancer cells. For the study, we used two cell lines, HT-29 and Colo205, newlinebenign and metastatic colon cancer cells with Smad4 mutation. The cells were treated with newlineincreasing levels of dox (0.23 and#956;M to 1.61 and#956;M) for 7-days to induce resistance development newlinein the presence or absence of 5 ng/ml TGF-and#946;2 ligand. The cells were evaluated for the effect newlineof treatment by cell proliferation assay using MTT, cell viability by trypan blue, cell newlinecytotoxicity by lactate dehydrogenase enzyme (LDH) activity newline