Influência da superexpressão da claudina-3 na radiorresposta de células de câncer de cólon

Abstract

Colorectal cancer (CRC) is the third more incident cancer for males, the second for females worldwide and radiotherapy is one of the first-line treatments to fighting this type of cancer. During the progression of CRC cells undergo morphogenetic alterations and the apical junctional complex disorganization (AJC) is one of the initial events of this process. The tight junctions (TJs) is a major component of AJC and play an important role in paracellular flux control, determination of cell polarity and in signal transduction related to tumor progression. Claudins are transmembrane proteins, members of TJs and play an important role on these events. Changes on claudins expression are found in tumors of different organs and have been associated with tumor progression. However the mechanisms that regulate these changes and their consequences in the CRC progression are not completely understood. Thus, this study aimed to evaluate the influence of claudin-3 overexpression on cellular response after radiation treatment of CRC cells. Our results show that claudin-3 overexpression minimizes morphological changes caused by the radiation, decrease transepithelial electrical resistance, and has no effect on macromolecules permeability after irradiation. Moreover, we observed that claudin-3 overexpression increases the proliferation rate of cells and that this feature makes the cells more sensitive to radiation. However, when evaluating the cellular events associated tumor progression we observed that despite decrease on migratory capacity caused by radiation, cells that overexpress claudin-3 have higher migration. In addition, we found that claudin-3 overexpression decreases the invasion and the capacity to form colonies after treatment with radiation. Then we evaluate the effect of inhibition of proliferation (MEK / ERK) and survival (PI3K-Akt) pathways in cells that overexpress claudin-3 in the response to radiation. We observed that inhibition of MEK could sensitize cells overexpressing claudin-3 radiation on cell proliferation assay, but the inhibition of MEK and PI3K before radiation exposure can increase the migration and colony forming ability cells overexpressing claudin-3 contributes to the increase of malignant potential. Altogether, our results show that claudin-3 overexpression contributes to a more malignant phenotype, however, claudin-3 overexpression is able to sensitize the cells to radiation.