RESUMO
BACKGROUND AND PURPOSE: The SCF/c-Kit pathway is often overexpressed in human tumors leading to an enhanced tumorigenesis, proliferation and migration. It was now tested for NSCLC and prostate cancer cells growing in 2D and 3D whether the inhibition of this pathway can be used to achieve a significant radiosensitization and whether a respective biomarker may be identified. MATERIAL AND METHODS: Experiments were performed with different cancer cell lines (NSCLC: H23, H520, H226, H1975 and PrCa: DU145) growing either under 2D or 3D conditions. Expression of SCF and c-Kit was determined by RT-PCR and Western blot, SCF was knocked down by siRNA, c-Kit was inhibited by ISCK03 inhibitor and cell survival was determined by colony formation assay. RESULTS: There is a profound variation in the expression of both c-Kit and SCF with no association between each other. Neither levels did correlate with the respective cellular radiosensitivity determined for 2D or 3D with only a trend seen for SCF. Knock-down of SCF was generally found to result in no or only minor reduction of plating efficiency or cellular radioresistance. A significant reduction was only obtained for H520 cells characterized by an extreme over-expression of SCF. The inhibition of c-Kit by a specific inhibitor was also found to result only in minor radiosensitization. CONCLUSION: Generally, the SCF/c-Kit pathway does not have a dominant effect on both, cell survival and radioresponse and, as a consequence, knockdown of this pathway does not result in a strong effect on radioresistance, except when SCF is strongly over-expressed.
RESUMO
BACKGROUND AND PURPOSE: Success of radiotherapy is often limited by therapy resistance and metastasis resulting from cancer cell motility. It was tested in vitro whether this cancer cell motility is affected by growth condition, active SCF/c-Kit pathway or X-irradiation. MATERIALS AND METHODS: Cell motility was measured with BioCoat™ Matrigel™ invasion chamber using four different cancer cell lines (NSCLC: H23, H520, H226 and PrCa: DU145). Cells were grown in 2D or 3D, SCF was knocked down by siRNA and cells were irradiated with 2 or 6Gy. RESULTS: All cell lines except H520 showed a 2-3-fold increase in cell motility when grown in 3D. This effect was considered to result from the EMT-like change seen when cells were grown in 3D as indicated by the enhanced expression of vimentin and N-cadherin and reduction of E-cadherin. Just the opposite trends were found for H520 cells. Knockdown of SCF was found to result in reduced cell motility for both 2D and 3D. In contrast, X-irradiation did not modulate cell motility neither under 2D nor 3D. In line with this, X-irradiation did neither induce the expression of EMT-associated genes nor SCF. CONCLUSION: X-irradiation affects neither the expression of important EMT genes such as vimentin, E-cadherin and N-cadherin nor SCF/c-Kit signaling and, as a consequence, does not alter cell motility.
