{Reference Type}: Journal Article
{Title}: The impact of the IGF-1 system of cancer cells on radiation response - An in vitro study.
{Author}: Venkatachalam S;Mettler E;Fottner C;Miederer M;Kaina B;Weber MM;
{Journal}: Clin Transl Radiat Oncol
{Volume}: 7
{Issue}: 0
{Year}: Dec 2017
{Factor}: 4.739
{DOI}: 10.1016/j.ctro.2017.09.006
{Abstract}: <B>UNASSIGNED: </B>Overexpression of the insulin-like growth factor-1 receptor (IGF-1R) is associated with increased cell proliferation, differentiation, transformation, and tumorigenicity. Additionally, signaling involved in the resistance of cancer cells to radiotherapy originates from IGF-1R. The purpose of this study was to investigate the role of the IGF-1 system in the radiation response and further evaluate its effect on the expression of DNA repair pathway genes.<BR><B>UNASSIGNED: </B>To inhibit the IGF-1 system, we stably transfected the Caco-2 cell line to express a kinase-deficient IGF-1R mutant. We then studied the effects of this mutation on cell growth, the response to radiation, and clonogenic survival, as well as using a cell viability assay to examine DNA damage and repair. Finally, we performed immunofluorescence for γ-H2AX to examine double-strand DNA breaks and evaluated the expression of 84 key genes involved in DNA repair with a real-time PCR array.<BR><B>UNASSIGNED: </B>Mutant IGF-1R cells exhibited significantly blunted cell growth and viability, compared to wild-type cells, as well as reduced clonogenic survival after γ-irradiation. However, mutant IGF-1R cells did not show any significant delays in the repair of radiation-induced DNA double-strand breaks. Furthermore, expression of mutant IGF-1R significantly down-regulated the mRNA levels of BRCA2, a major protein involved in homologous recombination DNA repair.<BR><B>UNASSIGNED: </B>These results indicate that blocking the IGF-1R-mediated signaling cascade, through the expression of a kinase-deficient IGF-1R mutant, reduces cell growth and sensitizes cancer cells to ionizing radiation. Therefore, the IGF-1R system could be a potential target to enhance radio-sensitivity and the efficacy of cancer treatments.