Abstract
We have previously reported that insulin sensitizes cells to low-dose irradiation (0.25 Gy) in human breast cancer cells (MCF7). Insulin appears to affect cell survival via protein kinase C (PKC)-related signal cascades in the cells after low-dose irradiation. Insulin-mediated sensitization of cells to low-dose radiation is thought to be a unique model, demonstrate signal cascades induced by low-dose irradiation. In this study, insulin-mediated sensitization of MCF7 cells was characterized by measuring cell survival using MTS assay, which is based on measuring the total viable cell number and by colony-forming assays. Five hours after seeding, it was observed that insulin reduced cell survival in MTS assay. Using colony-forming assays, however, no change in the cell survival was observed. These results suggest that insulin induces growth inhibition in the cells after low-dose irradiation. In addition, it was observed that insulin also reduces cell survival using MTS assay, 24h after seeding, when cells have been fully attached to dishes and spread. This result implies that cell-cell contact and cell spreading have no effect on the insulin mediation. Since PKC-related or phosphatidylinositol 3 (PI3) kinase-related cascades are known to participate in the insulin-related cascades, effects of PKC inhibitor and PI3 kinase inhibitor on the insulin mediation in the cells will be also discussed.
