An in-vitro tumour microenvironment model using adhesion to type I collagen reveals Akt-dependent radiation resistance in renal cancer cells

Methods. RCC cell adhesion to matrix was studied via pre-coating a variety of ECM glycoproteins onto plates. Cancer cell apoptosis and cell cycle were evaluated with flow cytometry using annexin V and propidium iodide stains, respectively. Activation of cellular survival signalling was analysed with western blots, and specific molecular inhibitors were correspondingly employed to block signalling. Hypoxia (< 1%) was induced via N-2/CO2 gas flow in a specialized chamber. Results. While adherence to col(I) enhanced RCC cell proliferation in general, col(I) and fibronectin, but not fibrinogen, could confer specific anti-apoptotic RR to RCC cells. The radioprotective effect of col(I) was maintained during both hypoxia/reoxygenation and normoxia conditions. In contrast to intact col(I), micronized col(I), lacking the natural fibrillar structure, was not radioprotective. The effect of col(I) in RCC cells is mediated via attenuation of apoptosis rather than cell cycle redistribution, involving the PI3 kinase/Akt pathway but not the MAP kinase pathway. Conclusions. Adherence to col(I) appears to be a relevant environmental cue enhancing RR in RCC cells, Akt dependently. Our results support inhibition of the PI3-kinase/Akt pathway as a radiosensitizing approach.