The influence of Ras pathway signaling on tumor radiosensitivity.

Radiotherapy is used to treat approximately 60% of solid tumors in the US. The relative radiosensitivity of these tumors can have a significant impact upon local control. One factor that has been shown to contribute to the increased survival of tumor cells is the activation of signaling pathways in which oncogene products play a central role. The Ras oncoprotein family, comprised of H-, K-, and N-Ras are frequently activated by mutation in certain tumors such as pancreatic and non-small cell lung cancers and are activated by receptor tyrosine kinase activity in an even wider range of tumor types. The role of ras mutation and more recently Ras signaling has been an area of intense study in both radiobiology and tumor biology in general. In this review, we focus on findings from our lab and others that led to the current hypotheses relating to the role of Ras signaling in tumor radiation survival and the strategies used to block Ras activation. We will also point out new means of studying the contribution of Ras and Ras pathway components that could contribute to defining new targets for inhibition in the context of radiation therapy.