Why is it not surprising that signal receptors are overexpressed in most types of cancer?

This is because cancer cells are due to mutations proto - oncogenes or tumor suppressor genes that cause the biochemical and biological process of the cell to go into overdrive and failure of regulation by tumor suppressors. An example of a common cancer trait is an overexpression of growth factor receptors and G-protein-coupled receptors. It is through these receptors that cells receive information to regulate diverse processes, such as protein synthesis and cell growth, motility, cell architecture and polarity, differentiation, and programmed cell death. The overexpression of surface receptors, therefore, causes abnormal overexpression of the mentioned biochemical activities.