Figure 1: Signal transduction mechanism of anti-apoptosis in cancer cells. Highlighted here is the involvement of PTK signaling via nonreceptor PTKs such as SFKs, receptor PTKs such as EGFR, and cytoplasmic PTKs such as Abl and FAK in and around the plasma membranes. Several kinds of microenvironmental shortage for cell viability (e.g., hypoxia, lack of cell-cell or cell-ECM contact, hypoglycemia, deprivation of serum) act as signals (MESs, microenvironmental signals) for the responses of cancer cells (sensing of MESs, PTK signaling, other genomic and nongenomic signaling, and their crosstalk). These signaling networks support the cancer cells to undergo anti-apoptosis and active proliferation that lead to the other malignant features of cancer.