**4. Conclusions**

Apoptosis is an essential process for the growth and development of organisms, while cancer cells obtain immortality by escaping programed cell death. Understanding the underlying mechanism of cancer resistance to chemotherapy is fundamental for efficient cancer treatment agents. In this chapter, we have discussed the mechanisms of cancer cells evading apoptosis, including downregulation of pro-apoptotic signals, upregulation of anti-apoptotic signals and abnormal cross talk of autophagy and apoptosis. Chemotherapeutic drugs induce pro-apoptosis in cancer cells; however, the upregulation of anti-apoptotic proteins, e.g. Bcl-2 and IAPs, would cause cancer resistance. Death receptors including NF-κB-, PI3/AKT-, and p53-related signaling pathways are also involved in the chemoresistance. Additionally, the aberrant autophagy may cause apoptosis evasion as well through autophagic protein regulation, caspase activation, and autophagic degradation. A further, in-depth understanding of apoptosis evasion would be helpful for developing strategies to circumvent cancer resistant to chemotherapy. Combined chemotherapeutic treatment, drugs targeting multiple targets, and using nanoscale drug delivery (nanomedicine) show promising potentials to overcome chemoresistance and achieve precision therapy.
