Cancer, Mankind′s Challenge

Cancer, or malignant tumour, is a group of diseases defined by the uncontrollable growth of the transformed cells, and their capabilities of invasion into surrounding healthy tissues and metastasis to remote sites in the body of organisms[1, 2]. According to different origins, it can be further divided into five subtypes: carcinoma, adenocarcinoma, sarcoma, lymphoma/leukemia and myeloma. Cancer is the second leading cause of death worldwide after cardiovascular disease (GBD 2013 Mortality and Causes of Death Collaborators 2015)[3]. Usually, scientists attribute tumorigenesis to the control loss of cell proliferation, inhibition of cell differentiation and blockade of cell senescence and death at cellular level; chromosome aneuploidy[4, 5] and hyperactive telomerase[6] at sub-cellular level; excessive activation of oncogenes and excessive inhibition of anti-oncogenes, gene mutation and epigenetic modification (DNA methylation and histone acetylation, etc.)[7] at molecular level, respectively. Mutagens in in vitro environment, including physical carcinogens (UV, X-rays, etc.), chemical carcinogens (Benzopyrene, Aflatoxin B1, etc.) and biological carcinogens (DNA viruses, RNA retroviruses) can promote the transformation of benign tumours to malignant tumours with the help of factors in in vivo envi-