Cancer, human, various causes

In 1981, two eminent British cancer experts. Sir Richard Doll and Richard Peto published a paper in the Journal of the National Cancer Institute entitled The causes of cancer Quantitative estimates of avoidable risks of cancer in the United States today. The authors drew upon a vast body of literature of the type mentioned above, and attempted to allocate the deaths caused by cancers among various responsible factors. The authors concluded that a certain percentage of human cancer deaths could be avoided if exposure to the responsible factors could be eliminated or controlled in some way, although the appropriate degree and nature of control for some of the lifestyle factors, especially diet, is still highly uncertain. The Doll and Peto estimates are presented in Table 5.2. The factors are listed in a somewhat different order from how they were listed by the original authors, because of our interest in clearly separating lifestyle factors (the first... 

Recent epidemiological studies have accounted for all these factors and endorse the role of exposure to Cd in the development of cancer of various organs in humans, such as female breast and endometrial [171,172], lung [173], pancreatic [174,175], and bladder cancer [176]. Though of 11 cohort studies, only 3 implied Cd as a cause... 

Defects have been found in these mechanisms that cause various human diseases. For example, patients with the genetic disease xeroderma pigmentosum are especially sensitive to ultraviolet light and develop skin cancer. Skin fibroblasts cultured from these patients have been shown to be defective in DNA repair. 

Additional studies illustrate that IFN-y stimulates phagocytic activity in humans suffering from various cancers, AIDS and lepromatous leprosy (leprosy is caused by the bacterium Mycobacterium leprae. Lepromatous leprosy is a severe contagious form of the disease leading to disfigurement). IFN-y may thus prove useful in treating such conditions. 

Certain RNA viruses, particularly retroviruses, have also proven capable of inducing cancer. Retroviruses known to induce cancer in animals include Rous sarcoma virus, Kirsten murine sarcoma virus, avian myelocytomatosis virus, as well as various murine leukaemia viruses. Thus far, the only well-characterized human RNA transforming virus is that of human T cell lymphocytotropic virus-1 (HTLV-1), which can induce adult T cell leukaemia/lymphoma (ATL). Identification of antigens uniquely associated with various tumour types, and identification of additional cancer-causing viruses, remain areas of very active research. 

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