Infectious agents cancer associated with

Note The remaining 13-15% are due to infectious agents (certain viruses and parasites) and some genetic factors that predispose certain individuals. The authors have recently reduced the percent associated with occupation to about 1. The minus end of the range for food additives takes into account the fact that some of these substances, particularly the antioxidants, may protect against certain cancers. 

Immunosuppressants such as azathioprine and mercaptopurine have a significant potential for adverse reactions. Azathioprine causes bone marrow suppression and has been associated with lymphomas (in renal transplant patients), skin cancer, and pancreatitis (about 3% of patients). Some investigators believe that induction of leukopenia may be necessary for therapeutic effect. Mercaptopurine causes adverse reactions similarly to azathioprine however, there are fewer reports of lymphomas with this agent. In one cohort of IBD patients, adverse effects from mercaptopurine were as follows pancreatitis, 1.2% allergic reactions, 3.9%, significant leukopenia, 11.5% and infectious complications, 14%. Ten percent of patients who received azathioprine or mercaptopurine required discontinuation of treatment because of adverse effects. Allopurinol inhibits the metabolism of mercaptopurine, and a dosage reduction of the latter is required when the two are used in combination. 

The evaluation of the risks associated with cancer virus research is extremely difficult, since we lack much scientific data on such vital characteristics as agent host range, infec-tivity, host susceptibility, and infectious dose (see Section 11.2). Because the potential consequences of accidental inoculation of laboratory workers with oncogenic viruses are so serious, standards have been developed for work with these agents (476, 477). The technique of risk assessment, which classifies both agents and experimental procedures on the basis of their relative hazards, is very useful for assigning particular ents into hazard categories based upon available data. 

However, cytotoxicity still remains the serious problem. Chen et al. [234] have studied the cytotoxicity of CdTe/CdS (core-shell) as well as CdTe/CdS/ZnS (core-shell-shell) structured aqueous synthesized QDs, and their results suggest that the cytotoxicity of CdTe QDs not only comes from the release of Cd ions but also intracellular distribution of QDs in cells and the associated nanoscale effects [235], Recently, clinical applications of QDs have been reviewed [233], The application areas include (1) biomarker detection in various cancers, (2) imaging and sensing of infectious diseases, and (3) other clinical therapeutic applications. QDs with intense and stable fluorescent properties could enable the detection of tens to hundreds of cancer biomarkers in blood assays, on cancer tissue biopsies, or as contrast agents for medical imaging. 

---