The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.
Serum TT, SHBG, DHEAS and ADT levels are significantly lower in Arab men compared to those reported for Caucasian men, especially in early adulthood. Arab men with newly diagnosed prostate cancer have higher circulating androgens compared to healthy controls. We suggest that low circulating androgens and their adrenal precursors in Arab men when compared to Caucasians may partially account for the relatively lower risk for prostate cancer among Arab men.
N-acetyl-i-glucosaminidase (NAG) activity measured in sera from 129 breast cancer patients was elevated (mean 18.2 units/l) compared with that in sera from 28 healthy women (11.6 units/l) (p =0.001). There was a weak correlation between NAG activity and carcinoembryonic antigen (CEA) and CA-153, but no relationship to age, menopausal status, node status, stage, histology of tumour or to steroid receptors. NAG, CEA and CA-153 were measured in periodic follow-up samples taken after surgery (up to 26 months) from 17 patients. NAG activity fluctuated within a narrow range, unlike CEA and CA-153. In 70% of cases the pattern was similar to at least one of the other markers, and was generally maintained at a higher level in patients who suffered relapse compared with those who remained disease-free up to the last follow-up, but was not significantly altered before relapse. The measurement of NAG activity is unlikely to be of value in predicting time or occurrence of relapse or of clinical utility in post-surgical therapy. Increased appearance in serum may aid metastasis by degrading the extracellular matrix and it may be better investigated as a predictor of progression from in situ to invasive and metastatic cancer.
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