The nature of cancer and the mechanisms of its control: a review.

Observations on the nature of spontaneous tumours of mammary gland origin in mice, published over a 60-year period in 320 papers, are reviewed. Data presented are (1) development of adequate experimental mice; (2) comparative studies on transplantable, chemically induced and spontaneous tumours by diverse genetic procedures, and (3) tumour regressions obtained with nucleosides. The fundamental conclusion derived from these data is that a genetic change, comparable to a somatic mutation, is involved in the origin of cancer. Nucleosides, especially 5-methyl cytidine (a mild mutagen), have been indicated in the controlling mechanism for this genetic change. The nucleosides appear to be involved in the stabilization of the helical formation of the chromatid strand. The concept of induced stability of chromosome behaviour is discussed, and a number of other aspects including viral and endocrine influence, and histocompatibility.