Abstract
The paper collates a series of data arrived at by different authors in the study of molecular and cellular phenomena which are observed in chemical carcinogenesis and during the formation and turnover of macromolecules of normal cell plasma membrane at different phases of the cell cycle. The principal peculiarities of chemical carcinogenesis are: (1) hereditary nature of cell transformation; (2) absence of full correlation between mutagenic and carcinogenic activity; (3) the obligatory formation of a covalent bond between the chemical carcinogen and the macromolecule target; (4) the carcinogen’s ability to bond with H protein(s); (5) the absence of H protein(s) in transformed cells; (6) the induction of passivity of the overwhelming mass of cells of organs and tissues sensitive to the chemical carcinogen and subject to it, and the reversibility of this passivity in the case of all affected cells, except transformed ones; (7) the different immunological specificity of new transplantation antigens induced in cells of a single clone by one and the same carcinogen. The idea is advanced that these principal peculiarities can be understood from a single position if it is assumed that the key events during chemical carcinogenesis are the alterations of the conformation of certain proteins of plasma and perhaps other cell membranes, which is coupled to a loss of reversibility of their conformational transitions. It is asserted that as a result of the peculiarities of the formation and turnover of cell membrane macromolecules, which are characteristic of resting and dividing cells, these alterations of conformation are inherited according to Sonneborn’s heredity mechanism only by cells that have emerged from the Go phase of the cell cycle. The malignant cell which has arisen during chemical, or some other types of carcinogenesis, is thus a cell ‘locked’ in the G1 phase of the cell cycle, and therefore is continuously dividing, while bypassing the Go phase.