Cycling ⇄ Noncycling Cell Transitions in Tissue Aging, Immunological Surveillance, Transformation, and Tumor Growth

Abstract

Publisher Summary This chapter discusses the model for cell and tissue proliferation, which interrelates the problems of tissue aging, immunological surveillance, transformation, and tumor growth. The chapter illustrates diagrams that depict cycling and noncycling cell proliferative transitions as they apply to the problems of aging, immunological surveillance, transformation, and tumor growth. It also describes the cycling to noncycling cell transitions, which lead to the establishment of normal tissues composed of four major categories of cycling, noncycling G 1 -, G 0 -, and G 2 -blocked cells, which are arrested at different temporal and biochemical points in the G 1 and the G 2 periods of the cell cycle. Tissue proliferative aging and immunosenescence (age-related decline in immune function) are depicted as being caused by impaired release of noncycling cells to the proliferative cycling state. A primary tumor may arise from the immunological release and proliferation of preexisting, previously transformed dormant noncycling tumor cells, which had been held in restraint by immunological suppression.