Sustaining Proliferative Signaling

Increased and sustained proliferation is one of the most important characteristics of both tumor initiation and progression. Growth-promoting factors are involved in the regulation of cell proliferation, regulating both cell growth and cell division. The maintenance of an adequate number of cells in a given tissue is the result of tissue homeostatic regulations that determine the number and type of cells in the tissue as well as their distribution in the different compartments of the tissue. Disruption of these regulations, which allows tumor cells to divide uncontrollably, is the result of altered expression and/or activity of proteins related to cell cycle regulation. Proliferation is also promoted by the constitutive activation of multiple signal transduction pathways (Feitelson et al. 2015; Summya 2017).