Cell Kinetics

Abstract

Cell kinetic concepts have pervaded radiation therapy since the early part of the 20th century and have been instrumental in the development of modern radiotherapy. In this review, the fundamental radiobiological concepts that have been developed based on cell kinetic knowledge will be revisited and discussed in the context of contemporary radiation therapy. This will include how the proliferation characteristics, variation in sensitivity during the cell cycle and the extent of radiation-induced cell cycle delay translate into a variable time for the expression of damage, how cell kinetics interacts with hypoxia and how the response to fractionated radiation schedules is influenced by cell kinetics in terms of repair, redistribution, reoxygenation and repopulation. The promise of combining radiation with new biologically targeted agents and the potential of non-invasive positron emission tomography imaging of proliferation are areas where cell kinetics will continue to influence radiotherapy practice.

Gamma radiation tolerance of a tropical species of midge,Chironomus ramosusChaudhuri (Diptera: Chironomidae)

“…In many arthropods studied so far (reviewed by Tilton andBrower 1983, Bakri et al 2005), the effect of gamma radiation was found to vary inversely with the developmental stage of the concerned species. It has been argued that there exists a direct relationship between radiosensitivity and the mitotic activity of the individual (Grosch 1962, Proverbs 1969, Pawlik and Keyomarsi 2004, Wilson 2007. Therefore, adults are more radioresistant than the juvenile stages while the eggs are the most sensitive to radiation.…”

Chronic Hypoxia Decreases Synthesis of Homologous Recombination Proteins to Offset Chemoresistance and Radioresistance

“…Therefore, numerous factors could alter overall DNA repair and cell fate within tumor subpopulations: the relative percentage of oxic or hypoxic or anoxic cells, the relative duration of hypoxic exposure and cell transit times (e.g., proportion of acute to chronic hypoxia), and differential protein function under a range of O 2 levels (e.g., differential biology between 0.0% and 5.0%; ref. 22). These factors need investigation as nonrepaired DNA breaks, as a function of the microenvironment, could activate oncogenes or inactivate tumor suppressor genes and drive a mutator phenotype and aggressive tumor cell phenotypes (4).…”

Cell kinetics of the marine spongeHalisarca caeruleareveal rapid cell turnover and shedding

“…Cell loss can occur by different mechanisms, including necrosis, programmed cell death (apoptosis) and shedding of cells. Knowledge of the cell kinetics is important for understanding the growth characteristics of a cell or cell populations in tissues or organisms (Wilson, 2007). Sponges possess most of the core elements of apoptosis, including members of the caspase family (Wiens and Müller, 2006), which are pivotal enzymes in apoptosis (Kumar, 2007).…”