Tissue-specific proliferation

Promoters may well proliferate initiated cells that have formed spontaneously by erroneous cell division as well as those due to exposure to chemicals. Some promoters are tissue specific. 

Ohta, Y., Kijima, H., Ohkawa, T., Kashani-Sabet, M. and Scanlon, K.J. (1996) Tissue-specific expression of an anti-ras ribozyme inhibits proliferation of human malignant melanoma cells. Nucleic Acids Res., 24, 938-942. 

A great number of tissue-specific promoters has been isolated and characterized, and some of these have been used in experimental cancer gene therapy (see Table 1). Obviously, tissue-specific promoters are also active in the normal tissue from which the tumor originated. Unless the loss of these normal cells is acceptable (as in the case of melanocytes), additional specificity mechanisms need to be considered to make the resulting vector useful for a systemic delivery. This can be achieved, for example, by introducing an additional level of specificity, such as a specificity for proliferating cells or a selectivity for other conditions that are characteristic of tumor cells (see later). 

Jones, P. S., Savory, R., Barratt, P., Bell, A. R., Gray, T.J., Jenkins, N. A., Gilbert, D.J., Copeland, N. G., and Bell, D. R. (1995). Chromosomal Localisation, Inducibility, Tissue-Specific Expression and Strain Differences in Three Murine Peroxisome-Proliferator-Activated- Receptor Genes. Eur. J. Biochem. 233, 219-226. 

Mechanosensing is used to describe the process by which cells sense mechanical forces. Mechanochemical transduction is the phrase that is used to try to describe the biological processes by which external forces such as gravity influence the biochemical and genetic responses of cells and tissues. Specifically, these responses include stimulation of cell proliferation or apoptosis (death) and synthesis or catabolism of components of the extracellular matrix. These processes cause either increases in chemical energy (conversion of amino acids or other small molecules into macromolecules) or decreases in chemical energy (depolymerization of macromolecules). 

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