Tyrosine kinases in control of cell growth and transformation.

The growth of normal cells in tissues is strictly controlled, partly through intercellular communication by polypeptide growth factors. Malignantly transformed cells are independent from external growth factors to a certain extent, but their mechanisms for achieving growth autonomy differ from case to case. Several of the oncogene-encoded proteins are known to participate in the hormonal regulation of cell growth (for a recent review on tyrosine kinase oncogenes see ref. 21). Recent advances in molecular biology have shown important mechanisms for cell emancipation from growth regulatory hormonal signaling systems. A few such examples are discussed below.