[Growth factors. A new dimension in understanding oncogenesis]

The current understanding in biology and function of 4 growth factors is reviewed. PDGF suggests functions for proto-oncogens in normal cells, which may interact in tightly linked hierachies to induce malignant growth. PDGF-requirement of normal fibroblast cell-lines is lost when the cells are infected with tumor viruses. TGF is able to stimulate growth of normally anchorage dependent cells in an anchorage independent manner in soft agar. This ability is thought to be the best in-vitro correlate of neoplastic transformation. The peptide hormones bombesin/gastrin releasing factor and EGF can act as autocrine growth factors in various lung cancer cell-lines and stimulate clonal tumor cell growth in-vitro. The potential clinical application of these types of growth factors may enable the in-vitro growth from any lung cancer patient and allow individual drug testing. TCGF produced by T-cells to activate T-cells, is central to immune stimulation and immune response. Models for potential indirect anticancer effects either by in-vivo administration or by in-vivo incubation plus passive transfer of T-cells are presented to be initiated in future clinical trials.