Growth regulation and co-stimulation of human colorectal cancer cell lines by insulin-like growth factor I, II and transforming growth factor alpha.

We have tested growth factor responsiveness of a panel of eight human colorectal carcinoma cell lines. Insulin-like growth factors I and II (IGF-I and IGF-II) stimulated growth of five lines (HT-29, LS411N, LS513, SW480, WiDr). At 30 ng ml-1 both factors enhanced growth up to 3-fold. They induced half-maximal stimulation at 1.9-6.51 ng ml-1. Even after delayed addition IGF-I and II significantly enhanced growth in a short-term proliferation assay. They exerted maximal effects under limiting serum conditions (0.5% FCS) and at low cell density (1.25-5 x 10(4) ml-1). Using these conditions transforming growth factor alpha (TGF alpha) enhanced proliferation of all IGF-responsive cell lines, except SW480. 1.11-3.31 ng ml-1 were required to obtain a half-maximal response. With 10-20 ng ml-1 maximal stimulation occurred at plateau values different from those for IGF-I/II. Proliferation of all cell lines responsive to both IGF-I and TGF alpha was further enhanced by combining both factors, resulting a synergistic response of LS513, while the effects on HT-29, LS411N and WiDr were additive. With HT-29 and LS411N a 24 h exposure to TGF alpha was sufficient to obtain a full response in the co-stimulatory assay. Our results illustrate the importance of IGF-I/II and TGF alpha as stimulators of growth of colorectal carcinomas

Interactions of interferon-alpha 2a with 5'-deoxy-5-fluorouridine in colorectal cancer cells in vitro

The biological activity of 5'-deoxy-5-fluorouridine (5'-dFUrd) depends upon intracellular enzymatic cleavage by pyrimidine phosphorylase to form 5-fluorouracil (5-FU). Interferon-alpha 2a (IFN-alpha) effect was analysed alone and combined with 5-FU or 5'-dFUrd, on proliferation inhibition of eight human colorectal cancer cell lines. The toxicity of 5-FU was enhanced by IFN-alpha in only one line (SW-480). In contrast, interactive enhancement of IFN-alpha was observed with 5'-dFUrd in five lines (WiDr, HT-29, 513, SW-480 and Co-115). In each of the lines showing potentiation by IFN/5'dFUrd but not by IFN/5-FU, cytoplasmic pyrimidine phosphorylase activity was increased after 5 days' incubation with IFN-alpha in a dose-dependent manner. Two lines (LISP-1 and SW-620) showed no potentiation of either 5-FU or 5'-dFUrd toxicity by IFN-alpha, and no change in pyrimidine phosphorylase activity. Potentiation of 5'-dFUrd effect by IFN-alpha may thus be explained by an enhancement of its conversion to 5-FU through stimulation of pyrimidine phosphorylase activity

Interleukin 4 down-regulates expression of c-kit and autocrine stem cell factor in human colorectal carcinoma cells

Stem cell factor (SCF) is a cytokine which plays an important role in the development of precursor cells. We have investigated the expression of SCF and its receptor, the c-kit proto-oncogene, in human colorectal carcinoma cell lines. Using reverse transcription-PCR, we confirmed the expression of c-kit in two lines (151 74T and 151 034) and of SCF in 9 of 1 1 cell lines tested. In a Northern blot, a single transcript of 6.6 kb was detected for SCF mRNA. In addition, two lines (LS1 74T and HT29) synthesized SCF protein, as detected by Western blot analysis. SCF stimulated proliferation and colony formation of 151 74T in a dose-dependent manner up to 160%. A half-maximal effect was obtained with about 5.5 ng/ml of SCF under both growth conditions. 151 74T cells expressed the Mr 1 45,000 c-kit protein on the cell surface and a neutralizing anti-c-kit mAb inhibited colony formation of 151 74T by 40%. Interleukin 4 (11-4) completely inhibited SCF-induced proliferation of 151 74T cells. Interestingly, 11-4 induced an almost complete down-regulation of both c-kit and SCF expression in [Si 74T. Our findings suggest that in LS1 74T cells, an SCF-mediated autocrine loop is functional and that 11-4 down-regulates the expression of both the receptor and the ligand of this circuit