PRO-NEUROTENSIN NEUROMEDIN-N EXPRESSION AND PROCESSING IN HUMAN COLON-CANCER CELL-LINES/

The regulatory peptide neurotensin NT has been proposed to exert an au tocrine trophic effect on human colon cancers. In the present study, p ro-neurotensin/neuromedin N (proNT/NN) expression and processing were investigated in 13 human colon cancer cell lines using a combination o f radioimmunoassay and HPLC techniques. All 13 cell lines displayed lo w to moderate levels of proNT/NN ranging from 10 to 250 fmol/mg protei n. However, only 6 (HCT8, LoVo, HT29, C119A, LS174T, and coloDM320) pr ocessed the precursor. Three of the latter (HCT8, LS174T, and coloDM32 0) were analysed in detail with regard to proNT/NN processing pattern and were found to produce NT and large precursor fragments ending with the NT or NN sequence. They had no detectable level of NN. Such a pro cessing pattern resembles that generated by the prohormone convertase PC5. Northern and Western blot analysis of prohormone convertase expre ssion in the 3 cell lines revealed that they were devoid of PC1 and PC 2, whereas they all expressed PC5. These data indicate that proNT/NN i s a good marker of human colon cancer cell lines while NT is found in only about half of the cell lines. They also suggest that, in addition to NT, several proNT/NN-derived products, Possibly generated by PC5, might exert an autocrine positive effect on human colon cancer growth. (C) 1998 Academic Press.