Inhibitory epidermal pentapeptide modulates proliferation and differentiation of transformed mouse epidermal cells in vitro

Novel lymphocyte growth-inhibiting tripeptide: N-acetyl-glu-ser-GlyNH(2)

The limited and predetermined number of cells that constitutes an organ or specialized cell population is to all appearances regulated according to a negative feedback principle involving growth inhibitors with sufficient tissue specificity. To find growth-inhibiting factors in lymphoid cells, we followed established purification procedures and assays. We found a single-peak fraction in water extracts of dog spleen homogenates that inhibited proliferation of Molt (T cell) lymphoma cells at low concentrations in vitro, with no significant effect on a B cell lymphoma cell line (Ramos). C-terminal amino acid sequencing and MS analysis showed the factor to be a tripeptide: N-acetyl-Glu-Ser-GlyNH(2). Treatment with a synthetic tripeptide with the structure N-acetyl-Glu-Ser-GlyNH(2) decreased the number of cell doublings of Molt cells. The peptide also delayed cell flux at the G(2)-M transition of the cell cycle, while incorporation of tritiated thymidine was not altered at the examined time points in this cell line. However, DNA synthesis in PPD-stimulated normal human lymphocytes was significantly inhibited and with a bell-shaped dose-response curve.

Regeneration of rat corneal epithelium is delayed by the inhibitory epidermal pentapeptide (EPP)

The effect of the inhibitory epidermal pentapeptide (EPP) on regeneration of rat corneal epithelium was studied over a 24-h period after removal of the central part of the corneal epithelium by means of n-heptanol and scraping. Both unphosphorylated and phosphorylated EPP inhibited the mitotic rate and the formation of new cells to the same extent. Thus, the mitosis inhibitor that originally was isolated from mouse epidermis, acts even on the ectodermally derived corneal epithelial cells.

Modulation of KB and A431 cell adhesion by epidermal growth inhibitory pentapeptide

A pentapaptide, pyroGlu-Glu-Asp-Ser-GlyOH (EPP), isolated from mouse epidermis, inhibits mitoses and enhances differentiation in primary cultures and in transformed mouse epidermal cells in vitro (Elgjo et al. 1986 b). The present work demonstrates that EPP also modulates the adhesiveness of two human tumour cell lines (KB and A431) of epidermal origin to uncoated plastic and to plastic coated with fibrinogen or collagen type 1. The adhesion modulatory effect of EPP was observed over a broad range of concentrations (10(-12)-10(-6) M), and depended on the substrate the cells were growing on. Thus, when cells were seeded on plastic or collagen, the attachment to the substrate was suppressed at the highest concentrations of EPP, and stimulated at the lowest ones. The opposite concentration-response pattern was observed when fibrinogen was used as substrate.