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Abstract
Parathyroid hormone-like peptide (PLP) has been shown to be widely expressed in normal and neoplastic tissues. PLP gene expression was studied in a rat keratinocyte cell line. PLP mRNA transcripts and PLP secretion were induced following exposure to serum. The PLP mRNA 1/2 life was approximately 90$\sp\prime$ in both control and serum-stimulated cells. The serum induction was blocked by actinomycin D, implying a role for increased gene transcription in the serum induction of PLP gene expression. Cycloheximide induced PLP mRNA transcripts however, PLP gene expression was not superinduced in response to both serum and cycloheximide. Dexamethasone and vitamin D3 decreased the basal levels of PLP mRNA transcripts, while only the vitamin D3 caused a decrease in the serum induction. Epidermal growth factor (EGF) or transforming growth factor-$\beta$ (TGF-$\beta$) alone induced PLP mRNA transcripts, but no induction was observed following exposure to EGF and TGF-$\beta$ together. TPA treatment for 90$\sp\prime$ did not induce PLP mRNA transcripts but blocked the rapid serum induction of PLP gene expression. These features suggest that PLP is a member of the growth factor-regulated early response gene family. (Abstract shortened by UMI.)
