Epidermal growth factor-stimulated parathyroid hormone-related protein expression involves increased gene transcription and mRNA stability

Abstract

Epidermal growth factor (EGF) produced rapid and striking effects on parathyroid hormone-related protein (PTHrP) gene expression in the immortalized human keratinocyte cell line, HaCaT. Steady-state levels of PTHrP mRNA and secreted PTHrP were increased 10-fold by maximally effective concentrations of EGF. EGF increased both PTHrP gene transcription and PTHrP mRNA stability. Nuclear run-on assays demonstrated a 4-fold increase in transcriptional rate in EGF-stimulated cells while transient transfection analysis indicated that the action of EGF on transcription involved both the GC-rich promoter, P2, and the downstream TATA promoter, P3, but apparently not the upstream TATA promoter, P1. In experiments where EGF treatment produced more stable PTHrP transcripts, the half-life of c-fos mRNA was unaltered, suggesting a relatively specific effect of EGF. Moreover, only those species of PTHrP mRNA containing two of the alternative 3' exons (exons VII and VIII) were stable, those containing exon IX were not. Reverse-transcription PCR demonstrated that EGF produced differential increases in the abundance of PTHrP mRNA species initiated by the three PTHrP promoters. The major effect was seen on the abundance of transcripts initiated by P1 and P2, with less marked regulation of P3-initiated transcripts. Thus EGF regulation of PTHrP gene expression in HaCaT cells is multifactorial and the combination of its actions at the 5' and 3' ends of the gene favours the accumulation of subpopulations of PTHrP mRNA containing exons I, VII and VIII.

PTHrP promotes malignancy of human oral cancer cell downstream of the EGFR signaling

“…PTHrP expression is regulated by various humoral factors including TGF-1 and EGF, which is expressed in cancer cells, and can increase transcription and stability of PTHrP mRNA, and secretion of the protein [9,10]. Our study clearly identified that EGF, but not TGF- 1, mediated transcriptional activation of PTHrP in OSCC (Fig.…”

Inhibition of epidermal growth factor receptor signalling reduces hypercalcaemia induced by human lung squamous-cell carcinoma in athymic mice

“…It has been known for over a decade that exogenous EGF stimulates PTHrP gene expression in a human lung SCC and keratinocyte lines (Tait et al, 1994;Heath et al, 1995), but it has not been determined whether EGFR signalling contributes to cancermediated syndromes such as HHM. We have established that the EGFR ligand, AREG, stimulated EGFR signalling and PTHrP gene expression in two human lung SCC lines that induce hypercalcaemia when grown in vivo.…”

PTHrP Gene Expression in Cancer: Do All Paths Lead to Ets?

“…Studies examining the effect of EGF on PTHrP mRNA stability demonstrated stabilization of PTHrP mRNA containing exon 7 (PTHrP 139), but not 9 (PTHrP 141), in human immortalized keratinocytes (HaCaT). 112 Sellers et al also showed that when the PTHrP 1-141 UTR was removed, TGF-b treatment was able to dramatically increase the stability of the transcript in squamous carcinoma cells in an in vitro system. 111 The authors attributed the effect to the decreased binding of various proteins (18 to 33 kDa) to a cis-element present within the PTHrP terminal coding region.…”

“…21 The halflife of PTHrP mRNA can also be increased in keratinocytes and squamous carcinoma cell lines by stimulation with TGF-β109-111 and epidermal growth factor (EGF). 112 In HTLV-1-infected cell lines, interleukin-2 (IL-2) 113 also stabilized PTHrP mRNA.…”