Activation of PTHrP gene expression in squamous carcinoma cell lines by mutant isoforms of the tumor suppressor p53

John Foley, Connie S. King, Juan A. Jiménez, John J. Wysolmerski, William M. Philbrick

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

We have evaluated the status of p53 expression in three squamous carcinoma cell lines that express high levels of PTHrP mRNA and protein and also cause hypercalcemia when grown in nude mice. All three of these lines possess a single p53 allele, each of which harbors a missense point mutation that gives rise to a mutant p53 protein with a denatured conformation. Using site-directed mutagenesis, we created a p53 expression construct bearing a missense mutation at codon 158, identical to that expressed by one of the cell lines. This construct and p53 constructs expressing representative denatured conformation mutants were then used to develop stably transfected lines, which expressed increased levels of PTHrP mRNA. Promoter-specific RNase protection indicated that this increase was due primarily to transcripts originating from the two TATA promoters, and not the GC-rich initiator clement within the PTHrP gene. Cotransfection of mutant p53 expression vectors with a scries of reporter constructs under the control of the human PTHrP promoter region showed that mutant p53 isoforms activated constructs containing multiple promoter elements and flanking sequences, but failed to activate constructs with individual promoters in isolation. These findings suggest that the activation of PTHrP gene expression by mutant p53 isoforms displaying a denatured conformation is dependent on interactions with sequences in the PTHrP gene regulatory region beyond the basal TATA promoters.

Original languageEnglish (US)
Pages (from-to)71-81
Number of pages11
JournalOncology Research
Volume12
Issue number2
DOIs
StatePublished - 2000

Keywords

  • Gain of function
  • Humoral hypercalcemia of malignancy
  • Mutant p53
  • PTHrp
  • Squamous cell carcinoma

ASJC Scopus subject areas

  • Cancer Research

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