Regulation of parathyroid-hormone related peptide in a squamous cervical carcinoma cell line, CaSki

Buckle, Joy Ann (1999) Regulation of parathyroid-hormone related peptide in a squamous cervical carcinoma cell line, CaSki. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (16MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

PTHrP is produced by primary and established cervicalkeratinocytes. However, the factors involved in the expression and regulation of PTHrP in malignant cervical cells has not been characterized. The ectocervtcal epithelium is normally under the control of the sex steroid hormones, estrogen and progesterone. Here I report the effects of known regulators of PTHrP (EGF, dexamethasone and 1,25-dihydroxyvitamin D3) as well as the effects of potential tissue-specific regulators, 17β-estradiol and progesterone, on PTHrP expression and secretion in the human papillomavirus type 16 (HPV-16) infected squamous cervical cancer cell line, CaSki, using Northern analysis and radioimmunoassay. -- A dose-dependent increase in PTHrP mRNA levels was observed in response to EGF in the absence of FCS, with maximal stimulation (normalized to cyclophilin) at 20 ng/mL and a 3-fold increase in immunoreactive (i) PTHrP at 24 hours. 17β-Estradiol produced a dose- dependent increase in PTHrP mRNA expression with maximal stimulation observed at 10⁻⁸ M At this concentration, 17β-estradioi produced a 2.5-fold increase in iPTHrP at 24 hours. Progesterone did not produce a significant dose-dependent change in PTHrP mRNA expression. Nevertheless, the effects of progesterone were examined in time course studies at a concentrationof 10⁻⁸ M. A dose-dependentinhibitionof PTHrP mRNA expression was observed for both dexamethasone and 1,25-dihydroxyvitamin D₃, with maximal effects at 10⁻⁸ M. Both produced a 50% reduction in iPTHrP relative to control values at 24 hours in the presence of FCS. -- Time course studies were subsequently performed using those doses which showed maximal effects in dose-response experiments. An early increase in PTHrP mRNA expression (relative to control) was observed in response to EGF with a peak of 4.5-fold at 2 hours. Both dexamethasoneand 1,25-dihydroxyvitaminD₃ producedonly slight increases in PTHrP mRNA expression, relative to the time zero (basal), which were maximal at 2 and 4 hours, respectively. However, 24 hours after stimulation, a 50% inhibition of PTHrP mRNA expression was observed (relative to control) for both hormones. Stimulation with progesterone resulted in a 2-fold increase in PTHrP mRNA expression with peak effects at 2 hours. Treatment of the cells with 17β-estradiol produced a 3.5-fold increase in PTHrP mRNA expression with peak effects at 6 hours. -- In HPV-16 established human ectocervical cells (HEC-16), it had been previously demonstrated that known regulators as well as tissue-specific regulators (progesterone and 17β-estradiol) modified PTHrP production. The pattern of expression of PTHrP in CaSki cervical carcinoma cells was similar to that observed in HEC-16 cells. However, the level of iPTHrP secretion was significantly less in CaSki cells. This suggests a dysregulation of PTHrP in malignant cervical cells. The response to the tissue-specificsex steroid hormones, progesterone and 17β-estradiol, suggests an interaction with PTHrP and thus a possible regulatory role for PTHrP in the control of cellularproliferationand differentiationof cervical tissue. These results suggest that this model of cervical carcinoma could be used to assess the effects of other potential modulatory factors such as selective estrogen agonists or progesterone antagonists.

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