Regulation of parathyroid hormone-related protein production by a squamous carcinoma cell line in vitro.
BACKGROUND
Humoral hypercalcemia of malignancy is a paraneoplastic syndrome associated with a variety of solid neoplasms including squamous cell carcinomas of various sites. Parathyroid hormone-related protein (PTHrP) is a newly recognized hormone that has been implicated as one of the major causative factors in the pathogenesis of this syndrome. A canine oral squamous carcinoma cell line (SCC 2/88) was used to investigate the regulation of production of PTHrP in response to agents that alter keratinocyte differentiation/proliferation in vitro.


METHODS
SCC 2/88 cells grown in serum-free media were exposed to various factors and PTHrP production was measured by radioimmunoassay. This cell line spontaneously produced substantial amounts of PTHrP (up to 7,000 pg/ml) without the need for a fibroblast-feeder layer. Production of PTHrP decreased at cellular confluence, and with increasing passage number.


RESULTS
Epidermal growth factor, cholera toxin, calcium, 1,25-dihydroxyvitamin D, ionomycin, trans-retinoic acid, transforming growth factor-beta 1 and hydrocortisone stimulated production of PTHrP by SCC 2/88 cells to various degrees. Transforming growth factor-beta 1 was the most potent stimulator of PTHrP production, with a maximal stimulation of 25-fold over control. Monensin decreased PTHrP secretion as early as 6 hours post-treatment and by 48 hours, there was no detectable PTHrP in the conditioned cell culture medium. Calcium, cholera toxin, ionomycin, and transforming growth factor-beta 1 decreased keratinocyte proliferation as measured by cell counts at all doses tested.


CONCLUSIONS
The results of this study revealed that SCC 2/88 cells spontaneously produced substantial amounts of PTHrP under baseline conditions and that compounds known to affect keratinocyte differentiation/proliferation up-regulated production of PTHrP. These cells will be valuable to investigate the molecular regulation of PTHrP production by squamous cell carcinomas.
Merryman
J I
JI
Department of Veterinary Pathobiology, Ohio State University College of Veterinary Medicine, Columbus.
Capen
C C
CC
McCauley
L K
LK
Werkmeister
J R
JR
Suter
M M
MM
Rosol
T J
TJ
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000662:veterinary; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology; D004283:Dog Diseases; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects; D007700:Kinetics; D009062:Mouth Neoplasms / Q000378:metabolism / Q000662:veterinary; D009363:Neoplasm Proteins / Q000096:biosynthesis; D044162:Parathyroid Hormone-Related Protein; D014176:Protein Biosynthesis; D011863:Radioimmunoassay; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D009363:Neoplasm Proteins; C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D016212:Transforming Growth Factor beta; D015759:Ionomycin; D014212:Tretinoin; D004815:Epidermal Growth Factor; D002772:Cholera Toxin; D002117:Calcitriol; D002118:Calcium; D006854:Hydrocortisone