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.
Department of Veterinary Pathobiology, Ohio State University College of Veterinary Medicine, Columbus.
J I
JI
Merryman
C C
CC
Capen
L K
LK
McCauley
J R
JR
Werkmeister
M M
MM
Suter
T J
TJ
Rosol
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