Identification of Parathyroid Hormone-related Protein in Canine Apocrine Adenocarcinoma of the Anal Sac

Abstract

Abstract. The presence of parathyroid hormone-related protein (PTHrP) in the apocrine adenocarcinoma tumor line (CAC-8) derived from a hypercalcemic dog was demonstrated by western and northern blot analyses. Western blots of CAC-8 tumor extracts revealed a major protein with a molecular weight of approximately 18,000 daltons that cross-reacted with antiserum to human PTHrP. Northern blots demonstrated multiplesized messenger RNA transcripts in CAC-8 that hybridized to a full-length cDNA probe to human PTHrP. Adenocarcinomas derived from apocrine glands of the anal sac also were stained immunohistochemically for antigens that cross-react with antiserum to human PTHrP. The tumor line (CAC-8) maintained in nude mice stained positively for PTHrP in 13 of 24 tumors. Three of ten apocrine adenocarcinomas from dogs with hypercalcemia stained for PTHrP, whereas zero of ten tumors were positive from normocalcemic dogs. Normal canine epidermal keratinocytes and areas of squamous metaplasia in a perianal gland carcinoma also were positive for PTHrP. These data demonstrated that canine tissues contained a homologue to human PTHrP that likely is important in the pathogenesis of humoral hypercalcemia of malignancy.Key words: Anal sac; apocrine adenocarcinoma; dog; humoral hypercalcemia of malignancy; hypercalcemia; parathyroid hormone-related protein.The adenocarcinoma derived from apocrine glands of the anal sac commonly induces the syndrome of humoral hypercalcemia of malignancy (HHM) in dogs.15 An animal model of HHM has been developed in nude mice using a serially transplantable canine apocrine adenocarcinoma (CAC-8) derived from a hypercalcemic dog.26 Dogs and nude mice with the apocrine adenocarcinoma develop a syndrome of HHM that closely parallels the condition in human beings.16,26 Nude mice with transplanted CAC-8 develop the following: severe hypercalcemia and hypophosphatemia, increased serum 1,25-dihydroxycholecalciferol concentrations, decreased serum immunoreactive parathyroid hormone (PTH), hypercalciuria, increased urinary excretion of CAMP and hydroxyproline, and increased osteoclastic bone resorption and bone formation.22.26 Serum calcium concentration returns to the normal range within 2 days of surgical removal of the tumor.22The clinical disturbances of HHM are due to the release of humoral factors from neoplasms that have effects in tissues distant from the tumor, e.g., bone, kidney, and intestine.22 The factors most likely involved in the pathogenesis of HHM include PTH-like factors (proteins that bind to PTH receptors but do not cross-react immunologically with PTH), transforming growth factors a and /3, colony stimulating factors, and interleukin-1 .22 Many of the functional disturbances of HHM mimic the effects of excess PTH and result from a PTH-like protein(s) that binds to and stimulates PTH receptors in bone and kidney.18 Extracts of CAC-8 contain parathyroid hormone-like activity that will induce bone resorption and stimulate adenylate cyclase in vitro by binding to the PTH receptors of bone a...

Stromal and epithelial cells of the canine prostate express parathyroid hormone-related protein, but not the PTH/PTHrP receptor

“…As previously demonstrated in canine cells [34], only one transcript (1.2 kb) was detected in both stromal and epithelial prostate cells. PTHrP mRNA was abundant in both types of prostatic cells and compared with levels in a canine carcinoma previously shown to produce abundant amounts of PTHrP and to cause humoral hypercalcemia of malignancy in vivo [35]. PTHrP mRNA was detected as soon as 45 min and up to 24 hr after replacement of medium.…”

Parathyroid Hormone-related Protein in Normal and Neoplastic Canine Tissues: Immunohistochemical Localization and Biochemical Extraction

“…Neoplastic tissues included samples of adenocarcinoma of the apocnne glands of the anal sac (22), lymphoma (lo), oral squamous cell carcinoma (6), parathyroid gland adenoma (6), and pheochromocytoma (1) from either surgical biopsies or necropsies performed in the Department of Veterinary Pathobiology at Ohio State University. Serum calcium concentrations were determined during routine serum profile analysis.…”

Cloning of bovine parathyroid hormone-related protein (PTHrP) cDNA and expression of PTHrP mRNA in the bovine mammary gland

“…The membrane was washed in 1 SSC and 0·1% SDS at 50 C for 1 h and exposed to X-ray film overnight at 80 C. Total RNA (10 µg) isolated from a canine apocrine adenocarcinoma associated with humoral hypercalcemia of malignancy was used as a positive control for PTHrP (Rosol et al 1990). …”