Parathyroid hormone and PTHmRNA in a human small cell lung cancer

Parathyroid Carcinoma and Ectopic Secretion of Parathyroid hormone

The most common causes of hypercalcemia are primary hyperparathyroidism (PHPT) and malignancy. Parathyroid carcinoma (PC), causing a severe PHPT, is the rarest parathyroid tumor. A diagnosis of PC is challenging because the clinical profile overlaps with that of benign counterpart. Surgery is the mainstay treatment. CDC73 mutations have been detected in up to 80% of sporadic PCs. Ectopic production of parathyroid hormone (PTH) by malignant nonparathyroid tumors is a rare condition accounting for less than 1% of hypercalcemia of malignancy. PTH secretion can be considered an aberration in the tissue specificity of gene expression and may involve heterogeneous molecular mechanisms.

Establishment and characterization of a novel cell line derived from a human small cell lung carcinoma that secretes parathyroid hormone, parathyroid hormone-related protein, and pro-opiomelanocortin

There are few case reports describing small cell lung carcinoma (SCLC), which secrete parathyroid hormone (PTH)-related protein (PTHrP) and result in hypercalcemia. We have established a novel cell line, derived from a 37-year-old woman with SCLC, which produced PTH, PTH-rP, and a part of proopiomelanocortin (POMC), and led to hypercalcemia. The cell line, named SS-1, was grown as floating cell clusters in DMEM/F12 medium supplemented with 10% fetal bovine serum and had a population doubling time of 72 h. The modal chromosome number was 47 (88%); marker chromosomes were not observed. The SS-1 cell line secreted not only PTHrP but also PTH, and both were decreased by CaCl(2) administration. Decreasing the concentration of Ca(++) in the growth medium stimulated the secretion of both PTHrP and PTH. The cell line had calcium sensing receptor (Cas-R). Since PTHrP and PTH secretion from the SS-1 cells was related to Ca(++) concentration in the growth medium, the cell line might be useful for the study of PTH-rP and PTH regulation as well as for SCLC analysis. In addition, the cells secreted N terminal POMC, the precursor of adrenocorticotropic hormone, in response to stimulation with corticotropin releasing hormone. In summary, we established a novel cell line, SS-1 from SCLC, which produced PTHrP, PTH and N terminal POMC.

Recurrent hypercalcemia due to ectopic production of parathyroid hormone-related protein and intact parathyroid hormone in a single patient with multiple malignancies

OBJECTIVE

To report a case of recurrent hypercalcemia due to ectopic production of parathyroid hormone (PTH) and parathyroid hormone-related protein (PTH-rP) from transitional cell carcinoma of the urinary bladder.

METHODS

We present clinical, laboratory, and pathologic findings in a 73-year-old man with recurrent hypercalcemia. Results of serum calcium, PTH, PTH-rP and immunostaining of tumors for PTH and PTH-rP over 9 years are presented.

RESULTS

In 1990 this patient was diagnosed with primary hyperparathyroidism, which was cured by resection of a parathyroid adenoma in the neck. Hypercalcemia recurred in 1992, and he was found to have squamous cell carcinoma of the right lung. PTH-rP levels were not measured, but the resected tumor immunostained positive for the presence of PTH-rP. The patient subsequently remained normocalcemic until 1996, when the plasma calcium and PTH levels increased again. Surgical exploration of the neck revealed no parathyroid adenoma. Elevated plasma levels of calcium and PTH persisted after surgery. In 1998 the patient was diagnosed with stage IV invasive transitional cell carcinoma (TCC) of the urinary bladder and underwent radical cystectomy. The tumor tissue was not immunoreactive to PTH-rP. A year later, plasma levels of PTH and PTH-rP increased, but surgical re-exploration of the neck again revealed no parathyroid adenoma. CT scanning identified a large retroperitoneal mass, and a CT-guided biopsy of the mass showed metastatic, poorly differentiated TCC immunopositive for PTH and PTH-rP.

CONCLUSION

This is the first report of ectopic production of PTH from metastatic TCC of the urinary bladder coexisting with PTH-rP mediated hypercalcemia.

MEN type 1 associated with mediastinal carcinoid producing parathyroid hormone, calcitonin and chorionic gonadotropin

A 34-year-old Japanese woman was admitted to our hospital with a mediastinal tumor. Laboratory data showed high levels of calcitonin (CT), human chorionic gonadotropin (hCG) and parathyroid hormone (PTH) in the serum. Surgery was performed, but the tumor could not be completely resected. The patient died in the 10th postoperative month due to systemic metastasis and cachexia. At autopsy, diffuse parathyroid hyperplasia and multiple islet cell tumors of the pancreas were found. A pathological diagnosis of multiple endocrine neoplasia (MEN) type 1 associated with mediastinal atypical carcinoid tumor was made. Immunohistochemical study indicated the tumor cells of the mediastinum to be positively stained for hCG beta but not for PTH or CT. The tumor tissue contained significantly high levels of CT, PTH and whole hCG. This is the first case report on MEN type 1 associated with mediastinal carcinoid tumor producing PTH, CT and hCG beta.