transforming-growth-factor-alpha and Hypercalcemia

Tumors are frequently associated with factors that affect bone cell function and calcium homeostasis. As a result, many patients with cancer develop paraneoplastic syndromes. The commonest is hypercalcemia of malignancy. Other related paraneoplastic syndromes are hypocalcemia, hypophosphatemia, and osteomalacia.

Topics: Calcium; Cathepsin D; Enzyme Precursors; Hormones, Ectopic; Humans; Hypercalcemia; Hypocalcemia; Interleukin-1; Lymphotoxin-alpha; Osteomalacia; Paraneoplastic Endocrine Syndromes; Parathyroid Hormone; Parathyroid Hormone-Related Protein; Proteins; Transforming Growth Factor alpha; Tumor Necrosis Factor-alpha

The pathogenesis of cancer-associated hypercalcemia is not yet completely understood. This syndrome appears to be a consequence of the tumor production of humoral factors, mainly parathyroid hormone related protein (PTHrP). However, patients with humoral hypercalcemia of malignancy have features suggesting that factors other than PTHrP might play a role in this syndrome. We performed a case-control study in cancer patients with and without hypercalcemia. A total of 105 patients with a variety of tumors, 60 of them with hypercalcemia (corrected serum calcium over 2.6 mmol/l), and 45 without hypercalcemia. In a previous study, we demonstrated that plasma PTHrP was highly associated with hypercalcemia in these patients. In the present study, we measured the plasma levels of various bone cytokines: interleukin-1beta (IL-1beta), interleukin-6 (IL-6), transforming growth factor (TGF) alpha, and tumor necrosis factor (TNF) alpha, in these cancer patients. We also determined C-terminal type I procollagen (PICP) and C-terminal telopeptide of type I collagen (ICTP), bone formation and bone resorption markers, respectively, in serum in these patients. We found that these osteolytic cytokines do not increase in plasma by the presence of hypercalcemia. In fact, using a logistic regression analysis, a significant (P<0.02) association was found between the low plasma levels of IL-1beta and TGFalpha and hypercalcemia, independent of plasma PTHrP and the presence of bone metastasis, in these patients. No significant association between the plasma levels of IL-6 or TNFalpha and hypercalcemia was found in these cancer patients. Serum ICTP correlated (r=0.35; P=0.008) with hypercalcemia in these patients, but none of the cytokines studied in plasma correlated with either ICTP or PICP in these hypercalcemic patients. Our data indicate that the circulating levels of several bone cytokines are not enhanced by PTHrP in hypercalcemic cancer patients. The mechanism responsible for the association between the low plasma levels of some of these cytokines and hypercalcemia in these patients remains obscure. However, this finding does not rule out the possible local bone effects of these cytokines, contributing to hypercalcemia in cancer patients.

Topics: Adult; Aged; Aged, 80 and over; Biomarkers; Bone and Bones; Bone Development; Bone Resorption; Collagen; Collagen Type I; Cytokines; Humans; Hypercalcemia; Interleukin-1; Interleukin-6; Middle Aged; Neoplasms; Parathyroid Hormone-Related Protein; Peptide Fragments; Peptides; Procollagen; Proteins; Transforming Growth Factor alpha; Tumor Necrosis Factor-alpha

Osteoclastogenesis inhibitory factor (OCIF) is a novel secreted protein that inhibits osteoclastogenesis both in vitro and in vivo. In this study, we examined the effects of OCIF on serum calcium (Ca) concentrations in normal mice and in hypercalcemic nude mice carrying tumors associated with humoral hypercalcemia of malignancy. In normal mice, a single intraperitoneal injection of OCIF reduced serum Ca levels in a dose-dependent manner. Significant decrease in serum Ca (by 1.6 +/- 0.3 mg/dL, n = 5) was observed 2 h after the injection of OCIF at 20 mg/kg and the hypocalcemic effect continued for up to 12 h. Serum phosphate (Pi) concentrations also decreased in response to OCIF. Urinary excretion of Ca, Pi, and creatinine did not change significantly after injection of OCIF or vehicle. In hypercalcemic, tumor-bearing nude mice, a single intraperitoneal injection of OCIF at 20 mg/kg resulted in a dramatic decrease in serum Ca (maximal decrease 2.8 +/- 0.37 mg/dL, n = 11), which continued for up to 24 h. The results suggest that OCIF decreased serum Ca through its inhibitory effect on bone resorption. Furthermore, it is suggested that OCIF has therapeutic potential for the treatment of hypercalcemic conditions such as malignancy-associated hypercalcemia.

Topics: Animals; Calcium; Creatinine; Disease Models, Animal; Dose-Response Relationship, Drug; Glycoproteins; Hypercalcemia; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Proteins; Neoplasms, Experimental; Osteoprotegerin; Parathyroid Hormone-Related Protein; Phosphates; Proteins; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Recombinant Proteins; Transforming Growth Factor alpha

Ascites sarcoma 180 (S180A) is a transplantable tumor which causes hypercalcemia in tumor-bearing mice, and stimulates bone resorption without parathyroid hormone-like activity. In the present study, parathyroid hormone-related protein (PTHrP) mRNA could not be detected in total RNA from S180A cells. Bone-resorbing activity (BRA) derived from serum-free conditioned medium of S180A cells (S180A-CM) was coeluted with either transforming growth factor alpha (TGF alpha) activity (peak A, approximate M(r), 29 kDa) or lymphocyte-activating factor (LAF) activity (peak B, M(r), 20.1-24 kDa) in Bio-Gel P-100 column chromatography. Fractions in peak A and B contained IL-6 but not tumor necrosis factor alpha (TNF alpha). Subsequent separation of peak A by reverse-phase high performance liquid chromatography produced a single fraction which contained both BRA and TGF alpha activity. Recombinant human TGF alpha-induced bone resorption was completely inhibited by indomethacin. The BRA in peak A was partially inhibited by indomethacin and almost completely inhibited by simultaneous treatment of indomethacin and anti-IL-6 antibody. The BRA in peak B was partially inhibited by neutralization with anti-IL-1 alpha antibody and was completely inhibited by simultaneous treatment with anti-IL-1 alpha and anti-IL-6 antibody in the absence of indomethacin. Bone resorption induced by S180A-CM was associated with an increased production of prostaglandin E2 (PGE2) by calvaria. The BRA in S180A-CM, however, was not completely abolished by the simultaneous addition of indomethacin and anti-IL-1 alpha, anti-IL-1 beta and anti-IL-6 antibodies. Our findings indicate that (1) BRA derived from S180A cells includes TGF alpha, IL-1 alpha, IL-6 and some other unknown factor(s), distinct from PTHrP, IL-1 beta and TNF alpha, and (2) these unknown factors resorb bone in part via a PGE2-independent pathway.

Topics: Animals; Antibodies; Blotting, Northern; Bone Resorption; Culture Media, Conditioned; Cyclic AMP; Dinoprostone; Hypercalcemia; Indomethacin; Interleukin-1; Interleukin-6; Mice; Sarcoma 180; Transforming Growth Factor alpha; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

Humoral hypercalcemia of malignancy is a multifactorial syndrome caused by the action of tumor-produced factors on target organs of bone, kidney, and intestine to disrupt normal calcium homeostasis. Although parathyroid hormone-related protein (PTHrP) plays an integral role in the syndrome, tumors also produce other hypercalcemic factors, such as transforming growth factor-alpha (TGF-alpha), which may modulate the effects of PTHrP. In order to determine if the effects of PTHrP on calcium homeostasis can be modulated by TGF-alpha, we have used a human squamous cell carcinoma cell line (RWGT2) which produces PTHrP alone and Chinese hamster ovarian (CHO) cells expressing only transfected human TGF-alpha complementary DNA (CHO/TGF-alpha). We studied the effects of these tumors on calcium homeostasis in nude mice bearing both tumors or each tumor alone. Whole blood ionized calcium concentrations (mean +/- SEM in mmol/L) were significantly higher in mice bearing both RWGT2 and CHO/TGF-alpha tumors (3.11 +/- 0.06, P < 0.05) when compared with mice bearing either RWGT2 alone (2.02 +/- 0.06), CHO/TGF-alpha alone (1.42 +/- 0.01), or RWGT2 and nontransfected CHO tumors (1.86 +/- 0.01). This enhanced effect was also observed using continuous PTHrP-(1-34) infusion (2 micrograms/day) in mice bearing CHO/TGF-alpha tumors. In addition, tumor cell conditioned media was tested for bone resorbing activity in organ cultures of fetal rat long bones previously incorporated with 45calcium (45Ca++). Conditioned medium at 0.1% (vol/vol) from either RWGT2 or CHO/TGF-alpha had no bone resorbing activity over control (%45Ca++ release, mean +/- SEM; control 23 +/- 1, RWGT2 19 +/- 1, CHO/TGF-alpha 23 +/- 1). However, the combination of 0.1% conditioned medium from RWGT2 and CHO/TGF-alpha significantly increased bone resorption (53 +/- 2, P < 0.05). These data demonstrate that the hypercalcemic effects of tumor-produced PTHrP are enhanced by TGF-alpha and that this effect may be due to increased bone resorption.

Topics: Animals; Bone and Bones; Bone Resorption; Carcinoma, Squamous Cell; CHO Cells; Cricetinae; Culture Media, Conditioned; Humans; Hypercalcemia; Lung Neoplasms; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Middle Aged; Neoplasms; Parathyroid Hormone-Related Protein; Protein Biosynthesis; Proteins; Rats; Recombinant Proteins; Transfection; Transforming Growth Factor alpha; Tumor Cells, Cultured

Transforming growth factor alpha (TGF-alpha) is a polypeptide regulator of cell growth produced by many malignant tumors. It stimulates osteoclastic resorption in bone organ culture and osteoclast-like cell formation in marrow culture. To determine whether tumor production of TGF-alpha can cause hypercalcemia in vivo, we used Chinese hamster ovarian (CHO) cells transfected with the human TGF-alpha gene (TCHO), which stably express and secrete TGF-alpha. We used nontransfected CHO cells as controls (CCHO). TCHO and CCHO were inoculated intramuscularly into one hindlimb of nude mice and grew as local solid tumors. After 4 weeks of TCHO tumor growth, plasma ionized calcium (Ca2+) increased to reach 1.48 +/- 0.03 mM (mean +/- SEM), whereas mice bearing similarly sized CCHO tumors and non-tumor-bearing mice (NTB) remained normocalcemic (normal range for Ca2+, 1.15-1.30 mM). Plasma TGF-alpha was undetectable by an ELIFA assay in all NTB mice, was markedly increased in all TCHO mice (5.75 +/- 0.78 ng/ml), and was slightly increased in CCHO mice (0.50 +/- 0.22 ng/ml). Quantitative bone histomorphometry showed a prominent increase in osteoclastic bone resorption in TCHO mice. These data suggest that TGF-alpha is a mediator of hypercalcemia and increased osteoclastic bone resorption in tumors that produce it in sufficient quantity.

Topics: Animals; Bone and Bones; Bone Resorption; Cell Division; CHO Cells; Cricetinae; Cricetulus; Female; Hypercalcemia; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Neoplasm Transplantation; Ovarian Neoplasms; Transfection; Transforming Growth Factor alpha