Etsuro Onuma

Involvement of parathyroid hormone–related protein in experimental cachexia induced by a human lung cancer–derived cell line established from a bone metastasis specimen

Cachexia often causes deterioration in the quality of life in cancer patients; however, its mechanism remains poorly understood. Cachexia has often been observed in experimental animals with bone metastases, and parathyroid hormone–related protein (PTHrP) plays an important role in the formation of such metastases. We therefore investigated the possible involvement of PTHrP in an experimental cachexia model using human lung‐cancer cells (HARA‐B). HARA‐B cells produce a high amount of PTHrP but no TNF‐α, IL‐6 or leukemia inhibitory factor. The s.c. inoculation of HARA‐B cells into nude mice caused reductions in body weight, adipose tissue weight, muscle weight and serum glucose levels. Serum levels of calcium and PTHrP increased. Neutralization of PTHrP with antibody caused rapid weight gain along with a rapid decrease in serum calcium levels. Our findings suggest that PTHrP plays an important role in the development of cancer cachexia. PTHrP therefore is a possible target molecule for the treatment of cancer cachexia.

Parathyroid Hormone-Related Protein Induces Cachectic Syndromes without Directly Modulating the Expression of Hypothalamic Feeding-Regulating Peptides

Purpose: Parathyroid hormone-related protein (PTHrP) is a causative factor of humoral hypercalcemia of malignancy (HHM) and concurrent anorexia and wasting. Because changes in the expression of hypothalamic feeding-regulating peptides can directly affect appetites and thereby can cause anorexia and wasting, we addressed whether the cachectic syndromes induced by PTHrP rely on the action of hypothalamic feeding-regulating peptides. Experimental Design: Rats were inoculated with a LC-6 human cancer xenograft that secreted PTHrP, and the mRNA levels of the hypothalamic feeding-regulating peptide genes and serum leptin levels were examined before and after the development of HHM by in situ hybridization histochemistry and ELISA, respectively. Some rats were given the anti-PTHrP antibody. Results and Conclusion: The mRNA levels for the orexigenic peptides, such as the agouti-related protein and the neuropeptide Y in the arcuate nucleus (Arc), were significantly increased after the development of HHM, whereas the mRNA levels for the anorexigenic peptides, such as the proopiomelanocortin in the Arc, the cocaine and amphetamine-regulated transcript in the Arc, and the corticotropin-releasing factor in the paraventricular nucleus, were significantly decreased after the development of HHM. Plasma leptin levels were also reduced in cachectic rats, and the administration of anti-PTHrP antibody to the cachectic rats not only improved the cachectic symptoms but also restored the mRNA levels of these orexigenic and anorexigenic peptides, except for orexin. Thus, PTHrP induces HHM and concurrent cachectic syndromes by mechanisms other than directly modulating the leptin or hypothalamic feeding-regulated peptides.

Increased Renal Calcium Reabsorption by Parathyroid Hormone–Related Protein Is a Causative Factor in the Development of Humoral Hypercalcemia of Malignancy Refractory to Osteoclastic Bone Resorption Inhibitors

Purpose: Bisphosphonate and calcitonin lower blood calcium in humoral hypercalcemia of malignancy (HHM) by suppressing osteoclastic bone resorption, but repeated administration of these drugs often leads to relapse. In this study, we examined the roles of parathyroid hormone–related protein (PTHrP) in the development of bisphosphonate- and calcitonin-refractory HHM. Experimental Design: Nude rats bearing the LC-6 JCK tumor xenograft (LC-6 rats) exhibited high bone turnover and HHM. Repeated administration of alendronate induced a sustained suppression of the bone resorption, but it caused only early and transient reduction of the blood calcium levels, leading to unresponsiveness to the drug. Because high blood levels of PTHrP were detected in the LC-6 rats, those that developed alendronate-refractory HHM were treated with an anti-PTHrP antibody. Results: Administration of anti-PTHrP antibody to animals that received repeated administration of alendronate, thereby developing alendronate-refractory HHM, resulted in an increase in fractional excretion of calcium and a marked decrease of blood calcium level. Drug-refractory HHM was also observed in animals that received another osteoclast inhibitor, an eel calcitonin analogue elcatonin. The blood calcium level decreased after the initial administration of elcatonin, but it eventually became elevated during repeated administration. Administration of the anti-PTHrP antibody, but not of alendronate, effectively reduced the blood calcium of the animals that developed elcatonin-refractory HHM. Conclusion: High levels of circulating PTHrP and the resulting augmentation of renal calcium reabsorption is one of the major causes of the emergence of osteoclast inhibitor-refractory HHM. Thus, blockage of PTHrP functions by a neutralizing antibody against PTHrP would benefit patients who develop bisphosphonate- or calcitonin-refractory HHM.

Parathyroid hormone–related protein (PTHrP) as a causative factor of cancer-associated wasting: Possible involvement of PTHrP in the repression of locomotor activity in rats bearing human tumor xenografts

Nude rats bearing the LC‐6‐JCK human lung cancer xenograft displayed cancer‐associated wasting syndrome in addition to humoral hypercalcemia of malignancy. In these rats, not only PTHrP but also several other human proinflammatory cytokines, such as IL‐6, leukemia‐inducing factor, IL‐8, IL‐5 and IL‐11, were secreted to the bloodstream. Proinflammatory cytokines induce acute‐phase reactions, as evidenced by a decrease of serum albumin and an increase in α1‐acid glycoprotein. Tumor resection abolished the production of proinflammatory cytokines and improved acute‐phase reactions, whereas anti‐PTHrP antibody affected neither proinflammatory cytokine production nor acute‐phase reactions. Nevertheless, tumor resection and administration of anti‐PTHrP antibody similarly and markedly attenuated not only hypercalcemia but also loss of fat, muscle and body weight. Body weight gain by anti‐PTHrP antibody was associated with increased food consumption; increased body weight from anti‐PTHrP antibody was observed when animals were freely fed but not when they were given the same feeding as those that received only vehicle. Furthermore, nude rats bearing LC‐6‐JCK showed reduced locomotor activity, less eating and drinking and low blood phosphorus; and anti‐PTHrP antibody restored them. Although alendronate, a bisphosphonate drug, decreased blood calcium, it affected neither locomotor activity nor serum phosphorus level. These results indicate that PTHrP represses physical activity and energy metabolism independently of hypercalcemia and proinflammatory cytokine actions and that deregulation of such physiologic activities and functions by PTHrP is at least in part involved in PTHrP‐induced wasting syndrome.

Capecitabine improves cancer cachexia and normalizes IL-6 and PTHrP levels in mouse cancer cachexia models

PurposeTo clarify the potential of parathyroid hormone-related protein (PTHrP) and interleukin-6 (IL-6) as cachectic factors in a colon 26 model and the effects of capecitabine on cancer cachexia as determined by plasma levels of IL-6 and PTHrP and body weight loss.MethodsFrom two colon 26 sublines-cancer cachectic clone20 and non-cachectic clone5 plasma levels of PTHrP protein and mRNA expression levels in tumor tissues were compared. An IL-6 neutralizing antibody, a PTHrP neutralizing antibody, and capecitabine were administered into mice bearing clone20 and their anticachectic effects evaluated.ResultsThe plasma level of PTHrP protein in mice bearing clone20 was higher than that in mice bearing clone5. The expression level of PTHrP mRNA was 49-fold higher in tumor tissues of clone20 than of clone5, according to GeneChip® analysis. PTHrP antibody as well as IL-6 antibody suppressed wasting of the body and gastrocnemius and adipose tissue weights. PTHrP antibody suppressed the induction of hypercalcemia but not hypoglycemia or elevation of IL-6, whereas IL-6 antibody suppressed the induction of hypoglycemia but not hypercalcemia or elevation of PTHrP. Capecitabine, a fluorinated pyrimidine anticancer agent, improved body wasting of mice bearing clone20 at a low dose with no reduction of tumor volume. Furthermore, capecitabine lowered the levels of PTHrP and IL-6 in plasma and suppressed hypoglycemia and hypercalcemia in this model. Capecitabine also showed anticachectic effects on cachexia in a cancer model induced by human cervical cancer cell line Y (also known as Yumoto).ConclusionsPTHrP and IL-6 were found to be factors in the development of cachexia in a colon 26 cancer model, and capecitabine improved cancer cachexia by suppressing the plasma levels of IL-6 and PTHrP in colon 26 and Y cachectic models.

The Activity of AA-193, A New Uricosuric Agent, in Animals

A new uricosuric agent, 5-chloro-7, 8-dihydro-3-phenylfuro[2, 3-g]-1, 2-benzisoxazole-7-carboxylic acid (AA–193), was compared with other uricosurics in the rat, mouse and cebus monkey.

Effect of dual inhibition of 5-alpha-reductase and aromatase on spontaneously developed canine prostatic hypertrophy.

Our aim was to assess the effect of dual inhibition of 5‐alpha‐reductase and aromatase on prostate glands.

Similar changes of hypothalamic feeding-regulating peptides mRNAs and plasma leptin levels in PTHrP-, LIF-secreting tumors-induced cachectic rats and adjuvant arthritic rats

Parathyroid hormone‐related protein (PTHrP) is a causative factor of humoral hypercalcemia in malignancy. However, it is difficult to explain the mechanism of anorexia/cachexia with PTHrP secretion in detail. Previously, we demonstrated that the expressions of orexigenic peptides increased and anorexigenic peptides decreased under cachectic conditions in rats carrying tumors secreting PTHrP. In this study, we investigated whether such changes in the expression of hypothalamic feeding‐regulating peptides can be solely attributed to PTHrP or are a general response under cachectic conditions. Cachectic syndromes were induced in rats by: (i) inoculation of human lung cancer LC‐6 cells that secreted PTHrP, (ii) inoculation of human melanoma SEKI cells that secrete not PTHrP but LIF1, (iii) injection of heat‐killed Mycobacterium leading to arthritis (AA) and (iv) oral administration of a high dose of 1α,25(OH)2D3 that resulted in hypercalcemia. The LC‐6‐bearing rats and AA rats were treated with or without anti‐PTHrP antibody and indomethacin, respectively, and the expression of the hypothalamic feeding‐regulating peptide mRNAs were examined by in situ hybridization histochemistry. The orexigenic peptide mRNAs, such as neuropeptide Y and agouti‐related protein, were significantly increased, and that of anorexigenic peptide mRNAs, such as proopiomelanocortin, cocaine‐ and amphetamine‐regulated transcript and corticotropin‐releasing hormone were significantly decreased when they developed cachectic syndromes and AA. A high dose of 1α,25(OH)2D3 caused hypercalcemia and body weight loss but did not affect the expression of hypothalamic feeding‐regulating peptide mRNAs. The expressions of the hypothalamic feeding‐regulating peptides change commonly in different chronic cachectic models without relating to serum calcium levels.

Structure–activity relationships of bioisosteric replacement of the carboxylic acid in novel androgen receptor pure antagonists

A series of 5,5-dimethylthiohydantoin derivatives were synthesized and evaluated for androgen receptor pure antagonistic activities for the treatment of hormone refractory prostate cancer. CH4933468 (32d) with a sulfonamide side chain not only exhibited antagonistic activity with no agonistic activity in the reporter gene assay but also inhibited the growth of bicalutamide-resistant cell lines. This compound also inhibited tumor growth of the LNCaP xenograft in mice dose-dependently.

Structural Basis for Antibody Discrimination between Two Hormones That Recognize the Parathyroid Hormone Receptor

Parathyroid hormone-related protein (PTHrP) plays a vital role in the embryonic development of the skeleton and other tissues. When it is produced in excess by cancers it can cause hypercalcemia, and its local production by breast cancer cells has been implicated in the pathogenesis of bone metastasis formation in that disease. Antibodies have been developed that neutralize the action of PTHrP through its receptor, parathyroid hormone receptor 1, without influencing parathyroid hormone action through the same receptor. Such neutralizing antibodies against PTHrP are therapeutically effective in animal models of the humoral hypercalcemia of malignancy and of bone metastasis formation. We have determined the crystal structure of the complex between PTHrP (residues 1–108) and a neutralizing monoclonal anti-PTHrP antibody that reveals the only point of contact is an α-helical structure extending from residues 14–29. Another striking feature is that the same residues that interact with the antibody also interact with parathyroid hormone receptor 1, showing that the antibody and the receptor binding site on the hormone closely overlap. The structure explains how the antibody discriminates between the two hormones and provides information that could be used in the development of novel agonists and antagonists of their common receptor.