Parathyroid Hormone-related Protein Secretion Research Articles

Interrogating Estrogen Signaling Pathways in Human ER-Positive Breast Cancer Cells Forming Bone Metastases in Mice.

Breast cancer bone metastases (BMET) are incurable, primarily osteolytic, and occur most commonly in estrogen receptor-α positive (ER+) breast cancer. ER+ human breast cancer BMET modeling in mice has demonstrated an estrogen (E2)-dependent increase in tumor-associated osteolysis and bone-resorbing osteoclasts, independent of estrogenic effects on tumor proliferation or bone turnover, suggesting a possible mechanistic link between tumoral ERα-driven osteolysis and ER+ bone progression. To explore this question, inducible secretion of the osteolytic factor, parathyroid hormone-related protein (PTHrP), was utilized as an in vitro screening bioassay to query the osteolytic potential of estrogen receptor- and signaling pathway-specific ligands in BMET-forming ER+ human breast cancer cells expressing ERα, ERß, and G protein-coupled ER. After identifying genomic ERα signaling, also responsibility for estrogen's proliferative effects, as necessary and sufficient for osteolytic PTHrP secretion, in vivo effects of a genomic-only ER agonist, estetrol (E4), on osteolytic ER+ BMET progression were examined. Surprisingly, while pharmacologic effects of E4 on estrogen-dependent tissues, including bone, were evident, E4 did not support osteolytic BMET progression (vs robust E2 effects), suggesting an important role for nongenomic ER signaling in ER+ metastatic progression at this site. Because bone effects of E4 did not completely recapitulate those of E2, the relative importance of nongenomic ER signaling in tumor vs bone cannot be ascertained here. Nonetheless, these intriguing findings suggest that targeted manipulation of estrogen signaling to mitigate ER+ metastatic progression in bone may require a nuanced approach, considering genomic and nongenomic effects of ER signaling on both sides of the tumor/bone interface.

Severe hypercalcemia due to metastatic pancreatic neuroendocrine tumor: a case report

BackgroundHypercalcemia of malignancy, as a paraneoplastic syndrome, is the most common metabolic disorder that accounts for 30% of malignancies and usually has a poor prognosis. Neuroendocrine tumors are uncommon and arise from neuroendocrine cells throughout the body. Actually, paraneoplastic hypercalcemia in neuroendocrine tumors is unusual and mostly associated with parathyroid hormone-related protein (PTHrP) secretion.Case presentationWe report a 51-year-old Iranian man who presented with nausea, vomiting, and significant weight loss for 1 month. Laboratory data revealed calcium of 26 mg/dl, accompanied by low level of PTH. Octreotide scan revealed a large donut-shaped octreotide avid lesion in the epigastric region at the right side of the mid-abdomen, with multiple varying size foci of abnormally increased radiotracer uptake in the epigastric region and both lobes of the liver. Endoscopic ultrasonography demonstrated a large heterogeneous mass lesion with irregular outline and good demarcation in the body of the pancreas with diffuse foci of calcification. Percutaneous biopsy of the liver mass demonstrated a well-differentiated neuroendocrine tumor (low grade) confirmed by immunohistochemistry with strongly positive chromogranin and synaptophysin stain. Hypercalcemia was treated with hydration, few sessions of hemodialysis, calcitonin, and denosumab injection. However, the patient developed symptomatic hypocalcemia. Oncology consultation led to prescription of long-acting octreotide 30 mg monthly and everolimus daily.ConclusionPancreatic neuroendocrine tumor could lead to malignant hypercalcemia; secretion of PTHrP is the most common cause, and signs and symptoms are usually milder than paraneoplastic syndrome due to hematologic and solid tumor. Generally, survival is better; however, its treatment is challenging, and primary debulking surgery is often required. A team approach to management is important at all points.

What Lies behind Paraneoplastic Hypercalcemia Secondary to Well-Differentiated Neuroendocrine Neoplasms? A Systematic Review of the Literature.

Background: Neuroendocrine neoplasms (NEN) originate from neuroendocrine cells ubiquitously spread throughout the body. Hypercalcemia associated with cancer is the most common life-threatening metabolic disorder in patients with advanced stage cancer. Paraneoplastic hypercalcemia is more commonly associated with hematological malignancies, renal and breast carcinomas, and squamous cell carcinomas, but it has also been described in patients with well-differentiated NEN, where it often remains undiagnosed. Among its causes, systemic secretion of parathyroid hormone-related protein (PTHrP) and ectopic production of 1,25-dihydroxyvitamin D and parathyroid hormone (PTH) may be considered paraneoplastic causes of hypercalcemia. In order to clarify the diagnostic work up of paraneoplastic hypercalcemia in patients with NEN, we perform a systematic review, which is lacking in the literature. Methods: We performed a data search using MEDLINE and SCOPUS including papers from 1961 to 2021. We selected articles on paraneoplastic hypercalcemia associated with well-differentiated NEN. Results: The search led to the selection of 78 publications for a total of 114 patients. Pooled data showed that the most frequent primary tumor site associated with paraneoplastic hypercalcemia was pancreatic NEN, followed by Pheochromocytoma. In most cases, paraneoplastic hypercalcemia was caused by PTHrP production and secretion. In more than two thirds of cases, paraneoplastic hypercalcemia was present at the time of NEN diagnosis and, in metachronous cases, was related to local recurrence, distant metastasis development, or tumor progression. In most patients, a combination of therapeutic approaches was employed, and reduction of the tumor burden was essential to control the paraneoplastic syndrome. Discussion: The onset of hypercalcemia associated with cancer in patients with well-differentiated NEN represents a major clinical challenge. The complex clinical and therapeutical management of paraneoplastic hypercalcemia implies the need for a multidisciplinary approach, aimed at controlling the clinical syndrome and tumor growth.

Abstract #1183557: Parathyroid Hormone-Related Protein Causing Hypercalcemia in a Patient with Large Cell Lung Cancer

Secretion of parathyroid hormone-related protein (PTHrP) accounts for up to 80% of cases with hypercalcemia of malignancy. It is most commonly associated with lung cancer, with a reported incidence up to 12.5% in those at advanced stages. While elevated PTHrP levels have been reported with all histologic types of lung cancer, it is rare in large cell carcinoma, with only 3 previously reported cases.

Abstract #1159516: A Rare Case of Hypercalcemia Mediated by PTHrP and 1,25-dihyroxyvitamin D in a Patient with Pancreatic Neuroendocrine Tumor

In patients with hypercalcemia of malignancy, the secretion of parathyroid hormone-related protein (PTHrP) is commonly seen. Rarely, neoplasms can cause hypercalcemia from multiple mechanisms, which can affect the treatment options. We present a patient with metastatic pancreatic neuroendocrine tumor who developed hypercalcemia secondary to simultaneous elevations in both PTHrP and 1,25-dihydroxyvitamin D.

Abstract 2827: Inactivating calcium-sensing receptor polymorphisms at rs1801725 are associated with increased risk of secondary malignancies

Abstract The dysregulation of systemic calcium homeostasis during malignancy is common in most patients with high-grade tumors. The associated comorbidity is known as cancer-induced hypercalcemia (CIH) which affects up to 30% of cases, in the absence of metastasis. In the course of breast cancer progression, the secretion of parathyroid hormone-related protein (PTHrP) by tumor cells and the associated destruction of bone tissues, leads to a progressive increase in systemic calcium or CIH. The increase in circulating Ca2+ is sensed by the calcium-sensing receptor (CaSR), which plays a significant role in maintaining Ca2+ homeostasis. More than 200 mutations and single nucleotide polymorphisms (SNPs) in the CaSR gene have been described, including the A986S CaSR at rs1801725 and Q1011E CaSR at rs1801726 SNPs with reduced sensitivity to Ca2+. Interestingly, high circulating Ca2+ is associated with aggressive breast tumors in premenopausal women and larger tumors in postmenopausal women; however, the contribution of the CaSR in breast cancer progression remains poorly understood. Unlike SNPs at rs1801726, up to 20% of breast cancer patients with SNPs at rs1801725 may be predisposed to higher circulating Ca2+ in the course of their disease. Since breast cancer frequently metastasizes to Ca2+ rich skeletal tissues, we hypothesize that the development of CIH and subsequent desensitization of the CaSR by sustained high Ca2+ is critical for both the adaptation of TNBC cells to CIH in Ca2+ rich microenvironments and TNBC progression. Our preliminary data reveal that the expression level and mutational status of the CaSR is cell type-specific, and that sustained high Ca2+ desensitizes the receptor, but promotes tumor cell growth and motility. In addition, our preliminary data show that the A986S SNP is associated with hypercalcemia, secondary malignancy of bone and respiratory organs, and deficiency of humoral immunity. This study provides novel insights into not only the adaptation of TNBC cells to high circulating Ca2+, but also suggests that mutations of the CaSR at rs1801725 are predictive of the likelihood for metastasis to lungs and bone. Citation Format: Heather K. Beasley, Ky'Era V. Actkins, Annika B. Faucon, Lea K. Davis, Amos M. Sakwe. Inactivating calcium-sensing receptor polymorphisms at rs1801725 are associated with increased risk of secondary malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2827.

The Calcium-Sensing Receptor (CaSR) Variants at rs1801725 Increase the Risk of Developing Secondary Malignant Cancers

The dysregulation of systemic calcium homeostasis during malignancy is common in most patients with high-grade tumors. The associated comorbidity is known as cancer-induced hypercalcemia (CIH) which affects up to 30% of cases, in the absence of metastasis. In the course of breast cancer progression, the secretion of parathyroid hormone-related protein (PTHrP) by tumor cells and the associated destruction of bone tissues, leads to a progressive increase in systemic calcium or CIH. The increase in circulating Ca2+ is sensed by the calcium-sensing receptor (CaSR), which plays a significant role in maintaining Ca2+ homeostasis. More than 200 mutations and single nucleotide polymorphisms (SNPs) in the CaSR gene have been described, including the A986S CaSR at rs1801725 and Q1011E CaSR at rs1801726 SNPs with reduced sensitivity to Ca2+. Interestingly, high circulating Ca2+ is associated with aggressive breast tumors in premenopausal women and larger tumors in postmenopausal women; however, the contribution of the CaSR in breast cancer progression remains poorly understood. Unlike SNPs at rs1801726, up to 20% of breast cancer patients with SNPs at rs1801725 may be predisposed to higher circulating Ca2+ in the course of their disease. Since breast cancer frequently metastasizes to Ca2+ rich skeletal tissues, we hypothesize that the development of CIH and subsequent desensitization of the CaSR by sustained high Ca2+ is critical for both the adaptation of TNBC cells to CIH in Ca2+ rich microenvironments and TNBC progression. Our preliminary data reveal that the expression level and mutational status of the CaSR is cell type-specific, and that sustained high Ca2+ desensitizes the receptor, but promotes tumor cell growth and motility. Sustained high Ca2+ also triggers the expression of metastasis promoting genes, including the cancer/testis antigen, MAGEC2, and Plasminogen Activator Inhibitor, PAI-2, potentially via the early response genes FOS/FOSB. In addition, our preliminary data show that the A986S SNP is associated with hypercalcemia, secondary malignancy of bone and respiratory organs, and deficiency of humoral immunity. This study provides novel insights into not only the adaptation of TNBC cells to high circulating Ca2+, but also suggests that mutations of the CaSR at rs1801725 are predictive of the likelihood for metastasis to lungs and bone.

Treatment-Resistant Hypercalcemia Secondary to Ectopic PTH Hypersecretion From Disseminated Ovarian Cancer

Background: Hypercalcemia of malignancy (HCM) can present secondary to hypersecretion of parathyroid hormone (PTH)-related protein (PTHrP) from malignant tumors, but rare cases of HCM have also been documented due to inappropriate PTH secretion from ectopic neoplasms. Here, we report an unusual case of HCM due to hypersecretion of PTH from a disseminated mucinous ovarian adenocarcinoma. Case Presentation: A 45-year-old female presented with confusion, constipation, fatigue, and abdominal pain two weeks after total abdominal hysterectomy with bilateral salpingo-oophorectomy and suboptimal debulking of a newly discovered left ovarian mucinous adenocarcinoma with metastasis to the bladder, parametrium, vagina, right ovary, and rectosigmoid. Subsequent CT revealed numerous bilateral pulmonary nodules, hilar adenopathy, liver lesions, and abdominal adenopathy. On exam, she was tachycardic and hypertensive with diaphoresis, dry mucous membranes, respiratory distress, guarded abdominal tenderness, and altered mental status. Her labs were significant for a serum calcium of 21.7 mg/dL, creatinine of 1.93 mg/dL, ferritin of 2,379 ng/mL, leukocytosis of 21.9 bil/L, PTH of 1,061 pg/mL, and PTHrP of 29 pmol/L. Ectopic PTH secretion was highly suspected after negative parathyroid ultrasound. Pamidronate (60 mg IV), calcitonin (200 U IM), and fluid resuscitation were unable to normalize her serum calcium, resulting in the need for dialysis and subsequent continuous renal replacement therapy. Further intervention with denosumab (120 mg SQ), etelcalcetide (5 mg IV), and cinacalcet (60 mg PO) was also attempted. Serum calcium began to decline, but repeat PTH resulted greater than 2,500 pg/mL. Unfortunately, the patient died just one week into her hospital course from septic shock and multi-organ system failure. Discussion: Hypercalcemia of malignancy typically arises from tumor secretion of PTHrP, cytokine release from osteolytic metastases, or tumor production of calcitriol. In cases of hypercalcemia due to excess PTH secretion, primary parathyroid etiologies are typically considered while ectopic PTH-secreting tumors are rare. PTH staining of biopsy specimens and total body sestamibi scan may prove useful in the early detection and treatment of these tumors, but HCM offers a poor prognosis with mean survival of 2 to 3 months and in-hospital mortality of 6.8%. Currently, there are only three cases in the reported literature of ectopic PTH-induced hypercalcemia related to ovarian cancer. To our knowledge, this is the fourth reported case. Conclusion: Ectopic PTH-secreting tumors carry a poor prognosis and should be considered in cancer patients presenting with PTH-associated hypercalcemia. Biopsy staining for PTH and total body sestamibi scan may assist in the early detection of these tumors, but current treatment strategies offer suboptimal outcomes.

Annexin A1 is a potential biomarker of bone metastasis in small cell lung cancer.

Small cell lung cancer (SCLC) is a subtype of lung cancer with a poor prognosis, with bone metastasis being one of the main causes of treatment failure. Therefore, investigating new biomarkers associated with bone metastasis may result in positive treatment outcomes. The present study detected the expression levels of annexin A1 (ANXA1) in the serum of 82 patients with SCLC using ELISA. ANXA1 expression in patients with SCLC with bone metastasis was significantly higher compared with that in patients without bone metastasis. Receiver operating characteristic analysis revealed that ANXA1 expression was significant in the diagnosis of bone metastasis in SCLC. ANXA1 was inhibited in SBC-5 cells and overexpressed in SBC-3 cells. Results revealed that ANXA1 was able to enhance SCLC cell proliferation, invasion, migration and bone adhesion in vitro. In vivo xenograft bone metastasis assays indicated that ANXA1 had the potential to promote the bone-metastasis ability of SCLC cells in NOD/SCID mice. Furthermore, ANXA1 increased parathyroid hormone-related protein secretion and enhanced Smad2 phosphorylation following TGF-β treatment in SCLC cells. Overall, ANXA1 may be involved in the pathogenesis of bone metastasis in SCLC and may be a potential biomarker for the diagnosis of SCLC.

SAT-346 Hypercalcemia Secondary to Calcitriol and PTHrP Cosecretion Only Responsive to Hydroxychloroquine

Background: Hypercalcemia of malignancy mediated by concurrent elevations in both 1,25-dihydroxyvitamin D (calcitriol) and parathyroid hormone (PTH)-related protein (PTHrP) is a rare phenomenon previously only reported with solid tumors. The preferred treatment for calcitriol-mediated hypercalcemia is glucocorticoid therapy and second-line therapy is traditionally ketoconazole. Hydroxychloroquine has previously been reported as efficacious only in cases of calcitriol excess related to sarcoidosis. Clinical case: A sixty-two year-old female with a history of diffuse large B cell lymphoma, complicated by disease progression despite multiple treatment regimens over the preceding five years, developed acute hypercalcemia to a corrected value of 14.7 mg/dL (8.9-10.3). Work-up revealed a suppressed PTH, PTHrP <2.0 pmol/L (0.0-3.4), and calcitriol elevation of 136.0 pg/mL (19.9-79.3). She was treated with zolendronate with rapid normalization of calcium levels. Upon recurrence of hypercalcemia six months later, repeat calcitriol was 176.0 pg/mL with a new PTHrP elevation of 7.0 pmol/L. Repeat dosing of zolendronate was less efficacious. She was prescribed prednisone 60 mg daily with subsequent addition of denosumab 120 mg weekly with continued hypercalcemia. Given rising levels of calcitriol and PTHrP (up to 285.6 pg/mL and 43.5 pmol/L, respectively) and potential drug interactions between ketoconazole and her chemotherapy, she was started on hydroxychloroquine 400 mg daily. Her calcium normalized and calcitriol dropped to 61.1 pg/mL despite imaging evidence of continued lymphoma progression. Three weeks later, she developed septic shock and was transitioned to hospice. Conclusion: In reviewing the literature, this appears to be the first reported case of a hematologic malignancy with pathologic levels of both calcitriol and PTHrP. It is also the first reported efficacy of hydroxychloroquine in malignant hypercalcemia. Interestingly, PTHrP secretion occurred months after the initial development of hypercalcemia. Control of both calcitriol and calcium levels did not occur until initiation of hydroxychloroquine despite preceding use of high-dose glucocorticoids and anti-resorptive therapy. Our case suggests that hydroxychloroquine should be considered in cases of calcitriol-mediated hypercalcemia resistant to glucocorticoids, particularly as it has less drug interactions and a more favorable side effect profile when compared to ketoconazole.

Abstract 133: The role of the calcium-sensing receptor (CaSR) in the adaptation of breast cancer cells in high Ca2+ microenvironments

Abstract Cancer-induced hypercalcemia (CIH) is common in cancer patients with metastatic disease and in up to 30% of cases without metastasis. During malignancy, tumor cells secrete factors such as parathyroid hormone related protein (PTHrP) that causes the destruction of bone tissue, or osteolysis. The resulting persistent osteolysis leads to a progressive increase in systemic calcium or CIH. High circulating Ca2+ is sensed by the calcium-sensing receptor (CaSR), which plays a significant role in maintaining Ca2+ homeostasis, and also stimulates the secretion of PTHrP which promotes tumor cell proliferation and motility. Moreover, more than 200 mutations including single nucleotide polymorphisms (SNPs) in the CaSR gene have been described, including the inactivating A986S CaSR at rs1801725 and Q1011E CaSR at rs1801726 SNPs with reduced sensitivity to Ca2+ . Although the CaSR is the major cell surface Ca2+ sensor in most cell types, its function in the Ca2+ rich bone microenvironment remains unclear. We show that high Ca2+ adaptation of MDA-MB-231 cells, did not lead to altered expression of the receptor in the surviving cells. However, the receptor was desensitized to high Ca2+ and the cells were more motile and formed larger colonies in 3D cultures. Meanwhile, gene expression profiling of triple negative breast cancer cells (TNBC) cells transiently exposed to high Ca2+ reveals the expression of early response genes and Ca2+ -inducible genes with known functions in tumor growth and/or motility. Since breast cancer (BC) frequently metastasizes to skeletal tissues, these data suggest that BC cells that successfully colonize the bone microenvironment undergo high Ca2+ adaptation or priming via the expression of high Ca2+ inducible genes that facilitate cell growth and/or motility. Citation Format: Heather K. Beasley, Ky'Era V. Actkins, Sarrah E. Widatalla, Diva S. Whalen, Stephen D. Williams, Olga Y. Korolkova, Amos M. Sakwe. The role of the calcium-sensing receptor (CaSR) in the adaptation of breast cancer cells in high Ca2+ microenvironments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 133.

THE ROLE OF PARATHYROID HORMONE-RELATED PROTEIN IN PATHOGENESIS OF DISORDERS OF BLADDER CONTRACTILE FUNCTION

Aim. Based on the analysis of the scientific literature sources, the authors aimed to summarize and present the existing information about the role of parathyroid hormone-related protein (PTHrP) in pathogenesis of disorders of bladder contractile function. Materials and methods . Analysis of literature in databases Google Scholar, Scopus, Web of Scence, PabMed for the whole time period of studying the stated problem. Results . In the recent years, one can observe a growing interest to dysfunction of bladder with insuffi contractile activity of detrusor. The low level activity of bladder can be often observed, while its diagnostics and treatment remain problematic. The existing ideas about the role of parathyroid hormone-related protein (PTHrP) in regulation of bladder’s functional condition are based on the results of few and mostly experimental research studies. It is proved that PTHrP secretion is induced in bladder as a result of bladder stretching, and prevents spontaneous contraction of detrusor’s smooth muscles, which has PTH/PTHrPreceptors, and also reduces contraction amplitude of bladder. It was stated that increased PTHrP secretion in response to the stretching smooth muscles is a part of autocrine effect, relaxing the bladder during its fi The existing scientifi data show that PTHrP is a unique endogenous detrusor relaxant, which functions by means of PTH/PTHrP-receptors located in bladder. It is assumed that PTHrP can also have a paracrine effect on vessels that regulate the blood fl bladder fi or can change neural activity. Thus, PTHrP is a powerful endogenous relaxant of bladder contraction, while autocrine or paracrine mechanisms of this effect are physiologically relevant processes happening in bladder. It is assumed that disturbed binding PTHrP with its receptor can be part ofpathogenesis of bladder disorders. In our opinion, the infl of chronic high PTHrP level in blood fl on the detrusor muscle structures can be also considered as one of the reasons that cause functional insuffi of bladder. This assumption is based on comparison of the PTHrP-effects on the bladder functional condition, presented in the experiment, as well as in the few clinical studies. Direct infl targeting the interaction of PTHrP with its specifi PTH/PTHrP-receptor is considered as a potential therapeutic approach to treat pathological conditions related to disorder of bladder contractile function. Conclusion . The literature survey covers general ideas about functional insufficiency of bladder, as well as information about the role of PTHrP in its development. The studied problem is rather relevant and frequent in the population, and besides being seen as a urological pathology, it is associated with a considerable reduction of the quality of life for patients. More detailed clinical studies will let us specify the diagnostics criteria of this syndrome and develop the schemes for pathogenetic therapy .

Inhibition effects of total flavonoids from Sculellaria barbata D. Don on human breast carcinoma bone metastasis via downregulating PTHrP pathway.

It is abundantly clear that tumor-derived parathyroid hormone-related protein (PTHrP), receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) are central contributors in promoting osteolytic process of breast carcinoma bone metastasis. Forcusing on this molecular basis, the study was undertaken to explore the inhibition effects of total flavonoids from Scutellaria barbata D. Don (TF-SB) on human breast carcinoma bone metastasis. MDA-MB-231 cells and nude mouse models of breast cancer bone metastasis were given TF-SB in different concentrations. The proliferation, migration and invasion potentials of MDA-MB-231 cells were respectively tested. The effects of TF-SB on tumor weights and bone destruction were investigated. The mRNA and protein expression of PTHrP, OPG and RANKL were assessed by qPCR and western blot analysis. In vitro, TF-SB inhibited the proliferation, migration and invasion of MDA-MB-231 cells in a dose-dependent manner. In vivo, TF-SB prevented bone metastasis of breast cancer by decreasing the number of osteoclast cells per field in a dose-dependent manner, but not affecting tumor growth or mouse survival. Molecular analysis revealed that TF-SB controled the secretion of osteolysis-related factors PTHrP and its downstream RANKL/OPG. Together, by controlling the expression of PTHrP and its downstream OPG/RANKL, TF-SB has significant inhibition effects on breast cancer bone metastasis, which indicates a new therapeutic method.

Bioactivity of Turmeric-derived Curcuminoids and Related Metabolites in Breast Cancer

While the chemotherapeutic effect of curcumin, one of three major curcuminoids derived from turmeric, has been reported, largely unexplored are the effects of complex turmeric extracts more analogous to traditional medicinal preparations, as well as the relative importance of the three curcuminoids and their metabolites as anti-cancer agents. These studies document the pharmacodynamic effects of chemically-complex turmeric extracts relative to curcuminoids on human breast cancer cell growth and tumor cell secretion of parathyroid hormone-related protein (PTHrP), an important driver of cancer bone metastasis. Finally, relative effects of structurallyrelated metabolites of curcuminoids were assessed on the same endpoints. We report that 3 curcuminoid-containing turmeric extracts differing with respect to the inclusion of additional naturally occurring chemicals (essential oils and/or polar compounds) were equipotent in inhibiting human breast cancer MDA-MB-231 cell growth (IC50=10-16µg/mL) and secretion of osteolytic PTHrP (IC50=2-3µg/mL) when concentrations were normalized to curcuminoid content. Moreover, these effects were curcuminoid-specific, as botanically-related gingerol containing extracts had no effect. While curcumin and bis-demethoxycurcumin were equipotent to each other and to the naturally occurring curcuminoid mixture (IC50=58µM), demethoxycurcumin did not have any effect on cell growth. However, each of the individual curcuminoids inhibited PTHrP secretion (IC50=22-31µM) to the same degree as the curcuminoid mixture (IC50=16µM). Degradative curcuminoid metabolites (vanillin and ferulic acid) did not inhibit cell growth or PTHrP, while reduced metabolites (tetrahydrocurcuminoids) had inhibitory effects on cell growth and PTHrP secretion but only at concentrations ≥10-fold higher than the curcuminoids. These studies emphasize the structural and biological importance of curcuminoids in the anti-breast cancer effects of turmeric and contradict recent assertions that certain of the curcuminoid metabolites studied here mediate these anti-cancer effects.

Cinacalcet attenuates hypercalcemia observed in mice bearing either Rice H-500 Leydig cell or C26-DCT colon tumors

Excessive secretion of parathyroid hormone-related protein (PTHrP) by tumors stimulates bone resorption and increases renal tubular reabsorption of calcium, resulting in hypercalcemia of malignancy. We investigated the ability of cinacalcet, an allosteric modulator of the calcium-sensing receptor, to attenuate hypercalcemia by assessing its effects on blood ionized calcium, serum PTHrP, and calcium-sensing receptor mRNA in mice bearing either Rice H-500 Leydig cell or C26-DCT colon tumors. Cinacalcet effectively decreased hypercalcemia in a dose- and enantiomer-dependent manner; furthermore, cinacalcet normalized phosphorus levels, but did not affect serum PTHrP. Ribonuclease protection assay results demonstrated presence of PTHrP receptor, but not calcium-sensing receptor mRNA in C26-DCT tumors. The mechanism by which cinacalcet lowered serum calcium was investigated in parathyroidectomized rats (i.e., without PTH) made hypercalcemic by PTHrP. Cinacalcet attenuated PTHrP-mediated elevations in blood ionized calcium, which were accompanied by increased plasma calcitonin. Taken together these results suggest that the cinacalcet-mediated decrease in serum calcium is not the result of a direct effect on tumor cells, but rather is the result of increased calcitonin release. In summary, cinacalcet effectively reduced tumor-mediated hypercalcemia and corrected hypophosphatemia in mice. Further investigation of cinacalcet for treatment of hypercalcemia of malignancy is warranted.

PTHrP is a novel mediator for TGF-β-induced apoptosis

Parathyroid hormone-related protein (PTHrP) is a polyhormone secretory protein that plays fundamental roles in the development and function of various tissues. Transforming growth factor (TGF)-β is an important tumor suppressor that induces cell cycle arrest and apoptosis. Increased PTHrP expression has been implicated in TGF-β-induced growth inhibition in human hepatocellular carcinoma cells. However, whether PTHrP is involved in TGF-β-induced apoptosis remains unknown. Using Hep3B and HuH-7, two human hepatocellular carcinoma cell lines, the current study examined the hypothesis that TGF-β-induced apoptosis is mediated by the induction of PTHrP expression. We found that (1) TGF-β induces PTHrP mRNA expression, protein expression and secretion in a time-dependent fashion; (2) knockdown of PTHrP gene expression or neutralization of secreted PTHrP isoforms blocks TGF-β-induced apoptosis; and (3) TGF-β-induced PTHrP expression is Smad3-dependent. Thus, we have identified PTHrP as a novel mediator for TGF-β-induced apoptosis in Hep3B cells. Our findings provide further insights into the mechanisms through which TGF-β conveys tumor suppression activity.

Abstract 5313: Sustained hypercalcemia primes non-invasive breast cancer cells for metastasis to high calcium microenvironments

Abstract Breast cancer frequently spreads to calcium-rich organs/metastatic sites such as skeletal tissues but the role of hypercalcemia in breast cancer progression remains poorly understood. While patients with metastatic or end-stage cancer are likely to become hypercalcemic, up to 30% of breast cancer patients develop cancer-induced hypercalcemia (CIH) in the absence of metastases or bone diseases. The resulting high extracellular ionized calcium (Ca2+) activates the calcium sensing receptor (CaSR) that not only promotes the proliferation of breast cancer cells but also the secretion of parathyroid hormone-related protein by the tumor cells. This suggests that CIH may promote both the vicious osteolytic cycle and breast cancer progression. In this study, we examined whether sustained hypercalcemia primes breast cancer cells for metastasis to high Ca2+ microenvironments. We demonstrate that sustained hypercalcemia enables Ca2+-sensitive non invasive breast cancer cells such as MCF-7 to become high Ca2+-adapted and that this adaptation is accompanied by increased motility and more aggressive growth (increased proliferation). Consistent with this observation, invasive and metastatic breast cancer cells are high Ca2+-adapted cells that efficiently grow over a wide range of Ca2+ concentrations (up to 10 mM). Interestingly, we also show that at high Ca2+ (5 mM) breast cancer cells expressing the Q1011E CaSR variant that is common among African Americans proliferate faster than those expressing the A986S CaSR variant that is common among Caucasians. These data suggest that differences in the adaptation of breast cancer cells to hypercalcemia due in part to the expression of distinct CaSR variants underlie the distinct race-related breast cancer outcomes. This work is funded by the following grants made available to JO: DOD-W81XWH-07-1-0254 and 1SC1CA134018-01 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5313. doi:1538-7445.AM2012-5313

Non-metastatic squamous cell carcinoma in two Hermann’s tortoises (Testudo hermanni)

Squamous cell carcinomas (SCC) are malignant tumors of the epidermal cells with varying degrees of keratinocyte differentiation. They are common tumors in mammalian and avian species but there are, however, only two description of SCC in tortoises. In this case report we describe two cases of non-metastatic squamous cell carcinomas of the carapax and the plastron in Hermann’s tortoises with evidence of humoral hypercalcemia of malignancy (HHM) in one case. HHM is thought to be associated with SCC in mammals due to de novo secretion of parathyroid hormone-related protein (PTHrP) by the tumor cells or tumor induced osteolysis but has not been described in reptiles so far.

Non-metastatic squamous cell carcinoma in two Hermann’s tortoises (Testudo hermanni)

Squamous cell carcinomas (SCC) are malignant tumors of the epidermal cells with varying degrees of keratinocyte differentiation. They are common tumors in mammalian and avian species but there are, however, only two description of SCC in tortoises. In this case report we describe two cases of non-metastatic squamous cell carcinomas of the carapax and the plastron in Hermann’s tortoises with evidence of humoral hypercalcemia of malignancy (HHM) in one case. HHM is thought to be associated with SCC in mammals due to de novo secretion of parathyroid hormone-related protein (PTHrP) by the tumor cells or tumor induced osteolysis but has not been described in reptiles so far.

Mammary gland serotonin regulates parathyroid hormone-related protein and other bone-related signals

Breast cells drive bone demineralization during lactation and metastatic cancers. A shared mechanism among these physiological and pathological states is endocrine secretion of parathyroid hormone-related protein (PTHrP), which acts through osteoblasts to stimulate osteoclastic bone demineralization. The regulation of PTHrP has not been accounted for fully by any conventional mammotropic stimuli or tumor growth factors. Serotonin (5-HT) synthesis within breast epithelial cells is induced during lactation and in advancing breast cancer. Here we report that serotonin deficiency (knockout of tryptophan hydroxylase-1) results in a reduction of mammary PTHrP expression during lactation, which is rescued by restoring 5-HT synthesis. 5-HT induced PTHrP expression in lactogen-primed mammary epithelial cells from either mouse or cow. In human breast cancer cells 5-HT induced both PTHrP and the metastasis-associated transcription factor Runx2/Cbfa1. Based on receptor expression and pharmacological evidence, the 5-HT2 receptor type was implicated as being critical for induction of PTHrP and Runx2. These results connect 5-HT synthesis to the induction of bone-regulating factors in the normal mammary gland and in breast cancer cells.