Estrogens and antiestrogens stimulate release of bone resorbing activity by cultured human breast cancer cells

Breast Cancer and Microcalcifications: An Osteoimmunological Disorder?

The presence of microcalcifications in the breast microenvironment, combined with the growing evidences of the possible presence of osteoblast-like or osteoclast-like cells in the breast, suggest the existence of active processes of calcification in the breast tissue during a woman’s life. Furthermore, much evidence that osteoimmunological disorders, such as osteoarthritis, rheumatoid arthritis, or periodontitis influence the risk of developing breast cancer in women exists and vice versa. Antiresorptive drugs benefits on breast cancer incidence and progression have been reported in the past decades. More recently, biological agents targeting pro-inflammatory cytokines used against rheumatoid arthritis also demonstrated benefits against breast cancer cell lines proliferation, viability, and migratory abilities, both in vitro and in vivo in xenografted mice. Hence, it is tempting to hypothesize that breast carcinogenesis should be considered as a potential osteoimmunological disorder. In this review, we compare microenvironments and molecular characteristics in the most frequent osteoimmunological disorders with major events occurring in a woman’s breast during her lifetime. We also highlight what the use of bone anabolic drugs, antiresorptive, and biological agents targeting pro-inflammatory cytokines against breast cancer can teach us.

The Emerging Roles of Steroid Hormone Receptors in Ductal Carcinoma in Situ (DCIS) of the Breast

Ductal carcinoma in situ (DCIS) is a non-obligate precursor to most types of invasive breast cancer (IBC). Although it is estimated only one third of untreated patients with DCIS will progress to IBC, standard of care for treatment is surgery and radiation. This therapeutic approach combined with a lack of reliable biomarker panels to predict DCIS progression is a major clinical problem. DCIS shares the same molecular subtypes as IBC including estrogen receptor (ER) and progesterone receptor (PR) positive luminal subtypes, which encompass the majority (60-70%) of DCIS. Compared to the established roles of ER and PR in luminal IBC, much less is known about the roles and mechanism of action of estrogen (E2) and progesterone (P4) and their cognate receptors in the development and progression of DCIS. This is an underexplored area of research due in part to a paucity of suitable experimental models of ER+/PR + DCIS. This review summarizes information from clinical and observational studies on steroid hormones as breast cancer risk factors and ER and PR as biomarkers in DCIS. Lastly, we discuss emerging experimental models of ER+/PR+ DCIS.

Parathyroid hormone independent hypercalcemia in adults

Parathyroid independent hypercalcemia is characterized by suppressed parathyroid hormone (PTH) in the presence of hypercalcemia. Well known causes and mechanisms are redistribution of calcium from the skeleton, by malignant diseases; inadequately increased intestinal calcium uptake mediated by increased vitamin D activity, and reduced renal elimination due to medications. Frequent and infrequent causes are discussed, and more recent mechanistic models presented in this review. Most hypercalcemic conditions are stable and in equilibrium between the different organs, whereas the utmost severe cases are characterized by rapid rising calcium levels and renal failure, resulting in a vicious circle where a disequilibrium state is developed. Management and treatment depends on the underlying condition and severity. The aim of this review is to discuss non-parathyroid hypercalcemic conditions as seen in the modern clinic, with a focus on areas where recent gain of knowledge has been achieved.

Hypercalcemia in the Critically Ill Patient

Hypercalcemia is now frequently recognized in hospitalized patients, including those who are critically ill. Hypercalcemia in critically ill patients may be life threatening or an indication of an underlying but unsuspected disease process. All of the common causes of hypercalcemia can occur in the critically ill patient and are reviewed here. As in the general patient population, the two most common causes are probably malignant disease and primary hyperparathyroidism. Hypercalcemia is now readily reversible in most patients, particularly when the underlying pathophysiologic mechanisms responsible are recognized, and it should be treated actively.

Bone extracellular matrix stimulates invasiveness of estrogen-responsive human mammary MCF-7 cells

Bone is the most frequent site of metastasis in breast cancer. This causes destructive osteolytic lesions. To achieve metastasis to bone, breast cancer cells must proliferate in a new microenvironment, arrest on extracellular matrix and invade. Breast cancer cells progress in the invasive processes only if they destroy bone with the assistance of osteoclasts. In this work, we present data suggesting that MCF-7 cells, an estradiol receptor-positive cell line that exhibits modest invasive capacity, proliferate in the presence of soluble factors secreted by the osteogenic cell line SaOS-2. The cells acquire a more aggressive phenotype when cultured on an extracellular matrix produced by the same osseous cell line. Acquisition of the invasive phenotype appears to be related to the capacity of bone extracellular matrix to induce the expression of urokinase-like plasminogen activator by MCF-7 cells, which is specific for MCF-7 cells, given that MDA-231 cells, an estradiol receptor-negative and more aggressive cell line, did not show significant changes when cultured in the presence of soluble and insoluble bone factors.

Regulation of parathyroid hormone-related protein expression in MCF-7 breast carcinoma cells by estrogen and antiestrogens

Expression of parathyroid hormone-related protein (PTHrP) in breast carcinoma is a frequent cause of the paraneoplastic syndrome of hypercalcemia. In response to treatment with estrogen or tamoxifen, some breast cancer patients also develop a transient hypercalcemia. Therefore, the effect of 17beta-estradiol (E2), tamoxifen, or its more potent metabolite, 4-hydroxytamoxifen (OH-tamoxifen), on PTHrP expression in an estrogen receptor (ER)-positive breast carcinoma cell line (MCF-7) was evaluated. E2 increased PTHrP mRNA levels in MCF-7 cells and stimulated PTHrP(1-86) release in a dose-dependent fashion (10(-10)-10(-6) M). Tamoxifen and OH-tamoxifen also stimulated PTHrP release in a concentration-dependent fashion that paralleled their relative ER binding affinities (10(-6) or 10(-8)-10(-6) M, respectively). Combined treatment with the partial estrogen agonist, OH-tamoxifen, and E2 decreased E2-stimulated PTHrP secretion in MCF-7 cells to the levels seen with OH-tamoxifen treatment alone. These results suggest that transient estrogen- or tamoxifen-induced hypercalcemia in patients with breast carcinoma may be a PTHrP-mediated effect that is a marker of ER positivity.

Effect of hormonal status on the expression of the cyclooxygenase 1 and 2 genes and prostaglandin synthesis in rat mammary glands

Hormonal effects on mammary carcinogenesis have been linked to prostaglandin (PG) synthesis. The purpose of the present study was to examine the expression of the cyclooxygenase (COX) 1 and 2 genes and levels of PG synthesis in the mammary glands of rats that have different levels of susceptibility to mammary gland carcinogenesis associated with pregnancy, lactation, post-lactation involution, and ovariectomy. The expression of COX-1 mRNA, measured by Northern blot analysis, was similar in virgin, lactating, pregnant, and post-lactational animals of the same age. Ovariectomized animals exhibited significantly lower levels of COX-1 mRNA (approximately 40%) compared to the sham-operated controls or the ovariectomized animals treated with estradiol and progesterone. COX-2 mRNA, measured by RT-PCR, was detectable only in the mammary glands of lactating animals and ovariectomized animals administered estradiol and progesterone. Induction on COX-2 expression occurred in both stromal and epithelial cells in lactating rat mammary glands. COX enzymatic activities, determined by measuring the conversion rate of [1-14 C]-arachadonic acid to prostanoids, showed that lactating animals had a significantly higher activity compared to virgin (approximately 40%), pregnant (approximately 30%), or postlactational animals (approximately 40%). Ovariectomized animals had significantly lower COX enzymatic activity compared to the sham operated animals. Significant induction of COX activity, however, was observed in ovariectomized animals administered estradiol and progesterone. These changes in COX enzymatic activity were paralleled by similar changes in the mammary gland PGE2 content, measured by enzyme immunoassay. Our results suggest that the effect of hormones on the genesis of mammary cancer in the rat may be mediated, at least in part, by their effects on COX-2 expression and PG synthesis.

Experimental study on the role of osteoclasts and free radicals in the mandibular invasion of VX2 carcinoma in Japanese white rabbits

Oxygen-derived free radicals are stimulators of bone resorption in vitro and in vivo. We hypothesized that oxygen-derived free radicals or reactive oxygen species (ROS) generated around bone matrix invaded by cancer cells might be associated with the activation or formation of osteoclasts in bone metastasis, and thus the administration of an ROS scavenger or a free-radical scavenger might control osteoclastic bone destruction in tumor metastasis. We examined the ability of VX2 carcinoma cells to generate superoxide anion (O2-) as well as the effects of the O2- scavenger superoxide dismutase (SOD) and the hydrogen peroxide (H2O2) scavenger catalase (CAT) on the activation and formation of osteoclasts in VX2 carcinoma tissue of rabbits. VX2 carcinoma cells generated more O2- than tartrate-resistant acid phosphatase-positive (TRAP+) cells. The TRAP activity from TRAP+ cells in the presence of VX2 carcinoma cells was higher than that from TRAP+ cells in the absence of the carcinoma cells. The addition of SOD but not of CAT into the incubation medium inhibited the TRAP activity from TRAP+ cells in the presence or absence of VX2 carcinoma cells. Similar inhibitory effects were also observed with SOD plus CAT on TRAP+ cells in the presence or absence of carcinoma cells. Intravenous administration of SOD and SOD plus CAT, but not of CAT, caused a decrease in the number of osteoclasts in mandibles implanted with VX2 carcinoma cells, and showed a predominant occupation by osteoclasts with poorly developed ruffled borders in lesions of bone resorption. In contrast, the administration of CAT, but not of SOD and SOD plus CAT, decreased the more mature forms of osteoclasts in implanted mandibles. From the results obtained, it is suggested that O2- may stimulate bone resorption by increasing the activity and number of osteoclasts, and H2O2 may stimulate resorption by enhancing the formation of mature osteoclasts in tumor metastasis. The administration of some ROS or free-radical scavengers to patients with cancer may provide a defense against bone destruction in bone metastatic lesions.

The management of hypercalcemia of malignancy

Hypercalcemia (HCM) occurs in 10-15% of all malignancies, predominantly in patients with solid tumors. This metabolic complication leads to significant morbidity and impairment of quality of life. Recent insights into the pathophysiology of HCM include an understanding of the role of parathyroid-hormone-related peptide and several cytokines secreted by tumors. The osteoclast plays a central role as the final common pathway through which these hormones and cytokines act to cause bone lysis. These findings have led to the development of new treatment strategies. Foremost among these has been the introduction of agents such as the newer bisphosphonates and gallium nitrate, which are potent inhibitors of osteoclast-mediated bone resorption. The clinician can now choose from an array of therapeutic approaches based on a consideration of the mechanisms of action, individual clinical circumstances, efficacy, toxicities and costs of available agents. In addition to their use in the management of HCM, non-toxic drugs that effectively inhibit osteoclast function, such as the bisphosphonates, are playing an emerging role in the palliative treatment of the more common clinical problems of painful lytic bone metastases and osteoporosis.

Modulation of tumour-induced bone resorption by bisphosphonates

Tumour cells produce systemic or local factors which can stimulate osteoclast development and activity leading to increased bone resorption. The clinical consequences are bone pain, fractures and hypercalcaemia. Inhibitors of osteoclast-mediated bone resorption, such as the bisphosphonates, are now the treatment of choice for tumour-induced hypercalcaemia. Recent evidence indicates that these compounds, especially the newer ones, reduce skeletal morbidity in patients with metastatic bone disease and improve their quality of life. Better understanding of the mechanisms underlying tumour-induced bone resorption and development of more potent and less toxic bisphosphonates will lead to improved management of patients with malignant diseases involving the skeleton.

Phase I clinical and pharmacokinetics study of high-dose toremifene in postmenopausal patients with advanced breast cancer

Toremifene is an antiestrogen that binds strongly to estrogen receptors (ER). A total of 19 previously treated postmenopausal women with metastatic breast cancer whose performance status was good and whose ER status was positive or unknown were studied to determine the maximum tolerated dose of toremifene. Cohorts of patients received 200, 300, or 400 mg/m2 p.o. daily until relapse or unacceptable toxicity had occurred. Nausea, vomiting, and dizziness were dose-related. Three of five patients receiving 400 mg/m2 experienced moderate or severe vomiting and another developed reversible disorientation and hallucinations. Mild sweating, peripheral edema, vaginal discharge, and hot flushes were encountered at all doses. Reversible corneal pigmentation was identified in seven cases but was not of clinical importance. The pharmacokinetics of toremifene was studied weekly and in detail on day 42 using a high-performance liquid chromatographic (HPLC) assay that identified the parent compound and three active metabolites, N-desmethyltoremifene, (deaminohydroxy)toremifene, and didemethyltoremifene. Steady state was achieved at 1-3 weeks. The toremifene area under the curve and the maximal concentration were dose-dependent at high doses. The recommended phase II dose is 300 mg/m2 p.o. daily.

Mechanisms of osteolytic bone destruction

Tumours which involve the skeleton do so by producing humoral factors which increase osteoclast and osteoblast activity. Increases in osteoclast activity lead to osteolytic bone destruction and sometimes to hypercalcaemia. Osteolytic metastases are common, and are found most often in patients with lung and breast cancer and in myeloma. The tumour-associated factors responsible are multiple and probably different in each case. Osteoblastic metastases occur most frequently in metastatic cancer of the prostate, and are due to osteoblast stimulating factors released by the tumour cells which have not, as yet, been identified. Agents such as bisphosphonates which inhibit osteoclastic bone resorption are useful in the prevention and treatment of patients with osteolytic metastases, although the precise mechanisms by which these agents work are not yet understood.

Incidence and pathophysiology of hypercalcemia

Hypercalcemia occurs for various reasons in patients with malignant diseases. Most of these patients show a relative increase in bone resorption over bone formation. Increased renal tubular calcium reabsorption is also important for maintaining hypercalcemia in the majority of patients. Calcium absorption from the gut is usually decreased. In a few patients, fixed impairment of glomerular filtration contributes to hypercalcemia. Because the pathophysiology of hypercalcemia is heterogeneous, it may be considered as three separate syndromes: the humoral hypercalcemia of malignancy caused by systemic mediators; the hypercalcemia associated with localized osteolytic disease; and the hypercalcemia associated with myeloma and related hematologic malignancies. Increased bone resorption is a key feature in each of these syndromes. In malignant disease, bone resorption is enhanced because osteoclast activity is increased by the production of humoral mediators. These mediators are often produced by the tumor cells but are also produced by normal host cells that have been activated by the presence of the tumor. some of these mediators of hypercalcemia are systemic factors, but some act only locally. They include parathyroid hormone-related protein, transforming growth factor alpha, lymphotoxin, tumor necrosis factor, interleukin-1 alpha and 1,25-dihydroxyvitamin D.

Histological grade and steroid receptor content of primary breast cancer--impact on prognosis and possible modes of action

The clinical course of breast cancer was related to degree of anaplasia (DA) and steroid receptor (SR) content of primary tumours in 743 patients (pts) with clinical recurrence, initially enrolled in the DBCG-77 protocols. The oestrogen receptor (ER) and the progesterone receptor (PgR) content was known in 110 and 67 pts. The recurrence-free interval, survival after recurrence, and the overall survival were all prolonged in patients with well differentiated tumours or with high SR content. The tumour growth rates were estimated as clinical rates of progression (i.e., the time elapsed from a single distant metastasis until dissemination). The progression rate was prolonged in relatively well differentiated as well as in receptor rich tumours. The extent of dissemination, as indicated by the number of metastatic sites, was not associated with either DA or SR content. However, the anatomical distribution of metastases varied with both DA and SR content: signs of poor prognosis (high DA or low SR content) were associated with occurrence of visceral metastases. In contrast, SR rich tumours had a propensity for recurrence in bone. The results suggest that the impact on prognosis of the features examined here includes both variations in growth rate and metastatic pattern.

Bone metastases: pathogenesis, treatment, and rationale for use of resorption inhibitors

Tumors in bone are usually metastatic, with breast, prostate, and lung tumors accounting for more than 80 percent of clinically manifest lesions. Untreated, such metastases can produce the symptoms that most concern cancer patients--pain, pathologic fractures, and paralysis through epidural cord compression. Recent advances in the understanding of the metastatic cascade and the regulation of bone formation and resorption provide unique therapeutic approaches for prevention and treatment of these lesions. This article reviews the prevalence, distribution, diagnosis, and treatment of metastatic cancer in the skeleton, as well as the processes involved in the development of such metastases, the local mediators responsible for some of the destructive changes in bone, and their pathologic results. In addition to considering some of the conventional therapeutic approaches, a rationale for the use of bone resorption inhibitors, such as the diphosphonates (bisphosphonates), is presented for the prevention and amelioration of the pathologic consequences of skeletal metastases.

The hypercalcemia of malignancy

The hypercalcemia of malignancy is mediated by complex and heterogeneous mechanisms. Once thought of as a simple paraneoplastic syndrome mediated by the effects of tumor production of PTH, it is now clear that multiple mechanisms are involved and that these mechanisms involve abnormalities in calcium transport in bone, kidney, and gut. Calcium homeostasis in normal individuals is complex and tightly regulated. Although much has been learned over the last 20 years about the effects of individual hormones on target organs, much remains to be understood about how these hormonal systems interact to control extracellular fluid calcium. Future studies on disturbances in calcium homeostasis, such as that occurring in association with malignant disease, should do much to clarify how these complex hormonal mechanisms function in the normal individual.

Androgens increase osteoblast-stimulating activity of human breast cancer cells in vitro

Bone metastases of breast cancers produce not only osteolytic but also osteosclerotic lesions. The latter are often observed after androgenic treatment of the tumor. Potential production of osteoblast stimulating activity (ObSA) in breast cancer cell lines, and possible androgen control of this activity have been investigated. Conditioned media (CM) collected from 4 breast cancer cell lines (MCF-7, ZR75, MDA-MB 231, BT20) was tested in vitro on ROS 17/2,8 osteoblast-like cells and on osteoblasts derived from human bone biopsies. The parameters monitored in osteoblasts were [3H]thymidine incorporation, alkaline phosphatase activity, and osteocalcin secretion. Serum-free media conditioned during 24 h by MCF-7 cells presented the highest ObSA. CM decreased thymidine incorporation in DNA and increased alkaline phosphatase activity in a dose-dependent manner. Bone GLA protein (osteocalcin) secretion by human osteoblasts was not increased however in the presence of CM. MCF-7 cells were cultured in the presence of dihydrotestosterone (DHT) [1-100 nM] for 5 days. Serum-free, DHT-free CM collected after an additional 24 h, contained alkaline-phosphatase stimulating activity which was DHT dose-dependent. Estradiol and 1,25(OH)2D3 failed to elicit a comparable increase of the ObSA in the CM. In conclusion, MCF-7 cells product factor(s) that interfere with bone remodeling. The DHT modulation of ObSA parallels the estradiol control of MCF-7 cells osteolytic lesions in relation with Prostaglandin E secretion. Sex hormones at physiological and pharmacological levels might thus control both osteosclerotic and osteolytic lesions observed in bone deposits of hormone dependent cancers.

Pathogenesis of hypercalcaemia of malignancy

The hypercalcaemia of malignancy is multi-factorial, even within individual tumours. In most cases, hypercalcaemia is due to a combination of increased bone resorption associated with decreased renal capacity to excrete the increased extracellular fluid calcium. In solid tumours such as carcinoma of the lung, tumour-derived growth factors are probably primarily responsible for the increased bone resorption, and a separate family of factors which interact with some parathyroid hormone (PTH) receptors cause increased renal tubular calcium reabsorption. PTH production by non-parathyroid tumours rarely if ever occurs. In contrast, haematological malignancies such as myeloma and T-cell lymphomas produce locally acting bone resorbing lymphokines in excessive amounts. Some T-cell lymphomas in addition have the capacity to metabolize 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. In myeloma, impaired glomerular filtration frequently contributes to the pathogenesis of hypercalcaemia by impairing renal compensatory mechanisms for maintaining normal serum calcium concentrations in the presence of increased bone resorption.