Rankl genetic deficiency and functional blockade undermine skeletal stem and progenitor cell differentiation.

BACKGROUND: Skeletal Stem Cells (SSCs) are required for skeletal development, homeostasis, and repair. The perspective of their wide application in regenerative medicine approaches has supported research in this field, even though so far results in the clinic have not reached expectations, possibly due also to partial knowledge of intrinsic, potentially actionable SSC regulatory factors. Among them, the pleiotropic cytokine RANKL, with essential roles also in bone biology, is a candidate deserving deep investigation. METHODS: To dissect the role of the RANKL cytokine in SSC biology, we performed ex vivo characterization of SSCs and downstream progenitors (SSPCs) in mice lacking Rankl (Rankl-/-) by means of cytofluorimetric sorting and analysis of SSC populations from different skeletal compartments, gene expression analysis, and in vitro osteogenic differentiation. In addition, we assessed the effect of the pharmacological treatment with the anti-RANKL blocking antibody Denosumab (approved for therapy in patients with pathological bone loss) on the osteogenic potential of bone marrow-derived stromal cells from human healthy subjects (hBMSCs). RESULTS: We found that, regardless of the ossification type of bone, osteochondral SSCs had a higher frequency and impaired differentiation along the osteochondrogenic lineage in Rankl-/- mice as compared to wild-type. Rankl-/- mice also had increased frequency of committed osteochondrogenic and adipogenic progenitor cells deriving from perivascular SSCs. These changes were not due to the peculiar bone phenotype of increased density caused by lack of osteoclast resorption (defined osteopetrosis); indeed, they were not found in another osteopetrotic mouse model, i.e., the oc/oc mouse, and were therefore not due to osteopetrosis per se. In addition, Rankl-/- SSCs and primary osteoblasts showed reduced mineralization capacity. Of note, hBMSCs treated in vitro with Denosumab had reduced osteogenic capacity compared to control cultures. CONCLUSIONS: We provide for the first time the characterization of SSPCs from mouse models of severe recessive osteopetrosis. We demonstrate that Rankl genetic deficiency in murine SSCs and functional blockade in hBMSCs reduce their osteogenic potential. Therefore, we propose that RANKL is an important regulatory factor of SSC features with translational relevance.

Preventive Effects of Dental Pulp Stem Cell-conditioned Media on Anti-RANKL Antibody-Related Osteonecrosis of the Jaw.

Medication-related osteonecrosis of the jaw is a serious disease occurring in patients with cancer and osteoporosis, who are undergoing treatment with antiresorptive agents (ARAs) such as bisphosphonate (BP) or denosumab, an antibody targeting receptor activator of NF-κB ligand. Recently, stem cell-based therapy has been shown to be effective in preventing the development of bisphosphonate-related osteonecrosis of the jaw. However, studies on denosumab-related osteonecrosis of the jaw (DRONJ) remain limited. Here, the efficacy of treatment with dental pulp stem cell conditioned media (DPSC-CM) in preventing DRONJ in a murine model was evaluated. Local administration of DPSC-CM into the extraction socket of a mouse with DRONJ decreased the number of empty osteocyte lacunae and the prevalence of ONJ. In tissues surrounding the extraction sockets in the DPSC-CM-treated group, the expression of inflammatory cytokines was attenuated and that of osteogenesis-related molecules was enhanced compared to that in the control group. Further, the expression of Wnt signaling molecules, which had been suppressed, was improved. These findings collectively suggest that DPSC-CM prevents ONJ development in a murine DRONJ model.

Temporal patterns of osteoclast formation and activity following withdrawal of RANKL inhibition.

Rebound bone loss following denosumab discontinuation is an important clinical challenge. Current treatment strategies to prevent this fail to suppress the rise and overshoot in osteoclast-mediated bone resorption. In this study, we use a murine model of denosumab treatment and discontinuation to show the temporal changes in osteoclast formation and activity during RANKL inhibition and withdrawal. We show that the cellular processes that drive the formation of osteoclasts and subsequent bone resorption following withdrawal of RANKL inhibition precede the rebound bone loss. Furthermore, a rise in serum TRAP and RANKL levels is detected before markers of bone turnover used in current clinical practice. These mechanistic advances may provide insight into a more defined window of opportunity to intervene with sequential therapy following denosumab discontinuation.

Stopping denosumab, a medication commonly used to improve bone mass by blocking formation of bone resorbing osteoclasts, leads to a rebound loss in the bone which was gained during treatment. Current strategies to prevent this bone loss fail in most cases as they are unable to prevent the rise and overshoot in bone resorption by osteoclasts. Thie stems from an incomplete understanding of how osteoclasts behave during denosumab treatment and after treatment is discontinued. We use a mouse model of this phenomenon to show how osteoclast formation and activity changes throughout this process. We show that increases in the processes that drive the formation of osteoclasts can be detected in the circulation before bone loss occurs. These findings could therefore provide insight into a targeted 'window of opportunity' to intervene and prevent the rebound bone loss following stopping denosumab in patients.

RANKL inhibition reduces lesional cellularity and Gαs variant expression and enables osteogenic maturation in fibrous dysplasia.

Fibrous dysplasia (FD) is a rare, disabling skeletal disease for which there are no established treatments. Growing evidence supports inhibiting the osteoclastogenic factor receptor activator of nuclear kappa-B ligand (RANKL) as a potential treatment strategy. In this study, we investigated the mechanisms underlying RANKL inhibition in FD tissue and its likely indirect effects on osteoprogenitors by evaluating human FD tissue pre- and post-treatment in a phase 2 clinical trial of denosumab (NCT03571191) and in murine in vivo and ex vivo preclinical models. Histological analysis of human and mouse tissue demonstrated increased osteogenic maturation, reduced cellularity, and reduced expression of the pathogenic Gαs variant in FD lesions after RANKL inhibition. RNA sequencing of human and mouse tissue supported these findings. The interaction between osteoclasts and mutant osteoprogenitors was further assessed in an ex vivo lesion model, which indicated that the proliferation of abnormal FD osteoprogenitors was dependent on osteoclasts. The results from this study demonstrated that, in addition to its expected antiosteoclastic effect, denosumab reduces FD lesion activity by decreasing FD cell proliferation and increasing osteogenic maturation, leading to increased bone formation within lesions. These findings highlight the unappreciated role of cellular crosstalk between osteoclasts and preosteoblasts/osteoblasts as a driver of FD pathology and demonstrate a novel mechanism of action of denosumab in the treatment of bone disease.TRIAL REGISTRATION: ClinicalTrials.gov NCT03571191.

Immunomodulatory Effects of RANK/RANKL Blockade in Patients with Cancer.

In cancer, multiple factors converge upon receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) signaling to promote the development of bone metastases; agents that inhibit RANKL signaling reduce skeletal-related events (SRE) in patients with cancer. In addition, RANKL signaling is important in augmenting the ability of dendritic cells (DC) to stimulate both naïve T-cell proliferation and the survival of RANK+ T cells. In this issue, Chang and colleagues using high-dimensional cytometry to evaluate immunomodulatory effects of denosumab in patients with advanced solid, observe early on treatment changes in multiple compartments, and greater effects in patients receiving concurrent chemotherapy or steroids. See related article by Chang et al., p. 453 (4).

Denosumab improves trabecular bone score in relationship with decrease in fracture risk of women exposed to aromatase inhibitors.

PURPOSE: Trabecular bone score (TBS) is a gray-level textural metric that has shown to correlate with risk of fractures in several forms of osteoporosis. The value of TBS in predicting fractures and the effects of bone-active drugs on TBS in aromatase inhibitors (AIs)-induced osteoporosis are still largely unknown. The primary objective of this retrospective study was to assess the effects of denosumab and bisphosphonates (BPs) on TBS and vertebral fractures (VFs) in women exposed to AIs. METHODS: 241 consecutive women (median age 58 years) with early breast cancer undergoing treatment with AIs were evaluated for TBS, bone mineral density (BMD) and morphometric VFs at baseline and after 18-24 months of follow-up. During the study period, 139 women (57.7%) received denosumab 60 mg every 6 months, 53 (22.0%) BPs, whereas 49 women (20.3%) were not treated with bone-active drugs. RESULTS: Denosumab significantly increased TBS values (from 1.270 to 1.323; P < 0.001) accompanied by a significant decrease in risk of VFs (odds ratio 0.282; P = 0.021). During treatment with BPs, TBS did not significantly change (P = 0.849) and incidence of VFs was not significantly different from women untreated with bone-active drugs (P = 0.427). In the whole population, women with incident VFs showed higher decrease in TBS vs. non-fractured women (P = 0.003), without significant differences in changes of BMD at any skeletal site. CONCLUSIONS: TBS variation predicts fracture risk in AIs treated women. Denosumab is effective to induce early increase of TBS and reduction in risk of VFs.

Effect of Pelvic External Beam Radiation Therapy on Bone Mineral Density: A Secondary Analysis of a Phase 3 Randomized Controlled Trial.

PURPOSE: Pelvic radiation therapy may lead to decreased bone mineral density (BMD) and increased risk of fracture that could be of particular concern in patients with prostate cancer who also receive androgen deprivation therapy (ADT). We performed an exploratory analysis of a randomized, double-masked, placebo-controlled trial to determine whether exposure to prior pelvic external beam radiation therapy (XRT) affects BMD and risk of fracture in patients with prostate cancer treated with ADT. METHODS AND MATERIALS: Patients with nonmetastatic prostate cancer aged ≥70 years or <70 years with low BMD (T-score < -1) or osteoporotic fracture who had been receiving ADT for ≥12 months were randomly assigned to receive densoumab or placebo every 6 months for 3 years. BMD was measured at baseline and at months 1, 3, 6, 12, 24, and 36. We applied multivariable linear mixed-effects models with an interaction term between the treatment arm and exposure to prior pelvic XRT to evaluate differential XRT effect on percent BMD change between the 2 treatment arms. RESULTS: Among 1407 eligible patients, 31% (n = 447) received prior pelvic XRT. There was no significant difference in any clinical fractures among patients with (5.8%, 26 of 447) or without (5.2%, 50 of 960) prior pelvic XRT (P = .42). Prior pelvic XRT was associated with a significant (0.54%) improvement in BMD (95% CI, 0.05-1.02) in the placebo group and a nonsignificant (0.04%) decline in BMD (95% CI, -0.47 to -0.35) in the denosumab group (interaction P = .007). There was no significant difference in pelvic XRT effect on percent BMD change in the lumbar spine (P = .65) or total hip (P = .39) between the 2 treatment groups. CONCLUSIONS: We did not find sufficient evidence to suggest any detrimental effect of pelvic XRT on the treatment effect from denosumab on percent BMD change, with only an approximately 5% incidence of clinical fractures.

Effect of denosumab on glucose metabolism in postmenopausal osteoporotic women with prediabetes: a study protocol for a 12-month multicenter, open-label, randomized controlled trial.

BACKGROUND: Participants with prediabetes are at a high risk of developing type 2 diabetes (T2D). Recent studies have suggested that blocking the receptor activator of nuclear factor-κB ligand (RANKL) may improve glucose metabolism and delay the development of T2D. However, the effect of denosumab, a fully human monoclonal antibody that inhibits RANKL, on glycemic parameters in the prediabetes population is uncertain. We aim to examine the effect of denosumab on glucose metabolism in postmenopausal women with osteoporosis and prediabetes. METHODS: This is a 12-month multicenter, open-label, randomized controlled trial involving postmenopausal women who have been diagnosed with both osteoporosis and prediabetes. Osteoporosis is defined by the World Health Organization (WHO) as a bone mineral density T score of ≤ - 2.5, as measured by dual-energy X-ray absorptiometry (DXA). Prediabetes is defined as (i) a fasting plasma glucose level of 100-125 mg/dL, (ii) a 2-hour plasma glucose level of 140-199 mg/dL, or (iii) a glycosylated hemoglobin A1c (HbA1c) level of 5.7-6.4%. A total of 346 eligible subjects will be randomly assigned in a 1:1 ratio to receive either subcutaneous denosumab 60 mg every 6 months or oral alendronate 70 mg every week for 12 months. The primary outcome is the change in HbA1c levels from baseline to 12 months. Secondary outcomes include changes in fasting and 2-hour blood glucose levels, serum insulin levels, C-peptide levels, and insulin sensitivity from baseline to 12 months, and the incidence of T2D at the end of the study. Follow-up visits will be scheduled at 3, 6, 9, and 12 months. DISCUSSION: This study aims to provide evidence on the efficacy of denosumab on glucose metabolism in postmenopausal women with osteoporosis and prediabetes. The results derived from this clinical trial may provide insight into the potential of denosumab in preventing T2D in high-risk populations. TRIAL REGISTRATION: This study had been registered in the Chinese Clinical Trials Registry. REGISTRATION NUMBER: ChiCTR2300070789 on April 23, 2023. https://www.chictr.org.cn .

RANKL/RANK is required for cytokine-induced beta cell death; osteoprotegerin, a RANKL inhibitor, reverses rodent type 1 diabetes.

Treatment for type 1 diabetes (T1D) requires stimulation of functional ß cell regeneration and survival under stress. Previously, we showed that inhibition of the RANKL/RANK [receptor activator of nuclear factor kappa Β (NF-κB) ligand] pathway, by osteoprotegerin and the anti-osteoporotic drug denosumab, induces rodent and human ß cell proliferation. We demonstrate that the RANK pathway mediates cytokine-induced rodent and human ß cell death through RANK-TRAF6 interaction and induction of NF-κB activation. Osteoprotegerin and denosumab protected ß cells against this cytotoxicity. In human immune cells, osteoprotegerin and denosumab reduce proinflammatory cytokines in activated T-cells by inhibiting RANKL-induced activation of monocytes. In vivo, osteoprotegerin reversed recent-onset T1D in nonobese diabetic/Ltj mice, reduced insulitis, improved glucose homeostasis, and increased plasma insulin, ß cell proliferation, and mass in these mice. Serum from T1D subjects induced human ß cell death and dysfunction, but not α cell death. Osteoprotegerin and denosumab reduced T1D serum-induced ß cell cytotoxicity and dysfunction. Inhibiting RANKL/RANK could have therapeutic potential.

Denosumab and Zoledronic Acid Differently Affect Circulating Immune Subsets: A Possible Role in the Onset of MRONJ.

This work investigated whether the anti-resorptive drugs (ARDs) zoledronic acid (Zol) and denosumab (Dmab) affect differently the levels of circulating immune cell subsets, possibly predicting the risk of developing medication-related ONJ (MRONJ) during the first 18 months of treatment. Blood samples were collected from 10 bone metastatic breast cancer patients receiving cyclin inhibitors at 0, 6, 12, and 18 months from the beginning of Dmab or Zol treatment. Eight breast cancer patients already diagnosed with MRONJ and treated with cyclin inhibitors and ARDs were in the control group. PBMCs were isolated; the trend of circulating immune subsets during the ARD treatment was monitored, and 12 pro-inflammatory cytokines were analyzed in sera using flow cytometry. In Dmab-treated patients, activated T cells were stable or increased, as were the levels of IL-12, TNF-α, GM-CSF, IL-5, and IL-10, sustaining them. In Zol-treated patients, CD8+T cells decreased, and the level of IFN-γ was undetectable. γδT cells were not altered in Dmab-treated patients, while they dramatically decreased in Zol-treated patients. In the MRONJ control group, Zol-ONJ patients showed a reduction in activated T cells and γδT cells compared to Dmab-ONJ patients. Dmab was less immunosuppressive than Zol, not affecting γδT cells and increasing activated T cells.

Romosozumab is associated with greater trabecular bone score improvement compared to denosumab in postmenopausal osteoporosis.

In this study, romosozumab demonstrated significantly greater improvement in trabecular bone score compared to denosumab therapy in postmenopausal women previously treated with antiresorptive agents. Notably, in patients previously treated with anti-resorptive agents, treatment with romosozumab resulted in similar increases in trabecular bone score compared to that of drug-naïve patients. PURPOSE: Romosozumab significantly increases bone mineral density (BMD) and rapidly reduces fracture risk. Whether romosozumab can improve the spinal trabecular bone score (TBS) as a bone quality indicator merits further investigation. METHODS: Data for postmenopausal women starting romosozumab or denosumab treatment at Severance Hospital, Korea, were analyzed. Romosozumab and denosumab groups were 1:1 matched using propensity scores, considering relevant covariates. Good responders were defined as those with TBS improvement of 5.8% or greater. RESULTS: Overall, 174 patients (romosozumab, n = 87; denosumab, n = 87) were analyzed. Matched groups did not differ in age (64 years), weight, height, previous fracture (38%), lumbar spine or femoral neck BMD (T-score, -3.4 and -2.6, respectively), or prior bisphosphonate or selective estrogen receptor modulator (SERM) exposure (50%). The romosozumab group exhibited a greater increase in lumbar spine BMD (15.2% vs. 6.9%, p < 0.001) and TBS (3.7% vs. 1.7%, p = 0.013) than the denosumab group. In patients transitioning from bisphosphonate or SERM, romosozumab users showed greater improvement in TBS compared to denosumab users (3.9% versus 0.8%, P = 0.006); the drug-naive group showed no significant difference (3.6% versus 2.7%, P = 0.472). The romosozumab group had a higher proportion of good responders than the denosumab group (33.3% vs. 18.4%, p = 0.024). Romosozumab therapy for 12 months resulted in 3.8-fold higher odds of a good response in TBS than denosumab after covariate adjustment (adjusted odds ratio 3.85, p = 0.002). CONCLUSION: Romosozumab could improve bone mass and bone quality, measured by TBS, in postmenopausal osteoporosis, particularly as a subsequent regimen in patients previously taking anti-resorptive agents.

Reduced osteoprotegerin expression by osteocytes may contribute to rebound resorption after denosumab discontinuation.

Denosumab is an anti-RANKL Ab that potently suppresses bone resorption, increases bone mass, and reduces fracture risk. Discontinuation of denosumab causes rapid rebound bone resorption and bone loss, but the molecular mechanisms are unclear. We generated humanized RANKL mice and treated them with denosumab to examine the cellular and molecular conditions associated with rebound resorption. Denosumab potently suppressed both osteoclast and osteoblast numbers in cancellous bone in humanized RANKL mice. The decrease in osteoclast number was not associated with changes in osteoclast progenitors in bone marrow. Long-term, but not short-term, denosumab administration reduced osteoprotegerin (OPG) mRNA in bone. Localization of OPG expression revealed that OPG mRNA is produced by a subpopulation of osteocytes. Long-term denosumab administration reduced osteocyte OPG mRNA, suggesting that OPG expression declines as osteocytes age. Consistent with this, osteocyte expression of OPG was more prevalent near the surface of cortical bone in humans and mice. These results suggest that new osteocytes are an important source of OPG in remodeling bone and that suppression of remodeling reduces OPG abundance by reducing new osteocyte formation. The lack of new osteocytes and the OPG they produce may contribute to rebound resorption after denosumab discontinuation.

Histopathological response to denosumab in giant cell tumours of bone - A review of 11 cases.

Background: Giant cell tumor (GCT) of the bone is a locally aggressive primary bone tumor, that can rarely metastasize. Arising mostly in epiphysis of the long bones in young adults, the tumor is composed of mononuclear cells that are admixed with osteoclastic giant cells(OLGCs), which express RANK ligand and RANK respectively. Denosumab a monoclonal antibody against RANK ligand has been shown to reduce the tumor by causing bone lysis by inhibiting RANKL. Histological changes in 11 patients of GCT who were treated with denosumab are presented here. Materials and Methods: Clinical records and slides of 11 patients of GCT who had been administered neoadjuvant denosumab were included in the study. Evaluation of pre and post therapy GCT specimens was performed by two pathologists (RK and VM). There were 4 males and 7 females. Their mean age was 30 years. All the patients received 120 mg denosumab subcutaneously every week with additional 120 mg on days 8 and 15 of therapy. The histological slides were reviewed and following points noted: 1) degree of ossification,2) fibrosis,3) loss of osteoclastic giant cells,4) proliferation of mononuclear cells,5) atypia,6) Permeation of osteoid by malignant cells. Results: Out of 11 cases, 2 cases did not show any significant histological improvement. 7 cases showed reduction in giant cells, increased fibrosis, enhanced mononuclear cell proliferation and ossification consistent with a pathological response. Atypia and osteoid permeation were noted in 2 cases which showed transformation to osteosarcoma. Conclusion: Denosumab treated giant cell tumor show dramatic histological changes. The post therapy lesions may bear no resemblance to pretherapy lesion. There may be complete resolution or may be confused with benign or malignant lesions Rarely they may show sarcomatous transformation. It is imperative that the pathologist is aware of these changes to prevent diagnostic pitfalls as it poses therapeutic and prognostic implications.

Denosumab use in bone fibrous dysplasia refractory to bisphosphonate: A retrospective multicentric study.

INTRODUCTION: Increased RANKL expression is observed in the bone tissue of fibrous dysplasia of bone/McCune-Albright syndrome (FD/MAS). In one animal model of FD/MAS, the inhibition of RANKL reduced tumor volume. A beneficial effect of denosumab on pain in patients refractory to bisphosphonates has been reported, but without systematic quantification of pain improvement. This work describes the clinical experience of our group on the efficacy on pain of denosumab treatment, along with safety, in FD/MAS patients refractory to bisphosphonates. MATERIALS AND METHODS: We have conducted a retrospective multicenter study in 6 academic rheumatology centers in France. We have collected patients and FD/MAS characteristics, duration of prior exposure to bisphosphonates, denosumab treatment modalities (dosage - administration regimen - number of courses); evolution of pain evaluated by Visual Analogic Scale (VAS). RESULTS: 13 patients were included (10 women and 3 men) 45 years on average, 5 MAS, 4 monostotic and 4 polyostotic forms. The average duration post-diagnosis of FD/MAS was 25 years and the mean duration of prior exposure to bisphosphonates was 4.7 years. Pain could be analyzed in 7 patients, showing a significant improvement from a mean VAS of 7.8 to 2.9 (-4.9 points, p = 0.003). In one patient with fronto-orbital FD/MAS, a 30 % decrease in lesional volume, assessed by MRI, was observed within 6 months of treatment, that was sustained over the following 12 months. Treatment regimens were heterogeneous. No hypercalcemia was observed after treatment cessation and the clinical tolerance was good. DISCUSSION: This study suggests that denosumab reduces pain in patients with DF/MAS refractory to bisphosphonates, and quantifies this improvement for the first time in a multicenter study. In our cohort, no patients who discontinued denosumab developed hypercalcemia and clinical tolerance was overall good. This study also provides encouraging data regarding lesion volume control. Further controlled studies are required to determine the place and modalities of the denosumab treatment of FD/MAS. CONCLUSION: Denosumab significantly decreased pain in FD/MAS refractory to bisphosphonate. This study paves the way for a randomized clinical trial to validate and standardize the prescription of denosumab in FD/MAS.

Denosumab Attenuates Glucolipotoxicity-Induced ß-Cell Dysfunction and Apoptosis by Attenuating RANK/RANKL Signals.

Obesity is strongly associated with insulin sensitivity in type 2 diabetes (T2D), mainly because free fatty acids (FFAs) are released from excess fat tissue. Long-term exposure to high levels of FFAs and glucose leads to glucolipotoxicity, causing damage to pancreatic ß-cells, thus accelerating the progression of T2D. Therefore, the prevention of ß-cell dysfunction and apoptosis is essential to prevent the development of T2D. Unfortunately, there are currently no specific clinical strategies for protecting ß-cells, highlighting the need for effective therapies or preventive approaches to improve the survival of ß-cells in T2D. Interestingly, recent studies have shown that the monoclonal antibody denosumab (DMB), used in osteoporosis, displays a positive effect on blood glucose regulation in patients with T2D. DMB acts as an osteoprotegerin (OPG) by inhibiting the receptor activator of the NF-κB ligand (RANKL), preventing the maturation and function of osteoclasts. However, the exact mechanism by which the RANK/RANKL signal affects glucose homeostasis has not been fully explained. The present study used human 1.4 × 107 ß-cells to simulate the T2D metabolic condition of high glucose and free fatty acids (FFAs), and it investigated the ability of DMB to protect ß-cells from glucolipotoxicity. Our results show that DMB effectively attenuated the cell dysfunction and apoptosis caused by high glucose and FFAs in ß-cells. This may be caused by blocking the RANK/RANKL pathway that reduced mammalian sterile 20-like kinase 1 (MST1) activation and indirectly increased pancreatic and duodenal homeobox 1 (PDX-1) expression. Furthermore, the increase in inflammatory cytokines and ROS caused by the RANK/RANKL signal also played an important role in glucolipotoxicity-induced cytotoxicity, and DMB can also protect ß-cells by reducing the mechanisms mentioned above. These findings provide detailed molecular mechanisms for the future development of DMB as a potential protective agent of ß-cells.

Differences between zoledronic acid and denosumab for breast cancer treatment.

Zoledronic acid and denosumab are bone-modifying agents that are clinically important in multiple aspects of bone management for breast cancer patients. These aspects include the prevention of osteoporosis induced by cancer-treatment bone loss, treatment and prevention of bone metastasis, and improvement of survival directly or indirectly by maintaining bone health. Interestingly, zoledronic acid and denosumab have different anticancer activities, and they may be associated with the improvement of survival of breast cancer patients under different mechanisms. Zoledronic acid is the most potent bisphosphonate. It provides significant benefits for improving breast cancer mortality in patients with suppressed estrogen level such as in postmenopausal or ovarian suppression condition. Although denosumab's anticancer activity has not been clearly proven compared with zoledronic acid's anticancer activity, denosumab is promising in preventing BRCA1 mutant breast cancer because RANKL is a targetable pathway in BRCA1-associated tumorigenesis. Further studies and more effective clinical use of these agents are anticipated to contribute to the improvement of the clinical outcome of breast cancer patients.

RANK is a poor prognosis marker and a therapeutic target in ER-negative postmenopausal breast cancer.

Despite strong preclinical data, the therapeutic benefit of the RANKL inhibitor, denosumab, in breast cancer patients, beyond the bone, is unclear. Aiming to select patients who may benefit from denosumab, we hereby analyzed RANK and RANKL protein expression in more than 2,000 breast tumors (777 estrogen receptor-negative, ER- ) from four independent cohorts. RANK protein expression was more frequent in ER- tumors, where it associated with poor outcome and poor response to chemotherapy. In ER- breast cancer patient-derived orthoxenografts (PDXs), RANKL inhibition reduced tumor cell proliferation and stemness, regulated tumor immunity and metabolism, and improved response to chemotherapy. Intriguingly, tumor RANK protein expression associated with poor prognosis in postmenopausal breast cancer patients, activation of NFKB signaling, and modulation of immune and metabolic pathways, suggesting that RANK signaling increases after menopause. Our results demonstrate that RANK protein expression is an independent biomarker of poor prognosis in postmenopausal and ER- breast cancer patients and support the therapeutic benefit of RANK pathway inhibitors, such as denosumab, in breast cancer patients with RANK+ ER- tumors after menopause.

Inhibition of RANKL Expression in Osteocyte-like Differentiated Tumor Cells in Giant Cell Tumor of Bone After Denosumab Treatment.

Giant cell tumors of bone (GCTBs) are locally aggressive tumors with the histological features of giant cells and stromal cells. Denosumab is a human monoclonal antibody that binds to the cytokine receptor activator of nuclear factor-kappa B ligand (RANKL). RANKL inhibition blocks tumor-induced osteoclastogenesis, and survival, and is used to treat unresectable GCTBs. Denosumab treatment induces osteogenic differentiation of GCTB cells. In this study, the expression of RANKL, special AT-rich sequence-binding protein 2 (SATB2, a marker of osteoblast differentiation), and sclerostin/SOST (a marker of mature osteocytes) was analyzed before and after treatment with denosumab in six cases of GCTB. Denosumab therapy was administered a mean of five times over a mean 93.5-day period. Before denosumab treatment, RANKL expression was observed in one of six cases. After denosumab therapy, spindle-like cells devoid of giant cell aggregation were RANKL-positive in four of six cases. Bone matrix-embedded osteocyte markers were observed, although RANKL was not expressed. Osteocyte-like cells were confirmed to have mutations, as identified using mutation-specific antibodies. Our study results suggest that treatment of GCTBs with denosumab results in osteoblast-osteocyte differentiation. Denosumab played a role in the suppression of tumor activity via inhibition of the RANK-RANKL pathway, which triggers osteoclast precursors to differentiate into osteoclasts.

[Effect of different schemes of androgen deprivation therapy on bone mass density in prostate cancer patients]. / Efecto de diferentes esquemas de terapia de deprivación androgénica sobre la densidad mineral ósea de pacientes con cáncer de próstata.

OBJECTIVES: To evaluate the aspects of the basal bone health status in prostate cancer patients. Furthermore, to evaluate in a real-world setting the effect of different schemes (intermittent or continuous) of androgen deprivation therapy (ADT) and the effect of denosumab in bone mass density (BMD). METHODS: Observational, retrospective study of a cohort of prostate cancer patients in treatment with luteinizing hormone-releasing hormone (LH-RH) agonists, evaluated in the rheumatology department of a tertiary center. Demographics, FRAX score, LH-RH treatment scheme, osteoporosis treatment, laboratory data and BMD were collected. Mixed effect regression models to analyze the interaction between LH-RH treatment scheme, denosumab and BMD evolution were used. RESULTS: Eighty-three patients (mean age 71±8years) were included. At the basal evaluation, 16% of patients presented densitometric osteoporosis and 27% of patients presented high fracture risk. Eighty percent of patients had inadequate vitaminD levels. VitaminD >30ng/mL was correlated with higher T-scores. There was no association between LH-RH treatment scheme and BMD evolution, however there was a positive association with denosumab. CONCLUSION: A high proportion of patients presented elevated fracture risk or inadequate vitaminD levels, not previously recognized. Bone health assessment and fracture risk evaluation are convenient in these patients. In a real-world setting, the effect of denosumab in BMD is detected, however the effect of intermittent LH-RH schema treatment is less evident.