Osteocytes and Bone Metastasis

BIGH3 mediates apoptosis and gap junction failure in osteocytes during renal cell carcinoma bone metastasis progression

Renal cell carcinoma (RCC) bone metastatis progression is driven by crosstalk between tumor cells and the bone microenvironment, which includes osteoblasts, osteoclasts, and osteocytes. RCC bone metastases (RCCBM) are predominantly osteolytic and resistant to antiresorptive therapy. The molecular mechanisms underlying pathologic osteolysis and disruption of bone homeostasis remain incompletely understood. We previously reported that BIGH3/TGFBI (transforming growth factor-beta-induced protein ig-h3, shortened to BIGH3 henceforth) secreted by colonizing RCC cells drives osteolysis by inhibiting osteoblast differentiation, impairing healing of osteolytic lesions, which is reversible with osteoanabolic agents. Here, we report that BIGH3 induces osteocyte apoptosis in both human RCCBM tissue specimens and in a preclinical mouse model. We also demonstrate that BIGH3 reduces Cx43 expression, blocking gap junction (GJ) function and osteocyte network communication. BIGH3-mediated GJ inhibition is blocked by the lysosomal inhibitor hydroxychloroquine (HCQ), but not osteoanabolic agents. Our results broaden the understanding of pathologic osteolysis in RCCBM and indicate that targeting the BIGH3 mechanism could be a combinational strategy for the treatment of RCCBM-induced bone disease that overcomes the limited efficacy of antiresorptives that target osteoclasts.

Antibody-activation of connexin hemichannels in bone osteocytes with ATP release suppresses breast cancer and osteosarcoma malignancy

Bone tissue represents the most frequent site of cancer metastasis. We developed a hemichannel-activating antibody, Cx43-M2. Cx43-M2, directly targeting osteocytes in situ, activates osteocytic hemichannels and elevates extracellular ATP, thereby inhibiting the growth and migration of cultured breast and osteosarcoma cancer cells. Cx43-M2 significantly decreases breast cancer metastasis, osteosarcoma growth, and osteolytic activity, while improving survival rates in mice. The antibody's inhibition of breast cancer and osteosarcoma is dose dependent in both mouse and human cancer metastatic models. Furthermore, Cx43-M2 enhances anti-tumor immunity by increasing the population and activation of tumor-infiltrating immune-promoting effector T lymphocytes, while reducing immune-suppressive regulatory T cells. Our results suggest that the Cx43-M2 antibody, by activating Cx43 hemichannels and facilitating ATP release and purinergic signaling, transforms the cancer microenvironment from a supportive to a suppressive state. Collectively, our study underscores the potential of Cx43-M2 as a therapeutic for treating breast cancer bone metastasis and osteosarcoma.

A Comprehensive Review of Organ-on-a-Chip Technology and Its Applications

Organ-on-a-chip (OOC) is an emerging technology that simulates an artificial organ within a microfluidic cell culture chip. Current cell biology research focuses on in vitro cell cultures due to various limitations of in vivo testing. Unfortunately, in-vitro cell culturing fails to provide an accurate microenvironment, and in vivo cell culturing is expensive and has historically been a source of ethical controversy. OOC aims to overcome these shortcomings and provide the best of both in vivo and in vitro cell culture research. The critical component of the OOC design is utilizing microfluidics to ensure a stable concentration gradient, dynamic mechanical stress modeling, and accurate reconstruction of a cellular microenvironment. OOC also has the advantage of complete observation and control of the system, which is impossible to recreate in in-vivo research. Multiple throughputs, channels, membranes, and chambers are constructed in a polydimethylsiloxane (PDMS) array to simulate various organs on a chip. Various experiments can be performed utilizing OOC technology, including drug delivery research and toxicology. Current technological expansions involve multiple organ microenvironments on a single chip, allowing for studying inter-tissue interactions. Other developments in the OOC technology include finding a more suitable material as a replacement for PDMS and minimizing artefactual error and non-translatable differences.

Head-to-head comparison of [68Ga]Ga-FAPI PET and [18F]FDG PET in the detection of bone and lymph node metastasis in various cancers: A systematic review and meta-analysis

PURPOSE

The aim of our meta-analysis and systematic review was to contrast the positivity rates of [68Ga]Ga-FAPI PET and [18F]FDG PET in detecting bone and lymph node metastases across diverse cancer types.

METHODS

We conducted a comprehensive search for eligible articles up until August 2023, utilizing databases including PubMed, Embase, and Web of Science. Studies focusing on the positivity rate of [68Ga]Ga-FAPI PET vs. [18F]FDG PET for bone and lymph metastasis were included. Using random-effect model, the positivity rate for [68Ga]Ga-FAPI PET and [18F]FDG PET were generated. In order to gauge the heterogeneity among aggregated studies, we utilized the I2 statistic. Additionally, we applied the Quality Assessment of Diagnostic Performance Studies (QUADAS-2) methodology to evaluate the caliber of the studies encompassed in our analysis.

RESULTS

A total of 430 publications were initially identified in the search. Eventually, 25 studies, involving 779 patients, met the inclusion criteria. In terms of bone metastasis, the findings indicate no statistically significant difference between the use of [68Ga]Ga-FAPI PET and [18F]FDG PET (P = 0.34). However, concerning lymph node metastasis, the results demonstrate significant difference between the two imaging agents (P = 0.04).

CONCLUSIONS

This systematic review suggests that [68Ga]Ga-FAPI PET appears to outperform [18F]FDG PET in detecting lymph node metastases. However, when it comes to bone metastasis, no statistically significant difference was observed. It is crucial to acknowledge that the insights concerning bone metastasis stem from studies with comparatively modest sample sizes. Consequently, there is a pressing demand for further, expansive prospective studies in this field.

Role of the osteocyte in bone metastasis - The importance of networking

Metastatic bone disease is a complex condition resulting from the migration and colonization of cancer cells from their primary site to the bone microenvironment, where they typically develop a metastatic niche. Osteocytes, the most abundant cells in bone tissue and the master regulators of bone remodelling, are increasingly thought to play a crucial role in this process through intricate interactions with cancer cells. This review covers the recent progress made in exploring the multifaceted interactions between osteocytes and cancer cells in the metastatic microenvironment, highlighting the importance of signalling networks in bone metastases. Though these interactions are particularly complex, the renewed focus of researchers on osteocytes within the last 5 years has uncovered multiple new potential molecular mechanisms underlying osteocyte-mediated regulation of cancer cell survival, proliferation, and invasion. A number of key papers will be discussed in detail, emphasizing the significance of signalling pathways and molecular crosstalk, and exploring potential therapeutic strategies targeting osteocyte-cancer cell interactions to improve patient treatment and outcomes.

Icariin inhibits prostate cancer bone metastasis and destruction via suppressing TAM/CCL5-mediated osteoclastogenesis

BACKGROUND

Bone metastasis occurs in nearly 70% of patients with metastatic prostate cancer (PCa), and represents the leading cause of death in patients with PCa. Emerging evidence has demonstrated the potential activities of icariin in modulating bone metabolism and remodelling the tumor microenvironment (TME). However, whether icariin could inhibit PCa bone metastasis and destruction by modulating the TME as well as the underlying mechanisms remains unclear.

PURPOSE

This study investigated whether icariin could inhibit PCa bone metastasis and destruction by modulating the bone TME as well as the underlying mechanisms.

METHODS

Osteoclasts were induced from mouse bone marrow-derived macrophages (BMMs) or Raw264.7 cells. PCa cells were cultured in the conditional medium (CM) of macrophages in vitro or co-injected with macrophages in vivo to simulate their coexistence in the TME. Multiple molecular biology experiments and the mouse RM1-Luc PCa bone metastasis model were used to explore the inhibitory activity and mechanism of icariin on PCa metastasis and bone destruction.

RESULTS

Icariin treatment significantly suppressed PCa growth, bone metastasis and destruction as well as osteoclastogenesis in vivo. Furthermore, icariin remarkably inhibited osteoclast differentiation, even in the presence of the CM of tumor-associated macrophages (TAMs), while exhibiting no obvious effect on osteoblasts. Moreover, icariin suppressed the M2 phenotype polarization of Raw264.7-derived TAMs and transcriptionally attenuated their CC motif chemokine ligand 5 (CCL5) expression and secretion via inhibiting SPI1. Additionally, CCL5 induced the differentiation and chemotaxis of osteoclast precursor cells by binding with its receptor CCR5. The clinicopathological analysis further verified the positive correlation between the TAM/CCL5/CCR5 axis and osteoclastogenesis within the TME of PCa patients. More importantly, icariin remarkably suppressed PCa metastasis-induced bone destruction in vivo by inhibiting osteoclastogenesis via downregulating the TAM/CCL5 pathway.

CONCLUSION

Altogether, these results not only implicate icariin as a promising candidate immunomodulator for PCa bone metastasis and destruction but also shed novel insight into targeting TAM/CCL5-mediated osteoclastogenesis as a potential treatment strategy for osteolytic bone metastasis. This study helps to advance the understanding of the crosstalk between bone TME and bone homeostasis.

Conditional knockout of PDK1 in osteoclasts suppressed osteoclastogenesis and ameliorated prostate cancer-induced osteolysis in murine model

BACKGROUND

The development and maintenance of normal bone tissue is maintained by balanced communication between osteoblasts and osteoclasts. The invasion of cancer cells disrupts this balance, leading to osteolysis. As the only bone resorbing cells in vivo, osteoclasts play important roles in cancer-induced osteolysis. However, the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1) in osteoclast resorption remains unclear.

METHODS

In our study, we used a receptor activator of nuclear factor-kappa B (RANK) promoter-driven Cre-LoxP system to conditionally delete the PDK1 gene in osteoclasts in mice. We observed the effect of osteoclast-specific knockout of PDK1 on prostate cancer-induced osteolysis. Bone marrow-derived macrophage cells (BMMs) were extracted and induced to differentiate osteoclasts in vitro to explore the role of PDK1 in osteoclasts.

RESULTS

In this study, we found that PDK1 conditional knockout (cKO) mice exhibited smaller body sizes when compared to the wild-type (WT) mice. Moreover, deletion of PDK1 in osteoclasts ameliorated osteolysis and rPDK1educed bone resorption markers in the murine model of prostate cancer-induced osteolysis. In vivo, we discovered that osteoclast-specific knockout of suppressed RANKL-induced osteoclastogenesis, bone resorption function, and osteoclast-specific gene expression (Ctsk, TRAP, MMP-9, NFATc1). Western blot analyses of RANKL-induced signaling pathways showed that conditional knockout of PDK1 in osteoclasts inhibited the early nuclear factor κB (NF-κB) activation, which consequently suppressed the downstream induction of NFATc1.

CONCLUSION

These findings demonstrated that PDK1 performs an important role in osteoclastogenesis and prostate cancer-induced osteolysis by modulating the PDK1/AKT/NF-κB signaling pathway.

Spatially patterned 3D model mimics key features of cancer metastasis to bone

Bone is the most common target of metastasis in breast cancer and prostate cancer, leading to significant mortality due to lack of effective treatments. The discovery of novel therapies has been hampered by a lack of physiologically relevant in vitro models that can mimic key clinical features of bone metastases. To fill this critical gap, here we report spatially patterned, tissue engineered 3D models of breast cancer and prostate cancer bone metastasis which mimic bone-specific invasion, cancer aggressiveness, cancer-induced dysregulation of bone remodeling, and in vivo drug response. We demonstrate the potential of integrating such 3D models with single-cell RNA sequencing to identify key signaling drivers of cancer metastasis to bone. Together, these results validate that spatially patterned 3D bone metastasis models mimic key clinical features of bone metastasis and can serve as a novel research tool to elucidate bone metastasis biology and expedite drug discovery.

Bone serves as a transfer station for secondary dissemination of breast cancer

Metastasis is responsible for the majority of deaths among breast cancer patients. Although parallel polyclonal seeding has been shown to contribute to organ-specific metastasis, in the past decade, horizontal cross-metastatic seeding (metastasis-to-metastasis spreading) has also been demonstrated as a pattern of distant metastasis to multiple sites. Bone, as the most frequent first destination of breast cancer metastasis, has been demonstrated to facilitate the secondary dissemination of breast cancer cells. In this review, we summarize the clinical and experimental evidence that bone is a transfer station for the secondary dissemination of breast cancer. We also discuss the regulatory mechanisms of the bone microenvironment in secondary seeding of breast cancer, focusing on stemness regulation, quiescence-proliferation equilibrium regulation, epigenetic reprogramming and immune escape of cancer cells. Furthermore, we highlight future research perspectives and strategies for preventing secondary dissemination from bone.

Obacunone inhibits RANKL/M-CSF-mediated osteoclastogenesis by suppressing integrin- FAK-Src signaling

Disrupted osteoblastogenesis or aberrant activation of osteoclastogenesis usually results in the break of bone homeostasis thus causing bone-associated diseases like osteoporosis. Obacunone, as a natural compound present in citrus fruits, has been demonstrated for various biological activities including anti-cancer and anti-inflammatory properties. However, the role of obacunone in regulating osteoclastogenesis has not been elucidated so far. Here, using in vitro cell models of RANKL (Receptor activator of nuclear factor-kB ligand) and M-CSF (Macrophage-colony-stimulating factor)-induced osteoclastogenesis, we showed that obacunone inhibited osteoclast differentiation in RAW264.7 cells and bone marrow macrophages (BMMs), as evidenced by obacunone dose-dependent reduction in numbers of osteoclasts and downregulated expressions of osteoclastogenesis-associated key genes. The anti-osteoclastic properties of obacunone were associated with downregulated expressions of Integrin α1 and attenuated activation of Focal adhesion kinase (FAK) and Steroid receptor coactivator (Src) signaling. Functional Integrin α1 blockade or FAK-Src inhibition suppressed RANKL/M-CSF-induced osteoclastogenesis, while Integrin α1 overexpression or FAK/Src activation partially attenuated obacunone's effects on suppressing RANKL/M-CSF-induced osteoclast differentiation. Furthermore, in vivo administration of obacunone displayed super therapeutic effects in attenuating ovariectomy-induced bone loss in mice, as indicated by decreases in serum biomarkers of bone turnover, restoring of femur fracture maximum force, and reversing of the worsened bone-related parameters in ovariectomized animals. Taken together, these findings demonstrate that obacunone has pharmacological activities to suppress osteoclast differentiation through modulating the Integrin-FAK-Src pathway, and suggest that obacunone is a therapeutic candidate for the treatment and prevention of bone diseases such as osteoporosis.

CHIR99021-Treated Osteocytes with Wnt Activation in 3D-Printed Module Form an Osteogenic Microenvironment for Enhanced Osteogenesis and Vasculogenesis

Finding a bone implant that has high bioactivity that can safely drive stem cell differentiation and simulate a real in vivo microenvironment is a challenge for bone tissue engineering. Osteocytes significantly regulate bone cell fate, and Wnt-activated osteocytes can reversely regulate bone formation by regulating bone anabolism, which may improve the biological activity of bone implants. To achieve a safe application, we used the Wnt agonist CHIR99021 (C91) to treat MLO-Y4 for 24 h, in a co-culture with ST2 for 3 days after withdrawal. We found that the expression of Runx2 and Osx increased, promoted osteogenic differentiation, and inhibited adipogenic differentiation in the ST2 cells, and these effects were eliminated by the triptonide. Therefore, we hypothesized that C91-treated osteocytes form an osteogenic microenvironment (COOME). Subsequently, we constructed a bio-instructive 3D printing system to verify the function of COOME in 3D modules that mimic the in vivo environment. Within PCI3D, COOME increased the survival and proliferation rates to as high as 92% after 7 days and promoted ST2 cell differentiation and mineralization. Simultaneously, we found that the COOME-conditioned medium also had the same effects. Therefore, COOME promotes ST2 cell osteogenic differentiation both directly and indirectly. It also promotes HUVEC migration and tube formation, which can be explained by the high expression of Vegf. Altogether, these results indicate that COOME, combined with our independently developed 3D printing system, can overcome the poor cell survival and bioactivity of orthopedic implants and provide a new method for clinical bone defect repair.

LncRNA TRG-AS1 inhibits bone metastasis of breast cancer by the miR-877-5p/WISP2 axis

TRG-AS1 has been proved to inhibit cancer progression, whereas its effect on bone metastases of breast cancer is unknown. In this study, we determined breast cancer patients with disease free survival is longer in breast cancer patients with high TRG-AS1 expression. Moreover, TRG-AS1 was downregulated in breast cancer tissues and even lower in bone metastatic tumor tissues. Compared with parental breast cancer cell MDA-MB-231, TRG-AS1 expression was downregulated in MDA-MB-231-BO cells with strong bone-metastatic characteristics. Next, the binding sites of miR-877-5p on TRG-AS1 and WISP2 mRNA were predicted and result showed that miR-877-5p could bind to 3'UTR of TRG-AS1 and WISP2. Subsequently, BMMs and MC3T3-E1 cells were cultured in the conditioned media of MDA-MB-231 BO cells transfected with TRG-AS1 overexpression vector, shRNA and/or miR-877-5p mimics or inhibitor and/or overexpression vector and small interfering RNA of WISP2. TRG-AS1 silencing or miR-877-5p overexpression promoted MDA-MB-231 BO cell proliferation and invasion. TRG-AS1 overexpressing reduced TRAP positive cells, decreased TRAP, Cathepsin K, c-Fos, NFATc1 and AREG expression in BMMs, and promoted OPG, Runx2 and Bglap2 expression, and decreased RANKL expression in MC3T3-E1 cells. Silencing WISP2 rescued the effect of TRG-AS1 on BMMs and MC3T3-E1 cells. In vivo results showed that tumor volumes significantly decreased in mice injected with LV-TRG-AS1 transfected MDA-MB-231 cells. TRG-AS1 knockdown markedly reduced the number of TRAP+ cells and the percentage of Ki-67+ cells and decreased E-cadherin expression in xenograft tumor mice. In summary, TRG-AS1 acts an endogenous RNA, inhibited breast cancer bone metastasis by competitively binding with miR-877-5p to upregulate WISP2 expression.

Osteoid cell-derived chemokines drive bone-metastatic prostate cancer

One of the greatest challenges in improving prostate cancer (PCa) survival is in designing new therapies to effectively target bone metastases. PCa regulation of the bone environment has been well characterized; however, bone-targeted therapies have little impact on patient survival, demonstrating a need for understanding the complexities of the tumor-bone environment. Many factors contribute to creating a favorable microenvironment for prostate tumors in bone, including cell signaling proteins produced by osteoid cells. Specifically, there has been extensive evidence from both past and recent studies that emphasize the importance of chemokine signaling in promoting PCa progression in the bone environment. Chemokine-focused strategies present promising therapeutic options for treating bone metastasis. These signaling pathways are complex, with many being produced by (and exerting effects on) a plethora of different cell types, including stromal and tumor cells of the prostate tumor-bone microenvironment. ​This review highlights an underappreciated molecular family that should be interrogated for treatment of bone metastatic prostate cancer (BM-PCa).

Proteomes from AMPK-inhibited peripheral blood mononuclear cells suppress the progression of breast cancer and bone metastasis

Background: During a developmental process, embryos employ varying tactics to remove unwanted cells. Using a procedure analogous to some of the embryonic cells, we generated a tumor-eliminating conditioned medium (CM) from AMPK-inhibited lymphocytes and monocytes in peripheral blood mononuclear cells (PBMCs). Methods: AMPK signaling was inhibited by the application of a pharmacological agent, Dorsomorphin, and the therapeutic effects of their conditioned medium (CM) were evaluated using in vitro cell cultures, ex vivo breast cancer tissues, and a mouse model of mammary tumors and tumor-induced osteolysis. The regulatory mechanism was evaluated using mass spectrometry-based proteomics, Western blotting, immunoprecipitation, gene overexpression, and RNA interference. Results: While AMPK signaling acted mostly anti-tumorigenic, we paradoxically inhibited it to build induced tumor-suppressing cells and their tumor-eliminating CM. In a mouse model of breast cancer, the application of AMPK-inhibited lymphocyte-derived CM reduced mammary tumors additively to a chemotherapeutic agent, Taxol. It also prevented bone loss in the tumor-bearing tibia. Furthermore, the application of CM from the patient-derived peripheral blood diminished ex vivo breast cancer tissues isolated from the same patients. Notably, proteins enriched in CM included Moesin (MSN), Enolase 1 (ENO1), and polyA-binding protein 1 (PABPC1), which are considered tumorigenic in many types of cancer. The tumor-suppressing actions of MSN and ENO1 were at least in part mediated by Metadherin (Mtdh), which is known to promote metastatic seeding. Conclusion: We demonstrated that PBMCs can be used to generate tumor-suppressive proteomes, and extracellular tumor-suppressing proteins such as MSN, ENO1, and PABPC1 are converted from tumor-promoting factors inside cancer cells. The results support the possibility of developing autologous blood-based therapy, in which tumor-suppressing proteins are enriched in engineered PBMC-derived CM by the inhibition of AMPK signaling.

Electroactive Biomaterials for Facilitating Bone Defect Repair under Pathological Conditions

Bone degeneration associated with various diseases is increasing due to rapid aging, sedentary lifestyles, and unhealthy diets. Living bone tissue has bioelectric properties critical to bone remodeling, and bone degeneration under various pathological conditions results in significant changes to these bioelectric properties. There is growing interest in utilizing biomimetic electroactive biomaterials that recapitulate the natural electrophysiological microenvironment of healthy bone tissue to promote bone repair. This review first summarizes the etiology of degenerative bone conditions associated with various diseases such as type II diabetes, osteoporosis, periodontitis, osteoarthritis, rheumatoid arthritis, osteomyelitis, and metastatic osteolysis. Next, the diverse array of natural and synthetic electroactive biomaterials with therapeutic potential are discussed. Putative mechanistic pathways by which electroactive biomaterials can mitigate bone degeneration are critically examined, including the enhancement of osteogenesis and angiogenesis, suppression of inflammation and osteoclastogenesis, as well as their anti-bacterial effects. Finally, the limited research on utilization of electroactive biomaterials in the treatment of bone degeneration associated with the aforementioned diseases are examined. Previous studies have mostly focused on using electroactive biomaterials to treat bone traumatic injuries. It is hoped that this review will encourage more research efforts on the use of electroactive biomaterials for treating degenerative bone conditions.

MiRNAs and snoRNAs in Bone Metastasis: Functional Roles and Clinical Potential

Bone is a frequent site of metastasis. Bone metastasis is associated with a short-term prognosis in cancer patients, and current treatments aim to slow its growth, but are rarely curative. Thus, revealing molecular mechanisms that explain why metastatic cells are attracted to the bone micro-environment, and how they successfully settle in the bone marrow-taking advantage over bone resident cells-and grow into macro-metastasis, is essential to propose new therapeutic approaches. MicroRNAs and snoRNAs are two classes of small non-coding RNAs that post-transcriptionally regulate gene expression. Recently, microRNAs and snoRNAs have been pointed out as important players in bone metastasis by (i) preparing the pre-metastatic niche, directly and indirectly affecting the activities of osteoclasts and osteoblasts, (ii) promoting metastatic properties within cancer cells, and (iii) acting as mediators within cells to support cancer cell growth in bone. This review aims to highlight the importance of microRNAs and snoRNAs in metastasis, specifically in bone, and how their roles can be linked together. We then discuss how microRNAs and snoRNAs are secreted by cancer cells and be found as extracellular vesicle cargo. Finally, we provide evidence of how microRNAs and snoRNAs can be potential therapeutic targets, at least in pre-clinical settings, and how their detection in liquid biopsies can be a useful diagnostic and/or prognostic biomarker to predict the risk of relapse in cancer patients.

Advanced 3D Magnetic Scaffolds for Tumor-Related Bone Defects

The need for bone substitutes is a major challenge as the incidence of serious bone disorders is massively increasing, mainly attributed to modern world problems, such as obesity, aging of the global population, and cancer incidence. Bone cancer represents one of the most significant causes of bone defects, with reserved prognosis regarding the effectiveness of treatments and survival rate. Modern therapies, such as hyperthermia, immunotherapy, targeted therapy, and magnetic therapy, seem to bring hope for cancer treatment in general, and bone cancer in particular. Mimicking the composition of bone to create advanced scaffolds, such as bone substitutes, proved to be insufficient for successful bone regeneration, and a special attention should be given to control the changes in the bone tissue micro-environment. The magnetic manipulation by an external field can be a promising technique to control this micro-environment, and to sustain the proliferation and differentiation of osteoblasts, promoting the expression of some growth factors, and, finally, accelerating new bone formation. By incorporating stimuli responsive nanocarriers in the scaffold's architecture, such as magnetic nanoparticles functionalized with bioactive molecules, their behavior can be rigorously controlled under external magnetic driving, and stimulates the bone tissue formation.

An insight into cancer palaeobiology: does the Mesozoic neoplasm support tissue organization field theory of tumorigenesis?

BACKGROUND

Neoplasms are common across the animal kingdom and seem to be a feature plesiomorphic for metazoans, related with an increase in somatic complexity. The fossil record of cancer complements our knowledge of the origin of neoplasms and vulnerability of various vertebrate taxa. Here, we document the first undoubted record of primary malignant bone tumour in a Mesozoic non-amniote. The diagnosed osteosarcoma developed in the vertebral intercentrum of a temnospondyl amphibian, Metoposaurus krasiejowensis from the Krasiejów locality, southern Poland.

RESULTS

A wide array of data collected from gross anatomy, histology, and microstructure of the affected intercentrum reveals the tumour growth dynamics and pathophysiological aspects of the neoplasm formation on the histological level. The pathological process almost exclusively pertains to the periosteal part of the bone composed from a highly vascularised tissue with lamellar matrix. The unorganised arrangement of osteocyte lacunae observed in the tissue is characteristic for bone tissue types connected with static osteogenesis, and not for lamellar bone. The neoplastic bone mimics on the structural level the fast growing fibrolamellar bone, but on the histological level develops through a novel ossification type. The physiological process of bone remodelling inside the endochondral domain continued uninterrupted across the pathology of the periosteal part.

CONCLUSIONS

Based on the results, we discuss our case study's consistence with the Tissue Organization Field Theory of tumorigenesis, which locates the causes of neoplastic transformations in disorders of tissue architecture.

Microfluidic Co-culture Platforms for Studying Osteocyte Regulation of Other Cell Types under Dynamic Mechanical Stimulation

PURPOSE OF REVIEW

Osteocytes are the most abundant cell type in bone. These unique cells act primarily as mechanosensors and play crucial roles in the functional adaptation of bone tissue. This review aims to summarize the recent microfluidic studies on mechanically stimulated osteocytes in regulating other cell types.

RECENT FINDINGS

Microfluidics is a powerful technology that has been widely employed in recent years. With the advantages of microfluidic platforms, researchers can mimic multicellular environments and integrate dynamic systems to study osteocyte regulation under mechanical stimulation. Microfluidic platforms have been developed to investigate mechanically stimulated osteocytes in the direct regulation of multiple cell types, including osteoclasts, osteoblasts, and cancer cells, and in the indirect regulation of cancer cells via endothelial cells. Overall, these microfluidic studies foster the development of treatment approaches targeting osteocytes under mechanical stimulation.

FCGR3A: A new biomarker with potential prognostic value for prostate cancer

To screen target gene cluster by bioinformatics analysis and verify them by in vitro experiment and clinicopathological correlation analysis. We try to find a new biomarker with prognostic value for prostate cancer (PCa). 42 candidate marker genes were constructed by protein protein interaction (PPI) network and enriched by KEGG pathway to find out the gene cluster we are interested in. Prognostic model was established to preliminarily analyze the prognostic value of this gene cluster in PCa, and Cox risk regression was used for comparative analysis. Immunohistochemistry was used to detect the expression of each gene in clinical tissue microarray. Finally, we analyzed the correlation between each gene and their clinicopathological features of PCa combined with TCGA clinical data. Based on the analysis of PPI and KEGG, we found the target gene cluster (FCGR3A, HAVCR2, CCR7 and CD28). Prognostic model analysis showed that this gene cluster had the ability to predict biochemical recurrence, and the survival rate and ROC analysis showed favorable prediction effect. Univariate Cox regression analysis showed that the risk scores of Gleason score (GS), T stage, N stage and PSA were significantly different (P<0.05), and the risk ratio of high expression was 2.30 times that of low expression (P=0.004). However, it was not statistically significant in multivariate Cox regression analysis (P>0.05). The results of tissue microarray showed that FCGR3A and HAVCR2 were highly expressed in PCa (P<0.01), while the expression of CCR7 and CD28 had no significant difference (P>0.05). Kaplan-Meier analysis showed that there was significant difference in BCR free survival of FCGR3A and HAVCR2 (FCGR3A, P=0.010; HAVCR2, P=0.018), while the expression of CCR7 and CD28 had no significant difference on the survival and prognosis of PCa patients (P>0.05). TCGA clinical data analysis found that the expression of FCGR3A had a unique correlation with the clinicopathological features of PCa, which was closely related to the tumor stage. The expression of FCGR3A is related to BCR free survival of PCa patients. Therefore, FCGR3A is a new biomarker with potential prognostic value of PCa.

A systematic review of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT in the diagnostic value of malignant tumor bone metastasis

OBJECTIVE

This study aims to perform a systemic analysis of [68Ga]Ga-DOTA-FAPI-04 positron emission tomography (PET)/computerized tomography (CT) and [18F]FDG PET/CT for the diagnosis of malignant tumor bone metastasis based on existing clinical evidence.

METHODS

This systematic review followed the guidelines of the Preferred Reporting Project (PRISMA) for systematic reviews and meta-analysis. This is a retrospective study of articles published in PubMed. Embase was searched online from the start of May 2022. The main endpoints were the maximum standardized uptake value and the tumor-to-background ratio to determine the examination performance of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG for bone transfer stoves. Based on the entry and discharge standards, two researchers extracted documents and data and then performed the quality evaluation.

RESULTS

A total of eight studies on the metastasis of malignant tumors on bone were included, which involved 358 patients in the final analysis.

CONCLUSION

[68Ga]Ga-DOTA-FAPI-04 showed better detection performance for bone metastasis. The sensitivity of [68Ga]Ga-DOTA-FAPI-04 for the diagnosis of the primary tumor was higher than that of [18F]FDG, whereas the specificity of [18F]FDG was higher than that of [68Ga]Ga-DOTA-FAPI-04. However, further randomized controlled trials and prospective clinical trials are warranted to compare the diagnostic performance of [68Ga]Ga-DOTA-FAPI-04 PET/CT and [18F]FDG PET/CT.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier (CRD42022313019).

Role of Interleukin-1 family in bone metastasis of prostate cancer

Prostate cancer (PCa) is one of the most fatal diseases in male patients with high bone metastatic potential. Bone metastasis severely shortens overall survival and brings skeletal-related events (SREs) which reduces the life quality of patients, and this situation is currently regarded as irreversible and incurable. The progression and metastasis of PCa are found to be closely associated with inflammatory cytokines and chemokines. As pivotal members of inflammatory cytokines, Interleukin-1 (IL-1) family plays a crucial role in this process. Elevated expression of IL-1 family was detected in PCa patients with bone metastasis, and accumulating evidences proved that IL-1 family could exert vital effects on the progression and bone metastasis of many cancers, while some members have dual effects. In this review, we discuss the role of IL-1 family in the bone metastasis of PCa. Furthermore, we demonstrate that many members of IL-1 family could act as pivotal biomarkers to predict the clinical stage and prognosis of PCa patients. More importantly, we have elucidated the role of IL-1 family in the bone metastasis of PCa, which could provide potential targets for the treatment of PCa bone metastasis and probable directions for future research.

A lipid metabolism-related risk signature for patients with gliomas constructed with TCGA and CGGA data

Lipid metabolism affects cell proliferation, differentiation, membrane homeostasis and drug resistance. An in-depth exploration of lipid metabolism in gliomas might provide a novel direction for gliomas treatment. A lipid metabolism-related risk signature was constructed in our study to assess the prognosis of patients with gliomas. Lipid metabolism-related genes were extracted. Differentially expressed genes (DEGs) were screened, and a risk signature was built. The ability of the risk signature to predict the outcomes of patients with gliomas was assessed using the log-rank test and Cox regression analysis. The relationships between immunological characteristics, drug sensitivity and the risk score were evaluated, and the risk-related mechanisms were also estimated. Twenty lipid metabolism-related DEGs associated with the patient prognosis were included in the risk signature. The survival rate of high-risk patients was worse than that of low-risk patients. The risk score independently predicted the outcomes of patients. Immunological parameters, drug sensitivity, immunotherapy benefits, and numerous molecular mechanisms were significantly associated with the risk score. A lipid metabolism-related risk signature might effectively assess the prognosis of patients with gliomas. The risk score might guide individualized treatment and further clinical decision-making for patients with gliomas.

Extracellular Vesicle-Packaged CDH11 and ITGA5 Induce the Premetastatic Niche for Bone Colonization of Breast Cancer Cells

Although most breast cancer metastases in bone cause osteolytic lesions, the osteogenic niche has commonly been described as an initiator of early-stage bone colonization of disseminated cancer cells. Tumor cell-derived extracellular vesicles (EV) have been shown to determine the organotropism of cancer cells by transferring their cargo, such as nucleic acids and proteins, to resident cells at future metastatic sites and preparing a favorable premetastatic niche. Runt-related transcription factor 2 (RUNX2) and its regulated genes have been shown to facilitate the acquisition of osteomimetic features and to enhance the bone metastatic potential of breast cancer cells. In this study, we present in vivo and in vitro evidence to clarify the role of EVs released by breast cancer cells with high RUNX2 expression in the education of osteoblasts to form an osteogenic premetastatic niche. Furthermore, different extracellular vesicular proteins were identified that mediate events subsequent to the specific recognition of tumor-derived EVs by osteoblasts via cadherin 11 (CDH11) and the induction of the osteogenic premetastatic niche by integrin α5 (ITGA5). CDH11high/ITGA5high EVs were demonstrated to be responsible for the formation of a premetastatic niche that facilitates RUNX2 high-expressing breast cancer cell colonization in bone, revealing a potential EV-based premetastatic niche blockage strategy.

SIGNIFICANCE

This study provides mechanistic insights into the generation of an osteogenic premetastatic niche by breast cancer-derived EVs and identifies potential EV-derived diagnostic biomarkers and targets for breast cancer bone metastasis.

The gut microbiota can be a potential regulator and treatment target of bone metastasis

The gut microbiota, an often forgotten organ, have a tremendous impact on human health. It has long been known that the gut microbiota are implicated in cancer development, and more recently, the gut microbiota have been shown to influence cancer metastasis to distant organs. Although one of the most common sites of distant metastasis is the bone, and the skeletal system has been shown to be a subject of interactions with the gut microbiota to regulate bone homeostasis, little research has been done regarding how the gut microbiota control the development of bone metastasis. This review will discuss the mechanisms through which the gut microbiota and derived microbial compounds (i) regulate gastrointestinal cancer disease progression and metastasis, (ii) influence skeletal remodeling and potentially modulate bone metastasis, and (iii) affect and potentially enhance immunotherapeutic treatments for bone metastasis.

The Osteocyte Stimulated by Wnt Agonist SKL2001 Is a Safe Osteogenic Niche Improving Bioactivities in a Polycaprolactone and Cell Integrated 3D Module

Finding and constructing an osteogenic microenvironment similar to natural bone tissue has always been a frontier topic in orthopedics. We found that osteocytes are targeting cells controlling bone anabolism produced by PTH (JBMR 2017, PMID: 27704638), and osteocytes with activated Wnt signaling orchestrate bone formation and resorption (PNAS 2015, PMID: 25605937). However, methods for taking advantage of the leading role of osteocytes in bone regeneration remain unexplored. Herein, we found that the osteocytes with SKL2001-activated Wnt signaling could be an osteogenic microenvironment (SOOME) which upregulates the expression of bone transcription factor Runx2 and Bglap and promotes the differentiation of bone marrow stromal cell ST2 into osteoblasts. Interestingly, 60 μM SKL2001 treatment of osteocytic MLO-Y4 for 24 h maintained Wnt signaling activation for three days after removal, which was sufficient to induce osteoblast differentiation. Triptonide, a Wnt inhibitor, could eliminate this differentiation. Moreover, on day 5, the Wnt signaling naturally decreased to the level of the control group, indicating that this method of Wnt-signaling induction is safe to use. We quickly verified in vivo function of SOOME to a good proximation in 3D bioprinted modules composed of reciprocally printed polycaprolactone bundles (for support) and cell bundles (for bioactivity). In the cell bundles, SOOME stably supported the growth and development of ST2 cells, the 7-day survival rate was as high as 91.6%, and proliferation ability increased linearly. Similarly, SOOME greatly promoted ST2 differentiation and mineralization for 28 days. In addition, SOOME upregulated the expression of angiopoietin 1, promoted endothelial cell migration and angiogenesis, and increased node number and total length of tubes and branches. Finally, we found that the function of SOOME could be realized through the paracrine pathway. This study reveals that osteocytes with Wnt signaling activated by SKL2001 are a safe osteogenic microenvironment. Both SOOME itself and its cell-free culture supernatant can improve bioactivity for osteoblast differentiation, with composite scaffolds especially bearing application value.

Intervention with the Bone-Associated Tumor Vicious Cycle through Dual-Protein Therapeutics for Treatment of Skeletal-Related Events and Bone Metastases

Bone metastasis is a common metastasis site such as lung cancer, prostate cancer, and other malignant tumors. The occurrence of bone metastases of lung cancer is often accompanied by bone loss, fracture, and other skeletal-related events (SREs) caused by tumor proliferation and osteoclast activation. Furthermore, along with the differentiation and maturation of osteoclasts in the bone microenvironment, it will further promote the occurrence and development of bone metastasis. Protein drugs are one of the most promising therapeutic pharmaceuticals, but in vivo delivery of protein therapeutics still confronts great challenges. In order to more effectively conquer bone metastases and alleviate SREs, herein, we constructed biomineralized metal-organic framework (MOF) nanoparticles carrying protein toxins with both bone-seeking and CD44-receptor-targeting abilities. More importantly, through combination with Receptor Activator of Nuclear Factor-κ B Ligand (RANKL) antibody, in vivo results demonstrated that these two protein agents not only enhanced the detraction effects of protein toxin agents as ribosome-inactivating protein (RIP) on bone metastatic tumor cells but also exhibited synergistic intervention of the crosstalk between bone cells and tumor cells and reduced SREs such as bone loss. Collectively, we expect that this strategy can provide an effective and safe option in regulating bone-tumor microenvironments to overcome bone metastasis and SREs.

Advancing Treatment of Bone Metastases through Novel Translational Approaches Targeting the Bone Microenvironment

Bone metastases represent a lethal condition that frequently occurs in solid tumors such as prostate, breast, lung, and renal cell carcinomas, and increase the risk of skeletal-related events (SREs) including pain, pathologic fractures, and spinal cord compression. This unique metastatic niche consists of a multicellular complex that cancer cells co-opt to engender bone remodeling, immune suppression, and stromal-mediated therapeutic resistance. This review comprehensively discusses clinical challenges of bone metastases, novel preclinical models of the bone and bone marrow microenviroment, and crucial signaling pathways active in bone homeostasis and metastatic niche. These studies establish the context to summarize the current state of investigational agents targeting BM, and approaches to improve BM-targeting therapies. Finally, we discuss opportunities to advance research in bone and bone marrow microenvironments by increasing complexity of humanized preclinical models and fostering interdisciplinary collaborations to translational research in this challenging metastatic niche.

Evolving cancer-niche interactions and therapeutic targets during bone metastasis

Many cancer types metastasize to bone. This propensity may be a product of genetic traits of the primary tumour in some cancers. Upon arrival, cancer cells establish interactions with various bone-resident cells during the process of colonization. These interactions, to a large degree, dictate cancer cell fates at multiple steps of the metastatic cascade, from single cells to overt metastases. The bone microenvironment may even influence cancer cells to subsequently spread to multiple other organs. Therefore, it is imperative to spatiotemporally delineate the evolving cancer-bone crosstalk during bone colonization. In this Review, we provide a summary of the bone microenvironment and its impact on bone metastasis. On the basis of the microscopic anatomy, we tentatively define a roadmap of the journey of cancer cells through bone relative to various microenvironment components, including the potential of bone to function as a launch pad for secondary metastasis. Finally, we examine common and distinct features of bone metastasis from various cancer types. Our goal is to stimulate future studies leading to the development of a broader scope of potent therapies.

Spine Metastases in Immunocompromised Mice after Intracardiac Injection of MDA-MB-231-SCP2 Breast Cancer Cells

Simple Summary

Breast cancer cells typically metastasize to bone, where their interaction with bone remodeling cell types enhances metastatic outgrowth and osteolytic bone destruction. The respective knowledge is largely based on xenograft models, where human breast cancer cells are injected into immunocompromised mice. Importantly, however, whereas skeletal analyses in these animals are usually restricted to hindlimb bones, human skeletal metastases are far more frequent in the spine. Therefore, our study addressed the question, if breast cancer cells injected into immunocompromised mice would also metastasize to the spine, and if this process is influenced by the amount of trabecular bone. We injected an established breast cancer cell line into immunocompromised mice with or without a transgene causing severe osteoporosis. Importantly, we found more tumor cell clusters of different size in spine sections than in femora, but the presence of the transgene did not affect their spreading and metastatic outgrowth.

Abstract

Breast cancer cells frequently metastasize to bone, where their interaction with bone remodeling cell types enhances osteolytic bone destruction. Importantly, however, whereas skeletal analyses of xenograft models are usually restricted to hindlimb bones, human skeletal metastases are far more frequent in the spine, where trabecular bone mass is higher compared to femur or tibia. Here, we addressed whether breast cancer cells injected into immunocompromised mice metastasize to the spine and if this process is influenced by the amount of trabecular bone. We also took advantage of mice carrying the Col1a1-Krm2 transgene, which display severe osteoporosis. After crossing this transgene into the immunocompromised NSG background we injected MDA-MB-231-SCP2 breast cancer cells and analyzed their distribution three weeks thereafter. We identified more tumor cells and clusters of different size in spine sections than in femora, which allowed influences on bone remodeling cell types to be analyzed by comparing tumor-free to tumor-burdened areas. Unexpectedly, the Col1a1-Krm2 transgene did not affect spreading and metastatic outgrowth of MDA-MB-231-SCP2 cells, suggesting that bone tumor interactions are more relevant at later stages of metastatic progression.

Precise Diagnosis and Therapy of Bone Cancer Using Near-Infrared Lights

Bone is a preferred site for both primary and metastasis tumors. Current diagnosis of osteopathia typically relies on noninvasive skeleton radiography technology. However, due to the limited resolution of ionizing radiation, accurate diagnosis and effective identification impairment areas are still lacking. Near-infrared (NIR) bioimaging, especially in the NIR-II (1000-1700 nm) regions, can provide high sensitivity and spatiotemporal resolution bioimaging compared to the conventional radiography. Thus, NIR bioimaging affords intraoperative visualization and imaging-guided surgery, aiming to overcome challenges associated with theranostics of osteopathia and bone tumors. The present review aimed to summarize the latest evidence on the use of NIR probes for the targeting bone imaging. We further highlight the recent advances in bone photoX (X presents thermal, dynamic, and immuno) therapy through NIR probes, in particular combination with other customized therapeutic agents could provide high-efficiency treatment for bone tumors.

Moderate tibial loading and treadmill running, but not overloading, protect adult murine bone from destruction by metastasized breast cancer

Osteolytic bone lesions, which develop in many metastatic breast cancer patients, impair bone integrity and lead to adverse skeletal related events that are difficult to treat and sometimes fatal. Moderate mechanical loading has been shown to suppress osteolysis in young mice with breast cancer. In this study, we aimed to investigate the dose-dependent effects of mechanical loading on protecting the integrity of adult skeletons with breast cancer. Localized tibial loading and aerobic treadmill running with three levels of varying intensity were tested in a syngeneic mammary tumor bone metastasis model. Adult C57BL/6J female mice (14-week-old, N = 88 mice) received intra-tibial injections of Py8119 triple-negative murine breast cancer cells or PBS and underwent 4 to 5 weeks of exercise or acted as sedentary/non-loaded controls. The bone structure was monitored longitudinally with weekly in vivo micro-computed tomography imaging, while the cellular responses in bone and marrow were examined using immunohistochemistry. Moderate treadmill running (16 m/min, 50 min/day, 5 days/week, and 5 weeks) and tibial loading (4.5 N, 630 με, 4 Hz, 300 cycles/day, 5 days/week, and 4 weeks) suppressed tumor-induced bone destruction, as evaluated by full-thickness perforation of tibial cortex and the volume of osteolytic lesions in the cortex. In contrast, tibial loading at higher magnitude (8 N, 1100 με) induced woven bone and accelerated bone destruction, compared with the non-loaded controls. The three exercise regimens differentially affected osteocyte apoptosis, osteocyte hypoxia, osteoclast activity, bone marrow vasculature, and tumor proliferation. In conclusion, the relationship between exercise intensity and the risk of breast cancer-induced osteolysis was found to follow a J-shaped curve in a preclinical model, suggesting the need to optimize exercise parameters in order to harness the skeletal benefits of exercise in metastatic breast cancers.

Comparison of the Relative Diagnostic Performance of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT for the Detection of Bone Metastasis in Patients With Different Cancers

Purpose

The present retrospective analysis sought to compare the relative diagnostic efficacy of [⁶⁸Ga]Ga-DOTA-FAPI-04 to that of [¹⁸F]FDG PET/CT as a means of detecting bone metastases in patients with a range of cancer types.

Materials

In total, 30 patients with bone metastases associated with different underlying malignancies were retrospectively enrolled. All patients had undergone [⁶⁸Ga]Ga-DOTA-FAPI-04 and [¹⁸F]FDG PET/CT, and the McNemar test was used to compare the relative diagnostic performance of these two imaging modalities. The maximum standard uptake value (SUVmax) was used to quantify radiotracer uptake by metastatic lesions, with the relative uptake associated with these two imaging strategies being compared via the Mann-Whitney U test. The cohort was further respectively divided into two (osteolytic and osteoblastic bone metastases) and three clinical subgroups (lung cancer, thyroid cancer, and liver cancer).

Results

[⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT was found to be significantly more sensitive as a means of diagnosing bone metastases relative to [¹⁸F]FDG PET/CT ([109/109] 100% vs [89/109] 81.7%; P< 0.01), consistent with the significantly increased uptake of [⁶⁸Ga]Ga-DOTA-FAPI-04 by these metastatic lesions relative to that of [¹⁸F]FDG (n=109, median SUVmax, 9.1 vs. 4.5; P< 0.01). [⁶⁸Ga]Ga-DOTA-FAPI-04 accumulation was significantly higher than that of [¹⁸F]FDG in both osteolytic (n=66, median SUVmax, 10.6 vs 6.1; P < 0.01), and osteoblastic metastases (n=43, median SUVmax, 7.7 vs 3.7; P < 0.01). [⁶⁸Ga]Ga-DOTA-FAPI-04 uptakes were significantly higher than that of [¹⁸F]FDG in bone metastases from lung cancer (n = 62, median SUVmax, 10.7 vs 5.2; P < 0.01), thyroid cancer (n = 18, median SUVmax, 5.65 vs 2.1; P < 0.01) and liver cancer (n = 12, median SUVmax, 5.65 vs 3.05; P < 0.01). However, [⁶⁸Ga]Ga-DOTA-FAPI-04 detected 10 false-positive lesions, while only 5 false-positive were visualized by [¹⁸F]FDG PET/CT.

Conclusion

[⁶⁸Ga]Ga-DOTA-FAPI-04 PET/CT exhibits excellent diagnostic performance as a means of detecting bone metastases, and is superior to [¹⁸F]FDG PET/CT in this diagnostic context. Furthermore, [⁶⁸Ga]Ga-DOTA-FAPI-04 tracer uptake levels are higher than those of [¹⁸F]FDG for most bone metastases. However, owing to the potential for false-positive bone lesions, it is critical that physicians interpret all CT findings with caution to ensure diagnostic accuracy.

Bone-modifying Agents (BMAs) in Breast Cancer

Bone-modifying agents (BMAs) are mainstays in breast cancer and prevent and treat osteoporosis in early-stage disease and reduce skeletal metastases complications in advanced disease. There is some evidence to support that BMA also prevents skeletal metastases and improves overall survival. Bone loss occurs with chemotherapy-induced ovarian failure, gonadotrophin-releasing hormone (GnRH) agonists, and aromatase inhibitors. In some women, the bone loss will be of sufficient magnitude to increase the risks of osteoporosis or fractures. Recommended steps in osteoporosis prevention or treatment include risk factor assessment, taking adequate amounts of calcium and vitamin D3, and periodic evaluations with dual-energy x-ray absorptiometry scanning. If clinically indicated by the T-scores and fracture-risk prediction algorithms treat with oral, IV bisphosphonates or subcutaneous denosumab (DEN). Zoledronic acid (ZA) or DEN reduces skeletal metastases complications, including pathological fracture, spinal cord compression, or the necessity for radiation or surgery to bone. Also, both of these drugs have the side-effect of osteonecrosis at a similar incidence. Monthly administration of ZA or DEN is standard, but several recent randomized trials show noninferiority between ZA monthly and every 3-month ZA. Every 3-month ZA is a new standard of care. Similar trials of the schedule of DEN are ongoing. ZA anticancer effect is only in postmenopausal women or premenopausal women rendered postmenopausal by GnRH agonists or bilateral oopherectomy. High-risk women, either postmenopausal or premenopausal, receiving GnRH/oopherctomy should consider adjuvant ZA. There are insufficient data to support DEN in this setting. Herein, this narrative review covers the mechanism of action of BMA, randomized clinical trials, and adverse events, both common and rare.