Pathological Crosstalk between Metastatic Breast Cancer Cells and the Bone Microenvironment

Unveiling the Link Between Breast Cancer Treatment and Osteoporosis: Implications for Anticancer Therapy and Bone Health

Background: The interplay between breast cancer treatment and osteoporosis has important consequences for anticancer therapy and patient bone health. Many breast cancer therapies involve hormonal treatments that lower estrogen levels, which can lead to an increased risk of osteoporosis due to reduced bone mineral density. Aromatase inhibitors, chemotherapy, and surgeries such as oophorectomy can further aggravate bone loss, highlighting the necessity of prioritizing bone health during cancer treatment. Objective: This review is aimed at investigating the complex relationship between breast cancer therapies and bone health by examining the molecular and cellular mechanisms through which anticancer treatments lead to bone loss. It also seeks to assess the effects of various treatment options, such as selective estrogen receptor modulators (SERMs) and bisphosphonates, on reducing bone loss and maintaining bone health during cancer therapy. Method: The review explores the mechanisms underlying bone loss in breast cancer patients undergoing treatment, focusing on factors such as estrogen depletion, inflammatory cytokines, and changes in bone remodelling processes. Additionally, it evaluates the efficacy of different therapeutic interventions, including pharmacological treatments like bisphosphonates and third-generation SERMs, in mitigating bone-related side effects. Results: The findings indicate a critical need to balance the effectiveness of breast cancer treatments with the preservation of bone health. Pharmacological treatments like bisphosphonates and denosumab have been identified as essential for managing bone health in breast cancer patients. Furthermore, third-generation SERMs show potential in reducing bone loss associated with cancer therapy.

Tryptophan 2,3-dioxygenase-positive matrix fibroblasts fuel breast cancer lung metastasis via kynurenine-mediated ferroptosis resistance of metastatic cells and T cell dysfunction

BACKGROUND

Tumor metastasis is a major threat to cancer patient survival. The organ-specific niche plays a pivotal role in tumor organotropic metastasis. Fibroblasts serve as a vital component of the metastatic microenvironment, but how heterogeneous metastasis-associated fibroblasts (MAFs) promote organotropic metastasis is poorly characterized. Here, we aimed to decipher the heterogeneity of MAFs and elucidate the distinct roles of these fibroblasts in pulmonary metastasis formation in breast cancer.

METHODS

Mouse models of breast cancer pulmonary metastasis were established using an in vivo selection method of repeated injections of metastatic cells purified from the mouse lung. Single-cell RNA-sequencing (scRNA-seq) was employed to investigate the heterogeneity of MAFs. Transgenic mice were used to examine the contribution of tryptophan 2,3-dioxygenase-positive matrix fibroblasts (TDO2+ MFs) in lung metastasis.

RESULTS

We uncovered 3 subtypes of MAFs in the lung metastatic microenvironment, and their transcriptome profiles changed dynamically as lung metastasis evolved. As the predominant subtype, MFs were exclusively marked by platelet-derived growth factor receptor alpha (PDGFRA) and mainly located on the edge of the metastasis, and T cells were enriched around MFs. Notably, high MF signatures were significantly associated with poor survival in breast cancer patients. Lung metastases were markedly diminished, and the suppression of T cells was dramatically attenuated in MF-depleted experimental metastatic mouse models. We found that TDO2+ MFs controlled pulmonary metastasis by producing kynurenine (KYN), which upregulated ferritin heavy chain 1 (FTH1) level in disseminated tumor cells (DTCs), enabling DTCs to resist ferroptosis. Moreover, TDO2+ MF-secreted chemokines C-C motif chemokine ligand 8 (CCL8) and C-C motif chemokine ligand 11 (CCL11) recruited T cells. TDO2+ MF-derived KYN induced T cell dysfunction. Conditional knockout of Tdo2 in MFs diminished lung metastasis and enhanced immune activation.

CONCLUSIONS

Our study reveals crucial roles of TDO2+ MFs in promoting lung metastasis and DTCs' immune evasion in the metastatic niche. It suggests that targeting the metabolism of lung-specific stromal cells may be an effective treatment strategy for breast cancer patients with lung metastasis.

Efficacy of Surgical Intervention in Treating Pathological Fractures of the Upper Extremity: A Retrospective Case Series

BACKGROUND

We conduct a retrospective analysis of patients with pathological fractures resulting from upper extremity malignancies, focusing on the evaluation of treatment strategies employed.

MATERIALS AND METHODS

We retrospectively studied 10 patients with metastatic bone tumors of the upper extremities. The study variables included tumor site, primary pathology, duration from the first diagnosis of the primary lesion to the occurrence of the pathological fracture, use of bone-modifying drugs, surgical technique, adjuvant therapy, postoperative functional assessment, Katagiri's score, American Society of Anesthesiologists physical status (ASA-PS), outcome, and correlations between the Eastern Cooperative Oncology Group Performance Status (ECOG-PS) and Musculoskeletal Tumor Society (MSTS) score.

RESULTS

The sites involved were the humerus and radius in eight and two patients, respectively. Primary pathologies were liver cancer in three patients, lung cancer and renal cancer in two patients each, and one patient each with multiple myeloma, plasmacytoma, and Hodgkin's lymphoma. Nine patients experienced pathological fractures, and one had an impending fracture. The median time from primary tumor diagnosis to fracture was 12.5 months. Bone-modifying drugs were administered in all cases. Surgical procedures included intramedullary nails in seven patients and plate fixation in two. Chemotherapy served as adjuvant therapy in nine cases. The mean MSTS score was 26.5, and Katagiri's score averaged 6. The median ASA-PS stood at 2. Outcomes showed seven patients alive with disease and three dead from disease. A significant association between the ECOG-PS and MSTS score was not observed.

CONCLUSION

Pathological fractures caused by malignant bone tumors of the upper extremity should be treated proactively with surgery regardless of prognosis.

Microenvironment-Responsive Targeted Nanomedicine for a Collaborative Integration of Tumor Theranostics and Bone Defect Repair

Despite advancements in breast cancer treatment, bone metastases remain a significant concern for advanced breast cancer patients. Current theranostics strategies face challenges in integrating tumor theranostics and bone formation. Herein, this work develops an activatable targeted nanomedicine AuMnCO@BSA-N3 (AMCBN) to enable a novel collaborative integration of second near-infrared (NIR-II) fluorescence imaging guided precise theranostics for breast cancer bone metastases and osteogenic microenvironment remolding. This strategy employs a chemical coordination between noble metal complex and metal carbonyl (MnCO), with surface modification of azide groups to enhance tumor affinity through passive and active targeting. The initiated respondent behavior of AMCBN by tumor microenvironment accelerate the degradation of coordinated MnCO, resulting in a rapid release of multifunctional agents for efficient chemodynamic therapy (CDT)/gas synergistic therapy. Meanwhile, the exceptional bone-binding properties enable the efficient and controlled release of Mn2+ ions and carbon monoxide (CO) in the bone microenvironment, thereby facilitating the expression of osteogenesis-related proteins and establishing a novel synchronous theranostics process for tumor-bone repair.

Immune mediated support of metastasis: Implication for bone invasion

Bone is a common organ affected by metastasis in various advanced cancers, including lung, breast, prostate, colorectal, and melanoma. Once a patient is diagnosed with bone metastasis, the patient's quality of life and overall survival are significantly reduced owing to a wide range of morbidities and the increasing difficulty of treatment. Many studies have shown that bone metastasis is closely related to bone microenvironment, especially bone immune microenvironment. However, the effects of various immune cells in the bone microenvironment on bone metastasis remain unclear. Here, we described the changes in various immune cells during bone metastasis and discussed their related mechanisms. Osteoblasts, adipocytes, and other non-immune cells closely related to bone metastasis were also included. This review also summarized the existing treatment methods and potential therapeutic targets, and provided insights for future studies of cancer bone metastasis.

Role of flavonoids in inhibiting triple-negative breast cancer

Increasing incidences of metastasis or recurrence (or both) in triple-negative breast cancer (TNBC) are a growing concern worldwide, as these events are intricately linked to higher mortality rates in patients with advanced breast cancer. Flavonoids possess several pharmaceutical advantages with multi-level, multi-target, and coordinated intervention abilities for treating TNBC, making them viable for preventing tumor growth and TNBC metastasis. This review focused on the primary mechanisms by which flavonoids from traditional Chinese medicine extracts inhibit TNBC, including apoptosis, blocking of cell cycle and movement, regulation of extracellular matrix degradation, promotion of anti-angiogenesis, inhibition of aerobic glycolysis, and improvement in tumor microenvironment. This review aims to improve the knowledge of flavonoids as a promising pharmacological intervention for patients with TNBC.

A novel NIR-II FL/ PA imaging-guided synergistic photothermal-immune therapy: Biomineralizing nanosystems integrated with anti-tumor and bone repair

Advanced stages of breast cancer are frequently complicated by bone metastases, which cause significant cancer-related bone destruction and mortality. However, the early precise theranostics of bone metastasis remains a formidable challenge in clinical practice. Herein,a novel all-in-one nanotheranostic system (ABI NYs) combining NIR-II FL/PA dual-modal imaging with photothermal-immunity therapeutic functionalities in one component was designed to precisely localize bone metastasis microscopic lesions and achieve complete tumor ablation at an early stage. The surface modification of the nanosystem with ibandronate (IBN) facilitates both passive and active targeting, significantly improving the detection rate of bone metastasis and suppressing the bone resorption. Superior photothermal performance produces sufficient heat to kill tumor cells while stimulating the upregulation of heat shock proteins 70 (HSP70), which triggers the immunogenic cell death (ICD) effect and the anti-tumor immune response. These all-in-one nanosystems precisely demonstrated early lesion localization in bone metastases and total tumor ablation with a single integration via "one-component, multi-functions" technique. To sum up, ABI NYs, as novel biomineralizing nanosystems integrated with anti-tumor and bone repair, present a synergistic therapy strategy, providing insight into the theranostics of bone metastases and clinical research.

Morusin inhibits breast cancer-induced osteolysis by decreasing phosphatidylinositol 3-kinase (PI3K)-mTOR signalling

Bone metastases caused by breast cancer pose a major challenge to the successful treatment of breast cancer patients. Many researchers have suggested that herbal medicines are extremely effective at preventing and treating cancer-associated osteolysis. Previous studies have revealed that Morusin (MOR) is cytotoxic to many cancer cells ex vivo. Nevertheless, how MOR contributes to osteolysis induced by breast cancer is still unknown, and the potential mechanism of action against osteolysis is worthy of further study. The protective effect and molecular mechanism of MOR in inhibiting breast cancer cell-induced osteolysis were verified by experiments and network pharmacology. Cell function was assessed by cell proliferation, osteoclast (OC) formation, bone resorption, and phalloidin staining. Tumour growth was examined by micro-CT scanning in vivo. To identify potential MOR treatments, the active ingredient-target pathway of breast cancer was screened using network pharmacology and molecular docking approaches. This study is the first to report that MOR can prevent osteolysis induced by breast cancer cells. Specifically, our results revealed that MOR inhibits RANKL-induced osteoclastogenesis and restrains the proliferation, invasion and migration of MDA-MB-231 breast cells through restraining the PI3K/AKT/MTOR signalling pathway. Notably, MOR prevented bone loss caused by breast cancer cell-induced osteolysis in vivo, indicating that MOR inhibited the development of OCs and the resorption of bone, which are essential for cancer cell-associated bone distraction. This study showed that MOR treatment inhibited osteolysis induced by breast cancer in vivo. MOR inhibited OC differentiation and bone resorption ex vivo and in vivo and might be a potential drug candidate for treating breast cancer-induced osteolysis.

Multidimensional analysis to elucidate the possible mechanism of bone metastasis in breast cancer

BACKGROUND

Breast cancer (BC) patients tend to suffer from distant metastasis, especially bone metastasis.

METHODS

All the analysis based on open-accessed data was performed in R software, dependent on multiple algorithms and packages. The RNA levels of specific genes were detected using quantitative Real-time PCR as a method of detecting the RNA levels. To assess the ability of BC cells to proliferate, we utilized the CCK8 test, colony formation, and the 5-Ethynyl-20-deoxyuridine assay. BC cells were evaluated for invasion and migration by using Transwell assays and wound healing assays.

RESULTS

In our study, we identified the molecules involved in BC bone metastasis based on the data from multiple BC cohorts. Then, we comprehensively investigated the effect pattern and underlying biological role of these molecules. We found that in the identified molecules, the EMP1, ACKR3, ITGA10, MMP13, COL11A1, and THY1 were significantly correlated with patient prognosis and mainly expressed in CAFs. Therefore, we explored the CAFs in the BC microenvironment. Results showed that CAFs could activate multiple carcinogenic pathways and most of these pathways play an important role in cancer metastasis. Meanwhile, we noticed the interaction between CAFs and malignant, endothelial, and M2 macrophage cells. Moreover, we found that CAFs could induce the remodeling of the BC microenvironment and promote the malignant behavior of BC cells. Then, we identified MMP13 for further analysis. It was found that MMP13 can enhance the malignant phenotype of BC cells. Meanwhile, biological enrichment and immune infiltration analysis were conducted to present the effect pattern of MMP13 in BC.

CONCLUSIONS

Our result can improve the understanding of researchers on the underlying mechanisms of BC bone metastasis.

MicroRNAs mediated interaction of tumor microenvironment cells with breast cancer cells during bone metastasis

Breast cancer (BC) bone metastasis is primarily osteolytic and has limited therapeutic options. Metastasized BC cells prime the secondary environment in bone by forming a tumor niche, which favors their homing and colonization. The tumor microenvironment (TME) is primarily generated by the cancer cells. Bone TME is an intricate network of multiple cells, including altered bone, tumor, stromal, and immune cells. Recent findings highlight the significance of small non-coding microRNAs (miRNAs) in influencing TME during tumor metastasis. MiRNAs from TME-resident cells facilitate the interaction between the tumor and its microenvironment, thereby regulating the biological processes of tumors. These miRNAs can serve as oncogenes or tumor suppressors. Hence, both miRNA inhibitors and mimics are extensively utilized in pre-clinical trials for modulating the phenotypes of tumor cells and associated stromal cells. This review briefly summarizes the recent developments on the functional role of miRNAs secreted directly or indirectly from the TME-resident cells in facilitating tumor growth, progression, and metastasis. This information would be beneficial in developing novel targeted therapies for BC.

Senescent mesenchymal stem/stromal cells in pre-metastatic bone marrow of untreated advanced breast cancer patients

Breast cancer is the predominant form of carcinoma among women worldwide, with 70% of advanced patients developing bone metastases, with a high mortality rate. In this sense, the bone marrow (BM) mesenchymal stem/stromal cells (MSCs) are critical for BM/bone homeostasis, and failures in their functionality, transform the BM into a pre-metastatic niche (PMN). We previously found that BM-MSCs from advanced breast cancer patients (BCPs, infiltrative ductal carcinoma, stage III-B) have an abnormal profile. This work aims to study some of the metabolic and molecular mechanisms underlying MSCs shift from a normal to an abnormal profile in this group of patients. A comparative analysis was undertaken, which included self-renewal capacity, morphology, proliferation capacity, cell cycle, reactive oxygen species (ROS) levels, and senescence-associated β‑galactosidase (SA‑β‑gal) staining of BM-derived MSCs isolated from 14 BCPs and 9 healthy volunteers (HVs). Additionally, the expression and activity of the telomerase subunit TERT, as well as telomere length, were measured. Expression levels of pluripotency, osteogenic, and osteoclastogenic genes (OCT-4, SOX-2, M-CAM, RUNX-2, BMP-2, CCL-2, M-CSF, and IL-6) were also determined. The results showed that MSCs from BCPs had reduced ,self-renewal and proliferation capacity. These cells also exhibited inhibited cell cycle progression and phenotypic changes, such as an enlarged and flattened appearance. Additionally, there was an increase in ROS and senescence levels and a decrease in the functional capacity of TERT to preserve telomere length. We also found an increase in pro-inflammatory/pro-osteoclastogenic gene expression and a decrease in pluripotency gene expression. We conclude that these changes could be responsible for the abnormal functional profile that MSCs show in this group of patients.

The Role of Hedgehog Signaling in the Melanoma Tumor Bone Microenvironment

A crucial regulator in melanoma progression and treatment resistance is tumor microenvironments, and Hedgehog (Hh) signals activated in a tumor bone microenvironment are a potential new therapeutic target. The mechanism of bone destruction by melanomas involving Hh/Gli signaling in such a tumor microenvironment is unknown. Here, we analyzed surgically resected oral malignant melanoma specimens and observed that Sonic Hedgehog, Gli1, and Gli2 were highly expressed in tumor cells, vasculatures, and osteoclasts. We established a tumor bone destruction mouse model by inoculating B16 cells into the bone marrow space of the right tibial metaphysis of 5-week-old female C57BL mice. An intraperitoneal administration of GANT61 (40 mg/kg), a small-molecule inhibitor of Gli1 and Gli2, resulted in significant inhibition of cortical bone destruction, TRAP-positive osteoclasts within the cortical bone, and endomucin-positive tumor vessels. The gene set enrichment analysis suggested that genes involved in apoptosis, angiogenesis, and the PD-L1 expression pathway in cancer were significantly altered by the GANT61 treatment. A flow cytometry analysis revealed that PD-L1 expression was significantly decreased in cells in which late apoptosis was induced by the GANT61 treatment. These results suggest that molecular targeting of Gli1 and Gli2 may release immunosuppression of the tumor bone microenvironment through normalization of abnormal angiogenesis and bone remodeling in advanced melanoma with jaw bone invasion.

In vitro models of breast cancer bone metastasis: analyzing drug resistance through the lens of the microenvironment

Even though breast cancers usually have a good outcome compared to other tumors, the cancer can progress and create metastases in different parts of the organism, the bone being a predilection locus. These metastases are usually the cause of death, as they are mostly resistant to treatments. This resistance can be caused by intrinsic properties of the tumor, such as its heterogeneity, but it can also be due to the protective role of the microenvironment. By activating signaling pathways protecting cancer cells when exposed to chemotherapy, contributing to their ability to reach dormancy, or even reducing the amount of drug able to reach the metastases, among other mechanisms, the specificities of the bone tissue are being investigated as important players of drug resistance. To this date, most mechanisms of this resistance are yet to be discovered, and many researchers are implementing in vitro models to study the interaction between the tumor cells and their microenvironment. Here, we will review what is known about breast cancer drug resistance in bone metastasis due to the microenvironment and we will use those observations to highlight which features in vitro models should include to properly recapitulate these biological aspects in vitro. We will also detail which elements advanced in vitro models should implement in order to better recapitulate in vivo physiopathology and drug resistance.

Secreted microRNAs in bone metastasis

Bone metastasis is a common complication in several solid cancers, including breast, prostate, and lung. In the bone microenvironment, metastatic cancer cells disturb bone homeostasis leading to osteolytic or osteosclerotic lesions. Osteolytic lesions are characterized by an increased osteoclast-mediated bone resorption while osteosclerotic lesions are caused by enhanced activity of osteoblasts and formation of poor-quality bone. A common feature in bone metastasis is the complex interplay between the cancer cells and the cells of the bone microenvironment, which can occur already before the cancer cells enter the distant site. Cancer cells at the primary site can secrete soluble factors and extracellular vesicles to bone to create a "pre-metastatic niche" i.e., prime the microenvironment permissive for cancer cell homing, survival, and growth. Once in the bone, cancer cells secrete factors to activate the osteoclasts or osteoblasts and the so called "vicious cycle of bone metastases". These pathological cell-cell interactions are largely dependent on secreted proteins. However, increasing evidence demonstrates that secreted RNA molecules, in particular small non-coding microRNAs are critical mediators of the crosstalk between bone and cancer cells. This review article discusses the role of secreted miRNAs in bone metastasis development and progression, and their potential as non-invasive biomarkers.

Correlation between Blood Lipid Level and Osteoporosis in Older Adults with Type 2 Diabetes Mellitus—A Retrospective Study Based on Inpatients in Beijing, China

Objective: to analyze the association between blood lipid metabolism and osteoporosis (OP) in older adults with type 2 diabetes mellitus (T2DM). Methods: a total of 1158 older patients with T2DM treated by the Department of Endocrinology, Peking University International Hospital, were retrospectively analyzed, including 541 postmenopausal women and 617 men. Results: (1) Levels of low-density lipoprotein cholesterol (LDL-C) were significantly higher in the OP group, while levels of high-density lipoprotein cholesterol (HDL-C) were higher in the non-osteoporotic group (both p < 0.05). (2) Age, parathyroid hormone (PTH), total cholesterol (TC) and LDL-C were negatively linked to the patients’ bone mineral density (BMD) (all p < 0.05), while the body mass index (BMI), uric acid (UA) level, HDL-C level and glomerular filtration rate (eGFR) were positively related to their BMD (all p < 0.05). (3) In postmenopausal women, after adjustment for other indexes, raised LDL-C is an independent risk factor for OP (OR = 3.38, 95% CI 1.64, 6.98, p < 0.05) while raised HDL-C is protective (OR = 0.49, 95% CI 0.24, 0.96, p < 0.05). However, raised HDL-C was protective against OP (OR = 0.07, 95% CI 0.01, 0.53, p < 0.05). Conclusion: In older T2DM patients, the effect of blood lipid levels is related to sex. Our study conducted a detailed sex stratification. In addition to seeing the traditional risk factors of OP, such as age, sex, and BMI, we comprehensively analyzed the correlation between the blood glucose level, complications, and blood lipids with OP. HDL-C is a protective factor for OP in both men and women, while LDL-C independently predicts OP in postmenopausal women.

ICAM1 promotes bone metastasis via integrin-mediated TGF-β/EMT signaling in triple-negative breast cancer

Bone-related events caused by breast cancer bone metastasis substantially compromise the survival and quality of life of patients. Because triple-negative breast cancer (TNBC) lacks hormone receptors and Her2-targeted therapeutic options, progress in the treatment of TNBC bone metastasis has been very slow. Intercellular adhesion molecule 1 (ICAM1) is highly expressed in various cancers and plays an important role in tumorigenesis and metastasis. However, the effect and mechanism of ICAM1 in TNBC bone metastasis are still unknown. We found that ICAM1 was highly expressed in TNBC and correlated with prognosis in TNBC patients. Cell lines with high expression of ICAM1 exhibited enhanced bone metastasis in tumor-bearing mice, and silencing ICAM1 expression significantly inhibited bone metastasis in mice. ICAM1 interacted with integrins to activate the epithelial-to-mesenchymal transition (EMT) program through TGF-β/SMAD signaling, ultimately enhancing cell invasiveness. Therefore, the findings of the present study provide a strong rationale for the application of ICAM1-targeted therapy in TNBC patients with bone metastasis.

MicroRNAs: Emerging Regulators of Metastatic Bone Disease in Breast Cancer

Bone metastasis is a frequent complication in patients with advanced breast cancer. Once in the bone, cancer cells disrupt the tightly regulated cellular balance within the bone microenvironment, leading to excessive bone destruction and further tumor growth. Physiological and pathological interactions in the bone marrow are mediated by cell-cell contacts and secreted molecules that include soluble proteins as well as RNA molecules. MicroRNAs (miRNAs) are short non-coding RNAs that post-transcriptionally interfere with their target messenger RNA (mRNA) and subsequently reduce protein abundance. Since their discovery, miRNAs have been identified as critical regulators of physiological and pathological processes, including breast cancer and associated metastatic bone disease. Depending on their targets, miRNAs can exhibit pro-tumorigenic or anti-tumorigenic functions and serve as diagnostic and prognostic biomarkers. These properties have encouraged pre-clinical and clinical development programs to investigate miRNAs as biomarkers and therapeutic targets in various diseases, including metastatic cancers. In this review, we discuss the role of miRNAs in metastatic bone disease with a focus on breast cancer and the bone microenvironment and elaborate on their potential use for diagnostic and therapeutic purposes in metastatic bone disease and beyond.

The tumor microenvironment as driver of stemness and therapeutic resistance in breast cancer: New challenges and therapeutic opportunities

BACKGROUND

Breast cancer (BC), the second most common cause of cancer-related deaths, remains a significant threat to the health and wellness of women worldwide. The tumor microenvironment (TME), comprising cellular components, such as cancer-associated fibroblasts (CAFs), immune cells, endothelial cells and adipocytes, and noncellular components such as extracellular matrix (ECM), has been recognized as a critical contributor to the development and progression of BC. The interplay between TME components and cancer cells promotes phenotypic heterogeneity, cell plasticity and cancer cell stemness that impart tumor dormancy, enhanced invasion and metastasis, and the development of therapeutic resistance. While most previous studies have focused on targeting cancer cells with a dismal prognosis, novel therapies targeting stromal components are currently being evaluated in preclinical and clinical studies, and are already showing improved efficacies. As such, they may offer better means to eliminate the disease effectively.

CONCLUSIONS

In this review, we focus on the evolving concept of the TME as a key player regulating tumor growth, metastasis, stemness, and the development of therapeutic resistance. Despite significant advances over the last decade, several clinical trials focusing on the TME have failed to demonstrate promising effectiveness in cancer patients. To expedite clinical efficacy of TME-directed therapies, a deeper understanding of the TME is of utmost importance. Secondly, the efficacy of TME-directed therapies when used alone or in combination with chemo- or radiotherapy, and the tumor stage needs to be studied. Likewise, identifying molecular signatures and biomarkers indicating the type of TME will help in determining precise TME-directed therapies.

Mediterranean Diet Food Components as Possible Adjuvant Therapies to Counteract Breast and Prostate Cancer Progression to Bone Metastasis

Bone metastasis is a serious and often lethal complication of particularly frequent carcinomas, such as breast and prostate cancers, which not only reduces survival but also worsens the patients’ quality of life. Therefore, it is important to find new and/or additional therapeutic possibilities that can counteract the colonization of bone tissue. High adherence to the Mediterranean diet (MD) is effective in the prevention of cancer and improves cancer patients’ health, thus, here, we considered its impact on bone metastasis. We highlighted some molecular events relevant for the development of a metastatic phenotype in cancer cells and the alterations of physiological bone remodeling, which occur during skeleton colonization. We then considered those natural compounds present in MD foods with a recognized role to inhibit or reverse the metastatic process both in in vivo and in vitro systems, and we reported the identified mechanisms of action. The knowledge of this bioactivity by the dietary components of the MD, together with its wide access to all people, could help not only to maintain healthy status but also to improve the quality of life of patients with bone metastases.

Exosomal tumor necrosis factor-α from hepatocellular cancer cells (Huh-7) promote osteoclast differentiation

Bone is the common extra-hepatic site for cancer metastasis. Hepatic cancer is associated with a higher incidence of pathological fracture. However, this important regulatory mechanism remains unexplored. Thus, exosome-mediated cell-cell communication between hepatocellular cancer and bone might be key to osteolytic bone destruction. Huh-7 exosomes were characterized for size and exosome marker expressions (CD63, Alix). Exosome mediated osteoclast differentiation in the RAW 264.7 cells was monitored from day 1 to 6 and multinucleated osteoclast formation and bone resorption activity were analyzed. The osteoclastogenic factor expressions in the exosomes and osteoclast differentiation markers such as tumor necrosis factor receptor 6 (TRAF6), nuclear factor κB (NF-κB), nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), and cathepsin K (CTSK) were analyzed using western blot. Exosomes released by liver cancer cells (Huh-7) promoted osteoclast differentiation in RAW 264.7 cells. Analysis of osteoclastogenic factors in the exosomes showed that exosomes were specifically enriched with tumor necrosis factor α (TNF-α). Huh-7 exosomes promoted osteoclast differentiation by significantly increasing the number of TRAP-positive multi nucleated osteoclasts and resorption pits. Importantly, exosomes upregulated osteoclast markers TRAF6, NF-κB, and CTSK expressions. Further, neutralizing exosomal TNF-α reverted exosome-mediated osteoclast differentiation in RAW 264.7 cells. Collectively, our findings show that cellular communication of exosomal TNF-α from hepatocellular cancer cells (Huh-7) regulates osteoclast differentiation through NF-κB/CTSK/TRAP expressions. Thus, exosomal TNF-α might act as an important therapeutic target to prevent hepatocellular cancer mediated pathological bone disease.

Bone marrow/bone pre-metastatic niche for breast cancer cells colonization: The role of mesenchymal stromal cells

Breast cancer is one of the most common oncological pathologies in women worldwide. While its early diagnosis has considerably improved, about 70 % of advanced patients develop bone metastases with a high mortality rate. Several authors demonstrated that primary breast cancer cells prepare their future metastatic niche -known as the pre-metastatic niche- to turn it into an "optimal soil" for colonization. The role of the different cellular components of the bone marrow/bone niche in bone metastasis has been well described. However, studying the changes that occur in this microenvironment before tumor cells arrival has become a novel research field. Therefore, the purpose of this review is to describe the current knowledge about the modulation of the normal bone marrow/bone niche by the primary breast tumor, in particular, highlighting the role of mesenchymal stem/stromal cells in transforming this soil into a pre-metastatic niche for breast cancer cells colonization.

Expression of Neurokinin B Receptor in the Gingival Squamous Cell Carcinoma Bone Microenvironment

Gingival squamous cell carcinoma (SCC) frequently invades the maxillary or mandibular bone, and bone destruction is known as a key prognostic factor in gingival SCCs. Recently, Neurokinin 3 receptor (NK-3R), the receptor ligand for NK-3, which is a member of the tachykinin family expressed in the central nervous system, was identified through pathway analysis as a molecule expressed in osteoclasts induced by the hedgehog signal. Although the expression of NK-3R has been detected in osteoclast and SCC cells at the bone invasion front, the relationship between NK-3R expression and the prognosis of gingival SCC patients remains unclear. In the present study, we retrospectively reviewed 27 patients with gingival SCC who had undergone surgery with curative intent. Significantly higher NK-3R expression in tumor cells was found in a case of jawbone invasion than in a case of exophytic poor jawbone invasion. On the other hand, no significant association was observed between NK-3R tumor-positive cases and tumor size, TNM stage, or tumor differentiation. The survival rate tended to be lower in NK-3R tumor-positive cases, but not significantly. However, the disease-specific survival rate was significantly lower in patients with a large number of NK-3R-positive osteoclasts than in those with a small number of them at the tumor bone invasion front. Our results suggest that NK-3R signaling in the gingival SCC bone microenvironment plays an important role in tumor bone destruction and should be considered a potential therapeutic target in advanced gingival SCC with bone destruction.

Bone targeting nano-aggregates prepared from self-assembled polyaspartamide graft copolymers for pH sensitive DOX delivery

Nanoparticles with bone targeting ability and pH-sensitivity were prepared with polyaspartamide (PASPAM) derivatives based on polysuccinimide (PSI) grafted with octadecylamine (C18), hydrazine (HYD) and polyethylene glycol (PEG, Mw: 5000). For the bone targeting, alendronate (ALN), which has bone affinity, was grafted to PEG and doxorubicin (DOX) was conjugated with linkers of acid sensitive hydrazone bonds, which can be cleaved most effectively in an intracellular acidic environment. At pH 5.0, ∼75% of the drug was released from ALN-PEG/C18/HYD-DOX-g-PASPAM due to the effective cleavage of HYD under the acidic condition. Also, ALN-PEG/C18/HYD-DOX-g-PASPAM particles were more effectively adsorbed on the surface of bone than PEG/C18/HYD-DOX-g-PASPAM. According to an in vivo antitumor activity test, the volume of tumor treated with ALN-PEG/C18/HYD-DOX-g-PASPAM decreased (1550 mm3) when compared with the PBS control sample (3850 mm3), proving that ALN-PEG/C18/HYD-DOX-g-PASPAM is an effective drug delivery system for the treatment of bone metastasis of breast cancer.

The Role of Inflammation in Breast and Prostate Cancer Metastasis to Bone

Tumor metastasis to bone is a common event in multiple forms of malignancy. Inflammation holds essential functions in homeostasis as a defense mechanism against infections and is a strategy to repair injured tissue and to adapt to stress conditions. However, exaggerated and/or persistent (chronic) inflammation may eventually become maladaptive and evoke diseases such as autoimmunity, diabetes, inflammatory tissue damage, fibrosis, and cancer. In fact, inflammation is now considered a hallmark of malignancy with prognostic relevance. Emerging studies have revealed a central involvement of inflammation in several steps of the metastatic cascade of bone-homing tumor cells through supporting their survival, migration, invasion, and growth. The mechanisms by which inflammation favors these steps involve activation of epithelial-to-mesenchymal transition (EMT), chemokine-mediated homing of tumor cells, local activation of osteoclastogenesis, and a positive feedback amplification of the protumorigenic inflammation loop between tumor and resident cells. In this review, we summarize established and evolving concepts of inflammation-driven tumorigenesis, with a special focus on bone metastasis.

Interleukins as Mediators of the Tumor Cell-Bone Cell Crosstalk during the Initiation of Breast Cancer Bone Metastasis

Patients with advanced breast cancer are at high risk of developing bone metastasis. Despite treatment advances for primary breast cancer, metastatic bone disease remains incurable with a low relative survival. Hence, new therapeutic approaches are required to improve survival and treatment outcome for these patients. Bone is among the most frequent sites of metastasis in breast cancer. Once in the bone, disseminated tumor cells can acquire a dormant state and remain quiescent until they resume growth, resulting in overt metastasis. At this stage the disease is characterized by excessive, osteoclast-mediated osteolysis. Cells of the bone microenvironment including osteoclasts, osteoblasts and endothelial cells contribute to the initiation and progression of breast cancer bone metastasis. Direct cell-to-cell contact as well as soluble factors regulate the crosstalk between disseminated breast cancer cells and bone cells. In this complex signaling network interleukins (ILs) have been identified as key regulators since both, cancer cells and bone cells secrete ILs and express corresponding receptors. ILs regulate differentiation and function of bone cells, with several ILs being reported to act pro-osteoclastogenic. Consistently, the expression level of ILs (e.g., in serum) has been associated with poor prognosis in breast cancer. In this review we discuss the role of the most extensively investigated ILs during the establishment of breast cancer bone metastasis and highlight their potential as therapeutic targets in preventing metastatic outgrowth in bone.

Clinical management and biology of tumor dormancy in breast cancer

Clinical tumor dormancy is specified as an extended latency period between removal of the primary tumor and subsequent relapse in a cancer patient who has been clinically disease-free. In particular, patients with estrogen receptor-positive breast cancer can undergo extended periods of more than five years before they relapse with overt metastatic disease. Recent studies have shown that minimal residual disease in breast cancer patients can be monitored by different liquid biopsy approaches like analysis of circulating tumor cells or cell-free tumor DNA. Even though the biological principles underlying tumor dormancy in breast cancer patients remain largely unknown, clinical observations and experimental studies have identified emerging mechanisms that control the state of tumor dormancy. In this review, we illustrate the latest discoveries on different molecular aspects that contribute to the control of tumor dormancy and distant metastatic relapse, then discuss current treatments affecting minimal residual disease and dormant cancer cells, and finally highlight how novel liquid biopsy based diagnostic methodologies can be integrated into the detection and molecular characterization of minimal residual disease.

Bone Marrow Adipocytes, Adipocytokines, and Breast Cancer Cells: Novel Implications in Bone Metastasis of Breast Cancer

Accumulating discoveries highlight the importance of interaction between marrow stromal cells and cancer cells for bone metastasis. Bone is the most common metastatic site of breast cancer and bone marrow adipocytes (BMAs) are the most abundant component of the bone marrow microenvironment. BMAs are unique in their origin and location, and recently they are found to serve as an endocrine organ that secretes adipokines, cytokines, chemokines, and growth factors. It is reasonable to speculate that BMAs contribute to the modification of bone metastatic microenvironment and affecting metastatic breast cancer cells in the bone marrow. Indeed, BMAs may participate in bone metastasis of breast cancer through regulation of recruitment, invasion, survival, colonization, proliferation, angiogenesis, and immune modulation by their production of various adipocytokines. In this review, we provide an overview of research progress, focusing on adipocytokines secreted by BMAs and their potential roles for bone metastasis of breast cancer, and investigating the mechanisms mediating the interaction between BMAs and metastatic breast cancer cells. Based on current findings, BMAs may function as a pivotal modulator of bone metastasis of breast cancer, therefore targeting BMAs combined with conventional treatment programs might present a promising therapeutic option.

Coumarin Ameliorates Impaired Bone Turnover by Inhibiting the Formation of Advanced Glycation End Products in Diabetic Osteoblasts and Osteoclasts

Accumulating evidence demonstrates that the risk of osteoporotic fractures increases in patients with diabetes mellitus. Thus, diabetes-induced bone fragility has recently been recognized as a diabetic complication. As the fracture risk is independent of the reduction in bone mineral density, deterioration in bone quality may be the main cause of bone fragility. Coumarin exists naturally in many plants as phenylpropanoids and is present in tonka beans in significantly high concentrations. This study investigated whether coumarin ameliorated the impaired bone turnover and remodeling under diabetic condition. The in vitro study employed murine macrophage Raw 264.7 cells differentiated to multinucleated osteoclasts with receptor activator of nuclear factor-κΒ ligand (RANKL) in the presence of 33 mM glucose and 1–20 μM coumarin for five days. In addition, osteoblastic MC3T3-E1 cells were exposed to 33 mM glucose for up to 21 days in the presence of 1–20 μM coumarin. High glucose diminished tartrate-resistant acid phosphatase activity and bone resorption in RANKL-differentiated osteoclasts, accompanying a reduction of cathepsin K induction and actin ring formation. In contrast, coumarin reversed the defective osteoclastogenesis in diabetic osteoclasts. Furthermore, high glucose diminished alkaline phosphatase activity and collagen type 1 induction of osteoblasts, which was strongly enhanced by submicromolar levels of coumarin to diabetic cells. Furthermore, coumarin restored the induction of RANK and osteoprotegerin in osteoclasts and osteoblasts under glucotoxic condition, indicating a tight coupling of osteoclastogenesis and osteoblastogenesis. Coumarin ameliorated the impaired bone turnover and remodeling in diabetic osteoblasts and osteoclasts by suppressing the interaction between advanced glycation end product (AGE) and its receptor (RAGE). Therefore, coumarin may restore optimal bone turnover of osteoclasts and osteoblasts by disrupting the hyperglycemia-mediated AGE–RAGE interaction.

Pulmonary tumor thrombotic microangiopathy associated with extramammary Paget's disease: An autopsy case report

Pulmonary tumor thrombotic microangiopathy (PTTM) is histologically characterized by micro tumor cell embolism and intimal fibrocellular proliferation of pulmonary arteries or arterioles. We report a secondary case of PTTM associated with extramammary Paget's disease (EMPD). The patient was a 72-year-old man with exertional dyspnea. Clinical examinations found he had pulmonary hypertension and multiple osteolytic lesions of vertebra. Cytological analysis of pulmonary wedge artery sample detected malignant cells and he was dead before treatment was started. Multiple tumor embolisms (>17) were identified in pulmonary arteries or arterioles at autopsy, consistent with PTTM. Metastatic nodules were found in liver and lymph node. Furthermore, disseminated carcinomatosis of the bone marrow (DCBM) was seen. Immunostaining results pointed out that tumor cells possessed mammary gland phenotype. He had 4-years history of EMPD in the left axilla without recurrence, and immunohistochemistry results were the same as the autopsy specimen. Thus, we diagnosed the primary site of PTTM to be EMPD. Our case highlights the usefulness of the recent proposed classification of PTTM, potential association between PTTM and DCBM, and the necessity for long-term follow-up in EMPD. EMPD can rarely cause PTTM to manifest as a paraneoplastic syndrome.