Bone metastases in gastric cancer follow a RANKL-independent mechanism

Tumor Microenvironment, Clinical Features, and Advances in Therapy for Bone Metastasis in Gastric Cancer

Gastric cancer (GC) is one of the most malignant neoplasms worldwide, accounting for about 770,000 deaths in 2020. The incidence of gastric cancer bone metastasis (GC-BM) is low, about 0.9–13.4%, and GC patients develop GC-BM because of a suitable bone microenvironment. Osteoblasts, osteoclasts, and tumor cells interact with each other, secreting cytokines such as PTHrP, RANK-L, IL-6, and other growth factors that disrupt the normal bone balance and promote tumor growth. The functions and numbers of immune cells in the bone microenvironment are continuously inhibited, resulting in bone balance disorder due to the cytokines released from destroyed bone and growing tumor cells. Patients with GC-BM are generally younger than 65 years old and they often present with a later stage of the disease, as well as more aggressive tumors. They usually have shorter overall survival (OS) because of the occurrence of skeletal-related events (SREs) and undetected bone destruction due to the untimely bone inspection. Current treatments of GC-BM focus mainly on gastric cancer and SRE-related treatment. This article reviews the clinical features, possible molecular pathogeneses, and the most commonly used diagnostic methods and treatments of bone metastasis in gastric cancer.

Bone Metastasis From Gastric Adenocarcinoma-What Are the Risk Factors and Associated Survival? A Large Comprehensive Population-Based Cohort Study

Background

While bone metastasis is not common in gastric adenocarcinoma (GaC), it can have important impacts on prognosis. This large cohort study aimed at exploring factors associated with bone metastasis in GaC and investigating the time-dependent cumulative mortalities and prognostic factors in GaC patients with bone metastasis at the population level.

Methods

Data on patients with GaC diagnosed in 2010–2016 were retrieved from a large population-based database. We explored factors associated with bone metastasis using the multivariable-adjusted logistic model. We then calculated the time-dependent cancer-specific mortalities in GaC patients with bone metastasis using the cumulative incidence function and compared mortalities across subgroups using Gray’s test. We further assessed factors associated with mortality using the multivariable-adjusted Fine–Gray subdistribution hazard model.

Results

Together 11,072 eligible patients with metastatic GaC were enrolled, which comprised 1,511 (14%) people with bone metastasis and 9,561 (86%) with other metastasis, encompassing 6,999 person-years of follow-up. Bone metastasis was more frequently detected in 2014 or later, in younger patients, in patients with gastric cardia cancers, in people with signet-ring cell carcinoma, and in those with poorly differentiated/undifferentiated cancers; it was less commonly observed in black patients. Bone metastasis was associated with more frequent brain and lung metastases. The median survival of patients with bone metastasis was 4 months; the 6-month and 3-year cancer-specific cumulative mortalities were 56% and 85%, respectively. In patients receiving chemotherapy, American Indians/Alaskan Natives, patients with gastric antrum/pylorus cancers, and those with positive lymph nodes had higher mortality risks, while those undergoing resection had lower mortality hazards.

Conclusion

In GaC patients, bone metastasis was associated with various clinicopathologic factors including age, ethnicity, tumor location, histology, differentiation, and metastasis to other sites. Patients with bone metastasis had poor prognosis which was associated with ethnicity, tumor location, lymph node involvement, and treatment. Our findings provide important hints for tailed patient management and for further mechanistic investigations.

Bone Metastases from Gastric Cancer: What We Know and How to Deal with Them

Gastric cancer (GC) is the third cause of cancer-related death worldwide; the prognosis is poor especially in the case of metastatic disease. Liver, lymph nodes, peritoneum, and lung are the most frequent sites of metastases from GC; however, bone metastases from GC have been reported in the literature. Nevertheless, it is unclear how the metastatic sites may affect the prognosis. In particular, knowledge about the impact of bone metastases on GC patients’ outcome is scant, and this may be related to the rarity of bone lesions and/or their underestimation at the time of diagnosis. In fact, there is still a lack of specific recommendation for their detection at the diagnosis. Then, the majority of the evidences in this field came from retrospective analysis on very heterogeneous study populations. In this context, the aim of this narrative review is to delineate an overview about the evidences existing about bone metastases in GC patients, focusing on their incidence and biology, the prognostic role of bone involvement, and their possible implication in the treatment choice.

Interleukin (IL)-7 Signaling in the Tumor Microenvironment

Interleukin (IL)-7 plays an important immunoregulatory role in different types of cells. Therefore, it attracts researcher's attention, but despite the fact, many aspects of its modulatory action, as well as other functionalities, are still poorly understood. The review summarizes current knowledge on the interleukin-7 and its signaling cascade in context of cancer development. Moreover, it provides a cancer-type focused description of the involvement of IL-7 in solid tumors, as well as hematological malignancies.The interleukin has been discovered as a growth factor crucial for the early lymphocyte development and supporting the growth of malignant cells in certain leukemias and lymphomas. Therefore, its targeting has been explored as a treatment modality in hematological malignancies, while the unique ability to expand lymphocyte populations selectively and without hyperinflammation has been used in experimental immunotherapies in patients with lymphopenia. Ever since the early research demonstrated a reduced growth of solid tumors in the presence of IL-7, the interleukin application in boosting up the anticancer immunity has been investigated. However, a growing body of evidence indicative of IL-7 upregulation in carcinomas, facilitating tumor growth and metastasis and aiding drug-resistance, is accumulating. It therefore becomes increasingly apparent that the response to the IL-7 stimulus strongly depends on cell type, their developmental stage, and microenvironmental context. The interleukin exerts its regulatory action mainly through phosphorylation events in JAK/STAT and PI3K/Akt pathways, while the significance of MAPK pathway seems to be limited to solid tumors. Given the unwavering interest in IL-7 application in immunotherapy, a better understanding of interleukin role, source in tumor microenvironment, and signaling pathways, as well as the identification of cells that are likely to respond should be a research priority.

TNFRSF11B activates Wnt/β-catenin signaling and promotes gastric cancer progression

Tumor necrosis factor receptor superfamily member 11B (TNFRSF11B) has been studied to be involved in the development and progression of several human malignancies. However, little is unveiled regarding the complex mechanisms of TNFRSF11B in human gastric cancer (GC). The clinical significance of TNFRSF11B was assessed in 70 and 160 GC tissues using immunohistochemistry method and gene microarray analysis, respectively. The biological function of TNFRSF11B was studied in vitro and in vivo assays. Immunofluorescence assay was used to evaluate the expression of β-catenin in the nucleus. The expression of β-catenin and related protein was determined by Western blot. The interaction between TNFRSF11B and GSK3β was detected by co-immunoprecipitation. We demonstrated that TNFRSF11B was highly expressed in the cytoplasm of GC and associated with the patient poor outcome. Our studies showed that TNFRSF11B in GC cells significantly promoted cell proliferation, migration, invasion in vitro and tumorigenic ability in vitro and in vivo. Meanwhile, TNFRSF11B inhibited GC cell apoptosis. The proportion of nuclear active β-catenin showed positively correlation with TNFRSF11B expression. TNFRSF11B directly combined with GSK-3β upregulating its phosphorylation, and increased expression of β-catenin and its downstream effectors. Collectively, these findings demonstrate that TNFRSF11B promote the aggressive phenotypes of GC cells and activated Wnt/β-catenin signaling. Accordingly, TNFRSF11B had potential as a biomarker and inhibition of TNFRSF11B expression might offer a new therapeutic target for GC patients.

What Are the Peripheral Blood Determinants for Increased Osteoclast Formation in the Various Inflammatory Diseases Associated With Bone Loss?

Local priming of osteoclast precursors (OCp) has long been considered the main and obvious pathway that takes place in the human body, where local bone lining cells and RANKL-expressing osteocytes may facilitate the differentiation of OCp. However, priming of OCp away from bone, such as in inflammatory tissues, as revealed in peripheral blood, may represent a second pathway, particularly relevant in individuals who suffer from systemic bone loss such as prevalent in inflammatory diseases. In this review, we used a systematic approach to review the literature on osteoclast formation in peripheral blood in patients with inflammatory diseases associated with bone loss. Only studies that compared inflammatory (bone) disease with healthy controls in the same study were included. Using this core collection, it becomes clear that experimental osteoclastogenesis using peripheral blood from patients with bone loss diseases in prevalent diseases such as rheumatoid arthritis, osteoporosis, periodontitis, and cancer-related osteopenia unequivocally point toward an intrinsically increased osteoclast formation and activation. In particular, such increased osteoclastogenesis already takes place without the addition of the classical osteoclastogenesis cytokines M-CSF and RANKL in vitro. We show that T-cells and monocytes as OCp are the minimal demands for such unstimulated osteoclast formation. In search for common and disease-specific denominators of the diseases with inflammation-driven bone loss, we demonstrate that altered T-cell activity and a different composition—such as the CD14+CD16+ vs. CD14+CD16– monocytes—and priming of OCp with increased M-CSF, RANKL, and TNF- α levels in peripheral blood play a role in increased osteoclast formation and activity. Future research will likely uncover the barcodes of the OCp in the various inflammatory diseases associated with bone loss.

Gastric cancer: The times they are a-changin'

Gastric cancer is the third leading cause of cancer death worldwide. Even though during these last decades gastric cancer incidence decreased in Western countries, it remains endemic and with a high incidence in Eastern countries. The survival in advanced and metastatic stage of gastric cancer is still very poor. Recently the Cancer Genoma Atlas Research Network identified four subtypes with different molecular profiles to classify gastric cancer in order to offer the optimal targeted therapies for pre-selected patients. Indeed, the key point is still the selection of patients for the right treatment, on basis of molecular tumor characterization. Since chemotherapy reached a plateau of efficacy for gastric cancer, the combination between cytotoxic therapy and biological agents gets a better prognosis and decreases chemotherapeutic toxicity. Currently, Trastuzumab in combination with platinum and fluorouracil is the only approved targeted therapy in the first line for c-erbB2 positive patients, whereas Ramucirumab is the only approved targeted agent for patients with metastatic gastric cancer. New perspectives for an effective treatment derived from the immunotherapeutic strategies. Here, we report an overview on gastric cancer treatments, with particular attention to recent advances in targeted therapies and in immunotherapeutic approach.

Targeting mast cells in gastric cancer with special reference to bone metastases

Bone metastases from gastric cancer (GC) are considered a relatively uncommon finding; however, they are related to poorer prognosis. Both primary GC and its metastatic progression rely on angiogenesis. Several lines of evidence from GC patients strongly support the involvement of mast cells (MCs) positive to tryptase (MCPT) in primary gastric tumor angiogenesis. Recently, we analyzed infiltrating MCs and neovascularization in bone tissue metastases from primary GC patients, and observed a significant correlation between infiltrating MCPT and angiogenesis. Such a finding suggested the involvement of peritumoral MCPT by infiltrating surrounding tumor cells, and in bone metastasis angiogenesis from primary GC. Thus, an MCPT-stimulated angiogenic process could support the development of metastases in bone tissue. From this perspective, we aim to review the hypothetical involvement of tumor-infiltrating, peritumoral MCPT in angiogenesis-mediated GC cell growth in the bone microenvironment and in tumor-induced osteoclastic bone resorption. We also focus on the potential use of MCPT targeting agents, such as MCs tryptase inhibitors (gabexate mesylate, nafamostat mesylate) or c-KitR tyrosine kinase inhibitors (imatinib, masitinib), as possible new anti-angiogenic and anti-resorptive strategies for the treatment of GC patients affected by bone metastases.

Bone-immune cell crosstalk: bone diseases

Bone diseases are associated with great morbidity; thus, the understanding of the mechanisms leading to their development represents a great challenge to improve bone health. Recent reports suggest that a large number of molecules produced by immune cells affect bone cell activity. However, the mechanisms are incompletely understood. This review aims to shed new lights into the mechanisms of bone diseases involving immune cells. In particular, we focused our attention on the major pathogenic mechanism underlying periodontal disease, psoriatic arthritis, postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, metastatic solid tumors, and multiple myeloma.

Infiltrating mast cells correlate with angiogenesis in bone metastases from gastric cancer patients

While gastric cancer is a well established angiogenesis driven tumor, no data has been published regarding angiogenesis stimulated by mast cells (MCs) positive for tryptase in bone metastases from gastric cancer patients (BMGCP). It is well established that MCs play a role in immune responses and more recently it was demonstrated that MCs have been involved in tumor angiogenesis. We analyzed infiltrating MCs and neovascularization in BMGCP diagnosed by histology. A series of 15 stage T3-4N2-3M1 (by AJCC for Gastric Cancer Staging 7th Edition) BMGCP from bone biopsies were selected. Tumour tissue samples were evaluated by mean of immunohistochemistry and image analysis methods in terms of MCs density positive to tryptase (MCDPT), MCs area positive to tryptase (MCAPT), microvascular density (MVD) and endothelial area (EA). A significant correlation between MCDPT, MCAPT, MVD and EA groups to each other was found by Pearson and t-test analysis (r ranged from 0.68 to 0.82; p-value ranged from 0.00 to 0.02). Our very preliminary data suggest that infiltrating MCs positive for tryptase may play a role in BMGCP angiogenesis, and could be further evaluated as a novel target of anti-angiogenic therapy.

Nuclear factor-kappa B ligand and osteoprotegerin levels in serum and gingival crevicular fluid in patients with bone metastases treated with zoledronic acid

Bone metastases are frequently observed in patients with certain types of cancer and are significant cause of morbidity. Zoledronic acid (ZA) is routinely prescribed for patients with bone metastases by affecting osteoclast function. We aimed to assess the effect of ZA over time in patients with bone metastases by analyzing novel bone turnover marker levels including receptor activator of nuclear factor-k B ligand (RANKL) and osteoprotegerin (OPG) in serum and gingival crevicular fluid (GCF). Also, associations between these bone turnover markers with hematological and biochemistry dysregulation were studied. The study enrolled patients with bone metastases including 32 patients diagnosed with solid tumors and 15 patients with multiple myeloma. In these patients, GCF and serum RANKL and OPG levels were measured and compared with measures of hematological and biochemical parameters before and after 3 months of ZA therapy. Mean subject age was 54 years old with a range of 28-80 years. Skeletal-related events were observed in 8.5% of all patients. After the 3-month treatment of ZA therapy, no significant differences were found in serum and GCF levels of RANKL and OPG when compared with before treatment levels. GCF RANKL levels at baseline and following 3 months of ZA therapy were significantly higher in patients with solid tumors when compared patients diagnosed with multiple myeloma (p=0.001; p<0.001, respectively). GCF OPG levels after the entire course of ZA therapy were greater in patients with 5 or more bone metastases (p=0.04). For patients with multiple myeloma, control GCF OPG was negatively correlated with control platelet and WBC counts (p=0.018 and p=0.027, respectively). A negative correlation was observed between control serum RANKL and control serum OPG levels in myeloma patients (p=0.001). After 3 months of ZA therapy, no significant differences were observed in GCF and serum RANKL and OPG levels when compared with baseline. A negative correlation was observed between serum control RANKL and OPG levels in myeloma patients. OPG levels were greater in patients with 5 or more bone metastases. In patients diagnosed with multiple myeloma, GCF OPG levels were negatively associated with WBC and platelet counts.