Osteoclast-derived apoptotic bodies inhibit naive CD8+ T cell activation via Siglec15, promoting breast cancer secondary metastasis.

The bone microenvironment promotes cancer cell proliferation and dissemination. During periodic bone remodeling, osteoclasts undergo apoptosis, producing large numbers of apoptotic bodies (ABs). However, the biological role of osteoclast-derived ABs, which are residents of the bone-tumor niche, remains largely unknown. Here, we discover that AB-null MRL/lpr mice show resistance to breast cancer cell implantation, with more CD8+ T cell infiltrations and a higher survival rate. We uncover that the membranous Siglec15 on osteoclast-derived ABs binds with sialylated Toll-like receptor 2 (TLR2) and blocks downstream co-stimulatory signaling, leading to the inhibition of naive CD8+ T cell activation. In addition, our study shows that treatment with Siglec15 neutralizing antibodies significantly reduces the incidence of secondary metastases and improves the survival rate of mice with advanced breast cancer bone metastasis. Our findings reveal the immunosuppressive function of osteoclast-derived ABs in the bone-tumor niche and demonstrate the potential of Siglec15 as a common target for anti-resorption and immunotherapy.

PTP1B knockdown alleviates BMSCs senescence via activating AMPK-mediated mitophagy and promotes osteogenesis in senile osteoporosis.

The senescence of bone marrow mesenchymal stem cells (BMSCs) is the basis of senile osteoporosis (SOP). Targeting BMSCs senescence is of paramount importance for developing anti-osteoporotic strategy. In this study, we found that protein tyrosine phosphatase 1B (PTP1B), an enzyme responsible for tyrosine dephosphorylation, was significantly upregulated in BMSCs and femurs with advancing chronological age. Therefore, the potential role of PTP1B in BMSCs senescence and senile osteoporosis was studied. Firstly, significantly upregulated PTP1B expression along with impaired osteogenic differentiation capacity was observed in D-galactose (D-gal)-induced BMSCs and naturally-aged BMSCs. Furthermore, PTP1B silencing could effectively alleviate senescence, improve mitochondrial dysfunction, and restore osteogenic differentiation in aged BMSCs, which was attributable to enhanced mitophagy mediated by PKM2/AMPK pathway. In addition, hydroxychloroquine (HCQ), an autophagy inhibitor, significantly reversed the protective effects from PTP1B knockdown. In SOP animal model, transplantation of LVsh-PTP1B-transfected D-gal-induced BMSCs harvested double protective effects, including increased bone formation and reduced osteoclastogenesis. Similarly, HCQ treatment remarkably suppressed osteogenesis of LVsh-PTP1B-transfected D-gal-induced BMSCs in vivo. Taken together, our data demonstrated that PTP1B silencing protects against BMSCs senescence and mitigates SOP via activating AMPK-mediated mitophagy. Targeting PTP1B may represent a promising interventional strategy to attenuate SOP.

Reduced osteoclast-derived apoptotic bodies in bone marrow characterizes the pathological progression of osteoporosis.

Osteoporosis is associated with excessive activity of osteoclasts. In bone turn over, most osteoclasts undergo apoptosis after bone resorption and produce a large number of apoptotic bodies (ABs). However, the biological function of osteoclast-derived apoptotic bodies (OC-ABs) in the progression of osteoporosis is still unknow. In our study, we identified a reduction of OC-AB quantity in the bone marrow cavity during the progression of osteoporosis, an apoptotic body-deficient MRL/lpr mice were used to study the pro-osteogenic ability of OC-ABs. Mechanistically, OC-ABs promote osteogenesis of bone mesenchymal stem cells (BMSCs) by activating the downstream mTOR pathway via RANKL-mediated reverse signaling. Moreover, systemic infusion of exogenous OC-ABs effectively delayed the bone loss in ovariectomized (OVX) mice, validated the role of OC-ABs as bone protective factor in the pathogenesis of osteoporosis. Taken together, our study elucidates the biological function of OC-ABs in the pathological progression of osteoporotic bone loss and suggests a potential therapeutic strategy to delay bone loss.

Prognosticators and Prognostic Nomograms for Leiomyosarcoma Patients With Metastasis.

Individual survival prediction and risk stratification are of vital importance to optimize the individualized treatment of metastatic leiomyosarcoma (LMS) patients. This study aimed to identify the prognostic factors for metastatic LMS patients and establish prognostic models for overall survival (OS) and cancer-specific survival (CSS). The data of LMS patients with metastasis between 2010 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. The entire cohort was randomly divided into a training cohort and a validation cohort. The influences of primary tumor site, localized and distant metastases, and sites and number of metastases on the prognosis of metastatic LMS patients were firstly explored by Kaplan-Meier curves and log-rank tests. Furthermore, the effective therapeutic regimens and prognosticators for metastatic LMS patients were also analyzed by Cox analysis. In addition, two prognostic nomograms for OS and CSS were established, and their predictive performances were evaluated by the methods of receiver operating characteristic (ROC) curves, time-dependent ROC curves, calibration curves, and decision curve analysis (DCA). A total of 498 patients were finally collected from the SEER database and were randomly assigned to the training set (N = 332) and validation set (N = 166). No significant differences in OS were observed in patients with distant organ metastasis and localized metastasis. For patients who have already developed distant organ metastasis, the sites and number of metastases seemed to be not closely associated with survival. Patients who received chemotherapy got significantly longer survival than that of their counterparts. In univariate and multivariate Cox analyses, variables of surgery, chemotherapy, age, and tumor size were identified as independent predictors for OS and CSS, and distant metastasis was also independently associated with CSS. The areas under the curve (AUCs) of ROC curves of the nomogram for predicting 1-, 3-, and 5-year OS were 0.770, 0.800, and 0.843, respectively, and those for CSS were 0.777, 0.758, and 0.761, respectively. The AUCs of time-dependent AUCs were all over 0.750. The calibration curves and DCA curves also showed excellent performance of the prognostic nomograms. Metastasis is associated with reduced survival, while the sites and the number of metastases are not significantly associated with survival. The established nomogram is a useful tool that can help to perform survival stratification and to optimize prognosis-based decision-making in clinical practice.