Departmental sources Background:Osteosarcoma (OS) is the most prevalent malignant primary bone tumor, resulting from severe transformation of primitive mesenchymal cells, which induces osteogenesis. Long non-coding RNA (lncRNA) MSC-AS1 triggers osteogenic differentiation by sponging microRNA (miR)-140-5p. The present study assessed the mechanism of lncRNA MSC-AS1 in OS biological features and sensitivity to cisplatin (DDP) by binding to miR-142. Material/Methods:Firstly, lncRNA MSC-AS1 expression in OS tissues and cells was analyzed. OS cells were transfected with silenced MSC-AS1 to determine its role in OS biological behaviors, and we also assessed the effect of MSC-AS1 on OS sensitivity to DDP. Then, website prediction and dual-luciferase reporter gene assay were utilized for verification of the binding site between MSC-AS1 and miR-142. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were performed to determine the effect of MSC-AS1 on expression of miR-142, cyclin-dependent kinase 6 (CDK6), and the PI3K/AKT signaling pathway. Xenograft transplantation was also applied to confirm the in vitro experiments. Results:Overexpressed MSC-AS1 was associated with poor prognosis of OS patients. OS cell proliferation, invasion, and migration were reduced after silencing MSC-AS1, while cell apoptosis was enhanced. Moreover, silencing MSC-AS1 made OS cells more sensitive to DDP. Interestingly, MSC-AS1 knockdown induced miR-142 expression and reduced CDK6 levels, thereby decreasing the protein expression of p-PI3K/t-PI3K and p-AKT/t-AKT. Silencing MSC-AS1 repressed OS progression in vivo. Conclusions:Our study demonstrated that silencing MSC-AS1 inhibited OS biological behaviors by enhancing miR-142 to decrease CDK6 and inactivating the PI3K/AKT axis. Our results may provide new insights for OS treatment.

BackgroundThis study aims to compare the efficacy and safety between zoledronic acid combined with calcium and calcium alone to prevent aromatase inhibitor-associated bone loss for postmenopausal breast cancer patients receiving adjuvant letrozole.MethodsOne hundred twenty patients were randomly divided into two groups, A and B. Patients in group A (n=60) received modified radical mastectomy or breast-conserving surgery + four cycles of AC followed by T regimen (optional) + radiotherapy (optional) + letrozole 2.5 mg daily + calcium 500 mg twice daily + vitamin D 400 international units daily +4 mg of zoledronic acid every 6 months, while patients in group B (n=60) were not given zoledronic acid and the rest of the treatments of group B were the same as group A. All the patients were followed up for 1 year. The primary endpoint was the intrapatient percentage change in lumbar spine (LS) bone mineral density (BMD) from baseline to month 12. Secondary endpoints included the percentage change in total hip (TH) and femoral neck (FN) BMD, the incidence of osteoporosis, the incidence of a clinically meaningful 5% decline in BMD at 1 year, change of serum N-telopeptide of type 1 collagen (NTX) and bone-specific alkaline phosphatase (BSAP) concentrations.ResultsPatients in group A had a statistically significant higher average change and average percent change in LS, FN, and TH than group B. Group A had a statistically significant lower incidence of a clinically meaningful loss of bone density at the LS, FN, or TH than Group B. The incidence of osteoporosis in group A was significantly lower than group B. The decreases in NTX and BSAP concentrations from baseline to month 12 in patients of group A were significant; in contrast, patients in group B were found to have increases in NTX and BSAP concentrations from baseline. The most common adverse reactions in patients are flu-like symptoms (38%), bone pain (28%), and joint pain (20%).ConclusionAI-associated bone loss can be prevented by concurrent zoledronic acid for postmenopausal breast cancer patients.

The bone morphogenetic protein‐2 (BMP2) plays a crucial role in bone formation, growth and regeneration, which adopts a conformational wrist epitope and a linear knuckle epitope to interact with its type‐I (BRI) and type‐II (BRII) receptors, respectively. In this study, we systematically examine the BRII‐recognition site of BMP2 at structural, energetic and dynamic levels and accurately locate hotspots of the recognition at BMP2–BRII complex interface. It is revealed that the traditional knuckle epitope (BMP2 residue range 73–92) do fully match the identified hotspots; the BMP2‐recognition site includes the C‐terminal region of traditional knuckle epitope as well as its flanked β‐strands. In addition, the protein context of full‐length BMP2 is also responsible for the recognition by addressing conformational constraint on the native epitope segment. Therefore, we herein redefine the knuckle epitope to BMP2 residue range 84–102, which has a similar sequence length but is slid along the protein sequence by ~10 residues as compared to traditional knuckle epitope. The redefined one is also a linear epitope that is natively a double‐stranded β‐sheet with two asymmetric arms as compared to the natively single β‐strand of the traditional version, although their sequences are partially overlapped to each other. It is revealed that the redefined epitope‐derived peptide LN84–102 exhibits an improved affinity by >3‐fold relative to the traditional epitope‐derived peptide KL73–92. Even so, the LN84–102 peptide still cannot fully represent the BMP2 recognition event by BRII that has been reported to have a nanomolar affinity. We further introduce a disulfide bond across the two arms of double‐stranded β‐sheet to constrain the free LN84–102 peptide conformation, which mimics the conformational constraint addressed by protein context. Consequently, several cyclic peptides are redesigned, in which the LN84–102(cyc89‐101) is determined to exhibit a sub‐micromolar affinity; this value is ~5‐fold higher than its linear counterpart. Structural analysis also reveals that the cyclic peptide can interact with BRII in a similar binding mode with the redefined knuckle epitope region in full‐length BMP2 protein.