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BRCA1 deficiencies cause breast, ovarian, prostate and other cancers, and render tumours hypersensitive to poly(ADP-ribose) polymerase (PARP) inhibitors. To understand the resistance mechanisms, we conducted whole-genome CRISPR–Cas9 synthetic-viability/resistance screens in BRCA1-deficient breast cancer cells treated with PARP inhibitors. We identified two previously uncharacterized proteins, C20orf196 and FAM35A, whose inactivation confers strong PARP-inhibitor resistance. Mechanistically, we show that C20orf196 and FAM35A form a complex, ‘Shieldin’ (SHLD1/2), with FAM35A interacting with single-stranded DNA through its C-terminal oligonucleotide/oligosaccharide-binding fold region. We establish that Shieldin acts as the downstream effector of 53BP1/RIF1/MAD2L2 to promote DNA double-strand break (DSB) end-joining by restricting DSB resection and to counteract homologous recombination by antagonizing BRCA2/RAD51 loading in BRCA1-deficient cells. Notably, Shieldin inactivation further sensitizes BRCA1-deficient cells to cisplatin, suggesting how defining the SHLD1/2 status of BRCA1-deficient tumours might aid patient stratification and yield new treatment opportunities. Highlighting this potential, we document reduced SHLD1/2 expression in human breast cancers displaying intrinsic or acquired PARP-inhibitor resistance. Through CRISPR–Cas9 screen, Dev et al. identified that SHLD1/2 inhibition contributes to PARP-inhibitor resistance. Mechanistically, SHLDs promote non-homologous end-joining and antagonize homologous recombination.

Relapsed or refractory osteosarcoma carries a poor prognosis after standard chemotherapy. We conducted a multicenter, randomized, phase II trial (NCT05277480) to compare apatinib plus ifosfamide/etoposide (IE) with IE alone in patients who had progressed following at least one prior line of chemotherapy. Patients were randomized 2:1 to receive apatinib (500 mg orally once daily) plus IE (ifosfamide 1.8 g/m²/day and etoposide 100 mg/m²/day, days 1–3 every 3 weeks) or IE alone (same doses, days 1–5 every 3 weeks). The primary endpoint was progression-free survival (PFS). Between April 14, 2022, and August 22, 2023, 81 patients were enrolled (53 in apatinib plus IE group and 28 in IE group). After a median follow-up of 19.9 months, the median PFS was 5.5 months (95% confidence interval [CI]: 3.9, 6.4) with apatinib plus IE compared with 3.4 months (95% CI: 1.4, 4.6) with IE (hazard ratio, 0.60; 95% CI: 0.37, 0.98; P  = 0.0402). The trial met its pre-specified primary endpoint. These results suggest that apatinib plus IE may improve PFS in relapsed or refractory osteosarcoma, but as a randomized phase II study, the findings are exploratory and require confirmation in phase III trials. In patients with metastatic osteosarcoma who have progressed on first-line chemotherapy, the prognosis is poor. Here, the authors report a phase II randomized clinical trial comparing the combination of apatinib (multi tyrosine kinase inhibitor) and chemotherapy (ifosfamide and etoposide) against chemotherapy alone in patients with relapsed or refractory metastatic osteosarcoma.

Background Whether current postoperative surveillance regimes result in improved overall survival (OS) of patients with extremity sarcomas is unknown. Questions/purposes We hypothesized that a less intensive followup protocol would not be inferior to the conventional followup protocol in terms of OS. We (1) assessed OS of patients to determine if less intensive followup regimens led to worsened survival and asked (2) whether chest radiograph followup group was inferior to CT scan followup group in detecting pulmonary metastasis; and (3) whether less frequent (6-monthly) followup interval was inferior to more frequent (3-monthly) followup in detecting pulmonary metastasis and local recurrence. Methods A prospective randomized single-center noninferiority trial was conducted between January 2006 and June 2010. On the basis of 3-year survival of 60% with intensive, more frequent followup, 500 nonmetastatic patients were randomized to demonstrate noninferiority by a margin (delta) of 10% (hazard ratio [HR], 1.36). The primary end point was OS at 3 years. The secondary objective was to compare disease-free survival (DFS) (time to recurrence) at 3 years. At minimum followup of 30 months (median, 42 months; range, 30–81 months), 178 deaths were documented. Results Three-year OS and DFS for all patients was 67% and 52%, respectively. Three-year OS was 67% and 66% in chest radiography and CT groups, respectively (HR, 0.9; upper 90% confidence interval [CI], 1.13). DFS rate was 54% and 49% in chest radiography and CT groups, respectively (HR, 0.82; upper 90% CI, 0.97). Three-year OS was 64% and 69% in 6-monthly and 3-monthly groups, respectively (HR, 1.2; upper 90% CI, 1.47). DFS was 51% and 52% in 6-monthly and 3-monthly groups, respectively (HR, 1.01; upper 90% CI, 1.2). Almost 90% of local recurrences were identified by patients themselves. Conclusions Inexpensive imaging detects the vast majority of recurrent disease in patients with sarcoma without deleterious effects on eventual outcomes. Patient education regarding self-examination will detect most instances of local recurrence although this was not directly assessed in this study. Although less frequent visits adequately detected metastasis and local recurrence, this trial could not conclusively demonstrate noninferiority in OS for a 6-monthly interval of followup visits against 3-monthly visits. Level of Evidence Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The phase III clinical study of adjuvant liposomal muramyl tripeptide (MTP-PE) in resected high-grade osteosarcoma (OS) documented positive results that have been translated into regulatory approval, supporting initial promise for innate immune therapies in OS. There remains, however, no new approved treatment such as MTP-PE for either metastatic or recurrent OS. Whilst the addition of different agents, including liposomal MTP-PE, to surgery for metastatic or recurrent high-grade osteosarcoma has tried to improve response rates, a mechanistic hiatus exists in terms of a detailed understanding the therapeutic strategies required in advanced disease. Here we report a Bayesian designed multi-arm, multi-centre, open-label phase II study with randomisation in patients with metastatic and/or recurrent OS, designed to investigate how patients with OS might respond to liposomal MTP-PE, either given alone or in combination with ifosfamide. Despite the trial closing because of poor recruitment within the allocated funding period, with no objective responses in eight patients, we report the design and feasibility outcomes for patients registered into the trial. We demonstrate the feasibility of the Bayesian design, European collaboration, tissue collection with genomic analysis and serum cytokine characterisation. Further mechanistic investigation of liposomal MTP-PE alone and in combination with other agents remains warranted in metastatic OS.

Background The prognosis of patients with metastatic or advanced sarcomas is poor and there are few options for treatment. Several studies have shown that gemcitabine and docetaxel (GD) combination chemotherapy has antitumor activity against various subtypes of sarcoma. Recently, some studies have shown a favourable outcome for GD combination chemotherapy for relapsed high-grade osteosarcoma and spindle cell sarcoma of bone. If the effectiveness of GD is proven, this will result in new treatment options for advanced bone and soft tissue sarcomas (STS). The aim of this prospective Phase 2 study is to evaluate the efficacy and toxicity of the GD combination in patients with advanced bone sarcomas and STS. Methods This is a Phase 2, single-arm, open-label study to investigate the efficacy and safety of combination chemotherapy with GD for advanced bone sarcomas and STS and will enrol 20 patients. The patients will receive gemcitabine 900 mg/m 2 on Days 1 and 8, and docetaxel 70 mg/m 2 on Day 8 in 3-week cycles until disease progression or other evidence of treatment failure. The primary aim of this study is to analyse GD’s effect on progression-free survival (PFS). The secondary objectives are to analyse treatment efficacy and safety in terms of response rate, tumour control rate, overall survival, and adverse event rate. The length of follow-up will be 5 years. Discussion This study will evaluate the efficacy and safety of combination therapy with gemcitabine and docetaxel for bone sarcomas and STS. If this combination proves to be acceptable, it could be used for as second, third, or later line therapy for patients with sarcomas (especially bone sarcomas). In the future, the role of various treatments, including GD therapy, will be clarified for specific subtypes of sarcoma. Trial registration This study was registered as UMIN000031004 (University Hospital Medical Information Network-Clinical Trial Registry: UMIN-CTR) on 1 March 1 2018 and with the Japan Registry of Clinical Trials (jRCT) as jRCTs051180042 on 30 January 2019. The posted information will be updated as needed to reflect protocol amendments and study progress.

Citrus aurantium is rich in flavonoids, which may prevent osteosarcoma progression, but its related molecular mechanism remains unclear. Flavonoids were extracted from C. aurantium and purified by reparative HPLC. Each fraction was identified by using electrospray ionisation mass spectrometry (ESI-MS). Three main components (naringin, naringenin, and hesperetin) were isolated from C. aurantium. Naringenin inhibited the growth of MG-63 cells, whereas naringin and hesperetin had no inhibitory function on cell growth. ROS production was increased in naringin- and hesperetin-treated groups after one day of culture while the level was always lowest in the naringenin-treated group after three days of culture. 95 osteosarcoma patients who underwent surgery were assigned into two groups: naringenin group (NG, received 20 mg naringenin daily, n=47) and control group (CG, received 20 mg placebo daily, n=48). After an average of two-year follow-up, osteosarcoma volumes were smaller in the NG group than in the CG group (P>0.01). The rate of osteosarcoma recurrence was also lower in the NG group than in CG group. ROS levels were lower in the NG group than in the CG group. Thus, naringenin from Citrus aurantium inhibits osteosarcoma progression and local recurrence in the patients who underwent osteosarcoma surgery by improving antioxidant capability.

Osteosarcoma is the most frequent primary bone tumor with poor prognosis. Through RNA-sequencing of 100,987 individual cells from 7 primary, 2 recurrent, and 2 lung metastatic osteosarcoma lesions, 11 major cell clusters are identified based on unbiased clustering of gene expression profiles and canonical markers. The transcriptomic properties, regulators and dynamics of osteosarcoma malignant cells together with their tumor microenvironment particularly stromal and immune cells are characterized. The transdifferentiation of malignant osteoblastic cells from malignant chondroblastic cells is revealed by analyses of inferred copy-number variation and trajectory. A proinflammatory FABP4 + macrophages infiltration is noticed in lung metastatic osteosarcoma lesions. Lower osteoclasts infiltration is observed in chondroblastic, recurrent and lung metastatic osteosarcoma lesions compared to primary osteoblastic osteosarcoma lesions. Importantly, TIGIT blockade enhances the cytotoxicity effects of the primary CD3 + T cells with high proportion of TIGIT + cells against osteosarcoma. These results present a single-cell atlas, explore intratumor heterogeneity, and provide potential therapeutic targets for osteosarcoma. Osteosarcomas are difficult to treat and have a limited response to immunotherapy. Here, the authors analyse osteosarcomas at the single-cell level, and identify both the transdifferentiation of malignant cells and an array of immune cells that could have implications for metastasis and immunotherapy.

Abstract Periosteal chondrosarcoma is a rare tumor. It can be difficult to diagnose radiographically and pathologically and can be confused with periosteal osteosarcoma; however, the treatment of these two lesions is quite different. Increased awareness of imaging features of this lesion, particularly those that can help differentiate it from other surface-based tumors, can help one recognize this entity. We report the case of a periosteal chondrosarcoma in a young woman, highlighting the diagnostic imaging features of this disease, and her treatment with a joint-sparing geometric resection of the distal femur, using patient-specific 3D-printed cutting guides and matched allograft reconstruction.

Osteosarcoma is the most common primary bone cancer in children and young adults. Limited progress has been made in improving the survival outcomes in patients with osteosarcoma over the past four decades. Especially in metastatic or recurrent osteosarcoma, the survival rate is extremely unsatisfactory. The treatment of osteosarcoma urgently needs breakthroughs. In recent years, immunotherapy has achieved good therapeutic effects in various solid tumors. Due to the low immunogenicity and immunosuppressive microenvironment of osteosarcoma, immunotherapy has not yet been approved in osteosarcoma patients. However, immune-based therapies, including immune checkpoint inhibitors, chimeric antigen receptor T cells, and bispecfic antibodies are in active clinical development. In addition, other immunotherapy strategies including modified-NK cells/macrophages, DC vaccines, and cytokines are still in the early stages of research, but they will be hot topics for future study. In this review, we showed the functions of cell components including tumor-promoting and tumor-suppressing cells in the tumor microenvironment of osteosarcoma, and summarized the preclinical and clinical research results of various immunotherapy strategies in osteosarcoma, hoping to provide new ideas for future research in this field.