Cabozantinib in patients with advanced Ewing sarcoma or osteosarcoma (CABONE): a multicentre, single-arm, phase 2 trial

High Dose Ifosfamide in Relapsed and Unresectable High-Grade Osteosarcoma Patients: A Retrospective Series

Background: The evidence on high-dose ifosfamide (HD-IFO) use in patients with relapsed osteosarcoma is limited. We performed a retrospective study to analyze HD-IFO activity. Methods: Patients with osteosarcoma relapsed after standard treatment [methotrexate, doxorubicin, cisplatin +/- ifosfamide (MAP+/-I)] with measurable disease according to RECIST1.1 were eligible to ifosfamide (3 g/m2/day) continuous infusion (c.i.) days 1-5 q21d. RECIST1.1 overall response rate (ORR) (complete response (CR) + partial response (PR)), progression-free survival at 6-month (6m-PFS), duration of response (DOR), and 2-year overall survival (2y-OS) were assessed. PARP1 expression and gene mutations were tested by immunohistochemistry and next-generation sequencing. Results: 51 patients were included. ORR was 20% (1 CR + 9 PR). Median DOR was 5 months (95%CI 2-7). Median PFS, 6m-PFS, OS, and 2y-OS were 6 months (95%CI 4-9), 51%, 15 months (10-19), and 30%, respectively. A second surgical complete remission (CR2) was achieved in 26 (51%) patients. After multivariate analysis, previous use of ifosfamide (HR 2.007, p = 0.034) and CR2 (HR 0.126, p < 0.001) showed a significant correlation with PFS and OS, respectively. No significant correlation was found between outcomes and PARP1 or gene mutations. Conclusions: HD-IFO should be considered as the standard first-line treatment option in relapsed osteosarcoma and control arm of future trial in this setting.

Targeting Molecular Mechanisms Underlying Treatment Efficacy and Resistance in Osteosarcoma: A Review of Current and Future Strategies

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Due to micrometastatic spread, radical surgery alone rarely results in cure. Introduction of combination chemotherapy in the 1970s, however, dramatically increased overall survival rates from 20% to approximately 70%. Unfortunately, large clinical trials aiming to intensify treatment in the past decades have failed to achieve higher cure rates. In this review, we revisit how the heterogenous nature of osteosarcoma as well as acquired and intrinsic resistance to chemotherapy can account for stagnation in therapy improvement. We summarise current osteosarcoma treatment strategies focusing on molecular determinants of treatment susceptibility and resistance. Understanding therapy susceptibility and resistance provides a basis for rational therapy betterment for both identifying patients that might be cured with less toxic interventions and targeting resistance mechanisms to sensitise resistant osteosarcoma to conventional therapies.

Receptor Tyrosine Kinases in Osteosarcoma Treatment: Which Is the Key Target?

Recent clinical trials have shown several multi-target tyrosine kinase inhibitors (TKIs) to be effective in the treatment of osteosarcoma. However, these TKIs have a number of targets, and it is yet unclear which of these targets has a key role in osteosarcoma treatment. In this review, we first summarize the TKIs that were studied in clinical trials registered on ClinicalTrials.gov. Further, we compare and discuss the targets of these TKIs. We found that TKIs with promising therapeutic effect for osteosarcoma include apatinib, cabozantinib, lenvatinib, regorafenib, and sorafenib. The key targets for osteosarcoma treatment may include VEGFRs and RET. The receptor tyrosine kinases (RTKs) MET, IGF-1R, AXL, PDGFRs, KIT, and FGFRs might be relevant but unimportant targets for osteosarcoma treatment. Inhibition of one type of RTK for the treatment of osteosarcoma is not effective. It is necessary to inhibit several relevant RTKs simultaneously to achieve a breakthrough in osteosarcoma treatment. This review provides comprehensive information on TKI targets relevant in osteosarcoma treatment, and it will be useful for further research in this field.

EWSAT1 Acts in Concert with Exosomes in Osteosarcoma Progression and Tumor-Induced Angiogenesis: The "Double Stacking Effect"

The prognosis for osteosarcoma (OS) continues to be unsatisfactory due to tumor recurrence as a result of metastasis and drug resistance. Several studies have shown that Ewing sarcoma associated transcript 1 (EWSAT1) plays an important role in the progression of OS. Exosomes (Exos) act as important carriers in intercellular communication and play an important role in the tumor microenvironment, especially in tumor-induced angiogenesis. Nonetheless, the specific mechanism via which EWSAT1 and Exos regulate OS progression is unknown, and whether they can be effective therapeutic targets also requires verification. Hence, in this study, it is aimed to investigate the mechanisms of action of EWSAT1 and Exos. EWSAT1 significantly promotes proliferation, migration, colony formation, and survival of OS. EWSAT1 regulates OS-induced angiogenesis via two mechanisms, called the "double stacking effect," which is a combination of the increase in sensitivity/reactivity of vascular endothelial cells triggered by Exos-carrying EWSAT1, and the EWSAT1-induced increase in angiogenic factor secretion. In vivo experiments further validates the "double stacking effect" and shows that EWSAT1-KD effectively inhibits tumor growth in OS. The above observations indicate that EWSAT1 can be used as not only a potential diagnostic and prognostic marker, but also as a precise therapeutic target for OS.

Endothelial-to-Mesenchymal Transition in Cancer

Cancer is one of the most important causes of morbidity and mortality worldwide. Tumor cells grow in a complex microenvironment constituted of immune, stromal, and vascular cells that supports growth, angiogenesis, and metastasis. Endothelial cells (ECs) are major components of the vascular microenvironment. These cells have been described for their plasticity and potential to transdifferentiate into mesenchymal cells through a process known as endothelial-to-mesenchymal transition (EndMT). This complex process is controlled by various factors, by which ECs convert into a phenotype characterized by mesenchymal protein expression and motile, contractile morphology. Initially described in normal heart development, EndMT is now identified in several pathologies, and especially in cancer. In this review, we highlight the process of EndMT in the context of cancer and we discuss it as an important adaptive process of the tumor microenvironment that favors tumor growth and dissemination but also resistance to treatment. Thus, we underline targeting of EndMT as a potential therapeutic strategy.

Molecular Biology of Osteosarcoma

Osteosarcoma (OS) is the most frequent primary bone cancer in children and adolescents and the third most frequent in adults. Many inherited germline mutations are responsible for syndromes that predispose to osteosarcomas including Li Fraumeni syndrome, retinoblastoma syndrome, Werner syndrome, Bloom syndrome or Diamond-Blackfan anemia. TP53 is the most frequently altered gene in osteosarcoma. Among other genes mutated in more than 10% of OS cases, c-Myc plays a role in OS development and promotes cell invasion by activating MEK-ERK pathways. Several genomic studies showed frequent alterations in the RB gene in pediatric OS patients. Osteosarcoma driver mutations have been reported in NOTCH1, FOS, NF2, WIF1, BRCA2, APC, PTCH1 and PRKAR1A genes. Some miRNAs such as miR-21, -34a, -143, -148a, -195a, -199a-3p and -382 regulate the pathogenic activity of MAPK and PI3K/Akt-signaling pathways in osteosarcoma. CD133+ osteosarcoma cells have been shown to exhibit stem-like gene expression and can be tumor-initiating cells and play a role in metastasis and development of drug resistance. Although currently osteosarcoma treatment is based on adriamycin chemoregimens and surgery, there are several potential targeted therapies in development. First of all, activity and safety of cabozantinib in osteosarcoma were studied, as well as sorafenib and pazopanib. Finally, novel bifunctional molecules, of potential imaging and osteosarcoma targeting applications may be used in the future.

A Review of T-Cell Related Therapy for Osteosarcoma

Osteosarcoma is one of the most common primary malignant tumors of bone. The combination of chemotherapy and surgery makes the prognosis better than before, but therapy has not dramatically improved over the last three decades. This is partially because of the lack of a novel specialized drug for osteosarcoma, which is known as a tumor with heterogeneity. On the other hand, immunotherapy has been one of the most widely used strategies for many cancers over the last ten years. The therapies related to T-cell response, such as immune checkpoint inhibitor and chimeric antigen receptor T-cell therapy, are well-known options for some cancers. In this review, we offer the accumulated knowledge of T-cell-related immunotherapy for osteosarcoma, and discuss the future of the therapy.

Cabozantinib for relapsed neuroblastoma: Single institution case series

Relapsed high-risk neuroblastoma has few effective therapies currently available or in development. Cabozantinib is an Food and Drug Administration approved multitargeted tyrosine kinase inhibitor for select adult malignancies with preclinical data suggesting efficacy against neuroblastoma. A safe and tolerable dose has been identified for children, but its efficacy remains unknown. We describe four children with relapsed metastatic neuroblastoma treated with cabozantinib. All four patients had extended disease control (two complete responsesfor >12 months, 2 stable disease >6 months) with manageable predictable toxicities requiring dose reduction in two patients. We discuss the potential for the use of cabozantinib in neuroblastoma.

The Osteosarcoma Microenvironment: A Complex But Targetable Ecosystem

Osteosarcomas are the most frequent primary bone sarcomas, affecting mainly children, adolescents, and young adults, and with a second peak of incidence in elderly individuals. The current therapeutic management, a combined regimen of poly-chemotherapy and surgery, still remains largely insufficient, as patient survival has not improved in recent decades. Osteosarcomas are very heterogeneous tumors, both at the intra- and inter-tumor level, with no identified driver mutation. Consequently, efforts to improve treatments using targeted therapies have faced this lack of specific osteosarcoma targets. Nevertheless, these tumors are inextricably linked to their local microenvironment, composed of bone, stromal, vascular and immune cells and the osteosarcoma microenvironment is now considered to be essential and supportive for growth and dissemination. This review describes the different actors of the osteosarcoma microenvironment and gives an overview of the past, current, and future strategies of therapy targeting this complex ecosystem, with a focus on the role of extracellular vesicles and on the emergence of multi-kinase inhibitors.