β-Catenin Does Not Confer Tumorigenicity When Introduced into Partially Transformed Human Mesenchymal Stem Cells

Multifunctional 3D-printed bioceramic scaffolds: Recent strategies for osteosarcoma treatment

Osteosarcoma is the most prevalent bone malignant tumor in children and teenagers. The bone defect, recurrence, and metastasis after surgery severely affect the life quality of patients. Clinically, bone grafts are implanted. Primary bioceramic scaffolds show a monomodal osteogenesis function. With the advances in three-dimensional printing technology and materials science, while maintaining the osteogenesis ability, scaffolds become more patient-specific and obtain additional anti-tumor ability with functional agents being loaded. Anti-tumor therapies include photothermal, magnetothermal, old and novel chemo-, gas, and photodynamic therapy. These strategies kill tumors through novel mechanisms to treat refractory osteosarcoma due to drug resistance, and some have shown the potential to reverse drug resistance and inhibit metastasis. Therefore, multifunctional three-dimensional printed bioceramic scaffolds hold excellent promise for osteosarcoma treatments. To better understand, we review the background of osteosarcoma, primary 3D-printed bioceramic scaffolds, and different therapies and have a prospect for the future.

Osteosarcoma

Osteosarcoma is the most common primary malignant tumour of the bone. Osteosarcoma incidence is bimodal, peaking at 18 and 60 years of age, and is slightly more common in males. The key pathophysiological mechanism involves several possible genetic drivers of disease linked to bone formation, causing malignant progression and metastasis. While there have been significant improvements in the outcome of patients with localized disease, with event-free survival outcomes exceeding 60%, in patients with metastatic disease, event-free survival outcomes remain poor at less than 30%. The suspicion of osteosarcoma based on radiographs still requires pathological evaluation of a bone biopsy specimen for definitive diagnosis and CT imaging of the chest should be performed to identify lung nodules. So far, population-based screening and surveillance strategies have not been implemented due to the rarity of osteosarcoma and the lack of reliable markers. Current screening focuses only on groups at high risk such as patients with genetic cancer predisposition syndromes. Management of osteosarcoma requires a multidisciplinary team of paediatric and medical oncologists, orthopaedic and general surgeons, pathologists, radiologists and specialist nurses. Survivors of osteosarcoma require specialized medical follow-up, as curative treatment consisting of chemotherapy and surgery has long-term adverse effects, which also affect the quality of life of patients. The development of osteosarcoma model systems and related research as well as the evaluation of new treatment approaches are ongoing to improve disease outcomes, especially for patients with metastases.

Genetically transforming human osteoblasts to sarcoma: development of an osteosarcoma model

Osteosarcoma is the most common primary malignant bone tumor in children and young adults. Although histologically defined by the presence of malignant osteoid, the tumor possesses lineage multipotency suggesting it could be derived from a cell anywhere on the differentiation pathway between a mesenchymal stem cell (MSC) and a mature osteoblast. To determine if preosteoblasts (pOB) could be the cell of origin differentiated MSCs were transformed with defined genetic elements. MSCs and pOB differentiated from the same MSCs were serially transformed with the oncogenes hTERT, SV40 large T antigen and H-Ras. Assays were performed to determine their tumorigenic properties, differentiation capacity and histologic appearance. When subcutaneously implanted in immunocompromised mice, cell lines derived from transformed MSC and pOB formed tumors in 4 weeks. In contrast to the transformed MSC, the pOB tumors demonstrated a histological appearance characteristic of osteosarcoma. The cell lines derived from the transformed pOB only had osteogenic and chondrogenic differentiation potential, but not adipogenic ones. However, the transformed MSC cells and standard osteosarcoma cell lines maintained their tri-lineage differentiation capacity. The inability of the transformed pOB cell line to undergo adipogenic differentiation, may suggest that osteosarcoma is derived from a cell intermediate in differentiation between an MSC and a pOB, with partial commitment to the osteoblastic lineage.

β-catenin is a valuable marker for differential diagnosis of osteoblastoma and osteosarcoma

Osteoblastoma (OB) and osteosarcoma (OS) are 2 bone tumors that predominantly affect young adults. The clinical management of OS differs significantly from that of OB, and thus, accurate diagnosis of OB and OS is critical in determining appropriate treatment modality. However, in certain cases, OS significantly overlaps with OB in clinical and radiographic characteristics, and therefore, the differential diagnosis of OB and OS can be difficult, especially when biopsy material is insufficient. To date, there have been few reports on markers for differential diagnosis of OB and OS. We have previously shown that the Wnt/β-catenin pathway is inactivated in OS. In this study, we aimed to investigate whether the cellular distribution pattern of β-catenin is a potential marker for the differential diagnosis of OB and OS. Immunohistochemical staining was studied in 17 OB samples (21 biopsies; 17 primary and 4 recurrent) and 37 OS samples with complete follow-up information. Moderate-to-strong nuclear β-catenin staining was found in all OB specimens (17/17). In contrast, positive staining of β-catenin was found in the cytoplasm and/or membrane but not the nucleus in all 32 cases of nonchondroblastic OS (32/32) and the classic OS component in chondroblastic OS (5/5). The only positive nuclear β-catenin staining detected in OS biopsies was in chondroblastic OS cells (5/5). In summary, our results indicate that, in addition to conventional histopathologic evaluation, cellular distribution of β-catenin may be used as a valuable marker in the differential diagnosis of OB and OS. Nuclear β-catenin staining strongly suggests OB, whereas cytoplasmic/membranous staining of β-catenin suggests OS.