Abstract 5574: High prevalence of germline TP53 mutations in young osteosarcoma cases

Suppression of Estrogen Receptor Alpha Inhibits Cell Proliferation, Differentiation and Enhances the Chemosensitivity of P53-Positive U2OS Osteosarcoma Cell

Osteosarcoma is a highly malignant musculoskeletal tumor that is commonly noticed in adolescent children, young children, and elderly adults. Due to advances in surgery, chemotherapy and imaging technology, survival rates have improved to 70–80%, but chemical treatments do not enhance patient survival; in addition, the survival rate after chemical treatments is still low. The most obvious clinical feature of osteosarcoma is new bone formation, which is called “sun burst”. Estrogen receptor alpha (ERα) is an essential feature of osteogenesis and regulates cell growth in various tumors, including osteosarcoma. In this study, we sought to investigate the role of ERα in osteosarcoma and to determine if ERα can be used as a target to facilitate the chemosensitivity of osteosarcoma to current treatments. The growth rate of each cell clone was assayed by MTT and trypan blue cell counting, and cell cycle analysis was conducted by flow cytometry. Osteogenic differentiation was induced by osteogenic induction medium and quantified by ARS staining. The effects of ERα on the chemoresponse of OS cells treated with doxorubicin were evaluated by colony formation assay. Mechanistic studies were conducted by examining the levels of proteins by Western blot. The role of ERα on OS prognosis was investigated by an immunohistochemical analysis of OS tissue array. The results showed an impaired growth rate and a decreased osteogenesis ability in the ERα-silenced P53(+) OS cell line U2OS, but not in P53(−) SAOS2 cells, compared with the parental cell line. Cotreatment with tamoxifen, an estrogen receptor inhibitor, increased the sensitivity to doxorubicin, which decreased the colony formation of P53(+) U2OS cells. Cell cycle arrest in the S phase was observed in P53(+) U2OS cells cotreated with low doses of doxorubicin and tamoxifen, while increased levels of apoptosis factors indicated cell death. Moreover, patients with ER−/P53(+) U2OS showed better chemoresponse rates (necrosis rate > 90%) and impaired tumor sizes, which were compatible with the findings of basic research. Taken together, ERα may be a potential target of the current treatments for osteosarcoma that can control tumor growth and improve chemosensitivity. In addition, the expression of ERα in osteosarcoma can be a prognostic factor to predict the response to chemotherapy.

Identification of characteristic gene modules of osteosarcoma using bioinformatics analysis indicates the possible molecular pathogenesis

The aim of the present study was to investigate the possible pathogenesis of osteosarcoma using bioinformatics analysis to examine gene‑gene interactions. A total of three datasets associated with osteosarcoma were downloaded from the Gene Expression Omnibus. The differentially expressed genes (DEGs) were identified using the significance analysis of microarrays method, which then were subjected to the Human Protein Reference Database to identify the protein‑protein interaction (PPI) pairs and to construct a PPI network of the DEGs. Subsequent multilevel community analysis was applied to mine the modules in the network, followed by screening of the differential expression module using the GlobalAncova package. The genes in the differential expression modules were verified in the valid datasets. The verified genes underwent functional and pathway enrichment analysis. A total of 616 DEGs were selected to construct the PPI network, which included 5,808 osteosarcoma‑specific interaction pairs and 8,012 normal‑specific pairs. Tumor protein p53 (TP53), mitogen-activated protein kinase 1 (MAPK1) and estrogen receptor 1 (ESR1) were identified the most important osteosarcoma‑associated genes, with the highest levels of topological properties. Neurogenic locus notch homolog protein 3 (NOTCH3) and caspase 1 (CASP1) were identified as the osteosarcoma‑specific interaction pairs. Among all 23 mined modules, three were identified as differential expression modules, which were verified in the other two datasets. The genes in these modules were predominantly enriched in the FGFR, MAPK and Notch signaling pathways. Therefore, TP53, MAPK1, ESR1, NOTCH3 and CASP1 may be important in the development of osteosarcoma, and provides valuable clues to investigate the pathogenesis of osteosarcoma using the three differential expression modules.

TP53 Mutations and Survival in Osteosarcoma Patients: A Meta-Analysis of Published Data

Several research groups have examined the association between TP53 mutations and prognosis in human osteosarcoma. However, the results were controversial. The purpose of this study was to evaluate the prognostic value of TP53 mutations in osteosarcoma patients. A meta-analysis was conducted with all eligible studies which quantitatively evaluated the relationship between TP53 mutations and clinical outcome of osteosarcoma patients. Eight studies with a total of 210 patients with osteosarcoma were included in this meta-analysis. The risk ratio (RR) with a 95% confidence interval (95% CI) was calculated to assess the effect of TP53 mutations on 2-year overall survival. The quantitative synthesis of 8 published studies showed that TP53 mutations were associated with 2-year overall survival in osteosarcoma patients. These data suggested that TP53 mutations had an unfavorable impact on 2-year overall survival when compared to the counterparts with wild type (WT) TP53 (RR: 1.79; 95% CI: 1.12 to 2.84; P = 0.01; I (2) = 0%). There was no between-study heterogeneity. TP53 mutations are an effective prognostic marker for survival of patients with osteosarcoma. However, further large-scale prospective trials should be performed to clarify the prognostic value of TP53 mutations on 3- or 5-year survival in osteosarcoma patients.