Relationship between chromosomal aberrations by fluorescence in situ hybridization and DNA ploidy by cytofluorometry in osteosarcoma

Knockdown of Mad2 induces osteosarcoma cell apoptosis-involved Rad21 cleavage

BACKGROUND

Besides Mad2's role in carcinogenesis, recent study has shown that it is essential in cell survival. Here we found that knockdown of Mad2 causes osteosarcoma cell death through apoptosis, with the apoptotic signal resulting from Rad21 cleavage.

METHODS

U2OS and MG63 cells were divided into three groups: the Mad2 siRNA group, mock group and normal control group; the Mad2 siRNA group and mock group are transfected with Mad2 shRNA plasmid and mock plasmid, respectively. G418 was used to increase the transfection efficacy, which was evaluated by GFP fluorescence. Quantitative PCR and Western blotting analyses were used to detect the transcription and expression of Mad2, Rad21 and caspase-3, respectively. Flow cytometry assay using PE-labeled Annexin-V and PI, TUNEL assay and Hoechst 33258 staining were used to evaluate cell apoptosis.

RESULTS

We successfully achieved knockdown of Mad2 expression in cancer cells using RNA interference. We observed obvious apoptosis in the Mad2 siRNA group compared with the Mock and control group. We found that the apoptosis induced by Mad2 knockdown correlated with Rad21 cleavage.

CONCLUSION

These results confirmed that knockdown of Mad2 causes osteosarcoma cell death through apoptosis and provides evidence that the apoptotic signal resulted from Rad21 cleavage. This study suggested that Mad2 has potential to be a novel target for cancer therapy.

Mitotic arrest defective protein 2 expression abnormality and its clinicopathologic significance in human osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. Overexpression of mitotic arrest defective protein 2 (MAD2) is found in many human neoplasms, but its role in the oncogenesis of osteosarcoma is an untouched topic. The objective of this research was to observe the expression of MAD2 in human osteosarcoma and explore its clinicopathologic significance. MAD2 expression was analyzed in 48 primary osteosarcoma cases (19 osteoblastic osteosarcomas, 17 chondroblastic osteosarcomas and 12 fibroblastic osteosarcomas) using immunohistochemistry. A total of 20 normal bone specimens formed a control group. MAD2 was commonly overexpressed in human osteosarcoma. Immunopositivity was higher in tumors with lower differentiation and higher clinical stage. Increased expression of MAD2 was associated with earlier metastasis and poorer survival. Our findings provide evidence that MAD2 contributes to the pathogenesis and development of human osteosarcoma, Testing may have a clinical role in predicting prognosis, selecting appropriate chemotherapeutic strategies and providing novel strategies for osteosarcoma therapy.

Chromosomal instability in osteosarcoma and its association with centrosome abnormalities

The mechanism that generates the extreme aneuploidy that characterizes osteosarcoma (OS) is poorly understood. In this study, interphase fluorescence in situ hybridization (FISH) analysis was used to enumerate cell-to-cell variation of several different chromosomes. We also investigated whether there was an association between TP53 mutation and centrosome aberrations in the generation of chromosomal aneuploidy in OS in four OS cell lines (HOS, SAOS2, U2OS, and MG63) and in a subset of seven tumors. Our analysis showed that there was a wide range of numerical changes affecting multiple chromosomes in OS cell lines and tumors. These data suggest that chromosomal instability (CIN) could be responsible for the extensive aneuploidy associated with this tumor. The results also showed an increased frequency of atypical mitotic figures in three OS cell lines with defective TP53, function and significantly, a more marked CIN phenotype was present in these lines. Furthermore, numerical aberrations of centrosomes were also present in these three OS cell lines with TP53 mutations. In two of three OS patients' tumors there was a large increase in the percentage of abnormal centrosome numbers. We conclude that CIN is a consistent feature of OS and that an intrinsic disturbance of the chromosomal segregation mechanisms is likely associated with centrosome aberrations.

Comparative genomic hybridization analysis identifies gains of 1p35 approximately p36 and chromosome 19 in osteosarcoma

Osteosarcomas (OS) are aggressive tumors of the bone and often have a poor prognosis. Conventional cytogenetic analyses of OS have revealed highly complex karyotypes, with numerous abnormalities. In this study, we analyzed 18 untreated OS tumors from 17 patients of the younger incidence age group by comparative genomic hybridization (CGH), 4 tumors by spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH). Comparative genomic hybridization identified frequent copy number changes of the chromosomal region 1p (10/17) and gain of part or all of chromosome 19(8/17). In addition gains were observed at 5p(3/17), 8q(3/17), 16p(3/17), and 17p(5/17); and losses at chromosomes 2q(3/17), 10(4/17) and 13(3/17). High level gains were detected in the 8q23 approximately q24 region in two tumors as well as at 17p in one primary and a metastatic tumor. Minimal regions of gain were present at 1p35 approximately p36.3 (8/17); 5p14 approximately p15.2 (3/17), and 8q22 approximately q24.3 (3/17). SKY analysis demonstrated that OS has a complex pattern of clonal and non-clonal rearrangements and helped confirm the structural basis for the imbalances detected by CGH. Spectral karyotyping confirmed an overall pattern of chromosomal gain affecting 1p in all four tumors. Fluorescence in situ hybridization analysis from these tumors confirmed the gain of the 1p36 region in 2 tumors as determined by CGH analysis as well as the amplification of 8q.