Tissue expression levels of miR-29b and miR-422a in children, adolescents, and young adults' age groups and their association with prediction of poor prognosis in human osteosarcoma.

Osteosarcoma is the most common type of bone cancer in children and adolescents. MicroRNAs (miRNAs) play important roles in the development, differentiation, and function of different cell types and in the pathogenesis of various human diseases. miRNAs are differentially expressed in normal and cancer cells. The investigation of miRNA expression between healthy subjects and patients with osteosarcoma is crucial for future clinical trials. In this study, the expression levels of miRNAs were detected by qRT-PCR. Correlation between expression levels of tow miRNAs and different clinicopathological characteristics were analyzed using the χ (2) test. Survival rate was detected using the log-rank test and Kaplan-Meier method. qRT-PCR was shown that expression levels of miR-29b and miR-422a were strongly decreased in osteosarcoma bone tissue compared with noncancerous bone tissues. Our result indicated that the low expression levels of miR-29b and miR-422a showed strong correlation with large tumor size (P = 0.20; 0.029), advanced TNM stage (P = 0.001; 0.012), distant metastasis (P = 0.008; 0.019), and grade of tumor (P = 0.009; 0.016). Kaplan-Meier survival analysis showed that the low expressions of miR-29b/miR-422a were correlated with shorter time overall survival (log-rank test, P = 0.009; P = 0.013). Moreover, multivariate Cox proportional hazards model indicated that miR-29b and miR-422a (P = 0.024; P = 0.016) were independent prognostic markers of overall survival of patients. Our result indicated that downregulation of miR-29b and miR-422a may be linked to the prediction of poor prognosis, indicating that miR-29b and miR-422a may be a valuable prognostic marker for osteosarcoma patients.