CDK2 gene expression analyses in human osteosarcoma.

A) CDK2 expression in high-grade osteosarcoma tumour samples and cell lines in comparison with normal tissues. Numbers indicate the samples analysed in each group. Asterisks (**) indicate statistically significant differences with the osteosarcoma tumour samples (P<0.01 by ANOVA test). The bottom and top of each box are, respectively, the first and third quartiles of gene expression level values. The band inside each box is the median (second quartile) of gene expression level values, whereas outliers (values below the first or above the third quartile) are plotted outside the box. The "OS Tumors 21 (ITCC)" data set was a series of 21 primary, high-grade osteosarcomas of the extremities, non-metastatic at diagnosis, arisen in patients younger than 40 years collected at the Orthopaedic Rizzoli Institute (IOR, Bologna, Italy) (GEO ID: GSE87437). The "OS Cell Lines 9 (ITCC)" data set included nine IOR human osteosarcoma cell lines. Both data sets were shared within the Innovative Therapies for Children with Cancer European Consortium (ITCC; http://www.itcc-consortium.org/). The GEO ID of the other data sets are: Normal Muscle 22 (Gordon) (GEO ID: GSE38718), Mixed Muscle (skeletal) 29 (Skov) (GEO ID: GSE6798), Mixed (skeletal) Muscle 40 (Asmann) (GEO ID: GSE9103), Normal Tissues 504 (Roth) (GEO ID: GSE7307). B) CDK2 expression level in high-grade osteosarcoma tumour samples in comparison with normal human normal osteoblasts and normal muscles assessed by qRT-PCR. C) Relative CDK2 gene expression level in the nine human osteosarcoma cell lines of the "OS Cell Lines 9 (ITCC)" data set, assessed by qRT-PCR and western blot. D) Event-free survival probability of the 21 high-grade osteosarcoma patients (GEO ID: GSE87437) stratified according to the CDK2 gene expression levels. The group of high expressors included patients with CDK2 expression levels at diagnosis equal or higher to the 75 percentile of the whole group. Curves were drawn by using the Kaplan-Meyer method and significance was calculated with the log-rank test.