ABSTRACT. Immune cells might participate in the ontogenesis of osteosarcoma. B7-H3 is a new discovered T cell co-stimulatory molecule that was found to be overexpressed in malignant tumors. We aimed to investigate the dynamic expression level of B7-H3 in nude mice with osteosarcoma. A nude mouse osteosarcoma model was successfully established. B7-H3 expression and distribution changes in the early, middle, and late phases of osteosarcoma formation after tumor implantation were observed. Reverse transcription-polymerase chain reaction and western blot analyses were applied to measure the B7-H3 mRNA and protein dynamic changes. Confocal microscopy and immunohistochemistry were used to determine B7-H3 localization and CD3+ T cell expression, respectively, in osteosarcoma tissue. B7-H3 mRNA and protein levels fluctuated during the process of osteosarcoma formation in the nude mouse model. Expression levels were lower in the early and middle phases, while B7-H3 mRNA and protein were overexpressed in the late stage. Accordingly, CD3+ T cell numbers in the early, middle, and late phases in osteosarcoma tissue were 93 ± 13, 92 ± 12, and 46 ± 15, respectively; they can be seen to have decreased significantly in the late stage (P < 0.05). Overall, our results indicated that the B7-H3 expression level is correlated with tumor volume and severity; therefore, it might serve as a tumor biomarker for osteosarcoma.

ABSTRACT. Past studies have revealed the critical role of runt-related transcription factor 2 (RUNX2) in the proliferation and differentiation of mesenchymal stem cells (MSCs). This study therefore aimed to investigate the expression profile of the RUNX2 gene in human bone marrow MSCs and its biological characteristics. Bone marrow MSCs were separated from 12 patients who had received hip joint replacement surgery. After purification and culture, the MSCs were subjected to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry, the alkaline phosphatase assay, reverse transcription polymerase chain reaction, and RUNX2 protein quantification. The cell growth curve, staining images, and information on the membrane antigens and the levels of RUNX2 mRNA and protein were obtained based on the results. The growth curve showed, after a 2-day lag period, cultured MSCs entered into the log phase between d3 (Day 3) and d6, when they reached a plateau. Flow cytometry data suggested 94.38% of MSCs were CD90-positive, while only 3.99 and 1.71% of total cells were positive for CD35 and CD45, respectively. With the elongated induction period, cultured MSCs were polygonal in shape. After a 14-day induction, cell fusion occurred in the center of the cell nodule accompanied by the disappearance of cellular structure to form the calcium nodule, which was stained red. There was also a statistically significant increase in the level of RUNX2 protein at d7 and d14. An osteogenic medium is required for the differentiation of adult MSCs, which is also under RUNX2 regulation. These findings are potentially valuable for clinical practice.