Objective:To investigate whether hUCMSCs exist over activation and expression of STAT3 and undergo biological behavior transformation when exposed to U251 human glioma microenvironment. Methods:Cells was divided into three groups in this experiment:blank group(h UCMSCs were separately cultured)

experimental group(hUCMSCs were indirectly co-cultured with U251 human glioma cells)

positive control group(U251 human glioma cells were separately cultured). Morphology of cells was detected by invertedmicroscope. Cell cycle was detected by flow cytometry. The m RNA expressions of STAT3

c-Myc and Bcl-xl were tested by realtime PCR. The protein expressions and locations of p-STAT3

c-Myc and Bcl-xl were detected by immunofluorescence. The protein expressions of p-STAT3

STAT3

c-Myc and Bcl-xl were also measured by Western blot. The ability of migration and invasion were tested by Transwell. Results:The experimental group cells arranged in disorder and clustered

showing mild atypia. The cells proportion of experiment group in G1 phase was significantly lower than that of the blank group(P=0.000). The m RNA expression levels of STAT3

c-Myc and Bcl-xl in experimental group were significantly higher than those in blank group(P<0.05). p-STAT3

STAT3

c-Myc and Bcl-xl protein expressions were significantly higher than blank group(P<0.05)

and they were mainly situated in the nuclei.The protein expressions of STATS also showed significant changes in experimental group. Migration and invasion ability of the experimental group were significantly higher than those of blank group(P<0.05). Conclusion:h UCMSCs exist abnormal activation and over expression of STAT3 and trend to biological behavior transformations when exposed to U251 human glioma microenvironment. And these factors may lead to malignant transformation of h UCMSCs.