Abstract:

Objective：To investigate the effect and mechanism of targeted B7-H3 gene silencing on the tumorigenesis and metastasis of human hematological malignancy xenograft tumor in nude mice. Methods: Real-time fluorogentic quantitative PCR (qPCR) and flow cytometry (FCM) were used to detect the expression of B7-H3 in 13 strains of malignant hematologic cells. Then, U937, Maver and Z138 cells which expressed high level of B7-H3 were screened out. Targeted B7H3 knockdown in U937, Ma-ver and Z138 was performed by lentivirus transduction and the effect of B7-H3 silencing in stable cell lines was tested by qPCR and FCM. Injecting the nine groups subcutaneously into the nude mice to establish xenograft models after dividing the U937, Maver and Z138 into non-infected control group (CON), B7-H3 knockdown group (KD) and negative non-targeted control infected group (NC),respectively, for detecting the tumorigenicity and metastasis in vivo. Furthermore, the expression of Ki-67 in xenograft tumors was detected by immunohistochemistry (IHC). The expression of metalloproteinase 2 (MMP-2) was detected by western blot.  Results: The stable B7-H3 silencing cell lines of U937, Maver and Z138 were successfully established. Compared with the NC group, the KD groups of U937, Maver and Z138 had an obviously slower tumor growth. The average tumor inhibition rates at the end of observation period were 61.83% (F=43.78, P<0.05), 59.12% (F=36.51, P<0.05) and 67.37% (F=40.29, P<0.05); there was no significant difference in tumor volume growth between the NC group and the CON group (P>0.05). The liver distant metastasis of all the xenograft tumor models in nude mice was the most common and the rates of distant metastasis in KD groups were significantly lower than that of the corresponding NC groups. The Ki-67 indexes of the KD groups were significantly lower than those of the relative NC groups in three cell lines (U937: 40.3%±5.2% vs. 79.1%±6.3%, q=30.31, P<0.05, Maver: 35.2%±6.4% vs. 69.6%±5.1%， q=24.82, P<0.05; Z138: 38.4%±7.1% vs. 75.7%±4.8%, q=28.07, P<0.05); there was no significant difference in the expression of Ki-67 between the NC group and the CON group (P>0.05). The expressions of MMP-2 were also significantly lower in the KD groups than in the NC groups (U937: q=14.59, P<0.05; Maver: q=9.25, P<0.05; Z138: q=11.04, P<0.05); there was no significant difference in the expression of MMP-2 between the NC group and the CON group (P>0.05).Conclusion: Targeted B7-H3 gene silencing could inhibit the tumorigenesis and metastasis of human hematological malignancy xenograft tumor in nude mice. The mechanism may be related to the down-regulation of Ki-67 and MMP2.

Key words: Hematological malignancies, B7-H3, Gene silencing, Nude mice