The Expression and Effect of B7-H3 in Mantle Cell Lymphoma

Objective: To investigate the effects of B7-H3 (CD276) on oncogenesis and chemosensitivity in mantle cell lymphoma (MCL).

Methods: The B7-H3 expression was detected by flow cytometry in cell lines, 20 patients with MCL and 20 volunteers. B7-H3 knockdown was performed using lentivirus transduction in the Maver and Z138 mantle cell lymphoma cell lines, respectively. The effects of B7-H3 on cell proliferation, cycle, migration and invasion were investigated by CCK-8 assay, methyl cellulose colony forming assay, PI staining, and Transwell assays in vitro. By establishing Maver and Z138 xenograft models, the effects of B7-H3 on tumourigenicity were observed, and Ki-67 and PCNA was detected through immunohistochemical. Moreover, the impacts of B7-H3 RNAi on the anti-tumor effect of chemotherapy drugs were determined with CCK-8, Annexin V-FITC/PI and Hoechst 33342 staining assays in vitro and with xenograft models in vivo.

Results: The frequency of B7-H3positive expression cases was 65.0% (13/20) in MCL patients and 10.0% (2/20) in volunteers. The down-regulation of B7-H3 significantly decreased tumor proliferation in MCL in vitro and in vivo. In the B7-H3 knockdown groups of Maver and Z138 xenograft models, the mean inhibition rate of tumor growth was 59.1% and 65.0% (p = 0.010 and 0.003), and the expression of both Ki-67 and PCNA were significantly lower, respectively. After B7-H3 silencing, the cell cycles of Maver and Z138 were both arrested at G0/G1 phase, and the expression of cell cycle-related proteins Cyclin D1 and CDK4 was lower. The cell migration rates and invasion capacity were decreased, and the rates of distant metastasis in B7-H3 knockdown both Maver and Z138 xenografts were significantly declined as well. The expression of invasion-related proteins MMP-2 and MMP-9 was lower in B7-H3 knockdown cells and xenografts. The silencing of B7-H3 increased the sensitivity of Maver and Z138 cells to Rituximab and Bendamustine and enhanced the drug-induced apoptosis, respectively. The activity of caspase-3 in vitro and the expression of caspase-3 in both Maver and Z138 xenografts was significantly increased in the B7-H3 shRNA combined with chemotherapy drugs groups.

Conclusions: B7-H3 levels in MCL patients were signifiantly higher than that in volunteers. Our study demonstrates for the first time that B7-H3 promotes mantle cell lymphoma progression and B7-H3 knockdown significantly enhances the chemosensitivity. This may provide a new therapeutic approach to mantle cell lymphoma.