[Effect of Notch ligand Delta1-RNA interference by lentivirus on proliferation and differentiation of human dental pulp stem cells].

OBJECTIVE: To investigate the effects of specific RNA interference (RNAi) to Notch ligand Delta1 on proliferation and differentiation of human dental pulp stem cells (DPSC). METHODS: DPSC were infected by lentivirus vectors carrying Delta1-RNAi. DPSC were divided into three groups, DPSC/Delta1-RNAi group, DPSC/wt group and DPSC/vector group as control. Cell counting kit-8 (CCK-8) assay and flow cytometry were used to evaluate the proliferation of DPSC. Expression of proliferating cell nuclear antigen (PCNA) was examined with immunohistochemical staining. All groups were cultured in an odonto-inductive medium and were observed under microscope. The number of mineralization nodules was counted after Alizarin red staining. Alkaline phosphatase (ALP) activity and the expression of dentin sialophosphoprotein (DSPP) were detected by ALP activity assay and Western blotting. RESULTS: Compared with DPSC/wt or DPSC/vector separately, proliferating rate and S-cycle of DPSC/Delta1-RNAi was significantly lower. The S phase and proliferation index (PI) decreased markedly from 22.32 ± 2.35 and 33.68 ± 4.19 (DPSC/Delta1-RNAi) to 5.44 ± 0.91 and 16.00 ± 6.07 (DPSC/wt). The PCNA staining of DPSC/Delta1-RNAi was evidently weaker. DPSC/Delta1-RNAi group had more calcified cell nodules than the other two control groups, and ALP activity and DSPP expression of DPSC/Delta1-RNAi group increased markedly. CONCLUSIONS: Delta1-RNAi induced by the lentivirus vectors may inhibit DPSC proliferation and differentiation. Notch-Delta signal pathway plays an important role in self-renewal and differentiation.

Effective gene-virotherapy for complete eradication of tumor mediated by the combination of hTRAIL (TNFSF10) and plasminogen k5.

Virotherapy with oncolytic viruses is a highly promising approach for cancer therapy. To improve further the therapeutic effect of oncolytic viruses, therapeutic genes have been incorporated into these types of vectors. In this study, we have inserted hTRAIL (approved gene symbol TNFSF10) into the ZD55 vector, which was based on deletion of the adenoviral E1B 55-kDa gene and could replicate in and lyse p53-deficient tumors. Our data shows that infection of colorectal carcinoma cells with ZD55-hTRAIL resulted in tumor cell death that was much greater than that induced by ZD55 vector or replication-defective adenovirus expressing hTRAIL. In contrast to these, ZD55-hTRAIL did not induce any cytopathic effect in normal cells. Treatment of established tumor with ZD55-hTRAIL resulted in dramatic inhibition of tumor growth in an animal model of colorectal carcinoma. However, when the established tumors were treated by coadministration of ZD55-hTRAIL and Ad-k5, we observed complete eradication of the established tumors in all animals treated with the combined therapy. This strong anti-tumor activity was due to the fact that two genes may act with compensative (or synergic) effect through different mechanisms to kill tumors. Therefore, targeting dual gene-virotherapy may be one of the best strategies for cancer therapy if two suitable genes are chosen.