Introduction

MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate various biological processes. We previously developed a clinically applicable synthetic microRNA-214 (miR-214/5AE) for canine hemangiosarcoma (HSA). In this preliminary study, we evaluated the effect of intraperitoneal injections of miR-214/5AE in an intraperitoneal dissemination model of HSA.

Methods

The HSA cell line, Re21, was used for in vivo assessment. miR-214/5AE was developed using the methods previously described. Re21 cells were inoculated intraperitoneally. Two weeks after the cells were inoculated, miR-214/5AE or nonspecific miRNA (2 nmol) in 150 µL OptiMEM was mixed with 10 µl of Lipofectamine RNAiMAX, and the mixture was injected intraperitoneally every 2 days for a total of four times. The control group received injection of nonspecific miRNA, and the treatment group received injection of miR-214/5AE (each group contained two mice). The mice were then sacrificed, and peritoneal dissemination was evaluated by counting the number of tumors and the tissues were processed for histological examination.

Results

In the treatment group, the number of disseminated foci was lower than that in the control group. (control: 152, 103; treat: 31, 72) Furthermore, the number of Ki-67 positive cells was lower in the treatment group than in the control group. (control: 19, 19%; treatment: 6, 12%) The protein expressions of caspase-3 and p53 in the treatment group were higher than those in the control group.

Conclusion

These findings indicated miR-214/5AE induces tumor growth suppressive effects and apoptosis in vivo.