To explore the functions of LIN28B, two specific siRNAs against LIN28B mRNA were synthesized. As shown in Fig. 6A, both siRNAs remarkably reduced the expression of LIN28B protein. Cell proliferation assays showed that both si-LIN28B-1 and si-LIN28B-2 significantly inhibited the proliferation of Huh-7 cells (Fig. 6B). Furthermore, we investigated the effect of si-LIN28B on cell cycle progression by way of fluorescence-activated

cell sorting analysis. The results showed that both si-LIN28B-1 and si-LIN28B-2 blocked G1/S transition and retained Huh-7 cells at G1 phase (P = 0.0476 and 0.0221, respectively) (Fig. 6C). The suppression of proliferation and blockade of cell cycle progression by si-LIN28B-1 and si-LIN28B-2 mimicked the phenotype induced by enforced expression of miR-125b in HCC cells. We next CP690550 investigated the effect of si-LIN28B on the migration and invasion of Huh-7 cells. Remarkably, transwell assay without matrigel coating showed that si-LIN28B-1 elicited an inhibitory effect on Huh-7 cell migration

compared with the control group (Fig. 6D). Si-LIN28B-2 showed a greater inhibitory effect than si-LIN28B-1, because si-LIN28B-2 had a better knockdown of the LIN28B protein level. Transwell assay with matrigel coating showed that si-LIN28B-1 and si-LIN28B-2 significantly reduced the invasion LY2109761 price ability of HCC cells (Fig. 6E). Together, our results indicate that reduction of LIN28B through siRNA interference has similar effects on the HCC cells to those induced by miR-125b, suggesting that LIN28B may act as a downstream functional mediator for miR-125b. If LIN28B

indeed acts as a functional target of miR-125b, reintroduction of LIN28B into miR-125b–expressing cells Myosin should be able to antagonize the effects of miR-125b. To test the hypothesis, we first constructed a lentiviral expression vector of LIN28B without the 3′-UTR and infected miR-125b–expressing cells. As shown in Supporting Fig. 7A, the expression of LIN28B was recovered after LIN28B lentivirus infection. Interestingly, cell proliferation assay demonstrated that reintroduction of LIN28B enhanced the proliferation of miR-125b–expressing cells (Fig. 7A). Moreover, the inhibition of miR-125b on the colony formation was also antagonized by enforced expression of LIN28B (Supporting Fig. 7B). Furthermore, enforced expression of LIN28B significantly counteracted the G1 arrest induced by miR-125b (Fig. 7B). In addition, in vitro migration and invasion assays showed that enforced expression of LIN28B rescued the migration and invasion suppression induced by miR-125b (Fig. 7C,D). It is noteworthy that the LIN28B overexpressing cells displayed a phenotype of faster growth and increased aggressiveness compared with the other cells due to higher expression of LIN28B in these cells.