The expression of miR-126 was down-regulated in PBMC and lung tissue of NSCLC patients
To investigate whether miR-126 involves in pathogenesis of NSCLC, expression of miR-126 in PBMC of NSCLC patients (n = 81) and healthy control (n-81). It was indicated that the expression of miR-126 was significantly lower in NSCLC compared to health control (P < 0.001, Fig. 1A). To further explore whether miR-126 involves in pathogenesis of NSCLC. The expression of miR126 in lung cancer needle biopsies and paracancerous tissues, which indicated that expression of the miR-126 was significantly higher in lung cancer tissues than lung paracancerous tissues (P < 0.001, Fig. 1B). Thus, it was confirmed that expression of miR-126 was higher in PBMC of NSCLC patients than health controls, and it was higher in lung cancer tissue than in paracancerous tissues in NSCLC patients.
Knockdown (KD) of miR-126 induced apoptosis of A549 and H1650 cells
To investigate effects of miR-126 on growth of lung cancer cells. Two miR-126 vectors (#1 and #2) and control vector (siRNA-scramble) were transfected in A549 cells, which indicated that both miR-126 vectors significantly increased expression of the caspase3 in A549 cells (**P < 0.01, n = 4, Fig. 2A). Moreover, it was found that both miR-126 vectors significantly increased expression of the caspase9 in A549 cells (**P < 0.01, n = 4, Fig. 2B). In addition, it was found that two miR-126 vectors significantly decreased growth of A549 cells (***P < 0.001, n = 6, Fig. 2C). To further validate effects of miR-126 on growth of lung cancer cells, another NSCLC cell line named H1650 was used. Two miR-126 vectors (#1 and #2) and control vector were transfected in H1650 cells, which indicated that both miR-126 vectors significantly increased expression of the caspase3 in H1650 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 2D). It was also found that both miR-126 vectors significantly increased expression of the caspase9 in H1650 cells (***P < 0.001, n = 4, Fig. 2E). The MTT assay indicated that two miR-126 vectors significantly decreased growth of H1650 cells (***P < 0.001, n = 6, Fig. 2F). Collectively, it was confirmed that KD of miR-126 induced apoptosis of A549 and H1650 cells.
miR-126 targets PIK3R2 and PI3K/mTOR signaling in lung cancer cells
The functions of miRNAs are elucidated with analyses of the genes they target. PIK3R2 was identified as a putative target of miR-126 using target prediction programs (Targetscan 7.2, http://www.targetscan.org/vert_72/) (Fig. 3A). To further investigate the interaction of miR-126 and PI3K/mTOR signaling, effects of miR-126 on elements of mTOR signaling were studied using WB. It was found that KD of miR-126 could increase protein level of phospharylated PI3K and mTOR in both A549 (Fig. 3B) and H1650 cells (Fig. 3C), while KD of miR-126 did not change protein level of total PI3K and mTOR in both A549 (Fig. 3B) and H1650 cells (Fig. 3C). Thus, we confirmed that miR-126 could interact with mTOR signaling in lung cancer cells.
Blocking PI3K compromised increase of miR-126 KD on apoptosis in lung cancer cells
To investigate the mechanism of action (MOA) of effects of miR-126 KD on apoptosis in lung cancer cells, two si-PI3KR2 vectors and si-scramble vectors were transfected in A549 cells, which indicated that two si-PI3KR2 vectors significantly decreased mRNA expression of PI3KR2 in A549 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4A). Interestingly, it was found that KD of PI3KR2 compromised increase of miR-126 KD on increase of caspase3 mRNA expression in A549 cells (**P < 0.01, n = 4, Fig. 4B). In parallel, it was found that KD of PI3KR2 compromised increase of miR-126 KD on increase of caspase9 mRNA expression in A549 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4C). Moreover, it was found that KD of PI3KR2 compromised increase of miR-126 KD on decrease of cell viability in A549 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4D). To further investigate, two si-PI3KR2 vectors and si-scramble vectors were transfected in H1650 cells, which indicated that two si-PI3KR2 vectors significantly decreased mRNA expression of PI3KR2 in H1650 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4E). Interestingly, it was found that KD of PI3KR2 compromised increase of miR-126 KD on increase of caspase3 mRNA expression in H1650 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4F). In parallel, it was found that KD of PI3KR2 compromised increase of miR-126 KD on increase of caspase9 mRNA expression in H1650 cells (**P < 0.01, n = 4, Fig. 4G). KD of PI3KR2 compromised increase of miR-126 KD on decrease of cell viability in H1650 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 4H). Collectively, it was demonstrated that blocking PI3K compromised increase of miR-126 KD on apoptosis in lung cancer cells.
Blocking mTOR compromised increase of miR-126 KD on apoptosis in lung cancer cells
To further explore effects of mTOR signaling on increase of miR-126 KD on apoptosis in lung cancer cells, two si-mTOR vectors and si-scramble vectors were transfected in A549 cells, which indicated that two si-mTOR vectors significantly decreased mRNA expression of PI3KR2 in A549 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 5A). It was found that KD of mTOR compromised increase of miR-126 KD on increase of caspase3 mRNA expression in A549 cells (*P < 0.05, **P < 0.01, n = 4, Fig. 5B). Moreover, it was found that KD of mTOR compromised increase of miR-126 KD on increase of caspase9 mRNA expression in A549 cells (*P < 0.05, **P < 0.01, ***P < 0.001, n = 4, Fig. 5C). It was also found that KD of mTOR compromised increase of miR-126 KD on decrease of cell viability in A549 cells (*P < 0.5, **P < 0.01, n = 4, Fig. 5D). To further investigate, two si-mTOR vectors and si-scramble vectors were transfected in H1650 cells, which indicated that two si-mTOR vectors significantly decreased mRNA expression of mTOR in H1650 cells (**P < 0.01, n = 4, Fig. 5E). Interestingly, it was found that KD of mTOR compromised increase of miR-126 KD on increase of caspase3 mRNA expression in H1650 cells (*P < 0.05, **P < 0.01, n = 4, Fig. 5F). In parallel, it was found that KD of mTOR compromised increase of miR-126 KD on increase of caspase9 mRNA expression in H1650 cells (*P < 0.05, n = 4, Fig. 5G). KD of mTOR compromised increase of miR-126 KD on decrease of cell viability in H1650 cells (**P < 0.01, ***P < 0.001, n = 4, Fig. 5H). Collectively, it was demonstrated that mTOR closely involved in increase of miR-126 KD on apoptosis in lung cancer cells.