WFDC21P Increases in Lung Carcinoma Cells and Tissues
Carcinoma tissue lysates prepared from 3 NSCLC patients and controls from their corresponding para-carcinoma tissues were subjected to RNA-seq analysis to detect mRNA expression. Mining of the RNA-seq dataset identified that the expression of 1392 mRNAs were elevated, and 1303 were down-regulated (fold change > 2.0, p < 0.05) (Fig. 1A). Accumulated evidence indicated that WFDC family played great roles in the progression of carcinoma.[28–31] Additionally, some of them has been identified as biomarkers of diagnosis of lung cancer.[32–34] Here, the members of WFDC family were selected to do further comprehensive analysis of their roles in lung cancer. Our results demonstrated that WFDC1 was attenuated while WFDC2 was significantly elevated in carcinoma tissue. As a member of WFDC family, we also found that lncRNA-WFDC21P may have enhanced expression in carcinoma tissue (Fig. 1B). Moreover, the role of WFDC21P in tumorigenesis of lung cancer is unclear till now. Therefore, we collected more NSCLC sample tissues and corresponding non-tumor tissues to further investigate the WFDC21P expression in lung cancer. Compared with lung para-carcinoma samples, WFDC21P levels were elevated in lung carcinoma samples (Fig. 1C). Additionally, we also found that the expression of WFDC21P in cancer cell lines (A549, H1299 and H1975) was markedly elevated compared with human bronchial epithelial cells (HBE) (Fig. 1D). These results indicate that WFDC21P may play significant roles in lung carcinoma pathogenesis.
WFDC21P Enhances Cell Proliferation and Migration
In order to examine the effects of WFDC21P on cell proliferation, migration and apoptosis, overexpression or interference of WFDC21P was performed in A549 or H1975 cells (Fig. 2A and C). It was found that WFDC21P overexpression markedly enhanced A549 or H1975 cell growth (Fig. 2B and S1A), while transfection with an effective si-WFDC21P inhibited cell proliferation (Fig. 2D and S1B). The role of WFDC21P in apoptosis was also examined, and WFDC21P knockdown increased apoptosis (Fig. 2E and S1C). WFDC21P can promote STAT3 phosphorylation in dendritic cells.[23] To further investigate whether the role WFDC21P in cell apoptosis is related to STAT3 signals, the expression of apoptotic factors related to STAT3 was examined. The expression of STAT3 and anti-apoptosis factors (Bcl2 and BIRC3) was significantly attenuated in si-WFDC21P-treated cells, but was elevated by WFDC21P overexpression. WFDC21P knockdown resulted in Bax elevation, while WFDC21P overexpression decreased Bax levels. Additionally, WFDC21P knockdown resulted in higher levels of cleaved caspases (caspase-3, 8 and 9). As expected, WFDC21P overexpression suppressed cleavage of caspases. The effects of WFDC21P on the examined apoptosis factors in A549 or H1975 cells may be owned to the enhanced phosphorylation of STAT3 resulted from WFDC21P elevation (Fig. 2F and S1D). Therefore, we next examined the effects of WFDC21P on tumor cell migration. WFDC21P overexpression increased the number of cells penetrating the Transwell membrane. Conversely, WFDC21P knockdown attenuated the cell penetration (Fig. 2G-J and S1E-H). In the colony formation assay, overexpression of WFDC21P resulted in an elevation of colony number. As expected, WFDC21P knockdown decreased the number of colonies (Fig. 2K-N and S1I-L). These results indicate that WFDC21P is proto-oncogene in lung carcinoma.
WFDC21P Interacts with, and is Regulated by DCP2
Although WFDC21P has the function of promoting carcinoma, the detail mechanisms were still unknown. DCP2, a key component for degrading RNA, is involved in the pathogenesis of some carcinoma.[35] We assumed that WFDC21P is regulated by DCP2, and is involved in the pathogenesis of lung cancer. To investigate this hypothesis, we first screened for an effective siRNA against DCP2 (Fig. 3A). Then, we detected the role of DCP2 in regulating WFDC21P expression. As expected, pcDNA-WFDC21P transfection elevated WFDC21P levels compared with the scrambled control. After DCP2 knockdown, irrespective of whether WFDC21P was overexpressed or not, WFDC21P was significantly elevated compared with the scrambled control. More importantly, DCP2 knockdown combined with pcDNA-WFDC21P transfection resulted in further increased WFDC21P expression compared with control treatment (pcDNA-WFDC21P + Scram) (Fig. 3B). As a regulated target of WFDC21P, STAT3 phosphorylation was also used to evaluate the effects of DCP2 on WFDC21P. As expected, WFDC21P overexpression after attenuating DCP2 by siRNA could further enhance STAT3 phosphorylation compared with scrambled control treatment. STAT3 phosphorylation was also higher in cells co-transfected with si-DCP2 and pcDNA-WFDC21P compared with control treatment (Fig. 3C). DCP2 can bind to RNA and promote its degradation by decapping. Therefore, RNA immunoprecipitation (RIP) was performed to check the direct interaction between WFDC21P and DCP2. As a result, WFDC21P was significantly enriched by DCP2 immunoprecipitation compared with control IgG precipitation, indicating that WFDC21P directly interacts with DCP2 (Fig. 3D). These results indicate that DCP2 may promote WFDC21P degradation by directly interacting with WFDC21P.
DCP2 is a Direct Target of miR-4293
Furthermore, we predicted that DCP2 mRNA might be a target of miR-4293 by using miRNA TargetScan (http://www.targetscan.org/vert_72/) (Fig. 3E). A GFP reporter plasmid containing DCP2-3′UTR was then constructed and used to co-transfect cells with miR-4293. miR-4293 transfection resulted in considerable attenuation of both GFP intensity and the percentage of GFP-positive cells. Cells were then co-transfected with mu-4293 (containing a mutated site of DCP2 mRNA binding) and the DCP2-3′-UTR GFP reporter plasmid. mu-4293 could not reduce the percentage of GFP positive cells compared with the wide type miR-4293. To further confirm that miR-4293 binds to the DCP2-3′UTR sequence, we constructed a mu-DCP2-3′UTR GFP reporter plasmid (with a mutant binding site for miR-4293) in which we deleted the “CTG” sequence from the DCP2-3′UTR GFP reporter plasmid. As a result, cells, co-transfected with mu-DCP2-3′UTR and miR-4293, had no significant attenuation in the percentage of GFP-positive cells (Figure S2). Next, we transfected cancer cells (A549 and H1975) with miR-4293 and its inhibitor (ASO-4293). As expected, miR-4293 transfection significantly attenuated DCP2 expression compared to transfection of both ASO-4293 and scrambled control both in A549 and H1299 cells (Fig. 3F). These results indicate that miR-4293 can directly bind to the DCP2-3′UTR to regulate the expression of DCP2.
miR-4293 Increases WFDC21P and STAT3 Levels through Regulating DCP2
The above results indicate that WFDC21P is degraded by interaction with DCP2 and DCP2 expression is suppressed by miR-4293. However, the effects of miR-4293 on WFDC21P were still to be elucidated. Firstly, we prepared miR-4293 (mimic), ASO-4293 (inhibitor) and mu-4293 (mutant). A549 cells were then transfected with miR-4293, ASO-4293 or mu-4293 respectively. After transfection, miR-4293 mimic could significantly elevate miR-4293 level, which could be markedly attenuated by ASO-4293 (Fig. 3G). By detecting WFDC21P level, we found that miR-4293 treatment could markedly enhance WFDC21P expression compared with the scrambled control. In contrast, ASO-4293 treatment suppressed WFDC21P expression compared with the scrambled control (Fig. 3H). In addition, miR-4293 treatment further increased WFDC21P levels (Fig. 3I). These results indicate that miR-4293 elevation can promote the expression of WFDC21P.
Next, STAT3 activation was used to evaluate the relationship between WFDC21P and miR-4293. As expected, overexpression of both WFDC21P and miR-4293 resulted in more STAT3 phosphorylation compared with only WFDC21P or miR-4293 treatment (Fig. 3J). To further investigate the role of WFDC21P in stimulating STAT3 pathway, we treated WFDC21P-overexpressed cells with AG490 (a specific inhibitor to STAT3 signaling, 50 µmol/L), and found that AG490 treatment reduced WFDC21P-induced STAT3 activation (Fig. 3K).
We also found that WFDC21P, by regulating STAT3 pathway, may have a positive feedback effect on the expression of miR-4293. STAT3 pathway was deactivated by AG490 treatment, which also could result in the decreased levels of miR-4293. Moreover, miR-4293 elevation resulting from WFDC21P overexpression was further alleviated by using AG490 to deactivate STAT3 pathway (Fig. 3L). These results indicate that there might be a feedback loop between miR-4293 and WFDC21P in which miR-4293 increases WFDC21P levels and WFDC21P might upregulate miR-4293 expression by activation of STAT3 pathways.
MiR-4293 and STAT3 Levels also Increased in NSCLC Cells and Tissues
The above results indicate that WFDC21P expression and STAT3 activation can be upregulated by miR-4293. However, the role of miR-4293 and STAT3 in the pathogenesis of NSCLC requires clarification. Firstly, we examined the expression of miR-4293 in carcinoma cell lines (A549, H1299 and H1975) and found that miR-4293 expression was significantly elevated compared to HBE (Fig. 4A). As expected, miR-4293 elevation was also found in NSCLC tissues compared with para-carcinoma tissues (Fig. 4B). As a direct target of WFDC21P, STAT3 phosphorylation was increased in lung carcinoma cells (Fig. 4C). Similarly, STAT3 expression was also increased in lung carcinoma tissue (Fig. 4D). Based on the above results, we further analyzed possible correlations among WFDC21P, STAT3 and miR-4293 in the NSCLC samples. We found that WFDC21P expression was positively correlated with STAT3 expression (p < 0.01, Fig. 4E). miR-4293 and WFDC21P expression was also in positive correlation (p = 0.015, Fig. 4F), as was the relationship between miR-4293 and STAT3 expression (p < 0.01, Fig. 4G).
MiR-4293 Promotes Cell Proliferation and Migration
In order to further study the role of miR-4293 in lung carcinoma, MTT assays were performed and showed that miR-4293 transfection could significantly promote A549 or H1975 cell proliferation compared with cells transfected with scrambled control or ASO-4293 inhibitor. ASO-4293 transfection suppressed cancer cell proliferation compared with the scrambled control (Fig. 5A and S3A). The apoptosis assay showed that miR-4293 treatment decreased lung cancer cell (A549 or H1975) apoptosis compared with the scrambled control. More importantly, miR-4293 treatment significantly increased survival capacity compared with ASO-4293 treatment (Fig. 5B and S3B).
Next, we investigated the effects of miR-4293 on apoptosis related factors. We found that the expression of anti-apoptosis factors (Bcl2 and BIRC3) could be elevated by miR-4293 transfection, but was attenuated by ASO-4293 treatment compared with scrambled control. However, the expression of Bax, a pro-apoptosis factor was suppressed by miR-4293 treatment and enhanced by ASO-4293 transfection. We also examined the expression of caspases influenced by miR-4293 and ASO-4293. miR-4293 treatment resulted in less cleavage of caspase-3, caspase-8 and caspase-9, which play essential roles in apoptosis. Whereas, ASO-4293 treatment induced the cleavage of caspase-3, caspase-8 and caspase-9 compared with miR-4293. Importantly, the apoptotic factors examined are closely related to STAT3 signaling pathways; therefore, we detected STAT3 expression and found that miR-4293 treatment could significantly enhance STAT3 phosphorylation compared with scrambled control, in contrast, ASO-4293 treatment suppressed STAT3 phosphorylation compared with miR-4293 transfection (Fig. 5C and S3C). To investigate the possible role of miR-4293 in tumor cell migration, we conducted Transwell migration assays, which demonstrated that A549 or H1975 cells transfected with miR-4293 have enhanced migration capacity compared with cells transfected with scrambled control (Fig. 5D and E, S3D and E). Additionally, miR-4293 treatment could significantly increase survival of A549 or H1975 cells seeded sparsely in a clonogenic assay compared with the scrambled control. Conversely, cells transfected with ASO-4293 formed fewer colonies compared with scrambled control (Fig. 5F and G, S3F and G). miR-4293 promoted cell proliferation and migration but inhibited apoptosis. These results indicate that miR-4293 has oncogenic potential in lung carcinoma.
Knockdown of WFDC21P Attenuates the Oncogenic Role of miR-4293
The above results show that miR-4293 exert an oncogenic role and increases WFDC21P expression, which indicates that miR-4293 may exert its oncogenic role by promoting WFDC21P expression. To better understand whether the role of miR-4293 can be attenuated by WFDC21P knockdown, we first evaluated cell proliferation co-influenced by miR-4293 and si-WFDC21P. WFDC21P knockdown suppressed cell proliferation and miR-4293 transfection promoted cell proliferation. More importantly, the increase in cell proliferation resulting from miR-4293 transfection was markedly alleviated by si-WFDC21P (Fig. 6A). The apoptosis assay showed that WFDC21P knockdown promoted apoptosis and also significantly abolished the increased cell viability resulting from miR-4293 transfection (Fig. 6B).
We then examined the expression of Bcl2, anit-apoptosis factors, which was enhanced by miR-4293 transfection and suppressed by WFDC21P knockdown compared with scrambled control. Moreover, Bcl2 elevation caused by miR-4293 treatment was attenuated by WFDC21P knockdown. Besides, miR-4293 transfection with WFDC21P knockdown resulted in lower expression of Bcl2 compared with miR-4293 transfection with scrambled control. The expression of Bax was elevated by WFDC21P knockdown but was suppressed by miR-4293 transfection compared with scrambled control. si-WFDC21P alleviated the downregulation of Bax expression affected by miR-4293. Accordingly, WFDC21P knockdown induced more caspase-3 cleaved than miR-4293 treatment. miR-4293 transfection attenuated the elevation of cleavage caspase-3 induced by WFDC21P knockdown. More importantly, we found that miR-4293 transfection enhanced STAT3 phosphorylation, which was alleviated by si-WFDC21P (Fig. 6C). RTCA station analysis was performed to continuously observe cells migration, which gradually increased in miR-4293-treated cells but was blocked by si-WFDC21P treatment (Fig. 6D and E).
To further study whether the oncogenic role of miR-4293 can be attenuated by blocking WFDC21P, we investigated whether ASO-4293 inhibition of lung cancer cell proliferation can be restored by WFDC21P overexpression. We found that the proliferative capacity was suppressed by ASO-4293 inhibitor and enhanced by WFDC21P overexpression compared with control. More interestingly, the inhibition of cell proliferation by ASO-4293 was restored to a certain extent after WFDC21P overexpression (Fig. 6F). Compared with control treatment, ASO-4293 transfection increased apoptosis. Even though WFDC21P overexpression could promote cell viability, the percentage of apoptotic cells was still elevated by ASO-4293 transfection (Fig. 6G). By examination of apoptosis related factors, we found that the expression of Bcl2 was decreased in ASO-4293-transfected cells, but increased in WFDC21P overexpression cells. ASO-4293 transfection with WFDC21P overexpressing resulted in attenuation of Bcl2 expression compared with control treatment. In contrast, Bax expression was significantly enhanced by ASO-4293 transfection. WFDC21P overexpression partially attenuated Bax expression induced by ASO-4293. As expected, WFDC21P overexpression decreased the cleavage of caspase-3 compared with scramble control. And attenuation of caspase-3 cleavage caused by WFDC21P overexpression was alleviated by ASO-4293 treatment. We also found that ASO-4293 resulted in less activated STAT3, while WFDC21P overexpression increased STAT3 activation. WFDC21P overexpression also partially increased STAT3 levels induced by ASO-4293 (Fig. 6H). As expected, ASO-4293 treatment could also alleviate migration capacity by WFDC21P overexpression (Fig. 6I-L). Together, these results indicate that oncogenic activity of miR-4293 can be attenuated by blocking WFDC21P expression.
WFDC21P and MiR-4293 Promote Tumorigenesis in vivo.
Both miR-4293 and WFDC21P have oncogenic activities in lung carcinoma cells. To further investigate the roles of miR-4293 and WFDC21P in vivo, we hypodermically injected A549 cells stably treated with plasmid, or miRNA, or siRNA, or controls into nude mice to produce xenografts. Every 3 days, we measured the volumes of the xenografts. One month after injection, the mice were sacrificed. Stably expression of WFDC21P resulted in enhanced tumor growth both in volumes and weights compared with pcDNA control (Fig. 7A-C). We examined expression of WFDC21P and STAT3 phosphorylation in the xenografts. As expected, WFDC21P overexpression in injected xenografts resulted in elevation of WFDC21P and STAT3 phosphorylation (Figure S 4A and B).
We then evaluated the effects of miR-4293 or WFDC21P knockdown on xenograft growth. miR-4293 treatment enhanced growth in both volumes and weights of xenografts compared with scrambled control. In contrast, WFDC21P knockdown resulted in xenografts growth that was significantly lower than that produced by miR-4293 overexpression and also than scrambled control (Fig. 7D-F). Compared with scrambled control, miR-4293 treatment resulted in elevation of miR-4293, WFDC21P and STAT3 phosphorylation in xenografts. Conversely, these measures were attenuated by WFDC21P knockdown (Figure S4C-E).
To better understand the cooperative action of miR-4293 and WFDC21P in tumor growth, we established xenografts with A549 cells co-treated with miR-4293 and scrambled control, miR-4293 and ASO-4293, as well as miR-4293 and siRNA-WFDC21P. As expected, xenografts with miR-4293 and scrambled co-treatment had the highest growth rate of these three groups. Interestingly, ASO-4293 and si-WFDC21P could abolish the tumor promoting effect of miR-4293 almost equally (Fig. 7G-I). Moreover, ASO-4293 attenuated the decrease in WFDC21P or STAT3 levels in xenografts by miR-4293 and si-WFDC21P (Figure S4F-H). Similarly, tumor promotion resulting from WFDC21P stable overexpression was also alleviated by ASO-4293 treatment (Fig. 7J-L). ASO-4293 treatment could also alleviate elevation of WFDC21P and STAT3 phosphorylation in xenografts resulting from WFDC21P overexpression in injected cells (Figure S4I and J). The above results support the ability of miR-4293 and WFDC21P to promote tumor growth in vivo.