LncRNA PLAC 2 downregulated miR-21 in non-small cell lung cancer and predicted survival

Abstract

Background: LncRNA PLAC2 has been characterized as a tumor suppressive lncRNA in glioma. We investigated the role of PLAC2 in non-small cell lung cancer (NSCLC).

Methods: A total of 187 NSCLC patients were admitted by The First Hospital of Jilin University from December 2010 to December 2014. All the patients were diagnosed by histopathological approaches. Transient cell transfections, RT-qPCR, invasion, and migration ability measurement, were applied for the experiments.

Results: PLAC2 was down-regulated, while miR-21 was up-regulated in NSCLC tissues compared to non-cancer tissues. Low PLAC2 levels in NSCLC tissues were associated with poor survival of NSCLC patients. PLAC2 and miR-21 were inversely correlated, and PLAC 2 over-expression in NSCLC cells resulted in the down-regulation of miR-21. However, miR-21 over-expression did not significantly affect PLAC2 expression. In addition, PLAC2 over-expression resulted in decreased migration and invasion rates of NSCLC cells. MiR-21 over-expression played the opposite role and attenuated the effects of PLAC2 over-expression.

Conclusions: In conclusion, lncRNA PLAC2 down-regulated miR-21 in NSCLC and inhibited cancer cell migration and invasion.

Keywords: Non-small cell lung cancer; Survival; lncRNA PLAC2; miR-21.

Fig. 1

Expression patterns of PLAC2 and miR-21 were opposite in NSCLC. This figure shows the comparison of PLAC2 (a) and miR-21 (b) expression levels between non-tumor and NSCLC tissues. Expression were detected by performing RT-qPCR and data were analyzed by paired t test (*, p < 0.05)

Fig. 2

Low PLAC2 levels predicted poor survival. Among 70 NSCLC patients, non-metastasis (NM) was found in 17 cases, lymph node metastasis-only (LNM) was found in 38 cases and distant metastasis (DM) was found in 17 cases. Expression levels of PLAC2 were compared among groups by performing one-way ANOVA and Tukey test. It was found that expression levels of PLAC2 were significantly lower in DM group than in LNM and NM groups. In addition, expression levels of PLAC2 were also significantly lower in LNM than in NM groups (a), (*, p < 0.05). Survival analysis was performed using K-M method and log-rank test. It was observed that patients with low PLAC2 levels in NSCLC tissues had much worse survival (b)

Fig. 3

PLAC2 over-expression resulted in miR-21 down-regulation in NSCLC cells. Linear regression was used to analyze the correlation between PLAC2 and miR-21. In NSCLC tissues, PLAC2 and miR-21 were inversely and significantly correlated (a). In non-tumor tissues, PLAC2 and miR-21 were not significantly correlated (b). PLAC2 and miR-21 over-expression was achieved at 24 h after transfection (c). Moreover, PLAC2 over-expression in NSCLC cells resulted in the down-regulation of miR-21 (d). However, miR-21 over-expression did not significantly affect PLAC2 expression (e)

Fig. 4

PLAC2 over-expression resulted in PTEN upregulation at the mRNA level in NSCLC cells. PTEN mRNA was detected at 24 h after the transfection of the PLAC2 expression vector, and expression data were analyzed by one-way ANOVA and Turkey test It was observed that PTEN mRNA levels were significantly increased in cells with PLAC2 over-expression (*, p < 0.05)

Fig. 5

PLAC2 regulated NSCLC cell invasion and migration through miR-21. Cell migration and invasion data analyzed by one-way ANOVA and Tukey test. It showed that compared to two controls (C and NC), PLAC2 over-expression resulted in decreased invasion a) and migration (b) rates of NSCLC cells. MiR-21 over-expression attenuated the effects of PLAC2 over-expression (*, p < 0.05)