LncRNA BRCAT54 inhibits the tumorigenesis of non-small cell lung cancer by binding to RPS9 to transcriptionally regulate JAK-STAT and calcium pathway genes.

OBJECTIVES: Increasing evidence suggest that long non-coding RNAs (lncRNAs) play critical roles in cancers. However, the expression pattern and underlying mechanisms of lncRNAs in non-small cell lung cancer (NSCLC) remain incompletely understood. This study aimed to elucidate the functions and molecular mechanisms of a certain lncRNA in NSCLC. METHODS: LncRNA microarray was performed to identify differential expressed lncRNAs between pre- and postoperation plasma in NSCLC patients. The expression level of candidate lncRNA in NSCLC tissues, plasma and cells was determined by quantitative real-time PCR (qRT-PCR) and in situ hybridization. The functional roles of lncRNA were assessed in vitro and in vivo. Furthermore, RNA pull-down, RNA immunoprecipitation, microarray, qRT-PCR and rescue assays were conducted to explore the mechanism action of lncRNA in NSCLC cells. RESULTS: We identified a novel lncRNA (BRCAT54), which was significantly upregulated in preoperative plasma, NSCLC tissues and NSCLC cells, and its higher expression was associated with better prognosis in patients with NSCLC. Overexpression of BRCAT54 inhibited proliferation, migration and activated apoptosis in NSCLC cells. Conversely, knockdown of BRCAT54 reversed the suppressive effects of BRCAT54. Moreover, overexpression of BRCAT54 repressed NSCLC cell growth in vivo. Mechanistically, BRCAT54 directly bound to RPS9. Knockdown of RPS9 substantially reversed the promoting effects of si-BRCAT54 on cell proliferation and enhanced the inhibitive effect of si-BRCAT54 on BRCAT54 expression. In addition, silencing of RPS9 activated JAK-STAT pathway and suppressed calcium signaling pathway gene expressions. CONCLUSION: This study identified BRCAT54 as a tumor suppressor in NSCLC. Targeting the BRCAT54 and RPS9 feedback loop might be a novel therapeutic strategy for NSCLC.

Inhibiting polo-like kinase 1 enhances radiosensitization via modulating DNA repair proteins in non-small-cell lung cancer.

To assure faithful chromosome segregation, cells make use of the spindle assembly checkpoint, which can be activated in aneuploid cancer cells. In this study, the efficacies of inhibiting polo-like kinase 1 (PLK1) on the radiosensitization of non-small-cell lung cancer (NSCLC) cells were studied. Clonogenic survival assay was performed to identify the effects of the PLK1 inhibitor on radiosensitivity within NSCLC cells. Mitotic catastrophe assessment was used to measure the cell death and histone H2AX protein (γH2AX) foci were utilized to assess the DNA double-strand breaks (DSB). The transcriptome was analyzed via unbiased profiling of microarray expression. The results showed that the postradiation mitotic catastrophe induction and the DSB repair were induced by PLK1 inhibitor BI-6727, leading to an increase in the radiosensitivity of NSCLC cells. BI-6727 in combination with radiation significantly induced the delayed tumor growth. PLK1-silenced NSCLC cells showed an altered mRNA and protein expression related to DNA damaging, replication, and repairing, including the DNA-dependent protein kinase (DNAPK) and topoisomerase II alpha (TOPO2A). Furthermore, inhibition of PLK1 blocked 2 important DNA repair pathways. To summarize, our study showed PLK1 kinase as an option in the therapy of NSCLC.