Objective: Circular ribonucleic acids (circRNAs) are considered as the key regulatory factors for human malignancies in recent years, and lung adenocarcinoma (LUAD) is a common malignancy worldwide, but the molecular mechanism of circRNAs in LUAD has not been completely investigated. Therefore, the mechanism by which circRNA protein kinase C iota (circPRKCI) regulates LUAD cell migration proliferation, and cycle was preliminarily explored in this research, so as to provide new ideas for the treatment of LUAD.
Patients and methods: First of all, the circPRKCI expression level in LUAD tissues was tested via quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay, and the relationship between circPRKCI and the patients' prognosis was analyzed. Then, circPRKCI expression was inhibited by small interfering RNA (siRNA), and the influence of circPRKCI on t LUAD cells' ability to proliferate was verified via 5-ethynyl-2'-deoxyuridine (EdU) and cell counting kit-8 (CCK-8) assays. Moreover, the influence of circPRKCI on LUAD cells' ability to migrate was testified by transwell assay, and the regulation of LUAD cell cycle by circPRKCI was confirmed by flow cytometry. The micro RNAs (miRNAs) with binding sites to the 3' untranslated region (UTR) of circPRKCI and the genes binding to miRNAs were discovered using bioinformatics websites, and their associative relation was further explored through Dual-Luciferase reporter gene assay, qRT-PCR assay, Pearson correlation analysis and reverse experiment.
Results: It was verified via qRT-PCR assay that circPRKCI was expressed at a remarkably higher level in LUAD tissues relative to that in paracancerous normal tissues. The highly expressed circPRKCI led to poor prognosis of patients. Besides, qRT-PCR assessment results indicated that circPRKCI expression level rose notably in LUAD cell lines, while it was lowered markedly in LUAD cells transfected with si-circPRKCI. According to CCK-8 and EdU assay results, the proliferative ability of LUAD cells was weakened clearly after knocking down circPRKCI. It was manifested in the results of transwell assay that the knockdown of circPRKCI significantly repressed the capacity of LUAD cells to migrate. Furthermore, the results of cell cycle test displayed that inhibiting circPRKCI could induce the arrest of LUAD cell cycle in the G1 phase. It was discovered through bioinformatics websites that miR-219a-5p had binding sites to circPRKCI 3'UTR, and the results of Dual-Luciferase reporter gene assay revealed that circPRKCI was able to bind to miR-219a-5p. It was uncovered by the qRT-PCR assay results that miR-219a-5p was lowly expressed in LUAD tissues, and its relative expression had an inverse relation with that of circPRKCI according to the Pearson correlation analysis. In addition, it was shown in the results of reverse experiment that miR-219a-5p could regulate the influence of circPRKCI on the malignant phenotype of LUAD. It was found by means of bioinformatics websites that calcium/calmodulin dependent protein kinase ID (CAMK1D) was a downstream target gene of miR-219a-5p and could the two conjugated with each other based on the results of Dual-Luciferase reporter gene assay. Moreover, qRT-PCR assay findings illustrated that CAMK1D was evidently highly expressed in LUAD tissues, and the results of Pearson correlation analysis revealed that CAMK1D expression exhibited a negative association with that of miR-219a-5p and a positive correlation with that of circPRKCI.
Conclusions: CircPRKCI is significantly highly expressed in LUAD, and the highly expressed circPRKCI is capable of facilitating LUAD cell migration, proliferation and cycle. CircPRKCI may regulate the malignant phenotype of LUAD via the miR-219a-5p/CAMK1D axis.