Our analyses of tumor-suppressive microRNAs (miRNAs) and their target oncogenes have identified novel molecular networks in lung adenocarcinoma (LUAD). Moreover, our recent studies revealed that some passenger strands of miRNAs contribute to cancer cell malignant transformation. Downregulation of both strands of the miR-143 duplex was observed in LUAD clinical specimens. Ectopic expression of these miRNAs suppressed malignant phenotypes in cancer cells, suggesting that these miRNAs have tumor-suppressive activities in LUAD cells. Here, we evaluated miR-143-5p molecular networks in LUAD using genome-wide gene expression and miRNA database analyses. Twenty-two genes were identified as potential miR-143-5p-controlled genes in LUAD cells. Interestingly, the expression of 11 genes (MCM4, RAD51, FAM111B, CLGN, KRT80, GPC1, MTL5, NETO2, FANCA, MTFR1, and TTLL12) was a prognostic factor for the patients with LUAD. Furthermore, knockdown assays using siRNAs showed that downregulation of MCM4 suppressed cell growth, migration, and invasion in LUAD cells. Aberrant expression of MCM4 was confirmed in the clinical specimens of LUAD. Thus, we showed that miR-143-5p and its target genes were involved in the molecular pathogenesis of LUAD. Identification of tumor-suppressive miRNAs and their target oncogenes may be an effective strategy for elucidation of the molecular oncogenic networks of this disease.

Asparagine-linked glycosylation (N-glycosylation) of proteins in the cancer secretome has been gaining increasing attention as a potential biomarker for cancer detection and diagnosis. Small extracellular vesicles (sEVs) constitute a large part of the cancer secretome, yet little is known about whether their N-glycosylation status reflects known cancer characteristics. Here, we investigated the N-glycosylation of sEVs released from small-cell lung carcinoma (SCLC) and non–small-cell lung carcinoma (NSCLC) cells. We found that the N-glycans of SCLC-sEVs were characterized by the presence of structural units also found in the brain N-glycome, while NSCLC-sEVs were dominated by typical lung-type N-glycans with NSCLC-associated core fucosylation. In addition, lectin-assisted N-glycoproteomics of SCLC-sEVs and NSCLC-sEVs revealed that integrin αV was commonly expressed in sEVs of both cancer cell types, while the epithelium-specific integrin α6β4 heterodimer was selectively expressed in NSCLC-sEVs. Importantly, N-glycomics of the immunopurified integrin α6 from NSCLC-sEVs identified NSCLC-type N-glycans on this integrin subunit. Thus, we conclude that protein N-glycosylation in lung cancer sEVs may potentially reflect the histology of lung cancers.

Based on our miRNA expression signatures, we focused on miR-150-5p (the guide strand) and miR-150-3p (the passenger strand) to investigate their functional significance in lung adenocarcinoma (LUAD). Downregulation of miR-150 duplex was confirmed in LUAD clinical specimens. In vitro assays revealed that ectopic expression of miR-150-5p and miR-150-3p inhibited cancer cell malignancy. We performed genome-wide gene expression analyses and in silico database searches to identify their oncogenic targets in LUAD cells. A total of 41 and 26 genes were identified as miR-150-5p and miR-150-3p targets, respectively, and they were closely involved in LUAD pathogenesis. Among the targets, we investigated the oncogenic roles of tensin 4 (TNS4) because high expression of TNS4 was strongly related to poorer prognosis of LUAD patients (disease-free survival: p = 0.0213 and overall survival: p = 0.0003). Expression of TNS4 was directly regulated by miR-150-3p in LUAD cells. Aberrant expression of TNS4 was detected in LUAD clinical specimens and its aberrant expression increased the aggressiveness of LUAD cells. Furthermore, we identified genes downstream from TNS4 that were associated with critical regulators of genomic stability. Our approach (discovery of anti-tumor miRNAs and their target RNAs for LUAD) will contribute to the elucidation of molecular networks involved in the malignant transformation of LUAD.