N-mytistoyltransferase 1 and 2 are potential tumor suppressors and novel targets of miR-182 in human non-small cell lung carcinomas

Abstract

Background & aims

Non-small cell lung cancer (NSCLC) accounts for about 80% of lung cancer diagnoses across the world. Despite recent appreciable improvements in treatment plans for patients with NSCLC, the prognosis for those with the cancer still remains poor. Recently, a growing number of studies have shown that N-myristoyltransferases (NMTs) may be critical in carcinogenesis, however, the functional and clinical significance of this pathway in NSCLC remains unclear and requires further research.

Methods

Initially, we evaluated the expression levels of NMT1 or NMT2 in a clinical cohort comprising of 303 paired primary NSCLC tissues and matched normal mucosae by using ELISA. We subsequently performed a tissue microarray analysis (TMA) to confirm its expression pattern in an independent validation cohort (n = 78). Then, we used a publicly available KM plotter database (n = 1921) to evaluate the prognostic impact of NMT1 and NMT2 in NSCLC. Lastly, a series of in-vitro molecular/cellular and animal experiments were performed for mechanistic understanding of the role of N-myristoyltransferases in NSCLC.

Results

Our ELISA data revealed that the expression level of NMT1 and NMT2 was down-regulated in tumor tissues (n = 303, P < 0.0001), which was confirmed in an independent validation cohort by TMA (n = 78, P = 0.014 for NMT1 and P < 0.0001 for NMT2). On the other hand, patients with low expression of NMT1 or NMT2 had shorter overall survival (P = 0.013, HR = 0.85 for NMT1; P = 0.00059, HR = 0.8, for NMT2). Mechanistically, we revealed that the interaction and co-localization of NMT1 and NMT2 in NSCLC, and N-terminus of NMT1 and NMT2 was observed to be crucial for their interaction as well as for their catalytic activity. Moreover, we found that NMT1 can significantly promote the expression of NMT2 by enhancing its stability. We corroborated these findings by performing functional assays in which the knockout of NMT1 and NMT2 resulted in enhanced cell proliferation, migration and invasion as well as increased tumorxenograftgrowth. In addition, we identified miR-182 as a novel regulator of both NMT1 and NMT2. More specifically, the overexpression or inhibition of miR-182 modulated globe N-myristoylation level, contributed to phenotypic alterations in NSCLS cells.

Conclusions

NMT1 and NMT2 can act as potential tumor suppressors in NSCLC, and the inhibition of miR-182 expression or therapeutic NMTs replenishment may be a promising treatment option for patients with NSCLC.