IMP4 Silencing Inhibits the Malignancy of Lung Adenocarcinoma via ERK Pathway.

Our study aimed to elucidate the function of IMP U3 small nucleolar ribonucleoprotein 4 (IMP4) in lung adenocarcinoma (LUAD) and its potential molecular mechanisms. Cell counting kit-8, 5-ethynyl-20-deoxyuridine, flow cytometry, wound healing, and transwell assays were performed to examine the biological behaviour of LUAD cells. mRNA and protein expression levels were determined using quantitative real-time PCR, Western blotting, and immunohistochemistry. In addition, a mouse tumour xenograft model was used to evaluate the role of IMP4 in tumour progression. Furthermore, glycolysis-related indicators were measured. The levels of IMP4 were up-regulated in both human LUAD tissues and cells. IMP4 silencing significantly suppressed proliferation, migration, invasion, and glycolysis; promoted apoptosis; and induced cell cycle arrest in LUAD cells. IMP4 silencing also inactivated the extracellular signal-regulated kinase (ERK) pathway. Moreover, rescue experiments demonstrated that the function of LUAD cells induced by IMP4 overexpression could be reversed by treatment with an ERK pathway inhibitor (SCH772984). In vivo experiments further verified that IMP4 silencing repressed the growth of subcutaneous tumours and glycolysis. IMP4 silencing suppressed the malignancy of LUAD by inactivating ERK signalling.

PTS is activated by ATF4 and promotes lung adenocarcinoma development via the Wnt pathway.

Background: The effects and mechanism of 6-pyruvoyl-tetrahydropterin synthase (PTS) on lung adenocarcinoma (LUAD) were studied in LUAD cells and mice with subcutaneously transplanted tumors. Methods: PTS level in tissues and cells was tested by immunohistochemistry, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). The impacts of PTS on cell viability, proliferation, apoptosis, invasion, and migration were determined by Cell Counting Kit-8 (CCK-8), colony formation assay, flow cytometry, transwell assay, and wound healing assay, respectively. The Cancer Genome Atlas (TCGA) analysis and dual luciferase assay were conducted to predict and verify the relationship between PTS and activating transcription factor 4 (ATF4). A mouse model was established by subcutaneous injection with cancer cells. Tumor volume was calculated as V = ab2/2. Ki67 and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining were used to measure cell proliferation and apoptosis in tumors. Results: PTS was highly expressed in LUAD. Higher PTS level was correlated with late clinical stages and poor survival of patients. Down-regulation of PTS inhibited the viability and proliferation and induced apoptosis of LUAD cells. PTS was activated by ATF4, and up-regulation of ATF4 reversed the inhibitory effect of PTS silencing on LUAD cells. Silencing of PTS inhibited the Wnt pathway. Down-regulation of PTS inhibited tumor growth in mice. Conclusions: PTS was highly expressed in LUAD. PTS was activated by ATF4 and promoted LUAD development via the Wnt pathway.