Mechanistic Study of TTF-1 Modulation of Cellular Sensitivity to Cisplatin

Significance of NKX2-1 as a biomarker for clinical prognosis, immune infiltration, and drug therapy in lung squamous cell carcinoma

Background

This study was performed to determine the biological processes in which NKX2-1 is involved and thus its role in the development of lung squamous cell carcinoma (LUSC) toward improving the prognosis and treatment of LUSC.

Methods

Raw RNA sequencing (RNA-seq) data of LUSC from The Cancer Genome Atlas (TCGA) were used in bioinformatics analysis to characterize NKX2-1 expression levels in tumor and normal tissues. Survival analysis of Kaplan-Meier curve, the time-dependent receiver operating characteristic (ROC) curve, and a nomogram were used to analyze the prognosis value of NKX2-1 for LUSC in terms of overall survival (OS) and progression-free survival (PFS). Then, differentially expressed genes (DEGs) were identified, and Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Gene Set Enrichment Analysis (GSEA) were used to clarify the biological mechanisms potentially involved in the development of LUSC. Moreover, the correlation between the NKX2-1 expression level and tumor mutation burden (TMB), tumor microenvironment (TME), and immune cell infiltration revealed that NKX2-1 participates in the development of LUSC. Finally, we studied the effects of NKX2-1 on drug therapy. To validate the protein and gene expression levels of NKX2-1 in LUSC, we employed immunohistochemistry(IHC) datasets, The Gene Expression Omnibus (GEO) database, and qRT-PCR analysis.

Results

NKX2-1 expression levels were significantly lower in LUSC than in normal lung tissue. It significantly differed in gender, stage and N classification. The survival analysis revealed that high expression of NKX2-1 had shorter OS and PFS in LUSC. The multivariate Cox regression hazard model showed the NKX2-1 expression as an independent prognostic factor. Then, the nomogram predicted LUSC prognosis. There are 51 upregulated DEGs and 49 downregulated DEGs in the NKX2-1 high-level groups. GO, KEGG and GSEA analysis revealed that DEGs were enriched in cell cycle and DNA replication.The TME results show that NKX2-1 expression was positively associated with mast cells resting, neutrophils, monocytes, T cells CD4 memory resting, and M2 macrophages but negatively associated with M1 macrophages. The TMB correlated negatively with NKX2-1 expression. The pharmacotherapy had great sensitivity in the NKX2-1 low-level group, the immunotherapy is no significant difference in the NKX2-1 low-level and high-level groups. The analysis of GEO data demonstrated concurrence with TCGA results. IHC revealed NKX2-1 protein expression in tumor tissues of both LUAD and LUSC. Meanwhile qRT-PCR analysis indicated a significantly lower NKX2-1 expression level in LUSC compared to LUAD. These qRT-PCR findings were consistent with co-expression analysis of NKX2-1.

Conclusion

We conclude that NKX2-1 is a potential biomarker for prognosis and treatment LUSC. A new insights of NKX2-1 in LUSC is still needed further research.

Loss of Gap Junction Factor Connexin 43 Results in an Increase of Exosomal Tetraspanins in Human Lung Cancer Cell Line A549

Gap junctions (GJs) and small extracellular vesicles such as exosomes are two fundamental intercellular communication (IC) mechanisms. We tested the hypothesis that the two IC mechanisms are connected by gene editing to inactivate a ubiquitously expression GJ factor (i.e., Cx43) in the human lung cancer cell line A549. Surprisingly, we observed that loss of Cx43 led to a buildup of exosomal tetraspanin proteins such as CD63 and CD9. Given the known activities of tetraspanins in cell-cell adhesion and vesicle uptake, our observation establishes an impetus to investigate further how these two IC mechanisms are intertwined.

CRISPR-Induced Loss of Connexin 43 Expression Sensitizes KRAS Mutant Cells to Cisplatin

Gap Junction intercellular communication (GJIC) is often dysregulated in cancers, and this dysregulation has been shown to have pro-tumorigenic effects. Connexins (Cxs) are transmembrane proteins that make up gap junctions. Previous studies have indicated that RNA interference (RNAi)-based suppression of Cx43 increases cellular resistance to the chemotherapeutic agent cisplatin. Interestingly, we found that the loss of Cx43 expression induced by the CRISPR-Cas9 technology sensitizes cells to cisplatin in a KRAS mutant-dependent manner.

Cisplatin sensitivity mediated by NKX2-1 in lung adenocarcinoma is dependent on p53 mutational status via modulating TNFSF10 expression

NKX2-1 was shown to enhance cisplatin sensitivity in KRAS-mutated cells, but it conferred cisplatin resistance in EGFR-mutated lung adenocarcinoma cells. However, NKX2-1 as a dual role in tumor progression depended on p53 mutational status via modulation of the NF-κB pathway. We hypothesized that NKX2-1 may confer cisplatin resistance in p53-mutated (p53-MT) lung adenocarcinoma cells but may enhance cisplatin sensitivity in wild-type (p53-WT) cells. In the present study, six p53-MT and -p53-WT cell lines were treated with various concentrations of cisplatin to calculate the inhibitory concentration of cisplatin for 50% cell viability (IC₅₀). The IC₅₀ value was positively correlated with NKX2-1 expression in the p53-MT cells but negatively correlated in the p53-WT cells. TNFSF10 was identified in a microarray analysis as a potential candidate responsible for NKX2-1-mediated apoptosis induced by cisplatin. The retrospective study evaluated 97 surgically resected lung adenocarcinoma patients receiving cisplatin-based chemotherapy to explore the possible association between NKX2-1 expression and tumor response. Patients with higher TNFSF10 mRNA levels, as determined by real-time reverse transcription-polymerase Chain Reaction (RT-PCR), typically showed an favorable response when compared with patients with lower TNFSF10 mRNA levels. Additionally, the association of higher TNFSF10 mRNA levels with favorable response was only revealed in p53-WT patients, not in p53-MT patients. Higher NKX2-1 mRNA levels were associated with an unfavorable response in patients with p53-MT tumors but a favorable response in patients with p53-WT tumors. In summary, modulation of TNFSF10 expression by NKX2-1 may be a potential indicator for predicting the response to cisplatin-based chemotherapy in patients with lung adenocarcinomas.

CD44 contributes to hyaluronan-mediated insulin resistance in skeletal muscle of high-fat-fed C57BL/6 mice

Extracellular matrix hyaluronan is increased in skeletal muscle of high-fat-fed insulin-resistant mice, and reduction of hyaluronan by PEGPH20 hyaluronidase ameliorates diet-induced insulin resistance (IR). CD44, the main hyaluronan receptor, is positively correlated with type 2 diabetes. This study determines the role of CD44 in skeletal muscle IR. Global CD44-deficient (cd44^-/-) mice and wild-type littermates (cd44^+/+) were fed a chow diet or 60% high-fat diet for 16 wk. High-fat-fed cd44^-/- mice were also treated with PEGPH20 to evaluate its CD44-dependent action. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp (ICv). High-fat feeding increased muscle CD44 protein expression. In the absence of differences in body weight and composition, despite lower clamp insulin during ICv, the cd44^-/- mice had sustained glucose infusion rate (GIR) regardless of diet. High-fat diet-induced muscle IR as evidenced by decreased muscle glucose uptake (Rg) was exhibited in cd44^+/+ mice but absent in cd44^-/- mice. Moreover, gastrocnemius Rg remained unchanged between genotypes on chow diet but was increased in high-fat-fed cd44^-/- compared with cd44^+/+ when normalized to clamp insulin concentrations. Ameliorated muscle IR in high-fat-fed cd44^-/- mice was associated with increased vascularization. In contrast to previously observed increases in wild-type mice, PEGPH20 treatment in high-fat-fed cd44^-/- mice did not change GIR or muscle Rg during ICv, suggesting a CD44-dependent action. In conclusion, genetic CD44 deletion improves muscle IR, and the beneficial effects of PEGPH20 are CD44-dependent. These results suggest a critical role of CD44 in promoting hyaluronan-mediated muscle IR, therefore representing a potential therapeutic target for diabetes.