Increased IR-A/IR-B ratio in non-small cell lung cancers associates with lower epithelial-mesenchymal transition signature and longer survival in squamous cell lung carcinoma

BACKGROUND: To evaluate the insulin receptor isoform mRNA expression status in non-small cell lung cancer (NSCLC) patients. METHODS: RNA-seq data from 614 NSCLC [355 adenocarcinomas (LUAD) and 259 squamous cell carcinomas (LUSC)] and 92 normal lung specimens were obtained from The Cancer Genome Atlas (TCGA) to evaluate the mRNA expression of insulin receptor isoform A (IR-A) and insulin receptor isoform B (IR-B). The differential expression status of the insulin receptor isoforms in NSCLC patients was confirmed using qRT-PCR assays with lung cancer cDNA arrays and primary tumor samples. RESULTS: The mRNA expression levels of IR-B were significantly lower in some NSCLC samples compared to normal lung specimens, including both LUAD and LUSC. Notably, no IR-B transcripts were detected - only the IR-A isoform was expressed in 11% of NSCLC patients. This decrease in IR-B expression contributed to an elevated IR-A/IR-B ratio, which was also associated with lower epithelial-mesenchymal transition gene signatures in NSCLC and longer patient survival under standard of care in LUSC. In addition to NSCLC, RNA-seq data from TCGA revealed a similar increase in IR-A/IR-B ratio in many other cancer types, with high prevalence in acute myeloid leukemia, glioblastoma multiforme, and brain lower grade glioma. CONCLUSIONS: Our results indicate a common reduction of the mRNA expression level of IR-B and an increased IR-A/IR-B mRNA ratio in NSCLC and other tumor types. The relationship of altered IR-A/IR-B ratios with cancer progression and patient survival should be prospectively explored in future studies.