Clinical analysis of NSCLC patients reveals lack of association between EGFR mutation and TET1 downregulation

Lung cancer is one of the leading causes of death from cancer worldwide, with a poor prognosis in advanced cases. In the past decade, epidermal growth factor receptor (EGFR) inhibitors have shown significant efficacy towards treatment for EGFR mutant lung cancer. Expanding our knowledge of oncogenic EGFR signaling pathways is therefore of highly importance for the cancer field. Recently it has been proposed that mutant EGFR transcriptionally silences the TET1 (ten-eleven translocation methylcytosine dioxygenase 1) gene in cellular and animal models of lung cancer. Since TET1 is a known DNA demethylase, EGFR-mediated TET1 silencing therefore downregulates demethylation of tumor suppressor genes, which then leads to tumor growth inhibition, potentiating the role of TET1 as a tumor suppressor gene in NSCLC. In our study, we examined the role of EGFR-TET1 silencing in NSCLC patient samples. By independently analyzing the TCGA (The Cancer Genome Atlas) NSCLC data set as well as a cohort of patient samples from our hospital and a data set from publicly deposited databases, we did not observe the aforementioned mutant EGFR silencing of TET1. Conversely, in our cohort, TET1 expression levels were significantly elevated in EGFR mutant samples (P=0.007). Patients with higher TET1 levels showed a trend of better response rates to EGFR inhibitors compared to low TET1 staining levels, although the result was not significant (P=0.08). Furthermore, we did not observe a correlation between TET1 expression levels and patient survival. We conclude that while oncogenic EGFR suppression of TET1 is established in cellular and animal models of lung cancer, its role in patient outcome and prognosis remains inconclusive and warrants further investigation.