Abstract
Relapse rates in surgically resected non-small-cell lung cancer (NSCLC) patients are between 30% and 45% within five years of diagnosis, which shows the clinical need to identify those patients at high risk of recurrence. The eighth TNM staging system recently refined the classification of NSCLC patients and their associated prognosis, but molecular biomarkers could improve the heterogeneous outcomes found within each stage. Here, using two independent cohorts (MDA and CIMA-CUN) and the eighth TNM classification, we show that TMPRSS4 protein expression is an independent prognostic factor in NSCLC, particularly for patients at stage I: relapse-free survival (RFS) HR, 2.42 (95% CI, 1.47–3.99), p < 0.001; overall survival (OS) HR, 1.99 (95% CI, 1.25–3.16), p = 0.004). In stage IA, high levels of this protein remained associated with worse prognosis (p = 0.002 for RFS and p = 0.001 for OS). As TMPRSS4 expression is epigenetically regulated, methylation status could be used in circulating tumor DNA from liquid biopsies to monitor patients. We developed a digital droplet PCR (ddPCR) method to quantify absolute copy numbers of methylated and unmethylated CpGs within the TMPRSS4 and SHOX2 (as control) promoters in plasma and bronchoalveolar lavage (BAL) samples. In case-control studies, we demonstrated that TMPRSS4 hypomethylation can be used as a diagnostic tool in early stages, with an AUROC of 0.72 (p = 0.008; 91% specificity and 52% sensitivity) for BAL and 0.73 (p = 0.015; 65% specificity and 90% sensitivity) for plasma, in early stages. In conclusion, TMPRSS4 protein expression can be used to stratify patients at high risk of relapse/death in very early stages NSCLC patients. Moreover, analysis of TMPRSS4 methylation status by ddPCR in blood and BAL is feasible and could serve as a non-invasive biomarker to monitor surgically resected patients.
Highlights
Management of lung cancer, the leading type of cancer worldwide, is still challenging, and mortality rates did not substantially decrease in the latest years [1]
We previously showed in animal models that abrogation of Transmembrane protease serine 4 (TMPRSS4) using short hairpin RNA strategies impedes tumor homing and growth [5], suggesting that targeting this protein in non-small-cell lung cancer (NSCLC) may result in a strong therapeutic effect
We proved that methylation status of TMPRSS4 and stature homeobox 2 (SHOX2) can be accurately quantified by Digital droplet PCR (ddPCR) in both plasma and bronchoalveolar lavage (BAL) from NSCLC patients and healthy individuals
Summary
Management of lung cancer, the leading type of cancer worldwide, is still challenging, and mortality rates did not substantially decrease in the latest years [1]. When diagnosed in early stages, patients with lung cancer can be successfully treated with surgery. Recurrence rates after complete surgical resection are between 30% and 45% within five years of diagnosis [2]. Identification of factors that could predict patients at risk of recurrence after surgery is necessary for a better management of the disease. The tumor-node-metastasis (TNM) staging system is the only routine method to estimate prognosis in non-small-cell lung cancer (NSCLC) patients. In spite of the new classification (eighth edition [3]), survival prediction is not totally accurate, as different clinical outcomes are observed in patients within the same TNM stage. It was suggested that molecular biomarkers could help identifying patients with poor prognosis based on biological malignant features [4], incorporation of such biomarkers into the clinical practice remains to be implemented
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