Experimental validation was performed using clinical samples from NSCLC patients (n = 12) and <i>in vitro</i> assays with A549 and H1299 cell lines to assess CLK1 expression and its effect on proliferation.<h4>Results</h4>Contrary to its oncogenic role in other cancers, CLK1 acts as a tumor suppressor in NSCLC. The gene discussed is CLK1; the disease is neoplasm.