Targeting Na+/K+-ATPase in non-small cell lung cancer (NSCLC)

18144 Background: Non-small cell lung cancer patients that present with grade IIIB or stage IV disease have a median survival of 5–7 months if left untreated. With modern chemotherapy overall survival may be 11–12 months, but still no patients are cured. We have investigated the impact of modulation of the a-1 subunit of Na+/K+-ATPase in NSCLC. Methods: Cancer tissue from 59 patients with NSCLC (30 adenocarcinomas and 29 squamous cell cancers) and 25 normal lung samples as well as four human NSCLC cell lines (A549, Cal-12T, NCI-H727, A427) were assessed with regard to expression of the a-1 subunit of Na+/K+-ATPase (sodium pump) by use of immunohistochemistry. In addition, A549 cells were transfected with specific a-1 siRNA for study of a-1 subunit expression and of cell proliferation and migration. Protein expression was analyzed by Western blotting. Cell proliferation was assessed by MTT and cell migration by video microscopy. Cell lines were exposed to varying concentrations of ouabain, digoxin, digitoxin and UNBS1450, a novel cardenolide targeting the a-1 subunit of Na+/K+-ATPase for study of proliferation, migration, and inhibition of the target. Results: Expression of the a-1 subunit of Na+/K+- ATPase was elevated in almost half of the tissue samples from patients with NSCLC compared to normal controls. The a-1 subunit was also overexpressed in A549, Cal-12T and NCI-H727 cells. Transfection of A549 cells with siRNA resulted in markedly decreased expression of the a- 1 subunit and also to reduced migration and proliferation of such cells. UNBS1450 at 10 and 100 nM for 72 hours reduced A549 cell migration and proliferation similar to that observed with anti- a-1 siRNA. Digoxin had no activity at these concentrations. Conclusions: Inhibition of the a-1 subunit of Na+/K+-ATPase is associated with significant decrease of cell migration and proliferation and has potential as a therapeutic strategy in NSCLC. No significant financial relationships to disclose.