Cell membrane fluidity and prognosis of lung cancer

Background. Membranes of tumor cells have been found to posses higher fluidity than membranes of nontumor cells. Plasma membrane fluidity is significantly correlated with malignant potential of these cells. Methods. Seventy-five patients operated on for lung cancer were studied prospectively. During the operation, lung tumor samples were taken from the resected lung for evaluation by electron paramagnetic resonance. The fluidity variable H13, which is proportional to the plasma membrane fluidity, was determined from the electron paramagnetic resonance spectra. The association between H13 and survival was determined by survival analysis using Kaplan-Meier curves and Cox regression. Results. Pathologic TNM stage and the fluidity variable H13 were the only prognostic variables significantly associated with survival time in multivariate proportional hazards regression model. Thus, H13 was shown to be an independent prognostic variable for survival, which was also confirmed by a separate analysis relating the TNM stage and H13. Dividing the patients into two groups, one with an H13 value higher than the median and another with H13 below the median, resulted in significantly different survival curves (p = 0.01). Conclusions. Patients with high plasma membrane fluidity, indicated by high H13 of the resected lung tumor tissue, seem to have poorer prognosis than those with less fluid membranes. We suggest that the fluidity variable could be used as an independent additional prognostic factor and a tool to identify patients who may be helped by adjuvant postoperative therapy.