Epidermal growth factor receptor up-regulation is associated with lung growth after lobectomy

Background. We hypothesized that compensatory lung growth after lobectomy i s characterized by a combination of cellular hyperplasia and hypertrophy an d that upregulation of epidermal growth factor receptor (EGFR) is involved in these processes. Methods. Age-matched mature pigs were divided into four groups. The control group (group C) did not have operation. Two groups underwent left upper lo bectomy and were studied 2 weeks (group L2) or 3 months (group L3) later. T he last group underwent a sham left thoracotomy, and the left lower lobe wa s harvested 2 weeks later for EGFR analysis. Left lower lobes were studied using wet weight, cell proliferation index through immunostaining for 5-bro mo-2 ' -deoxyuridine, morphometry, and Western blot analysis for EGFR. Cont ent of protein and DNA (deoxyribonucleic acid) in the lung tissue was also determined. Results. Left lower lobe weights were elevated in both groups L2 and L3 com pared with group C. We noted a significant rise in the proliferation index, with a concomitant increase in EGFR expression, in group L2 compared with group C. In group L3, there was an increase in the protein to DNA ratio com pared with group C. Conclusions. We conclude that compensatory lung growth after lobectomy comp rises an early increase in the cell proliferation index (ie, cellular hyper plasia) and a late increase in the protein to DNA ratio (ie, cellular hyper trophy). The early proliferative phase is associated with EGFR up-regulatio n. (C) 2001 by The Society of Thoracic Surgeons.