Neutrophils promote aerogenous spread of lung adenocarcinoma with bronchioloalveolar carcinoma features.

PURPOSE Adenocarcinoma with bronchioloalveolar carcinoma (BAC) features is a subtype of non-small cell lung cancers characterized by an intense inflammatory reaction composed of macrophages and neutrophils and by a distinct natural history with intrapulmonary spread leading to death due to respiratory failure. We hypothesized that neutrophils could promote aerogenous spread of lung adenocarcinoma with BAC features. EXPERIMENTAL DESIGN We examined the effect of neutrophils on A549 cell line detachment in vitro and we quantified desquamation of tumor cells on tumor tissue (n = 25) and on matched bronchioloalveolar lavage (n = 17) in vivo in a series of patients with adenocarcinoma with BAC features. RESULTS Neutrophils induced A549 detachment mediated by signals through cell-to-cell contact. Detached A549 cells were still viable and able to proliferate in vitro. Neutralization studies identified several membrane-bound molecules involved in detachment (i.e., intercellular adhesion molecule-1/lymphocyte function-associated antigen-1, tumor necrosis factor alpha/tumor necrosis factor alpha receptor inhibitor, interleukin-1alpha /interleukin-1alpha receptor, and neutrophil elastase). In tumor tissue, shedding was detected in all samples, with a median shedding score of 42% (range, 4-95%). Micropapillary clusters were detected in 23 of the 25 tumor tissue samples, with a median micropapillary score of 1.40 (range, 0-2.1), and tumor cells were detected in 7 of 17 lavages. The micropapillary score was associated with a high neutrophil count in bronchioloalveolar lavage (P = 0.051). The shedding cell percentage was a significant factor in shorter survival (P = 0.034, univariate Cox analysis). CONCLUSIONS Tumor shedding is induced by neutrophils. It is a significant factor of shorter survival and may be an important event in adenocarcinoma progression.