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 α/tumor necrosis factor α receptor inhibitor, interleukin-1α /interleukin-1α 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.