Influence of pleural macrophages on proliferative activity and apoptosis regulating proteins of malignant cells.

Malignant tumors contain numerous macrophages as a major component of the leukocytic infiltrate. Only few studies have evaluated the interaction between products secreted by macrophages and tumor cells. Our objective was to study soluble factors produced by pleural macrophages. We sampled pleural effusions from patients with cancer and used human tumor cell lines as targets. Pleural macrophages were cultured and the supernatants were used as a conditioned medium for cultures of human cell lines A549, HT29, HCT116, SW620, MCF7, MDA-MB231, JURKAT, and HL60. We investigated apoptosis, proliferative activity, and expression of apoptosis regulating proteins Fas, Bcl2, Caspase-3, and survivin of malignant cells cultured in the conditioned medium. Our findings raise the possibility that macrophages from malignant pleural effusions can act as a factor inhibiting apoptosis of malignant cells.