The aim of the present study was to investigate whether tumour cell supernatants of 4 different malignant tumour cell lines with different aggressive behaviour show comparable pathobiological reactions.
Mature mouse (C57/Bl6) macrophages were incubated with the a.m. different tumour cell supernatants and followed by the investigation of apoptosis factors using immunocytochemistry. In addition, the experiments were performed with Fas-knock-out mouse macrophages and PCR in order to investigate the involvement of the Fas/FasL system.
All tumour cell supernatants investigated induced a significant increase of apoptototic activities in macrophages compared with control groups. Interestingly, the tumour cell supernatants showed differences in their intensities of apoptosis-inducing effects on the macrophages one to each other. The Fas/FasL system has been identified as one of the involved factors from tumours which induce apotoses in macrophages.
Our observation of the induction of apoptoses in macrophages due to so far undefined tumour cell factors supports the counterattack hypothesis which supposes the active destruction of the tumoricidal cell system by neoplastic cells. For now, the counterattack is an exciting new way for research in tumour immunology and probably offers a therapeutic potential.