[Intercellular communication and Tumor Invasion in the Petri Dish]

Malignant tumor cells are characterized by their ability to invade and destroy normal tissues, whereas benign tumor cells grow locally and, therefore, can be treated with more success. Tumor cell invasion proceeds the formation of metastases, which account for the high mortality of cancer patients. We investigated whether tumor cells which communicate via trans-membrane channels (gap junctions) with each other as well as with normal cells can more easily invade normal tissues than non-communicating tumor cells. Five tumor cell lines were cultured as monolayers and investigated with histological methods for gap junction formation and with electrophysiological methods for intercellular communication. Tumor cells were tested with an in vitro invasion model: spheroidal cell aggregates of normal and of malignant cells were confronted in petri dishes and co-cultured for varying time spans. Thin sections revealed that only tumor cells with gap junctions can actively invade aggregates of normal cells. Tumor cells without gap junctions are unable to invade the normal tissue: they may, however, destroy the normal cells by a completely different mechanism which may be a result of particular culture conditions.