[New aspects in oncological research (author's transl)].

Following the presentation of some theories of cancer etiology the significance of the cell membrane in neoplastic transformation is stressed. Alterations of the cell surface are blamed responsible for the abnormal proliferative behaviour and metastasis of cancer cells. In addition, the disturbance of membrane-bound receptor structures might result in defects of "endocrine" control mechanisms leading to the typical uncontrolled growth of tumor cells. In this context, the membrane-bound adenylate-cyclase system deserves special interest, since hormone impulses stimulate this enzyme via specific receptors to produce cyclic AMP. This nucleotide transmits hormonal signals within the cell. Our own studies on lymphoma and leukemic cells are mentioned because they demonstrate alterations of the cAMP producing system in malignant cells. Finally, the phenomenon of cell fusion is discussed. Recently great attention has been paid to this technique, since hybridization experiments enable us to get new insight into the process of neoplastic transformation.