Preliminary results of first clinical studies with the
enzyme neuraminidase call attention to a new kind of
cancer treatment. This promising approach to
tumor immunotherapy was entered into the clinical phase as a consequence of successful experimental studies in
tumor-bearing mice, rats and dogs. In this review, the presently known and essential results of experimental and clinical studies on
tumor immunotherapy by means of
neuraminidase are presented as well as some necessary and critical considerations in this context. Moreover, out of a broad variety of results of biochemical and
biological in vitro studies, it was attempted to select the more essential knowledge which could contribute to a better understanding of the still rather unclear in vivo mode of action of the
enzyme neuraminidase. In a first brief paragraph (1.0), the biochemically characteristic data of the
enzyme neuraminidase is presented. In the second section (2.0), the basic knowledge about the effects of
neuraminidase on cell behavior is rather amply contained. Here, on the one hand, the biophysical and biochemical alterations are mentioned, the so-called ""unmasking'' effects are reconsidered and, on the other hand, the effects on the immunologically responding cell are discussed. In a third section (3.0), the diverse findings from animal experiments using
neuraminidase-treated
tumor cells are confronted, whereby
tumor transplantation experiments and
tumor therapy experiments are dealt with separately. The last section (4.0) reports about the first clinical studies with
neuraminidase-treated autologous as well as homologous
tumor cells, which partly brought about rather surprising and astonishing success. On the basis of recent findings by the study group of the authors, the more prior and sometimes discrepant results of various groups are critically considered. The problems of alteration of antigenicity and of other properties of cells through splitting off membrane-bound neuraminic
acid, the facts of adjuvanticity of
neuraminidase itself, the relation of successful therapy to dose dependency as well as the relation of undesirable methods for
tumor mass reduction to the immunological responsiveness of the
tumor bearer were especially looked into.