Abnormal growth processes in plants and animals: a comparison

Tumorigenesis in eukaryotic organisms is based on the deregulation of normal cell growth and development. This deregulation may be elicited by external as well as endogenous factors. We distinguish between benign and malignant growths depending on the inducing tumorigenic agents and on the genetic make-up of the affected organism. This review discusses similarities of neoplasmatic (epigenetic) and neoplastic transformations in plants and animals as well as inherent differences in the growth parameters between the two kingdoms. Examples given for neoplasmatic tissues are the hyperplasias and insect galls (zoocecidia) in plants and hypoplasia, aplasia and agenesis in animals (and man). Neoplastic transformation in plants is the result of either the incorporation of foreign nuclear material into the plant genome or an imbalance of inherited chromosomes (in hybrids). Examples for neoplasias are the crown gall disease and Kostoff's genetic tumors in plants, and the carcinomas and leukemias in animals. The more than 80 year old, but neglected, concept of a correlation between tumorigenesis in animals and plants has been revived through advances in molecular and cell biology and molecular genetics which will stimulate a new form of biological reasoning and thought, fueled by new insights into cellular regulatory processes.