Homeobox genes: molecular link between congenital anomalies and cancer.

Homeobox-containing genes play a major role in the control of segmental identity during embryonic development in Drosophila. Abnormalities of these genes have been shown to produce a wide variety of congenital anomalies in invertebrates and in vertebrates. Many transgenic mice, which are mutant for homeobox genes, show a specific skeletal abnormality, similar to the human cervical rib. In humans, a relationship exists between malformations and tumours. Human cervical rib has been shown to be associated with an increased incidence of malignancy. Recent evidence indicates that homeobox genes might also play a role in carcinogenesis. In this article, we explore the possibility that alterations of homeobox genes might be the basic underlying aetiology for the association between congenital malformations and tumours, at least in a proportion of cases. We provide evidence in support of this argument and suggest areas of further research which would confirm this concept.