Transgenic animals receptor overexpression

Overexpression of the EGF receptor (or any of its ligands), can also induce cancer in both cell lines and transgenic animal models. Monoclonal antibodies capable of blocking receptor activity can promote tumour regression in mice suffering from various carcinomas. A direct correlation also exists between elevated EGF receptor numbers and a shorter patient survival span in the case of several forms of breast, oesophageal, bladder and squamous cell carcinomas. 

If the biological effects of retinoids are mediated through their receptors, then alterations in the receptors are expected to be detrimental to the normal maintenance of structure and function of skin. In fact, in receptor gene knock-out mice and in mice in which dominant negative retinoid receptor transgenes are overexpressed, normal skin development and function are lost [24-27, 28]. Furthermore, when simultaneous null mutations of two RARs are introduced, the resultant phenotypic changes are similar to those observed in vitamin A-deficient animals [29]. 

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