Other examples for sudden qualitative changes of biological phenotypes that could be modeled by a dynamical system are (i) induction of tumor growth in non-tumor bearing areas in Rous sarcoma virus infected chicken by wounding or TGF-β [15], (ii) tumor stem cell fate decisions, or (iii) clinically observed but unexplained spontaneous tumor regression. This evidence concerns the gene TGFB1 and neoplasm.