TKT and cancer: Thus, specific inhibition of EGFR and its intrinsic TK activity by different strategies (e.g. monoclonal antibodies, TK-inhibitors) has become a rationale for innovative cancer treatment (Ciardiello et al, 2000; Cullinane et al, 2000; Sirotnak et al, 2000; Overholser et al, 2000; Chan et al, 2001; Di Lorenzo et al, 2002; Sewell et al, 2002; Mendelsohn, 2003), – especially since the EGF receptor system is not only involved in tumour growth but also plays a significant role in tumour invasion, angiogenesis and adhesion (Woodburn, 1999; Ritter and Arteaga, 2003).