Differences in the tumour's microenvironment are known to determine antitumour efficacy of the treatment (Fidler, 1978, 1999) The precursor of endostatin, the long form of collagen XVIII, is almost exclusively found in the liver (Saarela et al, 1998) and mainly expressed by hepatocytes (Schuppan et al, 1998; Lietard et al, 2000). The gene discussed is COL18A1; the disease is neoplasm.