23. Tsushima H, Kawata S, Tamura S, Ito N, Shirai Y, Kiso S, Imai Y, Shimomukai H, Nomura Y, Matsuda Y et al : High levels of transforming growth factor beta 1 in patients with colorectal cancer: association with disease progression . Gastroenterology 1996, 110(2):375-382.