APC and malignant colon neoplasm: Besides the loss of heterozygosity affecting the APC locus that we have found in HGUE-C-1 cells, we have studied different signal transduction pathways looking for modifications that we could associate with HGUE-C-1 tumourigenesis and, we have compared these results with the findings obtained in HT-29 colon cancer cells, since this cell line constitutes a paradigm of the colon carcinogenesis pathway proposed by Vogelstein et al. [25].