Four distinct sequence alterations were identified: (a) in one gastric and one esophageal tumor, an A to C transversion occurred at nucleotide 5795 (CAC-->CCC), leading to a His-->Pro substitution at codon 179; (b) a second esophageal tumor had a C to T transition at nucleotide 8291 (ACC-->ATC), leading to a Thr-->Ile substitution at codon 277 of IGFBP-3; (c) one alteration comprised a G to C transversion in exon 1 at nucleotide 2132 (GGG-->GCG), leading to a Gly-->Ala substitution at codon 32 in two gastric cancers, seven esophageal cancers, and nine colon cancers; and (d) a C to G transversion located 17 nucleotides from the 3' splice site in intron 1 was observed in three colon cancers and four esophageal cancers.