Expression of high‐mobility group‐1 mRNA in human gastrointestinal adenocarcinoma and corresponding non‐cancerous mucosa

An 1194‐nucleotide complementary DNA clone, FMI, encoding a human high‐mobility group‐I protein (HMG‐I) was isolated from a well‐differentiated human gastric‐carcinoma cell line complementary DNA library by a differential screening method. FMI is similar to the published human HMG‐I in mature protein, with only 3 different codons at positions 11, 149, and 190. We analyzed 33 gastric and colorectal adenocarcinomas for expression of the FMI gene. Northern‐blot analysis revealed that all of the cancers expressed FMI at a higher level than in corresponding non‐cancerous mucosa, with 2 transcripts of approximately 1.4 and 2.4 kilobases. The FMI expression level in the non‐cancerous tissues increased with the depth of accompanying cancer invasion. Only 18.2% of well‐differentiated cancers showed a higher expression level in corresponding non‐cancerous tissues, whereas the expression in corresponding non‐cancerous tissues was significantly higher in moderately (60%) and poorly differentiated (83.3%) cancers. In situ hybridization demonstrated the location of FMI mRNA in well‐ and poorly differentiated gastric‐cancer cells as well as in non‐cancerous tissue adjacent to poorly differentiated gastric cancer, but no hybridization was detected in normal epithelial cells adjacent to well‐differentiated gastric cancer. These findings may provide new information on HMG‐I mRNA expression in human gastrointestinal cancer and suggest a correlation between FMI mRNA expression to the differentiation and the stage of human gastrointestinal adenocarcinomas. Int. J. Cancer 74:1–6. © 1997 Wiley‐Liss, Inc.