We previously reported frequent loss of heterozygosity on chromosome 9p in esophageal carcinomas and suggested that a tumor suppressor gene located on this chromosomal arm might be involved in development of these cancers. Since recently published studies have shown that a gene mapped on chromosome 9p21, MTS1/CDK4I (multiple tumor suppressor 1/cyclin-dependent kinase 4 inhibitor), is frequently mutated in various types of tumors, we chose to examine esophageal squamous cell carcinomas for mutations in this candidate gene. DNA sequence analyses revealed somatic mutations of MTS1/CDK4I in 14 of 27 tumors examined; 8 were frame-shift mutations and 6 were missense mutations. These results suggested that the MTS1/CDK4I gene is a tumor suppressor the inactivation of which plays an important role during carcinogenesis of the squamous cell type of esophageal carcinoma.

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This work was supported by a Grant-in-Aid from the Ministry of Science, Culture, and Education, Japan.

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