Frequent loss of SMAD4/DPC4 protein in colorectal cancers

• BACKGROUND AND AIMS: Loss of DNA sequences from chromosome 18q21 is a major genetic change in colorectal tumorigenesis. Multiple genes have been identified in this area. One of these, DPC4 (deleted in pancreatic cancer 4, also known as SMAD4), is mutated in a minor subset of colorectal carcinomas as well as in germlines of humans predisposed to colon tumours. PATIENTS AND METHODS: The involvement of SMAD4 in sporadic colorectal neoplasia was evaluated by immunohistochemistry in 53 unselected cases and 27 cases displaying microsatellite instability. RESULTS: SMAD4 expression was absent in 20 of 53 (38%) unselected colorectal carcinomas, and reduced in another 15 (28%) cases. However, 26 of 27 cancers displaying microsatellite instability and TGF-betaIIR mutations were positive for SMAD4 immunostaining. CONCLUSIONS: Loss of SMAD4 expression may play a more prominent role in colon cancer than anticipated based on genetic evidence, but not in mutator phenotype tumours.

Nyckelord

Chromosomes; Human; Pair 18/*genetics

Colorectal Neoplasms/chemistry/*genetics

DNA Mutational Analysis

DNA-Binding Proteins/analysis/*genetics

Gene Deletion

Genetic Markers

Humans

Immunohistochemistry/methods

Loss of Heterozygosity

Microsatellite Repeats

Receptors; Transforming Growth Factor beta/genetics

Smad4 Protein

Trans-Activators/analysis/*genetics

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