DPC4 gene mutation in colitis associated neoplasia

Area of Science:

• Oncology
• Genetics
• Gastroenterology

Background:

• Colitis-associated dysplasia and cancer frequently exhibit deletions on chromosome 18q.
• This suggests the presence of a critical tumor suppressor gene in this region.
• The DPC4 gene, known to be inactivated in other cancers, is located at 18q21.1.

Purpose of the Study:

• To investigate the hypothesis that the DPC4 gene is a mutated tumor suppressor in colitis-associated neoplasms.
• To determine if DPC4 mutations contribute to tumorigenesis in chronic colitis.

Main Methods:

• Analysis of advanced neoplastic lesions from six patients with chronic colitis.
• Polymerase chain reaction (PCR) amplification and sequencing of individual DPC4 exons.
• Genomic DNA extraction from cryostat-dissected tissue specimens.

Main Results:

• Biallelic inactivation of the DPC4 gene was observed in one of three neoplasms with 18q allelic loss.
• The mutation occurred somatically within a high-grade dysplasia plaque.
• The identified mutation resulted in a premature stop codon, leading to truncated protein translation.

Conclusions:

• The DPC4 gene is a direct target of 18q loss of heterozygosity (LOH) events in colitis-associated neoplasia.
• These findings implicate DPC4 as a tumor suppressor gene in the development of cancer in chronic colitis.