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Genetic alterations and epithelial dysplasia in juvenile polyposis syndrome and sporadic juvenile polyps
1Department of Pathology, Johns Hopkins University School of Medicine and Hospital, Baltimore, Maryland, USA.
Insights
Juvenile polyposis syndrome increases gastrointestinal cancer risk. Genetic changes, including APC gene mutations and loss of cell cycle control, are linked to neoplastic transformation in these polyps, especially in syndromic cases.
Area of Science:
- Gastroenterology
- Molecular Biology
- Oncology
Background:
- Juvenile polyps are hamartomatous polyps associated with sporadic and familial syndromic settings.
- Juvenile polyposis syndrome carries an increased risk of gastrointestinal neoplasia, but underlying molecular mechanisms remain unclear.
Purpose of the Study:
- To investigate epithelial dysplasia and genetic alterations in juvenile polyps from patients with and without juvenile polyposis syndrome.
- To identify molecular mechanisms contributing to neoplastic transformation in juvenile polyps.
Main Methods:
- Analysis of 78 colorectal juvenile polyps from 12 patients with juvenile polyposis syndrome and 34 sporadic juvenile polyps.
- Assessment of epithelial dysplasia, p21(WAFI/CIP1) expression, and mutations in Adenomatous Polyposis Coli (APC) and K-ras genes.
- Immunohistochemical staining for p53 gene product overexpression.
Main Results:
- Dysplasia was observed in 31% of syndromic juvenile polyps but not in sporadic ones.
- Loss of topographic control of proliferation and p21(WAFI/CIP1) expression occurred in 79% of dysplastic and 8% of non-dysplastic polyps.
- Somatic APC mutations were found in 50% of dysplastic polyps, while K-ras mutations were present in 14% of both types, unrelated to dysplasia. p53 overexpression was rare.
Conclusions:
- Genetic alterations common in colorectal neoplasia, such as APC mutations, are involved in the neoplastic transformation of juvenile polyps.
- These molecular changes are particularly relevant in the context of juvenile polyposis syndrome, highlighting its association with increased cancer risk.
Abstract:
Juvenile polyps are regarded as hamartomatous polyps and occur in sporadic and familial syndromic settings. There is increased risk of gastrointestinal neoplasia in patients with juvenile polyposis syndrome, but the molecular mechanisms are not known. We therefore studied 78 colorectal juvenile polyposis from 12 patients with juvenile polyps syndrome and 34 sporadic juvenile polyps for epithelial dysplasia and genetic changes associated with colorectal neoplasia. Dysplasia occurred in 31% of syndromic juvenile polyps but not in sporadic juvenile polyps (P < 0.0001). Topographic control of proliferation and expression of the cyclin-dependent kinase inhibitor p21(WAFI/CIP1) seen in native colorectal epithelium was lost in 79% of dysplastic juvenile polyps and in 8% of nondysplastic juvenile polyps (P < 0.000001). Somatic mutations in the adenomatous polyposis coli (APC) gene were demonstrated in 50% of dysplastic juvenile polyps (3 of 6) but not in any of 16 juvenile polyps without dysplasia (P = 0.01). Both sporadic and syndromic juvenile polyps had K-ras mutations (14%) and there was no relationship to dysplasia. p53 gene product overexpression identified by immunohistochemical staining occurred rarely in dysplastic juvenile polyps (2 of 24, 8%). Our results indicate that the multiple genetic alterations involved in usual colorectal neoplasia also play a role in neoplastic transformation of juvenile polyps, predominantly in juvenile polyposis syndrome.