Laterally spreading type of colorectal adenoma exhibits a unique methylation phenotype and K-ras mutations

Sakiko Hiraoka ¹, Jun Kato , Masashi Tatsukawa

⁰Department of Gastroenterology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.

Gastroenterology +

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August 8, 2006

View abstract on PubMed

Summary

Granular-type laterally spreading tumors (G-LST) show high prevalence of CpG island methylator phenotype (CIMP-high) and K-ras mutations, particularly in the proximal colon. This suggests a distinct carcinogenic pathway for G-LST.

Area Of Science

Gastroenterology and Oncology
Molecular Pathology
Colorectal Cancer Research

Background

Laterally spreading tumors (LST) are superficial colorectal tumors detected by colonoscopy.
Genetic and epigenetic profiles of LSTs, particularly granular-type LST (G-LST), are not well-characterized.

Purpose Of The Study

To investigate the genetic and epigenetic characteristics of different types of colorectal laterally spreading tumors (LST).
To analyze the association between macroscopic appearance, CpG island methylator phenotype (CIMP) status, and K-ras mutations in LSTs.

Main Methods

Analysis of 205 sporadic colorectal adenoma tissues, including protruded-type, granular-type LST (G-LST), and flat-type LST (F-LST).
Determination of CpG island methylator phenotype (CIMP) status and examination of K-ras point mutations.
Statistical analysis of the relationship between tumor morphology, CIMP, and K-ras mutations.

Main Results

G-LSTs (61%) showed a significantly higher prevalence of CIMP-high compared to protruded-type adenomas (25%).
K-ras mutations were significantly more frequent in G-LSTs (78%) than in protruded-type adenomas (25%).
G-LSTs in the proximal colon exhibited even higher rates of CIMP-high (85%) and K-ras mutations (92%), while F-LSTs had low prevalence of both.

Conclusions

The high prevalence of CIMP-high and K-ras mutations in G-LST, especially in the proximal colon, indicates a unique carcinogenic pathway.
These findings highlight distinct molecular features of G-LST, differentiating them from other colorectal adenomas.

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