J Pathol Transl Med.  2019 Jul;53(4):225-235. 10.4132/jptm.2019.03.12.

CpG Island Methylation in Sessile Serrated Adenoma/Polyp of the Colorectum: Implications for Differential Diagnosis of Molecularly High-Risk Lesions among Non-dysplastic Sessile Serrated Adenomas/Polyps

• Lee JA
• Park HE
• Yoo SY
• Jeong S
• Cho NY
• Kang GH
• Kim JH

• KMID: 2454602
• DOI: http://doi.org/10.4132/jptm.2019.03.12

Abstract

BACKGROUND
Although colorectal sessile serrated adenomas/polyps (SSA/Ps) with morphologic dysplasia are regarded as definite high-risk premalignant lesions, no reliable grading or risk-stratifying system exists for non-dysplastic SSA/Ps. The accumulation of CpG island methylation is a molecular hallmark of progression of SSA/Ps. Thus, we decided to classify non-dysplastic SSA/Ps into risk subgroups based on the extent of CpG island methylation.
METHODS
The CpG island methylator phenotype (CIMP) status of 132 non-dysplastic SSA/Ps was determined using eight CIMP-specific promoter markers. SSA/Ps with CIMP-high and/or MLH1 promoter methylation were regarded as a high-risk subgroup.
RESULTS
Based on the CIMP analysis results, methylation frequency of each CIMP marker suggested a sequential pattern of CpG island methylation during progression of SSA/P, indicating MLH1 as a late-methylated marker. Among the 132 non-dysplastic SSA/Ps, 34 (26%) were determined to be high-risk lesions (33 CIMP-high and 8 MLH1-methylated cases; seven cases overlapped). All 34 high-risk SSA/Ps were located exclusively in the proximal colon (100%, p = .001) and were significantly associated with older age (≥ 50 years, 100%; p = .003) and a larger histologically measured lesion size (> 5 mm, 100%; p = .004). In addition, the high-risk SSA/Ps were characterized by a relatively higher number of typical base-dilated serrated crypts.
CONCLUSIONS
Both CIMP-high and MLH1 methylation are late-step molecular events during progression of SSA/Ps and rarely occur in SSA/Ps of young patients. Comprehensive consideration of age (≥ 50), location (proximal colon), and histologic size (> 5 mm) may be important for the prediction of high-risk lesions among non-dysplastic SSA/Ps.

Keyword

Colorectal neoplasms; DNA methylation; Serrated lesion; Serrated pathway; Serrated polyp

MeSH Terms

Colon
Colorectal Neoplasms
CpG Islands*
Diagnosis, Differential*
DNA Methylation
Humans
Methylation*
Phenotype

Figure

• 

  Fig. 1. Histomorphometric analyses used in this study. (A) A representative example for measurement of maximum size of a sessile serrated adenomas/polyp (SSA/P). (B) A representative example for counting of typical base-dilated serrated crypts. The total number of typical crypts in an SSA/P was used as a variable in this study. Asterisks indicate typical crypts. (C) A representative example for measurement of diameters of typical base-dilated serrated crypts. The largest diameter of typical crypts in an SSA/P was used as a variable in this study.

• 

  Fig. 2. An inference of developmental pattern of CpG island methylation in colorectal serrated neoplasia pathway. (A) Frequencies of methylation-positive cases for each CpG island methylator phenotype (CIMP) marker, based on the number of concurrently methylated markers in 132 non-dysplastic sessile serrated adenomas/polyps (SSA/Ps). Group A markers can be methylated independently and alone, whereas methylation of group C markers accompanies at least two or three other methylated markers. (B) A sequence model of methylation of CIMP markers during progression of SSA/Ps.

• 

  Fig. 3. The high-risk subgroup of non-dysplastic sessile serrated adenomas/polyps (SSA/Ps) is characterized by old age and proximal colonic location. (A) Percentages of CpG island methylator phenotype (CIMP)-high, -low, and -negative subsets of non-dysplastic SSA/Ps in the different age subgroups. Note the presence of CIMP-high cases only in ≥50 years age subgroups. (B) Frequencies of high-risk SSA/Ps according to the lesion location bowel subsites. Note the presence of high-risk SSA/Ps only in the proximal colon. (C) Frequencies of low-risk SSA/Ps according to the lesion location bowel subsites. (D) Two-dimensional (age-location) scatter plot of 132 non-dysplastic SSA/Ps. S-colon, sigmoid colon; D-colon, descending colon; SF, splenic flexure; T-colon, transverse colon; HF, hepatic flexure; A-colon, ascending colon.

• 

  Fig. 4. Differences in histologically measured lesion size and number of typical base-dilated serrated crypts between high-risk and low-risk subgroups of 132 non-dysplastic sessile serrated adenomas/polyps (SSA/Ps). (A) A box-whisker-scatter plot for histologically measured lesion size. The p-value was obtained using the Student’s t test. (B) Frequencies of high-risk SSA/Ps and low-risk SSA/Ps according to histologically measured lesion size. (C) A box-whisker-scatter plot for number of typical base-dilated serrated crypts. The p-value was obtained using the Mann-Whitney U test. (D) Frequencies of high-risk SSA/Ps and low-risk SSA/Ps according to number of typical base-dilated serrated crypts.

• 

  Fig. 5. A graphical summary of this study. Age, location, and size are potential predictive factors for a high-risk subgroup of non-dysplastic sessile serrated adenomas/polyps (SSA/Ps). CIMP, CpG island methylator phenotype; MSI, microsatellite instability.

Reference

1. Bae JM, Kim JH, Kang GH. Molecular subtypes of colorectal cancer and their clinicopathologic features, with an emphasis on the serrated neoplasia pathway. Arch Pathol Lab Med. 2016; 140:406–12.

2. Lochhead P, Chan AT, Giovannucci E, et al. Progress and opportunities in molecular pathological epidemiology of colorectal premalignant lesions. Am J Gastroenterol. 2014; 109:1205–14.

3. Snover DC. Update on the serrated pathway to colorectal carcinoma. Hum Pathol. 2011; 42:1–10.

4. Batts KP. The pathology of serrated colorectal neoplasia: practical answers for common questions. Mod Pathol. 2015; 28 Suppl 1:S80–7.

5. Bosman FT, Carneiro F, Hruban RH, Theise ND. WHO classification of tumours of the digestive system. 4th ed. Lyon: International Agency for Research on Cancer;2010.

6. Rex DK, Ahnen DJ, Baron JA, et al. Serrated lesions of the colorectum: review and recommendations from an expert panel. Am J Gastroenterol. 2012; 107:1315–29.

7. IJspeert JE, Vermeulen L, Meijer GA, Dekker E. Serrated neoplasiarole in colorectal carcinogenesis and clinical implications. Nat Rev Gastroenterol Hepatol. 2015; 12:401–9.

8. Kim JH, Bae JM, Cho NY, Kang GH. Distinct features between MLH1-methylated and unmethylated colorectal carcinomas with the CpG island methylator phenotype: implications in the serrated neoplasia pathway. Oncotarget. 2016; 7:14095–111.

9. Bateman AC, Shepherd NA. UK guidance for the pathological reporting of serrated lesions of the colorectum. J Clin Pathol. 2015; 68:585–91.

10. Crockett SD, Snover DC, Ahnen DJ, Baron JA. Sessile serrated adenomas: an evidence-based guide to management. Clin Gastroenterol Hepatol. 2015; 13:11–26. e1.

11. Parker HR, Orjuela S, Martinho Oliveira A, et al. The proto CpG island methylator phenotype of sessile serrated adenomas/polyps. Epigenetics. 2018; 13:1088–105.

12. Sakai E, Nakajima A, Kaneda A. Accumulation of aberrant DNA methylation during colorectal cancer development. World J Gastroenterol. 2014; 20:978–87.

13. Bae JM, Kim JH, Oh HJ, et al. Downregulation of acetyl-CoA synthetase 2 is a metabolic hallmark of tumor progression and aggressiveness in colorectal carcinoma. Mod Pathol. 2017; 30:267–77.

14. Oh HJ, Kim JH, Bae JM, Kim HJ, Cho NY, Kang GH. Prognostic impact of Fusobacterium nucleatum depends on combined tumor location and microsatellite instability status in stage II/III colorectal cancers treated with adjuvant chemotherapy. J Pathol Transl Med. 2019; 53:40–9.

15. Ogino S, Cantor M, Kawasaki T, et al. CpG island methylator phenotype (CIMP) of colorectal cancer is best characterised by quantitative DNA methylation analysis and prospective cohort studies. Gut. 2006; 55:1000–6.

16. Ogino S, Kawasaki T, Kirkner GJ, Kraft P, Loda M, Fuchs CS. Evaluation of markers for CpG island methylator phenotype (CIMP) in colorectal cancer by a large population-based sample. J Mol Diagn. 2007; 9:305–14.

17. Nosho K, Irahara N, Shima K, et al. Comprehensive biostatistical analysis of CpG island methylator phenotype in colorectal cancer using a large population-based sample. PLoS One. 2008; 3:e3698.

18. Kim JH, Shin SH, Kwon HJ, Cho NY, Kang GH. Prognostic implications of CpG island hypermethylator phenotype in colorectal cancers. Virchows Arch. 2009; 455:485–94.

19. Wen X, Jeong S, Kim Y, et al. Improved results of LINE-1 methylation analysis in formalin-fixed, paraffin-embedded tissues with the application of a heating step during the DNA extraction process. Clin Epigenetics. 2017; 9:1.

20. Bettington M, Walker N, Rosty C, et al. Clinicopathological and molecular features of sessile serrated adenomas with dysplasia or carcinoma. Gut. 2017; 66:97–106.

21. Burgess NG, Tutticci NJ, Pellise M, Bourke MJ. Sessile serrated adenomas/polyps with cytologic dysplasia: a triple threat for interval cancer. Gastrointest Endosc. 2014; 80:307–10.

22. Weisenberger DJ, Siegmund KD, Campan M, et al. CpG island methylator phenotype underlies sporadic microsatellite instability and is tightly associated with BRAF mutation in colorectal cancer. Nat Genet. 2006; 38:787–93.

23. Liu C, Bettington ML, Walker NI, et al. CpG island methylation in sessile serrated adenomas increases with age, indicating lower risk of malignancy in young patients. Gastroenterology. 2018; 155:1362–5. e2.

24. Bettington M, Brown I, Rosty C, et al. Sessile serrated adenomas in young patients may have limited risk of malignant progression. J Clin Gastroenterol. 2019; 53:e113–6.

25. He EY, Wyld L, Sloane MA, Canfell K, Ward RL. The molecular characteristics of colonic neoplasms in serrated polyposis: a systematic review and meta-analysis. J Pathol Clin Res. 2016; 2:127–37.

26. Edelstein DL, Axilbund JE, Hylind LM, et al. Serrated polyposis: rapid and relentless development of colorectal neoplasia. Gut. 2013; 62:404–8.