Claudin-1 Expression Is Elevated in Colorectal Cancer Precursor Lesions Harboring the BRAF V600E Mutation

Abstract

BACKGROUND: Sessile serrated adenomas/polyps (SSA/P) are now recognised precursors of colorectal cancer (CRC) including cancers harbouring somatic BRAF (V600E) mutations. While the morphological diagnostic criteria of SSA/P have been established, distinguishing between small/early SSA/P and microvesicular hyperplastic polyps (MVHP) is challenging and may not be possible in routine practice. METHODS: Gene expression profiling of MVHP (n=5, all BRAF V600E wild-type) and SSA/P (n=5, all BRAF V600E mutant) samples was performed. Quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and immunohistochemical analysis was performed to verify the expression of claudin 1 (CLDN1) in MVHP and SSA/P. RESULTS: Gene expression profiling studies conducted between MVHP and SSA/P identified CLDN1 as the most statistically significant differentially expressed gene (p<0.05). Validation with qRT-PCR confirmed an up-regulation of CLDN1 in BRAF V600E mutant polyps regardless of polyp type (p<0.0005). Immunohistochemical analysis of CLDN1 expression in BRAF V600E mutant SSA/Ps (n=53) and MVHPs (n=111) and BRAF wild-type MVHPs (n=58), demonstrated a strong correlation between CLDN1 expression and the BRAF V600E mutation in both SSA/P and MVHP samples when compared to wild-type polyps (p<0.0001). CONCLUSION: This study demonstrates an up regulation of CLDN1 protein in serrated colorectal polyps including MVHP harbouring the BRAF V600E mutation. Our results demonstrated an apparent heterogeneity on the molecular level within the MVHP group and suggest that MVHP with somatic BRAF V600E mutation and up-regulated expression of CLDN1 are closely related to SSA/P and may in fact represent a continuous spectrum of the same neoplastic process within the serrated pathway of colorectal carcinogenesis.

Gene Signature in Sessile Serrated Polyps Identifies Colon Cancer Subtype

“…Eleven of 51 genes showed frequent overexpression in CIMP-H and/or MLH1 -silenced colon cancers including all seven that showed frequent increased expression in hypermutated cancers (Supplementary Table 3). We did not observe frequent increased expression of previous SSA/P markers (annexin A10 - ANXA10 and claudin 1 - CLDN1 ) in hypermutated, CIMP-H and/or MLH1 silenced colon cancers (Table 1 and Supplementary Table 3) (19, 31). …”

“…Using the cBioPortal we evaluated concurrent genomic alterations (RNA expression and somatic mutation) in each of our 51-gene panel and two genes from previous microarray studies ( ANXA10 and CLDN1 ) with alterations in BRAF (19, 31). Thirteen of 51 genes showed statistically significant associations with BRAF mutation both by Fisher exact test and log odds ratio (Supplementary Table 4).…”

Effects of supplemental calcium and vitamin D on tight‐junction proteins and mucin‐12 expression in the normal rectal mucosa of colorectal adenoma patients

“…The BRAF V600E mutation, specifically, has been hypothesized to be an early event in tumorigenesis . CLDN1 was found to be upregulated in polyps bearing the BRAF V600E somatic mutation, on both the gene expression and protein level . Another study that investigated immunohistochemical detection of CLDN18 in serrated pathway lesions found higher expression of this TJ protein in sessile‐serrated adenomas than in hyperplastic polyps or conventional adenomas .…”

Morphological and Immunohistochemical Classification Aspects of Serrated Formations of the Large Intestine.

“…Nominally, based on the frequency of detecting crypt branching, CSL without dilation of the basal portions of the crypts, CSL with doubtful dilation and with significant dilation of the basal portions of one crypt can be combined into one group, and CSL with dilation of the basal portions of two and more crypts and with horizontal growth of the basal portions of the crypts -into the other (Figure 4). 6. By the size, CSLs without dilation of the basal portions of the crypts and CSLs with doubtful dilation of the basal portions are significantly smaller than formations of the remaining groups, while CSLs with horizontal growth of the basal portions of the crypts are larger ( Figure 5).…”