Frequent mutations of the CA simple sequence repeat in intron 1 of EGFR in mismatch repair-deficient colorectal cancers

Figure 1 Examples of MSI and AI of EGFR CA-SSR I in colorectal tumors. (A, B, C, and D) show heterozygosity for CA-SSR I in normal tissue (N). (A) shows no instability nor AI (AI score = 0.99) in colorectal tumor (T) of the same patient; (B) shows MSI with additional shortened alleles in colorectal tumor; (C) shows MSI with combined shortened and elongated alleles in colorectal tumor; and (D) shows AI (AI score = 3.03) in colorectal tumor. Arrows indicate germline alleles.

Figure 2 Graphical representation of the influence of the CA-SSRI genotype on EGFR mRNA expression in normal colon. Expression levels were determined by QRT-PCR. Relative expression levels are given in percent, relative to expression levels determined in normal colons with a 16/16 genotype. Median values with the corresponding standard deviations are indicated. Two by two comparisons, P > 0.468 (Mann-Whitney U test).

Figure 3 Examples of EGFR immunohistochemical stainings in colorectal tumors harboring identical EGFR CA-SSR I status and genotype. (A and B) are CA-SSR I MSS colorectal tumors with genotype 16/20; (A) shows a moderate membranous staining for EGFR (score ++), whereas (B) is negative (x 400; hematoxylin counterstain).