Qualification of the three regions as a fraction marker.

<p>(A) Methylation levels of the three regions were analyzed in i) eight LCM-purified non-cancer cell samples from three ESCCs, ii) eight LCM-purified cancer cell samples from the three ESCCs, iii) the eight ESCCs before LCM, iv) peripheral leukocytes of one healthy volunteer, and v) four ESCC cell lines. One or more of the three regions were almost completely methylated in purified cancer cells and cancer cell lines, and all were hardly methylated in non-cancer cells. (B) Copy number alterations of the three regions were analyzed by quantitative PCR using 15 ESCCs.