SNK/PLK2 is preferentially and selectively methylated in primary hematologic malignancies. (A) Methylation of the CpG island of SNK/PLK2 occurs in primary B-cell lymphomas but not in breast cancer. MSP analysis of the SNK/PLK2 CpG island was performed as described in “Materials and methods.” The figure shows MSPs for unmethylated (U) and methylated (M) DNA. Specificity controls are denoted C1 (control unmethylated DNA) and C2 (control methylated DNA). Examples of methylation are shown for primary mantle-cell lymphomas, posttransplantation lymphoproliferative disease (PTLD), chronic lymphocytic leukemia (CLL), and primary breast cancer. The lymphoblastoid cell line Otis is included as a further specificity control. (B) PLK3 (FNK/PRK/PLK3) is unmethylated in B-cell, breast, and head and neck cancer. MSP to detect methylation in the CpG island of FNK/PRK/PLK3 was performed as described in “Materials and methods.” The figure shows MSPs for unmethylated (U) and methylated (M) DNA. Shown are analysis of primary BL, primary mantle-cell lymphomas, primary breast cancer, and primary squamous carcinomas of the head and neck (HN).