Figure 1.

Lymphoid ASS1 immunostaining and methylation profiling. (a) Representative immunohistochemical stains for ASS1 as follows: ASS1-negative tonsillar lymphocytes; ASS1-negative FL, DLBCL, CTCL (Pautrier's microabcess) biopsies with internal positive controls (i.e., endothelial and epithelial cells); and an ASS1-positive MZL biopsy. Images were obtained using a Zeiss Axiophot microscope, magnification × 200, with Axiovision image acquisition software. (b) Differential methylation of the ASS1 promoter in a panel of normal and malignant lymphoid cell lines and primary tissues. Quantitative methylation values (beta values) were obtained as previously described.²⁶ Beta values are reported for two CpG loci within the ASS1 gene (373 bp 5′ to the TSS and 7 bp 3′ to the TSS). The overall incidence of CpG island methylation was increased in malignant compared with benign samples