Coordinated regulation of STAT6 by PTP1B and TCPTP and PTP1B expression in DLBCL. (A) HeLa cells were transfected with either SMART pool siRNA for PTP1B, TCPTP, or scrambled control (200 pmol). At 72 hours after transfection, the cells were stimulated with IL-4 (100 U/mL) for 15 minutes. Cytoplasmic and nuclear lysates were extracted and blotted for tyrosine-phosphorylated STAT6 (pSTAT6), STAT6, PTP1B, TCPTP, actin, and nucleolin. (B) Immunohistochemical staining for PTP1B in tonsils and DLBCL. Low magnification image of normal tonsil sections shows PTP1B-specific staining mainly outside germinal centers (original magnification ×40); PTP1B staining is localized to the cytoplasm. Also demonstrated are representative examples of PTP1B immunostaining in DLBCL (original magnification ×400). Images of immunohistologic staining were acquired using a Nikon Eclipse E400 microscope (Nikon, Tokyo, Japan) and a Nikon DS-L1 digital camera. (C) Hierarchical cluster analysis of immunohistologic data. The expression patterns of 7 proteins (LMO2, HGAL, CD10, BCL6, MUM1/IRF4 (MUM1), BCL2, and PTP1B) in 80 cases of DLBCL are shown. Positive staining is indicated in red, lack of staining in green, and uninformative data in white. PTP1B protein expression is clustered on the same branch of the dendrogram as nongerminal-center proteins MUM1 and BCL2 and away from germinal-center proteins HGAL, BCL6, LMO2, and CD10.