Protein tyrosine phosphatase activity and expression in GCB-like and ABC-like DLBCL cell lines. (A) Nuclear protein tyrosine phosphatase activity in GCB-like (SUDHL4 and SUDHL6) and ABC-like (OCILY10 and OCILY3) DLBCL cell lines. Nuclear extracts from unstimulated (□) and IL-4-stimulated (▦) cell lines were prepared and global protein tyrosine phosphatase activity was measured in triplicates as described in “Protein tyrosine phosphatase assay.” These experiments were repeated 2 times. Error bars indicate SD. (B) Nuclear and cytoplasmic extracts blotted with anti-PTPN2 and anti-PTPN1 antibodies, respectively. Equal loading was assessed by blotting for nucleolin and actin, respectively. (C) PTPN1 and PTPN2 dephosphorylation assays. Nuclear extracts prepared from the SUDHL4 cells stimulated with IL-4 (100 U/mL) were incubated with (+) and without (-) PTPN1 or PTPN2 for 10 minutes at 30°C and then separated on 10% SDS-polyacrylamide gels, transferred to a polyvinylidene difluoride membrane, and blotted with anti-pSTAT6, anti-STAT6, and anti-pTyr antibodies, as described in “Protein tyrosine phosphatase assay.” Arrows indicate predicted position of STAT6.