Higher intensity of Low Molecular Weight Protein Tyrosine Phosphatase/ ACP-1 in survivors of patients diagnosed with Diffuse Large B Cell Lymphoma (DLBCL) compared to non-survivors

Abstract

Adult Diffuse Large B Cell Lymphoma (DLBCL) is a heterogeneous form of hematopoietic cancer and difficult to treat. In order to find a better diagnostic indication for the disease, we analyzed Low Molecular Weight Protein Tyrosine Phosphatase (LMWPTP) that in humans is encoded by the ACP1 gene. LMWPTP is an enzyme shown to counteract Protein Tyrosine Kinases (PTK) and was suggested to be a negative growth factor regulator. However, the 18 kDa PTP can also have a positive effect on cell growth and proliferation, indicating a controversial role in the tumorigenic process. LMWPTP exists in different isoforms which are electrophoretically, kinetically and immunologically distinct. We have studied two subgroups of DLBCL consisting of a Germinal Center B cell like (GCB) and a non-Germinal Center B cell like (non-GCB) group. The two subgroups have been defined by gene-expressing profiling and are associated with differential outcome. The expression levels of LMWPTP protein was compared and showed significant differences between the GCB and non- GCB subgroups (p=0.012). Interestingly, when the samples were divided into survivors and non-survivors, and thereafter analyzed for LMWPTP expression, the samples from patients with a higher survival rate showed increased staining intensity, whereas the samples from patients with lower intensity of LMWPTP did not survive the disease (p=0.001). In conclusion, we have shown that DLBCL patients with worse outcome express LMWPTP with a lower intensity, suggesting a tumor suppressor role for this form of the enzyme