PTPIP51 is phosphorylated by Lyn and c-Src kinases lacking dephosphorylation by PTP1B in acute myeloid leukemia.

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) is known to be expressed in blood cells with restriction to the myeloid lineage. All myeloid progenitor cells are PTPIP51 positive except for the myeloblasts. To define the expression of PTPIP51 in acute myeloid leukemia (AML), we performed immunohistochemical experiments with peptide specific antibodies (C-terminus, N-terminus and aas 114-129) to PTPIP51 with samples of AML bone marrow trephine biopsy specimens. AML blasts reacted positive for PTPIP51 protein encompassing the C-terminal sequence. Healthy bone marrow displayed an exclusive staining for the N-terminal containing form of PTPIP51. Moreover, PTPIP51 protein was highly phosphorylated at its tyrosine 176 residue. Acquired confocal images of AML cells displayed an absence of PTP1B and revealed a co-localization of PTPIP51 and Lyn. Duolink proximity ligation assays (DPLA) corroborated an interaction for PTPIP51 with Lyn and c-Src. In AML blasts rarely an interaction of PTPIP51 with PTP1B and Raf-1 was seen. Furthermore, DPLA signals were also obtained for PTPIP51 and c-Kit in AML cells. Therefore, PTPIP51 was identified as a new signal molecule of the c-Kit signaling pathway. By the phosphorylation done by Lyn, c-Src and c-Kit, PTPIP51 is prevented to influence mitogen activated protein kinase pathway on Raf-1 level contributing to increased proliferation of AML cells.

PTPIP51-a myeloid lineage specific protein interacts with PTP1B in neutrophil granulocytes.

Protein tyrosine phosphatase interacting protein 51 (PTPIP51) was identified as an in vitro interacting partner of protein tyrosine phosphatase 1B (PTP1B) and T-cell protein tyrosine phosphatase (TCPTP). The full-length form of PTPIP51 encompasses 470aas and has a molecular weight of 52kDa. The physiological function is poorly understood but an involvement in differentiation processes and apoptosis has been suggested. Preliminary observations suggested differences in PTPIP51 expression in blood cells. To analyze a possible involvement of PTPIP51 in hematopoietic processes, we studied its expression in samples of peripheral venous blood (PVB), umbilical cord blood (UCB) and human bone marrow (HBM). In both, PVB and UCB PTPIP51 expression was restricted to neutrophil granulocytes. In HBM samples, besides in mature neutrophil ganulocytes PTPIP51 protein and mRNA was present in myeloid precursor cells of neutrophils. The expression of PTPIP51 in neutrophil granulocytes was corroborated by immunoblot analysis exhibiting different molecular weight forms of PTPIP51 protein. Anti-peptide antibodies, identifying specific regions of the PTPIP51 protein (C-terminus, N-terminus and aas114-129) revealed a distinct isoform expression pattern in neutrophil granulocytes of different sources. In PVB and UCB neutrophil granulocytes reacted positive for all three peptide antibodies. In contrast, neutrophils of HBM express solely an N-terminal variant of PTPIP51 protein, lacking the C-terminal and aas114-129 sequence. Immunocytochemical results displayed a strict co-localization of PTPIP51 and PTP1B in PVB and UCB. The interaction of both proteins was verified by a proximity ligation assay. Neither proliferating cells, as identified by PCNA immunostaining, nor apoptotic cells, labeled by TUNEL assay, displayed an immunoreactivity for PTPIP51 in HBM. In fact, PTPIP51 expression was restricted to myeloid precursor cells undergoing differentiation. In blood cells therefore, PTPIP51 expression is restricted to differentiating and mature neutrophil granulocytes.

Hypermutation in mantle cell lymphoma does not indicate a clinical or biological subentity.

Mantle cell lymphoma is a prime example of a well-defined entity based on morphology, phenotype, genetics and also clinical features. Although most patients have an adverse clinical course, some have a better survival than others. The most consistently reported adverse prognostic parameter is a high mitotic rate. Recently, it has been shown that hypermutation in the immunoglobulin heavy-chain gene occurs in a subset of mantle cell lymphomas. It is, however, unclear whether the mutational status is stable over time within a given case, whether hypermutation might be influenced by therapy and how it is related to other relevant biological features of mantle cell lymphoma. In this study, we analyzed 23 typical mantle cell lymphoma cases with respect to mutational status and compared the results with clinicopathological and genetic data to determine whether the presence of mutation indicates a subentity with clinical or pathological relevance. We found somatic hypermutation in 26% of our cases and, interestingly, one case showed ongoing somatic hypermutation. In tumor cells of both mutated and unmutated cases, we found a preferential usage of V(H)3-21 (23%) and V(H)4-34 (19%). No significant correlations were found between mutation status and the other morphological and genetic features analyzed. In conclusion, our results provide additional evidence that mutation status in mantle cell lymphoma is better interpreted as a feature within the spectrum of disease that seems to have little clinical or pathological relevance.

Bone marrow trephines containing lymphoid aggregates from patients with rheumatoid and other autoimmune disorders frequently show clonal B-cell infiltrates.

In bone marrow trephines, morphological and immunohistochemical criteria may not be sufficient to discriminate reactive from malignant lymphoid infiltrates. The aim of this study was to determine whether the detection of clonal immunoglobulin heavy chain (IGH) gene rearrangements is a reliable and specific marker for malignant B-cell clones in bone marrow biopsies. Bone marrow trephines with infiltration by different types of low-grade B-cell non-Hodgkin lymphoma (n = 32), reactive lymphoid hyperplasia (n = 18), and reactive lymphoid aggregates (n = 15), including 5 patients with rheumatoid or other autoimmune disorders, were analyzed by morphology, immunohistochemistry, IGH gene rearrangement (polymerase chain reaction), and DNA sequence analysis in selected cases. In 22 (68.8%) of 32 patients with B-cell non-Hodgkin lymphoma, a clonal IGH gene rearrangement was detected. Of the reactive cases, 1 of 18 patients with lymphoid hyperplasia demonstrated clonality, and 9 (60%) of 15 patients with reactive lymphoid aggregates gave a clonal result (GeneScan analysis). DNA sequence analysis was performed in 7 of the latter patients confirming clonality in 6. Four of the patients with B-cell clonality had an autoimmune disorder. None of these patients developed a malignant lymphoma during follow-up. Thus, the molecular detection of a clonal rearrangement of the IGH gene may support the diagnosis of a malignant lymphoma infiltrating the bone marrow. However, morphologically and immunohistochemically benign lymphoid aggregates might also harbor B-cell clones especially in patients with autoimmune disorders. Therefore, the detection of clonality has to be interpreted with utmost care and does not qualify for the unequivocal diagnosis of a malignant B-cell lymphoma.

Nodular lymphoid lesion of the liver with simultaneous focal nodular hyperplasia and hemangioma: discrimination from primary hepatic MALT-type non-Hodgkin's lymphoma.

Nodular lymphoid lesion (NLL) of the liver is a rare but unique entity and has also been termed reactive lymphoid hyperplasia of the liver. We describe the histological, immunohistochemical and molecular biologic findings of a case with NLL and two other tumors of the liver. The nodular lymphoid mass found in the liver was composed of heterogeneous small lymphocytes forming reactive follicles. Plasma cells, few immunoblasts, centroblasts, few macrophages, epithelioid cells, and giant cells were seen. The lymphoid infiltrate displaced the adjacent hepatic parenchyma. By immunohistochemistry and molecular studies, the lymphocytes were found to be polyclonal. The diagnosis of NLL was made. In addition to NLL, focal nodular hyperplasia and hemangioma were detected. The discrimination of NLL from primary hepatic malignant non-Hodgkin's lymphoma of mucosa-associated lymphoid tissue-type may pose diagnostic difficulties and may require the use of immunohistochemical and molecular techniques. The simultaneous occurrence of NLL with focal nodular hyperplasia and hemangioma in the liver has not been described before.

Differentiated thyroid carcinoma: the new UICC 6th edition TNM classification system in a retrospective analysis of 169 patients.

AIM: To compare the new, 6th edition, UICC TNM staging system with the former edition, we updated TNM staging in patients with differentiated thyroid carcinoma. METHODS: The new and old TNM classification systems for differentiated thyroid carcinoma were applied in a retrospective analysis of 169 patients who underwent therapy with radioiodine (131I) from 1975 through 2002 at the Department of Nuclear Medicine, Frankfurt. RESULTS: According to the new staging system, 83 patients (49%) were classified as T1 compared to 54 patients (32%) based on the former edition; 32 patients (19%) as T2 compared to 61 (36%) patients formerly. In 44 patients with minimal extrathyroid extension, formerly classified T4, the new TNM staging changed to T3, and no patient was classified T4. The one year relapse-free survival fraction under the former edition staging was 100% for T1 and 92.2% for T2, compared to 96.8% for new edition T1 and 93.3% for T2. CONCLUSION: The new TNM classification causes a significant change in staging. New T1 classified tumors had a slightly worse relapse-free survival fraction compared with the old T1 carcinomas. For patients treated at our department, the altered criteria for classifying extrathyroid extensions have had only a minor impact on disease management.

Tumor cell dissemination in follicular lymphoma.

The derivation of follicular lymphomas (FLs) from germinal centers is not only supported by their morphologic appearance with a nodular growth pattern and a germinal center-like cellular composition, but also by the presence of ongoing somatic hypermutation (a germinal center B cell-specific process) during their clonal expansion. The intraclonal sequence diversity of the tumor cells and their follicular growth pattern allows one to analyze lymphoma cell dissemination and the way the tumor "metastasizes" to distinct follicles. In the present study, we analyzed individual follicles of 3 FLs by micromanipulation of single cells from individual lymphoma follicles and amplification of immunoglobulin V region genes. Genealogical trees for the V(H) and the V(L) gene rearrangements were constructed to analyze the clonal relationship among individual cells of 3 distinct follicles of each case. In all 3 cases there is evidence that distinct tumor follicles are founded by many tumor cells, suggesting that there is extensive migration of the tumor cells among follicles. The observation that the tumor cells of FLs retain their follicular growth patterns despite this cellular migration supports the idea that they depend on the follicular microenvironment for their clonal expansion.