BORA Collection: Section for Haematology (Institute of Medicine)

Immunological aspects of acute myelogenous leukemia

Thu, 22 Feb 2007 22:58:59 GMT

Title: Immunological aspects of acute myelogenous leukemia

Authors: Ersvær, Elisabeth

Abstract: Acute myelogenous leukemia (AML) is an aggressive malignancy characterized by accumulation of immature myeloid cells in the bone marrow. The overall disease-free survival is less than 50% even for the younger patients who can receive the most intensive treatment and hence, there is obviously a need for an improved therapy. Short time until lymphoid reconstitution after chemotherapy seems to be a good prognostic factor in several malignancies, including AML, and targeting of autologous T cells is considered a possible therapeutic approach. Thus, the major aim of this thesis was to further characterize the immune system of patients with AML. Disease and therapy induced T lymphocyte defects may contribute to the immune defects in AML. We therefore characterized the T lymphocytes of untreated AML patients as well as the remaining T cells in AML patients receiving intensive chemotherapy. Untreated AML patients were found to have close to normal lymphocyte subset ratios and also the in vitro T cell activation response, release of IFNγ, was close to normal after adjustment of cell numbers. In contrast, the released levels of IFNγ and GM-CSF cytokines from in vitro activated T cells in whole blood from cytopenia AML patients were lower than for healthy controls. However, the IFNγ and GM-CSF levels could be further increased by the protein kinase C agonist Pep005. The direct effects of the IFNγ on AML blasts included altered i) cytokine-dependent AML cell proliferation, ii) viability, and iii) balance between pro- and antiangiogenic chemokine release. Several mutated or overexpressed proteins seem to be processed and presented to the immune system as tumor antigens leading to humoral and/or cellular responses. Autoantibodies are thus common in cancer patients but the autoantibody response in AML patients has been included in relatively few previous studies. Our studies report aberrant cyclin B1 expression in primary AML cells and detection of anti-cyclin B1 in a subset of sera from AML patients. In contrast, no autoantibodies against the typically SLE associated antigen P-protein could be detected in sera from untreated and chemotherapy treated AML patients. To conclude, both the cellular and humoral immune system in AML patients differ from healthy controls. However, our results support the hypothesis that even these immunocompromized patients have remaining immunocompetent cells that can be targeted by immunotherapy.

Correlation analysis of two-dimensional gel electrophoretic protein patterns and biological variables

Sun, 09 Apr 2006 22:58:59 GMT

Title: Correlation analysis of two-dimensional gel electrophoretic protein patterns and biological variables

Authors: Belle, Werner van; Ånensen, Nina; Haaland, Ingvild; Bruserud, Øystein; Høgda, Kjell-Arild; Gjertsen, Bjørn Tore

Abstract: Background: Two-dimensional gel electrophoresis (2DE) is a powerful technique to examine post-translational modifications of complexly modulated proteins. Currently, spot detection is a necessary step to assess relations between spots and biological variables. This often proves time consuming and difficult when working with non-perfect gels. We developed an analysis technique to measure correlation between 2DE images and biological variables on a pixel by pixel basis. After image alignment and normalization, the biological parameters and pixel values are replaced by their specific rank. These rank adjusted images and parameters are then put into a standard linear Pearson correlation and further tested for significance and variance. Results: We validated this technique on a set of simulated 2DE images, which revealed also correct working under the presence of normalization factors. This was followed by an analysis of p53 2DE immunoblots from cancer cells, known to have unique signaling networks. Since p53 is altered through these signaling networks, we expected to find correlations between the cancer type (acute lymphoblastic leukemia and acute myeloid leukemia) and the p53 profiles. A second correlation analysis revealed a more complex relation between the differentiation stage in acute myeloid leukemia and p53 protein isoforms. Conclusion: The presented analysis method measures relations between 2DE images and external variables without requiring spot detection, thereby enabling the exploration of biosignatures of complex signaling networks in biological systems.

p53 protein biosignatures in acute myeloid leukemia

Thu, 09 Mar 2006 22:58:59 GMT

Title: p53 protein biosignatures in acute myeloid leukemia

Authors: Ånensen, Nina

Abstract: p53 is a tumor suppressor protein often regarded as the guardian of the genome. It is a highly connected protein involved in many signaling processes in the cell. The inactivation of p53 through genetic mutations in TP53 is common in human cancers and can be detected in more than 50% of malignant tumors. In acute leukemia however, p53 inactivation is not normally a part of leukemogenesis and TP53 is found to be wild-type in >90% of the cases. This thesis has sought to elucidate the nature of the p53 protein regulation in acute myeloid leukemia to increase our understanding of disease development. The experiments have proposed that p53 is wild type, expressed and capable of transactivation of target genes. However, p53 phosphorylation could be correlated to expression of the anti-apoptotic protein Bcl-2 suggesting that Bcl-2 can function as a downstream block to p53-mediated apoptosis. Furthermore, Bcl-2 levels could be associated to a specific mutation in the receptor tyrosine kinase Flt3. Flt3 mutation has been found to be a strong predictor of disease relapse in AML, and driving Bcl-2 expression, thereby inhibiting the p53 pathway, may propose a new important event in leukemogenesis. This thesis has further shown that p53 exists as two main isoforms in patient material from acute myeloid leukemia. The expression of these was influenced by chemotherapy in vivo and induction of one specific form correlated to induction of known p53 target genes. The p53 protein has many known sites for post-translational modifications and serves as a substrate for many enzymes. The p53 protein may thus be a central node in a large network of proteins whose activities are critical for cell life and death. This may suggest that specific p53 signatures could serve as a ‘read-out’ for the p53 network. The expression of the described p53 isoforms were, using a novel correlation algorithm, found to be correlated to several clinical parameters including survival, remission and Flt3 mutation. This could imply that p53 may be used as a possible biomarker for clinical stratification of leukemia patients.

Description: This doctoral thesis is based on the following articles: Paper I Wild type p53 is expressed and phosphorylated in leukemia cells with Flt3 Y591 amplification and Bcl-2 overexpression Irish JM*, Ånensen N*, Hovland R, Børresen-Dale AL, Bruserud Ø, Nolan GP, and Gjertsen BT. Manuscript. Paper II A distinct p53 protein isoform signature reflects the onset of induction chemotherapy for acute myeloid leukemia Ånensen N, Øyan AM, Abrahamsen JF, Kalland KH, Bruserud Ø, and Gjertsen BT. Manuscript submitted. Paper III Correlation analysis of two-dimensional gel electrophoretic protein patterns and biological parameters: p53 biosignatures reflect origin of cancer and stage of differentiation Van Belle W, Ånensen N, Haaland I, Bruserud Ø, and Gjertsen BT. Manuscript. Paper IV p53 protein biosignatures correlate with chemotherapy response and survival in acute leukemia Ånensen N, Van Belle W, Bruserud Ø, and Gjertsen BT. Manuscript. Paper V Acute myelogenous leukemia in a patient with Li-Fraumeni syndrome treated with valproic acid, theophyllamine and all-trans retinoic acid: A case report Ånensen N, Skavland J, Stapnes C, Ryningen A, Gjertsen BT, and Bruserud Ø. Manuscript.