Proposed characterization of POSH function in human T-cell Acute Lymphoblastic Leukemia
Abstract
T-cell Acute Lymphoblastic Leukemia (T-ALL) is an aggressive malignancy that is characterized by leukemic T-cells that can express reduced T-cell markers (such as CD5, CD4, or CD8) reflecting their transformation from an early developmental state. These transformed immature cells can proliferate uncontrollably crowding out the mature, non-transformed, normal T-cells. This significantly weakens the immune response and contribute to escape by this cancer from immune surveillance. As treatment strategies have advanced over time, the 5-year overall survival rate has increased to 85 percent event-free, with the best treatment resulting in the pediatric population. However, relapsed patients have severely limited options for treatment since their disease is often resistant to standard treatments, such as chemotherapy. There is an unmet clinical need to find new molecular targets/immunotherapies to prevent relapse and improve overall long-term survival. The focus on the present work is to look at human T-ALL signaling pathways and mutations to identify crucial points for developing more effective therapeutic strategies for personalized treatments. In T-ALL, there can be several irregularities in MAPK signaling pathways and downstream products. An important question remains to be answered: is there a central factor that joins many of the molecules participating in dysregulated signaling? Plausible candidates for such a role involve scaffolding proteins, which are known to play a large part in regulating MAPK signaling pathways. In this proposed work, we addressed the proposed POSH function in human T-ALL. Most studies investigating POSH function in normal T-cells have focused primarily on the composition of the scaffolding complex and its downstream effects. In contrast, few studies have focused on POSH function in leukemic T-cells or expanded on the theme of identifying possible regulators of the formation of the scaffolding complex. The primary research questions that should be investigated are (1) what is the composition and function of the POSH scaffolding complex between different human T-ALL cell lines; (2) how do PTMs on POSH impact the formation of the scaffolding complex; and (3) what is the function of full-length POSH in human T-ALL and how does it differ between different types of human T-ALL? In order to answer these questions, we propose to utilize CRISPR-Cas technology to (A) develop mutant human T-ALL cell lines targeting phosphotyrosine-based modifications on POSH's SH3.3 domains; and (B) develop POSH-KO human T-ALL cell lines. Additionally, we proposed to conduct these experiments on HBP-ALL, Jurkat, and MOLT-14 cell lines on the basis of having different cell surface expression markers, different sensitivities to the Tat-POSH inhibitor, as well as similarities and differences in mutations. We anticipate the proposed research in this document would mark the beginning of the much-needed investigation of whether POSH or other types of markers can be used in personalized therapies for treating human T-ALL.
Degree
M.S.