Discovery and validation of biomarkers to myeloid leukemia cancer stem cells by the generation of monoclonal antibodies
Tools and Technologies I
The aim of this proposal is to identify new biomarkers by the generation of specific monoclonal antibodies specific to the Chronic Myeloid Leukemia – Blast Crisis (CML-BC) and Acute Myeloid Leukemia (AML) Cancer Stem Cells (CSC). Cancer stem cells arise from normal stem and progenitor cells though a number of gene mutations. The CSC is a small population of cells within the tumor that drives its growth. Most cells in the tumor are derived from the cancer stem cell, however they do not have growth potential. The CSC are also responsible for the recurrence of the disease following treatment. Since these cells are very resistant to current chemotherapies, treatment will only be successful if the CSC is targeted and eliminated. By defining the characteristic cell surface markers on these cells, scientists will be able to isolate them and study their properties. Discovery of novel biomarkers will not only be useful to study cancer stem cell biology, but may also be useful clinically as a diagnostic for diagnosis or as a prognostic indicator. Identification of cell surface targets in CSC may also lead to the development of new, highly specific targets for therapy.
Statement of Benefit to California:
Myeloid leukemias are devastating diseases especially in the elderly who can not tolerate intensive chemotherapeutic treatments. The aim of this research proposal is to discover and validate new biomarkers through the generation of monoclonal antibodies specific to the acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) cancer stem cells (CSC) which are not present on the normal hematopoietic stem cell (HSC). Known cell surface characteristics of these myeloid CSC are similar to normal stem and progenitor cells. Specific markers to the CSC that distinguish them from the normal HSC have not yet been identified. Discovery of novel biomarkers will not only be useful to study cancer stem cell biology, but may also be useful clinically as a diagnostic for confirmatory diagnosis or as a prognostic indicator. Identification of cell surface targets or active gene pathways in CSC but not normal HSC may lead to the development of new, highly specific targets for therapy. Approximately 3000 cases of myeloid leukemia will be diagnosed in the state of California in 2008 according to National Cancer Institute estimates. With current therapies, the 5 year survival rate for acute myeloid leukemia is 21%. Improved cancer diagnosis and treatment would directly benefit the people of California.
This proposal focuses on the identification and validation of new biomarkers for detecting cancer stem cells and investigating their underlying biology. To achieve these ends, the Principal Investigator (PI) proposes to generate monoclonal antibodies (Mabs) by an immunization strategy and screen for those that are reactive with human leukemia cancer stem cells (CSCs), but not with normal hematopoietic stem cells. In the second aim, the selected antibodies of interest will be evaluated by multiparameter FACs analysis, and the corresponding antigen targets will be identified and characterized. Finally, the PI will perform in vivo, serial transplantation experiments to validate the use of the Mab candidates for selectively recognizing cells that form tumors. The reviewers were enthusiastic about the technology in this proposal but questioned its overall feasibility. While extremely well written and designed, certain technical deficiencies were noted in the research plan that lowered their enthusiasm. Finally, while PI was found to be exceptionally capable, the reviewers questioned whether the overall level of commitment, as well as a key lack of expertise, might hinder the pace of the investigation. The reviewers noted that this proposal addresses an important deficiency in cancer cell biology - a lack of biomarkers for defining the tumor initiating cancer stem cell. If successfully realized, the proposed tools could lay the groundwork for improved diagnostics and more importantly, provide potential new therapies for cancer. Such tools would also prove useful for advancing the mechanistic understanding of leukemia. While uncertain of the extent to which the theoretical potential would be realized, the reviewers believed that at least some useful reagents could emerge from this effort. The reviewers noted several strengths of the proposal. It was well written, the rationale and milestones were clearly defined, and there was excellent discussion of the potential difficulties and alternative strategies that would be employed. The preliminary data were compelling. Nevertheless, the reviewers noted several weaknesses. They expressed concern that the project was under resourced in terms of staff commitment. As the research plan was considered to be straightforward and obvious, some worried that the PI and his/her team would be outdistanced by competitors in this active area of investigation. In addition, they commented that the PI’s lack of experience with protein biochemistry could negatively impact efforts at antigen identification. Beyond these general concerns, the reviewers noted specific weaknesses that could affect the overall feasibility of this proposal. One commented that the in vivo model could introduce noise to the screen for CSC by selecting any cells with in vivo growth advantages rather than true cancer stem cells. Finally, the reviewers commented on the unrealistic expectation by the PI that Mabs would be identified to markers unique to cancer stem cells. Most therapeutic antibodies target markers that are not specific to cancer cell subtypes but rather are generally overexpressed markers also present on normal cells. By the criteria proposed in this study, such markers would be missed. The reviewers described the PI as highly qualified and appropriate for the work described in this proposal. The PI has world class expertise in flow cytometry and appears to have the necessary training and experience to oversee the transplantation assays. However, the reviewers expressed concern at an insufficient level of commitment that the PI and his/her team propose to dedicate to this effort in what is a very competitive field. The proposed budget was judged to be appropriate. In summary, while the proposed technology addresses an important area of cancer cell research, the applicants did not convince the reviewers of its overall feasibility.