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RL1-00680-1: MicroRNA (miRNA)-induced Pluripotent Stem Cells (mirPS)

Recommendation: Not recommended for funding

Public Abstract (provided by applicant)

Studying stem cells will help us understand how they transform into specialized cells that make us what we are. Potential application of stem cells centers on cancer, birth defects, and replacement of diseased or destroyed organs, including Parkinson's and Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, and rheumatoid arthritis. Yet, there have been concerns about destruction of human embryos to obtain stem cells. Recent methods of induced pluripotent stem (iPS) cells allow for development of stem cells from adult body cells by introducing four genes into these cells. Still, there is concern that to maintain pure, undifferentiated human stem cells they need to be grown on a layer of animal cells, called feeder, so that there are animal antigen contaminations for its use in human beings. Our previous work has shown that a new class of molecule, microRNA (miRNA), modulates expression of numerous genes at the same time, which allows us to develop effective strategies to induce human stem-like cells from three different cancer cell lines in feeder-free conditions. We take this approach because eggs deficient in enzymes for making miRNA stop developing, suggesting that miRNA is important in stem cell research. We also noticed that the level of a family of miRNA, mir-302s, is high in eggs and human stem cells. We therefore hypothesize that mir-302 is required for reprogramming human cells to become embryonic stem cells. Our long term goal is to understand how mir-302s transform cancer cells to stem cells and find out effective ways to guide these feeder-free stem cells to treat diseases and/or disorders. Before we are able to do that, we need to make sure our miRNA-induced stem cells (termed mirPS) are similar to those of human stem cells derived from human embryos (hES). We propose to study: (I) genetic and epigenetic changes between mirPS and hES; (2) whether mirPS cells; possess pluripotency by transplanting them into mice; and (3) whether mirPS cells can be guided to form specific cell types in cultured dishes so that they can treat specific diseases. These studies will make clear that mirES cells are the same as hES cells. Our mir-302s-expressing strategy has the following advantages: (a) simple, efficient, and effective for generation of ES-like cells, (b) short transgene insertion allows 100% tranfection, (c) cells grown in feeder-free conditions, and (d) native maternal material compatible to human hSE, and (e) no oncogene is involved. Completion of the project will generate extensive public health benefits by proving that the mirES is a novel cell line for treating cancer and other diseases/disorders, and providing the foundation and rationale to develop patient-friendly specific ES-mediated drugs. Ultimately, we hope to translate this knowledge to eventualIy extend survival and reduce cancer/disease deaths and improve quality of life of patients with various cancer/diseases.

Statement of Benefit to California (provided by applicant)

The proposed research, when completed, will benefit the state of California and its citizens in three major areas. First, this study will provide an opportunity to explore the patient-tailored human stem cells for potential treatment if the same approach is also feasible with somatic cells taken from patients. There is no other technology that has the capacity to reprogram cancer cells or somatic cells for iPS cells by using miRNA to suppressing differentiation genes. The successful outcome of the proposed work would result in a paradigm shift in the approach to diagnosis, imaging and treatment of diseases as well as using mirPS cells for studying stem cell-associated treating cancer/diseases/disorders. Second, the application of mirPS cells will provide immediate guidance of specific cell lineages for treating specific diseases under feeder-free conditions. For instance, the mirPS cells will differentiate into pancreatic ß cells and dopaminergic neurons for treating diabetes and Parkinson's disease, respectively. Third, this study will provide novel insights into how maternal micorRNA modulates somatic gene silencing and embryonic gene activation in cancer cells so that the cells would reprogram to form human pluripotent embryonic stem-like cells. For instance, skin cancer is the most common form of cancer that affects many people in Southern California. Currently, early detection is the key to surviving skin cancer. If mir-302-mediated pluripotent embrynoic stem cells (mirPS) derived from Colo skin cancer cells are proven to be capable of reprogramming cancer cells into stem cells and not inducing tumors, knowledge of the molecular mechanisms of the reprogramming process initiated by miR-302s will lead to improvements in the diagnosis and management of skin cancer. By the same token, the mirPS derived from PC3 and MCF-7 will benefit the state of California and its citizens because it is estimated that 19,710 women and 35,716 men will be diagnosed with breast cancer and prostate cancer in 2007, respectively. It is estimated that 4,165 women and 4,462 men will die from breast cancer or prostate in California, respectively.

Review

This is a project based on the idea that micro RNAs (miRNAs) could be used to reprogram cancer cells into induced pluripotent stem (iPS) cells. The proposal seeks to generate micro RNA-induced pluripotent stem cells (mirPS cells) by driving expression of mir-302.

The proposed idea of using miRNAs to reprogram cancer cells is an interesting idea, particularly in the context of the mir-302 cluster, which the principal investigator (PI) indicates is highly expressed in oocytes and embryonic stem (ES) cells. However, one of the strongest disagreements with this proposal voiced by reviewers concerned the scientific rationale of utilizing cancer cells for reprogramming and subsequently for therapeutic applications in human. It is likely that the inherent genetic instability of cancer cells leads to undesired alterations, thus limiting the potential utility of the derived cells, even if such cells can be reprogrammed and pluripotency is demonstrated. In addition reviewers disagreed with the applicant’s notion that the use of mirPS cells is advantageous because they will bypass immunocompatibility issues faced by the use of human ES cell-derived tissues. iPS cells derived from normal somatic cells potentially have the same advantage without the risk of exposing patients to cancer cell-derived tissues. In addition, strong criticism was expressed about the statement that this approach will “immediately provide patient-friendly stem/differentiated cell lines useful for clinical trials”, as the PI claims.

In terms of feasibility of the proposal, the premise behind using mir-302 to reprogram cells appears to be sound. mir-302 is expressed at high levels in mouse oocytes and human ES cells and preliminary data supports that expression of the mir-302 family can induce ESC-like changes in a melanoma cell line. The major issue with the proposed experiments is that it is not clear that this approach will produce useful human cell lines.

The proposal to investigate the role the mir-302 cluster potentially plays in reprogramming cells is interesting from the standpoint of miRNA biology. However, the rationale for using tumor cells to generate pluripotent cell lines for regenerative medicine is not well justified. It is not likely that new, useful human ES cell lines will be generated from the proposed experiments.

The following Working Group members had a conflict of interest with this application and were therefore recused from participating in review of, discussion of, and voting on the application:

• ffrench-Constant, Charles