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A novel DNA/peptide based library for breast cancer therapy
Tumor Cell Biology III
Background: Targeted therapies have recently been developed for certain forms of leukemia and lung cancer that exploit genetic changes unique to cancer cells. In order to develop compounds specifically targeted against genetic anomalies found in breast cancer, novel drugs that interfere with new aberrant pathways involved with breast carcinogenesis must be identified. Objective/Hypothesis: It has recently been shown that the gene encoding the phosphatidylinositol 3-kinase p110 alpha subunit PIK3CA is the most mutated oncogene in breast cancer. Moreoever, it has also been demonstrated that these mutations confer a neoplastic phenotype in cell culture. In this proposal, we wish to exploit this finding for therapeutic benefit. We hypothesize that we can create and identify specific DNA/peptide sequences that will target this aberrant pathway. Specific Aims: The goal of this study is to isolate new drugs by finding novel DNA/peptide sequences that kill breast cancer cells carrying specific genetic mutations. We will accomplish this via the following aims: Aim 1) Targeting the PIK3CA proto-oncogene. We will ?knock in? recently discovered oncogenic PIK3CA mutations into our breast epithelial cells and then use these isogenic cell lines in our DNA/peptide screening (Aim 2). Aim 2) Genotype based high throughput DNA/peptide screening. We will create a DNA expression library and use this library in a high throughput screen to identify short DNA/peptide sequences that can specifically target cells with mutant PIK3CA. Study Design: We will create pairs of isogenic cell lines that differ only by the presence or absence of oncogenic PIK3CA mutations. We will then synthesize a novel DNA expression library using nucleic acid fragments from genomic DNA cloned into a mammalian expression vector. This strategy will allow for a practically unlimited diverse novel ?drug? library that is relatively inexpensive to create. Using robotic technology, we will screen these libraries to isolate DNA/peptide sequences that can specifically kill breast epithelial cells that contain mutant PIK3CA, but do not kill cells containing wild type PIK3CA. This ?genotype? based drug screening will therefore enable us to identify DNA/peptide sequences that kill breast cancer cells with specific genetic alterations. Potential outcomes and benefits: This study has the potential of creating new gene specific therapeutic compounds. We and others have already identified the importance of PIK3CA oncogenic mutations in breast cancers. Thus, our study has the potential to isolate novel therapeutic compounds with an immediate and meaningful impact toward the therapy of breast cancer. Our long term goal is the creation of a ?breast cancer drug library? consisting of drugs that each target a specific genetic pathway involved with breast cancer growth and/or drug resistance, allowing for more effective therapy and cure.
No single drug will be capable of curing all breast cancers. This is because breast cancer is a heterogeneous disease as evidenced by the different types of breast cancers known to exist. For example, some breast cancers express estrogen receptors (ER) and the Her2/Neu receptors, while others do not. The cure for breast cancer will rely upon new therapies that target mutations that lead to cancer, while leaving normal cells without these mutations unharmed. Recently, we and others have demonstrated that a gene called PIK3CA is often changed or mutated and "turned on" in many breast cancers, causing them to grow uncontrollably. Other groups have subsequently demonstrated that these mutations contribute to the development of breast cancer. We now wish to exploit these findings for therapeutic benefit. We will create DNA based drug libraries consisting of tens of thousands of different compounds that could potentially be new cancer drugs. We will then use these libraries to find drugs that can target the PIK3CA pathway. We will accomplish this by creating pairs of breast epithelial cell lines that differ only by the presence or absence of mutated PIK3CA. We will use these paired cell lines with our DNA drug library to find new compounds that can kill cells containing mutated PIK3CA, but do not harm cells with normal PIK3CA. Because these paired cell lines are otherwise identical, any drugs we identify that kill cells containing mutant PIK3CA but not the normal counterpart, must by definition, be killing in a targeted fashion. This work therefore has great potential for isolating new therapeutic drugs that kill breast cancer cells in a very specific manner. Although no one drug will cure all breast cancers, it is our belief that the identification of new drugs that target known genetic anomalies will eventually lead to the cure for all breast malignancies. We envision that in the future, a woman?s breast cancer will be screened for mutated genes, and based upon this information, a tailored regimen consisting of drugs that target these mutated genes will be administered. The work proposed here is the first step towards this goal.