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The information below details the evolution of my research topic from preliminary ideas to my finalized research proposal.
Small-Molecule Drugs—Discovering PARP Inhibitors
I started with one goal in mind: tumor cells. After going through the research process with C. elegans (microscopic nematode worms that are a common model organism in the drug and therapy research field) last year in Experimental Design, I wanted to try my hand at cell culture. Tumor cells were the logical choice considering my goal for my undergraduate research is cancer focused.
I came across an article from the National Cancer Institute while doing the summer homework for the AP Research class titled "Can an Antibiotic Treat Cancers that Become Resistant to PARP Inhibitors?", where a through high-throughput small molecule screen (a study in which a lot of potential compounds are tested on various cell strains, which usually follows up a virtual molecular modeling screen study) identified Novobiocin as an effective treatment against Homologous Recombination Repair (HRR) deficient tumor cells.
This got me on the track of small molecule drugs as a targeted treatment for tumor cells based on emergent cell process deficiency in cancer cells. Next, I dove into the properties of PARP and PARPi.
PARP, PARPi, and Tumor Reduction
I used the keywords in the first study I came across to investigate the literature surrounding HRR deficiency in cancer cells. HRR is a cell process for repairing double stranded breaks in DNA (dsDNA breaks), which can lead to cell death if left unrepaired (Fig. 1). HRR is heavily reliant on a couple proteins initiating the repair process, most notably BRCA 1/2 and DNA polymerase theta. In tumor cells that are HRR deficient, it is most common that one of these genes is disrupted; however, other gene mutations can occur that lead to HRR deficiency. HRR deficiency is present in around 13-17% of tumor incidences, so its potential as a target for non-invasive cancer therapies is huge.
From there, I investigated how HRR deficiency is targeted. One avenue that has been targeted is preventing the repair of a singled strand DNA break (just one side of the double helix). These occur naturally due to normal oxidative stress, and if they are not repaired before DNA synthesis (the creation of a new DNA strand), it causes a double stranded break in the DNA. In HRR deficient tumor cells, that spells cell death. Single stranded break repair is initiated by the PARP enzyme, so scientists have developed PARP inhibitors (PARPi) in order to cause that cell death. PARP inhibitors prevent the repair of single stranded breaks.
Novobiocin kills HRR deficient cells using a different, alternative pathway of DNA polymerase theta inhibition to prevent restored HRR function through the DNA polymerase theta pathway. My novel research pathway then resulted from the combination of these two mechanisms, an uninvestigated pathway.
Developing My Research
With the pathways laid out, and Novobiocin selected, I simply had to choose a PARPi and a tumor strain. I selected Olaparib as my PARPi, as it is the most common PARPi in the prior research I investigated. My cell strain of RIN-m insulinoma cells resulted from their availability to the RCHS Biotechnology Lab (we had stock cultures already purchased at CU Anschutz Medical Campus), as they were one of the cells that met my criteria. With this, I developed the research design that you now see in the abstract on the home page.
Sources
All factual information in this post was taken directly from my AP Research Proposal, which can be accessed here.
Visuals:
HRR: Thacker, J. (2011). Homologous recombination repair. Encyclopedia of Cancer, 1725–1729. https://doi.org/10.1007/978-3-642-16483-5_2801.
PARPi: Zheng, F., Zhang, Y., Chen, S., Weng, X., Rao, Y., & Fang, H. (2020). Mechanism and current progress of poly ADP-ribose polymerase (PARP) inhibitors in the treatment of ovarian cancer. Biomedicine & Pharmacotherapy, 123, 109661. https://doi.org/10.1016/j.biopha.2019.109661.
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