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Thesis
Roles of Timeless in Fanconi-anemia mediated repair pathway and effect on cancer growth in esophageal cancer cells
Master of Science (M.S.), Drexel University
Aug 2020
DOI:
https://doi.org/10.17918/00000260
Abstract
Timeless protects the DNA replication fork in response to DNA damage to preserve genomic integrity. Recent studies have suggested a role of Timeless in cancer development. Timeless is frequently overexpressed in breast, colon, esophageal, and other several types of cancers and is associated with poor patient survival. Importantly, studies have reported that Timeless confers resistance to cisplatin, a commonly used cancer chemotherapeutic agent. However, how Timeless supports cancer development and cisplatin resistance is not well understood. Cisplatin induces formation of inter-strand crosslinks (ICLs). ICLs are a deadly form of DNA damage because they physically impede the replication machinery, leading to DNA double-stranded breaks (DSBs) during DNA replication. In response to ICLs, cells activate the Fanconi anemia (FA) DNA repair pathway, responsible for the removal of ICLs. Mutations in this pathway result in Fanconi Anemia, which is characterized by bone marrow failure and increased risk for esophageal cancer. In this study, we used human esophageal squamous cell carcinoma (ESCC) cells to investigate the mechanism by which Timeless confers cisplatin resistance and esophageal cancer development. Our results suggest that Timeless and FA proteins are reduced in response to acetaldehyde or cisplatin, which are both ICL-inducing agents. We observed that Timeless depletion further decreased the levels of FANCD2 in the presence of acetaldehyde and sensitized cells to cisplatin. Cisplatin treatment led to elevated phosphorylation of replication protein A, indicative of activation of the DNA Damage Response (DDR). Furthermore, Timeless depletion resulted in a deficiency in organoid formation, suggesting that Timeless is involved in self-renewal capability. This result is consistent with the reduced ALDH1 level in Timeless-depleted cells. Interestingly, Timeless depletion also led to the formation of abnormal 3D structures, which suggests a role of Timeless in preventing cancer phenotypes. These results suggest that Timeless regulates the FA pathway to augment DNA repair processes in order to promote esophageal cancer growth. Thus, our study contributes to understanding the pathogenesis of FA-associated esophageal cancer. Considering that acetaldehyde is the primary metabolite of alcohol, our studies also serve as a guiding investigation into the mechanisms of esophageal carcinogenesis where alcohol consumption has been implicated.
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Details
- Title
- Roles of Timeless in Fanconi-anemia mediated repair pathway and effect on cancer growth in esophageal cancer cells
- Creators
- Shivani Sandeep Sheth
- Contributors
- Eishi Noguchi (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- x, 71 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Medicine (Graduate); College of Medicine; Hematology and Oncology; Drexel University
- Other Identifier
- 991014695538104721