Dissertation/Thesis Abstract

Exploring Novel Roles for Cytosolic Malic Enzyme in Intestinal Tumorigenesis using Mouse and Human Models
by Fernandes, Lorenzo Mario, Ph.D., University of Arkansas for Medical Sciences, 2018, 217; 10815342
Abstract (Summary)

Colorectal cancer (CRC) is one of the leading causes of cancer-associated deaths in the US and globally. Malic Enzyme 1 (ME1) is a cytosolic enzyme that converts malate to pyruvate and furnishes NADPH for anabolic pathways as well as the maintenance of redox balance. While ME1 has been implicated in CRC the mechanisms by which it contributes to oncogenesis is poorly understood. To determine the role of ME1 in Intestinal cancers we crossed mice overexpressing ME1 in the gastrointestinal mucosa (ME1-Tg mice) with ApcMin/+ mice that are used to study Familial Adenomatous Polyposis (FAP) a rare form of inherited CRC in humans. The resultant ApcMin/+/ME1-Tg progeny exhibited a higher number of adenomas in the small intestine than their Apc Min/+ littermates at 16 weeks of age. Gene expression analysis revealed significantly higher levels of Me1 gene in the small intestine while ME1 protein levels were significantly higher within the villi and adenomas of ApcMin/+/ME1-Tg compared to ApcMin/+ mice littermates. Small intestine crypt depths and villus lengths were greater in ApcMin/+ /ME1-Tg compared to ApcMin/+ mice. Our study revealed a significant increase in SP/KLF family members Sp5 and KLF9 gene and protein levels respectively in the small intestine of ApcMin/+/ME1-Tg compared to ApcMin/+ mice littermates. Inhibition of ME1 using a small molecule inhibitor in human HCT116 and HT29 CRC cells resulted in reduced cell numbers, diameters, and colonies while normal IEC6 intestinal cells were resistant to ME1 inhibition at comparable doses. To further assess the role of ME1 on CRC systemically and locally we generated ME1FLOX/FLOX mice that can be crossed with adiponectin or villin-driven Cre to ablate ME1 in the adipose tissue and gastrointestinal tract respectively. Adipose tissue-specific knock out of ME1 led to embryonic lethality. We confirmed that the embryonic lethality was due to successful ablation of ME1 since ME1 FLOX/+ adiponectin Cre mice exhibited half the amount of ME1 gene and protein expression. Our work sheds light on the role of ME1 in CRC and genetic syndromes of intestinal cancer as well as its role in embryonic development. Targeting of ME1 may be a potential therapeutic target for cancer treatment.

Indexing (document details)
Advisor: Simmen, Frank A.
Commitee: Kelly, Thomas, McGehee, Robert E., Morello, Roy, Simmen, Frank A., Simmen, Rosalia C.M
School: University of Arkansas for Medical Sciences
Department: Interdisciplinary Biomedical Sciences
School Location: United States -- Arkansas
Source: DAI-B 79/10(E), Dissertation Abstracts International
Subjects: Biology, Molecular biology
Keywords: Cancer, Hct116, Ht29, Intestinal cancers, Malic enzyme, Metabolism
Publication Number: 10815342
ISBN: 978-0-438-03762-5
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