Leghorn Chickens: Preclinical model for ovarian cancer prevention and early diagnosis
Restricted (Penn State Only)
- Author:
- Gopalan, Lalitha
- Graduate Program:
- Animal Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 10, 2022
- Committee Members:
- Francisco Diaz, Major Field Member
Ramesh Ramachandran, Chair & Dissertation Advisor
Troy Ott, Major Field Member
Kumble Prabhu, Outside Unit & Field Member
Adele Turzillo, Program Head/Chair - Keywords:
- Ovarian cancer
Chickens
Metformin
Transcriptomics
EpCAM - Abstract:
- Ovarian cancer (OC) is the most lethal gynecological malignancy in women. The American Cancer Society estimates that approximately 19,880 new cases of ovarian cancer will be diagnosed, and about 12,810 women are likely to die due to this disease in the United States in the year 2022. The laying hen is the only animal that develops ovarian cancer naturally, with characteristics similar to the disease in women. Several studies have indicated that detecting circulating tumor cells (CTCs) in peripheral blood can be a valuable tool for early cancer diagnosis of ovarian cancer. Epithelial cell adhesion molecule (EpCAM) is frequently expressed on CTCs derived from epithelial tumors, including ovarian cancer. The objective of the first study was to diagnose OC in chickens using non-invasive methods. We found that EpCAM protein was overexpressed in the peripheral blood mononuclear cells (PBMCs) of chickens even before they exhibited clinical signs and, in combination with an ultrasonogram, can be a valuable tool in diagnosing OC. Retrospective studies and meta-analyses have shown that oral metformin intake by women with type 2 diabetes mellitus reduced the overall incidence of ovarian cancer, increased the 5-year survival rate, and sensitivity to chemotherapeutic drugs. The objective of the second study was to determine the in vitro effect of metformin on chicken ovarian cancer (COVCAR) cells. We found that in vitro metformin treatment significantly decreased sphere formation and invasiveness of COVCAR cells. Transcriptomic and Ingenuity pathway analysis (IPA) revealed that in vitro metformin treatment caused significant downregulation of several genes (MMP7, AICDA, GDPD2, APOC3, APOA1) and inhibition of upstream regulators NFKB, STAT3, TP53 that are involved in epithelial-mesenchymal transition, DNA repair, and lipid metabolism. Furthermore, a prospective pilot study was conducted to determine if dietary metformin supplementation affects the overall incidence of ovarian cancer in chickens. Dietary administration of 112 mg/kg bw metformin for 12 months was associated with lesser (37%) overall cancer incidence compared to controls (49%). The likelihood of ovarian cancer (odds ratio: 0.66; 95% CI: 0.3749- 1.1960, p= 0.175) was the least in chickens that received 112 mg/kg bw metformin supplementation compared to the control group. Additionally, western blot analysis indicated that cancerous ovaries from chickens in metformin-supplemented groups had an altered expression of two ovarian cancer markers, E-cadherin and EpCAM. These findings suggest that metformin could have significant effects on ovarian tumors, therefore, warrants further investigations for use in women. ` Lastly, transcriptomic analysis was conducted to elucidate the molecular pathways involved in conferring stemness and chemoresistance to aldehyde dehydrogenase (ALDH)+ ovarian cancer stem cells. Downstream analysis using IPA and STRING indicated significant protein-protein interaction between upregulated genes (RELN, TNC, ITGA8) responsible for stemness, extracellular matrix formation, cell migration, adhesion, and cell metabolism in ALDH+ cells. Furthermore, IPA analysis showed that immune response pathways were inhibited in ALDH+ cells. Analysis using Metascape revealed significant protein-protein interaction among a set of genes (EGFR, KRT14, KRT18, AP1, VCL, CTTN, MYO1C) involved in cell morphogenesis, polarity, and cell junction assembly in ALDH+ cells. These findings on ALDH+ CSCs closely resemble the profile of CSCs derived from human ovarian cancer patients. Therefore, further studies using chickens can have significant translational value for understanding ovarian cancer in women.