Event Title

Session 2B: Polyploid Hepatocytes and Implications for Liver Cancer

Session Number

Session 2B: 2nd Presentation

Advisor(s)

Drs. Andrew Duncan and Evan Delgado and Mr. Patrick Wilkinson, University of Pittsburgh

Location

Lecture Hall

Start Date

26-4-2018 10:35 AM

End Date

26-4-2018 11:20 AM

Abstract

Around 50% of human liver cells and 90% of mouse liver cells are polyploid, containing more than two sets of chromosomes. However, polyploidy’s relationship to liver cancer is not yet known. We examined whether polyploidy protects against liver oncogenesis by comparing tumor growth in mostly polyploid and mostly diploid livers. To model loss of polyploid hepatocytes, we used a conditional Cre/lox system to knock out the genes E2f7 and E2f8 in mice. These knockout (KO) mice along with wild-type (control) mice were given carcinogens DEN and phenobarbital. At three, six, and nine months, control and KO livers were harvested and paraffin-embedded. Tissue sections were cut and then stained with either glutamine synthetase or hematoxylin and eosin to count tumors and measure tumor area. We also examined the mRNA from WT and KO mice by qRT-PCR prior to tumor induction to determine if KO mice have gene expression differences in enzymes that metabolize DEN or phenobarbital – making KOs potentially more susceptible to tumorigenesis. The Cre/lox system was effective since E2f8 expression was lower in KO mice than control. As expected, Cyp2e1 and Car had similar expression for WT and KO mice. Interestingly, GS+ tumors were more common than GS- across genotypes. KO livers had a substantially higher tumor burden, both in numbers of GS+ and GS- nodules, as well as larger tumor areas. Therefore, our data supports the idea that polyploidy may help protect against cancer formation in the liver.

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Apr 26th, 10:35 AM Apr 26th, 11:20 AM

Session 2B: Polyploid Hepatocytes and Implications for Liver Cancer

Lecture Hall

Around 50% of human liver cells and 90% of mouse liver cells are polyploid, containing more than two sets of chromosomes. However, polyploidy’s relationship to liver cancer is not yet known. We examined whether polyploidy protects against liver oncogenesis by comparing tumor growth in mostly polyploid and mostly diploid livers. To model loss of polyploid hepatocytes, we used a conditional Cre/lox system to knock out the genes E2f7 and E2f8 in mice. These knockout (KO) mice along with wild-type (control) mice were given carcinogens DEN and phenobarbital. At three, six, and nine months, control and KO livers were harvested and paraffin-embedded. Tissue sections were cut and then stained with either glutamine synthetase or hematoxylin and eosin to count tumors and measure tumor area. We also examined the mRNA from WT and KO mice by qRT-PCR prior to tumor induction to determine if KO mice have gene expression differences in enzymes that metabolize DEN or phenobarbital – making KOs potentially more susceptible to tumorigenesis. The Cre/lox system was effective since E2f8 expression was lower in KO mice than control. As expected, Cyp2e1 and Car had similar expression for WT and KO mice. Interestingly, GS+ tumors were more common than GS- across genotypes. KO livers had a substantially higher tumor burden, both in numbers of GS+ and GS- nodules, as well as larger tumor areas. Therefore, our data supports the idea that polyploidy may help protect against cancer formation in the liver.