Expansion of hepatic tumor progenitor cells in Pten-null mice requires liver injury and is reversed by loss of AKT2.
OBJECTIVE
The tumor suppressor PTEN inhibits AKT2 signaling; both are aberrantly expressed in liver tumors. We investigated how PTEN and AKT2 regulate liver carcinogenesis. Loss of PTEN leads to spontaneous development of liver tumors from progenitor cells. We investigated how the loss of PTEN activates liver progenitor cells and induces tumorigenesis.


METHODS
We studied mice with liver-specific disruptions in Pten and the combination of Pten and Akt2 to investigate mechanisms of liver carcinogenesis.


RESULTS
PTEN loss leads to hepatic injury and establishes selective pressure for tumor-initiating cells (TICs), which proliferate to form mixed-lineage tumors. The Pten-null mice had increasing levels of hepatic injury before proliferation of hepatic progenitors. Attenuation of hepatic injury by deletion of Akt2 reduced progenitor cell proliferation and delayed tumor development. In Pten/Akt2-null mice given 3,5-diethoxycarbonyl-1,4 dihydrocollidine (DDC), we found that the primary effect of AKT2 loss was attenuation of hepatic injury and not inhibition of progenitor-cell proliferation in response to injury.


CONCLUSIONS
Liver carcinogenesis in Pten-null mice requires not only the transformation of TICs but selection pressure from hepatic injury and cell death, which activates TICs. Further research is required to elucidate the mechanism for hepatic injury and its relationship with TIC activation.
Galicia
Vivian A
VA
Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California, USA.
He
Lina
L
Dang
Hien
H
Kanel
Gary
G
Vendryes
Christopher
C
French
Barbara A
BA
Zeng
Ni
N
Bayan
Jennifer-Ann
JA
Ding
Wei
W
Wang
Kasper S
KS
French
Samuel
S
Birnbaum
Morris J
MJ
Rountree
C Bart
CB
Stiles
Bangyan L
BL
D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D056486:Chemical and Drug Induced Liver Injury / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D051059:PTEN Phosphohydrolase / Q000235:genetics* / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics* / Q000378:metabolism*; D011725:Pyridines / Q000633:toxicity; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000473:pathology
C530773:3,5-diethoxycarbonyl-1,4-dihydrocollidine; D036341:Intercellular Signaling Peptides and Proteins; D011725:Pyridines; C494922:Akt2 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse