Journal Article

Transcription coactivator PBP/MED1-deficient hepatocytes are not susceptible to diethylnitrosamine-induced hepatocarcinogenesis in the mouse

Kojiro Matsumoto, Jiansheng Huang, Navin Viswakarma, Liang Bai, Yuzhi Jia, Yiwei Tony Zhu, Gongshe Yang, Jayme Borensztajn, M.Sambasiva Rao, Yi-Jun Zhu and Janardan K. Reddy

in Carcinogenesis

Volume 31, issue 2, pages 318-325
Published in print February 2010 | ISSN: 0143-3334
Published online December 2009 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgp306

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Nuclear receptor coactivator [peroxisome proliferator-activated receptor-binding protein (PBP)/mediator subunit 1 (MED1)] is a critical component of the mediator transcription complex. Disruption of this gene in the mouse results in embryonic lethality. Using the PBP/MED1 liver conditional null (PBP/MED1ΔLiv) mice, we reported that PBP/MED1 is essential for liver regeneration and the peroxisome proliferator-activated receptor α ligand Wy-14,643-induced receptor-mediated hepatocarcinogenesis. We now examined the role of PBP/MED1 in genotoxic chemical carcinogen diethylnitrosamine (DEN)-induced and phenobarbital-promoted hepatocarcinogenesis. The carcinogenic process was initiated by a single intraperitoneal injection of DEN at 14 days of age and initiated cells were promoted with phenobarbital (PB) (0.05%) in drinking water. PBP/MED1ΔLiv mice, killed at 1, 4 and 12 weeks, revealed a striking proliferative response of few residual PBP/MED1-positive hepatocytes that escaped Cre-mediated deletion of PBP/MED1 gene. No proliferative expansion of PBP/MED1 null hepatocytes was noted in the PBP/MED1ΔLiv mouse livers. Multiple hepatocellular carcinomas (HCCs) developed in the DEN-initiated PBP/MED1fl/fl and PBP/MED1ΔLiv mice, 1 year after the PB promotion. Of interest is that all HCC developing in PBP/MED1ΔLiv mice were PBP/MED1 positive. None of the tumors was PBP/MED1 negative implying that hepatocytes deficient in PBP/MED1 are not susceptible to neoplastic conversion. HCC that developed in PBP/MED1ΔLiv mouse livers were transplantable in athymic nude mice and these maintained PBP/MED1fl/fl genotype. PBP/MED1fl/fl HCC cell line derived from these tumors expressed PBP/MED1 and deletion of PBP/MED1fl/fl allele by adeno-Cre injection into tumors caused necrosis of tumor cells. These results indicate that PBP/MED1 is essential for the development of HCC in the mouse.

Journal Article.  5896 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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