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

Matsumoto K, Huang J, Viswakarma N, Bai L, Jia Y, Zhu YT, Yang G, Borensztajn J, Rao MS, Zhu YJ, Reddy JK - Carcinogenesis (2009)

Bottom Line: Nuclear receptor coactivator [peroxisome proliferator-activated receptor-binding protein (PBP)/mediator subunit 1 (MED1)] is a critical component of the mediator transcription complex.None of the tumors was PBP/MED1 negative implying that hepatocytes deficient in PBP/MED1 are not susceptible to neoplastic conversion.PBP/MED1(fl/fl) HCC cell line derived from these tumors expressed PBP/MED1 and deletion of PBP/MED1(fl/fl) allele by adeno-Cre injection into tumors caused necrosis of tumor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.

ABSTRACT
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 (PBP/MED1(DeltaLiv)) mice, we reported that PBP/MED1 is essential for liver regeneration and the peroxisome proliferator-activated receptor alpha 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/MED1(DeltaLiv) 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 hepatocytes was noted in the PBP/MED1(DeltaLiv) mouse livers. Multiple hepatocellular carcinomas (HCCs) developed in the DEN-initiated PBP/MED1(fl/fl) and PBP/MED1(DeltaLiv) mice, 1 year after the PB promotion. Of interest is that all HCC developing in PBP/MED1(DeltaLiv) 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/MED1(DeltaLiv) mouse livers were transplantable in athymic nude mice and these maintained PBP/MED1(fl/fl) genotype. PBP/MED1(fl/fl) HCC cell line derived from these tumors expressed PBP/MED1 and deletion of PBP/MED1(fl/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.

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Hepatocellular proliferation in PBP/MED1fl/fl and PBP/MED1ΔLiv mouse livers following DEN initiation and PB promotion. Representative illustrations from PBP/MED1fl/fl (A–D) and PBP/MED1ΔLiv (E–H) mouse livers. Hepatocellular proliferation was assessed by BrdUrd labeling at 0 (A and E), 1 (B and F), 12 (C and G) and 52 (D and H) weeks. BrdUrd incorporation was evaluated by immunohistochemistry. Many nuclei are labeled in PBP/MED1fl/fl mouse livers (B–D) at 1 (see arrows and boxed area in B), 12 (see arrows and boxed areas in C) and 52 (arrows in D) weeks when compared with PBP/MED1ΔLiv mouse livers (F–H see arrows). In PBP/MED1ΔLiv livers, BrdUrd labeling was observed only in PBP/MED-positive large hepatocytes (see arrows in F–H). At 52 weeks, the non-tumor areas in PBP/MED1ΔLiv livers expanding populations of large hepatocytes are seen and PBP/MED1-negative hepatocytes are smaller (see boxed in H).
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fig4: Hepatocellular proliferation in PBP/MED1fl/fl and PBP/MED1ΔLiv mouse livers following DEN initiation and PB promotion. Representative illustrations from PBP/MED1fl/fl (A–D) and PBP/MED1ΔLiv (E–H) mouse livers. Hepatocellular proliferation was assessed by BrdUrd labeling at 0 (A and E), 1 (B and F), 12 (C and G) and 52 (D and H) weeks. BrdUrd incorporation was evaluated by immunohistochemistry. Many nuclei are labeled in PBP/MED1fl/fl mouse livers (B–D) at 1 (see arrows and boxed area in B), 12 (see arrows and boxed areas in C) and 52 (arrows in D) weeks when compared with PBP/MED1ΔLiv mouse livers (F–H see arrows). In PBP/MED1ΔLiv livers, BrdUrd labeling was observed only in PBP/MED-positive large hepatocytes (see arrows in F–H). At 52 weeks, the non-tumor areas in PBP/MED1ΔLiv livers expanding populations of large hepatocytes are seen and PBP/MED1-negative hepatocytes are smaller (see boxed in H).

Mentions: In the present study, it was decided to ascertain whether PBP/MED1 hepatocytes function as targets for tumor development following DEN-initiation and PB promotion (35,37). DEN, in contrast to PPARα ligand Wy-14,643, is a genotoxic chemical carcinogen and the DEN-initiated hepatocytes are readily promotable when exposed to liver tumor promoter PB, an activator of nuclear receptor CAR (38). In the present study, following DEN initiation, PBP/MED1fl/fl and PBP/MED1ΔLiv mice were given PB in drinking water and mice were killed at selected intervals to examine changes in the liver. Liver weight:body weight ratio was slightly lower in PBP/MED1ΔLiv mice at 4 and 12 weeks on PB promotion and by 52 weeks, the ratios were similar and the increase in ratio at this interval is due to liver tumor burden (Figure 1). In mice given PB for 52 weeks without DEN initiation, the liver weight:body weight ratio remained lower compared with DEN-initiated animals (Figure 1). It should be noted that 1 year of PB treatment had similar effect of liver weight:body weight ratio in normal and PBP/MED1 liver mice and this is attributed to PB accelerated expansion of the residual PBP/MED1 expressing hepatocytes in PBP/MED1ΔLiv mice. In PBP/MED1fl/fl mice, the histological appearance of liver was unremarkable at 0, 1 and 12 weeks of PB promotion following DEN initiation (Figure 2A and C). All hepatocytes revealed PBP/MED1 nuclear staining (Figure 2B and D). In PBP/MED1ΔLiv mice, nuclear staining of PBP/MED1 was not present in hepatocytes at 0 day (Figure 2E and I), except for positive staining in a rare hepatocyte that apparently escaped Cre-mediated gene deletion. By 1 week of PB promotion, large hepatocytes begin to emerge in DEN-initiated PBP/MED1ΔLiv mouse livers (Figure 2F and J) and they revealed PBP/MED1 nuclear staining implying PBPMED1fl/fl genotype of these cells, in the background of PBP/MED1-deficient hepatocytes (Figure 2J). The PBP/MED1 expressing large hepatocytes in PBP/MED1ΔLiv livers increased in number and began to dominate the liver phenotype in that they formed large expanding colonies between 12 and 52 weeks of PB promotion (Figure 2G, H, K and L). The volume occupied by large PBP/MED1-positive hepatocytes in PBP/MED1ΔLiv mice was estimated by using Scion Image software (Figure 3). The data on PBP/MED1 expressing large hepatocytes obtained at 52 weeks (Figure 3) represents only the proportion of these cells in non-neoplastic areas (see Figure 2H; Figure 4H). These results indicate that few PBP/MED1 expressing hepatocytes present in PBP/MED1ΔLiv mouse livers exhibit profound growth advantage in a milieu where the majority of hepatocytes do not express this coactivator.


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

Matsumoto K, Huang J, Viswakarma N, Bai L, Jia Y, Zhu YT, Yang G, Borensztajn J, Rao MS, Zhu YJ, Reddy JK - Carcinogenesis (2009)

Hepatocellular proliferation in PBP/MED1fl/fl and PBP/MED1ΔLiv mouse livers following DEN initiation and PB promotion. Representative illustrations from PBP/MED1fl/fl (A–D) and PBP/MED1ΔLiv (E–H) mouse livers. Hepatocellular proliferation was assessed by BrdUrd labeling at 0 (A and E), 1 (B and F), 12 (C and G) and 52 (D and H) weeks. BrdUrd incorporation was evaluated by immunohistochemistry. Many nuclei are labeled in PBP/MED1fl/fl mouse livers (B–D) at 1 (see arrows and boxed area in B), 12 (see arrows and boxed areas in C) and 52 (arrows in D) weeks when compared with PBP/MED1ΔLiv mouse livers (F–H see arrows). In PBP/MED1ΔLiv livers, BrdUrd labeling was observed only in PBP/MED-positive large hepatocytes (see arrows in F–H). At 52 weeks, the non-tumor areas in PBP/MED1ΔLiv livers expanding populations of large hepatocytes are seen and PBP/MED1-negative hepatocytes are smaller (see boxed in H).
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fig4: Hepatocellular proliferation in PBP/MED1fl/fl and PBP/MED1ΔLiv mouse livers following DEN initiation and PB promotion. Representative illustrations from PBP/MED1fl/fl (A–D) and PBP/MED1ΔLiv (E–H) mouse livers. Hepatocellular proliferation was assessed by BrdUrd labeling at 0 (A and E), 1 (B and F), 12 (C and G) and 52 (D and H) weeks. BrdUrd incorporation was evaluated by immunohistochemistry. Many nuclei are labeled in PBP/MED1fl/fl mouse livers (B–D) at 1 (see arrows and boxed area in B), 12 (see arrows and boxed areas in C) and 52 (arrows in D) weeks when compared with PBP/MED1ΔLiv mouse livers (F–H see arrows). In PBP/MED1ΔLiv livers, BrdUrd labeling was observed only in PBP/MED-positive large hepatocytes (see arrows in F–H). At 52 weeks, the non-tumor areas in PBP/MED1ΔLiv livers expanding populations of large hepatocytes are seen and PBP/MED1-negative hepatocytes are smaller (see boxed in H).
Mentions: In the present study, it was decided to ascertain whether PBP/MED1 hepatocytes function as targets for tumor development following DEN-initiation and PB promotion (35,37). DEN, in contrast to PPARα ligand Wy-14,643, is a genotoxic chemical carcinogen and the DEN-initiated hepatocytes are readily promotable when exposed to liver tumor promoter PB, an activator of nuclear receptor CAR (38). In the present study, following DEN initiation, PBP/MED1fl/fl and PBP/MED1ΔLiv mice were given PB in drinking water and mice were killed at selected intervals to examine changes in the liver. Liver weight:body weight ratio was slightly lower in PBP/MED1ΔLiv mice at 4 and 12 weeks on PB promotion and by 52 weeks, the ratios were similar and the increase in ratio at this interval is due to liver tumor burden (Figure 1). In mice given PB for 52 weeks without DEN initiation, the liver weight:body weight ratio remained lower compared with DEN-initiated animals (Figure 1). It should be noted that 1 year of PB treatment had similar effect of liver weight:body weight ratio in normal and PBP/MED1 liver mice and this is attributed to PB accelerated expansion of the residual PBP/MED1 expressing hepatocytes in PBP/MED1ΔLiv mice. In PBP/MED1fl/fl mice, the histological appearance of liver was unremarkable at 0, 1 and 12 weeks of PB promotion following DEN initiation (Figure 2A and C). All hepatocytes revealed PBP/MED1 nuclear staining (Figure 2B and D). In PBP/MED1ΔLiv mice, nuclear staining of PBP/MED1 was not present in hepatocytes at 0 day (Figure 2E and I), except for positive staining in a rare hepatocyte that apparently escaped Cre-mediated gene deletion. By 1 week of PB promotion, large hepatocytes begin to emerge in DEN-initiated PBP/MED1ΔLiv mouse livers (Figure 2F and J) and they revealed PBP/MED1 nuclear staining implying PBPMED1fl/fl genotype of these cells, in the background of PBP/MED1-deficient hepatocytes (Figure 2J). The PBP/MED1 expressing large hepatocytes in PBP/MED1ΔLiv livers increased in number and began to dominate the liver phenotype in that they formed large expanding colonies between 12 and 52 weeks of PB promotion (Figure 2G, H, K and L). The volume occupied by large PBP/MED1-positive hepatocytes in PBP/MED1ΔLiv mice was estimated by using Scion Image software (Figure 3). The data on PBP/MED1 expressing large hepatocytes obtained at 52 weeks (Figure 3) represents only the proportion of these cells in non-neoplastic areas (see Figure 2H; Figure 4H). These results indicate that few PBP/MED1 expressing hepatocytes present in PBP/MED1ΔLiv mouse livers exhibit profound growth advantage in a milieu where the majority of hepatocytes do not express this coactivator.

Bottom Line: Nuclear receptor coactivator [peroxisome proliferator-activated receptor-binding protein (PBP)/mediator subunit 1 (MED1)] is a critical component of the mediator transcription complex.None of the tumors was PBP/MED1 negative implying that hepatocytes deficient in PBP/MED1 are not susceptible to neoplastic conversion.PBP/MED1(fl/fl) HCC cell line derived from these tumors expressed PBP/MED1 and deletion of PBP/MED1(fl/fl) allele by adeno-Cre injection into tumors caused necrosis of tumor cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.

ABSTRACT
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 (PBP/MED1(DeltaLiv)) mice, we reported that PBP/MED1 is essential for liver regeneration and the peroxisome proliferator-activated receptor alpha 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/MED1(DeltaLiv) 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 hepatocytes was noted in the PBP/MED1(DeltaLiv) mouse livers. Multiple hepatocellular carcinomas (HCCs) developed in the DEN-initiated PBP/MED1(fl/fl) and PBP/MED1(DeltaLiv) mice, 1 year after the PB promotion. Of interest is that all HCC developing in PBP/MED1(DeltaLiv) 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/MED1(DeltaLiv) mouse livers were transplantable in athymic nude mice and these maintained PBP/MED1(fl/fl) genotype. PBP/MED1(fl/fl) HCC cell line derived from these tumors expressed PBP/MED1 and deletion of PBP/MED1(fl/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.

Show MeSH
Related in: MedlinePlus