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Expression and localization of sterile alpha motif domain containing 5 is associated with cell type and malignancy of biliary tree

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ABSTRACT

Cholangiocarcinoma (CC) is a type of relatively rare neoplasm in adenocarcinoma. The characteristics of CCs as well as biliary epithelial cells are heterogeneous at the different portion of the biliary tree. There are two candidate stem/progenitor cells of the biliary tree, i.e., biliary tree stem/progenitor cell (BTSC) at the peribiliary gland (PBG) of large bile ducts and liver stem/progenitor cell (LPC) at the canals of Hering of peripheral small bile duct. Although previous reports suggest that intrahepatic CC (ICC) can arise from such stem/progenitor cells, the characteristic difference between BTSC and LPC in pathological process needs further investigation, and the etiology of CC remains poorly understood. Here we show that Sterile alpha motif domain containing 5 (SAMD5) is exclusively expressed in PBGs of large bile ducts in normal mice. Using a mouse model of cholestatic liver disease, we demonstrated that SAMD5 expression was upregulated in the large bile duct at the hepatic hilum, the extrahepatic bile duct and PBGs, but not in proliferating intrahepatic ductules, suggesting that SAMD5 is expressed in BTSC but not LPC. Intriguingly, human ICCs and extrahepatic CCs exhibited striking nuclear localization of SAMD5 while the normal hilar large bile duct displayed slight-to-moderate expression in cytoplasm. In vitro experiments using siRNA for SAMD5 revealed that SAMD5 expression was associated with the cell cycle regulation of CC cell lines. Conclusion: SAMD5 is a novel marker for PBG but not LPC in mice. In humans, the expression and location of SAMD5 could become a promising diagnostic marker for the cell type as well as malignancy of bile ducts and CCs.

No MeSH data available.


Expression profiles of SAMD5 in mouse.(A). Real-time RT-PCR analysis of Samd5 mRNA in EpCAM+ cells isolated from normal and DDC-fed mouse livers. (B) Real-time RT-PCR analysis of Samd5 mRNA in normal liver (n = 3), 70% PHx liver (n = 4), chronically injured liver by CCl4 (n = 5) or DDC diet (n = 4). The upregulation of SAMD5 expression is outstanding in DDC-fed mouse liver. Data are means ± standard error. *P <0.05; **P <0.01. (C). Immunostaining of SAMD5 and CK19 for DDC-fed mouse liver. SAMD5 is markedly expressed in a part of large bile ducts and PBGs at the hepatic hilum (arrowheads), whereas it is not detected in numerous ductular cells located in parenchymal region (arrows). Bars = 50 μm.
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pone.0175355.g001: Expression profiles of SAMD5 in mouse.(A). Real-time RT-PCR analysis of Samd5 mRNA in EpCAM+ cells isolated from normal and DDC-fed mouse livers. (B) Real-time RT-PCR analysis of Samd5 mRNA in normal liver (n = 3), 70% PHx liver (n = 4), chronically injured liver by CCl4 (n = 5) or DDC diet (n = 4). The upregulation of SAMD5 expression is outstanding in DDC-fed mouse liver. Data are means ± standard error. *P <0.05; **P <0.01. (C). Immunostaining of SAMD5 and CK19 for DDC-fed mouse liver. SAMD5 is markedly expressed in a part of large bile ducts and PBGs at the hepatic hilum (arrowheads), whereas it is not detected in numerous ductular cells located in parenchymal region (arrows). Bars = 50 μm.

Mentions: We have reported previously that potential LPCs reside in EpCAM+ cells in DDC-fed mouse livers [16]. The cDNA microarray analysis of EpCAM+ cells from normal and DDC-treated livers revealed that many genes including Samd5 were upregulated in DDC-treated EpCAM+ cells compared to normal EpCAM+ cells (Table 2). Quantitative RT-PCR analysis demonstrated that SAMD5 expression of DDC-treated EpCAM+ cells is more than 200 times higher than that of normal EpCAM+ cells (Fig 1A). Furthermore, the expression levels of SAMD5 in various liver injury models were determined by quantitative RT-PCR. SAMD5 was slightly but significantly upregulated in chronically injured livers by repeated injections of carbon tetrachloride (CCl4), but not in regenerating livers after partial hepatectomy (PHx) (Fig 1B). By contrast, Samd5 mRNA was markedly upregulated in DDC-fed livers, suggesting that its expression was induced in severely cholestatic livers.


Expression and localization of sterile alpha motif domain containing 5 is associated with cell type and malignancy of biliary tree
Expression profiles of SAMD5 in mouse.(A). Real-time RT-PCR analysis of Samd5 mRNA in EpCAM+ cells isolated from normal and DDC-fed mouse livers. (B) Real-time RT-PCR analysis of Samd5 mRNA in normal liver (n = 3), 70% PHx liver (n = 4), chronically injured liver by CCl4 (n = 5) or DDC diet (n = 4). The upregulation of SAMD5 expression is outstanding in DDC-fed mouse liver. Data are means ± standard error. *P <0.05; **P <0.01. (C). Immunostaining of SAMD5 and CK19 for DDC-fed mouse liver. SAMD5 is markedly expressed in a part of large bile ducts and PBGs at the hepatic hilum (arrowheads), whereas it is not detected in numerous ductular cells located in parenchymal region (arrows). Bars = 50 μm.
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Related In: Results  -  Collection

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pone.0175355.g001: Expression profiles of SAMD5 in mouse.(A). Real-time RT-PCR analysis of Samd5 mRNA in EpCAM+ cells isolated from normal and DDC-fed mouse livers. (B) Real-time RT-PCR analysis of Samd5 mRNA in normal liver (n = 3), 70% PHx liver (n = 4), chronically injured liver by CCl4 (n = 5) or DDC diet (n = 4). The upregulation of SAMD5 expression is outstanding in DDC-fed mouse liver. Data are means ± standard error. *P <0.05; **P <0.01. (C). Immunostaining of SAMD5 and CK19 for DDC-fed mouse liver. SAMD5 is markedly expressed in a part of large bile ducts and PBGs at the hepatic hilum (arrowheads), whereas it is not detected in numerous ductular cells located in parenchymal region (arrows). Bars = 50 μm.
Mentions: We have reported previously that potential LPCs reside in EpCAM+ cells in DDC-fed mouse livers [16]. The cDNA microarray analysis of EpCAM+ cells from normal and DDC-treated livers revealed that many genes including Samd5 were upregulated in DDC-treated EpCAM+ cells compared to normal EpCAM+ cells (Table 2). Quantitative RT-PCR analysis demonstrated that SAMD5 expression of DDC-treated EpCAM+ cells is more than 200 times higher than that of normal EpCAM+ cells (Fig 1A). Furthermore, the expression levels of SAMD5 in various liver injury models were determined by quantitative RT-PCR. SAMD5 was slightly but significantly upregulated in chronically injured livers by repeated injections of carbon tetrachloride (CCl4), but not in regenerating livers after partial hepatectomy (PHx) (Fig 1B). By contrast, Samd5 mRNA was markedly upregulated in DDC-fed livers, suggesting that its expression was induced in severely cholestatic livers.

View Article: PubMed Central - PubMed

ABSTRACT

Cholangiocarcinoma (CC) is a type of relatively rare neoplasm in adenocarcinoma. The characteristics of CCs as well as biliary epithelial cells are heterogeneous at the different portion of the biliary tree. There are two candidate stem/progenitor cells of the biliary tree, i.e., biliary tree stem/progenitor cell (BTSC) at the peribiliary gland (PBG) of large bile ducts and liver stem/progenitor cell (LPC) at the canals of Hering of peripheral small bile duct. Although previous reports suggest that intrahepatic CC (ICC) can arise from such stem/progenitor cells, the characteristic difference between BTSC and LPC in pathological process needs further investigation, and the etiology of CC remains poorly understood. Here we show that Sterile alpha motif domain containing 5 (SAMD5) is exclusively expressed in PBGs of large bile ducts in normal mice. Using a mouse model of cholestatic liver disease, we demonstrated that SAMD5 expression was upregulated in the large bile duct at the hepatic hilum, the extrahepatic bile duct and PBGs, but not in proliferating intrahepatic ductules, suggesting that SAMD5 is expressed in BTSC but not LPC. Intriguingly, human ICCs and extrahepatic CCs exhibited striking nuclear localization of SAMD5 while the normal hilar large bile duct displayed slight-to-moderate expression in cytoplasm. In vitro experiments using siRNA for SAMD5 revealed that SAMD5 expression was associated with the cell cycle regulation of CC cell lines. Conclusion: SAMD5 is a novel marker for PBG but not LPC in mice. In humans, the expression and location of SAMD5 could become a promising diagnostic marker for the cell type as well as malignancy of bile ducts and CCs.

No MeSH data available.