TY - JOUR
T1 - Hepatoma cells from mice deficient in glycine N-methyltransferase have increased RAS signaling and activation of liver kinase B1
AU - Martínez-López, Nuria
AU - García-Rodrgíuez, Juan L.
AU - Varela-Rey, Marta
AU - Gutiérrez, Virginia
AU - Fernández-Ramos, David
AU - Beraza, Naiara
AU - Aransay, Ana M.
AU - Schlangen, Karin
AU - Lozano, Juan Jose
AU - Aspichueta, Patricia
AU - Luka, Zigmund
AU - Wagner, Conrad
AU - Evert, Matthias
AU - Calvisi, Diego F.
AU - Lu, Shelly C.
AU - Mato, José M.
AU - Martínez-Chantar, María L.
N1 - Funding Information:
Funding Supported by National Institutes of Health grants AT-1576 and AT-004896 (to S.C.L., M.L.M.-C., and J.M.M.), SAF 2011-29851 (to J.M.M.), ETORTEK-2010 (to M.L.M.-C), Sanidad Gobierno Vasco 2008 and Educación Gobierno Vasco 2011 (to M.L.M.-C), FIS PI11/01588 (to M.L.M.-C), Sanidad Gobierno Vasco 2012 (to M.V.-R.), Educación Gobierno Vasco (to J.M.M.), FIS PS09/02010 and Program Ramón y Cajal (to N.B.), Deutsche Forschungsgemeinschaft DFG (grant number Ev168/2-1 to M.E.), and National Institutes of Health grants DK15289 and DK180010 (to C.W.). Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas is funded by the Instituto de Salud Carlos III.
PY - 2012/9
Y1 - 2012/9
N2 - BACKGROUND & AIMS: Patients with cirrhosis are at high risk for developing hepatocellular carcinoma (HCC), and their liver tissues have abnormal levels of S-adenosylmethionine (SAMe). Glycine N-methyltransferase (GNMT) catabolizes SAMe, but its expression is down-regulated in HCC cells. Mice that lack GNMT develop fibrosis and hepatomas and have alterations in signaling pathways involved in carcinogenesis. We investigated the role of GNMT in human HCC cell lines and in liver carcinogenesis in mice. METHODS: We studied hepatoma cells from GNMT knockout mice and analyzed the roles of liver kinase B1 (LKB1, STK11) signaling via 5′-adenosine monophosphateactivated protein kinase (AMPK) and Ras in regulating proliferation and transformation. RESULTS: Hepatoma cells from GNMT mice had defects in LKB1 signaling to AMPK, making them resistant to induction of apoptosis by adenosine 3′,5′-cyclic monophosphate activation of protein kinase A and calcium/calmodulin-dependent protein kinase kinase 2. Ras-mediated hyperactivation of LKB1 promoted proliferation of GNMT-deficient hepatoma cells and required mitogen-activated protein kinase 2 (ERK) and ribosomal protein S6 kinase polypeptide 2 (p90RSK). Ras activation of LKB1 required expression of RAS guanyl releasing protein 3 (RASGRP3). Reduced levels of GNMT and phosphorylation of AMPKα at Thr172 and increased levels of Ras, LKB1, and RASGRP3 in HCC samples from patients were associated with shorter survival times. CONCLUSIONS: Reduced expression of GNMT in mouse hepatoma cells and human HCC cells appears to increase activity of LKB1 and RAS; activation of RAS signaling to LKB1 and RASGRP3, via ERK and p90RSK, might be involved in liver carcinogenesis and be used as a prognostic marker. Reagents that disrupt this pathway might be developed to treat patients with HCC.
AB - BACKGROUND & AIMS: Patients with cirrhosis are at high risk for developing hepatocellular carcinoma (HCC), and their liver tissues have abnormal levels of S-adenosylmethionine (SAMe). Glycine N-methyltransferase (GNMT) catabolizes SAMe, but its expression is down-regulated in HCC cells. Mice that lack GNMT develop fibrosis and hepatomas and have alterations in signaling pathways involved in carcinogenesis. We investigated the role of GNMT in human HCC cell lines and in liver carcinogenesis in mice. METHODS: We studied hepatoma cells from GNMT knockout mice and analyzed the roles of liver kinase B1 (LKB1, STK11) signaling via 5′-adenosine monophosphateactivated protein kinase (AMPK) and Ras in regulating proliferation and transformation. RESULTS: Hepatoma cells from GNMT mice had defects in LKB1 signaling to AMPK, making them resistant to induction of apoptosis by adenosine 3′,5′-cyclic monophosphate activation of protein kinase A and calcium/calmodulin-dependent protein kinase kinase 2. Ras-mediated hyperactivation of LKB1 promoted proliferation of GNMT-deficient hepatoma cells and required mitogen-activated protein kinase 2 (ERK) and ribosomal protein S6 kinase polypeptide 2 (p90RSK). Ras activation of LKB1 required expression of RAS guanyl releasing protein 3 (RASGRP3). Reduced levels of GNMT and phosphorylation of AMPKα at Thr172 and increased levels of Ras, LKB1, and RASGRP3 in HCC samples from patients were associated with shorter survival times. CONCLUSIONS: Reduced expression of GNMT in mouse hepatoma cells and human HCC cells appears to increase activity of LKB1 and RAS; activation of RAS signaling to LKB1 and RASGRP3, via ERK and p90RSK, might be involved in liver carcinogenesis and be used as a prognostic marker. Reagents that disrupt this pathway might be developed to treat patients with HCC.
KW - AMP
KW - CaMKK2
KW - Liver Cancer
KW - Mouse Model
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UR - http://www.scopus.com/inward/citedby.url?scp=84865502592&partnerID=8YFLogxK
U2 - 10.1053/j.gastro.2012.05.050
DO - 10.1053/j.gastro.2012.05.050
M3 - Article
C2 - 22687285
AN - SCOPUS:84865502592
SN - 0016-5085
VL - 143
SP - 787-798.e13
JO - Gastroenterology
JF - Gastroenterology
IS - 3
ER -