DLC2 (deleted in liver cancer 2), a Rho GTPase-activating protein, was previously shown to be underexpressed in human hepatocellular carcinoma and has tumor suppressor functions in cell culture models. We generated DLC2-deficient mice to investigate the tumor suppressor role of DLC2 in hepatocarcinogenesis and the function of DLC2 in vivo. In this study, we found that, unlike homologous DLC1, which is essential for embryonic development, DLC2 was dispensable for embryonic development and DLC2-deficient mice could survive to adulthood. We also did not observe a higher incidence of liver tumor formation or diethylnitrosamine (DEN)-induced hepatocarcinogenesis in DLC2-deficient mice. However, we observed that DLC2-deficient mice were smaller and had less adipose tissue than the wild type mice. These phenotypes were not due to reduction of cell size or defect in adipogenesis, as observed in the 190B RhoGAP-deficient mouse model. Together, these results suggest that deficiency in DLC2 alone does not enhance hepatocarcinogenesis.
References
[1]
Ching YP, Wong CM, Chan SF, Leung TH, Ng DC, et al. (2003) Deleted in liver cancer (DLC) 2 encodes a RhoGAP protein with growth suppressor function and is underexpressed in hepatocellular carcinoma. J Biol Chem 278: 10824–10830.
[2]
Leung TH, Ching YP, Yam JW, Wong CM, Yau TO, et al. (2005) Deleted in liver cancer 2 (DLC2) suppresses cell transformation by means of inhibition of RhoA activity. Proc Natl Acad Sci U S A 102: 15207–15212.
[3]
Yuan BZ, Miller MJ, Keck CL, Zimonjic DB, Thorgeirsson SS, et al. (1998) Cloning, characterization, and chromosomal localization of a gene frequently deleted in human liver cancer (DLC-1) homologous to rat RhoGAP. Cancer Res 58: 2196–2199.
[4]
Schultz J, Ponting CP, Hofmann K, Bork P (1997) SAM as a protein interaction domain involved in developmental regulation. Protein Sci 6: 249–253.
[5]
Li H, Fung KL, Jin DY, Chung SS, Ching YP, et al. (2007) Solution structures, dynamics, and lipid-binding of the sterile alpha-motif domain of the deleted in liver cancer 2. Proteins 67: 1154–1166.
[6]
Ponting CP, Aravind L (1999) START: a lipid-binding domain in StAR, HD-ZIP and signalling proteins. Trends Biochem Sci 24: 130–132.
[7]
Ng DC, Chan SF, Kok KH, Yam JW, Ching YP, et al. (2006) Mitochondrial targeting of growth suppressor protein DLC2 through the START domain. FEBS Lett 580: 191–198.
[8]
Bar-Sagi D, Hall A (2000) Ras and Rho GTPases: a family reunion. Cell 103: 227–238.
[9]
Sahai E, Marshall CJ (2002) RHO-GTPases and cancer. Nat Rev Cancer 2: 133–142.
[10]
Qiu RG, Chen J, Kirn D, McCormick F, Symons M (1995) An essential role for Rac in Ras transformation. Nature 374: 457–459.
[11]
Roux P, Gauthier-Rouviere C, Doucet-Brutin S, Fort P (1997) The small GTPases Cdc42Hs, Rac1 and RhoG delineate Raf-independent pathways that cooperate to transform NIH3T3 cells. Curr Biol 7: 629–637.
[12]
Ng IO, Liang ZD, Cao L, Lee TK (2000) DLC-1 is deleted in primary hepatocellular carcinoma and exerts inhibitory effects on the proliferation of hepatoma cell lines with deleted DLC-1. Cancer Res 60: 6581–6584.
[13]
Goodison S, Yuan J, Sloan D, Kim R, Li C, et al. (2005) The RhoGAP protein DLC-1 functions as a metastasis suppressor in breast cancer cells. Cancer Res 65: 6042–6053.
[14]
Healy KD, Hodgson L, Kim TY, Shutes A, Maddileti S, et al. (2008) DLC-1 suppresses non-small cell lung cancer growth and invasion by RhoGAP-dependent and independent mechanisms. Mol Carcinog 47: 326–337.
[15]
Kim TY, Lee JW, Kim HP, Jong HS, Jung M, et al. (2007) DLC-1, a GTPase-activating protein for Rho, is associated with cell proliferation, morphology, and migration in human hepatocellular carcinoma. Biochem Biophys Res Commun 355: 72–77.
[16]
Wong CM, Lee JM, Ching YP, Jin DY, Ng IO (2003) Genetic and epigenetic alterations of DLC-1 gene in hepatocellular carcinoma. Cancer Res 63: 7646–7651.
[17]
Durkin ME, Avner MR, Huh CG, Yuan BZ, Thorgeirsson SS, et al. (2005) DLC-1, a Rho GTPase-activating protein with tumor suppressor function, is essential for embryonic development. FEBS Lett 579: 1191–1196.
[18]
Sordella R, Classon M, Hu KQ, Matheson SF, Brouns MR, et al. (2002) Modulation of CREB activity by the Rho GTPase regulates cell and organism size during mouse embryonic development. Dev Cell 2: 553–565.
[19]
Sordella R, Jiang W, Chen GC, Curto M, Settleman J (2003) Modulation of Rho GTPase signaling regulates a switch between adipogenesis and myogenesis. Cell 113: 147–158.
[20]
Tybulewicz VL, Crawford CE, Jackson PK, Bronson RT, Mulligan RC (1991) Neonatal lethality and lymphopenia in mice with a homozygous disruption of the c-abl proto-oncogene. Cell 65: 1153–1163.
[21]
Todaro GJ, Green H (1963) Quantitative studies of the growth of mouse embryo cells in culture and their development into established lines. J Cell Biol 17: 299–313.
[22]
Wong CC, Wong CM, Ko FC, Chan LK, Ching YP, et al. (2008) Deleted in liver cancer 1 (DLC1) negatively regulates Rho/ROCK/MLC pathway in hepatocellular carcinoma. PLoS ONE 3: e2779.
[23]
Wei L, Roberts W, Wang L, Yamada M, Zhang S, et al. (2001) Rho kinases play an obligatory role in vertebrate embryonic organogenesis. Development 128: 2953–2962.
[24]
Zhao Z, Rivkees SA (2003) Rho-associated kinases play an essential role in cardiac morphogenesis and cardiomyocyte proliferation. Dev Dyn 226: 24–32.
[25]
Manley NR, Capecchi MR (1997) Hox group 3 paralogous genes act synergistically in the formation of somitic and neural crest-derived structures. Dev Biol 192: 274–288.
[26]
Manley NR, Capecchi MR (1998) Hox group 3 paralogs regulate the development and migration of the thymus, thyroid, and parathyroid glands. Dev Biol 195: 1–15.
[27]
Stocco DM (2001) StAR protein and the regulation of steroid hormone biosynthesis. Annu Rev Physiol 63: 193–213.
[28]
Xiaorong L, Wei W, Liyuan Q, Kaiyan Y (2008) Underexpression of deleted in liver cancer 2 (DLC2) is associated with overexpression of RhoA and poor prognosis in hepatocellular carcinoma. BMC Cancer 8: 205.
[29]
Klocke R, Bartels T, Jennings G, Brand K, Halter R, et al. (2001) Lack of p53 accelerates hepatocarcinogenesis in transgenic mice constitutively overexpressing c-myc in the liver. FASEB J 15: 1404–1406.
[30]
Santoni-Rugiu E, Jensen MR, Factor VM, Thorgeirsson SS (1999) Acceleration of c-myc-induced hepatocarcinogenesis by Co-expression of transforming growth factor (TGF)-alpha in transgenic mice is associated with TGF-beta1 signaling disruption. Am J Pathol 154: 1693–1700.
[31]
Zender L, Spector MS, Xue W, Flemming P, Cordon-Cardo C, et al. (2006) Identification and validation of oncogenes in liver cancer using an integrative oncogenomic approach. Cell 125: 1253–1267.
[32]
Kawai K, Kiyota M, Seike J, Deki Y, Yagisawa H (2007) START-GAP3/DLC3 is a GAP for RhoA and Cdc42 and is localized in focal adhesions regulating cell morphology. Biochem Biophys Res Commun 364: 783–789.
[33]
Ullmannova V, Popescu NC (2006) Expression profile of the tumor suppressor genes DLC-1 and DLC-2 in solid tumors. Int J Oncol 29: 1127–1132.
