title: Nuclear α1-antichymotrypsin promotes chromatin condensation and inhibits proliferation of human hepatocellular carcinoma cells.
abstract: OBJECTIVE
  α1-Antichymotrypsin (α1-ACT), a member of the serpin family (SERPINA3), is an acute-phase protein secreted by hepatocytes in response to cytokines such as oncostatin M. α1-ACT is a protease inhibitor thought to limit tissue damage produced by excessive inflammation-associated proteolysis. However, α1-ACT also is detected in the nuclei of cells, where its activities are unknown. Expression of α1-ACT is down-regulated in human hepatocellular carcinoma (HCC) tissues and cells; we examined its roles in liver regeneration and HCC proliferation.
  
  
  METHODS
  We measured levels of α1-ACT messenger RNA in human HCC samples and healthy liver tissue. We reduced levels of α1-ACT using targeted RNA interference in human HCC (HepG2) and mouse hepatocyte (AML12) cell lines, and overexpressed α1-ACT from lentiviral vectors in Huh7 (HCC) cells and adeno-associated viral vectors in livers of mice. We assessed proliferation, differentiation, and chromatin compaction in cultured cells, and liver regeneration and tumor formation in mice.
  
  
  RESULTS
  Reducing levels of α1-ACT promoted proliferation of HCC cells in vitro. Oncostatin M up-regulated α1-ACT expression and nuclear translocation, which inhibited HCC cell proliferation and activated differentiation of mouse hepatocytes. We identified amino acids required for α1-ACT nuclear localization, and found that α1-ACT inhibits cell-cycle progression and anchorage-independent proliferation of HCC cells. HCC cells that overexpressed α1-ACT formed smaller tumors in mice than HCC cells that did not express the protein. α1-ACT was observed to self-associate and polymerize in the nuclei of cells; nuclear α1-ACT strongly bound chromatin to promote a condensed state that could prevent cell proliferation.
  
  
  CONCLUSIONS
  α1-ACT localizes to the nuclei of hepatic cells to control chromatin condensation and proliferation. Overexpression of α1-ACT slows the growth of HCC xenograft tumors in nude mice.
authors.affiliation: Division of Hepatology and Gene Therapy, Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain. msantamaria@unav.es
authors.forename: Mónica
authors.initials: M
authors.lastname: Santamaria
authors.forename: Ana
authors.initials: A
authors.lastname: Pardo-Saganta
authors.forename: Laura
authors.initials: L
authors.lastname: Alvarez-Asiain
authors.forename: Marianna
authors.initials: M
authors.lastname: Di Scala
authors.forename: Cheng
authors.initials: C
authors.lastname: Qian
authors.forename: Jesús
authors.initials: J
authors.lastname: Prieto
authors.forename: Matías A
authors.initials: MA
authors.lastname: Avila
mesh_terms: D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation; D056945:Hep G2 Cells; D006570:Heterochromatin / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008114:Liver Neoplasms, Experimental; D008115:Liver Regeneration / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D012333:RNA, Messenger / Q000032:analysis; D012680:Sensitivity and Specificity; D014183:Transplantation, Heterologous; D000514:alpha 1-Antichymotrypsin / Q000235:genetics / Q000378:metabolism*
chemical_list: D006570:Heterochromatin; D012333:RNA, Messenger; D000514:alpha 1-Antichymotrypsin