Estrogen induction of the granzyme B inhibitor, proteinase inhibitor 9, protects cells against apoptosis mediated by cytotoxic T lymphocytes and natural killer cells

Endocrinology. 2006 Mar;147(3):1419-26. doi: 10.1210/en.2005-0996. Epub 2005 Nov 23.


Exposure to estrogens is associated with an increased risk of developing breast, cervical, and liver cancer. Estrogens strongly induce the human granzyme B inhibitor, proteinase inhibitor 9 (PI-9). Because cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells use the granzyme pathway to induce apoptosis of target cells, we tested the ability of activated CTLs and the human NK cell line, YT cells, to lyse human liver cells. Estrogen induction of PI-9 protected the liver cells against CTL and NK cell-mediated, granzyme-dependent, apoptosis. Knockdown of PI-9 by RNA interference blocked the protective effect of estrogen. This work demonstrates that estrogens can act on target cells to control their destruction by immune system cells and shows that induction of PI-9 expression can inhibit both CTL and NK cell-mediated apoptosis. Estrogen induction of PI-9 may reduce the ability of cytolytic lymphocytes-mediated immune surveillance to destroy newly transformed cells, possibly providing a novel mechanism for an estrogen-mediated increase in tumor incidence.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis*
  • Blotting, Western
  • Cell Line
  • Cell Line, Transformed
  • Crosses, Genetic
  • DNA Fragmentation
  • Epidermal Growth Factor / metabolism
  • Estrogens / metabolism*
  • Ethanol / pharmacology
  • Flow Cytometry
  • Granzymes
  • Humans
  • Killer Cells, Natural / metabolism*
  • Killer Cells, Natural / pathology
  • Mice
  • Mice, Knockout
  • Models, Statistical
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Serine Endopeptidases / metabolism*
  • Serpins / biosynthesis*
  • T-Lymphocytes, Cytotoxic / metabolism*
  • T-Lymphocytes, Cytotoxic / pathology


  • Estrogens
  • SERPINB9 protein, human
  • Serpins
  • Ethanol
  • Epidermal Growth Factor
  • GZMB protein, human
  • Granzymes
  • Gzmb protein, mouse
  • Serine Endopeptidases