Interplay between the levels of estrogen and estrogen receptor controls the level of the granzyme inhibitor, proteinase inhibitor 9 and susceptibility to immune surveillance by natural killer cells

Oncogene. 2007 Jun 14;26(28):4106-14. doi: 10.1038/sj.onc.1210197. Epub 2007 Jan 22.


Estrogens promote cell proliferation and metastases in several human cancers. Here, we describe a different action of estrogens likely to contribute to tumor development-blocking immunosurveillance. In breast cancer cells, increasing concentrations of estrogen induce increasing levels of the granzyme B inhibitor, SerpinB9/proteinase inhibitor 9 (PI-9) and progressively block cell death induced by NK92 natural killer (NK) cells, but do not block killing by a second NK cell line, NKL cells. RNA interference knockdown of PI-9 abolishes estrogen's ability to block NK92 cell-induced cytotoxicity. Expressing elevated levels of estrogen receptor alpha (ERalpha) increases the induced level of PI-9, and makes tamoxifen (TAM), but not raloxifene or ICI 182,780, a potent inducer of PI-9. At elevated levels of ERalpha, induction of PI-9 by estradiol or TAM blocks killing by both NK92 and NKL cells. When the Erk pathway is activated with epidermal growth factor, the concentration of estrogen required to induce a protective level of PI-9 is reduced to 10 pM. Elevated concentrations of estrogen and ER may provide a dual selective advantage to breast cancer cells by controlling PI-9 levels and thereby blocking immunosurveillance. Expressing elevated levels of ERalpha reveals a potentially important difference in the effects of TAM, raloxifene and ICI 182,780 on immunosurveillance in breast cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cell Line, Tumor
  • Estrogens / metabolism*
  • Granzymes / antagonists & inhibitors*
  • Humans
  • Killer Cells, Natural / immunology*
  • Protease Inhibitors / pharmacology*
  • RNA Interference
  • Receptors, Estrogen / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction


  • Estrogens
  • Protease Inhibitors
  • Receptors, Estrogen
  • Granzymes