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.
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.
Jiang
X
X
Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA.
Ellison
S J
SJ
Alarid
E T
ET
Shapiro
D J
DJ
D045744:Cell Line, Tumor; D004967:Estrogens / Q000378:metabolism*; D053804:Granzymes / Q000037:antagonists & inhibitors*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D011480:Protease Inhibitors / Q000494:pharmacology*; D034622:RNA Interference; D011960:Receptors, Estrogen / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004967:Estrogens; D011480:Protease Inhibitors; D011960:Receptors, Estrogen; D053804:Granzymes