Transfection of transforming growth factor-beta producing tumor EMT6 with interleukin-2 elicits tumor rejection and tumor reactive cytotoxic T-lymphocytes.
One mechanism by which potentially immunogenic tumors evade the immune response is production of immunosuppressive factors. The murine mammary sarcoma EMT6 has previously been demonstrated to inhibit the proliferation of B-cells, suggesting that this tumor produces immunosuppressive factors. Here, we show that supernatant from EMT6 inhibits the development of cytotoxic T-lymphocytes (CTLs) and that this inhibition can be reversed by addition of recombinant interleukin (IL)-2. Furthermore, we show that EMT6 produces high levels of the immunosuppressant factor transforming growth factor (TGF)-beta. To determine if the T-cell growth factor IL-2 within the tumor microenvironment could reverse the immunosuppressive effect of EMT6, we transfected EMT6 with an expression vector containing the cDNA for murine IL-2 under the control of the beta-actin promoter. These transfectants produce significant levels of IL-2 (26 U/ml). EMT6/IL-2 is rejected by mice at 100-fold higher challenge than are parental cells or control transfectants (neomycin resistance only). Thy-1-expressing cells purified from EMT6/IL-2 tumors show greater cytotoxicity against the parental EMT6 cells than do those from the control transfectant. Thus, IL-2 can reverse the effects of TGF-beta on development and/or proliferation of CTL reactive with EMT6, allowing the establishment of mature effectors in vivo. This has significant implications for the development of CTL and immunotherapy for immunosuppressive tumors.
McAdam
A J
AJ
Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642.
Felcher
A
A
Woods
M L
ML
Pulaski
B A
BA
Hutter
E K
EK
Frelinger
J G
JG
Lord
E M
EM
D000818:Animals; D006084:Graft Rejection; D007376:Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology; D008213:Lymphocyte Activation; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D012513:Sarcoma, Experimental / Q000276:immunology* / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis*
D007376:Interleukin-2; D016212:Transforming Growth Factor beta