Abnormal signal transduction by T cells of mice with parental tumors is not seen in mice bearing IL-2-secreting tumors.
There is considerable evidence to demonstrate that immune function is abnormal in tumor-bearing mice, perhaps accounting, at least in part, for progressive tumor growth. In an attempt to generate an antitumor response, we used retroviral vectors to express IL-2 cDNA in CMS5, a murine fibrosarcoma. Mice inoculated with unmodified tumor cells suffered progressive tumor growth, whereas tumors secreting IL-2 were rejected or grew slowly. Animals bearing unmodified but not IL-2-secreting tumors also were immunosuppressed. On the basis of these observations, we were interested in how IL-2 secretion by the tumor cells prevented the onset of hyporesponsiveness. To identify biochemical differences between T cells of mice with parental vs slowly growing IL-2-secreting tumors, we examined signal transduction after activation through the CD3/TCR complex. Protein tyrosine phosphorylation was altered and calcium flux was reduced in cells of mice with parental tumors compared with animals with slowly growing IL-2-secreting tumors. In addition, levels of protein for the tyrosine kinases p56lck and p59fyn, as well as the TCR-zeta-chain, were reduced. These differences in signal transduction were observed for T cells of mice with parental and IL-2-secreting tumors of the same size, demonstrating that differences in tumor size alone could not explain our findings. Thus, IL-2 secretion by tumors seems to be able to prevent immunosuppression by maintaining normal signal transduction in T cells, facilitating the generation of antitumor responses.
Division of Clinical Immunology, Mount Sinai School of Medicine, New York, NY 10029.
S
S
Salvadori
B
B
Gansbacher
A M
AM
Pizzimenti
K S
KS
Zier
D000818:Animals; D002118:Calcium / Q000378:metabolism; D005354:Fibrosarcoma / Q000276:immunology*; D005434:Flow Cytometry; D015151:Immunoblotting; D007376:Interleukin-2 / Q000378:metabolism*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008565:Membrane Proteins / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
D007376:Interleukin-2; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D011505:Protein-Tyrosine Kinases; C494960:Fyn protein, mouse; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; D002118:Calcium