Mechanisms of escape from CD8+ T-cell clones specific for the HER-2/neu proto-oncogene expressed in ovarian carcinomas: related and unrelated to decreased MHC class 1 expression.
We have developed an in vitro model to study mechanisms by which ovarian tumor cells that over-express the HER-2/neu proto-oncogene escape recognition by TCD8+. Nine tumor-specific, HLA A2-restricted TCD8+ clones were isolated from 2 ovarian tumor-specific TCD8+ lines derived from tumor-infiltrating or -associated lymphocytes. Of these, 2 clones recognized the previously defined HER-2/neu epitope E75 (a.a. 369-377) and one recognized the C85 epitope (a.a. 971-979), whereas the specificity of the remaining 6 clones was unknown. Three different tumor escape variants (EVC8, EVC22 and EVC36) were produced by co-culturing an ovarian tumor line over-expressing HER-2/neu with these autologous TCD8+ clones. Cell surface expression of HLA A2 was markedly decreased on all 3 escape variants, relative to the parental tumor line, while no significant decrease in their expression of the HER-2/neu, ICAM-1 or LFA-3 molecules was found. There was a correlation between the level of tumor-specific recognition and HLA A2 expression among the tumor clones isolated from 2 of the escape variants (EVC8 and EVC36). In contrast, high HLA A2-expressing tumor clones isolated from the EVC22 variant, or EVC22 which had regained high HLA A2 expression through IFN-gamma treatment, were not recognized by the HER-2/neu-specific TCD8+ clone C-22. No mutations were found in the cDNA or the genomic DNA derived from the PCR product corresponding to a 496 bp fragment including the region coding for the E75 epitope of the HER2/neu gene in the EVC22 variant. Collectively, this in vitro model underlines the importance of decreased expression of the HLA restriction element for escape from tumor-specific TCD8+ but also demonstrates that additional mechanisms exist.
Kono
K
K
Microbiology and Tumor Biology Center, Karolinska Institute, Stockholm, Sweden.
Halapi
E
E
Hising
C
C
Petersson
M
M
Gerdin
E
E
Vanky
F
F
Kiessling
R
R
D015536:Down-Regulation; D005260:Female; D015789:HLA-A2 Antigen / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007157:Immunologic Surveillance / Q000276:immunology*; D010051:Ovarian Neoplasms / Q000276:immunology*; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014407:Tumor Cells, Cultured
D015789:HLA-A2 Antigen; D000090063:Proto-Oncogene Mas; D018719:Erb-b2 Receptor Tyrosine Kinases; C000715470:MAS1 protein, human