IN-VITRO STIMULATION OF OVARIAN TUMOR-ASSOCIATED LYMPHOCYTES WITH A PEPTIDE DERIVED FROM HER2 NEU INDUCES CYTOTOXICITY AGAINST AUTOLOGOUS TUMOR/

The proto-oncogene HER2/neu encodes for a 185 kDa transmembrane protei n with extensive homology to the epidermal growth factor (EGF) recepto r. We have previously shown a correlation between HERS/neu expression and the level of in vitro cytotoxicity of tumour-associated lymphocyte s (TAL) versus autologous tumour. In addition, we have recently demons trated that tumour-associated cytotoxic T-lymphocytes (CTL) from ovari an and breast cancer patients can recognize a HERS/neu derived peptide epitope when presented in the context of HLA-AP. Since repeated tumou r stimulation of CTL enhances both proliferation and cytotoxicity agai nst autologous tumour, we hypothesized that repeated peptide antigen s timulation would have a similar effect. To be therapeutically useful, the peptide antigen must meet the following conditions: (1) the peptid e must be immunogenic and cause a proliferation of CTL to adequate the rapeutic numbers, and (2) the peptide-specific CTL which are generated must be cytotoxic against autologous tumour. To test our hypothesis, T-lymphocytes isolated from the ascites of four consecutive HER2/neu() ovarian cancer patients were initially stimulated with solid phase a nti-CD3 antibody and divided into three groups: (1) treatment with rec ombinant interleukin-a (IL-2) alone, (2) IL-2 plus weekly stimulation with irradiated autologous tumour cells, and (3) IL-2 plus weekly stim ulation with a HER2/neu derived peptide. Peptide-stimulated and tumour -stimulated CTL showed similar increases in proliferation with both gr oups consistently reaching therapeutic numbers. Peptide-stimulated CTL demonstrated significantly enhanced cytotoxicity against autologous t umour in 4-h chromium release assays as compared to the IL-2 alone gro up. This cytotoxicity appeared to be HLA-A2 restricted as peptide-stim ulated CTL from HLA-A2(+) patients had significantly increased cytotox icity against allogeneic HLA-A2(+) tumour cells as compared with allog eneic HLA-AP(-) tumour cells. In addition, the cytotoxicity of peptide -stimulated CTL against autologous tumour was blocked with an anti-HLA -AS monoclonal antibody, BB7.2. These findings have potential clinical applicability in that an unlimited amount of synthetic peptide could be available for repeated CTL stimulation when culturing cells for ado ptive immunotherapy. This could be especially beneficial when adequate amounts of tumour cells for stimulation are unavailable. In addition, the identification of tumour-associated antigens which can be recogni zed by autologous CTL may ultimately be useful in the development of a ntitumour vaccine therapy.