[Chimeric T cell receptor N29gamma redirect T lymphocytes response specific to p185HER2 in A murine model of metastatic breast cancer].

BACKGROUND & OBJECTIVE: Chimeric T-cell receptors (chTCR) are recombinant immune receptors with the characteristics of combining exquisite antigen specificity of a monoclonal antibody and activating T lymphocyte function by signal transduction element. Compared to "classic" TCR in mediating T cells immune response to target cells,a significant potential advantage of chTCR is the lack of major histocompatibility complex (MHC) restriction and antigen processing. N29gamma is a chTCR specific for p185HER2. The current study is to investigate the efficacy of N29gamma redirect T cells in response to p185HER2 in a murine model of metastatic breast cancer.

METHODS: Splenic T cells from Balb/c mice were purificated by negative selection over sterile brushed nylon wool fiber,activated by immobilized purified anti-mouse CD3 and CD28 antibodies. Then the recombinant retrovirus pRet6N29gamma were transduced by centrifuging (1 300 g for 90 min, at 32 Centigrade). The transduction efficiency was indirectly defermined by green fluorescence protein (GFP) expression of T cells in control group tested by flow cytometry. Mice bearing 3 days or 8 days MT901 or MT901/HER2 were randomized into experiment group or control group to receive IV infusions of polyclonal activated Balb/c splenic T cells transduced with the N29gamma retroviral vector or a control GFP vector(5 x 10(6)-40 x 10(6) of T cells per mouse). Each mouse was injected intraperitoneal with IL-2 of 3 x 10(4) IU every 12 h for 10 times. Mice were sacrificed at 11 days (Day 3 model) or 13 days (Day 8 model) after T cells transfer to enumerate the lung metastases.

RESULTS: In Day 3 model, more than 200 lung metastases were present in mice in mock group, received non-transduced T cells group as well as GFP transduced T cells group. Treatment of mice bearing HER2 positive tumor with N29gamma transduced T cells resulted in a significant reduction in the number of lung metastases (3.4+/-3.3/lung). In contrast,N29gamma transduced T cells failed to induce the regression of HER2 negative MT901 pulmonary metastases (>200/lung). In Day 8 model, treatment with N29gamma modified T cells had a cell dose dependent effect on HER2+ lung metastases. Compared with 4 x 10(7) GFP T cells, 107 of N29gamma T cells were not enough to reduce the number of lung metastases (167+/-15.3) (P=0.198). With increasing dosage of N29gamma modified T cells from 2,3 to 4 x 10(7),there was a progressive decrease in the number of pulmonary metastases from 64+/-12.1,34+/-6.3,to 8+/-4.3,respectively (P< 0.01).

CONCLUSIONS: Gene engineered T cells expressing chimeric TCR N29gamma induced the HER2-specific regression of lung metastases in breast cancer. Higher doses of gene-modified T cells were necessary to eliminate more advanced lung metastases.