This proposal is designed to evaluate mechanisms of antitumor activity of IL2 or IL2 and human IL-2-activated effector cells in a series of in vitro studies and in vivo utilizing an animal model established in our laboratory. The model involves xenografting human oral squamous cell carcinoma (SCC) cell lines into immunosuppressed BALB/c nude mice (splendectomized and pretreated with cyclophosphamide and anti-asialo GMI antibody). The tumors, which develop following subcutaneous injection of sufficient numbers of tumor cells in these mice, histologically resemble the original human tumors. The model has been used by us to demonstrate that established SCC could be induced to regress completely as a result of local administration of interleukin 2 (IL2) plus human natural killer (A-NK) cells. Tumor regression was also induce by supernatants (SN) of A-NK cells in injected perilesionally to mice bearing established SCC. Our observation that SC of the head and neck (SCCHN) express functional receptors for IL2 (IL2R) and that IL2 inhibits growth of SCCHN cell lines in vitro and of established tumors in vivo, provide a strong rationale for further investigating direct effects of IL2 on tumor growth. The role of IL2R in IL2-induced tumor growth inhibition will be explored by studying expression of high-affinity (a,B,y) and intermediate-affinity (B,gamma) IL2R on SCCHN cell lines relative to the level of proliferation inhibition by IL2. Cell cycle analysis will be used to determine the proportion of tumor cells arrested in the G/G1 phase in the presence of IL2. SCCHN cell lines will be transfected with the IL2-a and gamma chain genes or anti-sense IL2R-B chain gene to alter tumor cell responsiveness to growth inhibitory effects of IL2. Tumor transfectants will be evaluated first in vitro and the in vivo for IL-2-mediated growth inhibition. In vivo locoregional delivery of IL-2, IL2 plus effector cells or SN or A-NK cells to SCC transfectants and parental tumors established in nude mice is expected to result in tumor regression. Therapeutic of IL2, SN or IL2 plus effector cells will be compared in this in vivo model, and tumor regression or extended survival of treated mice will be used as endpoints to optimize local immunotherapy. SCC will be transfected with the IL2 gene and implanted into animals. The tumor transfectants are expected to produce IL2, so that both autocrine IL2R-mediated cytostatic effects of IL2 and its immunostimulatory effects on adoptively transferred effector cells can be compared. To evaluate the biologic role of IL2R on human SCCHN, in situ expression of IL2R on rat mucosal epithelium, primary and recurrent SCC in the oral cavity and oropharynx will be determined by immunoperoxidase in situ hybridization, using fresh biopsy tissue. Expression of IL2R will be related to that of epidermal growth factor receptor (EGFR) and its ligand, EGF. In situ result should therapeutic efficacy of IL2 in the xenograft tumor model may lead to development of novel strategies for treatment of human SCCHN.
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