SummaryThe squamous cell carcinoma antigen (SCC Ag) is a tumour-associated protein and a member of the serine protease inhibitor (serpin) family. The SCC Ag has been used as a serologic tumour marker for SCC progression, and its elevated serum levels are a risk factor for disease relapse. However, the biologic significance of this intracytoplasmic protein in cancer cells remains unknown. In this report, we demonstrated that apoptosis induced by 7-ethyl-10-hydroxycamptothecin, tumour necrosis factor-α (TNF-α) or interleukin (IL)-2-activated natural killer (NK) cells was significantly inhibited in tumour cells transduced with the SCC Ag-1 cDNA, as compared to control cells in vitro. Also, inhibition of the SCC Ag-1 expression in tumour cells by transfection of antisense SCC Ag-1 cDNA was accompanied by significantly increased sensitivity of these cells to apoptosis induced by etoposide or TNF-α. The mechanism of protection of tumour cells from apoptosis involved inhibition of caspase-3 activity and/or upstream proteases. In vivo, tumour cells overexpressing the SCC Ag-1 formed significantly larger tumours in nude mice than the SCC Ag-1-negative controls. Thus, overexpression of the SCC Ag-1, a member of the serpin family, in human cancer cells contributed to their survival by mediating protection from drug-, cytokine-or effector cell-induced apoptosis.

A variety of strategies have been attempted in the past to stably transduce natural killer (NK) cells with cytokine or other cellular genes. Here, we demonstrate the successful delivery of the interleukin-2 (IL-2) gene into two human NK cell lines, IL-2–dependent NK-92 and IL-2–independent YT, by retroviral transduction. An MuLV-based retroviral vector expressing human IL-2 andneor markers from a polycistronic message was constructed and transduced into a CRIP packaging cell line. By coincubation of NK cells with monolayers of CRIP cells or by using retrovirus-containing supernatants in a flow-through method, 10% to 20% of NK cells were stably transduced. Upon selection in the presence of increasing G418 concentrations, transduced NK cells were able to proliferate independently of IL-2 for more than 5 months and to secrete up to 5.5 ng/106 cells/24 h of IL-2. IL-2 gene-transduced NK-92 cells had an in vitro cytotoxicity against tumor targets that was significantly higher than that of parental cells and secreted interferon gamma (IFNγ) and tumor necrosis factor alpha (TNFα) in addition to IL-2. Moreover, the in vivo antitumor activity of IL-2 gene-transduced NK-92 cells against established 3-day liver metastases in mice was greater than that of parental nontransduced NK cells. Stable expression of the IL-2 transgene in NK cells improved their therapeutic potential in tumor-bearing hosts. Thus, transduced NK cells secreted sufficient quantities of bioactive IL-2 to proliferate in vitro and mediated the antitumor effects both in vitro and in vivo in the absence of exogenous IL-2. These results suggest that genetic modification of NK cells ex vivo could be useful for clinical cancer therapy in the future.

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Anti-murine (m) interleukin-5 (IL-5) antibody was found to inhibit eosinophil (Eo) colony formation stimulated by recombinant human (rh) IL-5, but did not inhibit the production of Eo stimulated by rh IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF). Conditioned medium (CM) prepared from eosinophilic patients' T cells with interleukin-2 (IL-2) stimulation (T-IL-2-CM), was found to contain CFU- Eo growth-stimulating factor. Using anti-mIL-5 antibody, we demonstrated that T-IL-2-CM from patients with eosinophilia contained a significant amount of IL-5. We also detected IL-5 mRNA in T cells from eosinophilic patients with IL-2 stimulation. These results suggest that IL-5 plays an important role in the induction of selective eosinophilia in humans and that IL-5 is produced from T cells with IL-2 stimulation.

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