New therapeutic approaches based on gene transfer techniques

Sticky and smelly issues: lessons on tumour cell and leucocyte trafficking, gene and immunotherapy of cancer

The Second Meeting of the British Society for Immunology Tumour Immunology Affinity Group (TIAG) took place at King's College (London, UK) on 17-18 June 1997 and brought together over 100 tumour immunologists from the UK and abroad. In contrast to previous meetings the focus of the meeting was on the role of adhesion in immunosurveillance and tumour dissemination. In addition, recent achievements in the areas of chemokines, cytotoxic T-lymphocyte (CTL) and natural killer (NK) cells, co-stimulation, gene and adoptive immunotherapy were also addressed. The purpose of this report is to outline current trends in tumour immunology.

Generation of an anti-tumour immune response in a non-immunogenic tumour: HSVtk killing in vivo stimulates a mononuclear cell infiltrate and a Th1-like profile of intratumoural cytokine expression

Direct delivery of the herpes simplex virus thymidine kinase (HSVtk) gene, in combination with the prodrug ganciclovir (GC), has been used for the treatment of localised, inoperable tumours. Several groups have shown that when rodent tumours are ablated in vivo with suicide genes, anti-tumour immunity can also be generated. Hence, this approach may also be useful in treating disseminated disease. Here we have studied the mechanisms associated with this anti-tumour immunity. In B16 HSVtk+ tumours being killed in vivo with GC treatment, we observed the induction of a pronounced intratumoural infiltrate of macrophages, CD4+ and CD8+ T cells. In addition, using reverse transcriptase polymerase chain reaction, expression of interleukin (IL)-2, IL-12, interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and granulocyte/macrophage colony-stimulating factor (GM-CSF) but not IL-4, IL-6 or IL-10, was observed, a profile of cytokine expression which resembles that of a Th1 immune response. To complement these findings, we also investigated the mechanisms by which expression of HSVtk leads to cell death. Our data show that B16/HSVtk+ cells die predominantly by necrosis, rather than apoptosis, on exposure to GC, a process which may be associated with the generation of anti-tumour inflammatory responses. From these data we propose a model for the induction of anti-tumour immunity using suicide genes and discuss the development of improved vectors for gene therapy to augment these effects in vivo.