Gene therapy for cancer

Spontaneous regression of cancer: new insights

Suppression of oncogene expression and of host- or tumour-expressed growth factors and receptors may precipitate spontaneous regression or dormancy in human cancer. Loss of oncogenes necessary for progressive proliferation can lead to differentiation changes. Both natural factors and chemical agents can trigger such a change, and of the naturally occurring agents, growth factors and immunological factors have been most studied. We may find new clues to biological methods of prolonging arrest of cancer, by looking for cytogenetic abnormalities, alterations in oncogene expression and immunocytological composition, in patients showing prolonged dormancy of cancer.

Chemo-immunotherapy of murine solid tumors: enhanced therapeutic effects by interleukin-2 combined with interferon alpha and the role of specific T cells

The aim of the present study has been to assess the therapeutic efficacy of various cytokines, singly or in combination, with and without chemotherapy (cyclophosphamide, Cy), in mice carrying advanced, weakly immunogenic tumors (MCA-105 sarcoma, M109 carcinoma). Treatment of animals with i.p. growths or experimental pulmonary metastases began 8-18 days after i.p. or i.v. tumor cell inoculation respectively. None of the cytokines tested [interleukin-2 (IL-2), interferon alpha (IFN alpha), tumor necrosis factor alpha (TNF alpha) and macrophage-colony-stimulating factor (M-CSF)] nor Cy had by itself a significant curative effect. A synergistic therapeutic effect was obtained with IL-2 or IFN alpha (but not with TNF alpha or M-CSF) in combination with Cy. The most efficacious regimen (65%-90% cure of mice carrying i.p. tumors) was the combination of Cy+IL-2+IFN alpha. Preliminary experiments suggested that sequential administration of these cytokines might be more beneficial than concurrent administration. Following successful immunotherapy, long-term (3-6 months) survivors showed a tumor-specific resistance to a second tumor challenge and their spleen contained an increased number of specific antitumor cytotoxic T lymphocyte precursors (5- to 20-fold, compared to control mice). In vitro and in vivo cell-depletion experiments using monoclonal antibodies revealed that T cells (primarily CD8), but not NK cells, are crucial for the therapeutic effects. This study indicates that a potent specific antitumor T cell immunity can be elicited against advanced weakly immunogenic tumors by combining chemotherapy (Cy) with IL-2 and IFN alpha.