Cytokine Gene Therapy for Human Tumors

Setting optimal parameters for in vitro electrotransfection of B16F1, SA1, LPB, SCK, L929 and CHO cells using predefined exponentially decaying electric pulses

To achieve the maximal introduction of plasmid DNA into cells and, at the same time, to prevent undesirable cell deaths, electrotransfection conditions should be determined for every single cell type individually. In the present study, we determined the optimal electrotransfection parameters for in vitro transfection of B16F1, SA1, LPB, SCK, L929 and CHO cells. Some of these varying parameters were electric field strength, number of applied pulses and their duration, osmolarity of electroporation buffer, plasmid DNA concentration and temperature at which the electroporation was carried out. The maximal transfection rates at optimal electrotransfection parameters in B16F1, SA1, LPB, SCK, L929 and CHO were 85%, 40%, 60%, 1%, 40% and 65%, respectively. The obtained results confirmed that the electroporation is a useful procedure for an in vitro transfection of the majority of mammalian cells. The method, if optimized, may generate reproducibly high proportion of transfected cells among the cell types that are sensitive to electric field action. Thus, the determined parameters could serve for the subsequent implementations of this method.

Interleukin 12 secretion enhances antitumor efficacy of oncolytic herpes simplex viral therapy for colorectal cancer

OBJECTIVE

To assess the strategy of combining oncolytic herpes simplex virus (HSV) therapy with immunomodulatory therapy as treatment for experimental colon cancer. The oncolytic HSV recombinant NV1023 and the interleukin 12 (IL-12)-secreting oncolytic NV1042 virus were evaluated in vitro and in vivo with respect to antitumor efficacy.

SUMMARY BACKGROUND DATA

Genetically engineered, replication-conditional, attenuated HSVs have shown oncolytic activity against a wide variety of solid malignancies. Other strategies for treating cancer have involved immunomodulation and cytokine gene transfer using viral vectors. This study has combined both of these strategies by inserting the murine IL-12 gene into a replication-competent HSV. This approach allows oncolytic therapy to replicate selectively within and lyse tumor cells while providing the host immune system with the cytokine stimulus necessary to recruit and activate inflammatory cells needed to enhance the antitumor effect.

METHODS

NV1023 is a multimutant HSV based on the wild-type HSV-1 F strain. NV1042 was created by insertion of the mIL-12 gene into NV1023. Cytotoxicity and viral proliferation of both NV1023 and NV1042 within murine CT26 colorectal cancer cells were first shown. Cells infected with NV1042 were then shown to produce significant levels of IL-12. Using an experimental flank model of colon cancer, mice were treated with both high and low doses of NV1023 or NV1042 and were followed up for both cure and reduction in tumor burden.

RESULTS

Both viruses could replicate within and kill CT26 cells in vitro, with 100% cytotoxicity achieved after infection by either virus. Only NV1042 could produce mIL-12. Therapy using high viral doses to treat animals in vivo showed equal efficacy between NV1023 and NV1042, with five of seven cures for each virus. When viral doses were lowered, only the cytokine-producing NV1042 virus could reduce tumor burden and cure animals of their disease.

CONCLUSIONS

Both NV1023 and NV1042 have the oncolytic potential to kill colon cancer cells at higher doses. Cytokine production by NV1042 may allow lower doses of viral therapy to be used without losing antitumor efficacy. The combination of oncolytic viral therapy and immunomodulatory strategies should be further investigated as treatment for colon cancer.

HLA class I expression on human cancer cells. Implications for effective immunotherapy

Early studies demonstrated the role of cytotoxic T cells as an immune defence mechanism against tumour cells. The demonstration of tumour antigen peptides and their presentation to T cells on major histocompatibility complex class I molecules highlighted the importance of these molecules in effective anti-tumour responses. It is well established that many tumours escape T cell recognition by loss or down regulation of class I molecule expression on the cell surface of tumour cells. Tumours which have lost class I expression are immunoselected and as a result have a propensity for growth and metastatic spread. With the development of cancer vaccine strategies for clinical use, there will be a future role for histocompatibility laboratories in determining class I expression on tumour cells in individual patients. These studies of expression will require not just the demonstration of total class I expression but the demonstration of locus and allele specific class I molecules involved in the relevant tumour peptide presentation. These studies will be pivotal in tailoring individual patient therapies. The identification of appropriate monoclonal antibody reagents for class I expression and techniques used on different kinds of tissue sections will be a component of the forthcoming 13th International Histocompatibility Workshop.

Effect of Withania somnifera on cytokine production in normal and cyclophosphamide treated mice

Administration of an extract from the powdered root of the plant Withania somnifera (Family: Solanaceae) enhanced the levels of Interferon gamma (IFN-gamma) (75.87 pg/ml), Interleukin-2 (IL-2) (14.16 pg/ml) and Granulocyte macrophage colony stimulating factor (GM-CSF) (49.22 pg/ml) in normal Balb/c mice. The lowered levels of IFN gamma--(30 pg/ml), IL-2 (4.5 pg/ml) and GM-CSF (19.12 pg/ml) after treatment with cyclophosphamide (CTX) was reversed by the administration of Withania somnifera extract (IFN gamma--74 pg/ml; IL-2 7.5 pg/ml; GM-CSF 35.47 pg/ml). Withania extract lowered the levels of Tumour necrosis factor alpha (TNF alpha) production. Administration of bonemarrow cells from donor mice treated with Withania extract increased the spleen nodular colonies in irradiated mice (8.33) compared to those treated with normal bonemarrow cells (3.03). The number of nodular colonies increased significantly when these animals were continued with Withania extract treatment. These results indicate the immunopotentiating and myeloprotective effect of Withania somnifera as seen from the enhancement of cytokine production and stem cell proliferation and its differentiation.