Cancer gene therapy: Part 1. Vector development and regulation of gene expression

Unbiased selection of bone marrow derived cells as carriers for cancer gene therapy

BACKGROUND

There is currently great interest in development of cell-based carriers for delivery of viral vectors to metastatic tumors. To date, several cell carriers have been tested based largely upon their predicted tumor-localizing properties. However, cell types may exist which can be mobilized from the circulation by a tumor which have not yet been identified. Here we use an unbiased screen of bone marrow (BM) cells to identify cells which localize to tumors and which might serve as effective candidate cell carriers without any prior prediction or selection.

METHODS

Unsorted BM cells from green fluorescent protein (GFP)-transgenic donor mice were adoptively transferred into C57Bl/6 mice bearing pre-established subcutaneous B16 melanoma tumors. Forty-eight hours and eight days later, tumors, organs and blood were analyzed for GFP-expressing cells by flow cytometry. The phenotype of GFP cells in organs was determined by co-staining with specific cell surface markers.

RESULTS

CD45(+) hematopoietic cells were readily detected in tumor, spleen, bone marrow, blood and lung at both time points. Within these CD45(+) cell populations, preferential accumulation in the tumor was observed of cells expressing Sca-1, c-kit, NK1.1, Thy1.2, CD14, Mac-3 and/or CD11c. Lymphodepletion increased homing to spleen and bone marrow, but not to tumors.

CONCLUSIONS

We have used an in vivo screen to identify populations of BM-derived donor cells which accumulate within tumors. These studies will direct rational selection of specific cell types which can be tested in standardized assays of cell carrier efficiency for the treatment of metastatic tumors.

Targeting of products of genes to tumor sites using adoptively transferred A-NK and T-LAK cells

Despite successes in animals, cytokine gene expression selectively in human tumors is difficult to achieve owing to lack of efficient delivery methods. Since interleukin (IL)-2-activated natural killer (A-NK) and phytohemagglutinin and IL-2 activated killer T (T-LAK) cells, as previously demonstrated, localize and accumulate in murine lung tumor metastases following adoptive transfer, we transduced them to test their ability to deliver products of genes selectively to tumors. Assessments of transduction efficiency in vitro demonstrated that adenoviral transduction consistently resulted in high (>60%) transduction rates and substantial expression of transgenes such as GFP, Red2, luciferase, beta-galactosidase and mIL-12 for at least 4 days. In vivo experiments illustrated that Ad-GFP transduced A-NK and Ad-Red2 (RFP) transduced T-LAK or mIL-12 transduced A-NK cells localized 10-50-fold more or survived significantly better than mock transduced cells, respectively, within lung metastases than in the surrounding normal lung tissue. Most importantly, mIL-12 transduced A-NK cells provided a significantly greater antitumor response than non-transduced A-NK cells. Thus, adoptive transfer of A-NK and T-LAK cells represents an efficient method for targeting products of genes to tumor sites.

Gene therapy for head and neck cancer

The prognosis of patients with advanced head and neck cancer has not changed significantly in the last twenty years, despite concerted efforts to optimize treatment using conventional modalities such as surgery, radiotherapy and chemotherapy. Novel therapeutic approaches based on our increasing understanding of the molecular changes that underlie the development of cancer have the potential to alter this situation. Gene therapy involves the delivery of genetic sequences in to tumour or normal cells for a therapeutic purpose. A number of viral and non-viral vectors have been developed that have the ability to deliver therapeutic genes specifically to tumours. These therapeutic genes can exert their effects by correcting existing genetic abnormalities, by killing cells directly or indirectly through recruitment of the immune system. In this review, the various gene therapy strategies that are under development are presented with particular reference to the treatment of head and neck cancer.