Abstract B37: Interferon-beta gene transfer to human melanoma cell lines using a specialized adenoviral vector induces high levels of cell death
Authors: David Taynah , Strauss Bryan Eric 
Published: July 2015

Abstract
Melanoma represents only 4% of all skin cancers, yet its prognosis is especially grim once the metastatic disease state has been reached. However, the genotype of melanomas may provide an opportunity for therapeutic intervention. For example, 90% of cases retain wild-type p53 and a considerable number of these present deletions in the chromosome region that encodes interferon-beta; (IFN). In our previous work, we developed adenoviral vectors where transgene expression is controlled by p53 and propose that such vectors would be especially interesting for the treatment of melanoma. We have used these vectors to transfer the mouse IFN cDNA in murine models, including melanoma, and have observed a significant ability of IFN to inhibit cell proliferation in vitro and in vivo (Merkel et al, 2013). In addition, we have shown that the application of IFN contributes to an anti-tumor immune response (unpublished data). Here we present our recent efforts to adapt this strategy to a model of human melanoma. To this end, the human IFN cDNA was cloned into an adenoviral vector that offers CAR-independent transduction due to the incorporation of the RGD tripeptide in the fiber as well as expression of the transgene under the control of p53. We expect that the AdRGDPGhIbeta; vector will provide expression of human IFN in response to cellular p53 activity. Reliable vector expression was confirmed by ELISA. Then SK-MEL-05 and SK-MEL-147 (human melanoma cell lines harboring wild-type p53) were transduced, incubated for 48, 72 or 96 hours of incubation and then cell cycle alterations were assessed by PI/FACS analysis. We observed a time-dependent accumulation of hypodiploid cells in either cell line when treated with the AdRGDPGhIbeta; vector, yet non-treated or treatment with a GFP-expressing virus did not alter the cell cycle profile. At the final time point, more than 90% of cells treated with IFN were hypodiploid. This result suggests that endogenous p53 reliably induced vector expression and that IFN was an efficient inducer of cell death. We observed the paracrine effects of this treatment when we mixed non-transduced cells with transduced cells and obtained a dose-dependent accumulation of hypodiploid cells. In this assay, the presence of only 5% transduced cells was sufficient to kill 40% of the total cell population in both the SK-MEL-05 and SK-MEL-147 cell lines. We are especially encouraged by these results since our mouse models using Ad5 to transfer murine IFN were less efficient in inducing cell death than seen in the human model. At this time we are determining the mechanism of cell death as well as initiating a model of in situ gene therapy with human IFN.
Grants #2010/15025-0 and 2013/25167-5, São Paulo Research Foundation (FAPESP).
Citation Format: Taynah David, Bryan Eric Strauss. Interferon-beta gene transfer to human melanoma cell lines using a specialized adenoviral vector induces high levels of cell death. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Melanoma: From Biology to Therapy; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(14 Suppl):Abstract nr B37.