Abstract 3534: Development of the novel AAV-based vectors with selective tropism to human cancer cells
Authors: Sayroo Rana , Yin Zifei , Nolasco Diego , Pandya Munjal , Ling Chen , Aslanidi George 
Published: August 2015

Cancer is a leading cause of human death worldwide. Commonly used methods of treatment such as surgery, radiation and chemotherapy tend to be largely successful but are extremely invasive and have serious toxic side effects. The possibility of manipulating viral genomes and the natural ability of viruses to efficiently infect various cell types has increased an interest in using a virus-based delivery system to express cytotoxic products within target cells. Thus, oncolytic viruses represent an attractive alternative to currently used anti-cancer treatments. Among different viral methods for gene delivery, vectors based on a human parvovirus, the adeno-associated virus (AAV) has attracted much attention mainly because of its non-pathogenic nature, and its ability to mediate long-term, sustained therapeutic gene expression.

In current studies identified AAV serotype 6 being particularly effective in transduction of several human prostate (PC3), breast (T47D) and liver (Huh7) cancer cell in vitro. We also found that transduction efficiency of these vectors can be significantly, up to 3-5-fold, improved by site-direct mutagenesis of surface exposed residues involved in intracellular trafficking. Over thirty single tyrosine (Y), serine (S), threonine (T) and multiple capsid mutants were developed and AAV6-Y705-731F+T492V was identified the most efficient.

However, the vector promiscuity makes it difficult to use in vivo. In the more recent studies on AAV crystal structure, combined with various site-directed and insertion mutagenesis studies of the capsid gene, have identified specific regions of the capsid proteins that are surface-exposed and tolerant to insertion of the peptides. In the current studies, we developed novel AAV-based vectors for targeting of human cancer cells by incorporating Arg-Gly-Asp (RGD) containing peptide to enable AAV to infect integrin-expressing cells. These AAV6-RGD vectors improve transduction efficiency for approximately 3-fold compare with wild-type AAV6 vectors by enhancing viral entry to the cells.

Combination of RGD-peptide and mutations of surface-exposed residues on a single AAV6 capsid further increases transduction efficiency up to approximately 8-10-fold. We also introduced additional mutation at lysine (K531E) since this was shown to impart a heparan sulfate proteoglycan binding ability of vectors and, thus, decrease affinity to mice hepatocytes.

We are currently conducting studies on xenograft animal model in immune-deficient mice to prove specificity and high transduction efficiency of human cancer cells by AAV6-RGD-Y705-731F+T492V-K531E vectors in vivo.

In summary, this approach potentially can lead to the development of therapeutic AAV vectors with selective tropism to human cancer cells.

Citation Format: Rana Sayroo, Zifei Yin, Diego Nolasco, Munjal Pandya, Chen Ling, George Aslanidi. Development of the novel AAV-based vectors with selective tropism to human cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3534. doi:10.1158/1538-7445.AM2015-3534