HER3 targeting of adenovirus by fiber modification increases infection of breast cancer cells in vitro, but not following intratumoral injection in mice

Abstract

Despite the tremendous potential of adenovirus (Ad) as a delivery vector for cancer gene therapy, its use in clinical settings has been limited, mainly as a result of the limited infectivity in many tumors and the wide tissue tropism associated with Ad. To modify the tropism of the virus, we have inserted the epidermal growth factor-like domain of the human heregulin-a (HRG) into the HI loop of Ad5 fiber. This insertion had no adverse effect on fiber trimerization nor did it affect incorporation of the modified fiber into infectious viral particles. Virions bearing modified fiber displayed growth characteristics and viral yields indistinguishable from those of wild-type (wt) virus. Most importantly, HRG-tagged virions showed enhanced infection of cells expressing the cognate receptors HER3/ErbB3 and HER4/ErbB4. This was significantly reduced in the presence of soluble HRG. Furthermore, HER3-expressing Chinese hamster ovary (CHO) cells were transduced by the HRG-modified virus, but not by wt virus. In contrast, CHO cells expressing the coxsackie-Ad receptor were transduced with both viruses. However, infection of an in vivo breast cancer xenograft model after intratumoral injection was similar with both viruses, suggesting that the tumor microenvironment and/or the route of delivery have important roles in infection of target cells with fiber-modified Ads.Cancer Gene Therapy (2012) 2,3 In addition to being among the most extensively studied viral vectors, Ads can be easily and economically manipulated, maintained and propagated to produce high titer stocks. 4,5 Moreover, they have the capacity to carry relatively large fragments of exogenous DNA into a wide range of cell and tissue types. 4,5 Subgroup C Ads (exemplified by the most widely used Ad5 and Ad2) attach to and enter host cells in a two-step process. 6 The initial recognition/attachment step is mediated by interactions between the knob component of fiber protein on the Ad capsid and the extracellular domain of the coxsackieadenovirus receptor (CAR) on the host cell surface. 7-11 This attachment is followed by a second interaction between the RGD motif in the penton base of the virus capsid and a v b 3 or a v b 5 cell surface integrins (secondary Ad receptors), which allows viral entry via receptor-mediated endocytosis. [12][13][14][15] Both the primary and secondary Ad receptors are expressed on a wide range of tissues leading to the observed broad tissue tropism of Ads. 16,17 Unfortunately, a large number of tumor cells appear relatively refractory to Ad infection because of limited surface expression of the primary Ad receptor. 1,[18][19][20][21][22][23] This observation has been a driving force behind recent intensive efforts to generate Ad viral vectors with altered tropism.

New viruses for cancer therapy: meeting clinical needs

“…Nevertheless, short heterologous peptides and specificity domains that recognize tumour-associated antigens have been inserted into the HI loop and the C terminus of the receptor-binding trimeric fibre protein, which is located at the vertices of the capsid 53,68–71 . The HI loop, in particular, is flexible and the inserted short peptides have minimal negative effects on virus fitness, even in combination with mutations that detarget viruses from natural adenovirus receptors 68 .…”

Adenoviral vector-based strategies against infectious disease and cancer

“…The fiber-modified Ad virions showed enhanced infection of cells expressing the cognate receptors HER3/ErbB3 and HER4/ ErbB4, so the HER3-expressing Chinese hamster ovary (CHO) cells could be transduced by the HRG-modified virus, but not by wild type virus. 132 Other studies showed that the fiber-modified Ads had specific tropism to different cancer cells, which may provide a new strategy for Ad based cancer therapy. 133,134 Capsid-incorporation of foreign antigen into ad virions as vaccine candidate…”

Adenoviruses Using the Cancer Marker EphA2 as a Receptor In Vitro and In Vivo by Genetic Ligand Insertion into Different Capsid Scaffolds

“…Some studies reported lack of peptide mediated transduction after i.t. injection in the context of CAR-binding[41] or CAR binding-ablated HAdV-5 [37].Other studies reported increased transduction (3-fold) or selective oncolytic activity after i.t. injection of Ads with genetically inserted peptide in the HAdV-5 fiber binding or not binding CAR, respectively [42], [43].…”