A Transductionally Retargeted Adenoviral Vector for Virotherapy of Her2/neu-Expressing Prostate Cancer

Abstract

The efficacy of adenovirus (Ad)-based gene therapy of solid tumors, such as prostate cancer, is limited. One of the many problems is that the virus infects many different cell types in the body, resulting in high toxicity, whereas the target cancer cells are often less prone to wild-type Ad infection. Our aim was to develop genetically de- and retargeted Ad vectors to reduce off-target effects and increase target infection for prostate cancer. We have previously reported an Ad5 vector specific for the cancer-associated receptor Her2/neu, created by inserting Her2/neu-reactive Affibody(®) molecules (ZH) into the HI loop of a coxsackievirus and adenovirus receptor binding-ablated fiber (Ad[ZH/1]). In addition to virus retargeting to Her2/neu, this virus was further modified from wild-type Ad by changing the RGD motif in the penton base to EGD and by substitution of the KKTK motif in the third shaft repeat to RKSK, resulting in the vector Ad[ZH/3]. The ZH-containing vectors could be produced to high titers and were specific for their target, resulting in efficient infection and killing of Her2/neu-positive androgen-dependent PC346C prostate cancer cells in vitro. Here we show that the oncolytic Ad[ZH/3] vector significantly prolonged survival time and reduced serum prostate-specific antigen levels in an orthotopic prostate tumor model in nude mice to the same extent as wild-type Ad5. Our results show that Her2/neu targeting using Ad-based vectors for prostate cancer is feasible and may serve as a basis for the development of gene therapy of human prostate cancer as well as other Her2/neu-expressing cancers.

Adenovirus Serotype 5 Vectors with Tat-PTD Modified Hexon and Serotype 35 Fiber Show Greatly Enhanced Transduction Capacity of Primary Cell Cultures

“…Since CAR is expressed at low levels on some human primary cell types, especially cells of hematopoietic origin, and CAR expression is frequently downregulated on tumor cells, Ad5 transduction is often not efficient. Extensive efforts have been devoted to improve the therapeutic efficacy of adenovirus by modifying adenoviral surface proteins, which include fiber pseudotyping and/or modification [1], [2], [3], [4], pIX modification [5], [6] hexon modification [7], [8] and also chemically mediated surface modifications [9]. We have previously reported that modified Ad5 containing the protein transduction domain (PTD) from the HIV-1 Tat protein (Tat-PTD) inserted into the hexon hyper variable region 5 (HVR5) of the virus capsid, have significantly higher transduction capacity than wild-type Ad5 and show increased oncolytic efficacy on many tumor cell types including neuroendocrine tumors and neuroblastoma [10].…”

Development of a generic adenovirus delivery system based on structure-guided design of bispecific trimeric DARPin adapters

“…To retarget Ad5, two types of strategies have been followed: the genetic fusion to Ad coat proteins, mainly established for fiber fusions (16,(21)(22)(23)(24)(25), and the development of bispecific adapters (for review see refs. 14 and 26).…”

Adenovirus Strategies for Tissue-Specific Targeting

“…In addition to classical target-specific short peptides, Myhre et al (2009) inserted an Affibody, a small antibody mimetic, into the HI loop and showed HER2/neu and Taq polymerase-specific targeting. They also showed that HER2/neu-specific, Affibody-targeted oncolytic Ad provided increased transduction and killing in prostate cancer cells in vitro and increased survival time while decreasing serum prostate-specific antigen in an orthotopic mouse model of prostate cancer (Magnusson et al, 2011). …”