Oncolytic adenovirus armed with human papillomavirus E2 gene in combination with radiation demonstrates synergistic enhancements of antitumor efficacy

Abstract

High-risk human papillomavirus (hr-HPV) E6 and E7 oncogenes are associated with resistance to radiotherapy in cervical cancer. Efforts have been taken to employ HPV E2, a crucial negative transcriptional modulator of HPV E6 and E7 oncogenes, and also an apoptosis-inducing agent, for therapeutic intervention. Despite being conceptually attractive, the potency and feasibility of current hr-HPV E2-based therapies remain limited. Here, we designed a novel recombinant adenovirus, named M5, with a 27-bp deletion in E1A conserved region-2 by which to realize tumor-specific replication, and a total HPV type 16 (HPV16) E2 gene complementary DNA inserted into the E3 coding region. In this design, M5 exploited the adenovirus E3 promoters to express HPV16 E2 gene in a viral replication-dependent manner and preferentially silenced the hr-HPV E6 and E7 oncogenes in HPV-positive cervical cancer cells. In vitro and in vivo assays confirmed that M5 exhibited potent antitumoral efficacy. Moreover, the effects of combined treatment with M5 and radiation treatment resulted in synergistically enhanced potency (Po0.01). The increase in killing efficacy of M5 was also found in HPV-negative cervical cancer cells, for which the pro-apoptotic activity of HPV16 E2 was thus responsible. Our results indicated that the use of M5 that locally delivers HPV16 E2 to cancers has broad therapeutic windows and that the combination therapy with radiation for cervical cancer will be the more effective way of improving survival.

Human Papillomavirus 16 E2 as an Apoptosis-Inducing Protein for Cancer Treatment: A Systematic Review

“…All 11 records are experimental study designs involved in testing the HPV–16 E2 protein in vitro. There was only one in vivo study where the combination of radiation treatment and fusion protein E2 was carried out in mice [ 20 ]. A total of four studies were conducted in the United Kingdom (UK) [ 22 , 23 , 24 , 25 ] and China [ 19 , 20 , 21 , 26 ], respectively, two in India [ 27 , 28 ], and another one in Mexico [ 29 ].…”

“…In addition to controlling transcription and viral DNA replication, E2 proteins physically interacted with cellular proteins to have an impact on the biology of the host cell [ 16 ]. The involvement of the E2 protein in apoptosis occurred via the p53-dependent and p53-independent pathway, receptor-signaling pathway, and mitochondria-dependent pathway [ 16 , 17 , 18 , 19 , 20 , 21 ]. Published studies showed that E2 induces apoptosis indirectly, via its effects on the expression of E6 and E7, and directly, via its interaction with p53 [ 17 ].…”

Gene Therapy for Malignant and Benign Gynaecological Disorders: A Systematic Review of an Emerging Success Story

“…Regarding the oncolytic virotherapy approach, the use of five different Ads, i.e., rAd-M5, rAd-M6, rAd-53 [112], rAd-VEGFI-251, and rAd-H101 [113], demonstrated significant anti-tumour effects both in vitro and in vivo and led to increased apoptosis of cancer cells. rAd-M5 expressed the HPV E2 gene, which negatively regulated E6 and E7 expression and led to growth suspension and increased apoptosis [110], while rAd-M6 employing antisense HPV16 E6/E7 DNA inhibited the expression of E6 and E7 and induced apoptosis in vitro and in vivo [111]. In another study, Xiao et al used an oncolytic adenovirus expressing the VEGF inhibitor VEGI-251 and demonstrated the induction of apoptosis and the inhibition of neovascularisation [114], while Wang et al, employing rAd-p53 carrying the promoter of early growth response (Egr-1), and the anti-apoptotic TNF-related apoptosis-inducing ligand (TRAIL) gene showed increased radiotherapyinduced apoptosis in cell lines and tumour size reduction in xenograft mice [112].…”

Targeted Gene Delivery Therapies for Cervical Cancer

“…Wang et al developed a tumor-specific replication-competent oncolytic rAd, M5, expressing the HPV16 E2 gene. This combination of the oncolytic ability with gene silencing showed potent antitumoral efficacy in vitro and in vivo, due to viral replication, apoptosis and growth suppression [96]. Another system based on the insertion of a secreted isoform of VEGF inhibitor (VEGI-251) into an oncolytic adenoviral system with E1B 55 kDa gene deletion (ZD55) was described [97].…”

“…The synergistic effect of oncolytic virotherapy combined with RT has also been demonstrated in other studies. Wang et al showed that the combined treatment with radiation and M5 Ad expressing HPV16 E2 gene [96] or M6 Ad with antisense HPV16 E6 E7 DNA [99] inhibits the expression of these oncogenes and induced apoptosis in cervical cancer cells both in vitro and in vivo. M6 Ad could be improved by the introduction of the HPV18 E6 E7 DNA antisense, thus also achieving an antitumor effect in HPV18-related cancer cells.…”