E1A- and E1B-Double Mutant Replicating Adenovirus Elicits Enhanced Oncolytic and Antitumor Effects

Abstract

Gene-modified replication-competent adenoviruses (Ads) are emerging as a promising new modality for the treatment of cancer. We have previously shown that E1B 19kDa and E1B 55kDa gene-deleted Ad (Ad-DeltaE1B19/55) exhibits improved tumor-specific replication and cell lysis, leading to an enhanced antitumor effect. In an effort to increase cancer cell selectivity of a replicating adenovirus, we first generated 11 E1A mutant Ads (Ad-E1mt1 to Ad-E1mt11) with deletion or substitution in retinoblastoma (pRb)-binding sites of E1A. Of these, Ad-E1mt7 demonstrated significant improvement in cytopathic effect (CPE) and viral replication in a cancer cell-specific manner. To further enhance the cancer cell specificity of Ad-E1mt7, Ad-DeltaE1Bmt7 was generated, in which both the E1B 19kDa and E1B 55kDa genes were deleted. As assessed in CPE assay and immunoblot analysis for Ad fiber expression, Ad-DeltaE1Bmt7 exerted marked enhancement in cancer cell-specific killing as well as viral replication in comparison with its comparative controls (Ad-E1mt7, Ad-DeltaE1B55). Furthermore, the growth of established human cervical carcinoma in nude mice was significantly suppressed by intratumoral injection of Ad-DeltaE1Bmt7. In summary, we have developed an oncolytic adenovirus with a significantly improved therapeutic profile for cancer treatment.

Double E1B 19 kDa- and E1B 55 kDa-deleted oncolytic adenovirus in combination with radiotherapy elicits an enhanced anti-tumor effect

“…Moreover, the E1A protein present in oncolytic Ad may play a role as a potent inducer of p53 protein, ultimately increasing the rate of apoptosis caused by ionizing radiation. As shown by our earlier study, 31 infection with oncolytic Ad resulted in a larger increase in p53 levels relative to untreated cells. According to Portella et al,…”

Molecular characterization of apoptosis induced by CARF silencing in human cancer cells

“…Adenovirus carrying the E1B7 deletion (Ad-DB7) has been shown to markedly increase oncolysis and apoptosis, potentiating its development as a novel anticancer therapy, but its tumor-targeting effect is still considered mild, thus, it may be more effective as an adjuvant treatment. 31 Previously, adenovirus with E1 deletions exhibited enhanced efficacy and tumorilytic activities when administered in conjunction with radiotherapy or chemotherapeutic drugs. 32,33 Alternatively, using the mutant adenovirus as anticancer gene carriers had also demonstrated increased oncolytic efficacy.…”

S100A2 promoter-driven conditionally replicative adenovirus targets non-small-cell lung carcinoma

“…Rb7D19k was designed to carry E1B19k-deleted genome, which allowed a better anti-tumor effect than other E1B gene attenuation, 18 and in addition a pRb-binding mutant E1A (substitution of Glu with Gly at amino acid 45 in the CR1 and seven amino acids (DLTCHEA) with seven Gly (GGGGGGG) in the CR2) for better cancer cell selectivity (Figure 3a). 19 The innate E1A promoter of Rb7D19k was replaced with the S100A2 promoter in Ad/SA. We then evaluated the cytopathic effect of Ad/SA infection in the cell panel.…”

“…18) was digested with XbaI/KpnI, and the E1B55k fragment was subcloned into the XbaI/KpnI site of the plasmid pXC1/Mt no. 7 containing the pRb-binding mutant E1A, 19 generating pXC1/Rb7D19. The Rb7D19 gene (mutant E1A and E1B55k) was then excised from pXC1/ Rb7D19 using EcoRI and BamHI, and cloned into pDE1Sp1B to generate pDE1Sp1B/Rb7D19.…”