Human adenovirus oncolytic properties and the inhibitory role of E4 orf4 and E4 orf6/7 on endogenously activated NF-κB
Anran Wang1, Kazuki Uchida2, Atsuro Yokoyama1
1Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Faculty of Dental Medicine and Graduate School of Dental Medicine, Hokkaido University, Japan.
Abstract:
Human adenovirus is a promising tool for cancer therapy as an oncolytic virus. To predict which region of the oncolytic adenovirus E4 gene could be deleted, we investigated the relationship between the E4 proteins and NF-κB. Here, we report that TLR2-dependent NF-κB activation in Ad5-infected cells was significantly inhibited 24 h post-infection. Among the six E4 proteins, E4 orf4 and E4 orf6/7 exhibited notable suppressive effects on NF-κB activation. However, only E4 orf4 was co-immunoprecipitated with the RelA protein, also known as p65. It appears likely that E4 orf6/7 represses NF-κB activation via E2F-dependent pathways. Our results suggest that both E4 orf4 and E4 orf6/7 are novel inhibitors of NF-κB activation. The inhibition of endogenous NF-κB activation by E4 proteins during the late phase of infection also appears to elucidate the previously reported suppression of E1A expression in the late phase of infection. These redundant suppressive effects of E4 orf4 and E4 orf6/7 on NF-κB suggest that these proteins may play a major role in the anticancer properties of oncolytic adenovirus.
Insights
Human adenovirus E4 proteins, specifically E4orf4 and E4orf6/7, inhibit NF-κB activation, a key factor in cancer. This finding is crucial for developing effective oncolytic adenovirus cancer therapies.
Area of Science:
- Oncolytic virotherapy
- Molecular biology
- Cancer research
Background:
- Oncolytic adenoviruses are promising cancer therapeutics.
- Understanding viral gene functions is key to optimizing their efficacy.
- The E4 gene products of adenovirus play critical roles in viral replication and host interactions.
Purpose of the Study:
- To investigate the role of adenovirus E4 proteins in regulating NF-κB signaling.
- To identify specific E4 proteins that inhibit NF-κB activation.
- To elucidate the mechanisms by which E4 proteins modulate NF-κB during adenovirus infection.
Main Methods:
- Adenovirus type 5 (Ad5) infection of cells.
- Measurement of NF-κB activation via TLR2-dependent pathways.
- Co-immunoprecipitation assays to detect protein-protein interactions.
- Analysis of E4 protein expression and function.
Main Results:
- Ad5 infection significantly inhibited TLR2-dependent NF-κB activation 24 hours post-infection.
- Adenovirus E4orf4 and E4orf6/7 proteins demonstrated significant suppressive effects on NF-κB activation.
- E4orf4 specifically co-immunoprecipitated with RelA (p65), while E4orf6/7 appeared to act via E2F-dependent pathways.
- These E4 proteins were identified as novel inhibitors of NF-κB activation.
Conclusions:
- E4orf4 and E4orf6/7 are novel inhibitors of NF-κB activation during adenovirus infection.
- The inhibitory effects of E4 proteins on NF-κB may explain the suppression of E1A expression in the late phase of infection.
- These findings suggest that E4orf4 and E4orf6/7 play a significant role in the anticancer properties of oncolytic adenoviruses.
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