Abstract
Tissue-specific detargeting by miRNAs has been demonstrated to be a potent strategy to restrict adenoviral replication to cancer cells. These studies have generated adenoviruses with miRNA target sites placed in the 3'UTR of early gene products. In this work, we have studied the feasibility of providing tissue-specific selectivity to replication-competent adenoviruses through the regulation of the late structural protein fiber (L5 gene). We have engineered a 3'UTR containing eight miR-148a binding sites downstream the L5 coding sequence (Ad-L5-8miR148aT). We present in vitro and in vivo evidences of Ad-L5-8miR148aT miRNA-dependent regulation. In vitro data show that at 72 hours post-infection miR-148a-regulation impaired fiber expression leading to a 70% reduction of viral release. The application of seven consecutive rounds of infection in miR-148a cells resulted in 10.000-fold reduction of viral genomes released. In vivo, liver production of infective viral particles was highly impaired, similarly to that triggered by an adenovirus with miRNA target sites regulating the early E1A gene. Noticeably, mice treated with Ad-L5-8miR148aT showed an attenuation of adenoviral-induced hepatotoxicity but retained full lytic activity in cancer cells and exhibited robust antitumoral responses in patient-derived xenografts. Thus, miRNA-control of late proteins constitutes a novel strategy to provide selectivity to adenoviruses.
Highlights
Oncolytic adenoviruses hold great promise for cancer treatment since they can replicate and destroy cancer cells
Since low expression of miRNAs with respect to normal tissue represents a common trait in some neoplastic cells, this has been exploited as a mechanism to control the adenoviral tropism [4]. miRNA-122 recognition of engineered target sites in the 3’-untranslated region (3’UTR) of the E1A gene to control its expression and prevent viral replication of the adenovirus has been the most widely exploited strategy since miR-122 is abundantly expressed in human and murine liver [5, 6]
We have recently shown that www.impactjournals.com/oncotarget the inclusion of 8 target sites downstream E1A recognizing miR-148a/miR-152 family members efficiently detargeted adenovirus from mouse liver and normal pancreas while maintained its antitumoral activity in pancreatic tumors [8]
Summary
Oncolytic adenoviruses hold great promise for cancer treatment since they can replicate and destroy cancer cells. To improve the safety of oncolytic adenoviruses a control of the viral tropism based on tissue-specific miRNA regulation has been exploited. MicroRNAs (miRNAs) are small noncoding RNA molecules with important regulatory roles in gene expression They act by binding to the 3’-untranslated region (3’UTR) of targeted messenger RNAs (mRNAs), promoting either mRNA cleavage or repression of gene expression at post-transcriptional level [2]. MiRNA-122 recognition of engineered target sites in the 3’UTR of the E1A gene to control its expression and prevent viral replication of the adenovirus has been the most widely exploited strategy since miR-122 is abundantly expressed in human and murine liver [5, 6]. We have recently shown that www.impactjournals.com/oncotarget the inclusion of 8 target sites downstream E1A recognizing miR-148a/miR-152 family members efficiently detargeted adenovirus from mouse liver and normal pancreas while maintained its antitumoral activity in pancreatic tumors [8]
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