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Eva Encarnación Rufino-Palomares
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EP1.14 - Targeted Therapy (ID 204)
- Event: WCLC 2019
- Type: E-Poster Viewing in the Exhibit Hall
- Track: Targeted Therapy
- Presentations: 1
- Now Available
- Moderators:
- Coordinates: 9/08/2019, 08:00 - 18:00, Exhibit Hall
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EP1.14-36 - Suicide Gene Therapy Directed by MicroRNA Activity (Now Available) (ID 290)
08:00 - 18:00 | Author(s): Eva Encarnación Rufino-Palomares
- Abstract
Background
Lung cancer is one of the most prevalent types of malignancies worldwide, accounting for 1.6 million deaths every year. Despite last efforts, the overall survival rate at five years after diagnosis is under 15%. Therefore, new approaches are needed to improve the current clinic.
Suicide gene therapy is an interesting technology which consists in expressing a toxic gene into tumor cells. The most studied suicide gene system is the Herpes Simplex Virus Thymidine Kinase (HSV-TK) that converts the non-toxic prodrug ganciclovir (GCV) into a guanosine analog, promoting cell apoptosis. However, there are problems regarding the expression of the toxic gene in non-tumor cells, which would cause unwanted cell death.
MicroRNAs (miRNAs) have been revealed as one of the most important families of gene expression regulators, acting at a posttranscriptional level by binding messenger RNAs (mRNAs) and blocking protein translation. Alterations in the expression levels of these miRNAs in carcinogenesis have been largely described in the literature, being some of them biomarkers in the diagnosis of cancer. The aim of this work is to improve the selectivity of the HSV-TK suicide gene therapy to target exclusively tumor cells, taking advantage of the alterations in the expression of miRNAs in lung cancer.
Method
We have constructed a plasmid that expresses the HSV-TK mRNA under the control of an artificial 3’-UTR containing binding sites for different members of the let-7 family, a miRNA family whose expression is frequently lost during lung cancer development. Thus, we could direct the expression of the toxic gene preferably in tumor cells where the levels of let-7 are low, allowing the expression of the HSV-TK.
To determine the ability to direct the expression of the suicide gene on this system, we used a lung cancer cell line and a non-tumor, lung tissue one. Both lung cancer and non-tumor cell lines were infected with lentiviruses containing the plasmid construction and then cell viability assays, competitive cell growth assays by immunofluorescence and apoptosis assays were performed to check for differences between the GCV-treated and untreated cells.
Result
Our preliminary results suggest that miRNA expression can selectively drive the expression of the HSV-TK in lung cancer cells due to their low let-7 expression values, resulting in a decrease of cell viability in lung cancer cells compared to non-tumor cells after treating them with GCV.
Ectopically overexpressing let-7 into the lung cancer cells blocked the cell viability decrease caused by the GCV, meaning that our artificial 3'-UTR with binding sites for let-7 is working.
Conclusion
According to our results, we have successfully directed the expression of a suicide gene to tumor cells using miRNA activity. Thanks to that, our HSV-TK/GCV suicide gene therapy model adds an extra layer of safety by preventing off-target cell death.
Differential miRNA expression between tumor and normal tissues could be used to direct the expression of a gene of our choice to the tumor tissue, which could be an interesting approach and a potential tool to treat this disease.
