Researchers create viruses to selectively attack tumor cells

Scientists at the IDIBAPS Biomedical Research Institute and at the Institute for Research in Biomedicine (IRB Barcelona) lead a study in which they have designed a new strategy to achieve genetically modified viruses that selectively attack tumor cells without affecting healthy tissues. Published today by the journal Nature Communications, the study is part of Eneko Villanueva’s work for his PhD thesis and is co-led by Cristina Fillat, head of the Gene Therapy and Cancer Group at IDIBAPS, and Raúl Méndez, ICREA researcher at IRB Barcelona.

Conventional cancer treatment can cause undesirable side effects as a result of poor selectivity. To avoid them, it is important that new therapies efficiently remove cancer cells while preserving healthy ones. One of the new approaches in cancer therapy is based on the development of oncolytic viruses, that is to say, viruses modified to infect only tumor cells. In recent years several studies have focused on the development of genetically engineered viruses to maximize their anticancer effect; however, as their potency increases, so does associated toxicity. Limiting this effect on healthy cells is now the key to the application of this promising therapy.

An innovative and specific approach

In the study published in the journal Nature Communications, researchers from IDIBAPS and IRB Barcelona have developed an innovative approach to provide an adenovirus with high specificity against tumor cells. "We have taken advantage of the different expression of a type of protein, CPEBs, in normal and tumor tissues," explains Raúl Méndez from IRB Barcelona.

CPEB is a family of four RNA binding proteins (the molecules that carry information from genes to synthesize proteins) that regulate the expression of hundreds of genes and maintain functionality and the ability to repair tissues under normal conditions. When CPEBs become imbalanced, they change the expression of these genes in cells and contribute to the development of pathological processes such as cancer. "We have focused on the double imbalance of two of these proteins in healthy tissues and tumors. On the one hand, we have CPEB4, which in previous studies we demonstrate to be highly expressed in cancer cells and necessary for tumor growth. And, on the other hand, there is CPEB1, which is expressed in normal tissue and lost in cancer cells. We have taken advantage of this imbalance to develop a virus that attacks only cells with high levels of CPEB4 and low levels of CPEB1, which means that it affects only tumor cells, ignoring healthy tissues," says Méndez.

"In this study we have worked with adenoviruses, a family of viruses that can cause infections of the respiratory tract, the urinary tract, and also conjunctivitis and gastroenteritis but which have features that make them very attractive for tumor treatment," explains Cristina Fillat. To do this, it is necessary to modify the genome of these viruses. In the study, researchers inserted sequences that recognize CPEB proteins in key regions for the control of viral proteins. Their activity was checked in in vitro models of pancreatic cancer and control of tumor growth was observed in mouse models.

The oncoselective viruses developed in this study were very sophisticated, being activated by CPEB4 but repressed by CPEB1. Thus, researchers achieved attenuated viral activity in normal cells, while in tumor cells the virus potency was maintained or even increased. "When the modified viruses entered tumor cells they replicated their genome and, when leaving , they destroyed the cell and released more viral particles with the potential to infect more cancer cells," says Fillat. She adds that, “this new approach is very interesting since it is a therapy that is selectively amplified in the tumor".

Since CPEB4 is overexpressed in several tumors, this oncoselective strategy may be valid for other solid tumors. Researchers are now trying to combine this treatment with therapies that are already used in clinical practice or that are in a very advanced stage of development, with the aim to find synergies that make them more effective.

This technology is patent protected and ready for out-license.

This study has received funding from the Spanish Association Against Cancer (AECC) and Fundación Botín and Banco Santander, through Santander Universidades.

Reference article:

Eneko Villanueva, Pilar Navarro, María Rovira-Rigau, Annarita Sibilio, Raúl Méndez, Cristina Fillat

Translational reprogramming in tumor cells can generate oncoselectivity in viral therapies

Nature Communications. DOI: 10.1038/NCOMMS14833

About IRB Barcelona

Created in 2005 by the Generalitat de Catalunya (Government of Catalonia) and University of Barcelona, IRB Barcelona is a Severo Ochoa Centre of Excellence, a seal that was awarded in 2011. The institute is devoted to conducting research of excellence in biomedicine and to transferring results to clinical practice, thus improving people’s quality of life, while simultaneously promoting the training of outstanding researchers, technology transfer, and public communication of science. Its 23 laboratories and seven core facilities address basic questions in biology and are orientated to diseases such as cancer, metastasis, Alzheimer’s, diabetes, and rare conditions. IRB Barcelona is an international centre that hosts more than 400 employees and 36 nationalities. It is located in the Barcelona Science Park. IRB Barcelona forms part of the Barcelona Institute of Science and Technology (BIST) and the “Xarxa de Centres de Recerca de Catalunya” (CERCA).