- André Biernath – @andre_biernath
- BBC News Brazil
Photo credit, Getty Images
Some viruses have a greater affinity for cancer cells and can help destroy them.
Viruses have always been seen as the big bad guys in health – an even stronger notion during a pandemic like the one we are experiencing, in which the cause of Covid has been linked to 20 million deaths so far.
But within oncology, the specialty of medicine that deals with cancer, some of these infectious agents are increasingly seen as allies: viruses can become a valuable tool for treating a whole range of tumors, point out the experts.
Currently, several research groups are evaluating the possibility of using so-called oncolytic viruses as a means of directly attacking cancer cells or encouraging a more robust immune system response against these diseased units.
The most recent example of this scientific endeavor is CF33-hNIS Vaxinia, a virotherapy developed by City of Hope, a hospital in the United States, and the Australian pharmaceutical company Imugene.
The product provides infectious agents from the same family as smallpox that have been modified in the laboratory to specifically attack tumor cells.
In preclinical tests, carried out with cell and guinea pig samples, this strategy was able to reduce several types of tumors, such as those that appear in the large intestine, lungs, breasts, ovaries and pancreas.
Whether this same effect occurs in humans remains to be seen. At the end of May, scientists began clinical trials, which involve volunteers.
In the first phase of the studies, which will concern 100 patients, the objective is to verify whether the product, injected directly into the tumor or applied by infusion into a vein, is really safe and does not cause side effects.
The results of the experiment should come out within 24 months.
“We hope to harness the promise of virology and immunotherapy to treat a wide variety of deadly cancers,” predicts cancer surgeon Yuman Fong, one of the originators of virology at City of Hope, in a press release. .
Dual action
To understand how virotherapy works in practice, we first need to know how viruses work in nature.
Viruses are extremely simple pathogens whose sole function is to invade the cells of a living being and “hijack” this biological machinery to create new copies of themselves.
These new copies, in turn, will repeat the process for the duration of the infection.
In this rite of invasion, kidnapping and replication, the cells affected by the virus do not resist and die.
Photo credit, Science Photo Library
After invading the cell (green structure in the illustration), the virus (in red) replicates and releases thousands of copies of itself
From the observation of this viral mechanism, some scientists began to speculate: is it not possible to use the same principle to attack only the cells that form the tumour?
This is the basic premise of virotherapy: finding in nature, or developing in the laboratory, pathogens that specifically target cancer cells.
And, by investing in this type of treatment, it is possible to obtain two different positive effects.
“The first consists in invading the sick cell by the virus and killing it”, explains immunologist Martin Bonamino, researcher at the National Cancer Institute (Inca).
“The second is that some of these modified viruses carry specific genes that generate antibodies and stimulate the patient’s own immune system to recognize the tumor and start attacking it,” adds the specialist, who also works at the Oswaldo Cruz Foundation (FioCruz).
This double action can be further potentiated with the use of other remedies together. One possibility is to combine oncolytic viruses with immunotherapy, a type of treatment that encourages the immune system to identify and fight cancer.
But how can we guarantee that these therapeutic viruses will only infect tumor cells and spare the healthy units of the body? This is where biotechnology and genetic engineering come into play.
“The idea is to find pathogens that have an affinity with cancer cells and act specifically on them,” contextualizes clinical oncologist Vladmir Cordeiro de Lima, from the AC Camargo Cancer Center, in São Paulo.
decades of work
The first successful cancer virus therapy proposal was T-VEC, a drug approved by the US regulatory agency in 2015.
It is a therapeutic resource indicated for cases of melanoma, a generally aggressive type of skin cancer.
Since then, several other studies in this field have been initiated. Some of them are even underway in Brazil.
Two different research groups, one at the University of São Paulo (USP) and the other at the State University of Campinas (Unicamp), for example, are studying whether the Zika virus can be used as a treatment for certain types of cancer that affect the central nervous system.
The idea was born from the observation that this pathogen, which has caused a serious public health problem in the country since 2015, has a “preference” to attack the cells that make up the brain and nerves – this, by the way, explains the fact that it be behind microcephaly in babies during pregnancy.
Photo credit, Getty Images
The first successful cancer virus therapy proposal was T-VEC, a drug approved by the US regulatory agency in 2015
The first results, obtained in 2018 from experiments on guinea pigs, were encouraging: Zika effectively reduced the size of nervous system tumors in a significant part of the animals.
Wanted by BBC News Brazil, geneticist Mayana Zatz, who leads Zika research at USP, says investigations into the potential oncolytic virus are ongoing.
“We are working on several fronts. For example, we are looking for different strategies to obtain a modified Zika in the laboratory,” he explains.
The idea is that these genetic alterations made to the “original” virus allow an intensified response to treatment, to achieve even better results.
“We also inject the unmodified virus into dogs diagnosed with brain tumors and follow the clinical and neurological evolution of the cases,” adds the researcher, who coordinates the Center for Human Genome and Stem Cell Studies at the USP.
As knowledge in the field gradually advances, Bonamino stresses the importance of basic scientific research so that innovations such as oncolytic viruses can become a reality.
“These treatments are the result of many years of study, which have made it possible to unravel the basic mechanisms of viruses and to create genetic engineering techniques”, he specifies.
Cordeiro de Lima, in turn, understands that virotherapy could become, in the future, an auxiliary tool in the treatment of many tumors.
“There is great potential for it to be combined and integrated with other strategies, as a means of increasing the spectrum of patients who benefit from cancer treatments,” concludes the doctor.