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Matt Winkler
Matt Winkler
Articles (145) 

Zika Trial on Brain Tumors Helps Validate Cancer Stem Cell Theory

Researchers in Brazil used purified Zika virus to treat brain tumors in mice, with some success. The results could validate the cancer stem cell approach to treatment

May 01, 2018 | About:

If the Zika virus can infect brain cells, can it infect and kill brain tumors? A small research team in Brazil found out that yes, it can, by killing cancer stem cells. Specifically, what they discovered was that a dose of purified Zika virus was able to shrink two types of brain tumors in 20 out of 29 treated mice. Two mice with medulloblastoma had their tumors completely eliminated, and five with a different tumor called AT/RT were also eliminated, for a complete response rate of 24%. In some of those complete response cases, secondary tumors and metastases were also eliminated.

Can the Zika virus actually be commercialized, and is this an investible technology? Probably not in its current form, but consider that CAR-T technology is based on reprogrammed HIV, for example. Novartis’ (NVS) Kymriah, begins by using attenuated HIV as a vector to alter the antigen receptors of T-cells so they recognize cancer. The idea was that HIV is good at infecting T-cells, so if you arm HIV with the code to reprogram T-cells instead of kill them, it might be a good idea. And the idea spawned an industry based on reprogramming T-cells. Essentially all CAR-T drugs in development or in the market owe their origins to reprogrammed viral vectors.

The fact that Zika works in eradicating certain brain tumors makes some intuitive sense, because the virus primarily infects neural progenitor cells, basically brain stem cells. Since these are critical to fetal brain development, the virus can cause microcephaly in newborns, whereas in adults Zika infection isn’t so dangerous and symptoms are typically a fever and rash, if anything.

The implications of Zika successfully treating brain cancer go beyond its potential use as a viral vector. One of the reasons that brain tumors are so hard to eradicate is that they contain cancer stem cells that regrow the tumor after surgery. Brain cancer stem cells are genetically similar to the embryonic and fetal stem cells that Zika targets, so it seems Zika can recognize cancer stem cells specifically and attack.

This provides significant validation and evidence to the basic cancer stem cell theory, and to the biotech companies pursuing a cancer stem cell approach to treating cancer. These include companies like Geron Corp. (NASDAQ:GERN), which is developing imetelstat, a drug that targets cancer stem cells by inhibiting telomerase. Telomerase is an enzyme that lengthens telomeres, which are junk code at the end of chromosomes. Stem cells are more dependent on telomerase than regular cells.

Verastem Inc. (NASDAQ:VSTM) is also working on several small molecule compounds meant to target cancer stem cells.

As of now the cancer stem cell approach to treating cancer is not particularly popular, but after these latest Zika results, we could start seeing broader acceptance of the theory and approach. What is especially interesting is that Zika was able to elicit a complete response in some of the mice treated, which means that targeting cancer stem cells alone, in some cases evidently, can destroy the entire tumor, sort of like killing the queen of a hive or colony can destroy the entire hive.

Disclosure: No positions.

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