Can Zika virus treat brain tumours?

Sometimes in medicine, something that seems unequivocally bad turns out to have a therapeutic use—think of botulinum toxin. Zika virus has caused a devastating epidemic of microcephaly, mostly in South America, as result of maternal exposure in pregnancy. The virus has now been characterised, and researchers in Brazil wondered if its known neuro-destructive properties could be demonstrated in neurons that are rapidly dividing in postnatal life, as with some brain tumours (Kaid C et al. Cancer Research 2018. doi: 10.1158/0008-5472.CAN-17-3201).

First they exposed tumour cell lines in vitro to the Brazilian strain of the virus (ZIKVBR), and found that it selectively infected neuromalignant cells, especially embryonic cell lines, but was ineffective against other tumour cells (breast, prostate etc.). Then in mouse model experiments, they xeno-grafted human embryonic tumour cells (effectively medulloblastoma and teratoma cells) in to mice and injected ZIKVBR into their cerebral ventricles. This produced complete tumour remission in 20/29 animals. The virus did not appear to harm normal neurons. They even observed that the dying malignant cells deactivated the virus, thus further reducing potential harm.

Given that post-natal Zika virus exposure is generally benign, this opens up exciting opportunities for radically new treatments. Obviously far more research will be needed, but the …