His tumors were not made up of his own cells, but those of the parasitic worm that invaded his gut. The cells were clearly cancerous – they were invasive, grew rapidly and in a crowded, disordered manner, and all looked the same.
Baffled, scientists subjected them to a bounty of tests, which eventually revealed the tumor cells contained H. nana DNA. Unfortunately, it was too late for the patient, who died just 72 hours after the discovery was made.
Analysis of the tumor cells’ worm DNA when compared with a reference genome of an otherwise normal worm also revealed something quite striking.
“If they mutate in humans, they can lead to a cell becoming cancerous. That’s never really been shown, that sort of commonality between becoming malignant in a human cell line and an invertebrate cell line.”
Although cancerous cells naturally circulate in certain animals, like dogs, cancer isn’t really transmissible between humans – although agents that can cause cancer, like human papillomavirus and the trematode worm Schistosoma haematobium can be transmitted between people.
This man was immunocompromised by HIV, allowing the parasitic cells to grow uncontrollably, thus presenting the opportunity for cancer-causing mutations to arise from mistakes in cell division.