Billions of people worldwide are infected by tropical worms that might cause cancer.
“Helminths take many forms, but all of them harm their host in some way. In humans, they can live in the intestinal tract, urinary tract or bloodstream, causing a variety of illness from malnutrition to organ failure” explained the research co-editor, Dr. Monica Botelho.
“Three species of helminth are classified as class 1 carcinogens by the WHO,” said Botelho. “These are all designated trematodes – after the Latin name for the grisly feeding cavity with which they latch onto their host’s insides.”
“In endemic regions – predominantly sub-saharan Africa and Southeast Asia – flukes are responsible for the majority of all bladder and liver cancer cases,” explained the co-editor, Dr. Joachim Richter. “Cancers arise in sites of fluke infection including the bladder wall and the bile ducts of the liver.”
“Flukes constantly wound and re-wound their host as they latch on with their feeding cavity, burrow through organs, and deposit eggs in the bladder wall. This leads to chronic inflammation as the body tries endlessly to heal, meaning lots of cell division and so lots of opportunities for cancer-causing mutations to accumulate over years of infection.”.
“Worms and their eggs also excrete proteins that exacerbate this chronic inflammation, further promoting cell division as well as the blood vessel growth required to feed it,” Richter added.
“Flukes have been successfully eliminated in Japan by economic development and the filling and drainage of snail habitats,” Richter explained. “Eradication efforts are underway in Thailand, which has the world’s highest rates of liver fluke infection and bile duct cancer – but some high-risk countries like Ethiopia lack a coordinated monitoring or prevention program for fluke-related cancer and need more help.”
“Many parasites, including some helminths like the liver fluke Fasciola hepatica, inhibit cancer growth in vitro. Another of these – the ominously named ‘hyper tapeworm’ – is associated with a significantly lower rate of cancer in human hosts,” reported Botelho.
“In fact, there is evidence that proteins produced by hyper tapeworms as well as F. hepatica not only kill cancer cells directly – but might also enhance their host’s immune response to tumors.”
“Even cancer-promoting fluke proteins might be repurposed as treatments for other conditions: for example, those that promote new blood vessel growth could help resolve chronic non-healing wounds in diabetics, tobacco users, and the elderly.”