Tapeworm may have spread cancer cells in homosexual

[One Gay Experience Causes HIV-AIDS]

Cancer cells transmitted from a common tapeworm appear to have
caused cancer-like tumors in a Colombian man with HIV -- the
first known case of what's called "malignant transformation,"
U.S. health officials are reporting.

The parasite -- known as Hymenolepis nana, or the dwarf tapeworm
-- is the most common human tapeworm worldwide, particularly in
developing nations. At any given time, up to 75 million people
carry it, according to the U.S. Centers for Disease Control and
Prevention.

People can become infected with dwarf tapeworm eggs when they
eat food contaminated with mouse droppings or insects, or ingest
fecal matter from people carrying the parasite.

Usually, the invasion causes no symptoms, but in some people,
the dwarf tapeworm can continue to reproduce itself in the
intestines, according to the case report.

In the case of the man with HIV, CDC scientists suspect that his
weakened immune system allowed the dwarf tapeworm to thrive
unchecked. From there, mutations may have accumulated in some
tapeworm cells -- essentially causing cancer in the parasite --
and those cells eventually caused cancer-like tumors in their
human host.

That, at least, is the theory, according to Dr. Atis
Muehlenbachs, one of the CDC researchers who reported on the
case in the Nov. 5 New England Journal of Medicine.

"There's still a lot we'd like to learn," Muehlenbachs said.

The story began back in 2013, when doctors in Colombia asked the
CDC for help with a puzzling case.

A 41-year-old man with HIV had come to them suffering from
fatigue, weight loss, fever and coughing. CT scans revealed
growths in his lungs, liver and adrenal glands.

But biopsies from the man's lung tumors showed something
bizarre: The tumors were cancer-like, but the cells were tiny.

"They were way too small to be human," Muehlenbachs said. "They
were actually about 10 times smaller than a human cancer cell."

The tumor cells also seemed to be fusing together, the
researchers found -- a behavior not normally seen in human cells.

Ultimately, after a nearly three-month search for the root of
the man's illness, the CDC team found dwarf-tapeworm DNA in the
patient's tumor cells. Three days later, the man was dead. The
tumors didn't directly cause his death (kidney failure did), but
they did contribute to his decline, Muehlenbachs said.

It's not clear how or why the tapeworm cells became malignant
and ultimately caused tumors in their human host, Muehlenbachs
noted.

"We'd also like to know how common this is," he said. "We think
it's rare, but we don't know how rare."

A severely compromised immune system is probably necessary to
set the stage, according to Muehlenbachs: The patient in this
case had not been taking medication to suppress his HIV
infection, and he had very low numbers of infection-fighting T
cells.

But since both HIV and dwarf-tapeworm infection are common in
the developing world, the case raises concerns, the CDC team
said: Similar cases, if they do occur, could be misdiagnosed as
human cancer.

A red flag, Muehlenbachs said, would be tumor cells that seem
impossibly tiny.

And how should doctors treat tapeworm-derived tumors? No one
knows, Muehlenbachs said, but conventional cancer treatments
might work.

The case is unique in that cancerous cells appear to have been
transmitted from the tapeworm itself. But researchers have long
known that some chronic infections, including certain parasites,
can raise the risk of human cancers.

And that's how this case ties into a larger picture, said Dr.
Len Lichtenfeld, deputy chief medical officer for the American
Cancer Society (ACS), in Atlanta.

"We know that infections can cause cancer," Lichtenfeld said.
"Hepatitis B and C can lead to liver cancer, HPV (human
papillomavirus) can cause cervical cancer."

There are even some parasitic infections that have been linked
to an increased risk of developing cancers of the bladder and
bile ducts, according to the ACS.

Researchers don't know the precise mechanisms behind those
infection-cancer links, though.

"The elegance of the science they used in this case is
impressive," Lichtenfeld said. "The tools they used to get
answers weren't available just a few years ago."

The achievement, according to Lichtenfeld, raises the
possibility that those same tools could be used to better
understand the relationship between various infections and
cancer.

On a more everyday level, Muehlenbachs said, the case
underscores the importance of avoiding dwarf tapeworm infection.
For the typical American, he said, that means being careful
about hand-washing and consuming safe water and food when
traveling to countries where the parasite is widespread.

http://www.cbsnews.com/news/tapeworm-may-have-spread-cancer-
cells-in-man/