What causes prostate cancer？ 9/11 first responders provide new clues

Prostate cancer is one of the most common types of cancer for men, but scientists still don't understand how the disease works.

A new study looked 9/11 first responders with prostate cancer who were exposed to toxic dust.

The results provide some new clues about how the disease may progress over time, fueled by the inflammation of a cholesterol gene.

There are more cases of prostate cancer in 9/11 responders than lung cancer — a reminder that the ways cancer works in the body are complex and mysterious.

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Prostate cancer touches almost every American in some way.

It is the most common form of cancer that men get, according to the National Cancer Institute, and it affects more than one in every five men in the US at some point in their life. Though survival rates are improving, prostate cancer is still the second leading cancer killer for men, after lung cancer.

But the disease's cause is largely still a mystery to scientists and doctors.

Now, a new study of men with prostate cancer who were first responders during the September 11 World Trade Center attacks is giving researchers fresh clues about how the disease works. The results suggest that being exposed to toxic dust may change the ways that a body responds to cancer, even years later, in some devastating ways.

“It suggests that the dust could have somehow changed the person's immune system,” Dr. William Oh, the lead author of the new study and an oncologist at Mount Sinai in New York, told Business Insider.

In short, the study found that breathing in lots of toxic dust may trigger chronic inflammation and fuel tumor growth, changing the way a person's genes operate and leading to more cancer.

Overall, research suggests that first responders who were at Ground Zero nearly 18 years ago have a 65% increased risk of developing prostate cancer, compared to the general population. That's a much more noticeable difference than researchers have found for lung-cancer rates in 9/11 survivors, and its especially alarming that so many 9/11 survivors in their 30s and 40s are developing prostate cancer, given that the disease usually affects men in their 60s and older.

“If it was just a matter of exposing yourself to all of these terrible things, you'd have lung cancer before you'd have prostate cancer,” Oh said. “We're looking at an organ that's very far away from the lungs.”

Inhaling toxic dust might be more dangerous to a man's prostate than his lungs

The study, which was published in the journal of Molecular Cancer Research on Thursday, compared tumor samples from 15 men with prostate cancer who had been on “the pile” breathing toxic air on 9/11 to tumor samples from 14 other men with similar prostate cancer diagnoses.

There were a lot of potentially cancer-causing and tumor-promoting agents in the dust that 9/11 responders were exposed to in 2001, including some compounds which may interfere with our thyroid system. The list includes asbestos, silica, cement, PCBs (polychlorinated biphenyls), and PAHs (polycyclic aromatic hydrocarbons), to name a few.

Read More: A toxic-chemicals expert is sounding the alarm about 4 cancer-linked chemicals that could be making us sicker and fatter

When researchers took a look at the tumors of men who'd been exposed to that dust, they found their cells were more receptive and sensitive to cholesterol, a red flag for bad prostate cancer. (Cellular cholesterol is a precursor to androgens, the sex hormones which drive prostate cancer development.)

“This doesn't prove that inhaling the dust causes increases in these cholesterol genes that then lead to prostate cancer growth,” Oh said. “But it gives a potential biological hypothesis around why men who were exposed at the World Trade Center site might be having increased risk of prostate cancer, and maybe increased risk of more aggressive types of prostate cancer.”

To better investigate what might have been happening in first responders' bodies after initial exposure to this toxic dust, the researchers also dosed some rats with some of the rare remaining dust collected in the hours and days after the 9/11 attacks, and found that the rats, much like the men, had a heightened inflammatory response shortly after they were exposed to the dust. After a month, dust-exposed rats also had more cholesterol-receptive genes, again suggesting there's something in the dust that may be both fueling prostate cancer growth, and more aggressive prostate cancer cases.

Prostate cancer is stealthy and it can be deadly: it is often slow-growing and relatively symptom-less, quietly sitting in a gland no bigger than a golf ball, located just below a man's bladder.

Oh hopes that eventually his team's findings will help oncologists determine better ways to prevent aggressive cancer cases before they start, or treat them with novel immunotherapies, which often work by knocking out some of those cholesterol-fueled male sex hormones. He also noted that the study raises fresh questions about the ways in which the places we live and the pollution we breathe could contribute to our cancer risk.

“I don't think people downtown have anything more to worry about than anyone living in any other city at this point,” he said. “But what else are we breathing？ What else is changing our immune system in a way that might be facilitating the growth of cancers like prostate cancer？”