In a case of medicine meets earth science, the researchers discovered that cancer cells may be made from a different assortment of hydrogen atoms than healthy tissue. The findings could give doctors new strategies for studying how cancer grows and spreads — and may even, one day, lead to new ways to spot cancer early on in the body.

The team, led by CU Boulder geochemist Ashley Maloney, will publish its findings this week in the Proceedings of the National Academy of Sciences.

“This study adds a whole new layer to medicine, giving us the chance to look at cancer at the atomic level,” said Maloney, a research associate in the Department of Geological Sciences.

She explained that in nature, hydrogen comes in two main flavors, or isotopes. Some hydrogen atoms, called deuterium, are a little heavier, while others, usually just known as hydrogen, are a little lighter. On Earth, hydrogen atoms outnumber deuterium atoms by a ratio of about 6,420 to one.

For decades, scientists from a number of fields have turned to the natural distribution of these atoms to reveal clues about the history of our planet. Climate scientists, for example, examine the hydrogen atoms trapped in the ice on Antarctica to infer how hot or cool Earth was hundreds of thousands of years ago.

In the new study, Maloney and her colleagues wondered: Could those same, tiny atoms provide hints about the lives of complex biological organisms?

To find out, the team grew cultures of yeast and mouse liver cells in the lab, then analyzed their hydrogen atoms. The team found that cells that are growing really fast, such as cancer cells, contain a much different ratio of hydrogen versus deuterium atoms. Think of it like cancer leaving a fingerprint on the doorknob of a crime scene.

The research is still in its early stages, and the team isn’t sure how this signal might appear, or not, in the bodies of real cancer patients. But the potential could be big, said Sebastian Kopf, a co-author of the study and an assistant professor in geological sciences.

“Your chances of survival are so much higher if you catch cancer early on,” Kopf said. “If this isotopic signal is strong enough that you could detect it through something like a blood test, that could give you an important hint that something is off.”

The metabolism of cancer

The study centers around a concept that has intrigued cancer researchers for years: metabolism.

Under normal conditions, the cells of organisms like yeast and animals generate energy through a process called respiration, in which they take in oxygen and release carbon dioxide. But that’s not the only way to get a sugar high. Colonies of baker’s yeast (Saccharomyces cerevisiae), for example, can produce energy via fermentation, in which organisms break down sugars without help from oxygen and produce alcohol. It’s the same process that gives you beer.

“In humans, if an athlete performs beyond their aerobic limit, their muscles will also start fermenting, which doesn’t use oxygen,” Kopf said. “That gives you a quick energy boost.”

As it turns out, many cancer cells also fuel their growth through a similar get-rich-quick strategy.

Scientists have long searched for more ways to track these metabolic changes in cancer cells. Maloney, who led the new study as a Harry Hess Postdoctoral Fellow at Princeton, and her advisor Xinning Zhang developed an idea: Track hydrogen.

Inside the cell

Today, Maloney manages CU Boulder’s Earth Systems Stable Isotope Lab, one of more than 20 Core Facilities on campus. As a graduate student, she explored hydrogen atoms in algae from tropical islands. Her current work was inspired by an unlikely source: her father, a dermatologist.

“He takes skin cancer cells off people all the time,” Maloney said. “I wondered how the metabolism of those cells might be different from the cells growing next to them.”

To understand that question, it helps to know how hydrogen winds up in cells in the first place. In some cases, those atoms come from a hard-to-pronounce, but critically important, enzyme known as nicotinamide adenine dinucleotide phosphate (NADPH). Among its many roles in cells, NADPH collects hydrogen atoms then passes them to other molecules in the process of making fatty acids, an important building block for life.

NADPH, however, doesn’t always draw from the same pool of hydrogen. Previous research led by Zhang and focusingg on bacteria suggested that, depending on what other enzymes in a cell are doing, NADPH may sometimes use different hydrogen isotopes more or less often.

Which raised the question: If cancer rewires a cell’s metabolism, could it also alter how NADPH gets its hydrogen, ultimately altering the atomic makeup of a cell?

Window into cancer

To begin to find out, the researchers set up jars filled with flourishing colonies of yeast in labs at Princeton and CU Boulder. Separately, biologists at Princeton conducted an experiment with colonies of healthy and cancerous mouse liver cells. The researchers then pulled the fatty acids from the cells and used a machine called a mass spectrometer to identify the ratio of hydrogen atoms within.

“When we started the study, I thought, ‘Ooh, we have a chance to see something cool,” Maloney said. “It ended up creating a huge signal, which I didn’t expect.”

Fermenting yeast cells, the kind that resemble cancer, contained roughly 50 percent fewer deuterium atoms on average than the normal yeast cells, a startling change. Cancerous cells exhibited a similar but not quite as strong shortage in deuterium.

Zhang, the study’s senior author and an assistant professor of geosciences at Princeton, is hopeful that the research could one day help families around the world.

“Cancer, and other illnesses, are unfortunately a huge theme in many people’s lives. Seeing Ashley’s data was special, profound moment,” Zhang said. “It meant that a tool used to track planetary health might also be applied to track health and disease in lifeforms, hopefully one day in humans. Growing up in a family challenged by cancer, I hope to see this area expand.”

The new study fills in a big gap in what the researchers call “the water story on Venus.” Using computer simulations, the team found that hydrogen atoms in the planet’s atmosphere go whizzing into space through a process known as “dissociative recombination” — causing Venus to lose roughly twice as much water every day compared to previous estimates.

The team will publish their findings May 6 in the journal Nature.

The results could help to explain what happens to water in a host of planets across the galaxy.

“Water is really important for life,” said Eryn Cangi, a research scientist at the Laboratory for Atmospheric and Space Physics (LASP) and co-lead author of the new paper. “We need to understand the conditions that support liquid water in the universe, and that may have produced the very dry state of Venus today.”

Venus, she added, is positively parched. If you took all the water on Earth and spread it over the planet like jam on toast, you’d get a liquid layer roughly 3 kilometers (1.9 miles) deep. If you did the same thing on Venus, where all the water is trapped in the air, you’d wind up with only 3 centimeters (1.2 inches), barely enough to get your toes wet.

“Venus has 100,000 times less water than the Earth, even though it’s basically the same size and mass,” said Michael Chaffin, co-lead author of the study and a research scientist at LASP.

In the current study, the researchers used computer models to understand Venus as a gigantic chemistry laboratory, zooming in on the diverse reactions that occur in the planet’s swirling atmosphere. The group reports that a molecule called HCO+ (an ion made up of one atom each of hydrogen, carbon and oxygen) high in Venus’ atmosphere may be the culprit behind the planet’s escaping water.

For Cangi, co-lead author of the research, the findings reveal new hints about why Venus, which probably once looked almost identical to Earth, is all but unrecognizable today.

“We’re trying to figure out what little changes occurred on each planet to drive them into these vastly different states,” said Cangi, who earned her doctorate in astrophysical and planetary sciences at CU Boulder in 2023.

Spilling the water

Venus, she noted, wasn’t always such a desert.

Scientists suspect that billions of year ago during the formation of Venus, the planet received about as much water as Earth. At some point, catastrophe struck. Clouds of carbon dioxide in Venus’ atmosphere kicked off the most powerful greenhouse effect in the solar system, eventually raising temperatures at the surface to a roasting 900 degrees Fahrenheit. In the process, all of Venus’ water evaporated into steam, and most drifted away into space.

But that ancient evaporation can’t explain why Venus is as dry as it is today, or how it continues to lose water to space.

“As an analogy, say I dumped out the water in my water bottle. There would still be a few droplets left,” Chaffin said.

On Venus, however, almost all of those remaining drops also disappeared. The culprit, according to the new work, is elusive HCO+.

Missions to Venus

Chaffin and Cangi explained that in planetary upper atmospheres, water mixes with carbon dioxide to form this molecule. In previous research, the researchers reported that HCO+ may be responsible for Mars losing a big chunk of its water.

Here’s how it works on Venus: HCO+ is produced constantly in the atmosphere, but individual ions don’t survive for long. Electrons in the atmosphere find these ions, and recombine to split the ions in two. In the process, hydrogen atoms zip away and may even escape into space entirely — robbing Venus of one of the two components of water.

In the new study, the group calculated that the only way to explain Venus’ dry state was if the planet hosted larger than expected volumes of HCO+ in its atmosphere. There is one twist to the team’s findings. Scientists have never observed HCO+ around Venus. Chaffin and Cangi suggest that’s because they’ve never had the instruments to properly look.

While dozens of missions have visited Mars in recent decades, far fewer spacecraft have traveled to the second planet from the sun. None have carried instruments capable of detecting the HCO+ that powers the team’s newly discovered escape route.

“One of the surprising conclusions of this work is that HCO+ should actually be among the most abundant ions in the Venus atmosphere,” Chaffin said.

In recent years, however, a growing number of scientists have set their sights on Venus. NASA’s planned Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission, for example, will drop a probe through the planet’s atmosphere all the way to the surface. It’s scheduled to launch by the end of the decade.

DAVINCI won’t be able to detect HCO+, either, but the researchers are hopeful that a future mission might — revealing another key piece of the story of water on Venus.

“There haven’t been many missions to Venus,” Cangi said. “But newly planned missions will leverage decades of collective experience and a flourishing interest in Venus to explore the extremes of planetary atmospheres, evolution and habitability.”

Now, new research from scientists at UC San Diego’s Scripps Institution of Oceanography and San Diego State University (SDSU) finds deep-sea fish and sediments collected from near the Catalina Island offshore dump site are contaminated with numerous DDT-related chemicals.

The study, published May 6 in the journal Environmental Science and Technology Letters and funded by the National Oceanic and Atmospheric Administration, suggests that the DDT-related chemicals dumped into the ocean decades ago may still be making their way into marine food webs.

Since the rediscovery of the offshore dump site near Catalina Island, scientists have been working to discern the extent and severity of the problem today. Of particular urgency are the questions of whether the decades-old chemicals, now settled on the seafloor thousands of feet underwater, are staying put or whether they are circulating in marine ecosystems where the compounds could be harming wildlife or even posing health risks to humans.

“These are deep-sea organisms that don’t spend much time at the surface and they are contaminated with these DDT-related chemicals,” said Lihini Aluwihare, a professor of ocean chemistry at Scripps and co-author of the study. “Establishing the current distribution of DDT contamination in deep-sea food webs lays the groundwork for thinking about whether those contaminants are also moving up through deep-ocean food webs into species that might be consumed by people.”

From 1948 until at least 1961, barges contracted by DDT-producer Montrose Chemical Corporation would motor from the Port of Los Angeles out toward Catalina and pump manufacturing waste laden with sulfuric acid and up to 2% pure DDT directly into the Pacific Ocean. Legal until 1972, this offshore dumping largely escaped public scrutiny because it was overshadowed by Montrose’s other waste disposal practice: Pumping a more dilute acidic slurry that also contained DDT through L.A. County sewers and into the ocean off Palos Verdes. An estimated 100 tons of DDT ended up in the sediments of the Palos Verdes Shelf, and the Environmental Protection Agency declared it an underwater Superfund Site in 1996. In 2000, a judge ordered the company to pay $140 million to remedy the environmental damages. Research has since linked the DDT pollution on the Palos Verdes Shelf to contamination and health problems in local wildlife including sea lions, dolphins, bottom-feeding fish, and even coastal California condors (likely from consuming dead marine mammals).

In 2011, UC Santa Barbara researcher David Valentine used an undersea robot to rediscover Montrose’s offshore dumping near Catalina at a place now known as Dumpsite 2. The findings leapt into the public consciousness in 2020 when the Los Angeles Times published the first in a series of expose?s unspooling the region’s toxic legacy of offshore dumping.

Valentine and Scripps researchers have helped map the extent of the dumping. To date, they’ve found DDT-related chemicals across an area of the seafloor larger than the city of San Francisco. What’s still unknown is if that pollution is staying put or if it is moving through the undersea environment in ways that pose dangers to marine life or humans.

Beginning in 2021, Aluwihare, study co-author Eunha Hoh of SDSU, and other collaborators began a series of research efforts to work on two key questions: Are the DDT-related chemicals lurking on the seafloor near Dumpsite 2 being stirred up and ingested by marine life in the deep? And could they identify a kind of chemical fingerprint unique to the contamination from Dumpsite 2 and other offshore dump sites that could be used to distinguish them from pollutants emanating from the Palos Verdes Shelf?

The team opportunistically collected sediment samples and deep-sea animals from the water column in the San Pedro Basin near Dumpsite 2 to test for a wide range DDT-related compounds. The research cruises to collect these samples were funded by the National Science Foundation and the Schmidt Ocean Institute.

Typically, testing for DDT looks for four to eight chemicals, but a 2016 paper co-authored by Hoh and Aluwihare identified 45 DDT-related chemicals in the blubber of dolphins from off the coast of Southern California. The results demonstrated that wildlife was being exposed to a much larger suite of DDT compounds in the real world. In the present study, the team tested for this larger suite of DDT-related chemicals, known as DDT+, in hopes that it could help develop a chemical fingerprint for Dumpsite 2 and the other offshore dump sites used by Montrose. Also, testing for DDT+ will provide a more holistic picture of the degree of contamination in sediment and animals that might otherwise go undetected.

When the researchers analyzed the sediments for the presence of DDT+ they found no fewer than 15 chemicals, 14 of which had been previously detected in birds and marine mammals in Southern California.

The researchers collected 215 fish spanning three common species near Dumpsite 2. Chemical analysis revealed that the fish contained 10 DDT-related compounds, all of which were also present in the sediment samples.

Two of the fish species were collected between 546 meters (1,791 feet) and 784 meters (2,572 feet) — Cyclothone acclinidens and Melanostigma pammelas — and the third, Leuroglossus stilbius, was collected between 546 meters (1,791 feet) and the surface. The species collected at shallower depths contained a lower concentration of contaminants and were missing a pair of DDT-related compounds that were present in the deepest fishes.

“None of these fish species are known to feed in the sediment of the seafloor,” said Anela Choy, biological oceanographer at Scripps and co-author of the study. “There must be another mechanism that is exposing them to these contaminants. One possibility is that there are physical or biological processes resuspending sediments around Dumpsite 2 and allowing these contaminants to enter deeper water food webs.”

The findings can’t yet rule out the Palos Verdes Superfund Site as a potential source of the contamination in the fish, said Aluwihare. But several lines of evidence uncovered in the study — the lower overall concentrations and two missing DDT-related compounds in the shallower water fish species, as well as the overlap between contaminants found in the sediment and those found in marine mammals and birds — point to the alarming possibility that pollution is moving from the seafloor and into the marine food web.

“Regardless of the source, this is evidence that DDT compounds are making their way into the deep ocean food web,” said Margaret Stack, an environmental chemist at SDSU and the study’s lead author. “That is cause for concern because it’s not a big leap for it to end up in marine mammals or even humans.”

Hoh said understanding the pathways by which the DDT-related chemicals are entering the food web is vital and “will help us figure out what to do as far as mitigation and what not to do in terms of offshore development that could make this problem worse by stirring up these contaminants.”

Aluwihare said more work needs to be done to pinpoint the source of the DDT contaminants they found in the deep-sea fish and establish whether the same contamination exists in larger, open-ocean fish species that are consumed by people.

Numerous additional studies are ongoing to answer these urgent questions. Researchers at Scripps and SDSU are currently analyzing samples from fish species targeted by recreational anglers and commercial fisheries, including basses and sanddab, for DDT+. Comparing the chemicals and their concentrations found in these fish with sediment samples collected from the Palos Verdes Shelf and Dumpsite 2 may allow the team to determine the source of the toxins in these fish.

“We are still seeing this DDT contamination in deep-sea organisms and ocean sediments more than 50 years after they were dumped there,” said Hoh. “I’m not sure if that company expected the consequences of their pollution to last this long, but they have.”

In addition to Aluwihare, Stack, Choy, and Hoh, Raymmah Garcia, Tran Nguyen,, Paul Jensen, and Johanna Gutleben of Scripps as well as, William Richardot, and Nathan Dodder of SDSU co-authored the study.