Author: Ivy Nguyen

While staying out of the warm California sun is still the best way to prevent skin cancer, a new study authored by a Stanford researcher has found that a common arthritis drug similar to aspirin can prevent some of the damage caused by the disease.

According to a study by dermatology Prof. Jean Tang published in Cancer Prevention Research last week, the non-steroidal anti-inflammatory drug (NSAID) celecoxib, also known by its trade name, Celebrex, has been shown to reduce the occurrence of basal cell carcinoma (BCC) in mice and humans. Tang’s study, conducted during her time at UC-San Francisco from 2001 to 2004, involved 60 patients with Gorlin syndrome, a genetic disorder that makes affected individuals particularly prone to developing the most common type of skin cancer in the U.S., BCC.

Half the patients were given a 200-mg celecoxib pill twice a day, the same dose prescribed to treat arthritis and the other half received a placebo. The celecoxib group saw a 50 percent reduction in their tumor count and these results persisted one year after treatment stopped.

“It seemed like some of the tumors didn’t grow as big, or some of the tumors shrank significantly,” Tang said.

BCCs present as a new bump or growth and arise from the top layer of the skin. These tumors commonly occur on the face and neck, areas that undergo frequent sun exposure. Caucasians and those in sunny areas like California are particularly susceptible to developing BCCs: one in five Caucasians living in California will develop a BCC in their lifetime, according to Tang.

Celecoxib works to prevent or slow cancer growth by inhibiting the enzyme cyclooxygenase, which causes tissue inflammation and is one of the many mechanisms behind BCC tumor development. Previous studies have also shown that celecoxib can reduce the incidence of cancers associated with chronic inflammation, such as colon cancer and squamous cell carcinoma (another type of skin cancer) in groups genetically predisposed to these diseases.

Well over one million cases of BCC are diagnosed annually in the U.S., said dermatology Prof. Susan Swetter, who was not involved in the study.  While BCCs are not associated with a tendency to spread to other organs or cause cancer mortality and can be cured by surgical removal, this and other treatments can cause significant disfigurement and discomfort, she added. Recovery time is also an issue, as is cost.

“The economic cost of treating non-melanoma skin cancer is enormous, with an annual estimated cost of $2.5 billion in the U.S.,” Swetter said.

While celecoxib has been FDA approved and spent over a decade on the market, Tang warns against applying the results of this study to people who only have a few BCCs, since this study only tested celecoxib’s effects on Gorlin syndrome patients, who have hundreds of BCCs.

“A lot of people might ask me, ‘Gosh, the majority of BCC tumors occur in healthy patients who are non-Gorlins — would this drug work for patients with one or two BCC tumors?’” Tang said. “We don’t know that because we didn’t test that group.”

Celecoxib has also been associated with various side effects ranging from stomach ulcers to increased risk of cardiovascular disease. The increase in the occurrence of cardiovascular disease in patients taking these drugs prompted a 2003 recall of Vioxx and Bextra, NSAID drugs that are chemically similar to celecoxib. Tang had a study halted in the midst of the recall, though her patients only reported mild stomach upset.

“A lot of that work has been frozen due to [this type of drug’s] effects on cardiovascular disease,” Tang said. “Here, we show another cancer that can be reduced again with celecoxib and we’re hoping that there’s a renewed interest in this class of molecules.”

Tang also plans to study the possibility of administering celecoxib topically, by rubbing it onto skin, to reduce the risk of cardiovascular toxicity that occurs when the drug is taken orally.

Swetter said that Tang’s research is taking place within an emerging field.

“The field of cancer chemoprevention, i.e. preventing cancer at the outset in at-risk individuals, is still relatively young,” Swetter said. “Studies such as Dr. Tang’s do a great deal to advance our knowledge.”

Air travel responsible for 4-8 percent of global climate change, says study

That flight back to Stanford may have had a bigger impact on climate change than previously thought.

According to a study by civil and environmental engineering Prof. Mark Jacobson, commercial aircraft flights have contributed four to eight percent of global surface warming since air temperature records began in 1850.

The first study of its kind analyzing commercial airlines, the results also showed that aircraft flights are responsible for an estimated 15 to 20 percent of warming in the Arctic.

Jacobson ran simulations using the aircraft emissions data for every commercial flight in the year 2004 and repeated the process for data from 2006. These numbers were entered into a computer model that also analyzed background pollution, clouds and radiation fields to predict how the emitted particles interacted chemically with atmospheric gases and aerosols.

“It’s a really complex soup of interactions occurring, but in the end it’s pretty relatively organized,” Jacobson said.

“We can then look at differences between running simulations with and without aircraft to see the changes in temperature and atmospheric composition of the clouds that result,” he added.

Aircraft engines emit particles that serve as sites on which clouds condense, forming the trail of vapor, known as “contrails,” that are sometimes seen behind planes. These contrails reflect sunlight but also absorb infrared radiation – due to the black carbon found in emitted soot – which changes atmospheric radiation balance.

Once contrails dissipate they also affect larger-scale cloud formation because the remnants of the contrails serve as nuclei on which other clouds form.

The impact of these emissions is magnified in the Arctic, where contrails absorb infrared radiation from both direct sunlight and light reflected back upward by the highly reflective snow and ice. Once the edges of the ice melt to reveal the water below, the ocean absorbs even more radiation, accelerating climate change.

Aircraft emission pollutants are short-lived, but they can still have a significant effect on the environment, Jacobson explained.

“You can ramp up those temperature changes with short-lived pollutants,” he said. “I mean, you can have that temperature effect due to brief periods of emissions – you don’t need hundred-year emissions to get that temperature change,” he added.

World airline passenger traffic fell 3.1 percent amid last year’s global financial crisis, the biggest drop in aviation industry history, according to figures from the International Civil Aviation Organization. Even so, black carbon emissions would have to be reduced 20-fold to halt Arctic warming, Jacobson said.

“There’s a general statement that can be made about all pollution sources – we should take action to reduce all pollution,” Jacobson explained. “All combustion causes some kind of air pollution or climate problem, so we should always be aggressively trying to reduce combustion toward alternatives that don’t combust or combust much cleaner materials.”

To meet this challenge, airplane manufacturer Boeing recently designed a lighter-weight, more energy efficient plane, according to Jacobson. The company is also developing lower sulfur emission fuels.

Still, even cleaner-burning fuel is possible, Jacobson said.

“If you really were to take it to the next level, you would want to go to maybe liquid hydrogen airplanes,” he said.

Studies from the European Commission have shown that a hydrogen-fueled airplane is possible, but the technology must still undergo rigorous safety tests, Jacobson said. Though hydrogen fuel has been used for the space shuttle, Jacobson predicts that hydrogen-fueled planes are still 10 to 20 years away.

“We have plenty of examples of hydrogen being used, but it’s a question of whether you can do it at low cost or not,” he said. “There’s also transforming the whole fleet – it’s a long process.”

Jacobson presented his study at the Geophysical Union’s annual meeting in December. The paper is currently being peer reviewed and is awaiting publication.