Starving a cancer instead of feeding it poison
by Neal Singer
A patent application for a drug that could destroy the deadly childhood disease known as acute lymphoblastic leukemia — and potentially other cancers as well — has been submitted by researchers at Sandia, the University of Maryland, and the MD Anderson Cancer Center in Houston.
“Most drugs have to go inside a cell to kill it,” says Sandia researcher Susan Rempe (8635). “Our method instead withholds an essential nutrient from the cell, essentially starving it until it self-destructs.”
The removed nutrient is called asparagine, which cancer cells can’t produce on their own. But there’s more to the story.
It’s well-known that chemical attempts to kill cancers often sicken the patient. In the case of the cancer drug L-asparaginase type 2 (L-ASN2), whose primary effect is depletion of asparagine, side effects are generally attributed to the corresponding depletion of a chemically similar molecule called glutamine. All human cells need asparagine and glutamine to survive because each is essential to key biological processes. While most normal cells can synthesize their own asparagine, certain cancer cells cannot. So the ideal nutrient-deprivation strategy for cancers requires a difficult balancing act: remove asparagine from the blood to cripple the cancer, but leave glutamine intact so that the patient can tolerate the chemotherapy.
The researchers at Sandia and Maryland did molecular simulations to predict which mutations would produce that desirable result when introduced into the enzyme-drug L-ASN2, commonly used to treat certain types of leukemia. The scientists’ simulations succeeded in identifying a point in that enzyme’s chain of amino acids where a mutation theoretically would eliminate the drug’s unwanted attack on glutamine.
“Technically,” says Susan, “we simulated which parts of the two molecules came in contact with the enzyme. Then we realized that by substituting a single amino acid in the enzyme’s chain, we might avoid glutamine degradation by eliminating its contact with the enzyme.”
In computer simulations, the change looked promising because the most notable difference between asparagine and glutamine was the way they interacted with that specific amino acid.
“That made us feel that a chemical change at that single location was the key,” says Susan.
Tests underway on laboratory mice
It required a mutation to change the amino acid’s chemistry. The mutation was achieved by collaborators at MD Anderson, who used DNA substitutions to effect the change.
“Most researchers agree that removing glutamine from a patient’s blood was the problem in previous use of this enzyme-drug,” says Susan. “Our simulations showed how to avoid that.”
In test tube experiments, the new drug left glutamine untouched. Follow-up tests in petri dishes showed that the mutated enzyme killed a variety of cancers.
Tests underway on laboratory mice at MD Anderson should be completed by early 2016, and if they are successful, Susan says, human testing will follow.
“If we’re wrong, and keeping glutamine intact is not the answer to the cancer problem, we’ll continue investigating because we think we’re onto something,” she adds.
That’s because, she says, “we used high-resolution computational methods to redesign the cancer drug to act differently, in this case to act only on asparagine. Laboratory tests showed that the predictions worked and that the new drug kills a variety of leukemias. We hope our method can do that in a patient, and for many more cancers. But if it doesn’t, then we’ll test the opposite strategy: redesign the enzyme to destroy glutamine and keep asparagine intact. Or fine-tune the enzyme to degrade the two molecules in a chosen ratio. We’re learning to control this enzyme.”
The joint work among Sandia, the University of Maryland, and M D Anderson began in 2009. Sandia managers Wahid Hermina (1200) and Steve Casalnuovo (1710) spearheaded the effort to bring Sandia and MDACC together for mutual benefit, using computational and biochemical expertise developed in national defense to help cure cancer.
Sandia, a national defense lab, is interested in curing cancers, and is also interested in developing expertise in building enzymes that can assist with biodefense.
Says Susan, “If we could redesign an enzyme to break down specific small molecules, and not get diverted by interactions with non-toxic molecules, then we could apply our technique to develop safer and more effective enzymes.”
Classical modeling was performed at the University of Maryland by Andriy Anishkin and Sergei Sukharev; at Sandia, post-doctoral researcher David Rogers (now at the University of South Florida) also carried out modeling studies.
Sandia post-doctoral researcher Juan Vanegas is performing quantum modeling to map out the chemical degradation process to better understand how to optimize the enzyme, says Susan. The experiments at MD Anderson were carried out by Wai Kin Chan, Phil Lorenzi, and colleagues in John Weinstein’s group. Earlier results have been published in the journal Blood.
This work is supported by Sandia’s Laboratory Directed Research and Development office.
-- Neal Singer
Christopher Kliewer wins $2.5 million DOE Early Career Research Program award
by Patti Koning
Sandia researcher Christopher Kliewer (8353) has won a $2.5 million, five-year Early Career Research Program award from DOE’s Office of Science for his fundamental science proposal to develop new optical diagnostic tools to study interfacial combustion interactions, which are major sources of pollution and vehicle inefficiency.
Christopher’s winning submission describes an approach to develop and use optical diagnostic tools to study the complex surface chemistry involved when gas-phase combustion interacts with solid or liquid interfaces. His proposal is titled “Interactions between Surface Chemistry and Gas-Phase Combustion: New Optical Tools for Probing Flame-Wall Interactions and the Heterogeneous Chemistry of Soot Growth and Oxidation in Flames.”
“I’m interested in interfacial combustion phenomena, like when a flame interacts with a wall. These heterogeneous processes dominate some of the most stubborn and technologically critical problems in combustion, yet they are not well understood,” says Christopher. “This is due in part to the lack of experimental approaches capable of probing locations very close to an interface, especially in the hostile environment of combustion.”
In engine and power generator combustors, flames interact with metal walls during the combustion process. These interactions are a major source for pollutant emissions, such as unburned hydrocarbon and particulate emissions, and cause aging and failure in engines and generators. Christopher’s project will develop a new nonlinear optical surface scattering technique to capture the dynamic chemistry of the flame-wall interactions.
This tool will be further developed to correct a deficit in existing experimental techniques for studying soot particles collected from flames. Nearly all these techniques require ex-situ analysis — meaning a sample must be removed from the flame to be studied. The act of removing the soot changes both the sample and the surrounding combustion, limiting the accuracy of results.
Ultimately, new insights into the chemical mechanisms of flame-wall interactions and soot growth and oxidation will inform combustion chemistry models that increase the fidelity of predictive numerical simulations of combustion devices, chemistry, and processes. Better simulations can help designers optimize engines and other devices to reduce pollution formation and increase efficiency.
The project builds on and uses other recent advances in Christopher’s lab, such as two-dimensional gas-phase coherent anti-Stokes Raman spectroscopy (2D-CARS). The technique, developed by Christopher and Sandia researcher Alexis Bohlin (8353), increased the capability of this optical diagnostic tool from capturing a CARS spectrum at a single point in space to a planar array of thousands of points within a single laser pulse.
“We developed that technique for gas-phase combustion,” he says. “Now we’re applying that technique to better measure and define the chemistry occurring at the interfaces.”
Christopher joined Sandia in 2009. He has received two distinguished paper awards from the Combustion Institute for papers presented in optical diagnostics at the 2010 and 2014 International Symposium on Combustion. His paper on 2D-CARS was the most read paper in Journal of Chemical Physics for June 2013. He has a doctorate in physical chemistry from the University of California, Berkeley, and a bachelor’s degree in chemistry from George Fox University in Newberg, Oregon.
Christopher is one of 44 winners from DOE labs and US universities chosen by peer review. The Early Career Research Program, now in its sixth year, is designed to bolster the nation’s scientific workforce by providing support to exceptional researchers during the crucial early career years, when many scientists do their most formative work.
-- Patti Koning
Davis gun tests aid B61-12 LEP
Three years of designing, planning, and preparing came down to a split second, a loud boom, and an enormous splash in a successful impact test of hardware in the nose assembly of a mock B61-12 bomb.
The Sandia test also captured data that will allow analysts to validate computer modeling for the bomb, part of Sandia’s decade-long effort in the B61-12 Life Extension Program (LEP). The B61-12 LEP is an $8.1 billion NNSA program coordinated across the nation’s nuclear security enterprise. Sandia is working with NNSA, the program lead; and five NNSA partner sites, industry partners, and the US Air Force, the B61-12 customer.
The Jan. 28 test, the first of three with Sandia’s Davis gun, shot the assembly and its diagnostics into an 8-foot-deep steel-reinforced concrete water tank with a soil-filled bunker underneath to capture the hardware. The packed-dirt bunker makes it easier for engineers to recover data recorders and reusable parts and ensures that a test piece isn’t damaged.
The tests, designed to validate a systems requirement for the B61-12, represented a worst-case scenario: a slow velocity into a soft target, in this case, 10,500 gallons of water. Shots were set for a prescribed velocity and angle to validate the impact sensor response for ground fuzing and to help understand the design margin, says Tyler Keil (2153), lead engineer for the B61-12 Davis gun test series.
Tyler and more than a dozen colleagues who worked on the test watched the first shot from a hill a half-mile from the mobile Davis gun, stationed at New Mexico Tech’s Energetic Materials Research & Testing Center (EMRTC) in the hills west of the Socorro campus.
‘Awesome’ test highlighted years of work
“It was awesome,” Tyler said after the shot. Tyler, who worked toward the test for more than three years, brought members of the team to EMRTC so they could watch a highlight of their work: shooting a bomb out of the cannon-like gun. Waning sunlight meant waiting until the next day to recover test data, and Tyler joked he’d “determine how happy I really am” after seeing the data from the recorder custom-designed and built by Ryan Layton (8133) and a separate recorder from Dept. 2627.
The Davis gun series marked the end of testing for the nose design, and by the end of the week, Tyler knew the test captured what the team needed. “Our team will assess these data, make note of any findings we see where improvements are needed to meet requirements, brainstorm ideas to address the findings, and incorporate them into the next design,” Tyler says. “We’ll then repeat the tests on the new design to verify that the changes were successful.”
Manager Doug Dederman, whose Terminal Ballistics Technology Dept. 5431 conducted the test, explained how the gun works: Imagine the barrel as a straw, open at both ends, with an explosive charge sandwiched between the test nose assembly and a 2,000-pound steel slug, called the reaction mass. The test component and reaction mass are positioned to simultaneously blow out opposite ends of the barrel, the projectile slamming into the water of the adjacent pool and underlying bunker, and the reaction mass arcing to land behind a small hill. Using a reaction mass eliminates the recoil load in the gun chassis during firing and enables the gun to be towed on a trailer to different target sites. The gun’s operation is under the control of James Dykes (5431) in partnership with EMRTC.
Crews from Sandia and EMRTC spent most of two days in final test preparations. On test day, the nose assembly, mounted on an aluminum tube to replicate the B61-12 body, sat in a stand about 200 yards from the pool. There it waited until time to load it into the 40-foot long, 16-inch diameter barrel of the white Davis gun, stark against the backdrop of blue sky and a red jagged volcanic hill.
It took more than 20 minutes to move the projectile with the attached nose assembly from the assembly pad to the gun. The crew removed the assembly stand brackets, then suspended the projectile from the tines of a forklift equipped with a long hydraulic boom. They steadied the test projectile with tag lines as the forklift driver maneuvered up a dirt ramp to the Davis gun. There, it was bracketed into another stand to hold and roll it under the barrel where it was attached to a threaded rod and drawn up into the vertical barrel. The gun’s dual-sheave hoisting system minimized rotation as the projectile was lifted into test position in the barrel.
High-speed cameras captured test footage in water pool
High-speed cameras at three levels in window ports in a small hut on one side of the pool and flash bulbs in a hut on the other side were synchronized with the gun’s explosive charge to catch the action underwater.
As the arming and firing crew finished final preparations, everyone else evacuated to the viewing area for safety. The gun — which can be set at any angle — was tilted to firing position, the end with the nose piece pointed toward the pool. The crew at the gun finished local arming preparations and drove to the remote gun firing trailer at the viewing area. A roll call assured that everyone was accounted for and away from the test site. The gunner announced “Charged,” counted down “five, four, three, two, one,” and fired the gun just before 4 p.m.
Water splashed into the air as the nose assembly hit the pool at the lower end of the gun and a cloud of smoke drifted from the raised end as the reaction mass flew behind a hill well away from the action and the observers. “The reaction mass landed just where we expected it to, a first indication that we are close to the velocity we wanted,” Tyler says.
Once the firing crew gave the all-clear, onlookers returned to the site and climbed onto the steel platform around the pool. Water had splashed a large radius of the dirt clearing around the pool, and the rest drained into a ramp leading down to the bunker. A large plastic tube dropped into the ramp with an attached fireman’s hose siphoned the remaining water toward a nearby arroyo while a member of the crew shoveled mud out of the bunker to locate the test piece for the next day’s final excavation.
About an hour after the firing, a small convoy of vans and pickups drove back across a winding dirt road through the hills to EMRTC headquarters. Some of the crew would be back the next day to recover the data recorders so engineering analysts could begin their work.
Analysts will spend the next year using the data to calibrate their models, then explore impact scenarios that weren’t tested to evaluate the impact sensor’s performance.
“The B61-12 LEP has performed several impact tests of various target types and velocities over the last year to verify its ground fuzing performance,” Tyler says. “The Davis gun test series specifically tests the B61-12 ground fuzing performance during a water impact. All of the impact testing contributes to how reliably the B61-12 will fuze upon a ground impact.”-- Sue Major Holmes