KRAS Targeted Cancer Strategy Shows Early Promise

KRAS in active and inactive states

Caption: Mutant KRAS protein (white) keeps switch (red/pink) open in active state for GTP (arrow). After treatment with ARS-1620 (blue), switch is trapped in inactive GDP-bound state.
Credit: Adapted from Cell. 2018 Jan 25;172(3):578-589.

Of the more than 1.7 million Americans expected to be diagnosed with cancer this year, nearly one-third will have tumors that contain at least one mutation in the RAS family of genes [1]. That includes 95 percent of pancreatic cancers and 45 percent of colon cancers. These mutations result in the production of defective proteins that can drive cancer’s uncontrolled growth, as well as make cancers resistant to therapies. As you might expect, RAS has emerged as a major potential target for fighting cancer. Unfortunately, it is a target that’s proven very difficult to “hit” despite nearly three decades of work by researchers in both the private and public sectors, leading NIH’s National Cancer Institute to begin The RAS Initiative in 2013. This important effort has made advances with RAS that have translational potential.

Recently, I was excited to hear of progress in targeting a specific mutant form of KRAS, which is a protein encoded by a RAS gene involved in many lung cancers and some pancreatic and colorectal cancers. The new study, carried out by a pharmaceutical research team in mouse models of human cancer, is the first to show that it is possible to shrink a tumor in a living creature by directly inhibiting mutant KRAS protein [2].

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Creative Minds: Potential Diabetes Lessons from Binge-Eating Snakes

Secor with a snake

Stephen Secor/Credit: Secor Lab

Many people would do just about anything to avoid an encounter with a snake. Not Stephen Secor. Growing up in central New York State, Secor was drawn to them. He’d spend hours frolicking through forest and field, flipping rocks and hoping to find one. His animal-loving mother encouraged him to keep looking, and she even let him keep a terrarium full of garter snakes in his bedroom. Their agreement: He must take good care of them—and please make sure they don’t get loose.

As a teen, Secor considered a career as a large-animal veterinarian. But a college zoology course led him right back to his fascination with snakes. Now a professor at the University of Alabama, Tuscaloosa, he’s spent 25 years trying to understand how some snakes, such as the Burmese python shown above, can fast for weeks or even months, and then go on a sudden food binge. Secor’s interest in the feast-or-famine digestive abilities of these snakes has now taken an unexpected turn that he never saw coming: a potential treatment to help people with diabetes.

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Creative Minds: The Human Gut Microbiome’s Top 100 Hits

Michael Fishbach

Michael Fishbach

Microbes that live in dirt often engage in their own deadly turf wars, producing a toxic mix of chemical compounds (also called “small molecules”) that can be a source of new antibiotics. When he started out in science more than a decade ago, Michael Fischbach studied these soil-dwelling microbes to look for genes involved in making these compounds.

Eventually, Fischbach, who is now at the University of California, San Francisco, came to a career-altering realization: maybe he didn’t need to dig in dirt! He hypothesized an even better way to improve human health might be found in the genes of the trillions of microorganisms that dwell in and on our bodies, known collectively as the human microbiome.

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Fighting Parasitic Infections: Promise in Cyclic Peptides

Cyclic peptide bound to iPGM

Caption: Cyclic peptide (middle) binds to iPGM (blue).
Credit: National Center for Advancing Translational Sciences, NIH

When you think of the causes of infectious diseases, what first comes to mind are probably viruses and bacteria. But parasites are another important source of devastating infection, especially in the developing world. Now, NIH researchers and their collaborators have discovered a new kind of treatment that holds promise for fighting parasitic roundworms. A bonus of this result is that this same treatment might work also for certain deadly kinds of bacteria.

The researchers identified the potential new  therapeutic after testing more than a trillion small protein fragments, called cyclic peptides, to find one that could disable a vital enzyme in the disease-causing organisms, but leave similar enzymes in humans unscathed. Not only does this discovery raise hope for better treatments for many parasitic and bacterial diseases, it highlights the value of screening peptides in the search for ways to treat conditions that do not respond well—or have stopped responding—to more traditional chemical drug compounds.

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Got It Down Cold: Cryo-Electron Microscopy Named Method of the Year

Cryo-EM

Caption: Composite image of beta-galactosidase showing how cryo-EM’s resolution has improved dramatically in recent years. Older images to the left, more recent to the right.
Credit: Veronica Falconieri, Subramaniam Lab, National Cancer Institute

In the quest to find faster, better ways of mapping the structure of proteins and other key biological molecules, a growing number of researchers are turning to an innovative method that pushes the idea of a freeze frame to a whole new level:  cryo-electron microscopy (cryo-EM). The technique, which involves flash-freezing molecules in liquid nitrogen and bombarding them with electrons to capture their images with a special camera, has advanced dramatically since its inception thanks to the efforts of many creative minds. In fact, cryo-EM has improved so much that its mapping performance now rivals that of X-ray crystallography [1], the long-time workhorse of drug developers and structural biologists.

To get an idea of just how far cryo-EM has come over the last decade, take a look at the composite image above, which shows a bacterial enzyme (beta-galactosidase) bound to a drug-like molecule (phenylethyl beta-D-thiogalactopyranoside). To the left, you see a blob-like area generated by cryo-EM methods that would have been considered state-of-the-art just a few years ago. To the right, there’s an exquisitely detailed structure, which was produced at more than 10-times greater resolution using the latest advances in cryo-EM. In fact, today’s cryo-EM is so powerful that researchers can almost make out individual atoms! Very impressive, and just one of the many reasons why the journal Nature Methods recently named cryo-EM its “Method of the Year” for 2015 [2].

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