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Tag: mutations

09.10.2012

are we near drug treatments for lung cancer?

Exciting news from the New York Times regarding drug treatments for certain lung cancers:

The first large and comprehensive study of the genetics of a common lung cancer has found that more than half the tumors from that cancer have mutations that might be treated by new drugs that are already in the pipeline or that could be easily developed.

For the tens of thousands of Americans with that cancer — squamous cell lung cancer — the results are promising because they could foretell a new type of treatment in which drugs are tailored to match the genetic abnormality in each patient, researchers say.

“This is a disease where there are no targeted therapies,” said Dr. Matthew Meyerson of the Dana-Farber Cancer Institute in Boston, referring to modern drugs that attack genetic abnormalities. He is a lead author of a paper on the study, with more than 300 authors, which was published online in the journal Nature on Sunday.

“What we found will change the landscape for squamous cell carcinoma,” Dr. Meyerson said. “I think it gives hope to patients.”

The study is part of the Cancer Genome Atlas, a large project by the National Institutes of Healthto examine genetic abnormalities in cancer.

Read the original Nature paper here.

09.06.2012

branched-chain amino acid deficiency linked to rare form of autism

Lots of interesting reads in Scientific American & Nature these past few weeks.  Ewen Callaway of Nature magazine brings us this story:

A rare, hereditary form of autism has been found — and it may be treatable with protein supplements.

Genome sequencing of six children with autism has revealed mutations in a gene that stops several essential amino acids being depleted. Mice lacking this gene developed neurological problems related to autism that were reversed by dietary changes, a paper published today in Scienceshows1.

“This might represent the first treatable form of autism,” says Joseph Gleeson, a child neurologist at the University of California, San Diego, who led the study. “That is both heartening to families with autism, and also I think revealing of the underlying mechanisms of autism.”

The children came from three families with Middle Eastern ancestry; in each case the parents were first cousins. Studying such families makes the hunt for the rare recessive mutations underlying some forms of autism simpler than it would be among the general population, Gleeson says, because the odds are higher that children will be born with two copies of the recessive mutation.

In each family, Gleeson’s team identified mutations that inactivate the enzyme BCKD-kinase, which normally prevents the body from breaking down branched-chain amino acids called leucine, isoleucine and valine after a meal. Humans cannot synthesize these amino acids and must obtain them from food.

“We predicted that patients would burn through these amino acids,” says Gleeson. The prediction was correct: after eating, the children had low blood levels of the branched-chain amino acids. Mice lacking the gene that codes for BCKD-kinase also had low levels of the amino acids in their blood and tissue.

The sample size of six is extremely limited due to the rarity of the disease, so we don’t know if the result are generalizable. But the results are interesting nonetheless.

03.09.2012

how cancers become resistant

From ScienceNOW:

The big push in cancer treatment these days is to sample a person’s tumor, test it for mutations, and give the patient a drug tailored to a genetic weak spot in the tumor. A new study suggests one reason why this targeted drug strategy doesn’t always work. A solid tumor, it turns out, is not a mass of identical cancerous cells but a mosaic of genetically different cells that aren’t captured with a single biopsy. Some of these distinct cells may be resistant to the targeted drugs, allowing a tumor to persist or grow.

The classic view of how cancer develops is that a single, normal cell accumulates mutations that eventually allow or force it to divide uncontrollably. This “clone” then grows into a tumor of identical cells, which can also sow seed cells into the bloodstream that then take root somewhere else in the body, or metastasize. The assumption that tumors grow out from a single clone has spurred a rush to find drugs that block one of the clone’s genetic weak spots. But although the strategy has resulted in some very effective drugs—Iressa for lung cancer and a new melanoma drug called Zelboraf, for example—these drugs often stop working within a year or two. One reason could be that solid tumors already harbor a few cells, or clones, with “resistance” mutations that take over when the cells targeted by the drug are wiped out.

More here.

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