Cancers can resist destruction by drugs with the help of proteins recruited from surrounding tissues, find two studies published by Naturetoday. The presence of these cancer-assisting proteins in the stromal tissue that surrounds solid tumours could help to explain why targeted drug therapies rapidly lose their potency.
Targeted cancer therapies are a class of drugs tailored to a cancer’s genetic make-up. They work by identifying mutations that accelerate the growth of cancer cells and selectively blocking copies of the mutated proteins. Although such treatments avoid the side effects associated with conventional chemotherapy, their effectiveness tends to be short-lived. For example, patients treated with the recently approved drug vemurafenib initially show dramatic recovery from advanced melanoma, but in most cases the cancer returns within a few months.
Many forms of cancer are rising in prevalence: for example, in the United States, the incidence of invasive cutaneous melanoma — the deadliest form of skin cancer — increased by 50% in Caucasian women under 39 between 1980 and 2004. So there is a pressing need to work out how to extend the effects of targeted drug therapies. But, until now, researchers have focused on finding the mechanism of drug resistance within the cancerous cells themselves.
Two teams, led by Jeff Settleman of Genentech in South San Francisco, California, and Todd Golub at the Broad Institute in Cambridge, Massachusetts, expanded this search into tumours’ surrounding cellular environment.
Settleman’s team tested 41 human cancer cell lines, ranging from breast to lung to skin cancers. The researchers found that 37 of these became desensitized to a handful of targeted drugs when in the presence of proteins that are usually found in the cancer’s stroma, the supportive tissue that surrounds tumours. In the absence of these proteins, the drugs worked well1. By growing cancer cells along with cells typically found in a tumour’s immediate vicinity, Golub and his colleagues showed that these neighbouring cells are the likely source of the tumour-aiding proteins2.
One of the most startling results of the teams’ experiments was the discovery that a protein called hepatocyte growth factor (HGF) boosts melanoma’s resistance to treatment with vemurafenib. Intrigued by this result, both teams looked at blood samples from people who had undergone treatment with vemurafenib, and found the higher a patient’s HGF levels, the less likely they were to remain in remission.
Martin McMahon, a cancer biologist at the University of California, San Francisco, who was not affiliated with either study, explains that the results have immediate implications for the design of clinical trials, which he says could combine targeted drug therapy with drugs capable of knocking down the production of proteins such as HGF.
“These papers show that the influence of the cell’s microenvironment is important not only for melanoma, but also for pancreatic, lung and breast cancer,” McMahon says, adding that they are “very exciting, because they expand the focus of where we should be looking for the mechanisms of drug resistance”.
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New results suggest that insecticide use in the tropics is to blame for the re-emergence of bed-bug infestations.
Exposure to treated bed nets and linens meant that populations of bed-bugs had become resistant to the chemicals used to kill them, researchers said.
The findings could help convince pest controllers to find alternative remedies to deal with the problem.
The results were presented at the American Society of Tropical Medicine and Hygiene’s 60th annual meeting.
Since almost vanishing from homes in industrialised countries in the 1950s, populations of the common bed-bug have become re-established in these regions over the past decade or so.
These mostly nocturnal feeders are difficult to control, not only because they are adept at avoiding detection by crawling into creases of soft furnishing but also because they have developed a resistance to many of the chemicals that have been used to kill them.
Findings presented at the gathering in Philadelphia showed that 90% of 66 populations sampled from 21 US states were resistant to a group of insecticides, known as pyrethroids, commonly used to kill unwanted bugs and flies.
One of the co-authors – evolutionary biologist Warren Booth, from North Caroline State University in Raleigh – explained that the genetic evidence he and his colleagues had collected showed that the bed-bugs infecting households in the US and Canada in the last decade were not domestic bed bugs, but imports.
“If bed-bugs emerged from local refugia, such as poultry farms, you would expect the bed-bugs to be genetically very similar to each other,” explained entomologist and co-author Coby Schal, also from North Carolina State University. “This isn’t what we found.”
In samples collected from across the eastern US, the team discovered populations of bed-bugs that were genetically very diverse.
This suggested that the bugs originated from elsewhere, and relatively recently because the different populations had not had time to interbreed, Dr Schal explained.
He suggested that the source for the new outbreaks was warmer climes, where the creatures would have probably developed a resistance to chemicals.
“The obvious answer is the tropics, where they have used treated bed nets [and] high levels of insecticides on clothing and bedding to protect the military,” Dr Booth told BBC News.
He explained that although bed-bugs were essentially eradicated from industrialised countries in the 1950s, they continued to thrive in Africa and Asia.
“Its very likely that it is from one of these areas where insecticide resistance evolved,” he said.
However, UK-based pest management specialist Clive Boase questioned that hypothesis.
He said bed nets, to protect against mosquito-transmitted malaria and dengue, were only used in parts of Africa that were hot, where the tropical bed-bug (Cimex hemipterus) was found.
But, he added, it was not the tropical bed-bug that was the problem in the US and UK; instead it was their temperate cousin, Cimex lectularius.
Dr Boase explained that comprehensive records showed that infestations of bed-bugs in Europe were less pervasive in the 1970s and 80s, but they were still present.
By continually exposing these populations to insecticides, which came on the market in the late 1970s, these creatures likely developed resistance, he said.
“We don’t have to invoke stories of disease control programmes in Africa; all the evidence here in the UK is that our problem is home-grown.”
Dr Boase wondered that if the US had similar long-term records whether the researchers would have reached a different conclusion.
Evolutionary biologist Richard Naylor from the University of Sheffield agreed: “I am kind of surprised by [their interpretation].
“It doesn’t seem that difficult to develop resistance or lose it; in lab cultures, if you stop exposing [bed-bugs] to pyrethroids it drops out of lab populations very quickly,” he said.
Mr Naylor asked that if the US bed bugs had been exposed to the chemicals elsewhere in the past, “why would they still be resistant?”
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Scientists have developed a vaccine that protects mice against a deadly form of the Ebola virus.
First identified in 1976, Ebola fever kills a majority of the people it infects.
The researchers say that this is the first Ebola vaccine to remain viable long-term and can therefore be successfully stockpiled.
The results are reported in the journal Proceedings of National Academy of Sciences.
Ebola is transmitted via bodily fluids, and can become airborne. Sufferers experience nausea, vomiting, internal bleeding and organ failure before they die.
Although few people contract Ebola each year, its effects are so swift and devastating that it is often feared that it could be used against humans in an act of terroism.
All previously developed vaccines have relied on injecting intact, but crippled, viral particles into the body.
Long-term storage tends to damage the virus, paralysing the vaccine’s effectiveness.
The new vaccine contains a synthetic viral protein, which prompts the immune system to better recognise the Ebola virus, and is much more stable when stored long-term.
The vaccine protects 80% of the mice injected with the deadly strain, and survives being “dried down and frozen,” said biotechnologist Charles Arntzen from Arizona State University who was involved in its development.
He said the next step is to try the vaccine on a strain of Ebola that is closer to the one that infects humans.
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Scientists have shown that women who were first to settle in a new land had more children and grandchildren than those who followed.
Researchers analysed the family trees of French settlers who colonised Canada in the 17th and 18th centuries.
Their results could help to explain why some rare genetics diseases are common in communities established by migrations.
The findings have been published in the journal Science.
The team of researchers from Canada and Europe relied on data collected by the parish councils of Charlevoix and Saguenay Lac Saint-Jean, a region 170km north of Quebec, Canada.
The towns not only boast dairy farms, charming villages and sandy beaches but some of the best ever-kept marriage records – comprising more than a million people.
By building a picture of marriages and how many children the pairings produced, the researchers showed that woman who arrived as part of the first wave of immigration had 15% more children than those who arrived a generation later.
The pioneering woman married younger and benefited from scooping up the best local resources, they added.
But the study also found that the pioneering women’s children also had more children.
Lead author Laurent Excoffier, from the University of Bern in Switzerland, explained that the children of women at the front of the wave inherited their mother’s higher rate of fertility.
Yet, the researchers added, there was no such correlation between generations that arrived 30 years later behind the first wave.
Dr Excoffier drew parallels with cane toads. Scientists have observed that the toads at the edge of their range have bigger front legs and stronger back legs; all the better to invade new areas.
And when toads at the frontiers breed, their offspring inherit these longer, stronger limbs.
Such an effect is not unexpected, but until now no one has seen this phenomenon in humans.
“This was a rare chance to study a relatively recent human migration,” said co-author Damian Labuda, a geneticist from the University of Montreal, Canada.
Population geneticist Montgomery Slatkin from University of California, who was not involved in the work, called the study one of the “most interesting, detailed studies” he had seen.
“I think what happened [here] could easily have happened in other populations,” he added.
The findings suggest that families at the front of the wave of migration contributed more to the contemporary gene pool than those that were slower to arrive, explained Dr Labuda.
This could help explain why some rare genetic diseases are more common than expected in the Charlevoix and Saguenay Lac Saint-Jean regions.
That is because any disease causing mutations carried by people by the frontiers would be pass onto their descendents, who make up a large proportion of subsequent generations in the population.
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The world’s only known white kiwi has survived surgery to remove stones from her gizzard, reports a New Zealand Wildlife Centre.
Over a week ago, rangers noted that Manukura, the six-month-old chick, was off her food.
X-rays revealed that two large stones were obstructing the chick’s guts.
In two separate operations, vets at Wellington Hospital in New Zealand used lasers to successfully break apart the rocks.
Pukaha Mount Bruce, New Zealand’s North Island wildlife centre, where Manukura lives, reported that the bird’s heart slowed suddenly during the surgery giving the operating team “a bit of a scare”.
But the little white bird pulled through and is recovering in isolation from other animals.
Kiwis, like other birds, swallow stones to help them digest their food. But Manukura, it seems, swallowed more than she could stomach.
Manukura, a North Island Brown Kiwi, is the 13th kiwi hatched in captivity at the centre this year.
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