Tag: Cancer

Leukemia Vaccine Effective in Mice

In October, researchers reported in the journal Nature Medicine of their successful tests of a DNA vaccine in mice. In January, further evidence from a trial of the vaccine demonstrated that it could protect at least some of the mice for very long periods of time.

The research focused on acute promyeloctyic leukemia which is currently treated with chemotherapy which cures about 75 percent of cases.

The researchers used a mice model of the disease, exposing one experimental group to the vaccine and another experimental group to the vaccine and chemotherapy. In half the mice receiving the combination of the vaccine and chemotherapy, half the mice lived an additional 300 days — the equivalent of 25 human years.

The vaccine uses fragments of a faulty gene found in cancer cells to train the immune system of the animals to recognize and destroy cancerous cells.

As lead researcher Dr. Rose Padua told the BBC, this sort of approach might one day help improve survival odds for those patients who don’t respond to chemotherapy alone,

Currently, despite a major improvement in the survival of APL patients, a cure is still not achieved in all patients. The DNA based vaccine has proven to induce protective immunity. This example of a target therapy in an APL animal model may provide us with an alternative therapy, which if translated to humans, will improve quality of life and survival rates for leukemia patients.

Obviously, any human application would still be many years away.

Source:

Hope for leukemia vaccine. The BBC, January 7, 2004.

DNA drug offers leukaemia hope. The BBC, October 20, 2003.

Cancer-Resistant Strain of Mice Discovered

Researchers at Wake Forest University Baptist Medical Center made news in April when they announced a strain of mice that appear to be especially resistant to cancer.

The mice strain was discovered accidentally by researchers doing cancer research. The BBC reported that researchers noted that one male mouse remained resistant to the cancer they were researching despite repeated injections with cancer cells.

So the researchers bred that male mouse and discovered that the mouse’s cancer resistance was genetically inheritable. Of the 700 mice they bred, some were completely resistant to cancer while others would get cancer when exposed to it, but the tumor would be stopped spontaneously in its tracks within a day.

Dr. Zheng Cui of Wake Forest told The BBC,

The mice became healthy and immediately resumed normal activities including mating. . . . They are healthy, cancer-free and have a normal lifespan.

The cancer resistance was attributed to an immune response that the mice exhibited in response to the presence of cancer cells.

As Dr. Susan Aldridge said of the discovery in an article for Health and Age,

Clearly this colony of animals will be a valuable model for studying mechanisms of immune protection against cancer. Immunotherapy is one of the most exciting new approaches in cancer treatment. This research may help show how it can be made more effective.

Sources:

Scientists breed cancer-beating mice. The BBC, April 28, 2003.

Researchers develop mice resistant to cancer. Associated Press, May 7, 2003.

Mice that fight off cancer shed light on human remission. Susan Aldridge, Health and Age, April 2003.

The First Successful Anti-Cancer Vaccine

Has the world already seen the first successful anti-cancer vaccine? Probably, and all thanks to animal research.

The Daily Telegraph ran an interesting article on a luncheon to honor Prof. Baruch Lumberg. Lumberg was instrumental in the creation of a vaccine to fight Hepatitis B. In fact, Lumberg won the 1976 Nobel Prize for medicine and has recently written a book, Hepatitis B: The Hunt for a Killer Virus, about his efforts to find a vaccine for the disease.

But the Hepatitis B vaccine should be — and apparently is — an anti-cancer vaccine as well. Hepatitis B plays a major role in causing liver cancer. As many as 85 percent of liver cancer cases are believed to be caused by the virus.

So widespread use of the Hepatitis B vaccine should result in declining liver cancer incidence. And in places where Hepatitis B was a major problem, that in fact has happened. In Taiwan, for example, the incidence of liver cancer has declined by half since the introduction of the Hepatitis B vaccine.

Lumberg first isolated the Hepatitis B virus in 1967 with epidemiological studies in human beings, but it was animal research that relied largely on guinea pigs and non-human primates that led to the development and approval of a vaccine for the disease in the early 1980s.

Source:

The world’s first cancer vaccine. Roger Highfield, The Daily Telegraph (London), June 26, 2002.

Are Mice Models of Cancer Fundamentally Unsound?

A common refrain from animal rights activists is that there are fundamental differences between humans and non-human animals that makes cross-species comparisons for medical research purposes pointless. It turns out, for example, that many mice models of cancer may have a fundamental flaw that makes it difficult, if not impossible, to compare them to human cancers.

But contrary to what animal rights activists seem to believe, such discoveries also help advance human understanding of disease and, ironically, do not mean that mouse models of cancer need to be abandoned.

In this case the debate is over telomeres. When human cells are placed in a culture in a laboratory, they will not divide indefinitely. Instead, after about 50 or so cell divisions, the cells will no stop dividing. This point at which cells stop dividing is called the Hayflick Limit.

It turns out that the Hayflick limit is determined by telomeres — these are long stretches of noncoded sequences at the end of DNA. In most cells, every time the cell divides, the length of the telomere sequences declines and the cell will stop dividing once the telomeres are exhausted. Only cells that divide a lot such as skin cells, germ cells and others maintain their telomere lengths intact.

What does this have to do with cancer? In some cases it is believed that mutations in a cell can cause it to keep dividing past the Hayflick Limit which eventually an become malignant growths. Researchers suspect that some cancers associated with aging are caused by this process.

But this is a major problem for mouse models, because mice have telomeres that are about twice as long as human beings. This means that, unlike human beings, mice cells keep dividing throughout the life of the mouse and they do not tend to experience the gradual fraying of the ends of the DNA strand that aged human cells do.

If this is true it means that existing mouse models of cancer are probably not appropriate for studying such cancers. In fact, mice do not tend to suffer from cancers which are associated with aging in humans, such as breast and colon cancer.

This is the point where animal rights activists would say, “aha, told you — there is no point in conducting cancer research in mice.”

But a much better response is to simply not study those particular forms of cancer in mice, or created genetically modified mice or use existing strains of mice that are more like human beings in this respect.

Both solutions are currently being investigated. Carol Greider, professor of molecular biology and genetics at the Johns Hopkins University School of Medicine, collaborated with another researcher to create a mouse that has telomeres that are similar in length to those in human beings. And wouldn’t you know it, such mice contract a range of cancers that is far closer to the human distribution of cancers than the traditional mice used in laboratories. That discovery in and of itself provided nice confirmation that telomeres indeed do play a role in cancers.

As an article in The Scientist summed it up,

DePhino and Greider’s diligence notwithstanding, Harrison says that, in general, researchers need to be more careful with their models. “We’re not looking at the whole mouse genome here; we tend to look at a very limited number of mouse strains, and that’s probably a mistake,” he says. Researchers must instead ask themselves, which kinds of mice are appropriate models for a given type of cancer? It may even be necessary to determine which mice make the best models for given groups of people, he adds.

Mucch genetic diversity has been captured by producing inbred mouse strains from previously unsampled, wild populations. These strains offer the genetic reproducibility that is so valuable in lab mice, but with a wider variety of genotypes and phenotypes. But Harrison stresses that using mice as models for cancer development has already been quite successful. For instance, every chemical that induces cancer in humans does so in mice as well, proving that the use of mice is an effective and powerful research tool. “If you lose the mouse as a tool, just because of some prejudice about telomeres,” he concludes, “you take away a lot of the opportunity for advancement.”

Source:

Telomeres as the key to cancer: could hundreds of mouse models be wrong? Jeffrey M. Perkel, The Scientist 16[11]:38, May 27, 2002.

Animal Rights Movement and Excessive Regulation "Delay Lifesaving Drugs"

Medical researchers told the European Breast Cancer Conference that animal rights attacks combined with excessive regulations governing clinical trials are delaying the development of life saving cancer treatments.

Dr. Michael Baum, who chaired the conference, said,

Women will die unnecessarily because of the delays these two threats cause.

. . .

Britain has led the world in reducing deaths from breast cancer because of the research and innovation we have in this country. That is being lost. We are already seeing delays in new drugs coming through and young researchers are deciding it’s not worth coming into the field because of all the restrctions.

As if animal rights attacks were not enough, in 1996 the European Agency for the Evaluation of Medicinal Products imposed additional regulations on the conduct of clinical trials. Many medical researchers believe those regulations went too far in protecting the privacy of patients in clinical trials. According to Baum,

I accept that we need to protect patients and protec thtier privacy but these restrictions are nonsensical. There is a pently to pay for them and that pentalty is in peoiple’s lives.

Source:

Animal rights ‘delay lifesaving drugs’. Helen Rumbelow, The Times (UK), March 23, 2002.

Meat, Milk Contribute to Cancer — Or Do They?

A study published in the January 2002 issue of the American Journal of Clinical Nutrition found that people who ate diets high in red meat and/or milk had much higher rates of stomach and esophageal cancer than those who did not. Some animal rights groups and activists are trumpeting this as the latest evidence that meat is not good for you. The activists might want to read the fine print since the study actually reinforces common sense advice about a balanced diet as exemplified by the U.S. Department of Agriculture’s nutrition guidelines — guidelines which have been much derided by animal rights activists and groups.

The study by Honlei Chen examined the dietary patterns of white adult residents of eastern Nebraska. The study included 124 subjects whom had been diagnosed with stomach cancer, 124 who had been diagnosed with esophageal cancer, and 449 healthy controls. Researchers asked the subjects about their eating habits and they were then classified into groups such as “healthy,” “high meat,” “high milk,” etc.

Right off the bat there are a lot of limitations as to how generalizable the results of this study are due to its size and other related issues, but lets ignore those objections. What did the study actually find?

The result that made headlines was that people who ate “high meat” diets had 3.6 times the risk of esophageal cancer and twice the risk of stomach cancer compared to those eating a “healthy” diet, while those who had “high milk” diets had a 2-fold risk of both esophageal and stomach cancers compared to the “healthy” diet group.

The first thing to note is that the “healthy” eating groups were those who followed existing USDA dietary guidelines — they ate about five servings of fruit and vegetables, lots of servings of grains, bread and pasta, and only 2-3 servings of meat daily. These are the same guidelines, of course, which groups like the Physicians Committee for Responsible Medicine have attacked as dangerous and racist (for their inclusion of milk).

Second, as with similar studies, what the study really seemed to track is not meat eating per se, but rather calorie consumption and lack of fruits and vegetables. The group designated as “healthy” consumed the fewest calories which should not be surprising given that someone who eats a lot of meat and/or drinks a lot of milk is very likely to be consuming a lot of calories (it would have been interesting to know about the weight distribution of the individuals in the various groups).

Similarly, recent studies have suggested that consumption of fruits and vegetables may play a role in reducing cancer risk, so people who consume lots of calories and get those calories mainly from meat without adequate fruits and vegetables may be increasing their risk of cancer due to not eating fruits and vegetables rather than from eating meat.

The upshot is that this is the latest study which simply reaffirms commonsense dietary advice. People need not adopt a strict vegan or vegetarian to reduce their risk of cancer and other diseases, but they do need to eat sensibly, consuming lots of fruits and vegetables and eating meat in moderation.

Source:

New research links meat with cancer. Reuters, December 20, 2001.

Diets high in red meat linked to stomach and esophageal cancers. Press Release, American Journal of Clinical Nutrition, December 14, 2001.