Tuesday, December 13, 2011

Promising new vaccines for cancer being developed

One of the reasons tumours are allowed to flourish in our body, is the fact that the immune system is unable to recognize the malicious cells. Normally, when cells start behaving oddly, they will be cleared by specialized immune cells. However, tumour cells have found a way to evade them, and that's why scientists try to come up with ways to train the immune system to successfully recognize cancer cells. Researchers from the Mayo Clinic in Arizona have developed a vaccine that trains the immune system to recognize breast cancer and pancreatic cancer. It significantly reduced the number of tumours in mice, highlighting the therapeutic potential of their findings.

A new treatment
In their experiments, the American researchers injected mice with a substance that helps the immune system to recognize a protein found predominantly on cancer cells, called MUC1. In tumours, the expression of this protein is higher, and the structure also differs from that of healthy cells. Notable, three sugar groups on the protein surface are different, and that is what the immune system is supposed to recognize. Because it only works for the different forms of sugars found in cancer, healthy cells are not being targeted. The vaccine treatment was tested in a mouse model that develops tumours which are also characterized by differences in MUC1, and is therefore compatible with what human patients experience.

After vaccinating mice with a substance that trains the immune system to recognize the aberrant MUC1, the scientists found that the vaccine elicits a very strong response. In turn, this caused a dramatic decrease in the number of tumours. The vaccination even appears to be effective when the tumour is resistant against conventional forms of treatment, highlighting the potential power of the new substance. 

Clinical use
MUC1 alteration and overexpression is found on 70 percent of lethal types of cancers. It is predominantly found in breast and pancreas. That means a vaccine could have a widespread use. And because it is so effective, it could save the lives of many patients. Equally important is the potential to prevent cancer. When the immune system is trained to recognize aberrant MUC1, then cancers that rely on it will not be able to grow to pathological sizes. Patients that have previously suffered from cancer could be given the vaccine as a prophylactic, to prevent recurrence of the disease.

The immune system
Our body's defence system has several components. When it comes to recognizing malicious or infected cells, we rely on so-called lymphocytes. These are specialized cells that recognize specific patterns, either on malicious or infected cells, or pathogens. As there are a lot of different molecular patterns, a huge variety of lymphocytes are needed. That is why the body pumps out millions of different lymphocytes, each specialized to recognize only one pattern. Immune cells may run into the pattern they are set to recognize, for example part of a protein coming from a bacterium during infection. The cells will then, with the help of other specialized cells in the immune system, clone itself. That way an army of lymphocytes trained to kill the bacterium in question arises. 

This way, the body always responds after a pathogen has already invaded, or after cells have already started to behave abnormally. However, that is a consequence of how the immune system works. If it were to have an army of cells destined to kill all possible pathogens or infected cells, it would require massive amounts of cells, which the body has no capability of providing. The body already churns out millions of cells per second, highlighting the bizarre maintenance requirement our body has. And that is why the normal state of the immune system is being dormant, instead of being armed to the teeth.

The newly discovered vaccine appears to work very well in mice. That does not mean it will work well in humans, but because the pathology is so similar, it is expected to work with similar efficacy. Of course, a lot of checks are needed to assess the safety of the novel vaccine, which is why clinical trials will most likely be performed as a next step. All in all it seems like a promising new therapy for cancer, and to prevent recurrence of cancer.

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