Itxaro Perez, a biochemist at the University of the Basque Country (UPV/EHU), has contributed in such a way that, in the long term, the early diagnosis of cancer of the large intestine could be feasible. Specifically, she has focused on certain enzymes known as peptidases and their activity (working rate): she has studied how their activity changes by comparing the tissue encountered at different stages of the disease. If these fluctuations could be correctly distinguished, they would be of use in the future when it comes to knowing how to go about detecting this type of cancer early. The line of research has only just begun, but it could provide many keys. The researcher has defended these initial results in a thesis entitled Peptidasen aktibitatearen aldaketak heste lodiko neoplasietan (Changes in the activity of peptidases in the neoplasms of the large intestine).
"Cancer of the large intestine does not display any symptoms until it has reached a fairly advanced stage," explains Perez. So the challenge for researchers in this discipline is to secure an early diagnosis. Fortunately, this specific disease has characteristics that lend themselves to research and comparisons: "It has an intermediate phase known as an adenoma. This can be regarded as a cancer since uncontrolled cell growth takes place, but it is benign. The fact that it has this intermediate phase is very good for comparison purposes: firstly we can extract healthy tissue, and then from the adenoma, and after that from the cancer itself. By contrast, in the case of other diseases, the cancer is malignant right away and can only be compared with healthy tissue." This way she has had the chance to observe how the activity of the peptidases evolves when three types of samples are extracted from the intestine (from the colon) of each patient: specifically, from healthy tissue, from an adenoma and from an already developed malignant tumour.
Blood samples, her greatest contribution
In addition to intestinal samples, Perez has also analysed the plasma by comparing blood samples from patients suffering this cancer with those of healthy individuals. This is in fact the main contribution of her thesis: the taking of steps to be able to identify evidence of the disease in the blood itself. "Obtaining plasma from the patient is straightforward. If it could help to make an early diagnosis, it would be a very valuable method for clinical applications", she explained.
Plasma has already been used with the same aim in other types of cancer. As proof of this, Perez has long been conducting research on renal cancer in collaboration with her colleagues at the Department of Physiology at the UPV/EHU. But this is a field that has not been studied very much in cancer of the large intestine, and considerable differences have been found: "In the kidneys we saw that the activity changes in many of the peptidases, but this does not happen in the large intestine. Some change, others do not. We were not aware of that."
So a plasma analysis of the peptidases that are susceptible to undergoing changes of activity could, in the long term, become a useful tool for diagnosing cancer of the large intestine. But that is not all: these changes also take place differently depending on the phase or condition that the cancer is in. This means that this analysis can also be used for prognosis purposes.
Although the results obtained do shed some light, more exhaustive research now needs to be undertaken to determine how relevant the peptidases are in the formation, evolution and causes of this type of cancer. For example, the conclusions need to be verified by other means, other characteristics of these enzymes (apart from their activity) need to be studied, etc. In connection with this, Perez and her colleagues will be taking another step forward from next year onwards: "The samples we studied date back to 2007. As five years have now passed, our next piece of research will be focusing on the survival of these patients (how many of them remain alive, among other things). We want to see what happens; above all, what the prognosis is."
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