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| Golgi in 3D. Brad et al, 2001 |
Cancer causes a high number of deaths each year. However, most of the cancers are treatable and get cured if they are detected early. But how doctors detect cancer? One way is to take a sample of the suspicious tissue and check for the presence of cancer cells and/or proteins that are present in those cancer cells. This has a big problem. Imagine that for detecting a cancer every person has to have a surgery. Well, the process would be very long, expensive and uncomfortable for the patients. But don’t worry. There are other ways of detecting cancer. One of them is the detection of tumor biomarkers in blood. These biomarkers are proteins that cancer cells produce and are present in the blood. In this way the patients only need a blood test to know if they have cancer.
But these biomarkers are not just important to detect the presence of cancer, but also to see if the cancer has spread to other organs (metastasis) and to check that the treatment received by the patient is working and the cancer is being cured. In the last years there has been a big effort from many research groups to identify good biomarkers for several types of cancer and many research papers have been published about this using different approaches. A very interesting one is the study of the cancer secretome . The secretome is the group of proteins that cells secret outside. These proteins are very likely to go to the blood or other biological liquids and therefore they will be easier to detect in a blood sample and could be potential good biomarkers.
However, there is another factor that establishes if a protein can be a potential biomarker. This is the availability of commercial antibodies against it, because the most common ways of detecting biomarkers (Western blot and ELISA) use antibodies. Therefore commercially available antibodies can facilitate the identification of new and valuable biomarkers for the detection of cancer.
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| Western blot. Xue et al, 2010 |
A good example of the identification of new biomarkers studying the secretome of different kind of cancers is a study in colorectal cancer. In addition, it shows how having commercially available antibodies has been an important factor to choose the final candidates. Patients with colorectal cancer get cured but half of them develop further diseases within 5 years (mostly metastases). In this study they identified differences between the secretomes of regular cancer cells (SW480 cells) and metastatic cancer cells (SW620 cells) of colorectal cancer.
At the end of the process they chose 6 proteins because they were present in much higher or lower amount in the metastatic cells than in the regular cancer cells (Figure 2). Out of these 6 proteins, 3 were up regulated in metastatic cells. They kept working with only two of them, because, even if there was an antibody that detected the third protein in western blots, it could not be used for the assay that they used for further validation of these potential biomarkers.
At the end of the process they chose 6 proteins because they were present in much higher or lower amount in the metastatic cells than in the regular cancer cells (Figure 2). Out of these 6 proteins, 3 were up regulated in metastatic cells. They kept working with only two of them, because, even if there was an antibody that detected the third protein in western blots, it could not be used for the assay that they used for further validation of these potential biomarkers.
The result of the study is impressive, because they found two proteins that are clearly present in metastatic colorectal cancer and not in the primary tumor and can be used as biomarkers to detect the presence of metastatic disease giving the opportunity of an early intervention and more chances for the patients to be cured.
Xue H, Lü B, Zhang J, Wu M, Huang Q, Wu Q, Sheng H, Wu D, Hu J, & Lai M (2010). Identification of serum biomarkers for colorectal cancer metastasis using a differential secretome approach. Journal of proteome research, 9 (1), 545-55 PMID: 19924834
Published originally in Spanish in E-ciencia.com
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