Colorectal cancer tumor markers. Cancer therapy efficacy prediction. 14
Cancer prevention is the best cancer treatment. New tumor marker helps to diagnose colon cancer. It is called miR-21 microRNA. It can be found in blood and in fecal samples. Leading colorectal cancer genetics expert discusses colon cancer treatment and prognosis. Dr. C. Richard Boland, MD. Molecular tumor markers in colorectal cancer form the basis of precision medicine approach to treatment. You have identified a new diagnostic and prognostic marker for colorectal cancer called miR-21. You showed that miR-21 is an independent prognostic factor in colorectal cancer miR-21 also plays a role in assessment of quality of colon cancer surgical treatment. What is miR-21 tumor marker? How does it help with diagnosis and follow-up of patients with colorectal cancer? So we have about 2,000 microRNAs in our genome. The microRNAs are called “mi” for “micro” and a capital “R” and then a number. MicroRNAs didn’t get names, they got numbers. So you can use an RNA sequencing technique and measure all of microRNAs at once. You can take colon cancer tissue, and do my microRNA sequencing and tell exactly the quantitative expression of each of the microRNAs. So there were certain microRNA genetic signatures that came up again and again in colon cancers. miR-21 was one of the very commonly overexpressed microRNAs. We didn’t anticipate this initially, but this is what turned out to be the case. These microRNAs get packaged into the exosomes and released into the blood. So first we found out that there were unique microRNA signatures in colon cancer tissue. Then we found out that some of microRNAs appeared in the blood. And microRNA is significantly increased in the blood of people with colon cancers. MicroRNA levels also decrease after primary colon cancer tumor is removed. So it looks like a pretty good tumor marker for colon cancer. Dr. C. Richard Boland, MD. We have a number of technical problems to solve. MicroRNAs degrade pretty quickly in the refrigerator. So you have to measure microRNA levels right away. Then there are complications when there is hemolysis. Red blood cells have a lot of microRNAs. So when there is hemolysis, it’s hard to interpret the results of microRNA level measurement. Other medical problems, for example, heart failure and other cancers cause elevations of microRNA levels. But we will overcome these problems. It is just a matter of finding the right combination of microRNAs and overcoming the technical issues. We’d like to find a tumor biomarker in fecal test, but having a biomarker for blood test would be the best. So we can say to patient, “You are safe because you don’t have a very high level of microRNAs in blood”. Your likelihood of having colon cancer is so low that you can wait another year, or even several years, and then you can have another microRNA blood test.” Or if microRNA levels are high, maybe you need to have a colonoscopy. We’d like to find simpler, safer, cheaper ways to screen for colon cancer and separate people into those who might need a more invasive procedure like a colonoscopy, and those who are are safe for another year or two years. So that’s an amazing approach, because it can triage the patients and have a blood test with negative predictive value for cancer detection, those who will benefit from a colonoscopy, and those who can wait longer. Dr. C. Richard Boland, MD. What we really hope for is to find a blood test which says, “You don’t need a colonoscopy”. It’s better, of course, if we can say that a positive test will tell you that you may have a tumor. But I’m not so worried if such microRNA blood test for cancer is not perfectly sensitive. What we’d like to have is a cancer screening test with high specificity. So that we could reassure person that they don’t need to have expensive, invasive, uncomfortable, and potentially dangerous test for colon cancer [optical colonoscopy]. That’s what we’d like to do. Dr. Anton Titov, MD.
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