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Posted on 26th Mar 2015 @ 8:46 AM
More and more evidence have suggested that micrornA in circulating tumor cells (CTC) have diagnostic and prognostic potential. However, it is not easy to detect. Recently, researchers in Spain introduced a new technology in "Science Reports" that could take advantage of in situ hybridization to detect such small non-coding RNA. CTC is a kind of cell , which is shed from the primary tumor, and then enter the circulatory system. They reach other tissues or organs, leading to tumor metastasis. Given the progress of CTC detection technique in recent years, researchers are able to take advantage of these epithelial cells to monitor the progress of cancer, and track patient response to treatment. Nevertheless, most of the CTC analysis is less sensitive. According to GENYO research team , it is mainly because only a small number of epithelial markers can be used to identify and isolate circulating tumor cells within whole blood , usually epithelial cell adhesion molecule (EpCAM) and cytokeratin (CK).
However, these epithelial cells may also be derived from other epithelial tissues, rather than the tumor. To make things even more complicated is that the latest data indicate a part of CTC do not express EpCAM or CK. Instead, these cells exhibit epithelial - mesenchymal transition (EMT) features. This process is associated with tumor metastasis, of which , epithelial cells showed mesenchymal characteristics, promote migration, invasion and resistance to apoptosis. Based on these reasons, the exploration of miRNA biomarker potential in CTC miRNA was limited. To solve this problem, GENYO researchers developed a method called MishCTC , which combined the in situ hybridization method , immunomagnetic selection based on CK expression with immunocytochemistry , using locked nucleic acid (LNA) probes to detect miRNA . To validate this technology , the researchers selected miR-21, this miRNA targeted multiple tumor suppressor genes , and it was expressed in cancer cells , rather than in hematopoietic cells , thus it was an ideal marker for CTC detection.
They won 25 cases of peripheral blood samples of patients with metastatic cancer, and utilized MishCTC methods to carry out the analysis. In these 25 samples, 11 samples contained CTC expressing CK and miR-21. For CK expression deficient EMT-induced epithelial tumor cell line (MCF-7), MishCTC technology has successfully tracked the expression of miR-21, indicating that miR-21 may be a good marker for the detection of EMT phenotype CTC . According to the researchers ,these data for the first time demonstrated the in situ hybridization method can be used to identify in CTC . They are currently recruiting a large number of cancer patients, in order to study the heterogeneity of CTC according to miRNA expression