Can Plasma miR-122-5p and miR-142-5p Predict Relapse in Metastatic Colorectal Cancer Patients?

Approximately 20% of colorectal cancer patients already suffer from metastases at the time of diagnosis. Perhaps more serious, about 50% of the patients with localized tumours will eventually develop metastases during the course of their disease. A current hypothesis suggests that acquired or intrinsic chemoresistance is one of the major causes of metastasis. Recently, we found that circulating miR-122-5p and miR-142-5p could be used to predict both patient outcome and response to therapy. In the present study, we validate our previous results in patients with metastatic colorectal cancer (n=18), taking blood samples at three different times; i.e. metastasis resection surgery (T0), ~1 month after surgery (T1), and~8 months after surgery (T2). The expression levels of miR-122-5p and miR-142-5p were analysed in plasma and plasma extracellular vesicles (EVs) through RT-qPCR. The obtained results were compared against serum CEA and CA 19-9 levels, and computed tomography scans. The rectal cancer patients in the good prognostic group showed significantly increased miR-142-5p expression profile between T1 and T2; whereas the poor prognostic group showed a lower expression during T2 when compared with T1. The decreased expression of miR-142-5p in the latter group could also be seen in the EVs of the patients. This is consistent with our previous study, where the downregulation of miR-142-5p could be associated with poor response to therapy. In addition, the individual analyses showed that the downregulation of both miRNAs predicted tumour relapse at an earlier time point than the markers CEA and CA 19-9. In conclusion, the obtained data from this study demonstrates that miR-142-5p and miR-122-5p could be used as predictive bio-markers of tumour relapse in cases of metastatic rectal cancer, although further validation is still needed.