Circulating microRNA-21 as noninvasive predictive biomarker for response in cancer immunotherapy

A pre-existing T cell-inflamed tumor microenvironment is predictive of clinical outcome to immunotherapy, but the mechanisms of immune effector cells infiltration of tumors are not clear. MicroRNAs are a class of small non-coding RNAs that regulate gene expression at the posttranscriptional level. Additionally, circulating miRNAs might be useful as noninvasive biomarkers of disease and therapy response. Previous studies indicate that STAT3 activity in tumor cells affects immune cells recruitment, which is prerequisite for effective T cell therapy. MiRNA-21 is one of the cell-free miRNAs that has recently been identified as a potential regulator of STAT3. Meanwhile, miRNA-21 is an oncogenic miRNA that could be detected in various tumors. Therefore, we get the hypotheses that circulating miRNA-21 is a potential predictive biomarker for response in cancer immunotherapy and so a novel therapeutic target.