Exosomal miRNA in chemoresistance, immune evasion, metastasis and progression of cancer

•Exosomal miRNA plays a vital part in the initiation of dysregulated molecular events.•Understanding exosomal miRNA in chemoresistance, immune-escape and metastasis is imperative.•An engrossed understanding of the role of exosomal miRNA and mechanics of transmission is described.•A crosstalk on the position of exosomal miRNA in cancer drug discovery is also provided. In the treatment of cancer, there are three significant limitations causing high mortality and recurrence rates among cancer patients. First, the escape of tumor cells from the immune system; second, the development of multi‐drug resistance (MDR) to chemotherapeutic drugs; and, third, the noxious metastases of cancer cells. Exosomes are vesicular cargos involved in the transportation of miRNA, mRNA and proteins from one cell to another cell. This review details the current understanding of the exosomal transmission of miRNA and crosstalk with the downstream consequences, ultimately leading to the progression and metastasis of cancer. Further, this review also discusses how exosomal miRNA can provide promising novel targets for the treatment and detection of cancer.