The potential of exosomes derived from colorectal cancer as a biomarker.

Colorectal cancer (CRC) is one of the most frequent causes of cancer death. The diagnosis and treatment for metastatic CRC and patients with drug resistance remains poor. Cancer cells characteristically produce and release exosomes, which act as a new signal pattern in the occurrence and development of tumors. Circulating exosomes constitute promising biomarkers for early diagnosis of cancer patients. However, the potential of exosomes for clinical biomarker is hampered by their variousness and multi-sources. To this aim, we set out to solve the problem of discrimination and classification of exosomes. The cell culture supernatants of CRC cells, renal cell carcinoma cells and breast cancer cells were used for isolating exosomes. Then characteristic exosomal tumor markers were explored by Roche Cobas E601 fully automated electrochemiluminescence immunoassay systems, western blot and flow cytometry analysis. The results showed that CK19 was commonly expressed in exosomes derived from colorectal cells, TAG72 was mainly expressed in exosomes of 5-FU-resistant CRC cells and CA125 in those of high metastatic CRC cells. In addition, tumor interstitial fluid derived exosomes and patients' plasma derived exosomes showed different levels of CK19, TAG72 and CA125. Collectively, these data indicated that exosomes derived CK19 is correlated with colorectal tissue. TAG72-rich exosomes indicate that CRC patients might be resistant to 5-Fluorouraci. CA125-rich exosomes might be as metastatic CRC markers. These provide a good prospect for cell exosomes as novel, non-invasive clinical tool for diagnosing CRC and predicting its progression.