MUC5AC and cancer: The overexpression of mucin 5ac in cancer has been documented by other researchers 37–39 and has also been observed by us in one of our unpublished studies, with increasing occurrences of lymph node and distant metastasis and deeper invasion.20,35,40 Moreover, a 2013 study showed mucin 5ac could protect cancer cells from neutrophils’ attacking by suppressing TRAIL-mediated apoptosis .27 Therefore, mucin 5ac may serve as an important indicator in cancer prognosis.