Mucin 1-mediated chemo-resistance in lung cancer cells

Paclitaxel (PTX) is a commonly used drug to treat diverse cancer types. However, its treatment can generate resistance and the mechanisms of PTX-resistance in lung cancers are still unclear. We demonstrated that non-small cell lung cancers (NSCLCs) survive PTX treatment. Compared with the progenitor NSCLC A549 cells, the PTX-resistant A549 cells (A549/PTX) displayed enhanced sphere-formation ability. The proportion of the cancer stem cell marker, aldehyde dehydrogenase-positive cells, and epithelial–mesenchymal transition signaling protein levels were also elevated in A549/PTX. Importantly, the levels of oncoproteins phosphoinositide-3 kinase/Akt, mucin 1 cytoplasmic domain (MUC1-C) and β-catenin were also significantly elevated in A549/PTX. Furthermore, nuclear translocation of MUC1-C and β-catenin increased in A549/PTX. The c-SRC protein, an activator of MUC1-C, was also overexpressed in A549/PTX. These observations led to the hypothesis that enhanced expression of MUC1-C is associated with stemness and PTX resistance in NSCLCs. To test this, we knocked down or overexpressed MUC1-C in A549/PTX and found that inhibition of MUC1-C expression coupled with PTX treatment was sufficient to reduce the sphere-forming ability and survival of A549/PTX. In summary, our in vitro and in vivo studies have revealed a potential mechanism of MUC1-C-mediated PTX resistance and provided insights into a novel therapeutic measure for lung cancers.