A potential role for myosin light chain kinase in lung adenocarcinoma tumorigenesis.

e22051 Background: Treatment of non-small cell lung cancer remains a clinical challenge despite the migration from cytotoxic chemotherapies to targeted agents. Myosin light chain kinase (MLCK) is a protein involved in phosphorylation of regulatory chains of myosin, thereby regulating the contraction of myosin II. The 210 KDa non-muscle MLCK isoform (nmMLCK), expressed in endothelial cells, regulates cell shape and motility, and increases EGFR-mediated proliferation of hepatocytes. Furthermore, inhibitors of MLCK such as ML-7 and ML-9 have been shown to decrease invasiveness of pancreatic prostate cancer cell lines. Clinically, levels of MLCK gene (MYLK) mRNA correlate with increased risk of disease recurrence and development of distant metastasis in lung cancer. These data suggest a potential role for MLCK in lung cancer tumorigenesis and metastasis. Methods: H-23 and H-441 human lung adenocarcinoma cell lines were treated for 12hrs with MLCK chemical inhibitor, ML-7 (20uM), and harvested at 24hr, 48hr, and 72hr for MTS Assay. Cell proliferation was assessed with MTS Assay per manufacturer protocol (Promega). H-23 cells were transiently transfected with a FLAG-tagged (WT) nmMLCK overexpression vector using Fugene Transfection Kit per manufacturer protocol (Promega). Results: While no significant difference in proliferation was noted in A-549 cells, both H-23 and H-441 cells showed a decrease in cell proliferation with inhibition of MLCK. H-23 cells also showed an increase in proliferation when transiently transfected with an MLCK-overexpression vector. Conclusions: Inhibition of endogenous nmMLCK decreases H-23 and H-441 proliferation. Conversely, an increase in nmMLCK expression in vitro increases cell proliferation in H23 cells. These results suggest that MLCK/MYLK may participate in regulation of lung adenocarcinoma cell proliferation.