Effect of NELL1 on lung cancer stem‑like cell differentiation.

The cancer stem cell theory recently has received enormous attention in cancer biology. Lung cancer stem-like cells are a subpopulation of undifferentiated lung tumor cells critical for lung cancer tumorigenesis, metastasis and resistance to therapy and disease relapse. The neural EGFL like 1 (NELL1) is a potent growth factor believed to preferentially target cells committed to the osteochondral lineage; yet, its expression and function in lung cancer are largely unknown. In the present study, we used specific medium to accumulate lung cancer stem-like cells of 95-D cells in spheres and obtained these highly expressed CD133 cells through flow cytometric cell sorting of CD133-stained cells which were termed 95-D lung cancer stem-like cells (95-D LCSCs). These 95-D LCSCs highly expressed stemness genes CD133, Oct4 and Sox2 determined by western blot analysis and quantitative real-time polymerase chain reaction (qPCR) analysis. Notably, we found that overexpression of NELL1 significantly reduced colony formation and invasion of 95-D LCSCs tested by soft agar colony formation and cell invasion assay. In addition, as determined by cell proliferation assay, overexpression of NELL1 increased the chemotherapeutic sensitivity of 95-D LCSCs to carboplatin and cisplatin. NELL1 also reduced the expression of phospho-MET (p-MET), Notch3 and HES1, which suggests that NELL1 may induce 95-D LCSC differentiation by inhibiting the expression of c-MET-Notch signaling. Our results suggest that NELL1 induces lung cancer stem-like cell differentiation, which provides a new potential therapeutic target for cancer stem cells.