PLK1 and lung cancer: To explore the antiproliferative effect of PLK1 inhibition in combination with an apoptotic potentiator, we first determined the concentration of the PLK1 inhibitor BI2536 and the BH3-mimetic Navitoclax, able to cause 50% cell viability inhibition (IC50), after 48 h exposure, in the two lung cancer cell lines, A549 and NCI-H460.