Moreover, there are significantly increased reports indicating that cancer stem cells naturally possess the ability to evade chemotherapy partly because of ABC-transporter expression, and ABCG2 expression has a close correlation with etoposide resistance.48 To investigate whether LSH WT and mutants play roles in etoposide resistance, PC9 cells with stable expression of either WT or mutants were treated with etoposide for 48 h. The gene discussed is ABCG2; the disease is cancer.