Previous studies have shown that despite similarities in sequence, structure, and function of MDR between ABCG2 (BCRP) and ABCG4, ABCG2 is not associated with gender, smoking history, performance status (PS), histological type, and TNM stage in NSCLC [35,36], while we observed associations between ABCG4 and histological type, differentiation grade, and TNM stage. The gene discussed is ABCG2; the disease is non-small cell lung carcinoma.