ABCB1 and small cell lung carcinoma: In SCLC (Figure 1), several studies have correlated the expression of MDR1 and multidrug resistance associated protein 1 (MRP1) with chemoresistance and poor prognosis in SCLC patient samples and cell lines [213,214,215,216,217,218], and some relapse patients were found to have amplifications of ABCC1, which encodes MRP1 [140].