As the binding of aptamer to a protein peptide does not assure the binding of the aptamer to the native protein exposed in the cell-membrane surface, we performed the last round of selection (R11) by Cell-SELEX by using the chemotherapy-resistant tumor cell line that has high MRP1 expression (H69AR) [10] and as counter selection the parental cell line H69. The gene discussed is ABCC1; the disease is neoplasm.