The treatment of RLS40 cells with the bcl-2 siRNA followed by cyclophosphamide administration had no effect on the RLS40 tumor growth (data not shown), which is explainable by a major contribution of mdr1a and mdr1b gene products to MDR development (Pgp-mediated MDR phenotype) as compared with bcl-2 gene. Here, PGP is linked to neoplasm.