Effects of combining siRNAs against CAV1, ENO2, PKCα and DHFR on MTX sensitivity. Treatments with combinations of siRNAs at100 nM each were performed both in sensitive (A) and in resistant cells (B). MTX was added after 48 h and cell viability was determined by the MTT assay after 5 days from the beginning of the treatment. The triple combination includes the siRNAs against CAV1, ENO2 and PKCα; the quadruple combination includes the three previous siRNAs plus siDHFR. Results are presented as percentages referred to the untreated cells. Values are the mean of three independent experiments ± SE.