ABCB1 and ovarian cancer: However, changes in tumor volume in mice treated with either the combination of HA-PEI/HA-PEG/non-specific siRNA CD44 targeted nanoparticle and paclitaxel or the combined naked MDR1 siRNA and paclitaxel was similar to that with paclitaxel treated alone in this ovarian cancer MDR model (Fig. 4B).