Cancer Therapy: Preclinical Nab-Paclitaxel Is an Active Drug in Preclinical Model of Pediatric Solid Tumors

Purpose: To investigate the antitumor effect of nab-paclitaxel, an albumin-stabilized nanoparticle formulation of paclitaxel, on pediatric solid tumor models. Experimental Design: A panel of three rhabdomyosarcoma, one osteosarcoma and seven neuroblastoma cell lines were exposed to increasing concentrations of nab-paclitaxel in vitro. Cell viability was evaluated using the Alamar Blue Assay. Antitumor effect was further assessed in vivo inNOD/SCID xenograft andmetastatic neuroblastomamousemodels. Tumor sectionswere analyzed by immunohistochemistry for cleaved caspase-3 and phospho-histone H3. Plasma and intratumoral paclitaxel concentrations were measured by liquid chromatography–mass spectrometry. Ratio of intratumoral and plasma concentration was compared between nab-paclitaxel and paclitaxel treatment groups. Results: Nab-paclitaxel displayed significant cytotoxicity against most pediatric solid tumor cell lines in vitro in a dose-dependent manner. In vivo, nab-paclitaxel showed antitumor activity in both rhabdomyosarcoma (RH4 and RD) and neuroblastoma [SK-N-BE(2) and CHLA-20] xenograft models. In the SK-N-BE (2) metastatic model, nab-paclitaxel treatment significantly extended animal survival compared with control (P < 0.01). Nab-paclitaxel treatment induced tumor cell-cycle arrest and apoptosis in vivo. In the RH4 model, increased local relapse-free intervals were observed with nab-paclitaxel treatment (37.7 3.2 days) comparing with paclitaxel (13.6 2.07 days). Local relapsed tumors following paclitaxel treatment proved to be paclitaxel-resistant and remained responsive to nab-paclitaxel. Mechanistically, a higher tumor/plasma paclitaxel drug ratio in favor of nab-paclitaxel was observed. Conclusions: Nab-paclitaxel showed significant antitumor activity against all pediatric solid tumors associated with an enhanced drug intratumor delivery. Furthermore, testing of nab-paclitaxel in pediatric solid-tumor patient population is under development. Clin Cancer Res; 19(21); 5972–83. 2013 AACR.