Intralymphatic nanocarrier chemotherapy for breast cancer: Improved delivery to locoregional lymph nodes

AACR Centennial Conference: Translational Cancer Medicine-- July 20-23, 2008; Monterey, CA A3 Background: One problem of breast cancer chemotherapeutics is their ability to penetrate locoregional tissues and lymph node metastases. We have previously shown that hyaluronan (HA) cisplatin conjugates can be transported intralymphatically via a subcutaneous breast injection in rodents. The purpose of this study is to compare the ability of hyaluronan nanocarrier conjugates to deliver cisplatin to locoregional tissues over the standard drug formulation in a murine orthotopic model of lymphatically metastatic human breast cancer. Methods: Cisplatin was conjugated to hyaluronan (35 kDa) by ionic displacement of the hyaluronate sodium with silver nitrate followed by addition of cisplatin to achieve 25% w/w Pt(II)-HA determined by atomic absorption spectroscopy (AAS). Cytotoxicity of cisplatin-HA conjugates were verified in human breast cancer cell lines MCF-7, MDA-MB-231 and MDA-MB-468LN. Cisplatin and cisplatin-HA in saline were injected s.c. into the right mammary fat pad of female Sprague-Dawley rats (150-180g)[previously injected in the right mammary fat pad with 106MDA-MB-468LN cells and followed 6 weeks until both primary and axillary metastases developed] at 3.5 mg/kg equivalent cisplatin. Alternatively cisplatin was given as an intravenous (i.v.) tail vein injection at 3.5 mg/kg. At 1, 6, 12, 24, 48, and 96 hours post-injection, the right axilla nodes, left contralateral axilla nodes (control), and major organs were excised. The levels of total Pt in tissues were determined digesting the homogenized tissue with 0.1% nitric acid, followed by AAS analysis. Standard cisplatin AUC (μg/g*h tissues and μg/mL*h serum) and peak concentration was determined for each tissue and serum sampled. Statistical analysis was performed using a student’s unpaired t-test (differences between 2 means), or one-way ANOVA followed by Duncan’s multiple range test (2+ means), with significance set at p < 0.05. Results: Cisplatin-HA conjugate demonstrated antiproliferative efficacy similar to standard cisplatin formulation in breast cancer models in vitro with IC50 concentration of 3 to 7 μg/mL for all cell lines. HA-cisplatin injected s.c. in the breast demonstrated an AUC in ipsilateral axillary lymph nodes 1.6 fold higher than s.c. cisplatin and 20 fold higher than i.v. cisplatin (p<0.0001). In contralateral lymph nodes HA-cisplatin had an AUC 1.2 fold higher than cisplatin s.c and 2 fold higher than i.v cisplatin. Peak plasma concentrations were higher with i.v cisplatin 4μg/mL compared with HA-cisplatin (2μg/mL ) which maintained a more sustained release delivery. AUCs and peak levels in 10 organ sites tested demonstrated no significant differences between HA-cisplatin s.c and i.v. cisplatin. There was no nephrotoxicity or local injection site toxicity noted histologically and by serum and urine creatinine measurements. Conclusions: HA-cisplatin is a novel nanocarrier drug conjugate with excellent intralymphatic uptake and retention. It can be given subcutaneously without any local toxicity and generates cisplatin concentrations in regional breast lymph nodes 20 fold higher than standard i.v. cisplatin, while maintaining effective serum levels and no added systemic toxicity. Further in vivo efficacy data will determine if this drug formulation would make an effective neoadjuvant or adjuvant therapy for locally advanced breast cancer.