Hyaluronic acid-paclitaxel: antitumor efficacy against CD44(+) human ovarian carcinoma xenografts

Abstract

Numerous human tumor types, including ovarian cancer, display a significant expression of the CD44 family of cell surface proteoglycans. To develop tumor-targeted drugs, we have initially evaluated whether the CD44 ligand hyaluronic acid (HA) could serve as a backbone for paclitaxel (TXL) prodrugs. HA-TXL was prepared by modification of previous techniques. The in vitro cytotoxicity of HA-TXL against the CD44(+) human ovarian carcinoma cell lines SKOV-3ip and NMP-1 could be significantly blocked by preincubation with a molar excess of free HA. Female nude mice bearing intraperitoneal implants of NMP-1 cells were treated intraperitoneally with a single sub-maximum tolerated dose dose of HA-TXL or with multiple-dose regimens of paclitaxel (Taxol; Mead Johnson, Princeton, NJ) to determine the effects of these regimens on host survival and intraperitoneal tumor burden, with the latter being assessed by magnetic resonance imaging. NMP-1 xenografts were highly resistant to Taxol regimens, as host survival was only nominally improved compared to controls (T//C approximately 120), whereas single-dose HA-TXL treatment significantly improved survival in this model (T//C approximately 140; P = .004). In both NMP-1 and SKOV-3ip models, MR images of abdomens of HA-TXL-treated mice obtained shortly before controls required humane sacrifice revealed markedly reduced tumor burdens compared to control mice. This study is among the first to demonstrate that HA-based prodrugs administered locoregionally have antitumor activity in vivo.

Figure 1

T₂-weighted coronal MR image of the abdomen of an NMP-1-implanted nude mouse (199 days following tumor inoculation) that was treated with a single intraperitoneal injection of 200 mg/kg HA-TXL 8 days post-tumor inoculation. No tumors were observed; compare to day 28 images of NMP-1 control mice in Figure 3A.

Figure 2

Kaplan-Meier survival plot of NMP-1- implanted mice treated intraperitoneally either with saline (controls), with 10 or 15 mg/kg Taxol on regimens of every 7 days x 3 beginning on day 7 post-tumor implantation, or with a single injection of 180 mg/kg HA-TXL (paclitaxel equivalents) on day 7. T/C values were 105 and 120 for the 10- and 15-mg/kg multiple-dose Taxol groups, respectively, and 140 for the single-dose HA-TXL group (P = .004 vs controls; Mantel-Cox).

Figure 3

Representative day 28 T₂-weighted coronal abdominal MR images of NMP-1- implanted (A) control mice sham-treated with saline; arrows indicate examples of tumor masses throughout the abdomen; note the heavy tumor burden and areas of high signal intensity indicating ascites. (B) Mice treated with a multiple-dose intraperitoneal injection regimen of 10 mg/kg Taxol; arrows indicate examples of tumor masses throughout the abdomen; note evidence for ascites. (C) Mice treated with a multiple-dose intraperitoneal injection regimen of 15 mg/kg Taxol; note heavy tumor burden and ascites. (D) Mice treated with a single intraperitoneal injection of HA-TXL; note the comparatively modest tumor burden and few areas of high signal intensity indicating ascites. B = bladder.

Figure 4

Representative day 84 coronal T₂-weighted MR images of the abdomens of SKOV-3ip-implanted mice from the control group (A) and the 180-mg/kg HA-TXL treatment group (B). Arrows indicate examples of intraperitoneal tumors; note the greater tumor burden in control versus treated mice. B = bladder. Comparison of tumor weights derived from MR images of mice bearing SKOV-3ip tumors (C; P < .03, n = 3; t-test).