Hyaluronan oligomers-HPMA copolymer conjugates for targeting paclitaxel to CD44-overexpressing ovarian carcinoma

Purpose: To evaluate the effect of the size of low molecular weight hyaluronan (LMW-HA) oligomers on the targeting ability of the HA-containing copolymers to the CD44-overexpressing cells for delivering Paclitaxel (PTX) to ovarian cancer. Methods: LMW-HA oligosaccharides of 4, 6, 8, 10, 12 and 14 sugar residues were attained by digestion of HMW-HA using hyaluronate lyase at different incubation times and then attached to FITC-labeled HPMA copolymer precursor. The binding and uptake of the HA-modified HPMA-copolymer into CD44- expressing cells was studied by flow cytometry and confocal microscopy. PTX was further attached to HPMA-copolymer precursor bearing HA oligosaccharide at the size of 34 monosaccharides, through an acid-sensitive hydrazone linker. The cytotoxicity of the polymer was tested using cell viability assay. Results: Polymer conjugates bearing HA oligomers at the size of 10 oligosaccharides and above (HA _10-14) bind actively and profoundly to CD44-overexpressing ovarian cancer cells (SKOV- 3) and internalize to the greatest extent relative to HA-polymer conjugates of 8 oligomers and below (HA _4-8). The HA-modified HPMA-copolymer PTX conjugate (P-(HA) ₃₄- PTX) exhibited 50-times higher cytotoxicity towards CD44- overexpressing cells relative to the control, non-targeted, HPMA-copolymer PTX conjugate (P-PTX). Conclusions: P-(HA) ₃₄-PTX was significantly more toxic than the non-targeted P-PTX in cells expressing high levels of CD44.