Overcoming drug resistance in osteosarcoma with MTX-CuB-NLC: An in vitro and in vivo study.

Osteosarcoma (OS) is the predominant bone tumor affecting pediatric and adolescent populations. The standard treatment regimen involves preoperative chemotherapy, surgical intervention, and postoperative chemotherapy. Methotrexate (MTX) serves as the first-line pharmacological agent for OS treatment; however, the emergence of tumor resistance to chemotherapeutic agents poses a significant challenge. Cucurbitacin B (CuB) exhibits intrinsic anti-OS properties and can synergistically enhance OS suppression by reversing drug resistance and augmenting the therapeutic effects of MTX. Nevertheless, the clinical application of CuB and MTX is hindered by their low aqueous solubility, necessitating the development of an effective drug delivery system to precisely target tumor tissues and maximize therapeutic efficacy. Consequently, this study focuses on the development of a nanostructured lipid carrier (NLC) co-loaded with MTX and CuB (MTX-CuB-NLC) to address these limitations. MTX-CuB-NLC is characterized as a spherical nanoparticle with a mean particle size of 44.13 ± 1.40 nm, a polydispersity index (PDI) of 0.279 ± 0.120, and a zeta potential of -17.10 ± 4.98 mV. The encapsulation efficiency (EE%) and drug loading (DL%) were determined to be 61.03 ± 2.40 % and 0.25 ± 0.02 % for MTX, and 81.02 ± 1.61 % and 0.23 ± 0.02 % for CuB, respectively. The formulation demonstrated substantial storage stability over a 14-day period. In vitro release studies indicated that MTX-CuB-NLC possesses sustained release capabilities. Furthermore, the nanoparticle exhibited significantly enhanced uptake and cytotoxicity against U-2 OS cells compared to the free drug. Notably, MTX-CuB-NLC displayed pronounced cytotoxic effects on methotrexate-resistant U-2 OS cells (U-2 OS/MTX), underscoring its potential to induce apoptosis and circumvent multidrug resistance in these cells. In an OS nude mouse model exhibiting drug resistance, MTX-CuB-NLC demonstrated superior tumor targeting and suppression efficacy. This research has culminated in the development of an effective continuous drug delivery system for osteosarcoma, presenting a promising strategy to combat drug resistance in this malignancy.