Engineered Nanoliposomes to Mitigate Osteolytic Bone Lesions in Breast Cancer

Despite advances in breast cancer therapy, its metastasis, particularly to bone, remains a significant challenge. Chemotherapeutic treatment with doxorubicin (DOX) elevates the circulating levels of TGF-β, potentially exacerbating bone metastasis. Moreover, DOX possesses several limitations, such as cardiotoxicity, rapid clearance, and multidrug resistance. Combinatorial therapy utilizing a (transforming growth factor) TGF-β inhibitor along with DOX could substantially reduce the metastatic burden. Baicalein (BAC), a key flavonoid, inhibits the TGF-β signaling pathway, potentially decreasing the bone metastatic ability of DOX. However, BAC is limited by poor solubility, low bioavailability, and a short half-life. Despite these challenges, a low combination index at a molar weight ratio of 1:4 (DOX:BAC) confirmed the synergistic potential of the combination. To deliver the ratiometric dose of both drugs, a PEGylated liposomal formulation loaded with DOX and BAC was developed using the ethanol injection method and evaluated for its anticancer and antimetastatic potential. The particle size of 132.53 ± 1.42 nm with narrow polydispersity and a ζ potential of -26.83 ± 2.2 mV were obtained for the developed nanoliposomes. The ratiometric combination loaded within the liposomal delivery carrier exhibited maximum synergistic activity in the syngeneic 4T1 BALB/c mice tumor model when administered intravenously through the tail vein. Moreover, the liposomal delivery vehicle showed a higher binding affinity toward hydroxyapatite, demonstrating selective bone accumulation. The results indicated efficient targetability and retention at the tumor site, as confirmed by pharmacokinetic profiling. Furthermore, micro-CT analysis revealed the preservation of bone architecture and minimal skeletal damage in treated groups. There was a 4.5-fold increase in the percent bone volume/total volume after treatment with nanoliposomes. These results highlight the promising therapeutic potential of combinatorial DOX and BAC delivery in the treatment of breast cancer-induced bone metastasis.