Sensitivity to antitubulin chemotherapeutics is potentiated by a photoactivable nanoliposome

Anti-microtubule therapy represents one of the most strategic cancer therapeutics. Tublin inhibitor such as paclitaxel (PTX) is well known to disturb the dynamic nature of microtubules, being considered as the first-line drug for various malignancies. However, PTX does not show favorable clinical outcomes due to serious systemic toxicities and low selectivity. The development of PTX delivery systems and combinational therapies has been conducted to enhance PTX efficacy with poorly defined mechanisms. Herein, we introduced a reactive oxygen species producible composite liposome based on a new photosensitizer sinoporphyrin sodium (DVDMS) to enhance the therapeutic effect of PTX through photochemical stimulation, and more importantly, the pivotal molecular regulation mechanisms were specifically explored. Compared with DVDMS-liposome (DL) or PTX-liposome (PL), the composite liposome DVDMS-PTX-liposome (PDL) exhibited a superior anti-tumor advantage following laser irradiation against MCF-7 breast cancer. The localized PTX release after PDL administration greatly decreased the drug dosage and laser power required, leading to much higher safety and lower costs. In vitro, the combined treatment significantly suppressed cell viability and potentiated cell apoptosis. The apoptotic central regulator Mcl-1 as a favorable target, was evaluated in association with photochemically enhanced sensitivity to anti-tubulin chemotherapeutics. Phosphorylation of Mcl-1 led to its direct degradation with the proteasome system, making it relatively unstable and potentiating cell death resulting from photochemical synergy via PDL plus laser irradiation. Further, a decrease in ATP production and glycolysis after PDL plus laser would prevent the possible energy-switch and apoptosis-escape by PTX alone treatment, thereby resulted in increased cell death in combinational therapy. Systemic administration of PDL followed by in vivo photochemotherapy achieved significantly improved therapeutic effects compared to either alone. And, the intrinsic fluorescence of DVDMS facilitated real-time imaging of PDL in tumors. Therefore, the present strategy with details at the molecular regulation could be a promising platform for antitublin chemotherapeutics.