Studies related to the enhanced the effect of 5-aminolevulinic acid-based photodynamic therapy combined with tirapazamine

•The combination of 5-aminolevulinic acid-mediated photodynamic therapy with tirapazamine utilizes the activation of tirapazamine in the hypoxic environment to overcome the hypoxic environment and the hypoxia caused by photodynamic oxygen depletion in the tumor.•Photodynamic therapy relies on the presence of oxygen molecules, while tirapazamine is enzymatically converted to a cytotoxic product under hypoxic conditions. The combined intervention increased apoptosis and provided a new mode of hypoxia-dependent cytotoxicity.•The combination therapy can inhibit the PI3K/Akt/mTOR pathway and suppress tumor growth and metastasis, thus promoting the effects of photodynamic therapy. 5-aminolevulinic acid (5-ALA) is a precursor of the photosensitizer Protoporphyrin IX (PpIX) and photodynamic therapy (PDT) with 5-ALA has been used in clinical practice. However, tumor cellular hypoxia severely affects the efficiency of photodynamic therapy. In this study, photodynamic therapy was combined with tirapazamine to investigate the effects of the combined intervention and the related mechanisms it may involve. Colony formation assays were used to demonstrate cell proliferation. Transwell assays were performed to observe the effect on cell invasion and metastasis after the corresponding intervention. DCFH-DA probe was used to detect the reactive oxygen species content. Flow cytometry was used to detect the effects of the interventions on apoptosis and cell cycle. The relevant pathways that may be involved are explored by examining the expression levels of the relevant proteins and genes. Colony formation assays indicated that the combined intervention inhibited cell proliferation. Transwell assays demonstrated that PDT combined with TPZ effectively inhibited tumor cell invasion and metastasis. In addition, fluorescence intensity generated by DCFH-DA oxidation was detected indicating that the combined intervention increased the formation of reactive oxygen species. Flow cytometry clearly showed that the combination of PDT and TPZ further increased apoptosis and cell cycle arrest. The results of western blotting and qRT-PCR experiments confirmed that the combination therapy inhibited HIF-1α/VEGF axis and the PI3K/Akt/mTOR pathway activation. 5-ALA-PDT combined with TPZ can inhibit cell proliferation, increase apoptosis, and inhibit the PI3K/Akt/mTOR pathway, thus inhibiting tumor growth and metastasis and improving anti-cancer effects.