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Human tumor necrosis factor-related apoptosis-inducing ligand (hTRAIL) and its variants are attractive antitumor drug candidates. The predicted amino acid sequence of the functional extracellular domain of Macaca mulatta TRAIL (mmTRAIL) was found to differ from that of hTRAIL at four positions. In this study, the gene encoding mmTRAIL was cloned and recombinantly expressed in Escherichia coli at a yield of approximately 20-30 mg/L, which was two times higher than that of hTRAIL. SDS-PAGE showed that denatured mmTRAIL and hTRAIL had similar molecular weights. However, size-exclusion chromatography and dynamic light scattering (DLS) analysis demonstrated that the molecular size of native mmTRAIL was smaller than that of native hTRAIL. Cooling solutions of these proteins from room temperature to 0 °C induced considerable precipitation of hTRAIL but not of mmTRAIL, indicating that mmTRAIL was more soluble than hTRAIL at low temperatures. Additionally, mmTRAIL was more resistant than hTRAIL to N-bromosuccinimide (NBS)-induced precipitation. Although mmTRAIL and hTRAIL showed comparable nanomolar affinities for human death receptors, the dissociation rate of the mmTRAIL-receptor complex was slower than that of the hTRAIL-receptor complex, suggesting that the mmTRAIL-receptor complex was more stable. Moreover, mmTRAIL induced caspase-dependent apoptosis in human tumor cells with an IC50 that was two to three times lower than that of hTRAIL. However, in vivo evaluation demonstrated that mmTRAIL or hTRAIL led to a similar level of tumor suppression in mice bearing COLO205 xenografts. Nevertheless, the advantage of its better solubility should promote the production and further use of mmTRAIL in cancer biotherapy.

Background Solid tumor hypoxic conditions prevent the generation of reactive oxygen species (ROS) and the formation of DNA double-strand breaks (DSBs) induced by ionizing radiation, which ultimately contributes to radiotherapy (RT) resistance. Recently, there have been significant technical advances in nanomedicine to reduce hypoxia by facilitating in situ O2 production, which in turn serves as a “radiosensitizer” to increase the sensitivity of tumor cells to ionizing radiation. However, off-target damage to the tumor-surrounding healthy tissue by high-energy radiation is often unavoidable, and tumor cells that are further away from the focal point of ionizing radiation may avoid damage. Therefore, there is an urgent need to develop an intelligent targeted nanoplatform to enable precise enhanced RT-induced DNA damage and combined therapy. Results Human epidermal growth factor receptor 2 (Her2)-specific dimeric affibody (ZHer2) mediated cisplatin-loaded mesoporous polydopamine/MnO2/polydopamine nanoparticles (Pt@mPDA/MnO2/PDA-ZHer2 NPs) for MRI and enhanced chemo-radiotherapy of Her2-positive ovarian tumors is reported. These NPs are biodegradable under a simulated tumor microenvironment, resulting in accelerated cisplatin release, as well as localized production of O2. ZHer2, produced using the E. coli expression system, endowed NPs with Her2-dependent binding ability in Her2-positive SKOV-3 cells. An in vivo MRI revealed obvious T1 contrast enhancement at the tumor site. Moreover, these NPs achieved efficient tumor homing and penetration via the efficient internalization and penetrability of ZHer2. These NPs exhibited excellent inhibition of tumor growth with X-ray irradiation. An immunofluorescence assay showed that these NPs significantly reduced the expression of HIF-1α and improved ROS levels, resulting in radiosensitization. Conclusions The nanocarriers described in the present study integrated Her2 targeting, diagnosis and RT sensitization into a single platform, thus providing a novel approach for translational tumor theranostics. Graphic abstract