Sulfate-reducing bacteria loaded in hydrogel as a long-lasting H2S factory for tumor therapy.

The continuous supply of hydrogen sulfide (H2S) gas at high concentrations to tumors is considered a promising and safe strategy for tumor therapy. However, the absence of a durable and cost-effective H2S-producing donor hampers its extensive application. Sulfate-reducing bacteria (SRB) can serve as an excellent H2S factory due to their ability to metabolize sulfate into H2S. Herein, a novel injectable chondroitin sulfate (ChS) hydrogel loaded with SRB (SRB@ChS Gel) is proposed to sustainably produce H2S in tumor tissues to overcome the limitations of current H2S gas therapy. In vitro, the ChS Gel not only supports the growth of encapsulated SRB, but also supplies a sulfate source to the SRB to produce high concentrations of H2S for at least 7 days, resulting in mitochondrial damage and immunogenic cell death. Once injected into tumor tissue, the SRB@ChS Gel can constantly produce H2S for >5 days, significantly inhibiting tumor growth. Furthermore, such treatment activates systemic anti-tumor immune responses, suppresses the growth of distant and recurrent tumors, as well as lung metastases, meanwhile with negligible side effects. Therefore, the injectable SRB@ChS Gel, as a safe and long-term, self-sustained H2S-generating factory, provides a promising strategy for anti-tumor therapy.

Azurin Regulates P21 and Enhances the Sensitivity of Osteosarcoma Cells to Cisplatin.

Background: Osteosarcoma (OS) is the most common bone malignancy, with a high mortality rate in adolescents. Despite advancements in therapeutic interventions, OS prognosis remains poor due to drug resistance. P21, a cyclin-dependent kinase inhibitor, plays a critical role in cell cycle regulation and has been implicated in OS pathogenesis. Cisplatin (DDP) is a conventional chemotherapeutic agent for OS, but its efficacy is often limited due to drug resistance. Azurin, a bacterial redox protein, has been reported to exhibit antitumor activity. However, its interaction with P21 in OS remains unexplored. In this study, we sought to investigate the impact of azurin on the cytotoxic effect of DDP against OS cells in relation to P21 expression. Methods: Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to determine the level of p21 and apoptosis-related factors in U2OS cells. A Cell Counting Kit-8 (CCK-8) was used to examine the effects of azurin-p21 on the U2OS cell proliferation rate. Flow cytometry (FCM)was used to analyze the impact of azurin-P21 on the apoptosis/cell cycle. Enzyme-linked immunosorbent assay (ELISA) was used to analyze the effects of azurin-P21 on the secretion of oxygen free radicals, glutathione and glutathione peroxidase. Results: Azurin exhibited significant cytotoxic activity against U2OS cells expressing wild-type (WT) P21, with minimal impact on SAOS-2 and MG63 cells lacking endogenous P21. Azurin treatment resulted in increased expression of procaspase-3 and Bax, decreased expression of B-cell lymphoma-2 (Bcl-2) and a consequential increase in apoptosis. The depletion of P21 attenuated these effects, suggesting the crucial role of P21 in azurin-mediated cytotoxicity. Furthermore, azurin synergistically enhanced the cytotoxic effect of DDP against U2OS cells, which was mitigated by P21 depletion. Conclusions: Our findings demonstrated that azurin selectively induces apoptosis and cell cycle arrest in U2OS cells, which is mediated via P21. This study highlights the potential of azurin as a sensitizer for DDP in the treatment of OS. Future studies on DDP-resistant OS cells may further elucidate the clinical relevance of our findings.

Near-Infrared Nano-Optogenetic Activation of Cancer Immunotherapy via Engineered Bacteria.

Certain anaerobic microbes with the capability to colonize the tumor microenvironment tend to express the heterologous gene in a sustainable manner, which will inevitably compromise the therapeutic efficacy and induce off-tumor toxicity in vivo. To improve the therapeutic precision and controllability of bacteria-based therapeutics, Escherichia coli Nissle 1917 (EcN), engineered to sense blue light and release the encoded flagellin B (flaB), is conjugated with lanthanide upconversion nanoparticles (UCNPs) for near-infrared (NIR) nano-optogenetic cancer immunotherapy. Upon 808 nm photoirradiation, UCNPs emit at the blue region to photoactivate the EcN for secretion of flaB, which subsequently binds to Toll-like receptor 5 expressed on the membrane of macrophages for activating immune response via MyD88-dependent signal pathway. Such synergism leads to significant tumor regression in different tumor models and metastatic tumors with negligible side effects. These studies based on the NIR nano-optogenetic platform highlight the rational of leveraging the optogenetic tools combined with natural propensity of certain bacteria for cancer immunotherapy.

Hypoxia-alleviated sonodynamic therapy based on a hybrid protein oxygen carrier to enhance tumor inhibition.

Sonodynamic therapy (SDT) is a highly attractive therapy due to its advantages of being non-invasive and having good penetration depth, but tumor hypoxia extremely restricts its therapeutic effect. Here, a novel oxygen-enhanced hybrid protein nanosonosensitizer system (MnPcS@HPO) is designed using human serum albumin (HSA) and hemoglobin (Hb) through disulfide reconfiguration, followed by encapsulating Mn-phthalocyanine (MnPcS), aiming to develop O2 self-supplementing nanoparticles (NPs) for enhanced SDT. Benefitting from the O2-carrying ability of Hb and the tumor-targeting property of HSA, the MnPcS@HPO NPs are able to target tumor sites and alleviate hypoxia. Meanwhile, as a sonosensitizer, MnPcS is excited under US irradiation and activates dioxygen to generate abundant singlet oxygen (1O2), resulting in oxidative damage of tumor cells. Guided by photoacoustic and magnetic resonance dual-modal imaging, the MnPcS@HPO NPs alleviate tumor hypoxia and achieve good SDT efficiency for suppressing tumor growth. This work presents a novel insight into enhanced SDT antitumor activity through natural protein-mediated tumor microenvironment improvement.

Noninvasively immunogenic sonodynamic therapy with manganese protoporphyrin liposomes against triple-negative breast cancer.

Sonodynamic therapy (SDT) is a promising approach for tumor treatment because of the noninvasion, and future would be perfect while it activates systemic immune responses through deep penetration to effectively avoid tumor recurrence. Here, a multifunctional nanosonosensitizer system (FA-MnPs) is designed by encapsulating manganese-protoporphyrin (MnP) into folate-liposomes. The nanoparticles of FA-MnPs not only exhibit excellent depth-responsive SDT but also simultaneously activate SDT-mediated immune response. Under US irradiation, FA-MnPs show the high acoustic intensity in mimic tissue up to 8 cm depth and generate amount of singlet oxygen (1O2). Density functional theory (DFT) calculations reveal that metal coordination in MnP has enhanced the US response ability. The good depth-responsed SDT of FA-MnPs efficiently suppresses the growth of not only the superficial tumors but also the deep lesion in the triple-negative breast cancer (TNBC) mice model. Importantly, FA-MnPs-induced SDT further re-polarizes immunosuppressive M2 macrophages to antitumor M1 macrophages, and elicits immunogenic cell death (ICD) to activate dendritic cells, T lymphocytes, and natural killercells (NK), which consequently trigger the antitumor immune, contributing to the tumor growth inhibition. This study put forward an idea for curing deep-seated and metastatic tumors through noninvasively depth-irradiated immunogenic SDT by reasonably designing multifunctional sonosensitizers.