HOCl oxidation-modified CT26 cell vaccine inhibits colon tumor growth in a mouse model

Identification of reaction sites and chlorinated products of purine bases and nucleosides during chlorination: a computational study

Hypochlorous acid (HOCl) released from activated leukocytes plays a significant role in the human immune system, but is also implicated in numerous diseases due to its inappropriate production. Chlorinated nucleobases induce genetic changes that potentially enable and stimulate carcinogenesis, and thus have attracted considerable attention. However, their multiple halogenation sites pose challenges to identify them. As a good complement to experiments, quantum chemical computation was used to uncover chlorination sites and chlorinated products in this study. The results indicate that anion salt forms of all purine compounds play significant roles in chlorination except for adenosine. The kinetic reactivity order of all reaction sites in terms of the estimated apparent rate constant kobs-est (in M-1 s-1) is heterocyclic NH/N (102-107) > exocyclic NH2 (10-2-10) > heterocyclic C8 (10-5-10-1), but the order is reversed for thermodynamics. Combining kinetics and thermodynamics, the numerical simulation results show that N9 is the most reactive site for purine bases to form the main initial chlorinated product, while for purine nucleosides N1 and exocyclic N2/N6 are the most reactive sites to produce the main products controlled by kinetics and thermodynamics, respectively, and C8 is a possible site to generate the minor product. The formation mechanisms of biomarker 8-Cl- and 8-oxo-purine derivatives were also investigated. Additionally, the structure-kinetic reactivity relationship study reveals a good correlation between lg kobs-est and APT charge in all purine compounds compared to FED2 (HOMO), which proves again that the electrostatic interaction plays a key role. The results are helpful to further understand the reactivity of various reaction sites in aromatic compounds during chlorination.

Whole tumour cell-based vaccines: tuning the instruments to orchestrate an optimal antitumour immune response

Immunotherapy, particularly those based on immune checkpoint inhibitors (ICIs), has become a useful approach for many neoplastic diseases. Despite the improvements of ICIs in supporting tumour regression and prolonging survival, many patients do not respond or develop resistance to treatment. Thus, therapies that enhance antitumour immunity, such as anticancer vaccines, constitute a feasible and promising therapeutic strategy. Whole tumour cell (WTC) vaccines have been extensively tested in clinical studies as intact or genetically modified cells or tumour lysates, injected directly or loaded on DCs with distinct adjuvants. The essential requirements of WTC vaccines include the optimal delivery of a broad battery of tumour-associated antigens, the presence of tumour cell-derived molecular danger signals, and adequate adjuvants. These factors trigger an early and robust local innate inflammatory response that orchestrates an antigen-specific and proinflammatory adaptive antitumour response capable of controlling tumour growth by several mechanisms. In this review, the strengths and weaknesses of our own and others' experiences in studying WTC vaccines are revised to discuss the essential elements required to increase anticancer vaccine effectiveness.

Reaction Mechanisms of Histidine and Carnosine with Hypochlorous Acid Along with Chlorination Reactivity of N-Chlorinated Intermediates: A Computational Study

Hypochlorous acid (HOCl) released from activated leukocytes not only plays a significant role in the human immune system but is also implicated in numerous diseases including atherosclerosis and some cancers due to its inappropriate production. Histidine (His) and carnosine (Car), as a respective mediator and protective agent of HOCl damage, have attracted considerable attention; however, their detailed reaction mechanisms are still unclear. In this study, using a His residue with two peptide bond groups (HisRes) as a model, the reaction mechanisms of HisRes and Car including N_εH and N_δH tautomers with HOCl along with the chlorination reactivity of N-chlorinated intermediates were investigated by quantum chemical methods. The obtained results indicate that in the imidazole side chain, the pyridine-like N is the most reactive site rather than the pyrrole-like N, and the kinetic order of all of the possible reaction sites in HisRes follows pyridine-like N > imidazole C_δ ≫ imidazole C_ε > pyrrole-like N, while that in Car is pyridine-like N ≫ imidazole C_δ ≫ amide N. As for N-chlorinated intermediates at imidazole, although the unprotonated form has a low chlorination reactivity as expected, it can still chlorinate tyrosine. Especially, the protonated form exhibits similar ability to HOCl, causing secondary damage in vivo. N-Chlorinated Car features higher internal chlorine migration ability than its intermolecular transchlorination, preventing further HOCl-induced damage. Additionally, a generally overlooked nucleophilic Cl^- shift is also found in N-chlorinated Car/HisRes, indicating that nucleophilic sites in biomolecules also need to be considered. The outcomes of this study are expected to expand our understanding of secondary damage and protective mechanisms involved in HOCl in humans.

Secretions from hypochlorous acid-treated tumor cells delivered in a melittin hydrogel potentiate cancer immunotherapy

Autologous tumor cells and cell-derived secretions (CDS) can induce antitumor immune responses. The conditions in which cells are cultured and treated impact CDS, and cellular insults alter their composition and function. In this study, we generated CDS from tumor cells exposed to normal culture conditions, hypoxia, cisplatin, radiotherapy, photodynamic therapy, or hypochlorous acid (HOCl). In vitro HOCl-CDS showed the strongest stimulatory effects on dendritic cells and macrophages compared to CDS generated by hypoxia, cisplatin, radiotherapy or photodynamic therapy. To improve HOCl-CDS activity at the tumor site, we loaded HOCl-CDS into a melittin-encapsulated hydrogel scaffold. When injected intratumorally, the HOCl-CDS hydrogel promoted tumor cell death, cytotoxic T lymphocyte infiltration, and tumor-associated macrophage reprogramming towards an M1 phenotype. The hydrogel inhibited tumor growth and prolonged the survival of mice bearing B16–F10 melanoma. Furthermore, hydrogel-delivered HOCl-CDS augmented the antitumor effects of immune checkpoint blockade. These results underscore the importance of the CDS generation method and delivery approach for improving cancer immunotherapy.

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HOCl-treated tumor cell-derived secretions (HOCl-CDS) is a robust immune-stimulator on dendritic cells and macrophages.

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A multifunctional HOCl-CDS hydrogel was developed by loading HOCl-CDS into a melittin-encapsulated hydrogel scaffold.

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HOCl-CDS hydrogel promoted tumor cell death, cytotoxic T lymphocyte infiltration and M1-TAM polarization in mice.

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HOCl-CDS hydrogel synergistically augmented the therapeutic effect of anti-PD-1 and further potentiated cancer immunotherapy.

Hypochlorous acid selectively promotes toxicity and the expression of danger signals in human abdominal cancer cells

Tumors of the abdominal cavity, such as colorectal, pancreatic and ovarian cancer, frequently metastasize into the peritoneum. Large numbers of metastatic nodules hinder curative surgical resection, necessitating lavage with hyperthermic intraperitoneal chemotherapy (HIPEC). However, HIPEC not only causes severe side effects but also has limited therapeutic efficacy in various instances. At the same time, the age of immunotherapies such as biological agents, checkpoint‑ inhibitors or immune‑cell therapies, increasingly emphasizes the critical role of anticancer immunity in targeting malignancies. The present study investigated the ability of three types of long‑lived reactive species (oxidants) to inactivate cancer cells and potentially complement current HIPEC regimens, as well as to increase tumor cell expression of danger signals that stimulate innate immunity. The human abdominal cancer cell lines HT‑29, Panc‑01 and SK‑OV‑3 were exposed to different concentrations of hydrogen peroxide (H2O2), hypochlorous acid (HOCl) and peroxynitrite (ONOO‑). Metabolic activity was measured, as well as determination of cell death and danger signal expression levels via flow cytometry and detection of intracellular oxidation via high‑content microscopy. Oxidation of tumor decreased intracellular levels of the antioxidant glutathione and induced oxidation in mitochondria, accompanied by a decrease in metabolic activity and an increase in regulated cell death. At similar concentrations, HOCl showed the most potent effects. Non‑malignant HaCaT keratinocytes were less affected, suggesting the approach to be selective to some extent. Pro‑immunogenic danger molecules were investigated by assessing the expression levels of calreticulin (CRT), and heat‑shock protein (HSP)70 and HSP90. CRT expression was greatest following HOCl and ONOO‑ treatment, whereas HOCl and H2O2 resulted in the greatest increase in HSP70 and HSP90 expression levels. These results suggested that HOCl may be a promising agent to complement current HIPEC regimens targeting peritoneal carcinomatosis.

Therapeutic potential of oncolytic Newcastle disease virus: a critical review

Newcastle disease virus (NDV) features a natural preference for replication in many tumor cells compared with normal cells. The observed antitumor effect of NDV appears to be a result of both selective killing of tumor cells and induction of immune responses. Genetic manipulations to change viral tropism and arming the virus with genes encoding for cytokines improved the oncolytic capacity of NDV. Several intracellular proteins in tumor cells, including antiapoptotic proteins (Livin) and oncogenic proteins (H-Ras), are relevant for the oncolytic activity of NDV. Defects in the interferon system, found in some tumor cells, also contribute to the oncolytic selectivity of NDV. Notwithstanding, NDV displays effective oncolytic activity in many tumor types, despite having intact interferon signaling. Taken together, several cellular systems appear to dictate the selective oncolytic activity of NDV. Some barriers, such as neutralizing antibodies elicited during NDV treatment and the extracellular matrix in tumor tissue appear to interfere with spread of NDV and reduce oncolysis. To further understand the oncolytic activity of NDV, we compared two NDV strains, ie, an attenuated virus (NDV-HUJ) and a pathogenic virus (NDV-MTH-68/H). Significant differences in amino acid sequence were noted in several viral proteins, including the fusion precursor (F0) glycoprotein, an important determinant of replication and pathogenicity. However, no difference in the oncolytic activity of the two strains was noted using human tumor tissues maintained as organ cultures or in mouse tumor models. To optimize virotherapy in clinical trials, we describe here a unique organ culture methodology, using a biopsy taken from a patient’s tumor before treatment for ex vivo infection with NDV to determine the oncolytic potential on an individual basis. In conclusion, oncolytic NDV is an excellent candidate for cancer therapy, but more knowledge is needed to ensure success in clinical trials.