Arsenic trioxide elicits prophylactic and therapeutic immune responses against solid tumors by inducing necroptosis and ferroptosis

Boosting tumor immunosurveillance with vaccines has been proven to be a feasible and cost-effective strategy to fight cancer. Although major breakthroughs have been achieved in preventative tumor vaccines targeting oncogenic viruses, limited advances have been made in curative vaccines for virus-irrelevant malignancies. Accumulating evidence suggests that preconditioning tumor cells with certain cytotoxic drugs can generate whole-cell tumor vaccines with strong prophylactic activities. However, the immunogenicity of these vaccines is not sufficient to restrain the outgrowth of existing tumors. In this study, we identified arsenic trioxide (ATO) as a wide-spectrum cytotoxic and highly immunogenic drug through multiparameter screening. ATO preconditioning could generate whole-cell tumor vaccines with potent antineoplastic effects in both prophylactic and therapeutic settings. The tumor-preventive or tumor-suppressive benefits of these vaccines relied on CD8^(+) T cells and type I and II interferon signaling and could be linked to the release of immunostimulatory danger molecules. Unexpectedly, following ATO-induced oxidative stress, multiple cell death pathways were activated, including autophagy, apoptosis, necroptosis, and ferroptosis. CRISPR‒Cas9-mediated knockout of cell death executors revealed that the absence of Rip3, Mlkl, or Acsl4 largely abolished the efficacy of ATO-based prophylactic and therapeutic cancer vaccines. This therapeutic failure could be rescued by coadministration of danger molecule analogs. In addition, PD-1 blockade synergistically improved the therapeutic efficacy of ATO-based cancer vaccines by augmenting local IFN-γ production.

Double-edged roles of IFNγ in tumor elimination and immune escape

Interferon-gamma (IFNγ) is a pleiotropic cytokine implicated in tumor immune surveillance, with its antiproliferative, pro-apoptotic, and immune-provoking effects. Regarding the antitumor effects of IFNγ, IFNγ-dependent therapies have been proposed and have undergone many clinical trials for various cancer types but the outcomes were not satisfactory. Recent studies have suggested that cancer cells develop immune evasion strategies to escape from IFNγ-dependent immunosurveillance by various mechanisms. In this review, we summarize recent advances in the effects and molecular mechanisms of IFNγ on target cells, as well as potential immune escape mechanisms of tumor cells. Furthermore, we discuss how to target IFNγ signaling and overcome immune evasion to provide promising therapeutic strategies for the treatment of patients with cancer.

Immunogenic effects of chemotherapyinduced tumor cell death

Emerging evidence suggests that the clinical success of conventional chemotherapy is not solely attributed to tumor cell toxicity,but also results from the restoration of immunosurveillance,which has been largely neglected in the past preclinical and clinical research.Antitumor immune response can be primed by immunogenic cell death(ICD),a type of cell death characterized by cell-surface translocation of calreticulin(CRT),extracellular release of ATP and high mobility group box 1(HMGB1),and stimulation of type I interferon(IFN)responses.Here we summarize recent studies showing conventional chemotherapeutics as ICD inducers,which are capable of modulating tumor infiltrating lymphocytes(TILs)and reactivating antitumor immunity within an immuno-suppressive microenvironment.Such immunological effects of conventional chemotherapy are likely critical for better prognosis of cancer patients.Furthermore,combination of ICD-inducing chemotherapeutics with immunotherapy is a promising approach for improving the clinical outcomes of cancer patients.