Background: Newly emerging cancer immunotherapy has led to significant progress in cancer treatment; however, its efficacy is limited in solid tumors since the majority of them are “cold” tumors. Oncolytic viruses, especially when properly armed, can directly target tumor cells and indirectly modulate the tumor microenvironment (TME), resulting in “hot” tumors. These viruses can be applied as a cancer immunotherapy approach either alone or in combination with other cancer immunotherapies. Cytokines are good candidates to arm oncolytic viruses. IL-23, an IL-12 cytokine family member, plays many roles in cancer immunity. Here, we used oncolytic vaccinia viruses to deliver IL-23 variants into the tumor bed and explored their activity in cancer treatment on multiple tumor models.

Ferroptosis is a type of programmed cell death dependent on iron and characterized by the accumulation of lipid peroxides. In this study, we explore the combination of a ferroptosis activator with an oncolytic vaccinia virus in tumor models. Erastin induced cell death in hepatoma, colon, and ovarian cancer cells, but not in melanoma cancer cells. Erastin, not the oncolytic vaccinia virus (OVV), induced the expression of key marker genes for ferroptosis in cancer cells. In hepatocellular carcinoma and colon cancer models, either erastin or OVV inhibited tumor growth, but a combination of the two yielded the best therapeutic effects, as indicated by inhibited tumor growth or regression and longer host survival. Immunological analyses indicate that erastin alone had little or no effect on systemic immunity or local immunity in the tumor. However, when combined with OV, erastin enhanced the number of activated dendritic cells and the activity of tumor-infiltrating T lymphocytes as indicated by an increase in IFN-γ⁺CD8⁺ and PD-1⁺CD8⁺ T cells. These results demonstrate that erastin can exert cytotoxicity on cancer cells via ferroptosis, but has little effect on immune activity by itself. However, when combined with an OVV, erastin promoted antitumoral immunity and efficacy by increasing the number of activated dendritic cells and promoting the activities of tumor specific CD8⁺ T cells in the tumor.

In this study, we aimed to apply the cytokine IL-36γto cancer immunotherapy by constructing new oncolytic vaccinia viruses (OV) expressing interleukin-36γ(IL-36γ-OVs), leveraging unique synergism between OV and IL-36γ’s ability to promote antitumor adaptive immunity and modulate tumor microenvironment (TME). IL-36γ-OV had dramatic therapeutic efficacies in multiple murine tumor models, frequently leading to complete cancer eradication in large fractions of mice. Mechanistically, IL-36-γ-armed OV induced infiltration of lymphocytes and dendritic cells, decreased myeloid-derived suppressor cells and M2-like tumor-associated macrophages, and T cell differentiation into effector cells. Further study showed that IL-36γ-OV increased the number of tumor antigen-specific CD4⁺and CD8⁺T cells and the therapeutic efficacy depended on both CD8⁺and CD4⁺T cells. These results demonstrate that these IL36γ-armed OVs exert potent therapeutic efficacy mainly though antitumor immunity and they may hold great potential to advance treatment in human cancer patients.

The success of cancer immunotherapy is largely associated with immunologically hot tumors. Approaches that promote the infiltration of immune cells into tumor beds are urgently needed to transform cold tumors into hot tumors. Oncolytic viruses can transform the tumor microenvironment (TME), resulting in immunologically hot tumors. Cytokines are good candidates for arming oncolytic viruses to enhance their function in this transformation. Here, we used the oncolytic vaccinia virus (oVV) to deliver interleukin-9 (IL-9) into the tumor bed and explored its antitumor effects in colon and lung tumor models. Our data show that IL-9 prolongs viral persistence, which is probably mediated by the up-regulation of IL-10. The vvDD-IL-9 treatment elevated the expression of Th1 chemokines and antitumor factors such as IFN-γ, granzyme B, and perforin. IL-9 expression increased the percentages of CD4⁺ and CD8⁺ T cells in the TME and decreased the percentage of oVV-induced immune suppressive myeloid-derived suppressor cells (MDSC), leading to potent antitumor effects compared with parental virus treatment. The vvDD-IL-9 treatment also increased the percentage of regulatory T cells (Tregs) in the TME and elevated the expression of immune checkpoint molecules such as PD-1, PD-L1, and CTLA-4, but not GITR. The combination therapy of vvDD-IL-9 and the anti-CTLA-4 antibody, but not the anti-GITR antibody, induced systemic tumor-specific antitumor immunity and significantly extended the overall survival of mice, indicating a potential translation of the IL-9-expressing oncolytic virus into a clinical trial to enhance the antitumor effects elicited by an immune checkpoint blockade for cancer immunotherapy.

Background: Oncolytic virus (OV)-mediated immunotherapy has been shown limited efficacy. Small molecule inhibitors specific to the KRAS^G12C driver oncoprotein have recently been developed for cancer treatment. The combination of a potent OV with a KRAS^G12C inhibitor could be a potent combination strategy for treating KRAS^G12C cancer. Methods: We explored combination therapies using KRAS^G12C inhibitor and OV in cancer cells in vitro and in two KRAS^G12C cancer models. We employed flow cytometry to evaluate the immune cell profiles, including dendritic cells, macrophages, myeloid-derived suppressor cells, natural killer (NK), subsets of CD4⁺ and CD8⁺ T cells, and exhaustion markers (CTLA-4, PD-1, TIM-3), activation markers (granzyme B, IFN-γ and 4-1BB) as well as enzyme-linked immunospot assay to identify tumor-antigen specific T cells. The importance of CD4⁺, CD8⁺ T and NK cells in the therapeutic effects was evaluated by antibody-mediated depletion in vivo. Results: We confirmed that three inhibitors for KRAS^G12C, AMG510 (sotorasib), MRTX849 (adagrasib) and MRTX1257, all displayed potent cytotoxicity to cancer cells harboring KRAS^G12C, but not to cancer cells without this specific KRAS mutation in vitro. All three inhibitors exhibited potent antitumor activity in KRAS^G12C Lewis lung cancer, but not in MC38 colon cancer with wild-type KRAS. In two KRAS^G12C tumor models, either an IL-36γ-armed OV or orally delivered MRTX1257 inhibited tumor growth, but the combination worked much more efficiently, and efficacy was further improved with PD-1 blockade although with no statistical difference in survival, leading to complete tumor remission in a large fraction of the mice. Mechanistic studies revealed that MRTX1257, and other KRAS^G12C inhibitors as well, are potent inducers of antitumor immunity by themselves, and that it worked with OV to elicit potent innate and adaptive tumor-specific immunity. The combination therapeutic efficacy depended largely on increased tumor-specific CD8⁺ cytotoxic T cells, and to a smaller degree, on CD4⁺ T and NK cells. Conclusions: Small molecule inhibitors of KRAS^G12C are novel inducers of tumor-specific immunity, and a unique triple combination regimen is highly efficacious through elicited potent antitumor immunity for KRAS^G12C cancers.

Peritoneal carcinomatosis (PC) is a late-stage manifestation of abdominopelvic malignancies with poor prognosis and limited treatment options. Unique biochemical mechanisms within the peritoneal cavity play a key role in disease progression and resistance to therapy. Despite current therapies like systemic chemotherapy and cytoreductive surgery, patients frequently develop severe complications, including bowel obstruction, nutritional decline, and ascites, driving the need to address the pro-tumorigenic niche in the peritoneal cavity. The immune microenvironment in PC is marked by elevated proinflammatory mediators, such as IL-6 and IL-8, which skew the response toward innate rather than adaptive immune responses. IL-8 signaling, through its receptors CXCR1 and CXCR2, promotes neutrophil recruitment, chronic inflammation, angiogenesis, epithelial–mesenchymal transition, and immune evasion, making the IL-8/CXCR1/CXCR2 axis a potential therapeutic target in PC. Pre-clinical models provide evidence that IL-8 or CXCR1/CXCR2 blockade may be a valuable therapeutic strategy. IL-8 targeting agents such as monoclonal antibodies (BMS-986253) and small-molecule inhibitors (SX-682, AZD5069, navarixin) have shown efficacy in mitigating tumor growth and improving the efficacy of immune checkpoint inhibitors. Phase I and II trials have demonstrated encouraging safety profiles and preliminary efficacy when treating multiple abdominopelvic malignancies. In this review, we discuss the influence of the IL-8/CXCR1/CXCR2 axis within the peritoneal immune environment in PC and highlight recent work using IL-8 or CXCR1/CXCR2 blockade as a therapeutic strategy for PC. Continued research into the peritoneal immune microenvironment and the development of targeted therapies are essential for improving the management and prognosis of PC, potentially enhancing antitumor immunity and patient outcomes.