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Clonal variation in interferon response determines the outcome of oncolytic virotherapy in mouse CT26 colon carcinoma
J J Ruotsalainen1, M U Kaikkonen1, M Niittykoski1
1A.I. Virtanen Institute for Molecular Sciences, Department of Biotechnology and Molecular Medicine, University of Eastern Finland, Kuopio, Finland.
Abstract:
In our earlier studies, Semliki Forest virus vector VA7 completely eliminated type I interferon (IFN-I)-unresponsive human U87-luc glioma xenografts, whereas interferon-responsive mouse gliomas proved refractory. Here, we describe in two clones of CT26 murine colon carcinoma, opposed patterns of IFN-I responsiveness and sensitivity to VA7. Both CT26WT and CT26LacZ clones secreted biologically active interferon in vitro upon virus infection but only CT26WT cells were protected. Focal infection of CT26WT cultures was self-limiting but could be rescued using IFN-I pathway inhibitor Ruxolitinib or antibody against IFNβ. Whole transcriptome sequencing (RNA-Seq) and protein expression analysis revealed that CT26WT cells constitutively expressed 56 different genes associated with pattern recognition and IFN-I signaling pathways, spanning two reported anti-RNA virus gene signatures and 22 genes with reported anti-alphaviral activity. Whereas CT26WT tumors were strictly virus-resistant in vivo, infection of CT26LacZ tumors resulted in complete tumor eradication in both immunocompetent and severe combined immune deficient mice. In double-flank transplantation experiments, CT26WT tumors grew despite successful eradication of CT26LacZ tumors from the contralateral flank. Tumor growth progressed uninhibited also when CT26LacZ inoculums contained only a small fraction of CT26WT cells, demonstrating dominance of IFN responsiveness when heterogeneous tumors are targeted with interferon-sensitive oncolytic viruses.
Insights
Semliki Forest virus (SFV) vector VA7 effectively eradicated interferon-I-unresponsive tumors but struggled with responsive ones. Interferon-responsive CT26LacZ tumors were eliminated by VA7, while resistant CT26WT tumors persisted, highlighting interferon signaling
Area of Science:
- Virology
- Immunology
- Oncology
Background:
- Semliki Forest virus (SFV) vector VA7 effectively eliminates type I interferon (IFN-I)-unresponsive human glioma xenografts.
- Interferon-responsive mouse gliomas are refractory to VA7 treatment.
- Two clones of CT26 murine colon carcinoma, CT26WT and CT26LacZ, exhibit opposing IFN-I responsiveness and sensitivity to VA7.
Purpose of the Study:
- To investigate the differential response of CT26 murine colon carcinoma clones to SFV vector VA7.
- To elucidate the role of type I interferon (IFN-I) signaling in tumor resistance and sensitivity to oncolytic viruses.
- To understand the impact of tumor heterogeneity on oncolytic virotherapy efficacy.
Main Methods:
- In vitro infection of CT26WT and CT26LacZ cells with SFV vector VA7.
- Treatment with IFN-I pathway inhibitor Ruxolitinib and anti-IFNβ antibody.
- Whole transcriptome sequencing (RNA-Seq) and protein expression analysis.
- In vivo studies using immunocompetent and severe combined immune deficient mice.
- Double-flank transplantation experiments to assess tumor heterogeneity effects.
Main Results:
- Both CT26WT and CT26LacZ cells secreted biologically active interferon in vitro upon VA7 infection, but only CT26WT cells were protected.
- Focal infection of CT26WT cultures was self-limiting and could be rescued by IFN-I pathway inhibition.
- CT26WT cells constitutively expressed 56 genes related to pattern recognition and IFN-I signaling.
- CT26WT tumors were virus-resistant in vivo, while CT26LacZ tumors were completely eradicated in both immunocompetent and SCID mice.
- In heterogeneous tumors, CT26WT tumors grew despite CT26LacZ tumor eradication, demonstrating the dominance of IFN responsiveness.
Conclusions:
- Tumor cells' intrinsic type I interferon (IFN-I) responsiveness dictates sensitivity to SFV vector VA7.
- Constitutive expression of IFN-I pathway genes confers resistance to oncolytic virotherapy.
- Tumor heterogeneity, specifically the presence of IFN-I-responsive cells, can lead to therapeutic failure.
- Targeting interferon-sensitive oncolytic viruses in heterogeneous tumors is dominated by the resistant cell population.
