Project description:We previously identified stress keratin 17 (K17) as a host factor that contributes to immune evasion in the context of mouse papillomavirus-induced disease. Analyses of head and neck squamous cell carcinoma (HNSCC) patient TCGA and tissue microarray data revealed that K17 can be overexpressed in both HPV+ and HPV- human cancer samples, with a more profound upregulation in HPV- HNSCC samples. In this report, we investigated the role of K17 in regulating immune response in HPV- head and neck cancer. To test whether K17 mediates immune evasion and resistance to immune checkpoint blockade (ICB) therapy in HPV- HNC, we used MOC2, a K17-expressing murine HNC cell line, and knocked out the K17 gene from it using CRISPR/Cas9 (K17KO MOC2 cells). Then we injected K17KO MOC2 cells or parental MOC2 cells into NSG and C57BL/6 mice and monitored tumor growth, immune cell infiltration, and response to ICB treatment in vivo. In NSG mice, the K17KO MOC2 cell lines grew as fast as parental MOC2 tumors. In C57BL/6 mice, K17KO MOC2 tumors grew significantly slower than parental MOC2 tumors, with 50% tumor rejection rate, in a T-cell dependent manner. Flow cytometry of tumor infiltrating T cells and bulk tumor RNA seq analyses show an active anti-tumor microenvironment in the K17KO MOC2 tumors, compared to parental MOC2 tumors. In addition, we observed that 5 out of 5 anti-PD1 + anti-CTLA4 treated K17KO MOC2 tumors completely regressed, while only 1 out of 5 parental MOC2 tumors similarly treated at the same size completely regressed (p<0.05). In exploring the role of chemokine CXCL9 in increased T cell infiltration, we blocked the receptor CXCR3, a receptor often upregulated on activated T cells, and saw a delay in the immune-mediated rejection K17KO MOC2 tumors. Single cell RNA seq analyses revealed a completely different immune landscape including both lymphoid and myeloid populations in K17KO MOC2 tumors. Overall, we demonstrated that K17 expression in HNSCC contributes to immune evasion and resistance to immune checkpoint blockade treatment through modulating the immune landscape in the tumor microenvironment.

Project description:Human papilloma virus (HPV) is an etiological factor of head and neck squamous cell carcinoma (HNSCC). To investigate the role of HPV antigen in anti-tumor immunity, we established mouse models by expressing HPV16 E6 and E7 in a SCC tumor cell line. We obtained two HPV antigen-expressing clones (C-225 and C-100) transplantable into C57BL/6 recipients. We found that C-225 elicited complete eradication in C57BL/6 mice (eradicated), whereas C-100 grew progressively (growing). We examined immune tumor microenvironment (TME) using flow cytometry and found that eradicated or growing tumors exhibited differential immune profiles that may influence the outcome of anti-tumor immunity. Surprisingly, the percentage of CD8 and CD4 tumor-infiltrating lymphocytes (TILs) was much higher in growing (C-100) than eradicated (C-225) tumor. However, the TILs upregulated PD-1 and LAG-3 more potently and exhibited impaired effector functions in growing tumor compared to their counterparts in eradicated tumor. C-225 TME is highly enriched with myeloid cells, especially polymorphonuclear (PMN) myeloid-derived suppressor cells (MDSC), whereas the percentage of M-MDSC and tumor-associated macrophages (TAMs) was much higher in C-100 TME, especially M2-TAMs (CD206+). The complete eradication of C-225 depended on CD8 T cells and elicited anti-tumor memory responses upon secondary tumor challenge. We employed DNA sequencing to identify differences in the T cell receptor of peripheral blood lymphocytes pre- and post-secondary tumor challenge. Lastly, C-225 and C-100 tumor lines harbored different somatic mutations. Overall, we uncovered differential immune TME that may underlie the divergent outcomes of anti-tumor immunity by establishing two SCC tumor lines, both of which express HPV16 E6 and E7 antigens. Our experimental models may provide a platform for pinpointing tumor-intrinsic versus host-intrinsic differences in orchestrating an immunosuppressive TME in HNSCCs and for identifying new targets that render tumor cells vulnerable to immune attack.

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Investigating Immune and Non-Immune Cell Interactions in Head and Neck Tumors by Single-Cell RNA Sequencing

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