Abstract C010: Tumor MK2 drives tumor progression and an immunosuppressive microenvironment in head and neck squamous cell carcinoma
Authors: Okwuone Dakota D.D. , Morgan Deri , Schmidt Alyssa , Shrock Devin , Lin Yuting , Gao Hao , Thomas Sufi M. , Gan Gregory N. 
Published: November 2024

Abstract
Background: Head and neck squamous carcinoma (HNSCC) results in poor patient outcomes driven primarily by locoregional and distant metastatic tumor spread. We have demonstrated that highly phosphorylated/active MAPKAPK-2 (MK2) is a poor prognostic factor in HNSCC patients. MK2 is associated with the expression of pro-inflammatory cytokines that are linked with creating a pro-tumorigenic microenvironment. Nevertheless, how MK2 contributes to HNSCC development has not been established. In this study, we aimed to identify the effect of MK2 on cancer progression, immune infiltration, and cytokine secretion. Method: To assess the effect of tumor MK2 in vivo, we used CRISPR-Cas9 to knock out (KO) MK2 in a metastatic murine HNSCC cell line, Ly2, and orthotopically implanted wildtype (WT) or MK2 KO cells into the floor-of-mouth of Balb/c mice. At the endpoint of the experiment, the tumors were excised, and myeloid and lymphocyte immune profiling was done via flow cytometry. Mouse lungs and cervical lymph nodes were dissected, paraffin-fixed, sectioned, and H&E stained, and the presence/quantity of metastatic foci was evaluated by a blinded board-certified pathologist. We broadly evaluated the tumor secretome via a 105-cytokine dot blot array using 8 mg of the same resected tumor sample and performed densitometric analysis comparing WT and KO tumors. Results: Loss of MK2 significantly reduced primary tumor growth, as well as lymph node and lung metastasis, compared to WT tumors. Tumor immunophenotyping by flow cytometry revealed that MK2 KO tumors had increased overall immune cell (CD45+) infiltration, but decreased quantities of immunosuppressive neutrophils (CD11b+Ly6G+Arg1+Ly6C-) and a shift in macrophage polarity favoring M1 (anti-tumor) macrophages (CD11b+Ly6G-F4-80+CD80+). In addition, there were increased quantities of anti-tumor immune cells including natural killer (NK)-T, CD4+, and CD8+ T cells in the MK2-KO tumors, while the proportion of CD4+CD25+ Tregs and exhausted CD8 T cells (CD8+PD1+) was decreased compared to WT tumors. Furthermore, cytokine array analysis revealed that secreted levels of several cytokines, including CXCL1, CXCL2, GM-CSF, G-CSF, IL-1alpha, and IL-6, were significantly lower in MK2 KO tumors compared to WT tumors. Conclusion: These results show that tumoral MK2 signaling promotes tumor growth, metastasis, immunosuppressive inflammation, and pro-tumorigenic cytokine release which substantiates future therapeutic targeting of this pathway.
Citation Format: Dakota D.D. Okwuone, Deri Morgan, Alyssa Schmidt, Devin Shrock, Yuting Lin, Hao Gao, Sufi M. Thomas, Gregory N. Gan. Tumor MK2 drives tumor progression and an immunosuppressive microenvironment in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C010.