HIF-α/MIF and NF-κB/IL-6 Axes Contribute to the Recruitment of CD11b+Gr-1+ Myeloid Cells in Hypoxic Microenvironment of HNSCC

CD11b+Gr-1+ myeloid cells have gained much attention due to their roles in tumor immunity suppression as well as promotion of angiogenesis, invasion, and metastases. However, the mechanisms by which CD11b+Gr-1+ myeloid cells recruit to the tumor site have not been well clarified. In the present study, we showed that hypoxia could stimulate the migration of CD11b+Gr-1+ myeloid cells through increased production of macrophage migration inhibitory factor (MIF) and interleukin-6 (IL-6) by head and neck squamous cell carcinoma (HNSCC) cells. Hypoxia-inducible factor-1α (HIF-1α)- and HIF-2α-dependent MIF regulated chemotaxis, differentiation, and pro-angiogenic function of CD11b+Gr-1+ myeloid cells through binding to CD74/CXCR2, and CD74/CXCR4 complexes, and then activating p38/mitogen-activated protein kinase (MAPK) and phosphatidylinositide 3-kinases (PI3K)/AKT signaling pathways. Knockdown (KD) of HIF-1α and HIF-2α in HNSCC cells decreased MIF level but failed to inhibit the CD11b+Gr-1+ myeloid cell migration, because HIF-1α/2α KD enhanced nuclear factor κB (NF-κB) activity that increased IL-6 secretion. Simultaneously blocking NF-κB and HIF-1α/HIF-2α had better inhibitory effect on CD11b+Gr-1+ myeloid cell recruitment in the hypoxic zone than individually silencing HIF-1α/2α or NF-κB. In conclusion, the interaction between HIF-α/MIF and NF-κB/IL-6 axes plays an important role in the hypoxia-induced accumulation of CD11b+Gr-1+ myeloid cells and tumor growth in HNSCC

HPV infection correlates with the progression of oropharyngeal carcinogenesis.

<p>(A) Percentage of HPV 16 positive infection in patient tissues with normal oral mucosa, dysplasia, cancer in situ and cancer was shown. (B) Representative flow cytometry image of CD11b+ LIN- HLA-DR- CD33+ MDSCs in tissues of OPSCC patients with HPV-negative and HPV-positive. We first examined the percentage of LIN- HLA-DR- cells, and then screened the percentage of CD11b+ CD33+ cells in LIN- HLA-DR- cells. This image showed that the percentage of CD11b+ LIN- HLA-DR- CD33+ MDSCs in HPV-negative and HPV-positive OPSCC patients was 9.39% and 13.81%, respectively. (C) Representative immunohistochemical image (C3) of MPO in cancer tissues of OPSCC patients. C1 and C2 were H& E staining and C2 was amplification of C1.</p

Schematic diagram of persistent chronic inflammation-related HPV infection response contributes to oropharyngeal carcinogenesis.

<p>Schematic diagram of persistent chronic inflammation-related HPV infection response contributes to oropharyngeal carcinogenesis.</p

Chronic inflammation correlates with the progression of oropharyngeal carcinogenesis.

<p>(A) The morphology of neutrophils (Black arrow) and lymphocytes (White arrow) in cell smear. (B) Percentage of different degrees of chronic inflammation in cell smear of indicated types of tissues were shown. The results showed that there was significantly difference between the percentage of moderate-severe inflammation in the cell smear of dysplasia and normal oral mucous (<i>P</i><0.001), and the inflammation degrees showed no different in the cell smear of dysplasia, cancer in situ and cancer (<i>P</i>>0.05). Error bars represent the mean±SD of triplicate experiments. (C) Representative image of normal oral mucosa, dysplasia, cancer in situ and cancer with mild inflammation. (D) Percentage of different degrees of chronic inflammation in indicated types of tissues are shown. The results showed that there was significantly difference between the percentage of moderate-severe inflammation in the tissues of dysplasia and normal oral mucous (<i>P</i><0.001), and the inflammation degrees showed no different in dysplasia, cancer in situ and cancer specimens (<i>P</i>>0.05). Error bars represent the mean±SD of triplicate experiments. (E) Transcription levels of IFN-γ, IL-10, IL-12, and IL-2 in normal oral mucosa, dysplasia, cancer in situ and cancer tissue, relative to GAPDH, determined by quantitative RT-PCR. Error bars represent the mean±SD of triplicate experiments.</p