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The IL-6R and Bmi-1 axis controls self-renewal and chemoresistance of head and neck cancer stem cells

ABSTRACT: Despite major progress in elucidating the pathobiology of head and neck squamous cell carcinoma (HNSCC), the high frequency of disease relapse correlates with unacceptably deficient patient survival. We previously showed that cancer stem-like cells (CSCs) drive tumorigenesis and progression of HNSCC. Although CSCs constitute only 2–5% of total tumor cells, CSCs contribute to tumor progression by virtue of their high tumorigenic potential and their resistance to chemo-, radio-, and immunotherapy. Not only are CSCs resistant to therapy, but cytotoxic agents actually enhance cancer stemness by activating transcription of pluripotency factors and by inducing expression of Bmi-1, a master regulator of stem cell self-renewal. We hypothesized therapeutic inhibition of interleukin-6 receptor (IL-6R) suppresses Bmi-1 to overcome intrinsic chemoresistance of CSCs. We observed that high Bmi-1 expression correlates with decreased (p = 0.04) recurrence-free survival time in HNSCC patients (n = 216). Blockade of IL-6R by lentiviral knockdown or pharmacologic inhibition with a humanized monoclonal antibody (Tocilizumab) is sufficient to inhibit Bmi-1 expression, secondary sphere formation, and to decrease the CSC fraction even in Cisplatin-resistant HNSCC cells. IL-6R inhibition with Tocilizumab abrogates Cisplatin-mediated increase in CSC fraction and induction of Bmi-1 in patient-derived xenograft (PDX) models of HNSCC. Notably, Tocilizumab inhibits Bmi-1 and suppresses growth of xenograft tumors generated with Cisplatin-resistant HNSCC cells. Altogether, these studies demonstrate that therapeutic blockade of IL-6R suppresses Bmi-1 function and inhibits cancer stemness. These results suggest therapeutic inhibition of IL-6R might be a viable strategy to overcome the CSC-mediated chemoresistance typically observed in HNSCC patients.

SUBMITTER: Herzog A

PROVIDER: S-EPMC8542035 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Prostate cancer (PCa) is a key public health problem worldwide; at diagnosis, a high percentage of patients exhibit tumor cell invasion of adjacent tissue. STAT‑3, IL‑6 receptor (R) and IL‑6 serum levels are associated with enhanced PCa migratory, invasive, clonogenic and metastatic ability. Inhibiting the STAT‑3 pathway at different levels (cytokines, receptors, and kinases) exhibits relative success in cancer. The present study investigated the effect of Stattic (Stt) + Tocilizumab (Tcz) on proliferative, clonogenic, migratory and invasive ability of human metastatic PCa (assessed by colony formation, wound healing and migration assay). RWPE‑1 (epithelial prostate immortalized cells), 22Rv1 (Tumor cells), LNCaP (Metastatic cells) and DU‑145 (metastatic, castration‑resistant prostate cells) cells were used in vitro to evaluate levels of cytokines, chemokines, growth factors (Cytometric Bead Array), STAT‑3, phosphorylated STAT‑3 (In‑Cell Western), IL‑6R, vimentin and epithelial (E‑) cadherin (Western Blot). The effect of inhibition of STAT‑3 (expressed constitutively in DU‑145 cells) with Stt and/or Tcz on expression levels of vimentin, VEGF, and E‑cadherin, as well as proliferative, clonogenic, migratory and invasive capacity of metastatic PCa cells was assessed. The expression levels of IL‑6, C‑X‑C chemokine ligand 8, VEGF and vimentin, as well as proliferation and migration, were increased in metastatic PCa cells. Treatment with Stt or Tcz decreased vimentin and VEGF and increased E‑cadherin expression levels and inhibited proliferative, clonogenic, migratory and invasive capacity of DU‑145 cells; addition of IL‑6 decreased this inhibitory effect. However, Stt + Tcz maintained inhibition even in the present of high concentrations of IL‑6. Stt + Tcz decreased expression of vimentin and VEGF and inhibited the proliferative, clonogenic, migratory and invasive capacity of metastatic PCa cells. To the best of our knowledge, the present study is the first to combine Stt, a STAT‑3 inhibitor, with Tcz, an antibody against IL‑6R, to target tumor cells.

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The IL-6R and Bmi-1 axis controls self-renewal and chemoresistance of head and neck cancer stem cells

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