STAT3/HOTAIR signaling axis regulates HNSCC growth in an EZH2-dependent manner

Purpose: Phosphotidylinositol-3-kinase (PI3K)and signal transducers and activators of transcription 3 (STAT3) are frequently activated in cancer progression. However, little is known about the underlying mechanisms by which PI3K and STAT3 regulate HNSCC growth. The lncRNA HOX transcript antisense RNA (HOTAIR) was found to modulate the progression of head and neck squamous cell cancer (HNSCC). In this study, we attempted to establish the correlation of PI3K-STAT3-HOTAIR signaling with the progression of HNSCC and its sensitivity towards platinum-based and targeted anti-EGFR combination therapy. Experimental Design: We first analyzed the STAT3/HOTAIR and PI3K/AKT level in human HNSCC samples. We then activated or suppressed STAT3/HOTAIR and determined the effects on HNSCC cell proliferation in vitro and the growth of UM1 xenograft tumor, an orthotopic model of HNSCC. The sensitivity of HNSCC cells towards cisplatin and cetuximab was determined by in vitro assays. Results: HNSCC samples showed significantly robust expression/activation of STAT3, HOTAIR, PI3K, and AKT, compared with normal squamous epithelium. STAT3 inhibition with WP1066 decreased HOTAIR level and sensitized HNSCC to cisplatin or cetuximab. STAT3 promoted HOTAIR transcription and its interaction with pEZH2-S21, resulting in enhanced growth of HNSCC cells. In addition, overexpression of HOTAIR promoted the growth of UM1 xenograft tumors in vivo. Conclusions: Our results suggest that STAT3 signaling promotes HNSCC progression via regulating HOTAIR and pEZH2-S21 in HNSCC with PI3K overexpression/activation. These findings provide a rationale to target the STAT3/HOTAIR/pEZH2-S21 regulatory axis for treating patients with HNSCC.

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