Abstract 3998: miRNA associated with distal metastasis and local recurrence after post-operative radiotherapy in high-risk head and neck cancer

Distal metastasis and local-regional recurrence after radiation therapy is a major cause of treatment failure for patients with head and neck squamous cell carcinoma. miRNA have been proposed as biomarkers in cancer to predict therapeutic outcomes and has been associated with the cellular response to radiation. The advantages of miRNA as a biomarker lies in its stability in tissues as well as body fluids, hence the potential for non-invasive diagnosis and prognosis. In this study, we performed miRNA expression profiling using tumor samples from 114 head and neck cancer patients treated by post-operative radiotherapy (PORT) at M.D. Anderson Cancer Center from 1992 to 1999. All patients were considered to be at high-risk for recurrence having histologically proven advanced squamous cell carcinoma. Amongst these samples, 41 had distal metastasis (DM), 24 recurred locally or local/regional (LR) and 49 responded to PORT (no evidence of disease (NED)). Total RNA was extracted using a modified protocol of the Qiagen RNeasy Plus kit which retains small RNA fractions. miRNA profiling was performed using miRCURY 7th gen LNA™ microRNA Array from Exiqon. Microarray data were background-subtracted using mis-match control probes and normalized with median scaling. An ANOVA model based on clinical outcome was used to compare of miRNA expression between DM vs. NED and LR vs NED. There are 94 miRNAs that differentially expressed in DM and 60 miRNAs differentially expressed in LR with statistical significance (p 1.4). Among them, miR-551a and miR-551b-3p are significantly associated with the DM group and have been validated using qPCR. By transfection of either mimic or an inhibitor of these miRNAs using the HN5 head and neck cancer cell line, we have confirmed that both miR-551a and miR-551b-3p promote cell proliferation, enhance cell migration and invasion. We have further discovered GLIPR2, an autophagy inhibitor, as a direct binding target of both miRNAs using luciferase assay. By over-expressing miR-551a/miR-551b-3p or suppressing GLIPR2 expression, we detected higher level autophagy with increased LC3 foci and overexpression of lipidated LC3B. Base on the above data, we propose a model that miR-551a and miR-551b-3p enhance radio-resistance and metastasis by promoting autophagy via suppressing GLIPR2 expression. A panel of 49 head and neck cancer cell lines were used for aCGH study and miRNA profiling. Further analysis is underway to correlate the patterns of DNA copy number variation and miRNA expression with radio-sensitivity. The findings in these cell lines will also be validated in tumor tissue samples. In summary, our data demonstrated the potential of miRNAs as biomarkers that predict therapeutic outcomes and mechanistic studies of miRNA markers will lead to novel pathway discovery and further improvement of cancer treatment. Citation Format: Lianghao Ding, Narasimha Kumar Karanam, John S. Yordy, Uma Giri, Michael D. Story. miRNA associated with distal metastasis and local recurrence after post-operative radiotherapy in high-risk head and neck cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3998. doi:10.1158/1538-7445.AM2015-3998