ACLY (ATP Citrate Lyase) Mediates Radioresistance in Head and Neck Squamous Cell Carcinomas and is a Novel Predictive Radiotherapy Biomarker.

Eva-Leonne Göttgens,Corina NAM van den Heuvel,Monique C de Jong,Johannes HAM Kaanders,William PJ Leenders,Marleen Ansems,Paul N Span,Johan Bussink

doi:10.3390/cancers11121971

Abstract

Radiotherapy is an important treatment modality of head and neck squamous cell carcinomas (HNSCC). Multiple links have been described between the metabolic activity of tumors and their clinical outcome. Here we test the hypothesis that metabolic features determine radiosensitivity, explaining the relationship between metabolism and clinical outcome. Radiosensitivity of 14 human HNSCC cell lines was determined using colony forming assays and the expression profile of approximately 200 metabolic and cancer-related genes was generated using targeted RNA sequencing by single molecule molecular inversion probes. Results: Correlation between radiosensitivity data and expression profiles yielded 18 genes associated with radiosensitivity or radioresistance, of which adenosine triphosphate (ATP) citrate lyase (ACLY) was of particular interest. Pharmacological inhibition of ACLY caused an impairment of DNA damage repair, specifically homologous recombination, and lead to radiosensitization in HNSCC cell lines. Examination of a The Cancer Genome Atlas (TCGA) cohort of HNSCC patients revealed that high expression of ACLY was predictive for radiotherapy failure, as it was only associated with poor overall survival in patients who received radiotherapy (hazard ratio of 2.00, 95% CI: 1.12–3.55; p = 0.0184). These data were further validated in an independent cohort of HNSCC patients treated with chemoradiation. Furthermore, patients with poor locoregional control after radiotherapy have significantly higher nuclear ACLY protein levels. Together, we here show that ACLY affects DNA damage repair, and is a predictive factor for radiotherapy outcome in HNSCC.

Highlights

Head and neck squamous cell carcinomas (HNSCC) are malignancies of the epithelium lining the nasal and oral cavity as well as the pharynx, and annually affects 650,000 people worldwide [1]
To investigate the link between radiosensitivity and the metabolic gene profile, we first characterized the radiosensitivity of a panel of HNSCC cell lines
The dose permitting 37% survival (D37) was significantly lower for human papillomavirus (HPV)-positive HNSCC cell lines compared to HPV-negative HNSCC cell lines (p = 0.013)

Summary

Introduction

Head and neck squamous cell carcinomas (HNSCC) are malignancies of the epithelium lining the nasal and oral cavity as well as the pharynx, and annually affects 650,000 people worldwide [1]. In HNSCC originating in the oropharynx, the odds of treatment success are significantly affected by the human papillomavirus (HPV) status of the Cancers 2019, 11, 1971; doi:10.3390/cancers11121971 www.mdpi.com/journal/cancers. HPV-positive tumors constitute approximately 5%–60% of HNSCC cases, depending on the specific anatomical location [3]. HPV positive oropharynx tumors have been shown to be significantly more radiosensitive, and this is reflected in the patient population where HPV-positive patients have a strikingly better prognosis, locoregional control, and five year survival [4,5,6,7,8]. The mechanisms leading to radioresistance especially in HPV-negative patients have been extensively studied and have been attributed to DNA damage repair, cell cycle arrest, activation of oncogenes, microenvironmental changes, as well as changes in tumor metabolism [9]

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