Abstract
While a shift in energy metabolism is essential to cancers, the knowledge about the involvement of the mitochondrial genome in tumorigenesis and progression in oral squamous cell carcinoma (OSCC) is still very limited. In this study, we evaluated 37 OSCC tumors and the corresponding benign mucosa tissue pairs by deep sequencing of the complete mitochondrial DNA (mtDNA). After extensive quality control, we identified 287 variants, 137 in tumor and 150 in benign samples exceeding the 1% threshold. Variant heteroplasmy levels were significantly increased in cancer compared to benign tissues (p = 0.0002). Furthermore, pairwise high heteroplasmy frequency difference variants (∆HF% > 20) with potential functional impact were increased in the cancer tissues (p = 0.024). Fourteen mutations were identified in the protein-coding region, out of which thirteen were detected in cancer and only one in benign tissue. After eight years of follow-up, the risk of mortality was higher for patients who harbored at least one ∆HF% > 20 variant in mtDNA protein-coding regions relative to those with no mutations (HR = 4.6, (95%CI = 1.3–17); p = 0.019 in primary tumor carriers). Haplogroup affiliation showed an impact on survival time, which however needs confirmation in a larger study. In conclusion, we observed a significantly higher accumulation of somatic mutations in the cancer tissues associated with a worse prognosis.
Highlights
The oral squamous cell carcinoma (OSCC) represents over 90% of the most frequent types of cancer in the oral cavity and accounts for 38% of head and neck tumors [1]
The unambiguous identification of potentially pathological mitochondrial DNA (mtDNA) mutations is crucial for the interpretation and functional assessment of any aspects of tumorigenesis
We presented an extensive profiling of the mitochondrial genome in OSCC
Summary
The oral squamous cell carcinoma (OSCC) represents over 90% of the most frequent types of cancer in the oral cavity and accounts for 38% of head and neck tumors [1]. Tumor incidence has increased up to approximately 300,000 newly diagnosed cases per year and 2.1% of total cancer deaths worldwide. Known risk factors include tobacco use in any form, especially in combination with heavy alcohol consumption [2]. The prognosis of OSCC is generally poor. The five-year survival rate of OSCC is only 50% and has remained unchanged for a decade [3]. Mitochondria have been implicated in carcinogenesis due to their crucial role in energy metabolism
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