Head and neck cancer (HNC) is among the most common neoplasms worldwide, with global estimates indicating over 1.7 million new cases per year and approximately 530,000 deaths (Bray et al., 2024). The primary histological type is squamous cell carcinoma (HNSCC), which accounts for 90 % of cases (Pai & Westra, 2009). The multifactorial etiology of HNSCC involves genetic, environmental, and epigenetic factors (Johnson et al., 2020, Mody et al., 2021). Smoking, alcohol abuse, and human papillomavirus (HPV) infection are the main risk factors for HNSCC (American Cancer Society, 2021, Shaw and Beasley, 2016).

Patients with HNSCC are often diagnosed at advanced disease stages (Morais-Faria et al., 2020). Late diagnosis is associated with a poorer prognosis and reduced cure rates (Leoncini et al., 2015). Despite advances in the diagnosis and treatment of HNSCC, the long-term survival rates remain low (Cadoni et al., 2017). In this context, the search for diagnostic and prognostic biomarkers has led to the discovery of microRNA-375 (miR-375), a tumor suppressor miRNA, as one of the most promising biomarkers of HNSCC (Al Rawi et al., 2021, Dioguardi et al., 2023, Tu et al., 2013; P. Wang et al., 2019; Yu et al., 2018).

MiR-375 expression has been evaluated in various tumors (Elshafei et al., 2017, Jia-yuan et al., 2020, Kong et al., 2012, Li et al., 2018, Lian et al., 2016; J. Wang & Sun, 2018; W. Wu et al., 2021; Xu et al., 2019; Zhao et al., 2018), including HNSCC (Dioguardi et al., 2023, Ferreira et al., 2022, Jimenez et al., 2017; P. Wang et al., 2019), and it has been reported to be an important cancer biomarker that acts as a tumor suppressor (Lian et al., 2016, Luo and Wu, 2019; P. Wang et al., 2019; Wei et al., 2021; Yan et al., 2014). This miRNA plays key roles in cellular proliferation, apoptosis, invasion, migration, metastasis, and autophagy (Yan et al., 2014) by targeting oncogenes, such as AEG-1, YAP1, IGF1R, SP1, and YWHAZ (Wei et al., 2021, Yan et al., 2014, Zhao et al., 2018). Interestingly, miR-375 is downregulated in various cancers (Jia-yuan et al., 2020, Kinoshita et al., 2012, Yan et al., 2014), including HNSCC (Al Rawi et al., 2021, Dioguardi et al., 2023, Ferreira et al., 2022; P. Wang et al., 2019). Low miR-375 expression may play an important role in cancer progression as it is associated with poorer prognosis, distant metastasis (Kong et al., 2012), and lower survival rates (Gao et al., 2018, Luo and Wu, 2019; P. Wang et al., 2019; Xu et al., 2019). Additionally, downregulation may be influenced by hypermethylation of the MIR375 gene and its regulatory regions (Gaździcka et al., 2020, Kong et al., 2012, Lopez-Serra and Esteller, 2012; S. Wang et al., 2017; Yan et al., 2014), suggesting that downregulated miR-375 may be a prognostic biomarker that favors carcinogenesis (P. Wang et al., 2019). Therefore, investigating the methylation status of miRNA genes in patients with HNSCC appears to be a promising approach to establish new biomarkers with therapeutic potential.

The Cancer Genome Atlas (TCGA) is an open database that includes information from various cohort studies on cancer genomes and the molecular aspects of various tumors, including HNSCC. Additionally, TCGA allows for a comprehensive joint assessment of data, integrated analysis of tumor molecular data with other outcomes, and confirmation of findings (Beltrami et al., 2017, Lima et al., 2018), as well as for research guidance (Luo & Wu, 2019). This study aimed to conduct a TCGA exploratory analysis of the potential prognostic value of DNA methylation patterns in regions that may regulate the expression of miR-375.