Obstructive sleep apnea syndrome (OSAS) is characterized by intermittent hypoxia (IH) during sleep due to recurrent upper airway obstruction. The derived oxidative stress (OS) leads to complications that do not only concern the sleep-wake rhythm but also systemic dysfunctions. The aim of this narrative literature review is to investigate molecular alterations, diagnostic markers, and potential medical therapies for OSAS. We analyzed the literature and synthesized the evidence collected. IH increases oxygen free radicals (ROS) and reduces antioxidant capacities. OS and metabolic alterations lead OSAS patients to undergo endothelial dysfunction, osteoporosis, systemic inflammation, increased cardiovascular risk, pulmonary remodeling, and neurological alterations. We treated molecular alterations known to date as useful for understanding the pathogenetic mechanisms and for their potential application as diagnostic markers. The most promising pharmacological therapies are those based on N-acetylcysteine (NAC), Vitamin C, Leptin, Dronabinol, or Atomoxetine + Oxybutynin, but all require further experimentation. CPAP remains the approved therapy capable of reversing most of the known molecular alterations; future drugs may be useful in treating the remaining dysfunctions.

Programmed cell death ligand-1 (PD-L1) binds PD-1 on CD⁸⁺ lymphocytes, inhibiting their cytotoxic action. Its aberrant expression by head and neck squamous cell carcinoma (HNSCC) cells leads to immune escape. Pembrolizumab and nivolumab, two humanized monoclonal antibodies against PD-1, have been approved in HNSCC treatment, but ~60% of patients with recurrent or metastatic HNSCC fail to respond to immunotherapy and only 20 to 30% of treated patients have long-term benefits. The purpose of this review is to analyze all the fragmentary evidence present in the literature to identify what future diagnostic markers could be useful for predicting, together with PD-L1 CPS, the response to immunotherapy and its durability. We searched PubMed, Embase, and the Cochrane Register of Controlled Trials and we summarize the evidence collected in this review. We confirmed that PD-L1 CPS is a predictor of response to immunotherapy, but it should be measured across multiple biopsies and repeatedly over time. PD-L2, IFN-γ, EGFR, VEGF, TGF–β, TMB, blood TMB, CD73, TILs, alternative splicing, tumor microenvironment, and some macroscopic and radiological features are promising predictors worthy of further studies. Studies comparing predictors appear to give greater potency to TMB and CXCR9.

Aberrant expression of the programmed cell death protein ligand 1 (PD-L1) constitutes one of the main immune evasion mechanisms of cancer cells. The approval of drugs against the PD-1-PD-L1 axis has given new impetus to the chemo-therapy of many malignancies. We performed a literature review from 1992 to August 2022, summarizing evidence regarding molecular structures, physiological and pathological roles, mechanisms of PD-L1 overexpression, and immunotherapy evasion. Furthermore, we summarized the studies concerning head and neck squamous cell carcinomas (HNSCC) immunotherapy and the prospects for improving the associated outcomes, such as identifying treatment response biomarkers, new pharmacological combinations, and new molecules. PD-L1 overexpression can occur via four mechanisms: genetic modifications; inflammatory signaling; oncogenic pathways; microRNA or protein-level regulation. Four molecular mechanisms of resistance to immunotherapy have been identified: tumor cell adaptation; changes in T-cell function or proliferation; alterations of the tumor microenvironment; alternative immunological checkpoints. Immunotherapy was indeed shown to be superior to traditional chemotherapy in locally advanced/recurrent/metastatic HNSCC treatments.

Alcohol consumption is associated with oxidative stress and an increased risk of carcinoma of the upper aero-digestive tract (UADT). Recently, it has been found that some microorganisms in the human oral cavity may locally metabolize ethanol, forming acetaldehyde, a carcinogenic metabolite of alcohol. In a cohort of patients first visited for UADT cancers, we estimated their alcohol consumption by measuring Ethyl Glucuronide/EtG (a long-lasting metabolite of ethanol) in the hair and carbohydrate-deficient transferrin/CDT (short-term index of alcohol intake) in the serum. Moreover, we analyzed, by culture-based methods, the presence of Neisseria subflava, Streptococcus mitis, Candida albicans, and glabrata (microorganisms generating acetaldehyde) in the oral cavity. According to the EtG values, we correlated drinking alcohol with endogenous oxidative stress and the investigated microorganism’s presence. We found that 55% of heavy drinkers presented microorganisms generating acetaldehyde locally. Moreover, we found that the presence of oral acetaldehyde-producing bacteria correlates with increased oxidative stress compared to patients without such bacteria. As for the study of alcohol dehydrogenase gene polymorphisms (the enzyme that transforms alcohol to acetaldehyde), we found that only the “CGTCGTCCC” haplotype was more frequent in the general population than in carcinoma patients. This pilot study suggests the importance of estimating alcohol consumption (EtG), the presence of bacteria producing acetaldehyde, and oxidative stress as risk factors for the onset of oral carcinomas.

The treatment of unresectable or metastatic Head and Neck Squamous Cell Carcinoma (HNSCC) has traditionally relied on chemotherapy or radiotherapy, yielding suboptimal outcomes. The introduction of immunotherapy has significantly improved HNSCC treatment, even if the long-term results cannot be defined as satisfactory. Its mechanism of action aims to counteract the blockade of tumor immune escape. This result can also be obtained by stimulating the immune system with vaccines. This review scope is to comprehensively gather existing evidence and summarize ongoing clinical trials focused on therapeutic vaccines for HNSCC treatment. The current landscape reveals numerous promising drugs in the early stages of experimentation, along with a multitude of trials that have been suspended or abandoned for years. Nonetheless, there are encouraging results and ongoing experiments that instill hope for potential paradigm shifts in HNSCC therapy.

The accurate diagnosis of regional lymph node metastasis is critical for guiding treatment decisions in head and neck cancer patients. Despite advances in imaging techniques, detecting nodal metastasis using radiology remains challenging, leading to potential undertreatment or overtreatment. This review aims to identify molecular markers associated with occult metastasis in head and neck squamous cell carcinoma (HNSCC) patients. We divided the results by subsite for markers: lymph node analysis (microRNAs, myosin-5a (MYO5A), ring finger protein 145 (RNF145), F-box only protein 32 (FBXO32), CTONG2002744, cytokeratin 14 (CK14), eukaryotic initiation factor 4E (eIF4E), desmoglein-3 (DSG3), microsatellite D9S171, squamous cell carcinoma antigen, cytokeratin, tumor budding score, human papillomavirus-DNA (HPV-DNA), tumor infiltrating lymphocytes, sentinel lymph node analysis techniques, single fiber reflectance spectroscopy, radiological techniques), tumor tissue analysis (activin A, carcinoma-associated fibroblasts, cyclins, β-catenin, histopathology, genetic amplifications, DNA methylation, ecotropic viral integration site 1, CC-chemokine receptor 7, melanoma associated-A antigens, vascular endothelial growth factor-C (VEGF-C), panitumumab, epidermal growth factor receptor (EGFR), cornulin, total protein analysis, CD133, NANOG homeobox, neurogenic locus notch homolog protein 1 (NOTCH1), metastasis-associated protein 1, 14-3-3-zeta, E-cadherin, focal adhesion kinase, p-epithelial-mesenchymal transition (EMT), small proline rich protein 1B (SPRR1B), transcription factor NKX3-1, DNA copy number aberrations, microfibril-associated protein 5 (MFAP5), troponin C1, slow skeletal and cardiac type (TNNC1), matrix Gla protein (MGP), fibroblast growth factor binding protein 1 (FBFBP1), F-box protein 32 (FBXO32), fatty acid binding protein 5, B cell-specific Moloney murine leukemia virus integration site 1, podoplanin, p53, Bcl-2, epidermal growth factor receptor (EGFR), Ki67, cyclin D1, cox-2, semaphorin-3F, neuropilin-2, histologic features, cellular dissociation grade, prospero homeobox protein 1, radiologic features, Ki-67, poly (ADP-ribose) polymerase (PARP), Bcl-2 associated agonist of cell death (BAD), caspase-9, vascular endothelial growth factor A (VEGF-A), HPV, p16, methylation status of long interspersed element 1 (LINE-1) and Alu elements, mesenchymal-epithelial transition (MET), gene expression analyses, molecular subtypes) and blood markers (standard blood analysis indexes and ratios, circulating tumor cells, HPV-DNA, CD-31, bone marrow analysis). Several promising markers were identified, including miR-205, desmoglein 3 (DSG3), pan-cytokeratin (CK) AE1/AE3, HPV-16, activin-A, cyclin D1, E-cadherin, and neural progenitor lineage (NPL) that demonstrated effectiveness across multiple studies. Future research should focus on exploring combination scoring systems to improve diagnostic precision and optimize treatment selection in HNSCC patients.