Saliva has been useful as a liquid biopsy for the diagnosis of various oral or systemic diseases, and oral squamous cell carcinoma (OSCC) is no exception. While its early detection and prevention is important, salivary cytokines expression, specifically of Interleukin-8 (IL-8), Interleukin-6 (IL-6) and Tumor necrosis factor (TNF-α), does contribute to the pathogenesis of cancer and these cytokines serve as potential biomarkers. Their excessive production plays a role in cancer progression and establishment of angiogenesis. However, other inflammatory or immunological conditions may affect the levels of cytokines in saliva. This article reviews the expression of levels of specific cytokines i.e., IL-8, IL-6 and TNF-α, their signaling pathways in the development of oral cancer, and how they are essential for the diagnosis of OSCC and updates related to it. Apart from serum, the saliva-based test can be a cost-effective tool in the follow-up and diagnosis of OSCC. Moreover, large-scale investigations are still needed for the validation of salivary cytokines.

Human whole mouth saliva (WMS) is secreted by salivary glands, namely parotid, submandibular/sublingual and other minor glands of the oral cavity. It is secreted in a systematic way, and contain informative proteins and peptides for the early detection of contagious diseases and organ-related diseases. The role of WMS as a liquid biopsy for the detection of cardiovascular diseases (CVD) through Myoglobin (MYO), Cardiac troponin I (cTnI), Creatine phosphokinase MB (CK-MB), Myeloperoxidase (MPO), brain natriuretic peptide (NT-proBNP), Exosomal miRNA, C-Reactive Protein (CRP), Matrix metalloproteinase-8 (MMP-8), MMP-9 and tissue inhibitor of MMP-8 (TIMP-1), leukotriene B4 has been well reported in last decade, that have been reviewed in the literature comprehensively below.

Cathelicidins are a group of oral antimicrobial peptides that play multiple vital roles in the human body, such as their antimicrobial (broad spectrum) role against oral microbes, wound healing, and angiogenesis, with recent evidences about their role in cancer regulation. Cathelicidins are present in humans and other mammals as well. By complex interactions with the microenvironment, it results in pro-inflammatory effects. Many in vitro and in vivo experiments have been conducted to ultimately conclude that these unique peptides play an essential role in innate immunity. Peptides are released in the precursor form (defensins), which after cleavage results in cathelicidins formation. Living in the era where the major focus is on non-invasive and nanotechnology, this ultimately leads to further advancements in the field of salivaomics. Based on current spotlight innovations, we have highlighted the biochemistry, mode of action, and the importance of cathelicidins in the oral cavity.