Exosomes represent one of the most prevalent types of extracellular vesicles (EVs) (1). They encapsulate a diverse array of bioactive constituents, such as proteins, lipids, nucleic acids, among others, and are abundantly found in saliva, blood, and various bodily fluids (2). Through engaging in intercellular communication among cancer cells, exosomes modulate cancer proliferation and migration (3). Wei et al. (4) demonstrated that OSCC cells inhibited the expression of Phosphatase and tensin homolog deleted on chromosome 10 by releasing exosomes carrying miR-130b-3p, which promoted OSCC tumor proliferation and angiogenesis. Guillaume (5) has demonstrated that proteins contained in extracellular vesicles, such as CD63, can reprogram target cells by altering cholesterol metabolism. However, there is still a lack of direct evidence regarding the precise regulatory impact of extracellular vesicles on cancer growth. The communication mechanism of extracellular vesicles needs further clarification, and their exact role in the early diagnosis and treatment of cancer deserves comprehensive investigation (6). Consequently, this review provides a succinct depiction of exosome structure, examines the mechanisms through which exosomes regulate cancers, and evaluates the advancements made in utilizing exosomes for the early detection and treatment of cancers.

EVs secreted by cells can be broadly categorized into two types: ectosomes and exosomes. Ectosomes are vesicles released directly from the plasma membrane, ranging in diameter from 50 nm to 1 μm (7). EVs exhibit clear heterogeneity and can be roughly categorized into exosomes microvesicles and apoptotic bodies, with significant differences in size, function, and formation processes (8). Apoptotic bodies have the largest size, approximately 1000nm, and are vesicular structures containing DNA and cellular organelles formed during the process of cell apoptosis through cell membrane wrinkling and invagination (9). The diameter of microvesicles has a wide range of limitations and the mainstream view is that the diameter should be between 50-1000 nm (10). They are composed of an outer membrane with a lipid bilayer structure and various bioactive molecules, and play a role in disease diagnosis, cell communication, and microenvironment modulation (11). Exosomes are EVs with a smaller diameter and a microvesicle-like structure, which participate in cellular communication by carrying nucleic acids, proteins, metabolites, etc (12).

This review centers on exosomes, which derive from the endosomal pathway and typically exhibit a narrow diameter range of approximately 40-160 nm ( Figure 1 ) (13). Exosomes possess an outer layer consisting of a double lipid membrane and exhibit a density ranging from 1.13 to 1.19 g/ml (14). In an aqueous environment, they display an almost perfectly spherical structure; however, upon desiccation, they assume a distinctive cup-shaped morphology (15). Internally, exosomes are enriched with cholesterol and a diverse array of proteins (16). Initially characterized as cellular “garbage bags” replete with discarded cellular components, exosomes gained recognition in the 1990s for their role in B cell antigen presentation, prompting a reassessment of their significance in intercellular communication (17). Recent research has unveiled that cancer cells release exosomes containing cancer-specific molecules to engage in intercellular communication, a process intricately linked to cancer progression.

The movement of exosomes within the extracellular space plays a crucial role in mediating intercellular communication and is contingent upon the stability of the bilateral lipid layer structure of exosomes (18). Once exosomes are released into the extracellular milieu, only a fraction of their structure remains intact for a brief period (19). These exosomes have the capacity to promptly discharge bioactive molecules they encapsulate, including interleukin, transforming growth factor-β (TGF-β), vascular endothelial growth factor(VEGF), among others, which can bind to neighboring cells through specific receptors, facilitating intercellular communication (20). The outer membrane of most exosomes exhibits resistance to rupture due to the presence of various enzymatically active surface components acquired during intracellular modification (21). Consequently, these exosomes can traverse intercellular or bodily fluids to reach proximal or distal cells. This distinctive biological trait of exosomes implies their potential profound involvement in cancer progression.

The biological functionality of exosomes predominantly relies on the transportation of their bioactive contents. In this section, we will elaborate on the various biological roles of distinct exosome types in Oral Squamous Cell Carcinoma (OSCC) based on their diverse contents.

The detection of exosomes in OSCC harbors substantial potential in cancer diagnosis. In a systematic analysis conducted by Sahu et al. (56), it was concluded that various biomarkers including human papillomavirus type 16 protein E7 (HPV-16-E7), Mucin 16, signal-regulatory-protein-α (SIRPA), annexin A1, phosphorylated epidermal growth factor receptor antibody (phospho-EGFR) and heat shock protein 90 (HSP90) serve as promising early diagnostic indicators for OSCC, offering significant enhancements in patient prognosis. Kisho et.al (57) has found that knocking down HSP90 can effectively inhibit lymphatic metastasis in OSCC, and detecting HSP90 can effectively determine the presence of lymphatic metastasis in OSCC. The transmembrane glycoprotein SIRPA can induce heterotrimeric G protein signaling by interacting with integrins of the β1, β2, and β3 families, promoting the evasion of OSCC from macrophage phagocytosis, and has the potential to be used as a diagnostic marker (58). Utilizing body fluid biopsies to analyze exosome contents like miRNA, mRNA, and ncRNA for OSCC screening presents advantages such as cost reduction, minimal invasiveness, and early detection (59).

The composition of exosomes in the cancer microenvironment exhibited significant variations across distinct stages of OSCC (60). Investigating the exosome content profiles in OSCC, the disease progression statuses, and the potential targeted therapeutic approaches holds theoretical promise. Regrettably, owing to the current deficiency in detection techniques, the limited understanding of exosome subtypes, and the incomplete comprehension of OSCC pathogenesis, this framework remains purely theoretical, necessitating further empirical validation.

Prognostic assessment is another important application of exosome testing in diagnosis. Detecting the contents of exosomes in OSCC also aids in assessing the prognosis of cancer patients (61). Chen et al. (62) observed that up-regulation of miRNA-155 and miRNA-21 in exosomes corresponded with a significant down-regulation of gene of phosphate and tension homology deleted on chromosome ten (PTEN) and B-cell CLL/lymphoma 6 (Bcl-6) expression in OSCC, indicating heightened proliferative activity and invasion potential in the cancer. MiR-21, which is transported by exosomes, can target PTEN and programmed cell death 4 (PDCD4) proteins by reprogramming the NF-κB pathway in OSCC cells, conferring cisplatin-resistance in OSCC cells (63). Patients with high miR-21 expression may have a less favorable prognosis. Pang et al. (64) demonstrated that elevated levels of CKLF-like MARVEL transmembrane domain-containing 6 in exosomes were associated with a notably poorer prognosis in OSCC.

Some of the exosome tumor diagnosis tests have entered the clinical trial stage. Krug utilizes the changes in exoRNA from the peripheral exosomes to diagnose nonsmall-cell-lung-cancer with a sensitivity of 98% using epidermal growth factor receptor (EGFR) mutations (65). Lee (66) extracted extracellular vesicles from 310 urine samples and amplified the extracellular vesicle miRNA cDCA library using RT-PCR and qPCR were used to measure the content of bkv-miR-B1-5p, achieving positive results in the assessment of immunologic risk and tolerance in kidney transplantation (ARKTK). However, clinical trials using exosomes and related assays for the diagnosis of OSCC have not been reported.

Currently, utilizing exosomes for diagnosing OSCC offers several advantages over traditional pathological biopsy methods: (i) Exosome-based diagnosis requires only a small sample, enabling the assessment of OSCC with minimal specimen sizes following a straightforward extraction and purification process (67); (ii) Exosomes exhibit high sensitivity, directly interacting with cancer cells to provide immediate feedback on the current state of OSCC development (61); (iii) Advancements in detection technologies and theoretical understanding enhance the potential application of exosome-based diagnostics for early detection and grading of OSCC (68). The team led by LEE (66)has successfully utilized urinary exosomes to detect whether the BK virus (BKV) has recurred, thereby assessing the risk of tumors after kidney transplantation. This demonstrates the potential clinical application of exosomes. Despite the numerous benefits of exosome-based OSCC diagnosis, its diagnostic accuracy still lags behind that of tissue biopsy, conventionally regarded as the gold standard for OSCC diagnosis (59). Cheng et al. (69) found in diagnostic testing for high-risk ground-glass opacities in the lungs that exosome testing detected 9 out of 10 cases, while immunohistochemistry achieved a detection rate of 100%. The reason for the problem is insufficient technology in the extraction, classification, and purification of exosomes (70). Microfluidic-based exosome isolation technology uses an automated centrifugal microfluidic disc system with functionalized membranes to concentrate and collect exosomes in as rapid as 8 minutes (71). Unfortunately, the integration of the concentration, purification, and identification steps in this plan has not yet been achieved. Further research and evidence are still required for clinical translation (71). Unfortunately, there have been no reported specific methods for isolating OSCC tumor-derived extracellular vesicles at present.

In conclusion, further refinement of detection techniques is essential for the diagnostic strategy involving exosome-related OSCC, along with the accumulation of additional clinical evidence to support these methods. These investigations remain focal areas in the field of exosome-related OSCC diagnosis.

Exosomes possess significant potential for cancer therapy owing to their excellent biosafety profile and effective delivery capabilities. In the realm of cancer treatment, exosomes can be categorized into artificially modified exosomes and naive exosomes based on their characteristics (72). Naive exosomes, extracted unaltered from cells in vivo, harbor bioactive molecules from their cellular source and demonstrate therapeutic efficacy accordingly (73). Modified exosomes are typically generated through two primary methods: (i) Genetic engineering techniques are employed to induce low or high expression of specific proteins/nucleic acids in secretory cells, yielding modified exosomes (74). (ii) Exogenous nucleic acids or nanoparticles are introduced into exosomes via processes such as electroporation, liposome transfection, or ultrasound (75). Modified exosomes, in contrast to naive exosomes, exhibit enhanced therapeutic potential due to their richer cargo of bioactive molecules (72).

Currently, several clinical trials investigating exosome-based therapeutics are in progress. For instance, mesenchymal stem cell-derived exosomes are being explored for the treatment of conditions such as diabetes mellitus (NCT02138331), lymphoma (NCT04223622), osteoarthritis (NCT04223622), Alzheimer’s disease (NCT04388982), and ischemic stroke (NCT02458755) (62, 76). Despite these advancements, the efficacy of exosome-based drugs in managing OSCC remains uncertain. This review aims to delve into the effects and underlying mechanisms of exosome-related therapeutics in OSCC treatment.

Although the potential application of exosomes in OSCC diagnosis and treatment holds promise, there are several associated challenges. One such challenge pertains to isolation and purification of exosomes. Being minute, membrane-bound vesicles that can be difficult to isolate and purify from other EVs and contaminants in biological fluids. The methods employed for isolation and purification can significantly impact the purity, and quality of exosomes, which affects their therapeutic efficacy. Therefore, standardized isolation and purification protocols need to be developed to ensure consistent and reproducible results (33).

Another challenge is the scalability of exosome production. Exosomes are typically produced in small quantities, and the process of isolating and purifying exosomes can be time-consuming and costly. To facilitate the clinical utilization of exosomes, it is crucial to devise scalable production techniques capable of generating substantial quantities of exosomes cost-effectively.

Furthermore, the safety of exosome-based therapy necessitates thorough evaluation. While exosomes have exhibited good tolerance in animal trials, the enduring impacts of exosome therapy on human well-being remain inadequately elucidated. Moreover, the probability of off-target repercussions and inadvertent outcomes stemming from exosome treatment demands meticulous scrutiny.

Finally, the regulatory framework for exosome-based therapies in OSCC is still evolving. Exosomes are considered biological products by regulatory agencies, such as the U.S. Food and Drug Administration (FDA), and their clinical use is subject to regulation and approval. Therefore, establishing a regulatory pathway for the development and approval of exosome-based therapies in dental medicine is important.

In general, challenges related to the utilization of exosomes in OSCC diagnosis and treatment encompass isolation and purification, scalability, safety, and regulatory aspects. Effectively tackling these challenges will be vital in unlocking the complete therapeutic potential of exosomes within the realm of dental medicine.