Introduction
HNSC are a group of cancers that arise in the mucosal linings of the upper aerodigestive tract, which have an incidence of approximately 600,000 new cases worldwide per year and ranks the 6th most common cancer worldwide [
1‐
3]. Epidemiological evidence indicates that HNSC predominantly affects males and has a fatal outcome in approximately 51% of cases [
4]. The management of HNSC typically involves a combination of modalities, including surgical resection, induction chemotherapy, radiotherapy, or a combination of radiotherapy and concurrent chemotherapy, depending on the stage of the disease [
5]. Despite the combination therapy approaches available for HNSC, cancers in the head and neck region often exhibit aggressive behavior and are known to poorly respond to both irradiation and chemotherapy. Therefore, patients with locally advanced HNSC typically have a 5-year survival rate of only 50% with the current standard treatment of concurrent chemoradiotherapy [
6]. With the improvement of current treatments, the prognosis of head and neck squamous cell carcinoma remains unfavorable. Therefore, novel targeted drugs or other small-molecule–based strategies to the current treatment regimen is eagerly awaited.
The main risk factors associated with the development of HNSCs include tobacco use, excessive alcohol consumption, and infection with oncogenic viruses, such as human papillomavirus (HPV) [
7]. It is well known that Chronic usage of tobacco and alcohol has a synergistic effect in disrupting the oral mucosa structure, causing epithelial lesions [
8]. Alcohol causes oral epithelial atrophy by interfering with the lipid’s composition of the epithelial layer, hence leading to damage in the DNA synthesis and repair processes, thus contributes to the development of HNSC [
4]. While tobacco and alcohol were historically the risk factors for HNSCs, more recently, the proportion of HPV-positive (HPV+) HNSC is projected to become the most common form of head and neck cancer in many developed countries [
9]. Which may contribute to different social norms and sexual activities. In the United States, for example, approximately 70% of all oropharyngeal cancers are attributable to HPV [
10]. Studies showed that HNSC represent a heterogeneous disease that consists of two clinically distinct entities distinguished by HPV infection [
11], showing significantly different survival outcomes and pathway activity [
12].
Early studies revealed that Tumor-infiltrating lymphocytes (TILs) have been shown to affect cancer prognosis, and the presence of TIL is associated with improved survival which is increasingly recognized as an important biomarker in [
13,
14]. The presence of an inflammatory infiltrate composed of CD8-positive T lymphocytes correlates with improved outcomes in HNSC and this phenomenon may develop because the infiltrated CD8 lymphocytes in the local inflammatory may be available to combat the tumor [
15,
16]. Moreover, a higher number of TILs, in particular CD8+ T cells in carcinomas of the head and neck has often been found in HPV+ tumor and stroma, which collectively tend to have a better prognosis than HPV-negative tumors [
16‐
18]. Besides, their function and location of the TILs in the microenvironment appear important and may differ by tumor site and extent in HNSC [
19].
In the past decades, little progress has been made in understanding the biological foundation of HNSC, which has significantly hindered the development of more effective treatments. As a result, there is a critical need for novel therapeutic approaches, predictive marker models, and drug delivery systems that can advance the development of effective treatments for HNSC [
4]. Indeed, the identification and analysis of genetic aberrations in HNSC samples provide an opportunity for breakthroughs in the development of effective treatments. Oral squamous cell carcinoma, like other head and neck cancers, exhibits a high degree of intratumor heterogeneity, which significantly complicates individualized treatment and directly affects prognosis. Multi-OMICs approaches, which integrate data from DNA mutations, transcriptome, and proteome, have improved our understanding of the molecular mechanisms underlying HNSC and revealed a high degree of inter- and intratumor heterogeneity. Single-cell sequencing techniques have also uncovered RNA-expression signatures related to cell cycle, cell stress, hypoxia, and epithelial differentiation, among others. These findings hold significant promise for advancing the development of novel, more effective treatments for HNSC [
20]. For example, studies showed that oral squamous cell carcinoma can be divided into distinct subtypes and these have a preferential response to different types of therapies, suggesting that these gene-based molecular subtype could have clinical implications. Several genes have been found to be involved in the progression of HNSC, however, the role of MYO5A in HNSC remained unclear. Previous studies found that MYO5A mediates melanosome transport and the transport of vesicles to the plasma membrane [
21,
22]. In the current study, we examined the expression pattern and functional role of MYO5A by novel bioinformatic data analysis methods and further analyzed the diagnostic and prognostic significance of MYO5A in HNSC tumorigenesis.
Discussion
This study observed that the inhibition of MYO5A genes resulted in the significant inhibition of cell migration and invasion of FaDu cells. Furthermore, vimentin expression was observed to be downregulated upon MYO5A knockdown. Known for its ability to regulate cytoskeletal organization in various cancer cell types, including HNSC, vimentin is an important protein in tumor invasion and migration. Changes in vimentin expression potentially reflect the molecular mechanisms that play a role in the migration and invasiveness of FaDu cells. The findings suggest that MYO5A perhaps suppresses the migration and invasion of HNSC cells by indirectly downregulating vimentin in vitro.
This study conducted a Kaplan-Meier survival analysis, which demonstrated a statistically significant shorter survival rate in the MYO5A-high group, as compared to the MYO5A-low group, in HPV-positive HNSC samples. Furthermore, we defined MYO5A as a risky gene (HR =1.81,
P < 0.006) for HPV-positive HNSC samples, after employing Cox proportional hazard model analysis of MYO5A in HNSC. Previous studies showed that HNSC represent a heterogeneous disease that consists of two clinically distinct entities distinguished by HPV infection [
11] and the mutational makeup of HPV+ and HPV- HNSC differs significantly [
35]. These findings suggest that MYO5A may be responsible for some of the variance and may trigger a worse prognosis in HPV+ HNSC. Enrichment analysis indicated that MYO5A had a correlation with HPV. We also observed an overexpression of MYO5A in HPV+ HNSC with metastasis, when compared to none-metastatic cases. Taken together, these results indicate that MYO5A likely plays a role in HPV infection and progression of HPV+ HNSC. However, the direct impact of MYO5A genes on HPV infection will require further exploration. p16/CDKN2A is a surrogate marker for HPV infection and is overexpressed when the E7 protein binds to pRb, thereby releasing the E2F transcription factor in HPV-infected cells [
36]. In KEYNOTE-012, for the head-and-neck cohorts, when stratified by p16 status, response rates were higher in p16 + patients compared to p16- patients, with demonstrated ORRs of 24% (95% CI, 13–40%) and 16% (95% CI, 10–23) respectively [
37,
38]. These results insist that certain HPV-related biomarkers may have a crucial role in predicting prognosis and stratifying patients for adjuvant treatment in HNSC. Considering the aberrant oncogenic potential of HPV (low-risk and high-risk types), the description of HPV genotype variants could also be of interest.
Interestingly, studies revealed a higher number of TILs, in particular CD8+ T cells in HPV+ HNSC tumor, which collectively tend to have a better prognosis than HPV-negative tumors [
16‐
18]. We observed that patients with high MYO5A expression had reduced immune cell infiltration, especially CD8+ T cells and B cells, as well as a concomitant decrease in immunostimulators in HNSC. Research has shown that the microenvironmental characteristics influence the response to immunotherapy. For instance, treatment with checkpoint inhibitory drugs, such as PD-1, may have more effectiveness in tumors with a more pronounced lymphocytic infiltrate [
39]. More recently, with the approval of checkpoint inhibitors for the treatment of cancers including oral squamous cell carcinoma(OSCC), genomics studies also dissected the genetic signatures of the immune compartment to delineate immune-active and -exhausted subtypes and guide the development of novel therapies to improve response to immunotherapy [
40]. Research is also investigating innovative therapeutic approaches, such as gene therapy, and immunotherapy [
4]. New targets is being explored, involved in the way how tumor cells interact with stroma cells and the immune cells [
41]. The above results suggested that MYO5A may exert a specific function in immune infiltration of HNSC. and may hamper the efficacy of immunotherapy.
This study proposes differential expression and the promoting effect of MYO5A on the migration and invasion of HNSC, but it has some limitations that need addressing. Firstly, some bioinformatics analyses based on TCGA database have not yet been verified by other independent databases. Nonetheless, we verified some of the results with our molecular biology experiments to strengthen the validity of our findings. Secondly, this study primarily focused on correlation analysis, and biostatistical correlations alone cannot elucidate direct interactions and regulatory mechanisms. As a result, our future experiments aim to explore the interactions of various molecules in HNSC and understand the potential mechanisms.
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