In the present study, we conducted a comprehensive bioinformatics analysis to identify MYSM1 as a potential predictive biomarker for the prognosis of HNSC. MYSM1 was positively correlated with immune cells infiltration of CD8 + T cells, Th1 cells, DCs, Macrophage and Treg cells. And the specific mechanism of MYSM1 regulating immune infiltration may be involved in the PD-L1 expression and PD-1 checkpoint pathway in cancer and TNF signaling pathway. In addition, we found MYSM1 expression was correlated with m6A RNA methylation.
MYSM1, one of the histone H2A deubiquitination enzymes, plays a pivotal role in the development and functions of various cells. Over the past decade, researchers have provided MYSM1 as a critical transcriptional regulator of immune cell development and hematopoiesis. The recently discovered role of MYSM1 are focused on its regulation of signal transduction in innate immunity and a few cancers. However, except for recent insightful discovers, functions and mechanisms of MYSM1 beyond hematopoiesis and immunity remain poorly clarified yet. This study is the first to explore MYSM1 expression levels by comprehensive bioinformatics analysis, and to explore the prognostic value, effects on immune cells, and m6A methylation regulators in HNSC prognosis. We obtained the gene expression profiles of MYSM1 and clinical data from Oncomine database. We observed the variations of MYSM1 expression in different cancer types, and high expression of MYSM1 correlates with favorable prognosis in HNSC and BRCA. Interestingly, the expression of MYSM1 was highly expressed in metastatic SKCM compared to SKCM, indicating that MYSM1 may be used as a predictor for tumor metastasis. Our results also showed that high levels of MYSM1 expression associated with high risk of recurrence in patient survival. Functional enrichment analysis co-regulatory proteins with MYSM1 in the PPI network, and data from online database identify the hallmark pathways of HNSC carcinogenesis-related.
The tumor-infiltrating immune cells play a pivotal role in tumor progression[26]. Due to the complexity of immune cells activity and tumor heterogeneity. The main methods for analyzing tumor-infiltrating immune cells are immunohistochemistry and flow cytometry[27]. However, the evaluation of immune cells by these methods are vary depending on the cell types, number of tumor tissue and the observer. The bioinformatics analysis applied to gene expression profile of tumors provides an alternative option for evaluating immune cell status in tumor tissues[28]. Despite the treatment and prognosis prediction have been improved in HNSC, it remains with high mortality rates and limitation of immunotherapy. Due to the poor mortality of HNSC, it is necessary to explore prognostic biomarkers for patients in order to choose appropriate treatment-strategy, including immunotherapy. In this study, we established an integration analysis to quantity the tumor immune milieu in HNSC, and the outcome of our study indicated that MYSM1 expression was significantly correlated with immune cell markers and immune cell infiltration levels in different manners, which proved that MYSM1 played a pivotal role in tumor immune escape and explained the difference in survival. Besides, this difference may be ascribe to the different enrichment patterns of MYSM1 in tumor microenvironment (TME). TME is composed of heterogeneous populations of cells, including malignant and non-malignant cells, which may support tumor cell proliferation, invasion and metastasis through extensive crosstalk[29]. Intra-tumor immune landscape is a key factor affecting patient survival. To improve the efficiency of immunotherapy, it is firstly to determine immune-associated prognostic biomarkers. According to our results, higher expression of MYSM1 in HNSC predicted a better survival. However, the association between MYSM1 expression in tissues and patients overall survival need to be further studied. Previous study indicated that MYSM1−/− macrophages increased the production of pro-inflammatory cytokines, cell proliferation, induced apoptosis and enhanced melanoma tumor growth[15]. Consistent with the above result, we found that macrophages are the most principal infiltrating immune cells in HNSC. Further analysis such as signal-cell sequencing and the cellular and molecular mechanism need to be further clarified. It was reported that TNF family Fas signaling pathway could promote terminal differentiation of CD8+ T and CD4+ T cells, while non-apoptotic Fas induce tumor cell proliferation and impair the efficacy of T cell adoptive immunotherapy[30]. PD-1 was reported to be significantly correlated with better OS and DFS in Ren et al.’s study[31]. MYSM1 is involved in the TNF signaling pathway and PD-L1 expression and PD-1 checkpoint pathway in cancer. Therefore, our study provides insights into understanding the potential role of MYSM1 in tumor immunology and its use as a cancer biomarker.
Recent years, m6A modification has been recognized as a trigger of cancer biology and becoming the focus of research. However, the involvement of m6A regulators in progression of HNSC remains unexplored. In this study, we reported for the first time that MYSM1 expression was correlated with 9 of m6A RNA regulators in HNSC, including HNRNPA2B1, METTL14, IGF2BP2, RBM14, VIRMA, YTHDC1, YTHDC2, YTHDF3 and ZC3H13. We also found that the levels of HNRNPA2B1, METTL14, RBM14, VIRMA, YTHDC1, YTHDC2, YTHDF3, ZC3H13, METTL3, RBM15B, WTAP, RBMX, YTHDF1, and YTHDF2 increased in MYSM1 high expression group. However, there are still some limitations in our study. Clinical analysis with large samples are required to verify our predictive value of MYSM1. The molecular mechanisms and cellular functions of MYSM1 in HNSC are warrant for subsequent experimental verification work. As a biomarker candidate, MYSM1 should be evaluated in the context of HNSC immunotherapy. Further analysis is required to investigate the detailed mechanism between MYSM1 expression and carcinogenesis of HNSC and other carcinomas.
In summary, by using integrated bioinformatics analysis, this is the first comprehensive study to identify MYSM1 expression with survival, immune cell infiltration levels and m6A modification in HNSC. Our study provide a new and promising insight for subsequent research to elucidate the molecular mechanisms of HNSC progression. MYSM1 may be considered as an effective biomarker for predicting prognosis and treatment of HNSC.