Comprehensive Analysis Of M~5C Regulators Mediating Immune Cell Modification Patterns In Melanoma Tumor Microenvironment Infiltration

BackgroundSkin malignant melanoma is a highly malignant form of skin cancer that occurs as a result of the cancerous transformation of pigment-producing cells(melanocytes).If not detected and treated early,malignant melanoma can grow rapidly and spread to other parts of the body.If left unchecked,it can spread rapidly and become life-threatening.5-methylcytosine(m~5C)methylation,a novel post-transcriptional RNA regulatory modification,has been closely associated with the development of many cancers.However,the prognostic value of m5C regulatory genes in cutaneous malignant melanoma and the relevance of m5C methylation to the tumour microenvironment(TME)are unclear.MethodsWe downloaded m RNA expression profiles,copy number variation data,somatic mutation data and clinical characteristics data of all SKCM patients from The Cancer Genome Atlas(TCGA)database and collected 13 m~5C regulatory factors from previous studies.Based on the expression profiles of the 13 m~5C regulatory factors,we used the Consensus Cluster Plus algorithm to classify patients with cutaneous malignant melanoma into 3 clusters and analyzed the differences in molecular characteristics between the 3 clusters.The prognostic differences between the 3 m~5C clusters were assessed according to the K-M method,and differentially expressed genes(DEGs)between the 3 clusters were screened.Gene set variation analysis(GSVA)was used to investigate potential pathways associated with m~5C modification patterns.We used univariate COX regression for these DEGs to identify genes of prognostic significance among them.Using the expression levels of these prognostically relevant differentially expressed genes,a PCA algorithm was used to construct an m~5C score that represents the m5C modification pattern of each patient.For immunity,we applied multiple algorithms to assess the level of immune cell infiltration in the tumour microenvironment.We also used tumour mutational load to assess differences in mutations between patients with high m~5C scores and those with low m5C scores.We used tumour immune dysfunction and rejection(TIDE)prediction for treatment to assess the potential response to immune checkpoint blockade(ICB)therapy.The sensitivity of all SKCM patients to chemotherapeutic agents was calculated by the"p RRophetic"R package.ResultsWe found that four m5C regulators were expressed differently in different tumours and normal cells.The three m~5C subgroups we obtained exhibited different clinical manifestations and biological characteristics in cutaneous melanoma patients.The results showed that cluster A patients had a poorer prognosis among the 3 m~5C clusters we obtained,and cluster B patients had a higher degree of immune infiltration.We further made the principal component analysis(PCA)algorithm to establish the m~5C score and divided the patients into a high m~5C score group and the low m~5C score group.The results of the principal component analysis showed that patients with higher T-stage and higher clerk classification had higher m~5C scores.Patients in the high m~5C score group had a better prognosis and responded better to immune checkpoint blockade therapy.In addition,we observed significant differences in drug sensitivity between patients in the two m~5C score groups.We then further used the m~5C score and clinical characteristics of patients with cutaneous malignant melanoma to develop a model to predict overall patient survival at 1,5,and 10 years,and the receiver operating characteristic(ROC)curves showed that the model had good predictive power.ConclusionsThe m~5C modification of RNA plays an important role in the occurrence,development,tumour microenvironment formation,and gene mutation of cutaneous malignant melanoma.Significant differences exist in chemotherapy and immunotherapy responses as well as prognosis in patients with different m~5C modification patterns.Therefore,assessing the m~5C modification profile of clinical patients using our constructed m~5C score may help enhance our understanding of the characteristics of cutaneous malignant melanoma and further guide future clinical decisions.