Bioinformatics analysis of gene expression alterations conferring drug resistance in tumor samples from melanoma patients with EGFR-activating mutations.

Melanoma is a highly malignant tumor of the skin melanocytes. Patients with this cancer have a high frequency (~50%) of oncogenic mutations, particularly BRAF V600E. Treatments for melanoma often target mutations or involve mitogen-activated protein kinase kinase/extracellular signal-regulated kinase inhibitors. A major challenge in melanoma treatment is resistance to inhibitor treatment, which may be enhanced by the mutation itself and/or epidermal growth factor receptor (EGFR) activation, leading to poor prognosis. However, no effective clinical treatment exists for patients with EGFR-activating feedback. The aim of the present study was to analyze gene expression changes in tumors from patients with EGFR-activating mutations during development of drug resistance. RNA-seq data was downloaded from the Gene Expression Omnibus (GEO) database for pre- and post-treatment tumor samples from three melanoma patients with EGFR-activating BRAF V600E mutations, and from The Cancer Genome Atlas (TCGA) melanoma database for tumor and non-tumor samples from patients with the BRAF V600E mutation and unknown EGFR activation status. Using functional enrichment and KEGG pathway analyses, the present study analyzed differentially expressed genes (DEGs) between pre- vs. post-treatment data from the GEO database and tumor or non-tumor sample data from the TCGA database. The results of the present study indicated that functional and structural changes to the plasma membrane may be associated with drug resistance. The present study identified 9 DEGs that were significantly different between tumor and non-tumor samples and also between prior to and following treatment. Thus, it was confirmed that patients with EGFR-activating BRAF V600E mutations undergo gene expression changes during disease development, and during therapy. These findings may provide potential directions for melanoma-specific therapy.