Expression patterns and the prognostic value of the SMYD family members in human breast carcinoma using integrative bioinformatics analysis

Suppressor of variegation, Enhancer of Zeste, Trithorax and Myeloid-Nervy-DEAF1 domain-containing (SMYD) proteins are a set of lysine methyltransferases involved in a range of diverse biological functions, including gene expression, and regulation of skeletal and cardiac-muscle development. These proteins may additionally serve roles in a number of different types of cancer. However, the roles of the five SMYD proteins, SMYD 1/2/3/4/5, their expression patterns and prognostic value remain unclear. In the present study, the transcriptional expression levels of the five SMYD proteins were compared with the survival data of patients with breast carcinoma (BC) from the ONCOMINE dataset, Breast Cancer Gene-Expression Miner v4.0, Kaplan-Meier Plotter, The Cancer Genome Atlas and cBioPortal. An increase in the SMYD2/3/5 mRNA expression levels and a decrease in SMYD1/4 mRNA expression levels in BC tissues compared with normal tissues were identified. Increased SMYD3 mRNA and decreased SMYD5 mRNA expression levels were associated with decreased levels of histological differentiation, according to the Scarff-Bloom-Richardson grading system. Kaplan-Meier curves demonstrated that the increased SMYD1/4 and decreased SMYD2/3 mRNA expression levels were associated with good relapse-free survival (RFS) in patients with BC. Furthermore, SMYD2 mRNA expression levels were associated with the RFS of patients with BC with metastatic relapse, and SMYD4 may serve as a tumor suppressor in patients with BC, as patients with increased SMYD4 mRNA expression levels had significantly better RFS compared with decreased SMYD4 mRNA expression levels. The present data suggested that SMYD2 and SMYD3 may be potential biomarkers for diagnosis of BC. Additionally, SMYD2 and SMYD4 may be potential prognostic indicators of patients with BC.