MSLN and mesothelioma: Mesothelioma biomarkers can be roughly divided into soluble glycoproteins (mesothelin, fibulin), genetic biomarkers (DNA markers, such as single nucleotide polymorphisms (SNPs), RNA expression levels, epigenetic biomarkers (DNA methylation, chromatin modifications, non-coding RNAs, such as microRNAs), and newly emerging proteomic biomarkers [5,6].