Sir,
We would like to congratulate Völler et al (2013) on their recent study showing an unchanged mRNA AGO2 expression in melanoma and a strong reduction of AGO2 expression on protein level. This goes along with the findings in our study on the miRNA processing machinery performed in melanoma, which likewise has previously shown an unchanged mRNA AGO2 expression level in melanoma (Sand et al, 2012c). Interestingly, in contrast to melanoma skin cancer, mRNA AGO2 expression levels in epithelial skin cancer (both cutaneous squamous cell and basal cell carcinoma) were significantly higher (P<0.05) compared with healthy controls (Sand et al, 2010, 2012a, 2012b). Although we do agree with the authors that a deregulation of microRNA (miRNA) was observed in several types of cancer and particularly in skin cancer, with reference to our previous studies we do not agree that changes in the miRNA processing enzymes have not been analysed until today as stated in their abstract (Sand et al, 2009, 2011, 2012d, 2012e, 2013; 2014; Sand and Skrygan, 2014).
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