CST6 and skin squamous cell carcinoma: Contrariwise, proteome profiling of primary and metastatic cSCC lesions by mass spectrometry-based proteomics demonstrated a decrease in cystatin M/E in metastatic cSCC lesions relative to the primary phenotypes (fold change = −3.9), and the authors suggested that cSCC metastasis may be partly attributed to the decreased level of cystatin M/E in metastatic lesion phenotype [106].