MARK2 and rheumatoid arthritis: To further investigate the clinical significance of MTOR, p21, MMP-9, and caspase 3 relative gene expression in whole blood from RA patients we analyzed the protein levels of phospho-p70-S6K serine/threonine kinase (a direct target for phosphorylation by mTOR [33, 34]), p21, MMP-9, and active caspase 3 in the PBMC fraction.