COPS5 and diffuse large B-cell lymphoma: Alternatively, given that DLBCL cells accumulates doxycycline to such high concentrations (Figure 6D), it may be possible that doxycycline acts in these cells through additional targets independent of CSN5, although our data are inconsistent with the idea that MMP inhibition is responsible for the growth inhibition by doxycycline in these cells (Supplementary Figure 2).