Diverse cardiac glycosides (CGs) and non-steroidal NKA inhibitors induce PML-NB formation.

<p><b>A,</b> Structures of diverse cardiac glycosides (CGs). All CGs share a common structural motif comprised of a steroidal core adorned with an unsaturated lactone at ring position 17. CG lactone head-groups come in two varieties, unsaturated butyrolactones, such as gitoxigenin, ouabain and uzarin, and α-pyrones such as proscillaridin A. With the exception of the aglycones (e.g. gitoxigenin), the core is double substituted to contain a sugar moiety at ring position 3. <b>B and C,</b> HeLa cells were treated with increasing concentrations of CGs for 18h. PML NB formation and cell count was determined as described in Materials and Methods. <b>D,</b> Structures of non-steroidal NKA inhibitors are shown. <b>E and F,</b> HeLa cells were treated with increasing concentrations of non-steroidal NKA inhibitors for 18h. PML NB formation and cell count was determined as described in Materials and Methods. The data are means of four replicates and the error bars are SEMs. PML NB values at high concentrations are shown with open symbols in B and E and are excluded from the fitted curve due to the cytotoxicity as evident from dramatic decrease in cell counts at these concentrations (C and F).