MCF-7 cells are known to be defective in caspase-3 activity. Can I still use the Peviva M30 CytoDeath™ ELISA?

Yes, M30 CytoDeath™ ELISA can be used in cells lacking active caspase-3 as also other caspases, but no other proteases can generate the M30 neo-epitope. Apoptotic MCF-7 cells generate M30-activity due to activity of those other caspases.