MCL1 and lymphoma: However, the lymphoma cells with upregulation of BCL-XL/A1 could be re-sensitised to apoptosis by co-inhibition of BCL-XL alongside MCL-1, illustrating that inhibition of compensatory, non-targeted pro-survival BCL-2 proteins is an effective therapeutic strategy to kill malignant cells that have become resistant to a particular BH3-mimetic drug.