Therefore, future studies are needed before MDK is targeted therapeutically and, in our opinion, should focus on: (1) dissecting the effects of chronic increases in circulating and myocardial MDK, (2) investigating the off-target effects of therapeutic targeting of MDK in pathologies where inhibition of MDK is indicated (such as in cancer), (3) identifying how patient comorbidities and medications affect MDK. The gene discussed is MDK; the disease is cancer.