CDK9-mediated transcription of several prosurvival and antiapoptotic proteins (e.g., c-Myc, Mcl-1 and survivin) plays an important role in the proliferation and apoptosis resistance of cancer cells [19, 20], and the aforementioned prosurvival and antiapoptotic proteins are also involved in the pathology of PH [21, 22]. Here, MCL1 is linked to cancer.