Amongst 26 primary ovarian cancer patient samples (serous-20, squamous-1, high-grade serous-1, endometroid-1, transitional cell-1, endometroid and serous-1 and endometroid and clear cell-1), Wang et al. had shown significantly lower CDK9 expression in primary cancer tissues than patient-paired metastatic and recurrent cancer tissues. Here, CDK9 is linked to cancer.