Transcription-associated CDK7 promotes initiation and transcription by regulating eukaryotic translation initiation factors (eIFs) such as eIF4B and eIF5B, which promote cancer and immunosuppression.48,49 CDK13 directly phosphorylates eIF4B at S422 and promotes tumorigenesis.50 Our study showed that SP2509 treatment reduced the activities of eIF4B, eIF5B, and other initiation factors. This evidence concerns the gene CDK7 and cancer.