Fig. 1: Chemical biology screening identifies a vulnerability to CDK9 inhibition of CTCL.

a HH and Hut78 cells were treated with compounds (2 µM) from inhibitor library (L1200) and cell viability was evaluated using CCK8 assay after treatment for 48 hours. CDK Cyclin-dependent kinase, JAK/STAT Janus kinase-signal transducer and activator of transcription, PI3K Phosphoinositide 3-kinases, mTOR mammalian target of rapamycin complex. b The most effective kinase inhibitors (cell viability < 25%) identified from compound screening for HH and Hut78 cells. c Numbers of effective (red, cell viability < 25%) and ineffective (gray, cell viability\(\geq\)25%) CDK inhibitors from each different CDK subfamilies were shown. d IC₅₀ curve of five representative CDK9 inhibitors, AT7519, Dinaciclib, Flavopiridol, SNS-032 and P276-00 in HH and Hut78 cells. Cell viability was counted by trypan blue staining. Results represent biologically independent experiments of n  =  3. e–h Nude mice were subcutaneously injected with HH cells and randomly divided into Vehicle, Flavopiridol and SNS-032 groups (n = 8). Tumor volumes were measured at different time points (e, g). At 17 days after subcutaneous injection, tumors were harvested and weighed (f, h). i Western blot analysis of indicated proteins from Hut78 cells infected with lentivirus encompassing shNC, shCDK9-1 or shCDK9-2. j Growth curve of Hut78 cells upon CDK9 depletion. Cell number was counted by trypan blue. Experiments were performed in triplicate and repeated twice with similar results. k Western blot analysis of indicated proteins from HH cells infected with lentivirus encompassing shNC, shCDK9-1, or shCDK9-2. l Growth curve of HH cells upon CDK9 depletion. Cell number was counted by trypan blue. Experiments were performed in triplicate and repeated twice with similar results. m, n HH cells were infected with shNC, shCDK9-1, or shCDK9-2 lentiviruses, and subcutaneously injected into nude mice (n = 6). Tumor volumes were measured at different time points (m). At 12 days after subcutaneous injection, tumors were harvested and weighed (n). Data are presented as mean ± SEM. Unpaired, two-tailed Student’s t-test. Source data are provided as a Source Data file. i, k n = 3, independent experiments, a representative example is shown. The samples derive from the same experiment each but different gels for CDK9 and another for β-actin were processed in parallel. Band intensities were analyzed and compared using Image J. Relative densitometric values are provided below the blot images.