Inhibition of oncogenic transcriptional programs is a promising therapeutic strategy. A substituted tricyclic benzimidazole, SEL120-34A, is a novel inhibitor of Cyclin-dependent kinase 8 (CDK8), which regulates transcription by associating with the Mediator complex. X-ray crystallography has shown SEL120-34A to be a type I inhibitor forming halogen bonds with the protein's hinge region and hydrophobic complementarities within its front pocket. SEL120-34A inhibits phosphorylation of STAT1 S727 and STAT5 S726 in cancer cells in vitro. Consistently, regulation of STATs- and NUP98-HOXA9- dependent transcription has been observed as a dominant mechanism of action in vivo. Treatment with the compound resulted in a differential efficacy on AML cells with elevated STAT5 S726 levels and stem cell characteristics. In contrast, resistant cells were negative for activated STAT5 and revealed lineage commitment. In vivo efficacy in xenotransplanted AML models correlated with significant repression of STAT5 S726. Favorable pharmacokinetics, confirmed safety and in vivo efficacy provide a rationale for the further clinical development of SEL120-34A as a personalized therapeutic approach in AML.

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In the present study, animals with a genetic defect in copper metabolism were used as a model organism to study the role of copper in reproduction and to determine whether the disturbances in copper and zinc metabolism affect the testicular tissue and gamete quality in males. Mice with an X-linked mosaic mutation (Atp7a(mo-ms)) exhibit pathological features characteristic of affected copper metabolism. This mutation usually leads to lethality of the mutant males which generally expire on about day 16. Only 4% of mutant animals survive the critical period, achieve maturity, and become fertile. To improve the mutants' viability they were treated with subcutaneous injections of cupric chloride. We measured copper and zinc concentration in the gonads of young (14-day-old) and adult (5-month-old) mutant and control males. Results indicate that copper content was increased but zinc was decreased in the mutant testes. Analysis of the morphology of the testis of the young animals indicate that apoptosis (characteristic for the gonads of young males) was increased in the gonads of the 14-day-old mutants. This process was less advanced in the group of 14-day-old copper treated control males. Apoptosis was also increased in the testes of the adult mutants. Moreover in adult mutants we observed pathological changes in testes morphology (atrophic and sclerotic tubules). Copper and zinc disorders also negatively influenced semen quality parameters, including sperm motility, head morphology, tail cytoplasmic membrane integrity, and number of viable spermatozoa. Poor semen quality of the mutant males seems to be responsible for affected in vivo fertilization efficiency. Treatment with cupric chloride did not influence semen quality except in maturation rate, which was even slower in both mutant and control males after treatment. Additionally, in mutants, copulatory plugs and fertile copulation outcome were decreased after copper treatment.