These data suggested that CDK12 enhanced CSC self\renewal in a HER2\independent manner in breast malignancy. Open in a separate window Figure 2 CDK12 regulates cancer stemness and response to trastuzumab therapy in HER2+ breast malignancy FACS analysis of the percentages of CD44+/CD24?/ESA+ breast CSC\like populations in CDK12\overexpressing ZR\75\30 and HCC\1419 cells and trastuzumab response of HER2+ breast cancer. due to its ability to regulate DNA damage repair in human cancers, but little is known about the role of CDK12 in driving tumorigenesis. Here, we demonstrate that CDK12 promotes tumor initiation as a novel regulator of cancer stem cells (CSCs) and induces anti\HER2 therapy resistance in human breast cancer. High CDK12 expression caused by concurrent amplification of and in breast cancer patients is usually associated with disease recurrence and poor survival. CDK12 induces self\renewal of breast CSCs and tumor\initiating ability, and also reduces susceptibility to trastuzumab. Furthermore, CDK12 kinase activity inhibition facilitates anticancer efficacy of trastuzumab in HER2+ tumors, and mice bearing trastuzumab\resistant HER2+ tumor show sensitivity to an inhibitor of CDK12. Mechanistically, the catalytic activity of CDK12 is required for the expression of genes involved in the activation of ErbB\PI3K\AKT or WNT\signaling cascades. These results suggest that CDK12 is usually a major oncogenic driver and an actionable target for HER2+ breast cancer to replace or augment current anti\HER2 therapies. amplification or overexpression, accounts for 15C20% of all breast cancers, is usually clinically defined as a distinct subtype of breast cancer that benefits from anti\HER2 therapies 1, 2. INHA Trastuzumab, the first approved anti\HER2 monoclonal antibody, is the most commonly used drug in the world as a standard regimen for HER2+ breast malignancy patients 3, 4. However, accumulating clinical evidence reveals that this response of HER2+ breast cancers to trastuzumab therapy varies widely 4, with Avoralstat ?50% of patients either not responding or acquiring resistance to trastuzumab 5, 6, 7. Recent large\scale whole\genome sequencing and transcriptome analysis of HER2+ breast cancer showed that it comprises several subgroups exhibiting different gene expression and distinct genomic features 8. Furthermore, this genomic heterogeneity causes a variety of responses to HER2\targeted therapies 4, 9, 10. Although the abnormalities in chromosome 17 (chr17) that cause amplification are among the most representative characteristics of HER2+ breast malignancy 1, 2, 11, it remains largely unknown whether genes co\amplified with at chr17 play a key role in driving tumorigenesis and serve as option therapeutic targets in HER2+ breast malignancy with anti\HER2 therapy. (through mutation, rearrangements, or amplification in various types of human tumors, including breast, Avoralstat ovarian, and prostate cancers 12, 19, 20, 21, 22. In large\scale screening of phosphoproteins, CDK12 has been nominated as a candidate of highly phosphorylated kinase related to breast malignancy 12, 23. Indeed, CDK12 was associated with aggressive phenotypes of breast cancer in clinical specimens 18, 24, and its kinase activity promoted increased the migration and invasion ability of breast malignancy cells mutation, CDK12 deficiency enhanced the sensitivity to olaparib, a poly (ADP\ribose) polymerase (PARP)1/2 inhibitor 25. Similarly, resistance to the PARP1/2 inhibitor was reversed by administration of dinaciclib, a pan\CDK inhibitor with potent activity against CDK12 and other CDKs, in triple\unfavorable breast malignancy (TNBC) 26. Despite the therapeutic potential of targeting CDK12 in human cancer, little is known about the putative role of CDK12 in driving tumor initiation and progression. In this study, we explored potential actionable targets among chr17q12 genes to improve current anti\HER2 therapy and found that CDK12 regulates cancer stem cell (CSC)\like properties to drive breast tumor initiation and induce trastuzumab resistance in a manner impartial on its ability to modulate DNA repair. Furthermore, we propose that CDK12 kinase inhibition represents a broadly effective therapy against different types of HER2+ breast cancers and could be a replacement therapy for trastuzumab in breast cancer treatment. Results and Discussion Chr17q12 encompasses genes with distinct clinical implications Growing evidence suggests that several genes co\amplified with can influence biological behavior of HER2+ breast malignancy, with co\silencing Avoralstat of these genes improving the growth\inhibitory effects of or apoptosis induction in HER2+ breast malignancy 11, 27. Moreover, higher levels of copy number alterations in chr17q12 were associated with non\responsiveness to anti\HER2 therapy 11. Despite the potential importance of 17q12\amplicon genes in breast cancer, the clinical relevance and functional significance of these genes remain largely unknown. To discover possible candidate drivers and druggable target genes, besides PGAP3TCAPGRB7STARD3PIP4K2Bamplification is usually a candidate of druggable target that is associated with poor prognosis in breast malignancy The schematic diagram showing the process to determine candidate target genes from chr17q12 amplicons in the METABRIC dataset. Forest plots display the hazard ratios of genes at the 17q12 amplicon according to the DFS (top right) and OS (bottom right) of breast cancer patients in the METABRIC dataset. Genes located at the amplicon were nominated according to hazard ratio levels (all co\amplification percentage of the indicated genes is usually represented as bar graphs (left). The frequency of amplification in and co\amplified cases among the patients with gene amplification (left)..
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