Abstract 1540
The PIM serine/threonine kinase family is composed of three highly homologous members; PIM1, PIM2 and PIM3, identified by the ability of the prototype member PIM1 to drive ...lymphomagenesis in mice. Upregulation of PIM1 and PIM2 is observed in leukemias and lymphomas, including AML, NHL and CLL, highlighting the potential of these kinases as therapeutic targets in these indications. PIMs are downstream effectors of many cytokine and growth factor signaling pathways and are direct transcriptional targets of STAT transcription factors activated by these pathways. PIMs can phosphorylate multiple substrates to mediate cell proliferation and survival. Here we describe the function of AZD1208, an orally available, potent and highly selective PIM inhibitor that effectively inhibits all three isoforms. AZD1208 inhibits the growth of several AML cell lines and sensitivity correlates with the level of PIM1 expression, STAT5 activation and presence of protein tyrosine kinase mutation. AZD1208 causes cell cycle arrest and apoptosis in MOLM-16 cells in culture. This is accompanied by a dose-dependent reduction in pBAD serine 112 and other substrates, as well as an increase in cleaved caspase 3. AZD1208 suppresses the growth of MOLM-16 and KG-1a xenograft tumors in vivo in a dose proportional manner. In addition, AZD1208 leads to potent inhibition of colony growth of primary AML cells from bone marrow aspirates and downregulates phosphorylation of PIM targets. These results underscore the therapeutic potential of PIM kinase inhibition by AZD1208 for the treatment of AML.
Keeton:AstraZeneca: Employment, Equity Ownership. Palakurthi:AstraZeneca: Employment, Equity Ownership. Alimzhanov:AstraZeneca: Employment, Equity Ownership. Grondine:AstraZeneca: Employment, Equity Ownership. Chen:AstraZeneca: Employment, Equity Ownership. Brown:AstraZeneca: Employment, Equity Ownership. McEachern:AstraZeneca: Employment, Equity Ownership. Cao:AstraZeneca: Employment, Equity Ownership. Chinnappan:AstraZeneca: Employment, Equity Ownership. Shen:AstraZeneca: Employment, Equity Ownership. Dakin:AstraZeneca: Employment, Equity Ownership. Zheng:AstraZeneca: Employment, Equity Ownership. Lamb:AstraZeneca: Employment, Equity Ownership. Wu:AstraZeneca: Employment, Equity Ownership. Chen:AstraZenenca: Employment, Equity Ownership. Lyne:AstraZeneca: Employment, Equity Ownership. Huszar:AstraZeneca: Employment, Equity Ownership.
BRCA1, a tumor suppressor protein, functions in DNA repair, cell cycle control, and transcriptional transactivation. The global changes in gene expression following the transient expression of the ...full-length and exon 11-deleted BRCA1 variants were evaluated by cDNA expression array in human non-tumorigenic mammary epithelial cells. Over 30 genes were identified that displayed an altered expression pattern following expression of BRCA1 splice variants. The loss of NFκB inducing kinase (NIK) expression in BRCA1L transfected cells was confirmed by Northern analysis. Rather than the loss of NIK correlating with a decrease in NFκB activity, a NFκB-responsive promoter was activated in BRCA1L expressing cells in the absence of stimulation and following TNF-α and lymphotoxin-β treatment. This activation by BRCA1L correlated with increased binding of nuclear proteins to the κB consensus site. The transcriptional activity of additional promoters was evaluated following expression of wild type and mutant BRCA1 constructs. Full-length BRCA1 transactivated the ERα and BCL2 promoters as well as AP-1, SRE, and CRE-responsive promoters. In parallel experiments, the exon 11-deleted variant, BRCA1s, exhibited a more restricted transactivation activity. Mutant BRCA1 variants retained wild type levels of transcriptional activity for the ERα-promoter as well as for the NFκB, and AP-1-responsive promoters but had reduced or no activity for the BCL2, SRE, and CRE promoters. These results show that BRCA1 isoforms have specific transcriptional transactivation functions, some of which are likely to mediate its role as a tumor suppressor in human mammary epithelial cells. The evidence for BRCA1's role in chromatin remodeling and histone deacetylation lead us to evaluate the level of CpG methylation in ERα-negative BRCA1-associated versus non BRCA1-associated primary breast cancers. Methylation of the ER promoter is associated with a significant portion of ERα-negative breast cancers. Given the high proportion of ERα-negative cancers among BRCA1 mutation carriers, we hypothesized that a difference in the level of methylation of the ERα promoter would exist between these two groups. Overall, we found an increase in methylation among BRCA1-associated cancers compared to non BRCA1-associated cancers. Specifically, we identified critical CpGs within the ERα promoter that may contribute to the ERα-negative phenotype seen in most BRCA1-associated cancers.
