PERIOD phosphorylation leads to feedback inhibition of CK1 activity to control circadian period.

PERIOD (PER) and Casein Kinase 1δ regulate circadian rhythms through a phosphoswitch that controls PER stability and repressive activity in the molecular clock. CK1δ phosphorylation of the familial advanced sleep phase (FASP) serine cluster embedded within the Casein Kinase 1 binding domain (CK1BD) of mammalian PER1/2 inhibits its activity on phosphodegrons to stabilize PER and extend circadian period. Here, we show that the phosphorylated FASP region (pFASP) of PER2 directly interacts with and inhibits CK1δ. Co-crystal structures in conjunction with molecular dynamics simulations reveal how pFASP phosphoserines dock into conserved anion binding sites near the active site of CK1δ. Limiting phosphorylation of the FASP serine cluster reduces product inhibition, decreasing PER2 stability and shortening circadian period in human cells. We found that Drosophila PER also regulates CK1δ via feedback inhibition through the phosphorylated PER-Short domain, revealing a conserved mechanism by which PER phosphorylation near the CK1BD regulates CK1 kinase activity.

Defining the susceptibility of colorectal cancers to BH3-mimetic compounds.

Novel targets are required to improve the outcomes for patients with colorectal cancers. In this regard, the selective inhibitor of the pro-survival protein BCL2, venetoclax, has proven highly effective in several hematological malignancies. In addition to BCL2, potent and highly selective small molecule inhibitors of its relatives, BCLxL and MCL1, are now available, prompting us to investigate the susceptibility of colorectal cancers to the inhibition of one or more of these pro-survival proteins. While targeting BCLxL, but not BCL2 or MCL1, on its own had some impact, most (15/17) of the immortalized colorectal cancer cell lines studied were efficiently killed by the combined targeting of BCLxL and MCL1. Importantly, these in vitro findings were confirmed in a xenograft model and, interestingly, in all (5/5) patient derived tumor organoids evaluated. Our results lend strong support to the notion that BCLxL and MCL1 are highly promising targets for further evaluation in efforts to improve the treatment of colorectal cancers.

IMiDs prime myeloma cells for daratumumab-mediated cytotoxicity through loss of Ikaros and Aiolos.

Recent studies have demonstrated that the immunomodulatory drugs (IMiDs) lead to the degradation of the transcription factors Ikaros and Aiolos. However, why their loss subsequently leads to multiple myeloma (MM) cell death remains unclear. Using CRISPR-Cas9 genome editing, we have deleted IKZF1/Ikaros and IKZF3/Aiolos in human MM cell lines to gain further insight into their downstream gene regulatory networks. Inactivation of either factor alone recapitulates the cell intrinsic action of the IMiDs, resulting in cell cycle arrest and induction of apoptosis. Furthermore, evaluation of the transcriptional changes resulting from their loss demonstrates striking overlap with lenalidomide treatment. This was not dependent on reduction of the IRF4-MYC "axis," as neither protein was consistently downregulated, despite cell death occurring, and overexpression of either factor failed to rescue for Ikaros loss. Importantly, Ikaros and Aiolos repress the expression of interferon-stimulated genes (ISGs), including CD38, and their loss led to the activation of an interferon-like response, contributing to MM cell death. Ikaros/Aiolos repressed CD38 expression through interaction with the nucleosome remodeling and deacetylase complex in MM. IMiD-induced loss of Ikaros or treatment with interferon resulted in an upregulation of CD38 surface expression on MM cells, priming for daratumumab-induced NK cell-mediated antibody-dependent cellular cytotoxicity. These results give further insight into the mechanism of action of the IMiDs and provide mechanistic rationale for combination with anti-CD38 monoclonal antibodies.

Discovery and SAR of novel pyrazolo[1,5-a]pyrimidines as inhibitors of CDK9.

The serine-threonine kinase CDK9 is a target of emerging interest for the development of anti-cancer drugs. There are multiple lines of evidence linking CDK9 activity to cancer, including the essential role this kinase plays in transcriptional regulation through phosphorylation of the C-terminal domain (CTD) of RNA polymerase II. Indeed, inhibition of CDK9 has been shown to result in a reduction of short-lived proteins such as the pro-survival protein Mcl-1 in malignant cells leading to the induction of apoptosis. In this work we report our initial studies towards the discovery of selective CDK9 inhibitors, starting from the known multi-kinase inhibitor PIK-75 which possesses potent CDK9 activity. Our series is based on a pyrazolo[1,5-a]pyrimidine nucleus and, importantly, the resultant lead compound 18b is devoid of the structural liabilities present in PIK-75 and possesses greater selectivity.

Targeting acute myeloid leukemia by dual inhibition of PI3K signaling and Cdk9-mediated Mcl-1 transcription.

Resistance to cell death is a hallmark of cancer and renders transformed cells resistant to multiple apoptotic triggers. The Bcl-2 family member, Mcl-1, is a key driver of cell survival in diverse cancers, including acute myeloid leukemia (AML). A screen for compounds that downregulate Mcl-1 identified the kinase inhibitor, PIK-75, which demonstrates marked proapoptotic activity against a panel of cytogenetically diverse primary human AML patient samples. We show that PIK-75 transiently blocks Cdk7/9, leading to transcriptional suppression of MCL-1, rapid loss of Mcl-1 protein, and alleviation of its inhibition of proapoptotic Bak. PIK-75 also targets the p110α isoform of PI3K, which leads to a loss of association between Bcl-xL and Bak. The simultaneous loss of Mcl-1 and Bcl-xL association with Bak leads to rapid apoptosis of AML cells. Concordantly, low Bak expression in AML confers resistance to PIK-75-mediated killing. On the other hand, the induction of apoptosis by PIK-75 did not require the expression of the BH3 proteins Bim, Bid, Bad, Noxa, or Puma. PIK-75 significantly reduced leukemia burden and increased the survival of mice engrafted with human AML without inducing overt toxicity. Future efforts to cotarget PI3K and Cdk9 with drugs such as PIK-75 in AML are warranted.

A gene expression signature for insulin resistance.

Insulin resistance is a heterogeneous disorder caused by a range of genetic and environmental factors, and we hypothesize that its etiology varies considerably between individuals. This heterogeneity provides significant challenges to the development of effective therapeutic regimes for long-term management of type 2 diabetes. We describe a novel strategy, using large-scale gene expression profiling, to develop a gene expression signature (GES) that reflects the overall state of insulin resistance in cells and patients. The GES was developed from 3T3-L1 adipocytes that were made "insulin resistant" by treatment with tumor necrosis factor-α (TNF-α) and then reversed with aspirin and troglitazone ("resensitized"). The GES consisted of five genes whose expression levels best discriminated between the insulin-resistant and insulin-resensitized states. We then used this GES to screen a compound library for agents that affected the GES genes in 3T3-L1 adipocytes in a way that most closely resembled the changes seen when insulin resistance was successfully reversed with aspirin and troglitazone. This screen identified both known and new insulin-sensitizing compounds including nonsteroidal anti-inflammatory agents, ß-adrenergic antagonists, ß-lactams, and sodium channel blockers. We tested the biological relevance of this GES in participants in the San Antonio Family Heart Study (n = 1,240) and showed that patients with the lowest GES scores were more insulin resistant (according to HOMA_IR and fasting plasma insulin levels; P < 0.001). These findings show that GES technology can be used for both the discovery of insulin-sensitizing compounds and the characterization of patients into subtypes of insulin resistance according to GES scores, opening the possibility of developing a personalized medicine approach to type 2 diabetes.

The characterization of Abelson helper integration site-1 in skeletal muscle and its links to the metabolic syndrome.

The human Abelson helper integration site-1 (AHI1) gene is associated with both neurologic and hematologic disorders; however, it is also located in a chromosomal region linked to metabolic syndrome phenotypes and was identified as a type 2 diabetes mellitus susceptibility gene from a genomewide association study. To further define a possible role in type 2 diabetes mellitus development, AHI1 messenger RNA expression levels were investigated in a range of tissues and found to be highly expressed in skeletal muscle as well as displaying elevated levels in brain regions and gonad tissues. Further analysis in a rodent polygenic animal model of obesity and type 2 diabetes mellitus identified increased Ahi-1 messenger RNA levels in red gastrocnemius muscle from fasted impaired glucose-tolerant and diabetic rodents compared with healthy animals (P < .002). Moreover, elevated gene expression levels were confirmed in skeletal muscle from fasted obese and type 2 diabetes mellitus human subjects (P < .02). RNAi-mediated suppression of Ahi-1 resulted in increased glucose transport in rat L6 myotubes in both the basal and insulin-stimulated states (P < .01). Finally, single nucleotide polymorphism association studies identified 2 novel AHI1 genetic variants linked with fasting blood glucose levels in Mexican American subjects (P < .037). These findings indicate a novel role for AHI1 in skeletal muscle and identify additional genetic links with metabolic syndrome phenotypes suggesting an involvement of AHI1 in the maintenance of glucose homeostasis and type 2 diabetes mellitus progression.

NDRG2, a novel regulator of myoblast proliferation, is regulated by anabolic and catabolic factors.

Skeletal muscle tissue undergoes adaptive changes in response to stress and the genes that control these processes are incompletely characterised. NDRG2 (N-myc downstream-regulated gene 2), a stress- and growth-related gene, was investigated in skeletal muscle growth and adaption. While NDRG2 expression levels were found to be up-regulated in both differentiated human and mouse myotubes compared with undifferentiated myoblasts, the suppression of NDRG2 in C2C12 myoblasts resulted in slowed myoblast proliferation. The increased expression levels of the cell cycle inhibitors, p21 Waf1/Cip1 and p27 Kip1, and of various muscle differentiation markers in NDRG2-deficient myoblasts indicate that a lack of NDRG2 promoted cell cycle exiting and the onset of myogenesis. Furthermore, the analysis of NDRG2 regulation in C2C12 myotubes treated with catabolic and anabolic agents and in skeletal muscle from human subjects following resistance exercise training revealed NDRG2 gene expression to be down-regulated during hypertrophic conditions, and conversely, up-regulated during muscle atrophy. Together, these data demonstrate that NDRG2 expression is highly responsive to different stress conditions in skeletal muscle and suggest that the level of NDRG2 expression may be critical to myoblast growth and differentiation.

Nonvascular complications following spinal manipulation.

BACKGROUND CONTEXT: Spinal manipulation is associated with various vascular and nonvascular complications. Most prior studies have focused on the vascular complications. PURPOSE: The purpose of this study is to better clarify the spectrum of nonvascular complications following spinal manipulation, and to help define the risks of manipulative treatment. STUDY DESIGN: Review of medical records and radiographic studies of appropriate subjects. PATIENT SAMPLE: Patients presenting to a neurosurgical practice over a 6-year period who suffered a qualitative worsening of symptoms immediately after spinal manipulative treatment. OUTCOME MEASURES: Neurological conditions were compared pre-manipulation, post-manipulation, and post-surgery. METHODS: Record review of 18 patients. RESULTS: Eighteen patients were identified who had received spinal manipulation and whose neurological condition immediately worsened. Injuries were sustained to the cervical, thoracic, and lumbar spine and resulted, variously, in myelopathy, paraparesis, cauda equina syndrome, and radiculopathy. Eighty-nine percent required surgery. Outcome was excellent in 50% and good in 37.5%. Three patients died from unrecognized malignancies. CONCLUSION: Spinal manipulation can be associated with significant complications, often requiring surgical intervention. Pretreatment scanning may help identify patients with significant risk factors, such as substantial disc herniations or occult malignancies. Prompt evaluation and intervention is necessary when symptoms worsen or neurological deficits develop.