A first-in-human phase I study of the oral Notch inhibitor LY900009 in patients with advanced cancer.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 3008-3008
Author(s):  
Shubham Pant ◽  
Suzanne Fields Jones ◽  
Carla Kurkjian ◽  
Jeffrey R. Infante ◽  
Kathleen N. Moore ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Advanced Cancer ◽  
Critical Role ◽  
Notch Pathway ◽  
Amyloid Β ◽  
Maximum Tolerated Dose ◽  
Amyloid Β Peptide ◽  
Dependent Manner ◽  
Gamma Secretase ◽  
Dose Dependent

3008 Background: Notch signaling plays a critical role during stem cell self-renewal and is deregulated in multiple human cancers. The Notch pathway may be activated inappropriately by receptor mutation and overexpression as well as aberrant signals from the tumor microenvironment. LY900009 is a selective small-molecule inhibitor of gamma secretase, the enzyme that cleaves and thereby activates Notch receptors. Methods: Dose escalation was performed in cohorts of 3 patients (pts) using a modified continual reassessment method. LY900009 was taken orally thrice weekly (every MWF) during a 28-day cycle. Safety, pharmacokinetic, pharmacodynamic, and clinical endpoints were evaluated. Results: 22 patients received LY900009 across 6 dose levels: 2mg (3pts), 4mg (4pts), 8mg (3pts), 15mg (3pts), 30mg (6pts), and 60mg (3pts). The most common treatment emergent adverse events possibly related to LY900009 across all grades included diarrhea (27%), vomiting (23%), nausea (18%), fatigue (23%), anorexia (23%), hypophosphatemia (14%), and rash (18%). Dose-limiting toxicities of fatigue/N/V (G3) and diarrhea (G3) were seen in 2 patients, respectively, treated at 60mg. The maximum tolerated dose (MTD) was tentatively identified at 30mg. After a single dose, mean Cmax increased from 4 to 158 ng/ml and mean AUC0-t(last) increased from 14 to 1160 ng-hr/ml. Both Cmax and AUC0-t(last) increased in a dose-dependent manner. Elimination half-life of LY900009 was approximately 2-3 hrs. LY900009 inhibited plasma levels of amyloid-β peptide (a downstream product of gamma secretase) in a dose-dependent manner with 80-90% inhibition observed in the 30 and 60mg cohorts. In the 15mg cohort, one patient had colonic biopsy that showed markedly increased glandular mucin consistent with pharmacologic inhibition of the Notch pathway. Two patients (10%) with leiomyosarcoma and ovarian cancer received 4 cycles of therapy. Conclusions: LY900009 demonstrates acceptable safety and pharmacokinetics in patients with advanced cancer. Pharmacodynamic endpoints show pathway inhibition at tolerable doses. One more cohort at 45mg is ongoing to refine the MTD and will be followed by an expansion cohort for patients with ovarian cancer.

scholarly journals Phosphorylation of p66Shc and forkhead proteins mediates Aβ toxicity

2005 ◽  
Vol 169 (2) ◽  
pp. 331-339 ◽  
Author(s):  
Wanli W. Smith ◽  
Darrell D. Norton ◽  
Myriam Gorospe ◽  
Haibing Jiang ◽  
Shino Nemoto ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Redox Regulation ◽  
Critical Role ◽  
Ectopic Expression ◽  
Amyloid Β ◽  
Dominant Negative ◽  
Neuronal Cultures ◽  
Amyloid Β Peptide ◽  
Dependent Manner ◽  
Primary Neuronal Cultures

Excessive accumulation of amyloid β-peptide (Aβ) plays an early and critical role in synapse and neuronal loss in Alzheimer's Disease (AD). Increased oxidative stress is one of the mechanisms whereby Aβ induces neuronal death. Given the lessened susceptibility to oxidative stress exhibited by mice lacking p66Shc, we investigated the role of p66Shc in Aβ toxicity. Treatment of cells and primary neuronal cultures with Aβ caused apoptotic death and induced p66Shc phosphorylation at Ser36. Ectopic expression of a dominant-negative SEK1 mutant or chemical JNK inhibition reduced Aβ-induced JNK activation and p66Shc phosphorylation (Ser36), suggesting that JNK phosphorylates p66Shc. Aβ induced the phosphorylation and hence inactivation of forkhead transcription factors in a p66Shc-dependent manner. Ectopic expression of p66ShcS36A or antioxidant treatment protected cells against Aβ-induced death and reduced forkhead phosphorylation, suggesting that p66Shc phosphorylation critically influences the redox regulation of forkhead proteins and underlies Aβ toxicity. These findings underscore the potential usefulness of JNK, p66Shc, and forkhead proteins as therapeutic targets for AD.

The P-element-induced silencing effect of KP transposons is dose dependent in Drosophila melanogaster

Genome ◽  
2011 ◽  
Vol 54 (9) ◽  
pp. 752-762 ◽  
Author(s):  
Alireza Sameny ◽  
John Locke
Keyword(s):  
Drosophila Melanogaster ◽  
Critical Role ◽  
Mutagenic Effect ◽  
P Element ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
P Elements ◽  
Single Well ◽  
Dose Dependent

Transposable elements are found in the genomes of all eukaryotes and play a critical role in altering gene expression and genome organization. In Drosophila melanogaster, transposable P elements are responsible for the phenomenon of hybrid dysgenesis. KP elements, a deletion-derivative of the complete P element, can suppress this mutagenic effect. KP elements can also silence the expression of certain other P-element-mediated transgenes in a process called P-element-dependent silencing (PDS), which is thought to involve the recruitment of heterochromatin proteins. To explore the mechanism of this silencing, we have mobilized KP elements to create a series of strains that contain single, well-defined KP insertions that show PDS. To understand the quantitative role of KP elements in PDS, these single inserts were combined in a series of crosses to obtain genotypes with zero, one, or two KP elements, from which we could examine the effect of KP gene dose. The extent of PDS in these genotypes was shown to be dose dependent in a logarithmic rather than linear fashion. A logarithmic dose dependency is consistent with the KP products interacting with heterochromatic proteins in a concentration-dependent manner such that two molecules are needed to induce gene silencing.

scholarly journals Live Cell FRET Imaging Reveals Amyloid β-Peptide Oligomerization in Hippocampal Neurons

2021 ◽  
Author(s):  
Yang Gao ◽  
Stefan Wennmalm ◽  
Bengt Winblad ◽  
Sophia Schedin-Weiss ◽  
Lars Tjernberg
Keyword(s):  
Hippocampal Neurons ◽  
Resonance Energy Transfer ◽  
Amyloid Β ◽  
Resonance Energy ◽  
Live Cell ◽  
Amyloid Β Peptide ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Late Endosomes ◽  
Aβ Oligomerization

Amyloid β-peptide (Aβ) oligomerization is believed to contribute to the neuronal dysfunction in Alzheimer disease (AD). Despite decades of research, many details of Aβ oligomerization in neurons still need to be revealed. Förster Resonance Energy Transfer (FRET) is a simple but effective way to study molecular interactions. Here we use a confocal microscope with a sensitive Airyscan detector for FRET detection. By live cell FRET imaging, we detect Aβ42 oligomerization in primary neurons. The neurons were incubated with fluorescently labelled Aβ42 in the cell culture medium for 24 hours. Aβ42 were internalized and oligomerized into the lysosomes/late endosomes in a concentration-dependent manner. Both the cellular uptake and intracellular oligomerization of Aβ42 were significantly higher than for Aβ40. These findings provide a better understanding of Aβ42 oligomerization in neurons.

Cu2+-induced modification of the kinetics of Aβ(1-42) channels

2003 ◽  
Vol 285 (4) ◽  
pp. C873-C880 ◽  
Author(s):  
Randa Bahadi ◽  
Peter V. Farrelly ◽  
Bronwyn L. Kenna ◽  
Cyril C. Curtain ◽  
Colin L. Masters ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Chelating Agent ◽  
Common Mechanism ◽  
Amyloid Β Peptide ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Channel Inhibition ◽  
Low Concentrations ◽  
Redox Agents ◽  
In Cis

We found that the amyloid β peptide Aβ(1-42) is capable of interacting with membrane and forming heterogeneous ion channels in the absence of any added Cu2+ or biological redox agents that have been reported to mediate Aβ(1-42) toxicity. The Aβ(1-42)-formed cation channel was inhibited by Cu2+ in cis solution ([Cu2+] cis) in a voltage- and concentration-dependent manner between 0 and 250 μM. The [Cu2+] cis-induced channel inhibition is fully reversible at low concentrations between 50 and 100 μM [Cu2+] cis and partially reversible at 250 μM [Cu2+] cis. The inhibitory effects of [Cu2+] cis between 50 and 250 μM on the channel could not be reversed with addition of Cu2+-chelating agent clioquinol (CQ) at concentrations between 64 and 384 μM applied to the cis chamber. The effects of 200-250 μM [Cu2+] cis on the burst and intraburst kinetic parameters were not fully reversible with either wash or 128 μM [CQ] cis. The kinetic analysis of the data indicate that Cu2+-induced inhibition was mediated via both desensitization and an open channel block mechanism and that Cu2+ binds to the histidine residues located at the mouth of the channel. It is proposed that the Cu2+-binding site of the Aβ(1-42)-formed channels is modulated with Cu2+ in a similar way to those of channels formed with the prion protein fragment PrP(106-126), suggesting a possible common mechanism for Cu2+ modulation of Aβ and PrP channel proteins linked to neurodegenerative diseases.

scholarly journals A Mechano-Activated Cell Reporter System as a Proxy for Flow-Dependent Endothelial Atheroprotection

2018 ◽  
Vol 23 (8) ◽  
pp. 869-876
Author(s):  
Bendix R. Slegtenhorst ◽  
Oscar R. Fajardo Ramirez ◽  
Yuzhi Zhang ◽  
Zahra Dhanerawala ◽  
Stefan G. Tullius ◽  
...  
Keyword(s):  
Vascular Endothelium ◽  
Critical Role ◽  
Green Fluorescence Protein ◽  
Dependent Manner ◽  
Reporter System ◽  
Health And Disease ◽  
Fluorescence Protein ◽  
Biomechanical Stimuli ◽  
Dose Dependent

The vascular endothelium plays a critical role in the health and disease of the cardiovascular system. Importantly, biomechanical stimuli generated by blood flow and sensed by the endothelium constitute important local inputs that are translated into transcriptional programs and functional endothelial phenotypes. Pulsatile, laminar flow, characteristic of regions in the vasculature that are resistant to atherosclerosis, evokes an atheroprotective endothelial phenotype. This atheroprotective phenotype is integrated by the transcription factor Kruppel-like factor-2 (KLF2), and therefore the expression of KLF2 can be used as a proxy for endothelial atheroprotection. Here, we report the generation and characterization of a cellular KLF2 reporter system, based on green fluorescence protein (GFP) expression driven by the human KLF2 promoter. This reporter is induced selectively by an atheroprotective shear stress waveform in human endothelial cells, is regulated by endogenous signaling events, and is activated by the pharmacological inducer of KLF2, simvastatin, in a dose-dependent manner. This reporter system can now be used to probe KLF2 signaling and for the discovery of a novel chemical-biological space capable of acting as the “pharmacomimetics of atheroprotective flow” on the vascular endothelium.

Characterization of the role of CaMKI-like kinase (CKLiK) in human granulocyte function

Blood ◽  
2005 ◽  
Vol 106 (3) ◽  
pp. 1076-1083 ◽  
Author(s):  
Sandra Verploegen ◽  
Laurien Ulfman ◽  
Hanneke W. M. van Deutekom ◽  
Corneli van Aalst ◽  
Henk Honing ◽  
...  
Keyword(s):  
Respiratory Burst ◽  
Critical Role ◽  
Neutrophil Migration ◽  
Platelet Activating Factor ◽  
Dependent Manner ◽  
Functional Responses ◽  
Effector Functions ◽  
C Terminus ◽  
Human Granulocytes ◽  
Dose Dependent

AbstractActivation of granulocyte effector functions, such as induction of the respiratory burst and migration, are regulated by a variety of relatively ill-defined signaling pathways. Recently, we identified a novel Ca2+/calmodulin-dependent kinase I-like kinase, CKLiK, which exhibits restricted mRNA expression to human granulocytes. Using a novel antibody generated against the C-terminus of CKLiK, CKLiK was detected in CD34+-derived neutrophils and eosinophils, as well as in mature peripheral blood granulocytes. Activation of human granulocytes by N-formyl-methionyl-leucyl-phenylalanine (fMLP) and platelet-activating factor (PAF), but not the phorbol ester PMA (phorbol 12-myristate-13-acetate), resulted in induction of CKLiK activity, in parallel with a rise of intracellular Ca2+ [Ca2+]i. To study the functionality of CKLiK in human granulocytes, a cell-permeable CKLiK peptide inhibitor (CKLiK297-321) was generated which was able to inhibit kinase activity in a dose-dependent manner. The effect of this peptide was studied on specific granulocyte effector functions such as phagocytosis, respiratory burst, migration, and adhesion. Phagocytosis of Aspergillus fumigatus particles was reduced in the presence of CKLiK297-321 and fMLP-induced reactive oxygen species (ROS) production was potently inhibited by CKLiK297-321 in a dose-dependent manner. Furthermore, fMLP-induced neutrophil migration on albumin-coated surfaces was perturbed, as well as β2-integrin-mediated adhesion. These findings suggest a critical role for CKLiK in modulating chemoattractant-induced functional responses in human granulocytes.

Phase I study of ZEN-008 (AN-152), a targeted cytotoxic LHRH analog, in female patients with cancers expressing LHRH receptors

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 3571-3571 ◽  
Author(s):  
G. Emons ◽  
M. Kaufmann ◽  
A. Günthert ◽  
C. Gründker ◽  
S. Loibl ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Maximum Tolerated Dose ◽  
Breast Cancers ◽  
Female Patients ◽  
Prior Therapy ◽  
Maximum Lifetime ◽  
Allergic Skin ◽  
Heavily Pretreated ◽  
Dose Dependent ◽  
Allergic Skin Reaction

3571 Background: Human ovarian, endometrial, and breast cancers commonly express receptors for luteinizing hormone releasing hormone (LHRH-R). LHRH-R can be used for targeted chemotherapy with ZEN-008 (AN-152), in which doxorubicin (DOX) is linked to [D-Lys(6)]- LHRH. Preclinical studies showed a significantly reduced cardiotoxic potential of ZEN-008 compared with DOX, as well as activity in multi-drug resistant tumor models. This study assessed dose limiting toxicities (DLTs), maximum tolerated dose (MTD), and pharmacokinetics (PK) of ZEN- 008 given once every 3 weeks in female patients. Methods: Patients (pts) with tumors proven immunohistochemically to be LHRH- R positive and had progressive disease following chemotherapy were eligible if prior therapy did not exceed 70% of the recommended maximum lifetime dose for DOX. Starting at 10 mg/m2, doses were doubled between pts until side effects of CTCAE grade 2 or higher, then escalation following a modified Fibonacci scheme, with 3–6 pts/group. Safety monitoring included pituitary and cardiac function. Response evaluation followed the RECIST criteria. HPLC with fluorescence detection was used for plasma PK of ZEN-008 and free DOX. Results: Seventeen pts (13 with ovarian, 2 with breast cancer) received ZEN-008 by intravenous infusion over 2 hours at dosages of 10, 20, 40, 80 mg/m2 (1 pt and 2 cycles each). At 160 mg/m2 6 pts had 24 cycles, 1 pt ongoing at 3+ cycles), and at 267 mg/m2 7 pts had a total of 30 cycles, 1 pt ongoing at 4+ cycles). Short-lasting leukopenia/neutropenia of CTCAE Grade 4 was dose limiting in 2 pts at 267 mg/m2. One pt at this dose level had an allergic skin reaction during infusion, subsequent cycles with anti-allergic pre-medication were tolerated. At 160 mg/m2 1 pt with ovarian cancer had CR (lymph node metastasis), at 267 mg/m2 1 pat with ovarian cancer had a transient PR, and 3 pts had stable disease for 5+ cycles. PK analyses showed dose- dependent plasma levels of ZEN-008 and only minor (10–30%) release of DOX. Conclusions: Leukocytopenia was identified as a rapidly reversible DLT in heavily pretreated pts at a ZEN-008 dose of 267 mg/m2, given three-weekly, which is therefore also considered recommended Phase II dosage. Evidence of therapeutic activity was found at 160 and 267 mg/m2. [Table: see text]

A first-in-human phase I study of the oral p38 MAPK inhibitor LY2228820 dimesylate in patients with advanced cancer.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 3001-3001 ◽  
Author(s):  
Matthew P. Goetz ◽  
Anthony W. Tolcher ◽  
Paul Haluska ◽  
Kyriakos P. Papadopoulos ◽  
Charles Erlichman ◽  
...  
Keyword(s):  
Adverse Events ◽  
Phase I ◽  
P38 Mapk ◽  
Advanced Cancer ◽  
Phase I Study ◽  
Single Agent ◽  
Clinical Activity ◽  
Dependent Manner ◽  
Dose Levels ◽  
Dose Dependent

3001 Background: p38 MAPK regulates production of cytokines by the tumor microenvironment and its activation enables cancer cells to survive in the presence of oncogenic stress, radiation, chemotherapy, and targeted therapies. LY2228820 is a selective small-molecule inhibitor of p38 MAPK and preclinical studies demonstrate antitumor activity as a single agent and in combination with standard agents. We performed a phase I study to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) of LY2228820 and to characterize its pharmacokinetics and pharmacodynamics. Methods: Dose escalation was performed in a 3+3 design. LY2228820 was taken orally every 12 hours on days 1-14 of a 28-day cycle. Results: 54 patients received either capsules at 8 dose levels (10, 20, 40, 65, 90, 120, 160, and 200mg) or tablets at 5 dose levels (160, 200, 300, 420, and 560mg). For both formulations, Cmax and AUC increased in a dose-dependent manner. LY2228820 inhibited p38 MAPK induced phosphorylation of MAPKAP-K2 in peripheral blood with dose-dependent maximum inhibition from 10 to 70% across the dose range 10-200mg. The most common drug-related adverse events included fatigue, nausea, rash, constipation, vomiting, and pruritus. 1 patient (200mg) had DLT of erythema multiforme (Gr3) and 2 patients (560mg) had DLT of ataxia (Gr3) and dizziness (Gr2), respectively. Although the MTD was 420mg, the frequency of Gr1/2 adverse events (mainly rash, dizziness, and tremor) and observation of clinical activity at lower dose levels led to a recommended dose of 300mg (mean AUC0-24 = 11.7ug-hr/ml at steady state). Early clinical activity has been observed in ovary, breast, and kidney cancers. One patient with metastatic clear cell carcinoma of the kidney refractory to sorafenib, sunitinib, and temsirolimus had confirmed near partial response (29% decrease) after 8 cycles and remains on therapy. 15 patients (28%) achieved best overall response of stable disease, which in 12 patients (22%) was prolonged (≥4 cycles). Conclusions: LY2228820 demonstrates acceptable pharmacokinetics, safety, and early clinical activity as a single agent in advanced cancer. A phase II study for patients with ovary cancer is planned.

A first-in-human phase I study of the CDK4/6 inhibitor, LY2835219, for patients with advanced cancer.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 2500-2500 ◽  
Author(s):  
Geoffrey Shapiro ◽  
Lee S. Rosen ◽  
Anthony W. Tolcher ◽  
Jonathan Wade Goldman ◽  
Leena Gandhi ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Ovarian Cancer ◽  
Antitumor Activity ◽  
Advanced Cancer ◽  
Human Cancer ◽  
Phase 1 ◽  
Single Agent ◽  
Maximum Tolerated Dose ◽  
Ca 125 ◽  
Clinical Activity

2500 Background: Cyclin dependent kinases 4 and 6 (CDK4/6) act with D-type cyclins to inactivate the retinoblastoma (Rb) tumor suppressor protein and enable cell cycle progression from G1 to S phase. LY2835219 is a selective inhibitor of CDK4/6 that shows antitumor activity in preclinical models of human cancer and also distributes efficiently to the brain. We performed a phase 1 study to evaluate safety, pharmacokinetics, pharmacodynamics, and antitumor activity of LY2835219. Methods: 3+3 dose escalation was followed by expansions in 5 tumor types (brain metastases permitted): non-small cell lung cancer (NSCLC), glioblastoma, breast cancer, melanoma, and colorectal cancer. LY2835219 was taken orally every 12 or 24 hours (in escalation) and every 12 hours (in expansions) on days 1-28 of a 28-day cycle. Results: 55 patients (pts) received LY2835219. In escalation, 33 pts received LY2835219 on 1 of 2 schedules: 50, 100, 150, 225 mg every 24 hours (Q24H) or 75, 100, 150, 200, 275 mg every 12 hours (Q12H). On the Q24H schedule, the maximum tolerated dose (MTD) was not identified. On the Q12H schedule, the MTD was 200mg Q12H with dose limiting toxicity of G3 fatigue at 200 mg (1/6 evaluable pts) and 275 mg (2/3 evaluable pts). At 200mg Q12H, the mean Cmax and AUC0-24hr at steady state were 285 ng/mL and 5502 ng-hr/ml, respectively. In skin, LY2835219 induced pharmacodynamic inhibition of both Rb phosphorylation and topoisomerase IIα expression. In the ongoing expansions, 22 pts have received LY2835219. Across the study, the most common related adverse events were diarrhea (52%, including 5% G3), nausea (30%, 4% G3), fatigue (21%, 7% G3), vomiting (18%, 2% G3), and neutropenia (16%, 7% G3). 15 pts have reached ≥4 cycles for stable disease or better with 3 pts achieving 8, 16, and 26 cycles. One pt with ovarian cancer had a durable CA-125 response with >50% decrease for 16 cycles. One pt with KRAS mutant NSCLC had a 27% decrease by RECIST. One pt with CDKN2A-/- NRAS mutant melanoma had a confirmed partial response. Early clinical activity has been observed in ovarian cancer, NSCLC, breast cancer, and melanoma. Conclusions: LY2835219 shows acceptable safety and early clinical activity as a single agent for patients with advanced cancer. Clinical trial information: NCT01394016.

Inhibition of Human Plasmacytoma Cell Growth by a Novel JAK Kinase Inhibitor.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 644-644
Author(s):  
Renate Burger ◽  
Steven Legouill ◽  
Yu-Tzu Tai ◽  
Reshma Shringarpure ◽  
Klaus Podar ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Growth ◽  
Cell Lines ◽  
Hormone Receptors ◽  
Critical Role ◽  
Myeloma Cell ◽  
Thymidine Uptake ◽  
Dependent Manner ◽  
Jak Kinase ◽  
Dose Dependent

Abstract Novel strategies in cancer therapy aim at inhibiting distinct signal transduction pathways that are aberrantly activated in malignant cells. Protein tyrosine kinases of the JAK family are associated with a number of cytokine and cytokine-like hormone receptors and regulate important cellular functions such as proliferation, survival, and differentiation. Constitutive or enhanced JAK activation has been implicated in neoplastic transformation and abnormal cell proliferation in various hematological malignancies. In multiple myeloma (MM), JAK kinases play a critical role because of their association with cytokine receptors of the IL-6/gp130 family. A novel small-molecule inhibitor was developed that shows a 100 to 1,000-fold selectivity for JAK1, JAK2, JAK3, and TYK2 relative to other kinases including Abl, Aurora, c-Raf, FGFR3, GSK3b, IGF-1R, Lck, PDGFRa, PKBb, and Zap-70. Growth of MM cell lines and primary patient cells was inhibited by this compound in a dose-dependent manner. The IL-6 dependent cell line INA-6 and derived sublines were sensitive to the drug, with IC50’s of less than 1 mM, in [3H]-thymidine uptake and a colorimetric, tetrazolium compound (MTS) based assay (CellTiter 96® Aqueous One Solution Cell Proliferation Assay, Promega, Madison, WI). Importantly, INA-6 and patient tumor cell growth was also inhibited in the presence of bone marrow stromal cells, which by themselves remained largely unaffected. Growth suppression of INA-6 correlated with a significant and dose-dependent increase in the percentage of apoptotic cells, as evaluated by Apo2.7 staining after 48 hours of drug treatment. In addition, the compound blocked IL-6 induced phosphorylation of STAT3, a direct downstream target of JAK kinases and important transcription factor triggering anti-apoptotic pathways. In other myeloma cell lines, the drug overcame the protective effect of gp130 cytokines on dexamethasone induced apoptosis. In MM1.S cells, it completely blocked IL-6 induced phosphorylation of SHP-2 and AKT, both known to mediate the protective effects of IL-6. In contrast, AKT phosphorylation induced by IGF-1 remained unchanged, demonstrating selectivity of the compound. These studies show that disruption of JAK kinase activity and downstream signaling pathways inhibits myeloma cell growth and survival as well as circumvents drug resistance, thereby providing the conceptual basis for the use of JAK kinase inhibitors as a novel therapeutic approach in MM.

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