ROS Induction Targets Persister Cancer Cells with Low Metabolic Activity in NRAS-Mutated Melanoma

Clinical management of melanomas with NRAS mutations is challenging. Targeting MAPK signaling is only beneficial to a small subset of patients due to resistance that arises through genetic, transcriptional, and metabolic adaptation. Identification of targetable vulnerabilities in NRAS-mutated melanoma could help improve patient treatment. Here, we used multiomics analyses to reveal that NRAS-mutated melanoma cells adopt a mesenchymal phenotype with a quiescent metabolic program to resist cellular stress induced by MEK inhibition. The metabolic alterations elevated baseline reactive oxygen species (ROS) levels, leading these cells to become highly sensitive to ROS induction. In vivo xenograft experiments and single-cell RNA sequencing demonstrated that intratumor heterogeneity necessitates the combination of a ROS inducer and a MEK inhibitor to inhibit both tumor growth and metastasis. Ex vivo pharmacoscopy of 62 human metastatic melanomas confirmed that MEK inhibitor-resistant tumors significantly benefited from the combination therapy. Finally, oxidative stress response and translational suppression corresponded with ROS-inducer sensitivity in 486 cancer cell lines, independent of cancer type. These findings link transcriptional plasticity to a metabolic phenotype that can be inhibited by ROS inducers in melanoma and other cancers.

SIGNIFICANCE

Metabolic reprogramming in drug-resistant NRAS-mutated melanoma cells confers sensitivity to ROS induction, which suppresses tumor growth and metastasis in combination with MAPK pathway inhibitors.

MLN0128, a novel mTOR kinase inhibitor, disrupts survival signaling and triggers apoptosis in AML and AML stem/ progenitor cells

mTOR activation leads to enhanced survival signaling in acute myeloid leukemia (AML) cells. The active-site mTOR inhibitors (asTORi) represent a promising new approach to targeting mTOR in AKT/mTOR signaling. MLN0128 is an orally-administered, second-generation asTORi, currently in clinical development. We examined the anti-leukemic effects and the mechanisms of action of MLN0128 in AML cell lines and primary samples, with a particular focus on its effect in AML stem/progenitor cells. MLN0128 inhibited cell proliferation and induced apoptosis in AML by attenuating the activity of mTOR complex 1 and 2. Using time-of-flight mass cytometry, we demonstrated that MLN0128 selectively targeted and functionally inhibited AML stem/progenitor cells with high AKT/mTOR signaling activity. Using the reverse-phase protein array technique, we measured expression and phosphorylation changes in response to MLN0128 in 151 proteins from 24 primary AML samples and identified several pro-survival pathways that antagonize MLN0128-induced cellular stress. A combined blockade of AKT/mTOR signaling and these pro-survival pathways facilitated AML cell killing. Our findings provide a rationale for the clinical use of MLN0128 to target AML and AML stem/progenitor cells, and support the use of combinatorial multi-targeted approaches in AML therapy.

Signaling through PI3Kγ: a common platform for leukocyte, platelet and cardiovascular stress sensing

The concerted activation of leukocytes and vessels shapes multiple physiological and pathological responses. A large number of these processes shares a common signal transduction platform involving the activation of plasma membrane bound G protein-coupled receptors (GPCRs). This event is usually amplified by the production of different intra-cellular second messenger molecules. Among these mediators, the phosphorylated lipid phosphatidylinositol (3,4,5)-trisphosphate (PIP3) produced by phosphoinositide 3-kinase γ (PI3Kγ) has recently emerged as a crucial signal in both vascular and white blood cells. The generation of mice lacking PI3Kγ showed that the GPCR/PI3Kγ/PIP3 signaling pathway controls diverse immune modulatory and vascular functions like respiratory burst, cell recruitment, mast cell reactivity, platelet aggregation, endothelial activation as well as smooth muscle contractility. The relative specificity of these events suggests that blocking PI3Kγ function might turn out beneficial for diseases like inflammation, allergy, thrombosis, and major cardiovascular disorders like hypertension, thus offering a wide range of therapeutic opportunities.

PI3K-δ and PI3K-γ inhibition by IPI-145 abrogates immune responses and suppresses activity in autoimmune and inflammatory disease models

Phosphoinositide-3 kinase (PI3K)-δ and PI3K-γ are preferentially expressed in immune cells, and inhibitors targeting these isoforms are hypothesized to have anti-inflammatory activity by affecting the adaptive and innate immune response. We report on a potent oral PI3K-δ and PI3K-γ inhibitor (IPI-145) and characterize this compound in biochemical, cellular, and in vivo assays. These studies demonstrate that IPI-145 exerts profound effects on adaptive and innate immunity by inhibiting B and T cell proliferation, blocking neutrophil migration, and inhibiting basophil activation. We explored the therapeutic value of combined PI3K-δ and PI3K-γ blockade, and IPI-145 showed potent activity in collagen-induced arthritis, ovalbumin-induced asthma, and systemic lupus erythematosus rodent models. These findings support the hypothesis that inhibition of immune function can be achieved through PI3K-δ and PI3K-γ blockade, potentially leading to significant therapeutic effects in multiple inflammatory, autoimmune, and hematologic diseases.

Selective inhibition of phosphoinositide 3-kinase p110α preserves lymphocyte function

Class IA phosphoinositide 3-kinase (PI3K) is essential for clonal expansion, differentiation, and effector function of B and T lymphocytes. The p110δ catalytic isoform of PI3K is highly expressed in lymphocytes and plays a prominent role in B and T cell responses. Another class IA PI3K catalytic isoform, p110α, is a promising drug target in cancer but little is known about its function in lymphocytes. Here we used highly selective inhibitors to probe the function of p110α in lymphocyte responses in vitro and in vivo. p110α inhibition partially reduced B cell receptor (BCR)-dependent AKT activation and proliferation, and diminished survival supported by the cytokines BAFF and IL-4. Selective p110δ inhibition suppressed B cell responses much more strongly, yet maximal suppression was achieved by targeting multiple PI3K isoforms. In mouse and human T cells, inhibition of single class IA isoforms had little effect on proliferation, whereas pan-class I inhibition did suppress T cell expansion. In mice, selective p110α inhibition using the investigational agent MLN1117 (previously known as INK1117) did not disrupt the marginal zone B cell compartment and did not block T cell-dependent germinal center formation. In contrast, the selective p110δ inhibitor IC87114 strongly suppressed germinal center formation and reduced marginal zone B cell numbers, similar to a pan-class I inhibitor. These findings show that although acute p110α inhibition partially diminishes AKT activation, selective p110α inhibitors are likely to be less immunosuppressive in vivo compared with p110δ or pan-class I inhibitors.

Efficacy of INK128, an mTORC1/mTORC2 kinase inhibitor, in breast cancer models driven by HER2-PI3K-AKT-mTOR pathway

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Background: Downstream of the PI3K-AKT pathway, the mTOR has been shown to be essential effector in promoting cell proliferation, survival, mRNA translation and tumor susceptibility. Aberrant activation of the PI3K-AKT-mTOR pathway occurs frequently in breast tumor (BT) and contributes to resistance to trastuzumab (T). Using a HER2 amplified BT model; we investigated the antitumor efficacy of the dual mTORC1/mTORC2 kinase inhibitor INK128 alone and in combination with T. Methods: The antiproliferative and HER2-mediated cellular signaling (pAKT, pP70S6K, pS6RP, p4EBP1 and p-ERK) effects of INK128 alone and in combination with T were evaluated in HER2 amplified T-sensitive (BT474), T-resistant (BT474HR), and HER2 amplified/PIK3CA mutated (HCC1954, UACC893) BT cell lines by MTT assay and Western blots. Athymic mice bearing BT474 and BT474HR xenograft tumors were treated with INK128 and T (alone and in combination). Results: (1)INK128 exhibited excellent in vitro cell killing activity in MTT assay with IC50’s below 50nM. INK128 was more potent when combined with T, (2) INK128 blocked mTORC1, mTORC2 and thus did not cause the mTORC2 activation of AKT observed with rapalogues, (3) inhibition of phosphorylation of AKT(S473), P70S6K, S6RP, and 4EBP1(T37/46, T70) was observed following INK128 treatment, and the combination of INK128 and T more effectively blocked the PI3K-AKT-mTOR pathway, (4) INK128 dose-dependently blocked 3D-ON-TOP clonogenic growth of HER2+ cells. This effect was potentiated in the presence of T and (5) xenograft data show that the combination of INK128 and T has strongly enhanced anti-tumor effect in both sensitive and resistant models, something that cannot be achieved by either monotherapy. Conclusions: Our data suggest that 1) therapeutic targeting of the PI3K-AKT-mTOR signaling should be effective in abrogating resistance to T therapy in HER2+ BT, 2) INK128 mitigates the feedback activation of AKT caused by selective inhibition of mTORC1 and 3) targeting both the HER2 and the mTORC1/2 signaling pathways is an attractive strategy to enhance the clinical activity of T therapy, as well as to prevent or delay the development of resistance.

Abstract 1811: Antitumor activity of lapatinib in combination with the dual mTORC1/2 inhibitor INK-128 in breast tumors resistant to anti-HER2 therapy

Purpose: The PI3K/Akt/mTOR pathway is an attractive target in HER2 positive breast cancer refractory to anti-HER2 therapy. The hypothesis is that suppression of this pathway results in sensitization to anti-HER2 agents. However, this combinatorial strategy has not been comprehensively tested in models of trastuzumab and lapatinib resistance. Experimental Design: We analyzed in vitro cell viability and induction of apoptosis in five different cell lines resistant to trastuzumab and lapatinib. Inhibition of HER2/HER3 phosphorylation, PI3K/Akt/mTOR and ERK signaling pathways was evaluated by western blot. Tumor growth inhibition following treatment with lapatinib, INK-128 or the combination of both agents was evaluated in three different animal models: two cell-based xenograft models refractory to both trastuzumab and lapatinib and a xenograft derived from a patient who relapsed to trastuzumab-based therapy. Results: The addition of lapatinib to INK-128 prevented both HER2 and HER3 phosphorylation induced by INK-128, resulting in inhibition of both PI3K/Akt/mTOR and ERK pathways. This dual blockade synergistically enhanced cell death in five different HER2 positive cell lines resistant to trastuzumab and lapatinib. In vivo, both cell line-based and patient-derived xenografts showed exquisite sensitivity to the antitumor activity of the combination of lapatinib and INK-128, causing durable tumor shrinkage in the absence of any sign of toxicity. Conclusions: The simultaneous blockade of PI3K/Akt/mTOR and ERK pathways achieved by combining lapatinib with INK-128 acts synergistically in inducing cell death and tumor regression in breast cancer refractory to anti-HER2 therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1811. doi:1538-7445.AM2012-1811

Abstract 2812: mTOR kinase mediates dissemination and colonization of breast cancer metastasis

Background: Early events of metastatic dissemination arise from the ability of tumor cells to acquire a number of biological changes which allow for their survival in distal microenvironments. Among the early events that initiate disseminated tumor populations include epithelial-to-mesenchymal transition (EMT) and increased potential for invasion that will ultimately lead to colonization of distal sites. The PI3K/mTOR pathway has been linked to clinic-pathalogical features of invasion and metastasis of multiple tumor types. Results: We sought to investigate using both in vitro and in vivo models of metastasis a panel of PI3K/mTOR selective inhibitors, in which INK128, a selective mTOR kinase inhibitor in clinical development was included. Using live-cell time lapse imaging experiments to monitor cell migration and invasion we found that INK128 significantly inhibited motility and velocity of metastatic breast cancer models in wound assays and decreased the ability of tumor cells to migrate through membranes and matrigel. The ability of INK128 to selectively inhibit tumor cell migration in vitro prompted us to assess whether INK128 can prevent tumor dissemination in vivo. In metastatic breast cancer xenograft models we monitored the growth of tumors implanted in mammary fat pads (MFP) and metastatic dissemination by serial noninvasive whole body bioluminescent imaging. We first assessed and characterized the degree of spontaneous metastasis to the lung, liver, auxillary lymph nodes, chest cavity of mice and subsequently the effect of mTOR kinase inihibition on primary tumor growth on the MFP versus overt metastatic dissemination upon daily, oral treatment with INK128. We show that INK128 blocked drastically metastatic spread in a dose-dependent manner without significantly affecting the growth of primary tumors. Interestingly, we found that INK128 did not affect the ability of breast cancer cells to enter into the lungs following an alternative experimental lung metastasis model by lateral tail vein injection but INK128 greatly diminished the capacity of breast cancer cells to subsequently colonize and expand. Conclusion: Our results position mTOR on a metastasis-sustaining axis that engages downstream pathways to support the biological machinery of migration, invasion, and fitness of initiating breast cancer cells during the establishment of thoracic metastases.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2812. doi:1538-7445.AM2012-2812

Abstract 2230: Preclinical activity of INK128, a TORC1/2 inhibitor, in triple negative breast cancer: A combination of PARP inhibitor with PI3K-mTOR pathway-targeted inhibitor

Introduction: Recent understanding of the biology of Triple Negative (TN) tumor cells has resulted in the recognition of following molecular targets for the development of novel therapeutics, (1) cell surface receptor tyrosine kinases (RTKs, e.g. EGFR, IGFR, c-MET, FGFR), (2) intracellular signaling pathway(s) (PI3K-AKT-mTOR, RAS-MAPK-ERK), and (3) DNA-damage (chemo- or radiotherapy) repair pathway. INK128 is an orally bioavailable, potent and selective ATP site kinase inhibitor of mTOR complexes TORC1 and TORC2 that together play a crucial role in regulating tumor cell growth, metabolism and motility. INK128 is structurally and mechanistically distinct from allosteric rapamycin-based mTOR inhibitors such as RAD001. Methods: We tested effects of INK128 (alone or in combination with carboplatin and ABT888) on, (a) cell survival/proliferation, (b) cell signaling marker(s) of proliferation, (c) fibronectin-mediated migration, (d) fibronectin-directed matrigel-invasion, and (e) clonogenic survival (3D-ON-TOP assay) in different TNBT cell lines with high expression of EGFR (MDA-MB468, SUM149), BRCA mutations (HCC1937, SUM149) no expression of PTEN protein (HCC70, HCC1937, MDA-MB468, SUM149), PIK3CA mutation (BT20) and RAS/RAF mutation (MDA-MB231). Results: Data showed that, (1) although the range of EC50s for INK128 varied from 50 nM-500 nM in different TNBT cells, the PTEN-null cells exhibited favorable EC50s compared to the rest of the cell lines (with exception to HCC1937), (2) inhibition of phosphorylation of AKT (S473), S6RP, and 4EBP1 was observed following INK128 treatment (100 nM and 200 nM) as early as 6 hours, (3) treatment with 200 nM INK128 for 24 hours differentially blocked pERK in PTEN-null MDA-MB468 as compared to MDA-MB231 cells, (4) INK128 treatment (100 nM) inhibited migration of different TNBT cells (as compared to 2 uM RAD001, allosteric, partial TORC1 inhibitor)) and the inhibition was differentially pronounced in PTEN-null TNBT cells lines, (5) INK128 treatment (100 nM) also blocked invasion of MDA-MB468 cells, and (6) INK128 dose-dependently blocked clonogenic growth of TNBT cells. This effect was potentiated in the presence of ABT888 (10uM; small molecule PARP inhibitor) plus carboplatin (10uM; chemotherapeutic agent). Conclusion: INK128 (alone or in combination with carboplatin and ABT888) has anti-proliferative effect on TNBT cells. INK128 has anti-migratory and anti-invasive effects on TNBT cells. Interestingly, the anti-migratory effect of INK128 was most prominent in PTEN-null TNBT cells. We are currently pursuing studies to test the effect of INK128 on the endothelial cells, the results of which will be presented in the meeting.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2230. doi:1538-7445.AM2012-2230

Abstract 2745: INK128, a TORC1/2 kinase inhibitor, enhances the efficacy of cytotoxic therapies in endometrial tumor models

Background: The mammalian target of rapamycin (mTOR), which comprises two protein complexes, TORC1 and TORC2, regulates tumor cell growth, metabolism and motility. In endometrial cancer, the mTOR pathway is aberrantly activated by constitutive mitogen stimuli, such as FGFR2 and multiple genetic mutations such as PIK3CA, PIK3R1/2, PTEN and LKB1. The activation of multiple signaling pathways, cross-feedback and redundancy of these pathways led us to explore the combination of mTOR kinase inhibitor with chemotherapeutic agents for achieving maximal efficacy in preclinical mouse models of endometrial cancer. Results: INK128 is a potent and selective TORC1/2 inhibitor with excellent drug-like properties currently advancing in clinical development. INK128 inhibits endometrial tumor cell proliferation in vitro and displays tumor growth inhibition in endometrial tumor models. In most instances, the anti-tumor activity of INK128 is cytostatic compared to the cytotoxic effect of taxol and carboplatin. In endometrial tumor cells of diverse genetic backgrounds, combining INK128 with taxol resulted in a synergistic inhibition of tumor cell proliferation, sustained suppression of PI3K/AKT/mTOR pathway activity, skewed cell cycle and an increase in apoptosis. INK128 decreased the expression of anti-apoptotic protein MCL-1 and therefore mechanistically enhanced taxol-triggered apoptosis. In endometrial mouse tumor models with PTEN and FGFR2 mutations, the combination induced marked tumor regression and significantly delayed tumor re-growth upon discontinuation of the treatment compared to taxol treatment alone. The combination therapy was well-tolerated and the enhanced anti-tumor efficacy correlated with mechanism-based inhibition of several TORC1 and TORC2 pharmacodynamic markers and induction of apoptosis in vivo. Additionally, combining INK128 with taxol or carbotaxol resulted in tumor regression in taxol-resistant endometrial tumor models. The opportunity of optimizing dose and schedule combination regimens as well as biomarkers predicting sensitivity/resistance to INK128/taxol combination will be discussed. Conclusion: The combination of mTOR kinase inhibitors with chemotherapeutic agents is a compelling strategy to improve therapeutic outcome and to overcome chemo-resistance for tumor types with aberrant activation of the PI3K/mTOR pathway such as endometrial cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2745. doi:1538-7445.AM2012-2745

Dual mTORC1/2 and HER2 blockade results in antitumor activity in preclinical models of breast cancer resistant to anti-HER2 therapy

PURPOSE

The PI3K/Akt/mTOR pathway is an attractive target in HER2-positive breast cancer that is refractory to anti-HER2 therapy. The hypothesis is that the suppression of this pathway results in sensitization to anti-HER2 agents. However, this combinatorial strategy has not been comprehensively tested in models of trastuzumab and lapatinib resistance.

EXPERIMENTAL DESIGN

We analyzed in vitro cell viability and induction of apoptosis in five different cell lines resistant to trastuzumab and lapatinib. Inhibition of HER2/HER3 phosphorylation, PI3K/Akt/mTOR, and extracellular signal-regulated kinase (ERK) signaling pathways was evaluated by Western blotting. Tumor growth inhibition after treatment with lapatinib, INK-128, or the combination of both agents was evaluated in three different animal models: two cell-based xenograft models refractory to both trastuzumab and lapatinib and a xenograft derived from a patient who relapsed on trastuzumab-based therapy.

RESULTS

The addition of lapatinib to INK-128 prevented both HER2 and HER3 phosphorylation induced by INK-128, resulting in inhibition of both PI3K/Akt/mTOR and ERK pathways. This dual blockade produced synergistic induction of cell death in five different HER2-positive cell lines resistant to trastuzumab and lapatinib. In vivo, both cell line-based and patient-derived xenografts showed exquisite sensitivity to the antitumor activity of the combination of lapatinib and INK-128, which resulted in durable tumor shrinkage and exhibited no signs of toxicity in these models.

CONCLUSIONS

The simultaneous blockade of both PI3K/Akt/mTOR and ERK pathways obtained by combining lapatinib with INK-128 acts synergistically in inducing cell death and tumor regression in breast cancer models refractory to anti-HER2 therapy.

PI3Kδ inhibitors in cancer: rationale and serendipity merge in the clinic

Several phosphoinositide 3-kinase (PI3K) inhibitors are in the clinic and many more are in preclinical development. CAL-101, a selective inhibitor of the PI3Kδ isoform, has shown remarkable success in certain hematologic malignancies. Although PI3Kδ signaling plays a central role in lymphocyte biology, the degree of single-agent therapeutic activity of CAL-101 during early-phase development has been somewhat unexpected. CAL-101 works in part by blocking signals from the microenvironment that normally sustain leukemia and lymphoma cells in a protective niche. As PI3Ks enter the arena of molecular-targeted therapies, CAL-101 provides proof of principle that isoform-selective compounds can be effective in selected cancer types and patient populations.

SIGNIFICANCE

A key question is whether compounds targeting a single PI3K catalytic isoform can provide meaningful single agent efficacy in cancer cells that express multiple isoforms. Clinical studies of the drug CAL-101 have provided a significant advance by showing that selective targeting of PI3Kδ achieves efficacy in chronic lymphocytic leukemia, in part through targeting the tumor microenvironment.

Abstract A172: INK128, an orally active TORC1/2 kinase inhibitor, displays enhanced efficacy when combined with cytotoxic agents

Background: The mammalian target of rapamycin (mTOR) comprises two protein complexes, TORC1 and TORC2, which together regulate cell growth, metabolism, angiogenesis, and cell survival. Because TORC1 and TORC2 play a crucial role in several pathways that are frequently dysregulated in human cancer, the TORC1/2 kinase inhibitors provide a promising class of anti-cancer agents. Activation of multiple genomic and signaling pathways, cross-feedback, pathway redundancy and the capacity for compensatory adaptive response in cancer suggest that the optimal therapeutic effect of mTOR inhibitors will be better exploited by the strategy of rational combination therapies.

Results: INK128 is a potent and selective TORC1/2 inhibitor with excellent drug-like properties currently in multiple phase 1 studies. Daily, oral administration of INK128 inhibits tumor growth in multiple xenograft models with predicted pharmacokinetic/pharmacodynamic relationship. In most instances the anti-tumor effect of INK128 is cytostatic compared to the cytotoxic effect of chemotherapeutic agents such as Taxol. To enhance the anti-tumor activity of INK128, we investigated the combination of INK128 with cytotoxic agents such as conventional chemo drugs or apoptosis inducing agents. Treatment of tumors with the cytotoxic agents such as Taxol often leads to activation of the PI3K/AKT/mTOR pathway, which limits the anti-tumor activity of Taxol and may eventually lead to drug resistance. Additionally, Taxol resistance mechanisms include the over-expression of members of the Bcl-2 family of proteins such as MCL-1 and BCL-XL, whose expression is regulated by TORC1 and their function possibly by TORC2. Therefore, there is a strong scientific rationale to investigate the combination of a TORC1/2 inhibitor and Taxol. To this end, we have investigated the preclinical efficacy of INK128 in combination with Taxol in vitro and in vivo. Combining INK128 with Taxol resulted in a synergistic inhibition of tumor cell proliferation and the suppression of PI3K/AKT/mTOR signaling pathways in various cancer types. In most instances alterations in cell cycle and an increase in apoptosis was observed. INK128 decreases the expression of anti-apoptotic protein Mcl-1 and therefore resensitizes Taxol-resistant tumor cells to Mcl-1-dependent build up. In various xenograft models, the combination therapies were well-tolerated and displayed enhanced anti-tumor efficacy, inhibited pharmacodynamic markers, and induced apoptosis. Combination of INK128 with a small molecule inhibitor of Bcl-2 (ABT-263) also led to significant increase of apoptosis in tumor cells but not in normal cells in vitro and enhanced anti-tumor activity in mouse tumor models in vivo.

Conclusion: In summary, our data show a potential benefit for combining INK128 with cytotoxic agents. INK128 is currently in a Taxol combination phase Ib study in patients with advanced solid malignancies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A172.

Abstract 4486: INK128, a novel TORC1/2 inhibitor with potent oral antitumor activity in preclinical models of renal cancer

Objective: Preclinical characterization and evaluation of INK128 alone and in combination with anti-angiogenic agents in models of renal cell carcinoma.

Background: mTOR kinase comprises two distinct multi-protein complexes, TORC1 and TORC2, which together regulate processes critical for cell growth and survival. TORC1 regulates protein translation of cell cycle regulators, angiogenic factors, and factors that control cell motility. TORC2 regulates pathways involved in cell metabolism, survival and motility. Through rational drug design we have identified INK128, a potent and selective small molecule, active-site kinase inhibitor of mTOR with excellent drug-like properties. Activity seen with temsirolimus and everolimus, pharmaceutical derivatives of rapamycin and allosteric partial inhibitors of TORC1, provide clinical proof-of-concept for targeting mTOR for cancer therapy. TORC1 is upstream of HIF1/2 and TORC1 and TORC2 are downstream of the VEGF pathways implicated in the tumorigenesis of metastatic renal cell carcinoma (RCC). We have investigated INK128 in preclinical in vitro and in vivo models of renal cell carcinoma (RCC) and compared its activity to other standard of care agents commonly used to treat this disease.

Results: INK128 selectively inhibited phosphorylation of S6 and 4EBP1, downstream substrates of TORC1, as well as phosphorylation of AKT downstream of TORC2 in vitro and in vivo. INK128 demonstrated very potent inhibition of tumor cell proliferation and induction of G1 cell cycle arrest in vitro. In mouse tumor models, INK128, rapamycin, avastin and sorafenib displayed anti-tumor efficacy; however, they differ in the mechanisms underlying the anti-tumor activity. INK128 inhibits phosphorylation of AKT, PRAS40, NDRG1, S6 and 4EBP1; rapamycin only inhibits S6 phosphorylation and induces phosphorylation of AKT; sorafenib activates several pathway components that are downstream of TORC1/2. INK128 and rapamycin suppressed tumor growth by directly inhibiting tumor cell proliferation; however neither had much impact on tumor-associated angiogenesis. In contrast, sorafenib and avastin suppressed tumor growth by potently inhibiting tumor angiogenesis. The activity of the combination of INK128 with sorafenib or avastin yielded sustained tumor regression by targeting tumor cells and the microenvironment.

Conclusion: INK128 offers a novel approach for the treatment of renal cell carcinoma by targeting TORC1/2 signaling. Additionally, the mechanism of action of INK128 is different than current therapies and may not display cross resistance with current standard of care agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4486. doi:10.1158/1538-7445.AM2011-4486

Abstract 653: Combination of TORC1/2 and MEK kinase inhibitors in colorectal cancer models

MAPK pathway mutations are frequent in colorectal cancer (CRC) and associated with resistance to standard therapies. This provides a rationale for the use of targeted therapies against the MAPK pathway. However, the response of CRC cells to MEK inhibitors varies depending on coexisting mutations in both MAPK and PI3K pathways. As a matter of fact, dual inhibition of MEK and PI3K or AKT in mouse models of CRC has proven effective due to aberrations in both pathways. Inhibition of TORC1, a shared downstream effector of the MAPK and PI3K pathways, was described to be partly responsible for the efficacy of the dual blockade.

In order to explore additional mechanisms involved in the superior antitumor activity of combined MAPK and PI3K pathway suppression we directly targeted TORC1/2 by active-site kinase inhibitor of mTOR, in addition to MEK, in our cell models. We tested the antiproliferative activity of INK128, a selective and potent TORC1/2 inhibitor, in combination with a MEK inhibitor, PD-0325901, in a panel of colon cancer cell lines with diverse alterations of the MAPK and PI3K pathways. PD-0325901 treatment effectively inhibited ERK phosphorylation, which resulted in decreased phosphorylation of Rb and reduced expression of E2F in all the cell lines tested. In CRC cell lines harboring sole mutations in the MAPK pathway, we observed sensitivity to PD-0325901 that was not further enhanced when combining with INK-128. In contrast, CRC cell lines harboring concurrent mutations of both pathways exhibited a striking sensitivity to dual ERK and TORC1/2 blockade associated with an enhanced arrest in cell cycle and, above all, a concomitant increase in apoptosis. Inhibition of TORC1 and TORC2 by INK128 could not be further enhanced by MEK inhibition in any of the cell lines tested. These data suggest that, besides complete suppression of both pathways, additional mechanisms must be at work to explain the observed enhanced cell death following dual suppression of PI3K and MEK. Interestingly, we observed differential regulation of key components of the cell cycle in response to dual blockade. We are currently investigating whether this specific biochemical behaviour plays a causative role in the observed phenotype.

In summary, dual inhibition of TORC1/2 and MEK has potential for effective antitumor activity in CRCs with dysregulation of both signaling cascades. A better understanding of the molecular mechanisms responsible for the enhanced efficacy of this therapeutic combination will help defining the best biomarkers that need to be assessed in phase I combination trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 653. doi:10.1158/1538-7445.AM2011-653

Chemical inducers and transcriptional markers of oligodendrocyte differentiation

Oligodendrocytes generate and maintain myelin, which is essential for axonal function and protection of the mammalian central nervous system. To advance our molecular understanding of differentiation by these cells, we screened libraries of pharmacologically active compounds and identified inducers of differentiation of Oli-neu, a stable cell line of mouse oligodendrocyte precursors (OPCs). We identified four broad classes of inducers, namely, forskolin/cAMP (protein kinase A activators), steroids (glucocorticoids and retinoic acid), ErbB2 inhibitors, and nucleoside analogs, and confirmed the activity of these compounds on rat primary oligodendrocyte precursors and mixed cortical cultures. We also analyzed transcriptional responses in the chemically induced mouse and rat OPC differentiation processes and compared these with earlier studies. We confirm the view that ErbB2 is a natural signaling component that is required for OPC proliferation, whereas ErbB2 inhibition or genetic knockdown results in OPC differentiation.

Abstract 1798: TORC1/2 inhibitors have more potent anti-leukemic efficacy and are less immunosuppressive than rapamycin

The purpose of this study was to evaluate the anti-leukemic and immunosuppressive properties of novel, ATP-competitive inhibitors of the mammalian target of rapamycin (mTOR). The mTOR inhibitors currently in clinical use, exemplified by rapamycin and related analogs (“rapalogs”), have achieved some success as anticancer therapies. However, these agents also suppress proliferation of both B and T lymphocytes. In addition, rapalogs have a mechanistic limitation: not only are they allosteric inhibitors that selectively bind to mTOR complex-1 (TORC1) and not to mTOR complex-2 (TORC2), but they do not fully inhibit TORC1. In contrast, novel ATP-competitive active-site inhibitors of the mTOR kinase overcome these limitations, displaying full inhibitory activity of both TORC1 and TORC2. We compared rapamycin with active-site TORC1/2 inhibitors in models of Philadelphia chromosome-positive pre-B acute lymphoblastic leukemia (Ph+ B-ALL). We find that PP242 and INK128, active-site TORC1/2 inhibitors, but not rapamycin cause death of murine and primary human leukemia cells. These compounds are also more potent than rapamycin in growth assays of solid tumor cell lines. Biochemical assays confirm that PP242 and INK128 inhibit rapamycin-resistant outputs of both TORC1 and TORC2. In vivo, oral administration of PP242 or INK128 delays leukemia onset and augments the effects of tyrosine kinase inhibitors. Surprisingly, active-site TORC1/2 inhibitors have much weaker effects on proliferation and function of normal B and T cells than rapamycin. Selective TORC1/2 inhibitors are also less immunosuppressive than PI-103, a panPI3K-mTORC1/2 inhibitor. These findings establish that transformed lymphocytes are selectively sensitive to TORC1/2 inhibitors and support the development of such inhibitors for leukemia therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1798.

Abstract 4488: INK128: An orally active TORC1/2 kinase inhibitor demonstrates potent antitumor activity in preclinical models of renal cell carcinoma

Anti-angiogenic agents have demonstrated promising activity in patients with renal cell carcinoma (RCC). Patients with clear cell RCC often have mutations or silencing of the von Hippel-Lindau gene, leading to an accumulation of HIF 1 alpha (HIF1α), a key mediator of hypoxia-triggered neo-angiogenesis. The mammalian target of rapamycin (mTOR) is upstream of HIF1a and downstream of the VEGF pathway. mTOR kinase comprises two distinct multi-protein complexes, TORC1 and TORC2, which together regulate growth, metabolism, angiogenesis and survival. Pharmaceutical derivatives of rapamycin, a partial allosteric inhibitor of TORC1, provide clinical proof of concept for targeting mTOR in RCC as well as insights into how ATP-competitive TORC1/2 inhibitors might provide superior efficacy. Through rational drug design we have discovered INK128, a potent, selective TORC1/2 inhibitor with outstanding drug-like properties. We investigated INK128 in preclinical in vitro and in vivo models of RCC. Interestingly, while both INK128 and rapamycin exhibit comparable anti-angiogenic activity in vitro, INK128 correlated with potent and complete blockade of cell proliferation, while rapamycin failed to establish a dose-dependent maximum inhibition of tumor cell proliferation. A comparison of INK128, rapamycin, Nexavar and Avastin demonstrated that all exhibited potent inhibition of tumor growth, via different molecular mechanisms. INK128 inhibits phosphorylation of AKT, S6 and 4EBP1; rapamycin inhibits only S6 phosphorylation and induces AKT phosphorylation; Nexavar and Avastin have little effect on the PI3K/AKT/mTOR pathway. Only INK128 induced autophagy and decreased expression of cyclin D1. INK128 and rapamycin both inhibit expression of HIF-1α and VEGF, which contributes to their anti-angiogenic activity. We conclude that, although Nexavar, Avastin and rapamycin exert their activity primarily through effects on the tumor microenvironment, the anti-tumor activity of INK128 is derived from direct inhibition of tumor cell growth as well as anti-angiogenic activities. In summary, targeting TORC1/2 signaling with INK128 offers a compelling approach to the treatment of RCC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4488.

Abstract 4496: INK128, an orally active TORC1/2 kinase inhibitor, shows broad antitumor activity and enhances efficacy of cytotoxic as well as targeted agents

mTOR kinase operates via two distinct multi-protein complexes, TORC1 and TORC2, which together regulate growth, metabolism, angiogenesis and survival. Because the PI3K/Akt/mTOR pathway integrates nutrient and hormonal signaling and is frequently dysregulated in human cancer, the mTOR kinase has become an important target for oncology drug development. However, multiple genomic and signaling pathways are often simultaneously activated in cancer, and pathway redundancy and compensatory feedback can blunt the activity of even the most potent anticancer agents. Thus, it is important to study the anti-tumor efficacy of potential anticancer agents, both alone and in combination with cytotoxic and targeted agents, to achieve the optimal therapeutic effect. Through rational drug design we have discovered INK128, a potent and selective TORC1/2 inhibitor with outstanding drug-like properties. INK128 inhibits both the phosphorylation of S6 and 4EBP1, downstream substrates of TORC1, and selectively inhibits AKT phosphorylation at Ser473, the downstream substrate of TORC2, both in vitro and in vivo. Potent inhibition was also observed in cell lines resistant to rapamycin and PanPI3K inhibitors. Daily, oral administration of INK128 inhibited angiogenesis and tumor growth in multiple xenograft models with predicted PK/PD relationship. We have studied INK128 in combination with chemotherapeutic agents as well as with molecular targeted agents both in vitro and in vivo tumor models. In most cases, INK128 demonstrated a synergistically enhanced inhibition of tumor growth and suppression of respective signaling pathways. Additionally, induction of apoptosis was observed only when INK128 was used in combination, suggesting apoptosis as a potential contributor to the observed synergy. A subset of the agents that displayed synergy when combined with INK128 in vitro were evaluated in a number of xenograft models. The combinations were well-tolerated and displayed both enhanced anti-tumor efficacy and enhanced inhibition of key pharmacodynamic markers. In summary, INK128 offers a compelling approach to the treatment of cancer either as a single agent or in combination with other anti-cancer agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4496.

Abstract 1668: Pharmacodynamic biomarker development for INK128, a potent and selective inhibitor of TORC1/2 for the treatment of cancer

Pharmacokinetic / pharmacodynamic (PK/PD) modeling is a valuable strategy to achieve target inhibition as well as predictable and meaningful therapeutic efficacy. The mammalian target of rapamycin (mTOR) comprises two protein complexes, TORC1 and TORC2, which together regulate cell growth, metabolism, angiogenesis, and cell survival. Because TORC1 and TORC2 play a crucial role in several pathways that are frequently dysregulated in human cancer, the mTOR kinase is a compelling target for oncology drug development. Through rational drug design we have identified INK128, a potent and selective small molecule, ATP-competitive, active-site TORC1/2 kinase inhibitor with excellent drug-like properties. Inhibition of phosphorylation of S6 and 4EBP1, downstream markers of TORC1 signaling, was selected for PD analysis in peripheral blood cells (PBCs), skin tissue, and tumor tissue biopsy in mice xenograft tumor models. Time- and dose-dependent inhibition of S6 and 4EBP1 was demonstrated in PBCs by phospho-flow (FACS) analysis. Immunohistochemistry and immunoblot analysis demonstrated a correlation between S6 and 4EBP1 inhibition in tumors or skin tissue and antitumor effect. Additionally, site-selective inhibition of AKT phosphorylation at Ser473, the downstream substrate of TORC2, was also demonstrated in tumors and skin biopsies in mouse xenograft models. Our results demonstrate that daily, oral administration of INK128 selectively inhibits PI3K/AKT/mTOR signaling at the level of TORC1/2, and show that INK128 inhibits growth, and in some cases induces regression, of various tumor xenograft models. Results from these studies display a clear pharmacokinetic and pharmacodynamic relationship. Moreover, the activity of several of these downstream markers can be reproducibly measured in human peripheral blood cells and may permit development of a PK/PD model that might assist to predict PBC and skin tissue PD marker inhibition time-profiles in patients. In summary, INK128 presents a compelling, biomarker-guided approach for the treatment of a variety of cancer by targeting TORC1/2 signaling.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1668.

Abstract 4489: The activity of novel, potent, selective PI3K/mTOR pathway inhibitors in B-cell malignancies

Background: Activation of the PI3K pathway is implicated in a number of tumour types, including haematological malignancies. Agents that target this pathway at different levels (e.g. RTK, PI3K, mTOR etc) have shown promising activity in preclinical models and in early phase trials. We have therefore investigated the activity of novel, potent, pan- and isoform-selective PI3K pathway inhibitors in lymphoma and myeloma models. Methods: Compounds studied included those with selectivity for mTOR (INK128, mTOR IC50 1.6 nM), PI3Kδ/γ (INK713, INK1048, IC50s <10 nM for δ/γ isoforms, >50 nM for others) and PI3Kδ/γ/β (INK1138, IC50s <10 nM for each isoform). IC87114 (δ- selective), GDC-0941 (α/δ selective), rapamycin and doxorubicin were included as comparators. Agents were studied in a panel of lymphoma and myeloma cell lines, in normal PBMCs and in primary tumours cultured with stromal cells. Effects on cell viability and proliferation were assessed using the Guava Viacount assay, on apoptosis induction by annexin V labelling, and on cell cycle distribution by flow cytometry. PI3K pathway activity and inhibition was determined by Western blotting as well as mass spectrometry. Results: In cell lines, inhibition of mTOR by INK128 resulted in potent inhibition of cell proliferation, in many at concentrations as low as 10 nM. Selective PI3K inhibitors were less potent anti-proliferative agents, although activity was seen in cells with activation of the PI3K pathway as determined by western blot analysis. For all compounds tested, the major impact was on cell proliferation rather than cell viability. PI3K inhibitors showed little effect on cell viability at concentrations < 1µM. The effect of these compounds in primary mantle cell lymphoma, follicular lymphoma, chronic lymphocytic leukaemia and myeloma samples was variable, both between and within tumour types, possibly due to differences in basal PI3K pathway activity. Effects in normal PBMCs were markedly different to those seen in tumour cells, with a concentration-dependent increase in cell number with either mTOR or PI3K inhibition. Conclusion: Selective PI3K pathway inhibition, particularly at the level of mTOR, results in cytostatic, and at higher concentrations cytotoxic, responses in haematological malignancies. The variable activity of these compounds between cell lines and primary samples suggests it will be important to characterise the activity of the PI3K pathway in individual tumours to identify patients likely to benefit from such agents.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4489.

Abstract 4490: INK128, a novel TORC1/2 inhibitor, demonstrates potent oral antitumor activity in a VEGF-reinforced murine model of breast cancer and enhances efficacy of bevacizumab

Background: Aberrant activation of the mammalian target of rapamycin (mTOR) signaling plays an important role in breast cancer progression and represents a potential therapeutic target for breast cancer. mTOR, existing in two distinct multi-protein complexes, TORC1 and TORC2, plays a key role in several signaling pathways controlling tumor growth, hypoxia, metabolism as well as angiogenesis. Through rational drug design we have identified INK128, a potent and selective small molecule active-site TORC1/2 kinase inhibitor, with excellent drug-like properties. In this study, we evaluated the potential therapeutic impact of INK128 alone or in combination with bevacizumab, the recombinant humanized VEGF targeting antibody, on tumor growth and angiogenesis using a genetically engineered xenograft model of breast cancer.

Methods: MCF-7 cells transfected with vector (ML20) or VEGF (MV165) were implanted into mammary fat pads of athymic mice. Treatment of INK128 alone (0.3 mg/kg or 1 mg/kg/daily to 3 mg/kg thrice weekly for 4 weeks) or vehicle control was started when tumors were palpable. Target proteins of PI3K/Akt/ mTORC1/2 signaling were analyzed by immunoblotting, while Ki-67, VEGF, VEGFR2, and carbonic anhydrase IX (CA IX) were assessed by immunohistochemistry (IHC). The potential of INK128 in combination with bevacizumab was also evaluated in this model.

Results: INK128 inhibited primary tumor growth significantly in MV165 xenografts in all doses tested (p=0.014), compared with vehicle control, while the impact of INK128 on ML20 xenografts was only significant at 3 mg/kg dose (p=0.05). Treatment with INK128 decreased the phosphorylation of AktS473, pS6S240/244, and p4EBP1T37/45 in both ML20 and MV165 xenograft tumors. Inhibition of the PRAS40T246 phosphorylation is more prominent in MV165 tumors in a dose-dependent manner. INK128 blocked phosphorylation of NDRG1 potently. Among the markers analyzed by IHC, only CA IX cytoplasmic expression in MV165 tumors was significantly reduced in the 3 mg/kg group as compared to control (p=0.008). Combination therapy with INK128 and bevacizumab reduced the tumor growth in both ML20 (p=0.040) and MV165 (p=0.002) xenografts significantly, when compared to vehicle groups, while the impact of inhibition was greater in MV165 than in ML20. Combination therapy was superior to INK128 alone in MV165 (p=0.009) but not in ML20 (p=0.145); in contrast, combination therapy was superior to bevacizumab in both ML20 (p=0.043) and MV165 (0.005).

Conclusions: INK128 inhibits TORC1 and TORC2-dependent signaling in VEGF-overexpressing xenograft model. Addition of INK128 to bevacizumab, a VEGF-targeting antibody, provided further benefit in xenograft models, even with transgenically elevated levels of VEGF, suggesting a promising approach in breast cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4490.

Effective and selective targeting of leukemia cells using a TORC1/2 kinase inhibitor

Targeting the mammalian target of rapamycin (mTOR) protein is a promising strategy for cancer therapy. The mTOR kinase functions in two complexes, TORC1 (target of rapamycin complex-1) and TORC2 (target of rapamycin complex-2); however, neither of these complexes is fully inhibited by the allosteric inhibitor rapamycin or its analogs. We compared rapamycin with PP242, an inhibitor of the active site of mTOR in both TORC1 and TORC2 (hereafter referred to as TORC1/2), in models of acute leukemia harboring the Philadelphia chromosome (Ph) translocation. We demonstrate that PP242, but not rapamycin, causes death of mouse and human leukemia cells. In vivo, PP242 delays leukemia onset and augments the effects of the current front-line tyrosine kinase inhibitors more effectively than does rapamycin. Unexpectedly, PP242 has much weaker effects than rapamycin on the proliferation and function of normal lymphocytes. PI-103, a less selective TORC1/2 inhibitor that also targets phosphoinositide 3-kinase (PI3K), is more immunosuppressive than PP242. These findings establish that Ph(+) transformed cells are more sensitive than normal lymphocytes to selective TORC1/2 inhibitors and support the development of such inhibitors for leukemia therapy.

PI3K: from the bench to the clinic and back

From humble beginnings over 25 years ago as a lipid kinase activity associated with certain oncoproteins, PI3K (phosphoinositide 3-kinase) has been catapulted to the forefront of drug development in cancer, immunity and thrombosis, with the first clinical trials of PI3K pathway inhibitors now in progress. Here, we give a brief overview of some key discoveries in the PI3K area and their impact, and include thoughts on the current state of the field, and where it could go from here.PI3K has become a very intense area of research, with over 2,000 publications on PI3K in PubMed for 2009 alone. The expectations for a therapeutic impact of intervention with PI3K activity are high, and progress in the clinical arena is being monitored by many. However, targeted therapies almost invariably encounter roadblocks, often exposing unresolved questions in the basic understanding of the target. PI3K will most likely be no exception. Below, we describe some of these early "surprises" and how these inform and shape basic science investigations.

Functional whole-genome analysis identifies Polo-like kinase 2 and poliovirus receptor as essential for neuronal differentiation upstream of the negative regulator alphaB-crystallin

This study aimed at identifying transcriptional changes associated to neuronal differentiation induced by six distinct stimuli using whole-genome microarray hybridization analysis. Bioinformatics analyses revealed the clustering of these six stimuli into two categories, suggesting separate gene/pathway dependence. Treatment with specific inhibitors demonstrated the requirement of both Janus kinase and microtubule-associated protein kinase activation to trigger differentiation with nerve growth factor (NGF) and dibutyryl cAMP. Conversely, activation of protein kinase A, phosphatidylinositol-3-kinase alpha, and mammalian target of rapamycin, although required for dibutyryl cAMP-induced differentiation, exerted a negative feedback on NGF-induced differentiation. We identified Polo-like kinase 2 (Plk2) and poliovirus receptor (PVR) as indispensable for NGF-driven neuronal differentiation and alphaB-crystallin (Cryab) as an inhibitor of this process. Silencing of Plk2 or PVR blocked NGF-triggered differentiation and Cryab down-regulation, while silencing of Cryab enhanced NGF-induced differentiation. Our results position both Plk2 and PVR upstream of the negative regulator Cryab in the pathway(s) leading to neuronal differentiation triggered by NGF.

GLEPP1/protein-tyrosine phosphatase phi inhibitors block chemotaxis in vitro and in vivo and improve murine ulcerative colitis

We describe novel, cell-permeable, and bioavailable salicylic acid derivatives that are potent and selective inhibitors of GLEPP1/protein-tyrosine phosphatase . Two previously described GLEPP1 substrates, paxillin and Syk, are both required for cytoskeletal rearrangement and cellular motility of leukocytes in chemotaxis. We show here that GLEPP1 inhibitors prevent dephosphorylation of Syk1 and paxillin in resting cells and block primary human monocyte and mouse bone marrow-derived macrophage chemotaxis in a gradient of monocyte chemotactic protein-1. In mice, the GLEPP1 inhibitors also reduce thioglycolate-induced peritoneal chemotaxis of neutrophils, lymphocytes, and macrophages. In murine disease models, the GLEPP1 inhibitors significantly reduce severity of contact hypersensitivity, a model for allergic dermatitis, and dextran sulfate sodium-induced ulcerative colitis, a model for inflammatory bowel disease. Taken together, our data provide confirmation that GLEPP1 plays an important role in controlling chemotaxis of multiple types of leukocytes and that pharmacological inhibition of this phosphatase may have therapeutic use.

Chemokine receptor CCR2 undergoes transportin1-dependent nuclear translocation

Chemokines (CCs) are small chemoattractant cytokines involved in a wide variety of biological and pathological processes. Released by cells in the milieu, and extracellular matrix and activating signalling cascades upon binding to specific G protein-coupled receptors (GPCRs), they trigger many cellular events. In various pathologies, CCs are directly responsible for excessive recruitment of leukocytes to inflammatory sites and recent studies using chemokine receptor (CCR) antagonists permitted these molecules to reach the market for medical use. While interaction of CCs with their receptors has been extensively documented, downstream GPCR signalling cascades triggered by CC are less well understood. Given the pivotal role of chemokine receptor 2 (CCR2) in monocyte recruitment, activation and differentiation and its implication in several autoimmune-inflammatory pathologies, we searched for potential new CCR2-interacting proteins by engineering a modified CCR2 that we used as bait. Herein, we show the direct interaction of CCR2 with transportin1 (TRN1), which we demonstrate is followed by CCR2 receptor internalization. Further characterization of this novel interaction revealed that TRN1-binding to CCR2 increased upon time in agonist treated cells and promotes its nuclear translocation in a TRN1-dependent manner. Finally, we provide evidence that following translocation, the receptor localizes at the outer edge of the nuclear envelope where it is finally released from TRN1.

Phosphoinositide 3-kinase p110beta activity: key role in metabolism and mammary gland cancer but not development

The phosphoinositide 3-kinase (PI3K) pathway crucially controls metabolism and cell growth. Although different PI3K catalytic subunits are known to play distinct roles, the specific in vivo function of p110beta (the product of the PIK3CB gene) is not clear. Here, we show that mouse mutants expressing a catalytically inactive PIK3CB(K805R) mutant survived to adulthood but showed growth retardation and developed mild insulin resistance with age. Pharmacological and genetic analyses of p110beta function revealed that p110beta catalytic activity is required for PI3K signaling downstream of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors as well as to sustain long-term insulin signaling. In addition, PIK3CB(K805R) mice were protected in a model of ERBB2-driven tumor development. These findings indicate an unexpected role for p110beta catalytic activity in diabetes and cancer, opening potential avenues for therapeutic intervention.

Isoform-specific functions of phosphoinositide 3-kinases: p110 delta but not p110 gamma promotes optimal allergic responses in vivo

The leukocyte-enriched p110gamma and p110delta isoforms of PI3K have been shown to control in vitro degranulation of mast cells induced by cross-linking of the high affinity receptor of IgE (FcepsilonRI). However, the relative contribution of these PI3K isoforms in IgE-dependent allergic responses in vivo is controversial. A side-by-side comparative analysis of the role of p110gamma and p110delta in mast cell function, using genetic approaches and newly developed isoform-selective pharmacologic inhibitors, confirms that both PI3K isoforms play an important role in FcepsilonRI-activated mast cell degranulation in vitro. In vivo, however, only p110delta was found to be required for optimal IgE/Ag-dependent hypersensitivity responses in mice. These observations identify p110delta as a key therapeutic target among PI3K isoforms for allergy- and mast cell-related diseases.

Genetic and pharmacological targeting of phosphoinositide 3-kinase-gamma reduces atherosclerosis and favors plaque stability by modulating inflammatory processes

BACKGROUND

The role of inflammation at all stages of the atherosclerotic process has become an active area of investigation, and there is a notable quest for novel and innovative drugs for the treatment of atherosclerosis. The lipid kinase phosphoinositide 3-kinase-gamma (PI3Kgamma) is thought to be a key player in various inflammatory, autoimmune, and allergic processes. These properties and the expression of PI3Kgamma in the cardiovascular system suggest that PI3Kgamma plays a role in atherosclerosis.

METHODS AND RESULTS

Here, we demonstrate that a specific PI3Kgamma inhibitor (AS605240) is effective in murine models of established atherosclerosis. Intraperitoneal administration of AS605240 (10 mg/kg daily) significantly decreased early atherosclerotic lesions in apolipoprotein E-deficient mice and attenuated advanced atherosclerosis in low-density lipoprotein receptor-deficient mice. Furthermore, PI3Kgamma levels were elevated in both human and murine atherosclerotic lesions. Comparison of low-density lipoprotein receptor-deficient mice transplanted with wild-type or PI3Kgamma-deficient bone marrow demonstrated that functional PI3Kgamma in the hematopoietic lineage is required for atherosclerotic progression. Alleviation of atherosclerosis by targeting of PI3Kgamma activity was accompanied by decreased macrophage and T-cell infiltration, as well as increased plaque stabilization.

CONCLUSIONS

These data identify PI3Kgamma as a new target in atherosclerosis with the potential to modulate multiple stages of atherosclerotic lesion formation, such as fatty streak constitution, cellular composition, and final fibrous cap establishment.

Tissue- and stimulus-dependent role of phosphatidylinositol 3-kinase isoforms for neutrophil recruitment induced by chemoattractants in vivo

PI3K plays a fundamental role in regulating neutrophil recruitment into sites of inflammation but the role of the different isoforms of PI3K remains unclear. In this study, we evaluated the role of PI3Kgamma and PI3Kdelta for neutrophil influx induced by the exogenous administration or the endogenous generation of the chemokine CXCL1. Administration of CXCL1 in PI3Kgamma(-/-) or wild-type (WT) mice induced similar increases in leukocyte rolling, adhesion, and emigration in the cremaster muscle when examined by intravital microscopy. The induction of neutrophil recruitment into the pleural cavity or the tibia-femoral joint induced by the injection of CXCL1 was not significantly different in PI3Kgamma(-/-) or WT mice. Neutrophil influx was not altered by treatment of WT mice with a specific PI3Kdelta inhibitor, IC87114, or a specific PI3Kgamma inhibitor, AS605240. The administration of IC87114 prevented CXCL1-induced neutrophil recruitment only in presence of the PI3Kgamma inhibitor or in PI3Kgamma(-/-) mice. Ag challenge of immunized mice induced CXCR2-dependent neutrophil recruitment that was inhibited by wortmannin or by blockade of and PI3Kdelta in PI3Kgamma(-/-) mice. Neutrophil recruitment to bronchoalveolar lavage induced by exogenously added or endogenous production of CXCL1 was prevented in PI3Kgamma(-/-) mice. The accumulation of the neutrophils in lung tissues was significantly inhibited only in PI3Kgamma(-/-) mice treated with IC87114. Neutrophil recruitment induced by exogenous administration of C5a or fMLP appeared to rely solely on PI3Kgamma. Altogether, our data demonstrate that there is a tissue- and stimulus-dependent role of PI3Kgamma and PI3Kdelta for neutrophil recruitment induced by different chemoattractants in vivo.

Inactivation of PI3Kgamma and PI3Kdelta distorts T-cell development and causes multiple organ inflammation

Mice lacking both the p110gamma and p110delta isoforms display severe impairment of thymocyte development. Here, we show that this phenotype is recapitulated in p110gamma-/-/p110delta(D910A/D910A) (p110gamma(KO)delta(D910A)) mice where the p110delta isoform has been inactivated by a point mutation. Moreover, we have examined the pathological consequences of the p110gammadelta deficiency, which include profound T-cell lymphopenia, T-cell and eosinophil infiltration of mucosal organs, elevated IgE levels, and a skewing toward Th2 immune responses. Using small-molecule selective inhibitors, we demonstrated that in mature T cells, p110delta, but not p110gamma, controls Th1 and Th2 cytokine secretion. Thus, the pathology in the p110gammadelta-deficient mice is likely to be secondary to a developmental block in the thymus that leads to lymphopenia-associated inflammatory responses.

A chemical proteomics approach to phosphatidylinositol 3-kinase signaling in macrophages

Prior work using lipid-based affinity matrices has been done to investigate distinct sets of lipid-binding proteins, and one series of experiments has proven successful in mammalian cells for the proteome-wide identification of lipid-binding proteins. However, most lipid-based proteomics screens require scaled up sample preparation, are often composed of multiple cell types, and are not adapted for simultaneous signal transduction studies. Herein we provide a chemical proteomics strategy that uses cleavable lipid "baits" with broad applicability to diverse biological samples. The novel baits were designed to avoid preparative steps to allow functional proteomics studies when the biological source is a limiting factor. Validation of the chemical baits was first confirmed by the selective isolation of several known endogenous phosphatidylinositol 3-kinase signaling proteins using primary bone marrow-derived macrophages. The use of this technique for cellular proteomics and MS/MS analysis was then demonstrated by the identification of known and potential novel lipid-binding proteins that was confirmed in vitro for several proteins by direct lipid-protein interactions. Further to the identification, the method is also compatible with subsequent signal transduction studies, notably for protein kinase profiling of the isolated lipid-bound protein complexes. Taken together, this integration of minimal scale proteomics, lipid chemistry, and activity-based readouts provides a significant advancement in the ability to identify and study the lipid proteome of single, relevant cell types.

Targeting dual-specificity phosphatases: manipulating MAP kinase signalling and immune responses

Dual-specificity phosphatases (DUSPs) are a subset of protein tyrosine phosphatases, many of which dephosphorylate threonine and tyrosine residues on mitogen-activated protein kinases (MAPKs), and hence are also referred to as MAPK phosphatases (MKPs). The regulated expression and activity of DUSP family members in different cells and tissues controls MAPK intensity and duration to determine the type of physiological response. For immune cells, DUSPs regulate responses in both positive and negative ways, and DUSP-deficient mice have been used to identify individual DUSPs as key regulators of immune responses. From a drug discovery perspective, DUSP family members are promising drug targets for manipulating MAPK-dependent immune responses in a cell-type and disease-context-dependent manner, to either boost or subdue immune responses in cancers, infectious diseases or inflammatory disorders.

T-cell function is partially maintained in the absence of class IA phosphoinositide 3-kinase signaling

The class IA subgroup of phosphoinositide 3-kinase (PI3K) is activated downstream of antigen receptors, costimulatory molecules, and cytokine receptors on lymphocytes. Targeted deletion of individual genes for class IA regulatory subunits severely impairs the development and function of B cells but not T cells. Here we analyze conditional mutant mice in which thymocytes and T cells lack the major class IA regulatory subunits p85alpha, p55alpha, p50alpha, and p85beta. These cells exhibit nearly complete loss of PI3K signaling downstream of the T-cell receptor (TCR) and CD28. Nevertheless, T-cell development is largely unperturbed, and peripheral T cells show only partial impairments in proliferation and cytokine production in vitro. Both genetic and pharmacologic experiments suggest that class IA PI3K signaling plays a limited role in T-cell proliferation driven by TCR/CD28 clustering. In vivo, class IA-deficient T cells provide reduced help to B cells but show normal ability to mediate antiviral immunity. Together these findings provide definitive evidence that class IA PI3K regulatory subunits are essential for a subset of T-cell functions while challenging the notion that this signaling mechanism is a critical mediator of costimulatory signals downstream of CD28.