Abstract C88: The CDK4/6 inhibitor LY2835219 overcomes vemurafenib resistance resulting from MAPK reactivation and cyclin D1 upregulation

B-RAFV600E mutation is found in approximately 50% of melanoma patients. It activates the MEK/ERK pathway and drives tumor progression. Vemurafenib, a B-RAF selective inhibitor was recently approved as an effective therapy for metastatic melanoma with B-RAF V600E mutation. However, most patients treated with vemurafenib eventually develop resistance in an average of 6-7 months. We and others have found that MAPK reactivation is a common mechanism of vemurafenib resistance. However, inhibitors of MAPK pathway, such as the MEK inhibitor trametinib, showed minimal clinical benefit in patients who had previously developed resistance to vemurafenib. Thus, overcoming resistance to vemurafenib remains an urgently unmet medical need. In this report, we have developed several in vitro models and an in vivo model resistant to vemurafenib and found that, in addition to MAPK reactivation, Cyclin D1 upregulation is common in these models. We demonstrated that these resistant cells are sensitive to inhibition of the Cyclin D1-CDK4/6 axis by LY2835219, a selective CDK4/6 inhibitor. LY2835219 inhibited growth of melanoma A375 xenografts, and delayed tumor recurrence in combination with vemurafenib. We further developed a vemurafenib-resistant xenograft model by continuous dosing of vemurafenib in A375 xenografts. Consistent with our in vitro observation, we found that Cyclin D1 is elevated and the MAPK pathway is reactivated in the resistant tumors, as well as in the cell lines generated from these tumors. Importantly, treatment with LY2835219 induced significant growth inhibition in these vemurafenib-resistant tumors. Additional mechanistic analysis demonstrated that LY2835219 preferably induced apoptosis in vemurafenib-resistant cells, while it primarily arrested cells in G1 phase in the parental A375 cells. Similar to CDK4/6 inhibition by LY2835219, Cyclin D1 knockdown by siRNA also induced a significantly higher rate of apoptotic cell death in the resistant cells, suggesting that Cyclin D1 may play an important role in the survival of resistant cells. Altogether, our data suggest that inhibition of the Cyclin D1-CDK4/6 axis by LY2835219 represents an effective strategy for overcoming resistance to B-RAF inhibition in melanoma patients with oncogenic BRAF mutation.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C88.

Citation Format: Vipin Yadav, Teresa F. Burke, Lysiane Huber, Robert D. Van Hoen, Youyan Zhang, Sean Buchanan, Edward M. Chan, James J. Starling, Richard P. Beckmann, Sheng-Bin Peng. The CDK4/6 inhibitor LY2835219 overcomes vemurafenib resistance resulting from MAPK reactivation and cyclin D1 upregulation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C88.

Abstract B229: TBKI kinase inhibition blocks RANTES secretion and exhibits minimal tumor growth inhibition in oncogenic Ras-driven tumor models

TANK-binding kinase 1 (TBK1) is a non-canonical IKK family member and plays a critical role in innate immunity by modulating cytokine production, interferon, and NF-kB signaling. It is recently reported that TBK1 directly engages Akt survival signaling to support oncogenic Ras-driven transformation. TBK1 is also identified as a synthetic lethal partner in KRas mutant NSCLC through systematic RNA interference. In this study, we have characterized LSN3090729, a 4-aryl-2-aminopyrimidine derivative as a selective TBK1 kinase inhibitor. Biochemical and cellular analyses demonstrate that LSN3090729 is a potent TBK1 kinase inhibitor, and selectively inhibits TBK1 based on in vitro activities in biochemical assays developed with a panel of protein kinases. In Panc-1, a pancreatic tumor cell line with KRas mutation, LSN3090729 inhibits EGF-induced phosphorylation of AKT at both Thr308 and Ser473 sites. Pharmacokinetic analysis shows that LSN3090729 has an over 70% of oral bioavailability with an acceptable half life in rodents. In a mouse pharmacology model, LSN3090729 blocks LPS-induced RANTES secretion in a dose-dependent manner with 67%, 79%, and 90% inhibition at 10, 30, and 100 mg/kg, respectively. LSN3090729 is assessed for its anti-proliferation activities in vitro in a panel of tumor cells with KRas mutation or other genetic background. The sensitivity of these tumor cells to LSN3090729 in two dimensional proliferation or three dimensional soft agar growth assays appears not correlated with status of KRas mutation. In xenograft models of HCT116 and Panc-1, both with a KRas mutation, treatment of LSN3090729 exhibits minimal anti-tumor growth activities, suggesting that a combination approach might be required for TBK1 kinase inhibition to be effective in cancer settings.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B229.

Citation Format: Robert Van Horn, Tinggui Yin, Xiaoyi Zhang, Chunping Yu, Youyan Zhang, Xue-Qian Gong, Sean Buchanan, Xiang S. Ye, William McMillen, David Barda, Sheng-Bin Peng. TBKI kinase inhibition blocks RANTES secretion and exhibits minimal tumor growth inhibition in oncogenic Ras-driven tumor models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B229.

Reactivation of mitogen-activated protein kinase (MAPK) pathway by FGF receptor 3 (FGFR3)/Ras mediates resistance to vemurafenib in human B-RAF V600E mutant melanoma

Oncogenic B-RAF V600E mutation is found in 50% of melanomas and drives MEK/ERK pathway and cancer progression. Recently, a selective B-RAF inhibitor, vemurafenib (PLX4032), received clinical approval for treatment of melanoma with B-RAF V600E mutation. However, patients on vemurafenib eventually develop resistance to the drug and demonstrate tumor progression within an average of 7 months. Recent reports indicated that multiple complex and context-dependent mechanisms may confer resistance to B-RAF inhibition. In the study described herein, we generated B-RAF V600E melanoma cell lines of acquired-resistance to vemurafenib, and investigated the underlying mechanism(s) of resistance. Biochemical analysis revealed that MEK/ERK reactivation through Ras is the key resistance mechanism in these cells. Further analysis of total gene expression by microarray confirmed a significant increase of Ras and RTK gene signatures in the vemurafenib-resistant cells. Mechanistically, we found that the enhanced activation of fibroblast growth factor receptor 3 (FGFR3) is linked to Ras and MAPK activation, therefore conferring vemurafenib resistance. Pharmacological or genetic inhibition of the FGFR3/Ras axis restored the sensitivity of vemurafenib-resistant cells to vemurafenib. Additionally, activation of FGFR3 sufficiently reactivated Ras/MAPK signaling and conferred resistance to vemurafenib in the parental B-RAF V600E melanoma cells. Finally, we demonstrated that vemurafenib-resistant cells maintain their addiction to the MAPK pathway, and inhibition of MEK or pan-RAF activities is an effective therapeutic strategy to overcome acquired-resistance to vemurafenib. Together, we describe a novel FGFR3/Ras mediated mechanism for acquired-resistance to B-RAF inhibition. Our results have implications for the development of new therapeutic strategies to improve the outcome of patients with B-RAF V600E melanoma.

Abstract B21: Resistance to B-RAF inhibitor is mediated by reactivation of MAPK pathway by FGFR3/Ras signaling in B-RAF V600E mutant melanoma

Melanoma is the most aggressive form of skin cancer. The RAF/MEK/ERK MAP kinase signaling plays a key role in melanoma progression and etiology, and is considered an important target for anti-melanoma therapies. Approximately 50% of melanomas carry an activating B-RAF V600E mutation that results in constitutive activation of B-RAF and downstream MAPK signaling. Recently, vemurafenib (PLX4032), a selective B-RAF inhibitor, was recently approved by U.S. FDA for treatment of metastatic and unresectable melanomas that carry an activating B-RAF V600E mutation. However, patients eventually developed resistance to vemurafenib and relapsed within an average of 7 months. To improve the clinical benefit of B-RAF inhibitors, it is critical to identify the molecular mechanisms that confer resistance to B-RAF inhibition. Recent reports indicate that multiple mechanisms may render mutant B-RAF expressing melanoma cells resistant to B-RAF inhibition. In this study, we generated vemurafenib-resistant cell lines by chronic treatment of the human B-RAF V600E melanoma cell lines, and investigated the underlying mechanism(s) of resistance. Our analysis revealed that MAPK pathway reactivation through Ras is the key resistance mechanism in these cells. Furthermore, microarray-based gene expression profiling confirmed a significant elevation of RTK and Ras gene signatures in the vemurafenib-resistant cells. Mechanistically, we found that the enhanced activation of FGFR3 is linked to elevated Ras and MAPK activation in the resistant cells, therefore conferring resistance to vemurafenib. Constitutive or inducible activation of FGFR3 sufficiently reactivated Ras/MAPK signaling and conferred resistance to vemurafenib in the parental B-RAF V600E melanoma cells. Additionally, genetic or pharmacological inhibition of the FGFR3/Ras axis restored the sensitivity of the resistant cells to vemurafenib. Finally, we demonstrated that vemurafenib-resistant cells are sensitive to MEK or pan-RAF inhibition and maintain their addiction to the MAPK pathway. Therefore, inhibition of MEK or pan-RAF activities is an effective therapeutic strategy to overcome acquired-resistance to vemurafenib. Together, we describe a novel FGFR3/Ras mediated mechanism for acquired-resistance to B-RAF inhibition. Our results shed new light on the complexity of the resistance mechanisms and have implications for the development of new therapeutic strategies to improve the outcome of patients with B-RAF V600E melanoma.

Institutional work amidst the financial crisis: emerging positions of elite actors

We draw on the institutional work literature to analyse the rhetoric in mainstream media spawned by the global financial crisis. We identify the emerging positions (status quo, neutral and change) of actors on major themes (policy, practices, recovery and regulation) related to the crisis and the rhetorical processes used (appeals to expert authority, finding someone to blame, use of scenarios, and avoidance of critical discussion) to communicate these positions. We find that academics lead the charge for change in policy, relying mostly on rhetorical processes that involve the use of past scenarios and blame, but also often avoid critical discussion through over-generalization. In contrast, banks focus on changes in practices, mostly using future scenarios, finding specific others to blame, and also appealing to expert authority. The US Federal Reserve takes the lead on maintaining the status quo on regulation-related issues, largely through using various scenarios and appeals to expert authority. We also find a large number of neutral positions and interpret this as tacit support for existing institutions. We conclude by charting out a broader research agenda for further investigation of the actors-institutions interplay, particularly within the context of the financial crisis.

Abstract LB-305: Why two are better than one: Suppression of carcinoma cell growth in vitro and in human HGF/SF transgenic SCID by inhibitors of MET (SGX523) and EGFR (erlotinib)

The signaling cascade originating from hepatocyte growth factor/scatter factor (HGF/SF)-MET ligand-receptor pair is frequently observed in a broad spectrum of human cancers. Inappropriate activation of this pathway has been shown to occur via: paracrine/autocrine activation; by amplification or mutation in the MET gene; or through ligand independent mechanisms (www.vai.org/met). Various MET drugs targeting this pathway are under development and in need of relevant in vivo tumor models to allow assessment of drug efficacy alone or in combination against human MET expressing tumors. Conventional mouse models post a significant limitation on fulfilling such demand as mouse HGF/SF has low affinity/activity on the human MET. Such limitations are abrogated in human HGF/SF transgenic SCIDs (designated hHGFtg-SCID), which, unlike its non-transgenic littermates, produce human HGF/SF to allow human MET signaling on cells of human cancer xenografts. Here, we show that the hHGFtg-SCID mouse significantly enhances tumor xenograft growth of many MET-expressing human carcinoma cell lines including lung, breast, kidney, colon, gastric and pancreatic cancers. Using the hHGFtg-SCID mouse model systems, we demonstrated that SGX523, a MET small molecule kinase inhibitor which suppressed MET phosphorylation and downstream signaling activation in vitro, partially inhibits the growth of xenografts derived from NCI-H596 lung cancer cells, HCC1954 breast cancer cells and HPAF II pancreatic cancer cells. Furthermore, we found that the partial tumor growth inhibition by SGX523 was significantly enhanced by co-administration of erlotinib, the EGFR small molecule kinase inhibitor. In vitro, erlotinib also enhanced SGX523 inhibitory activity in cell proliferation and G1/S cell cycle progression assays. Our data suggest that the hHGFtg-SCID mouse is a valuable system for evaluating MET drugs, and simultaneously targeting MET and EGFR pathways may provide a better treatment for cancers harboring inappropriate activation of both pathways.

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 LB-305.

Mapping water table depth using geophysical and environmental variables

Despite its importance, accurate representation of the spatial distribution of water table depth remains one of the greatest deficiencies in many hydrological investigations. Historically, both inverse distance weighting (IDW) and ordinary kriging (OK) have been used to interpolate depths. These methods, however, have major limitations: namely they require large numbers of measurements to represent the spatial variability of water table depth and they do not represent the variation between measurement points. We address this issue by assessing the benefits of using stepwise multiple linear regression (MLR) with three different ancillary data sets to predict the water table depth at 100-m intervals. The ancillary data sets used are Electromagnetic (EM34 and EM38), gamma radiometric: potassium (K), uranium (eU), thorium (eTh), total count (TC), and morphometric data. Results show that MLR offers significant precision and accuracy benefits over OK and IDW. Inclusion of the morphometric data set yielded the greatest (16%) improvement in prediction accuracy compared with IDW, followed by the electromagnetic data set (5%). Use of the gamma radiometric data set showed no improvement. The greatest improvement, however, resulted when all data sets were combined (37% increase in prediction accuracy over IDW). Significantly, however, the use of MLR also allows for prediction in variations in water table depth between measurement points, which is crucial for land management.

Functional neuroimaging with MEG: normative language profiles

The reliability of language-specific brain activation profiles was assessed using Magnetoencephalography (MEG) in five experiments involving ninety-seven normal volunteers of both genders ranging in age from seven to eighty-four years. MEG data were analyzed with a fully automated method to eliminate subjective judgments in the process of deriving the activation profiles. Across all experiments, profiles were characterized by significant bilateral activity centered in the superior temporal gyrus, and in activity lateralized to the left middle temporal gyrus. These features were invariant across age, gender, variation in task characteristics, and mode of stimulus presentation. The absolute amount of activation, however, did decline with age in the auditory tasks. Moreover, contrary to the commonly held belief that left hemisphere dominance for language is greater in men than in women, our data revealed an opposite albeit a not consistently significant trend.

Comparative changes in plasma concentrations of progesterone, oestradiol and LH during the ovulatory cycle in a multiple ovulating male line and a single ovulating traditional line of turkeys

The aim of this study was to compare the profile of circulating concentrations of LH, progesterone and oestradiol in a multiple ovulating male line with that of a single ovulating line of traditional turkeys. Plasma samples from seven traditional and 12 male-line turkeys were obtained every 3 h for 36 h. Male-line and traditional turkeys had single peaks of LH and progesterone that were of similar duration in both lines. The mean height of the plasma peaks of LH and progesterone were similar in the two lines and there was no detectable peak plasma oestrogen concentration. Mean plasma concentrations of LH and oestrogen were higher in single compared with multiple ovulating turkeys, whereas there were no differences in mean plasma progesterone concentrations. The results indicate that the multiple ovulation state in genetically selected high-growth lines of turkey may be the result of a correlated response in the steroidogenic capacity of ovarian tissue associated with low plasma concentrations of oestrogen rather than of a disturbance in the hormone profile of the ovulatory cycle.

Comparative changes in plasma concentrations of progesterone, oestradiol and LH during the ovulatory cycle in a multiple ovulating male line and a single ovulating traditional line of turkeys

The aim of this study was to compare the profile of circulating concentrations of LH, progesterone and oestradiol in a multiple ovulating male line with that of a single ovulating line of traditional turkeys. Plasma samples from seven traditional and 12 male-line turkeys were obtained every 3 h for 36 h. Male-line and traditional turkeys had single peaks of LH and progesterone that were of similar duration in both lines. The mean height of the plasma peaks of LH and progesterone were similar in the two lines and there was no detectable peak plasma oestrogen concentration. Mean plasma concentrations of LH and oestrogen were higher in single compared with multiple ovulating turkeys, whereas there were no differences in mean plasma progesterone concentrations. The results indicate that the multiple ovulation state in genetically selected high-growth lines of turkey may be the result of a correlated response in the steroidogenic capacity of ovarian tissue associated with low plasma concentrations of oestrogen rather than of a disturbance in the hormone profile of the ovulatory cycle.

Sequestration and phosphorylation of the prostaglandin E2 EP4 receptor: dependence on the C-terminal tail

The prostaglandin E2 (PGE2) EP4 subtype is one of four prostanoid receptors that use PGE2 as the preferred ligand. We have investigated the agonist-mediated regulation of EP4 using a multifaceted approach. Short-term (30 min) agonist challenge of recombinant EP4 expressed in human embryonic kidney 293 cells (EP4-HEK293 cells) with PGE2 (1 microM) resulted in the desensitization of intracellular cyclic AMP (cAMP) accumulation and a reduction in cell surface [3H]PGE2 specific binding sites. These events correlated with sequestration of EP4, as visualized by immunofluorescence confocal microscopy and phosphorylation, as shown by [32P]orthophosphate labeling of the receptor. Stimulation of protein kinase A activity in EP4-HEK293 cells (10 microM forskolin or 1 mM 8-bromo-cAMP) did not induce EP4 desensitization, sequestration, or phosphorylation. In contrast, stimulation of protein kinase C activity (100 nM phorbol 12-myristate 13-acetate) attenuated PGE2-induced adenylyl cyclase activity and increased EP4 phosphorylation, but did not induce sequestration or a reduction in [3H]PGE2 specific binding sites. EP4 receptors containing a third intracellular loop deletion [EP4 (del. 215-263)] or a carboxyl-terminal tail truncation [EP4 (del. 355)] of EP4 were used to demonstrate that the C-terminal tail governs sequestration as well as phosphorylation of the receptor.

Prospective randomised concurrent comparison of the COBE spectra version 4.7, COBE spectra version 6 (Auto PBSCtrade mark), and haemonetics MCS+ cell separators for leucapheresis in patients with haematological and non haematological malignancies

A prospective study of three cell separators was undertaken to compare the mononuclear cell, CD34+ cell and CFU-GM yield. Twenty patients were entered in the study; all had received chemotherapy and daily G-CSF (5 microg/kg subcutaneously) up to and including the first day of leucapheresis. The first leucapheresis was performed on the first day the peripheral blood absolute CD34+ cell count was > or =20 cells/microl. All patients underwent two leucaphereses on consecutive days. The patients were randomised to undergo either the first or second leucapheresis using the COBE Spectra Version 4.7 and then randomised to either the COBE Spectra Version 6 or Haemonetics MCS+ for the other leucapheresis. The target durations of the procedure on the COBE Spectra Version 4.7 and Version 6 were 180 minutes or 2 total blood volumes (TBV), and for the Haemonetics MCS+ was 20 cycles with four recirculations. All machines were operated on the 1997 software supplied by the respective manufacturers. The time taken for the procedure was significantly longer with both the Haemonetics MCS+ and the COBE Spectra Version 6 than the COBE Spectra Version 4.7. Both COBE Spectra versions processed significantly larger volumes of blood than the Haemonetics MCS+. The absolute yield of mononuclear cells, CFU-GM and CD34+ cells were all significantly lower with the Haemonetics MCS+ compared with both COBE Spectra versions, as were the yields per unit volume of blood processed. The product volume was significantly higher with the COBE Spectra Version 4.7 compared to the other two machines. There was no significant difference in the reduction in the platelet count following leucapheresis with any of the machines. The COBE Spectra Version 6 is particularly useful for patients with potentially poor peripheral venous access because of its increased interface stability.

Ovarian steroid hormone production in a multiple ovulating male line and a single ovulating traditional line of turkeys

Ovarian production of oestradiol and progesterone was investigated in a single ovulating traditional line and a multiple ovulating male line of turkeys. The oestradiol output from small follicles in response to LH stimulation and the aromatase activity of the residual ovary were also compared. The multiple hierarchy of follicles in the male line was shown to consist of a series of follicles of a similar size and stage of physiological maturation. The follicles of the traditional line produced significantly greater quantities of oestradiol than those of the male line. Impaired oestradiol production may have resulted in the lower plasma oestradiol concentration observed in the male line. There was no difference in follicular progesterone output between the traditional-line and male-line turkeys. The oestradiol output of whole small white follicles in response to LH stimulation was similar in the two lines and the depressed steroidogenesis of the male line was not changed. The aromatase activity of the small follicles was also lower in the male line, and there was no evidence that the male line ovary produced oestradiol in quantities proportional to its size. The results demonstrated that the hierarchy of follicles in the male line consisted of groups of follicles of similar mass and hormone output and indicated that selection for increased meat yield may have resulted in reduced ovarian steroidogenesis in male-line turkeys, in comparison with traditional, unselected turkeys.

Ovarian steroid hormone production in a multiple ovulating male line and a single ovulating traditional line of turkeys

Ovarian production of oestradiol and progesterone was investigated in a single ovulating traditional line and a multiple ovulating male line of turkeys. The oestradiol output from small follicles in response to LH stimulation and the aromatase activity of the residual ovary were also compared. The multiple hierarchy of follicles in the male line was shown to consist of a series of follicles of a similar size and stage of physiological maturation. The follicles of the traditional line produced significantly greater quantities of oestradiol than those of the male line. Impaired oestradiol production may have resulted in the lower plasma oestradiol concentration observed in the male line. There was no difference in follicular progesterone output between the traditional-line and male-line turkeys. The oestradiol output of whole small white follicles in response to LH stimulation was similar in the two lines and the depressed steroidogenesis of the male line was not changed. The aromatase activity of the small follicles was also lower in the male line, and there was no evidence that the male line ovary produced oestradiol in quantities proportional to its size. The results demonstrated that the hierarchy of follicles in the male line consisted of groups of follicles of similar mass and hormone output and indicated that selection for increased meat yield may have resulted in reduced ovarian steroidogenesis in male-line turkeys, in comparison with traditional, unselected turkeys.