Abstract C254: Discovery of a novel and potent BRAF (V600E) inhibitor with a unique kinase targeting profile, EBI-907: Pharmacological characterization and potential to overcome drug resistance and paradoxical activation

The RAS/RAF/MEK/ERK pathway plays a central role in regulating cell proliferation, differentiation, and growth. The oncogenic mutation of BRAF (V600E) has been found in 8% of all human cancers, including more than 60% of melanoma, 45% of papillary thyroid cancer, 10% of colorectal cancers, and a small subset of ovarian, breast, lung cancers, and leukemia. Although BRAF-specific inhibitors such as Vemurafenib (PLX-4032) and Dabrafenib (GSK2118436) have been approved by FDA and several other BRAF inhibitors are at different stages of clinical development, they carry some liabilities and drug resistance rapidly developed. We have sought to identify and develop more potent BRAF (V600E) inhibitors with favorable pharmacological and safety profiles. Our chemistry effort has led to the discovery of EBI-907 as a novel BRAF (V600E) inhibitor with potent anti-tumor activity in vitro and in vivo. In a LanthaScreen BRAF (V600E) kinase assay, EBI-907 is a highly potent inhibitor displaying a low single-digit nanomolar activity (IC50 = 4.9 nM), which is >10-fold more potent than Vemurafenib (IC50 = 59 nM). EBI-907 also exhibits high potency in selectively inhibiting the proliferation of BRAF (V600E)-dependent cell lines (A375 and Colo205) and cellular Erk phosporylation, with superior activity to Vemurafenib. In multiple preclinical species (mice, rats, and dogs), EBI-907 exhibited an excellent oral bioavailability. In a BRAF (V600E)-dependent human Colo-205 tumor xenograft mouse model, EBI-907 caused a partial or complete tumor regression in a dose-dependent manner, with superior efficacy than Vemurafenib. In addition, we have also observed a broader kinase selectivity profile for EBI-907, displaying potent activity against a number of important oncogenic kinases including BRK, FGFR1, c-Kit, and PDGFRb. Preliminary toxicity studies in rodent models showed that EBI-907 was well tolerated and has a high safety margin. More importantly, EBI-907 showed a favorable pattern of drug-induced paradoxical activation of MAPK pathway, pointing to a possibility to “break” the inhibitor paradox. Finally, our results showed that combined use of EBI-907 and a MEK inhibitor completely abolished the paradoxical activation and overcame the drug resistance induced by BRAF inhibitor alone. Our findings not only present EBI-907 as a potent and promising BRAF inhibitor, but also point out a possibility to develop next generation targeted therapies to treat BRAF mutated cancers.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C254.

Citation Format: Jiayin Zhang, Dong Liu, Ru Shen, Yinfa Yan, Liuqing Yang, Minsheng Zhang, Guoqing Cao, Hu Cao, Beibei Fu, Aishen Gong, Biao Lu, Qiming Sun, Hong Wan, Pangke Yan, Lei Zhang, Lianshan Zhang, Jingsong Cao. Discovery of a novel and potent BRAF (V600E) inhibitor with a unique kinase targeting profile, EBI-907: Pharmacological characterization and potential to overcome drug resistance and paradoxical activation. [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 C254.

A weight-of-evidence approach to integrate suspended sediment source information

Sediment monitoring, tracing and modelling are widely used to identify suspended sediment sources. Although each method has inherent limitations and uncertainties, their integration provides opportunities to form collective knowledge and encourages robust management strategies. This paper presents a Weight-of-Evidence approach to integrate multiple Lines-of-Evidence for identifying suspended sediment sources. Three sources of evidence were used: i) stream flow and suspended sediment monitoring at river gauges; ii) geochemical sediment tracing at river junctions; and iii) catchment-scale suspended sediment modelling of hillslope, gully, streambank and unsealed road erosion. We applied this approach on two data-poor catchments in Australia. Some reaches were consistently identified as major sources of sediment from all Lines-of-Evidence. However, inconsistencies between the types of evidence in other areas highlighted the high uncertainty in identifying suspended sediment sources in these areas and the need for further investigation. The integration framework maximised the use of scarce information, enabled explicit consideration of uncertainties for catchment management and identified where future monitoring and research should be targeted.

Tracking chromosome evolution in southern African gerbils using flow-sorted chromosome paints

Desmodillus and Gerbilliscus (formerly Tatera) comprise a monophyletic group of gerbils (subfamily Gerbillinae) which last shared an ancestor approximately 8 million years ago; diploid chromosome number variation among the species ranges from 2n = 36 to 2n = 50. In an attempt to shed more light on chromosome evolution and speciation in these rodents, we compared the karyotypes of 7 species, representing 3 genera, based on homology data revealed by chromosome painting with probes derived from flow-sorted chromosomes of the hairy footed gerbil, Gerbillurus paeba (2n = 36). The fluorescent in situ hybridization data revealed remarkable genome conservation: these species share a high proportion of conserved chromosomes, and differences are due to 10 Robertsonian (Rb) rearrangements (3 autapomorphies, 3 synapomorphies and 4 hemiplasies/homoplasies). Our data suggest that chromosome evolution in Desmodillus occurred at a rate of ~1.25 rearrangements per million years (Myr), and that the rate among Gerbilliscus over a time period spanning 8 Myr is also ~1.25 rearrangements/Myr. The recently diverged Gerbillurus (G. tytonis and G. paeba) share an identical karyotype, while Gerbilliscus kempi, G. afra and G. leucogaster differ by 6 Rb rearrangements (a rate of ~1 rearrangement/Myr). Thus, our data suggests a very slow rate of chromosomal evolution in Southern African gerbils.

Mesenchymal stem cells modified to express interferon-β inhibit the growth of prostate cancer in a mouse model

OBJECTIVE

This study investigated use of mesenchymal stem cells (MSCs) genetically engineered to produce interferon-β (IFN-β) as a gene delivery system to treat prostate cancer in an animal model.

METHODS

To measure the effects on tumour cell growth in vitro, IFN-β-producing MSCs (IFN-β-MSCs) were co-cultured with the prostate cancer cell line PC-3. The in vivo migration of intravenously injected fluorescently-labelled MSCs to healthy tissues and PC-3 xenograft tumours grown in immuno-deficient mice was determined by fluorescence microscopy. The antitumour effects of intravenously injected IFN-β-MSCs on PC-3 xenograft growth and animal survival were also investigated.

RESULTS

IFN-β-MSCs inhibited the growth of PC-3 cells in vitro. Fluorescently-labelled MSCs migrated to the margins and centre of tumour masses but not into healthy tissues. Intravenously injected IFN-β-MSCs significantly reduced PC-3 xenograft tumour weight and increased animal survival compared with controls.

CONCLUSIONS

Intravenously injected IFN-β-MSCs inhibited PC-3 xenograft growth. This could be an effective gene delivery system for treatment of solid human tumours.

First Report of Fusarium pseudograminearum Causing Crown Rot of Wheat in Henan, China

Fusarium pseudograminearum (O'Donnell & Aoki), a residue-borne pathogen, is responsible for crown rot of wheat (Triticum aestivum L.). Since its first detection in Queensland, Australia in 1951, it has been reported in many other countries, but not China (2). In May 2011, a crown rot disease was observed in wheat cv. Aikang 58 in a wheat-maize rotation, irrigable and loam field in Henan Province, China. Diseased wheat plants showed honey brown discoloration in the stem bases and whitehead in some plants, which are symptoms of crown rot with about 70% incidence in a surveyed field (2). The pathogen was isolated from diseased stem base on potato dextrose agar (PDA) after being surface-disinfested with 5% NaClO solution for 2 min. Pure cultures were established on carnation leaf agar (CLA) through a single spore technique and identified by morphological and molecular methods according to protocols described previously (1,3,4). Macroconidia of F. pseudograminearum were formed in abundant sporodochia on CLA cultures grown under the BLB light. Macroconidia were usually five septate (about three to seven) and 27 to 91 × 2.7 to 5.5 μm. Colonies grown on PDA from a single conidium in the dark at 25°C had average radial growth rates of ~4.7 to 9.9 mm per day. Colony pigment on PDA grown under light varied from rose to burgundy, while mycelium ranged from rose to yellow white. Two isolates (WZ-8A and WZ-2B) were selected for molecular identification. The translation elongation factor 1-α gene and rDNA ITS gene were amplified by PCR using the specific primers described previously (4). PCR products were sequenced (GenBank Accession Nos. JN862232 to JN862235). Phylogenic analysis of the sequence indicated that the isolates were identified as F. pseudograminearum. The identification was further confirmed by the F. pseudograminearum species-specific PCR primers (Fp1-1: CGGGGTAGTTTCACATTTCCG and Fp1-2: GAGAATGTGATGACGACAATA) (1). The expected PCR products of 520 bp were produced only in F. pseudograminearum. Isolates WZ-2B and WZ-8A were deposited in the Agriculture Culture Collection of China as ACCC38067 and ACCC 38068, respectively. Pathogenicity tests were conducted by inoculating winter wheat cultivar Wenmai 19 with isolates WZ-8A and WZ-2B through soil inoculation. Inoculum was prepared by growing cultures on sterilized wheat bran and chopped wheat-straw (4:1, v/v) after incubation at 25°C for 2 weeks. This inoculum was added to sterilized soil at 1% by volume and no inoculum was added in control treatment. Five seeds were planted in a 15 cm wide pot in a 20 to 25°C greenhouse, with six replications. Seedling death and crown browning occurred in the inoculated wheat plants after 4 weeks with over 90% incidence, while no symptoms developed in the control plants. The fungus was reisolated from inoculated plants, fulfilling Koch's postulates. To our knowledge, this is the first report of F. pseudograminearum causing crown rot of wheat in China. Considering Henan is the largest wheat production province in China with over 5 million hectares planting area, and the soil and climate conditions are suitable for this disease, it will be a important pathogen of wheat in Henan in the future. References: (1) T. Aoki et al. Mycologia 91:597, 1999. (2) L. W. Burgess. Page 271 in: Crown Rot of Wheat: Fusarium. B. A. Summerell et al., eds. APS Press, St. Paul, MN, 2001. (3) R. G. Francis et al. Trans. Brit. Mycol. Soc. 68:421, 1977. (4) J. B. Scott et al. Mycol. Res. 110:1413, 2006.

Correlation between expression of S100A4 and VEGF-C, and lymph node metastasis and prognosis in gastric carcinoma

This semiquantitative immunohistochemical study investigated the clinical significance of S100A4 and vascular endothelial growth factor C (VEGF-C) protein expression in gastric carcinoma. Correlations between S100A4 and VEGF-C immunoreactivity and clinicopathological characteristics were evaluated using 108 gastric carcinoma specimens and 20 specimens of tissue adjacent to gastric carcinoma. S100A4 and VEGF-C expression in carcinoma was higher than that in adjacent tissues. S100A4 expression was significantly related to tumour size and lymph node metastasis, whereas VEGF-C expression was associated with invasion depth, lymph node metastasis and tumour, node, metastasis (TNM) stage. A significant correlation was found between S100A4 and VEGF-C expression. Patients expressing S100A4 or VEGF-C showed no significant reduction in 5-year survival rate compared with those not expressing these proteins. Sex, age, tumour size, invasion depth, lymph node involvement, TNM stage, S100A4 expression and VEGF-C expression had a common effect on carcinoma prognosis but none was an independent prognostic factor.

The proteasome inhibitor bortezomib reverses P-glycoprotein-mediated leukemia multi-drug resistance through the NF-kappaB pathway

Multi-drug resistance (MDR) is one of the obstacles for leukemia therapy, the major cause is an overexpression of P-glycoprotein (P-gp) leading to increased drug efflux. We investigated the reversion of multi-drug resistance and the possible mechanism by which the proteasome inhibitor bortezomib affects the expression of the multi-drug resistance gene mdrl in the K562/DNR cell line. The drug resistance of the cells and the cellular toxicity of bortezomib were confirmed by MTT. Intracellular drug concentrations and cell apoptosis were detected by flow cytometry. The expression of mdrl mRNA was examined by fluorescence quantitative PCR. The expression levels of nuclear factor-kappa B (NF-kappaB), inhibitor of NF-kappaB (IkappaB) and P-gp were detected by western blotting, and NF-kappaB activity was detected by ELISA. DNR-induced apoptosis increased in a dose-dependent manner after adding bortezomib. Bortezomib decreased IkappaB degradation, decreased NF-kappaB and NF-kappaB p65 activity, reduced P-gp/mdr1 mRNA expression, and increased the intracellular DNR concentration in K562/DNR cells in vitro. The bortezomib reversed leukemic multi-drug resistance in a dose-dependent manner as the result of decreasing IkappaB degradation, thus preventing the translocation of NF-kappaB into the nucleus and leading the down-regulation of mdr1 and a reduction in P-gp expression. Therefore, the intracellular drug concentration increased, and then apoptosis was induced.

Antigen-specific T-regulatory cells can extend skin graft survival time in mice

This study investigated the effects of donor antigen-specific CD4(+)CD25(+) T-regulatory cells (Tregs) on skin allografts in mice. An allogeneic skin transplant model was established using donor C57BL/6 or DBA and recipient BALB/c mice. Recipients were divided into 4 groups: control group without intervention (CON; C57BL/6 to BALB/c), rapamycin gavage group (RAP; C57BL/6 to BALB/c), CD4(+)CD25(+) Tregs-treated group (TRE; C57BL/6 to BALB/c), in which recipients received transfusions of CD4(+)CD25(+) Tregs stimulated with C57BL/6-derived immature dendritic cells, and the third-party donor group (DBA; DBA to BALB/c) in which recipients received transfusions of BALB/c CD4(+)CD25(+) Tregs stimulated with C57BL/6-derived immature dendritic cells. Mean (SD) survival time of the skin allografts in the TRE group was 17.0 (3.4) days, significantly longer than in the other groups: CON, 6.9 (1.9) days; RAP, 10.3 (3.0) days; and DBA, 10.8 (3.6) days. The TRE group demonstrated a significantly greater expression of transforming growth factor-β and interleukin (IL)-10. Donor antigen-specific CD4(+)CD25(+) Tregs effectively extend skin allograft survival in mice.