Thrombospondin-I is a critical modulator in non-alcoholic steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) is a progressive liver disease characterized by dysregulated lipid metabolism and chronic inflammation ultimately resulting in fibrosis. Untreated, NAFLD may progress to non-alcoholic steatohepatitis (NASH), cirrhosis and death. However, currently there are no FDA approved therapies that treat NAFLD/NASH. Thrombospondin-I (TSP-1) is a large glycoprotein in the extracellular matrix that regulates numerous cellular pathways including transforming growth factor beta 1 (TGF-β1) activation, angiogenesis, inflammation and cellular adhesion. Increased expression of TSP-1 has been reported in various liver diseases; however, its role in NAFLD/NASH is not well understood. We first examined TSP-1 modulation in hepatic stellate cell activation, a critical initiating step in hepatic fibrosis. Knockdown or inhibition of TSP-1 attenuated HSC activation measured by alpha smooth muscle actin (α-SMA) and Collagen I expression. To investigate the impact of TSP-1 modulation in context of NAFLD/NASH, we examined the effect of TSP-1 deficiency in the choline deficient L-amino acid defined high fat diet (CDAHFD) model of NASH in mice by assessing total body and liver weight, serum liver enzyme levels, serum lipid levels, liver steatosis, liver fibrosis and liver gene expression in wild type (WT) and TSP-1 null mice. CDAHFD fed mice, regardless of genotype, developed phenotypes of NASH, including significant increase in liver weight and liver enzymes, steatosis and fibrosis. However, in comparison to WT, CDAHFD-fed TSP-1 deficient mice were protected against numerous NASH phenotypes. TSP-1 null mice exhibited a decrease in serum lipid levels, inflammation markers and hepatic fibrosis. RNA-seq based transcriptomic profiles from the liver of CDAHFD fed mice determined that both WT and TSP-1 null mice exhibited similar gene expression signatures following CDAHFD, similar to biophysical and histological assessment comparison. Comparison of transcriptomic profiles based on genotype suggested that peroxisome proliferator activated receptor alpha (PPARα) pathway and amino acid metabolism pathways are differentially expressed in TSP-1 null mice. Activation of PPARα pathway was supported by observed decrease in serum lipid levels. Our findings provide important insights into the role of TSP-1 in context of NAFLD/NASH and TSP-1 may be a target of interest to develop anti-fibrotic therapeutics for NAFLD/NASH.

Abstract 3126: H3B6527, a selective and potent FGFR4 inhibitor for FGF19-driven hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has limited treatment options and generally poor prognosis. Recent genomic studies have identified FGF19 as a driver oncogene in HCC. FGF19 is a gut secreted hormone that acts in the liver through FGFR4 to regulate bile acid synthesis. Consistent with the notion that FGF19 is a driver oncogene in HCC, transgenic mice overexpressing FGF19 form liver tumors and genetic ablation of FGFR4 prevented tumor formation. These data suggest targeting FGFR4 would have therapeutic benefit in HCC with altered FGF19 signaling. While a number of Pan-FGFR inhibitors are being clinically evaluated, their application to FGF19-driven HCC may be limited by their FGFR1-3 related dose limiting toxicities. Using structure guided drug design, we have generated a highly selective covalent FGFR4 inhibitor, H3B-6527. Biochemical and cellular selectivity assays showed that H3B-6527 is >300 fold selective towards FGFR4 compared to other FGFR isoforms. Addition of H3B-6527 to FGF19 amplified HCC cell lines led to dose dependent inhibition of FGF19/FGFR4 signaling and concomitant reduction in cell viability. In a panel of 40 HCC cell lines, H3B-6527 selectively reduced the viability of cells that harbor FGF19 amplification and showed no effect in FGF19 non-amplified HCC cell line models. Oral dosing of H3B-6527 to mice led to dose-dependent pharmacodynamic modulation of FGFR4 signaling and tumor regression in FGF19 altered HCC cell line derived xenograft models. H3B-6527 demonstrated inhibition of tumor growth in an orthotopic liver xenograft model of FGF19 altered HCC grown in nude mice. Importantly, the inhibition of tumor growth occurred at doses that were well tolerated in mice and no evidence of FGFR1-3 related toxicities were observed at efficacious doses. In a panel of 30 HCC patient-derived xenograft (PDX) models, H3B-6527 demonstrated tumor regressions in the context of FGF19-amplified tumors. In addition, H3B-6527 showed antitumor activity and tumor regressions in PDX models with high FGF19 expression but no FGF19 amplification. The mechanism for FGF19 overexpression in the absence of gene amplification is under investigation. In conclusion, our preclinical studies demonstrate that FGF19 expression is a predictive biomarker for response to FGFR4 inhibitor therapy. Genomic analysis of public and proprietary data sets indicates that at least approximately 30% of HCC patients exhibit altered FGF19 expression and could potentially benefit from H3B-6527 monotherapy treatment.

Citation Format: Anand Selvaraj, Erik Corcoran, Heather Coffey, Sudeep Prajapati, Ming-Hong Hao, Nicholas Larsen, Jennifer Tsai, Takashi Satoh, Kana Ichikawa, Julie Jaya Joshi, Raelene Hurley, Jeremy Wu, Chia-Ling Huang, Suzanna Bailey, Craig Karr, Pavan Kumar, Victoria Rimkunas, Crystal Mackenzie, Nathalie Rioux, Amy Kim, Sandeep Akare, George Lai, Lihua Yu, Peter Fekkes, John Wang, Markus Warmuth, Peter Smith, Dominic Reynolds. H3B6527, a selective and potent FGFR4 inhibitor for FGF19-driven hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3126. doi:10.1158/1538-7445.AM2017-3126

Apratoxin A Shows Novel Pancreas-Targeting Activity through the Binding of Sec 61

Apratoxin A is a natural product with potent antiproliferative activity against many human cancer cell lines. However, we and other investigators observed that it has a narrow therapeutic window in vivo Previous mechanistic studies have suggested its involvement in the secretory pathway as well as the process of chaperone-mediated autophagy. Still the link between the biologic activities of apratoxin A and its in vivo toxicity has remained largely unknown. A better understanding of this relationship is critically important for any further development of apratoxin A as an anticancer drug. Here, we describe a detailed pathologic analysis that revealed a specific pancreas-targeting activity of apratoxin A, such that severe pancreatic atrophy was observed in apratoxin A-treated animals. Follow-up tissue distribution studies further uncovered a unique drug distribution profile for apratoxin A, showing high drug exposure in pancreas and salivary gland. It has been shown previously that apratoxin A inhibits the protein secretory pathway by preventing cotranslational translocation. However, the molecule targeted by apratoxin A in this pathway has not been well defined. By using a (3)H-labeled apratoxin A probe and specific Sec 61α/β antibodies, we identified that the Sec 61 complex is the molecular target of apratoxin A. We conclude that apratoxin A in vivo toxicity is likely caused by pancreas atrophy due to high apratoxin A exposure. Mol Cancer Ther; 15(6); 1208-16. ©2016 AACR.

Assessment of the translational value of mouse lupus models using clinically relevant biomarkers

Lupus is an autoimmune disease with a poorly understood etiology that manifests with a diverse pathology. This heterogeneity has been a challenge to clinical drug development efforts. A related difficulty is the uncertain translational power of animal models used for evaluating potential drug targets and candidate therapeutics, because it is unlikely that any 1 preclinical model will recapitulate the spectrum of human disease. Therefore, multiple models, along with an understanding of the immune mechanisms that drive them, are necessary if we are to use them to identify valid drug targets and evaluate candidate therapies successfully. To this end, we have characterized several different mouse lupus models and report their differences with respect to biomarkers and symptoms that are representative of the human disease. We compared the pristane-induced mouse lupus disease model using 3 different strains (DBA/1, SJL, BALB/c), and the spontaneous NZB x NZW F1(NZB/W) mouse model. We show that the models differ significantly in their autoantibody profiles, disease manifestations such as nephritis and arthritis, and expression of type I interferon-regulated genes. Similar to the NZB/W model, pristane-induced disease in SJL mice manifests with nephritis and proteinuria, whereas the pristane-treated DBA/1 mice develop arthritis and an interferon-driven gene signature that closely resembles that in human patients. The elucidation of each model's strengths and the identification of translatable biomarkers yields insight for basic lupus research and drug development, and should assist in the proper selection of models for evaluating candidate targets and therapeutic strategies.

Brunner's gland lesions in rats induced by a vascular endothelial growth factor receptor inhibitor

Vascular endothelial growth factor (VEGF) receptor tyrosine kinase (RTK) inhibitors are reported to cause reversible mucosal hyperplasia (adenosis) in the duodenum of rats; however, the pathogenesis is not fully elucidated. Using lenvatinib, a VEGF RTK inhibitor, we characterized the histologic time course of this duodenal change in rats. At 4 weeks, there was degeneration and necrosis of Brunner's gland epithelium accompanied by neutrophil infiltration around the affected glands. At 13 weeks, the inflammation was more extensive, and Brunner's gland epithelium was attenuated and flattened and was accompanied by reactive hyperplasia of duodenal epithelium. At 26 weeks, the changes became more severe and chronic and characterized by marked cystic dilation, which extended to the external muscular layer. These dilated glands exhibited morphological characteristics of duodenal crypt epithelium, suggestive of replacement of disappeared Brunner's glands by regenerative duodenal crypt epithelial cells. Similar changes were not present in similar time course studies in dog and monkey studies, suggesting that this is a rodent- or species-specific change. Based on the temporal progression of Brunner's gland lesion, we identify degeneration and necrosis of the Brunner's glands as the primary change leading to inflammation, cystic dilatation, and regeneration with cells that are morphologically suggestive of duodenal crypt epithelium.

Evaluation of a candidate anti-arthritic drug using the mouse collagen antibody induced arthritis model and clinically relevant biomarkers

The most rigorous scenario for testing a candidate rheumatoid arthritis therapeutic would be to use clinically relevant biomarkers and readouts to monitor disease development in an animal model that has a mechanism of disease that reflects the human condition. Treatment should begin when the full spectrum of arthritic processes, including bone damage, is present. We have tried to take this approach to evaluate a novel EP4 receptor antagonist (ER-886046) for its anti-arthritic potential. This work aimed not only to test a potential drug, but to also demonstrate a strategy for performing a more clinically relevant evaluation of future candidate arthritis treatments. A variety of biomarkers including: radiographic evaluation, clinical scoring, histology analysis, F4/80 macrophage immunohistochemistry, luminol bioluminescent imaging and (99m)Tc-MDP-SPECT imaging were evaluated as disease readouts in the mouse anti-collagen antibody induced arthritis model (CAIA). CAIA mice were treated either prophylactically or therapeutically with ER-886046 and the compound's efficacy was probed using the various biomarkers and compared to the reference drugs prednisolone and celecoxib. The various biomarkers effectively measured different aspects of arthritis pathology and consistently demonstrated the efficacy of ER-886046. The compound was found to be effective even when dosed therapeutically after bone damaging processes had initiated. The results presented herein demonstrate how biomarkers and a clinically relevant experimental design can be used to evaluate a candidate therapeutic. Utilization of clinically relevant biomarkers may provide a means for more translatable pre-clinical testing of candidate therapeutics and may provide information on their mechanism of action.

Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence

Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

Resistance to ursodeoxycholic acid-induced growth arrest can also result in resistance to deoxycholic acid-induced apoptosis and increased tumorgenicity

BACKGROUND

There is a large body of evidence which suggests that bile acids increase the risk of colon cancer and act as tumor promoters, however, the mechanism(s) of bile acids mediated tumorigenesis is not clear. Previously we showed that deoxycholic acid (DCA), a tumorogenic bile acid, and ursodeoxycholic acid (UDCA), a putative chemopreventive agent, exhibited distinct biological effects, yet appeared to act on some of the same signaling molecules. The present study was carried out to determine whether there is overlap in signaling pathways activated by tumorogenic bile acid DCA and chemopreventive bile acid UDCA.

METHODS

To determine whether there was an overlap in activation of signaling pathways by DCA and UDCA, we mutagenized HCT116 cells and then isolated cell lines resistant to UDCA induced growth arrest. These lines were then tested for their response to DCA induced apoptosis.

RESULTS

We found that a majority of the cell lines resistant to UDCA-induced growth arrest were also resistant to DCA-induced apoptosis, implying an overlap in DCA and UDCA mediated signaling. Moreover, the cell lines which were the most resistant to DCA-induced apoptosis also exhibited a greater capacity for anchorage independent growth.

CONCLUSION

We conclude that UDCA and DCA have overlapping signaling activities and that disregulation of these pathways can lead to a more advanced neoplastic phenotype.

Deoxycholic acid induces intracellular signaling through membrane perturbations

Secondary bile acids have long been postulated to be tumor promoters in the colon; however, their mechanism of action remains unclear. In this study, we examined the actions of bile acids at the cell membrane and found that they can perturb membrane structure by alteration of membrane microdomains. Depletion of membrane cholesterol by treating with methyl-beta-cyclodextrin suppressed deoxycholic acid (DCA)-induced apoptosis, and staining for cholesterol with filipin showed that DCA caused a marked rearrangement of this lipid in the membrane. Likewise, DCA was found to affect membrane distribution of caveolin-1, a marker protein that is enriched in caveolae membrane microdomains. Additionally, fluorescence anisotropy revealed that DCA causes a decrease in membrane fluidity consistent with the increase in membrane cholesterol content observed after 4 h of DCA treatment of HCT116 cells. Significantly, by using radiolabeled bile acids, we found that bile acids are able to interact with and localize to microdomains differently depending on their physicochemical properties. DCA was also found to induce tyrosine phosphorylation and activate the receptor tyrosine kinase epidermal growth factor receptor in a ligand-independent manner. In contrast, ursodeoxycholic acid did not exhibit any of these effects even though it interacted significantly with the microdomains. Collectively, these data suggest that bile acid-induced signaling is initiated through alterations of the plasma membrane structure and the redistribution of cholesterol.

Bile acid induces hydrophobicity-dependent membrane alterations

Elevated concentrations of fecal bile acids are a known risk factor for colon cancer, owing to alterations in cellular signaling. In colonic cells, where bile acid uptake is minimal, the hydrophobicity-induced membrane perturbation and alterations have been proposed, but these membrane alterations are largely uncharacterized. In this study, we examined the determinants and characteristics of bile acid-induced membrane alterations, utilizing PKCalpha activation and cholesterol up-regulation as model indicators. We found that bile acid-induced PKCalpha activation is a function of hydrophobicity and correlated with alteration in membrane lipid composition, as evident by the significant up-regulation in membrane cholesterol and phospholipid. We found that bile acid do not cause cell membrane disruption at a concentration sufficient to activate PKCalpha, but do induce drastic alterations in membrane composition. Bile acid also induced the modification and up-regulation of caveolin-1 in a hydrophobicity-dependent manner, implying widespread receptor dysregulation. Similarly, ERK1/2 activation was observed only in response to hydrophobic bile acids, suggesting hydrophobicity-induced caveolar or membrane stress. Experiments with sodium lauryl sarcosine and cholesteryl hemisuccinate showed that bile acid-induced membrane alterations can be mimicked by hydrophobic molecules unrelated to bile acids, strongly implicating hydrophobicity as an important determinant of bile acid signaling.

Ursodeoxycholic Acid Can Suppress Deoxycholic Acid-Induced Apoptosis by Stimulating Akt/PKB-Dependent Survival Signaling

The nontoxic bile acid ursodeoxycholic acid (UDCA) is reported to be an anti-apoptotic agent with efficacy against a variety of death stimuli including the cytotoxic bile acid deoxycholic acid (DCA). To gain insight into this anti-apoptotic property, we tested UDCA for its ability to protect the colon carcinoma-derived cell line HCT116 against DCA-induced apoptosis. We found that UDCA could suppress DCA-induced apoptosis in a time- and dose-dependent manner and that this effect correlated with Akt phosphorylation. Importantly, UDCA lost its ability to protect cells from DCA-induced cell death when Akt activity was suppressed genetically using a dominant negative Akt mutant or when PI3K activity was inhibited pharmacologically. These results suggest that UDCA can protect HCT116 cells against DCA-induced apoptosis by stimulating Akt-dependent survival signaling.