Preclinical Assessment of a MUC12-Targeted BiTE (Bispecific T-cell Engager) Molecule.

MUC12 is a transmembrane mucin that is highly expressed in >50% of primary and metastatic colorectal tumors. MUC12 is also expressed by normal epithelial cells of the colon and small intestine. Although MUC12 localization in normal epithelial cells is restricted to the apical membrane, expression in tumors is depolarized and shows broad membrane localization. The differential localization of MUC12 in tumor cells as compared with normal cells makes it a potential therapeutic target. Here, we evaluated targeting of MUC12 with a BiTE (bispecific T-cell engager) molecule. We generated a panel of proof-of-concept half-life extended (HLE) BiTE molecules that bind MUC12 on tumor cells and CD3 on T cells. We prioritized one molecule based on in vitro activity for further characterization in vivo In vitro, the MUC12 HLE BiTE molecule mediated T-cell-redirected lysis of MUC12-expressing cells with half-maximal lysis of 4.4 ± 0.9 to 117 ± 78 pmol/L. In an exploratory cynomolgus monkey toxicology study, the MUC12 HLE BiTE molecule administered at 200 µg/kg with a step dose to 1,000 µg/kg was tolerated with minimal clinical observations. However, higher doses were not tolerated, and there was evidence of damage in the gastrointestinal tract, suggesting dose levels projected to be required for antitumor activity may be associated with on-target toxicity. Together, these data demonstrate that the apically restricted expression of MUC12 in normal tissues is accessible to BiTE molecule target engagement and highlight the difficult challenge of identifying tumor-selective antigens for solid tumor T-cell engagers.

Characterization of a Novel FLT3 BiTE Molecule for the Treatment of Acute Myeloid Leukemia.

Despite advances in the treatment of acute myeloid leukemia (AML), novel therapies are needed to induce deeper and more durable clinical response. Bispecific T-cell Engager (BiTE) molecules, which redirect patient T cells to lyse tumor cells, are a clinically validated modality for hematologic malignancies. Due to broad AML expression and limited normal tissue expression, fms-related tyrosine kinase 3 (FLT3) is proposed to be an optimal BiTE molecule target. Expression profiling of FLT3 was performed in primary AML patient samples and normal hematopoietic cells and nonhematopoietic tissues. Two novel FLT3 BiTE molecules, one with a half-life extending (HLE) Fc moiety and one without, were assessed for T-cell-dependent cellular cytotoxicity (TDCC) of FLT3-positive cell lines in vitro, in vivo, and ex vivo FLT3 protein was detected on the surface of most primary AML bulk and leukemic stem cells but only a fraction of normal hematopoietic stem and progenitor cells. FLT3 protein detected in nonhematopoietic cells was cytoplasmic. FLT3 BiTE molecules induced TDCC of FLT3-positive cells in vitro, reduced tumor growth and increased survival in AML mouse models in vivo Both molecules exhibited reproducible pharmacokinetic and pharmacodynamic profiles in cynomolgus monkeys in vivo, including elimination of FLT3-positive cells in blood and bone marrow. In ex vivo cultures of primary AML samples, patient T cells induced TDCC of FLT3-positive target cells. Combination with PD-1 blockade increased BiTE activity. These data support the clinical development of an FLT3 targeting BiTE molecule for the treatment of AML.

Methyl-donor supplementation in obese mice prevents the progression of NAFLD, activates AMPK and decreases acyl-carnitine levels.

Non-alcoholic fatty liver disease (NAFLD) results from increased hepatic lipid accumulation and steatosis, and is closely linked to liver one-carbon (C1) metabolism. We assessed in C57BL6/N mice whether NAFLD induced by a high-fat (HF) diet over 8 weeks can be reversed by additional 4 weeks of a dietary methyl-donor supplementation (MDS). MDS in the obese mice failed to reverse NAFLD, but prevented the progression of hepatic steatosis associated with major changes in key hepatic C1-metabolites, e.g. S-adenosyl-methionine and S-adenosyl-homocysteine. Increased phosphorylation of AMPK-α together with enhanced ß-HAD activity suggested an increased flux through fatty acid oxidation pathways. This was supported by concomitantly decreased hepatic free fatty acid and acyl-carnitines levels. Although HF diet changed the hepatic phospholipid pattern, MDS did not. Our findings suggest that dietary methyl-donors activate AMPK, a key enzyme in fatty acid ß-oxidation control, that mediates increased fatty acid utilization and thereby prevents further hepatic lipid accumulation.

Increased plasma citrulline in mice marks diet-induced obesity and may predict the development of the metabolic syndrome.

In humans, plasma amino acid concentrations of branched-chain amino acids (BCAA) and aromatic amino acids (AAA) increase in states of obesity, insulin resistance and diabetes. We here assessed whether these putative biomarkers can also be identified in two different obesity and diabetic mouse models. C57BL/6 mice with diet-induced obesity (DIO) mimic the metabolic impairments of obesity in humans characterized by hyperglycemia, hyperinsulinemia and hepatic triglyceride accumulation. Mice treated with streptozotocin (STZ) to induce insulin deficiency were used as a type 1 diabetes model. Plasma amino acid profiling of two high fat (HF) feeding trials revealed that citrulline and ornithine concentrations are elevated in obese mice, while systemic arginine bioavailability (ratio of plasma arginine to ornithine + citrulline) is reduced. In skeletal muscle, HF feeding induced a reduction of arginine levels while citrulline levels were elevated. However, arginine or citrulline remained unchanged in their key metabolic organs, intestine and kidney. Moreover, the intestinal conversion of labeled arginine to ornithine and citrulline in vitro remained unaffected by HF feeding excluding the intestine as prime site of these alterations. In liver, citrulline is mainly derived from ornithine in the urea cycle and DIO mice displayed reduced hepatic ornithine levels. Since both amino acids share an antiport mechanism for mitochondrial import and export, elevated plasma citrulline may indicate impaired hepatic amino acid handling in DIO mice. In the insulin deficient mice, plasma citrulline and ornithine levels also increased and additionally these animals displayed elevated BCAA and AAA levels like insulin resistant and diabetic patients. Therefore, type 1 diabetic mice but not DIO mice show the "diabetic fingerprint" of plasma amino acid changes observed in humans. Additionally, citrulline may serve as an early indicator of the obesity-dependent metabolic impairments.

Hepatic methionine homeostasis is conserved in C57BL/6N mice on high-fat diet despite major changes in hepatic one-carbon metabolism.

Obesity is an underlying risk factor in the development of cardiovascular disease, dyslipidemia and non-alcoholic fatty liver disease (NAFLD). Increased hepatic lipid accumulation is a hallmark in the progression of NAFLD and impairments in liver phosphatidylcholine (PC) metabolism may be central to the pathogenesis. Hepatic PC biosynthesis, which is linked to the one-carbon (C1) metabolism by phosphatidylethanolamine N-methyltransferase, is known to be important for hepatic lipid export by VLDL particles. Here, we assessed the influence of a high-fat (HF) diet and NAFLD status in mice on hepatic methyl-group expenditure and C1-metabolism by analyzing changes in gene expression, protein levels, metabolite concentrations, and nuclear epigenetic processes. In livers from HF diet induced obese mice a significant downregulation of cystathionine ß-synthase (CBS) and an increased betaine-homocysteine methyltransferase (BHMT) expression were observed. Experiments in vitro, using hepatoma cells stimulated with peroxisome proliferator activated receptor alpha (PPARα) agonist WY14,643, revealed a significantly reduced Cbs mRNA expression. Moreover, metabolite measurements identified decreased hepatic cystathionine and L-α-amino-n-butyrate concentrations as part of the transsulfuration pathway and reduced hepatic betaine concentrations, but no metabolite changes in the methionine cycle in HF diet fed mice compared to controls. Furthermore, we detected diminished hepatic gene expression of de novo DNA methyltransferase 3b but no effects on hepatic global genomic DNA methylation or hepatic DNA methylation in the Cbs promoter region upon HF diet. Our data suggest that HF diet induces a PPARα-mediated downregulation of key enzymes in the hepatic transsulfuration pathway and upregulates BHMT expression in mice to accommodate to enhanced dietary fat processing while preserving the essential amino acid methionine.

C57Bl/6 N mice on a western diet display reduced intestinal and hepatic cholesterol levels despite a plasma hypercholesterolemia.

BACKGROUND: Small intestine and liver greatly contribute to whole body lipid, cholesterol and phospholipid metabolism but to which extent cholesterol and phospholipid handling in these tissues is affected by high fat Western-style obesogenic diets remains to be determined. METHODS: We therefore measured cholesterol and phospholipid concentration in intestine and liver and quantified fecal neutral sterol and bile acid excretion in C57Bl/6 N mice fed for 12 weeks either a cholesterol-free high carbohydrate control diet or a high fat Western diet containing 0.03% (w/w) cholesterol. To identify the underlying mechanisms of dietary adaptations in intestine and liver, changes in gene expression were assessed by microarray and qPCR profiling, respectively. RESULTS: Mice on Western diet showed increased plasma cholesterol levels, associated with the higher dietary cholesterol supply, yet, significantly reduced cholesterol levels were found in intestine and liver. Transcript profiling revealed evidence that expression of numerous genes involved in cholesterol synthesis and uptake via LDL, but also in phospholipid metabolism, underwent compensatory regulations in both tissues. Alterations in glycerophospholipid metabolism were confirmed at the metabolite level by phospolipid profiling via mass spectrometry. CONCLUSIONS: Our findings suggest that intestine and liver react to a high dietary fat intake by an activation of de novo cholesterol synthesis and other cholesterol-saving mechanisms, as well as with major changes in phospholipid metabolism, to accommodate to the fat load.

Upregulated expression of ENaC in human CF nasal epithelium.

Cystic fibrosis (CF) is characterised by the absence of CFTR function resulting in a reduced Cl(-) secretion and an increase in Na+ absorption. This Na+ hyperabsorption is mediated by the human amiloride-sensitive epithelial sodium channel (ENaC), but the underlying mechanisms are still unknown. After demonstrating functional differences of the Na+ absorption in CF and non-CF epithelia in Ussing chamber experiments with human primary cultures, we compared ENaC sequences from CF and non-CF human nasal tissue (hnENaC), investigated the mRNA transcription levels via real-time PCR and studied the protein expression in Western blot analyses. We found no differences in the sequences of CF and non-CF hnENaC, but identified some polymorphisms. The real-time experiments revealed an enhanced mRNA amount of all three hnENaC subunits in CF tissue. By comparing the two groups on the protein level, we observed differences in the abundance of the Na+ channel. While the alpha- and beta-hnENaC protein amount was increased in CF tissue the gamma-hnENaC was decreased. We conclude that the Na+ hyperabsorption in CF is not caused by mutations in hnENaC, but by an increase in the transcription of the hnENaC subunits. This could be induced by a disturbed regulation of the channel in CF.