Development of a Novel CLDN18.2-directed Monoclonal Antibody and Antibody-Drug Conjugate for Treatment of CLDN18.2-Positive Cancers.

Gastric and pancreatic cancers are malignancies of high unmet clinical need. Expression of CLDN18.2 in these cancers, coupled with it's absence from most normal tissues, provides a potential therapeutic window against this target. We present preclinical development and characterization of a novel therapeutic mAb and antibody-drug conjugate (ADC) targeting CLDN18.2. A humanized CLDN18.2 specific mAb, CLDN18.2-307-mAb, was generated through immunization in mice followed by full humanization of the mouse mAb sequences. Antibody clones were screened by flow cytometry for selective binding to membrane bound CLDN18.2. A CLDN18.2-directed ADC (CLDN18.2-307-ADC) was also generated by conjugating MMAE to CLDN18.2 mAb using a cleavable linker. Tissue expression of CLDN18.2 was determined by IHC assay using a CLDN18.2-specific mAb. CLDN18.2-307-mAb binds with high affinity to CLDN18.2-positive (CLDN18.2+) cells and induces antibody-dependent cell-mediated cytotoxicity (ADCC). Treatment with this CLDN18.2-mAb blocked the growth of CLDN18.2+ gastric and pancreas cancer cell line xenograft (CDX) models. Upon binding to the extracellular domain of this target, the CLDN18.2-ADC/CLDN18.2 protein was internalized and subsequently localized to the lysosomal compartment inducing complete and sustained tumor regressions in CLDN18.2+ CDXs and patient-derived pancreatic cancer xenografts (PDX). A screen of human cancer tissues, by IHC, found 58% of gastric, 60% of gastroesophageal junction, and 20% of pancreatic adenocarcinomas to be positive for membrane expression of CLDN18.2. These data support clinical development of the CLDN18.2-307-mAb and CLDN18.2-307-ADC for treatment of CLDN18.2+ cancers. Both are now being investigated in phase I clinical studies.

Four Immune Modulating Genes in Primary Melanoma That Predict Metastatic Potential.

INTRODUCTION: Histologic characteristics cannot adequately predict which patients are at risk of developing metastatic disease after excision of primary cutaneous melanoma. The aim of this study was to identify immunomodulatory genes in primary tumors associated with development of distant metastases. MATERIALS AND METHODS: Thirty-seven patients with primary melanoma underwent surgical excision. RNA was extracted from the primary tumor specimens. cDNA was synthesized and used with Human Gene Expression microarray. Differential expression of 74 immunomodulatory genes was compared between patients who developed distant metastases and those who did not. RESULTS: Six of 37 patients developed distant metastases during the time of the study. Differential expression of microarray data showed upregulation of four immunomodulatory genes in this group. These four genes-c-CBL, CD276, CXCL1, and CXCL2-were all significantly overexpressed in the metastatic group with differential expression fold change of 1.15 (P = 0.01), 1.16 (P = 0.04), 2.51 (P < 0.001), and 1.68 (P < 0.02), respectively. CXCL1 had particularly high predictive value with an area under the curve of 0.80. Multivariate analysis showed only expression of CXCL1 (P = 0.01) remains predictive of distant metastases in melanoma patients. This result was confirmed using quantitative real-time polymerase chain reaction. CONCLUSIONS: CXCL1, CXCL2, c-CBL, and CD276 are immunomodulatory genes present in primary melanoma that are strongly associated with development of metastatic disease. Identification of their presence, particularly CXCL1, in the primary tumor could be used as a predictor of future risk of metastatic disease and thereby to identify patients who might benefit early from immunotherapy.

Tucatinib has Selective Activity in HER2-Positive Cancers and Significant Combined Activity with Approved and Novel Breast Cancer-Targeted Therapies.

Pharmacologically targeting the HER2 oncoprotein with therapeutics such as the mAb, trastuzumab, provides clinical benefit for patients with HER2-positive (HER2+) cancers. However, a significant number of patients eventually progress on these therapies. Efforts to overcome therapeutic resistance through combination therapy with small-molecule inhibitors of HER2 have been limited by toxicities associated with off-target activity and/or limited efficacy. In this preclinical study, we explore single-agent and combined activity of tucatinib, a novel HER2-selective small-molecule inhibitor. Tucatinib demonstrated potent, selective activity in a panel of 456 human cancer cell lines, with activity restricted to cell lines (breast and non-breast) with HER2-amplification, including models of acquired resistance to trastuzumab. Within the HER2+ population, tucatinib response tracked strongly with HER2-driven signaling. Single-agent tucatinib induced tumor regressions in xenograft models of HER2+ breast cancer and combination with trastuzumab induced a complete and sustained blockade of HER2/PI3K/AKT signaling. Efficacy of the tucatinib/trastuzumab combination matched that induced by current standard-of-care trastuzumab/pertuzumab/docetaxel combination, with the exception that the chemotherapy-sparing tucatinib/trastuzumab combination did not require a dosing holiday to achieve the same efficacy. In xenograft models of HER2+ breast cancer that also express estrogen receptor (ER; HER2+/ER+), tucatinib showed combined efficacy with inhibitors of CDK4/6 and ER, indicating potential novel therapeutic strategies for difficult-to-treat subtypes of HER2+ breast cancer. These data support expanded clinical investigations of tucatinib as a combination partner for other novel and approved targeted therapies for HER2-driven malignancies.

Myeloid HO-1 modulates macrophage polarization and protects against ischemia-reperfusion injury.

Macrophages polarize into heterogeneous proinflammatory M1 and antiinflammatory M2 subtypes. Heme oxygenase 1 (HO-1) protects against inflammatory processes such as ischemia-reperfusion injury (IRI), organ transplantation, and atherosclerosis. To test our hypothesis that HO-1 regulates macrophage polarization and protects against IRI, we generated myeloid-specific HO-1-knockout (mHO-1-KO) and -transgenic (mHO-1-Tg) mice, with deletion or overexpression of HO-1, in various macrophage populations. Bone marrow-derived macrophages (BMDMs) from mHO-1-KO mice, treated with M1-inducing LPS or M2-inducing IL-4, exhibited increased mRNA expression of M1 (CXCL10, IL-1ß, MCP1) and decreased expression of M2 (Arg1 and CD163) markers as compared with controls, while BMDMs from mHO-1-Tg mice displayed the opposite. A similar pattern was observed in the hepatic M1/M2 expression profile in a mouse model of liver IRI. mHO-1-KO mice displayed increased hepatocellular damage, serum AST/ALT levels, Suzuki's histological score of liver IRI, and neutrophil and macrophage infiltration, while mHO-1-Tg mice exhibited the opposite. In human liver transplant biopsies, subjects with higher HO-1 levels showed lower expression of M1 markers together with decreased hepatocellular damage and improved outcomes. In conclusion, myeloid HO-1 expression modulates macrophage polarization, and protects against liver IRI, at least in part by favoring an M2 phenotype.

Genetic Dissection of Cardiac Remodeling in an Isoproterenol-Induced Heart Failure Mouse Model.

We aimed to understand the genetic control of cardiac remodeling using an isoproterenol-induced heart failure model in mice, which allowed control of confounding factors in an experimental setting. We characterized the changes in cardiac structure and function in response to chronic isoproterenol infusion using echocardiography in a panel of 104 inbred mouse strains. We showed that cardiac structure and function, whether under normal or stress conditions, has a strong genetic component, with heritability estimates of left ventricular mass between 61% and 81%. Association analyses of cardiac remodeling traits, corrected for population structure, body size and heart rate, revealed 17 genome-wide significant loci, including several loci containing previously implicated genes. Cardiac tissue gene expression profiling, expression quantitative trait loci, expression-phenotype correlation, and coding sequence variation analyses were performed to prioritize candidate genes and to generate hypotheses for downstream mechanistic studies. Using this approach, we have validated a novel gene, Myh14, as a negative regulator of ISO-induced left ventricular mass hypertrophy in an in vivo mouse model and demonstrated the up-regulation of immediate early gene Myc, fetal gene Nppb, and fibrosis gene Lgals3 in ISO-treated Myh14 deficient hearts compared to controls.

Paraoxonase-2 modulates stress response of endothelial cells to oxidized phospholipids and a bacterial quorum-sensing molecule.

OBJECTIVE: Chronic infection has long been postulated as a stimulus for atherogenesis. Pseudomonas aeruginosa infection has been associated with increased atherosclerosis in rats, and these bacteria produce a quorum-sensing molecule 3-oxo-dodecynoyl-homoserine lactone (3OC12-HSL) that is critical for colonization and virulence. Paraoxonase 2 (PON2) hydrolyzes 3OC12-HSL and also protects against the effects of oxidized phospholipids thought to contribute to atherosclerosis. We now report the response of human aortic endothelial cells (HAECs) to 3OC12-HSL and oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (Ox-PAPC) in relation to PON2 expression. METHODS AND RESULTS: Using expression profiling and network modeling, we identified the unfolded protein response (UPR), cell cycle genes, and the mitogen-activated protein kinase signaling pathway to be heavily involved in the HAEC response to 3OC12-HSL. The network also showed striking similarities to a network created based on HAEC response to Ox-PAPC, a major component of minimally modified low-density lipoprotein. HAECs in which PON2 was silenced by small interfering RNA showed increased proinflammatory response and UPR when treated with 3OC12-HSL or Ox-PAPC. CONCLUSION: 3OC12-HSL and Ox-PAPC influence similar inflammatory and UPR pathways. Quorum sensing molecules, such as 3OC12-HSL, contribute to the proatherogenic effects of chronic infection. The antiatherogenic effects of PON2 include destruction of quorum sensing molecules.

NF-E2-related factor 2 promotes atherosclerosis by effects on plasma lipoproteins and cholesterol transport that overshadow antioxidant protection.

OBJECTIVE: To test the hypothesis that NF-E2-related factor 2 (Nrf2) expression plays an antiatherogenic role by its vascular antioxidant and anti-inflammatory properties. METHODS AND RESULTS: Nrf2 is an important transcription factor that regulates the expression of phase 2 detoxifying enzymes and antioxidant genes. Its expression in vascular cells appears to be an important factor in the protection against vascular oxidative stress and inflammation. We developed Nrf2 heterozygous (HET) and homozygous knockout (KO) mice on an apolipoprotein (apo) E-null background by sequential breeding, resulting in Nrf2(-/-), apoE(-/-) (KO), Nrf2(-/+), apoE(-/-) (HET) and Nrf2(+/+), and apoE(-/-) wild-type littermates. KO mice exhibited decreased levels of antioxidant genes with evidence of increased reactive oxygen species generation compared with wild-type controls. Surprisingly, KO males exhibited 47% and 53% reductions in the degree of aortic atherosclerosis compared with HET or wild-type littermates, respectively. Decreased atherosclerosis in KO mice correlated with lower plasma total cholesterol in a sex-dependent manner. KO mice also had a decreased hepatic cholesterol content and a lower expression of lipogenic genes, suggesting that hepatic lipogenesis could be reduced. In addition, KO mice exhibited atherosclerotic plaques characterized by a lesser macrophage component and decreased foam cell formation in an in vitro lipid-loading assay. This was associated with a lower rate of cholesterol influx, mediated in part by decreased expression of the scavenger receptor CD36. CONCLUSIONS: Nrf2 expression unexpectedly promotes atherosclerotic lesion formation in a sex-dependent manner, most likely by a combination of systemic metabolic and local vascular effects.

Pharmacodynamic characterization of the efficacy signals due to selective BRAF inhibition with PLX4032 in malignant melanoma.

PURPOSE: About 65% to 70% of melanomas harbor a mutation in v-raf murine sarcoma viral oncogene homolog B1 (BRAF) that causes the steady-state activation of extracellular signal-regulated kinase (ERK). We sought to investigate the efficacy of PLX4032 (BRAF inhibitor) to identify patterns/predictors of response/resistance and to study the effects of BRAF in melanoma. EXPERIMENTAL DESIGN: Well-characterized melanoma cell lines, including several with acquired drug resistance, were exposed to PLX4032. Growth inhibition, phosphosignaling, cell cycle, apoptosis, and gene expression analyses were performed before and after exposure to drug. RESULTS: Using a growth-adjusted inhibitory concentration of 50% cutoff of 1 microM, 13 of 35 cell lines were sensitive to PLX4032, 16 resistant, and 6 intermediate (37%, 46%, and 17% respectively). PLX4032 caused growth inhibition, G(0)/G(1) arrest, and restored apoptosis in the sensitive cell lines. A BRAF mutation predicted for but did not guarantee a response, whereas a neuroblastoma RAS viral oncogene homolog mutation or wild-type BRAF conferred resistance. Cells with concurrent BRAF mutations and melanocortin 1 receptor germ line variants and/or a more differentiated melanocyte genotype had a preferential response. Acquired PLX4032 resistance reestablishes ERK signaling, promotes a nonmelanocytic genotype, and is associated with an increase in the gene expression of certain metallothioneins and mediators of angiogenesis. CONCLUSIONS: PLX4032 has robust activity in BRAF mutated melanoma. The preclinical use of this molecule identifies criteria for its proper clinical application, describes patterns of and reasons for response/resistance, and affords insight into the role of a BRAF mutation in melanoma.

Ambient particulate pollutants in the ultrafine range promote early atherosclerosis and systemic oxidative stress.

Air pollution is associated with significant adverse health effects, including increased cardiovascular morbidity and mortality. Exposure to particulate matter with an aerodynamic diameter of <2.5 microm (PM(2.5)) increases ischemic cardiovascular events and promotes atherosclerosis. Moreover, there is increasing evidence that the smallest pollutant particles pose the greatest danger because of their high content of organic chemicals and prooxidative potential. To test this hypothesis, we compared the proatherogenic effects of ambient particles of <0.18 microm (ultrafine particles) with particles of <2.5 microm in genetically susceptible (apolipoprotein E-deficient) mice. These animals were exposed to concentrated ultrafine particles, concentrated particles of <2.5 microm, or filtered air in a mobile animal facility close to a Los Angeles freeway. Ultrafine particle-exposed mice exhibited significantly larger early atherosclerotic lesions than mice exposed to PM(2.5) or filtered air. Exposure to ultrafine particles also resulted in an inhibition of the antiinflammatory capacity of plasma high-density lipoprotein and greater systemic oxidative stress as evidenced by a significant increase in hepatic malondialdehyde levels and upregulation of Nrf2-regulated antioxidant genes. We conclude that ultrafine particles concentrate the proatherogenic effects of ambient PM and may constitute a significant cardiovascular risk factor.

Air-pollutant chemicals and oxidized lipids exhibit genome-wide synergistic effects on endothelial cells.

BACKGROUND: Ambient air pollution is associated with increased cardiovascular morbidity and mortality. We have found that exposure to ambient ultrafine particulate matter, highly enriched in redox cycling organic chemicals, promotes atherosclerosis in mice. We hypothesize that these pro-oxidative chemicals could synergize with oxidized lipid components generated in low-density lipoprotein particles to enhance vascular inflammation and atherosclerosis. RESULTS: We have used human microvascular endothelial cells (HMEC) to study the combined effects of a model air pollutant, diesel exhaust particles (DEP), and oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (ox-PAPC) on genome-wide gene expression. We treated the cells in triplicate wells with an organic DEP extract, ox-PAPC at various concentrations, or combinations of both for 4 hours. Gene-expression profiling showed that both the DEP extract and ox-PAPC co-regulated a large number of genes. Using network analysis to identify coexpressed gene modules, we found three modules that were most highly enriched in genes that were differentially regulated by the stimuli. These modules were also enriched in synergistically co-regulated genes and pathways relevant to vascular inflammation. We validated this synergy in vivo by demonstrating that hypercholesterolemic mice exposed to ambient ultrafine particles exhibited significant upregulation of the module genes in the liver. CONCLUSION: Diesel exhaust particles and oxidized phospholipids synergistically affect the expression profile of several gene modules that correspond to pathways relevant to vascular inflammatory processes such as atherosclerosis.

Anti-HLA class I antibodies activate endothelial cells and promote chronic rejection.

Transplant recipients exhibiting a humoral immune response to the allograft demonstrate lower graft survival and increased risk for the development of chronic rejection and transplant arteriosclerosis. Our studies suggest that anti-HLA class I antibodies (Ab) play an important role in controlling endothelial cell (EC) function by binding to class I molecules on the surface of the EC and transducing intracellular signals. Anti-HLA Ab exhibit two primary effector functions: stimulation of cell proliferation and up-regulation of cell survival genes. Importantly, the intracellular events initiated by class I ligation appear to be influenced by the concentration of the Ab. High-titered anti-HLA Ab stimulate cell proliferation whereas low-titered Ab activate the PI3K/Akt pathway and promote expression of cell survival proteins including Bcl-2 and Bcl-xL. Anti-HLA class I Ab may contribute to the process of chronic allograft rejection by promoting EC survival and proliferation.