AGS-16C3F is an antibody-drug conjugate (ADC) against ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) containing the mcMMAF linker-payload currently in development for treatment of metastatic renal cell carcinoma. AGS-16C3F and other ADCs have been reported to cause ocular toxicity in patients by unknown mechanisms. To investigate this toxicity, we developed an assay using human corneal epithelial cells (HCEC) and show that HCECs internalized AGS-16C3F and other ADCs by macropinocytosis, causing inhibition of cell proliferation. We observed the same mechanism for target-independent internalization of AGS-16C3F in fibroblasts and human umbilical vein endothelial cells (HUVEC). Macropinocytosis-mediated intake of macromolecules is facilitated by the presence of positive charges or hydrophobic residues on the surface of the macromolecule. Modification of AGS-16C3F, either by attachment of poly-glutamate peptides, mutation of residue K16 to D on AGS-16C3F [AGS-16C3F(K16D)], or decreasing the overall hydrophobicity via attachment of polyethylene glycol moieties, significantly reduced cytotoxicity against HCECs and other primary cells. Rabbits treated with AGS-16C3F showed significant ocular toxicity, whereas those treated with AGS-16C3F(K16D) presented with less severe and delayed toxicities. Both molecules displayed similarantitumor activity in a mouse xenograft model. These findings establish a mechanism of action for target-independent toxicities of AGS-16C3F and ADCs in general, and provide methods to ameliorate these toxicities. These findings reveal a mechanism for nonreceptor-mediated toxicities of antibody drug conjugates and potential solutions to alleviate these toxicities. .
Liver insufficiency and damage is a major cause of death and disease worldwide and may result from exposure to environmental toxicants, specific combinations or dosages of pharmaceuticals and microbial metabolites. The generation of reactive intermediates, in particular 4-hydroxynonenal (4-HNE), is a common event in liver damage caused by a variety of hepatotoxic drugs and solvents. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that are involved in the transcriptional regulation of lipid metabolism as well as other biological functions. Importantly, we have observed that the PPARβ/δ −/− mouse is more susceptible to chemically-induced hepatotoxicity than its wildtype counterpart, and our objective in this study was to elucidate the mechanism(s) by which PPARβ/δ confers protection to hepatocytes. We hypothesized that PPARβ/ δ plays a protective role by responding to toxic lipids and altering gene expression accordingly. In support, oxidized-VLDL and constituents including 13-S-hydroxyoctadeca-dienoic acid (13(S)-HODE) and 4-HNE are PPARβ/δ ligands. A structure-activity relationship was established where 4-HNE and 4-hydroperoxynonenal (4-HpNE) enhanced the activity of the PPARβ/δ subtype while 4-hyroxy-hexenal (4-HHE), 4-oxo-2-Nonenal (4-ONE), and trans-4,5-epoxy-2(E)-decenal did not activate this receptor. Increasing PPARβ/δ activity with a synthetic agonist decreased sensitivity of hepatocytes to 4-HNE and other toxic agents, whereas inhibition of this receptor had the opposite result. Gene expression microarray analysis identified several important PPARβ/δ-regulated detoxification enzymes involved in 4-HNE metabolism that are regulated at the transcript level. This research established 4-HNE as an endogenous modulator of PPARβ/δ activity and raises the possibility that agonists of this nuclear receptor may be utilized to prevent or treat liver disease associated with oxidative damage.
PPARβ/δ is a ligand-activated transcription factor that regulates various cellular functions via induction of target genes directly or in concert with its associated transcriptional repressor, BCL-6. Matrix remodeling proteinases are frequently over-expressed in pancreatic cancer and are involved with metastasis. The present study tested the hypothesis that PPARβ/δ is expressed in human pancreatic cancer cells and that its activation could regulate MMP-9, decreasing cancer cells ability to transverse the basement membrane. In human pancreatic cancer tissue there was significantly higher expression of MMP-9 and PPARβ/δ, and lower levels of BCL-6 mRNA. PPARβ/δ activation reduced the TNFα-induced expression of various genes implicated in metastasis and reduced the invasion through a basement membrane in cell culture models. Through the use of short hairpin RNA inhibitors of PPARβ/δ, BCL-6, and MMP-9, it was evident that PPARβ/δ was responsible for the ligand-dependent effects whereas BCL-6 dissociation upon GW501516 treatment was ultimately responsible for decreasing MMP-9 expression and hence invasion activity. These results suggest that PPARβ/δ plays a role in regulating pancreatic cancer cell invasion through regulation of genes via ligand-dependent release of BCL-6 and that activation of the receptor may provide an alternative therapeutic method for controlling migration and metastasis.
Here, we report the development of an antibody-drug conjugate, ASG-5ME, which targets the solute carrier receptor SLC44A4. SLC44A4 is a member of a family of putative choline transporters that we show to be markedly upregulated in a variety of epithelial tumors, most notably prostate and pancreatic cancer. SLC44A4 is normally expressed on the apical surface of secretory epithelial cells, but in cancer we show expression is not restricted to the luminal surface in advanced and undifferentiated tumors. ASG-5ME consists of a human IgG2 anti-SLC44A4 antibody conjugated through a cleavable linker to the microtubule-disrupting agent monomethylauristatin E. It has potent antitumor activity in both cell line-and patient-derived xenograft models of pancreatic and prostate cancers. Combination studies with ASG-5ME and nab-paclitaxel demonstrated combination effect in both pancreatic and prostate tumor models. Altogether, the data presented here suggest that ASG-5ME may have the potential to offer a new therapeutic option for the treatment of pancreatic and prostate cancers. Mol Cancer Ther; 15(11); 2679-87. Ó2016 AACR.
Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) is a member of the nuclear receptor superfamily and a ligand-activated transcription factor that is involved in the regulation of the inflammatory response via activation of anti-inflammatory target genes and ligand-induced disassociation with the transcriptional repressor B-cell lymphoma 6 (BCL6). Chronic pancreatitis is considered to be a significant etiological factor for pancreatic cancer development, and a better understanding of the underlying mechanisms of the transition between inflammation and carcinogenesis would help further elucidate chemopreventative options. The aim of this study was to determine the role of PPARβ/δ and BCL6 in human pancreatic cancer of ductal origin, as well as the therapeutic potential of PPARβ/δ agonist, GW501516. Over-expression of PPARβ/δ inhibited basal and TNFα-induced Nfkb luciferase activity. GW501516-activated PPARβ/δ suppressed TNFα-induced Nfkb reporter activity. RNAi knockdown of Pparb attenuated the GW501516 effect on Nfkb luciferase, while knockdown of Bcl6 enhanced TNFα-induced Nfkb activity. PPARβ/δ activation induced expression of several anti-inflammatory genes in a dose-dependent manner, and GW501516 inhibited Mcp1 promoter-driven luciferase in a BCL6-dependent manner. Several pro-inflammatory genes were suppressed in a BCL6-dependent manner. Conditioned media from GW501516-treated pancreatic cancer cells suppressed pro-inflammatory expression in THP-1 macrophages as well as reduced invasiveness across a basement membrane. These results demonstrate that PPARβ/δ and BCL6 regulate anti-inflammatory signaling in human pancreatic cancer cells by inhibiting NFκB and pro-inflammatory gene expression, and via induction of anti-inflammatory target genes. Activation of PPARβ/δ may be a useful target in pancreatic cancer therapeutics.
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