Hexavalent TRAIL Fusion Protein Eftozanermin Alfa Optimally Clusters Apoptosis-Inducing TRAIL Receptors to Induce On-Target Antitumor Activity in Solid Tumors.

TRAIL can activate cell surface death receptors, resulting in potent tumor cell death via induction of the extrinsic apoptosis pathway. Eftozanermin alfa (ABBV-621) is a second generation TRAIL receptor agonist engineered as an IgG1-Fc mutant backbone linked to two sets of trimeric native single-chain TRAIL receptor binding domain monomers. This hexavalent agonistic fusion protein binds to the death-inducing DR4 and DR5 receptors with nanomolar affinity to drive on-target biological activity with enhanced caspase-8 aggregation and death-inducing signaling complex formation independent of FcγR-mediated cross-linking, and without clinical signs or pathologic evidence of toxicity in nonrodent species. ABBV-621 induced cell death in approximately 36% (45/126) of solid cancer cell lines in vitro at subnanomolar concentrations. An in vivo patient-derived xenograft (PDX) screen of ABBV-621 activity across 15 different tumor indications resulted in an overall response (OR) of 29% (47/162). Although DR4 (TNFSFR10A) and/or DR5 (TNFSFR10B) expression levels did not predict the level of response to ABBV-621 activity in vivo, KRAS mutations were associated with elevated TNFSFR10A and TNFSFR10B and were enriched in ABBV-621-responsive colorectal carcinoma PDX models. To build upon the OR of ABBV-621 monotherapy in colorectal cancer (45%; 10/22) and pancreatic cancer (35%; 7/20), we subsequently demonstrated that inherent resistance to ABBV-621 treatment could be overcome in combination with chemotherapeutics or with selective inhibitors of BCL-XL. In summary, these data provide a preclinical rationale for the ongoing phase 1 clinical trial (NCT03082209) evaluating the activity of ABBV-621 in patients with cancer. SIGNIFICANCE: This study describes the activity of a hexavalent TRAIL-receptor agonistic fusion protein in preclinical models of solid tumors that mechanistically distinguishes this molecular entity from other TRAIL-based therapeutics.

Discoidin domain receptor 1 contributes to tumorigenesis through modulation of TGFBI expression.

Discoidin domain receptor 1 (DDR1) is a member of the receptor tyrosine kinase family. The receptor is activated upon binding to its ligand, collagen, and plays a crucial role in many fundamental processes such as cell differentiation, adhesion, migration and invasion. Although DDR1 is expressed in many normal tissues, upregulated expression of DDR1 in a variety of human cancers such as lung, colon and brain cancers is known to be associated with poor prognosis. Using shRNA silencing, we assessed the oncogenic potential of DDR1. DDR1 knockdown impaired tumor cell proliferation and migration in vitro and tumor growth in vivo. Microarray analysis of tumor cells demonstrated upregulation of TGFBI expression upon DDR1 knockdown, which was subsequently confirmed at the protein level. TGFBI is a TGFß-induced extracellular matrix protein secreted by the tumor cells and is known to act either as a tumor promoter or tumor suppressor, depending on the tumor environment. Here, we show that exogenous addition of recombinant TGFBI to BXPC3 tumor cells inhibited clonogenic growth and migration, thus recapitulating the phenotypic effect observed from DDR1 silencing. BXPC3 tumor xenografts demonstrated reduced growth with DDR1 knockdown, and the same xenograft tumors exhibited an increase in TGFBI expression level. Together, these data suggest that DDR1 expression level influences tumor growth in part via modulation of TGFBI expression. The reciprocal expression of DDR1 and TGFBI may help to elucidate the contribution of DDR1 in tumorigenesis and TGFBI may also be used as a biomarker for the therapeutic development of DDR1 specific inhibitors.

COX-2 induction during murine gammaherpesvirus 68 infection leads to enhancement of viral gene expression.

The murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) model provides many advantages for studying virus-host interactions involved in gammaherpesvirus replication, including the role of cellular responses to infection. We examined the effects of cellular cyclooxygenase-2 (COX-2) and its by-product prostaglandin E(2) (PGE(2)) on MHV-68 gene expression and protein production following de novo infection of cultured cells. Western blot analyses revealed an induction of COX-2 protein in MHV-68-infected cells but not in cells infected with UV-irradiated MHV-68. Luciferase reporter assays demonstrated activation of the COX-2 promoter during MHV-68 replication. Two nonsteroidal anti-inflammatory drugs, a COX-2-specific inhibitor (NS-398) and a COX-1-COX-2 inhibitor (indomethacin), substantially reduced MHV-68 protein production in infected cells. Inhibition of viral protein expression and virion production by NS-398 was reversed in the presence of exogenous PGE(2). Global gene expression analysis using an MHV-68 DNA array showed that PGE(2) increased production of multiple viral gene products, and NS-398 inhibited production of many of the same genes. These studies suggest that COX-2 activity and PGE(2) production may play significant roles during MHV-68 de novo infection.

Diesel exhaust particle extracts and associated polycyclic aromatic hydrocarbons inhibit Cox-2-dependent prostaglandin synthesis in murine macrophages and fibroblasts.

Diesel exhaust particles (DEP) and their organic constituents modulate the immune system and exacerbate allergic airway inflammation. We investigated the role of DEP extract and associated polycyclic aromatic hydrocarbons (PAHs) on prostaglandin synthesis in endotoxin-activated murine macrophages and in mitogen-stimulated fibroblasts. In both macrophages and fibroblasts, DEP extract, phenanthrene, anthracene, phenanthrenequinone, and beta-napthoflavone inhibit prostaglandin production from endogenous arachidonic acid in response to ligand stimulation. However, DEP extract and PAHs do not block ligand induction of cyclooxygenase-2 (COX-2) protein, either in mitogen-stimulated fibroblasts or endotoxin-treated macrophages. Release of total arachidonic acid and total lipid products is not reduced by DEP or PAHs following ligand stimulation of macrophages or fibroblasts. DEP extract and the PAHs inhibit the activity of purified COX-2 enzyme in vitro but do not inhibit COX-1 activity. Thus, DEP and PAHs do not affect ligand-induced COX-2 gene expression, phospholipase activation, or arachidonic acid release in macrophages and fibroblasts but exert their inhibitory effect on prostaglandin production by preferentially blocking COX-2 enzyme activity.