The Anti-HER3 mAb Seribantumab Effectively Inhibits Growth of Patient-Derived and Isogenic Cell Line and Xenograft Models with Oncogenic NRG1 Fusions.

PURPOSE: Oncogenic fusions involving the neuregulin 1 (NRG1) gene are found in approximately 0.2% of cancers of diverse histologies. The resulting chimeric NRG1 proteins bind predominantly to HER3, leading to HER3-HER2 dimerization and activation of downstream growth and survival pathways. HER3 is, therefore, a rational target for therapy in NRG1 fusion-driven cancers. EXPERIMENTAL DESIGN: We developed novel patient-derived and isogenic models of NRG1-rearranged cancers and examined the effect of the anti-HER3 antibody, seribantumab, on growth and activation of signaling networks in vitro and in vivo. RESULTS: Seribantumab inhibited NRG1-stimulated growth of MCF-7 cells and growth of patient-derived breast (MDA-MB-175-VII, DOC4-NRG1 fusion) and lung (LUAD-0061AS3, SLC3A2-NRG1 fusion) cancer cells harboring NRG1 fusions or NRG1 amplification (HCC-95). In addition, seribantumab inhibited growth of isogenic HBEC cells expressing a CD74-NRG1 fusion (HBECp53-CD74-NRG1) and induced apoptosis in MDA-MB-175-VII and LUAD-0061AS3 cells. Induction of proapoptotic proteins and reduced expression of the cell-cycle regulator, cyclin D1, were observed in seribantumab-treated cells. Treatment of MDA-MB-175-VII, LUAD-0061AS3, and HBECp53-CD74-NRG1 cells with seribantumab reduced phosphorylation of EGFR, HER2, HER3, HER4, and known downstream signaling molecules, such as AKT and ERK1/2. Significantly, administration of seribantumab to mice bearing LUAD-0061AS3 patient-derived xenograft (PDX) and OV-10-0050 (ovarian cancer with CLU-NRG1 fusion) PDX tumors induced regression of tumors by 50%-100%. Afatinib was much less effective at blocking tumor growth. CONCLUSIONS: Seribantumab treatment blocked activation of the four ERBB family members and of downstream signaling, leading to inhibition of NRG1 fusion-dependent tumorigenesis in vitro and in vivo in breast, lung, and ovarian patient-derived cancer models.

Functionally Related Genes Cluster into Genomic Regions That Coordinate Transcription at a Distance in Saccharomyces cerevisiae.

Balancing gene expression is a fundamental challenge of all cell types. To properly regulate transcription on a genome-wide level, there are myriad mechanisms employed by the cell. One layer to this regulation is through spatial positioning, with particular chromosomal loci exerting an influence on transcription throughout a region. Many coregulated gene families utilize spatial positioning to coordinate transcription, with functionally related genes clustering together which can allow coordinated expression via adjacent gene coregulation. The mechanisms underlying this process have not been elucidated, though there are many coregulated gene families that exhibit this genomic distribution. In the present study, we tested for a role for the enhancer-promoter (EP) hypothesis, which demonstrates that regulatory elements can exert transcriptional effects over a broad distance, in coordinating transcriptional coregulation using budding yeast, Saccharomyces cerevisiae We empirically validated the EP model, finding that the genomic distance a promoter can affect varies by locus, which can profoundly affect levels of transcription, phenotype, and the extent of transcriptional disruption throughout a genomic region. Using the nitrogen metabolism, ribosomal protein, toxin response, and heat shock gene families as our test case, we report functionally clustered genes localize to genomic loci that are more conducive to transcriptional regulation at a distance compared to the unpaired members of the same families. Furthermore, we report that the coregulation of functional clusters is dependent, in part, on chromatin maintenance and remodeling, providing one mechanism underlying adjacent gene coregulation.IMPORTANCE The two-dimensional, physical positioning of genes along a chromosome can impact proper transcriptional regulation throughout a genomic region. The transcription of neighboring genes is correlated in a genome-wide manner, which is a characteristic of eukaryotes. Many coregulated gene families can be found clustered with another member of the same set-which can result in adjacent gene coregulation of the pair. Due to the myriad gene families that exhibit a nonrandom genomic distribution, there are likely multiple mechanisms working in concert to properly regulate transcriptional coordination of functionally clustered genes. In this study, we utilized budding yeast in an attempt to elucidate mechanisms that underlie this coregulation: testing and empirically validating the enhancer-promoter hypothesis in this species and reporting that functionally related genes cluster to genomic regions that are more conducive to transcriptional regulation at a distance. These clusters rely, in part, on chromatin maintenance and remodelers to maintain proper transcriptional coordination. Our work provides insight into the mechanisms underlying adjacent gene coregulation.