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Background and Purpose: Elevated fibroblast growth factor receptor (FGFR) activity correlates with pancreatic adenocarcinoma (PDAC) progression and poor prognosis. However, its potential as a therapeutic target remains largely unexplored. Experimental Approach: The mechanisms of action and therapeutic effects of selective pan‐FGFR inhibitors (pan‐FGFRi) were explored using in vitro and in vivo PDAC models ranging from gemcitabine‐sensitive to highly gemcitabine‐resistant (GemR). Gain‐/loss‐of‐function investigations were employed to define the role of individual FGFRs in cell proliferation, migration, and treatment response and resistance. Results: The pan‐FGFRi NVP‐BGJ398 significantly inhibited cell proliferation, migration, and invasion, and downregulated key cell survival‐ and invasiveness markers in multiple PDAC cell lines. Gemcitabine is a standard‐of‐care for PDAC, but development of resistance to gemcitabine (GemR) compromises its efficacy. Acquired GemR was modelled experimentally by developing highly GemR cells using escalating gemcitabine exposure in vitro and in vivo. FGFRi treatment inhibited GemR cell proliferation, migration, GemR marker expression, and tumour progression. FGFR2 or FGFR3 loss‐of‐function by shRNA knockdown failed to decrease cell growth, whereas FGFR1 knockdown was lethal. FGFR1 overexpression promoted cell migration more than proliferation, and reduced FGFRi‐mediated inhibition of proliferation and migration. Single‐agent FGFRi suppressed the viability and growth of multiple patient‐derived xenografts inversely with respect to FGFR1 expression, underscoring the influence of FGFR1‐dependent tumour responses to FGFRi. Importantly, secondary data analysis showed that PDAC tumours expressed FGFR1 at lower levels than in normal pancreas tissue. Conclusions and Implications: Single‐agent FGFR inhibitors mediate selective, molecularly‐targeted suppression of PDAC proliferation, and their effects are greatest in PDAC tumours expressing low‐to‐moderate levels of FGFR1. [ABSTRACT FROM AUTHOR]

Polyamine inhibition for cancer therapy is, conceptually, an attractive approach but has yet to meet success in the clinical setting. The aryl hydrocarbon receptor (AHR) is the central transcriptional regulator of the xenobiotic response. Our study revealed that AHR also positively regulates intracellular polyamine production via direct transcriptional activation of 2 genes, ODC1 and AZIN1, which are involved in polyamine biosynthesis and control, respectively. In patients with multiple myeloma (MM), AHR levels were inversely correlated with survival, suggesting that AHR inhibition may be beneficial for the treatment of this disease. We identified clofazimine (CLF), an FDA-approved anti-leprosy drug, as a potent AHR antagonist and a suppressor of polyamine biosynthesis. Experiments in a transgenic model of MM (Vk*Myc mice) and in immunocompromised mice bearing MM cell xenografts revealed high efficacy of CLF comparable to that of bortezomib, a first-in-class proteasome inhibitor used for the treatment of MM. This study identifies a previously unrecognized regulatory axis between AHR and polyamine metabolism and reveals CLF as an inhibitor of AHR and a potentially clinically relevant anti-MM agent., Introduction Polyamines are small polycationic molecules that have been implicated in virtually every aspect of eukaryotic cells, including DNA replication, transcription, translation, and proliferation (1-3). Polyamine levels are increased in [...]

Author(s): Ilya Shamovsky [1, 2]; Maxim Ivannikov [1]; Eugene S. Kandel [3]; David Gershon (corresponding author) [2, 4]; Evgeny Nudler (corresponding author) [1] The heat-shock transcription factor 1 (HSF1) has [...]

Genetic dissection of signaling pathways in mammalian cells involves screening or selecting phenotypic mutants obtained by a variety of techniques. Limitations in current methods include inadequate genome coverage and difficulty in validating the link between mutation and phenotype. We describe an improved method for insertional mutagenesis with retroviral vectors and show that the ability to induce mutations increases greatly if a randomly inserted promoter directs transcription into the host DNA. The mutant phenotype is due to the expression of a hybrid transcript derived from the vector and the insertion site. Because other alleles of the affected gene remain intact, the phenotype is dominant, but is reversible by inactivating the promoter, for example, by site-specific recombination. Importantly, in mutant clones with multiple inserts, limited excision yields progeny with different patterns of inserts remaining. Characterizing these progeny allows the mutant phenotype to be associated with a specific target gene. Relative simplicity and robust target validation make the method suitable for a broad range of applications. We have used this technique to search for proteins that regulate NF-[kappa]B- dependent signaling in human cells. Two validated targets are the re/A gene, which codes for the NF-[kappa]B p65 subunit, and the NF-[kappa]B regulator act1. Overexpression of the corresponding proteins, caused by insertion of a promoter into the first intron of each gene, leads to NF-[kappa]B-dependent secretion of factors that activate NF-[kappa]B through cell-surface receptors, establishing an autocrine loop. Act1 | forward genetics | p65 RelA