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The field of targeted protein degradation (TPD) is a rapidly developing therapeutic modality with the promise to tame disease-relevant proteins in ways that are difficult or impossible to tackle with other strategies. While we move into the third decade of TPD, multiple degrader drugs have entered the stage of the clinic and many more are expected to follow. In this review, we provide an update on the most recent advances in the field of targeted degradation with insights into possible clinical implications for cancer prevention and treatment.

Lung cancer is responsible for the majority of cancer-related deaths worldwide. Within this severe disease lung adenocarcinoma (LUAD) belongs to the most common form of lung cancer. LUAD is highly correlated with KRAS mutations. Although, the first KRAS inhibitors entered into clinics recently, therapy resistance arises. Since KRAS-mutant LUAD is an inflammation driven disease, we focus on the JAK-STAT pathway as an alternative target. Preliminary data suggests that human KRAS-mutant LUAD is correlated to enriched JAK-STAT signaling, as well as STAT1 upregulation. Accordingly, we aimed to explore the tumorigenic functions of STAT1 in this form of lung cancer. Genetically engineered C57BL6/N mice which develop autochthonous KRAS-driven and P53-deficient LUAD proficient (KP) and deficient for STAT1 (KPS) were used. In a second mouse model expression of ovalbumin was induced in tumor cells, mimicking a neoantigen to increase immune infiltration in the presence (KPO) or absence of STAT1 (KPOS). Kaplan-Meyer analysis was performed to assess the overall survival. Tumor burden, as well as immune infiltration was analyzed in lungs 6 and 10 weeks after tumor induction via H&E, IHC and IF staining. Furthermore, the lung fluid was collected by bronchoalveolar lavage and used to profile inflammatory cytokines. Deletion of STAT1 reduced the survival in KRAS-driven LUAD mice only when ovalbumin was expressed. Tumor burden and tumor grades were increased in tumors lacking STAT1 at 6 and 10 weeks after tumor initiation. Surprisingly, although tumors of KPOS mice showed a decreased infiltration by T cells and CD4 T cells, CD8 T cell infiltration did not change, suggesting a tumor suppressive function of STAT1 via T cell exhaustion. Moreover, the macrophage attracting cytokine CCL9 secretion was upregulated and the number of tumor infiltrating, immunosuppressive macrophages was increased in KPOS mice. This data implicates a tumor suppressive function of STAT1 by secretion of cytokines that can recruit suppressive myeloid immune cells to the TME leading to CD4 T cell exclusion and CD8 T cell exhaustion. Further studies are needed on the changes in the immune infiltrating cells to explain the mechanism behind these intriguing findings. Citation Format: Christoph Trenk, Rebecca Sagmeister, Jaqueline Horvath, Monika Homolya, Andreea Corina Luca, Robert Eferl, Herwig Moll, Emilio Casanova. STAT1 suppresses KRAS-driven lung adenocarcinoma depending on the tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3650.

Mutations that activate members of the RAS family of GTPases are associated with various cancers and drive tumor growth. The glucocorticoid receptor (GR), a member of the nuclear receptor family, has been proposed to interact with and inhibit the activation of components of the PI3K-AKT and MAPK pathways downstream of RAS. In the absence of activating ligands, we found that GR was present in cytoplasmic KRAS-containing complexes and inhibited the activation of wild-type and oncogenic KRAS in mouse embryonic fibroblasts and human lung cancer A549 cells. The DNA binding domain of GR was involved in the interaction with KRAS, but GR-dependent inhibition of RAS activation did not depend on the nuclear translocation of GR. The addition of ligand released GR-dependent inhibition of RAS, AKT, the MAPK p38, and the MAPKK MEK. CRISPR-Cas9–mediated deletion of GR in A549 cells enhanced tumor growth in xenografts in mice. Patient samples of non–small cell lung carcinomas showed lower expression ofNR3C1, the gene encoding GR, compared to adjacent normal tissues and lowerNR3C1expression correlated with a worse disease outcome. These results suggest that glucocorticoids prevent the ability of GR to limit tumor growth by inhibiting RAS activation, which has potential implications for the use of glucocorticoids in patients with cancer.

The histone acetyl reader bromodomain-containing protein 4 (BRD4) is an important regulator of chromatin structure and transcription, yet factors modulating its activity have remained elusive. Here we describe two complementary screens for genetic and physical interactors of BRD4, which converge on the folate pathway enzyme MTHFD1 (methylenetetrahydrofolate dehydrogenase, cyclohydrolase and formyltetrahydrofolate synthetase 1). We show that a fraction of MTHFD1 resides in the nucleus, where it is recruited to distinct genomic loci by direct interaction with BRD4. Inhibition of either BRD4 or MTHFD1 results in similar changes in nuclear metabolite composition and gene expression; pharmacological inhibitors of the two pathways synergize to impair cancer cell viability in vitro and in vivo. Our finding that MTHFD1 and other metabolic enzymes are chromatin associated suggests a direct role for nuclear metabolism in the control of gene expression.

Despite the essential role secretory IgAs play in the defense against pathogenic invasion and the proposed value of recombinant secretory IgAs as novel therapeutics, currently there are no IgA-based therapies in clinics. Secretory IgAs are complex molecules and the major bottleneck limiting their therapeutic potential is a reliable recombinant production system. In this report, we addressed this issue and established a fast and robust production method for secretory IgAs in CHO-K1 cells using BAC-based expression vectors. As a proof of principle, we produced IgAs against Clostridium difficile toxins TcdA and TcdB. Recombinant secretory IgAs produced using our expression system showed comparable titers to IgGs, widely used as therapeutic biologicals. Importantly, secretory IgAs produced using our method were functional and could efficiently neutralize Clostridium difficile toxins TcdA and TcdB. These results show that recombinant secretory IgAs can be efficiently produced, thus opening the possibility to use them as therapeutic agents in clinics.

Lung cancer is the most frequent cancer with an aggressive clinical course and high mortality rates. Most cases are diagnosed at advanced stages when treatment options are limited and the efficacy of chemotherapy is poor. The disease has a complex and heterogeneous background with non-small-cell lung cancer (NSCLC) accounting for 85% of patients and lung adenocarcinoma being the most common histological subtype. Almost 30% of adenocarcinomas of the lung are driven by an activating Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation. The ability to inhibit the oncogenic KRAS has been the holy grail of cancer research and the search for inhibitors is immensely ongoing as KRAS-mutated tumors are among the most aggressive and refractory to treatment. Therapeutic strategies tailored for KRAS+ NSCLC rely on the blockage of KRAS functional output, cellular dependencies, metabolic features, KRAS membrane associations, direct targeting of KRAS and immunotherapy. In this review, we provide an update on the most recent advances in anti-KRAS therapy for lung tumors with mechanistic insights into biological diversity and potential clinical implications.

Tumors have evolved mechanisms to escape anti-tumor immunosurveillance. They limit humoral and cellular immune activities in the stroma and render tumors resistant to immunotherapy. Sensitizing tumor cells to immune attack is an important strategy to revert immunosuppression. However, the underlying mechanisms of immune escape are still poorly understood. Here we discover Indoleamine-2,3-dioxygenase-1 (IDO1)+ Paneth cells in the stem cell niche of intestinal crypts and tumors, which promoted immune escape of colorectal cancer (CRC). Ido1 expression in Paneth cells was strictly Stat1 dependent. Loss of IDO1+ Paneth cells in murine intestinal adenomas with tumor cell-specific Stat1 deletion had profound effects on the intratumoral immune cell composition. Patient samples and TCGA expression data suggested corresponding cells in human colorectal tumors. Thus, our data uncovered an immune escape mechanism of CRC and identify IDO1+ Paneth cells as a target for immunotherapy., Pflügler, Svinka et al. identify a subset of Paneth cells in mouse intestinal crypts and tumors, which express the immune checkpoint molecule Ido1 in a Stat1-dependent manner and promote tumor growth. Gene expression data from human colorectal cancer (CRC) suggest that a similar population is present in human cancer and opens the door for further studies of immune escape mechanisms in CRC.

Signal Transducer and Activator of Transcription 3 (STAT3) activation is frequently found in non-small cell lung cancer (NSCLC) patient samples/cell lines and STAT3 inhibition in NSCLC cell lines markedly impairs their survival. STAT3 also plays a pivotal role in driving tumor-promoting inflammation and evasion of anti-tumor immunity. Consequently, targeting STAT3 either directly or by inhibition of upstream regulators such as Interleukin-6 (IL-6) or Janus kinase 1/2 (JAK1/2) is considered as a promising treatment strategy for the management of NSCLC. In contrast, some studies also report STAT3 being a tumor suppressor in a variety of solid malignancies, including lung cancer. Here, we provide a concise overview of STAT3‘s versatile roles in NSCLC and discuss the yins and yangs of STAT3 targeting therapies.

Se edita el texto más antiguo conocido sobre los valencianismos del castellano, los “valencianismos” del Dr. Juan de Ayala Manrique (Valencia, 1699), escrito a raíz de las disputas y discusiones de la época sobre la pertenencia o no al castellano de muchas palabras y construcciones usadas en Valencia. Se intenta con ello atraer la atención sobre las fases, mecanismos e interferencias lingüísticas producidas en el proceso de adquisición del castellano por los catanohablantes valencianos.

EGFR-mutated lung adenocarcinoma patients treated with gefitinib and osimertinib show a therapeutic benefit limited by the appearance of secondary mutations, such as EGFR(T790M) and EGFR(C797S). It is generally assumed that these secondary mutations render EGFR completely unresponsive to the inhibitors, but contrary to this, we uncovered here that gefitinib and osimertinib increased STAT3 phosphorylation (p-STAT3) in EGFR(T790M) and EGFR(C797S) tumoral cells. Interestingly, we also found that concomitant Notch inhibition with gefitinib or osimertinib treatment induced a p-STAT3–dependent strong reduction in the levels of the transcriptional repressor HES1. Importantly, we showed that tyrosine kinase inhibitor–resistant tumors, with EGFR(T790M) and EGFR(C797S) mutations, were highly responsive to the combined treatment of Notch inhibitors with gefitinib or osimertinib, respectively. Finally, in patients with EGFR mutations treated with tyrosine kinase inhibitors, HES1 protein levels increased during relapse and correlated with shorter progression-free survival. Therefore, our results offer a proof of concept for an alternative treatment to chemotherapy in lung adenocarcinoma osimertinib-treated patients after disease progression.

The most frequently mutated gene in human tumors is TP53 and its mutation significantly deteriorates patients' survival. However, to date no targeted therapy is established for TP53 mutated tumors. Here, our aim was to identify druggable kinases with higher expression in TP53 mutated tumors, as well as relate these to altered prognosis. We also aimed to validate a target gene in TP53 wild type and mutant isogenic cell lines using a specific kinase inhibitor. Gene expression and mutation data were collected from 994 lung tumor samples. Samples were separated based on TP53 mutation status, and differential gene expression was compared using Mann-Whitney test between patient cohorts. Prognostic value of identified genes was validated in an array-based lung cancer dataset (n=1926). Survival analysis was performed using Cox proportional hazards regression and Kaplan-Meier survival plots. Effect of TP53 mutations on CHEK1 expression was validated in the A549 isogenic lung cancer cell line. The cell line was also treated using Chk1 protein specific kinase inhibitor to monitor cell functions. Expression of CHEK1 was elevated significantly among targetable kinases and higher expression of CHEK1 related to worse prognosis. Our results confirm the higher expression of CHEK1 kinase associated to TP53 mutations and to shorter survival.Rosszindulatú daganatos megbetegedésekben leggyakrabban a prognózissal is összefüggõ, TP53 gént érintõ mutációk azonosíthatóak. Azonban mind ez idáig nem járt sikerrel a TP53-mutáns tumorok célzott kezelése. Célunk volt in silico azonosítani a TP53 gén mutációinak hatását a túléléssel is összefüggõ és terápiásan célozható gének expressziójára, majd az így kapott eredményeket in vitro igazolni TP53-vad és -mutáns izogén sejtvonalpárokon végzett gátlószeres kezeléssel. A TP53-mutációs státusz alapján 994 beteget két csoportra osztottunk, majd az összes génre Mann–Whitney-tesztet végeztünk, hogy meghatározzuk, a mutáció mely gének kifejezõdésével áll kapcsolatban. A célozható kinázok közt a CHEK1 expressziójának szignifikáns növekedését mutattuk ki a TP53-mutáns csoportban. Az A549 izogén tüdõkarcinóma-sejtvonalakon igazoltuk a CHEK1-expresszió változását a mutációval összefüggésben, majd egy Chk1 (checkpoint kinase 1) fehérjére specifikus gátlószer hatását vizsgáltuk a sejtek mûködésére. A gén prognosztikus szerepét Cox-regresszió és Kaplan–Meier túlélési analízis használatával, 1926 tüdõkarcinómás betegen vizsgáltuk, mely során a CHEK1 expressziójának növekedése rosszabb prognózissal társult. Eredményeink igazolják, hogy a CHEK1 kifejezõdése nagymértékben összefügg a TP53-mutációval és a túléléssel is a tüdõ rosszindulatú daganatai esetében.

Oncogenic K‐RAS has been difficult to target and currently there is no K‐RAS‐based targeted therapy available for patients suffering from K‐RAS‐driven lung adenocarcinoma (AC). Alternatively, targeting K‐RAS‐downstream effectors, K‐RAS‐cooperating signaling pathways or cancer hallmarks, such as tumor‐promoting inflammation, has been shown to be a promising therapeutic strategy. Since the JAK–STAT pathway is considered to be a central player in inflammation‐mediated tumorigenesis, we investigated here the implication of JAK–STAT signaling and the therapeutic potential of JAK1/2 inhibition in K‐RAS‐driven lung AC. Our data showed that JAK1 and JAK2 are activated in human lung AC and that increased activation of JAK–STAT signaling correlated with disease progression and K‐RAS activity in human lung AC. Accordingly, administration of the JAK1/2 selective tyrosine kinase inhibitor ruxolitinib reduced proliferation of tumor cells and effectively reduced tumor progression in immunodeficient and immunocompetent mouse models of K‐RAS‐driven lung AC. Notably, JAK1/2 inhibition led to the establishment of an antitumorigenic tumor microenvironment, characterized by decreased levels of tumor‐promoting chemokines and cytokines and reduced numbers of infiltrating myeloid derived suppressor cells, thereby impairing tumor growth. Taken together, we identified JAK1/2 inhibition as promising therapy for K‐RAS‐driven lung AC., What's new? A drug that inhibits the JAK–STAT pathway may score a hit against K‐RAS driven lung cancer. Here, the authors Investigated the JAK STAT pathway as a possible target in lung adenocarcinoma because of its role in inflammation‐mediated tumorigenesis. First, they showed that JAK1 and JAK2 are both activated in lung adenocarcinoma patients with oncogenic mutations in K‐RAS. Next, they treated the tumors with ruxolitinib, which inhibits JAK1/2. The drug successfully slowed tumor proliferation and progression in immunocompetent mouse models. Furthermore, treatment with ruxolitinib reduced the tumor‐promoting factors present in the microenvironment.

The use of mouse models is indispensable for studying the pathophysiology of various diseases. With respect to lung cancer, several models are available, including genetically engineered models as well as transplantation models. However, genetically engineered mouse models are time-consuming and expensive, whereas some orthotopic transplantation models are difficult to reproduce. Here, a non-invasive intratracheal delivery method of lung tumor cells as an alternative orthotopic transplantation model is described. The use of mouse lung adenocarcinoma cells and syngeneic graft recipients allows studying tumorigenesis under the presence of a fully active immune system. Furthermore, genetic manipulations of tumor cells before transplantation makes this model an attractive time-saving approach to study the impact of genetic factors on tumor growth and tumor cell gene expression profiles under physiological conditions. Using this model, we show that lung adenocarcinoma cells express increased levels of the T-cell suppressor programmed death-ligand 1 (PD-L1) when grown in their natural environment as compared to cultivation in vitro.

Endostatin, the C-terminal fragment of type XVIII collagen, was shown to be one of the most potent endothelial cell-specific inhibitors of angiogenesis. As altered circulating endostatin concentration is associated with impaired kidney function, new tools for measuring endostatin in rodents may be helpful to further investigate and understand its role within kidney disease progression. A novel and commercially available ELISA for the quantification of mouse and rat endostatin was developed and validated according to international quality guidelines including the parameters specificity, robustness, accuracy, dilution linearity, precision, limit of detection (LOD) and lower limit of quantification (LLOQ). Endostatin and blood urea nitrogen (BUN) concentration were measured in mice with a glomerulonephritis phenotype. The validation revealed that within the range of 0.5–32 nmol/L the immunoassay is robust and highly specific for the measurement of rodent endostatin with high sensitivity (LOD 0.24 nmol/L, LLOQ 0.5 nmol/L) and good reproducibility (intra- and inter-assay CV

We have demonstrated that the signal transducer and activator of transcription 3 (STAT3) protects from cholestatic liver injury. Specific ablation of STAT3 in hepatocytes and cholangiocytes (STAT3∆hc) aggravated liver damage and fibrosis in the Mdr2−/− (multidrug resistance 2) mouse model for cholestatic disease. Upregulation of bile acid biosynthesis genes and downregulation of epidermal growth factor receptor (EGFR) expression were observed in STAT3∆hc Mdr2−/− mice but the functional consequences of these processes in cholestatic liver injury remained unclear. Here, we show normal canalicular architecture and bile flow but increased amounts of bile acids in the bile of STAT3∆hc Mdr2−/− mice. Moreover, STAT3-deficient hepatocytes displayed increased sensitivity to bile acid-induced apoptosis in vitro. Since EGFR signaling has been reported to protect hepatocytes from bile acid-induced apoptosis, we generated mice with hepatocyte/cholangiocyte-specific ablation of EGFR (EGFR∆hc) and crossed them to Mdr2−/− mice. Importantly, deletion of EGFR phenocopied deletion of STAT3 and led to aggravated liver damage, liver fibrosis, and hyperproliferation of K19+ cholangiocytes. Our data demonstrate hepatoprotective functions of the STAT3-EGFR signaling axis in cholestatic liver disease. Key message STAT3 is a negative regulator of bile acid biosynthesis.STAT3 protects from bile acid-induced apoptosis and regulates EGFR expression.EGFR signaling protects from cholestatic liver injury and fibrosis.

The histone acetyl-reader BRD4 is an important regulator of chromatin structure and transcription, yet factors modulating its activity have remained elusive. Here we describe two complementary screens for genetic and physical interactors of BRD4, which converge on the folate pathway enzyme MTHFD1. We show that a fraction of MTHFD1 resides in the nucleus, where it is recruited to distinct genomic loci by direct interaction with BRD4. Inhibition of either BRD4 or MTHFD1 results in similar changes in nuclear metabolite composition and gene expression, and pharmacologic inhibitors of the two pathways synergize to impair cancer cell viability in vitro and in vivo. Our finding that MTHFD1 and other metabolic enzymes are chromatin-associated suggests a direct role for nuclear metabolism in the control of gene expression.

Oncogenic K-RAS mutations were believed to lock the molecular switch in the ON state, independent of upstream activation. However, we demonstrate in preclinical models that activity of mutated K-RAS depends on upstream signaling events involving EGF receptor family members. This finding reveals a potential therapeutic vulnerability using pan-ERBB inhibitors to fight K-RAS mutated lung tumors.

Sodium channel inhibitor drugs decrease pathological hyperactivity in various diseases including pain syndromes, myotonia, arrhythmias, nerve injuries and epilepsies. Inhibiting pathological but not physiological activity, however, is a major challenge in drug development. Sodium channel inhibitors exert their effects by a dual action: they obstruct ion flow ("block"), and they alter the energetics of channel opening and closing ("modulation"). Ideal drugs would be modulators without blocking effect, because modulation is inherently activity-dependent, therefore selective for pathological hyperactivity. Can block and modulation be separated? It has been difficult to tell, because the effect of modulation is obscured by confromation-dependent association/dissociation of the drug. To eliminate dynamic association/dissociation, we used a photoreactive riluzole analog which could be covalently bound to the channel; and found, unexpectedly, that drug-bound channels could still conduct ions, although with modulated gating. The finding that non-blocking modulation is possible, may open a novel avenue for drug development because non-blocking modulators could be more specific in treating hyperactivity-linked diseases.

Growth hormone (GH) resistance has been associated with liver cirrhosis in humans but its contribution to the disease remains controversial. In order to elucidate whether GH resistance plays a causal role in the establishment and development of liver fibrosis, or rather represents a major consequence thereof, we challenged mice lacking the GH receptor gene (Ghr–/–, a model for GH resistance) by crossing them with Mdr2 knockout mice (Mdr2–/–), a mouse model of inflammatory cholestasis and liver fibrosis. Ghr–/–;Mdr2–/– mice showed elevated serum markers associated with liver damage and cholestasis, extensive bile duct proliferation, and increased collagen deposition relative to Mdr2–/– mice, thus suggesting a more severe liver fibrosis phenotype. Additionally, Ghr–/–;Mdr2–/– mice had a pronounced down-regulation of hepatoprotective genes Hnf6, Egfr, and Igf-1, and significantly increased levels of reactive oxygen species (ROS) and apoptosis in hepatocytes, compared to control mice. Moreover, single knockout mice (Ghr–/–) fed with a diet containing 1% cholic acid displayed an increase in hepatocyte ROS production, hepatocyte apoptosis, and bile infarcts compared to their wild-type littermates, indicating that loss of Ghr renders hepatocytes more susceptible to toxic bile acid accumulation. Surprisingly, and despite their severe fibrotic phenotype, Ghr–/–;Mdr2–/– mice displayed a significant decrease in tumor incidence compared to Mdr2–/– mice, indicating that loss of Ghr signaling may slow the progression from fibrosis/cirrhosis to cancer in the liver. Conclusion: GH resistance dramatically exacerbates liver fibrosis in a mouse model of inflammatory cholestasis, therefore suggesting that GH resistance plays a causal role in the disease and provides a novel target for the development of liver fibrosis treatments. (Hepatology 2015;61:613-626)

The interferon‐inducible transcription factor STAT1 is a tumor suppressor in various malignancies. We investigated sex‐specific STAT1 functions in colitis and colitis‐associated colorectal cancer (CRC) using mice with specific STAT1 deletion in intestinal epithelial cells (STAT1∆IEC). Male but not female STAT1∆IEC mice were more resistant to DSS‐induced colitis than sex‐matched STAT1flox/flox controls and displayed reduced intraepithelial infiltration of CD8+ TCRαβ+ granzyme B+ T cells. Moreover, DSS treatment failed to induce expression of T‐cell‐attracting chemokines in intestinal epithelial cells of male but not of female STAT1∆IEC mice. Application of the AOM‐DSS protocol for induction of colitis‐associated CRC resulted in increased intestinal tumor load in male but not in female STAT1∆IEC mice. A sex‐specific stratification of human CRC patients corroborated the data obtained in mice and revealed that reduced tumor cell‐intrinsic nuclear STAT1 protein expression is a poor prognostic factor in men but not in women. These data demonstrate that epithelial STAT1 is a male‐specific tumor suppressor in CRC of mice and humans.

Salivary gland cancer is an aggressive and painful cancer, but a rare tumor type accounting for only ~0.5% of cancer cases. Tumors of the salivary gland exhibit heterogeneous histologic and genetic features and they are subdivided into different subtypes, with adenoid cystic carcinomas (ACC) being one of the most abundant. Treatment of ACC patients is afflicted by high recurrence rates, the high potential of the tumors to metastasize, as well as the poor response of ACC to chemotherapy. A prerequisite for the development of targeted therapies is insightful genetic information for driver core cancer pathways. Here, we developed a transgenic mouse model toward establishment of a preclinical model. There is currently no available mouse model for adenoid cystic carcinomas as a rare disease entity to serve as a test system to block salivary gland tumors with targeted therapy. Based on tumor genomic data of ACC patients, a key role for the activation of the PI3K‐AKT‐mTOR pathway was suggested in tumors of secretory glands. Therefore, we investigated the role of Akt3 expression in tumorigenesis and report that Akt3 overexpression results in ACC of salivary glands with 100% penetrance, while abrogation of transgenic Akt3 expression could revert the phenotype. In summary, our findings validate a novel mouse model to study ACC and highlight the druggable potential of AKT3 in the treatment of salivary gland patients.

On the basis of clinical trials using first-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), it became a doctrine that V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (K-RAS) mutations drive resistance to EGFR inhibition in non-small cell lung cancer (NSCLC). Conversely, we provide evidence that EGFR signaling is engaged in K-RAS-driven lung tumorigenesis in humans and in mice. Specifically, genetic mouse models revealed that deletion of Egfr quenches mutant K-RAS activity and transiently reduces tumor growth. However, EGFR inhibition initiates a rapid resistance mechanism involving non-EGFR ERBB family members. This tumor escape mechanism clarifies the disappointing outcome of first-generation TKIs and suggests high therapeutic potential of pan-ERBB inhibitors. On the basis of various experimental models including genetically engineered mouse models, patient-derived and cell line-derived xenografts, and in vitro experiments, we demonstrate that the U.S. Food and Drug Administration-approved pan-ERBB inhibitor afatinib effectively impairs K-RAS-driven lung tumorigenesis. Our data support reconsidering the use of pan-ERBB inhibition in clinical trials to treat K-RAS-mutated NSCLC.

Designing appropriate expression vectors is one of the critical steps in the generation of stable cell lines for recombinant protein production. Conventional expression vectors are severely affected by the chromatin environment surrounding their integration site into the host genome, resulting in low expression levels and transgene silencing. In the past, a new generation of expression vectors and different strategies was developed to overcome the chromatin effects. Bacterial artificial chromosomes (BACs) are cloning vectors capable of accommodating up to 350 Kb. Thus, BACs can carry a whole eukaryotic locus with all the elements controlling the expression of a gene; therefore, BACs harbor their own chromatin environment. Expression vectors based on BACs containing open/permissive chromatin loci are not affected by the chromatin surrounding their integration site in the host cell genome. Consequently, BAC-based expression vectors containing the appropriate loci confer predictable and high levels of expression over time. These properties make BAC-based expression vectors a very attractive tool applied to the recombinant protein production field.

Vector engineering approaches are commonly used to increase recombinant protein production in mammalian cells, and among various concepts, bacterial artificial chromosomes (BAC) have been proposed to serve as open chromatin regions to omit chromosome positional effects. For proof of concept, we developed stable recombinant Chinese hamster ovary (CHO) cell lines using different expression vector systems: the plasmid vectors contained the identical expression cassette as the BAC constructs. Two anti-HIV1 antibody derivates served as model proteins (3D6scFc and 2F5scFc) for generation of four stable recombinant CHO cell lines. The BAC-derived clones showed three to four times higher specific productivity, and therefore, gene copy numbers and transcript level were quantified. The active chromatin region provided with the BAC environment significantly improved transcription evidenced with both model proteins. Specific transcription was approximately six times higher from BAC-based vectors compared to the corresponding plasmid vectors for both single-chain fragment crystallizable (scFc) proteins. Our accurate investigations elucidated also differences between translational activities related to the protein of choice. 3D6scFc expressed specifically three to four times more product than 2F5scFc indicating that the product by itself also contributes to enhanced productivity. This study indicated comparable increase of transcription level for both scFc proteins when using the BAC system, but translation, maturation, and secretion of individual proteins seem to be protein specific.

Growth hormone (GH)-activated signal transducer and activator of transcription 5 (STAT5) and the glucocorticoid (GC)-responsive glucocorticoid receptor (GR) are important signal integrators in the liver during metabolic and physiologic stress. Their deregulation has been implicated in the development of metabolic liver diseases, such as steatosis and progression to fibrosis. Using liver-specific STAT5 and GR knockout mice, we addressed their role in metabolism and liver cancer onset. STAT5 single and STAT5/GR double mutants developed steatosis, but only double-mutant mice progressed to liver cancer. Mechanistically, STAT5 deficiency led to the up-regulation of prolipogenic sterol regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator activated receptor gamma (PPAR-γ) signaling. Combined loss of STAT5/GR resulted in GH resistance and hypercortisolism. The combination of both induced expression of adipose tissue lipases, adipose tissue lipid mobilization, and lipid flux to the liver, thereby aggravating STAT5-dependent steatosis. The metabolic dysfunctions in STAT5/GR compound knockout animals led to the development of hepatic dysplasia at 9 months of age. At 12 months, 35% of STAT5/GR-deficient livers harbored dysplastic nodules and ∼60% hepatocellular carcinomas (HCCs). HCC development was associated with GH and insulin resistance, enhanced tumor necrosis factor alpha (TNF-α) expression, high reactive oxygen species levels, and augmented liver and DNA damage parameters. Moreover, activation of the c-Jun N-terminal kinase 1 (JNK1) and STAT3 was prominent. Conclusion Hepatic STAT5/GR signaling is crucial for the maintenance of systemic lipid homeostasis. Impairment of both signaling cascades causes severe metabolic liver disease and promotes spontaneous hepatic tumorigenesis. (hepatology 2011;54:1398–1409)

Tumor invasion and metastasis is a multi-step process that requires adaptation of cancer cells to conditions that they encounter during their journey to distant body sites. Understanding the molecular processes that underlie this adaptation is of exceeding importance because most cancer patients die because of metastases rather than primary tumors. In this review we assess genetically engineered mouse models (GEMMs) that have been established to investigate mechanisms of cancer invasion and metastasis.

Lung cancer is still the leading cause of cancer deaths worldwide. While it is well documented that patients suffering from epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC) benefit from (EGFR) inhibition, there are still no successful targeted therapies for oncogenic mutations in the V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) gene available. Indeed, based on clinical trials using first generation EGFR tyrosine kinase inhibitors (TKI) it became a doctrine that K-RAS mutations drive resistance to EGFR inhibition in non-small cell lung cancer (NSCLC). Conversely, we demonstrate here that EGFR signaling is engaged in K-RAS driven lung tumorigenesis both in human and in mice. Genetic mouse models revealed that deletion of Egfr quenches mutant K-ras activity and transiently reduces tumor growth. However, EGFR inhibition initiates a resistance mechanism which involves non-EGFR ERBB family members. This escape mechanism not only clarifies the disappointing outcome of first generation TKI in clinical trials, but also suggests therapeutic potential of pan-ERBB inhibitors. Indeed, by using several experimental models, including genetically engineered mouse models, (patient derived-) xenografts and in vitro experiments, we demonstrate that the FDA approved pan-ERBB inhibitor afatinib formidably reduces K-RAS driven lung tumorigenesis, whereas first generation TKI erlotinib and gefitinib remained ineffective in our models. Altogether, our data strongly suggests revisiting the potential of EGFR TKI in clinical trials for the treatment of K-RAS mutated NSCLC, with a particular focus on pan-ERBB inhibitors, which are readily available. Citation Format: Herwig P. Moll, Klemens Pranz, Monica Musteanu, Luka Brcic, Helmut Popper, Judit Moldvay, Balázs Dome, Emilio Casanova. Afatinib restrains K-RAS driven lung tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 809.

Introduction Several clinical trials using first generation EGFR Tyrosine Kinase Inhibitors (TKIs, erlotinib and gefitinib) in patients suffering of lung adenocarcinoma (AC) harbouring activating mutations in the KRAS gene have shown disappointing results. Therefore, it has become a doctrine that KRAS driven lung AC do not respond to TKIs and targeting EGFR (and other ERBB family members) is not considered a therapeutic option to treat patients suffering of KRAS mutated lung AC. Challenging these observations, we demonstrate that KRAS driven lung AC responds to the pan-ERBB inhibitor afatinib. Material and methods Primary human tumour samples, human/murine cancer cell lines, xenografts, PDXs and GEMMs. Genetic and pharmacological manipulations. Results and discussions Analysis of human and murine tumour samples showed activation of the ERBB receptors and expression of their ligands in KRAS driven lung AC. Furthermore, human KRAS mutated advance tumours (stage II and more advance AC) were enriched in the ERBB gene expression signatures compared to stage I tumours. Experimentally, we found that genetic deletion of EGFR in a GEMM of KRAS driven lung AC or in human xenografted A549 cells significantly reduced tumorigenesis, irrespectively of the p53 status. Tumours lacking EGFR showed less cell proliferation and reduce activation of KRAS downstream effectors. Pharmacological inhibition of EGFR using erlotinib or gefitinib failed to inhibit tumorigenesis in KRAS driven lung AC experimental models. On the contrary, afatinib (an irreversible pan-ERBB inhibitor) was effective in human/murine cell lines, xenograft, PDXs and GEMMs models. Detailed analysis of this observation revealed that genetic deletion or pharmacology inhibition (erlotinib/gefitinib) of the EGFR in KRAS driven lung AC results in a tumor-escape mechanism relying in the activation of other ERBB receptor family members (namely ERBB2 and ERBB3) that can be blocked with the pan-ERBB inhibitor afatinib. Conclusion In conclusion, our data shows that KRAS driven lung AC is depending on ERBB signalling. Importantly, we have unravelled a tumor-escape mechanism depending on the (re)activation of non-EGFR ERBB receptors that explains the poor results in previous clinical trials using erlotinib and gefitinib in patients suffering KRAS mutated lung AC. In agreement with this, pan-ERBB inhibition using afatinib effectively abrogates KRAS driven lung AC. Thus, afatinib or other pan-ERBB inhibitors should be a therapeutic option to treat patients suffering of KRAS driven lung AC.

Background & Aims Signal transducer and activator of transcription 3 (Stat3) is the main mediator of interleukin-6–type cytokine signaling required for hepatocyte proliferation and hepatoprotection, but its role in sclerosing cholangitis and other cholestatic liver diseases remains unresolved. Methods We investigated the role of Stat3 in inflammation-induced cholestatic liver injury and used mice lacking the multidrug resistance gene 2 (mdr2−/−) as a model for SC. Results We show that conditional inactivation of Stat3 in hepatocytes and cholangiocytes (stat3Δhc) of mdr2−/− mice strongly aggravated bile acid–induced liver injury and fibrosis. A similar phenotype was observed in mdr2−/− mice lacking interleukin-6 production. Biochemical and molecular characterization suggested that Stat3 exerts hepatoprotective functions in both hepatocytes and cholangiocytes. Loss of Stat3 led to increased expression of tumor necrosis factor α, which might reduce the barrier function of bile ducts. Moreover, Stat3-deficient hepatocytes displayed up-regulation of bile acid biosynthesis genes and down-regulation of hepatoprotective epidermal growth factor receptor and insulin-like growth factor 1 signaling pathways. Consistently, stat3Δhc mice were more sensitive to cholic acid–induced liver damage than control mice. Conclusions Our data suggest that Stat3 prevents cholestasis and liver damage in sclerosing cholangitis via regulation of pivotal functions in hepatocytes and cholangiocytes.

Growth hormone (GH) resistance and low serum levels of insulinlike growth factor 1 (IGF-1) are common features in human liver fibrosis and cirrhosis. Signal transducer and activator of transcription 5 (STAT5) controls several vital functions in the liver, including GH-mediated transcription of IGF-1. To investigate the role of STAT5 in liver fibrogenesis, we specifically deleted the Stat5a/b locus both in hepatocytes and cholangiocytes in the multidrug resistance gene 2 knockout (Mdr2−/−) mouse model of cholestasis. Double knockout mice develop an early and severe liver fibrosis phenotype, accompanied by perturbed expression of key regulators of bile acid homeostasis. Deletion of Stat5 resulted in GH resistance, and IGF-1 levels in serum were undetectable. We could observe reduced expression of important hepatoprotective genes, such as epidermal growth factor receptor (Egfr), hepatocyte nuclear factor 6 (Hnf6), prolactin receptor (Prlr), and leukemia inhibitory factor receptor (Lifr) as well as increased numbers of apoptotic hepatocytes. Conclusion Our data suggest that loss of STAT5 sensitizes hepatocytes to bile acid–induced damage and apoptosis caused by disruption of GH-induced transcription of Igf-1 and down-regulation of hepatoprotective genes. These findings could contribute to the understanding of liver fibrosis and future treatment strategies for liver fibrosis.

Summary: Tissue-specific transgene expression in the prostate epithelium has previously been achieved using short prostate-specific promoters, rendering transgenic mouse lines susceptible to integration site-dependent effects. Here we demonstrate the applicability of bacterial artificial chromosome (BAC) technology to transgene expression in the prostate epithelium. We present mouse lines expressing an inducible Cre protein (MerCreMer) under the control of regulatory elements of the probasin gene on a BAC. These mouse lines show high organ specificity, high transgene expression in anterior, dorsal and lateral prostate lobes, no background Cre recombination using a reporter strain and adjustable amounts of Cre-induced recombination upon tamoxifen induction. Together with two recently reported transgenic lines expressing the Cre-ERT2 protein from small prostate-specific promoters, these mouse lines will be useful in research focused on prostate-specific disorders such as benign hyperplasia or cancer. genesis