Aberrant TIMP-1 production in tumor-associated fibroblasts drives the selective benefits of nintedanib in lung adenocarcinoma

The fibrotic tumor microenvironment is a pivotal therapeutic target. Nintedanib, a clinically approved multikinase antifibrotic inhibitor, is effective against lung adenocarcinoma (ADC) but not squamous cell carcinoma (SCC). Previous studies have implicated the secretome of tumor-associated fibroblasts (TAFs) in the selective effects of nintedanib in ADC, but the driving factor(s) remained unidentified. Here we examined the role of tissue inhibitor of metalloproteinase-1 (TIMP-1), a tumor-promoting cytokine overproduced in ADC-TAFs. To this aim, we combined genetic approaches with in vitro and in vivo preclinical models based on patient-derived TAFs. Nintedanib reduced TIMP-1 production more efficiently in ADC-TAFs than SCC-TAFs through a SMAD3-dependent mechanism. Cell culture experiments indicated that silencing TIMP1 in ADC-TAFs abolished the therapeutic effects of nintedanib on cancer cell growth and invasion, which were otherwise enhanced by the TAF secretome. Consistently, co-injecting ADC cells with TIMP1-knockdown ADC-TAFs into immunocompromised mice elicited a less effective reduction of tumor growth and invasion under nintedanib treatment compared to tumors bearing unmodified fibroblasts. Our results unveil a key mechanism underlying the selective mode of action of nintedanib in ADC based on the excessive production of TIMP-1 in ADC-TAFs. We further pinpoint reduced SMAD3 expression and consequent limited TIMP-1 production in SCC-TAFs as key for the resistance of SCC to nintedanib. These observations strongly support the emerging role of TIMP-1 as a critical regulator of therapy response in solid tumors.

Enhancing gastric cancer conventional chemotherapy effects by triple angiokinase inhibitor nintedanib in preclinical models

Background

Gastric adenocarcinoma (GAC) is the fourth leading cause of cancer death worldwide. Systemic chemotherapy is a preferred treatment option for advanced and recurrent GAC, but response rates and survival prolongation remain limited. Tumor angiogenesis plays a critical role in GAC growth, invasion and metastasis. We investigated the antitumor efficacy of nintedanib, a potent triple angiokinase inhibitor for VEGFR-1/2/3, PDGFR-α/β and FGFR-1/2/3, alone or in combination with chemotherapy, in preclinical models of GAC.

Methods

Animal survival studies were performed in peritoneal dissemination xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and KATO-III. Tumor growth inhibition studies were performed in subcutaneous xenografts in NOD/SCID mice using human GAC cell lines MKN-45 and SNU-5. The mechanistic evaluation involved Immunohistochemistry analyses in tumor tissues obtained from subcutaneous xenografts. In vitro cell viability assays were performed using a colorimetric WST-1 reagent.

Results

In MKN-45 GAC cell-derived peritoneal dissemination xenografts, animal survival was improved by nintedanib (33%), docetaxel (100%) and irinotecan (181%), while oxaliplatin, 5-FU and epirubicin had no effect. The addition of nintedanib to docetaxel (157%) or irinotecan (214%) led to a further extension in animal survival. In KATO-III GAC cell-derived xenografts carrying FGFR2 gene amplification, nintedanib extended survival by 209%. Again, the addition of nintedanib further enhanced the animal survival benefits of docetaxel (273%) and irinotecan (332%). In MKN-45 subcutaneous xenografts, nintedanib, epirubicin, docetaxel and irinotecan reduced tumor growth (range: 68-87%), while 5-FU and oxaliplatin had a smaller effect (40%). Nintedanib addition to all chemotherapeutics demonstrated a further reduction in tumor growth. Subcutaneous tumor analysis revealed that nintedanib attenuated tumor cell proliferation, reduced tumor vasculature and increased tumor cell death.

Conclusion

Nintedanib showed notable antitumor efficacy and significantly improved taxane or irinotecan chemotherapy responses. These findings indicate that nintedanib, alone and in combination with a taxane or irinotecan, has the potential for improving clinical GAC therapy.

Tumor and Stromal Cell Targeting with Nintedanib and Alpelisib Overcomes Intrinsic Bladder Cancer Resistance

Bladder cancer is a highly prevalent tumor, requiring the urgent development of novel therapies, especially for locally advanced and metastatic disease. Nintedanib is a potent antifibrotic angio-kinase inhibitor, which has shown clinical efficacy in combination with chemotherapy in patients with locally advanced muscle-invasive bladder cancer. Nintedanib inhibits fibroblast growth factor receptors (FGFRs), validated targets in patients with bladder cancer harboring FGFR3/2 genetic alterations. Here, we aimed at studying its mechanisms of action to understand therapy resistance, identify markers predictive of response, and improve the design of future clinical trials. We have used a panel of genetically well-characterized human bladder cancer cells to identify the molecular and transcriptomic changes induced upon treatment with nintedanib, in vitro and in vivo, at the tumor and stroma cell levels. We showed that bladder cancer cells display an intrinsic resistance to nintedanib treatment in vitro, independently of their FGFR3 status. However, nintedanib has higher antitumor activity on mouse xenografts. We have identified PI3K activation as a resistance mechanism against nintedanib in bladder cancer and evidenced that the combination of nintedanib with the PI3K inhibitor alpelisib has synergistic antitumor activity. Treatment with this combination is associated with cell-cycle inhibition at the tumoral and stromal levels and potent nontumor cell autonomous effects on α-smooth muscle actin-positive tumor infiltrating cells and tumor vasculature. The combination of nintedanib with PI3K inhibitors not only reversed bladder cancer resistance to nintedanib but also enhanced its antiangiogenic effects.

Abstract 2356: Aberrant TIMP-1 secretion by tumor-associated fibroblasts is a major contributor to the selective positive response to nintedanib in lung adenocarcinoma

Adenocarcinoma (ADC) and Squamous Cell Carcinoma (SCC) are the most frequent histologic subtypes of lung cancer, and both are rich in activated/myofibroblast-like tumor-associated fibroblasts (TAFs). Nintedanib is a potent antifibrotic drug that targets the tumor stroma and is clinically approved to treat advanced lung ADC patients owing to the survival benefits observed in the LUME-1 clinical trial in ADC but not SCC patients. Although the mechanism underlying the ADC-selective therapeutic effects of nintedanib remained poorly understood, we have previously reported that nintedanib abrogates the pro-tumoral traits of the secretome of ADC-TAFs but not SCC-TAFs, suggesting that secreted factor(s) in ADC-TAFs may be implicated. In addition, we recently unveiled an ADC-specific tumor-promoting crosstalk between TAFs and cancer cells driven by TIMP-1 and CD63, whereas others have shown that TIMP-1 is a molecular target of nintedanib. However, it remains unknown if TIMP-1 is involved in the ADC-selective benefits of nintedanib. To address this question, we used patient-derived TAFs obtained with the patient’s informed consent and using protocols approved by the Ethics Committee of the Hospital Clinic. We treated TGF-β1-activated ADC-TAFs and SCC-TAFs with nintedanib and determined the content of TIMP-1 in their conditioned medium by ELISA. Moreover, we used cell-based functional assays and tumor xenografts after knocking-down TIMP-1 in TAFs by siRNA to examine how silencing TIMP-1 altered their response to nintedanib. By analyzing TCGA data and the human protein atlas, we found that TIMP-1 is consistently upregulated in ADC compared to SCC tumors both at the mRNA and protein levels. Moreover, TCGA data revealed that TIMP-1 is increased in tumors compared to paired control tissue in ADC but not SCC. In culture, we observed that TIMP-1 secretion was higher in ADC-TAFs than SCC-TAFs, and that this secretion was downregulated by nintedanib to a larger extent in ADC-TAFs compared to SCC-TAFs. In vivo analyses revealed that ADC cells co-injected with fibroblasts silenced for TIMP-1 as in SCC-TAFs into immunocompromised mice exhibited a less invasive growth pattern compared to tumors bearing control fibroblasts. In addition, we observed that the inhibition of the pro-tumoral secretome of ADC-TAFs elicited by nintedanib was abrogated upon knocking-down TIMP-1 in TAFs both in vitro and in vivo. Collectively, these results reveal that the high secretion of TIMP-1 in ADC-TAFs render them more responsive to nintedanib, whereas the low TIMP-1 secretion of SCC-TAFs may be a major contributor to the selective resistance of SCC patients to nintedanib. Moreover, our results identify TIMP-1 as a promising predictive biomarker of nintedanib responses.

Citation Format: Paula Duch, Natalia Díaz-Valdivia, Marta Gabasa, Rafael Ikemori, Frank Hilberg, Noemí Reguart, Derek Radisky, Jordi Alcaraz. Aberrant TIMP-1 secretion by tumor-associated fibroblasts is a major contributor to the selective positive response to nintedanib in lung adenocarcinoma [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 2356.

Pharmacodynamic and Antitumor Activity of BI 836880, a Dual Vascular Endothelial Growth Factor and Angiopoietin 2 Inhibitor, Alone and Combined with Programmed Cell Death Protein-1 Inhibition

Vascular endothelial growth factor (VEGF) and angiopoietin (ANG)-2 have complementary roles in angiogenesis and promote an immunosuppressive tumor microenvironment. It is anticipated that the combination of VEGF and ANG2 blockade could provide superior activity to the blockade of either pathway alone and that the addition of VEGF/ANG2 inhibition to an anti-programmed cell death protein-1 (PD-1) antibody could change the tumor microenvironment to support T-cell-mediated tumor cytotoxicity. Here, we describe the pharmacologic and antitumor activity of BI 836880, a humanized bispecific nanobody comprising two single-variable domains blocking VEGF and ANG2, and an additional module for half-life extension in vivo. BI 836880 demonstrated high affinity and selectivity for human VEGF-A and ANG2, resulting in inhibition of the downstream signaling of VEGF/ANG2 and a decrease in endothelial cell proliferation and survival. In vivo, BI 836880 exhibited significant antitumor activity in all patient-derived xenograft models tested, showing significantly greater tumor growth inhibition (TGI) than bevacizumab (VEGF inhibition) and AMG386 (ANG1/2 inhibition) in a range of models. In a Lewis lung carcinoma syngeneic tumor model, the combination of PD-1 inhibition with VEGF inhibition showed superior efficacy versus the blockade of either pathway alone. TGI was further increased with the addition of ANG2 inhibition to VEGF/PD-1 blockade. VEGF/ANG2 inhibition had a strong antiangiogenic effect. Our data suggest that the blockade of VEGF and ANG2 with BI 836880 may offer improved antitumor activity versus the blockade of either pathway alone and that combining VEGF/ANG2 inhibition with PD-1 blockade can further enhance antitumor effects. SIGNIFICANCE STATEMENT: Vascular endothelial growth factor (VEGF) and angiopoietin (ANG)-2 play key roles in angiogenesis and have an immunosuppressive effect in the tumor microenvironment. This study shows that BI 836880, a bispecific nanobody targeting VEGF and ANG2, demonstrates substantial antitumor activity in preclinical models. Combining VEGF/ANG2 inhibition with the blockade of the PD-1 pathway can further improve antitumor activity.

Abstract 1043: Enhancing cytotoxic chemotherapy effects by nintedanib in gastric cancer preclinical models

Background: Gastric adenocarcinoma (GAC) remains the 3rd most common cause of cancer mortality in the world. Systemic chemotherapy is a preferred treatment option for advanced and recurrent GAC, but response rates and survival extension remain limited. Tumor angiogenesis plays a critical role in GAC growth, invasion and metastasis. In this study, we determined the antitumor efficacy of nintedanib, a potent triple angiokinase inhibitor for VEGFR-1/2/3, PDGFR-α/β and FGFR-1/2/3, alone or in combination with chemotherapy, in preclinical models of GAC.

Methods: Animal survival and tumor growth studies were performed in 4-6 week-old female NOD/SCID mice with human GAC cell xenografts (MKN-45, KATO-III, SNU-5). The mechanistic evaluation involved Immunohistochemistry and Immunoblot analyses of subcutaneous tumors. In vitro cell viability assays were performed using colorimetric WST-1 reagent.

Results: In MKN-45 cell-derived peritoneal dissemination xenografts, animal survival was improved by nintedanib (33%), docetaxel (100%) or irinotecan (181%), while oxaliplatin, 5-FU and epirubicin had no effect. The addition of nintedanib to docetaxel (157%) or irinotecan (214%) led to a further extension in animal survival. In KATO-III cell-derived xenografts carrying FGFR2 gene amplification, nintedanib monotherapy extended survival much more (209%). Docetaxel and irinotecan effects were again further enhanced by nintedanib. In MKN-45 subcutaneous xenografts, nintedanib, epirubicin, docetaxel or irinotecan reduced tumor growth (range: 68-87%), while 5-FU and oxaliplatin had a smaller effect (40%). The addition of nintedanib to all chemotherapy groups demonstrated a further reduction in tumor growth. Subcutaneous tumor analysis revealed that nintedanib attenuated tumor cell proliferation, reduced tumor vasculature and increased tumor cell death. Nintedanib (10 μM) inhibited in vitro cell proliferation of mutationally different GAC cells by 25% (MKN-45), 75% (KATO-III) or 82% (SNU-5), and confirmed additive inhibitory effects in combinations with chemotherapy agents.

Conclusion: Nintedanib showed notable antitumor efficacy and significantly improved taxane or irinotecan chemotherapy responses. Combination regimens with nintedanib have the potential for improving clinical GAC therapy.

Citation Format: Niranjan Awasthi, Margaret A. Schwarz, Frank Hilberg, Roderich E. Schwarz. Enhancing cytotoxic chemotherapy effects by nintedanib in gastric cancer preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1043.

Abstract 985: BI 905711 selectively induces apoptosis and anti-tumor response in TRAILR2/CDH17- expressing pancreatic cancer models

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal adult cancers with an average 5-year survival rate of less than 10% due in part to the limited number of effective therapies. Activation of TRAILR2 (Tumor necrosis factor (TNF)-Related Apoptosis-Inducing Ligand Receptor 2) has emerged as an important therapeutic concept in cancer treatment. Traditional TRAILR2 agonists have had limited clinical success due to lack of efficacy or, importantly, severe hepatotoxicity. Here we present anti-tumor activity in preclinical PDAC models for BI 905711, a first-in-class tetravalent bispecific antibody specifically designed to overcome the disadvantages of previous strategies targeting TRAILR2.

BI 905711 serves as a uniquely specific, and liver-sparing therapeutic by targeting tumors that co-express TRAILR2 and another cell surface protein CDH17, which has ~40% prevalence in PDAC and is not expressed in normal liver. Working from a large cohort of molecularly characterized PDAC PDX models, we provide the first preclinical evidence of BI 905711 exhibiting robust anti-tumor activity in difficult to treat PDAC PDX models. Anti-tumor efficacy in responding models correlated with strong induction of Caspases 3/7 and 8 activation in tumors 24 hours after a single dose of BI 905711, and was associated with the presence and expression levels of TRAILR2 and CDH17 proteins. Evaluation of models with differential TRAILR2 and CDH17 expression profiles helped define the expression threshold for each target that is associated with response, upon which clinical assay development is in process for future patient stratification. Additionally, response was also associated with PDAC molecular subtypes utilizing a novel proprietary gene co-expression network developed from a curated cohort of PDAC PDX tumors. Responders to BI 905711 were identified primarily within the classical and quasi-basal/hybrid subtypes when TRAILR2 was adequately co-expressed. This correlates with an enrichment pattern of CDH17 gene expression that is mostly within the classical gene cluster and strongly anti-correlated with basal-like cluster enrichment.

Robust preclinical anti-tumor activity of BI 905711 in TRAILR2 and CDH17-expressing PDAC PDX models, along with this antibody's potential for a favorable safety profile, has justified the enrollment of pancreatic cancer patients in the ongoing BI 905711 FIH Phase I clinical trial (NCT04137289).

Citation Format: Jing Han, Annette A. Machado, Mikhila Mahendra, Joseph R. Daniele, Christopher A. Bristow, Justin Kwang-Lay Huang, Alessandro Carugo, Robert A. Mullinax, Benjamin J. Bivona, Ningping Feng, Poojabahen Gandhi, Norbert Schweifer, Paolo Maria Chetta, Juan Manuel Garcia-Martinez, Frank Hilberg, Christopher P. Vellano, Timothy P. Heffernan, Joseph R. Marszalek. BI 905711 selectively induces apoptosis and anti-tumor response in TRAILR2/CDH17- expressing pancreatic cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 985.

Selective Tumor Cell Apoptosis and Tumor Regression in CDH17-Positive Colorectal Cancer Models using BI 905711, a Novel Liver-Sparing TRAILR2 Agonist

Activation of TRAILR2 has emerged as an important therapeutic concept in cancer treatment. TRAILR2 agonistic molecules have only had limited clinical success, to date, due either to lack of efficacy or hepatotoxicity. BI 905711 is a novel tetravalent bispecific antibody targeting both TRAILR2 and CDH17 and represents a novel liver-sparing TRAILR2 agonist specifically designed to overcome the disadvantages of previous strategies. Here, we show that BI 905711 effectively triggered apoptosis in a broad panel of CDH17-positive colorectal cancer tumor cells in vitro. Efficient induction of apoptosis was dependent on the presence of CDH17, as exemplified by the greater than 1,000-fold drop in potency in CDH17-negative cells. BI 905711 demonstrated single-agent tumor regressions in CDH17-positive colorectal cancer xenografts, an effect that was further enhanced upon combination with irinotecan. Antitumor efficacy correlated with induction of caspase activation, as measured in both the tumor and plasma. Effective tumor growth inhibition was further demonstrated across a series of different colorectal cancer PDX models. BI 905711 induced apoptosis in both a cis (same cell) as well as trans (adjacent cell) fashion, translating into significant antitumor activity even in xenograft models with heterogeneous CDH17 expression. In summary, we demonstrate that BI 905711 has potent and selective antitumor activity in CDH17-positive colorectal cancer models both in vitro and in vivo. The high prevalence of over 95% CDH17-positive tumors in patients with colorectal cancer, the molecule preclinical efficacy together with its potential for a favorable safety profile, support the ongoing BI 905711 phase I trial in colorectal cancer and additional CDH17-positive cancer types (NCT04137289).

Abstract 2982: Unraveling the antifibrotic mode of action of nintedanib against the TGF-β pathway in tumor-associated fibroblasts in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer related death, and its major histotypes are lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC). Nintedanib (Vargatef) is a multi-tyrosine kinase inhibitor of VEGF, FGF and PDGF receptors that has been approved as second-line treatment of advanced lung adenocarcinoma patients, owing to the positive therapeutic effects reported selectively on ADC but not SCC patients in the LUME-1 clinical trial. Nintedanib has been also approved to treat idiopathic pulmonary fibrosis due to its antifibrotic effects reported in the INPULSIS trial. Of note, we recently reported that tumor fibrosis is larger in ADC than SCC due to the stronger epigenetic repression of the pro-fibrotic TGF-β transcription factor SMAD3 in tumor-associated fibroblasts (TAFs) in SCC compared to ADC. Moreover, we also showed that nintedanib elicits a larger inhibition of TGF-β-induced fibrosis in ADC-TAFs compared to SCC-TAFs. However, the detailed antifibrotic mechanisms of nintedanib on the TGF-β1 pathway remain poorly understood. TGF-β1 signaling begins with its binding to type II TGF-β receptor, which phosphorylates type I TGF-β receptor ALK5, that subsequently phosphorylates SMAD2 and SMAD3, upon which they form heterotrimeric complexes with the co-factor SMAD4 that translocate to the nucleus to regulate gene expression. We found that nintedanib markedly inhibited both the activation of SMAD2 and SMAD3 as well as the increase in nuclear SMAD4 in response to TGF-β1 in pulmonary fibroblasts, thereby supporting that ALK5 may be an off-target of nintedanib. To examine this possibility, we performed a time-course analysis of phospho-ALK5 (pALK5) and pSMAD3 in fibroblasts in response to TGF-β1 with or without nintedanib. As expected, TGF-β1 elicited a peak in pALK5 before that of pSMAD3. Moreover, nintedanib downregulated pALK5 but not total ALK5, supporting that ALK5 is an unintended target of this drug. In addition, we examined the expression of total and phospho-Erk1/2 in the same samples, since Erk1/2 has been previously reported as a regulator of cellular responses to TGF-β. TGF-β1 elicited a peak in pErk1/2 within the same time-window than pSMAD3, which is consistent with previous observations on non-canonical TGF-β signaling. Interestingly, nintedanib abrogated both total and pErk1/2 expression in a time-dependent fashion. These results support that the antifibrotic effects of nintedanib may be mediated through their inhibition of the pro-fibrotic transcription factor SMAD3 as well as the downregulation of Erk1/2. In addition, our results support that Erk1/2 may be implicated in the limited responses of SCC-TAFs to nintedanib, since we previously showed that SCC-TAFs exhibit an enhanced activity of Erk1/2 compared to ADC-TAFs.

Citation Format: Rafael Ikemori, Marta Gabasa, Paula Duch, Frank Hilberg, Noemí Reguart, Jordi Alcaraz. Unraveling the antifibrotic mode of action of nintedanib against the TGF-β pathway in tumor-associated fibroblasts in non-small cell lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2982.

Epigenetic SMAD3 Repression in Tumor-Associated Fibroblasts Impairs Fibrosis and Response to the Antifibrotic Drug Nintedanib in Lung Squamous Cell Carcinoma

The tumor-promoting fibrotic stroma rich in tumor-associated fibroblasts (TAF) is drawing increased therapeutic attention. Intriguingly, a trial with the antifibrotic drug nintedanib in non-small cell lung cancer reported clinical benefits in adenocarcinoma (ADC) but not squamous cell carcinoma (SCC), even though the stroma is fibrotic in both histotypes. Likewise, we reported that nintedanib inhibited the tumor-promoting fibrotic phenotype of TAFs selectively in ADC. Here we show that tumor fibrosis is actually higher in ADC-TAFs than SCC-TAFs in vitro and patient samples. Mechanistically, the reduced fibrosis and nintedanib response of SCC-TAFs was associated with increased promoter methylation of the profibrotic TGFβ transcription factor SMAD3 compared with ADC-TAFs, which elicited a compensatory increase in TGFβ1/SMAD2 activation. Consistently, forcing global DNA demethylation of SCC-TAFs with 5-AZA rescued TGFβ1/SMAD3 activation, whereas genetic downregulation of SMAD3 in ADC-TAFs and control fibroblasts increased TGFβ1/SMAD2 activation, and reduced their fibrotic phenotype and antitumor responses to nintedanib in vitro and in vivo. Our results also support that smoking and/or the anatomic location of SCC in the proximal airways, which are more exposed to cigarette smoke particles, may prime SCC-TAFs to stronger SMAD3 epigenetic repression, because cigarette smoke condensate selectively increased SMAD3 promoter methylation. Our results unveil that the histotype-specific regulation of tumor fibrosis in lung cancer is mediated through differential SMAD3 promoter methylation in TAFs and provide new mechanistic insights on the selective poor response of SCC-TAFs to nintedanib. Moreover, our findings support that patients with ADC may be more responsive to antifibrotic drugs targeting their stromal TGFβ1/SMAD3 activation. SIGNIFICANCE: This study implicates the selective epigenetic repression of SMAD3 in SCC-TAFs in the clinical failure of nintedanib in SCC and supports that patients with ADC may benefit from antifibrotic drugs targeting stromal TGFβ1/SMAD3.

Abstract 2117: Different sensitivities of four protein tyrosine kinase inhibitors towards drug-resistant RET mutations

The RET protein tyrosine kinase (PTK) is a clinically validated target of therapy in non-small cell lung cancer (NSCLC) and thyroid cancer. Mutations in the targeted PTKs is a mechanism of drug resistance in cancer therapy with tyrosine kinase inhibitors (TKIs). Mutation-sensitive secondary drugs have been used successfully to overcome acquired drug-resistance to the first line TKIs. Cabozantinib, lenvatinib, vandetanib, and nintedanib are FDA-approved multikinase TKIs with anti-RET activity. Using RET kinase-dependent BaF3/KIF5B-RET cells, we isolated thirteen mutations resistant to one of these TKIs. Cross-analysis of sensitivities of these four TKIs on these drug-resistant RET mutants and the RETM918T mutant, which is found in medullary thyroid carcinoma, revealed different TKI resistance-sensitivity profiles. In particular, the RETM918T mutant was resistant to cabozantinib, lenvatinib, and vandetanib but did not affect the potency of nintedanib. RETL881V was isolated as a vandetanib-resistant mutation. The RETL881V mutation also induced resistance to cabozantinib and lenvatinib but did not affect the nintedanib sensitivity. Examination of the RET-vandetanib co-crystal structure and the chemical structures of vandetanib and nintedanib suggested that a phenyl group in nintedanib, which corresponds to a methoxy group in vandetanib, may form hydrophobic interaction with the shorter side chain of Val881 and thus allows nintedanib to inhibit RETL881V. To test this possibility, we synthesized two nintedanib analogs (Compound 1 and Compound 2) without the phenyl group and tested their activities. The data showed that RETL881V was resistant to Compound 1 and Compound 2, supporting a role of the phenyl group of nintedanib in mediating inhibition of RETL881V. Taken together, we have identified 13 RET mutations that display different resistance-sensitivity profiles against four anti-RET TKIs. Moreover, nintedanib is effective in inhibiting RETM918T and RETL881V mutants that are resistant to the other three TKIs.

Citation Format: Xuan Liu, Tao Shen, Qingling Huang, Teng Peng, Frank Hilberg, Jianfeng Cai, Blaine H. Mooers, Jie Wu. Different sensitivities of four protein tyrosine kinase inhibitors towards drug-resistant RET mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2117.

Abstract 2051: BI 905711, a novel CDH17-targeting TRAILR2 agonist, effectively triggers tumor cell apoptosis and tumor regressions selectively in CDH17-positive colorectal cancer models

The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has the capability to induce apoptosis in a wide variety of tumor cells and has emerged as an important therapeutic concept for cancer treatment. To date however, TRAILR2 agonistic antibodies, designed to trigger tumor cell apoptosis, have only had limited clinical success due either to lack of efficacy or liver toxicity. BI 905711, a tetravalent bispecific antibody targeting both TRAILR2 and CDH17, was designed to overcome the disadvantages of current TRAILR2 antibodies. CDH17-dependent clustering of TRAILR2 permits BI 905711 to selectively induce apoptosis in CDH17-expressing tumor cells. CDH17 was selected as the anchor target due to its restricted expression, in particular a lack of expression in normal liver tissue, thereby avoiding the clinical hepatotoxicity associated with TRAILR2 agonism. Here, we report the preclinical activity of BI 905711 using colorectal cancer (CRC)-derived cell lines and patient-derived xenograft (PDX) models. We demonstrated that BI 905711 effectively triggered apoptosis in a broad range of CDH17-positive CRC tumor cells in vitro. Furthermore, BI 905711 potently initiated the apoptosis cascade as evidenced by a strong post-treatment increase of both caspase-8 and caspase-3/7. Importantly, induction of extrinsic apoptosis signaling by BI 905711 was strictly CDH17-dependent, as further demonstrated using a pair of CDH17-positive and -negative clones of the CRC cell line GP2d. When comparing the CDH17-negative clone with the parental cell line, the absence of CDH17 translated into a more than 1000-fold drop in BI 905711-dependent efficacy. Moreover, BI 905711 demonstrated single-agent tumor regressions in the GP2d colorectal cancer xenograft model. The antitumor efficacy of BI 905711 was further investigated in vivo in different CRC PDX models, showing effective tumor growth inhibition in a q14d dosing schedule. In summary, we demonstrated that BI 905711 potently triggers the extrinsic apoptosis pathway specifically in CDH17-positive tumor cells, which translates into significant tumor growth inhibition in CRC patient-derived xenograft tumors. BI 905711 is a first-in-class molecule that shows superiority to existing TRAILR2 agonists, represents a targeted strategy for the treatment of CRC and additional CDH17-positive cancer types. Together with its potential for a favorable safety profile, these data support our plan for a phase I trial of BI 905711 in these patient populations.

Citation Format: Juan Manuel Garcia-Martinez, Andreas Wernitznig, Joerg Rinnenthal, Maria Antonietta Impagnatiello, Frank Hilberg, Craig Giragossian, Norbert Kraut, Mark Pearson, Klaus-Peter Kuenkele. BI 905711, a novel CDH17-targeting TRAILR2 agonist, effectively triggers tumor cell apoptosis and tumor regressions selectively in CDH17-positive colorectal cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2051.

Abstract 1225: Aberrant SMAD3 signaling in tumor-associated fibroblasts modulates fibrosis and response to the anti-fibrotic drug nintedanib in non-small cell lung cancer

A hallmark of non-small cell lung cancer (NSCLC) is a fibrotic/desmoplastic stroma rich in activated fibroblasts, which are critical regulators of cancer progression, response to therapies and radiotherapy resistance. Paradoxically, we recently reported that the important pro-fibrotic TGF-β transcription factor SMAD3 was epigenetically down-regulated through promoter hypermethylation in tumor associated fibroblasts (TAFs) from NSCLC patients compared to patient-matched control fibroblasts. In addition, we reported that the clinically approved antifibrotic drug nintedanib elicited a stronger inhibition of both the fibrotic phenotype and its associated tumor-promoting effects in TAFs from adenocarcinoma (ADC) patients compared to squamous cell carcinoma (SCC) patients upon TGF-β1 stimulation in vitro, which was consistent with the selective therapeutic response to nintedanib observed in a clinical trial in ADC (but not SCC) patients. Altogether, these previous results suggest that TGF-β1 signaling may be altered in lung TAFs, and that such alteration may depend on their histologic subtype. In this study we addressed these questions by determining the expression and activity of SMAD3 and its closely related homologue SMAD2 in patient-derived TAFs and paired control fibroblasts, and by dissecting their potential contribution to the differential therapeutic responses to nintedanib observed in ADC and SCC. In vitro studies revealed a marked SMAD3 epigenetic repression through promoter hypermethylation, a low pSMAD3/pSMAD2 ratio and a limited fibrotic phenotype selectively in SCC-TAFs. In contrast, ADC-TAFs overexpressed a panel of fibrotic markers upon TGF-β1 stimulation concomitantly with a high pSMAD3/pSMAD2 ratio and a limited SMAD3 promoter methylation. Histologic analysis of a large patient cohort (112 ADC, 96 SCC) confirmed that the extent of fibrosis is larger in ADC than SCC patients. In addition, knocking-down SMAD3 in ADC-TAFs was sufficient to reduce the antifibrotic and antigrowth effects of nintedanib in vitro and in tumor xenografts in vivo. On the other hand, long-term exposure of pulmonary fibroblasts to cigarette smoke condensate was sufficient to hypermethylate the SMAD3 promoter. Since SCC and ADC tumors typically arise in the upper airways and distal pulmonary sites, respectively, it is conceivable that fibroblasts might be more exposed to the smoking epigenetic effects on SMAD3 in SCC. In summary, we report for the first time that tumor fibrosis is higher in ADC than SCC patients, in association with a selective therapeutic response to the antifibrotic drug nintedanib in the former, and identify the subtype-specific extent of SMAD3 epigenetic repression in TAFs and the subsequent aberrant SMAD3/SMAD2 imbalance as major regulatory mechanisms of tumor fibrosis and response to nintedanib in NSCLC.

Citation Format: Rafael Ikemori, Marta Gabasa, Miguel Vizoso, Paula Duch, Sebastian Moran, Sabrina Gea-Sorli, Paloma Bragado, Toni Jauset, Manel Esteller, Laura Soucek, Eduard Monsó, Víctor Peinado, Cristina Fillat, Frank Hilberg, Noemí Reguart, Jordi Alcaraz. Aberrant SMAD3 signaling in tumor-associated fibroblasts modulates fibrosis and response to the anti-fibrotic drug nintedanib in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1225.

Structural basis of resistance of mutant RET protein-tyrosine kinase to its inhibitors nintedanib and vandetanib

RET is a transmembrane growth factor receptor. Aberrantly activated RET is found in several types of human cancer and is a target for treating RET aberration-associated cancer. Multiple clinically relevant RET protein-tyrosine kinase inhibitors (TKIs) have been identified, but how TKIs bind to RET is unknown except for vandetanib. Nintedanib is a RET TKI that inhibits the vandetanib-resistant RET(G810A) mutant. Here, we determined the X-ray co-crystal structure of RET kinase domain-nintedanib complex to 1.87 Å resolution and a RET(G810A) kinase domain crystal structure to 1.99 Å resolution. We also identified a vandetanib-resistant RET(L881V) mutation previously found in familial medullary thyroid carcinoma. Drug-sensitivity profiling of RET(L881V) revealed that it remains sensitive to nintedanib. The RET-nintedanib co-crystal structure disclosed that Leu-730 in RET engages in hydrophobic interactions with the piperazine, anilino, and phenyl groups of nintedanib, providing a structural basis for explaining that the p.L730V mutation identified in nine independently isolated cell lines resistant to nintedanib. Comparisons of RET-nintedanib, RET(G810A), and RET-vandetanib crystal structures suggested that the solvent-front Ala-810 makes hydrophobic contacts with a methyl group and aniline in nintedanib and blocks water access to two oxygen atoms of vandetanib, resulting in an energetic penalty for burying polar groups. Of note, even though the p.L881V mutation did not affect sensitivity to nintedanib, RET(L881V) was resistant to nintedanib analogs lacking a phenyl group. These results provide structural insights into resistance of RET mutants against the TKIs nintedanib and vandetanib.

Defining aggressive or early progressing nononcogene-addicted non-small-cell lung cancer: a separate disease entity?

A substantial proportion of patients with nononcogene-addicted non-small-cell lung cancer (NSCLC) has 'aggressive disease', as reflected in short time to progression or lack of disease control with initial platinum-based chemotherapy. Recently, clinical correlates of aggressive disease behavior during first-line therapy have been shown to predict greater benefit from addition of nintedanib to second-line docetaxel in adenocarcinoma NSCLC. Positive predictive effects of aggressive disease have since been reported with other anti-angiogenic agents (ramucirumab and bevacizumab), while such features may negatively impact on outcomes with nivolumab in nonsquamous NSCLC with low PD-L1 expression. Based on a review of the clinical data, we recommend aggressive nonsquamous NSCLC should be defined by progression within <6-9 months of first-line treatment initiation.

Therapeutic impact of Nintedanib with paclitaxel and/or a PD-L1 antibody in preclinical models of orthotopic primary or metastatic triple negative breast cancer

BACKGROUND

Triple negative breast cancer (TNBC) is an aggressive malignancy with poor prognosis, in part because of the current lack of any approved molecularly targeted therapy. We evaluated various combinations of three different drugs: nintedanib, an antiangiogenic TKI targeting VEGF receptors, paclitaxel (PTX), or a PD-L1 antibody, using models of orthotopic primary or advanced metastatic TNBC involving a metastatic variant of the MDA-MB-231 human cell line (called LM2-4) in SCID mice and two mouse lines (EMT-6 and a drug-resistant variant, EMT-6/CDDP) in immunocompetent mice. These drugs were selected based on the following: PTX is approved for TNBC; nintedanib combined with docetaxel has shown phase III clinical trial success, albeit in NSCLC; VEGF can act as local immunosuppressive factor; and PD-L1 antibody plus taxane therapy was recently reported to have encouraging phase III trial benefit in TNBC.

METHODS

Statistical analyses were performed with ANOVA followed by Tukey's Multiple Comparison Test or with Kruskal-Wallis test followed by Dunn's Multiple Comparison Test. Survival curves were analyzed using a Log-rank (Mantel Cox) test. Differences were considered statistically significant when p values were < 0.05.

RESULTS

Toxicity analyses showed that nintedanib is well tolerated when administered 5-days ON 2-days OFF; PTX toxicity differed in mice, varied with cell lines used and may have influenced median survival in the metastatic EMT6/CDDP model; while toxicity of PD-L1 therapy depended on the cell lines and treatment settings tested. In the LM2-4 system, combining nintedanib with PTX enhanced overall antitumor efficacy in both primary and metastatic treatment settings. In immunocompetent mice, combining nintedanib or PTX with the PD-L1 antibody improved overall antitumor efficacy. Using the advanced metastatic EMT-6/CDDP model, optimal efficacy results were obtained using the triple combination.

CONCLUSIONS

These results suggest circumstances where nintedanib plus PTX may be potentially effective in treating TNBC, and nintedanib with PTX may improve PD-L1 therapy of metastatic TNBC.

Drug resistance profiles of mutations in the RET kinase domain

BACKGROUND AND PURPOSE

Alterations in the tyrosine kinase enzyme RET are found in thyroid and lung cancer. While RET TK inhibitors (TKIs) are used to treat thyroid cancer and are in clinical trials for RET fusion-positive non-small cell lung cancer, the impact of mutations in the RET kinase domain on drug sensitivity is largely uncharacterized.

EXPERIMENTAL APPROACH

We identified and analysed mutations in the RET kinase domain that conferred resistance to the TKIs cabozantinib, lenvatinib, vandetanib and nintedanib using RET kinase-dependent BaF3/KIF5B-RET (BaF3/KR) cells. We also examined the sensitivity of RET (M918T), a RET mutation prevalent in aggressive multiple endocrine neoplasia type 2B, to these TKIs in the context of BaF3/KR cells.

KEY RESULTS

Fourteen mutations were analysed. Pan resistance to the four TKIs was found in six RET kinase domain mutations (L730I, V738A, V804L/M, Y806N, G810S). Seven RET kinase domain mutations (L730V, E732K, A807V, G810A, V871I, M918T, F998V) displayed selective resistance to one or more of these drugs. L730I/V and G810A/S had different drug resistance profiles. V871I, M918T and F998V mutations are located at distant sites away from the TKI binding pocket.

CONCLUSIONS AND IMPLICATIONS

A panel of TKI-resistant RET mutations were identified, and their drug sensitivities were cross-profiled. The results provide a reference for selecting appropriate TKIs to inhibit RET kinase domain mutants. Besides changes in the drug-interacting residues, mutations at distant sites could exert long-range effects resulting in TKI resistance. Among the four TKIs analysed here, nintedanib remained unaffected by mutations at the three distant sites.

Nintedanib Is Active in Malignant Pleural Mesothelioma Cell Models and Inhibits Angiogenesis and Tumor Growth In Vivo

Purpose: Malignant pleural mesothelioma (MPM) is an aggressive thoracic tumor type with limited treatment options and poor prognosis. The angiokinase inhibitor nintedanib has shown promising activity in the LUME-Meso phase II MPM trial and thus is currently being evaluated in the confirmatory LUME-Meso phase III trial. However, the anti-MPM potential of nintedanib has not been studied in the preclinical setting.Experimental Design: We have examined the antineoplastic activity of nintedanib in various in vitro and in vivo models of human MPM.Results: Nintedanib's target receptors were (co)expressed in all the 20 investigated human MPM cell lines. Nintedanib inhibited MPM cell growth in both short- and long-term viability assays. Reduced MPM cell proliferation and migration and the inhibition of Erk1/2 phosphorylation were also observed upon nintedanib treatment in vitro Additive effects on cell viability were detected when nintedanib was combined with cisplatin, a drug routinely used for systemic MPM therapy. In an orthotopic mouse model of human MPM, survival of animals receiving nintedanib per os showed a favorable trend, but no significant benefit. Nintedanib significantly reduced tumor burden and vascularization and prolonged the survival of mice when it was administered intraperitoneally. Importantly, unlike bevacizumab, nintedanib demonstrated significant in vivo antivascular and antitumor potential independently of baseline VEGF-A levels.Conclusions: Nintedanib exerts significant antitumor activity in MPM both in vitro and in vivo These data provide preclinical support for the concept of LUME-Meso trials evaluating nintedanib in patients with unresectable MPM. Clin Cancer Res; 24(15); 3729-40. ©2018 AACR.

Triple Angiokinase Inhibitor Nintedanib Directly Inhibits Tumor Cell Growth and Induces Tumor Shrinkage via Blocking Oncogenic Receptor Tyrosine Kinases

The triple-angiokinase inhibitor nintedanib is an orally available, potent, and selective inhibitor of tumor angiogenesis by blocking the tyrosine kinase activities of vascular endothelial growth factor receptor (VEGFR) 1-3, platelet-derived growth factor receptor (PDGFR)-α and -β, and fibroblast growth factor receptor (FGFR) 1-3. Nintedanib has received regulatory approval as second-line treatment of adenocarcinoma non-small cell lung cancer (NSCLC), in combination with docetaxel. In addition, nintedanib has been approved for the treatment of idiopathic lung fibrosis. Here we report the results from a broad kinase screen that identified additional kinases as targets for nintedanib in the low nanomolar range. Several of these kinases are known to be mutated or overexpressed and are involved in tumor development (discoidin domain receptor family, member 1 and 2, tropomyosin receptor kinase A (TRKA) and C, rearranged during transfection proto-oncogene [RET proto oncogene]), as well as in fibrotic diseases (e.g., DDRs). In tumor cell lines displaying molecular alterations in potential nintedanib targets, the inhibitor demonstrates direct antiproliferative effects: in the NSCLC cell line NCI-H1703 carrying a PDGFRα amplification (ampl.); the gastric cancer cell line KatoIII and the breast cancer cell line MFM223, both driven by a FGFR2 amplification; AN3CA (endometrial carcinoma) bearing a mutated FGFR2; the acute myeloid leukemia cell lines MOLM-13 and MV-4-11-B with FLT3 mutations; and the NSCLC adenocarcinoma LC-2/ad harboring a CCDC6-RET fusion. Potent kinase inhibition does not, however, strictly translate into antiproliferative activity, as demonstrated in the TRKA-dependent cell lines CUTO-3 and KM-12. Importantly, nintedanib treatment of NCI-H1703 tumor xenografts triggered effective tumor shrinkage, indicating a direct effect on the tumor cells in addition to the antiangiogenic effect on the tumor stroma. These findings will be instructive in guiding future genome-based clinical trials of nintedanib.

Nintedanib selectively inhibits the activation and tumour-promoting effects of fibroblasts from lung adenocarcinoma patients

BACKGROUND

Nintedanib is a clinically approved multikinase receptor inhibitor to treat non-small cell lung cancer with adenocarcinoma (ADC) histology in combination with docetaxel, based on the clinical benefits reported on ADC but not on squamous cell carcinoma (SCC), which are the two most common histologic lung cancer subtypes.

METHODS

We examined the potential role of tumour-associated fibroblasts (TAFs) in the differential effects of nintedanib in ADC and SCC. Because TAFs are largely quiescent and activated in histologic sections, we focused on the antifibrotic effects of nintedanib on TAFs stimulated with the potent fibroblast activator TGF-β1, which is upregulated in lung cancer.

RESULTS

Nintedanib dose-dependently inhibited the TGF-β1-induced expression of a panel of pro-fibrotic activation markers in both ADC-TAFs and control fibroblasts derived from uninvolved lung parenchyma, whereas such inhibition was very modest in SCC-TAFs. Remarkably, nintedanib abrogated the stimulation of growth and invasion in a panel of carcinoma cell lines induced by secreted factors from activated TAFs in ADC but not SCC, thereby supporting that TGF-β signalling and aberrant TAF-carcinoma cross-talk is regulated by different mechanisms in ADC and SCC.

CONCLUSIONS

These results reveal that nintedanib is an effective inhibitor of fibrosis and its associated tumour-promoting effects in ADC, and that the poor antifibrotic response of SCC-TAFs to nintedanib may contribute to the differential clinical benefit observed in both subtypes. Our findings also support that preclinical models based on carcinoma-TAF interactions may help defining the mechanisms of the poor antifibrotic response of SCC-TAFs to nintedanib and testing new combined therapies to further expand the therapeutic effects of this drug in solid tumours.

BIBF1120 (Vargatef) Inhibits Preretinal Neovascularization and Enhances Normal Vascularization in a Model of Vasoproliferative Retinopathy

PURPOSE

This study evaluated the effects of BIBF1120, a novel triple angiokinase inhibitor against pathological retinal neovascularization.

METHODS

BIBF1120 effect on development of the normal retinal vasculature was evaluated in Sprague-Dawley rat pups. Two models of ischemic oxygen-induced retinopathy (OIR) and the aortic ring assay were used to assess the antiangiogenic effects of BIBF1120. In the vaso-obliteration model (VO), rat pups were exposed to 80% O2 from postnatal day (P) 5 to P10. In the preretinal neovascularization (NV) model, rat pups were exposed to cycling O2 (50% and 10%) from P1 to P14, followed by room air until P18. Animals were intravitreally or orally treated with BIBF1120. Retinal vasculature, VO, and NV were evaluated in retinal flat mounts. Retinal expression of VEGF, Delta-like ligand 4 (Dll4), Netrin-1, Ephrin-B2, and EphB4 was analyzed by quantitative PCR and Western blot analysis.

RESULTS

BIBF1120 interfered with normal retinal vascular development and microvessel branching in the aortic assay. However, in VO model BIBF1120 did not accrue VO. On the contrary, in the NV model BIBF1120 accelerated normal retinal vascularization and robustly diminished preretinal neovascularization compared to vehicle (by ~80%). The expression levels of VEGF negative regulator Dll4 and repulsive cues EphrinB2 and EphB4 mRNA in the retina of vehicle-treated OIR animals were markedly increased compared to normoxia, but were normalized by BIBF1120.

CONCLUSIONS

Data reveal efficacy of BIBF1120 on preretinal neovascularization and, of greater interest, on acceleration of normal vascularization, consistent with interference of major repulsive cues expressed in the retina during OIR. Accordingly, BIBF1120 appears to exhibit preferable properties compared to anti-VEGF therapies for the treatment of ischemic retinopathies.

Nintedanib: from discovery to the clinic

Nintedanib (BIBF1120) is a potent, oral, small-molecule tyrosine kinase inhibitor, also known as a triple angiokinase inhibitor, inhibiting three major signaling pathways involved in angiogenesis. Nintedanib targets proangiogenic and pro-fibrotic pathways mediated by the VEGFR family, the fibroblast growth factor receptor (FGFR) family, the platelet-derived growth factor receptor (PDGFR) family, as well as Src and Flt-3 kinases. The compound was identified during a lead optimization program for small-molecule inhibitors of angiogenesis and has since undergone extensive clinical investigation for the treatment of various solid tumors, and in patients with the debilitating lung disease idiopathic pulmonary fibrosis (IPF). Recent clinical evidence from phase III studies has shown that nintedanib has significant efficacy in the treatment of NSCLC, ovarian cancer, and IPF. This review article provides a comprehensive summary of the preclinical and clinical research and development of nintedanib from the initial drug discovery process to the latest available clinical trial data.

Selective inhibition of the epidermal growth factor receptor tyrosine kinase by BIBX1382BS and the improvement of growth delay, but not local control, after fractionated irradiation in human FaDu squamous cell carcinoma in the nude mouse

PURPOSE

To investigate the effect of BIBX1382BS, an inhibitor of the epidermal growth factor receptor tyrosine kinase, on proliferation and clonogenic cell survival of FaDu human squamous cell carcinoma in vitro, and on tumour growth and local tumour control after fractionated irradiation over 6 weeks in nude mice. FaDu human squamous cell carcinoma is epidermal growth factor receptor positive and significant repopulation during fractionated irradiation was demonstrated in previous experiments.

MATERIALS AND METHODS

Receptor status, receptor phosphorylation, cell cycle distribution, cell proliferation and clonogenic cell survival after irradiation were assayed with and without BIBX1382BS (5 microM) in vitro. Tumour volume doubling time, BrdUrd and Ki67 labelling indices and apoptosis were investigated in unirradiated tumours growing in NMRI nude mice treated daily with BIBX1382BS (50 mg kg(-1) body weight orally) or carrier. Tumour growth delay and dose-response curves for local tumour control were determined after irradiation with 30 fractions within 6 weeks.

RESULTS

BIBX1382BS blocked radiation-induced phosphorylation of the epidermal growth factor receptor and reduced the doubling time of FaDu cells growing in vitro by a factor of 4.9 (p=0.008). Radiosensitivity in vitro remained unchanged after incubation with BIBX1382BS for 3 days and decreased moderately after 6 days (p=0.001). BIBX1382BS significantly reduced the volume doubling time of established FaDu tumours in nude mice by factors of 2.6 when given over 15 days (p<0.001) and 3.7 when applied over 6 weeks (p<0.001). When given simultaneously to fractionated irradiation, growth delay was significantly prolonged by an average of 33 days (p=0.003). Local tumour control was not improved by BIBX1382BS. The radiation doses necessary to control 50% of the tumours locally were 63.6 Gy (95% confidence interval 55; 73) for irradiation alone and 67.8 Gy (60; 77) for the combined treatment (p=0.5).

CONCLUSIONS

Despite clear antiproliferative activity in rapidly repopulating FaDu human squamous cell carcinoma and significantly increased tumour growth delay when combined with fractionated irradiation, local tumour control was not improved by BIBX1382BS. The results do not disprove that epidermal growth factor receptor inhibition might enhance the results of radiotherapy. However, the results imply that further preclinical investigations using relevant treatment schedules and appropriate endpoints are necessary to explore the mechanisms of action and efficacy of such combinations.

BIBF 1120: triple angiokinase inhibitor with sustained receptor blockade and good antitumor efficacy

Inhibition of tumor angiogenesis through blockade of the vascular endothelial growth factor (VEGF) signaling pathway is a novel treatment modality in oncology. Preclinical findings suggest that long-term clinical outcomes may improve with blockade of additional proangiogenic receptor tyrosine kinases: platelet-derived growth factor receptors (PDGFR) and fibroblast growth factor receptors (FGFR). BIBF 1120 is an indolinone derivative potently blocking VEGF receptor (VEGFR), PDGFR and FGFR kinase activity in enzymatic assays (IC(50), 20-100 nmol/L). BIBF 1120 inhibits mitogen-activated protein kinase and Akt signaling pathways in three cell types contributing to angiogenesis, endothelial cells, pericytes, and smooth muscle cells, resulting in inhibition of cell proliferation (EC(50), 10-80 nmol/L) and apoptosis. In all tumor models tested thus far, including human tumor xenografts growing in nude mice and a syngeneic rat tumor model, BIBF 1120 is highly active at well-tolerated doses (25-100 mg/kg daily p.o.), as measured by magnetic resonance imaging of tumor perfusion after 3 days, reducing vessel density and vessel integrity after 5 days, and inducing profound growth inhibition. A distinct pharmacodynamic feature of BIBF 1120 in cell culture is sustained pathway inhibition (up to 32 hours after 1-hour treatment), suggesting slow receptor off-kinetics. Although BIBF 1120 is rapidly metabolized in vivo by methylester cleavage, resulting in a short mean residence time, once daily oral dosing is fully efficacious in xenograft models. These distinctive pharmacokinetic and pharmacodynamic properties may help explain clinical observations with BIBF 1120, currently entering phase III clinical development.

CD44 suppresses TLR-mediated inflammation

The cell adhesion molecule CD44, which is the major hyaluronan receptor, has been implicated in the binding, endocytosis, and metabolism of hyaluronan. Previous studies have revealed that CD44 plays crucial roles in a variety of inflammatory diseases. In recent years, TLRs, which are ancient microbial pattern recognition receptors, have been shown to initiate an innate immune response and have been linked to a variety of inflammatory diseases. The present study shows that CD44 negatively regulates in vivo inflammation mediated by TLRs via NF-kappaB activation, which leads to proinflammatory cytokine production. Furthermore, our results show that CD44 directly associates with TLR2 when stimulated by the TLR2 ligand zymosan and that the cytoplasmic domain of CD44 is crucial for its regulatory effect on TLR signaling. This study indicates that CD44 plays a protective role in TLR-mediated inflammation and is the first to demonstrate a direct association between CD44 and a TLR.

DMBT1 confers mucosal protection in vivo and a deletion variant is associated with Crohn's disease

BACKGROUND & AIMS

Impaired mucosal defense plays an important role in the pathogenesis of Crohn's disease (CD), one of the main subtypes of inflammatory bowel disease (IBD). Deleted in malignant brain tumors 1 (DMBT1) is a secreted scavenger receptor cysteine-rich protein with predominant expression in the intestine and has been proposed to exert possible functions in regenerative processes and pathogen defense. Here, we aimed at analyzing the role of DMBT1 in IBD.

METHODS

We studied DMBT1 expression in IBD and normal tissues by quantitative reverse transcription-polymerase chain reaction, immunohistochemistry, and mRNA in situ hybridization. Genetic polymorphisms within DMBT1 were analyzed in an Italian IBD case-control sample. Dmbt1(-/-) mice were generated, characterized, and analyzed for their susceptibility to dextran sulfate sodium-induced colitis.

RESULTS

DMBT1 levels correlate with disease activity in inflamed IBD tissues. A highly significant fraction of the patients with IBD displayed up-regulation of DMBT1 specifically in the intestinal epithelial surface cells and Paneth cells. A deletion allele of DMBT1 with a reduced number of scavenger receptor cysteine-rich domain coding exons is associated with an increased risk of CD (P = .00056; odds ratio, 1.75) but not for ulcerative colitis. Dmbt1(-/-) mice display enhanced susceptibility to dextran sulfate sodium-induced colitis and elevated Tnf, Il6, and Nod2 expression levels during inflammation.

CONCLUSIONS

DMBT1 may play a role in intestinal mucosal protection and prevention of inflammation. Impaired DMBT1 function may contribute to the pathogenesis of CD.

Paracrine interactions of vascular endothelial growth factor and platelet-derived growth factor in endothelial and lung cancer cells

While the effects of single growth factors on endothelial cells (ECs) have been extensively studied, the importance of induction of growth factors such as PDGF-BB (platelet derived growth factor) in ECs and its impact on tumor cell functions are only partly understood. Human umbilical vein endothelial cells (HUVECs) were cultured under serum-free conditions and stimulated by 20 ng/ml VEGF (vascular endothelial growth factor) or 20 ng/ml bFGF (basic fibroblastic growth factor). As determined by real-time PCR, both VEGF and bFGF induced a significant (up to 4-fold) increase in PDGF-B RNA expression which was time- and dose-dependent (p<0.05). Similarly, conditioned medium (CM) from lung cancer cells (A549) which is known to contain multiple growth factors including VEGF and bFGF also induced PDGF-B RNA expression. Using ELISA assays, VEGF and bFGF significantly increased PDGF-BB protein secretion in HUVECs (p<0.01). By addition of BIBF 1000, a novel inhibitor of the VEGF and bFGF receptor kinases, the effect of VEGF on PDGF-B RNA induction was significantly antagonized (p<0.01). Furthermore, we studied the biological significance of EC-derived PDGF-BB on lung cancer cells. Interestingly, HUVEC-derived CM significantly stimulated migration of A549 cells (p<0.001) with a trend to further increased migration with the use of VEGF-stimulated (PDGF-BB rich) CM (p=0.2). Collectively, endothelial and lung cancer cells seem to interact via various paracrine pathways, e.g. by the reciprocal induction of VEGF and PDGF-BB. Thus, targeting key molecules would result in expression alterations of multiple factors and alter the biological functions of both stromal and tumor cells.

Inhibition of PDGF, VEGF and FGF signalling attenuates fibrosis

BIBF 1000 is a small molecule inhibitor targeting the receptor kinases of platelet-derived growth factor (PDGF), basic fibroblast growth factor and vascular endothelial growth factor, which have known roles in the pathogenesis of pulmonary fibrosis. The anti-fibrotic potential of BIBF 1000 was determined in a rat model of bleomycin-induced lung fibrosis and in an ex vivo fibroblast differentiation assay. Rats exposed to a single intra-tracheal injection of bleomycin were treated with BIBF 1000 starting 10 days after bleomycin administration. To gauge for anti-fibrotic activity, collagen deposition and pro-fibrotic growth factor gene expression was analysed in isolated lungs. Furthermore, the activity of BIBF 1000 was compared with imatinib mesylate (combined PDGF receptor, c-kit and c-abl kinase inhibitor) and SB-431542 (transforming growth factor (TGF)-beta receptor I kinase inhibitor) in an ex vivo TGF-beta-driven fibroblast to myofibroblast differentiation assay, performed in primary human bronchial fibroblasts. Treatment of rats with BIBF 1000 resulted in the attenuation of fibrosis as assessed by the reduction of collagen deposition and the inhibition of pro-fibrotic gene expression. In the cellular assay both SB-431542 and BIBF 1000 showed dose-dependent inhibition of TGF-beta-induced differentiation, whereas imatinib mesylate was inactive. BIBF 1000, or related small molecules with a similar kinase inhibition profile, may represent a novel therapeutic approach for the treatment of idiopathic pulmonary fibrosis.

Growth inhibition and induction of apoptosis in acute myeloid leukemia cells by new indolinone derivatives targeting fibroblast growth factor, platelet-derived growth factor, and vascular endothelial growth factor receptors

In acute myeloid leukemia (AML), receptor tyrosine kinase ligands promote growth and survival and contribute to AML-associated marrow neoangiogenesis. We have tested simultaneous inhibition of vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor receptor signaling by novel indolinone derivatives using 14 myeloid, including 11 human leukemic, cell lines. Compounds inhibited colony formation of all cell lines in a dose-dependent fashion. Inhibitory concentrations for 50% of the colony formation/survival (IC50) for BIBF1000 were <100 nmol/L for 3 of 11, <or=500 nmol/L for 6 of 11, and <1,000 nmol/L for 10 of 11 leukemic cell lines, with one cell line being resistant in the dose range <1,000 nmol/L. BIBF1120 was less effective with 4 of 11 leukemic cell lines being resistant within the dose range <1,000 nmol/L. Testing of myeloid 32D cells transfected with empty vector, wild-type Flt3, or Flt3 carrying an internal tandem duplication mutation revealed higher resistance for the internal tandem duplication mutant. These effects of the compounds were associated with inhibition of tyrosine phosphorylation and the mitogen-activated protein kinase pathway. Furthermore, both compounds induced apoptosis in the sensitive cell lines. In Mono-Mac1 cells, the compounds had a direct proapoptotic effect that was increasing the proapoptotic effect of 1-beta-D-arabinofuranosylcytosine. The data provide a rationale for clinical evaluation of these tyrosine kinase inhibitors in AML.

Targeting receptor kinases by a novel indolinone derivative in multiple myeloma: abrogation of stroma-derived interleukin-6 secretion and induction of apoptosis in cytogenetically defined subgroups

In multiple myeloma (MM), both vascular endothelial (VEGF) and basic fibroblast growth factor (bFGF) promote tumor growth and survival. We have used the novel indolinone BIBF 1000 to study effects of simultaneous inhibition of VEGF, FGF and transforming growth factor-beta on MM cells and their interactions with bone marrow stroma cells (BMSCs). Both, in the absence and presence of myeloma-stroma cell contacts, BIBF 1000 abrogated BMSC-derived secretion of interleukin-6 (IL-6). In addition, BIBF 1000 directly induced apoptosis in t(4;14)-positive cell lines as well as in CD138+ marrow cells from patients with t(4;14) myeloma. To a similar extent, BIBF 1000 induced apoptosis in MM.1S and MM.1R cells carrying the translocation t(14;16). In case of MM.1S and other dexamethasone-sensitive t(14;16) cell lines, BIBF 1000 and dexamethasone had additive proapoptotic effects. Induction of apoptosis by BIBF 1000 was associated with inhibition of the mitogen-activated protein kinases (MAPK) pathway in t(4;14) and inhibition of the phosphatidyl-inositol-3 kinase/AKT pathway in t(14;16) cells. Apoptotic effects did not occur in t(4;14)-or t(14;16)-positive MM cells carrying n- or k-Ras mutations. The data provide the rationale for clinical evaluation of this class of targeted kinase inhibitors in MM with focus on defined cytogenetic subgroups.

CD44 is a determinant of inflammatory bone loss

Chronic inflammation is a major trigger of local and systemic bone loss. Disintegration of cell–matrix interaction is a prerequisite for the invasion of inflammatory tissue into bone. CD44 is a type I transmembrane glycoprotein that connects a variety of extracellular matrix proteins to the cell surface. Tumor necrosis factor (TNF) is a major inducer of chronic inflammation and its overexpression leads to chronic inflammatory arthritis. By generating CD44^−/− human TNF-transgenic (hTNFtg) mice, we show that destruction of joints and progressive crippling is far more severe in hTNFtg mice lacking CD44, which also develop severe generalized osteopenia. Mutant mice exhibit an increased bone resorption due to enhanced number, size, and resorptive capacity of osteoclasts, whereas bone formation and osteoblast differentiation are not affected. Responsiveness of CD44-deficient osteoclasts toward TNF is enhanced and associated with increased activation of the p38 mitogen-activated protein kinase. These data identify CD44 as a critical inhibitor of TNF-driven joint destruction and inflammatory bone loss.

Adjuvant inhibition of the epidermal growth factor receptor after fractionated irradiation of FaDu human squamous cell carcinoma

BACKGROUND AND PURPOSE

Experiments performed by others have shown that inhibition of EGFR before and after single dose irradiation prolonged growth delay and improved local tumour control. This suggests that adjuvant EGFR inhibition can inactivate clonogens that survived irradiation. To test this hypothesis local tumour control was investigated after fractionated radiotherapy and adjuvant EGFR-TK inhibition.

MATERIALS AND METHODS

FaDu hSCC xenografts were irradiated with 30 fractions in 6 weeks with total doses of 30-100Gy. After the end of fractionated irradiation, BIBX1382BS was administered daily orally over a time period of 75 days. Tumour volumes were determined two times per week, the volume doubling time during adjuvant treatment was calculated for progressing and recurrent tumours. Local tumour control was investigated 120 days after end of irradiation.

RESULTS

Adjuvant BIBX1382BS significantly reduced the tumour growth rate but did not improve local tumour control. The TCD(50) values were 66.1Gy (95% C.I.: 59; 73Gy) after adjuvant BIBX1382BS treatment and 67.9Gy (61; 75Gy) for control tumours (P=0.9).

CONCLUSIONS

These data indicate that, although growth of recurrent tumour cells after irradiation is dependent on the EGFR pathway, tumour cells retain their clonogenic potential despite of EGFR inhibition. The results imply also that a decreased tumour growth rate does not necessarily allow conclusions on enhanced inactivation of clonogenic cells when antiproliferative drugs are combined with radiation.

Expression of the fibroblast activation protein during mouse embryo development

Human Fibroblast Activation Protein (FAP), a member of the serine prolyl oligopeptidase family, is a type II cell surface glycoprotein that acts as a dual-specificity dipeptidyl-peptidase (DPP) and collagenase in vitro. Its restricted expression pattern in embryonic mesenchyme, in wound healing and in reactive stromal fibroblasts of epithelial cancers, has suggested a role for the FAP protease in extracellular matrix degradation or growth factor activation in sites of tissue remodeling. The FAP homologue in Xenopus laevis has been reported to be induced in the thyroid hormone-induced tail resorption program during tadpole metamorphosis supporting a role for FAP in tissue remodeling processes during embryonic development. However, Fap-deficient mice show no overt developmental defects and are viable. To study the expression of FAP during mouse embryogenesis, a second Fap-deficient mouse strain expressing beta-Galactosidase under the control of the Fap promoter was generated by homologous recombination (Fap-/- lacZ mice). FAP deficiency was confirmed by the absence of FAP-specific dipeptidyl-peptidase activity in detergent-soluble extracts isolated from 17.5 d.p.c. Fap-/- lacZ embryos. We report that Fap-/- lacZ mice express beta-Galactosidase at regions of active tissue remodeling during embryogenesis including somites and perichondrial mesenchyme from cartilage primordia.

Targeted disruption of mouse fibroblast activation protein

Human fibroblast activation protein (FAP), a member of the serine prolyl oligopeptidase family, is a type II cell surface glycoprotein selectively expressed by fibroblastic cells in areas of active tissue remodeling, such as the embryonic mesenchyme, areas of wound healing, the gravid uterus, and the reactive stroma of epithelial cancers. Homologues of FAP have been identified in the mouse and Xenopus laevis. FAP is a dual-specificity enzyme that acts as a dipeptidyl peptidase and collagenase in vitro. To explore the role of FAP in vivo, Fap(-/-) mice were generated by homologous recombination. RNase protection analysis and reverse transcription-PCR confirmed the absence of full-length Fap transcripts in mouse embryonic tissues. No FAP protein was detected in Fap(-/-) animals by immunohistochemistry, and no FAP-specific dipeptidyl peptidase activity was found. We report that Fap(-/-) mice are fertile, show no overt developmental defects, and have no general change in cancer susceptibility.

CD44-deficient mice develop normally with changes in subpopulations and recirculation of lymphocyte subsets

Cell adhesion molecules are considered to be pivotal elements required for proper embryo development. The transmembrane glycoprotein CD44, which is expressed in numerous splice variants on the surface of many different cell types and tissues, has been suggested to be involved in several physiological processes such as cell-cell interactions, signal transduction, and lymphocyte homing and trafficking during embryogenesis and in the adult organism. Some splice variants are thought to play an important role in tumor progression. To investigate the physiological roles of CD44 in vivo, we abolished expression of all isoforms of CD44 in mice by targeted insertion of a lacZ/neo cassette into the reading frame of the leader peptide. CD44-deficient mice are viable without obvious developmental defects and show no overt abnormalities as adults. However, CD44-deficient lymphocytes exhibit impaired entry into the adult thymus, although lymphocyte development is apparently unaltered. Our data indicate that all splice variants of CD44 are dispensable for embryonic development and implicate a critical function for CD44 in lymphocyte recirculation.

CD44-Deficient Mice Develop Normally with Changes in Subpopulations and Recirculation of Lymphocyte Subsets

Cell adhesion molecules are considered to be pivotal elements required for proper embryo development. The transmembrane glycoprotein CD44, which is expressed in numerous splice variants on the surface of many different cell types and tissues, has been suggested to be involved in several physiological processes such as cell-cell interactions, signal transduction, and lymphocyte homing and trafficking during embryogenesis and in the adult organism. Some splice variants are thought to play an important role in tumor progression. To investigate the physiological roles of CD44 in vivo, we abolished expression of all isoforms of CD44 in mice by targeted insertion of a lacZ/neo cassette into the reading frame of the leader peptide. CD44-deficient mice are viable without obvious developmental defects and show no overt abnormalities as adults. However, CD44-deficient lymphocytes exhibit impaired entry into the adult thymus, although lymphocyte development is apparently unaltered. Our data indicate that all splice variants of CD44 are dispensable for embryonic development and implicate a critical function for CD44 in lymphocyte recirculation.

Functions of c-Jun in liver and heart development

Mice lacking the AP-1 transcription factor c-Jun die around embryonic day E13.0 but little is known about the cell types affected as well as the cause of embryonic lethality. Here we show that a fraction of mutant E13.0 fetal livers exhibits extensive apoptosis of both hematopoietic cells and hepatoblasts, whereas the expression of 15 mRNAs, including those of albumin, keratin 18, hepatocyte nuclear factor 1, beta-globin, and erythropoietin, some of which are putative AP-1 target genes, is not affected. Apoptosis of hematopoietic cells in mutant livers is most likely not due to a cell-autonomous defect, since c-jun-/- fetal liver cells are able to reconstitute all hematopoietic compartments of lethally irradiated recipient mice. A developmental analysis of chimeras showed contribution of c-jun-/- ES cell derivatives to fetal, but not to adult livers, suggesting a role of c-Jun in hepatocyte turnover. This is in agreement with the reduced mitotic and increased apoptotic rates found in primary liver cell cultures derived from c-jun-/- fetuses. Furthermore, a novel function for c-Jun was found in heart development. The heart outflow tract of c-jun-/- fetuses show malformations that resemble the human disease of a truncus arteriosus persistens. Therefore, the lethality of c-jun mutant fetuses is most likely due to pleiotropic defects reflecting the diversity of functions of c-Jun in development, such as a role in neural crest cell function, in the maintenance of hepatic hematopoiesis and in the regulation of apoptosis.

How tumor cells make use of CD44

A variant of CD44 containing exon v3 sequences is expressed in the apical ectodermal ridge of the limb bud during embryogenesis. This variant is modified by heparan sulfate moieties and acts as low affinity receptor for FGFs. These FGFs are presented by CD44 to mesenchymal cells which induces their proliferation and limb outgrowth. We suggest that a similar growthfactor presentation mechanism accounts for the function of CD44 variants on metastasizing tumor cells.

Generation of normal T and B lymphocytes by c-jun deficient embryonic stem cells

To determine the potential roles of c-jun in lymphocyte development, we generated somatic chimeric mice by injecting homozygous c-jun mutant embryonic stem (ES) cells into blastocysts from recombination activating gene-2 (RAG-2)-deficient mice. Chimeric mice had poor restoration of thymocytes, but contained substantial numbers of mature T and B lymphocytes in the periphery. Stimulation of c-jun-/- B cells resulted in normal levels of proliferation and immunoglobulin secretion. Likewise, stimulation of c-jun-/- T cells resulted in essentially normal levels of IL-2R alpha expression, IL-2 secretion, and proliferation. We further showed that the relatively normal activation responses of the c-jun-/- T cells probably results from the fact that other members of the Jun family contribute to the bulk of the activator protein-1 (AP-1) complexes in normal T cells and, as a result, AP-1 complexes are found at relatively normal levels in c-jun-/- T cells.

c-jun is essential for normal mouse development and hepatogenesis

The proto-oncogene c-jun is the cellular homologue of v-jun, the transforming oncogene of the avian sarcoma virus 17 (ref. 1). c-jun encodes one major component of the AP-1 transcription factor complex and is expressed in many organs during mouse development and in the adult. Because of its rapid induction in cells following growth stimulation and the presence of AP-1 binding sites in the promoter regions of many genes, the c-Jun protein is thought to have important functions in cell proliferation and differentiation. But embryonic stem (ES) cells lacking c-Jun are viable and have a normal in vitro differentiation capacity, although c-Jun appears to be important for growth of teratocarcinomas in vivo. To define the function of c-jun better, targeted ES cells were used to generate mice lacking c-Jun. Here we report that heterozygous mutant mice appear normal, but embryos lacking c-Jun die at mid- to late-gestation and exhibit impaired hepatogenesis, altered fetal liver erythropoiesis and generalized oedema. Interestingly, c-jun-/- ES cells can participate efficiently in the development of all somatic cells in chimaeric mice except liver cells, further suggesting an essential function of c-Jun in hepatogenesis.