Abstract ND07: JNJ-78306358: A first-in-class bispecific T cell redirecting HLA-G antibody

JNJ-78306358 is a first-in-class bispecific antibody (bsAb), engineered using the Zymeworks Azymetric™ platform, to treat advanced stage solid tumors. Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility class I molecule with an immune tolerance role at the maternal-fetal interface. HLA-G has limited normal tissue expression, mainly detected in placenta and pituitary gland. However, HLA-G is expressed in multiple human cancers, with a potential role in cancer immune evasion. Comprehensive immunohistochemistry analysis of patient-derived tumors revealed high prevalence of HLA-G expression in renal cell carcinoma (RCC, 75%), ovarian (61%), colon (64%) and rectal cancers (40%), and moderate HLA-G expression prevalence in lung adenocarcinoma, endometrial, and pancreatic cancer. JNJ-78306358 induces HLA-G-expressing tumor cell killing via T cell redirection. This bsAb features an anti-HLA-G single-chain fragment variable (scFv) domain that binds with high affinity (KD ~ 13 pM) to HLA-G on tumor cells and a Fab domain that binds with weaker affinity (KD ~22 nM) to the epsilon subunit of the cluster of differentiation 3 (CD3ε). The immunoglobulin (Ig)G1 heavy chains feature Fc region mutations that disrupt interaction with Fcγ receptors. JNJ-78306358 demonstrated potent PBMC- and T cell-mediated in vitro cytotoxicity (EC50 10.4 - 442.3 pM) against endogenous membrane HLA-G-expressing tumor cell lines and absence of killing against cancer cells lacking HLA-G membrane expression, highlighting the specificity against antigen-expressing tumor cells. JNJ-78306358 exhibited hallmarks of T cell engagement in vitro, including T cell proliferation and cytokine release. In addition, JNJ-78306358 showed HLA-G-expression-dependent anti-tumor activity in mice (humanized with human donor CD3+ pan-T cells or human umbilical cord-blood-derived CD34+ hematopoietic stem cells [HSCs]) bearing cell line- and patient-derived tumors. In these xenograft models, a dose-dependent increase in CD4+ and CD8+ T cell infiltration into tumors was observed with complete tumor regressions at low doses of JNJ-78306358 (0.03 mg/kg). JNJ-78306358’s safety, tolerability and preliminary anti-tumor activity are currently being evaluated in a first-in-human phase I study in advanced stage solid tumors with high prevalence of HLA-G protein expression (NCT04991740). This antigen-targeting approach may address an unmet medical need in patients with tumors expressing HLA-G.

Citation Format: Nataša Obermajer, Adam Zwolak, Kelly Van De Ven, Shana Versmissen, Aleksandra Brajic, Ted Petley, Dan Weinstock, Jason Aligo, Fang Yi, Stephen Jarantow, Keith Schutsky, Ken Tian, Angelilo Lorraine, Diana Alvarez Arias, Kristel Buyens, Vince Torti, Krista Menard, Katharine Rogers, Brian Geist, Marjolein Van Heerden, Gerald Chu, Bie Verbist, Maté Ongenaert, Julien Hasler, Kathryn Packman, Jacintha Shenton, Dirk Brehmer, Josh Lauring, Regina J. Brown, James Greger, Daphne Salick Ryan, Sanjaya Singh, Matthew V. Lorenzi, Laurie Lenox, Sylvie Laquerre. JNJ-78306358: A first-in-class bispecific T cell redirecting HLA-G antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr ND07.

Discovery and Pharmacological Characterization of JNJ-64619178, a Novel Small-Molecule Inhibitor of PRMT5 with Potent Antitumor Activity

The protein arginine methyltransferase 5 (PRMT5) methylates a variety of proteins involved in splicing, multiple signal transduction pathways, epigenetic control of gene expression, and mechanisms leading to protein expression required for cellular proliferation. Dysregulation of PRMT5 is associated with clinical features of several cancers, including lymphomas, lung cancer, and breast cancer. Here, we describe the characterization of JNJ-64619178, a novel, selective, and potent PRMT5 inhibitor, currently in clinical trials for patients with advanced solid tumors, non-Hodgkin's lymphoma, and lower-risk myelodysplastic syndrome. JNJ-64619178 demonstrated a prolonged inhibition of PRMT5 and potent antiproliferative activity in subsets of cancer cell lines derived from various histologies, including lung, breast, pancreatic, and hematological malignancies. In primary acute myelogenous leukemia samples, the presence of splicing factor mutations correlated with a higher ex vivo sensitivity to JNJ-64619178. Furthermore, the potent and unique mechanism of inhibition of JNJ-64619178, combined with highly optimized pharmacological properties, led to efficient tumor growth inhibition and regression in several xenograft models in vivo, with once-daily or intermittent oral-dosing schedules. An increase in splicing burden was observed upon JNJ-64619178 treatment. Overall, these observations support the continued clinical evaluation of JNJ-64619178 in patients with aberrant PRMT5 activity-driven tumors.

Abstract 5651: JNJ-61186372, an Fc enhanced EGFR/cMet bispecific antibody, mediates EGFR and cMet downmodulation and therapeutic efficacy preclinically through monocyte / macrophage mediated trogocytosis

Small molecule inhibitors targeting EGFR are now standard of care in NSCLC patients harboring EGFR mutations, but acquired resistance invariably develops through secondary mutations within EGFR and/or through activation of compensatory pathways such as cMet. JNJ-61186372 (JNJ-372) is an anti-EGFR and cMet bispecific antibody with enhanced binding to immune cell Fcγ receptors, designed to target tumors with activated EGFR and cMet signaling through a distinct mechanism of action. Ongoing first-in-human study in patients with advanced, treatment refractory EGFR mutant NSCLC revealed JNJ-372 to have clinical activity in patients with diverse EGFR-mutated NSCLC, including Exon 20 mutations, TKI resistance mutations (T790M, C797S), and resistance due to MET amplification.

However preclinically, despite potent anti-tumor activity in NSCLC xenograft models, only modest anti-proliferative effects were observed with JNJ-372 in cell lines in vitro. Interestingly, the addition of isolated human immune cells (PBMCs) to the in vitro assays enhanced JNJ-372-mediated EGFR and cMet downregulation, and dose-dependent tumor cell killing. Through depletion or enrichment of individual immune cell types, we demonstrated that monocytes and/or macrophages are necessary for JNJ-372 Fc interaction-mediated EGFR/cMet downmodulation. Depletion of macrophages in mice showed that they are required for JNJ-372 anti-tumor efficacy. Finally, we showed that the down-modulation of EGFR and cMet receptors occurs through monocyte or macrophage-mediated trogocytosis. Collectively, these results demonstrate a novel Fc-dependent mechanism of action for JNJ-372 and support its continued clinical development in patients with aberrant EGFR and cMet signaling.

Citation Format: Smruthi Vijayaraghavan, Lorraine Lipfert, Barbara Bushey, Kristen Chevalier, Benjamin Henley, Ryan Lenhart, Marilda Beqiri, Hillary J. Millar, Kathryn Packman, Matthew V. Lorenzi, Sylvie Laquerre, Sheri Moores. JNJ-61186372, an Fc enhanced EGFR/cMet bispecific antibody, mediates EGFR and cMet downmodulation and therapeutic efficacy preclinically through monocyte / macrophage mediated trogocytosis [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 5651.

Antitumor Activity of Amivantamab (JNJ-61186372), an EGFR-MET Bispecific Antibody, in Diverse Models of EGFR Exon 20 Insertion-Driven NSCLC

EGFR exon 20 insertion driver mutations (Exon20ins) in non-small cell lung cancer (NSCLC) are insensitive to EGFR tyrosine kinase inhibitors (TKI). Amivantamab (JNJ-61186372), a bispecific antibody targeting EGFR-MET, has shown preclinical activity in TKI-sensitive EGFR-mutated NSCLC models and in an ongoing first-in-human study in patients with advanced NSCLC. However, the activity of amivantamab in Exon20ins-driven tumors has not yet been described. Ba/F3 cells and patient-derived cells/organoids/xenograft models harboring diverse Exon20ins were used to characterize the antitumor mechanism of amivantamab. Amivantamab inhibited proliferation by effectively downmodulating EGFR-MET levels and inducing immune-directed antitumor activity with increased IFNγ secretion in various models. Importantly, in vivo efficacy of amivantamab was superior to cetuximab or poziotinib, an experimental Exon20ins-targeted TKI. Amivantamab produced robust tumor responses in two Exon20ins patients, highlighting the important translational nature of this preclinical work. These findings provide mechanistic insight into the activity of amivantamab and support its continued clinical development in Exon20ins patients, an area of high unmet medical need. SIGNIFICANCE: Currently, there are no approved targeted therapies for EGFR Exon20ins-driven NSCLC. Preclinical data shown here, together with promising clinical activity in an ongoing phase I study, strongly support further clinical investigation of amivantamab in EGFR Exon20ins-driven NSCLC.This article is highlighted in the In This Issue feature, p. 1079.

Gene signatures of tumor inflammation and epithelial-to-mesenchymal transition (EMT) predict responses to immune checkpoint blockade in lung cancer with high accuracy

OBJECTIVES

Treatment of non-small cell lung cancer (NSCLC) with immune checkpoint blockade (ICB) has resulted in striking clinical responses, but only in a subset of patients. The goal of this study was to evaluate transcriptional signatures previously reported in the literature in an independent cohort of NSCLC patients receiving ICB.

MATERIALS AND METHODS

This retrospective study analyzed transcriptional profiles from pre-treatment tumor samples of 52 chemotherapy-refractory advanced NSCLC patients treated with anti-PD1/PD-L1 therapy. Gene signatures based on published reports were created and examined for their association with response to therapy and progression-free and overall survival (PFS, OS).

RESULTS

Two signatures predicting response and outcomes were identified. One reflected the degree of immune infiltration and upregulation of interferon-gamma-induced genes. A second reflected the EMT status. Compared to those not responding to therapy, patients whose tumors responded to ICB had higher scores in an inflammatory gene signature (6.0 ± 2.9 vs -5.5 ± 3.4, p = 0.014) or a more epithelial phenotype (-1.7 ± 1.0 vs 2.1 ± 1.2, p = 0.016). Both signatures demonstrated a satisfactory predictive accuracy for response: AUC of 0.69 (95% CI: 0.54, 0.84) for the inflammatory and 0.70 (95% CI: 0.55, 0.85) for EMT signatures, respectively. A weighted score combining EMT and inflammatory signatures showed increased predictive value with AUC of 0.92 (95% CI: 0.85, 0.99). Kaplan-Meier curves for patients above and below the median combined score showed a significant separation for PFS and OS (all p < 0.01, log rank test).

CONCLUSIONS

The EMT/Inflammation signature score may be useful in directing checkpoint inhibitor therapy in lung cancer and suggests that reversal of EMT might augment efficacy of ICB.

Abstract 3393: Altered immune response in the transcriptome of patients with lung cancer

Introduction The immune system is critical to surveying and eradicating abnormal cells, but tumor cells develop ways to escape immunosurveillance and induce an immunosuppressive state. We previously developed and validated gene expression (GE) signatures measured in the normal airway-epithelial brushings in patients undergoing bronchoscopy for suspicion of lung cancer (LC). In this study, we seek to understand if the immunosuppressive environment extends to the airway field of injury via profiling of endobronchial biopsies from the central airway containing a broader range of cell types, including immune cells.

Methods Endobronchial biopsies from normal-appearing regions of the central airway were collected from ever smokers undergoing workup of indeterminate pulmonary nodules (7-30 mm in diameter) suspicious for LC at military and VA hospitals within the DECAMP consortium. Initially, total RNA from the biopsies (n=44, discovery-set) were isolated and sequenced. Reads were aligned to hg19 using STAR and gene level counts were quantified with RSEM. Poor quality samples were removed using FASTQC and RSEQC. Differential GE associated with cancer status was identified using edgeR, adjusting for smoking-status, COPD and sample quality. RNA from additional endobronchial biopsies (n=49, validation-set) were isolated and preprocessed similarly. Genes differentially expressed with LC status in the discovery-set were tested in the validation-set using gene set variation analysis (GSVA). Functional enrichment of cancer associated genes was explored using Enrichr. Comparison of cancer signatures identified in previously published LC studies was investigated using GSEA. CIBERSORT, xCell, TIMER software and single-cell RNA sequencing data generated from airway brushings were used to deconvolute the immune cell content of the bulk biopsy samples.

Results We identified a GE signature associated with LC which was significantly and concordantly enriched in the validation set of biopsies and two previously published studies of LC-associated GE in airway brushings. Genes decreased in LC patient biopsies were enriched for genes involved in immune-related pathways, including cytokine interactions, the inflammatory response and neutrophil degranulation. Computational deconvolution and comparison with single-cell RNAseq data predicts a decrease in neutrophils in the airway of LC patients.

Conclusion We identified LC-associated GE alterations in smokers presenting with indeterminate pulmonary nodules. Down-regulated genes in LC subjects are strongly associated with immune system function, specifically neutrophil biology. Subjects with LC appear to have an immunosuppressive environment directed towards myeloid cell populations, and this could have implications for the future development of immunoprevention therapies.

Citation Format: Kahkeshan Hijazi, Julian Lel, Ehab Billatos, Elizabeth Moses, Christopher S. Stevenson, Matthew V. Lorenzi, Gang Liu, Joshua D. Campbell, Yusuke Koga, Jiarui Zhang, Fenghai Duan, Helga Marques, Marc E. Lenburg, Avrum E. Spira, Jennifer Beane. Altered immune response in the transcriptome of patients with 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 3393.

Abstract 4818: Fc-mediated mechanism of action for the novel EGFR-cMET bispecific antibody (JNJ-61186372) in non-small cell lung cancer

JNJ-61186372 (JNJ-372) is an anti-EGFR and cMet bispecific antibody with an active Fc backbone (IgG1) designed to treat non-small cell lung cancer (NSCLC) disease. A first-in-human study is currently being conducted to assess the safety and preliminary efficacy of JNJ-372 in patients with advanced NSCLC. Early data suggests that JNJ-372 can induce partial responses in subjects with diverse populations of EGFR-mutated NSCLC, including Exon 20ins as well as TKI resistance mutations.

Our previous pre-clinical in vivo studies showed that the Fc inactive version (IgG2sigma) of the EGFR/cMet antibody was significantly impaired in its ability to inhibit tumor growth compared to the Fc active JNJ-372. The IgG2sigma variant also reduced the ability of the bispecific antibody to mediate downregulation of EGFR, cMet and downstream signaling components. This suggested that the interaction of the Fc arm with the Fc receptors on the innate immune cells play a crucial role in the mechanism of action of JNJ-372. While JNJ-372 has demonstrated antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) in vitro, the potential role of Fc interactions in downregulation of EGFR and cMet was not well understood.

We explored the different Fc-mediated immune effector functions of JNJ-372 and interrogated how they contribute to EGFR and cMet downregulation and overall efficacy. In NSCLC cell lines, JNJ-372 induced Fc-mediated dose-dependent ADCC and ADCP but not complement-dependent cytotoxicity. Further, the presence of isolated human immune cells (PBMC) significantly enhanced JNJ-372 mediated EGFR and cMet downregulation and dose-dependent tumor cell killing. Studies are in progress to better understand which immune cells and which Fc receptor interactions are essential for the drug efficacy through immune cell depletion and FcR blocking studies; such studies may help guide clinical biomarker development. This work elucidates a novel Fc-dependent mechanism of action for the EGFR-cMet bispecific antibody.

Citation Format: Smruthi Vijayaraghavan, Barbara Bushey, Lorriane Lipfert, Rupesh Nanjunda, Eilyn R. Lacy, Peter Buckley, Sylvie Laquerre, Matthew V. Lorenzi, Sheri Moores. Fc-mediated mechanism of action for the novel EGFR-cMET bispecific antibody (JNJ-61186372) 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 4818.

Preliminary immunogenicity, safety, and efficacy of JNJ-64041757 (JNJ-757) in non-small cell lung cancer (NSCLC): Results from two phase 1 studies

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Background: The immunogenicity, safety, and efficacy of JNJ-757, a live attenuated, double-deleted Listeria monocytogenes-based immunotherapy expressing human mesothelin (MSLN), were evaluated in patients (pts) with advanced NSCLC (adenocarcinoma) as monotherapy (phase 1) and in combination with nivolumab (phase 1b/2). Methods: Adult pts with Stage IIIB/IV NSCLC who had received prior systemic therapy (including 1 platinum-based chemotherapy, prior PD-1/PD-L1 therapy allowed) were included. Dose-limiting toxicities, adverse events (AEs), tumor response, T cell response, and JNJ-757 bacterial shedding profile were evaluated in pts treated with JNJ-757 (108 or 109 colony forming units [CFU]) alone or JNJ-757 (109 CFU)+nivolumab 240 mg combination therapy until progression. Results: In the monotherapy trial, 18 pts (median age 63.5 years; women 61%) were treated with JNJ-757 108 or 109 CFU with a median duration of 1.4 months (range 0-29). Most common AEs were pyrexia (72%) and chills (61%), which were usually mild and resolved within 48 hours, suggesting transient activation of an innate immune response to JNJ-757. Treatment-related grade ≥3 AEs were infrequent (4 [22%]). Induction of peripheral proinflammatory cytokines and lymphocyte activation was observed post-treatment with transient MSLN-specific T cell responses in 10/13 evaluable pts, consistent with the mechanism of action of JNJ-757. With monotherapy, 4/18 response-evaluable pts had stable disease (SD) ≥16 weeks, including 1 pt with a 53% reduction in target lesions. In the combination therapy study, 12 pts were enrolled (median age 63.5 years; women 33%). The most common AEs were pyrexia (67%) and chills (58%); 6 pts had grade ≥3 AEs including 2 cases of treatment-related fatal pneumonitis. Best overall response for the combination was SD in 4/9 evaluable pts. JNJ-757 in combination with nivolumab suggested increased risk of pneumonitis. Conclusions: As monotherapy, JNJ-757 was tolerable with mild infusion-related fever and chills supporting the initiation of the combination therapy study. However, the risk-benefit profile of JNJ-757+nivolumab, did not support proceeding to phase 2. Clinical trial information: NCT02592967, NCT03371381.

JNJ-61186372 (JNJ-372), an EGFR-cMet bispecific antibody, in EGFR-driven advanced non-small cell lung cancer (NSCLC)

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Background: JNJ-372 binds EGFR and cMet to block ligand binding, promote receptor degradation, and trigger antibody-dependent cellular cytotoxicity in models of EGFR-mutated (EGFRm) NSCLC. Here we describe the ongoing phase 1 safety, pharmacokinetics (PK), and activity of JNJ-372 in patients (pts) with NSCLC, including 3rd generation tyrosine kinase inhibitor (3GTKI)-relapsed EGFRm NSCLC and EGFR Exon20ins disease. Methods: Pts received JNJ-372 (140–1400 mg) IV weekly for the first 28-day cycle and biweekly thereafter. 1050–1400 mg doses are being explored in dose expansion. Blood samples were collected for PK analyses. Efficacy by investigator per RECIST v1.1 in pts with EGFRm NSCLC treated at ≥700 mg is presented. Tumors were characterized by next-generation sequencing of circulating tumor (ct)DNA and/or tumor tissue. Results: As of 17 Jan 2019, 116 enrolled pts with NSCLC were treated. Median age was 63 years, 38% were male, 77% were Asian, and 97% had EGFR mutations. Mean duration of treatment was 3.8 months, longest exposure was 20 cycles. The PK data set included pts from Korea (77%) and the US (23%). At the 1050 mg dose, 72% of pts achieved average concentrations above the EC90 based on preclinical models. Adverse events (AEs; ≥20%) were rash (59%), infusion related reaction (58%), paronychia (28%), and constipation (22%). Additional EGFR/cMet-related AEs include stomatitis (17%), pruritis (15%), peripheral edema (11%), and diarrhea (7%). Grade ≥3 AEs were reported in 34% (8% treatment-related) with dyspnea (6%) and pneumonia (3%) most frequently observed. Among response-evaluable pts, 25/88 (28%) achieved best timepoint response of partial response (PR). 10/47 pts with prior 3GTKI therapy had best timepoint response of PR (6 confirmed), including 4 with C797S, 1 with cMet amplification, and 5 without identifiable EGFR/cMet-dependent resistance. 6/20 pts with Exon20ins had best timepoint response of PR (3 confirmed). Conclusions: JNJ-372 has a manageable safety profile consistent with EGFR and cMet inhibition. Preliminary responses were achieved in 3GTKI-relapsed disease, including C797S and cMet amplification, and Exon20ins disease; enrollment in dose expansion is ongoing. Clinical trial information: NCT02609776.

Comprehensive genomic and immunological characterization of Chinese non-small cell lung cancer patients

Deep understanding of the genomic and immunological differences between Chinese and Western lung cancer patients is of great importance for target therapy selection and development for Chinese patients. Here we report an extensive molecular and immune profiling study of 245 Chinese patients with non-small cell lung cancer. Tumor-infiltrating lymphocyte estimated using immune cell signatures is found to be significantly higher in adenocarcinoma (ADC, 72.5%) compared with squamous cell carcinoma (SQCC, 54.4%). The correlation of genomic alterations with immune signatures reveals that low immune infiltration was associated with EGFR mutations in ADC samples, PI3K and/or WNT pathway activation in SQCC. While KRAS mutations are found to be significantly associated with T cell infiltration in ADC samples. The SQCC patients with high antigen presentation machinery and cytotoxic T cell signature scores are found to have a prolonged overall survival time.

Analysis of FGFR alterations from circulating tumor DNA (ctDNA) and Tissue in a phase II trial of erdafitinib in urothelial carcinoma (UC)

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Background: Plasma samples from a Phase 2 study of the pan-FGFR inhibitor erdafitinib in advanced UC patients (pts) with FGFR mutations (mut) or fusions, were tested using next generation sequencing (NGS) for circulating tumor DNA (ctDNA), and results compared to central FGFR status determination from tissue. Methods: FGFR alterations were measured in archival tissue using an RNA-based RT-PCR test and compared with FGFR alterations identified in pre-treatment plasma specimens using the Guardant360 ctDNA test. Sensitivity of the ctDNA test to detect the FGFR alterations identified by RT-PCR from tissue, the proportion of pts with a study-eligible FGFR alteration in ctDNA, and the ability to detect a tissue FGFR alteration in ctDNA in relation to clinical response were assessed. Results: Samples from 155 pts with detectable baseline ctDNA were included. Overall, concordance between ctDNA and tissue-based FGFR results was 56% (87/155): 63% (77/122) for tissue mut-positive pts vs 24% (7/29) in fusion-positive pts. 61% of pts (94/155) were positive for a study-eligible FGFR alteration from blood-based testing in the tissue-positive population. The response rate was 47% (36/77) for patients for which FGFR mutations could be detected in blood (ctDNA- FGFR-positive) compared with 32% (14/44) in patients for which mutations were not detected in blood (ctDNA- FGFR-negative), with an estimated odds ratio of 1.882 (95% CI: 0.866; 4.090) Conclusions: The 63% concordance rate for detecting FGFR mut in temporally unmatched blood and tissue supports potential for patient selection with blood-based testing, while ctDNA FGFR fusion detection may require further optimization. Although differences in clinical response rate were observed between ctDNA- FGFR-positive and negative patients, the results were not statistically significant. Importantly, a proportion of ctDNA-negative pts responded to erdafitinib, indicating that tissue-based testing may be warranted for pts negative for FGFR alterations via blood-based testing. (BLC2001, NCT02365597). Clinical trial information: NCT02365597.

Abstract 929: Discovery of novel covalent KRASG12C inhibitors that display high potency and selectivity in vitro and in vivo

Activating mutations in KRAS have a high prevalence in human cancer. The codon 12 glycine to cysteine missense mutation (KRASG12C) is among the most common KRAS mutations, present in non-small cell lung adenocarcinoma (~15 %), colorectal adenocarcinoma (~3 %), and pancreatic adenocarcinoma (~1 %). KRASG12C was previously identified as potentially druggable by allele-specific covalent targeting of cysteine 12 near the allosteric switch II pocket (S-IIP). Building on this early work, we recently described the ARS-853 series of S-IIP KRASG12C inhibitors that covalently react with the GDP-bound state of KRASG12C, trapping KRASG12C in this inactive state. In cells, ARS-853 series compounds profoundly deplete the signaling competent GTP-bound state of KRASG12C, thereby inhibiting downstream RAS signaling. However, this series of covalent KRASG12C inhibitors exhibited modest cellular potency and/or poor pharmacokinetic properties, making them unsuitable for further evaluation of covalent KRASG12C inhibition in animal models.

We now describe in further detail the discovery and characterization of a new series of structurally distinct quinazoline based S-IIP KRASG12C inhibitors with substantially improved potency and pharmacologic properties that overcome limitations of the ARS-853 series. Through structure-guided medicinal chemistry optimization we identified compound ARS-1620, a potent, orally bioavailable covalent inhibitor of KRASG12C. The co-crystal structure of ARS-1620 covalently bound to KRASG12C reveals a distinct binding mode and additional interactions, compared to ARS-853. ARS-1620 rapidly engages KRASG12C, depletes KRASG12C-GTP in tumor cell lines, and inhibits downstream RAS signaling in a dose-dependent manner. The compound potently inhibits the growth of cell lines harboring the KRASG12C mutation with little or no effect on control cell lines. ARS-1620 demonstrates robust dose-dependent efficacy with once daily oral administration across a panel of KRASG12C-positive mouse cell line (CDX) and patient-derived (PDX) tumor xenograft models, with no response observed at all doses tested in KRASG12C-negative tumor models. The anti-tumor activity of ARS-1620 correlates with target engagement in the tumors as well as with inhibition of downstream RAS signaling. The in vivo efficacy and mutant selectivity observed with ARS-1620 across a wide range of KRASG12C mouse tumor models provides the first in vivo evidence that the S-IIP targeted approach may be a promising therapeutic strategy for patients with KRASG12C mutant cancers.

Citation Format: Liansheng Li, Matthew R. Janes, Jingchuan Zhang, Rasmus Hansen, Ulf Peters, Xin Guo, Yuching Chen, Anjali Babbar, Sarah J. Firdaus, Jun Feng, Jeffrey H. Chen, Shuangwei Li, Shisheng Li, Carol Thach, Yuan Liu, Ata Zarieh, Jeff M. Kucharski, Tao Wu, Ke Yu, Yi Wang, Yvonne Yao, Xiaohu Deng, Patrick P. Zarrinkar, Dashyant Dhanak, Matthew V. Lorenzi, Dana Hu-Lowe, Pingda Ren, Yi Liu. Discovery of novel covalent KRASG12C inhibitors that display high potency and selectivity in vitro and in vivo [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 929.

Abstract B27: Improved survival with erdafitinib (JNJ-42756493) and PD-1 blockade mediated by enhancement of anti-tumor immunity in an FGFR2-driven genetically engineered mouse model of lung cancer

Targeted therapies against activated oncogenes, such as receptor tyrosine kinases, have significantly prolonged non-small cell lung cancer (NSCLC) patient survival, but the development of resistance limits the durability of clinical response. Genetic alterations which constitutively activate Fibroblast Growth Factor Receptors (FGFR) have been observed in patients with NSCLC. Erdafitinib (JNJ-42756493), an orally bioavailable pan-FGFR inhibitor discovered as part of a collaboration between Janssen and Astex Pharmaceuticals, has been shown to inhibit FGFR signaling pathways resulting in cell death and tumor growth inhibition in both in vitro and in vivo models of FGFR pathway aberration. Further, erdafitinib has been shown to have favorable pharmaceutical properties with manageable side effects in humans and several clinical trials are currently underway. One potential strategy to enhance the durability of response to targeted therapies, such as FGFR inhibitors, is to couple them with immunotherapy. In this setting, T cell responses primed and activated by increased antigen release resulting from the tumor cell targeted therapy could be enhanced and maintained by T-cell directed checkpoint blockade. To test this hypothesis, we evaluated erdafitinib in combination with an anti-programmed death-1 (PD-1) blocking antibody in an autochthonous FGFR2K660N/p53 genetically engineered mouse model (GEMM) of lung cancer, in which tumors develop within the context of an intact immune microenvironment. Cohorts of tumor bearing FGFR2K660N/p53 mutant mice treated with erdafitinib with or without anti-PD-1 showed significant tumor regressions compared to control and anti-PD-1 alone groups. Despite lack of differences in acute tumor responses between erdafitinib monotherapy and combination therapy, we observed significant survival benefit in the combination group erdafitinib alone (median survival 19.7 weeks vs 13.4 weeks, p&lt;0.004). In a separate study, similar tumor regressions were noted in the FGFR-driven GEMM at 1 week of erdafitinib with or without anti-PD-1 treatment, while no such response to these treatments was noted in a KRAS-driven lung cancer GEMM. Immune profiling of tumor specimens revealed high baseline expression of programmed death ligand-1 (PD-L1) expression by IHC and flow cytometry. Following combination treatment, subsequent immunohistochemistry (IHC) analyses showed a significant decrease in Ki67 and PD-L1 positive tumor cells, accompanied by an increase in cluster of differentiation 3 (CD3) positive tumor-infiltrating cells in combination group as compared to control. T cell function is not inhibited by erdafitinib, as measured in vitro by mixed lymphocyte reaction and cytomegalovirus recall assays. Additional changes observed in lung tumors across treatment groups in immune cell infiltration, functionality, and T-cell clonality will be discussed. These data suggest that combination treatment of erdafitinib and PD-1 blockade drives improved survival in FGFR2-driven model of lung cancer by simultaneous inhibition of FGFR pathway in tumor cells and enhancement of anti-tumor immunity. Thus, data here provide rationale for the combined clinical testing of erdafitinib and PD-1 blockade in patients with FGFR-altered lung cancers.

Citation Format: Sangeetha Palakurthi, Mari Kuraguchi, Sima Zacharek, Jeff Liu, Dennis Bonal, Wei Huang, Kristin Depeaux, Abha Dhaneshwar, Sam Regan, Dyane Bailey, Martha Gowaski, Mei Zheng, Roderick Bronson, Catherine Ferrante, Enrique Zudaire, Sylvie Laquerre, Mark Bittinger, Kirschmeier Paul, Kathryn Packman, Raluca I. Verona, Kwok-Kin Wong, Matthew V. Lorenzi. Improved survival with erdafitinib (JNJ-42756493) and PD-1 blockade mediated by enhancement of anti-tumor immunity in an FGFR2-driven genetically engineered mouse model of lung cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B27.

A Novel Bispecific Antibody Targeting EGFR and cMet Is Effective against EGFR Inhibitor-Resistant Lung Tumors

Non-small cell lung cancers (NSCLC) with activating EGFR mutations become resistant to tyrosine kinase inhibitors (TKI), often through second-site mutations in EGFR (T790M) and/or activation of the cMet pathway. We engineered a bispecific EGFR-cMet antibody (JNJ-61186372) with multiple mechanisms of action to inhibit primary/secondary EGFR mutations and the cMet pathway. JNJ-61186372 blocked ligand-induced phosphorylation of EGFR and cMet and inhibited phospho-ERK and phospho-AKT more potently than the combination of single receptor-binding antibodies. In NSCLC tumor models driven by EGFR and/or cMet, JNJ-61186372 treatment resulted in tumor regression through inhibition of signaling/receptor downmodulation and Fc-driven effector interactions. Complete and durable regression of human lung xenograft tumors was observed with the combination of JNJ-61186372 and a third-generation EGFR TKI. Interestingly, treatment of cynomolgus monkeys with JNJ-61186372 resulted in no major toxicities, including absence of skin rash observed with other EGFR-directed agents. These results highlight the differentiated potential of JNJ-61186372 to inhibit the spectrum of mutations driving EGFR TKI resistance in NSCLC. Cancer Res; 76(13); 3942-53. ©2016 AACR.

Structure-Based Design of Selective Janus Kinase 2 Imidazo[4,5-d]pyrrolo[2,3-b]pyridine Inhibitors

Early hit to lead work on a pyrrolopyridine chemotype provided access to compounds with biochemical and cellular potency against Janus kinase 2 (JAK2). Structure-based drug design along the extended hinge region of JAK2 led to the identification of an important H-bond interaction with the side chain of Tyr 931, which improved JAK family selectivity. The 4,5-dimethyl thiazole analogue 18 demonstrated high levels of JAK family selectivity and was identified as a promising lead for the program.

Discovery of a Highly Selective JAK2 Inhibitor, BMS-911543, for the Treatment of Myeloproliferative Neoplasms

JAK2 kinase inhibitors are a promising new class of agents for the treatment of myeloproliferative neoplasms and have potential for the treatment of other diseases possessing a deregulated JAK2-STAT pathway. X-ray structure and ADME guided refinement of C-4 heterocycles to address metabolic liability present in dialkylthiazole 1 led to the discovery of a clinical candidate, BMS-911543 (11), with excellent kinome selectivity, in vivo PD activity, and safety profile.

Selective JAK2/ABL dual inhibition therapy effectively eliminates TKI-insensitive CML stem/progenitor cells

Imatinib Mesylate (IM) and other tyrosine kinase inhibitor (TKI) therapies have had a major impact on the treatment of chronic myeloid leukemia (CML). However, TKI monotherapy is not curative, with relapse and persistence of leukemic stem cells (LSCs) remaining a challenge. We have recently identified an AHI-1-BCR-ABL-JAK2 protein complex that contributes to the transforming activity of BCR-ABL and IM-resistance in CML stem/progenitor cells. JAK2 thus emerges as an attractive target for improved therapies, but off-target effects of newly developed JAK2 inhibitors on normal hematopoietic cells remain a concern. We have examined the biological effects of a highly selective, orally bioavailable JAK2 inhibitor, BMS-911543, in combination with TKIs on CD34⁺ treatment-naïve IM-nonresponder cells. Combination therapy reduces JAK2/STAT5 and CRKL activities, induces apoptosis, inhibits proliferation and colony growth, and eliminates CML LSCs in vitro. Importantly, BMS-911543 selectively targets CML stem/progenitor cells while sparing healthy stem/progenitor cells. Oral BMS-911543 combined with the potent TKI dasatinib more effectively eliminates infiltrated leukemic cells in hematopoietic tissues than TKI monotherapy and enhances survival of leukemic mice. Dual targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may consequently lead to more effective disease eradication, especially in patients at high risk of TKI resistance and disease progression.

9H-Carbazole-1-carboxamides as potent and selective JAK2 inhibitors

The discovery, synthesis, and characterization of 9H-carbazole-1-carboxamides as potent and selective ATP-competitive inhibitors of Janus kinase 2 (JAK2) are discussed. Optimization for JAK family selectivity led to compounds 14 and 21, with greater than 45-fold selectivity for JAK2 over all other members of the JAK kinase family.

Dysregulated STAT1-SOCS1 control of JAK2 promotes mammary luminal progenitor cell survival and drives ERα(+) tumorigenesis

We previously reported that STAT1 expression is frequently abrogated in human estrogen receptor-α-positive (ERα(+)) breast cancers and mice lacking STAT1 spontaneously develop ERα(+) mammary tumors. However, the precise mechanism by which STAT1 suppresses mammary gland tumorigenesis has not been fully elucidated. Here we show that STAT1-deficient mammary epithelial cells (MECs) display persistent prolactin receptor (PrlR) signaling, resulting in activation of JAK2, STAT3 and STAT5A/5B, expansion of CD61(+) luminal progenitor cells and development of ERα(+) mammary tumors. A failure to upregulate SOCS1, a STAT1-induced inhibitor of JAK2, leads to unopposed oncogenic PrlR signaling in STAT1(-/-) MECs. Prophylactic use of a pharmacological JAK2 inhibitor restrains the proportion of luminal progenitors and prevents disease induction. Systemic inhibition of activated JAK2 induces tumor cell death and produces therapeutic regression of pre-existing endocrine-sensitive and refractory mammary tumors. Thus, STAT1 suppresses tumor formation in mammary glands by preventing the natural developmental function of a growth factor signaling pathway from becoming pro-oncogenic. In addition, targeted inhibition of JAK2 may have significant therapeutic potential in controlling ERα(+) breast cancer in humans.

Tumor grafts derived from patients with head and neck squamous carcinoma authentically maintain the molecular and histologic characteristics of human cancers

BACKGROUND

The patient-derived xenograft (PDX) model is likely to reflect human tumor biology more accurately than cultured cell lines because human tumors are implanted directly into animals; maintained in an in vivo, three-dimensional environment; and never cultured on plastic. PDX models of head and neck squamous cell carcinoma (HNSCC) have been developed previously but were not well characterized at the molecular level. HNSCC is a deadly and disfiguring disease for which better systemic therapy is desperately needed. The development of new therapies and the understanding of HNSCC biology both depend upon clinically relevant animal models. We developed and characterized the patient-derived xenograft (PDX) model because it is likely to recapitulate human tumor biology.

METHODS

We transplanted 30 primary tumors directly into mice. The histology and stromal components were analyzed by immunohistochemistry. Gene expression analysis was conducted on patient tumors and on PDXs and cell lines derived from one PDX and from independent, human tumors.

RESULTS

Five of 30 (17%) transplanted tumors could be serially passaged. Engraftment was more frequent among HNSCC with poor differentiation and nodal disease. The tumors maintained the histologic characteristics of the parent tumor, although human stromal components were lost upon engraftment. The degree of difference in gene expression between the PDX and its parent tumor varied widely but was stable up to the tenth generation in one PDX. For genes whose expression differed between parent tumors and cell lines in culture, the PDX expression pattern was very similar to that of the parent tumor. There were also significant expression differences between the human tumors that subsequently grew in mice and those that did not, suggesting that this model enriches for cancers with distinct biological features. The PDX model was used successfully to test targeted drugs in vivo.

CONCLUSION

The PDX model for HNSCC is feasible, recapitulates the histology of the original tumor, and generates stable gene expression patterns. Gene expression patterns and histology suggested that the PDX more closely recapitulated the parental tumor than did cells in culture. Thus, the PDX is a robust model in which to evaluate tumor biology and novel therapeutics.

Abstract DDT01-03: Discovery of BMS-911543, a highly selective JAK2 inhibitor, as a clinical candidate for the treatment of myeloproliferative disease and other malignancies

Myeloproliferative diseases (MPDs) are a subset of myeloid malignancies that are characterized by the expansion of a multipotent hematopoietic stem cell. Chronic MPDs can be classified into two categories, those harboring the BCR-ABL oncogene and those that are negative. This later category of neoplasms encompasses polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Recent discovery of activating mutations in the tyrosine kinase gene, JAK2 and constitutive activation of JAK2-STAT pathway, in large number of MPD patients has ignited considerable interest in MPD and has highlighted JAK2 as a therapeutic intervention point for drug discovery efforts. However, high-sequence homology with other JAK family members has posed a major challenge to design selective JAK2 inhibitors. Given that other JAK family members are involved in the regulation of immune function, it is important to maintain selectivity for JAK2 over these family members in order to mitigate the risks associated with undesired immunosuppression. Several JAK2 inhibitors with varying selectivity profiles are currently being evaluated in preclinical testing as well as in clinical trials for the treatment of MPD. Additionally, emerging genetic and pharmacologic evidence suggest that inhibition of the JAK2-STAT pathway may be an important therapeutic intervention point in other hematological malignancies as well as in certain solid tumors.

We report here the discovery and characterization of BMS-911543, a functionally selective small molecule inhibitor of the Janus kinase family (JAK) member, JAK2. BMS-911543 is a potent and reversible inhibitor of JAK2 with a biochemical Ki of 0.48 nM. It has over 65-, 74- and 350-fold selectivity against the other JAK family members, TYK2, JAK3 and JAK1, respectively. Importantly, examination of &gt; 450 other kinases in competition binding assays and in selected biochemical kinase assays did not reveal significant inhibitory activity for this JAK2 inhibitor, highlighting its high degree of biochemical selectivity for JAK2.

Functionally, BMS-911543 displayed potent antiproliferative and pharmacodynamic (PD) effects in mutated JAK2-expressing cell lines dependent upon JAK2-STAT signaling and had little activity in cell types dependent upon other pathways such as JAK1 and JAK3. Further, single agent antiproliferative activity was not observed for BMS-911543 in a variety of solid tumor cell lines dependent upon other signaling pathways. In contrast, BMS-911543 was evaluated in colony growth assays using primary progenitor cells isolated from patients with JAK2V617F-positive myeloproliferative disease (MPD) and resulted in an increased antiproliferative response in MPD cells as compared with those from healthy volunteers. Similar to these in vitro observations, BMS-911543 was also highly active in in vivo models of JAK2-pSTAT signaling in multiple species with durable and potent pathway suppression observed after a single oral dose. Additionally, BMS-911543 was evaluated for effects in a JAK2V617F-expressing SET-2 xenograft model system and displayed a minimally effective dose of &lt;2 mg/kg on pSTAT5 pathway suppression, which lasted up to 8 hours.

To test the hypothesis that a JAK2 selective inhibitor would have less effect on immune system function, BMS-911543 was compared to pan-JAK inhibitors in a mouse model of immunosuppression. At low dose levels active in JAK2-dependent PD models, no effects were observed on antigen-induced IgG and IgM production for BMS-911543 whereas a pan-JAK family inhibitor showed pronounced effects at all dose levels tested. The mechanistic selectivity of BMS-911543 to pan-JAK family inhibitors was extended through comparative analysis of these inhibitors in whole genome gene expression profiling experiments performed in sensitive and resistant cell types. In this comparison, BMS-911543 modulated a distinct subset of transcriptional changes as compared to pan-JAK inhibitors in clinical testing, thereby defining a minimal set of transcriptional changes underlying the pharmacologic effects of JAK2 inhibition. Collectively these results define the mechanistic basis for a differential therapeutic index between selective JAK2 and pan-JAK family inhibition pre-clinically and suggest a therapeutic rationale for the further characterization of BMS-911543 in patients with MPD and in other malignancies reliant upon constitutively active JAK2 signaling.

References:

Levine, R.L., et al. Role of JAK2 in the pathogenesis and therapy of myeloproliferative disorders (2007). Nature Rev. Cancer, 7, 673-683.

Atallah, E. and Verstovsek, S. Prospect of JAK2 inhibitor therapy in myeloproliferative neoplasms. (2009). Expert Rev. Anticancer Ther. 9, 663-670.

Ghoreschi, K., et al. Janus kinases in immune cell signaling. (2009). Immunol. Rev.,228, 273-287.

Mesa, R.A. and Tefferi, A. Emerging drugs for the therapy of primary and post essential thrombocythemia, post polycythemia vera myelofibrosis (2009). Expert Opin. Emerging Drugs, 14, 1-9.

Roll, J.D. and Reuther, G.W. CRLF2 and JAK2 in B-progenitor acute lymphoblastic leukemia: a novel association in oncogenesis. (2010) Cancer Res, 70, 7347-7352.

Rui et al., Cooperative epigenetic modulation by cancer amplicon genes (2010). Cancer Cell, 18, 590-605.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr DDT01-03. doi:10.1158/1538-7445.AM2011-DDT01-03

Pyrrolo[1,2-f]triazines as JAK2 inhibitors: achieving potency and selectivity for JAK2 over JAK3

SAR studies of pyrrolo[1,2-f]triazines as JAK2 inhibitors is presented. Achieving JAK2 inhibition selectively over JAK3 is discussed.

Drug discovery approaches to target Wnt signaling in cancer stem cells

Cancer stem cells (CSCs) represent a unique subset of cells within a tumor that possess self-renewal capacity and pluripotency, and can drive tumor initiation and maintenance. First identified in hematological malignancies, CSCs are now thought to play an important role in a wide variety of solid tumors such as NSCLC, breast and colorectal cancer. The role of CSCs in driving tumor formation illustrates the dysregulation of differentiation in tumorigenesis. The Wnt, Notch and Hedgehog (HH) pathways are developmental pathways that are commonly activated in many types of cancer. While substantial progress has been made in developing therapeutics targeting Notch and HH, the Wnt pathway has remained an elusive therapeutic target. This review will focus on the clinical relevance of the Wnt pathway in CSCs and tumor cell biology, as well as points of therapeutic intervention and recent advances in targeting Wnt/β-catenin signaling.

Constitutively active receptor tyrosine kinases as oncogenes in preclinical models for cancer therapeutics

Receptor tyrosine kinases (RTK) remain an area of therapeutic interest because of their role in epithelial tumors, and experimental models specific to these targets are highly desirable. Chimeric receptors were prepared by in-frame fusion of the CD8 extracellular sequence with the cytoplasmic sequences of RTKs. A CD8HER2 fusion protein was shown to form disulfide-mediated homodimers and to transform fibroblasts and epithelial cells. CD8RTK fusion proteins transform rat kidney epithelial cells and impart phenotypes that may reflect signaling specificity inherent in the native receptors. Transgenic expression of CD8HER2 and CD8Met in mice resulted in the formation of salivary and mammary gland tumors. The transgenic tumors allow the derivation of allograft tumors and cell lines that are sensitive to inhibition by small molecule kinase inhibitors. This approach provides excellent cell and tumor models for the characterization of signaling properties of diverse RTKs and for the evaluation of rationally designed antagonists targeting these kinases.

Identification of a novel series of tetrahydrodibenzazocines as inhibitors of 17β-hydroxysteroid dehydrogenase type 3

A novel series of 17beta-hydroxysteroid dehydrogenase type 3 (17beta-HSD3) inhibitors has been identified. These inhibitors, based on a dibenzazocine core, exhibited picomolar to low nanomolar inhibition of 17beta-HSD3 in cell-free enzymatic as well as in cell-based transcriptional reporter assays.

Identification of novel functional inhibitors of 17beta-hydroxysteroid dehydrogenase type III (17beta-HSD3)

BACKGROUND

Endocrine therapy of prostate cancer (PCa) relies on agents which disrupt the biosynthesis of testosterone in the testis and/or by direct antagonism of active hormone on the androgen receptor (AR) in non-gonadal target tissues of hormone action such as the prostate.

METHODS

In an effort to evaluate new therapies which could inhibit gonadal or non-gonadal testosterone biosynthesis, we developed high throughput biochemical and cellular screening assays to identify inhibitors of 17beta-hydroxysteroid dehydrogenase type III (17beta-HSD3), the enzyme catalyzing the conversion of androstenedione (AdT) to testosterone.

RESULTS

Initial screening efforts identified a natural product, 18beta-glycyrrhetinic acid, and a novel derivative of AdT, 3-O-benzylandrosterone, as potent inhibitors of the enzyme. Further efforts led to the identification of several classes of non-steroidal, low molecular weight compounds that potently inhibited 17beta-HSD3 enzymatic activity. One of the most potent classes of 17beta-HSD3 inhibitors was a series of anthranilamide small molecules identified from a collection of compounds related to non-steroidal modulators of nuclear hormone receptors. The anthranilamide based 17beta-HSD3 inhibitors were exemplified by BMS-856, a compound displaying low nanomolar inhibition of 17beta-HSD3 enzymatic activity. In addition, this series of compounds displayed potent inhibition of 17beta-HSD3-mediated cellular conversion of AdT to testosterone and inhibited the 17beta-HSD3-mediated conversion of testosterone necessary to promote AR-dependent transcription.

CONCLUSIONS

The identification of non-steroidal functional inhibitors of 17beta-HSD3 may be a useful complementary approach for the disruption of testosterone biosynthesis in the treatment of PCa.

Synthetic lethality of retinoblastoma mutant cells in the Drosophila eye by mutation of a novel peptidyl prolyl isomerase gene

Mutations that inactivate the retinoblastoma (Rb) pathway are common in human tumors. Such mutations promote tumor growth by deregulating the G1 cell cycle checkpoint. However, uncontrolled cell cycle progression can also produce new liabilities for cell survival. To uncover such liabilities in Rb mutant cells, we performed a clonal screen in the Drosophila eye to identify second-site mutations that eliminate Rbf(-) cells, but allow Rbf(+) cells to survive. Here we report the identification of a mutation in a novel highly conserved peptidyl prolyl isomerase (PPIase) that selectively eliminates Rbf(-) cells from the Drosophila eye.

Rho exchange factor ECT2 is induced by growth factors and regulates cytokinesis through the N-terminal cell cycle regulator-related domains

The ECT2 protooncogene plays a critical role in cytokinesis, and its C-terminal half encodes a Dbl homology-pleckstrin homology module, which catalyzes guanine nucleotide exchange on the Rho family of small GTPases. The N-terminal half of ECT2 (ECT2-N) contains domains related to the cell cycle regulator/checkpoint control proteins including human XRCC1, budding yeast CLB6, and fission yeast Cut5. The Cut5-related domain consists of two BRCT repeats, which are widespread to repair/checkpoint control proteins. ECT2 is ubiquitously expressed in various tissues and cell lines, but elevated levels of ECT2 expression were found in various tumor cell lines and rapidly developing tissues in mouse embryos. Consistent with these findings, induction of ECT2 expression was observed upon stimulation by serum or various growth factors. In contrast to other oncogenes whose expression is induced early in G1, ECT2 expression was induced later, coinciding with the initiation of DNA synthesis. To test the role of the cell cycle regulator/checkpoint control protein-related domains of ECT2 in cytokinesis, we expressed various ECT2 derivatives in U2OS cells, and analyzed their DNA content by flow cytometry. Expression of the N-terminal half of ECT2, which lacks the catalytic domain, generated cells with more than 4N DNA content, suggesting that cytokinesis was inhibited in these cells. Interestingly, ECT2-N lacking the nuclear localization signals inhibited cytokinesis more strongly than the derivatives containing these signals. Mutational analyses revealed that the XRCC1, CLB6, and BRCT domains in ECT2-N are all essential for the cytokinesis inhibition by ECT2-N. These results suggest that the XRCC1, CLB6, and BRCT domains of ECT2 play a critical role in regulating cytokinesis.

Deregulation and mislocalization of the cytokinesis regulator ECT2 activate the Rho signaling pathways leading to malignant transformation

The human ECT2 protooncogene encodes a guanine nucleotide exchange factor for the Rho GTPases and regulates cytokinesis. Although the oncogenic form of ECT2 contains an N-terminal truncation, it is not clear how the structural abnormality of ECT2 causes malignant transformation. Here we show that both the removal of the negative regulatory domain and alteration of subcellular localization are required to induce the oncogenic activity of ECT2. The transforming activity of oncogenic ECT2 was strongly inhibited by dominant negative Rho GTPases, suggesting the involvement of Rho GTPases in ECT2 transformation. Although deletion of the N-terminal cell cycle regulator-related domain (N) of ECT2 did not activate its transforming activity, removal of the small central domain (S), which contains two nuclear localization signals (NLSs), significantly induced the activity. The ECT2 N domain interacted with the catalytic domain and significantly inhibited the focus formation by oncogenic ECT2. Interestingly, the introduction of the NLS mutations in the S domain of N-terminally truncated ECT2 dramatically induced the transforming activity of this otherwise non-oncogenic derivative. Among the known Rho GTPases expressed in NIH 3T3 cells, RhoA was predominantly activated by oncogenic ECT2 in vivo. Therefore, the mislocalization of structurally altered ECT2 might cause the untimely activation of cytoplasmic Rho GTPases leading to the malignant transformation.

Selective retinoids and rexinoids in cancer therapy and chemoprevention

Natural and synthetic retinoids are effective inhibitors of tumor cell growth in vitro and in vivo. However, the toxicity of natural derivatives of vitamin A limits their therapeutic use. Recently, synthetic compounds selective for the different retinoid receptor isotypes have been generated that circumvent pan-retinoid toxicity. The tumor-suppressive activity of selective retinoid and/or rexinoid ligands has been established preclinically, and emerging clinical trials are supportive of the chemotherapeutic and chemopreventive potential of these compounds in multiple oncology indications, with reduced toxicity. Moreover, the combination of retinoids and/or rexinoids with chemotherapeutic agents for the synergistic modulation of specific pathways could also be of benefit in cancer therapy.

Synergistic cytotoxicity exhibited by combination treatment of selective retinoid ligands with taxol (Paclitaxel)

The focus of this study was to develop retinoic acid receptor (RAR) RAR alpha/beta selective agonists with anticancer efficacy and reduced toxicity associated with RAR gamma activity. In these studies, we report the identification and characterization of high-affinity RAR alpha/beta selective agonists with limited RAR gamma activity. These compounds inhibited human tumor cell line proliferation with similar efficacy to that observed for a pan-RAR agonist. However, for most tumor cell lines, the efficacy of these compounds was restricted to the micromolar range. To determine whether the RAR alpha/beta selective agonists could be additive or synergistic with existing agents, we investigated the effects of combining RAR alpha/beta selective agonists with various cytotoxic agents. Our results showed that the alpha/beta selective retinoids dramatically lowered the effective dose of Taxol needed to induce cytotoxicity of a wide range of tumor cell lines. This synergy was specific to tubulin-modifying agents and could not be observed with a variety of other cytotoxic agents of diverse function. Examination of pathways common to Taxol and retinoid signaling revealed that this synergy was related in part to effects on Bcl-2 expression/phosphorylation as well as the activity of the c-Jun NH(2)-terminal kinase and activator protein-1. In contrast, the tubulin polymerization induced by Taxol was not further affected by cotreatment with a variety of retinoid receptor ligands. These observations indicate that potent RAR alpha/beta selective agonists may be of therapeutic benefit in combination with Taxol therapy.

Tumor necrosis factor-alpha induces the expression of DR6, a member of the TNF receptor family, through activation of NF-kappaB

The tumor necrosis factor (TNF) receptor family are ligand-regulated transmembrane proteins that mediate apoptosis as well as activation of the transcription factor NF-kappaB. Exogenous expression of DR6, a recently identified member of the TNF receptor family, induced apoptosis in untransformed or tumor-derived cells and the apoptotic function of DR6 was inhibited by co-expression of Bcl-2, Bcl-x(L) or the inhibitor-of-apoptosis (IAP) family member, survivin. Expression of a dominant negative mutant of FADD failed to protect from DR6-mediated apoptosis indicating that unlike TNFR1 and Fas, DR6 induced apoptosis via a FADD-independent mechanism. Despite the ability of exogenous DR6 expression to induce apoptosis, DR6 mRNA and protein were found to be elevated in prostate tumor cell lines and in advanced stages of prostate cancer. Analysis of several anti-apoptotic proteins revealed that Bcl-x(L) levels and serine 32 phosphorylation of IkappaB, the natural inhibitor of NF-kappaB, were similarly elevated in cells expressing high levels of DR6, suggesting that NF-kappaB-regulated survival proteins may protect from DR6-induced apoptosis and that DR6 is a target of NF-kappaB regulation. Treatment of LnCAP cells with TNF-alpha resulted in increases in both DR6 mRNA and protein levels, and this induction was suppressed by inhibitors of NF-kappaB. Similarly, treatment of cells expressing high levels of DR6 with indomethacin and ibuprofen, compounds also known to perturb NF-kappaB function, resulted in a dose-dependent decrease in DR6 protein and mRNA levels. These results demonstrate that TNF-alpha signaling induces the expression of a member of its own receptor family through activation of NF-kappaB.

Ostip2, a novel oncoprotein that associates with the Rho exchange factor Ost

The ost protooncogene encodes a guanine nucleotide exchange factor for the Rho family of small GTPases, RhoA and Cdc42. The N-terminal domain of Ost (Ost-N) appears to negatively regulate the oncogenic activity of the protein, as deletion of this domain drastically increases its transforming activity in NIH 3T3 cells. Using a yeast two-hybrid system, we identified five genes encoding proteins that can interact with Ost-N. One of them, designated OSTIP2 (Ost interacting protein 2), encoded a previously uncharacterized protein. The OSTIP2 product is highly expressed in skeletal muscle as a 1.2-kb transcript. Full-length OSTIP2 cDNA contained an ORF of 193 amino acids. Transcription-coupled translation of OSTIP2 cDNA in reticulocyte lysates revealed a protein product of 20 kDa, which corresponded to the predicted size of the protein. Bacterially expressed glutathione S-transferase (GST)-Ostip2 fusion protein efficiently associated in vitro with baculovirus-expressed Ost. Interestingly, expression of Ostip2 in NIH 3T3 cells efficiently induced foci of morphologically transformed cells. Moreover, inoculation of athymic (nude) mice with OSTIP2 transfectants strongly induced tumor formation. These results suggest that Ostip2 is a novel oncoprotein that can interact with the Rho exchange factor Ost.

The RIP-like kinase, RIP3, induces apoptosis and NF-kappaB nuclear translocation and localizes to mitochondria

A RIP-like protein, RIP3, has recently been reported that contains an N-terminal kinase domain and a novel C-terminal domain that promotes apoptosis. These experiments further characterize RIP3-mediated apoptosis and NF-kappaB activation. Northern blots indicate that rip3 mRNA displays a restricted pattern of expression including regions of the adult central nervous system. The rip3 gene was localized by fluorescent in situ hybridization to human chromosome 14q11.2, a region frequently altered in several types of neoplasia. RIP3-mediated apoptosis was inhibited by Bcl-2, Bcl-x(L), dominant-negative FADD, as well as the general caspase inhibitor Z-VAD. Further dissection of caspase involvement in RIP3-induced apoptosis indicated inhibition by the more specific inhibitors Z-DEVD (caspase-3, -6, -7, -8, and -10) and Z-VDVAD (caspase-2). However, caspase-1, -6, -8 and -9 inhibitors had little or no effect on RIP3-mediated apoptosis. Mutational analysis of RIP3 revealed that the C-terminus of RIP3 contributed to its apoptotic activity. This region is similar, but distinct, to the death domain found in many pro-apoptotic receptors and adapter proteins, including FAS, FADD, TNFR1, and RIP. Furthermore, point mutations of RIP3 at amino acids conserved among death domains, abrogated its apoptotic activity. RIP3 was localized by immunofluorescence to the mitochondrion and may play a key role in the mitochondrial disruptions often associated with apoptosis.

Neu differentiation factor/heregulin induction by hepatocyte and keratinocyte growth factors

Hepatocyte growth-factor (HGF) is a potent, widely produced, pleiotropic mediator of mesenchymal-epithelial interaction. In a study of changes in gene expression initiated by HGF in Balb/MK keratinocytes, we observed the induction of Neu-differentiation factor (NDF) mRNA (also known as heregulin, or HRG). Further characterization of the regulation of NDF expression in Balb/MK keratinocytes revealed potent induction by keratinocyte growth factor (KGF) and epidermal growth factor (EGF), but not by HGF/NK2, an alternative HGF isoform with motogenic but not mitogenic or morphogenic activities. Sustained treatment (8 h) of Balb/MK cells with KGF stimulated secretion of mature NDF protein into the culture medium, and Balb/ MK cells treated with purified recombinant NDF protein showed increased DNA synthesis. We also found evidence of NDF induction in two models of tissue repair in mice: in full-thickness skin wounds, following locally increased KGF production, and in kidney after partial hepatectomy, following elevation of circulating HGF levels. These results reveal that mesenchymally-derived HGF and KGF can activate autocrine NDF signaling in their epithelial targets, and suggest that this mechanism contributes to the coordination of stages of wound repair, and possibly development, where these growth factors act in concert to direct epithelial proliferation, morphogenesis and differentiation.

Homocysteine exerts cell type-specific inhibition of AP-1 transcription factor

Homocysteine (Hcy) exerts either promoting or suppressive effects on mitogenesis in a cell type-specific manner. Hcy elicits proliferation of vascular smooth muscle cells, but is rather inhibitory to growth of endothelial cells and NIH/3T3 cells. In NIH/3T3 cells, we found that physiologically relevant concentrations (20-100 microM) of Hcy inhibit the activity of activating protein-1 (AP-1) transcription factor, although it is capable of eliciting immediate-early signaling events. Hcy induced p44/42 mitogen-activated protein kinase (MAPK) phosphorylation in control cells, but not in dominant negative p21ras transfected cells, indicating induction of the Ras-MAPK pathway. Hcy also induced the activity of serum response factor and expression of c-fos and c-jun genes. Despite the activation of these upstream events, Hcy potently inhibited AP-1 activity. Oxidized forms of Hcy (Hcy thiolactone, homocystine) were less effective in affecting AP-1. Hcy-mediated inhibition of AP-1 activity was not observed in A7r5 vascular smooth muscle cells. These results demonstrate that Hcy exerts cell type- and redox-specific inhibition of AP-1 dependent biological events.

Human FRAG1 encodes a novel membrane-spanning protein that localizes to chromosome 11p15.5, a region of frequent loss of heterozygosity in cancer

We have previously identified a chromosomal rearrangement between fibroblast growth factor receptor 2 (FGFR2) and a novel gene, FRAG1, in a rodent model of osteosarcoma. To assess the potential role of FRAG1 in disease further, we have isolated cDNA and genomic clones of human FRAG1. Sequence analysis of the cDNA revealed the presence of an insertion not contained in the original FRAG1 sequence. This insertion in human FRAG1 encoded a region highly homologous to and immediately following the first 55 amino acids of the protein, indicating the presence of a repetitive domain within FRAG1, designated the FRAG1 homology (FH) domain. Analysis of FRAG1 gene structure revealed that the FH domains were encoded by tandem duplicated exons. Database searches identified several transmembrane proteins displaying homology to the FH domain of FRAG1. In addition, hydropathy analysis predicted FRAG1 to encode an integral membrane protein with multiple membrane-spanning segments. FRAG1 mRNA was ubiquitously expressed in human adult tissues and several tumor cell lines at varying levels of abundance. Human FRAG1 was mapped by fluorescence in situ hybridization and radiation hybrid analysis to chromosome 11 at band p15.5, a region implicated in Beckwith-Wiedemann syndrome and a region of frequent loss of heterozygosity in multiple tumor types. These results suggest that FRAG1 may be a useful candidate gene for genetic disorders associated with alterations at 11p15.5.

The acidic domain and first immunoglobulin-like loop of fibroblast growth factor receptor 2 modulate downstream signaling through glycosaminoglycan modification

Fibroblast growth factor receptors (FGFRs) are membrane-spanning tyrosine kinases that have been implicated in a variety of biological processes including mitogenesis, cell migration, development, and differentiation. We identified a unique isoform of FGFR2 expressed as a diffuse band with an unusually large molecular mass. This receptor is modified by glycosaminoglycan at a Ser residue located immediately N terminal to the acidic box, a stretch of acidic amino acids. The acidic box and the glycosaminoglycan modification site are encoded by an alternative exon of the FGFR2 gene. The acidic box appears to play an important role in glycosaminoglycan modification, and the presence of this domain is required for modification by heparan sulfate glycosaminoglycan. Moreover, the presence of the first immunoglobulin-like domain encoded by another alternative exon abrogated the modification. The high-affinity receptor with heparan sulfate modification enhanced receptor autophosphorylation, substrate phosphorylation, and ternary complex factor-independent gene expression. It also sustained mitogen-activated protein kinase activity and increased eventual DNA synthesis, a long-term response to fibroblast growth factor stimulation, at physiological ligand concentrations. We propose a novel regulation mechanism of FGFR2 signal transduction through glycosaminoglycan modification.

Identification of a novel activated form of the keratinocyte growth factor receptor by expression cloning from parathyroid adenoma tissue

Parathyroid adenomas are benign tumors in the parathyroid glands, whose pathogenesis is largely unknown. We utilized an expression cDNA cloning strategy to identify oncogenes activated in parathyroid adenomas. An expression cDNA library was prepared directly from a clinical sample of parathyroid adenoma tissue, transfected into NIH3T3 cells, and foci of morphologically transformed cells were isolated. Following plasmid rescue, we identified cDNAs for the keratinocyte growth factor receptor at a high frequency. Interestingly, approximately half of the clones encoded a variant receptor containing an altered C-terminus. Analysis of the transforming activity of the variant receptor revealed that the altered C-terminus up-regulated the transforming activity in a ligand-independent manner. The higher transforming activity was not accompanied by increase of dimerization or overall autophosphorylation of the receptor. However, tyrosine phosphorylation of downstream receptor substrates, including Shc isoforms and possibly FRS2, are increased in the transfectants expressing the parathyroid tumor-derived receptor. Genomic analysis showed that a previously unidentified exon was used to form the novel isoform. This alternative splicing appears to occur preferentially in parathyroid adenomas.

Distinct expression patterns and transforming properties of multiple isoforms of Ost, an exchange factor for RhoA and Cdc42

A search for transforming genes expressed in brain led to the identification of a novel isoform of Ost, an exchange factor for RhoA and Cdc42. In addition to the Dbl-homology (DH) and pleckstrin-homology (PH) domains identified in the original Ost, this isoform contained a SH3 domain and a novel HIV-Tat related (TR) domain. The presence or absence of these domains in Ost defined multiple isoforms of the protein. RT - PCR and in situ hybridization analysis revealed that these isoforms were generated by tissue-specific and developmentally restricted alternative splicing events. Whereas deletion of the N-terminus activated the transforming properties of Ost, the presence of the SH3 domain reduced the transforming activity of the protein. This inhibition was relieved by the presence of a TR domain, which contained a potential SH3 ligand sequence. The transforming activity of all Ost isoforms was inhibited by dominant negative forms of the Rho family proteins. Expression of Ost isoforms potently induced the formation of actin stress fibers and filopodia as well as JNK activity and AP1- and SRF-regulated transcriptional pathways. Ost transfectants also displayed elevated levels of cyclins A and D1, suggesting that the de-regulation of these cyclins is linked to Ost-mediated transformation.

Human T-cell lymphotropic/leukemia virus type 1 Tax abrogates p53-induced cell cycle arrest and apoptosis through its CREB/ATF functional domain

Human T-cell lymphotropic/leukemia virus type 1 (HTLV-1) transforms human T cells in vitro, and Tax, a potent transactivator of viral and cellular genes, plays a key role in cell immortalization. Tax activity is mediated by interaction with cellular transcription factors including members of the CREB/ATF family, the NF-kappaB/c-Rel family, serum response factor, and the coactivators CREB binding protein-p300. Although p53 is usually not mutated in HTLV-1-infected T cells, its half-life is increased and its function is impaired. Here we report that transient coexpression of p53 and Tax results in the suppression of p53 transcriptional activity. Expression of Tax abrogates p53-induced G1 arrest in the Calu-6 cell line and prevents the apoptosis induced by overexpressing p53 in the HeLa/Tat cell line. The Tax mutants M22 and G148V, which selectively activate the CREB/ATF pathway, exert these same biological effects on p53 function. In contrast, the NF-kappaB-active Tax mutant M47 has no effect on p53 activity in any of these systems. Consistent with the negative effect of Tax on p53, no activity on a p53-responsive promoter was observed upon transfection of HTLV-1-infected T-cell lines. The p53 protein is expressed at high levels in the nucleus, and nuclear extracts of HTLV-1-infected T cells bind constitutively to a DNA oligonucleotide containing the p53 response element, indicating that Tax does not interfere with p53 binding to DNA. Tax is able to suppress the transactivation function of p53 in three different cell lines, and this suppression required Tax-mediated activation of the CREB/ATF, but not the NF-kappaB/c-Rel, pathway. Tax and the active Tax mutants were able to abrogate the G1 arrest and apoptosis induced by p53, and this effect does not correlate with an altered localization of nuclear p53 or with the disruption of p53-DNA complexes. The suppression of p53 activity by Tax could be important in T-cell immortalization induced by HTLV-1.

Identification and characterization of R-ras3: a novel member of the RAS gene family with a non-ubiquitous pattern of tissue distribution

Members of the Ras subfamily of GTP-binding proteins, including Ras (H-, K-, and N-), TC21, and R-ras have been shown to display transforming activity, and activating lesions have been detected in human tumors. We have identified an additional member of the Ras gene family which shows significant sequence similarity to the human TC21 gene. This novel human ras-related gene, R-ras3, encodes for a protein of 209 amino acids, and shows approximately 60-75% sequence identity in the N-terminal catalytic domain with members of the Ras subfamily of GTP-binding proteins. An activating mutation corresponding to the leucine 61 oncogenic lesion of the ras oncogenes when introduced into R-ras3, activates its transforming potential. R-ras3 weakly stimulates the mitogen-activated protein kinase (MAPK) activity, but this effect is greatly potentiated by the co-expression of c-raf-1. By the yeast two-hybrid system, R-ras3 interacts only weakly with known Ras effectors, such as Raf and RalGDS, but not with RglII. In addition, R-ras3 displays modest stimulatory effects on trans-activation from different nuclear response elements which bind transcription factors, such as SRF, ETS/TCF, Jun/Fos, and NF-kappaB/Rel. Interestingly, Northern blot analysis of total RNA isolated from various tissues revealed that the 3.8 kilobasepair (kb) transcript of R-ras3 is highly restricted to the brain and heart. The close evolutionary conservation between R-ras3 and Ras family members, in contrast to the significant differences in its biological activities and the pattern of tissue expression, raise the possibility that R-ras3 may control novel cellular functions previously not described for other GTP-binding proteins.