Novel OX40 and 4-1BB derived spacers enhance CD30 CAR activity and safety in CD30 positive lymphoma models.

The chimeric antigen receptor (CAR) derived from the CD30 specific murine antibody, HRS-3, has produced promising clinical efficacy with a favorable safety profile in the treatment of relapsed or refractory CD30-positive lymphomas. However, persistence of the autologous CAR-T cells was brief, and many patients relapsed a year after treatment. The lack of persistence may be attributed to the use of a wild-type immunoglobulin (Ig)G1 spacer that can associate with Fc receptors. We first identified the cysteine-rich domain (CRD) 5 of CD30 as the primary binding epitope of HRS-3 and armed with this insight, attempted to improve the HRS-3 CAR functionality with a panel of novel spacer designs. We demonstrate that HRS-3 CARs with OX40 and 4-1BB derived spacers exhibited similar anti-tumor efficacy, circumvented interactions with Fc receptors, and secreted lower levels of cytokines in vitro than a CAR employing the IgG1 spacer. Humanization of the HRS-3 scFv coupled with the 4-1BB spacer preserved potent on-target, on-tumor efficacy, and on-target, off-tumor safety. In a lymphoma mouse model of high tumor burden, T cells expressing humanized HRS-3 CD30.CARs with the 4-1BB spacer potently killed tumors with low levels of circulating inflammatory cytokines, providing a promising candidate for future clinical development in the treatment of CD30-positive malignancies.

Overexpression of an Engineered SERPINB9 Enhances Allogeneic T-cell Persistence and Efficacy.

Allogeneic chimeric antigen receptor (CAR)-expressing T cells offer many advantages over autologous therapies, but their benefits are curtailed by graft-versus-host disease and elimination by recipient immune cells. Moreover, just as with autologous therapies, allogeneic CAR T cells are susceptible to activation-induced cell death (AICD) caused by chronic antigen exposure (CAE). Granzyme B- and Fas/Fas ligand-initiated caspase-mediated apoptoses are key mechanisms of T-cell death caused by T/NK cell-mediated allorejection or CAE. We explored a protective strategy of engineering CAR T cells to overexpress variants of the Granzyme B-specific serine protease inhibitor SERPINB9 (SB9) to improve allogeneic T-cell persistence and antitumor efficacy. We showed that the overexpression of an SB9 variant with broadened caspase specificity, SB9(CAS), not only significantly reduced rejection of allogeneic CAR T cells but also increased their resistance to AICD and enabled them to thrive better under CAE, thus improving allogeneic T-cell persistence and antitumor activity in vitro and in vivo. In addition, although SB9(CAS) overexpression improved the efficacy of allogeneic CAR T-cell therapy by conferring protection to cell death, we did not observe any autonomous growth, and the engineered CAR T cells were still susceptible to an inducible suicide switch. Hence, SB9(CAS) overexpression is a promising strategy that can strengthen current development of cell therapies, broadening their applications to address unmet medical needs.

Targeting codon 158 p53-mutant cancers via the induction of p53 acetylation.

Gain of function (GOF) DNA binding domain (DBD) mutations of TP53 upregulate chromatin regulatory genes that promote genome-wide histone methylation and acetylation. Here, we therapeutically exploit the oncogenic GOF mechanisms of p53 codon 158 (Arg158) mutation, a DBD mutant found to be prevalent in lung carcinomas. Using high throughput compound screening and combination analyses, we uncover that acetylating mutp53R158G could render cancers susceptible to cisplatin-induced DNA stress. Acetylation of mutp53R158G alters DNA binding motifs and upregulates TRAIP, a RING domain-containing E3 ubiquitin ligase which dephosphorylates IĸB and impedes nuclear translocation of RelA (p65), thus repressing oncogenic nuclear factor kappa-B (NF-ĸB) signaling and inducing apoptosis. Given that this mechanism of cytotoxic vulnerability appears inapt in p53 wild-type (WT) or other hotspot GOF mutp53 cells, our work provides a therapeutic opportunity specific to Arg158-mutp53 tumors utilizing a regimen consisting of DNA-damaging agents and mutp53 acetylators, which is currently being pursued clinically.

A common MET polymorphism harnesses HER2 signaling to drive aggressive squamous cell carcinoma.

c-MET receptors are activated in cancers through genomic events like tyrosine kinase domain mutations, juxtamembrane splicing mutation and amplified copy numbers, which can be inhibited by c-MET small molecule inhibitors. Here, we discover that the most common polymorphism known to affect MET gene (N375S), involving the semaphorin domain, confers exquisite binding affinity for HER2 and enables METN375S to interact with HER2 in a ligand-independent fashion. The resultant METN375S/HER2 dimer transduces potent proliferative, pro-invasive and pro-metastatic cues through the HER2 signaling axis to drive aggressive squamous cell carcinomas of the head and neck (HNSCC) and lung (LUSC), and is associated with poor prognosis. Accordingly, HER2 blockers, but not c-MET inhibitors, are paradoxically effective at restraining in vivo and in vitro models expressing METN375S. These results establish METN375S as a biologically distinct and clinically actionable molecular subset of SCCs that are uniquely amenable to HER2 blocking therapies.

Sorafenib/MEK inhibitor combination inhibits tumor growth and the Wnt/ß­catenin pathway in xenograft models of hepatocellular carcinoma.

Mutations affecting the Wnt/ß­catenin pathway have been identified in 26­40% of hepatocellular carcinoma (HCC) cases. Aberrant activation of this pathway leads to uncontrolled cell proliferation and survival. Thus, identifying Wnt/ß­catenin pathway inhibitors may benefit a subset of patients with HCC. In the present study, the effects of sorafenib and a MEK inhibitor on tumor growth and Wnt/ß­catenin signaling in HCC models were evaluated. A ß­catenin mutant and ß­catenin wild­type HCC models were treated once daily with i) 10 mg/kg sorafenib, ii) 15 mg/kg refametinib (or 25 mg/kg selumetinib), or iii) sorafenib/refametinib. Western blotting was employed to determine changes in biomarkers relevant to Wnt/ß­catenin signaling. Apoptosis, cell proliferation and ß­catenin localization were analyzed by immunohistochemistry. Sorafenib/refametinib markedly inhibited tumor growth and cell proliferation, and caused cell death in naïve and sorafenib­resistant HCC models. Despite similar total ß­catenin levels, significant reductions in phosphorylated (p)­RanBP3 Ser58, p­ß­catenin Tyr142, active ß­catenin and ß­catenin target genes were observed in sorafenib/refametinib­treated tumors. Greater levels of ß­catenin in sorafenib/refametinib­treated tumors were accumulated at the membrane, as compared with in the control. In vitro, sorafenib/refametinib inhibited the Wnt/ß­catenin pathway and suppressed Wnt­3A­induced p­low­density lipoprotein receptor­related protein 6 Ser1490, p­RanBP3 Ser58 and p­ß­catenin Tyr142 in HCC cells. Combination of sorafenib and refametinib inhibits the growth of naïve and sorafenib resistant HCC tumors in association with active suppression of ß­catenin signaling regardless of ß­catenin mutational status. Thus, the sorafenib/MEK inhibitor combination may represent an alternative treatment for patients with HCC whose tumors develop resistance to sorafenib therapy.

Infigratinib Mediates Vascular Normalization, Impairs Metastasis, and Improves Chemotherapy in Hepatocellular Carcinoma.

The fibroblast growth factor (FGF) signaling cascade is a key signaling pathway in hepatocarcinogenesis. We report high FGF receptor (FGFR) expression in 17.7% (11 of 62) of hepatocellular carcinoma (HCC) models. Infigratinib, a pan-FGFR inhibitor, potently suppresses the growth of high-FGFR-expressing and sorafenib-resistant HCCs. Infigratinib inhibits FGFR signaling and its downstream targets, cell proliferation, the angiogenic rescue program, hypoxia, invasion, and metastasis. Infigratinib also induces apoptosis and vessel normalization and improves the overall survival of mice bearing FGFR-driven HCCs. Infigratinib acts in synergy with the microtubule-depolymerizing drug vinorelbine to promote apoptosis, suppress tumor growth, and improve the overall survival of mice. Increased expression levels of FGFR-2 and FGFR-3 through gene amplification correlate with treatment response and may serve as potential biomarkers for patient selection. Conclusion: Treatments with Infigratinib alone or in combination with vinorelbine may be effective in a subset of patients with HCC with FGFR-driven tumors.

Antitumor activity of the multikinase inhibitor regorafenib in patient-derived xenograft models of gastric cancer.

BACKGROUND: Unresectable gastric cancer is associated with poor outcomes, with few treatment options available after failure of cytotoxic chemotherapy. Clinical trials of targeted therapies have generally shown no survival benefit in gastric cancer, with the exceptions of the antibodies ramucirumab (anti-VEGFR2) and trastuzumab (anti-HER2/neu). Given the efficacy of the multikinase inhibitor regorafenib in other gastrointestinal tumors, we investigated its potential in gastric cancer. METHODS: The antitumor activity of oral regorafenib was assessed in eight murine patient-derived gastric cancer xenograft models. Dose-response experiments assessed the efficacy and tolerability of oral regorafenib 5, 10, and 15 mg/kg/day in two models, with 10 mg/kg/day selected for further investigation in all eight models. Tumor weight and volume was monitored during treatment; tumor cell proliferation, angiogenesis, apoptosis, and intracellular signaling were assessed using immunohistochemistry and Western blotting of total tumor lysates at the end of treatment. RESULTS: Regorafenib showed dose-dependent inhibition of tumor growth and was well tolerated, with no significant decreases in bodyweight or evident toxicity. Regorafenib 10 mg/kg/day significantly inhibited tumor growth in all eight models (72 to 96 %; all p < 0.01), resulting in reduced tumor weight versus vehicle controls. Regorafenib reduced tumor angiogenesis 3- to 11-fold versus controls in all models (all p < 0.05), reduced tumor proliferation 2- to 5-fold in six of the eight models (all p < 0.05), and induced apoptosis in seven models. CONCLUSION: Regorafenib was effective in patient-derived models of gastric cancer of different histological subtypes, with inhibition of tumor growth, angiogenesis, and tumor-cell proliferation observed in almost all models. These findings are consistent with the observed activity of regorafenib in preclinical models of other gastrointestinal tumors, and support further clinical investigation in gastric cancer.

Loss of Tuberous Sclerosis Complex 2 (TSC2) Is Frequent in Hepatocellular Carcinoma and Predicts Response to mTORC1 Inhibitor Everolimus.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide and hyperactivation of mTOR signaling plays a pivotal role in HCC tumorigenesis. Tuberous sclerosis complex (TSC), a heterodimer of TSC1 and TSC2, functions as a negative regulator of mTOR signaling. In the current study, we discovered that TSC2 loss-of-function is common in HCC. TSC2 loss was found in 4 of 8 HCC cell lines and 8 of 28 (28.6%) patient-derived HCC xenografts. TSC2 mutations and deletions are likely to be the underlying cause of TSC2 loss in HCC cell lines, xenografts, and primary tumors for most cases. We further demonstrated that TSC2-null HCC cell lines and xenografts had elevated mTOR signaling and, more importantly, were significantly more sensitive to RAD001/everolimus, an mTORC1 inhibitor. These preclinical findings led to the analysis of TSC2 status in HCC samples collected in the EVOLVE-1 clinical trial of everolimus using an optimized immunohistochemistry assay and identified 15 of 139 (10.8%) samples with low to undetectable levels of TSC2. Although the sample size is too small for formal statistical analysis, TSC2-null/low tumor patients who received everolimus tended to have longer overall survival than those who received placebo. Finally, we performed an epidemiology survey of more than 239 Asian HCC tumors and found the frequency of TSC2 loss to be approximately 20% in Asian HBV(+) HCC. Taken together, our data strongly argue that TSC2 loss is a predictive biomarker for the response to everolimus in HCC patients.

FGFR-Mediated Reactivation of MAPK Signaling Attenuates Antitumor Effects of Imatinib in Gastrointestinal Stromal Tumors.

UNLABELLED: Activating mutations in either KIT or PDGFRA are present in approximately 90% of gastrointestinal stromal tumors (GIST). Although treatment with the KIT and PDGFR inhibitor imatinib can control advanced disease in about 80% of GIST patients, the beneficial effect is not durable. Here, we report that ligands from the FGF family reduced the effectiveness of imatinib in GIST cells, and FGF2 and FGFR1 are highly expressed in all primary GIST samples examined. The combination of KIT and FGFR inhibition showed increased growth inhibition in imatinib-sensitive GIST cell lines and improved efficacy in patient-derived GIST xenografts. In addition, inhibition of MAPK signaling by imatinib was not sustained in GIST cells. An ERK rebound occurred through activation of FGF signaling, and was repressed by FGFR1 inhibition. Downregulation of Sprouty proteins played a role in the imatinib-induced feedback activation of FGF signaling in GIST cells. SIGNIFICANCE: We here show that FGFR-mediated reactivation of the MAPK pathway attenuates the antiproliferation effects of imatinib in GISTs. The imatinib-induced ERK rebound can be repressed by the FGFR inhibitor BGJ398, and combined KIT and FGFR inhibition leads to increased efficacy in vitro and in patient-derived xenografts.

Combination of the ERK inhibitor AZD6244 and low-dose sorafenib in a xenograft model of human renal cell carcinoma.

Sorafenib, a multikinase inhibitor, is currently used as monotherapy for advanced renal cell carcinoma (RCC). However, adverse effects associated with its use have been experienced by some patients. In this study, we examined the antitumor and antiangiogenic activities of low-dose sorafenib in combination with the MEK inhibitor AZD6244 (sorafenib/AZD6244) in a preclinical model of RCC. Primary RCC 08-0910 and RCC 786-0 cells as well as patient-derived RCC models were used to study the antitumor and antiangiogenic activities of sorafenib/AZD6244. Changes of biomarkers relevant to angiogenesis and cell cycle were determined by western immunoblotting. Microvessel density, apoptosis and cell proliferation were analyzed by immunohistochemistry. Treatment of RCC 786-0 cells with sorafenib/AZD6244 resulted in G1 cell cycle arrest and blockade of serum-induced cell migration. Sorafenib/AZD6244 induced apoptosis in primary RCC 08-0910 cells at low concentrations. In vivo addition of AZD6244 to sorafenib significantly augmented the antitumor activity of sorafenib and allowed dose reduction of sorafenib without compromising its antitumor activity. Sorafenib/AZD6244 potently inhibited angiogenesis and phosphorylation of VEGFR-2, PDGFR-ß and ERK, p90RSK, p70S6K, cdk-2 and retinoblastoma. Sorafenib/AZD6244 also caused upregulation of p27, Bad and Bim but downregulation of survivin and cyclin B1. These resulted in a reduction in cellular proliferation and the induction of tumor cell apoptosis. Our findings showed that AZD6244 and sorafenib complement each other to inhibit tumor growth. This study provides sound evidence for the clinical investigation of low-dose sorafenib in combination with AZD6244 in patients with advanced RCC.

Foretinib demonstrates anti-tumor activity and improves overall survival in preclinical models of hepatocellular carcinoma.

PURPOSE OF STUDY: Hepatocellular carcinoma (HCC) is the third leading cause of cancer death. Although sorafenib has been shown to improve survival of patients with advanced HCC, this improvement is modest and patients eventually have refractory disease. The purpose of this study is to assess the anti-tumor and anti-angiogenic activities of foretinib, a vascular endothelial growth factor receptor 2 (VEGFR-2) and c-Met inhibitor using mouse models of human HCC. EXPERIMENTAL TECHNIQUES: SK-HEP1 and 21-0208 HCC cells as well as patient-derived HCC models were employed to study the anti-tumor and antiangiogenic activities of foretinib. Changes of biomarkers relevant to hepatocyte growth factor (HGF) signaling pathways were determined by Western blotting. Microvessel density, apoptosis and cell proliferation were analyzed by immunohistochemistry. RESULTS: Treatment of SK-HEP1 cells with foretinib resulted in growth inhibition, G2/M cell cycle arrest, reduced colony formation and blockade of HGF-induced cell migration. In both orthotopic and ectopic models of HCC, foretinib potently inhibited tumor growth in a dose-dependent manner. Inhibition of angiogenesis correlated with inactivation of VEGFR-2/c-Met signaling pathways. Foretinib also caused elevation of p27 and Bim but reduced cyclin B1 expression and p-c-Myc, which resulted in a reduction in cellular proliferation and the induction of tumor cell apoptosis. In an orthotopic model, foretinib potently inhibited primary tumor growth and significantly prolonged mouse survival. DATA INTERPRETATIONS: Foretinib demonstrated significant antitumor activities in patient-derived HCC xenograft models. This study provides a compelling rationale for clinical investigation in patients with advanced HCC.

Dovitinib demonstrates antitumor and antimetastatic activities in xenograft models of hepatocellular carcinoma.

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is the third leading cause of cancer death. Although sorafenib has been shown to improve survival of patients with advanced HCC, this improvement is modest and patients eventually have refractory disease. This study aims at investigating the antitumor, antiangiogenesis and antimetastatic activities of dovitinib in preclinical models of HCC. METHODS: 21-0208 and SK-HEP1 cells as well as patient-derived HCC models were employed to study the antitumor effect of dovitinib. Changes of biomarkers relevant to FGFR/VEGFR/PDGFR pathways were determined by Western blotting. Microvessel density, apoptosis and cell proliferation were analyzed by immunohistochemistry. RESULTS: Treatment of SK-HEP1 cells with dovitinib resulted in G2/M cell cycle arrest, inhibition of colony formation in soft agar and blockade of bFGF-induced cell migration. Dovitinib inhibited basal expression and FGF-induced phosphorylation of FGFR-1, FRS2-α and ERK1/2. In vivo, dovitinib potently inhibited tumor growth of six HCC lines. Inhibition of angiogenesis correlated with inactivation of FGFR/PDGFR-ß/VEGFR-2 signaling pathways. Dovitinib also caused dephosphorylation of retinoblastoma, upregulation of p-histone H2A-X and p27, and downregulation of p-cdk-2 and cyclin B1, which resulted in a reduction in cellular proliferation and the induction of tumor cell apoptosis. In an orthotopic model, dovitinib potently inhibited primary tumor growth and lung metastasis and significantly prolonged mouse survival. CONCLUSIONS: Dovitinib demonstrated significant antitumor and antimetastatic activities in HCC xenograft models. This study provides a compelling rationale for clinical investigation in patients with advanced HCC.

Targeting receptor tyrosine kinase pathways in hepatocellular carcinoma.

Hepatocellular cancer (HCC) is the fifth most common malignancy worldwide with 660,000 deaths annually. Studies of the molecular pathophysiology of HCC have shown that growth factors and their corresponding receptors are commonly overexpressed and/or dysregulated in HCC. Activation of these receptors and their downstream signaling pathways can lead to angiogenesis, cell proliferation, survival and metastasis of HCC. Hence, agents that specifically block their activation and signaling cascades would be valuable for treatment of HCC. Many small molecular tyrosine kinase inhibitors (TKIs) and antibodies have been tested in various phases of clinical trials. Although sorafenib has been shown to improve overall survival of patients with advanced HCC, the improvement is marginal and many patients eventually turn out to be refractory to this therapy. Thus, there is a pressing need to identify new drugs and effective treatments for this fatal disease. This review summarizes the pre-clinical and clinical data on the efficacy of the emerging tyrosine kinase inhibitors as well as the rationale for combination therapies for advanced HCC treatment. Understanding the mechanisms of action of these therapeutic agents and methods of combining these drugs may help to increase their efficacy, reduce toxicity, and improve overall survival and quality of life in patients with HCC.