Stefan Kasper

A novel molecular mechanism of primary resistance to FLT3-kinase inhibitors in AML

Currently, FLT3 tyrosine kinase inhibitors (TKIs) are emerging as the most promising drug therapy to overcome the dismal prognosis of acute myelogenous leukemia (AML) patients harboring internal tandem duplications (ITDs) of FLT3. However, up-front drug resistance occurs in approximately 30% of patients, and molecular mechanisms of resistance are poorly understood. Here, we have uncovered a novel mechanism of primary resistance to FLT3 TKIs in AML: an FLT3 receptor harboring a nonjuxtamembrane ITD atypically integrating into the beta-2 sheet of the first kinase domain (FLT3_ITD627E) induces dramatic up-regulation of the anti-apoptotic myeloid cell leukemia 1 protein (MCL-1). Using RNA interference technology, deregulated MCL-1 protein expression was shown to play a major role in conferring the resistance phenotype of 32D_ITD627E cells. Enhanced and sustained binding of the adaptor protein GRB-2 to the FLT3_ITD627E receptor is involved in MCL-1 up-regulation and is independent from TKI (PKC412)-induced inhibition of the receptor kinase. Thus, we describe a new mechanism of primary resistance to TKIs, which operates by reprogramming local and distant signal transduction events of the FLT3 tyrosine kinase. The data presented suggest that particular ITDs of FLT3 may be associated with rewired signaling and differential responsiveness to TKIs.

Stabilization of Physical RAF/14-3-3 Interaction by Cotylenin A as Treatment Strategy for RAS Mutant Cancers

One-third of all human cancers harbor somatic RAS mutations. This leads to aberrant activation of downstream signaling pathways involving the RAF kinases. Current ATP-competitive RAF inhibitors are active in cancers with somatic RAF mutations, such as BRAF(V600) mutant melanomas. However, they paradoxically promote the growth of RAS mutant tumors, partly due to the complex interplay between different homo- and heterodimers of A-RAF, B-RAF, and C-RAF. Based on pathway analysis and structure-guided compound identification, we describe the natural product cotylenin-A (CN-A) as stabilizer of the physical interaction of C-RAF with 14-3-3 proteins. CN-A binds to inhibitory 14-3-3 interaction sites of C-RAF, pSer233, and pSer259, but not to the activating interaction site, pSer621. While CN-A alone is inactive in RAS mutant cancer models, combined treatment with CN-A and an anti-EGFR antibody synergistically suppresses tumor growth in vitro and in vivo. This defines a novel pharmacologic strategy for treatment of RAS mutant cancers.

LS104, a non-ATP-competitive small-molecule inhibitor of JAK2, is potently inducing apoptosis in JAK2V617F-positive cells

The activating JAK2V617F mutation has been described in the majority of patients with BCR-ABL-negative myeloproliferative disorders (MPD). In this report, we characterize the small-molecule LS104 as a novel non-ATP-competitive JAK2 inhibitor: Treatment of JAK2V617F-positive cells with LS104 resulted in dose-dependent induction of apoptosis and inhibition of JAK2 autophosphorylation and of downstream targets. Activation of these targets by JAK2 was confirmed in experiments using small interfering RNA. LS104 inhibited JAK2 kinase activity in vitro. This effect was not reversible using elevated ATP concentrations, whereas variation of the kinase substrate peptide led to modulation of the IC50 value for LS104. In line with these data, combination treatment using LS104 plus an ATP-competitive JAK2 inhibitor (JAK inhibitor I) led to synergistically increased apoptosis in JAK2V617F-positive cells. Furthermore, LS104 strongly inhibited cytokine-independent growth of endogenous erythroid colonies isolated from patients with JAK2V617F-positive MPD in vitro, whereas there was no significant effect on growth of myeloid colonies obtained from normal controls. Based on these data, we have recently started a phase I clinical trial of LS104 for patients with JAK2V617F-positive MPDs. To the best of our knowledge, this is the first report on a non-ATP-competitive kinase inhibitor being tested in a clinical trial. [Mol Cancer Ther 2008;7(5):1176–84]

Nivolumab versus standard, single-agent therapy of investigator's choice in recurrent or metastatic squamous cell carcinoma of the head and neck (CheckMate 141): health-related quality-of-life results from a randomised, phase 3 trial

BACKGROUNDnPatients with platinum-refractory recurrent or metastatic squamous cell carcinoma of the head and neck have few treatment options and poor prognosis. Nivolumab significantly improved survival of this patient population when compared with standard single-agent therapy of investigators choice in Checkmate 141; here we report the effect of nivolumab on patient-reported outcomes (PROs).nnnMETHODSnCheckMate 141 was a randomised, open-label, phase 3 trial in patients with recurrent or metastatic squamous cell carcinoma of the head and neck who progressed within 6 months after platinum-based chemotherapy. Patients were randomly assigned (2:1) to nivolumab 3 mg/kg every 2 weeks (n=240) or investigators choice (n=121) of methotrexate (40-60 mg/m2 of body surface area), docetaxel (30-40 mg/m2), or cetuximab (250 mg/m2 after a loading dose of 400 mg/m2) until disease progression, intolerable toxicity, or withdrawal of consent. On Jan 26, 2016, the independent data monitoring committee reviewed the data at the planned interim analysis and declared overall survival superiority for nivolumab over investigators choice therapy (primary endpoint; described previously). The protocol was amended to allow patients in the investigators choice group to cross over to nivolumab. All patients not on active therapy are being followed for survival. As an exploratory endpoint, PROs were assessed at baseline, week 9, and every 6 weeks thereafter using the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30), the EORTC head and neck cancer-specific module (EORTC QLQ-H&N35), and the three-level European Quality of Life-5 Dimensions (EQ-5D) questionnaire. Differences within and between treatment groups in PROs were analysed by ANCOVA among patients with baseline and at least one other assessment. All randomised patients were included in the time to clinically meaningful deterioration analyses. Median time to clinically meaningful deterioration was analysed by Kaplan-Meier methods. CheckMate 141 was registered with ClinicalTrials.org, number NCT02105636.nnnFINDINGSnPatients were enrolled between May 29, 2014, and July 31, 2015, and subsequently 361 patients were randomly assigned to receive nivolumab (n=240) or investigators choice (n=121). Among them, 129 patients (93 in the nivolumab group and 36 in the investigators choice group) completed any of the PRO questionnaires at baseline and at least one other assessment. Treatment with nivolumab resulted in adjusted mean changes from baseline to week 15 ranging from -2·1 to 5·4 across functional and symptom domains measured by the EORTC QLQ-C30, with no domains indicating clinically meaningful deterioration. By contrast, eight (53%) of the 15 domains in the investigators choice group showed clinically meaningful deterioration (10 points or more) at week 15 (change from baseline range, -24·5 to 2·4). Similarly, on the EORTC QLQ-H&N35, clinically meaningful worsening at week 15 was seen in no domains in the nivolumab group and eight (44%) of 18 domains in the investigators choice group. Patients in the nivolumab group had a clinically meaningful improvement (according to a difference of 7 points or greater) in adjusted mean change from baseline to week 15 on the EQ-5D visual analogue scale, in contrast to a clinically meaningful deterioration in the investigators choice group (7·3 vs -7·8). Differences between groups were significant and clinically meaningful at weeks 9 and 15 in favour of nivolumab for role functioning, social functioning, fatigue, dyspnoea, and appetite loss on the EORTC QLQ-C30 and pain and sensory problems on the EORTC QLQ-H&N35. Median time to deterioration was significantly longer with nivolumab versus investigators choice for 13 (37%) of 35 domains assessed across the three questionnaires.nnnINTERPRETATIONnIn this exploratory analysis of CheckMate 141, nivolumab stabilised symptoms and functioning from baseline to weeks 9 and 15, whereas investigators choice led to clinically meaningful deterioration. Nivolumab delayed time to deterioration of patient-reported quality-of-life outcomes compared with single-agent therapy of investigators choice in patients with platinum-refractory recurrent or metastatic squamous cell carcinoma of the head and neck. In view of the major unmet need in this population and the importance of maintaining or improving quality of life for patients with recurrent or metastatic squamous cell carcinoma of the head and neck, these data support nivolumab as a new standard-of-care option in this setting.nnnFUNDINGnBristol-Myers Squibb.

Buparlisib and paclitaxel in patients with platinum-pretreated recurrent or metastatic squamous cell carcinoma of the head and neck (BERIL-1): a randomised, double-blind, placebo-controlled phase 2 trial

BACKGROUNDnPhosphatidylinositol 3-kinase (PI3K) pathway activation in squamous cell carcinoma of the head and neck contributes to treatment resistance and disease progression. Buparlisib, a pan-PI3K inhibitor, has shown preclinical antitumour activity and objective responses in patients with epithelial malignancies. We assessed whether the addition of buparlisib to paclitaxel improves clinical outcomes compared with paclitaxel and placebo in patients with recurrent or metastatic squamous cell carcinoma of the head and neck.nnnMETHODSnIn this multicentre, randomised, double-blind, placebo-controlled phase 2 study (BERIL-1), we recruited patients aged 18 years and older with histologically or cytologically confirmed recurrent and metastatic squamous cell carcinoma of the head and neck after disease progression on or after one previous platinum-based chemotherapy regimen in the metastatic setting. Eligible patients were enrolled from 58 centres across 18 countries and randomly assigned (1:1) to receive second-line oral buparlisib (100 mg once daily) or placebo, plus intravenous paclitaxel (80 mg/m2 on days 1, 8, 15, and 22) in 28 day treatment cycles. Randomisation was done via a central patient screening and randomisation system with an interactive (voice and web) response system and stratification by number of previous lines of therapy in the recurrent and metastatic setting and study site. Patients and investigators (including local radiologists) were masked to treatment assignment from randomisation until the final overall survival analysis. The primary endpoint was progression-free survival by local investigator assessment per Response Evaluation Criteria In Solid Tumors (version 1.1) in all randomly assigned patients. Efficacy analyses were done on the intention-to-treat population, whereas safety was analysed in all patients who received at least one dose of study drug and had at least one post-baseline safety assessment according to the treatment they received. This trial is registered with ClinicalTrials.gov, number NCT01852292, and is ongoing but no longer enrolling patients.nnnFINDINGSnBetween Nov 5, 2013, and May 5, 2015, 158 patients were enrolled and randomly assigned to receive either buparlisib plus paclitaxel (n=79) or placebo plus paclitaxel (n=79). Median progression-free survival was 4·6 months (95% CI 3·5-5·3) in the buparlisib group and 3·5 months (2·2-3·7) in the placebo group (hazard ratio 0·65 [95% CI 0·45-0·95], nominal one-sided p=0·011). Grade 3-4 adverse events were reported in 62 (82%) of 76 patients in the buparlisib group and 56 (72%) of 78 patients in the placebo group. The most common grade 3-4 adverse events (occurring in ≥10% of patients in the buparlisib group vs the placebo group) were hyperglycaemia (17 [22%] of 76 vs two [3%] of 78), anaemia (14 [18%] vs nine [12%]), neutropenia (13 [17%] vs four [5%]), and fatigue (six [8%] vs eight [10%]). Serious adverse events (regardless of relation to study treatment) were reported for 43 (57%) of 76 patients in the buparlisib group and 37 (47%) of 78 in the placebo group. On-treatment deaths occurred in 15 (20%) of 76 patients in the buparlisib group and 17 (22%) of 78 patients in the placebo group; most were caused by disease progression and none were judged to be related to study treatment.nnnINTERPRETATIONnOn the basis of the improved clinical efficacy with a manageable safety profile, the results of this randomised phase 2 study suggest that buparlisib in combination with paclitaxel could be an effective second-line treatment for patients with platinum-pretreated recurrent or metastatic squamous cell carcinoma of the head and neck. Further phase 3 studies are warranted to confirm this phase 2 finding.nnnFUNDINGnNovartis Pharmaceuticals Corporation.

Transient ablation of regulatory T cells improves antitumor immunity in colitis-associated colon cancer.

Regulatory T cells (Treg) are supportive to cancer development in most tissues, but their role in colitis-associated colon cancer (CAC) remains unclear. In this study, we investigated the role of CD4(+)Foxp3(+) Treg in a mouse model of CAC and in patients with colon cancer. These Treg were increased strongly in number in a mouse model of CAC and in the peripheral blood of patients with colon cancer, exhibiting an activated phenotype as defined by elevated expression of GARP, CD103, CTLA-4, and IL10, along with an increased suppressive effect on the proliferation and Th1 cytokine expression of CD4(+)CD25(-) responder T cells ex vivo. Transient ablation of CD4(+)Foxp3(+) Treg during tumor development in the CAC model suppressed tumor outgrowth and distribution, accompanied by an increased number of CD8(+)IFNγ/granzyme B-producing effector T cells. Conversely, inactivation of IL10 in Treg did not elevate the antitumor response but instead further boosted tumor development. Our results establish a tumor-promoting function for Treg during CAC formation, but they also suggest that a selective, transient ablation of Treg can evoke antitumor responses, with implications for immunotherapeutic interventions in patients with CAC.

Targeted therapies in gastroesophageal cancer

Gastroesophageal cancers comprising gastric cancer (GC), and cancers of the distal oesophagus and gastroesophageal junction (GEJ) are a global health threat. In Western populations the incidence of GC is declining which has been attributed to effective strategies of eradicating Helicobacter pylori infection. To the contrary, GEJ cancers are on the rise, with obesity and reflux disease being viewed as major risk factors. During the past decade perioperative chemotherapy, pre- or postoperative radio-chemotherapy, and, in Asian populations, adjuvant chemotherapy have been shown to improve the outcome of patients with advanced GC and GEJ cancers suited for surgery. Less progress has been made in the treatment of metastatic disease. The introduction of trastuzumab in combination with platinum/fluoropyrimidine-based chemotherapy for patients with HER2-positive disease has marked a turning point. Recently, several novel agents targeting growth factor receptors, angiogenic pathways, adhesion molecules and mediators of intracellular signal transduction have been clinically explored. Here we summarise the current status and future developments of molecularly targeted therapies in GC and GEJ cancer.

Development of a highly sensitive and specific method for detection of circulating tumor cells harboring somatic mutations in non-small-cell lung cancer patients.

Background Oncogenic mutations are powerful predictive biomarkers for molecularly targeted cancer therapies. For mutation detection patients have to undergo invasive tumor biopsies. Alternatively, archival samples are used which may no longer reflect the actual tumor status. Circulating tumor cells (CTC) could serve as an alternative platform to detect somatic mutations in cancer patients. We sought to develop a sensitive and specific assay to detect mutations in the EGFR gene in CTC from lung cancer patients. Methods We developed a novel assay based on real-time polymerase chain reaction (PCR) and melting curve analysis to detect activating EGFR mutations in blood cell fractions enriched in CTC. Non-small-cell lung cancer (NSCLC) was chosen as disease model with reportedly very low CTC counts. The assay was prospectively validated in samples from patients with EGFR-mutant and EGFR-wild type NSCLC treated within a randomized clinical trial. Sequential analyses were conducted to monitor CTC signals during therapy and correlate mutation detection in CTC with treatment outcome. Results Assay sensitivity was optimized to enable detection of a single EGFR-mutant CTC/mL peripheral blood. CTC were detected in pretreatment blood samples from all 8 EGFR-mutant lung cancer patients studied. Loss of EGFR-mutant CTC signals correlated with treatment response, and its reoccurrence preceded relapse. Conclusions Despite low abundance of CTC in NSCLC oncogenic mutations can be reproducibly detected by applying an unbiased CTC enrichment strategy and highly sensitive PCR and melting curve analysis. This strategy may enable non-invasive, specific biomarker diagnostics and monitoring in patients undergoing targeted cancer therapies.

Functional expression cloning identifies COX-2 as a suppressor of antigen-specific cancer immunity

The efficacy of immune surveillance and antigen-specific cancer immunotherapy equally depends on the activation of a sustained immune response targeting cancer antigens and the susceptibility of cancer cells to immune effector mechanisms. Using functional expression cloning and T-cell receptor (TCR) transgenic mice, we have identified cyclooxygenase 2/prostaglandin-endoperoxide synthase 2 (COX-2) as resistance factor against the cytotoxicity induced by activated, antigen-specific T cells. Expressing COX-2, but not a catalytically inactive COX-2 mutant, increased the clonogenic survival of E1A-transformed murine cancer cells when cocultured with lymphocytes from St42Rag2−/− mice harboring a transgenic TCR directed against an E1A epitope. COX-2 expressing tumors established in immune-deficient mice were less susceptible to adoptive immunotherapy with TCR transgenic lymphocytes in vivo. Also, immune surveillance of COX-2-positive tumor cells in TCR transgenic mice was less efficient. The growth of murine MC-GP tumors, which show high endogenous COX-2 expression, in immunocompetent mice was effectively suppressed by treatment with a selective COX-2 inhibitor, celecoxib. Mechanistically, COX-2 expression blunted the interferon-gamma release of antigen-specific T cells exposed to their respective cellular targets, and increased the expression of interleukin-4 and indoleamine 2,3-dioxygenase by tumor cells. Addition of interferon-gamma sensitized COX-2 expressing cancer cells to tumor suppression by antigen-specific T cells. In conclusion, COX-2, which is frequently induced in colorectal cancer, contributes to immune evasion and resistance to antigen-specific cancer immunotherapy by local suppression of T-cell effector functions.

High Prevalence of Concomitant Oncogene Mutations in Prospectively Identified Patients with ROS1-Positive Metastatic Lung Cancer

Objectives: Chromosomal rearrangements involving ROS1 define a rare entity of lung adenocarcinomas with exquisite sensitivity to molecularly targeted therapy. We report clinical outcomes and genomic findings of patients with ROS1‐positive lung cancer who were prospectively identified within a multiplex biomarker profiling program at the West German Cancer Center. Methods: Standardized immunohistochemical (IHC) analysis, fluorescence in situ hybridization (FISH), and hotspot mutation analyses were performed in 1345 patients with advanced cancer, including 805 patients with metastatic lung adenocarcinoma. Clinical and epidemiological data were retrieved from the institutional database. Results: ROS1 positivity by IHC analysis was detected in 25 patients with lung cancer (4.8% of lung adenocarcinomas), including 13 patients (2.5%) with ROS1 FISH positivity with a cutoff of at least 15% of events. Of the ROS1 IHC analysis–positive cases, 36% presented with concomitant oncogenic driver mutations involving EGFR (six cases, five of which were clinically validated by response to EGFR‐targeting agents), KRAS (two cases), phosphatidylinositol‐4,5‐bisphosphate 3‐kinase catalytic subunit alpha gene (PIK3CA), and BRAF. Three cases initially classified as ROS1 FISH–negative passed the threshold of 15% positive events when repeat biopsies were analyzed at progression. The median overall survival of the ROS1‐positive patients (104 months) was significantly superior to that of the 261 patients with EGFR/anaplastic lymphoma kinase/ROS1–negative lung adenocarcinoma (24.4 months, p = 0.044). Interestingly, the overall survival of the 13 ROS1‐positive patients with lung cancer from initiation of pemetrexed‐based chemotherapy was significantly prolonged when compared with that of 169 pemetrexed‐treated patients with EGFR/anaplastic lymphoma kinase/ROS1–negative adenocarcinoma (p = 0.01). Conclusions: ROS1‐positive metastatic lung adenocarcinomas frequently harbor concomitant oncogenic driver mutations. Levels of ROS1 FISH–positive events are variable over time. This heterogeneity provides additional therapeutic options if discovered by multiplex biomarker testing and repeat biopsies.