Vorasidenib in IDH1- or IDH2-Mutant Low-Grade Glioma

BACKGROUND

Isocitrate dehydrogenase (IDH)-mutant grade 2 gliomas are malignant brain tumors that cause considerable disability and premature death. Vorasidenib, an oral brain-penetrant inhibitor of mutant IDH1 and IDH2 enzymes, showed preliminary activity in IDH-mutant gliomas.

METHODS

In a double-blind, phase 3 trial, we randomly assigned patients with residual or recurrent grade 2 IDH-mutant glioma who had undergone no previous treatment other than surgery to receive either oral vorasidenib (40 mg once daily) or matched placebo in 28-day cycles. The primary end point was imaging-based progression-free survival according to blinded assessment by an independent review committee. The key secondary end point was the time to the next anticancer intervention. Crossover to vorasidenib from placebo was permitted on confirmation of imaging-based disease progression. Safety was also assessed.

RESULTS

A total of 331 patients were assigned to receive vorasidenib (168 patients) or placebo (163 patients). At a median follow-up of 14.2 months, 226 patients (68.3%) were continuing to receive vorasidenib or placebo. Progression-free survival was significantly improved in the vorasidenib group as compared with the placebo group (median progression-free survival, 27.7 months vs. 11.1 months; hazard ratio for disease progression or death, 0.39; 95% confidence interval [CI], 0.27 to 0.56; P<0.001). The time to the next intervention was significantly improved in the vorasidenib group as compared with the placebo group (hazard ratio, 0.26; 95% CI, 0.15 to 0.43; P<0.001). Adverse events of grade 3 or higher occurred in 22.8% of the patients who received vorasidenib and in 13.5% of those who received placebo. An increased alanine aminotransferase level of grade 3 or higher occurred in 9.6% of the patients who received vorasidenib and in no patients who received placebo.

CONCLUSIONS

In patients with grade 2 IDH-mutant glioma, vorasidenib significantly improved progression-free survival and delayed the time to the next intervention. (Funded by Servier; INDIGO ClinicalTrials.gov number, NCT04164901.).

Vorasidenib and ivosidenib in IDH1-mutant low-grade glioma: a randomized, perioperative phase 1 trial

Vorasidenib and ivosidenib inhibit mutant forms of isocitrate dehydrogenase (mIDH) and have shown preliminary clinical activity against mIDH glioma. We evaluated both agents in a perioperative phase 1 trial to explore the mechanism of action in recurrent low-grade glioma (IGG) and select a molecule for phase 3 testing. Primary end-point was concentration of D-2-hydroxyglutarate (2-HG), the metabolic product of mIDH enzymes, measured in tumor tissue from 49 patients with mIDH1-R132H nonenhancing gliomas following randomized treatment with vorasidenib (50 mg or 10 mg once daily, q.d.), ivosidenib (500 mg q.d. or 250 mg twice daily) or no treatment before surgery. Tumor 2-HG concentrations were reduced by 92.6% (95% credible interval (CrI), 76.1-97.6) and 91.1% (95% CrI, 72.0-97.0) in patients treated with vorasidenib 50 mg q.d. and ivosidenib 500 mg q.d., respectively. Both agents were well tolerated and follow-up is ongoing. In exploratory analyses, 2-HG reduction was associated with increased DNA 5-hydroxymethylcytosine, reversal of 'proneural' and 'stemness' gene expression signatures, decreased tumor cell proliferation and immune cell activation. Vorasidenib, which showed brain penetrance and more consistent 2-HG suppression than ivosidenib, was advanced to phase 3 testing in patients with mIDH LGGs. Funded by Agios Pharmaceuticals, Inc. and Servier Pharmaceuticals LLC; ClinicalTrials.gov number NCT03343197.

RTID-02. A PHASE 1, SAFETY LEAD-IN AND RANDOMIZED, OPEN-LABEL, PERIOPERATIVE STUDY OF VORASIDENIB COMBINED WITH PEMBROLIZUMAB IN RECURRENT OR PROGRESSIVE ENHANCING IDH-1 MUTANT ASTROCYTOMAS: TRIAL IN PROGRESS

BACKGROUND

Astrocytomas are a subset of diffuse gliomas defined by intact 1p and 19q arms. Isocitrate dehydrogenase 1 mutations (mIDH-1) occur in ~70% of grade 2/3 gliomas, leading to accumulation of 2-hydroxyglutarate (2-HG). Vorasidenib (VOR) is an oral, brain-penetrant dual inhibitor of mIDH1/2 enzymes being investigated in a phase 3 study in non-enhancing gliomas. In an ongoing perioperative study in grade 2/3 gliomas, treatment with VOR was associated with interferon (IFN) signaling activation and increased T-cell infiltration, suggesting adequate 2-HG suppression renders the tumor immune microenvironment for immune checkpoint blockade, and supporting investigation of VOR in combination with an anti-programmed cell death (PD-1) antibody such as pembrolizumab in recurrent IDH-mutant gliomas treatment. This study will evaluate the safety and tolerability of VOR plus pembrolizumab to determine the recommended combination dose (RCD) of VOR, and evaluate CD3+ T-cell infiltration in tumors following preoperative treatment with the combination or VOR.

METHODS

This study will enroll ~70 patients with recurrent or progressive Grade 2/3 mIDH-1 astrocytoma. Key eligibility: enhancing disease, mIDH1-R132H, Karnofsky Performance Status ≥70, eligible for resection (perioperative phase only). Safety lead-in: Cohort 1 (Nf~6): VOR 40 mg QD plus pembrolizumab 200 mg Q3W in 21-day cycles. Based on DLT evaluation, cohort 2 may enroll an additional ~6 patients at VOR 20 mg QD plus pembrolizumab 200 mg Q3W. Randomized, perioperative phase (Nf~60): randomized 1:1:1 to the combination, VOR 40 mg QD, or untreated for 4 weeks preoperatively; all patients can opt to receive the combination postoperatively. Primary objectives: safety and tolerability, and VOR RCD with pembrolizumab; CD3+ T-cell infiltration in resected tumors following presurgical treatment with the combination compared to untreated tumors. Secondary objectives include clinical activity, VOR PK in tumor and blood, 2-HG concentration in tumors, and overall survival. This study will be active in the United States.

Early volumetric, perfusion, and diffusion MRI changes after mutant isocitrate dehydrogenase (IDH) inhibitor treatment in IDH1-mutant gliomas

Background

Inhibition of the isocitrate dehydrogenase (IDH)-mutant enzyme is a novel therapeutic target in IDH-mutant gliomas. Imaging biomarkers of IDH inhibitor treatment efficacy in human IDH-mutant gliomas are largely unknown. This study investigated early volumetric, perfusion, and diffusion MRI changes in IDH1-mutant gliomas during IDH inhibitor treatment.

Methods

Twenty-nine IDH1-mutant glioma patients who received IDH inhibitor and obtained anatomical, perfusion, and diffusion MRI pretreatment at 3-6 weeks (n = 23) and/or 2-4 months (n = 14) of treatment were retrospectively studied. Normalized relative cerebral blood volume (nrCBV), apparent diffusion coefficient (ADC), and fluid-attenuated inversion recovery (FLAIR) hyperintensity volume were analyzed.

Results

After 3-6 weeks of treatment, nrCBV was significantly increased (P = .004; mean %change = 24.15%) but not FLAIR volume (P = .23; mean %change = 11.05%) or ADC (P = .52; mean %change = -1.77%). Associations between shorter progression-free survival (PFS) with posttreatment nrCBV > 1.55 (P = .05; median PFS, 240 vs 55 days) and increased FLAIR volume > 4 cm³ (P = .06; 227 vs 29 days) trended toward significance. After 2-4 months, nrCBV, FLAIR volume, and ADC were not significantly different from baseline, but an nrCBV increase > 0% (P = .002; 1121 vs 257 days), posttreatment nrCBV > 1.8 (P = .01; 1121 vs. 270 days), posttreatment ADC < 1.15 μm²/ms (P = .02; 421 vs 215 days), median nrCBV/ADC ratio increase > 0% (P = .02; 1121 vs 270 days), and FLAIR volume change > 4 cm³ (P = .03; 421 vs 226.5 days) were associated with shorter PFS.

Conclusions

Increased nrCBV at 3-6 weeks of treatment may reflect transient therapeutic and/or tumor growth changes, whereas nrCBV, ADC, and FLAIR volume changes occurring at 2-4 months of treatment may more accurately reflect antitumor response to IDH inhibition.

NIMG-41. PH-WEIGHTED MOLECULAR MRI AS AN EARLY BIOMARKER OF METABOLIC RESPONSE TO IDH INHIBITION IN IDH MUTANT GLIOMAS

The current study tested the hypotheses that (1) pH-weighted MRI measurements of tumor acidity reflect glycolytic activity in human gliomas, (2) that tumor acidity, and thus glycolytic activity, differs between human IDH mutant (mIDH) and wild type gliomas, and (3) that an increase in tumor acidity, suggestive of increased glycolytic activity, occurs after inhibition of mutant IDH enzyme activity and reduction in 2HG, an oncometabolite. To test these hypotheses, we employed a custom pH-weighted amine chemical exchange saturation transfer echoplanar (CEST-EPI) technique in 152 patients with IDH mutant or wildtype glioma prior to surgery and 11 patients before and after treatment with AG120 or AG881 enrolled at our institution in a phase 1 perioperative study in patients with recurrent, non-enhancing, IDH mutant low-grade gliomas (NCT03343197). Results from image-guided biopsies in more than 100 patients demonstrated a significant correlation between MTRasym at 3ppm, a measure of tumor acidity from pH-weighted amine CEST-EPI, and expression of key glycolytic proteins including GLUT3 (R2=0.2188,P=0.0105), HK2 (R2=0.1788,P=0.0314), LDHA (R2=0.1111,P=0.0071), and MCT1 (R2=0.1228,P=0.0039) as well as ex vivo extracellular flux analysis estimates of ATP consumption from glycolysis (R2=0.6684,P=0.0021). Data suggests a significantly lower acidity (MTRasym@3ppm) within non-enhancing tumor in IDH mutant gliomas when compared to IDH wild type gliomas (P&lt; 0.0001). Patients in a phase 1 perioperative study showed a shift toward higher tumor acidity (i.e. higher glycolytic activity) following inhibition of IDH based on 2HG suppression in resected tumors, but at levels below that of IDH wild type gliomas. Levels of 2HG within the tumor after IDH inhibition were inversely correlated with post-treatment tumor acidity (R2=0.6342, P=0.0180). Overall, results suggest mIDH gliomas have low levels of glycolytic activity, and successful inhibition of the mutant IDH enzyme results in reduction in 2HG and a measurable metabolic shift toward elevated glycolysis as evidenced using pH-weighted molecular MRI.

NIMG-33. VOLUMETRIC TUMOR MEASUREMENTS ARE SUPERIOR TO 2D BIDIRECTIONAL MEASUREMENTS IN THE EVALUATION OF IDH INHIBITION IN DIFFUSE GLIOMAS: EVIDENCE FROM A PROSPECTIVE PHASE I TRIAL OF IVOSIDENIB

Since IDH mutant (mIDH) low-grade gliomas (LGGs) progress slowly and patients have a relatively long survival, testing of new therapies in clinical trials based solely on survival can take more than 20 years. Guidance on therapeutic evaluation using LGG RANO criteria recommends serial bidirectional (2D) measurements on a single slice; however, questions remain as to the best approach for evaluating LGGs in clinical trials including use of volumetric (3D) measurements, which would theoretically allow for more accurate measurements of irregular shaped lesions and allow readers to better assess areas of change within these tumors. A total of 21 (out of 24) non-enhancing, recurrent mIDH LGGs with imaging pre- and post-treatment enrolled in a phase I, multicenter, open-label study to assess the safety and tolerability of oral ivosidenib (NCT02073994) were included in this exploratory ad hoc analysis. 2D bidirectional and 3D volumetric measurements were centrally evaluated by one of 3 radiologists at an imaging CRO using a paired read and forced adjudication paradigm. The effects of 2D vs. 3D measurements on progression-free survival (PFS), growth rate measurement variability, and reader concordance and adjudication rates were then quantified. 3D volumetric measurements had significantly longer estimates of PFS (P=0.0181), more stable (P=0.0063) and considerably lower measures of tumor growth rate (P=0.0037), the highest inter-reader agreement (weighted Kappa=0.7057), and significantly lower reader discordance rates (P=0.0002) with comparable recommended LGG RANO 2D approaches. In summary, 3D volumetric measurements are better for determining response assessment in LGGs due to longer PFS and more stable measures of tumor growth rates (i.e. less “yo-yo-ing” of measurements over time causing fewer erroneous calls of progression and more accurate growth rates), highest inter-reader agreement, and lowest reader discordance rates. Future studies will focus on validating this in a larger cohort and determining whether these measurements better reflect clinical benefit.

Volumetric measurements are preferred in the evaluation of mutant IDH inhibition in non-enhancing diffuse gliomas: Evidence from a phase I trial of Ivosidenib

BACKGROUND

Since IDH mutant (mIDH) low-grade gliomas (LGGs) progress slowly and have a relatively long survival, there is a significant need for earlier measurements of clinical benefit. Guidance using the LGG RANO criteria recommends serial bidirectional (2D) measurements on a single slice; however, questions remain as to whether volumetric (3D) measurements are better, since they would allow for more accurate measurements in irregular shaped lesions and allow readers to better assess areas of subtle change.

METHODS

21 (out of 24) non-enhancing, recurrent mIDH1 LGGs were enrolled in a phase I, multicenter, open-label study of oral ivosidenib (NCT02073994), and with imaging pre- and post-treatment as part of this exploratory ad hoc analysis. 2D and 3D measurements on T2-weighted FLAIR images were centrally evaluated at an imaging CRO using a paired read and forced adjudication paradigm. The effects of 2D vs. 3D measurements on progression-free survival (PFS), growth rate measurement variability, and reader concordance and adjudication rates were quantified.

RESULTS

3D volumetric measurements showed significantly longer estimated PFS (P=0.0181), more stable (P=0.0063) and considerably slower measures of tumor growth rate (P=0.0037), the highest inter-reader agreement (weighted Kappa=0.7057), and significantly lower reader discordance rates (P=0.0002) with 2D LGG RANO.

CONCLUSION

3D volumetric measurements are better for determining response assessment in LGGs due to more stable measures of tumor growth rates (i.e. less "yo-yo-ing" of measurements over time), highest inter-reader agreement, and lowest reader discordance rates. Continued evaluation in future studies is warranted to determine whether these measurements reflect clinical benefit.

Vorasidenib, a Dual Inhibitor of Mutant IDH1/2, in Recurrent or Progressive Glioma; Results of a First-in-Human Phase I Trial

PURPOSE

Lower grade gliomas (LGGs) are malignant brain tumors. Current therapy is associated with short- and long-term toxicity. Progression to higher tumor grade is associated with contrast enhancement on MRI. The majority of LGGs harbor mutations in the genes encoding isocitrate dehydrogenase 1 or 2 (IDH1/IDH2). Vorasidenib (AG-881) is a first-in-class, brain-penetrant, dual inhibitor of the mutant IDH1 and mutant IDH2 enzymes.

PATIENTS AND METHODS

We conducted a multicenter, open-label, phase I, dose-escalation study of vorasidenib in 93 patients with mutant IDH1/2 (mIDH1/2) solid tumors, including 52 patients with glioma that had recurred or progressed following standard therapy. Vorasidenib was administered orally, once daily, in 28-day cycles until progression or unacceptable toxicity. Enrollment is complete; this trial is registered with ClinicalTrials.gov, NCT02481154.

RESULTS

Vorasidenib showed a favorable safety profile in the glioma cohort. Dose-limiting toxicities of elevated transaminases occurred at doses ≥100 mg and were reversible. The protocol-defined objective response rate per Response Assessment in Neuro-Oncology criteria for LGG in patients with nonenhancing glioma was 18% (one partial response, three minor responses). The median progression-free survival was 36.8 months [95% confidence interval (CI), 11.2-40.8] for patients with nonenhancing glioma and 3.6 months (95% CI, 1.8-6.5) for patients with enhancing glioma. Exploratory evaluation of tumor volumes in patients with nonenhancing glioma showed sustained tumor shrinkage in multiple patients.

CONCLUSIONS

Vorasidenib was well tolerated and showed preliminary antitumor activity in patients with recurrent or progressive nonenhancing mIDH LGG.

Impact of mutant IDH (mIDH) inhibition on DNA hydroxymethylation, tumor cell function, and tumor immune microenvironment (TIME) in resected mIDH1 lower-grade glioma (LGG)

2008

Background: Somatic mutations in IDH1 and IDH2 occur in ̃80% and ̃4% of LGGs, respectively, promoting tumorigenesis via increased levels of the oncometabolite D-2-hydroxyglutarate (2-HG). Vorasidenib (VOR; AG-881) is an oral, brain-penetrant, dual inhibitor of mIDH1/2; ivosidenib (IVO; AG-120) is a first-in-class oral inhibitor of mIDH1. In this ongoing perioperative study, treatment with IVO/VOR reduced 2-HG levels in resected tumors vs untreated control tumors in patients (pts) with LGG (NCT03343197; Mellinghoff SNO 2019). We assessed the biological impact of 2-HG suppression on tumors and TIME. Methods: Pts (n = 49) with recurrent, non-enhancing, mIDH1-R132H LGG eligible for resection were randomized to IVO (500 mg QD/250 mg BID), VOR (10/50 mg QD), or no treatment, for 4 weeks preoperatively. Tumor tissue samples collected at surgery were assessed in genomic (n = 42), transcriptomic (n = 42), and immunohistochemistry (IHC; n = 43) analyses. Unpaired t-test was used for statistical comparisons. Results: Optimal 2-HG suppression (post-treatment 2-HG below the upper limit of 2-HG levels in a reference set of 15 wild-type [wt] IDH samples) was observed in 23 of 40 pts, including 9 (90%) pts receiving VOR 50 mg QD and 6 (50%) receiving IVO 500 mg QD. Of samples with valid biomarker data, those with optimal 2-HG suppression (n = 21) showed upregulation of neural differentiation-related gene expression, but downregulation of stemness-related gene expression, vs those with suboptimal 2-HG suppression (post-treatment 2-HG above upper limit of wt IDH 2-HG levels; n = 17; p < 0.01). IHC analysis of the proliferation marker Ki-67 showed a ̃2-fold decrease in Ki-67–positive cells in samples with optimal 2-HG suppression (mean 2.7%; n = 22) vs those with suboptimal suppression (5.8%; n = 16; p < 0.05). Epigenetic analysis revealed a ̃2-fold increase in mean 5-hydroxymethylcytosine (5hmC) levels in samples with optimal (0.36%; n = 17) vs suboptimal 2-HG suppression (0.2%; n = 15; p < 0.05), suggesting reversal of TET2 inhibition. IHC analysis of TIME revealed increases in mean CD3+ and CD8+ tumor-infiltrating lymphocyte levels in samples with optimal (1.05% [CD3]/0.22% [CD8]; n = 22) vs suboptimal 2-HG suppression (0.44% [CD3]/0.07% [CD8]; n = 16; p < 0.05). Optimal 2-HG suppression was associated with upregulation of gene expression related to type I interferon signaling and antigen presentation (p < 0.01). Conclusions: These data suggest that both tumor-intrinsic and -extrinsic mechanisms underlie 2-HG suppression by VOR and IVO. VOR, and IVO to a lesser extent, increased 5hmC, promoted cellular differentiation, and inhibited tumor cell proliferation; both also increased T-cell infiltration, activated interferon signaling, and increased antigen presentation capability. These data support development of VOR in combination with immunotherapy. Clinical trial information: NCT03343197.

RTID-05. INDIGO: A GLOBAL, RANDOMIZED, DOUBLE-BLIND, PHASE 3 STUDY OF VORASIDENIB (AG-881) VS PLACEBO IN PATIENTS WITH RESIDUAL/RECURRENT GRADE II GLIOMA WITH AN ISOCITRATE DEHYDROGENASE 1/2 (IDH1/2) MUTATION

BACKGROUND

Low-grade gliomas (LGGs; WHO grade II) are incurable and ultimately progress to high-grade gliomas. The current treatment options are surgery followed by observation (“watch and wait”) for patients with lower risk for disease progression or postoperative chemoradiotherapy (high-risk population). There are no approved targeted therapies. IDH1 and IDH2 mutations (mIDH1/2) occur in approximately 80% and 4% of LGGs, respectively, and promote tumorigenesis via neomorphic production of D-2-hydroxyglutarate. Vorasidenib, an oral, potent, reversible, brain-penetrant pan-inhibitor of mIDH1/2, was evaluated in 76 patients with glioma in two phase 1 studies (dose escalation and perioperative) and was associated with a favorable safety profile at daily doses below 100 mg. Preliminary clinical activity was observed in non-enhancing glioma patients in both studies, with an objective response rate (ORR) of 18.2% and median progression-free survival of 31.4 months in the dose escalation study.

METHODS

Approximately 366 patients will be randomized 1:1 to vorasidenib (50 mg QD) or matched placebo and stratified by 1p19q status (intact vs co-deleted). Key eligibility criteria: age ≥ 12 years; grade II oligodendroglioma or astrocytoma (per WHO 2016 criteria) not in need of immediate treatment and without high-risk features; centrally confirmed mIDH1/2 status; ≥ 1 surgery for glioma with most recent ≥ 1 year but ≤ 5 years before randomization, and no other anticancer therapy; Karnofsky performance status ≥ 80%; and centrally confirmed measurable, non-enhancing disease evaluable by magnetic resonance imaging. Crossover from placebo to the vorasidenib arm is permitted upon centrally confirmed radiographic progression per RANO-LGG criteria. Primary endpoint: progression-free survival assessed by independent review. Secondary endpoints: safety and tolerability, tumor growth rate assessed by volume, ORR, overall survival, and quality of life. Clinical data will be reviewed regularly by an independent data monitoring committee. The study is currently enrolling patients in the US, with additional countries planned (NCT04164901).

Abstract 2046: Inhibiting IDH mutations in low-grade glioma alters cellular function and the immune environment

Somatic mutations in the genes encoding the metabolic enzymes isocitrate dehydrogenase (IDH) 1 and 2 occur in many cancers, including glioma, cholangiocarcinoma, and acute myeloid leukemia. Mutant IDH (mIDH) proteins have a gain-of-function enzyme activity, catalyzing the reduction of alpha-ketoglutarate (α-KG) to the oncometabolite D-2-hydroxyglutarate (2-HG). 2-HG competitively inhibits α-KG-dependent enzymes, leading to epigenetic dysregulation and tumorigenesis. TET2 is an α-KG-dependent enzyme mediating the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), which leads to DNA demethylation. In mIDH tumors, TET2 activity is inhibited by 2-HG, leading to DNA hypermethylation. In addition, IDH mutations are associated with immune evasion in gliomas. IDH mutations are common in low-grade gliomas (LGG; WHO grade 2/3) and include mutations in IDH1 (~80%) and IDH2 (~4%). Ivosidenib (AG-120, IVO) is a first-in-class, oral inhibitor of mIDH1, and vorasidenib (AG-881, VOR) is an oral, potent, brain-penetrant inhibitor of both mIDH1 and mIDH2. In an ongoing perioperative study (NCT03343197), IVO and VOR demonstrated brain penetrance and &gt;90% suppression of 2-HG in resected mIDH1 gliomas after pre-operative treatment for approximately 4 weeks. In this analysis, we examined the cellular mechanisms underlying mIDH inhibition in LGG using resected tumor tissues collected following treatment with IVO and VOR. Optimal 2-HG suppression (defined by post-treatment 2-HG levels equal to or lower than the upper range of IDH wild-type tumor 2-HG levels) in IVO- or VOR-treated samples (n=17) led to a ~2-fold increase in 5hmC compared with untreated controls and banked reference samples (n=35; P=0.04). Furthermore, immunohistochemistry (IHC) analysis of the proliferation marker Ki-67 showed a ~3-fold decrease in the percentage of Ki-67-positive cells in IVO- or VOR-treated samples with optimal 2-HG suppression (n=21) compared with untreated controls (n=5; P=0.02). Tumor immune microenvironment analyses were also conducted. Comparing IVO- or VOR-treated samples (n=21) with untreated controls and banked reference samples (n=33), RNAseq analysis showed a ~2-fold decrease in the expression of tumor-associated macrophage markers CD68 (P=0.01) and CD163 (P=0.03) in mIDH oligodendrogliomas. In addition, IHC analysis from paired pre-treatment (archival) and post-treatment samples showed an increase of CD3+ T-cell infiltration (P=0.03) and CD8+ T-cell infiltration (P=0.01) in IVO- or VOR-treated samples with optimal 2-HG suppression (n=21). Single-cell RNAseq was conducted for a subset of samples, and the results will be presented. Overall, these data suggest that mIDH inhibition decreases DNA hypermethylation and tumor cell proliferation, and activates the immune microenvironment in mIDH LGG. In conclusion, these data elucidate the mechanisms underlying mIDH inhibition and support further development of mIDH inhibitors in mIDH LGG.

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Citation Format: Min Lu, Ingo K. Mellinghoff, Aaron Diaz, Jennie W. Taylor, Sung Choe, Ania Tassinari, Dongwei Zhu, Katie Sellers, Kha Le, Feng Tai, Islam Hassan, Shuchi S. Pandya, Lori Steelman, Bin Wu. Inhibiting IDH mutations in low-grade glioma alters cellular function and the immune environment [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 2046.

Ivosidenib, an IDH1 inhibitor, in a patient with recurrent, IDH1-mutant glioblastoma: a case report from a Phase I study

Glioblastoma is the most common and aggressive primary brain tumor. Despite standard multimodality therapy, median overall survival remains poor with a 5-year survival rate of approximately 5% in most studies (range 4.7-13.0%). Strong interest in targeting IDH mutations has led to a variety of studies in both hematologic malignancies and solid tumors and to the approval of IDH inhibitors such as ivosidenib, an IDH1 inhibitor, in hematologic malignancies. Here, we present the first case study of a patient with a recurrent IDH1-mutant glioblastoma who experienced improved seizure control and radiographic stable disease for more than 4 years while treated with ivosidenib. Such findings support the further development of IDH inhibitors as single agents and/or in combination for the treatment of IDH-mutant glioma.

Ivosidenib in Isocitrate Dehydrogenase 1-Mutated Advanced Glioma

PURPOSE

Diffuse gliomas are malignant brain tumors that include lower-grade gliomas (LGGs) and glioblastomas. Transformation of low-grade glioma into a higher tumor grade is typically associated with contrast enhancement on magnetic resonance imaging. Mutations in the isocitrate dehydrogenase 1 (IDH1) gene occur in most LGGs (> 70%). Ivosidenib is an inhibitor of mutant IDH1 (mIDH1) under evaluation in patients with solid tumors.

METHODS

We conducted a multicenter, open-label, phase I, dose escalation and expansion study of ivosidenib in patients with mIDH1 solid tumors. Ivosidenib was administered orally daily in 28-day cycles.

RESULTS

In 66 patients with advanced gliomas, ivosidenib was well tolerated, with no dose-limiting toxicities reported. The maximum tolerated dose was not reached; 500 mg once per day was selected for the expansion cohort. The grade ≥ 3 adverse event rate was 19.7%; 3% (n = 2) were considered treatment related. In patients with nonenhancing glioma (n = 35), the objective response rate was 2.9%, with 1 partial response. Thirty of 35 patients (85.7%) with nonenhancing glioma achieved stable disease compared with 14 of 31 (45.2%) with enhancing glioma. Median progression-free survival was 13.6 months (95% CI, 9.2 to 33.2 months) and 1.4 months (95% CI, 1.0 to 1.9 months) for the nonenhancing and enhancing glioma cohorts, respectively. In an exploratory analysis, ivosidenib reduced the volume and growth rates of nonenhancing tumors.

CONCLUSION

In patients with mIDH1 advanced glioma, ivosidenib 500 mg once per day was associated with a favorable safety profile, prolonged disease control, and reduced growth of nonenhancing tumors.

INDIGO: A global, randomized, double-blind, phase III study of vorasidenib (VOR; AG-881) vs placebo in patients (pts) with residual or recurrent grade II glioma with an isocitrate dehydrogenase 1/2 (IDH1/2) mutation

TPS2574

Background: Low-grade gliomas (LGGs; WHO grade II) are incurable and ultimately progress to high-grade gliomas. The current treatment options consist of surgery followed by observation (“watch and wait”) for pts with lower risk for disease progression or post-operative chemo-radiotherapy (high-risk population). There are no approved targeted therapies. IDH1 and IDH2 mutations (m IDH1/2) occur in approximately 70% and 4% of LGGs, respectively, and promote tumorigenesis via neomorphic production of D-2-hydroxyglutarate (2-HG). VOR, an oral, potent, reversible, brain-penetrant inhibitor of mIDH1/2, was evaluated in 76 pts with glioma in two phase 1 studies (dose escalation and perioperative) and was associated with a favorable safety profile at doses of < 100 mg daily. Preliminary clinical activity was observed in non-enhancing glioma pts in both studies, most recently with an objective response rate (ORR) of 30.8% at 50 mg QD in the perioperative study and > 90% 2-HG suppression at this dose level relative to untreated control samples (Mellinghoff et al., J Clin Oncol 2019). Methods: Approximately 366 pts will be randomized 1:1 to VOR (50 mg QD) or matched placebo and stratified by 1p19q status (intact vs co-deleted). Key eligibility criteria include: age ≥12 years; grade 2 oligodendroglioma or astrocytoma (per WHO 2016 criteria) not in need of immediate treatment and without high-risk features; centrally confirmed m IDH1/2 status; ≥1 prior surgery for glioma within the previous 5 years but no other anticancer therapy; Karnofsky performance status ≥80%; and centrally confirmed measurable, non-enhancing disease evaluable by magnetic resonance imaging. Crossover from placebo to the VOR arm is permitted upon centrally confirmed radiographic progression per RANO-LGG criteria. Primary endpoint is progression-free survival assessed by independent review. Secondary endpoints include safety and tolerability, tumor growth rate assessed by volume, time to next intervention, ORR, overall survival, quality of life assessed by the Functional Assessment of Cancer Therapy–Brain questionnaire, and plasma pharmacokinetics. Exploratory endpoints include seizure activity and neuro-cognitive function. Clinical data will be reviewed regularly throughout the study by an independent data monitoring committee. The study is currently enrolling pts in the US, with additional countries planned (NCT04164901). Clinical trial information: NCT04164901 .

Vorasidenib (VOR; AG-881), an inhibitor of mutant IDH1 and IDH2, in patients (pts) with recurrent/progressive glioma: Updated results from the phase I non-enhancing glioma population

2504

Background: Isocitrate dehydrogenase 1 and 2 mutations (m IDH1/2) occur in approximately 70% and 4% of low-grade gliomas (LGGs), respectively, promoting oncogenesis via increased production of D-2-hydroxyglutarate. In this ongoing phase 1 trial, VOR, a potent, oral, reversible, brain-penetrant, first-in-class dual inhibitor of mIDH1/2, is being evaluated in advanced m IDH1/2 solid tumors, including gliomas. Safety and preliminary results were presented previously (Mellinghoff et al., J Clin Oncol 2018). Here, we report updated data for the non-enhancing glioma pt population. Methods: Pts with recurrent/progressive m IDH1/2 glioma received VOR daily (continuous 28-day cycles). Key eligibility criteria included: ≥18 years; histologically or cytologically confirmed glioma with documented m IDH1/2; ECOG 0-2; and evaluable disease by RANO-LGG criteria. Dose escalation cohorts enrolled using a Bayesian logistic regression model (BLRM) escalation guided by the overdose control (EWOC). Tumor response was evaluated by MRI every 8 weeks using RANO-LGG criteria by local assessment. Results: As of 28 Nov 2019, 22 pts with non-enhancing glioma had received VOR and 8 (36%) remain on treatment. M/F, 8/14; grade 2/3, 17/5; median age, 47 years; m IDH1/2, 20/1; 1p19q intact, 9/22; median (range) number of prior systemic therapies, 2 (1–4). Common (≥5 pts) treatment-emergent adverse events (AEs) of any grade and regardless of causality included increased ALT/AST (63.6%/59.1%), headache (45.5%), nausea (40.9%), neutropenia (31.8%), fatigue and hyperglycemia (27.3% each), and seizures and decreased white blood cell count (22.7% each). Transaminase elevations were grade 1 in severity at dose levels < 100mg and were less frequent (5 [38.5%] of 13 pts). Three subjects had related grade ≥3 AEs; 2 discontinued due to AEs. Objective response rate was 13.6% (1 partial response, 2 minor responses), and 17 (77.3%) pts achieved stable disease. 60.5% of pts were progression free and alive at 24 months. Conclusions: In this previously treated population with non-enhancing glioma, VOR was associated with a favorable safety profile. The study results also show encouraging preliminary activity within that population, with PFS duration extending to 24 months or longer in 60% of participants. A global randomized phase 3 study of VOR in grade 2 non-enhancing glioma pts who have had surgery only is currently enrolling (NCT04164901). Clinical trial information: NCT02481154 .

QOLP-37. QUALITATIVE RESEARCH IN LOWER GRADE GLIOMA: UNDERSTANDING SIGNS, SYMPTOMS, AND DISEASE IMPACTS DURING EXPECTANT MANAGEMENT

BACKGROUND

Patients with lower grade glioma (LGG) (i.e., grade II or III) have limited treatment options. After surgical resection of their tumor, patients will undergo either a period of expectant management (watch and wait) or treatment with adjuvant chemotherapy and/or radiotherapy. Approximately 80% of patients with LGG have an isocitrate dehydrogenase mutation, which is a viable target for molecular therapy. This offers a therapeutic intervention that could potentially delay the need for chemotherapy and/or radiotherapy in select patients. Several prognostic and patient-specific factors contribute to the decision to recommend expectant management, including concerns about the side effects of chemotherapy and radiotherapy. The aim of this project was to understand patients’ signs and symptoms during the expectant management period and how LGG impacts their lives.

METHODS

Concept elicitation interviews were conducted in the US with patients with LGG as well as key opinion leaders (KOLs) with experience treating patients with LGG. Interview data were analyzed using Atlas.ti, and patient data were reviewed against KOL data.

RESULTS

Seven patients with ≥ 3 months of expectant management experience and three KOLs were interviewed. During their expectant management periods, patients reported 12 signs/symptoms, mostly related to deficits in cognition. Patients reported 16 impacts across four categories, with a substantial proportion of the impacts identified as negatively affecting emotional function. The signs/symptoms and impacts reported by patients were generally also reported by KOLs. During expectant management, patients typically resume their original quality of life post-surgery, but may also experience anxiety. Patients and KOLs indicated a preference for expectant management and delaying chemotherapy or radiotherapy.

CONCLUSIONS

Patient and KOL interviews characterized the LGG experience and indicated a preference for expectant management, which may be supported by therapies that delay the initiation of chemotherapy and/or radiotherapy.

A phase I, open label, perioperative study of AG-120 and AG-881 in recurrent IDH1 mutant, low-grade glioma: Results from cohort 1

2003

Background: AG-120 (ivosidenib [IVO]) is a first-in-class oral inhibitor of mutant isocitrate dehydrogenase 1 (mIDH1) evaluated in 66 glioma patients (pts) in an ongoing phase 1 study. AG-881 (vorasidenib [VOR]) is an oral, potent, brain-penetrant inhibitor of mIDH1/2 evaluated in 52 glioma pts in an ongoing phase 1 study. In an orthotopic glioma model, IVO and VOR reduced 2-hydroxyglutarate (2-HG) by 85% and 98%, respectively, despite different brain:plasma ratios (<0.04 vs 1.33). Methods: Primary endpoint: brain tumor 2-HG concentration with IVO or VOR treatment in mIDH1 low-grade glioma. Pts with recurrent non-enhancing WHO-2016 Grade (Gr) 2 or 3 mIDH1-R132H oligodendroglioma or astrocytoma undergoing craniotomy were randomized 2:2:1 to IVO 500mg QD, VOR 50mg QD, or no treatment for 4 wks preoperatively in Cohort 1. Post-operatively, pts continued to receive IVO or VOR and control pts were randomized 1:1 to IVO or VOR. Tumors were assessed for mIDH1 status, cellularity, 2-HG, and drug concentration. Treated samples were compared to control pts and mIDH1 and wild type (WT) banked reference (ref) samples. Plasma and CSF 2-HG were assessed. Pts with non-evaluable tissue were replaced. Results: As of 29 Nov 2018, 26 pts (17M, 9F; 25 Gr 2, 1 Gr 3) were randomized preoperatively (IVO 10, VOR 11, control 5), 25 received drug (IVO 12, VOR 13). At the data cut, 19 tumors were analyzed with 16 evaluable. Common (>10%) TEAEs (all grade 1/2): diarrhea (36%), hypocalcemia and constipation (each 20%), anemia, hyperglycemia, pruritus, headache and nausea (each 16%), and hypokalemia and fatigue (each 12%). Mean brain:plasma ratio: 0.16 for IVO, 2.4 for VOR. Tumor 2-HG results are shown in Table. Updated data from Cohort 1 will be presented. Conclusions: In Cohort 1 of this phase 1 perioperative study, IVO and VOR were CNS penetrant and lowered 2-HG compared to untreated samples. Cohort 2 is open and will evaluate IVO 250mg BID and VOR 10mg QD. Brain tumor 2-HG concentration. Clinical trial information: NCT03343197. [Table: see text]

DYNAMO: A Phase II Study of Duvelisib (IPI-145) in Patients With Refractory Indolent Non-Hodgkin Lymphoma

PURPOSE

Indolent non-Hodgkin lymphoma (iNHL) remains largely incurable and often requires multiple lines of treatment after becoming refractory to standard therapies. Duvelisib was approved by the Food and Drug Administration for relapsed or refractory (RR) chronic lymphocytic leukemia or small lymphocytic lymphoma (SLL) and RR follicular lymphoma (FL) after two or more prior systemic therapies. On the basis of the activity of duvelisib, a first-in-class oral dual inhibitor of phosphoinositide 3-kinase-δ,-γ, in RR iNHL in a phase I study, the safety and efficacy of duvelisib monotherapy was evaluated in iNHL refractory to rituximab and either chemotherapy or radioimmunotherapy.

PATIENTS AND METHODS

Eligible patients had measurable iNHL (FL, SLL, or marginal zone B-cell lymphoma) double refractory to rituximab (monotherapy or in combination) and to either chemotherapy or radioimmunotherapy. All were treated with duvelisib 25 mg orally twice daily in 28-day cycles until progression, unacceptable toxicity, or death. The primary end point was overall response rate (ORR) using the revised International Working Group criteria for malignant lymphoma.

RESULTS

This open-label, global phase II trial enrolled 129 patients (median age, 65 years; median of three prior lines of therapy) with an ORR of 47.3% (SLL, 67.9%; FL, 42.2%; MZL, 38.9%). The estimated median duration of response was 10 months, and the estimated median progression-free survival was 9.5 months. The most frequent any-grade treatment-emergent adverse events (TEAEs) were diarrhea (48.8%), nausea (29.5%), neutropenia (28.7%), fatigue (27.9%), and cough (27.1%). Among the 88.4% of patients with at least one grade 3 or greater TEAE, the most common TEAEs were neutropenia (24.8%), diarrhea (14.7%), anemia (14.7%), and thrombocytopenia (11.6%).

CONCLUSION

In the DYNAMO study, oral duvelisib monotherapy demonstrated clinically meaningful activity and a manageable safety profile in heavily pretreated, double-refractory iNHL, consistent with previous observations. Duvelisib may provide a new oral treatment option for this patient population of which many are elderly and in need of additional therapies.

A Phase I dose-escalation study of the VEGFR inhibitor tivozanib hydrochloride with weekly paclitaxel in metastatic breast cancer

Tivozanib is a potent selective tyrosine kinase inhibitor (TKI) of vascular endothelial growth factor receptors (VEGFRs) 1, 2, and 3. This Phase Ib study investigated the safety/tolerability, pharmacokinetics (PK), and activity of tivozanib with weekly paclitaxel in metastatic breast cancer (MBC). MBC patients with no prior VEGFR TKI treatment received daily oral tivozanib (3 weeks on, 1 week off) with weekly paclitaxel 90 mg/m(2). Standard 3 + 3 dose escalation was used; tivozanib cohorts (C) included C1 0.5 mg, C2 1.0 mg, and C3 1.5 mg. Assessments included Response Evaluation Criteria in Solid Tumors response, PK, and vascular function. Eighteen patients enrolled. Toxicities in >20 % of patients included fatigue, alopecia, nausea, diarrhea, peripheral sensory neuropathy, and hypertension. Grade 3/4 toxicities in >15 % of patients included fatigue and neutropenia. Maximum tolerated dose was tivozanib 1.5 mg with paclitaxel 90 mg/m(2). Four patients withdrew because of toxicity and one due to progressive disease. Thirteen patients were evaluable for response: four (30.8 %) had confirmed partial response; four had stable disease ≥6 months (30.8 %). PK data suggest no influence of paclitaxel on tivozanib concentrations. Tivozanib plus weekly paclitaxel was tolerable at all dose levels, supporting their combination at full dose. Activity in this small population was encouraging.

Abstract OT2-3-11: Tivozanib in combination with paclitaxel vs placebo with paclitaxel in patients with locally advanced or metastatic triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive cancer with inferior survival outcomes. Although weekly paclitaxel (WP) is effective in the treatment (tx) of metastatic breast cancer (MBC), optimization of therapies for patients (pts) with TNBC is essential. Angiogenesis is a hallmark of advanced cancer, with subset analyses suggesting activity of angiogenesis inhibitors in TNBC. Tivozanib (TIVO) is a potent and selective inhibitor of vascular endothelial growth factor receptors (VEGFR) 1, 2, and 3 with a promising role in metastatic renal cell carcinoma, and established safety in Phase I combination with WP in MBC.

Purpose: This Phase II trial will assess the efficacy and safety of TIVO + WP in the first-line setting for pts with advanced or metastatic TNBC and evaluate the performance of candidate angiogenesis biomarkers.

Objectives: The primary objective of this study is to compare progression-free survival (PFS) of pts treated with TIVO + WP vs pts treated with placebo (PB) + WP. Secondary objectives include objective response rate (ORR), overall survival (OS), safety and tolerability, quality of life, and correlative candidate biomarker endpoints. The pharmacokinetics of TIVO + WP also will be characterized.

Study Design and Methods: This multicenter, randomized, PB-controlled, two-arm study will enroll pts with metastatic or unresectable TNBC (evaluable per RECIST) and no prior systemic therapy. Pts must have confirmed available archival tumor tissue. Pts will be stratified by ECOG performance score and number of metastatic sites, then randomized to receive either oral TIVO 1.5 mg once daily for 3 weeks (wks) on/1 wk off and intravenous WP 90 mg/m2 for 3 wks on/1 wk off, or PB + WP. One cycle will be 4 wks; tx will continue until disease progression or unacceptable toxicity. Archival tumor tissue and blood samples will be evaluated for response biomarkers, including a hypoxia sensitivity gene signature, a myeloid resistance gene signature, and angiogenic ligands. All pts will be followed for survival until death. Adverse events will be monitored throughout the study. Pharmacokinetic samples will be collected during cycles 1 and 2. PAM-50–defined intrinsic molecular subtype populations also will be evaluated retrospectively.

Recruitment of 130 patients is planned, with an interim analysis after 80 pts to measure ORR (130 pts with a total of 82 investigator-assessed PFS events provides 80% power to detect statistically significant PFS differences between tx arms). Endpoint analyses will use the intent-to-treat population. The primary efficacy analysis will use investigator assessments of response and a two-sided 95% confidence interval for the hazard ratio produced using Cox proportional hazards regression models. OS will be compared using the log-rank test. Analyses of candidate biomarkers and determination of an optimal predictive cutoff for response also are planned. Trial enrollment will commence in fall 2012.

Conclusion: This study will determine whether TIVO, a selective and potent VEGFR inhibitor, combined with WP improves clinical outcomes in pts with TNBC, and whether clinical activity is associated with candidate angiogenesis biomarkers.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr OT2-3-11.

Differential-effects of viral and cellular oncogenes on the growth factor-dependency of hematopoietic-cells

The effects of different viral and cellular oncogenes on the cytokine-dependency of murine hematopoietic cell lines were compared. The myeloid FDC-P1 cell line was sensitive to abrogation of growth factor-dependency by the constitutive expression of viral oncogenes (v-abl, v-src, v-Ha-ras, and v-fms) and the activated cellular oncogene BCR-ABL and Delta Nraf. The Delta Nraf encoded serine-threonine kinase was approximately 100-fold less efficient in relieving the factor-dependency of FDC-P1 cells than the other oncogenes examined. The synthesis of autocrine cytokines was not detected in the factor-independent FDC-P1 lines, indicating that the oncogene-mediated transformation occurred by a non-autocrine mechanism. A low frequency of cells were isolated after infection with the chronic retrovirus, murine leukemia virus and approximately 40% of these clones synthesized the autocrine lymphokine, granulocyte-macrophage colony stimulating factor. In contrast, only the v-abl and BCR-ABL oncogenes relieved the cytokine-dependency of the lymphoid FL5.12 cell line. In all the transformed cell lines, the rate of glucose transport was elevated above the basal level seen in uninfected cells indicating that this pivotal growth-regulated protein was associated with malignant transformation. In summary, these cell lines varied with respect to abrogation of growth factor-dependency as the myeloid FDC-P1 line was sensitive to transformation by all oncogenes examined whereas only the abl-family members would relieve the cytokine-requirement of lymphoid FL5.12 cells.

Regulation and targeting of antiapoptotic XIAP in acute myeloid leukemia

XIAP is a member of the inhibitors-of-apoptosis family of proteins, which inhibit caspases and block cell death, with prognostic importance in AML. Here we demonstrate that cytokines regulate the expression of XIAP in leukemic cell lines and primary AML blasts. Inhibition of phosphatidylinositol-3 kinase (PI3K) with LY294002 and of the mitogen-activated protein kinase (MAPK) cascade by PD98059 resulted in decreased XIAP levels (34+/-8.7 and 23+/-5.7%, respectively). We then generated OCI-AML3 cells with constitutively phosphorylated Akt (p473-Akt) by retroviral gene transfer. Neither these nor Akt inhibitor-treated OCI-AML3 cells showed changes in XIAP levels, suggesting that XIAP expression is regulated by PI3K downstream effectors other than Akt. The induction of XIAP expression by cytokines through PI3K/MAPK pathways is consistent with its role in cell survival. Exposure of leukemic cells to chemotherapeutic agents decreased XIAP protein levels by caspase-dependent XIAP cleavage. Targeting XIAP by XIAP antisense oligonucleotide resulted in downregulation of XIAP, activation of caspases and cell death, and sensitized HL-60 cells to Ara-C. Our results suggest that XIAP is regulated by cytokines through PI3K, and to a lesser degree through MAPK pathways. Selective downregulation of XIAP expression might be of therapeutic benefit to leukemic patients.

How do mothers' childrearing histories, stress and parenting affect children's behavioural outcomes?

BACKGROUND

Information is needed to understand the role of low to moderate levels of mothers' emotional stress and child characteristics (i.e. prematurity) on parenting behaviours and their impact on children's behaviour that might be deemed 'challenging' but not 'disordered'.

METHODS

The direct and indirect relations of maternal childrearing history and emotional stress, and observed parenting practices when children were 3 years of age on 4-year child behavioural outcomes was examined in a sample of low-income families with a term (n=112) or preterm (n=180) child. Parenting practices included displays of warmth and restrictiveness when interacting with their children. Child outcomes at 4 years included observation of social initiations with their mothers and maternal report of social and attentional problems.

RESULTS

A Structural Equation Model building approach guided by specific hypotheses indicated that preterm as compared to full-term children had more maternal reported social and attentional problems but did not differ in observed social initiating skills. Greater negative maternal childrearing history indirectly influenced social initiating skills through its direct influence on maternal emotional stress. Greater maternal emotional stress directly influenced mothers' parenting that, in turn, directly influenced social initiating. Prematurity and a more negative childrearing history had a direct negative influence on the maternal report of social and attentional behavioural outcomes.

CONCLUSIONS

These findings delineate the effects of prematurity and maternal parenting on the behaviour of 4-year-old-children and extend current knowledge of the influence of parental emotional stress on parenting. Even milder levels can negatively influence parenting, and in turn, contribute to children's less well developed social skills. The issues raised in this study could help with the identification and prioritization of medical and psychological services.

Synergy between Raf and BCL2 in abrogating the cytokine dependency of hematopoietic cells

The Raf oncoprotein plays critical roles in the transmission of mitogenic signals from cytokine receptors to the nucleus. There are three Raf family members: A-Raf, B-Raf and Raf-1. Conditionally active forms of the Raf proteins were created by ligating N-terminal truncated activated forms to the estrogen-receptor (ER) hormone-binding domain resulting in beta-estradiol-inducible constructs. We introduced these chimeric deltaRaf:ER oncoproteins into the murine FDC-P1 hematopoietic cell line. Two different types of cells were recovered after drug selection in medium containing either cytokine or beta-estradiol: (1) cytokine-dependent cells that expressed the deltaRaf:ER oncoproteins; and (2) Raf-responsive cells that grew in response to the deltaRaf:ER oncoprotein. Depending upon the particular deltaRaf:ER oncoprotein, cytokine-dependent cells were recovered 10(3) to 10(5) times more frequently than Raf-responsive cells. To determine whether BCL2 could synergize with the deltaRaf:ER oncoproteins and increase the frequency of cytokine-independent cells, cytokine-dependent deltaRaf:ER-expressing cells were infected with either a BCL2 containing retrovirus or an empty retroviral vector. BCL2 overexpression, by itself, did not relieve cytokine dependency of the parental cell line. However, BCL2 overexpression increased the frequency of Raf-responsive cells approximately five- to 100-fold. Cytokine-dependent deltaRaf:ER-infected cells entered the G1 phase of the cell cycle after cytokine withdrawal and entered S phase only after cytokine addition. Raf-responsive deltaRaf:ER cells entered the G1 phase of the cell cycle after estrogen deprivation and re-entered the cell cycle after addition of either IL-3 or the estrogen receptor antagonist tamoxifen which activates the deltaRaf:ER constructs. Expression of the BCL2 oncoprotein often delayed the exit from the S and G2/M phases demonstrating the protective effects BCL2 provided to these Raf and BCL2 infected cells. The deltaRaf:ER cells expressed the deltaRaf:ER proteins and downstream MEK and ERK activities after beta-estradiol treatment. Raf-responsive cells that were also infected with BCL2 expressed higher levels of BCL2 than the cells that were not infected with BCL2. Thus BCL2 can synergize with the activated Raf in the abrogation of cytokine dependency of certain hematopoietic cells. These cells will be useful in furthering our understanding of the roles of the Raf and BCL2 oncoproteins in hematopoietic cell growth, cell cycle progression and prevention of apoptosis.

Autocrine growth-factor secretion after transformation of human cytokine-dependent cells by viral and cellular oncogenes

The effects of viral and cellular oncogenes on a human erythroleukemic cell line (TF-1) were investigated. The TF-1 cell line required granulocyte/macrophage-colony stimulating factor (GM-CSF) for growth but this factor-dependency was abrogated by the constitutive expression of either viral (v-fms, v-Ha-ras and v-src) or cellular oncogenes (BCR-ABL and Delta N-raf). Furthermore the overexpression of the human insulin-like growth factor-1 (IGF-1) receptor could substitute the dependency on GM-CSF with a requirement for either IGF-1 or insulin as a proliferative signal. An autocrine cytokine, (GM-CSF) was found in the supernatant of cells transformed by Delta N-raf (and to a lesser extent in cells infected with other oncogenes. The level of GM-CSF secreted by the Delta N-raf transformants was sufficient to support the proliferation of the parental cell line. GM-CSF mRNA transcripts were detected in the Delta N-raf-infected but not in the parental cells. No structural alterations of the GMCSF locus were seen in these cells. Together these observations indicated that overexpression of a raf oncogene resulted in the expression of GM-CSF transcripts. The rates of glucose transport were elevated above basal levels by GMCSF and by oncogene expression indicating that this pivotal control point of metabolism correlated with mitogenesis and malignant transformation. These studies indicate the importance of raf in growth regulation as its deregulation can lead to autocrine synthesis of cytokines in certain hematopoietic cells. Furthermore these results suggest a synergy between oncogene and cytokine gene regulation leading to autocrine growth factor expression and tumor progression.

Differential-effects of tumor promoters and cytokines on protooncogene expression in a hematopoietic cytokine-dependent cell-line

In order to investigate the mechanisms by which cytokines and tumor promoters stimulate cell growth, the expression of genes implicated in the regulation of cellular proliferation were examined in an interleukin-3 (IL-3) dependent hematopoietic cell line. Upon stimulation of factor-deprived cells with IL-3, mRNA transcripts encoding the immediate-early genes: c-myc, jun-B, krox-20, beta-actin, and the cytokine genes: IL-4 and IL-6 were detected within 1 h. In contrast mRNA transcripts encoding the delayed-early genes: ornithine decarboxylase, p53, the IL-2 receptor-alpha, IL-4 receptor, and the T cell receptor c-gamma chains were observed at highest levels later. The tumor promoter, phorbol 12-myristate 13-acetate also stimulated the expression of many immediate-early genes, however, c-myc and the delayed-early genes were only detected when IL-3 was present. We conclude that cytokines and tumor promoters have distinct effects on proto-oncogene expression in hematopoietic cells which may affect the ability of these agents to promote cellular growth versus differentiation.

Differential regulation of glucose-transporter expression in hematopoietic-cells by oncogenic transformation and cytokine stimulation

Malignant transformation by the v-src oncogene and mitogenic stimulation by interleukin-3 (IL-3) both increased glucose transport into a hematopoietic cell line. These increases were additive and correlated with elevations in the level of GLUT1 mRNA. Glucose transport and GLUT1 mRNA were dependent on the presence of a functional v-src gene product in the absence of IL-3. Nuclear run-on analyses and mRNA turnover experiments demonstrated that GLUT1 gene transcription was enhanced by v-src while IL-3 stabilized GLUT1 mRNA. Introduction of retroviruses overexpressing GLUT1 into factor-dependent cells did not abrogate factor-dependency. Thus, GLUT1 induction is necessary but not sufficient for mitogenesis.

Absence of unsaturated fatty acid synthesis in murine T lymphocytes

Stearic acid is toxic for T lymphocytes in vitro but has little effect on B lymphocytes. To investigate the molecular basis for this difference, purified murine T and B lymphocytes were compared for their abilities to incorporate and metabolize stearic acid. Unstimulated T and B cells incorporated identical amounts of stearic acid into six different phospholipids and four neutral lipids. After mitogen stimulation, fatty acid uptake was increased in both lymphocyte types, but cell-specific differences were seen in the distribution of stearic acid among the various cellular lipids. Doses of stearic acid that selectively inhibited T-cell proliferation resulted in a 5-fold greater accumulation of distearoylphosphatidylcholine in T cells than in B cells. Whereas T cells did not desaturate the exogenously derived stearic acid, up to 25% of the saturated fatty acid was converted to oleic acid in B cells. These findings suggested a deficiency of stearoyl-CoA desaturase (acyl-CoA, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.5) activity in T cells, which was confirmed by subsequent studies. Cell-free extracts from B cells displayed nearly 20-fold more stearoyl-CoA desaturase activity than T-cell extracts, and the level of stearoyl-CoA desaturase mRNA was 30-fold higher in B cells. Collectively, our data indicate that murine T cells are deficient in unsaturated fatty acid synthesis. The deficiency of stearoyl-CoA desaturase in T cells may represent the basis for the differing sensitivities of T and B lymphocytes to inhibition by saturated fatty acids.