Pegargiminase Plus First-Line Chemotherapy in Patients With Nonepithelioid Pleural Mesothelioma: The ATOMIC-Meso Randomized Clinical Trial

Importance

Arginine deprivation using ADI-PEG20 (pegargiminase) combined with chemotherapy is untested in a randomized study among patients with cancer. ATOMIC-Meso (ADI-PEG20 Targeting of Malignancies Induces Cytotoxicity-Mesothelioma) is a pivotal trial comparing standard first-line chemotherapy plus pegargiminase or placebo in patients with nonepithelioid pleural mesothelioma.

Objective

To determine the effect of pegargiminase-based chemotherapy on survival in nonepithelioid pleural mesothelioma, an arginine-auxotrophic tumor.

Design, Setting, and Participants

This was a phase 2-3, double-blind randomized clinical trial conducted at 43 centers in 5 countries that included patients with chemotherapy-naive nonepithelioid pleural mesothelioma from August 1, 2017, to August 15, 2021, with at least 12 months' follow-up. Final follow-up was on August 15, 2022. Data analysis was performed from March 2018 to June 2023.

Intervention

Patients were randomly assigned (1:1) to receive weekly intramuscular pegargiminase (36.8 mg/m2) or placebo. All patients received intravenous pemetrexed (500 mg/m2) and platinum (75-mg/m2 cisplatin or carboplatin area under the curve 5) chemotherapy every 3 weeks up to 6 cycles. Pegargiminase or placebo was continued until progression, toxicity, or 24 months.

Main Outcomes and Measures

The primary end point was overall survival, and secondary end points were progression-free survival and safety. Response rate by blinded independent central review was assessed in the phase 2 portion only.

Results

Among 249 randomized patients (mean [SD] age, 69.5 [7.9] years; 43 female individuals [17.3%] and 206 male individuals [82.7%]), all were included in the analysis. The median overall survival was 9.3 months (95% CI, 7.9-11.8 months) with pegargiminase-chemotherapy as compared with 7.7 months (95% CI, 6.1-9.5 months) with placebo-chemotherapy (hazard ratio [HR] for death, 0.71; 95% CI, 0.55-0.93; P = .02). The median progression-free survival was 6.2 months (95% CI, 5.8-7.4 months) with pegargiminase-chemotherapy as compared with 5.6 months (95% CI, 4.1-5.9 months) with placebo-chemotherapy (HR, 0.65; 95% CI, 0.46-0.90; P = .02). Grade 3 to 4 adverse events with pegargiminase occurred in 36 patients (28.8%) and with placebo in 21 patients (16.9%); drug hypersensitivity and skin reactions occurred in the experimental arm in 3 patients (2.4%) and 2 patients (1.6%), respectively, and none in the placebo arm. Rates of poststudy treatments were comparable in both arms (57 patients [45.6%] with pegargiminase vs 58 patients [46.8%] with placebo).

Conclusions and Relevance

In this randomized clinical trial of arginine depletion with pegargiminase plus chemotherapy, survival was extended beyond standard chemotherapy with a favorable safety profile in patients with nonepithelioid pleural mesothelioma. Pegargiminase-based chemotherapy as a novel antimetabolite strategy for mesothelioma validates wider clinical testing in oncology.

Trial Registration

ClinicalTrials.gov Identifier: NCT02709512.

BAP1 Loss Is Associated with Higher ASS1 Expression in Epithelioid Mesothelioma: Implications for Therapeutic Stratification

The nuclear deubiquitylase BRCA1-associated protein 1 (BAP1) is frequently inactivated in malignant pleural mesothelioma (MPM) and germline BAP1 mutation predisposes to cancers including MPM. To explore the influence on cell physiology and drug sensitivity, we sequentially edited a predisposition mutation (w-) and a promoter trap (KO) into human mesothelial cells. BAP1w-/KO MeT5A cells express less BAP1 protein and phenocopy key aspects of BAP1 loss in MPM. Stable isotope labeling with amino acids in cell culture-mass spectrometry revealed evidence of metabolic adaptation, with concomitant alteration of cellular metabolites. In MeT5A, BAP1 deficiency reduces glycolytic enzyme levels but increases enzymes involved in the tricarboxylic acid cycle and anaplerotic pathways. Notably both argininosuccinate synthase 1 (ASS1), essential for cellular synthesis of arginine, and its substrate aspartate, are elevated in BAP1w-/KO MeT5A cells. Likewise, ASS1 expression is higher in BAP1-altered MPM cell lines, and inversely correlates with BAP1 in The Cancer Genome Atlas MESO dataset. Elevated ASS1 is also evident by IHC staining in epithelioid MPM lacking nuclear BAP1 expression, with improved survival among patients with BAP1-negative/ASS1-expressing tumors. Alterations in arginine metabolism may sensitize cells to metabolic drugs and we find that BAP1-negative/ASS1-expressing MPM cell lines are more sensitive to ASS1 inhibition, although not to inhibition of purine synthesis by mizoribine. Importantly, BAP1w-/KO MeT5A become desensitized to arginine deprivation by pegylated arginine deiminase (ADI-PEG20), phenocopying BAP1-negative/ASS1-expressing MPM cell lines.

IMPLICATIONS

Our data reveal an interrelationship between BAP1 and arginine metabolism, providing a potential means of identifying patients with epithelioid MPM likely to benefit from ADI-PEG20.

Abstract 1760: ADI-PEG20 and GC7 as a novel anti-metabolite strategy for the treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with less than 10% of patients surviving 5-years from diagnosis. Arginine deprivation using pegylated arginine deiminase (ADI-PEG20) is a novel treatment for mesothelioma deficient in the arginine biosynthetic enzyme ASS1. However, resistance to ADI-PEG20 in MPM is a significant problem and is characterized in part by reprogramming of the urea and polyamine metabolism pathway (Locke et al., 2016). We sought to identify a targeted metabolism-based therapy to overcome the emerging resistance and increase the efficiency of ADI-PEG20 treatment for patients with MPM.

New models of ADI-PEG20 resistance were generated by constant exposure of MPM cell lines to arginine deprivation for 6 months. ADI-PEG20 resistant and sensitive MPM cell lines were treated with a panel of polyamine targeting molecules. Metabolome alterations were studied by targeted metabolomics and glucose flux analyses.

Our results confirmed the up-regulation of ASS1 expression from (50 to 3000-fold) alongside upregulation of polyamine catabolism and upon generation of ADI-PEG20 resistance. Treatment of ADI-PEG20 resistant cell lines with a range of different polyamine inhibitors demonstrated that ADI-PEG20 resistant cell lines were significantly more sensitive to the spermidine-analogue GC7 than their respective ASS1-ve parental cell lines. Moreover, the combination of GC7 and ADI-PEG20 prevented the emergence of resistant cells in vitro. We observed a significant synergistic effect of GC7 and ADI-PEG20 in both ASS1-ve and ASS1+ve cell lines in 2D and 3D cell culture models as well as in our mice in vivo model. Metabolomics analysis revealed that GC7 treatment significantly impaired the TCA cycle. We hypothesize that GC7 is repurposing the fate of Acetyl-CoA to polyamine catabolism therefore shutting down the TCA cycle. Our findings provide novel insights into a polyamine targeted therapy that may prevent resistance to ADI-PEG20 treatment in MPM and related arginine-auxotrophic cancers.

Citation Format: Joséphine Carpentier, Peter W. Szlosarek, Sarah Anne Martin. ADI-PEG20 and GC7 as a novel anti-metabolite strategy for the treatment of malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1760.

A role for macrophages under cytokine control in mediating resistance to ADI-PEG20 (pegargiminase) in ASS1-deficient mesothelioma

BACKGROUND

Pegylated arginine deiminase (ADI-PEG20; pegargiminase) depletes arginine and improves survival outcomes for patients with argininosuccinate synthetase 1 (ASS1)-deficient malignant pleural mesothelioma (MPM). Optimisation of ADI-PEG20-based therapy will require a deeper understanding of resistance mechanisms, including those mediated by the tumor microenvironment. Here, we sought to reverse translate increased tumoral macrophage infiltration in patients with ASS1-deficient MPM relapsing on pegargiminase therapy.

METHODS

Macrophage-MPM tumor cell line (2591, MSTO, JU77) co-cultures treated with ADI-PEG20 were analyzed by flow cytometry. Microarray experiments of gene expression profiling were performed in ADI-PEG20-treated MPM tumor cells, and macrophage-relevant genetic "hits" were validated by qPCR, ELISA, and LC/MS. Cytokine and argininosuccinate analyses were performed using plasma from pegargiminase-treated patients with MPM.

RESULTS

We identified that ASS1-expressing macrophages promoted viability of ADI-PEG20-treated ASS1-negative MPM cell lines. Microarray gene expression data revealed a dominant CXCR2-dependent chemotactic signature and co-expression of VEGF-A and IL-1α in ADI-PEG20-treated MPM cell lines. We confirmed that ASS1 in macrophages was IL-1α-inducible and that the argininosuccinate concentration doubled in the cell supernatant sufficient to restore MPM cell viability under co-culture conditions with ADI-PEG20. For further validation, we detected elevated plasma VEGF-A and CXCR2-dependent cytokines, and increased argininosuccinate in patients with MPM progressing on ADI-PEG20. Finally, liposomal clodronate depleted ADI-PEG20-driven macrophage infiltration and suppressed growth significantly in the MSTO xenograft murine model.

CONCLUSIONS

Collectively, our data indicate that ADI-PEG20-inducible cytokines orchestrate argininosuccinate fuelling of ASS1-deficient mesothelioma by macrophages. This novel stromal-mediated resistance pathway may be leveraged to optimize arginine deprivation therapy for mesothelioma and related arginine-dependent cancers.

Arginine Deprivation in SCLC: Mechanisms and Perspectives for Therapy

Arginine deprivation has gained increasing traction as a novel and safe antimetabolite strategy for the treatment of several hard-to-treat cancers characterised by a critical dependency on arginine. Small cell lung cancer (SCLC) displays marked arginine auxotrophy due to inactivation of the rate-limiting enzyme argininosuccinate synthetase 1 (ASS1), and as a consequence may be targeted with pegylated arginine deiminase or ADI-PEG20 (pegargiminase) and human recombinant pegylated arginases (rhArgPEG, BCT-100 and pegzilarginase). Although preclinical studies reveal that ASS1-deficient SCLC cell lines are highly sensitive to arginine-degrading enzymes, there is a clear disconnect with the clinic with minimal activity seen to date that may be due in part to patient selection. Recent studies have explored resistance mechanisms to arginine depletion focusing on tumor adaptation, such as ASS1 re-expression and autophagy, stromal cell inputs including macrophage infiltration, and tumor heterogeneity. Here, we explore how arginine deprivation may be combined strategically with novel agents to improve SCLC management by modulating resistance and increasing the efficacy of existing agents. Moreover, recent work has identified an intriguing role for targeting arginine in combination with PD-1/PD-L1 immune checkpoint inhibitors and clinical trials are in progress. Thus, future studies of arginine-depleting agents with chemoimmunotherapy, the current standard of care for SCLC, may lead to enhanced disease control and much needed improvements in long-term survival for patients.

Role of 3'-Deoxy-3'-[18F] Fluorothymidine Positron Emission Tomography-Computed Tomography as a Predictive Biomarker in Argininosuccinate Synthetase 1-Deficient Thoracic Cancers Treated With Pegargiminase

Introduction

Pegargiminase (ADI-PEG 20I) degrades arginine in patients with argininosuccinate synthetase 1-deficient malignant pleural mesothelioma (MPM) and NSCLC. Imaging with proliferation biomarker 3'-deoxy-3'-[18F] fluorothymidine (18F-FLT) positron emission tomography (PET)-computed tomography (CT) was performed in a phase 1 study of pegargiminase with pemetrexed and cisplatin (ADIPemCis). The aim was to determine whether FLT PET-CT predicts treatment response earlier than CT.

Methods

A total of 18 patients with thoracic malignancies (10 MPM; eight NSCLC) underwent imaging. FLT PET-CT was performed at baseline (PET1), 24 hours post-pegargiminase monotherapy (PET2), post one cycle of ADIPemCis (PET3), and at end of treatment (EOT, PET4). CT was performed at baseline (CT1) and EOT (CT4). CT4 (modified) Response Evaluation Criteria in Solid Tumors (RECIST) response was compared with treatment response on PET (changes in maximum standardized uptake value [SUVmax] on European Organisation for Research and Treatment of Cancer-based criteria). Categorical responses (progression, partial response, and stable disease) for PET2, PET3, and PET4 were compared against CT using Cohen's kappa.

Results

ADIPemCis treatment response resulted in 22% mean decrease in size between CT1 and CT4 and 37% mean decrease in SUVmax between PET1 and PET4. PET2 agreed with CT4 response in 62% (8 of 13) of patients (p = 0.043), although decrease in proliferation (SUVmax) did not precede decrease in size (RECIST). Partial responses on FLT PET-CT were detected in 20% (3 of 15) of participants at PET2 and 69% (9 of 13) at PET4 with good agreement between modalities in MPM at EOT.

Conclusions

Early FLT imaging (PET2) agrees with EOT CT results in nearly two-thirds of patients. Both early and late FLT PET-CT provide evidence of response to ADIPemCis therapy in MPM and NSCLC. We provide first-in-human FLT PET-CT data in MPM, indicating it is comparable with modified RECIST.

A Phase 1 study of ADI-PEG20 (pegargiminase) combined with cisplatin and pemetrexed in ASS1-negative metastatic uveal melanoma

Metastatic uveal melanoma (UM) is a devastating disease with few treatment options. We evaluated the safety, tolerability and preliminary activity of arginine depletion using pegylated arginine deiminase (ADI‐PEG20; pegargiminase) combined with pemetrexed (Pem) and cisplatin (Cis) chemotherapy in a phase 1 dose‐expansion study of patients with argininosuccinate synthetase (ASS1)‐deficient metastatic UM. Eligible patients received up to six cycles of Pem (500 mg/m²) and Cis (75 mg/m²) every 3 weeks plus weekly intramuscular ADI (36 mg/m²), followed by maintenance ADI until progression (NCT02029690). Ten of fourteen ASS1‐deficient patients with UM liver metastases and a median of one line of prior immunotherapy received ADIPemCis. Only one ≥ grade 3 adverse event of febrile neutropenia was reported. Seven patients had stable disease with a median progression‐free survival of 3.0 months (range, 1.3–8.1) and a median overall survival of 11.5 months (range, 3.2–36.9). Despite anti‐ADI‐PEG20 antibody emergence, plasma arginine concentrations remained suppressed by 18 weeks with a reciprocal increase in plasma citrulline. Tumour rebiopsies at progression revealed ASS1 re‐expression as an escape mechanism. ADIPemCis was well tolerated with modest disease stabilisation in metastatic UM. Further investigation of arginine deprivation is indicated in UM including combinations with immune checkpoint blockade and additional anti‐metabolite strategies.

Phase 1, pharmacogenomic, dose-expansion study of pegargiminase plus pemetrexed and cisplatin in patients with ASS1-deficient non-squamous non-small cell lung cancer

Introduction

We evaluated the arginine‐depleting enzyme pegargiminase (ADI‐PEG20; ADI) with pemetrexed (Pem) and cisplatin (Cis) (ADIPemCis) in ASS1‐deficient non‐squamous non‐small cell lung cancer (NSCLC) via a phase 1 dose‐expansion trial with exploratory biomarker analysis.

Methods

Sixty‐seven chemonaïve patients with advanced non‐squamous NSCLC were screened, enrolling 21 ASS1‐deficient subjects from March 2015 to July 2017 onto weekly pegargiminase (36 mg/m²) with Pem (500 mg/m²) and Cis (75 mg/m²), every 3 weeks (four cycles maximum), with maintenance Pem or pegargiminase. Safety, pharmacodynamics, immunogenicity, and efficacy were determined; molecular biomarkers were annotated by next‐generation sequencing and PD‐L1 immunohistochemistry.

Results

ADIPemCis was well‐tolerated. Plasma arginine and citrulline were differentially modulated; pegargiminase antibodies plateaued by week 10. The disease control rate was 85.7% (n = 18/21; 95% CI 63.7%–97%), with a partial response rate of 47.6% (n = 10/21; 95% CI 25.7%–70.2%). The median progression‐free and overall survivals were 4.2 (95% CI 2.9–4.8) and 7.2 (95% CI 5.1–18.4) months, respectively. Two PD‐L1‐expressing (≥1%) patients are alive following subsequent pembrolizumab immunotherapy (9.5%). Tumoral ASS1 deficiency enriched for p53 (64.7%) mutations, and numerically worse median overall survival as compared to ASS1‐proficient disease (10.2 months; n = 29). There was no apparent increase in KRAS mutations (35.3%) and PD‐L1 (<1%) expression (55.6%). Re‐expression of tumoral ASS1 was detected in one patient at progression (n = 1/3).

Conclusions

ADIPemCis was safe and highly active in patients with ASS1‐deficient non‐squamous NSCLC, however, survival was poor overall. ASS1 loss was co‐associated with p53 mutations. Therapies incorporating pegargiminase merit further evaluation in ASS1‐deficient and treatment‐refractory NSCLC.

Phase 1b study of pegylated arginine deiminase (ADI-PEG 20) plus Pembrolizumab in advanced solid cancers

Background

Pegylated arginine deiminase (ADI-PEG 20) is a metabolism-based strategy that depletes arginine, resulting in tumoral stress and cytotoxicity. Preclinically, ADI-PEG 20 modulates T-cell activity and enhances the therapeutic efficacy of programmed death-1 (PD-1) inhibition.

Methods

A phase 1b study, including a dose-escalation cohort and an expansion cohort, was undertaken to explore the effects of ADI-PEG 20 in combination with pembrolizumab, an anti-PD-1 antibody, for safety, pharmacodynamics, and response. CD3 levels and programmed death-ligand 1 (PD-L1) expression were assessed in paired biopsies collected prior to and after ADI-PEG 20 treatment but before pembrolizumab.

Results

Twenty-five patients, nine in the dose-escalation cohort and sixteen in the expansion cohort, were recruited. Treatment was feasible with adverse events consistent with those known for each agent, except for Grade 3/4 neutropenia which was higher than expected, occurring in 10/25 (40%) patients. Mean arginine levels were suppressed for 1-3 weeks, but increased gradually. CD3+ T cells increased in 10/12 (83.3%) subjects following ADI-PEG 20 treatment, including in three partial responders (p = .02). PD-L1 expression was low and increased in 3/10 (30%) of subjects. Partial responses occurred in 6/25 (24%) heavily pretreated patients, in both argininosuccinate synthetase 1 proficient and deficient subjects.

Conclusions

The immunometabolic combination was safe with the caveat that the incidence of neutropenia might be increased compared with either agent alone. ADI-PEG 20 treatment increased T cell infiltration in the low PD-L1 tumor microenvironment. The recommended phase 2 doses are 36 mg/m2 weekly for ADI-PEG 20 and 200 mg every 3 weeks for pembrolizumab.

Expansion Phase 1 Study of Pegargiminase Plus Pemetrexed and Cisplatin in Patients With Argininosuccinate Synthetase 1-Deficient Mesothelioma: Safety, Efficacy, and Resistance Mechanisms

INTRODUCTION

Pegargiminase (ADI-PEG 20; ADI) degrades arginine and potentiates pemetrexed (Pem) cytotoxicity in argininosuccinate synthetase 1 (ASS1)-deficient malignant pleural mesothelioma (MPM). We conducted a phase 1 dose-expansion study at the recommended phase 2 dose of ADI-PEG 20 with Pem and cisplatin (ADIPemCis), to further evaluate arginine-lowering therapy in ASS1-deficient MPM and explore the mechanisms of resistance.

METHODS

A total of 32 patients with ASS1-deficient MPM (11 epithelioid; 10 biphasic;11 sarcomatoid) who were chemonaive received weekly intramuscular pegargiminase (36 mg/m2) with Pem (500 mg/m2) and cisplatin (75 mg/m2) intravenously, every 3 weeks (six cycles maximum). Maintenance pegargiminase was permitted until disease progression or withdrawal. Safety, pharmacodynamics, immunogenicity, and efficacy were determined. Biopsies were performed in progressing patients to explore the mechanisms of resistance to pegargiminase.

RESULTS

The treatment was well tolerated. Most adverse events were of grade 1/2, whereas four nonhematologic grade 3/4 adverse events related to pegargiminase were reversible. Plasma arginine decreased whereas citrulline increased; this was maintained by 18 weeks of ADIPemCis therapy. The disease control rate in 31 assessed patients was 93.5% (n = 29 of 31; 95% confidence interval [CI]: 78.6%-99.2%), with a partial response rate of 35.5% (n = 11 of 31; 95% CI: 19.2%-54.6%). The median progression-free and overall survivals were 5.6 (95% CI: 4.0-6.0) and 10.1 (95% CI: 6.1-11.1) months, respectively. Progression biopsies on pegargiminase revealed a statistically significant influx of macrophages (n = 6; p = 0.0255) and patchy tumoral ASS1 reexpression (n = 2 of 6). In addition, we observed increased tumoral programmed death-ligand 1-an ADI-PEG 20 inducible gene-and the formation of CD3-positive T lymphocyte aggregates on disease progression (n = 2 of 5).

CONCLUSIONS

The dose expansion of ADIPemCis confirmed the high clinical activity and good tolerability in ASS1-deficient poor-prognosis mesothelioma, underpinning an ongoing phase 3 study (ClinicalTrials.govNCT02709512). Notably, resistance to pegargiminase correlated with marked macrophage recruitment and-along with the tumor immune microenvironment-warrants further study to optimize arginine deprivation for the treatment of mesothelioma.

Abstract 2217: Pegylated arginine deiminase sensitizes ASS1-negative and KRAS mutant non-small cell lung cancer to PD-1 blockade immunotherapy

Cancer cells display dysregulated amino acid synthesis underlying a key metabolic hallmark of tumorigenesis that may be exploited therapeutically via specific amino acid deprivation. In particular, we have identified that arginine deprivation therapy with pegylated arginine deiminase (ADI-PEG20), which hydrolyses exogenous arginine to citrulline and ammonia, is clinically active in argininosuccinate synthetase 1 (ASS1)-deficient non-small cell lung cancer (NSCLC) and enhances the activity of the antifolate pemetrexed. Moreover, prior studies have shown that ADI-PEG20 also induces tumoral PD-L1 expression and T cell infiltration and is additive with anti-PD-1/PD-L1 antibodies in melanoma and colorectal murine models. Here, we reverse translated ADI-PEG20 studies from patients with ASS1-deficient NSCLC, co-associating with KRAS mutations, to analyze the impact of arginine deprivation with PD1-based checkpoint immunotherapy using murine NSCLC cell line models. First, we showed the CMT64 cell line, which harbors the KRAS-G12V mutation and is resistant to anti-programmed death antibodies, was ASS1-negative and highly sensitive to ADI-PEG20 in vitro. Next, CMT64 tumor cells were implanted subcutaneously into the right flank of syngeneic immunocompetent C57BL/6 mice. Once tumors reached 80mm3 animals were randomly assigned to four groups and treated with vehicle control (PBS), ADI-PEG20 (12 mg/kg), anti-PD-1 antibodies (10 mg/kg) or the combination of ADI-PEG20 and PD-1 blockade. CMT64 tumors were refractory to PD-1 blockade while ADI-PEG20 monotherapy induced a modest tumor response, with a two-fold decrease in tumor growth compared to control (p=0.0058). In contrast, the combination of ADI-PEG20 and PD-1 blockade elicited robust anti-tumor activity with a five-fold reduction in CMT64 tumor volume compared to control (p=0.0003). Modulation of the tumor microenvironment was observed by fluorescence activated cell sorting. In particular, we noted that tumor-associated macrophages showed higher expression of MHCII upon ADI-PEG20 and anti-PD-1 therapy (p&lt;0.05). Lastly, mice treated with ADI-PEG20 and anti-PD-1 therapy, survived longer than either ADI-PEG20 or anti-PD-1 therapy alone or PBS. In summary, arginine deprivation with ADI-PEG20 and PD-1 blockade is synthetically lethal in aggressive murine NSCLC and warrants further clinical investigation. A new clinical trial evaluating ADI-PEG20 with atezolizumab in combination with pemetrexed and platinum is opening in 2020 in patients with aggressive ASS1-deficient and PD-1/PD-L1 refractory lung adenocarcinoma (ClinicalTrials.gov Identifier: NCT03498222).

Citation Format: Iuliia Pavlyk, Julie Foster, Katie Dexter, Jane Sobasowski, John Bomalarski, Chiara Berlato, Frances Balkwill, Peter W Szlosarek. Pegylated arginine deiminase sensitizes ASS1-negative and KRAS mutant non-small cell lung cancer to PD-1 blockade immunotherapy [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 2217.

Cancer Burden Is Controlled by Mural Cell-β3-Integrin Regulated Crosstalk with Tumor Cells

Enhanced blood vessel (BV) formation is thought to drive tumor growth through elevated nutrient delivery. However, this observation has overlooked potential roles for mural cells in directly affecting tumor growth independent of BV function. Here we provide clinical data correlating high percentages of mural-β3-integrin-negative tumor BVs with increased tumor sizes but no effect on BV numbers. Mural-β3-integrin loss also enhances tumor growth in implanted and autochthonous mouse tumor models with no detectable effects on BV numbers or function. At a molecular level, mural-cell β3-integrin loss enhances signaling via FAK-p-HGFR-p-Akt-p-p65, driving CXCL1, CCL2, and TIMP-1 production. In particular, mural-cell-derived CCL2 stimulates tumor cell MEK1-ERK1/2-ROCK2-dependent signaling and enhances tumor cell survival and tumor growth. Overall, our data indicate that mural cells can control tumor growth via paracrine signals regulated by β3-integrin, providing a previously unrecognized mechanism of cancer growth control.

A Phase I Study of Pegylated Arginine Deiminase (Pegargiminase), Cisplatin, and Pemetrexed in Argininosuccinate Synthetase 1-Deficient Recurrent High-grade Glioma

PURPOSE

Patients with recurrent high-grade gliomas (HGG) are usually managed with alkylating chemotherapy ± bevacizumab. However, prognosis remains very poor. Preclinically, we showed that HGGs are a target for arginine depletion with pegargiminase (ADI-PEG20) due to epimutations of argininosuccinate synthetase (ASS1) and/or argininosuccinate lyase (ASL). Moreover, ADI-PEG20 disrupts pyrimidine pools in ASS1-deficient HGGs, thereby impacting sensitivity to the antifolate, pemetrexed.

PATIENTS AND METHODS

We expanded a phase I trial of ADI-PEG20 with pemetrexed and cisplatin (ADIPEMCIS) to patients with ASS1-deficient recurrent HGGs (NCT02029690). Patients were enrolled (01/16-06/17) to receive weekly ADI-PEG20 36 mg/m² intramuscularly plus pemetrexed 500 mg/m² and cisplatin 75 mg/m² intravenously once every 3 weeks for up to 6 cycles. Patients with disease control were allowed ADI-PEG20 maintenance. The primary endpoints were safety, tolerability, and preliminary estimates of efficacy.

RESULTS

Ten ASS1-deficient heavily pretreated patients were treated with ADIPEMCIS therapy. Treatment was well tolerated with the majority of adverse events being Common Terminology Criteria for Adverse Events v4.03 grade 1-2. The best overall response was stable disease in 8 patients (80%). Plasma arginine was suppressed significantly below baseline with a reciprocal increase in citrulline during the sampling period. The anti-ADI-PEG20 antibody titer rose during the first 4 weeks of treatment before reaching a plateau. Median progression-free survival (PFS) was 5.2 months (95% confidence interval (CI), 2.5-20.8) and overall survival was 6.3 months (95% CI, 1.8-9.7).

CONCLUSIONS

In this recurrent HGG study, ADIPEMCIS was well tolerated and compares favorably to historical controls. Additional trials of ADI-PEG20 in HGG are planned.

A major responder to ipilimumab and nivolumab in metastatic uveal melanoma with concomitant autoimmunity

The use of immune checkpoint inhibition has led to major improvements in outcome for patients with metastatic cutaneous melanoma. The combination of ipilimumab and nivolumab has demonstrated greater activity over single-agent immunotherapy in phase III trials. Clinical trials of combination CTLA-4 and PD-1 inhibition are underway in uveal melanoma, for which there are currently no data. Here, we present the case of a 74-year-old male patient with metastatic uveal melanoma, who was treated with a combination of ipilimumab and nivolumab. He developed sequential autoimmune transaminitis, diabetes and uveitis, which necessitated discontinuation of maintenance nivolumab 3 months after commencement of treatment. The patient continues to demonstrate an ongoing partial response 10 months from the initial combination immunotherapy, with the evidence of depigmentation of the primary ocular tumour.

Phase 1 Dose-Escalation Study of Pegylated Arginine Deiminase, Cisplatin, and Pemetrexed in Patients With Argininosuccinate Synthetase 1-Deficient Thoracic Cancers

Purpose Pegylated arginine deiminase (ADI-PEG 20) depletes essential amino acid levels in argininosuccinate synthetase 1 (ASS1) -negative tumors by converting arginine to citrulline and ammonia. The main aim of this study was to determine the recommended dose, safety, and tolerability of ADI-PEG 20, cisplatin, and pemetrexed in patients with ASS1-deficient malignant pleural mesothelioma (MPM) or non-small-cell lung cancer (NSCLC). Patients and Methods Using a 3 + 3 + 3 dose-escalation study, nine chemotherapy-naïve patients (five MPM, four NSCLC) received weekly ADI-PEG 20 doses of 18 mg/m2, 27 mg/m2, or 36 mg/m2, together with pemetrexed 500 mg/m2 and cisplatin 75 mg/m2 which were given every three weeks (maximum of six cycles). Patients achieving stable disease or better could continue ADI-PEG 20 monotherapy until disease progression or withdrawal. Adverse events were assessed by Common Terminology Criteria for Adverse Events version 4.03, and pharmacodynamics and immunogenicity were also evaluated. Tumor response was assessed by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 for NSCLC and by modified RECIST criteria for MPM. Results No dose-limiting toxicities were reported; nine of 38 reported adverse events (all grade 1 or 2) were related to ADI-PEG 20. Circulating arginine concentrations declined rapidly, and citrulline levels increased; both changes persisted at 18 weeks. Partial responses were observed in seven of nine patients (78%), including three with either sarcomatoid or biphasic MPM. Conclusion Target engagement with depletion of arginine was maintained throughout treatment with no dose-limiting toxicities. In this biomarker-selected group of patients with ASS1-deficient cancers, clinical activity was observed in patients with poor-prognosis tumors. Therefore, we recommend a dose for future studies of weekly ADI-PEG 20 36 mg/m2 plus three-weekly cisplatin 75 mg/m2 and pemetrexed 500 mg/m2.

Arginine Deprivation With Pegylated Arginine Deiminase in Patients With Argininosuccinate Synthetase 1-Deficient Malignant Pleural Mesothelioma: A Randomized Clinical Trial

IMPORTANCE

Preclinical studies show that arginine deprivation is synthetically lethal in argininosuccinate synthetase 1 (ASS1)-negative cancers, including mesothelioma. The role of the arginine-lowering agent pegylated arginine deiminase (ADI-PEG20) has not been evaluated in a randomized and biomarker-driven study among patients with cancer.

OBJECTIVE

To assess the clinical impact of arginine depletion in patients with ASS1-deficient malignant pleural mesothelioma.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter phase 2 randomized clinical trial, the Arginine Deiminase and Mesothelioma (ADAM) study, was conducted between March 2, 2011, and May 21, 2013, at 8 academic cancer centers. Immunohistochemical screening of 201 patients (2011-2013) identified 68 with advanced ASS1-deficient malignant pleural mesothelioma.

INTERVENTIONS

Randomization 2:1 to arginine deprivation (ADI-PEG20, 36.8 mg/m2, weekly intramuscular) plus best supportive care (BSC) or BSC alone.

MAIN OUTCOMES AND MEASURES

The primary end point was progression-free survival (PFS) assessed by modified Response Evaluation Criteria in Solid Tumors (RECIST) (target hazard ratio, 0.60). Secondary end points were overall survival (OS), tumor response rate, safety, and quality of life, analyzed by intention to treat. We measured plasma arginine and citrulline levels, anti-ADI-PEG20 antibody titer, ASS1 methylation status, and metabolic response by 18F-fluorodeoxyglucose positron-emission tomography.

RESULTS

Median (range) follow-up in 68 adults (median [range] age, 66 [48-83] years; 19% female) was 38 (2.5-39) months. The PFS hazard ratio was 0.56 (95% CI, 0.33-0.96), with a median of 3.2 months in the ADI-PEG20 group vs 2.0 months in the BSC group (P = .03) (absolute risk, 18% vs 0% at 6 months). Best response at 4 months (modified RECIST) was stable disease: 12 of 23 (52%) in the ADI-PEG20 group vs 2 of 9 (22%) in the BSC group (P = .23). The OS curves crossed, so life expectancy was used: 15.7 months in the ADI-PEG20 group vs 12.1 months in the BSC group (difference of 3.6 [95% CI, -1.0 to 8.1] months; P = .13). The incidence of symptomatic adverse events of grade at least 3 was 11 of 44 (25%) in the ADI-PEG20 group vs 4 of 24 (17%) in the BSC group (P = .43), the most common being immune related, nonfebrile neutropenia, gastrointestinal events, and fatigue. Differential ASS1 gene-body methylation correlated with ASS1 immunohistochemistry, and longer arginine deprivation correlated with improved PFS.

CONCLUSIONS AND RELEVANCE

In this trial, arginine deprivation with ADI-PEG20 improved PFS in patients with ASS1-deficient mesothelioma. Targeting arginine is safe and warrants further clinical investigation in arginine-dependent cancers.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01279967.

Abstract 1050: Inhibition of the polyamine synthesis pathway is synthetically lethal with loss of argininosuccinate synthase 1 in cancer

Argininosuccinate synthetase 1 (ASS1) is the rate-limiting enzyme for arginine biosynthesis. ASS1 expression is lost in a range of different tumour types, including 50% of malignant pleural mesotheliomas. Starving ASS1-deficient cells of arginine with arginine blockers such as ADI-PEG20 can induce selective lethality and has shown great promise in the clinic. However, recent data has shown that ASS1-deficient tumours can become resistant to this therapy although the mechanisms behind this resistance remain unclear. We have generated the first model of ADI-PEG20 resistance in mesothelioma cells whereby we observe re-expression of ASS1, via demethylation of the ASS1 promoter. Through coordinated transcriptomic and metabolomic profiling, we have shown that ASS1-deficient cells have decreased levels of acetylated polyamines, resulting in an increased activation of the polyamine synthesis pathway. Upon arginine deprivation, we observe a decrease in polyamine metabolites in the ASS1-deficient cells only, suggesting that exogenous arginine is required to maintain polyamine biosynthesis in the absence of ASS1. We identify for the first time a compensatory increase in polyamine synthesis gene expression upon ASS1 loss and highlight a synthetic lethal dependence between ASS1-deficiency and polyamine metabolism, which could potentially be exploited for the treatment of ASS1-negative cancers.

Citation Format: Peter W. Szlosarek, Matthew Locke, Essam Ghazaly, Laura Lattanzio, Cristiana Lo Nigro, Sarah A. Martin. Inhibition of the polyamine synthesis pathway is synthetically lethal with loss of argininosuccinate synthase 1 in cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1050.

Clinical activity and safety of Pembrolizumab in Ipilimumab pre-treated patients with uveal melanoma

BACKGROUND

Untreated metastatic uveal melanoma (UM) carries a grave prognosis. Unlike cutaneous melanoma (CM), there are no established treatments known to significantly improve outcomes for a meaningful proportion of patients. Inhibition of the PD1-PDL1 axis has shown promise in the management of CM and we here report a two center experience of UM patients receiving pembrolizumab.

METHODS

To assess the efficacy and safety of pembrolizumab, we retrospectively analyzed outcome data of 25 consecutive UM patients participating in the MK3475 expanded access program (EAP) who received pembrolizumab at 2 mg/kg 3 weekly. Tumor assessment was evaluated using RECIST 1.1 and immune-related Response Criteria (irRC) by CT scanning. Toxicity was recorded utilizing Common Terminology Criteria for Adverse Events ("CTCAE") v4.03.

RESULTS

Twenty-five patients were identified receiving a median of six cycles of treatment. Two patients achieved a partial response and six patients stable disease. After a median follow-up of 225 d median progression free survival (PFS) was 91 d and overall survival (OS) was not reached. There was a significant trend for improved outcomes in patients with extrahepatic disease progression as opposed to liver only progression at the outset. Five patients experienced grade 3 or 4 adverse events (AEs); there were no treatment related deaths.

CONCLUSIONS

Pembrolizumab 2mg/kg q3w is a safe option in UM patients. Disease control rates, particularly in the subgroup of patients without progressive liver disease at the outset are promising; these results merit further investigation in clinical trials possibly incorporating liver targeted treatment modalities.

Hypoxia-induced nitric oxide production and tumour perfusion is inhibited by pegylated arginine deiminase (ADI-PEG20)

The hypoxic tumour microenvironment represents an aggressive, therapy-resistant compartment. As arginine is required for specific hypoxia-induced processes, we hypothesised that arginine-deprivation therapy may be useful in targeting hypoxic cancer cells. We explored the effects of the arginine-degrading agent ADI-PEG20 on hypoxia-inducible factor (HIF) activation, the hypoxia-induced nitric oxide (NO) pathway and proliferation using HCT116 and UMUC3 cells and xenografts. The latter lack argininosuccinate synthetase (ASS1) making them auxotrophic for arginine. In HCT116 cells, ADI-PEG20 inhibited hypoxic-activation of HIF-1α and HIF-2α, leading to decreased inducible-nitric oxide synthase (iNOS), NO-production, and VEGF. Interestingly, combining hypoxia and ADI-PEG20 synergistically inhibited ASS1. ADI-PEG20 inhibited mTORC1 and activated the unfolded protein response providing a mechanism for inhibition of HIF and ASS1. ADI-PEG20 inhibited tumour growth, impaired hypoxia-associated NO-production, and decreased vascular perfusion. Expression of HIF-1α/HIF-2α/iNOS and VEGF were reduced, despite an increased hypoxic tumour fraction. Similar effects were observed in UMUC3 xenografts. In summary, ADI-PEG20 inhibits HIF-activated processes in two tumour models with widely different arginine biology. Thus, ADI-PEG20 may be useful in the clinic to target therapy-resistant hypoxic cells in ASS1-proficient tumours and ASS1-deficient tumours.

Abstract 1156: Widespread deficiency of ASS1 in uveal melanoma and sensitivity to pegylated arginine deiminase

Uveal melanoma, involving the iris, choroid and ciliary body, is the commonest intraocular tumor in adults. Approximately half of these patients will develop metastasis with a high mortality despite currently available systemic therapies including immune checkpoint blockade. The urea cycle enzyme argininosuccinate synthetase 1 (ASS1), responsible for arginine synthesis, is downregulated in melanoma and other cancers and these are therefore sensitive to arginine deprivation therapy. In early phase trials of the arginine depletor pegylated arginine deiminase, ADI-PEG20, uveal melanoma, in particular, was identified with potential for further therapeutic development. Here, we tested uveal melanoma cell lines for sensitivity to ADI-PEG20 and analyzed enucleated tumors for ASS1 expression to assess the extent of ASS1 deficiency.

Methods: ASS1 gene and protein expression were assessed in three uveal melanoma cell lines (OMM1, OMM2.5 and Mel270) by real-time quantitative PCR (qPCR) and western blot analysis, respectively. Sensitivity to ADI-PEG20 was performed using the cell viability MTS assay. We screened 102 enucleated choroidal and ciliary body melanomas for ASS1 protein using red chromogen for the immunohistochemistry (IHC) and selected the most positive area for scoring.

Results: The uveal melanoma cell lines expressed negligible ASS1 mRNA with a complete absence of ASS1 protein. All three ASS1 negative uveal melanoma cell lines were sensitive to ADI-PEG20 by day 6 of the MTS assay, whereas an ASS1-expressing positive control cell line was resistant. There was a convincing lack of ASS1 expression (&lt;5% staining) in the majority of uveal melanomas (75/102; 74%) and where ASS1 was present (5-30% staining) in the remainder (27/102; 26%) this was due to a mixture of melanoma cells and intratumoral macrophages, the latter being confirmed with CD68 (IHC) in the cases with the highest ASS1 expression.

Conclusion: ASS1 is absent in the tested uveal melanoma cell lines and predisposes to arginine sensitivity with ADI-PEG20 in vitro. Most primary uveal melanomas have a marked deficiency of ASS1, representing a good target for exploring arginine deprivation further in the clinic, either alone or in combination with rationally selected agents. A trial of ADI-PEG20 combined with carboplatin and paclitaxel is planned in metastatic malignant melanoma with an expanded cohort in patients with uveal disease.

Citation Format: Ramsay S. Khadeir, Melissa M. Phillips, Mandeep S. Sgoo, Amit Arora, Victoria Cohen, Caroline Thaung, Peter W. Szlosarek. Widespread deficiency of ASS1 in uveal melanoma and sensitivity to pegylated arginine deiminase. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1156. doi:10.1158/1538-7445.AM2015-1156

Abstract 3360: Macrophages promote resistance to pegylated arginine deiminase in malignant pleural mesothelioma

Background

Approximately 50% of all malignant pleural mesotheliomas (MPM) are deficient in argininosuccinate synthetase (ASS1), the rate-limiting enzyme in arginine biosynthesis, and are therefore sensitive to arginine deprivation. This discovery in MPM has been translated into the clinic using the arginine depletor pegylated arginine deiminase (ADI-PEG20) which showed a halving in the risk of disease progression in a randomized phase II study (Szlosarek et al, ASCO 2014). However, unstudied to date, stromal resistance to ADI-PEG20 may reduce its efficacy. Here, we studied the effect of macrophages, which are abundant in mesothelioma, on the tumor cytotoxicity of ADI-PEG20.

Methods

ASS1 negative MPM cell lines treated with ADI-PEG20 were analysed using the Affymetrix Human Genome U133 Plus 2.0 array, with validation of genes involved in stromal-tumor cell communication. Additional studies involved using tumor-macrophage co-culture experiments, mass spectrometry and an MPM xenograft model.

Results

A distinct pro-inflammatory cytokine gene expression signature involved in macrophage recruitment and activation was identified in the ADI-PEG20-treated ASS1 negative MPM cell lines. Notably, a significant increase in ASS1 negative MPM cell viability was seen upon co-culture with macrophages in the presence of ADI-PEG20. This was accompanied by a significant increase in ASS1 expression in co-cultured macrophages, with a corresponding increase in argininosuccinate lyase (ASL) expression in co-cultured tumor cells and a doubling in levels of the arginine precursor, argininosuccinate, in cell supernatant. The addition of argininosuccinate to tumor cell media rescued ASS1 negative MPM cells from ADI-PEG20 cytotoxicity, while the macrophage-mediated resistance to ADI-PEG20 was abrogated following ASL knockdown in MPM cells. Finally, xenograft studies demonstrated a significant reduction in tumor volume in mice treated with ADI-PEG20 in combination with macrophage depletion, compared with ADI-PEG20 monotherapy.

Conclusion

Collectively, our data indicate that as a result of metabolic ‘cross-talk’ between macrophages and ASS1 negative MPM cells, macrophages mediate MPM resistance to ADI-PEG20 via the provision of argininosuccinate. Our studies provide a rationale for combining ADI-PEG20 with an inhibitor of macrophage recruitment in the treatment of ASS1-deficient mesothelioma.

Citation Format: Melissa M. Phillips, Ramsay Khadeir, Laura Tookman, Fiona McCarthy, Jeremy Steele, John Bomalaski, Essam Ghazaly, Peter W. Szlosarek. Macrophages promote resistance to pegylated arginine deiminase in malignant pleural mesothelioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3360. doi:10.1158/1538-7445.AM2015-3360

Rewiring mitochondrial pyruvate metabolism: switching off the light in cancer cells?

Metabolic reprogramming is a characteristic of cancer cells. Three studies published in this month's Molecular Cell provide novel insights into the role of mitochondrial pyruvate in tumor metabolism and describe how targeting pyruvate transport and metabolism may afford therapeutic benefit.

Abstract 1431: Gene expression analysis of argininosuccinate synthetase loss and the effects of pegylated arginine deiminase in malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a devastating asbestos-related malignancy that is increasing in many countries worldwide with few systemic treatment options beyond platinum and antifolate chemotherapy. Deficiency of the arginine biosynthetic enzyme argininosuccinate synthetase (ASS1) occurs in up to 50% of MPM cell lines and primary tumors and is being validated as a biomarker in patients treated with the arginine-depleting agent, pegylated arginine deiminase (ADI-PEG20). To understand the role of ASS1 loss and the effect of the ADI-PEG20 in MPM we used pathway analysis tools on microarray gene expression data from a representative panel of MPM cell lines. First, we identified that ASS1 loss was linked to several protumorigenic functions including increased cell invasiveness and migration, which were confirmed subsequently using invasion assays and organotypic modelling, respectively. We also detected a large number of enriched pathways connected to the immune response including communication between innate and adaptive immune cells and interferon signalling. Furthermore, ASS1 deficiency was linked to worse outcome with a median survival of 6 months in ASS1 low expressors compared to 12 months for ASS1 high expressors using a retrospective dataset (n=41; p=0.003). Second, ADI-PEG20 treatment modulated numerous pathways in ASS1-deficient cells including suppression of mTOR and folate metabolism, while promoting stress, oxidant and amino acid signalling. Third, bioinformatics analyses of drug interactions using Connectivity map revealed that arginine deprivation using ADI-PEG20 may potentiate several chemotherapeutic and targeted agents in the clinic. Taken together, our bioinformatics approach links loss of ASS1 in MPM cells to a more aggressive phenotype and identifies several potential combination strategies with ADI-PEG20 for further clinical investigation.

Citation Format: Rosalind Cutts, Puthen V. Jithesh, Barbara Delage, Phuong Luong, Gareth Thomas, Claude Chelala, Peter W. Szlosarek. Gene expression analysis of argininosuccinate synthetase loss and the effects of pegylated arginine deiminase in malignant pleural mesothelioma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1431. doi:10.1158/1538-7445.AM2014-1431

Targeting arginine-dependent cancers with arginine-degrading enzymes: opportunities and challenges

Arginine deprivation is a novel antimetabolite strategy for the treatment of arginine-dependent cancers that exploits differential expression and regulation of key urea cycle enzymes. Several studies have focused on inactivation of argininosuccinate synthetase 1 (ASS1) in a range of malignancies, including melanoma, hepatocellular carcinoma (HCC), mesothelial and urological cancers, sarcomas, and lymphomas. Epigenetic silencing has been identified as a key mechanism for loss of the tumor suppressor role of ASS1 leading to tumoral dependence on exogenous arginine. More recently, dysregulation of argininosuccinate lyase has been documented in a subset of arginine auxotrophic glioblastoma multiforme, HCC and in fumarate hydratase-mutant renal cancers. Clinical trials of several arginine depletors are ongoing, including pegylated arginine deiminase (ADI-PEG20, Polaris Group) and bioengineered forms of human arginase. ADI-PEG20 is furthest along the path of clinical development from combinatorial phase 1 to phase 3 trials and is described in more detail. The challenge will be to identify tumors sensitive to drugs such as ADI-PEG20 and integrate these agents into multimodality drug regimens using imaging and tissue/fluid-based biomarkers as predictors of response. Lastly, resistance pathways to arginine deprivation require further study to optimize arginine-targeted therapies in the oncology clinic.

Prognostic and therapeutic impact of argininosuccinate synthetase 1 control in bladder cancer as monitored longitudinally by PET imaging

Targeted therapies have yet to have significant impact on the survival of patients with bladder cancer. In this study, we focused on the urea cycle enzyme argininosuccinate synthetase 1 (ASS1) as a therapeutic target in bladder cancer, based on our discovery of the prognostic and functional import of ASS1 in this setting. ASS1 expression status in bladder tumors from 183 Caucasian and 295 Asian patients was analyzed, along with its hypothesized prognostic impact and association with clinicopathologic features, including tumor size and invasion. Furthermore, the genetics, biology, and therapeutic implications of ASS1 loss were investigated in urothelial cancer cells. We detected ASS1 negativity in 40% of bladder cancers, in which multivariate analysis indicated worse disease-specific and metastasis-free survival. ASS1 loss secondary to epigenetic silencing was accompanied by increased tumor cell proliferation and invasion, consistent with a tumor-suppressor role for ASS1. In developing a treatment approach, we identified a novel targeted antimetabolite strategy to exploit arginine deprivation with pegylated arginine deiminase (ADI-PEG20) as a therapeutic. ADI-PEG20 was synthetically lethal in ASS1-methylated bladder cells and its exposure was associated with a marked reduction in intracellular levels of thymidine, due to suppression of both uptake and de novo synthesis. We found that thymidine uptake correlated with thymidine kinase-1 protein levels and that thymidine levels were imageable with [(18)F]-fluoro-L-thymidine (FLT)-positron emission tomography (PET). In contrast, inhibition of de novo synthesis was linked to decreased expression of thymidylate synthase and dihydrofolate reductase. Notably, inhibition of de novo synthesis was associated with potentiation of ADI-PEG20 activity by the antifolate drug pemetrexed. Taken together, our findings argue that arginine deprivation combined with antifolates warrants clinical investigation in ASS1-negative urothelial and related cancers, using FLT-PET as an early surrogate marker of response.

Abstract 1885: A comprehensive untargeted UPLC-MS based metabolomic analysis of ASS1-deficient solid tumor cell lines treated with arginine deiminase

Background

Arginine is an important amino acid for tumor cell growth and development. Argininosuccinate synthetase 1 (ASS1) is a key enzyme required for biosynthesis of arginine. Preclinically, ASS1-deficient tumor cells are particularly sensitive to arginine depletion, and randomised trials exploring this strategy are in progress in hepatocellular carcinoma and mesothelioma using the drug pegylated arginine deiminase (ADI-PEG20). In this study, we determined the metabolic changes induced by ADI-PEG20 treatment in a panel of bladder cancer and mesothelioma cell lines with promoter methylation-dependent silencing of ASS1. We used two cancer cell lines expressing ASS1 as a control.

Methods

Malignant mesothelioma, ASS1-negative (H2591, MSTO and JU77) and ASS1- positive (H28) cell lines were used. For bladder cancer, ASS1-negative (T24, 253J, UMUC-3) and ASS1-positive (RT112) cell lines were also used. All cells were treated with 750 ng/ml of ADI-PEG20 for 24 hours which induces up to 90% killing of arginine-dependent cell lines. Then, ultra performance liquid chromatography-mass spectrometry (UPLC-MS) technique was employed for untargeted quantitation of the metabolomic changes induced by ADI-PEG20.

Results:

All cell lines treated with ADI-PEG20 could be clearly discriminated from their untreated control pair when using PCA multivariate analysis. Arginine depletion was noted in all treated cell lines irrespective of ASS1 expression, however the reduction was at least one-log-fold greater in the ASS1-negative tumor cells. Citrulline, n-a-acetylcitrulline, and glutamine were upregulated specifically in ASS1-negative tumor cell lines. The main impact of ADI-PEG20 treatment was on pyrimidine metabolism in the ASS1-deficient tumor cells with upregulation of thymine and downregulation of thymidine, ureidosuccinic acid, uridine monophosphate and 5-hydroxymethyluracil. Notably, we identified that the reduction of the thymidine nucleotide pool was linked to suppression of thymidylate synthetase and dihydrofolate reductase, and paradoxically, reduced uptake of 3H-FLT. Finally, ADI-PEG20 caused variable effects on cytidine, uridine and ornithine levels in different cancer cell lines.

Conclusion

This study provides an insight into possible metabolic pathways affected by ADI-PEG20. The impact of ADI-PEG20 on thymidine metabolism, in particular, may be employed as a potential biomarker for optimizing the efficacy of ADI-PEG20 in the treatment of arginine auxotophic cancers.

Citation Format: Essam A. Ghazaly, Phuong Luong, Malgorzata Chmielewska-Kassasir, Chantelle Hudson, John S. Bomalaski, L Wozniak, Norbert E. Avril, Simon P. Joel, Peter W. Szlosarek. A comprehensive untargeted UPLC-MS based metabolomic analysis of ASS1-deficient solid tumor cell lines treated with arginine deiminase. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1885. doi:10.1158/1538-7445.AM2013-1885

Abstract B139: Arginine deprivation with pegylated arginine deiminase regulates key metabolic genes in RNA and DNA synthesis in ASS1-deficient malignant mesothelioma cells: Clinical implications

Tumors deficient in argininosuccinate synthetase-1 (ASS1), a key enzyme involved in arginine synthesis, are auxotrophic for arginine and sensitive to amino acid deprivation. Currently, several trials are testing the arginine-depleting agent, pegylated arginine deiminase (ADI-PEG20) in patients with cancer, including a randomised phase II multicenter UK study in patients with ASS1-deficient mesothelioma (NCT01279967). Here, we sought to identify key pathways involved in the mechanism of action of ADI-PEG20 using a panel of ASS1-deficient malignant mesothelioma (MPM) cell lines as our model. Epithelioid (2591), biphasic (MSTO) and sarcomatoid (JU77) mesothelioma cells were exposed to ADI-PEG20 and analysed using Affymetrix gene expression profiling with validation of candidate genes by qPCR and western blotting, and metabolic studies by LC-MS and 1H-NMR. ADI-PEG20 modulated several metabolic genes involved in nucleotide synthesis in the MPM cell lines. We identified suppression of ribonucleotide reductase (M1 and M2 isoforms), thymidylate synthase and dihydrofolate reductase by 24hrs, the latter enzymes being known targets of pemetrexed, a multitargeted antifolate used in the first-line therapy of mesothelioma. Moreover, metabolic profiling revealed upregulation of several modified nucleosides, including ribothymidine and downregulation of the nucleotide, guanosine monophosphate. Lastly, in vitro studies confirmed potentiation between ADI-PEG20 and pemetrexed and sequential therapy led to reduced tumor growth in vivo. In conclusion, arginine depletion modulates several key enzymes involved in nucleotide synthesis, providing a rationale for combining ADI-PEG20 with pemetrexed-containing regimens in the clinic.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B139.

Abstract 76: Epigenetic silencing of argininosuccinate synthetase renders human bladder cancer cells sensitive to pegylated arginine deiminase

Tumors deficient in argininosuccinate synthetase (ASS1), a key enzyme involved in arginine synthesis, are auxtrophic for arginine and sensitive to amino acid deprivation. Based on reports of instability at 9q34 in bladder cancer, the locus of ASS1, we investigated ASS1 status using a variety of molecular and genetic techniques and assessed the impact of arginine deprivation on the viability of bladder cancer cell lines in vitro and in vivo. Initially, we revealed very low mRNA levels and no ASS1 protein in 3 of 7 bladder cancer cell lines (253J, EJ28 and UMUC-3). The ASS1-negative cell lines were all hypermethylated at the ASS1 promoter, compared with the ASS1-positive cell lines, which were hypomethylated. There was no evidence for ASS1 mutations by gene sequencing or loss of heterozygosity by fluorescence in situ hybridization and single nucleotide polymorphism arrays. An analysis of 48 patients with bladder cancer revealed 65% were ASS1-negative by immunohistochemistry, with evidence for ASS1 methylation as the mechanism for ASS1 inactivation. The arginine depleting agent, pegylated arginine deiminase (ADI-PEG20), triggered caspase-dependent and independent apoptosis of 253J and EJ28 cell lines, respectively, whereas ASS1-positive control bladder cell lines were resistant to ADI-PEG20. We have identified downregulation of ribonucleotide reductase M2 (RRM2) as a biomarker of ADI-PEG20 activity and ongoing work is focused on combining ADI-PEG20 with cisplatin-doublet chemotherapy in vivo. In summary, we propose that epigenetic silencing of ASS1 renders bladder cancer sensitive to ADI-PEG20, providing a novel approach for the treatment of a common and therapeutically challenging cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 76. doi:10.1158/1538-7445.AM2011-76

Abstract 4067: Pegylated arginine deiminase (ADI-PEG20) as a potential novel therapy for argininosuccinate synthetase-deficient acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common leukemia in adults and the second most common leukemia in children, accounting for a significant share of health care costs with ten thousand cases diagnosed per annum in the US alone. Enzyme-based therapy in the form of asparaginase has revolutionized the treatment of acute lymphoblastic leukemia and there is increasing interest in exploiting analogous tractable metabolic defects in AML. Interestingly, arginine auxotrophic tumors due to deficiency of the rate-limiting enzyme for arginine production, argininosuccinate synthetase (ASS1) are susceptible to arginine-degrading enzymes. Here, we studied whether ASS1 negativity would predict for the efficacy of pegylated arginine deiminase (ADI-PEG20) using AML cell lines and primary AML samples. A lack of ASS1 protein was identified in three of seven leukemic cell lines (K562, Kasumi and KG-1) and in all nine samples from patients with cytogenetically normal and abnormal karotype AML. Methylation of the ASS1 promoter correlated with reduced levels of ASS1 mRNA and absence of ASS1 expression. Bone marrow trephines from patients with AML revealed absence of ASS1 protein in 87% (46/53) of samples by immunohistochemistry, indicating that ASS1 expression may be a biomarker of response to ADI-PEG20 in vivo. Increased levels of ASS1 mRNA and detectable ASS1 protein expression were noted in acute promyelocytic leukemia with the translocation t(15;17). Significantly, ADI-PEG20 reduced the viability of ASS1-negative AML lines whereas the ASS1-positive control lines, Fujioka and U937, were resistant to drug-induced arginine deprivation. Recently, we have identified primary ASS1-negative AML samples with good engraftment in NOD/SCID mice and are proceeding to test the efficacy of ADI-PEG20 using this primary AML xenograft model. Based on our preliminary data and the potential efficacy with low toxicity of arginine deprivation in humans, a phase II trial of ADI-PEG20 is planned in patients with relapsed AML.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4067. doi:10.1158/1538-7445.AM2011-4067

Arginine deprivation and argininosuccinate synthetase expression in the treatment of cancer

Arginine, a semi-essential amino acid in humans, is critical for the growth of human cancers, particularly those marked by de novo chemoresistance and a poor clinical outcome. In addition to protein synthesis, arginine is involved in diverse aspects of tumour metabolism, including the synthesis of nitric oxide, polyamines, nucleotides, proline and glutamate. Tumoural downregulation of the enzyme argininosuccinate synthetase (ASS1), a recognised rate-limiting step in arginine synthesis, results in an intrinsic dependence on extracellular arginine due to an inability to synthesise arginine for growth. This dependence on extracellular arginine is known as arginine auxotrophy. Several tumours are arginine auxotrophic, due to variable loss of ASS1, including hepatocellular carcinoma, malignant melanoma, malignant pleural mesothelioma, prostate and renal cancer. Importantly, targeting extracellular arginine for degradation in the absence of ASS1 triggers apoptosis in arginine auxotrophs. Several phase I/II clinical trials of the arginine-lowering drug, pegylated arginine deiminase, have shown encouraging evidence of clinical benefit and low toxicity in patients with ASS1-negative tumours. In part, ASS1 loss is due to epigenetic silencing of the ASS1 promoter in various human cancer cell lines and tumours, and it is this silencing that confers arginine auxotrophy. In relapsed ovarian cancer, this is associated with platinum refractoriness. In contrast, several platinum sensitive tumours, including primary ovarian, stomach and colorectal cancer, are characterised by ASS1 overexpression, which is regulated by proinflammatory cytokines. This review examines the prospects for novel approaches in the prevention, diagnosis and treatment of malignant disease based on ASS1 pathophysiology and its rate-limiting product, arginine.

Abstract 4445: Pegylated arginine deiminase induces mitochondrial apoptosis and synergizes with cisplatin in ASS1-negative malignant pleural mesothelioma

We have explored the role of pegylated arginine deiminase (ADI-PEG20), an arginine catabolizing enzyme, in argininosuccinate synthetase 1 (ASS1)-negative malignant pleural mesothelioma (MPM). MPM is a chemorefractory disease, increasing worldwide, with a median survival of less than 1 year. Novel treatments are urgently required. MPM tumors, lacking ASS1, are auxotrophic for arginine and therefore sensitive to arginine depletion driven by ADI-PEG20.

First we assessed the impact of ADI-PEG20 on global gene expression to identify novel interacting pathways in the ASS1-negative MPM cell line, JU77, using the human genome U133 Plus 2.0 Array from Affymetrix combined with bioinformatic analysis. Next, three ASS1-negative MPM cell lines (MSTO-211H, 2591 and JU77) were treated in triplicate with different fixed ratios of ADI-PEG20 and cisplatin. Cellular viability was determined 6 days post-treatment by MTS colorimetric assay. Apoptosis protein induction by ADI-PEG20 and platinum, alone and in combination, was measured by western blot after mitochondrial and cytosolic fractionation. Drug interactions were analyzed using the isobologram method of Chou and Talalay.

ADI-PEG20 modulated several thousand genes involved in cell cycle, DNA damage, immune, and inflammatory pathways in the ASS1-negative JU77 MPM cell line by 24hrs of drug treatment. In contrast, stable transfection of ASS1 cDNA in ASS1-negative MPM cell lines resulted in resistance to ADI-PEG20 with minimal evidence of gene modulation by 24hr of drug treatment as assessed in the JU77 MPM cell line. ADI-PEG20 triggered mitochondria-dependent apoptosis as evidenced by Smac release from mitochondria into the cytosol of ASS1-negative MPM cell lines. We confirmed that arginine depletion by ADI-PEG20 altered the mTOR/p70S6K signaling pathway and led to dephosphorylation of the translation regulation proteins S6K and E4-BP1. The expression of cell cycle regulating proteins p21 and cyclin D1 was decreased by arginine depletion, alone and in combination with cisplatin. The enhancement of cisplatin cytotoxicity by ADI-PEG20 with loss of ASS1-negative MPM cell viability as early as 24hr post treatment, supports the demonstrated strong synergy between the two drugs.

In summary, the antitumor effect of platinum was potentiated markedly using ADI-PEG20, suggesting that combining arginine depletion with the current standard of care, platinum and antifolates, may offer an improvement over doublet chemotherapy alone.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4445.

Epigenetic silencing of argininosuccinate synthetase confers resistance to platinum-induced cell death but collateral sensitivity to arginine auxotrophy in ovarian cancer

Evidence indicates that acquired resistance of cancers to chemotherapeutic agents can occur via epigenetic mechanisms. Down-regulation of expression of argininosuccinate synthetase (ASS1), the rate-limiting enzyme in the biosynthesis of arginine, has been associated with the development of platinum resistance in ovarian cancer treated with platinum-based chemotherapy. The aim of the present study was to analyse epigenetic regulation of ASS1 in ovarian cancer tissue taken at diagnosis and relapse and determine its significance as a predictor of clinical outcome in patients treated with platinum-based chemotherapy. In addition, expression and epigenetic regulation of ASS1 were analysed in human ovarian cancer cell lines, and ASS1 expression correlated with the ability of the lines to grow in media containing cisplatin, carboplatin or taxol or in arginine-depleted media. Our results show that aberrant methylation in the ASS1 promoter correlated with transcriptional silencing in ovarian cancer cell lines. ASS1 silencing conferred selective resistance to platinum-based drugs and conferred arginine auxotrophy and sensitivity to arginine deprivation. In ovarian cancer, ASS1 methylation at diagnosis was associated with significantly reduced overall survival (p = 0.01) and relapse-free survival (p = 0.01). In patients who relapse, ASS1 methylation was significantly more frequent at relapse (p = 0.008). These data establish epigenetic inactivation of ASS1 as a determinant of response to platinum chemotherapy and imply that transcriptional silencing of ASS1 contributes to treatment failure and clinical relapse in ovarian cancer. The collateral sensitivity of cells lacking endogenous ASS1 to arginine depletion suggests novel therapeutic strategies for the management of relapsed ovarian cancer.

In vivo loss of expression of argininosuccinate synthetase in malignant pleural mesothelioma is a biomarker for susceptibility to arginine depletion

PURPOSE

Malignant pleural mesothelioma (MPM) is an increasing health burden on many societies worldwide and, being generally resistant to conventional treatment, has a poor prognosis with a median survival of <1 year. Novel therapies based on the biology of this tumor seek to activate a proapoptotic cellular pathway. In this study, we investigated the expression and biological significance of argininosuccinate synthetase (AS), a rate-limiting enzyme in arginine production.

EXPERIMENTAL DESIGN

Initially, we documented down-regulation of AS mRNA in three of seven MPM cell lines and absence of AS protein in four of seven MPM cell lines. We confirmed that the 9q34 locus, the site of the AS gene, was intact using a 1-Mb comparative genomic hybridization array; however, there was aberrant promoter CpG methylation in cell lines lacking AS expression, consistent with epigenetic regulation of transcription. To investigate the use of AS negativity as a therapeutic target, arginine was removed from the culture medium of the MPM cell lines.

RESULTS

In keeping with the cell line data, 63% (52 of 82) of patients had tumors displaying reduced or absent AS protein, as assessed using a tissue microarray. Cell viability declined markedly in the AS-negative cell lines 2591 and MSTO but not in the AS-positive cell line, 28. This response was apparent by day 4 and maintained by day 9 in vitro. Arginine depletion induced BAX conformation change and mitochondrial inner membrane depolarization selectively in AS-negative MPM cells.

CONCLUSIONS

In summary, we have identified AS negativity as a frequent event in MPM in vivo, leading to susceptibility to cytotoxicity following restriction of arginine. A phase II clinical trial is planned to evaluate the role of arginine depletion in patients with AS-negative MPM.

Aberrant regulation of argininosuccinate synthetase by TNF-alpha in human epithelial ovarian cancer

The pro-inflammatory cytokine, tumour necrosis factor-alpha, TNF-alpha, is dysregulated in malignant compared with normal ovarian surface epithelium (OSE). Several epidemiological studies have associated inflammation with ovarian tumorigenesis, with TNF-alpha playing a key role in modulating invasion, angiogenesis and metastasis. Here, we show that TNF-alpha also induces expression of arate-limiting enzyme in arginine synthesis, argininosuccinate synthetase (AS), thereby linking inflammation with several arginine-dependent metabolic pathways, implicated in accelerated carcinogenesis and tumour progression. Having identified AS mRNA induction in TNF-alpha-treated IGROV-1 ovarian cancer cells, using RNA-arbitrarily primed-PCR, we then observed differential regulation of AS mRNA and protein in malignant, compared with normal, OSE cells. A cDNA cancer profiling array with matched normal ovarian and ovarian tumour samples revealed increased expression of AS mRNA in the latter. Moreover, AS protein co-localised with TNF-alpha in ovarian cancer cells, with significantly higher levels of AS in malignant compared with normal ovarian tissue. Increased co-expression of AS and TNF-alpha mRNA was also observed in 2 other epithelial tumours, non-small cell lung and stomach cancer, compared with normal corresponding tissues. In summary, high levels of AS expression, which may be required for several arginine-dependent processes in cancer, including the production of nitric oxide, proline, pyrimidines and polyamines, is regulated by TNF-alpha and may provide an important molecular pathway linking inflammation and metabolism to ovarian tumorigenesis.

Expression and regulation of tumor necrosis factor alpha in normal and malignant ovarian epithelium

Epidemiologic studies implicate inflammatory stimuli in the development of ovarian cancer. The proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) and both its receptors (TNFRI and TNFRII) are expressed in biopsies of this malignancy. Here, we tested the hypothesis that TNF-alpha is a regulator of the proinflammatory microenvironment of ovarian cancer. A cancer profiling array showed higher expression of TNF-alpha in ovarian tumors compared with normal ovarian tissue, and cultured ovarian cancer cells expressed up to 1,000 times more TNF-alpha mRNA than cultured normal ovarian surface epithelial cells; TNF-alpha protein was only detected in the supernatant of tumor cell cultures. Treatment with TNF-alpha induced TNF-alpha mRNA via TNFRI in both malignant and normal cells with evidence for enhanced TNF-alpha mRNA stability in tumor cells. TNF-alpha induced TNF-alpha protein in an autocrine fashion in tumor but not in normal ovarian surface epithelial cells. The TNF-alpha neutralizing antibody infliximab reduced the constitutive levels of TNF-alpha mRNA in tumor cell lines capable of autocrine TNF-alpha production. Apart from TNF-alpha mRNA expression, several other proinflammatory cytokines were constitutively expressed in malignant and normal ovarian surface epithelial cells, including interleukin (IL)-1alpha, IL-6, CCL2, CXCL8, and M-CSF. TNF-alpha treatment further induced these cytokines with de novo transcription of IL-6 mRNA contrasting with the increased stability of CCL2 mRNA. RNA interference directed against TNF-alpha was highly effective in abolishing constitutive IL-6 production by ovarian tumor cells. In summary, we show that TNF-alpha is differentially regulated in ovarian cancer cells compared with untransformed cells and modulates production of several cytokines that may promote ovarian tumorigenesis. Infliximab treatment may have a role in suppressing the TNF-alpha-driven inflammatory response associated with ovarian cancer.

Tumour necrosis factor alpha: a potential target for the therapy of solid tumours

Tumour necrosis factor alpha (TNFalpha), named for its antitumour properties, was isolated almost 30 years ago. It is a vital member of the multifunctional TNF superfamily and has important roles in immunity and cellular remodelling as well as influencing apoptosis and cell survival. Its central role in inflammation has led to the development of TNFalpha antagonists as effective therapies for rheumatoid arthritis and inflammatory bowel disease. In this review, we discuss the evidence which has accumulated during the past decade that implicates TNFalpha in inflammatory pathways that increase tumorigenesis. There is convincing evidence that under specific conditions TNFalpha is a tumour promoter and helps to produce the toxic effects associated with conventional cancer therapy, such as the cytokine release syndrome and cisplatin-induced nephrotoxicity. Several trials have been set up to investigate the role of TNFalpha antagonists in cancer. It is hoped that these agents inhibit the neoplastic process either alone or in combination with other agents, and ameliorate the side effects of cancer therapy.

Potential applications of gene therapy in the patient with cancer

The elderly population has much to gain from the advances of molecular medicine, although at present genetic pharmacology remains mostly at the conceptual level. Cancer, in particular, is an increasing health burden and the majority (over 70%) of gene therapy trials are aimed at tackling this problem. Available strategies employ both viral and synthetic vectors with the selective delivery and expression of therapeutic genes a pivotal requirement. Clinical trials are now in progress with a view to modulating disease at many different levels, including the direct replacement of abnormal genes. suicide-gene formulations, and the delivery of 'gain of function' genes, which seek to alter the malignant phenotype by indirect means, such as, immunopotentiation and stromal reorganisation. Early data from these studies is tantalising and we must remain optimistic that gene therapy will benefit the patient with cancer by both reducing morbidity and extending life.

Effective treatment of a patient with a high-grade endometrial stromal sarcoma with an accelerated regimen of carboplatin and paclitaxel

The rarity of endometrial stromal sarcoma (ESS) and its poor response to treatment provides fertile ground for investigational therapies. An accelerated regimen of carboplatin and paclitaxel is investigated. A patient with a recent history of treated tuberculosis of the lung represented with infertility and acute abdominal pain from suspected fibroids, and underwent a laparotomy with a diagnosis of a high-grade ESS. A novel therapeutic approach using a regimen of carboplatin and paclitaxel with the reinfusion of filgrastim-mobilized peripheral blood progenitor cells is described. A partial response was observed following six cycles of chemotherapy. Grade IV thrombocytopenia occurred after the last cycle, with recovery prior to pelvic radiotherapy. The patient remained well 1 year post-diagnosis. High-grade ESS is responsive to combination chemotherapy with paclitaxel and carboplatin, and requires further evaluation. The use of an accelerated regimen may also have contributed to the response and this question awaits randomized trials.