Abstract P3-08-04: Discovery of cancer genes and pathways operative in PI3K-activated mammary cancer reveals clinically relevant genotype-phenotype correlations

Human breast cancer (BRCA) shows tremendous genomic, gene expression, clinical, and phenotypic heterogeneity. Known driver gene alterations can only explain a portion of this heterogeneity, some of which likely arise from variation in the target cell for transformation, in addition to incompletely understood gene copy number and epigenetic alterations. These factors are difficult to identify with certainty using human patient samples due to widely varying germline genetic backgrounds, thousands of gene copy and epigenetic changes per sample, and, unknown target cell transformation. Activating mutations in the p110α catalytic subunit of PI3K are one of the most common genetic alterations in human BRCA. Here, we report results from two Sleeping Beauty (SB) transposon-accelerated mouse models of Pik3ca-mutant mammary cancer showing how genotype-phenotype correlations can be drawn providing strong candidates for mediating tumor phenotypes, including estrogen-receptor (ER)-dependent gene expression, high cell cycle activity, and immune cell exclusion. We used SB transposon mutagenesis in mice on a Pik3caH1047R activated mutant background to model mammary cancer development in two different mammary epithelial compartments. Both the target cell for mutagenesis and the specific transposon-induced mutations correlated with specific tumor phenotypes, including whether the tumors were ER positive or negative. RNA sequencing of tumors revealed novel genotype-phenotype correlations implicating specific transposon-altered gene drivers of high cell cycle activity, ER-dependent gene expression, and white blood cell exclusion from the tumor. Many transposon-implicated genes are altered at the gene copy number or epigenetic/methylation level in human BRCA, and several were functionally validated. These models provide a source of genetically heterogenous mouse mammary tumors with a uniform initiating mutation, Pik3caH1047R, useful for identifying cooperating pathways and drivers of specific tumor phenotypes.

Citation Format: Morito Kurata, Emiily Pope, Jingmin Shu, Wenlin Yuan, Wendy Hudson, Mark Sokolowski, Setareh Bagherzadeh, Zora Modrusan, Eric Stawiski, Steffen Durinck, Sekar Seshigiri, Aaron Sarver, Nuri Temiz, David Largaespada. Discovery of cancer genes and pathways operative in PI3K-activated mammary cancer reveals clinically relevant genotype-phenotype correlations. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-08-04.

Targeting TNF-α-producing macrophages activates antitumor immunity in pancreatic cancer via IL-33 signaling

Pancreatic ductal adenocarcinoma (PDA) remains resistant to immune therapies, largely owing to robustly fibrotic and immunosuppressive tumor microenvironments. It has been postulated that excessive accumulation of immunosuppressive myeloid cells influences immunotherapy resistance, and recent studies targeting macrophages in combination with checkpoint blockade have demonstrated promising preclinical results. Yet our understanding of tumor-associated macrophage (TAM) function, complexity, and diversity in PDA remains limited. Our analysis reveals significant macrophage heterogeneity, with bone marrow-derived monocytes serving as the primary source for immunosuppressive TAMs. These cells also serve as a primary source of TNF-α, which suppresses expression of the alarmin IL-33 in carcinoma cells. Deletion of Ccr2 in genetically engineered mice decreased monocyte recruitment, resulting in profoundly decreased TNF-α and increased IL-33 expression, decreased metastasis, and increased survival. Moreover, intervention studies targeting CCR2 with a new orthosteric inhibitor (CCX598) rendered PDA susceptible to checkpoint blockade, resulting in reduced metastatic burden and increased survival. Our data indicate that this shift in antitumor immunity is influenced by increased levels of IL-33, which increases dendritic cell and cytotoxic T cell activity. These data demonstrate that interventions to disrupt infiltration of immunosuppressive macrophages, or their signaling, have the potential to overcome barriers to effective immunotherapeutics for PDA.

Paroxysmal atrial fibrillation ablation with a novel flexible tip radiofrequency catheter incorporating contact force sensing: acute results of the TactiFlex AF IDE trial

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex™ Ablation Catheter, Sensor-Enabled™ (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip.

Purpose

To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF.

Methods

The TactiFlex AF IDE is a prospective, non-randomized, multi-center clinical study which enrolled 355 subjects worldwide. Enrollment in the main study began on June 26, 2020 and completed on June 18, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter.

Results

Subjects were divided into two as treated subgroups: High Standard Power (HSP, n=189), defined as subjects with 100% of left atrial lesions ablated at ≥40 W, and Low Standard Power (LSP, n=119), defined as subjects with at least one left atrial lesion ablated at <40W. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 93.5% (175/186) and 84.5% (98/116) of HSP and LSP subjects, respectively (p=0.0104). Significant decreases in the HSP versus LSP procedures were also seen in total procedure time (112.0 min [89.0, 139.5] and 149.0 [115.0, 182.0], respectively [p<0.001]), total RF time for PV ablation (14.0 min [11.0, 19.0] and 29.0 [19.0, 41.0], respectively [p<0.0001]), total fluoroscopy time (4.0 min [0.0, 11.0] and 8.0 [3.0, 17.0], respectively [p<0.0001]) and irrigation fluid volume (378.0 mL [310.0, 466.0] and 636.0 [476.0, 829.0], respectively [p<0.0001]) (values given as Median [Q1, Q3]), see Figure 1. Both HSP and LSP subjects had a low rate of repeat procedures (1.6% [3/182] and 4.3% [5/115], respectively [p=0.2684]) and primary safety endpoint events (4.8% [9/189] and 4.2% [5/119], respectively [p=0.8182]) through 90 days post-index procedure.

Conclusion

The acute data on the TactiFlex SE catheter demonstrates safe and effective treatment of PAF using either a HSP or LSP ablation strategy. Ablation procedures performed using a HSP strategy were shorter and required less irrigation fluid and fluoroscopy. It is anticipated these results will be reflected in the 12-month safety and effectiveness primary endpoints.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Abbott

Age as a factor in the molecular landscape and the tumor-microenvironmental signature of osteosarcoma

11525

Background: Osteosarcoma (OS) incidence is characterized by a bimodal age distribution, with peaks in early adolescence and in adults > 65 years of age. In contrast to adolescents, OS in adults is frequently considered as a secondary neoplasm (i.e., transformation of Paget´s disease of the bone, radiation induced). Yet, the literature is scarce regarding the impact of age on the molecular landscape of OS. Herein, we sought to explore the association between age and the genomic profile as well as the tumor immune microenvironment (TME) in a large cohort of OS patients. Methods: 208 specimens were centrally analysed at the Caris Life Sciences laboratory with DNA seq (NextSeq, 592 gene panel or NovaSeq, whole-exome sequencing), RNA seq (Archer fusion panel or whole-transcriptome sequencing) and immunohistochemistry (IHC). RNA deconvolution and differential expression analyses were performed using the Microenvironment Cell Populations counter method for quantification of immune cell populations and gene expression profiling. The cohort was stratified into three distinct age groups (< 25 years [n = 83], 25-45 years [n = 58], > 45 years [67]). Results: Overall, the most frequently detected mutations were in TP53 (37%), RB1 (13%), ATRX (9%), TERT (6%), PTEN (5%), PIK3CA (4%) and KMT2D (3%). Copy number alterations were most frequently detected in CDK4 (12%), LRIG3 (11%), FLCN (11%), MDM2 (9%), CCND3 (9%), VEGFA (8%), TFEB (8%). Interestingly, age-based stratification revealed an increased frequency of FLCN (19.7 vs 4.7%, p < 0.01), CCND3 (13.9 vs 3.1%, p < 0.05), and HSP90AB1 (11.3 vs 0.0%, p < 0.01), alterations in patients < 25 years compared to > 45 years. TME analysis revealed that patients > 45 years have decreased B-cell abundance compared to patients < 25 years (2.9-fold decrease, p < 0.05) and 25-45 years (4.8-fold decrease, p < 0.05). Although not statistically significant, median transcriptional expression of PD-L1 was numerically increased in patients > 45 years (1.8-fold compared to 25-45 years, p = 0.17; 2.0-fold compared to < 25 years, p = 0.27), which was consistent with increasing rates of IHC PD-L1 expression with age (5.3%, 9.4%, and 17.5%, respectively, p = 0.06). Conclusions: To the best of our knowledge, this study represents the largest cohort of molecularly characterized OS. Age-associated differences in the genetic landscape and TME composition, including increased gene amplifications observed in younger patients and decreased B-cell abundance in older patients, might suggest fundamental underlying molecular and biological differences.

Acute results of a novel flexible tip radiofrequency catheter incorporating contact force sensing

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex Ablation Catheter, Sensor-Enabled (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip. This is the first report of results from the TactiFlex IDE clinical study.

Purpose

To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF.

Methods

The TactiFlex IDE (NCT04356040) is a prospective, non-randomized, multi-center clinical study which enrolled 305 subjects worldwide in the main study. Enrollment in the main study began on June 26, 2020 and completed on June 8, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter.

Results

Acute procedural success was achieved in 98.6% (274/278) of the main study cohort who underwent an ablation procedure using the TactiFlex SE. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 89.6% (249/278) of subjects. This was a significant improvement versus the TactiSense IDE trial (TactiCath Ablation Catheter, Sensor-Enabled). Significant decreases were also seen in total procedure time (123 min [101.0, 163.5]), total PV ablation time (55.5 min [35.0, 81.0]), total fluoroscopy time (6.0 min [0.0, 13.0]) and irrigation fluid volume (450.0 mL [346.0, 636.0]) (values given as Median [Q1, Q3]), see FIGURE. All subjects have completed at least 90 days of follow-up. Only 2.6% (7/271) of subjects required a repeat procedure during the 90-day blanking period. The primary safety and effectiveness endpoints will be evaluated at 12-months. At 90 days, 4.3% (12/281) subjects had experienced a primary safety endpoint event.

Conclusions

The acute data from the TactiFlex IDE clinical study demonstrate safety and effectiveness of the TactiFlex SE catheter in the treatment of PAF. Ablation procedures performed using the next-generation TactiFlex SE catheter were shorter and had improved acute clinical effectiveness outcomes versus the TactiSense IDE. It is anticipated these results will also be reflected in the 12-month safety and effectiveness endpoints.

Final results from the EU focal impulse and rotor modulation (E-FIRM) registry

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): Abbott

Background

The exact pathophysiology of how pulmonary vein (PV) triggers initiate or maintain episodes of atrial fibrillation (AF) has been elusive. Catheter ablation at relatively circumscribed areas of rapidly spinning rotors or very rapid focal impulse formation can significantly affect AF. Targeted ablation of these sources using Focal Impulse and Rotor Modulation (FIRM™) shows promise.

Purpose

To assess the safety and effectiveness of FIRM-guided procedures for the treatment of any type of symptomatic atrial fibrillation (AF).

Methods

Two hundred and ninety-nine subjects were enrolled in the E-FIRM Registry at 9 clinical sites in Germany and the Netherlands. Subjects were eligible if they had reported incidence of at least 2 documented episodes of symptomatic AF during the preceding 3 months and had failed at least Class I or III anti-arrhythmia drug. Data was collected at enrollment/baseline, procedure, and at 3-, 6-, and 12-month follow-up visits.

Results

A majority (59.5%, 178/299) had a history of previous ablation, 81.1% (133/164) in the left side, with an average of 1.5 ± 0.8 [range 0, 5] prior ablations. The primary safety endpoint was defined as freedom from procedure related Serious Adverse Events (SAEs) through 7-days and at 12-months. At 7-days, freedom from procedure related SAEs was 94.8% (257/271). At 12-months, freedom from procedure related SAEs was 84.4% (184/218). There were no deaths. Acute effectiveness success, defined as the elimination of all identified rotors, occurred in 64.0% (165/258) of treated patients. All patients for which data was reported had at least 1 rotor identified. The most common regions to find rotors were the lateral wall of the right atrium, the anterior/septal wall of the left atrium, and the posterior inferior region of the left atrium. 75.2% (194/258) of patients had at least one rotor identified in the right atrium, and 84.1% (217/258) of patients had at least one rotor identified in the left atrium. Success was defined as two sequential endpoints: single procedure freedom from AF recurrence at 3-months and single procedure freedom from AF recurrence. At 12-months, success was achieved in 46.4% (13/28) Paroxysmal, 42.9% (87/203) Persistent, and 0% (0/9) Long Standing AF subjects. Conclusions: Since acute success was reported as being achieved in only ∼2/3 of the treated subjects, it is possible that the full potential benefit of the FIRM-guided ablation was hidden in this evaluation of the full cohort. Considering the previous ablation and disease history of subjects, a single-procedure success rate at 12-months over 40% was considered a positive result. Based on these results, FIRM-guided RF ablation in conjunction with conventional RF ablation practices is both a safe and effective treatment strategy for patients with symptomatic AF.

PI3Kγ inhibition suppresses microglia/TAM accumulation in glioblastoma microenvironment to promote exceptional temozolomide response

Precision medicine in oncology leverages clinical observations of exceptional response. Toward an understanding of the molecular features that define this response, we applied an integrated, multiplatform analysis of RNA profiles derived from clinically annotated glioblastoma samples. This analysis suggested that specimens from exceptional responders are characterized by decreased accumulation of microglia/macrophages in the glioblastoma microenvironment. Glioblastoma-associated microglia/macrophages secreted interleukin 11 (IL11) to activate STAT3-MYC signaling in glioblastoma cells. This signaling induced stem cell states that confer enhanced tumorigenicity and resistance to the standard-of-care chemotherapy, temozolomide (TMZ). Targeting a myeloid cell restricted an isoform of phosphoinositide-3-kinase, phosphoinositide-3-kinase gamma isoform (PI3Kγ), by pharmacologic inhibition or genetic inactivation disrupted this signaling axis by reducing microglia/macrophage-associated IL11 secretion in the tumor microenvironment. Mirroring the clinical outcomes of exceptional responders, PI3Kγ inhibition synergistically enhanced the anti-neoplastic effects of TMZ in orthotopic murine glioblastoma models. Moreover, inhibition or genetic inactivation of PI3Kγ in murine glioblastoma models recapitulated expression profiles observed in clinical specimens isolated from exceptional responders. Our results suggest key contributions from tumor-associated microglia/macrophages in exceptional responses and highlight the translational potential for PI3Kγ inhibition as a glioblastoma therapy.

TAMI-28. DIFFERENTIAL MIGRATION MECHANICS AND IMMUNE RESPONSES OF GLIOMA SUBTYPES

In Glioblastoma (GBM), tumor spreading is driven by tumor cells’ ability to infiltrate healthy brain parenchyma, which prevents complete surgical resection and contributes to tumor recurrence. GBM molecular subtypes, classical, proneural and mesenchymal, were shown to strongly correlate with specific genetic alterations (Mesenchymal: NF1; Classical: EGFRVIII; Proneural: PDGFRA). Here we tested the hypothesis that a key mechanistic difference between GBM molecular subtypes is that proneural cells are slow migrating and mesenchymal cells are fast migrating. Using Sleeping Beauty transposon system, immune-competent murine brain tumors were induced by SV40-LgT antigen in combination with either NRASG12V (NRAS) or PDGFB (PDGF) overexpression. Cross-species transcriptomic analysis revealed NRAS and PDGF-driven tumors correlate with human mesenchymal and proneural GBM, respectively. Similar to human GBM, CD44 expression was higher in NRAS tumors and, consistent with migration simulations of varying CD44 levels, ex vivo brain slice live imaging showed NRAS tumors cells migrate faster than PDGF tumors cells (random motility coefficient = 30µm2/hr vs. 2.5µm2/hr, p &lt; 0.001). Consistent with CD44 function as an adhesion molecule, migration phenotype was independent of the tumor microenvironment. NRAS and human PDX/MES tumor cells were found to migrate faster and have larger cell spread area than PDGF and human PDX/PN tumors cells, respectively, in healthy mouse brain slices. Furthermore, traction force microscopy revealed NRAS tumor cells generate larger traction forces than PDGF tumors cells which further supports our theoretical mechanism driving glioma migration. Despite increased migration, NRAS cohort had better survival than PDGF which was attributed to enhanced antitumoral immune response in NRAS tumors, consistent with increased immune cell infiltration found in human mesenchymal GBM. Overall our work identified a potentially actionable difference in migration mechanics between GBM subtypes and establishes an integrated biophysical modeling and experimental approach to mechanically parameterize and simulate distinct molecular subtypes in preclinical models of cancer.

TAMI-41. PI3K-GAMMA INHIBITION SUPPRESSES ACCUMULATION OF GLIOBLASTOMA-ASSOCIATED MICROGLIA TO RECAPITULATE THE MICROENVIRONMENT OF EXCEPTIONAL RESPONDERS

INTRODUCTION

Exceptional responders refer to the rare subset of patients who derive extraordinary benefits from a therapy compared to most treated patients. Understanding the basis for such responses represents a key pillar in the framework of precision medicine.

OBJECTIVE

Here, we examine the molecular basis underlying exceptional responses in glioblastoma patients who underwent concurrent radiation and temozolomide (TMZ) therapy.

METHODS

mRNA profiles derived from clinically annotated glioblastoma specimens were analyzed by Single sample gene set enrichment (ssGSEA) and Gene Cluster Expression Summary Score (GCESS). Key results were confirmed using cell-based assays and murine glioblastoma models.

RESULTS

Integrated, multi-platform analyses of RNA profiles derived from clinically annotated glioblastoma samples revealed decreased accumulation of microglia/macrophages in the tumor microenvironment of exceptional responders. Further analysis revealed that glioblastoma-associated microglia/macrophages secreted interleukin 11 (IL11) activate a STAT3-MYC signaling axis in glioblastoma cells. This signaling facilitated glioblastoma transition into stem cell states that confer enhanced tumorigenicity as well as resistance to the TMZ. Pharmacologic inhibition or genetic inactivation of a myeloid cell restricted isoform of PI3K, PI3K-gamma, disrupted this signaling axis by suppressing microglia/macrophage accumulation and IL11 secretion in the glioblastoma microenvironment. Mirroring the clinical outcome of exceptional responders, PI3K-gamma inhibition synergistically enhanced the anti-neoplastic effects of TMZ in orthotopic murine glioblastoma models. Moreover, inhibition or genetic inactivation of PI3K-gamma in murine glioblastoma models recapitulated expression profiles observed in clinical specimens isolated from exceptional responders.

CONCLUSIONS

Our results suggest key contributions from tumor-associated microglia/macrophages in exceptional responses and highlight the translational potential for PI3K-gamma inhibition as a glioblastoma therapy.

Stability and performance of the EnSite Precision cardiac mapping system for electrophysiology mapping and ablation procedures: results from the EnSite Precision observational study

Background

The EnSite Precision™ Cardiac Mapping System is a catheter navigation and mapping system capable of displaying the three-dimensional (3D) position of conventional and sensor enabled electrophysiology catheters, as well as displaying cardiac electrical activity as waveform traces and dynamic 3-D maps of cardiac chambers.

Objective

The EnSite Precision™ Observational Study was designed to quantify and characterize the use of the EnSite Precision™ Cardiac Mapping System for mapping and ablation of cardiac arrhythmias in a real-world environment and to evaluate procedural and subsequent clinical outcomes.

Methods

1065 patients were enrolled at 38 centers in the U.S. and Canada between 2017–2018. Eligible subjects were adults undergoing a cardiac electrophysiology mapping and radiofrequency ablation procedures using the EnSite Precision™ System.

Results

Of 989 patients who completed the protocol, a geometry was created in 936 (94.7%). Most initial maps were created using Automap (n=545, 67.0%) or a combination of Automap and manually mapping (n=151, 18.6%). Median time to create an initial map was 9.0 min (IQR 5.0–15.0), with a median number of used mapping points per minute of 92.7 (IQR 30.0–192.0). During ablation, AutoMark was used in 817 (82.6%) of procedures. The most frequent metrics for lesion color were Impedance Drop or Impedance Drop Percent (45.5% combined), time (23.9%) and average force (14.2%). At Canadian sites where LSI was an option, it was used as the color metric in 87 (45.8%) of cases (10.6% overall). The EnSite System was stable throughout 79.7% (n=788 of 989) of procedures. Factors affecting stability were respiratory change (n=88 of 989, 8.9%), patient movement (n=73, 7.4%), CS Positional Reference dislodgement (n=32, 3.2%), and cardioversion (n=19, 1.9%). Conscious sedation was used in 189 (19.1%) of patients. Acute success was reached based on the pre-defined endpoints for the procedure in 97.4% (n=963) of cases.

Conclusion

In a real-world study analysis, the EnSite Precision™ mapping system was associated with a high prevalence of acute procedural success, low mapping times, and high system stability.

Funding Acknowledgement

Type of funding source: None

B cell transcription factors define a novel tumor suppressor gene network In ALL

The transcription factors EBF1 and PAX5 are frequently mutated in B cell acute lymphoblastic leukemia (B-ALL). We demonstrated that Pax5+/− x Ebf1+/− compound heterozygous mice develop leukemia with high penetrance. Similar results were seen in Pax5+/− x Ikzf1+/− and Ebf1+/− x Ikzf1+/− mice for B-ALL, or in Tcf1+/− x Ikzf1+/− mice for T cell leukemia. To identify genetic defects that cooperate with Pax5 and Ebf1 compound heterozygosity to initiate leukemia, we carried out a Sleeping Beauty transposon screen. This screen identified a number of cooperating partners including gain-of-function mutations in Stat5 (~65%) and Jak1(~68%), as well as loss-of-function mutations in Cblb (61%)and Myb (32%). These findings highlight the key role of JAK/STAT5 signaling in cooperating with Pax5 and Ebf1 compound haploinsufficiency to drive B cell transformation. Moreover, these studies pointed to unexpected roles for loss of function mutations in CBL-b and MYB in B cell transformation. Subsequent RNA-Seq studies on WT, Pax5+/−, Ebf1+/−, Pax5+/− x Ebf1+/− pre-leukemic, Pax5+/− x Ebf1+/− leukemic cells and Pax5+/− x Ebf1+/− Sleeping Beauty leukemic cells demonstrated upregulation of a PDK1&gt;PLK1&gt;MYC pathway; treatment of Pax5+/− x Ebf1+/− leukemias with PDK1 specific inhibitors blocked their proliferation in vitro. Finally, we identified conserved transcriptional variation in a subset of genes between human leukemias and our mouse B-ALL models. Thus, compound haploinsufficiency for B cell transcription factors likely plays a critical role in transformation of human B cells and suggest that newly developed PDK1 inhibitors may be effective for treating patients characterized by such defects.

P2846Focal impulse and rotor modulation ablation versus pulmonary vein isolation for the treatment of paroxysmal atrial fibrillation (FIRMAP AF study)

Background

Based on the assumption of trigger elimination, pulmonary vein isolation (PVI) currently presents the gold standard of atrial fibrillation (AF) ablation. Recently, rapidly spinning rotors or focal impulse formation has been raised as a crucial sustaining mechanism of AF. Ablation of these rotors may potentially obviate the need for trigger elimination with PVI.

Purpose

This study sought to compare the safety and effectiveness of Focal Impulse and Rotor Modulation (FIRM) guided catheter ablation only with the gold standard of pulmonary vein isolation (PVI) in patients with paroxysmal AF.

Methods

This was a post-market, prospective, single-blinded, randomized, multi-center trial. Patients were enrolled at three centers and equally (1:1) randomized between those undergoing conventional RF ablation with PVI (PVI group) vs. those treated with FIRM-guided RF ablation without PVI (FIRM group). Data was collected at enrollment, procedure, and at 7-day, 3-month, 6-month, and 12-month follow-up visits. The study was closed early by the sponsor. At the time of study closure, any pending follow-up visits were waived.

Results

From February 2016 until February 2018, a total of 51 (out of a planned 170) patients (mean age 63±10.6 years, 57% male) were enrolled and randomized. Four patients withdrew from the study prior to treatment, resulting in 23 patients allocated to the FIRM group and 24 in the PVI group. Only 13 patients in the FIRM group and 11 patients in the PVI group completed the 12-month follow-up. Statistical analysis was not completed given the small number of patients.

Single-procedure effectiveness (freedom from AF/atrial tachycardia recurrence after blanking period) was 52.9% (9/17) in the FIRM group and 85.7% (12/14) in the PVI group at 6 months; and 31.3% (5/16) in the FIRM group and 80% (8/10) in the PVI group at 12 months. Repeat procedures were performed in 45.8% (11/24) patients in the FIRM group and 7.4% (2/27) in the PVI group.

The acute safety endpoint [freedom from procedure-related serious adverse events (SAE)] was achieved in 87% (20/23) of FIRM group patients and 100% (24/24) of PVI group patients. Procedure related SAEs occurred in three patients in the FIRM group: 1 femoral artery aneurysm and 2 injection site hematomas. No additional procedure-related SAEs were reported >7 days post-procedure.

Conclusions

These partial study effectiveness results reinforce the importance of PVI in paroxysmal atrial fibrillation patients and suggest that FIRM-guided ablation alone (without PVI) is not an effective strategy for treatment of paroxysmal AF in most patients. Further study is needed to understand the effectiveness of adding FIRM-guided ablation as an adjunct to PVI in this patient group.

Acknowledgement/Funding

Abbot

Abstract LB-086: Combination therapy of immune checkpoint and nuclear exporter inhibitors in a renal cell carcinoma mouse model

Selective inhibitor of nuclear export (SINE) compounds represent a novel class of drugs that have shown therapeutic equivalence to multiple kinase inhibitors in pre-clinical studies of renal cell carcinoma (RCC) and are currently in phase I/II clinical trials for patients with advanced malignancies including RCC. Immune checkpoint blockade using antibodies against PD-1 or PD-L1 has also shown promising results in phase I/II/III clinical trials for RCC, with objective tumor responses of around 20% that rise to 40-50% with the combination of antibodies against CTLA-4. Here, we tested the hypothesis that the oral SINE compound, selinexor (KPT-330), would induce rapid death of RCC tumor cells and prime the tumor microenvironment for a response to checkpoint inhibition with antibodies against PD-1 or CTLA-4. Groups of 10, six-week old, male, syngeneic (Balb/c) mice were injected heterotopically (subcutaneous) with 500,000 RENCA cells. After visible tumors appeared seven days later, mice were treated every three days with vehicle (controls), selinexor, anti-PD-1, or anti-CTLA4 alone, or with selinexor in combination with either antibody. Mice were euthanized 10 days after the initiation of treatment when the control groups reached the tumor endpoint. Tumor volume, tumor size, and tumor growth rate were determined by physical measurements; the composition of the tumor immune environment was determined by multi-parameter flow cytometry. As expected, selinexor significantly reduced the overall tumor burden (P&lt;0.05) and the checkpoint inhibitors had only modest effects on tumor growth in this acute 10-day treatment setting, both when used alone alone or in combination with selinexor. Consistent with the hypothesis, selinexor altered the local immune environment, increasing the relative number of T cells and NKT cells with a concomitant reduction in Gr1+ and CD11b+ myeloid cells, and Foxp3+ regulatory T cells (Tregs). Anti-CTLA4 and anti-PD-1 alone led to comparable increases in the relative number of T cells and NKT cells, but with an additional increase in the proportion of effector and activated T cells. The combination of selinexor with either checkpoint blockade antibody resulted in similar reorganization of the tumor immune landscape, with increases in the total number of T cells, effector and activated T cells, and NKT cells and reductions in myeloid cells and Tregs. The data suggest that treatment with selinexor promotes a rapid reduction in tumor burden, while priming the inflammatory and immune environment to potentially maximize the therapeutic effects of checkpoint inhibition. Additional pre-clinical assessments of dose and schedule for this combination can and will be feasibly done in the RENCA model of RCC.

Citation Format: Josephine Trott, Katie Anderson, Jeffrey Kim, Ashley Graef, Sharon Shacham, Yosef Landesman, Aaron Sarver, Jaime Modiano, Robert H. Weiss. Combination therapy of immune checkpoint and nuclear exporter inhibitors in a renal cell carcinoma mouse model. [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 LB-086.

A conditional piggyBac transposition system for genetic screening in mice identifies oncogenic networks in pancreatic cancer

Here we describe a conditional piggyBac transposition system in mice and report the discovery of large sets of new cancer genes through a pancreatic insertional mutagenesis screen. We identify Foxp1 as an oncogenic transcription factor that drives pancreatic cancer invasion and spread in a mouse model and correlates with lymph node metastasis in human patients with pancreatic cancer. The propensity of piggyBac for open chromatin also enabled genome-wide screening for cancer-relevant noncoding DNA, which pinpointed a Cdkn2a cis-regulatory region. Histologically, we observed different tumor subentities and discovered associated genetic events, including Fign insertions in hepatoid pancreatic cancer. Our studies demonstrate the power of genetic screening to discover cancer drivers that are difficult to identify by other approaches to cancer genome analysis, such as downstream targets of commonly mutated human cancer genes. These piggyBac resources are universally applicable in any tissue context and provide unique experimental access to the genetic complexity of cancer.

Abstract C43: A Sleeping Beauty forward genetic screen identifies novel cancer drivers that cooperate with Pten in lung cancer

Improved understanding of the genetic drivers of lung cancer will aid in the design of personalized therapy. To this end, we have conducted forward genetic screens in the lungs of mice using the DNA transposon Sleeping Beauty (SB), in order to identify novel cancer driver genes. We conducted the screens on four different backgrounds: wild-type, p19 deficient, p53 dominant negative, and Pten deficient mice. The Pten deficient background was the only screen that resulted in tumors developing at a rate significantly above controls. Experimental mice (SB/Pten-/-) harbored a concatamer of oncogenic transposons, a conditionally activated SB transposase and a floxed Pten gene. A Cre recombinase cDNA under control of the Surfactant Protein C promoter was introduced to simultaneously activate SB and inactivate Pten in alveolar epithelial cells. Two control groups were established. One control group (W/T) did not include the Cre recombinase allele and was essentially wild-type while the second control group (Pten-/-) expressed Cre recombinase but did not contain transposons, causing inactivation of Pten without SB activity. Survival of SB/Pten-/- and Pten-/- mice was similar and both were significantly reduced compared to W/T mice. Tumor penetrance was lowest for W/T mice (4%) followed by Pten-/- mice (11%) and was highest for SB/Pten-/- mice (29%). Histological analysis of tumors indicated the presence of adenomas, adenocarcinomas, and extensive alveolar epithelialization along with bronchiolar epithelial hyperplasia. The latter two findings were present in both SB/Pten-/- and Pten-/- mice. Transposon insertions in 24 tumors from 14 SB/Pten-/- mice were mapped to the mouse genome using linker-mediated PCR followed by amplicon sequencing using Illumina GAIIx. Common insertion sites (CISs) were defined using the TAPDANCE analysis pipeline and over 100 candidate cancer genes were identified. A majority of the CIS genes we discovered have documented mutations in human lung cancers based on recent large-scale genomic analyses. This overlap suggests our mouse data could be used to prioritize research into putative human oncogenes and tumor suppressors.

Cullin3 (Cul3) was highly ranked in our CIS list. The protein product of CUL3 is a core scaffolding protein in an E3 ubiquitin ligase complex that regulates ubiquitination of NRF2, IKBKB and other proteins. To determine the role of CUL3 in lung cancer we analyzed expression by western blot in human cancer cell lines and tumors and found CUL3 levels to be lower than normal bronchial epithelial cells. To directly test CUL3's tumor suppressor role we knocked down CUL3 using shRNA in stage II human lung cancer cell lines A549 and H522 either alone or in combination with an shRNA targeting PTEN. Reducing the level of CUL3 in these cell lines resulted in increased proliferation and an increased ability to grow in an anchorage-independent manner. These phenotypes were enhanced when both CUL3 and PTEN were coordinately knocked down. Western blot data indicate PTEN levels increase substantially, while mRNA levels maintain relatively static in CUL3 knockdown cells. In conclusion, we have performed studies that have identified a large number of candidate lung cancer genes and have confirmed a tumor suppressor role for CUL3. We are currently testing the effect of overexpressing CUL3 in both non-transformed and cancerous cell lines, as well as testing more of the candidate genes we have discovered. The results of these studies should lead to new treatment modalities for this deadly cancer.

Citation Format: Casey Dorr, Madison Weg, Raha Been, M. Gerard O'Sullivan, Aaron Sarver, David A. Largaespada, Timothy K. Starr. A Sleeping Beauty forward genetic screen identifies novel cancer drivers that cooperate with Pten in lung cancer. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr C43.

Triptolide induces the expression of miR-142-3p: a negative regulator of heat shock protein 70 and pancreatic cancer cell proliferation

Pancreatic ductal adenocarcinoma (PDAC), one of the deadliest malignancies, is resistant to current chemotherapies. We previously showed that triptolide inhibits PDAC cell growth in vitro and blocks metastatic spread in vivo. Triptolide downregulates HSP70, a molecular chaperone upregulated in several tumor types. This study investigates the mechanism by which triptolide inhibits HSP70. Because microRNAs (miRNA) are becoming increasingly recognized as negative regulators of gene expression, we tested whether triptolide regulates HSP70 via miRNAs. Here, we show that triptolide as well as quercetin, but not gemcitabine, upregulated miR-142-3p in PDAC cells (MIA PaCa-2, Capan-1, and S2-013). Ectopic expression of miR-142-3p inhibited cell proliferation, measured by electric cell-substrate impedance sensing, and decreased HSP70 expression, measured by real-time PCR and immunoblotting, compared with controls. We showed that miR-142-3p directly binds to the 3'UTR of HSP70, and that this interaction is important as HSP70 overexpression rescued miR-142-3p-induced cell death. We found that miR-142-3p regulates HSP70 independently of heat shock factor 1. Furthermore, Minnelide, a water-soluble prodrug of triptolide, induced the expression of miR-142-3p in vivo. This is the first description of an miRNA-mediated mechanism of HSP70 regulation in cancer, making miR-142-3p an attractive target for PDAC therapeutic intervention.

Profiling bortezomib resistance identifies secondary therapies in a mouse myeloma model

Multiple myeloma is a hematologic malignancy characterized by the proliferation of neoplastic plasma cells in the bone marrow. Although the first-to-market proteasome inhibitor bortezomib (Velcade) has been successfully used to treat patients with myeloma, drug resistance remains an emerging problem. In this study, we identify signatures of bortezomib sensitivity and resistance by gene expression profiling (GEP) using pairs of bortezomib-sensitive (BzS) and bortezomib-resistant (BzR) cell lines created from the Bcl-XL/Myc double-transgenic mouse model of multiple myeloma. Notably, these BzR cell lines show cross-resistance to the next-generation proteasome inhibitors, MLN2238 and carfilzomib (Kyprolis) but not to other antimyeloma drugs. We further characterized the response to bortezomib using the Connectivity Map database, revealing a differential response between these cell lines to histone deacetylase (HDAC) inhibitors. Furthermore, in vivo experiments using the HDAC inhibitor panobinostat confirmed that the predicted responder showed increased sensitivity to HDAC inhibitors in the BzR line. These findings show that GEP may be used to document bortezomib resistance in myeloma cells and predict individual sensitivity to other drug classes. Finally, these data reveal complex heterogeneity within multiple myeloma and suggest that resistance to one drug class reprograms resistant clones for increased sensitivity to a distinct class of drugs. This study represents an important next step in translating pharmacogenomic profiling and may be useful for understanding personalized pharmacotherapy for patients with multiple myeloma.

Abstract 5115: Genetic signature of histiocytic sarcoma revealed by an unbiased genetic screen in mice

Histiocytic Sarcomas (HS) are rare neoplasms derived from hematopoietic or mesenchymal stem cells and are known to have a poor prognosis. Primary lesions of HS appear in the spleen, lymph nodes, lung, bone marrow, skin and hypodermis. The definitive cell of origin, genetic etiology, and critical drug targets for HS therapy are unknown. To address all three questions we have utilized a forward genetic screening method in mice that can identify mutations capable of causing cancer initiation and progression. The forward genetic screen uses the Sleeping Beauty (SB) DNA transposon as a random somatic mutagen, capable of both activating proto-oncogenes and inactivating tumor suppressor genes. The system relies on the use of a Cre/LoxP-regulated SB transposase transgene and mutagenic transposon vector transgenes that are mobilized by the transposase. Using Cre recombinase under the control of a tissue specific promoter allows for selective, tissue specific mutagenesis in particular cells of interest. Tumors generated in these mice are analyzed for recurrent transposon insertion sites (called common insertion sites or CIS) using ligation-mediated PCR in combination with high-throughput sequencing. As in human cancer, our results often reveal a small number of frequently mutated genes that cooperate with a greater number of rare mutant genes that drive formation of tumors. We hypothesized that SB-mediated transposition of an oncogenic transposon in myeloid lineage cells in mice could cause mutations in oncogenes and tumor suppressor genes leading to the initiation and progression of HS. We generated and aged 190 experimental and control transgenic mice. The triple transgenic, experimental mice express SB transposase in myeloid lineage cells containing an oncogenic transposon by virtue of a Cre recombinase transgene under the control of the Lysozyme M promoter, which is expressed in committed myeloid lineage cells. Remarkably, triple transgenic mice became moribund much faster than controls. Histopathology suggests 30% of the experimental mice developed HS. We have performed immunohistochemistry to confirm the tumor type using antibodies to Mac-2, F4/80 and PAX5. Tumors were analyzed by mapping transposon insertions to the mouse genome from many independently generated tumors. We mapped 1,177 non-redundant insertions and generated a list of 23 candidate HS genes comprised of known cancer genes as well as novel candidate genes. Our top 3 hits are Raf1 and Fli1, known oncogenes associated with hematological neoplasms, and Mitf, a transcription factor associated with melanoma. Our list also includes known tumor suppressors Trp53 and Nf1. Our results show that 1: A mature myeloid lineage cell can serve as a target cell for HS. 2: ETS and basic helix-loop-helix (hHLH)-leucine zipper transcription factor networks can induce HS with Raf-activated pathways And 3: RAF-MEK-ERK signaling is likely a useful target for HS treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5115. doi:1538-7445.AM2012-5115

Abstract 2859: Identification of driver mutations in colon cancer using Sleeping Beauty mutagenesis

Human colon tumors contain hundreds of genetic and epigenetic anomalies, of which only a handful are responsible for the growth and development of the tumor. We have developed a forward genetic screen in mice that can identify those mutations capable of causing gastrointestinal tract tumors. By comparing the mutations identified in our screen with those found in human colon tumors we can pinpoint the drivers of carcinogenesis. The forward genetic screen uses the Sleeping Beauty (SB) DNA transposon as a random mutagen capable of both activating and inactivating genes. Using Cre recombinase under the control of the Villin promoter we can selectively activate this mutagenesis in intestinal epithelial cells in the mouse. Tumors generated in these mice are analyzed for transposon insertion sites using linker mediated-PCR in combination with high-throughput sequencing. This analysis provides us with genomic sequence that can be mapped to the mouse genome. Candidate cancer driver genes are identified because they are located in areas of the genome that are recurrently mutated by the SB transposon in multiple tumors.

We conducted the screen in wild-type mice and identified 77 candidate cancer genes, of which six were previously known human colon cancer genes (APC, BMPR1A, SMAD4, PTEN, FBXW7, CDK8). More importantly, we identified many novel candidate drivers that can now serve as potential targets in colon cancer therapy. We have extended our studies by conducting three more screens using mice that already contain a known driver mutation. The purpose of these new screens is to gain a better understanding of the genetic changes that cooperate with common mutations found in colon cancer. The three screens used mice that have a mutation in Apc (ApcMin), carry a dominant negative acting Trp53 (p53R270H), or are null for the tumor suppressor gene p19ARF. We have completed the screen in ApcMin mice and found an additional 30 candidate drivers of colon cancer that may specifically cooperate with the Apc mutation. The two final screens are in the process of completion and should uncover genes that cooperate with mutations in Trp53 and p19ARF. The results of these studies will greatly expand the list of potential therapeutic targets and will enhance our understanding of the genetic etiology of colon 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 2859. doi:10.1158/1538-7445.AM2011-2859

Abstract 4182: A screen for genes that define the strong gender bias nature of hepatocellular carcinoma using a transposon mutagenesis murine model

Introduction: Hepatocellular carcinoma (HCC) is a deadly disease where many of the underlying associated genetic mechanisms remain undiscovered. Although HCC has been relatively rare in the US, the growing number of patients with cirrhosis (due to hepatitis infection and/or obesity-related fatty liver) has accounted for a surge in the incidence of HCC. Using the conditional Sleeping Beauty (SB) transposon somatic insertional mutagenesis system in transgenic mice, a novel unbiased HCC genetic screen was performed to elucidate the important genes responsible for this disease1.

Methods: Triple transgenic (containing the conditional SB transposase, transposon mutagenic vector and liver-specific Cre transgenes) and quadruple transgenic (as above plus a conditional dominant negative p53 allele) mice were generated and aged for tumorigenesis1.

Results: Using this system combined with a conditional p53-deficient background, we were able to identify many HCC cancer candidate genes. In addition, liver tumor nodules were also isolated from experimental mice without a predisposed genetic background. Liver tumors were prevalent in male experimental mice, mimicking the strong gender bias in the incidence of HCC seen in humans. Liver tumors were isolated from female experimental mice with and without a p53-deficient background, only after a prolonged latency (&gt;432-days). From wild-type female liver tumors, we identified 17 candidate genes including the Pten tumor suppressor gene. From p53-deficient female liver tumors, we identified 6 candidate genes including some genes that are implicated in the miRNA18a pathway. This miRNA pathway has been associated with increased incidence of HCC in female patients.

Conclusion: SB system allows for the identification of putative genes involved in HCC development in female mice. Finally, our ultimate goal is that candidate genes will be useful in generating possible therapeutic agents for the treatment of HCC and increase our knowledge in defining the underlying genetic mechanisms associated with the strong gender bias nature of this deadly disease.

1. Keng, V.W., et al. (2009). A conditional transposon-based insertional mutagenesis screen for genes associated with mouse hepatocellular carcinoma. Nat Biotechnol. 27, 264-74.

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 4182.

Abstract 3295: The type I insulin-like growth factor receptor (IGF1R) pathway driven metastasis signature correlates with poor prognosis and decreased distant metastasis-free survival in human breast cancer

The insulin-like growth factors (IGFs) acting via the type I IGF receptor (IGF1R) regulate growth and metastasis of multiple types of cancers. Agents targeting IGF1R are currently being tested in phase II/III clinical trials. We have previously shown that IGF1R can regulate metastasis independently of primary tumor growth. In a model of high risk metastatic cancer using the MDA435/LCC6 metastatic cancer cells, we have shown that disruption of IGF signaling either with an antibody against IGF1R, AVE1642, or a dominant negative IGF-1R construct, does not affect growth in the mammary fat pad but inhibits pulmonary metastases and colonization of the lungs. Regulation of such a phenotype will not be measured in clinical trials and these findings imply that clinical trials of this therapeutic strategy may need to adjust their endpoints for assessing benefit by taking into account that inhibition of IGF1R signaling may inhibit metastasis but not primary tumor growth.

Here, we sought to develop an IGF1R driven metastasis signature that may be useful in selecting patients that could benefit from IGF1R targeted therapy and determine if changes in expression of the genes in the signature can be useful in monitoring response. Serum starved LCC6-WT cells (with wild-type functional IGF1R) and LCC6-DN (cells with dominant negative IGF1R) were treated with IGF-I, AVE1642 (antibody against IGF1R that inhibits metastasis but not tumor growth in the mammary fat pad), or AVE1642+ IGF-I for 4 and 24 hours and microarray analysis was performed using the U133 Plus 2.0 human arrays with 47,000 transcripts. Array data were analyzed to determine genes regulated by IGF1R signaling in these cells and if disruption of signaling with AVE1642 affected genes whose expression was regulated by IGF-I signaling. A total of 206 transcripts were regulated by IGF signaling in LCC6-WT cells and AVE1642 treatment reversed the effects of IGF1R signaling. 53 of the most significantly regulated genes were used to query two different human breast tumor datasets to determine if genes regulated by activation of IGF1R are associated with lymph node metastasis and poor prognosis in human tumors. IGF1R regulated metastasis signature genes were expressed in human tumors and were correlated to decreased survival and decreased distant metastasis free survival in breast cancer patients. Our results suggest that presence of IGF1R metastasis signature in patients confers prognostic value and identifying IGF1R driven metastasis signatures may be useful to identify and monitor patients who could benefit from IGF1R targeted therapy for inhibition of metastatic disease.

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 3295.

Long-term functional improvement and gene expression changes after bone marrow-derived multipotent progenitor cell transplantation in myocardial infarction

The study examined the long-term outcome of cardiac stem cell transplantation in hearts with postinfarction left ventricular (LV) remodeling. Myocardial infarction (MI) was created by ligating the first and second diagonal branches of the left anterior descending coronary artery in miniature swine. Intramyocardial injections of 50 million LacZ-labeled bone marrow-derived multipotent progenitor cells (MPC) were performed in the periscar region (Cell, n = 7) immediately after MI, whereas, in control animals (Cont, n = 7), saline was injected. Functional outcome was assessed monthly for 4 mo with MRI and (31)P-magnetic resonance spectroscopy. Engraftment was studied on histology, and gene chip (Affymetrix) array analysis was used to study differential expression of genes in the two groups. MPC treatment resulted in improvement of ejection fraction as early as 10 days after MI (Cell, 43.4 +/- 5.1% vs. Cont, 32.2 +/- 5.5%; P < 0.05). This improvement was seen each month and persisted to 4 mo (Cell, 51.2 +/- 4.8% vs. Cont, 35.7 +/- 5.0%; P < 0.05). PCr-to-ATP ratio (PCr/ATP) improved with MPC transplantation, which was most pronounced at high cardiac work states (subendocardial PCr/ATP was 1.70 +/- 0.10 vs. 1.34 +/- 0.14, P < 0.05). There was no significant difference in scar size (scar/LV area * 100) at 10 days postinfarction. However, at 4 mo, there was a significant decrease in scar size in the Cell group (Cell, 4.6 +/- 1.0% vs. Cont, 8.6 +/- 2.4%; P < 0.05). No significant engraftment of MPC was observed. MPC transplantation was associated with a downregulation of mitochondrial oxidative enzymes and increased levels of myocyte enhancer factor 2a and zinc finger protein 91. In conclusion, MPC transplantation leads to long-term functional and bioenergetic improvement in a porcine model of postinfarction LV remodeling, despite no significant engraftment of stem cells in the heart. MPC transplantation reduces regional wall stresses and infarct size and mitigates the adverse effects of LV remodeling, as seen by a reduction in LV hypertrophy and LV dilatation, and is associated with differential expression of genes relating to metabolism and apoptosis.

IGF-Induced Gene Profiles Are Dependent on IRS Expression and Convey Prognostic Value in Human Breast Cancer

The insulin-like growth factor (IGF) pathway mediates aberrant function during the initiation and progression of primary tumors and secondary metastases in cancer. As a result, a host of tyrosine kinase inhibitors and monoclonal antibodies directed against the type 1 IGF receptor (IGF-1R) have entered clinical trials with early positive results. However, no predictive biomarkers have yet emerged from these initial studies. We propose that expanding IGF biomarkers beyond IGF-1R alone may identify the most appropriate candidates for anti-IGF therapy. Previous work has shown that the insulin receptor substrate (IRS) proteins serve as the functional link between IGF-I-induced IGF-1R phosphorylation and downstream signaling linked to cellular behavior. Our work has demonstrated that IRS isoforms differentially mediate IGF-I action, whereby IRS-1 drives proliferation and IRS-2 triggers motility. Here we employed the T47D-YA (IRS null) breast cancer cell line and T47D-YA/IRS clones stably transfected with IRS-1 or IRS-2. In response to acute (4h) and chronic (24h) IGF-I stimulation, global gene expression patterns were assessed by Affymetrix U133 Plus 2.0 microarray analysis. Analysis revealed that IGF-1R activation alone was insufficient to affect gene expression as no genes were regulated by IGF-I in T47D-YA cells. Conversely, ligand stimulation of IRS-1 and IRS-2 clones induced or repressed hundreds of transcripts in both overlapping and distinct fashions. Direct comparison of IRS-1 to IRS-2 clones revealed a number of early (4h) IRS-2 genes linked to metastasis and late (24h) IRS-1 proliferative genes. Interestingly, a 10-fold upregulation in the transforming growth factor beta 2 (TGFβ2) gene by IGF-I in IRS-2 cells suggested a link between the IRS-derived gene signatures and the TGFβ pathway known to regulate breast cancer metastasis. We then compared our arrays with published IGF-I (MCF-7) and TGFβ-derived (MCF10A, MDA-231, HaCaT, HPL1) microarrays to find a list of commonly regulated genes and performed cluster analysis to reveal consistent patterns of gene expression (Creighton el al 2008 & Padua et al 2008). We found 75 genes that were regulated in common between these signatures. To explore the clinical relevance of the signatures we developed, we examined the NKI-295 dataset used to establish the 70-gene profile of prognosis and found 71 genes regulated in common between all four datasets (van de Vijver et al 2002). Strikingly, we discovered that patient survival was heavily influenced by the degree to which tumor expression correlated to the conserved signatures. A high degree of correlation resulted in the poorest disease free survival and an inverse correlation resulted in an improved disease free survival. Our data suggest that IGF stimulation of breast cancer cells results in distinct profiles of gene expression that are dependent on IRS adaptor protein expression. In addition, some of the “IRS-regulated” genes are shared in common with other gene signatures of poor prognosis. With the use of anti-IGF therapies in breast cancer, attention should focus on the use of these profiles as prognostic and predictive biomarkers.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3031.

Abstract B239: Profiling the type I insulin-like growth factor receptor (IGF1R) pathway regulated metastasis signature

The insulin-like growth factors (IGFs) acting via the type I IGF receptor (IGF1R) regulate growth and metastasis of multiple types of cancers. Agents targeting IGF1R are currently being tested in phase II/III clinical trials. We have previously shown that IGF1R can regulate metastasis independently of primary tumor growth in a model of high risk metastatic cancer using the MDA435/LCC6 metastatic cancer cells. Here we sought to develop an IGF1R driven metastasis signature that may be useful in selecting patients that could benefit from IGF1R targeted therapy and determine if changes in expression of the genes in the signature can be useful in predicting response. Serum starved LCC6-WT cells (with wild-type functional IGF1R) and LCC6-DN (cells with dominant negative IGF1R) were treated with IGF-I, AVE1642 (antibody against IGF1R that inhibits metastasis but not tumor growth in the mammary fat pad), or AVE1642+ IGF-I for 4 and 24 hours and microarray analysis was performed using the U133 Plus 2.0 human arrays with 47,000 transcripts. Array data were analyzed to determine genes regulated by IGF1R signaling in these cells and if disruption of signaling with AVE1642 affected genes whose expression was regulated by IGF-I signaling. A total of 91 transcripts were regulated by IGF signaling in LCC6-WT cells and AVE1642 treatment reversed the effects of IGF1R signaling. We are currently querying human tumor databases to determine if genes regulated by activation of IGF1R are associated with lymph node metastasis and poor prognosis in human tumors. Our results suggest that identifying IGF1R driven metastasis signatures may be useful to identify and monitor patients who could benefit from IGF1R targeted therapy for inhibition of metastatic disease and that patients with this IG

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B239.

MicroRNAs identified in highly purified liver-derived mitochondria may play a role in apoptosis

MicroRNAs (miRNAs) are a class of small approximately 22 nt noncoding (nc) RNAs that regulate gene expression post-transcriptionally by direct binding to target sites on mRNAs. They comprise more than 1,000 novel species in mammalian cells and exert their function by modulating gene expression through several different mechanisms, including translational inhibition, and/or degradation of target mRNAs. Mitochondria maintain and express their own genome, which is distinct from the nuclear transcriptional and translational apparatus. Thus, they provide a potential site for miRNA mediated post-transcriptional regulation. To determine whether they maintain a unique miRNA population, we examined the miRNA profile from highly purified and RNase treated mitochondria from adult rat liver. Fifteen miRNAs were identified by microarray analysis of which, five were confirmed by TaqMan 5'nuclease assays using rat specific probes. Functional analysis of the miRNAs indicated that they were not targeted to the mitochondrial genome nor were they complementary to nuclear RNAs encoding mitochondrial proteins. Rather, the mitochondria-associated miRNAs appear to be involved in the expression of genes associated with apoptosis, cell proliferation, and differentiation. Given the central role that mitochondria play in apoptosis, the results suggest that they might serve as reservoirs of select miRNAs that may modulate these processes in a coordinate fashion.

A Bayesian network driven approach to model the transcriptional response to nitric oxide in Saccharomyces cerevisiae

The transcriptional response to exogenously supplied nitric oxide in Saccharomyces cerevisiae was modeled using an integrated framework of Bayesian network learning and experimental feedback. A Bayesian network learning algorithm was used to generate network models of transcriptional output, followed by model verification and revision through experimentation. Using this framework, we generated a network model of the yeast transcriptional response to nitric oxide and a panel of other environmental signals. We discovered two environmental triggers, the diauxic shift and glucose repression, that affected the observed transcriptional profile. The computational method predicted the transcriptional control of yeast flavohemoglobin YHB1 by glucose repression, which was subsequently experimentally verified. A freely available software application, ExpressionNet, was developed to derive Bayesian network models from a combination of gene expression profile clusters, genetic information and experimental conditions.

Fzf1p regulates an inducible response to nitrosative stress in Saccharomyces cerevisiae

The mechanisms by which microorganisms sense and detoxify nitric oxide (*NO) are of particular interest due to the central role this molecule plays in innate immunity. We investigated the genetic basis of inducible nitric oxide (*NO) detoxification in Saccharomyces cerevisiae by characterizing the genome-wide transcriptional response to exogenously supplied *NO. Exposure to the *NO-generating compound dipropylenetriamine NONOate resulted in both a general stress response as well as a specific response characterized by the induction of a small set of genes, including the yeast flavohemoglobin YHB1, SSU1, and three additional uncharacterized open reading frames. Transcriptional induction of SSU1, which encodes a putative sulfite transporter, has previously been shown to require the zinc finger transcription factor Fzf1p. Deletion of Fzf1p eliminated the nitrosative stress-specific transcriptional response, whereas overexpression of Fzf1p recapitulated this response in the absence of exogenously supplied *NO. A cis-acting sequence unique to the promoter regions of Fzf1p-dependent genes was found to be sufficient to activate reporter gene activity in an *NO- and Fzf1p-dependent manner. Our results suggest that the presence of *NO or *NO derivatives activates Fzf1p leading to transcriptional induction of a discrete set of target genes that function to protect the cell from *NO-mediated stress.

Analysis of peptides and proteins containing nitrotyrosine by matrix-assisted laser desorption/ionization mass spectrometry

Oxidative damage to proteins can occur under physiological conditions through the action of reactive oxygen species, including those containing nitrogen such as peroxynitrite (ONO2-). Peroxynitrite has been shown in vitro to target tyrosine residues in proteins through free radical addition to produce 3-nitrotyrosine. In this work, we show that mass spectral patterns associated with 3-nitrotyrosine containing peptides allow identification of peptides containing this modification. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to characterize a synthetic peptide AAFGY(m-NO2)AR and several peptides containing 3-nitrotyrosine derived from bovine serum albumin treated with tetranitromethane. A unique series of ions were found for these peptides in addition to the mass shift of +45 Da corresponding to the addition of the nitro group. Specifically, two additional ions were observed at roughly equal abundance that correspond to the loss of one and two oxygens, and at lower abundances, two ions are seen that suggest the formation of hydroxylamine and amine derivatives. These latter four components appear to originate by laser-induced photochemical decomposition. MALDI-MS analysis of the synthetic peptide containing 3-nitrotyrosine revealed this same pattern. Post-source decay (PSD) MALDI-time-of-flight (TOF) and collisional activation using a prototype MALDI quadrupole TOF yielded extensive fragmentation that allowed site-specific identification of 3-nitrotyrosine. Conversion of peptides containing 3-nitrotyrosine to 3-aminotyrosine with Na2S2O4 yielded a single molecular ion by MALDI with an abundant sidechain loss under PSD conditions. These observations suggest that MALDI can provide a selective method for the analysis and characterization of 3-nitrotyrosine-containing peptides.