Targeted mutation detection in breast cancer using MammaSeq™

Background

Breast cancer is the most common invasive cancer among women worldwide. Next-generation sequencing (NGS) has revolutionized the study of cancer across research labs around the globe; however, genomic testing in clinical settings remains limited. Advances in sequencing reliability, pipeline analysis, accumulation of relevant data, and the reduction of costs are rapidly increasing the feasibility of NGS-based clinical decision making.

Methods

We report the development of MammaSeq, a breast cancer-specific NGS panel, targeting 79 genes and 1369 mutations, optimized for use in primary and metastatic breast cancer. To validate the panel, 46 solid tumors and 14 plasma circulating tumor DNA (ctDNA) samples were sequenced to a mean depth of 2311× and 1820×, respectively. Variants were called using Ion Torrent Suite 4.0 and annotated with cravat CHASM. CNVKit was used to call copy number variants in the solid tumor cohort. The oncoKB Precision Oncology Database was used to identify clinically actionable variants. Droplet digital PCR was used to validate select ctDNA mutations.

Results

In cohorts of 46 solid tumors and 14 ctDNA samples from patients with advanced breast cancer, we identified 592 and 43 protein-coding mutations. Mutations per sample in the solid tumor cohort ranged from 1 to 128 (median 3), and the ctDNA cohort ranged from 0 to 26 (median 2.5). Copy number analysis in the solid tumor cohort identified 46 amplifications and 35 deletions. We identified 26 clinically actionable variants (levels 1–3) annotated by OncoKB, distributed across 20 out of 46 cases (40%), in the solid tumor cohort. Allele frequencies of ESR1 and FOXA1 mutations correlated with CA.27.29 levels in patient-matched blood draws.

Conclusions

In solid tumor biopsies and ctDNA, MammaSeq detects clinically actionable mutations (OncoKB levels 1–3) in 22/46 (48%) solid tumors and in 4/14 (29%) of ctDNA samples. MammaSeq is a targeted panel suitable for clinically actionable mutation detection in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1102-7) contains supplementary material, which is available to authorized users.

Whole genome amplification of cell-free DNA enables detection of circulating tumor DNA mutations from fingerstick capillary blood

The ability to measure mutations in plasma cell-free DNA (cfDNA) has the potential to revolutionize cancer surveillance and treatment by enabling longitudinal monitoring not possible with solid tumor biopsies. However, obtaining sufficient quantities of cfDNA remains a challenge for assay development and clinical translation; consequently, large volumes of venous blood are typically required. Here, we test proof-of-concept for using smaller volumes via fingerstick collection. Matched venous and fingerstick blood were obtained from seven patients with metastatic breast cancer. Fingerstick blood was separated at point-of-care using a novel paper-based concept to isolate plasma centrifuge-free. Patient cfDNA was then analyzed with or without a new method for whole genome amplification via rolling-circle amplification (WG-RCA). We identified somatic mutations by targeted sequencing and compared the concordance of mutation detection from venous and amplified capillary samples by droplet-digital PCR. Patient mutations were detected with 100% concordance after WG-RCA, although in some samples, allele frequencies showed greater variation likely due to differential amplification or primer inaccessibility. These pilot findings provide physiological evidence that circulating tumor DNA is accessible by fingerstick and sustains presence/absence of mutation detection after whole-genome amplification. Further refinement may enable simpler and less-invasive methods for longitudinal or theranostic surveillance of metastatic cancer.

Circulating Tumor Cell Phenotyping via High-Throughput Acoustic Separation

The study of circulating tumor cells (CTCs) offers pathways to develop new diagnostic and prognostic biomarkers that benefit cancer treatments. In order to fully exploit and interpret the information provided by CTCs, the development of a platform is reported that integrates acoustics and microfluidics to isolate rare CTCs from peripheral blood in high throughput while preserving their structural, biological, and functional integrity. Cancer cells are first isolated from leukocytes with a throughput of 7.5 mL h-1 , achieving a recovery rate of at least 86% while maintaining the cells' ability to proliferate. High-throughput acoustic separation enables statistical analysis of isolated CTCs from prostate cancer patients to be performed to determine their size distribution and phenotypic heterogeneity for a range of biomarkers, including the visualization of CTCs with a loss of expression for the prostate specific membrane antigen. The method also enables the isolation of even rarer, but clinically important, CTC clusters.

Abstract 2050: Polyploid tumor cells: a chemoresistant cell type in triple-negative breast cancer

Background: Triple-negative breast cancers (TNBC) are associated with an extremely poor prognosis due to their aggressive behavior and rapid resistance to chemotherapy. Chemotherapy may select for resistant subclones and lead to tumor recurrence. Although, DNA aneuploidy has been a long known prognostic biomarker in breast cancer, the biological role of aneuploid or polyploid cancer cells in tumorigenesis and chemoresistance is largely undefined. Polyploid cells arise due to repeated rounds of DNA duplication in the absence of mitosis. Chemotherapeutic DNA-damaging agents or mitotic inhibitors can also induce formation of polyploid cells and subsequent senescence. However, recent reports indicate that polyploid cells represent a viable and proliferating subpopulation within a tumor that may escape chemotherapy and contribute to tumor recurrence.

Methods: In this study, we examined the prevalence and functional significance of polyploidy occurring de novo or induced by chemotherapy in TNBC cell lines. DNA ploidy was analyzed in Hoechst 33342 stained cells using FACS. Cells with greater than 4N DNA content were defined as polyploid. Live-cell imaging was done to observe cell division patters in polyploid cells using IncuCyte Zoom. Cell proliferation was assessed in the absence and presence of chemotherapy drugs with distinct modes of action (docetaxel and paclitaxel: mitotic inhibitors, cisplatin: DNA cross-linking agent, and etoposide or VP16: topoisomerase inhibitor). RNAseq was performed to compare gene expression profiles between treatment-naive diploid and polyploid cells.

Results: Hoechst 33342 staining determined the prevalence of polyploid cells in HCC1395(6.7%) and HCC1937 (5.8%) cells lines. Live-cell imaging in polyploid cells showed formation of mitotic structures suggesting multi-polar cell division. Cell proliferation assay revealed that polyploid cells grow slower than diploid cells and show reduced sensitivity to all four chemotherapy drugs. Docetaxel treatment resulted in induction of polyploidy and drug-induced senescence in parental TNBC cells. Drug-induced polyploid cells were resistant to subsequent docetaxel treatment. Time-lapse imaging showed budding of small daughter cells from polyploid senescent cells. Majority of senescent cells died, some cells survived and regenerated the diploid and polyploid subpopulations similar to those present in parental cells. RNAseq identified differentially expressed genes involved in G1-S and G2-M checkpoint pathways (BRCA1/2, RAD51), cell proliferation (Aurora kinase A/B) and apoptosis (BIM, BIRC3).

Conclusions: Above findings indicate that there are molecular and functional differences between diploid and polyploid cells that are both naturally occurring or induced by chemotherapy. In our future studies, we will examine combinatorial approaches to overcome polyploidy-associated chemoresistance.

Citation Format: Rekha Gyanchandani, Adrian Lee. Polyploid tumor cells: a chemoresistant cell type in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2050. doi:10.1158/1538-7445.AM2017-2050

cfDNA mutation frequency in early stage breast cancer

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Background: Though 93% of patient present with early stage breast cancer (EBC), metastatic recurrence is expected in 7-13%. To prevent estrogen receptor (ER) positive disease recurrence, endocrine therapy (ET) is given after local disease. ET guidelines recently extended therapy —specifically tamoxifen—from 5 years to 10 based on ATLAS and aTTom. This pilot study used blood samples from women 6 months post-ET to determine cell free DNA (cfDNA) mutation prevalence in disease-free patients Methods: Patients with EBC and continued follow-up after ET were recruited from the Magee Women’s Breast Cancer Clinic. Inclusion criteria were EBC, ER+, and completion of ET > 6 months prior to visit; the exclusion criterion was active disease. Patients gave 2 blood samples, placed in Streck and EDTA tubes and processed at 2 laboratory sites for cfDNA. Blood from patients with metastatic breast cancer (MBC) served as controls for mutation detection. cfDNA was amplified for ESR1 and PIK3CA genes. Targeted amplifications underwent digital droplet PCR to identify mutations: 4 for ESR1 (D538G, Y537C/N/S), 2 for PIK3CA (E545K, H1047R) Results: Ten EBC patients > 6 months post-ET (post-EBC; 2/5/3 of stage I/II/III) and 10 MBC patients gave samples. cfDNA yield between plasma isolated from EDTA and Streck tubes (including mutation allele frequencies) was not significantly different (p > 0.05); cfDNA yield from patients with MBC was > 2X higher than post-EBC (p < 0.001). MBC cfDNA had 2 monoclonal and 1 polyclonal (2 different) mutations in ESR1, while post-EBC cfDNA had none Conclusions: This pilot study shows cfDNA can be consistently isolated from Streck or EDTA-processed blood from patients with MBC and post-EBC; however, cfDNA levels are significantly higher in MBC. There were no mutations (ESR1 or PIK3CA) in post-EBC samples, though ESR1 mutations were found in MBC. Further studies are needed to determine if mutations in cfDNA can be found in patients without evidence of disease

Abstract P6-07-07: ESR1 amplification and 5'-3' exon imbalance in metastatic breast cancer

BACKGROUND: Growing evidence indicates that base pair mutations in ESR1 are relatively uncommon in newly diagnosed, treatment-naive breast cancer, but frequently acquired in hormone-resistant metastatic breast cancer (MBC). We and others have recently identified ESR1 gene fusion and amplification in MBC, with the ESR1 fusions generally encompassing AF1 and the DNA binding domain. The genomic break required for gene fusions often results in an imbalance in the DNA copy number of exons around the break. We examined ESR1 amplification and 5' and 3' exon copy number imbalance in MBC.

MATERIALS and METHODS: We designed NanoString DNA hybridization probes against coding and non-coding exons (n=9) in ESR1 and 15 reference probes. We analyzed 128 samples consisting of 61 ER-positive and 44 ER-negative metastases, and 23 primary breast cancers. DNA copy number (CN) was determined using nSolver, with &gt;2.7CN as copy number gain, and &gt;10 as CN amplification. ESR1 CN was calculated by averaging the DNA copy number obtained from all coding exons. The 5'-3' copy number ratio was the average copy number of the 5' exons (3-6) divided by the 3' exons (7-10).

RESULTS: 8 (13%) ER positive metastatic breast cancers showed ESR1 amplification with 5 (8%) having &gt;2.7CN, and 3 (5%) with &gt;10CN. In contrast, in ER-negative metastases, we did not detect any samples with amplification &gt;10CN, and a gain (&gt;2.7 CN) in one case. Similarly, in ER+ primary cancers we did not detect any samples with &gt;10 CN amplifications and 2 samples with CN gain (&gt;2.7 CN). ESR1 showed 5'-3' CN imbalance in 1 primary (5%) and in 5 metastatic (5%) breast cancers. We are currently confirming and expanding these data in a larger dataset.

CONCLUSIONS: In addition to ESR1 mutations, ESR1 CN amplifications and 5'-3' imbalance are represent frequent occurrences in endocrine resistant breast cancer. Future studies are aimed at understanding whether the observed exon imbalances are associated with generation of fusion proteins, and whether and how ESR1 amplifications cause changes in endocrine treatment response.

Citation Format: Oesterreich S, Basudan A, Preideigkeit N, Hartmaier RJ, Bahreini A, Gyanchandani R, Leone JP, Lucas PC, Hamilton RL, Brufsky AM, Lee AV. ESR1 amplification and 5'-3' exon imbalance in metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-07-07.

Pointwise mutual information quantifies intratumor heterogeneity in tissue sections labeled with multiple fluorescent biomarkers

BACKGROUND

Measures of spatial intratumor heterogeneity are potentially important diagnostic biomarkers for cancer progression, proliferation, and response to therapy. Spatial relationships among cells including cancer and stromal cells in the tumor microenvironment (TME) are key contributors to heterogeneity.

METHODS

We demonstrate how to quantify spatial heterogeneity from immunofluorescence pathology samples, using a set of 3 basic breast cancer biomarkers as a test case. We learn a set of dominant biomarker intensity patterns and map the spatial distribution of the biomarker patterns with a network. We then describe the pairwise association statistics for each pattern within the network using pointwise mutual information (PMI) and visually represent heterogeneity with a two-dimensional map.

RESULTS

We found a salient set of 8 biomarker patterns to describe cellular phenotypes from a tissue microarray cohort containing 4 different breast cancer subtypes. After computing PMI for each pair of biomarker patterns in each patient and tumor replicate, we visualize the interactions that contribute to the resulting association statistics. Then, we demonstrate the potential for using PMI as a diagnostic biomarker, by comparing PMI maps and heterogeneity scores from patients across the 4 different cancer subtypes. Estrogen receptor positive invasive lobular carcinoma patient, AL13-6, exhibited the highest heterogeneity score among those tested, while estrogen receptor negative invasive ductal carcinoma patient, AL13-14, exhibited the lowest heterogeneity score.

CONCLUSIONS

This paper presents an approach for describing intratumor heterogeneity, in a quantitative fashion (via PMI), which departs from the purely qualitative approaches currently used in the clinic. PMI is generalizable to highly multiplexed/hyperplexed immunofluorescence images, as well as spatial data from complementary in situ methods including FISSEQ and CyTOF, sampling many different components within the TME. We hypothesize that PMI will uncover key spatial interactions in the TME that contribute to disease proliferation and progression.

Intratumor Heterogeneity Affects Gene Expression Profile Test Prognostic Risk Stratification in Early Breast Cancer

PURPOSE

To examine the effect of intratumor heterogeneity (ITH) on detection of genes within gene expression panels (GEPs) and the subsequent ability to predict prognostic risk.

EXPERIMENTAL DESIGN

Multiplexed barcoded RNA analysis was used to measure the expression of 141 genes from five GEPs (Oncotype Dx, MammaPrint, PAM50, EndoPredict, and Breast Cancer Index) in breast cancer tissue sections and tumor-rich cores from 71 estrogen receptor (ER)-positive node-negative tumors, on which clinical Oncotype Dx testing was previously performed. If the tumor had foci of high Ki67 (n = 26), low/negative progesterone receptor (PR; n = 13), or both (n = 5), additional cores were obtained. In total, 181 samples were processed. Oncotype Dx recurrence scores were calculated from NanoString nCounter gene expression data.

RESULTS

Hierarchical clustering using all GEP genes showed that majority (61 of 71) of tumor samples clustered by patient, indicating greater interpatient heterogeneity (IPH) than ITH. We found a strikingly high correlation between Oncotype Dx recurrence scores obtained from whole sections versus tumor-rich cores (r = 0.94). However, high Ki67 and low PR cores had slightly higher but not statistically significant recurrence scores. For 18 of 71 (25%) patients, scores were divergent between sections and cores and crossed the boundaries for low, intermediate, and high risk.

CONCLUSIONS

Our study indicates that in patients with highly heterogeneous tumors, GEP recurrence scores from a single core could under- or overestimate prognostic risk. Hence, it may be a useful strategy to assess multiple samples (both representative and atypical cores) to fully account for the ITH-driven variation in risk prediction. Clin Cancer Res; 22(21); 5362-9. ©2016 AACR.

Abstract B48: Intratumor ploidy heterogeneity as a chemoresistance mechanism in triple-negative breastcancer

Background: Triple negative breast cancers (TNBC) are aggressive, heterogeneous tumors, and currently lack targeted therapies. Chemotherapy is the mainstay treatment, but tumor recurrence is a major cause of mortality and morbidity. Chemotherapy may select for resistant subclones that have a survival advantage over the bulk population of cancer cells and cause tumor relapse. DNA aneuploidy (abnormal number of chromosomes) is a common genetic feature in breast cancer and has been frequently associated with poor prognosis. Although, aneuploid or polyploid cancer cells can contribute to intratumor ploidy heterogeneity, their functional role in tumorigenesis and chemoresistance is largely undefined. Traditionally, polyploid cells were thought to arise due to defects in cell division and were considered to be senescent. However, recent reports have shown that polyploid cells represent a viable and proliferating subpopulation within a tumor and may have a direct role in regulating chemoresistance.

Methods: In this study, we isolated and functionally characterized the diploid and polyploid sub-populations derived from TNBC cell lines. DNA ploidy was assessed in Hoechst 33342 stained cells using flow cytometry. Cells with greater than 4N DNA content were considered as polyploid. Next, we analyzed cell proliferation in HCC1937 cells using CFSE and DNA labeling. Live-cell imaging was performed on flow-sorted diploid and polyploid cells using IncuCyte Zoom to monitor cell proliferation in the absence and presence of mitotic inhibitor (docetaxel).

Results: DNA ploidy analysis identified presence of polyploid cells in HCC1395 and HCC1937 cell lines at a frequency of 6.7% and 5.8% respectively. Polyploid cells have higher forward-scatter than diploid cells suggesting that they are larger in size. In addition, nuclear staining with Hoechst 33342 showed that giant polyploid cells contain enlarged and/or multiple nuclei. Time-lapse microscopy in polyploid cells revealed mitotic structures suggestive of multipolar cell division. Carboxyfluorescein diacetate, succinimidyl ester (CFSE) labeling showed that polyploid cycle slower than the predominant diploid population. Further, the IncuCyte cell proliferation assay also confirmed that sorted polyploid cells divide slower than the diploid cells and displayed resistance to docetaxel.

Concusions: These findings indicate that there are functional differences between diploid and polyploid sub-populations. In our future studies, we will examine the isolated diploid and polyploid cells for differences in their tumorigenic potential and role in tumor recurrence.

Citation Format: Rekha Gyanchandani, Adrian Lee. Intratumor ploidy heterogeneity as a chemoresistance mechanism in triple-negative breastcancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B48.

Sensitive Detection of Mono- and Polyclonal ESR1 Mutations in Primary Tumors, Metastatic Lesions, and Cell-Free DNA of Breast Cancer Patients

PURPOSE

Given the clinical relevance of ESR1 mutations as potential drivers of resistance to endocrine therapy, this study used sensitive detection methods to determine the frequency of ESR1 mutations in primary and metastatic breast cancer, and in cell-free DNA (cfDNA).

EXPERIMENTAL DESIGN

Six ESR1 mutations (K303R, S463P, Y537C, Y537N, Y537S, D538G) were assessed by digital droplet PCR (ddPCR), with lower limits of detection of 0.05% to 0.16%, in primary tumors (n = 43), bone (n = 12) and brain metastases (n = 38), and cfDNA (n = 29). Correlations between ESR1 mutations in metastatic lesions and single (1 patient) or serial blood draws (4 patients) were assessed.

RESULTS

ESR1 mutations were detected for D538G (n = 13), Y537S (n = 3), and Y537C (n = 1), and not for K303R, S463P, or Y537N. Mutation rates were 7.0% (3/43 primary tumors), 9.1% (1/11 bone metastases), 12.5% (3/24 brain metastases), and 24.1% (7/29 cfDNA). Two patients showed polyclonal disease with more than one ESR1 mutation. Mutation allele frequencies were 0.07% to 0.2% in primary tumors, 1.4% in bone metastases, 34.3% to 44.9% in brain metastases, and 0.2% to 13.7% in cfDNA. In cases with both cfDNA and metastatic samples (n = 5), mutations were detected in both (n = 3) or in cfDNA only (n = 2). Treatment was associated with changes in ESR1 mutation detection and allele frequency.

CONCLUSIONS

ESR1 mutations were detected at very low allele frequencies in some primary breast cancers, and at high allele frequency in metastases, suggesting that in some tumors rare ESR1-mutant clones are enriched by endocrine therapy. Further studies should address whether sensitive detection of ESR1 mutations in primary breast cancer and in serial blood draws may be predictive for development of resistant disease. See related commentary by Gu and Fuqua, p. 1034.

A proangiogenic signature is revealed in FGF-mediated bevacizumab-resistant head and neck squamous cell carcinoma

Resistance to antiangiogenic therapies is a critical problem that has limited the utility of antiangiogenic agents in clinical settings. However, the molecular mechanisms underlying this resistance have yet to be fully elucidated. In this study, we established a novel xenograft model of acquired resistance to bevacizumab. To identify molecular changes initiated by the tumor cells, we performed human-specific microarray analysis on bevacizumab-sensitive and -resistant tumors. Efficiency analysis identified 150 genes upregulated and 31 genes downregulated in the resistant tumors. Among angiogenesis-related genes, we found upregulation of fibroblast growth factor-2 (FGF2) and fibroblast growth factor receptor-3 (FGFR3) in the resistant tumors. Inhibition of the FGFR in the resistant tumors led to the restoration of sensitivity to bevacizumab. Furthermore, increased FGF2 production in the resistant cells was found to be mediated by overexpression of upstream genes phospholipase C (PLCg2), frizzled receptor-4 (FZD4), chemokine [C-X3-C motif] (CX3CL1), and chemokine [C-C motif] ligand 5 (CCL5) via extracellular signal-regulated kinase (ERK). In summary, our work has identified an upregulation of a proangiogenic signature in bevacizumab-refractory HNSCC tumors that converges on ERK signaling to upregulate FGF2, which then mediates evasion of anti-VEGF therapy. These findings provide a new strategy on how to enhance the therapeutic efficacy of antiangiogenic therapy.

IMPLICATIONS

Novel xenograft model leads to the discovery of FGF as a promising therapeutic target in overcoming the resistance of antiangiogenic therapy in HNSCC.

Interleukin-8 as a modulator of response to bevacizumab in preclinical models of head and neck squamous cell carcinoma

OBJECTIVES

Bevacizumab, a monoclonal antibody to VEGF-A, is under active clinical evaluation in head and neck squamous cell carcinoma (HNSCC) and appears to be a promising therapy in at least a subset of patients. However, there are no reliable predictive biomarkers to identify those patients most likely to benefit. In this study, we assessed the efficacy of bevacizumab in HNSCC xenograft models to characterize escape mechanisms underlying intrinsic resistance and identify potential biomarkers of drug response.

MATERIALS AND METHODS

We evaluated the angiogenic profile of HNSCC cells from sensitive and resistant cell lines using antibody array. We further examined the role of interleukin-8 (IL-8) in contributing to resistance both in vitro and in vivo, using a loss- and gain-of-function approach.

RESULTS

Angiogenic profiling indicated that resistant cells expressed higher levels of proangiogenic factors including IL-8, interleukin-1α (IL-1α), vascular endothelial growth factor (VEGF), fibroblast growth factor-a (FGF-a), and tumor necrosis factor-α (TNF-α). IL-8 was the most differentially expressed protein. IL-8 signaling compensated for VEGF inhibition in endothelial cells. Downregulation of IL-8 resulted in sensitization of resistant tumors to bevacizumab by disrupting angiogenesis and enhancing endothelial cell apoptosis. Overexpression of IL-8 in sensitive tumors conferred resistance to bevacizumab. Serum analysis of HNSCC patients treated with a bevacizumab-containing regime revealed high baseline IL-8 levels in a subset of patients refractory to treatment but not in responders.

CONCLUSIONS

These results implicate IL-8 in mediating intrinsic resistance to bevacizumab in HNSCC. Hence, co-targeting of VEGF and IL-8 may help overcome resistance and enhance therapeutic efficacy.

Predictive biomarkers to anti-VEGF therapy: progress toward an elusive goal

The search for reliable biomarkers predictive of response to anti-VEGF therapy has been elusive. VEGF-A, the therapeutic target of bevacizumab, is an intuitive candidate as a predictive biomarker to bevacizumab-based anticancer therapy. However, there remains much controversy in the use of VEGF-A as a predictor of response to bevacizumab.

Cetuximab and bevacizumab: preclinical data and phase II trial in recurrent or metastatic squamous cell carcinoma of the head and neck

BACKGROUND

We evaluated combined targeting with cetuximab, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody, and bevacizumab, an anti-vascular endothelial growth factor (VEGF) monoclonal antibody, in squamous cell carcinoma of the head and neck (SCCHN).

PATIENTS AND METHODS

The combination was studied in human endothelial cells and head and neck and lung cancer xenograft model systems. Patients with recurrent or metastatic SCCHN were treated with weekly cetuximab and bevacizumab, 15 mg/kg on day 1 given intravenously every 21 days, until disease progression. Analysis of tumor biomarkers and related serum cytokines was performed.

RESULTS

Cetuximab plus bevacizumab enhanced growth inhibition both in vitro and in vivo, and resulted in potent reduction in tumor vascularization. In the clinical trial, 46 eligible patients were enrolled. The objective response rate was 16% and the disease control rate 73%. The median progression-free survival and overall survival were 2.8 and 7.5 months, respectively. Grade 3-4 adverse events were expected and occurred in less than 10% of patients. transforming growth factor alpha, placenta-derived growth factor, EGFR, VEGFR2 increased and VEGF decreased after treatment but did not correlate with treatment efficacy.

CONCLUSIONS

Cetuximab and bevacizumab are supported by preclinical observations and are well tolerated and active in previously treated patients with SCCHN.

Abstract 1380: Mechanisms of resistance to antiangiogenic therapy in preclinical models of head and neck squamous cell carcinoma (HNSCC)

Purpose: The Vascular Endothelial Growth Factor (VEGF) is ubiquitously expressed and targeted with FDA-approved agent bevacizumab in many types of cancer including colon, lung and renal carcinoma. In head and neck cancer, bevacizumab is under active clinical investigation. However, its efficacy in most cases is limited, with only modest response rates observed in the clinical trials. These incomplete drug responses suggest the presence of alternative signaling mechanisms that compensate for VEGF blockade. The proinflammatory cytokine, Interleukin 8 (IL-8) is known to promote tumor angiogenesis, and is coexpressed with VEGF in HNSCC. Hence, IL-8 signaling may be a possible mechanism of resistance to anti-VEGF therapy. Experimental Design: In this study, we assessed the efficacy of bevacizumab in preclinical HNSCC models to identify tumors that were sensitive or resistant to the treatment. In order to identify potential mediators of bevacizumab resistance, we evaluated the angiogenic profile of HNSCC cells from the non-isogenic pair of sensitive and resistant cell lines by performing angiogenesis antibody array. We further examined the potential contribution of IL-8 signaling to the in vivo growth of bevacizumab-resistant xenografts, using shRNA-mediated knockdown of the IL-8 gene. Results: HNSCC cell lines showed a range of response to bevacizumab in vivo. Interestingly, the resistant cell lines expressed high levels of proangiogenic factors including IL-8, IL-1a and VEGF compared to the sensitive cell lines. Further, combined inhibition of VEGF and IL-8 in the resistant xenografts resulted in a significant reduction in tumor volume and microvessel density compared to targeting VEGF alone. Conclusions: Our results indicate that HNSCC xenografts display a differential response to anti-VEGF therapy. IL-8 was the most differentially expressed protein in the angiogenic signature of the bevacizumab-resistant and sensitive cells. Finally, abrogation of IL-8 signaling sensitized the resistant xenografts to anti-VEGF therapy. These findings suggest that IL-8 may be associated with anti-VEGF resistance in HNSCC. Hence, co-targeting of VEGF and IL-8 may improve antiangiogenic therapeutic efficacy.

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 1380. doi:1538-7445.AM2012-1380