Identifying Common Topics in Patient Portal Messages with Unsupervised Natural Language Processing

PURPOSE/OBJECTIVE(S)

Patient portal messaging is an increasingly important form of communication between patients and medical providers. This has become particularly relevant in oncology, where patients undergo intense longitudinal treatments that require frequent communication regarding symptoms, appointments, and diagnostic results. The rise in the volume of these messages has significantly increased the workload of medical providers and consequent physician burn-out. Natural language processing (NLP), particularly transformer-based models, may offer an automated approach to characterize the content of patient messages and improve message triage and routing. In this study, we employed a state-of-the-art language model (Bidirectional Encoder Representations from Transformers; BERT) to identify data-derived categories of representative topics from real-world data thereby providing basic information to build an appropriate routing system.

MATERIALS/METHODS

Patient-generated portal messages sent to a messaging pool for a single institution radiation oncology department from 2014 to 2023 were extracted. BERTopic, an NLP-based topic modeling technique based on BERT was optimized for topic modeling of patient messages. Uniform Manifold Approximation and Projection (UMAP) was used to reduce dimensionality and visualize topic relationships across messages. The BERTopic-identified topic categories were subsequently labeled manually by one of the physician investigators. Differences of number of messages over time were assessed using t-tests.

RESULTS

A total of 47,492 messages were retrieved. The average number of messages per month from a single patient ranged from 1 to 18 (median 1.67, interquartile range 1.0-2.4). The total volume of patient messages showed a ten-fold increase over the study period, with 101 messages per month sent in 2014 and 999 messages per month in 2022 (p<0.001). BERTopic initially identified 35 topics whose relationships and degrees of overlap were visualized by UMAP. Due to physician-identified similarities, these topics were reduced into 13 categories. The most frequent topic category was messages about laboratory tests or imaging studies: 24.3%, followed by messages expressing appreciation: 18.9%, scheduling discussions: 15.6%, symptom-related messages: 11%, and treatment-related messages: 10.7%.

CONCLUSION

Patient portal messages sent to a single institution radiation oncology department have increased dramatically in volume since implementation, corresponding to a broader national trend. NLP successfully identified common subject themes across patient messages, many of which are related to scheduling. This presents potential opportunities to apply NLP to automate message routing in the future.

Association of mental health diagnosis with race and all-cause mortality after a cancer diagnosis: Large-scale analysis of electronic health record data

BACKGROUND

Disparity in mental health care among cancer patients remains understudied.

METHODS

A large, retrospective, single tertiary-care institution cohort study was conducted based on deidentified electronic health record data of 54,852 adult cancer patients without prior mental health diagnosis (MHD) diagnosed at the University of California, San Francisco between January 2012 and September 2019. The exposure of interest was early-onset MHD with or without psychotropic medication (PM) within 12 months of cancer diagnosis and primary outcome was all-cause mortality.

RESULTS

There were 8.2% of patients who received a new MHD at a median of 197 days (interquartile range, 61-553) after incident cancer diagnosis; 31.0% received a PM prescription; and 3.7% a mental health-related visit (MHRV). There were 62.6% of patients who were non-Hispanic White (NHW), 10.8% were Asian, 9.8% were Hispanic, and 3.8% were Black. Compared with NHWs, minority cancer patients had reduced adjusted odds of MHDs, PM prescriptions, and MHRVs, particularly for generalized anxiety (Asian odds ratio [OR], 0.66, 95% CI, 0.55-0.78; Black OR, 0.60, 95% CI, 0.45-0.79; Hispanic OR, 0.72, 95% CI, 0.61-0.85) and selective serotonin-reuptake inhibitors (Asian OR, 0.43, 95% CI, 0.37-0.50; Black OR, 0.51, 95% CI, 0.40-0.61; Hispanic OR, 0.79, 95% CI, 0.70-0.89). New early MHD with PM was associated with elevated all-cause mortality (12-24 months: hazard ratio [HR], 1.43, 95% CI, 1.25-1.64) that waned by 24 to 36 months (HR, 1.18, 95% CI, 0.95-1.45).

CONCLUSIONS

New mental health diagnosis with PM was a marker of early mortality among cancer patients. Minority cancer patients were less likely to receive documentation of MHDs or treatment, which may represent missed opportunities to identify and treat cancer-related mental health conditions.

Residents-as-Teachers Curriculum for Radiation Oncology: A Targeted Needs Assessment

PURPOSE

Achieving competency as educators is increasingly recognized as a critical part of residents' training in graduate medical education across specialties. In addition to teaching medical students, radiation oncology residents often play a vital role in peer and interprofessional education. We conducted a survey to identify the needs of radiation oncology residents for developing skills in teaching.

METHODS AND MATERIALS

An anonymous, web-based survey was developed and distributed to resident physicians at US radiation oncology programs. Analyses describe respondent demographics, experiences with teaching, and interest in various aspects of a formal "residents-as-teachers" curriculum.

RESULTS

There were 171 completed survey responses (27.5% response rate). A total of 146 residents (85.4%) reported receiving no formal training in teaching before residency, and 121 (70.8%) reported no formal training during residency. Residents who had formal training in teaching were significantly more likely to be "quite" or "extremely" confident about teaching compared with residents who had no prior formal training (76.0% vs 51.4%; P = .022). Residents most commonly taught other residents and medical students (163 [95.3%] and 160 [93.6%] respondents, respectively). The most common settings for teaching were one-on-one teaching (164 respondents [95.9%]), small-group lectures (135 respondents [78.9%]), and intradepartmental lectures (136 respondents [79.5%]). In response to open-ended questions regarding desired teaching opportunities and domains for teaching development, many residents expressed a lack of confidence in teaching and were interested in improvement across many aspects of teaching.

CONCLUSIONS

Radiation oncology residents are expected and desire to teach in a multitude of settings across a wide variety of audiences. However, a significant proportion of radiation oncology residents lack formal training and rarely receive feedback for their teaching skills. The results of this national survey support the development of a residents-as-teachers curriculum for radiation oncology residents that would address the needs for and significant interest in this area.

Matrix compliance permits NF-κB activation to drive therapy resistance in breast cancer

Triple-negative breast cancers (TNBCs) are associated with poor survival mediated by treatment resistance. TNBCs are fibrotic, yet little is known regarding how the extracellular matrix (ECM) evolves following therapy and whether it impacts treatment response. Analysis revealed that while primary untreated TNBCs are surrounded by a rigid stromal microenvironment, chemotherapy-resistant residual tumors inhabit a softer niche. TNBC organoid cultures and xenograft studies showed that organoids interacting with soft ECM exhibit striking resistance to chemotherapy, ionizing radiation, and death receptor ligand TRAIL. A stiff ECM enhanced proapoptotic JNK activity to sensitize cells to treatment, whereas a soft ECM promoted treatment resistance by elevating NF-κB activity and compromising JNK activity. Treatment-resistant residual TNBCs residing within soft stroma had elevated activated NF-κB levels, and disengaging NF-κB activity sensitized tumors in a soft matrix to therapy. Thus, the biophysical properties of the ECM modify treatment response, and agents that modulate stiffness-dependent NF-κB or JNK activity could enhance therapeutic efficacy in patients with TNBC.

The Future of Radiobiology

Innovation and progress in radiation oncology depend on discovery and insights realized through research in radiation biology. Radiobiology research has led to fundamental scientific insights, from the discovery of stem/progenitor cells to the definition of signal transduction pathways activated by ionizing radiation that are now recognized as integral to the DNA damage response (DDR). Radiobiological discoveries are guiding clinical trials that test radiation therapy combined with inhibitors of the DDR kinases DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM), ataxia telangiectasia related (ATR), and immune or cell cycle checkpoint inhibitors. To maintain scientific and clinical relevance, the field of radiation biology must overcome challenges in research workforce, training, and funding. The National Cancer Institute convened a workshop to discuss the role of radiobiology research and radiation biologists in the future scientific enterprise. Here, we review the discussions of current radiation oncology research approaches and areas of scientific focus considered important for rapid progress in radiation sciences and the continued contribution of radiobiology to radiation oncology and the broader biomedical research community.

Abstract P5-02-02: Second harmonic generation in combination with nuclear morphometry in the evaluation of DCIS

Purpose/Objective: Collagen is a major extracellular matrix (ECM) constituent in normal breast and is extensively remodeled in breast carcinoma. Therefore, features of remodeled collagen in the stroma adjacent to ductal carcinoma in situ (DCIS) could indicate cancer progression. The major objective of this study is to identify potential tumor-associated collagen signatures unique to DCIS that will allow us to predict progression based on the collagen texture and nuclear morphology. In this present study, we develop two image analysis pipelines (SHG Texture Extraction and H&E Nuclear Morphology Extractor) to quantify 1) stromal changes, 2) collagen signatures and 3) nuclear morphology from normal breast to DCIS in order to predict local breast cancer recurrence.

Method: We used second harmonic generation (SHG) images and H&E to analyze collagen features and to study nuclear morphology using a data set of 336 patients (from which 310 normal and 327 DCIS regions were imaged). The 336 patients were a subset of patients with pure DCIS taken from a case-control study. Clinical-pathologic factors were associated with risk of subsequent ipsilateral cancer (DCIS or invasive). The SHG framework consisted of collagen segmentation using 1) adaptive thresholding and 2) morphological operations. The H&E framework consisted of nuclear segmentation using adaptive thresholding and a maker-controlled watershed algorithm; and nuclear feature extractions including intensity, texture and morphology. Overall, the SHG framework segments collagen regions and computes textural features specifically at collagen regions. Furthermore, the H&E framework segments nuclei and computes nuclei morphology and textural features. These features were used in L1-regularized logistic regression to construct classification models to discriminate normal vs DCIS regions; and to distinguish regions from DCIS patients with vs. without local recurrences.

Results: In first experiment, we performed L1-regularized logistic regression to construct a classification model to discriminate normal vs DCIS regions. Our results suggest that using only SHG collagen features, this logistic model selected 19 significant features to build a classification model that achieved area under curve (AUC) 90% and accuracy 83% using 5-Fold cross validation. When H&E nuclei features are used, the logistic model selected 88 significant features and achieved AUC 91% and accuracy 86%. By combined both SHG and H&E features, the model achieved classification AUC 93% and accuracy 88%. By using L1-regularized logistic model with combined significant SHG and H&E features, we achieved AUC 59% with an accuracy of 61% for DCIS and recurrent DCIS regions.

Conclusions: Our study suggests that SHG and nuclear morphology features extracted from H&E can improve the classification of normal and DCIS regions. Overall, these results suggest that second harmonic generation and H&E nuclear morphology analysis could aid in the assessment of prognosis and risk of progression to invasive breast cancer.

Citation Format: Park CC, Irshad H, Ziaee S, Martin-Tuite P, Habel L, Weaver VM, Schnitt SJ, Beck AH. Second harmonic generation in combination with nuclear morphometry in the evaluation of DCIS [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-02-02.

Features of MRI stromal enhancement with neoadjuvant chemotherapy: a subgroup analysis of the ACRIN 6657/I-SPY TRIAL

Although the role of cancer-activated stroma in malignant progression has been well investigated, the influence of an activated stroma in therapy response is not well understood. Using retrospective pilot cohorts, we previously observed that MRI detected stromal contrast enhancement was associated with proximity to the tumor and was predictive for relapse-free survival in patients with breast cancer receiving neoadjuvant chemotherapy. Here, to evaluate the association of stromal contrast enhancement to therapy, we applied an advanced tissue mapping technique to evaluate stromal enhancement patterns within 71 patients enrolled in the I-SPY 1 neoadjuvant breast cancer trial. We correlated MR stromal measurements with stromal protein levels involved in tumor progression processes. We found that stromal percent enhancement values decrease with distance from the tumor edge with the estimated mean change ranging [Formula: see text] to [Formula: see text] ([Formula: see text]) for time points T2 through T4. While not statistically significant, we found a decreasing trend in global stromal signal enhancement ratio values with the use of chemotherapy. There were no statistically significant differences between MR enhancement measurements and stromal protein levels. Findings from this study indicate that stromal features characterized by MRI are impacted by chemotherapy and may have predictive value in a larger study.

Effective treatment of HER2-amplified breast cancer by targeting HER3 and β1 integrin

The central role of HER2 as the disease driver and HER3 as its essential partner has made them rational targets for the treatment of HER2-amplifed breast cancers, and there is considerable interest in developing highly effective treatment regimens for this disease that consist of targeted therapies alone. Much of these efforts are focused on dual targeting approaches, particularly dual targeting of the HER2-HER3 tumor driver complex itself, or vertical combinations that target downstream PI3K or Akt in addition to HER2. There is also potential in lateral combinations based on evidence implicating cross-talk with other membrane receptor systems, particularly integrins, and such lateral combinations can potentially involve either HER2 or HER3. We established a preclinical model of targeting HER3 using doxycycline-inducible shRNA and determined the efficacy of a β1 integrin inhibitor in combination with targeting HER3. We report that targeting HER3 and β1 integrin provides a particularly effective combination therapy approach for HER2-amplified cancers, surpassing the combination of HER2 and β1 integrin targeting, and evading some of the safety concerns associated with direct HER2-targeting. This further validates HER3 as a major hub mediating the tumorigenic functions of HER2 and identifies it as a high value target for lateral combination therapy strategies.

ACR Appropriateness Criteria® Ductal Carcinoma in Situ

Ductal carcinoma in situ (DCIS) is a breast neoplasm with potential for progression to invasive cancer. Management commonly involves excision, radiotherapy, and hormonal therapy. Surgical assessment of regional lymph nodes is rarely indicated except in cases of microinvasion or mastectomy. Radiotherapy is employed for local control in breast conservation, although it may be omitted for select low-risk situations. Several radiotherapy techniques exist beyond standard whole-breast irradiation (ie, partial-breast irradiation [PBI], hypofractionated whole-breast radiation); evidence for these is evolving. We present an update of the American College of Radiology (ACR) Appropriateness Criteria® for the management of DCIS. The ACR Appropriateness Criteria® are evidence-based guidelines for specific clinical conditions, which are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review includes an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi technique) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

TH2-Polarized CD4(+) T Cells and Macrophages Limit Efficacy of Radiotherapy

Radiotherapy and chemotherapy following surgery are mainstays of treatment for breast cancer. Although multiple studies have recently revealed the significance of immune cells as mediators of chemotherapy response in breast cancer, less is known regarding roles for leukocytes as mediating outcomes following radiotherapy. To address this question, we utilized a syngeneic orthotopic murine model of mammary carcinogenesis to investigate if response to radiotherapy could be improved when select immune cells or immune-based pathways in the mammary microenvironment were inhibited. Treatment of mammary tumor-bearing mice with either a neutralizing mAb to colony-stimulating factor-1 (CSF-1) or a small-molecule inhibitor of the CSF-1 receptor kinase (i.e., PLX3397), resulting in efficient macrophage depletion, significantly delayed tumor regrowth following radiotherapy. Delayed tumor growth in this setting was associated with increased presence of CD8(+) T cells and reduced presence of CD4(+) T cells, the main source of the TH2 cytokine IL4 in mammary tumors. Selective depletion of CD4(+) T cells or neutralization of IL4 in combination with radiotherapy phenocopied results following macrophage depletion, whereas depletion of CD8(+) T cells abrogated improved response to radiotherapy following these therapies. Analogously, therapeutic neutralization of IL4 or IL13, or IL4 receptor alpha deficiency, in combination with the chemotherapy paclitaxel, resulted in slowed primary mammary tumor growth by CD8(+) T-cell-dependent mechanisms. These findings indicate that clinical responses to cytotoxic therapy in general can be improved by neutralizing dominant TH2-based programs driving protumorigenic and immune-suppressive pathways in mammary (breast) tumors to improve outcomes.

β1-Integrin via NF-κB signaling is essential for acquisition of invasiveness in a model of radiation treated in situ breast cancer

Introduction

Ductal carcinoma in situ (DCIS) is characterized by non-invasive cancerous cell growth within the breast ducts. Although radiotherapy is commonly used in the treatment of DCIS, the effect and molecular mechanism of ionizing radiation (IR) on DCIS are not well understood, and invasive recurrence following radiotherapy remains a significant clinical problem. This study investigated the effects of IR on a clinically relevant model of Akt-driven DCIS and identified possible molecular mechanisms underlying invasive progression in surviving cells.

Methods

We measured the level of phosphorylated-Akt (p-Akt) in a cohort of human DCIS specimens by immunohistochemistry (IHC) and correlated it with recurrence risk. To model human DCIS, we used Akt overexpressing human mammary epithelial cells (MCF10A-Akt) which, in three-dimensional laminin-rich extracellular matrix (lrECM) and in vivo, form organotypic DCIS-like lesions with lumina expanded by pleiomorphic cells contained within an intact basement membrane. In a population of cells that survived significant IR doses in three-dimensional lrECM, a malignant phenotype emerged creating a model for invasive recurrence.

Results

P-Akt was up-regulated in clinical DCIS specimens and was associated with recurrent disease. MCF10A-Akt cells that formed DCIS-like structures in three-dimensional lrECM showed significant apoptosis after IR, preferentially in the luminal compartment. Strikingly, when cells that survived IR were repropagated in three-dimensional lrECM, a malignant phenotype emerged, characterized by invasive activity, up-regulation of fibronectin, α5β1-integrin, matrix metalloproteinase-9 (MMP-9) and loss of E-cadherin. In addition, IR induced nuclear translocation and binding of nuclear factor-kappa B (NF-κB) to the β1-integrin promoter region, associated with up-regulation of α5β1-integrins. Inhibition of NF-κB or β1-integrin signaling abrogated emergence of the invasive activity.

Conclusions

P-Akt is up-regulated in some human DCIS lesions and is possibly associated with recurrence. MCF10A-Akt cells form organotypic DCIS-like lesions in three-dimensional lrECM and in vivo, and are a plausible model for some forms of human DCIS. A population of Akt-driven DCIS-like spheroids that survive IR progresses to an invasive phenotype in three-dimensional lrECM mediated by β1-integrin and NF-κB signaling.

Abstract 5438: Resistance to β1 integrin inhibition in HER2 amplified cancers is mediated by HER3

Our previous work focused on investigating β1 integrin as a target for BC, alone and with radiation therapy. It is well recognized that there is significant cross talk between the EGFR family of receptors and β1 integrin signaling, and a relative resistance of HER2+ BC to β1 integrin inhibitory agents. In 2006, we published our findings that β1 integrin inhibition enhanced the effect of trastuzumab in HER2+ BC. Subsequently, others and we reported that β1 integrin inhibition enhanced the cytostatic effect of multiple HER2-targeted therapies in HER2+ BC. However, the nature of cross talk between β1 integrins and HER2, and the role of β1 integrin in HER2+BC resistance remains unknown. In addition, HER2+BCs have higher rates of local recurrence after radiotherapy, consistent with previous work showing relative radioresistance in HER2+BC. The most potent mitogenic HER2 signaling in HER2+BC occurs upon heterodimerization with HER3. We hypothesized that HER3 could mediate significant resistance to β1 integrin targeting in HER2+BC.

To test this, we correlated β1 integrin and HER3 expression levels in SKBR3 cells over several time points using WB. Inhibitions of β1 integrin activity or shRNA knockdown of HER3 lead to upregulation of HER3 and β1 integrin, respectively. To test whether HER3 knockdown enhanced β1 integrin inhibition, we estimated proliferation by quantitating Ki-67 expression in SKBR3 cells in response to treatment. β1 integrin inhibition lead to a ∼50% reduction in Ki-67 positive cells (48%-22%), which was further enhanced by 50% with HER3 knockdown (12%), p&lt;0.05. In addition, HER3 knockdown enhanced the cytostatic effect of ionizing radiation (IR) by ∼50% (32% to 14%), p&lt;0.05. Enhanced cytostasis was correlated with a significant down modulation of p-HER2 and p-473 Akt on WB. In conclusion, our data indicate that HER3 plays a role in mediating resistance to β1 integrin inhibition in HER2+BC. Further mechanistic and in vivo validation are on going.

Citation Format: Catherine C. Park, Dhara Amin, Hui Zhang, Mark Moasser. Resistance to β1 integrin inhibition in HER2 amplified cancers is mediated by HER3. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5438. doi:10.1158/1538-7445.AM2014-5438

ACR Appropriateness Criteria local-regional recurrence (LRR) and salvage surgery-breast cancer

Although both breast-conserving surgery and mastectomy generally provide excellent local-regional control of breast cancer, local-regional recurrence (LRR) does occur. Predictors for LRR include patient, tumor, and treatment-related factors. Salvage after LRR includes coordination of available modalities, including surgery, radiation, chemotherapy, and hormonal therapy, depending on the clinical scenario. Management recommendations for breast cancer LRR, including patient scenarios, are reviewed, and represent evidence-based data and expert opinion of the American College of Radiology Appropriateness Criteria Expert Panel on LRR.The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel.The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Current status and recommendations for the future of research, teaching, and testing in the biological sciences of radiation oncology: report of the American Society for Radiation Oncology Cancer Biology/Radiation Biology Task Force, executive summary

In early 2011, a dialogue was initiated within the Board of Directors (BOD) of the American Society for Radiation Oncology (ASTRO) regarding the future of the basic sciences of the specialty, primarily focused on the current state and potential future direction of basic research within radiation oncology. After consideration of the complexity of the issues involved and the precise nature of the undertaking, in August 2011, the BOD empanelled a Cancer Biology/Radiation Biology Task Force (TF). The TF was charged with developing an accurate snapshot of the current state of basic (preclinical) research in radiation oncology from the perspective of relevance to the modern clinical practice of radiation oncology as well as the education of our trainees and attending physicians in the biological sciences. The TF was further charged with making suggestions as to critical areas of biological basic research investigation that might be most likely to maintain and build further the scientific foundation and vitality of radiation oncology as an independent and vibrant medical specialty. It was not within the scope of service of the TF to consider the quality of ongoing research efforts within the broader radiation oncology space, to presume to consider their future potential, or to discourage in any way the investigators committed to areas of interest other than those targeted. The TF charge specifically precluded consideration of research issues related to technology, physics, or clinical investigations. This document represents an Executive Summary of the Task Force report.

Cost-effectiveness analysis of intraoperative radiation therapy for early-stage breast cancer

BACKGROUND

Shortened courses of radiation therapy have been shown to be similarly effective to whole-breast external-beam radiation therapy (WB-EBRT) in terms of local control. We sought to analyze, from a societal perspective, the cost-effectiveness of two radiation strategies for early-stage invasive breast cancer: single-dose intraoperative radiation therapy (IORT) and the standard 6-week course of WB-EBRT.

METHODS

We developed a Markov decision-analytic model to evaluate these treatment strategies in terms of life expectancy, quality-adjusted life years (QALYs), costs, and the incremental cost-effectiveness ratio over 10 years.

RESULTS

IORT single-dose intraoperative radiation therapy was the dominant, more cost-effective strategy, providing greater quality-adjusted life years at a decreased cost compared with 6-week WB-EBRT. The model was sensitive to health state utilities and recurrence rates, but not costs. IORT was either the preferred or dominant strategy across all sensitivity analyses. The two-way sensitivity analyses demonstrate the need to accurately determine utility values for the two forms of radiation treatment and to avoid indiscriminate use of IORT.

CONCLUSIONS

With less cost and greater QALYs than WB-EBRT, IORT is the more valuable strategy. IORT offers a unique example of new technology that is less costly than the current standard of care option but offers similar efficacy. Even when considering the capital investment for the equipment ($425 K, low when compared with the investments required for robotic surgery or high-dose-rate brachytherapy), which could be recouped after 3-4 years conservatively, these results support IORT as a change in practice for treating early-stage invasive breast cancer.

MRI enhancement in stromal tissue surrounding breast tumors: association with recurrence free survival following neoadjuvant chemotherapy

RATIONALE AND OBJECTIVES

Normal-appearing stromal tissues surrounding breast tumors can harbor abnormalities that lead to increased risk of local recurrence. The objective of this study was to develop a new imaging methodology to characterize the signal patterns of stromal tissue and to investigate their association with recurrence-free survival following neoadjuvant chemotherapy.

MATERIALS AND METHODS

Fifty patients with locally-advanced breast cancer were imaged with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) before (V1) and after one cycle (V2) of adriamycin-cytoxan therapy. Contrast enhancement in normal-appearing stroma around the tumor was characterized by the mean percent enhancement (PE) and mean signal enhancement ratio (SER) in distance bands of 5 mm from the tumor edge. Global PE and SER were calculated by averaging all stromal bands 5 to 40 mm from tumor. Proximity-dependent PE and SER were analyzed using a linear mixed effects model and Cox proportional hazards model for recurrence-free survival.

RESULTS

The mixed effects model displayed a decreasing radial trend in PE at both V1 and V2. An increasing trend was less pronounced in SER. Survival analysis showed that the hazard ratio estimates for each unit decrease in global SER was statistically significant at V1 [estimated hazard ratio = 0.058, 95% Wald CI (0.003, 1.01), likelihood ratio p = 0.03]; but was not so for V2.

CONCLUSIONS

These findings show that stromal tissue outside the tumor can be quantitatively characterized by DCE-MRI, and suggest that stromal enhancement measurements may be further developed for use as a potential predictor of recurrence/disease-free survival following therapy.

β1 integrin targeting potentiates antiangiogenic therapy and inhibits the growth of bevacizumab-resistant glioblastoma

Antiangiogenic therapies like bevacizumab offer promise for cancer treatment, but acquired resistance, which often includes an aggressive mesenchymal phenotype, can limit the use of these agents. Upregulation of β1 integrin (ITGB1) occurs in some bevacizumab-resistant glioblastomas (BRG) whereby, mediating tumor-microenvironment interactions, we hypothesized that it may mediate a mesenchymal-type resistance to antiangiogenic therapy. Immunostaining analyses of β1 integrin and its downstream effector kinase FAK revealed upregulation in 75% and 86% of BRGs, respectively, compared with pretreatment paired specimens. Furthermore, flow cytometry revealed eight-fold more β1 integrin in primary BRG cells compared with cells from bevacizumab-naïve glioblastomas (BNG). Fluorescence recovery after photobleaching of cells engineered to express a β1-GFP fusion protein indicated that the mobile β1 integrin fraction was doubled, and half-life of β1 integrin turnover in focal adhesions was reduced markedly in BRG cells compared with bevacizumab-responsive glioblastoma multiforme cells. Hypoxia, which was increased with acquisition of bevacizumab resistance, was associated with increased β1 integrin expression in cultured BNG cells. BRGs displayed an aggressive mesenchymal-like phenotype in vitro. We found that growth of BRG xenograft tumors was attenuated by the β1 antibody, OS2966, allowing a 20-fold dose reduction of bevacizumab per cycle in this model. Intracranial delivery of OS2966 through osmotic pumps over 28 days increased tumor cell apoptosis, decreased tumor cell invasiveness, and blunted the mesenchymal morphology of tumor cells. We concluded that β1 integrin upregulation in BRGs likely reflects an onset of hypoxia caused by antiangiogenic therapy, and that β1 inhibition is well tolerated in vivo as a tractable strategy to disrupt resistance to this therapy.

Abstract 2312: Targeting beta1 integrin potentiates antiangiogenic therapy and inhibits growth of bevacizumab-resistant glioblastoma multiforme

INTRODUCTION: Antiangiogenic therapies like bevacizumab hold promise for cancer treatment. However, the development of acquired resistance, including an aggressive mesenchymal phenotype, limit utility of these agents. We previously published a report in which microarray and PCR analysis revealed beta1 integrin to be upregulated in bevacizumab-resistant glioblastomas (BRGs). Because the beta1 integrin subunit mediates tumor-microenvironment interactions, we further investigated its role in mesenchymal-type resistance to anti-angiogenic therapy.

METHODS: Immunostaining of BRG specimens and genetic or pharmacologic beta1 targeting in BRG cells and BRG-derived xenografts were used to study the role of beta1 integrin in anti-angiogenic therapy resistance in vitro and in vivo. Cells were transduced to express beta1-GFP fusion protein to measure beta1 integrin turnover in focal adhesions using fluorescence recovery after photobleaching (FRAP).

RESULTS: Beta1 integrin and downstream beta1-effector focal adhesion kinase immunostaining were upregulated in 75% and 86% of BRGs, resepectively, compared to pre-treatment paired specimens. Flow cytometry revealed 8-fold upregulation of beta1 integrin in BRG-derived primary GBM cells compared to cells from bevacizumab-naïve GBMs (P&lt;0.05). FRAP revealed more rapid beta1 integrin turnover in focal adhesion kinases in BRG-derived cells than in bevacizumab-naïve GBM cells, with 4-fold more time to achieve 37% recovery in bevacizumab-naïve GBM cells than in BRG-derived cells expressing a beta1-GFP fusion protein (95 versus 398 seconds; P&lt;0.05).

Hypoxia, which was increased 80% (as evidenced by CA9 immunostaining) (P&lt;0.05) after bevacizumab resistance, increased beta1 integrin expression 30% in cultured bevacizumab-naïve GBM cells (P&lt;0.01). Two hours of incubation with 10 and 100 ng/mL VEGF reduced adhesion of GBM cells to beta1 ligands fibronectin, collagen IV, and laminin by 10-50% in a dose-dependent fashion (P&lt;0.05).

BRGs demonstrated aggressive mesenchymal-like phenotype in vitro and growth of subcutaneous BRG xenografts was attenuated by beta1 antibody OS2966 (P&lt;0.05). Addition of OS2966 allowed 20-fold dose reduction of bevacizumab per cycle in subcutaneous GBM-derived xenografts (P&lt;0.05). Intracranial delivery of OS2966 through osmotic pumps in mice carrying intracranial BRG-derived xenografts over 28 days increased tumor cell apoptosis, decreased tumor cell invasiveness, and altered tumor cell morphology (P&lt;0.05).

CONCLUSIONS: Beta1 integrin expression and turnover in focal adhesion kinases is upregulated in BRGs due to 2 possible mechanisms - hypoxic upregulation and bevacizumab-induced VEGF depletion eliminating VEGF-mediated inhibition of beta1 activity. Beta1 inhibition is well tolerated in vivo and holds promise for disrupting anti-angiogenic therapy resistance.

Citation Format: W. Shawn Carbonell, Michael De Lay, Arman Jahangiri, Catherine C. Park, Manish Aghi. Targeting beta1 integrin potentiates antiangiogenic therapy and inhibits growth of bevacizumab-resistant glioblastoma multiforme. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2312. doi:10.1158/1538-7445.AM2013-2312

NF-κB regulates radioresistance mediated by β1-integrin in three-dimensional culture of breast cancer cells

β1-integrin induction enhances breast cancer cell survival after exposure to ionizing radiation (IR), but the mechanisms of this effect remain unclear. Although NF-κB initiates prosurvival signaling pathways post-IR, the molecular function of NF-κB with other key elements in radioresistance, particularly with respect to extracellular matrix-induced signaling, is not known. We discovered a typical NF-κB-binding site in the β1-integrin promoter region, indicating a possible regulatory role for NF-κB. Using three-dimensional laminin-rich extracellular matrix (3D lrECM) culture, we show that NF-κB is required for β1-integrin transactivation in T4-2 breast cancer cells post-IR. Inhibition of NF-κB reduced clonogenic survival and induced apoptosis and cytostasis in formed tumor colonies. In addition, T4-2 tumors with inhibition of NF-κB activity exhibit decreased growth in athymic mice, which was further reduced by IR with downregulated β1-integrin expression. Direct interactions between β1-integrin and NF-κB p65 were induced in nonmalignant breast epithelial cells, but not in malignant cells, indicating context-specific regulation. As β1-integrin also activates NF-κB, our findings reveal a novel forward feedback pathway that could be targeted to enhance therapy.

Rapid and automated multidimensional fluorescence microscopy profiling of 3D human breast cultures

Three-dimensional (3D) tissue culture provides a physiologically relevant microenvironment for distinguishing malignant from non-malignant breast cell phenotypes. 3D culture assays can also be used to test novel cancer therapies and predict a differential response to radiation between normal and malignant cells in vivo. However, biological measurements in such complex models are difficult to quantify and current approaches do not allow for in-depth multifaceted assessment of individual colonies or unique sub-populations within the entire culture. This is in part due to the limitations of imaging at a range of depths in 3D culture resulting from optical aberrations and intensity attenuation. Here, we address these limitations by combining sample smearing techniques with high-throughput 2D imaging algorithms to accurately and rapidly quantify imaging features acquired from 3D cultures. Multiple high resolution imaging features especially designed to characterize 3D cultures show that non-malignant human breast cells surviving large doses of ionizing radiation acquire a "swelled acinar" phenotype with fewer and larger nuclei, loss of cell connectivity and diffused basement membrane. When integrating these imaging features into hierarchical clustering classification, we could also identify subpopulations of phenotypes from individual human tumor colonies treated with ionizing radiation or/and integrin inhibitors. Such tools have therefore the potential to further characterize cell culture populations after cancer treatment and identify novel phenotypes of resistance.

Abstract P1-05-08: Targeting integrin signaling suppresses invasive recurrence in a three-dimensional model of radiation treated ductal carcinoma in situ

Background: DCIS (ductal carcinoma in situ) is comprised of cancerous cells that are contained within the milk duct and separated from the stroma by a basement membrane. Akt activation is implicated in breast cancer progression and also upregulated in ∼30% of DCIS lesions. We have previously shown that β1-integrin inhibition enhanced the efficacy of ionizing radiation (IR) in invasive breast cancer, via an Akt-mediated effect. Radiation therapy (RT) is commonly used to treat DCIS, resulting in a decrease in recurrence risk by ∼50%. However, DCIS still recurs in a substantial number of patients, and as invasive disease half of the time. This study aimed to identify the effects of IR on Akt-driven DCIS, and possible mechanisms underlying invasive progression in surviving cells.

Materials and Methods: To model DCIS, we took advantage of the ability of non-invasive mammary epithelial cells, MCF10A that form duct-like structures in 3-dimensional laminin-rich extracellular matrix (3D lrECM), and overexpressed an activated myristoylated form of the serine/threonine kinase, Akt. The 3D lrECM cultured MCF10A-Akt cells show filled lumen and retained basal polarity, characteristic of DCIS lesions in vivo. After DCIS structures formed in 3D lrECM, cultures were exposed to 8 Gy IR. Confocal microscopy analysis, western blot analysis, matrigel chemoinvasion assay and matix degradation assay were performed to characterize the IR effect on luminal or basal cells of the DCIS like structures.

Results: MCF10A-Akt structures post-8 Gy IR shows a significant increase in apoptosis measured by cleaved caspase-3 (n = 3, P &lt; 0.05). When we propagated cells post-IR in 3D lrECM, an invasive phenotype emerged in a sub-population of survivors (n = 3, P &lt; 0.01). We also confirmed that inhibitory antibodies to β1-integrin suppressed the invasive phenotype that was induced by 8 Gy IR. In addition to this, invasion activity emerged by 8 Gy IR was inhibited by nuclear factor-kappaB (NF-κB) inhibitor JSH-23 (n = 3, P &lt; 0.01). Finally, inhibition of β1-integrins or NF-κB translocation completely suppresses the formation of invasive colonies.

Discussion: In present study, we found that inhibition of β1-integrins abrogates the emergence of an invasive phenotype among surviving clones. Our current data suggest that regulation of β1-integrin signaling via NF-κB plays an important role in the emergence of invasive disease after radiation, and may be an important clinical target.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-05-08.

Abstract P4-06-05: NF-κB Upregulates β1-integrin via Increased Transcriptional Activity in Three-dimensional Culture: a Mechanism by which Malignant Breast Cells Acquire Radioresistance

The molecular mechanisms giving rise to tumor viability after therapeutic radiation remain elusive. We showed previously that β1-integrin is associated with enhanced cell survival of breast cancer cells after exposure to high dose ionizing radiation (IR). Recently, we discovered that a typical binding site for Nuclear factor-κB (NF-κB), a stress-sensitive heterodimeric transcription factor, was located in human β1-integrin promoter, which indicates that β1-integrin-mediated resistance to radiation may be functionally regulated by NF-κB. The aim of the present study was to investigate the relationship between NF-κB and β1-integrin pathways in radioprotection of malignant T4-2 breast cells in three-dimensional laminin-rich extracellular matrix (3D lrECM). We show that NF-κB is required for radiation-induced β1-integrin transactivation. Inhibition of NF-κB activity significantly reduced clonogenic survival with the inhibition of IR-induced total and phosphorylated (Thr 788/789) β1-integrins, correlated with increased DNA binding activity at the β1- integrin promoter. Treatment of T4-2 colonies with NF-κB activation inhibitor before IR resulted in a reduction of the size of colonies, associated with a decrease in proliferation and increase in apoptosis, indicating an increased susceptibility to IR. Further studies revealed that a direct interaction of β1-integrin with α5-integrin was highly induced, but not with NF-κB p65, in T4-2 cells surviving IR. These interactions were found to be oppositely regulated in radiosensitive S1 cells, suggesting that IR induces the formation of α5β1-integrin complexes leading to increased survival post-IR. Together these results provide the first evidence that NF-κB-induced β1-integrin transactivation is responsible for increased survival post IR in breast cancer. Since β1-integrin is shown to activate NF-κB, our data further suggest a loop-like β1-integrin–NF-κB–β1-integrin pathway in tumor radioresistance. This novel pathway may serve as an efficient drug target to re-sensitize radioresistant tumor cells.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-05.

P3-01-06: NF-kB Inhibition Promotes Radiosensitivity of Breast Cancer Cells in Three-Dimensional Culture through Abating b1-Integrin Expression

Therapy-associated tumor resistance, giving rise to recurrence and mortality, is a critical issue in cancer therapy. The molecular mechanisms causing tumor resistnace to the therapeutic radiation remain elusive. Nuclear factor-KB (NF-KB), a stress-sensitive heterodimeric transcription factor in the regulation of the stress-responsive genes, has been shown to initiate prosurvival signaling pathways. The cooperative function of NF-KB with other key stress elements in radioresistance remains to be elucidated. We have previously reported that induction of α5β1-integrin is associated with the enhanced cell survival of breast cancer cells after exposure to high dose IR (ionizing radiation). Because a typical NF-KB binding site was located in human β1-integrin promoter region, β1-integrin-mediated resistance to radiation may be regulated by NF-KB. The aim of the present study was to reveal a connection between NF-KB and β1-integrin pathways in radioprotection of malignant T4-2 mammary epithelial cells in 3D ***lrECM (three-dimensional laminin-rich extracellular matrix). We show that the elevated NF-KB activity was correlated with enhanced clonogenic survival, and increased NF-KB heterodimer p50/p65 levels were associated with an increase in total and phosphorylated (Thr 788/789) β1-integrins. Inhibition of NF-KB activation significantly reduced clonogenic survival with the inhibition of β1-integrin. These results indicate that NF-KB-mediated induction of β1-integrin is associated with an increased radiation resistance. Treatment of T4-2 colonies, formed at day 4, with NF-KB activation inhibitor in 3D lrECM before exposure to IR (4-Gy X-ray) resulted in a reduction of the size of colonies. The surviving colonies were associated with a decrease in proliferation and increase in apoptosis, indicating a decrease of resistance to IR. Together, these results provide the first evidence that NF-KB-mediated β1-integrin expression is responsible for tumor radioresistance. The NF-KB/β1-integrin pathway may serve as an efficient drug target to re-sensitize radioresistant tumor cells.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-01-06.

Abstract C130: Inhibition of NF-κB activity promotes radiosensitivity of breast cancer cells in three-dimensional culture via a β1-integrin-mediated pathway

Radioresistance markedly impairs the efficacy of tumor radiotherapy and involves prosurvival signal transduction pathways that prevent radiation-induced cell death. Nuclear factor-κB (NF-κB), a stress-sensitive heterodimeric transcription factor in the regulation of the stress-responsive genes, has been shown to initiate prosurvival signaling in response to ionizing radiation (IR). The cooperative function of NF-κB with other key stress elements in radioresistance has not been clearly defined. We have previously reported that induction of β1-integrin is associated with the enhanced cell survival of breast cancer cells after exposure to clinically relevant doses of IR. Because a typical NF-κB binding site was identified in human β1-integrin promoter region, β1-integrin-mediated resistance to radiation may be regulated by NF-κB. The aim of the present study was to reveal a connection between NF-κB and β1-integrin pathways in radioprotection of malignant T4-2 mammary epithelial cells in 3D lrECM (three-dimensional laminin-rich extracellular matrix). We show that the elevated NF-κB activity was correlated with enhanced clonogenic survival with an increase in total and phosphorylated (Thr 788/789) β1-integrins. Inhibition of NF-κB activation significantly reduced clonogenic survival with the inhibition of β1-integrin, suggesting that NF-κB-mediated induction of β1-integrin is associated with an increased radiation resistance. Treatment of malignant human breast cell colonies, T4-2 with NF-κB activation inhibitor at Day 4 in 3D lrECM before exposure to IR (4-Gy X-ray) resulted in a reduction of the size of colonies. The surviving colonies were associated with a decrease in proliferation and increase in apoptosis, indicating a decrease of resistance to IR. Using an ELISA-based DNA binding assay, we next determined that the binding of NF-κB to its target sequence on β1-integrin promoter region was significantly increased by IR. These data suggest that IR-induced increase in β1-integrin protein expression is mediated by NF-κB activation and subsequent binding of NF-κB to the β1-integrin promoter. Taken together, our results provide the first evidence that NF-κB-mediated β1-integrin expression is responsible for tumor radioresistance. The NF-κB/β1-integrin pathway could provide new insight into the development of new therapeutic modalities to re-sensitize radioresistant tumor cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C130.

β1 integrin mediates an alternative survival pathway in breast cancer cells resistant to lapatinib

INTRODUCTION

The overexpression of human epidermal growth factor receptor (HER)-2 in 20% of human breast cancers and its association with aggressive growth has led to widespread use of HER2-targeted therapies, such as trastuzumab (T) and lapatinib (L). Despite the success of these drugs, their efficacy is limited in patients whose tumors demonstrate de novo or acquired resistance to treatment. The β1 integrin resides on the membrane of the breast cancer cell, activating several elements of breast tumor progression including proliferation and survival.

METHODS

We developed a panel of HER2-overexpressing cell lines resistant to L, T, and the potent LT combination through long-term exposure and validated these models in 3D culture. Parental and L/T/LT-resistant cells were subject to HER2 and β1 integrin inhibitors in 3D and monitored for 12 days, followed by quantification of colony number. Parallel experiments were conducted where cells were either stained for Ki-67 and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) or harvested for protein and analyzed by immunoblot. Results were subjected to statistical testing using analysis of variance and linear contrasts, followed by adjustment with the Sidak method.

RESULTS

Using multiple cell lines including BT474 and HCC1954, we reveal that in L and LT resistance, where phosphorylation of EGFR/HER1, HER2, and HER3 are strongly inhibited, kinases downstream of β1 integrin--including focal adhesion kinase (FAK) and Src--are up-regulated. Blockade of β1 by the antibody AIIB2 abrogates this up-regulation and functionally achieves significant growth inhibition of L and LT resistant cells in 3D, without dramatically affecting the parental cells. SiRNA against β1 as well as pharmacologic inhibition of FAK achieve the same growth inhibitory effect. In contrast, trastuzumab-resistant cells, which retain high levels of phosphorylated EGFR/HER1, HER2, and HER3, are only modestly growth-inhibited by AIIB2.

CONCLUSIONS

Our data suggest that HER2 activity, which is suppressed in resistance involving L but not T alone, dictates whether β1 mediates an alternative pathway driving resistance. Our findings justify clinical studies investigating the inhibition of β1 or its downstream signaling moieties as strategies to overcome acquired L and LT resistance.

Abstract 2840: Efficacy of radiation therapy in mammary carcinomas is regulated by macrophages

In patients with locally advanced breast cancer, radiation therapy (RT) and chemotherapy following surgery has been a mainstay of treatment with demonstrated survival advantage in numerous randomized trials. However, despite recent advances in treatment, many women still ultimately succumb to disease highlighting the need to improve therapeutic strategies. Results from several groups have recently revealed that the therapeutic effects of RT are in part dependent on activation of immune-mediated mechanism(s); however, little is known regarding the mechanistic details of this activation. To address this, we examined changes in the immune microenvironment of mammary carcinomas following RT. We found that following RT (5 Gy), the density of infiltrating macrophages was significantly increased (20 vs 35%, p = 0.02) as compared to mammary tumors in mice not receiving RT. When macrophages were depleted following RT, via use of a CSF-1 antagonist, a significant delay in tumor growth, as compared to tumors treated with RT alone was observed. Since this data indicated that macrophage infiltration blunted RT responsiveness, we hypothesized that reprogramming tumor-infiltrating macrophages more towards a classical cytotoxic phenotype would result in enhanced RT response and delayed tumor re-growth. Thus, we treated tumor-bearing mice with anti-IL-4 neutralizing mABs in combination with RT, and evaluated tumor re-growth, as compared to tumor-bearing mice treated with either RT or anti-IL4 mAB alone, and found that indeed, reprogramming tumor-infiltrating macrophages to favor classical (M1)-type activity significantly enhanced RT response and delayed tumor re-growth. Together these studies indicate that: 1) RT induces macrophage infiltration into mammary tumors, 2) protumor-type macrophages infiltrating mammary carcinomas blunt response to RT, and 3) reprogramming of tumor-infiltrating macrophages to favor a cytotoxic phenotype improves efficacy of RT.

This work was supported by grants from the NIH/NCI, and Era of Hope (W81XWH-06-1-0416), and Program in Mesothelioma (PR080717) grants from the Department of Defense to LMC.

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 2840. doi:10.1158/1538-7445.AM2011-2840

Topographic enhancement mapping of the cancer-associated breast stroma using breast MRI

In animal and laboratory models, cancer-associated stroma, or elements of the supporting tissue surrounding a primary tumor, has been shown to be necessary for tumor evolution and progression. However, little is understood or studied regarding the properties of intact stroma in human cancer in vivo. In addition, for breast cancer patients, the optimal volume of local tissue to treat surrounding a primary tumor is not clear. Here, we performed an interdisciplinary study of normal-appearing breast tissue using breast magnetic resonance imaging (MRI), correlative histology and array comparative genomic hybridization to identify a cancer-associated stroma in humans. Using a novel technique for segmenting breast fibroglandular tissue, quantifiable topographic percent enhancement mapping of the stroma surrounding invasive breast cancer was found to be significantly elevated within 2 cm of the tumor edge. This region was also found to harbor increased microvessel density, and genomic changes that were closely associated with host normal breast tissue. These findings indicate that a cancer-associated stroma may be identified and characterized in human breast cancer using non-invasive imaging techniques. Identification of a cancer-associated stroma may be further developed to help guide local therapy to reduce recurrence and morbidity in breast cancer patients.

Breast cancer cells in three-dimensional culture display an enhanced radioresponse after coordinate targeting of integrin alpha5beta1 and fibronectin

Tactics to selectively enhance cancer radioresponse are of great interest. Cancer cells actively elaborate and remodel their extracellular matrix (ECM) to aid in survival and progression. Previous work has shown that beta1-integrin inhibitory antibodies can enhance the growth-inhibitory and apoptotic responses of human breast cancer cell lines to ionizing radiation, either when cells are cultured in three-dimensional laminin-rich ECM (3D lrECM) or grown as xenografts in mice. Here, we show that a specific alpha heterodimer of beta1-integrin preferentially mediates a prosurvival signal in human breast cancer cells that can be specifically targeted for therapy. 3D lrECM culture conditions were used to compare alpha-integrin heterodimer expression in malignant and nonmalignant cell lines. Under these conditions, we found that expression of alpha5beta1-integrin was upregulated in malignant cells compared with nonmalignant breast cells. Similarly, we found that normal and oncofetal splice variants of fibronectin, the primary ECM ligand of alpha5beta1-integrin, were also strikingly upregulated in malignant cell lines compared with nonmalignant acini. Cell treatment with a peptide that disrupts the interactions of alpha5beta1-integrin with fibronectin promoted apoptosis in malignant cells and further heightened the apoptotic effects of radiation. In support of these results, an analysis of gene expression array data from breast cancer patients revealed an association of high levels of alpha5-integrin expression with decreased survival. Our findings offer preclinical validation of fibronectin and alpha5beta1-integrin as targets for breast cancer therapy.

American Society for Therapeutic Radiology and Oncology (ASTRO) Emerging Technology Committee report on electronic brachytherapy

The development of novel technologies for the safe and effective delivery of radiation is critical to advancing the field of radiation oncology. The Emerging Technology Committee of the American Society for Therapeutic Radiology and Oncology appointed a Task Group within its Evaluation Subcommittee to evaluate new electronic brachytherapy methods that are being developed for, or are already in, clinical use. The Task Group evaluated two devices, the Axxent Electronic Brachytherapy System by Xoft, Inc. (Fremont, CA), and the Intrabeam Photon Radiosurgery Device by Carl Zeiss Surgical (Oberkochen, Germany). These devices are designed to deliver electronically generated radiation, and because of their relatively low energy output, they do not fall under existing regulatory scrutiny of radioactive sources that are used for conventional radioisotope brachytherapy. This report provides a descriptive overview of the technologies, current and future projected applications, comparison of competing technologies, potential impact, and potential safety issues. The full Emerging Technology Committee report is available on the American Society for Therapeutic Radiology and Oncology Web site.

beta1 integrin targeting to enhance radiation therapy

PURPOSE

Cell adhesion to extracellular matrix (ECM) proteins is mediated by the integrin family and has been known to modify radiation sensitivity and resistance in several cell types, including cancer cells. In particular, beta1 integrin signaling has been implicated in the progression and metastasis of various cancers and has been shown to facilitate resistance to radiation therapy.

CONCLUSION

In this mini-review, we provide a brief overview of integrin targeting in radiation therapy. We specifically focus on the updated findings of beta1 integrin-mediated signaling pathways after exposure to ionising radiation (IR) using in vitro and in vivo experimental models, which could represent promising therapeutic targets for breast cancer.

HER2 signaling pathway activation and response of breast cancer cells to HER2-targeting agents is dependent strongly on the 3D microenvironment

Development of effective and durable breast cancer treatment strategies requires a mechanistic understanding of the influence of the microenvironment on response. Previous work has shown that cellular signaling pathways and cell morphology are dramatically influenced by three-dimensional (3D) cultures as opposed to traditional two-dimensional (2D) monolayers. Here, we compared 2D and 3D culture models to determine the impact of 3D architecture and extracellular matrix (ECM) on HER2 signaling and on the response of HER2-amplified breast cancer cell lines to the HER2-targeting agents Trastuzumab, Pertuzumab and Lapatinib. We show that the response of the HER2-amplified AU565, SKBR3 and HCC1569 cells to these anti-HER2 agents was highly dependent on whether the cells were cultured in 2D monolayer or 3D laminin-rich ECM gels. Inhibition of beta1 integrin, a major cell-ECM receptor subunit, significantly increased the sensitivity of the HER2-amplified breast cancer cell lines to the humanized monoclonal antibodies Trastuzumab and Pertuzumab when grown in a 3D environment. Finally, in the absence of inhibitors, 3D cultures had substantial impact on HER2 downstream signaling and induced a switch between PI3K-AKT- and RAS-MAPK-pathway activation in all cell lines studied, including cells lacking HER2 amplification and overexpression. Our data provide direct evidence that breast cancer cells are able to rapidly adapt to different environments and signaling cues by activating alternative pathways that regulate proliferation and cell survival, events that may play a significant role in the acquisition of resistance to targeted therapies.

a5b1 integrin mediates survival of breast cancer cells in 3-dimensional culture that can be specifically targeted for therapy

Abstract #4126

Background: β1 integrin signaling has been implicated in breast cancer progression and has been shown to facilitate resistance to radiation that could be abrogated using β1 integrin inhibitory antibody, AIIB2. In the present study, we investigated whether a specific alpha heterodimer of β1 integrin was preferentially mediating a pro-survival signal in human breast cancer cells, and if it could specifically be targeted for therapy.&#x2028; Materials and Methods: We used three-dimensional (3D) laminin-rich extracellular matrix (lrECM) culture to compare the relative levels of alpha heterodimer expression in malignant HMT3522-T4-2 and nonmalignant cell line HMT3522-S-1. Total cell lysates were probed by western blot to detect several possible alpha integrins. In addition, to investigate whether α5β1 mediated an important pro-survival signal, we treated 3D lrECM cultures with a small peptide inhibitor of α5β1 integrin and fibronectin interaction, Ac-PHSCN-NH2 (ATN-161) and measured apoptotic response using TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated nick end labeling) assay.&#x2028; Results: We found that expression of α5β1 was upregulated in HMT3522-T4-2 malignant breast cell line compared to nonmalignant cell line HMT3522-S-1. Inhibition using ATN-161 resulted in a significant dose-dependent increase in TUNEL positive cells.&#x2028; Discussion: We have previously shown that inhibitory antibody to β1 integrin, AIIB2, leads to selective apoptosis and decreased proliferation in human breast cancer cells in 3DlrECM culture and in vivo. In addition, combining β1 integrin inhibition with IR allowed for reduction of IR dose necessary to achieve growth inhibition in vivo. Here, we show that in HMT3522-T4-2 breast cancer cell line, inhibition of α5 integrin and fibronectin interaction using ATN-161 significantly enhanced apoptosis in 3D lrECM. These data indicate that fibronectin and its receptor, α5β1 are important for survival signaling in breast cancer and may be an important target to enhance radiotherapy efficacy.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4126.

Beta1 integrin inhibition dramatically enhances radiotherapy efficacy in human breast cancer xenografts

Beta(1) integrin signaling has been shown to mediate cellular resistance to apoptosis after exposure to ionizing radiation (IR). Other signaling molecules that increase resistance include Akt, which promotes cell survival downstream of beta(1) integrin signaling. We previously showed that beta(1) integrin inhibitory antibodies (e.g., AIIB2) enhance apoptosis and decrease growth in human breast cancer cells in three-dimensional laminin-rich extracellular matrix (lrECM) cultures and in vivo. Here, we asked whether AIIB2 could synergize with IR to modify Akt-mediated IR resistance. We used three-dimensional lrECM cultures to test the optimal combination of AIIB2 with IR treatment of two breast cancer cell lines, MCF-7 and HMT3522-T4-2, as well as T4-2 myr-Akt breast cancer colonies or HMT3522-S-1, which form normal organotypic structures in three-dimensional lrECM. Colonies were assayed for apoptosis and beta(1) integrin/Akt signaling pathways were evaluated using Western blot. In addition, mice bearing MCF-7 xenografts were used to validate the findings in three-dimensional lrECM. We report that AIIB2 increased apoptosis optimally post-IR by down-regulating Akt in breast cancer colonies in three-dimensional lrECM. In vivo, addition of AIIB2 after IR significantly enhanced tumor growth inhibition and apoptosis compared with either treatment alone. Remarkably, the degree of tumor growth inhibition using AIIB2 plus 2 Gy radiation was similar to that of 8 Gy alone. We previously showed that AIIB2 had no discernible toxicity in mice; here, its addition allowed for a significant reduction in the IR dose that was necessary to achieve comparable growth inhibition and apoptosis in breast cancer xenografts in vivo.

High mammographic breast density is independent predictor of local but not distant recurrence after lumpectomy and radiotherapy for invasive breast cancer

PURPOSE

Biologically meaningful predictors for locoregional recurrence (LRR) in patients undergoing breast-conserving surgery (BCS) and radiotherapy (RT) are lacking. Tissue components, including extracellular matrix, could confer resistance to ionizing radiation. Fibroglandular and extracellular matrix components of breast tissue relative to adipose tissue can be quantified by the mammographic breast density (MBD), the proportion of dense area relative to the total breast area on mammography. We hypothesized that the MBD might be a predictor of LRR after BCS and RT for invasive breast cancer.

METHODS AND MATERIALS

We conducted a nested case-control study of 136 women with invasive breast cancer who had undergone BCS and RT and had had the MBD ascertained before, or at, diagnosis. Women with known recurrence were matched to women without recurrence by year of diagnosis. The median follow-up was 7.7 years. The percentage of MBD was measured using a computer-based threshold method.

RESULTS

Patients with a high MBD (>/=75% density) vs. low (</=25%) were at increased risk of LRR (hazard ratio, 4.30; 95% confidence interval, 0.88-021.0; p = 0.071) but not distant recurrence. In addition, we found a complete inverse correlation between high MBD and obesity (body mass index, >/=30 kg/m(2)). In a multivariate Cox proportional hazards model, patients with MBD in the greatest quartile were at significantly greater risk of LRR (hazard ratio, 6.6; 95% confidence interval, 1.6-27.7; p = 0.01). Obesity without a high MBD also independently predicted for LRR (hazard ratio, 19.3; 95% confidence interval, 4.5-81.7; p < 0.001).

CONCLUSION

The results of our study have shown that a high MBD and obesity are significant independent predictors of LRR after BCS and RT for invasive breast cancer. Additional studies are warranted to validate these findings.

Beta1 integrin inhibitory antibody induces apoptosis of breast cancer cells, inhibits growth, and distinguishes malignant from normal phenotype in three dimensional cultures and in vivo

Current therapeutic approaches to cancer are designed to target molecules that contribute to malignant behavior but leave normal tissues intact. beta(1) integrin is a candidate target well known for mediating cell-extracellular matrix (ECM) interactions that influence diverse cellular functions; its aberrant expression has been implicated in breast cancer progression and resistance to cytotoxic therapy. The addition of beta(1) integrin inhibitory agents to breast cancer cells at a single-cell stage in a laminin-rich ECM (three-dimensional lrECM) culture was shown to down-modulate beta(1) integrin signaling, resulting in malignant reversion. To investigate beta(1) integrin as a therapeutic target, we modified the three-dimensional lrECM protocol to approximate the clinical situation: before treatment, we allowed nonmalignant cells to form organized acinar structures and malignant cells to form tumor-like colonies. We then tested the ability of beta(1) integrin inhibitory antibody, AIIB2, to inhibit tumor cell growth in several breast cancer cell lines (T4-2, MDA-MB-231, BT474, SKBR3, and MCF-7) and one nonmalignant cell line (S-1). We show that beta(1) integrin inhibition resulted in a significant loss of cancer cells, associated with a decrease in proliferation and increase in apoptosis, and a global change in the composition of residual colonies. In contrast, nonmalignant cells that formed tissue-like structures remained resistant. Moreover, these cancer cell-specific antiproliferative and proapoptotic effects were confirmed in vivo with no discernible toxicity to animals. Our findings indicate that beta(1) integrin is a promising therapeutic target, and that the three-dimensional lrECM culture assay can be used to effectively distinguish malignant and normal tissue response to therapy.

Ionizing radiation induces heritable disruption of epithelial cell interactions

Ionizing radiation (IR) is a known human breast carcinogen. Although the mutagenic capacity of IR is widely acknowledged as the basis for its action as a carcinogen, we and others have shown that IR can also induce growth factors and extracellular matrix remodeling. As a consequence, we have proposed that an additional factor contributing to IR carcinogenesis is the potential disruption of critical constraints that are imposed by normal cell interactions. To test this hypothesis, we asked whether IR affected the ability of nonmalignant human mammary epithelial cells (HMEC) to undergo tissue-specific morphogenesis in culture by using confocal microscopy and imaging bioinformatics. We found that irradiated single HMEC gave rise to colonies exhibiting decreased localization of E-cadherin, beta-catenin, and connexin-43, proteins necessary for the establishment of polarity and communication. Severely compromised acinar organization was manifested by the majority of irradiated HMEC progeny as quantified by image analysis. Disrupted cell-cell communication, aberrant cell-extracellular matrix interactions, and loss of tissue-specific architecture observed in the daughters of irradiated HMEC are characteristic of neoplastic progression. These data point to a heritable, nonmutational mechanism whereby IR compromises cell polarity and multicellular organization.

A novel role for interleukin-18 in adhesion molecule induction through NF kappa B and phosphatidylinositol (PI) 3-kinase-dependent signal transduction pathways

Interleukin-18 (IL-18) is a novel proinflammatory cytokine found in serum and joints of patients with rheumatoid arthritis (RA). We studied a novel role for IL-18 in mediating cell adhesion, a vital component of the inflammation found in RA and other inflammatory diseases. We examined the expression of cellular cell adhesion molecules E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) on endothelial cells and RA synovial fibroblasts using flow cytometry. Adhesion of the monocyte-like cell line HL-60 to endothelial cells was determined by immunofluorescence. IL-18 significantly enhanced ICAM-1 and VCAM-1 expression on endothelial cells and RA synovial fibroblasts. In addition, IL-18 induced E-selectin expression on endothelial cells and promoted the adhesion of HL-60 cells to IL-18-stimulated endothelial cells. Neutralizing anti-VCAM-1 and anti-E-selectin could completely inhibit HL-60 adherence to endothelial cells. IL-18-induced adhesion molecule expression appears to be mediated through nuclear factor kappa B (NF kappa B) and phosphatidyl-inositol 3 kinase (PI 3-kinase) since addition of inhibitors to either NF kappa B (pyrrolidine dithiocarbamate and N-acetyl-l-cysteine) or PI 3-kinase (LY294002) inhibited RA synovial fibroblast VCAM-1 expression by 50 to 60%. Addition of both inhibitors resulted in inhibition of VCAM-1 expression by 85%. In conclusion, the ability of IL-18 to induce adhesion molecule expression on endothelial cells and RA synovial fibroblasts indicates that IL-18 may contribute to RA joint inflammation by enhancing the recruitment of leukocytes into the joint. IL-18 requires NF kappa B as well as PI 3-kinase to induce VCAM-1 on RA synovial fibroblasts, suggesting that there may be two distinct pathways in IL-18-induced adhesion molecule expression.

Interleukin-18 induces rheumatoid arthritis synovial fibroblast CXC chemokine production through NFkappaB activation

Interleukin-18 (IL-18) is a novel proinflammatory cytokine that was recently found in synovial fluids and in synovial tissues from patients with rheumatoid arthritis (RA). To determine the participation of IL-18 in the inflammation observed in RA, we investigated the effect of IL-18 on RA synovial fibroblast chemokine production. Using FACS analysis, we showed that IL-18 induced a doubling in the production of intracellular IL-8 by RA synovial fibroblasts, and this result was confirmed by Western blot. At the extracellular level, IL-18 up-regulated the secretion of IL-8 in a dose- and time-dependent manner. IL-18 also up-regulated the other CXC chemokines, epithelial-neutrophil activating protein (ENA-78) and growth-regulated oncogene (groalpha), in a dose dependent manner, but failed to induce the production of the CC chemokine, macrophage inflammatory protein (MIP)-1alpha. By immunofluorescence and Western blot, we demonstrated that IL-18 activates the translocation of the transcription factor nuclear factor kappa B (NFkappaB) into the nucleus of RA synovial fibroblasts. IL-18 induces IL-8 secretion through NFkappaB because RA synovial fibroblasts pretreated with antisense to NFkappaB p65 oligonucleotide produce a mean of 44% less IL-8 compared with cells pretreated with the control sense oligonucleotide. These results indicate a novel role for IL-18 in inducing RA synovial fibroblast expression of CXC chemokines through NFkappaB and place this cytokine in a strategic role in the local inflammation observed in RA.

Evidence of IL-18 as a novel angiogenic mediator

Angiogenesis, or new blood vessel growth, is a key process in the development of synovial inflammation in rheumatoid arthritis (RA). Integral to this pathologic proliferation are proinflammatory cytokines. We hypothesized a role for IL-18 as an angiogenic mediator in RA. We examined the effect of human IL-18 on human microvascular endothelial cell (HMVEC) migration. IL-18 induced HMVEC migration at 1 nM (p < 0.05). RA synovial fluids potently induced endothelial cell migration, but IL-18 immunodepletion resulted in a 68 +/- 5% decrease in HMVEC migration (p < 0.05). IL-18 appears to act on HMVECs via alpha(v)beta(3) integrin. To test whether IL-18 induced endothelial cell tube formation in vitro, we quantitated the degree of tube formation on Matrigel matrix. IL-18, 1 or 10 nM, resulted in a 77% or 87% increase in tube formation compared with control (p < 0.05). To determine whether IL-18 may be angiogenic in vivo, we implanted IL-18 in Matrigel plugs in mice, and IL-18 at 1 and 10 nM induced angiogenesis (p < 0.05). The angiogenesis observed appears to be independent of the contribution of local TNF-alpha, as evidenced by adding neutralizing anti-TNF-alpha Ab to the Matrigel plugs. In an alternative in vivo model, sponges embedded with IL-18 or control were implanted into mice. IL-18 (10 nM) induced a 4-fold increase in angiogenesis vs the control (p < 0.05). These findings support a novel function for IL-18 as an angiogenic factor in RA and may elucidate a potential therapeutic target for angiogenesis-directed diseases.

Fractalkine, a novel chemokine in rheumatoid arthritis and in rat adjuvant-induced arthritis

OBJECTIVE

To examine the expression of the novel CX3C chemokine fractalkine (Fkn) and its receptor (CX3CR1) in rheumatoid arthritis (RA) and rat adjuvant-induced arthritis (AIA), a model of RA.

METHODS

Immunohistochemistry, flow cytometry, enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RT-PCR), and chemotaxis assays were used.

RESULTS

In rat AIA, synovial tissue (ST) macrophages, fibroblasts, endothelial cells, and dendritic cells were Fkn immunopositive, whereas lymphocytes did not significantly express Fkn. Significant staining for CX3CR1 was found in ST macrophages, fibroblasts, and dendritic cells, whereas only a small percentage of endothelial cells stained for CX3CR1 in rat AIA. We immunolocalized Fkn to RA ST macrophages, fibroblasts, endothelial cells, and dendritic cells. We also found intense ST macrophage and dendritic cell staining for CX3CR1 in RA ST. Flow cytometry analysis of RA synovial fluid (SF) and peripheral blood revealed a greater percentage of monocytes expressing Fkn and CX3CR1 compared with T cells. By ELISA, we found significantly elevated soluble Fkn (sFkn) levels in RA SF compared with SF from patients with osteoarthritis or other forms of arthritis. By RT-PCR, we found enhanced expression of Fkn and CX3CR1 mRNA on day 18 in rat AIA, a time of pronounced inflammation in the rat joint. Soluble Fkn-depleted RA SF showed significantly decreased chemotactic activity for monocytes compared with sham-depleted RA SF.

CONCLUSION

These results indicate that Fkn and its receptor are both expressed in RA and in rat AIA, and that sFkn is up-regulated in RA SF. Furthermore, our data suggest a new role for Fkn in monocyte chemotaxis in the inflamed RA joint.

Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis

OBJECTIVE

Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects.

METHODS

We compared chemokine receptor expression on CD14+ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68+ macrophages.

RESULTS

Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68+ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)- and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1alpha (MIP-1alpha) was principally restricted to vascular endothelium, and MIP-1beta+ macrophages were found throughout the sections.

CONCLUSION

Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.

Systemic metastasis in glioblastoma may represent the emergence of neoplastic subclones

Glioblastomas only rarely metastasize to sites outside the central nervous system, for reasons that are poorly understood. We report the clinicopathological and molecular genetic findings in 6 patients with metastatic glioblastoma. Four patients were under the age of 32 and all but 1 patient died within 2 yr of diagnosis. The number of metastases ranged from 1 to 3. At the time of death, 3 patients had apparent tumor control at their primary site. We evaluated DNA from both primary and metastatic glioblastomas for genetic alterations commonly found in glioblastomas: TP53 mutations, CDKN2A/p16 deletions, EGFR amplification, and allelic loss of chromosomes 1p, 10q and 19q. Four of 6 cases had TP53 mutations and only single cases had EGFR amplification, CDKN2A/p16 deletions, or allelic loss of 1p, 10q and 19q; 2 cases had no detectable genetic alterations. In 2 cases, the primary and metastatic tumors had identical genotypes. Remarkably, however, 2 cases had different TP53 alterations in the primary and metastatic lesions, or among the metastatic tumors, which suggests that some metastatic deposits may represent emergence of subclones that were not necessarily dominant in the primary tumor. The present observations and a review of the recent literature demonstrate that metastatic glioblastomas tend to occur in younger adults who do not follow long clinical courses, and may be characterized by TP53 mutations and differential clonal selection.

The influence of the microenvironment on the malignant phenotype

Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. As tissue becomes cancerous, there are reciprocal interactions between neoplastic cells, adjacent normal cells such as stroma and endothelium, and their microenvironments. The current dominant paradigm wherein multiple genetic lesions provide both the impetus for, and the Achilles heel of, cancer might be inadequate to understand cancer as a disease process. In the following brief review, we will use selected examples to illustrate the influence of the microenvironment in the evolution of the malignant phenotype. We will also discuss recent studies that suggest novel therapeutic interventions might be derived from focusing on microenvironment and tumor cells interactions.

Flavonoid chemistry of Fallopia section Fallopia (Polygonaceae)

Five controversial species of Fallopia sect. Fallopia sensu Holub were examined for leaf flavonoid constituents. Twenty-one flavonoid compounds were isolated and identified; they were glycosylated derivatives of the flavonols kaempferol, quercetin, and myricetin, and of the flavones apigenin and luteolin. Among them, quercetin 3-O-galactoside and quercetin 3-O-glucoside were major flavonoid constituents and present in all species. Although the flavonoid data for some species are lacking, those available appear to be useful for species delimitation and for recognizing species relationships in the section. The flavonoid data, in conjunction with morphological evidence, strongly suggest that F. scandens, F. dentatoalata, F. dumetorum, and F. convolvulus are closely allied but distinct species. In addition, the flavonoid data for F. cilinodis lend additional support to the segregation of sect. Parogonum from sect. Fallopia.