Papers by Rebecca Riggins
Receptors & clinical investigation
Estrogen-related receptors (ERRs) are orphan members of the nuclear receptor superfamily that are... more Estrogen-related receptors (ERRs) are orphan members of the nuclear receptor superfamily that are important regulators of mitochondrial metabolism with emerging roles in cancer. In the absence of an endogenous ligand, ERRs are reliant upon other regulatory mechanisms that include protein/protein interactions and post-translational modification, though the cellular and clinical significance of this latter mechanism is unclear. We recently published a study in which we establish estrogen-related receptor gamma (ERRγ) as a target for extracellular signal-regulated kinase (ERK), and show that regulation of ERRγ by ERK has important consequences for the function of this receptor in cellular models of estrogen receptor-positive (ER+) breast cancer. In this Research Highlight, we discuss the implications of these findings from a molecular and clinical perspective.
Plos One, 2010
BCL2 family members affect cell fate decisions in breast cancer but the role of BCL-W (BCL2L2) is... more BCL2 family members affect cell fate decisions in breast cancer but the role of BCL-W (BCL2L2) is unknown. We now show the integrated roles of the antiapoptotic BCL-W and BCL2 in affecting responsiveness to the antiestrogen ICI 182,780 (ICI; Fulvestrant Faslodex), using both molecular (siRNA; shRNA) and pharmacologic (YC137) approaches in three breast cancer variants; MCF-7/LCC1 (ICI sensitive), MCF-7/LCC9 (ICI resistant), and LY2 (ICI resistant). YC137 inhibits BCL-W and BCL2 and restores ICI sensitivity in resistant cells. Co-inhibition of BCL-W and BCL2 is both necessary and sufficient to restore sensitivity to ICI, and explains mechanistically the action of YC137. These data implicate functional cooperation and/or redundancy in signaling between BCL-W and BCL2, and suggest that broad BCL2 family member inhibitors will have greater therapeutic value than targeting only individual proteins. Whereas ICI sensitive MCF-7/LCC1 cells undergo increased apoptosis in response to ICI following BCL-W6BCL2 co-inhibition, the consequent resensitization of resistant MCF-7/LCC9 and LY2 cells reflects increases in autophagy (LC3 cleavage; p62/SQSTM1 expression) and necrosis but not apoptosis or cell cycle arrest. Thus, de novo sensitive cells and resensitized resistant cells die through different mechanisms. Following BCL-W+BCL2 co-inhibition, suppression of functional autophagy by 3-methyladenine or BECN1 shRNA reduces ICI-induced necrosis but restores the ability of resistant cells to die through apoptosis. These data demonstrate the plasticity of cell fate mechanisms in breast cancer cells in the context of antiestrogen responsiveness. Restoration of ICI sensitivity in resistant cells appears to occur through an increase in autophagy-associated necrosis. BCL-W, BCL2, and BECN1 integrate important functions in determining antiestrogen responsiveness, and the presence of functional autophagy may influence the balance between apoptosis and necrosis.
Molecular Cancer Therapeutics, 2005
The molecular mechanisms underlying the acquisition of resistance to the antiestrogen Faslodex ar... more The molecular mechanisms underlying the acquisition of resistance to the antiestrogen Faslodex are poorly understood, although enhanced expression and activity of nuclear factor KB (NFKB) have been implicated as a critical element of this phenotype. The purpose of this study was to elucidate the mechanism by which NFKB up-regulation contributes to Faslodex resistance and to determine whether pharmacologic inhibition of NFKB by the small molecule parthenolide could restore Faslodexmediated suppression of cell growth. Basal expression of multiple NFKB-related molecules in MCF7-derived LCC1 (antiestrogen-sensitive) and LCC9 (antiestrogen-resistant) breast cancer cells was determined, and cells were treated with Faslodex or parthenolide. The effect of these drugs either singly or in combination was assessed by cell proliferation, estrogen receptor (ER) -dependent transcriptional activation, cell cycle analysis, and apoptosis assays. Expression of the p65 NFKB subunit and the upstream NFKB regulator IKB kinase ;/NFKB essential modulator were increased in the resistant MCF7/ LCC9 cells (P = 0.001 and 0.04, respectively). Whereas MCF7/LCC9 cells were unresponsive to Faslodex alone, parthenolide effectively inhibited MCF7/LCC9 cell proliferation and the combination of Faslodex and parthenolide resulted in a 4-fold synergistic reduction in cell growth (P = 0.03). This corresponded to a restoration of Faslodex-induced apoptosis (P = 0.001), with no observable changes in ER-dependent transcription or cell cycle phase distribution. Because parthenolide has shown safety in Phase I clinical trials, these findings have direct clinical relevance and provide support for the design of clinical studies combining antiestrogens and parthenolide in ER-positive breast cancer. [Mol Cancer Ther 2005; 4(1): 33 -41]
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
Bioinformatics, Apr 1, 2010
The identification of gene regulatory modules is an important yet challenging problem in computat... more The identification of gene regulatory modules is an important yet challenging problem in computational biology. While many computational methods have been proposed to identify regulatory modules, their initial success is largely compromised by a high rate of false positives, especially when applied to human cancer studies. New strategies are needed for reliable regulatory module identification. Results: We present a new approach, namely multilevel support vector regression (ml-SVR), to systematically identify conditionspecific regulatory modules. The approach is built upon a multilevel analysis strategy designed for suppressing false positive predictions. With this strategy, a regulatory module becomes ever more significant as more relevant gene sets are formed at finer levels. At each level, a two-stage support vector regression (SVR) method is utilized to help reduce false positive predictions by integrating binding motif information and gene expression data; a significant analysis procedure is followed to assess the significance of each regulatory module. To evaluate the effectiveness of the proposed strategy, we first compared the ml-SVR approach with other existing methods on simulation data and yeast cell cycle data. The resulting performance shows that the ml-SVR approach outperforms other methods in the identification of both regulators and their target genes. We then applied our method to breast cancer cell line data to identify condition-specific regulatory modules associated with estrogen treatment. Experimental results show that our method can identify biologically meaningful regulatory modules related to estrogen signaling and action in breast cancer. Availability and implementation: The ml-SVR MATLAB package can be downloaded at
The Faseb Journal, Apr 1, 2007
The Journal of Biological Chemistry, Jul 25, 2003
The adapter molecule p130 Cas (Cas) plays a role in cellular processes such as proliferation, sur... more The adapter molecule p130 Cas (Cas) plays a role in cellular processes such as proliferation, survival, cell adhesion, and migration. The ability of Cas to promote migration has been shown to be dependent upon its carboxyl terminus, which contains a bipartite binding site for the protein tyrosine kinase c-Src (Src). The association between Src and Cas enhances Src kinase activity, and like Cas, Src plays an important role in cell proliferation and migration. In this study, we show that Src and Cas function cooperatively to promote cell migration in a manner that depends upon kinase-active Src. Another carboxyl-terminal binding partner of Cas, AND-34/BCAR3 (AND-34), functions synergistically with Cas to enhance Src activation and cell migration. The carboxyl-terminal guanine nucleotide exchange factor domain of AND-34, as well as the activity of its putative target Rap1, contribute to these events. A mechanism through which AND-34 may regulate Cas-dependent cell migration is suggested by the finding that Cas becomes redistributed from focal adhesions to lamellipodia located at the leading edge of AND-34 overexpressing cells. These data thus provide insight into how Cas and AND-34 may function together to stimulate Src signaling pathways and promote cell migration.
Molecular Cancer Research Mcr, Apr 1, 2003
Cellular changes associated with oncogenic transformation are generally caused by deregulation of... more Cellular changes associated with oncogenic transformation are generally caused by deregulation of signal transduction pathways. We show that, in cells transformed by the v-crk oncogene, the adapter protein Cas forms a stable complex with the p85 regulatory subunit of phosphatidylinositol 3V-kinase (PI3K) coincident with the appearance of Cas-associated PI3K activity. The interaction between Cas and p85 PI3K appears to be driven primarily by Src-dependent tyrosine phosphorylation of Cas, and mapping studies indicate that the carboxyl terminus of Cas is necessary and sufficient for binding to p85 PI3K. One of the cellular effects of v-Crk expression is to promote DNA synthesis in the presence of low serum. This effect is potentiated in Cas-null fibroblasts when wild-type Cas is expressed, but not when a Cas variant is expressed that lacks the carboxylterminal p85 PI3K binding region. This suggests that the association of Cas with p85 PI3K may play a role in uncoupling growth regulatory pathways through v-Crk.
Molecular Cancer Therapeutics, Nov 1, 2007
Breast Cancer Research and Treatment, May 1, 2010
The interferon regulatory factor-1 (IRF1) gene, localized on chromosome 5q31.1, is mutated or rea... more The interferon regulatory factor-1 (IRF1) gene, localized on chromosome 5q31.1, is mutated or rearranged in several cancers including some hematopoietic and gastric cancers. However, whether loss of IRF1 occurs in sporadic breast cancer is unknown. Loss of 5q12-31 is reported in 11% of sporadic breast cancers, and high-resolution array-CGH studies have shown loss at 5q31.1 in 50% of breast cancers with a mutated BRCA1 gene. Functionally, overexpression of IRF1 reduces, and a dominant negative IRF1 construct increases, tumorigenesis of human breast cancer xenografts. Taken together, these observations indicate that the IRF1 gene may play a potentially important role as a breast cancer tumor suppressor gene. In this study, we investigated allelic loss of the IRF1 gene in breast tumor specimens from 52 women with invasive breast cancer using an IRF1 intragenic dinucleotide polymorphic marker. Thirty-seven cases were informative. LOH at the IRF1 locus was detected in 32% of these informative cases (12/ 37). There was a significant association between IRF1 loss and both older age (P = 0.0167) and earlier stage (Stages 1 and 2) (P = 0.0165). To assess the association of IRF1 mRNA expression with clinical outcomes in breast cancer, we studied data from two published gene expression microarray datasets. In breast cancer patients, low IRF1 mRNA expression is strongly correlated with both risk of recurrence (OR = 3.00; P = 0.003; n = 273 cases) and risk of death (OR = 4.18; P = 0.004; n = 191 cases). Our findings strongly imply a tumor suppressor role for the IRF1 gene in breast cancer.
Mol Cancer Ther, 2010
Antiestrogens are effective therapies for the management of many estrogen receptor-α (ER)-positiv... more Antiestrogens are effective therapies for the management of many estrogen receptor-α (ER)-positive breast cancers. Nonetheless, both de novo and acquired resistance occur and remain major problems in the clinical setting. IFNγ is an inflammatory cytokine that induces the expression and function of IFN regulatory factor 1 (IRF1), a tumor suppressor gene that can increase antiestrogen responsiveness. We show that IFNγ, but not IFNα, IFNβ, or fulvestrant (ICI; ICI 182,780; Faslodex), induces IRF1 expression in antiestrogen-resistant MCF7/LCC9 and LY2 cells. Moreover, IFNγ restores the responsiveness of these cells to fulvestrant. Increased IRF1 activation suppresses NF-κB p65 (RELA) activity, inhibits the expression of prosurvival (BCL2, BCL-W), and induces the expression of proapoptotic members (BAK, mitochondrial BAX) of the BCL2 family. This molecular signaling is associated with the activation of signal transducer and activator of transcription 1 and leads to increased mitochondrial membrane permeability; activation of caspase-7 (CASP7), CASP8, and CASP9; and induction of apoptosis but not autophagy. Whereas antiestrogen-resistant cells are capable of inducing autophagy through IFN-mediated signaling, their ability to do so through antiestrogen-regulated signaling is lost. The abilities of IFNγ to activate CASP8, induce apoptosis, and restore antiestrogen sensitivity are prevented by siRNA targeting IRF1, whereas transient overexpression of IRF1 mimics the effects of IFNγ treatment. These observations support the exploration of clinical trials combining antiestrogens and compounds that can induce IRF1, such as IFNγ, for the treatment of some ER-positive breast cancers. Mol Cancer Ther; 9(5); 1274-85.
Lecture Notes in Computer Science, 2008
Page 1. I. Măndoiu, R. Sunderraman, and A. Zelikovsky (Eds.): ISBRA 2008, LNBI 4983, pp. 244255,... more Page 1. I. Măndoiu, R. Sunderraman, and A. Zelikovsky (Eds.): ISBRA 2008, LNBI 4983, pp. 244255, 2008. © Springer-Verlag Berlin Heidelberg 2008 Sparse Decomposition of Gene Expression Data to Infer Transcriptional Modules Guided by Motif Information ...
Thesis (Ph. D.)--University of Virginia, 2003. Includes bibliographical references (leaves 211-254).
Molecular Cancer Therapeutics
The molecular mechanisms underlying the acquisition of resistance to the antiestrogen Faslodex ar... more The molecular mechanisms underlying the acquisition of resistance to the antiestrogen Faslodex are poorly understood, although enhanced expression and activity of nuclear factor kappaB (NFkappaB) have been implicated as a critical element of this phenotype. The purpose of this study was to elucidate the mechanism by which NFkappaB up-regulation contributes to Faslodex resistance and to determine whether pharmacologic inhibition of NFkappaB by the small molecule parthenolide could restore Faslodex-mediated suppression of cell growth. Basal expression of multiple NFkappaB-related molecules in MCF7-derived LCC1 (antiestrogen-sensitive) and LCC9 (antiestrogen-resistant) breast cancer cells was determined, and cells were treated with Faslodex or parthenolide. The effect of these drugs either singly or in combination was assessed by cell proliferation, estrogen receptor (ER)-dependent transcriptional activation, cell cycle analysis, and apoptosis assays. Expression of the p65 NFkappaB sub...
Cancer Research, 2013
3570: Phosphodependent regulation of ERRγ expression, transcriptional activity, and Tamoxifen res... more 3570: Phosphodependent regulation of ERRγ expression, transcriptional activity, and Tamoxifen resistance in ER+ breast cancer.
Journal of Experimental & Clinical Cancer Research, 2015
Background: One-third of estrogen (ER+) and/or progesterone receptor-positive (PGR+) breast tumor... more Background: One-third of estrogen (ER+) and/or progesterone receptor-positive (PGR+) breast tumors treated with Tamoxifen (TAM) do not respond to initial treatment, and the remaining 70% are at risk to relapse in the future. Estrogen-related receptor gamma (ESRRG, ERRγ) is an orphan nuclear receptor with broad, structural similarities to classical ER that is widely implicated in the transcriptional regulation of energy homeostasis. We have previously demonstrated that ERRγ induces resistance to TAM in ER+ breast cancer models, and that the receptor's transcriptional activity is modified by activation of the ERK/MAPK pathway. We hypothesize that hyper-activation or over-expression of ERRγ induces a pro-survival transcriptional program that impairs the ability of TAM to inhibit the growth of ER+ breast cancer. The goal of the present study is to determine whether ERRγ target genes are associated with reduced distant metastasis-free survival (DMFS) in ER+ breast cancer treated with TAM.
2009 International Joint Conference on Bioinformatics, Systems Biology and Intelligent Computing, 2009
Microarray technology and high-throughput proteomics have revolutionized cancer biology by genera... more Microarray technology and high-throughput proteomics have revolutionized cancer biology by generating vast amount of data for various cancers. To gain insights into the biological processes that drive breast cancer recurrence, we integrate gene expression profiles of breast cancer and protein interaction networks in search for affected regulatory and signaling networks statistically associated with endocrine resistance. To perform this integration systematically,
Cancer letters, Jan 18, 2007
Therapies that target the synthesis of estrogen or the function of estrogen receptor(s) have been... more Therapies that target the synthesis of estrogen or the function of estrogen receptor(s) have been developed to treat breast cancer. While these approaches have proven to be beneficial to a large number of patients, both de novo and acquired resistance to these drugs is a significant problem. Recent advances in our understanding of the molecular mechanisms that contribute to resistance have provided a means to begin to predict patient responses to these drugs and develop rational approaches for combining therapeutic agents to circumvent or desensitize the resistant phenotype. Here, we review common mechanisms of antiestrogen resistance and discuss the implications for prediction of response and design of effective combinatorial treatments.
Uploads
Papers by Rebecca Riggins