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author:("inahta, Rita")
1.  Mechanisms of Adipocytokine-Mediated Trastuzumab Resistance in HER2-Positive Breast Cancer Cell Lines 
Acquired resistance to trastuzumab is a clinical problem in the treatment of HER2-over-expressing metastatic breast cancer. Importantly, an earlier report suggested that high body mass index was associated with reduced overall survival and reduced time to progression in patients with early stage or metastatic HER2-positive breast cancer treated with trastuzumab. Adipocyte-secreted factors may stimulate growth of HER2-positive cancers, blocking the growth inhibitory action of trastuzumab. Leptin and growth differentiation factor 15 (GDF15) are two adipocytokines that have been reported to stimulate HER2-PI3K signaling. We previously showed that cells with acquired trastuzumab resistance express increased levels of GDF15, and that GDF15 knockdown restores sensitivity to trastuzumab. The objective of the current study was to identify potential molecular mechanisms by which adipocytes stimulate resistance to trastuzumab in HER2-over-expressing breast cancer cell lines. Cells were cultured in complete media or conditioned media from differentiated adipocytes (CM). Cell viability of trastuzumab-treated cells was examined under anchorage-dependent and -independent conditions. Phosphorylation of Akt was assessed by Western blotting, and response to trastuzumab was reassessed upon treatment with the PI3K inhibitor LY294002 or after transfection with kinase-dead Akt. We report that CM significantly reduced trastuzumab-mediated growth inhibition of HER2-positive cells, and stimulated rapid phosphorylation of Akt. Pharmacologic or genetic inhibition of PI3K overcame CM-mediated trastuzumab resistance. Leptin and GDF15 were both measured in CM, but only GDF15 conferred resistance to trastuzumab. Leptin, on the other hand, abrogated sensitivity to lapatinib but not trastuzumab. Our observations suggest that adipocyte-secreted factors such as GDF15 stimulate PI3K signaling, resulting in reduced response to trastuzumab. The utility of adipocytokines as predictors of drug resistance and approaches to mitigate the cancer-promoting effects of adipocyte-secreted factors should be further examined. Our work supports additional investigation into GDF15 as a potential biomarker of trastuzumab resistance, and development of approaches to therapeutically target GDF15 in HER2-positive breast cancers that have progressed on trastuzumab.
PMCID: PMC3811155  PMID: 24179558
Cancer therapeutics; GDF15; drug resistance; erbB2; Herceptin; lapatinib; pharmacogenetics; trastuzumab
2.  Catalytic Deoxyribozyme-Modified Nanoparticles for RNAi-Independent Gene Regulation 
ACS nano  2012;6(10):9150-9157.
DNAzymes are catalytic oligonucleotides with important applications in gene regulation, DNA computing, responsive soft materials, and ultrasensitive metal-ion sensing. The most significant challenge for using DNAzymes in vivo pertains to non-toxic delivery and maintaining function inside cells. We synthesized multivalent deoxyribozyme ‘10–23’ gold nanoparticle (DzNP) conjugates, varying DNA density, linker length, enzyme orientation, and linker composition in order to study the role of the steric environment and gold surface chemistry on catalysis. DNAzyme catalytic efficiency was modulated by steric packing and proximity of the active loop to the gold surface. Importantly, the 10–23 DNAzyme was asymmetrically sensitive to the gold surface, and when anchored through the 5′ terminus was inhibited 32-fold. This property was used to generate DNAzymes whose catalytic activity is triggered by thiol displacement reactions or by photoexcitation at λ = 532 nm. Importantly, cell studies revealed that DzNPs are less susceptible to nuclease degradation, readily enter mammalian cells, and catalytically down-regulate GDF15 gene expression levels in breast cancer cells, thus addressing some of the key limitations in the adoption of DNAzymes for in vivo work.
doi:10.1021/nn3034265
PMCID: PMC3482470  PMID: 22966955
Deoxyribozyme; DNAzyme; gold nanoparticle; gene regulation; GDF15; Herceptin; trastuzumab; breast cancer; synthetic biology
3.  Selective Inhibition of HER2-Positive Breast Cancer Cells by the HIV Protease Inhibitor Nelfinavir 
Background
Human epidermal growth factor receptor 2 (HER2)–positive breast cancer is highly aggressive and has higher risk of recurrence than HER2-negative cancer. With few treatment options available, new drug targets specific for HER2-positive breast cancer are needed.
Methods
We conducted a pharmacological profiling of seven genotypically distinct breast cancer cell lines using a subset of inhibitors of breast cancer cells from a screen of the Johns Hopkins Drug Library. To identify molecular targets of nelfinavir, identified in the screen as a selective inhibitor of HER2-positive cells, we conducted a genome-wide screen of a haploinsufficiency yeast mutant collection. We evaluated antitumor activity of nelfinavir with xenografts in athymic nude mouse models (n = 4–6 per group) of human breast cancer and repeated mixed-effects regression analysis. All statistical tests were two-sided.
Results
Pharmacological profiling showed that nelfinavir, an anti-HIV drug, selectively inhibited the growth of HER2-positive breast cancer cells in vitro. A genome-wide screening of haploinsufficiency yeast mutants revealed that nelfinavir inhibited heat shock protein 90 (HSP90) function. Further characterization using proteolytic footprinting experiments indicated that nelfinavir inhibited HSP90 in breast cancer cells through a novel mechanism. In vivo, nelfinavir selectively inhibited the growth of HER2-positive breast cancer cells (tumor volume index of HCC1954 cells on day 29, vehicle vs nelfinavir, mean = 14.42 vs 5.16, difference = 9.25, 95% confidence interval [CI] = 5.93 to 12.56, P < .001; tumor volume index of BT474 cells on day 26, vehicle vs nelfinavir, mean = 2.21 vs 0.90, difference = 1.31, 95% CI = 0.83 to 1.78, P < .001). Moreover, nelfinavir inhibited the growth of trastuzumab- and/or lapatinib-resistant, HER2-positive breast cancer cells in vitro at clinically achievable concentrations.
Conclusion
Nelfinavir was found to be a new class of HSP90 inhibitor and can be brought to HER2-breast cancer treatment trials with the same dosage regimen as that used among HIV patients.
doi:10.1093/jnci/djs396
PMCID: PMC3472971  PMID: 23042933
4.  New developments in the treatment of HER2-positive breast cancer 
Approximately 20%–30% of metastatic breast cancers show increased expression of the human epidermal growth factor receptor-2 (HER2) tyrosine kinase. Two HER2-specific therapies are currently approved for clinical treatment of patients with HER2-overexpressing metastatic breast cancer. Trastuzumab is a monoclonal antibody against HER2 and is approved for first-line treatment of HER2-positive metastatic breast cancer. Lapatinib is a small molecule dual inhibitor of epidermal growth factor receptor and HER2 tyrosine kinases, and is approved for trastuzumab-refractory disease. Although trastuzumab is a highly effective therapy for patients with HER2-overexpressing metastatic breast cancer, a significant number of patients in the initial clinical trials of trastuzumab monotherapy showed resistance to trastuzumab-based therapy. Further, among those who did respond, the initial trials indicated that the median time to progression was less than 1 year. Similarly, lapatinib is effective in a subset of trastuzumab-refractory cases, but the majority of patients display resistance. This review discusses the multiple molecular mechanisms of resistance that have been proposed in the literature. In addition, novel agents that are being tested for efficacy against HER2-positive breast cancer, including the antibodies pertuzumab and trastuzumab-DM1 and the immunotoxin affitoxin, are reviewed. The introduction of trastuzumab has revolutionized the clinical care of patients with HER2-positive metastatic breast cancer and has resulted in dramatic reductions in recurrences of early-stage HER2-positive breast cancer. The development and implementation of gene- and protein-based assays that measure potential molecular predictors of trastuzumab resistance will allow individualization of HER2-targeted therapeutic approaches, and may ultimately improve treatment of HER2-positive breast cancer.
doi:10.2147/BCTT.S24976
PMCID: PMC3712518  PMID: 23869176
ErbB2; Herceptin; trastuzumab; drug resistance; neratinib; lapatinib; affitoxin
5.  MEK inhibition increases lapatinib sensitivity via modulation of FOXM1 
Current medicinal chemistry  2013;20(19):2486-2499.
The standard targeted therapy for HER2-overexpressing breast cancer is the HER2 monoclonal antibody, trastuzumab. Although effective, many patients eventually develop trastuzumab resistance. The dual EGFR/HER2 small molecule tyrosine kinase inhibitor lapatinib is approved for use in trastuzumab-refractory metastatic HER2-positive breast cancer. However, lapatinib resistance is a problem as most patients with trastuzumab-refractory disease do not benefit from lapatinib. Understanding the mechanisms underlying lapatinib resistance may ultimately facilitate development of new therapeutic strategies for HER2-overexpressing breast cancer. Our current results indicate that MEK inhibition increases lapatinib-mediated cytotoxicity in resistant HER2-overexpressing breast cancer cells. We genetically and pharmacologically blocked MEK/ERK signaling and evaluated lapatinib response by trypan blue exclusion, anchorage-independent growth assays, flow cytometric cell cycle and apoptosis analysis, and in tumor xenografts. Combined MEK inhibition and lapatinib treatment reduced phosphorylated ERK more than single agent treatment. In addition, Western blots, immunofluorescence, and immunohistochemistry demonstrated that the combination of MEK inhibitor plus lapatinib reduced nuclear expression of the MEK/ERK downstream proto-oncogene FOXM1. Genetic knockdown of MEK was tested for the ability to increase lapatinib-mediated cell cycle arrest or apoptosis in JIMT-1 and MDA361 cells. Finally, xenograft studies demonstrated that combined pharmacological inhibition of MEK plus lapatinib suppressed tumor growth and reduced expression of FOXM1 in HER2-overexpressing breast cancers that are resistant to trastuzumab and lapatinib. Our results suggest that FoxM1 contributes to lapatinib resistance downstream of MEK signaling, and supports further study of pharmacological MEK inhibition to improve response to lapatinib in HER2-overexpressing trastuzumab-resistant breast cancer.
PMCID: PMC3650616  PMID: 23531216
lapatinib; HER2; erbB2; breast cancer; resistance; MEK
6.  Pharmacological Strategies to Overcome HER2 Cross-talk and Trastuzumab Resistance 
Current Medicinal Chemistry  2012;19(7):1065-1075.
Approximately 20–30% of breast cancers show increased expression of the HER2 receptor tyrosine kinase. Trastuzumab (Herceptin) is a clinically approved anti-HER2 monoclonal antibody. Many patients with HER2-overexpressing metastatic breast cancer respond to trastuzumab; however, a subset display primary drug resistance. In addition, many patients who initially respond to trastuzumab ultimately develop disease progression. Multiple molecular mechanisms contributing to trastuzumab resistance have been proposed in the literature. These mechanisms include cross-signaling from related HER/erbB receptors and compensatory signaling from receptors outside of the HER/erbB family, including receptors for insulin-like growth factor-I, vascular endothelial growth factor, and transforming growth factor beta. The major downstream signaling pathway activated by HER2 cross-talk is PI3K/mTOR, and a potential integrator of receptor crosstalk is Src-focal adhesion kinase (FAK) signaling. PI3K, Src, and FAK have independently been implicated in trastuzumab resistance. In this review, we will discuss pharmacological inhibition of HER2 cross-talk as a strategy to treat trastuzumab-refractory HER2-overexpresssing breast cancer.
PMCID: PMC3294049  PMID: 22229414
breast cancer; erbB2; Her2; Herceptin; resistance; Trastuzumab; cross-talk; lapatinib; pertuzumab; IGF-IR; VEGF; TGF beta; FAK
7.  Pharmacologic Inhibition of mTOR Improves Lapatinib Sensitivity in HER2-Overexpressing Breast Cancer Cells with Primary Trastuzumab Resistance 
Lapatinib, a dual EGFR/HER2 kinase inhibitor, is approved for use in patients with trastuzumab-refractory HER2-overexpressing breast cancer. Increased PI3K signaling has been associated with resistance to trastuzumab, although its role in lapatinib resistance remains unclear. The purpose of the current study was to determine if PI3K/mTOR activity affects lapatinib sensitivity. Reduced sensitivity to lapatinib was associated with an inability of lapatinib to inhibit Akt and p70S6K phosphorylation. Transfection of constitutively active Akt reduced lapatinib sensitivity, while kinase-dead Akt increased sensitivity. Knockdown of 4EBP1 also increased lapatinib sensitivity, in contrast to p70S6K knockdown, which did not affect response to lapatinib. Pharmacologic inhibition of mTOR using rapamycin or ridaforolimus increased lapatinib sensitivity and reduced phospho-Akt levels in cells that showed poor response to single-agent lapatinib, including those transfected with hyperactive Akt. Finally, combination mTOR inhibition plus lapatinib resulted in synergistic inhibition of proliferation, reduced anchorage-independent growth, and reduced in vivo tumor growth of HER2-overexpressing breast cancer cells that have primary trastuzumab resistance. Our data suggest that PI3K/mTOR inhibition is critical for achieving optimal response to lapatinib. Collectively, these experiments support evaluation of lapatinib in combination with pharmacologic mTOR inhibition as a potential strategy for inhibiting growth of HER2-overexpressing breast cancers that show resistance to trastuzumab and poor response to lapatinib.
PMCID: PMC3288300  PMID: 22043997
Akt; breast cancer; drug resistance; erbB2; HER2; Herceptin; lapatinib; MK-8669; mTOR; PI3K; p70S6K; rapamycin; ridaforolimus; Tykerb; trastuzumab
8.  Molecular Mechanisms of Trastuzumab-Based Treatment in HER2-Overexpressing Breast Cancer 
ISRN Oncology  2012;2012:428062.
The past decade of research into HER2-overexpressing breast cancer has provided significant insight into the mechanisms by which HER2 signaling drives tumor progression, as well as potential mechanisms by which cancer cells escape the anticancer activity of HER2-targeted therapy. Many of these preclinical findings have been translated into clinical development, resulting in novel combinations of HER2-targeted therapies and combinations of trastuzumab plus inhibitors of resistance pathways. In this paper, we will discuss proposed mechanisms of trastuzumab resistance, including epitope masking, cross signaling from other cell surface receptors, hyperactive downstream signaling, and failure to induce antibody-dependent cellular cytotoxicity. In addition, we will discuss the molecular mechanisms of action of dual HER2 inhibition, specifically the combination of trastuzumab plus lapatinib or trastuzumab with pertuzumab. We will also discuss data supporting therapeutic combinations of trastuzumab with agents targeted against molecules implicated in trastuzumab resistance. The roles of insulin-like growth factor-I receptor and the estrogen receptor are discussed in the context of resistance to HER2-targeted therapies. Finally, we will examine the major issues that need to be addressed in order to translate these combinations from the bench to the clinic, including the need to establish relevant biomarkers to select for those patients who are most likely to benefit from a particular drug combination.
doi:10.5402/2012/428062
PMCID: PMC3512309  PMID: 23227361
9.  Growth Differentiation Factor 15 (GDF15)-Mediated HER2 Phosphorylation Reduces Trastuzumab Sensitivity of HER2-Overexpressing Breast Cancer Cells 
Biochemical pharmacology  2011;82(9):1090-1099.
Resistance to the anti-HER2 monoclonal antibody trastuzumab is a major problem in the treatment of HER2-overexpressing metastatic breast cancer. Growth differentiation factor 15 (GDF15), which is structurally similar to TGF beta, has been reported to stimulate phosphorylation of HER2. We tested the hypothesis that GDF15-mediated phosphorylation of HER2 reduces the sensitivity of HER2-overexpressing breast cancer cell lines to trastuzumab. Gene microarray analysis, real-time PCR, and ELISA were used to assess GDF15 expression. Growth inhibition and proliferation assays in response to pharmacologic inhibitors of HER2, TGF beta receptor, or Src were performed on cells stimulated with recombinant human GDF15 or stable GDF15 transfectants. Western blotting was performed to determine effects of GDF15 on HER2 signaling. Cells were infected with lentiviral GDF15 shRNA plasmid to determine effects of GDF15 knockdown on cell survival in response to trastuzumab. Cells with acquired or primary trastuzumab resistance showed increased GDF15 expression. Exposure of trastuzumab-sensitive cells to recombinant human GDF15 or stable transfection of a GDF15 expression plasmid inhibited trastuzumab-mediated growth inhibition. HER2 tyrosine kinase inhibition abrogated GDF15-mediated Akt and Erk1/2 phosphorylation and blocked GDF15-mediated trastuzumab resistance. Pharmacologic inhibition of TGF beta receptor blocked GDF15-mediated phosphorylation of Src. Further, TGF beta receptor inhibition or Src inhibition blocked GDF15-mediated trastuzumab resistance. Finally, lentiviral GDF15 shRNA increased trastuzumab sensitivity in cells with acquired or primary trastuzumab resistance. These results support GDF15-mediated activation of TGF beta receptor-Src-HER2 signaling crosstalk as a novel mechanism of trastuzumab resistance.
doi:10.1016/j.bcp.2011.07.082
PMCID: PMC3191232  PMID: 21803025
breast cancer; erbB2; Herceptin; resistance; trastuzumab; lapatinib
10.  Deciphering the Role of Insulin-Like Growth Factor-I Receptor in Trastuzumab Resistance 
Resistance to the HER2-targeted antibody trastuzumab is a major clinical concern in the treatment of HER2-overexpressing metastatic breast cancer. Increased expression or signaling of the insulin-like growth factor-I receptor (IGF-IR) has been reported in a subset of cell lines and clinical samples derived from trastuzumab-resistant breast cancers. Genetic and pharmacologic inhibition of IGF-IR signaling has been shown to improve response to trastuzumab in trastuzumab-naïve and trastuzumab-resistant models. In this paper, we will discuss the role of IGF-IR signaling in trastuzumab resistance. Further, we will discuss cotargeting IGF-IR and HER2 as a potential therapeutic strategy for HER2-over-expressing breast cancers that have progressed on trastuzumab treatment.
doi:10.1155/2012/648965
PMCID: PMC3399380  PMID: 22830017
11.  Overcoming Trastuzumab Resistance in Breast Cancer by Targeting Dysregulated Glucose Metabolism 
Cancer research  2011;71(13):4585-4597.
Trastuzumab shows remarkable efficacy in treatment of ErbB2-positive breast cancers when used alone or in combination with other chemotherapeutics. However, acquired resistance develops in most treated patients, necessitating alternate treatment strategies. Increased aerobic glycolysis is a hallmark of cancer and inhibition of glycolysis may offer a promising strategy to preferentially kill cancer cells. In this study, we investigated the antitumor effects of trastuzumab in combination with glycolysis inhibitors in ErbB2-positive breast cancer. We found that trastuzumab inhibits glycolysis via downregulation of heat shock factor 1 (HSF1) and lactate dehydrogenase A (LDH-A) in ErbB2-positive cancer cells, resulting in tumor growth inhibition. Moreover, increased glycolysis via HSF1 and LDH-A contributes to trastuzumab resistance. Importantly, we found that combining trastuzumab with glycolysis inhibition synergistically inhibited trastuzumab-sensitive and -resistant breast cancers in vitro and in vivo, due to more efficient inhibition of glycolysis. Taken together, our findings show how glycolysis inhibition can dramatically enhance the therapeutic efficacy of trastuzumab in ErbB2-positive breast cancers, potentially useful as a strategy to overcome trastuzumab resistance.
doi:10.1158/0008-5472.CAN-11-0127
PMCID: PMC3129363  PMID: 21498634
Warburg effect; glycolysis; HSF1; LDH-A; trastuzumab; ErbB2; resistance
12.  New developments in the treatment of HER2-positive breast cancer 
Approximately 20%–30% of metastatic breast cancers show increased expression of the human epidermal growth factor receptor-2 (HER2) tyrosine kinase. Two HER2-specific therapies are currently approved for clinical treatment of patients with HER2-overexpressing metastatic breast cancer. Trastuzumab is a monoclonal antibody against HER2 and is approved for first-line treatment of HER2-positive metastatic breast cancer. Lapatinib is a small molecule dual inhibitor of epidermal growth factor receptor and HER2 tyrosine kinases, and is approved for trastuzumab-refractory disease. Although trastuzumab is a highly effective therapy for patients with HER2-overexpressing metastatic breast cancer, a significant number of patients in the initial clinical trials of trastuzumab monotherapy showed resistance to trastuzumab-based therapy. Further, among those who did respond, the initial trials indicated that the median time to progression was less than 1 year. Similarly, lapatinib is effective in a subset of trastuzumab-refractory cases, but the majority of patients display resistance. This review discusses the multiple molecular mechanisms of resistance that have been proposed in the literature. In addition, novel agents that are being tested for efficacy against HER2-positive breast cancer, including the antibodies pertuzumab and trastuzumab-DM1 and the immunotoxin affitoxin, are reviewed. The introduction of trastuzumab has revolutionized the clinical care of patients with HER2-positive metastatic breast cancer and has resulted in dramatic reductions in recurrences of early-stage HER2-positive breast cancer. The development and implementation of gene- and protein-based assays that measure potential molecular predictors of trastuzumab resistance will allow individualization of HER2-targeted therapeutic approaches, and may ultimately improve treatment of HER2-positive breast cancer.
doi:10.2147/BCTT.S24976
PMCID: PMC3712518  PMID: 23869176
ErbB2; Herceptin; trastuzumab; drug resistance; neratinib; lapatinib; affitoxin
13.  Targeting Bcl-2 in Herceptin-Resistant Breast Cancer Cell Lines 
Acquired resistance to Herceptin is a major clinical problem in the treatment of HER2-overexpressing breast cancer. Understanding the molecular mechanisms leading to resistance will allow identification of novel therapeutic targets and predictors of therapeutic response. To this end, up-regulation of anti-apoptotic proteins has been associated with resistance to the HER2-targeted drug lapatinib, but has not yet been linked to Herceptin resistance. The aim of the current study was to determine if the Bcl-2 anti-apoptotic protein is a potential therapeutic target in cells with acquired Herceptin resistance. The BT474 HER2-overexpressing breast cancer cell line and BT474-derived acquired Herceptin-resistant clones were used as models in this study. Bcl-2 and Bax expression were assessed by Western blotting. Proliferation assays were performed on cells treated with the Bcl-2 inhibitor ABT-737 in the absence or presence of Herceptin. Finally, the effect of PI3K inhibition or IKK inhibition on Bcl-2 expression and Herceptin sensitivity was examined by Western blotting and established proliferation assays. We show that cells with acquired resistance to Herceptin have an increased Bcl-2:Bax ratio. Resistant cells have increased sensitivity to ABT-737. Further, pharmacologic inhibition of Bcl-2 improved sensitivity to Herceptin in acquired resistant cells. Finally, PI3K and IKK inhibition down-regulated Bcl-2 expression and increased sensitivity to Herceptin in resistant cells. Taken together, these new observations support further study of Bcl-2-targeted therapies in Herceptin-resistant breast cancers, and importantly, future investigation of Bcl-2 expression as a potential predictor of Herceptin response in patients with HER2-overexpressing breast cancer.
PMCID: PMC3233239  PMID: 22162984
Bcl2; erbB2; Herceptin; lapatinib; trastuzumab
14.  Delphinidin Inhibits HER2 and Erk1/2 Signaling and Suppresses Growth of HER2-Overexpressing and Triple Negative Breast Cancer Cell Lines 
Delphinidin is a polyphenolic compound found in many brightly colored fruits and vegetables. Delphinidin is also the major bioactive component found in many dietary supplements that are currently consumed as complementary cancer medicine including pomegranate extract. The purpose of the current study was to determine the in vitro biological effects of delphinidin on established breast cancer cell lines of varying molecular subtypes in comparison to non-transformed breast epithelial cells. We examined cell proliferation, apoptosis, and growth inhibition in response to delphinidin using a tetrazolium salt-based assay, DNA fragmentation assay, and anchorage-independent growth assay. In comparison to vehicle control, delphinidin inhibited proliferation (P < 0.05), blocked anchorage-independent growth (P < 0.05), and induced apoptosis (P < 0.05) of ER-positive, triple negative, and HER2-overexpressing breast cancer cell lines with limited toxicity to non-transformed breast epithelial cells. MAPK signaling was partially reduced in triple negative cells and ER-negative chemically transformed MCF10A cells after treatment with delphinidin. In addition, delphinidin induced a significant level of apoptosis in HER2-overexpressing cells in association with reduced HER2 and MAPK signaling. Since delphinidin is often consumed as a complementary cancer medicine, the effect of delphinidin on response to specific HER2-targeted breast cancer therapies was examined by proliferation assay. Results of these drug combination studies suggested potential antagonism between delphinidin and HER2-directed treatments. In summary, the data presented here suggest that single agent delphinidin exhibits growth inhibitory activity in breast cancer cells of various molecular subtypes, but raise concerns regarding potential drug antagonism when used in combination with existing targeted therapies in HER2-overexpressing breast cancer.
doi:10.4137/BCBCR.S7156
PMCID: PMC3140266  PMID: 21792311
breast cancer; delphinidin; HER2; erbB2; triple negative
15.  In vitro evaluation of pan-PI3-kinase inhibitor SF1126 in trastuzumab-sensitive and trastuzumab-resistant HER2-over-expressing breast cancer cells 
Purpose
The purpose of the current study is to determine the in vitro cytotoxic effects of the novel pan-PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells.
Methods
Cell proliferation and cytotoxicity were examined by MTS colorimetric assay, FACS analysis, colony formation assay, and immunoblotting. PI3K signaling was assessed by immunoblotting for phosphorylated Akt. Combination effects of trastuzumab and SF1126 were examined in resistant cells by MTS and soft agar assay.
Results
SF1126 inhibited proliferation and induced G1 arrest and apoptosis of SKBR3 and BT474 parental and trastuzumab-resistant HER2-over-expressing cells. Colony formation was inhibited by SF1126, caspase 3 and PARP proteins were cleaved, and survivin was down-regulated. Inhibition of PI3-kinase was confirmed by reduced phosphorylation of Akt. Finally, the combination of SF1126 and trastuzumab synergistically inhibited proliferation of resistant cells, with SF1126-treated cells showing reduced anchorage-independent growth.
Conclusions
These results provide evidence that a clinically relevant pan PI-3 kinase inhibitor can reverse trastuzumab resistance in breast cancer cells, and support further study of PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells, including those that have progressed on trastuzumab.
doi:10.1007/s00280-009-1075-9
PMCID: PMC2808522  PMID: 19636556
targeted therapy; Herceptin; drug resistance; PI3-kinase
16.  Modulation of the BRCA1 protein and induction of apoptosis in triple negative breast cancer cell lines by the polyphenolic compound curcumin 
In the current study, we sought to examine the effects of curcumin in a specific type of breast cancer called triple negative breast cancer. These cancers lack expression of the estrogen and progesterone receptors and do not over-express HER2. Current treatment for triple negative breast cancers is limited to cytotoxic chemotherapy, and upon relapse, there are not any therapies currently available. We demonstrate here that the bioactive food compound curcumin induces DNA damage in triple negative breast cancer cells in association with phosphorylation, increased expression, and cytoplasmic retention of the BRCA1 protein. In addition, curcumin promotes apoptosis and prevents anchorage-independent growth and migration of triple negative breast cancer cells. Apoptosis and BRCA1 modulation were not observed in non-transformed mammary epithelial cells, suggesting curcumin may have limited non-specific toxicity. This study suggests that curcumin and potentially curcumin analogues should be tested further in the context of triple negative breast cancer. These results are novel, having never been previously reported, and suggest that curcumin could provide a novel, non-toxic therapy, which could lead to improved survival for patients with triple negative breast cancer. Curcumin should be studied further in this subset of breast cancer patients, for whom treatment options are severely limited.
PMCID: PMC2756684  PMID: 19809577
mammary carcinoma; triple negative; curcumin; DNA damage; BRCA1
17.  HER2 CROSS TALK AND THERAPEUTIC RESISTANCE IN BREAST CANCER 
The HER2 receptor tyrosine kinase is amplified and/or overexpressed in approximately 30% of metastatic breast cancers. Interactions and cross signaling from the HER2 receptor to other growth factor receptors may potentially contribute to therapeutic resistance. In this review, we discuss HER2 receptor cross talk with the estrogen receptor and implications toward resistance to endocrine therapies. We also review mechanisms of resistance to the HER2-targeted antibody trastuzumab, including signaling from other members of the HER family, increased signaling through the PI3-kinase pathway, and cross talk from the insulin-like growth factor-I receptor to HER2. Finally, we will provide perspective on how HER2 receptor cross talk may provide critical information for developing novel therapeutic options for HER2-overexpressing breast cancers.
PMCID: PMC2746389  PMID: 18508484
erbB2; epidermal growth factor receptor; insulin-like growth factor-I receptor; estrogen receptor; review
18.  Modulation of the BRCA1 Protein and Induction of Apoptosis in Triple Negative Breast Cancer Cell Lines by the Polyphenolic Compound Curcumin 
In the current study, we sought to examine the effects of curcumin in a specific type of breast cancer called triple negative breast cancer. These cancers lack expression of the estrogen and progesterone receptors and do not over-express HER2. Current treatment for triple negative breast cancers is limited to cytotoxic chemotherapy, and upon relapse, there are not any therapies currently available. We demonstrate here that the bioactive food compound curcumin induces DNA damage in triple negative breast cancer cells in association with phosphorylation, increased expression, and cytoplasmic retention of the BRCA1 protein. In addition, curcumin promotes apoptosis and prevents anchorage-independent growth and migration of triple negative breast cancer cells. Apoptosis and BRCA1 modulation were not observed in non-transformed mammary epithelial cells, suggesting curcumin may have limited non-specific toxicity. This study suggests that curcumin and potentially curcumin analogues should be tested further in the context of triple negative breast cancer. These results are novel, having never been previously reported, and suggest that curcumin could provide a novel, non-toxic therapy, which could lead to improved survival for patients with triple negative breast cancer. Curcumin should be studied further in this subset of breast cancer patients, for whom treatment options are severely limited.
PMCID: PMC2756684  PMID: 19809577
mammary carcinoma; triple negative; curcumin; DNA damage; BRCA1
19.  In vitro evaluation of pan-PI3-kinase inhibitor SF1126 in trastuzumab-sensitive and trastuzumab-resistant HER2-over-expressing breast cancer cells 
Purpose
The purpose of the current study is to determine the in vitro cytotoxic effects of the novel pan-PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells.
Methods
Cell proliferation and cytotoxicity were examined by MTS colorimetric assay, FACS analysis, colony formation assay, and immunoblotting. Phosphoinositol-3-kinase signaling was assessed by immunoblotting for phosphorylated Akt. Combination effects of trastuzumab and SF1126 were examined in resistant cells by MTS and soft agar assay.
Results
SF1126 inhibited proliferation, and induced G1 arrest and apoptosis of SKBR3 and BT474 parental and trastuzumab-resistant HER2-over-expressing cells. Colony formation was inhibited by SF1126, caspase 3 and PARP proteins were cleaved, and survivin was down-regulated. Inhibition of PI3-kinase was confirmed by reduced phosphorylation of Akt. Finally, the combination of SF1126 and trastuzumab synergistically inhibited proliferation of resistant cells, with SF1126-treated cells showing reduced anchorage-independent growth.
Conclusions
These results provide evidence that a clinically relevant pan-PI-3 kinase inhibitor can reverse trastuzumab resistance in breast cancer cells, and support further study of PI3-kinase inhibitor SF1126 in HER2-over-expressing breast cancer cells, including those that have progressed on trastuzumab.
doi:10.1007/s00280-009-1075-9
PMCID: PMC2808522  PMID: 19636556
Targeted therapy; Herceptin; Drug resistance; PI3-kinase
20.  Nordihydroguaiaretic Acid, a Cytotoxic IGF-IR/HER2 Inhibitor in Trastuzumab-Resistant Breast Cancer 
Molecular cancer therapeutics  2008;7(7):1900-1908.
The majority of patients with HER2-overexpressing metastatic breast cancer who initially respond to the HER2-targeted antibody trastuzumab demonstrate disease progression within one year. The identification of novel agents that effectively inhibit survival of cancer cells that have progressed on trastuzumab is critical for improving outcome for this patient population. In the current study, we demonstrate that the phenolic compound nordihydroguaiaretic acid (NDGA) promoted cell death of trastuzumab-naïve and trastuzumab-refractory HER2-overexpressing breast cancer cells. NDGA induced DNA fragmentation, cleavage of PARP and caspase 3, and inhibition of colony formation. In addition, NDGA inhibited IGF-I and HER2 signaling in trastuzumab-refractory cells, with reduced downstream PI3K/Akt signaling. Importantly, combination treatment with NDGA and trastuzumab suppressed proliferation and survival of trastuzumab-refractory cells to a greater degree than either agent alone, suggesting that NDGA increases the sensitivity of refractory cells to trastuzumab. Derivatives of NDGA are currently in clinical trial for other solid tumors. Our data strongly support further study of NDGA as a potential therapeutic against breast cancers that have progressed on trastuzumab.
doi:10.1158/1535-7163.MCT-08-0012
PMCID: PMC2586607  PMID: 18645000
Herceptin; drug resistance; erbB2; targeted therapy; apoptosis
21.  A Novel Unidirectional Cross talk from the Insulin-Like Growth Factor-I Receptor to Leptin Receptor in Human Breast Cancer Cells 
Molecular cancer research : MCR  2008;6(6):1052-1058.
Obesity is a major risk factor for the development and progression of breast cancer. Increased circulating levels of the obesity-associated hormones leptin and insulin-like growth factor-I (IGF-I), and overexpression of the leptin receptor (Ob-R) and IGF-I receptor (IGF-IR) have been detected in a majority of breast cancer cases and during obesity. Due to correlations between increased leptin, Ob-R, IGF-I, and IGF-IR in breast cancer, we hypothesized that molecular interactions may exist between these two signaling pathways. Co-immunoprecipitation and immunoblotting demonstrated that IGF-IR and Ob-R interact in the breast cancer cell lines MDA-MB-231, MCF7, BT474, and SKBR3. Stimulation of cells with IGF-I promoted Ob-R phosphorylation, which was blocked by IGF-IR kinase inhibition. In addition, IGF-I activated downstream signaling molecules in the leptin receptor and IGF-IR pathways. In contrast to IGFI, leptin did not induce phosphorylation of IGF-IR, indicating that receptor cross signaling is unidirectional, occurring from IGF-IR to Ob-R. Our results demonstrate for the first time a novel interaction and cross talk between the IGF-I and leptin receptors in human breast cancer cells.
doi:10.1158/1541-7786.MCR-07-2126
PMCID: PMC2440577  PMID: 18515755
growth factor receptors; mammary carcinoma; signal transduction
22.  HER2 therapy: Molecular mechanisms of trastuzumab resistance 
Breast Cancer Research  2006;8(6):215.
Trastuzumab is a monoclonal antibody targeted against the HER2 tyrosine kinase receptor. The majority of patients with metastatic breast cancer who initially respond to trastuzumab develop resistance within one year of treatment initiation, and in the adjuvant setting 15% of patients still relapse despite trastuzumab-based therapy. In this review, we discuss potential mechanisms of antitumor activity by trastuzumab, and how these mechanisms become altered to promote therapeutic resistance. We also discuss novel therapies that may improve the efficacy of trastuzumab, and that offer hope that the survival of breast cancer patients with HER2-overexpressing tumors can be vastly improved.
doi:10.1186/bcr1612
PMCID: PMC1797036  PMID: 17096862

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