Target In Human Breast Cancer Research Articles

Anticancer effects of alpelisib on PIK3CA-mutated canine mammary tumor cell lines.

Canine mammary tumors (CMTs) are commonly observed in old and unspayed female dogs. Recently, dogs have been increasingly spaying at a young age to prevent mammary tumors. These CMTs require extensive local excision and exhibit a high probability of metastasis to the regional lymph nodes and lungs during malignancy. However, the molecular and biological mechanisms underlying CMT development have not been fully elucidated, and research in this area is limited. Therefore, in this study, we established new CMT cell lines by isolating cells from tumor tissues and investigated phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), a target for human breast cancer. PIK3CA mutations were observed at a similar loci as in the human PIK3CA gene in half of all canine samples. Furthermore, we investigated whether alpelisib, a PIK3CA inhibitor approved by the U.S. Food and Drug Administration for human breast cancer treatment, along with fulvestrant, is effective for CMT treatment. Alpelisib exerted stronger anticancer effects on cell lines with PIK3CA mutations than on the wild-type cell lines. In conclusion, we established new CMT cell lines with PIK3CA mutations and confirmed the efficacy of alpelisib for CMT treatment in vitro.

ECSIT inhibits cell death to increase tumor progression and metastasis via p53 in human breast cancer

BackgroundCurrently, breast cancer has surpassed lung cancer as the most common cancer and the molecular mechanism involved in tumor initiation and metastasis was unclear. Therefore, it is necessary to advance our understanding of tumor progression and metastasis and find out new targets. An evolutionarily conserved signaling intermediate in Toll pathways (ECSIT) is involved in the innate immune response and has been shown as tumor suppressors by downregulating nuclear factor-kappa B (NF-κB) pathway. However, the role of ECSIT in the progression and metastasis of human breast cancer remains unknown.MethodsWe overexpressed ECSIT by transfection of a eukaryotic expression plasmid and constructed a breast cancer cell line with stable knockdown of ECSIT by short hairpin RNA. And we silenced p53 through small interfering RNA. In vivo, we replicated a xenograft mouse model in nude mice. The effects on the proliferation, viability, migration and invasion were studied by 5-ethynyl-2-deoxyuridine, cell counting Kit-8, wound healing and invasion assays. Propidium iodide/Hoechst 33342 staining and cleaved-caspase-3 staining were used to verify cell death. Western blot, immunohistochemistry (IHC) and histological analyses were used to explore the regulatory mechanism of tumor changes.ResultsWe reported the association of ECSIT with human breast cancer. In vitro assays demonstrated that ECSIT promoted MDA-MB-231 cell proliferation (by 66.15%), migration and invasion (by 58.29%). Knockdown of ECSIT significantly decreased cell proliferation (by 38.33%), viability, migration and invasion (by 62.37%), and increased cell death (by 41.1%). The in vivo results further confirmed that knockdown of ECSIT depressed tumorigenicity (by 29.46%) and metastasis (by 76.19%). Mechanistic investigations indicated that silencing of ECSIT could decrease the expression of p65 (by 46.05%), a subunit of NF-κB, and increase p53 protein expression in nuclei (by 89.53%). Moreover, we demonstrated that knockdown of p53 abolished the protection against cell death, which indicated that ECSIT might be involved in breast cancer progression through a p53-dependent pathway.ConclusionsOur studies provide new insight into the mechanisms underlying the role of ECSIT as well as a novel target for human breast cancer, and the development of novel ECSIT inhibitors is important for the management of TNBC.

Prognostic Value of NUSAP1 and Its Correlation with Immune Infiltrates in Human Breast Cancer.

Nucleolar and Spindle Associated Protein 1 (NUSAP1), a microtubule-associated protein, plays a critical role in maintaining spindle assembly and function. However, its clinical value and biological function in breast cancer have yet to be fully clarified. In the current study, the expression profile, prognostic value, genetic alterations of NUSAP1 were analyzed using Oncomine, UALCAN, HPA, bc-GenExMiner, Kaplan-Meier Plotter, and cBioPortal, besides, its correlation with tumor immune cell infiltration was explored via TIMER. Furthermore, enrichment analyses, protein-protein interaction, co-expression genes, and hub genes (KIF20A, BUB1, CDC20, CCNB2, BIRC5, MELK, KIF11, KIF23, TTK, MKI67) were performed using DAVID, STRING, LinkedOmics, and Cytoscape. Notably, NUSAP1 expression was upregulated in breast cancer, and was significantly correlated with clinicopathological features. High expression of NUSAP1 predicted a poor overall survival, relapse-free survival, distant metastases-free survival, post-progression survival, and disease-free survival. NUSAP1 was correlated with the infiltration of B cells, CD8+ T cells, neutrophil and dendritic cells, and the marker sets of monocytes, tumor-associated macrophages, M1 macrophages, M2 macrophages, dendritic cells, T cell exhaustion, regulatory T cells. Enrichment analyses showed NUSAP1 played an important role in the mitotic nuclear division, microtubule binding, nucleoplasm, and cell cycle. These findings confirmed NUSAP1 as a promising diagnostic biomarker and therapeutic target in human breast cancer.

Silencing of HMGA2 by siRNA Loaded Methotrexate Functionalized Polyamidoamine Dendrimer for Human Breast Cancer Cell Therapy.

The transcription factor high mobility group protein A2 (HMGA2) plays an important role in the pathogenesis of some cancers including breast cancer. Polyamidoamine dendrimer generation 4 is a kind of highly branched polymeric nanoparticle with surface charge and highest density peripheral groups that allow ligands or therapeutic agents to attach it, thereby facilitating target delivery. Here, methotrexate (MTX)- modified polyamidoamine dendrimer generation 4 (G4) (G4/MTX) was generated to deliver specific small interface RNA (siRNA) for suppressing HMGA2 expression and the consequent effects on folate receptor (FR) expressing human breast cancer cell lines (MCF-7, MDA-MB-231). We observed that HMGA2 siRNA was electrostatically adsorbed on the surface of the G4/MTX nanocarrier for constructing a G4/MTX-siRNA nano-complex which was verified by changing the final particle size and zeta potential. The release of MTX and siRNA from synthesized nanocomplexes was found in a time- and pH-dependent manner. We know that MTX targets FR. Interestingly, G4/MTX-siRNA demonstrates significant cellular internalization and gene silencing efficacy when compared to the control. Besides, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay demonstrated selective cell cytotoxicity depending on the FR expressing in a dose-dependent manner. The gene silencing and protein downregulation of HMGA2 by G4/MTX-siRNA was observed and could significantly induce cell apoptosis in MCF-7 and MDA-MB-231 cancer cells compared to the control group. Based on the findings, we suggest that the newly developed G4/MTX-siRNA nano-complex may be a promising strategy to increase apoptosis induction through HMGA2 suppression as a therapeutic target in human breast cancer.

Aberrant WNT/CTNNB1 Signaling as a Therapeutic Target in Human Breast Cancer: Weighing the Evidence.

WNT signaling is crucial for tissue morphogenesis during development in all multicellular animals. After birth, WNT/CTNNB1 responsive stem cells are responsible for tissue homeostasis in various organs and hyperactive WNT/CTNNB1 signaling is observed in many different human cancers. The first link between WNT signaling and breast cancer was established almost 40 years ago, when Wnt1 was identified as a proto-oncogene capable of driving mammary tumor formation in mice. Since that discovery, there has been a dedicated search for aberrant WNT signaling in human breast cancer. However, much debate and controversy persist regarding the importance of WNT signaling for the initiation, progression or maintenance of different breast cancer subtypes. As the first drugs designed to block functional WNT signaling have entered clinical trials, many questions about the role of aberrant WNT signaling in human breast cancer remain. Here, we discuss three major research gaps in this area. First, we still lack a basic understanding of the function of WNT signaling in normal human breast development and physiology. Second, the overall extent and precise effect of (epi)genetic changes affecting the WNT pathway in different breast cancer subtypes are still unknown. Which underlying molecular and cell biological mechanisms are disrupted as a result also awaits further scrutiny. Third, we survey the current status of targeted therapeutics that are aimed at interfering with the WNT pathway in breast cancer patients and highlight the importance and complexity of selecting the subset of patients that may benefit from treatment.

Abstract B11: HDAC6 as a therapeutic target in human breast cancer

Abstract Stat5 is a transcription factor utilized by several cytokine/hormone receptor signaling pathways that promotes transcription of genes associated with proliferation, differentiation, and survival of cancer cells. However, there are currently no clinically approved therapies that target Stat5, despite ample evidence that it contributes to breast cancer pathogenesis. Previous research in our lab has shown that the high mobility group nucleosome binding domain 2 (HGMN2) protein serves as a Stat5 co-activator. The activity of HMGN2 has been previously shown to be regulated by acetylation. Here, we show that deacetylation of HMGN2 on lysine residue K2 by histone deacetylase 6 (HDAC6) promotes Stat5-mediated transcription and breast cancer growth. Conversely, in vitro HDAC6 inhibition by pharmacologic and knockdown approaches enhanced HMGN2 acetylation with a concomitant reduction of in vitro Stat5-mediated signaling and global gene expression, and breast cancer growth. These data, combined with global in silico ChIP-Seq analysis, indicate that HDAC6 serves as a regulator of the pioneer function of HMGN2 for Stat5 transcriptional function. In vitro and in vivo treatment of traditional and patient-derived xenograft models with HDAC6 inhibitors resulted in a highly significant reduction of tumor growth. Translationally, it was also found that high levels of acetylated K2 were present in normal human breast tissue, which was lost in primary breast cancers and lymph node metastases. This suggests that blockade of HMGN2 deacetylation as described above is a novel treatment for breast cancer, given that existing HDAC6 inhibitors have a favorable toxicity profile in phase I trials of other tumor types. Altogether, these results reveal a novel mechanism through which HDAC6 regulates the transcription of Stat5 target genes and demonstrates the utility of HDAC6 inhibition as a potential breast cancer therapeutic. Citation Format: Justin M. Craig, Suzanne M. Schauwecker, Charles V. Clevenger. HDAC6 as a therapeutic target in human breast cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr B11.

HBXIP regulates etoposide-induced cell cycle checkpoints and apoptosis in MCF-7 human breast carcinoma cells

Etoposide, an anticancer DNA topoisomerase II poison, plays an important role in the therapy for human cancers. Unfortunately, many cancers develop etoposide resistance and do not respond to chemotherapy, leading to difficulty in treatment and poor prognosis. In this study, we investigate the effects of HBXIP gene silencing on etoposide chemosensitivity in MCF-7 human breast cancer cells. We find that etoposide increases HBXIP expression and promotes mobilization of HBXIP to the nucleus in MCF-7 cells. Knockdown of HBXIP alleviates etoposide-induced G2/M or S phase arrest. Upregulation of p53 and p21 upon etoposide treatment is attenuated in HBXIP knock-down cells. Moreover, HBXIP gene silencing sensitizes etoposide-induced cell apoptosis and cleavage of caspase-9 and PARP in MCF-7 cells. Knockdown of HBXIP expression by RNAi abrogates the etoposide-activated ERK and Akt. These results indicate that HBXIP can modulate the etoposide sensitivity of MCF-7 cell lines and further implicate HBXIP as a target for human breast cancer.

PAK5-mediated phosphorylation and nuclear translocation of NF-\u03baB-p65 promotes breast cancer cell proliferation in vitro and in vivo

BackgroundAbnormal proliferation is significantly associated with the promotion of malignant tumor. Growing evidence suggest that the signal pathways of p21cdc42/rac1-activated kinase 5 (PAK5) have been found in various tumor progression, however, the role of PAK5 in breast cancer remains largely unclear.MethodsWe evaluated PAK5 and p65 staining in breast cancer tissues (BCTs) and paired non-cancerous tissues (NTs) using tissue microarray (TMA) technology. The functions of PAK5 were studied in vitro and in vivo. Cell Counting Kit-8 (CCK-8) and flow cytometry were performed to determine proliferation of breast cancer cells. Phosphorylation assay and co-immunoprecipitation (co-IP) were employed to identify the regulation mechanism of p65 by PAK5. The activation of Cyclin D1 promoter was measured with luciferase reporter assay. Xenograft models in nude mice were established to explore the roles of PAK5 in breast cancer growth.ResultsIn this study, we show that PAK5 is highly expressed in breast cancer tissues and the increased PAK5 is significantly associated with breast cancer progression. Overexpression of PAK5 promotes the proliferation and cell-cycle progression by increasing the expression of Cyclin D1 in vitro and in vivo. Mechanistic studies demonstrated that PAK5 can promote the phosphorylation and the nuclear translocation of p65 subunit of nuclear factor-kappaB (NF-κB). Furthermore, p65 can directly bind to the promoter of Cyclin D1 and mediate an increase in its protein expression.ConclusionsTaken together, our findings suggest that PAK5 may serve as a potential prognosis marker and therapeutic target for human breast cancer.

Abstract 2020: Synergistic induction of apoptosis of combined mesupron and auranofin treatment in human breast cancer cells

Abstract Urokinase-type plasminogen activator (uPA) system may play a crucial role in cancer cell invasion and metastasis. uPA has been validated as a predictive or prognostic biomarker protein and considered as a therapeutic target in human breast cancer. Mesupron is a uPA inhibitor blocking uPA enzymatic activity to reduce tumor cell invasion, migration and cell growth. Auranofin has been known as an antirheumatic drug and a thioredoxin reductase inhibitor and recently its anticancer activity in ovarian and breast cancers has also been identified. To study whether cotreatment with mesupron and auranofin shows a significant anticancer activity, the synergistic induction of apoptosis of mesupron with auranofin was determined. Auranofin or mesupron alone inhibited cancer cell growth in MCF-7 cells with IC50 of 0.25 μM or 25 μM, respectively. Flow cytometric analysis also showed an increased apoptosis. When cells were treated with mesupron (0.125 μM) in combination with auranofin (10 μM), we found a significant induction of apoptosis although the cytotoxic effects of mesupron or auranofin alone at those concentrations were not quite strong. Interestingly, combined mesupron and auranofin treatment significantly suppressed mitochondrial antiapoptotic proteins including Bcl-2 and Bcl-xL. We also found the increase of caspase-3 and PARP cleavages. The combination index (CI) also indicated the synergistic induction of apoptosis by auranofin and mesupron. Taken together, these data suggest that the use of mesupron and auranofin in combination can be valuable to achieve higher anticancer activity. Note: This abstract was not presented at the meeting. Citation Format: Joo-Eun Lee, Yeo-Jung Kwon, Kyung-Soo Oh, Young-Jin Chun. Synergistic induction of apoptosis of combined mesupron and auranofin treatment in human breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2020. doi:10.1158/1538-7445.AM2017-2020

Estradiol Promotes Breast Cancer Cell Migration via Recruitment and Activation of Neutrophils

Estradiol (E2) plays a key role in breast cancer progression. Most breast cancer recurrences express the estrogen receptor (ER), but nearly 50% of patients are resistant to antiestrogen therapy. Novel therapeutic targets of ER-positive breast cancers are needed. Protumoral neutrophils expressing the lymphocyte function-associated antigen 1 (LFA-1) integrin may mediate cancer metastasis, and TGFβ1 is the major chemoattractant for neutrophils. The role of E2 in neutrophil-ER+ breast cancer cell interactions is unknown. We studied this in vivo using murine breast cancers in immunocompetent mice and human breast cancers in nude mice. Cell dissemination was evaluated in a zebrafish model, and microdialysis of breast cancer patients was performed. In vitro studies were done with mammosphere cultures of breast cancer cells and human neutrophils. We found that E2 increased the number of LFA-1+ neutrophils recruited to the invasive edge of mouse tumors, increased TGFβ1 secretion and promoted neutrophil infiltration in mammospheres, and induced overexpression of LFA-1 in neutrophils. In zebrafish, in the presence of E2, neutrophils increased dissemination of ER+ breast cancer cells via LFA-1 and TGFβ1, thus causing noninvasive cancer cells to be highly metastatic. Time-lapse imaging in zebrafish revealed close interactions of neutrophils with cancer cells, which drove breast cancer metastasis. We also found that extracellular TGFβ1 was overproduced in human breast cancer tissue compared with adjacent normal breast tissue. Thus, E2 can regulate immune/cancer cell interactions in tumor microenvironments. Our results indicate that extracellular TGFβ1 is a relevant target in human breast cancer. Cancer Immunol Res; 5(3); 234-47. ©2017 AACR.

The long non-coding RNA NEAT1 interacted with miR-101 modulates breast cancer growth by targeting EZH2

Nuclear enriched abundant transcript 1 (NEAT1), an important cancer-associated long non-coding RNA (lncRNA), contributes to the development and progression of several cancers. An increased expression of NEAT1 was observed in cancers including bladder cancer, lung cancer and breast cancer (BC). However, the exact effect of NEAT1 in BC progression and the underlying molecular mechanisms are still unknown up to now. Here, we investigated the detailed role of NEAT1 in human BC cell lines and clinical tumor samples in order to validate the function of this molecule. In our research, lncRNA-NEAT1 was specifically upregulated in BC cell lines and promoted BC cell growth through targeting miR-101. Knockdown of NEAT1 inhibited the proliferation and DNA synthesis of human BC cell in vitro. In addition, the regulation of EZH2 by miR-101 was required in NEAT1 induced BC cell growth. These findings indicated that NEAT1 might suppress the tumor growth via miR-101 dependent EZH2 regulation. Taken together, our data indicated that NEAT1 might be an oncogenic lncRNA that promoted proliferation of BC and could be regarded as a therapeutic target in human BC.

RNA Interference of IQ Motif Containing GTPase-Activating Protein 3 (IQGAP3) Inhibits Cell Proliferation and Invasion in Breast Carcinoma Cells

Breast cancer is a highly prevalent disease affecting women. The association of IQ motif containing GTPase-activating protein 3 (IQGAP3) and breast cancer is poorly defined. Here we reported that IQGAP3 is a key regulator of cell proliferation and metastasis during breast cancer progression. The expression of IQGAP3 was significantly increased in breast tissues compared to nontumor tissues at both protein and mRNA levels. Furthermore, IQGAP3 had a high expression level in ZR-75-30 and BT474 compared to other breast cancer cell lines. Depletion of IQGAP3 through RNA interference in ZR-75-30 and BT474 significantly inhibited cell proliferation. More importantly, IQGAP3 silencing in breast cancer cells notably repressed cell migration and invasion. Further analysis suggested that inhibition of cell proliferation and metastasis was associated with some proteins, including p53, MMP9, Snail, CDC42, p-ERK1/2, KIF2C, KIF4A, PCNA, and Twist. Since expression of IQGAP3 seems to be associated with the pathogenesis of breast cancer and suppression of it can inhibit cancer cell growth and metastasis, IQGAP3 may be a potential therapeutic target in human breast cancer.

The role of semaphorin 4D in tumor development and angiogenesis in human breast cancer.

BackgroundSemaphorin 4D (Sema4D) is highly expressed in certain types of tumors and functions in the regulation of tumor angiogenesis and growth. However, it is still not clear regarding the roles of Sema4D in breast cancer. This study was designed to explore the effects of Sema4D on proliferation, cell cycle progression, apoptosis, invasion, migration, tumor growth, and angiogenesis in breast cancer.Materials and methodsThe expression level of Sema4D was investigated in MCF10A, 184A1, HCC1937, MDA-MB-468, MDA-MB-231, Hs578T, BT474, MCF-7, and T47D breast cancer cell lines by Western blotting analysis. Sema4D downregulation or overexpression was established by infection with lentiviruses-encoding Sema4D short hairpin RNA (shRNA) or Sema4D. To evaluate the effects of Sema4D on cell proliferation, cell cycle progression, apoptosis, invasion, and migration of MDA-MB-231 and MDA-MB-468 cells, methods including MTT assay, flow cytometry, wound healing assay, and transwell experiments were applied. BALB/c nude mice were injected with MDA-MB-231 cells, which were respectively infected with lentiviruses-encoding Sema4D, Sema4D shRNA, and GFP, followed by tumor angiogenesis assay.ResultsSema4D was expressed at higher levels in breast cancer cell lines compared with the normal human breast epithelial cell lines, especially in MDA-MB-231 and MDA-MB-468 cells. Cell proliferation ability was remarkably inhibited in Sema4D downregulated condition, whereas the proportions of cells in the G0/G1 phase and apoptosis increased in MDA-MB-231 and MDA-MB-468 cells. In addition, the invasion and migration abilities of these cells were obviously reduced. Xenograft growth as well as angiogenesis was inhibited when infected with lentiviruses-encoding Sema4D shRNA in vivo.ConclusionDownregulation of Sema4D had notable influence on cell proliferation ability, invasion, migration, and apoptosis of both MDA-MB-231 and MDA-MB-468 cells. Furthermore, infection with lentiviruses-encoding Sema4D shRNA obviously inhibited tumor growth and angiogenesis in BALB/c nude mice. Our results showed that Sema4D may represent a novel therapeutic target for human breast cancer.

Abstract 3315: Breast cancer stem cell induction by COX-2 via EP4/PI3K-AKT/NOTCH-WNT axis: EP4 as therapeutic target

Abstract Cancer stem-like cells (SLC) resist conventional therapies, necessitating searches for SLC-specific targets. We established that cyclo-oxygenase(COX)-2 expression promotes human breast cancer progression by activation of the prostaglandin(PG)E-2 receptor EP4. Present study revealed that COX-2 induces SLCs by EP4-mediated NOTCH and WNT up-regulation. EP4 antagonist (EP4A) treatment ablated SLCs both in vitro and in vivo. Ectopic COX-2 over-expression in MCF-7 and SKBR-3 human breast cancer cell lines (named MCF-7-COX-2 and SKBR-3-COX-2) resulted in aggressive phenotypes: increased migration/invasion/proliferation, EMT, elevated SLCs, evidenced by spheroid formation for successive generations, increased ALDH activity and co-expression of COX-2/SLC markers. These changes were reversed with COX-2 inhibitor or EP4A, indicating dependence on COX-2/EP4 activities. COX-2 overexpression or EP4 agonist treatment of COX-2 low cells caused up-regulation of NOTCH/WNT pathway genes, blocked with PI3K/AKT inhibitors. Supporting above findings, micro-array analysis showed up-regulation of numerous SLC-regulatory and EMT-associated genes in MCF-7-COX-2 cells. MCF-7-COX-2 cells showed increased orthotopic tumorigenicity and spontaneous multi-organ metastases in NOD/SCID/IL-2Rγ-deficient mice for successive generations with limiting cell inocula. Orthotopic tumors showed significant up-regulation of VEGF-A/C/D, Vimentin and phospho-AKT, down-regulation of E-Cadherin and enrichment of SLC marker positive and spheroid forming cells. MCF-7-COX-2 cells also showed increased lung colonization in NOD/SCID/GUSB-null mice, an effect reversed with EP4 knockdown or EP4A treatment. COX-2, EP4 and ALDH1A expression in situ in human breast cancer tissues were highly correlated with one other, more marked in progressive stage of disease. High COX-2/EP4 expression was linked with poor survival. Thus EP4 represents a novel SLC-ablative target in human breast cancer. (Supported by a grant of the OICR to PKL and a TBCRU fellowship to MM) Citation Format: Mousumi Majumder, Xiping Xin, Ling Liu, Elena Tutunea-Fatan, Mauricio Rodriguez-Torres, Krista Vincent, Andrew Deweyert, Lynne-Marie Postovit, David Hess, Peeyush K. Lala. Breast cancer stem cell induction by COX-2 via EP4/PI3K-AKT/NOTCH-WNT axis: EP4 as therapeutic target. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3315.

Abstract 3078: GSK-3 inhibitor 9ING41 potentiates the antitumor effects of CPT-11 in human breast cancer

Abstract Glycogen Synthase Kinase-3beta (GSK-3beta), a serine/threonine protein kinase, has been demonstrated to be potential therapeutic target in human breast cancer. Our objective was to evaluate novel GSK-3 inhibitors alone and in combination with chemotherapeutic drugs for the targeted therapy of breast cancer. Using a short-term treatment, we found that the GSK-3 inhibitor 9ING41 significantly potentiates the antitumor effects of CPT-11, cisplatin and 5-FU to inhibit breast cancer cell growth. We established hormone-refractory BC-1 and BC-2 patient-derived xenograft (PDX) tumor models from metastatic pleural effusions that were obtained from breast cancer patients. We considered BC-1 and BC-2 PDX tumors as chemoresistant, because metastatic disease progressed in both cases in despite of the fact that patients received many cycles of chemotherapy. Although we found that BC-1 and BC-2 PDX tumors express estrogen receptor (ER), both PDX tumors carried activating mutations in ESR1. These mutations confer ligand-independent activity of the ER in tamoxifen-resistant breast tumors. We found that BC-1 and BC-2 PDX tumors grew without estradiol supplementation in immunodeficient mice, which suggests a hormone-refractory nature of these tumors. We found that GSK-3 inhibitor 9ING41 potentiates the effects of chemotherapeutic drug CPT-11, and leads to the regression of BC-1 and BC-2 breast PDX tumors. Our results demonstrate inhibition of GSK-3 as a promising therapeutic approach to overcome breast cancer chemoresistance, and identify GSK-3 inhibitor 9ING41 as a drug candidate for the targeted therapy of human breast cancer. Citation Format: Andrey Ugolkov, Irina Gaisina, Kevin White, Alan Kozikowski, Thomas O’Halloran, Andrew Mazar. GSK-3 inhibitor 9ING41 potentiates the antitumor effects of CPT-11 in human breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3078.

COX-2 Induces Breast Cancer Stem Cells via EP4/PI3K/AKT/NOTCH/WNT Axis.

Cancer stem-like cells (SLC) resist conventional therapies, necessitating searches for SLC-specific targets. We established that cyclo-oxygenase(COX)-2 expression promotes human breast cancer progression by activation of the prostaglandin(PG)E-2 receptor EP4. Present study revealed that COX-2 induces SLCs by EP4-mediated NOTCH/WNT signaling. Ectopic COX-2 over-expression in MCF-7 and SKBR-3 cell lines resulted in: increased migration/invasion/proliferation, epithelial-mesenchymal transition (EMT), elevated SLCs (spheroid formation), increased ALDH activity and colocalization of COX-2 and SLC markers (ALDH1A, CD44, β-Catenin, NANOG, OCT3/4, SOX-2) in spheroids. These changes were reversed with COX-2-inhibitor or EP4-antagonist (EP4A), indicating dependence on COX-2/EP4 activities. COX-2 over-expression or EP4-agonist treatments of COX-2-low cells caused up-regulation of NOTCH/WNT genes, blocked with PI3K/AKT inhibitors. NOTCH/WNT inhibitors also blocked COX-2/EP4 induced SLC induction. Microarray analysis showed up-regulation of numerous SLC-regulatory and EMT-associated genes. MCF-7-COX-2 cells showed increased mammary tumorigenicity and spontaneous multiorgan metastases in NOD/SCID/IL-2Rγ-null mice for successive generations with limiting cell inocula. These tumors showed up-regulation of VEGF-A/C/D, Vimentin and phospho-AKT, down-regulation of E-Cadherin and enrichment of SLC marker positive and spheroid forming cells. MCF-7-COX-2 cells also showed increased lung colonization in NOD/SCID/GUSB-null mice, an effect reversed with EP4-knockdown or EP4A treatment of the MCF-7-COX-2 cells. COX-2/EP4/ALDH1A mRNA expression in human breast cancer tissues were highly correlated with one other, more marked in progressive stage of disease. In situ immunostaining of human breast tumor tissues revealed co-localization of SLC markers with COX-2, supporting COX-2 inducing SLCs. High COX-2/EP4 mRNA expression was linked with reduced survival. Thus, EP4 represents a novel SLC-ablative target in human breast cancer. Stem Cells 2016;34:2290-2305.

HOXB7-S3 inhibits the proliferation and invasion of MCF-7 human breast cancer cells.

Homeobox B7 (HOXB7) has been found to be overexpressed in numerous types of human cancer. However, the role of HOXB7 in breast cancer remains to be elucidated. The aim of the present study was to investigate the effects of HOXB7 on the proliferation and invasion of breast cancer cells. Initially, reverse transcription quantitative polymerase chain reaction and western blotting were respectively employed to detect the mRNA and protein expression levels of the HOXB7 gene in the MDA-MB-231 and MCF-7 human breast cancer cell lines. Subsequently, small interfering RNAs designed to interfere with the expression of HOXB7 were used to knockdown the expression of HOXB7 in the MCF-7 cell line, the effects of which on cell proliferation, the apoptotic rate and invasion capacity were measured using a Cell Counting kit-8 assay, flow cytometry and transwell chambers, respectively. The results demonstrated that HOXB7 mRNA and protein were all overexpressed in MDA-MB-231 and MCF-7 breast cancer cell lines. Furthermore, HOXB7-S3 effectively inhibited the proliferation and invasion of MCF-7 breast cancer cells. In conclusion, these results demonstrated that HOXB7 may be a potential therapeutic target in human breast cancer.

Peroxisome Proliferator-Activated Receptor as a Therapeutic Target in Human Breast Cancer

Objective: Peroxisome proliferator-activated receptor γ (PPARγ) is aberrantly expressed in most breast tumors, suggesting the potential of agents that target this receptor in treatment and chemoprevention of breast cancer. However, whether PPARγ leads to the promotion or reduction of tumor formation has remained controversial and is further complicated by the ability of its available thiazolidinedione (TZD) ligands to activate another PPAR subtype, PPARδ. Method: To examine the role of each receptor in breast cancer biology, we performed a systematic evaluation of PPARγ and PPARδ agonists on the growth of human estrogen receptor (ER)-positive and -negative breast cancer cells. Results: In this manner we found that TZD-activated PPARγ was highly effective in suppressing the proliferation of estrogen-dependent cancer cells. Activated PPARδ, however, displayed growth-enhancing effects independent of estradiol and regardless of the ER status of the cells. Strikingly, in ER-negative cancer cells expressing a favorable PPARδ/γ ratio, TZDs promoted growth in a PPAR γ-independent manner by direct activation of PPARδ. A screen for ligands with increased receptor selectivity compared to TZDs revealed that GW7845 functioned as a full agonist of PPARγ, yet this agent lacked the ability to activate PPARδ and elicit its associated mitogenic effects. Conclusion: These studies indicate that selective PPAR γ modulators (SPPARγMs) that lack agonist activity on PPARδ may be clinically useful in future cancer treatment and chemoprevention.

Downregulation of high mobility group box 1 modulates telomere homeostasis and increases the radiosensitivity of human breast cancer cells.

The functions of the high mobility group box 1 (HMGB1) in tumor cells include replenishing telomeric DNA and maintaining cell immortality. There is a negative correlation between human telomerase reverse transcriptase (hTERT) and radiosensitivity in tumor cells. Our aim was to elucidate the relationship among HMGB1, telomere homeostasis and radiosensitivity in MCF-7 cells. In this study, we established stably transfected control (MCF-7-NC) and HMGB1 knockdown (MCF-7-shHMGB1) cell lines. The expression of HMGB1 mRNA and the relative telomere length were examined by real-time PCR. Radiosensitivity was detected by clonogenic assay. The protein expressions were determined by western blot analysis. The telomerase activity was detected by PCR-ELISA. Proliferation ability was examined by CCK-8 assay. Cell cycle and apoptosis were examined by flow cytometry. DNA damage foci were detected by immunofluorescence. ShRNA-mediated downregulation of HMGB1 expression increased the radiosensitivity of MCF-7 cells, and reduced the accumulation of hTERT and cyclin D1. Moreover, knockdown of HMGB1 in MCF-7 cells inhibited telomerase activity and cell proliferation, while increasing the extent of apoptosis. Downregulation of HMGB1 modulated telomere homeostasis by changing the level of telomere-binding proteins, such as TPP1 (PTOP), TRF1 and TRF2. This downregulation also inhibited the ATM and ATR signaling pathways. The current data demonstrate that knockdown of HMGB1 breaks telomere homeostasis, enhances radiosensitivity, and suppresses the repair of DNA damage in human breast cancer cells. These results suggested that HMGB1 might be a potential radiotherapy target in human breast cancer.

IL-32 promotes breast cancer cell growth and invasiveness.

Interleukin (IL)-32 is a newly identified cytokine in humans and primates. It has been established that IL-32 may antagonize cancer growth. However, to the best of our knowledge, the direct effect of IL-32 on breast cancer cell growth has not yet been investigated. In addition, rodents lack the expression of IL-32; hence, the effects of IL-32 on breast cancer xenografts in nude mice have not been studied. The present study aimed to examine the potential regulatory effects of IL-32 on breast cancer cells in nude mice. The effects of IL-32 on tumor cell growth in cell cuture and a tumor xenograft model were investigated, as well as the effects of IL-32 on apoptosis. The effects of IL-32 on cell proliferation and apoptosis were investigated by MTT assay and TUNEL staining, respectively. The results revealed that IL-32 increases the proliferation rate of cancer cells and decreases the rate of apoptosis, In addition, IL-32 was found to enhance the growth of tumor xenografts in vivo. In summary, IL-32 may represent a useful therapeutic target for human breast cancer.