Aggressive Breast Cancer Phenotype Research Articles

Abstract CC02-01: Regulation of FASN expression through a novel IGF-1R-mTORC1-SRPK2-SRSF1 pathway

Abstract BACKGROUND FASN expression is associated with a more aggressive breast cancer phenotype and is both transcriptionally and post-transcriptionally regulated downstream of receptor tyrosine kinase signaling pathways. Lipogenic transcripts, such as FASN, can be post-transcriptionally regulated through pre-mRNA splicing mediated through serine arginine rich protein kinases (SRPKs) and their respected substrates, serine-arginine rich splicing factors (SRSFs). Recent work has highlighted the mTORC1 signaling pathway as an upstream inducer of lipogenic pre-mRNA splicing, however, the role of extracellular environmental cues, such as growth factors and their respected receptors have not been explored. Here, an IGF-1-mTORC1-SRPK2 axis is demonstrated in the FASN regulation through SRSF-1 in breast cancer. METHODS: MDA-MB-231, MCF-7 breast cancer or MCF-10A non-transformed cells were exposed to IGF-1 followed by siRNA knockdown of IGF-1R, SRPK2, or SRSF-1. FASN expression was quantified by RT-qPCR or western blot analysis and de novo palmitate was measured by U-13C glucose incorporation followed by GS-MS. For mRNA stability, cells were pretreated with actinomycin-D with either vehicle or SRPK2 inhibitor for various timepoints followed by RT-qPCR for lipogenic and glycolytic mRNA abundance. eGFP-SRSF-1 was transfected in MDA-MB-231 and MCF-7 to visualize SRSF-1 localization in response to mTORC1 inhibition and/or SRPK2 knockdown and visualized by fluorescence microscopy. For intron retention, RT-PCR was performed with FASN intron and exon specific primers and resolved on a 2.5% agarose gel. RESULTS: Both IGF-1R and SRPK2 RNAi mediated knockdown significantly reduced FASN mRNA and protein and de novo synthesized palmitate levels. Similar results were obtained with mTORC1 inhibition. IGF-1 promoted the stabilization of FASN mRNA as well as reduced intron retention. This reduction of intron retention upon IGF-1 was abolished by SRPK2 knockdown. Additionally, IGF-1 contributed to a more diffuse localization in the nucleoplasm of SRSF-1, which become more retained in nuclear speckles upon both SRPK2 knockdown and mTORC1 inhibition. CONCLUSION These current findings establish a potential IGF-1-mTORC1-SRPK2 axis in breast cancer that contributes to metabolic programming through FASN. More specifically, SRSF-1 is the potential mediator of FASN expression through this pathway, which could be a potential therapeutic target for breast cancers that overexpress FASN and components of the IGF-1R signaling axis. Citation Format: Bryan Mcclellan, Paul Gries, Brittany Harlow, Andrew Brenner, Stefano Tiziani, Christopher Jolly, Linda deGraffenried. Regulation of FASN expression through a novel IGF-1R-mTORC1-SRPK2-SRSF1 pathway [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr CC02-01.

High endogenous CCL2 expression promotes the aggressive phenotype of human inflammatory breast cancer

Inflammatory Breast Cancer (IBC) is a highly aggressive malignancy with distinct clinical and histopathological features whose molecular basis is unresolved. Here we describe a human IBC cell line, A3250, that recapitulates key IBC features in a mouse xenograft model, including skin erythema, diffuse tumor growth, dermal lymphatic invasion, and extensive metastases. A3250 cells express very high levels of the CCL2 chemokine and induce tumors enriched in macrophages. CCL2 knockdown leads to a striking reduction in macrophage densities, tumor proliferation, skin erythema, and metastasis. These results establish IBC-derived CCL2 as a key factor driving macrophage expansion, and indirectly tumor growth, with transcriptomic analysis demonstrating the activation of multiple inflammatory pathways. Finally, primary human IBCs exhibit macrophage infiltration and an enriched macrophage RNA signature. Thus, this human IBC model provides insight into the distinctive biology of IBC, and highlights potential therapeutic approaches to this deadly disease.

The expression and significance of 8-hydroxydeoxyguanosine in breast cancer patients’ blood, urine and cancer tissue

Objective: To explore the expression and clinic significance of 8-OHdG in breast cancer. Methods: Pre-operative serum 8-OHdG levels were detected with an enzyme-linked immunosorbent assay in a well-defined series of 173 breast cancer patients. 8-OHdG expression in cancer cells from 150 of these patients was examined by immunohistochemistry. The HPLC-ECD method is used to determine 8-OHdG concentration in urine. Results: The serum 8-OHdG levels and immunohistochemical 8-OHdG expression were in concordance with each other (P < 0.05, r = 0.163). Breast cancer patients with negative 8-OHdG immunostaining show lower survival rate according to the multivariate analysis (P < 0.01). This observation was even more remarkable in ductal carcinomas (n = 140) patients (P < 0.001). A low serum 8-OHdG level was associated statistically significantly with lymphatic vessel invasion and a positive lymph node status. Comparison of 8-OHdG concentration in urine of breast cancer patients and healthy women was statistical significance (P < 0.01). Conclusion: Low serum 8-OHdG levels and a low immunohistochemical 8-OHdG expression were associated with an aggressive breast cancer phenotype. In addition, negative 8-OHdG immunostaining was an independent prognostic factor for breast cancer-specific death in breast carcinoma patients. Using 8-OHdG concentration in urine to predict DNA damage resulting from breast cancer can provide good biological indicators for detecting harm in early breast cancer.

Estrogen receptor variant ERα46 and insulin receptor drive in primary breast cancer cells growth effects and interleukin 11 induction prompting the motility of cancer-associated fibroblasts.

Among the prognostic and predictive biomarkers of breast cancer (BC), the role of estrogen receptor (ER)α wild‐type has been acknowledged, although the action of certain ERα splice variants has not been elucidated. Insulin/insulin receptor (IR) axis has also been involved in the progression and metastasis of BC. For instance, hyperinsulinemia, which is often associated with obesity and type 2 diabetes, may be a risk factor for BC. Similarly, an aberrant expression of IR or its hyperactivation may correlate with aggressive BC phenotypes. In the present study, we have shown that a novel naturally immortalized BC cell line (named BCAHC‐1) is characterized by a unique expression of 46 kDa ERα splice variant (ERα46) along with IR. Moreover, we have shown that a multifaceted crosstalk between ERα46 and IR occurs in BCAHC‐1 cells upon estrogen and insulin exposure for growth and pulmonary metastasis. Through high‐throughput RNA sequencing analysis, we have also found that the cytokine interleukin‐11 (IL11) is the main factor linking BCAHC‐1 cells to breast cancer‐associated fibroblasts (CAFs). In particular, we have found that IL11 induced by estrogens and insulin in BCAHC‐1 cells regulates pro‐tumorigenic genes of the “extracellular matrix organization” signaling pathway, such as ICAM‐1 and ITGA5, and promotes both migratory and invasive features in breast CAFs. Overall, our results may open a new scientific avenue to identify additional prognostic and therapeutic targets in BC.

Expression profile of tumour suppressor protein p53 and its regulator MDM2 in a cohort of breast cancer patients in a Tertiary Hospital in Ghana.

BackgroundInactivation or mutation of the tumour suppressor gene p53 or its regulator mouse double minute 2 (MDM2) is the commonest event in breast cancer. These altered genes usually express abnormally high levels of their proteins in many carcinomas. The phenotypic expression of p53 and MDM2 in breast cancer cases in our setting is not known. This study investigated the expression of the tumour suppressor protein p53 and its regulator MDM2, using immunohistochemistry in a Ghana breast cancer cohort.MethodA 9-year retrospective cross-sectional study on archived tissue blocks–formalin fixed paraffin embedded tissue (FFPE) was carried out. Demographic data were abstracted. Based on complete clinical data and availability of FFPE archived blocks 203 cases were selected for tissue micro array (TMA) construction. The TMA sections were subjected to immunohistochemistry (IHC) (ER, PR, HER2, p53, and MDM2). Expression of p53 and MDM2 were related to grade and molecular subtypes.ResultsThe age ranged from 17 to 92 years (mean = 49.34 ± 13.74). Most of the cases were high grade; grade II (34.9%) and grade III (55.7%). Fifty-four percent of the cases were triple negative. Invasive ductal carcinoma no special type was the commonest histotype (87.1%). Thirty-six percent (36%) of the cases expressed p53. Significant associations were found between p53 overexpression and histological grade (p = 0.034), triple negative (p = 0.0333) and luminal B (p<0.01) tumors. Most cases (93.1%) were negative for MDM2 expression. Significant association was found between MDM2 and HER2 over-expression as well as Ki-67. There was no significant positive correlation between MDM2 and p53 co-expression (p>0.05).ConclusionThe elevated level of p53 expression in the aggressive breast cancer phenotypes (high histological grade and triple negative) in our cohort suggest that P53 elevation may be a poor prognostic marker in our setting. High expression of MDM2 in our cohort with high Ki67; also in cases with Her2/neu overexpression known with predictable poor prognosis in the absence of target therapy suggest MDM2 may be associated with aggressive biological behaviour in our breast cancer cases. The non-significant association of p53 and MDM2 expression in the same cases as also documented by previous studies suggest independent genetic pathway in tumourigenesis.

In Vitro Investigations of miR-33a Expression in Estrogen Receptor-Targeting Therapies in Breast Cancer Cells.

Simple SummaryAltered metabolic pathways determine the aggressivity of breast cancer cells. To highlight the potential markers gains importance to understand early molecular signatures of disease. microRNAs are the small non-coding RNAs found in different biological samples. Due to the dysregulation of metabolic pathways, the expression and secretion of microRNAs are modulated.(1) Background: Increased fatty acid synthesis leads to the aggressive phenotype of breast cancer and renders efficiency of therapeutics. Regulatory microRNAs (miRNAs) on lipid biosynthesis pathways as miR-33a have potential to clarify the exact mechanism. (2) Methods: We determined miR-33a expression levels following exposure of MCF-7 and MDA-MB-231 breast cancer cells to estrogen receptor (ER) activator (estradiol-17β, E2) or anti-estrogens (ICI 182,780, Fulvestrant, FUL) at non-cytotoxic concentrations. We related miR-33a expression levels in the cells to cellular lipid biosynthesis-related pathways through immunoblotting. (3) Results: miR-33a mimic treatment led to significantly downregulation of fatty acid synthase (FASN) in MCF-7 cells but not in MDA-MB-231 cells in the presence of estradiol-17β (E2) or Fulvestrant (FUL). In contrast to the miR-33a inhibitor effect, miR-33a mimic co-transfection with E2 or FUL led to diminished AMP-activated protein kinase α (AMPKα) activity in MCF-7 cells. E2 increases FASN levels in MDA-MB-231 cells regardless of miR-33a cellular levels. miR-33a inhibitor co-treatment suppressed E2-mediated AMPKα activity in MDA-MB-231 cells. (4) Conclusions: The cellular expression levels of miR-33a are critical to understanding differential responses which include cellular energy sensors such as AMPKα activation status in breast cancer cells.

Haploinsufficient tumor suppressor PRP4K is negatively regulated during epithelial-to-mesenchymal transition.

The pre‐mRNA processing factor 4 kinase (PRP4K, also known as PRPF4B) is an essential gene. However, reduced PRP4K expression is associated with aggressive breast and ovarian cancer phenotypes including taxane therapy resistance, increased cell migration and invasion in vitro, and cancer metastasis in mice. These results are consistent with PRP4K being a haploinsufficient tumor suppressor. Increased cell migration and invasion is associated with epithelial‐to‐mesenchymal transition (EMT), but how reduced PRP4K levels affect normal epithelial cell migration or EMT has not been studied. Depletion of PRP4K by small hairpin RNA (shRNA) in non‐transformed mammary epithelial cell lines (MCF10A, HMLE) reduced or had no effect on 2D migration in the scratch assay but resulted in greater invasive potential in 3D transwell assays. Depletion of PRP4K in mesenchymal triple‐negative breast cancer cells (MDA‐MB‐231) resulted in both enhanced 2D migration and 3D invasion, with 3D invasion correlated with higher fibronectin levels in both MDA‐MB‐231 and MCF10A cells and without changes in E‐cadherin. Induction of EMT in MCF10A cells, by treatment with WNT‐5a and TGF‐β1, or depletion of eukaryotic translation initiation factor 3e (eIF3e) by shRNA, resulted in significantly reduced PRP4K expression. Mechanistically, induction of EMT by WNT‐5a/TGF‐β1 reduced PRP4K transcript levels, whereas eIF3e depletion led to reduced PRP4K translation. Finally, reduced PRP4K levels after eIF3e depletion correlated with increased YAP activity and nuclear localization, both of which are reversed by overexpression of exogenous PRP4K. Thus, PRP4K is a haploinsufficient tumor suppressor negatively regulated by EMT, that when depleted in normal mammary cells can increase cell invasion without inducing full EMT.

Pri-miR526b and Pri-miR655 Are Potential Blood Biomarkers for Breast Cancer.

Simple SummaryPreviously, we reported that the expression of two oncogenic miRNAs, miR526b and miR655, in poorly metastatic breast cancer cells enhances aggressive breast cancer phenotypes. Furthermore, miR526b and miR655 expression in breast tumors is associated with poor patient survival. We recently showed that both miRNAs are major regulators of the tumor microenvironment and can be detected in cell-free tumor cell secretions. Therefore, we wanted to test the biomarker potential of these two miRNAs. Early detection can improve breast cancer patient survival by 98%. Here, we report novel findings that precursors of both miRNAs, pri-miR526b and pri-miR655, are sensitive and robust blood biomarkers to distinguish cancer from benign plasmas. Pri-miR526b proved to be a very sensitive biomarker in detecting breast cancer at an early stage. Hence, pri-miR526b can be used as an early diagnostic biomarker for breast cancer.We reported that two microRNAs, miR526b and miR655, are oncogenic in breast cancer (BC). Overexpression of these two miRNAs in poorly metastatic BC cells promotes aggressive BC phenotypes in vitro and in vivo. High expression of each miRNA was associated with poor patient survival. In this pilot biomarker study, we report for the first time that miRNA precursor RNAs (pri-miRNAs) are robust and sensitive biomarkers for BC, detectable in both human blood plasma and biopsy tissues. Pri-miRNA detection and quantification do not require a special enrichment procedure, thus reducing specimen quantity. Blood plasma samples from 90 malignant tumor-bearing patients and 20 benign lesion-bearing participants (control) were analyzed for pri-miRNA expression with a quantitative real-time polymerase chain reaction. Results revealed that normalized expressions of plasma pri-miR526b and pri-miR655 are significantly upregulated in malignancy compared to benign plasmas (p = 0.002 and p = 0.03, respectively). Both pri-miRNAs showed more prominent results to distinguish stage I plasmas from benign plasmas (p = 0.001 for pri-miR526b and p = 0.0001 for pri-miR655). We have also validated pri-miRNA expression in independent tumor bank tissues, showing significant upregulation of both pri-miRNAs in BC; thus, pri-miRNAs are robust markers. The diagnostic relevance of pri-miRNAs was computed with the area under the curve (AUC). Pri-miR526b is a sensitive biomarker to distinguish cancer from control plasmas (sensitivity of 86%; AUC = 71.47%, p = 0.0027) with a positive predictive value of 88.89%; however, pri-miR655 did not show significant sensitivity. Furthermore, pri-miR526b could also significantly distinguish tumors as early as stage I from control (sensitivity of 75%; AUC = 72.71%, p = 0.0037). Therefore, pri-miR526b can be used as an early diagnostic biomarker. The expression of both pri-miRNAs was significantly high in ER-positive and HER2-negative subgroups of BC; hence, these biomarkers might play a role in the management of endocrine therapy designs. Additionally, with a case–control cohort study, we identified that high expression of pri-miR526b in the blood is also a risk factor associated with breast cancer (OR = 4.3, CI = 1.39–13.34, p = 0.01). Pri-miRNAs could be considered novel breast cancer blood biomarkers.

DIF-1 inhibits growth and metastasis of triple-negative breast cancer through AMPK-mediated inhibition of the mTORC1-S6K signaling pathway.

We have previously reported that the differentiation-inducing factor-1 (DIF-1), a compound identified in Dictyostelium discoideum, suppresses the growth of MCF-7 breast cancer cells by inactivating p70 ribosomal protein S6 kinase (p70S6K). Therefore, we first examined whether the same mechanism operates in other breast cancer cells, especially triple-negative breast cancer (TNBC), the most aggressive and refractory phenotype of breast cancer. We also investigated the mechanism by which DIF-1 suppresses p70S6K by focusing on the AMPK-mTORC1 system. We found that DIF-1 induces phosphorylation of AMPK and Raptor and dephosphorylation of p70S6K in multiple TNBC cell lines. Next, we examined whether AMPK-mediated inhibition of p70S6K leads to the suppression of proliferation and migration/infiltration of TNBC cells. DIF-1 significantly reduced the expression levels of cyclin D1 by suppressing the translation of STAT3 and strongly suppressed the expression levels of Snail, which led to the suppression of growth and motility, respectively. Finally, we investigated whether DIF-1 exerts anticancer effects on TNBC in vivo. Intragastric administration of DIF-1 suppressed tumor growth and spontaneous lung metastasis of 4T1-Luc cells injected into the mammary fat pad of BALB/c mice. DIF-1 is expected to lead to the development of anticancer drugs, including anti-TNBC, by a novel mechanism.

Abstract 2326: Differential lipid metabolism in mammary cancer cell progression

Abstract There is an association between increased lipid accumulation and aggressive breast cancer phenotypes, and therefore poorer clinical outcomes. The mechanism by which dysregulated lipid metabolism may promote metastasis remains incompletely understood. Several potential mechanisms by which the neutral lipid storage organelles, cytoplasmic lipid droplets, may promote metastasis include utilization of fatty acids (FAs) for oxidation, protection against lipotoxcity, and production of lipid signaling mediators. We have previously demonstrated that metastatic MCF10CA1a mammary cancer cells rely on fatty acid oxidation (FAO) compared to non-metastatic MCF10A-ras cells, using etomoxir to inhibit the rate-limiting enzyme of FAO, carnitine palmitoyltransferase 1 (CPT1). Previous literature indicates that there is an increase in various lipid metabolism pathways, including FA uptake, de novo lipogenesis, and FA storage in neutral lipid. We found that there is no significant difference between palmitic acid uptake between the non-metastatic and metastatic cells. In the current study, we show that MCF10CA1a cells have significantly higher levels of carbon incorporation into palmitic and oleic FAs from 13C-acetate (25% and 20% greater), 13C-glucose (21% and 11% greater), and 13C-lactate (29% and 22% greater) respectively, compared to the MCF10A-ras cells, as detected by LC-MS/MS. In order to determine the source of FAs that contributes to the migration-dependent FAO, we assessed MCF10CA1a cell migration following inhibition of lipolysis (adipose triglyceride lipase—ATGL; ATGListatin) alone or in combination with the FAO inhibitor, etomoxir. We determined that inhibition of ATGL, the initial enzyme of triglyceride lipolysis pathway, significantly reduces MCF10CA1a cell migration (20% decrease compared to vehicle). Inhibition of FAO and lipolysis did not induce additional reduction in cell migration. We also showed that MCF10CA1a cells are more dependent on FA metabolism than the non-metastatic MCF10A-ras cells, demonstrated by MCF10CA1a cells having a greater decrease in cell viability compared to the MCF10A-ras cells given each FA metabolism inhibition (p&amp;lt;0.05: 22% greater decrease for FAO inhibition and 16% greater decrease for dual FAO and lipolysis inhibition, p=0.05: 17% greater decrease for FA synthesis inhibition). These data suggest that metastatic MCF10CA1a cells rely on their increased FA metabolism to survive and migrate, and specifically that the catabolism of FAs from triglyceride supports the FAO-driven migration of metastatic cancer cells. Citation Format: Chaylen Andoline, Parik Pawar, Dorothy Teegarden. Differential lipid metabolism in mammary cancer cell progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2326.

Abstract 2396: Role of iron transporter DMT1 in endosome-mitochondria interactions and mitochondrial metabolism in breast cancer cells

Abstract Iron is essential to support tumor initiation, growth and metastasis. Recently, we have shown that interaction between early endosomes and mitochondria regulates intracellular iron transport in epithelial cells. Mitochondria are the ultimate cellular iron sink, where iron can be either used for Iron-Sulfur cluster and heme synthesis or stored in mitochondrial ferritin. Further understanding how endosomes interact with mitochondria to modulate iron transport in breast cancer cells should provide novel insights into both prevention and treatment of breast cancer. Here, we sought to evaluate the role of the iron transporter Divalent Metal Transporter 1 (DMT1) in endosome-mitochondria interactions, iron transport into mitochondria and its functional consequences in invasive migration and mitochondrial metabolism in breast cancer cells. For silencing experiments, we used CRISPR/Cas9 technology validated by immunoblotting. Leica Thunder microscope and LAS software were used for imaging. High resolution imaging was performed using Airyscan LSM880. Z-stack images were subjected to 3D rendering using IMARIS software to evaluate organelle morphology and organelle-organelle interactions. The Agilent Seahorse Cell Mito Stress assay was used to assess mitochondrial function. Expression of different proteins related to iron transport and signaling, e.g. DMT1, mitochondrial-ferritin, transferrin receptor and EGFR showed substantial heterogeneity between non-cancerous epithelial cells MCF10A and breast cancer cells triple negative MDA-MB-231 and estrogen receptor positive T47D cells. Live cell imaging experiments show that transferrin-containing endosomes in MDA-MB-231 and T47D are more motile compared to MCF10A. Moreover, events of “kiss and run” endosome-mitochondria interactions are more frequent in breast cancer cells. DMT1 knock-out (KO) seems to alter both early and late endosomes distribution and its colocalization with mitochondria in breast cancer cells. Functionally, DMT1 (KO) in both MDA-MB-231 and T47D decreases ERK and AKT activation which is consistent with measurable decrease in invasive migration. Metabolically, Seahorse Mito-Stress assay indicate that basal respiration, proton leak, spare capacity and non-mitochondrial oxygen consumption were severely impaired upon DMT1 KO in MDA-MB-231 and T47D cells. Overall, our results suggest that endosome-mitochondria interactions and dynamics that are required for iron import into mitochondria may be involved in the establishment of a more aggressive and invasive tumor phenotype in breast cancer. Citation Format: Jonathan Barra, Iram Nelson, Lauren Elder, Ling Wang, Margarida M. Barroso. Role of iron transporter DMT1 in endosome-mitochondria interactions and mitochondrial metabolism in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2396.

Targeting Pyruvate Kinase M2 Phosphorylation Reverses Aggressive Cancer Phenotypes.

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype with low survival rate and a lack of biomarkers and targeted treatments. Here, we target pyruvate kinase M2 (PKM2), a key metabolic component of oncogenesis. In patients with TNBC, PKM2pS37 was identified as a prominent phosphoprotein corresponding to the aggressive breast cancer phenotype that showed a characteristic nuclear staining pattern and prognostic value. Phosphorylation of PKM2 at S37 was connected with a cyclin-dependent kinase (CDK) pathway in TNBC cells. In parallel, pyruvate kinase activator TEPP-46 bound PKM2pS37 and reduced its nuclear localization. In a TNBC mouse xenograft model, treatment with either TEPP-46 or the potent CDK inhibitor dinaciclib reduced tumor growth and diminished PKM2pS37. Combinations of dinaciclib with TEPP-46 reduced cell invasion, impaired redox balance, and triggered cancer cell death. Collectively, these data support an approach to identify PKM2pS37-positive TNBC and target the PKM2 regulatory axis as a potential treatment. SIGNIFICANCE: PKM2 phosphorylation marks aggressive breast cancer cell phenotypes and targeting PKM2pS37 could be an effective therapeutic approach for treating triple-negative breast cancer.

PLAC8 promotes adriamycin resistance via blocking autophagy in breast cancer.

Adriamycin (ADM) is currently one of the most effective chemotherapeutic agents in breast cancer treatment. However, growing resistance to ADM could lead to treatment failure and poor outcome. PLAC8 was reported as a novel highly conserved protein and functioned as an oncogene or tumour suppressor in various tumours. Here, we found higher PLAC8 expression was correlated with worse outcome and aggressive phenotype in breast cancer. Breast cancer patients with higher PLAC8 expression showed potential ADM resistance. In vitro experiments further confirmed that PLAC8 inhibited by siRNA or enforced overexpression by infecting pcDNA3.1(C)‐PLAC8 plasmid correspondingly decreased or increased ADM resistance. Subsequently, we demonstrated that ectopic PLAC8 expression in MCF‐7/ADMR cell blocked the accumulation of the autophagy‐associated protein LC3 and resulted in cellular accumulation of p62. Rapamycin‐triggered autophagy significantly increased cell response to ADM, while the autophagy inhibitor 3‐MA enhanced ADM resistance. 3‐MA and PLAC8 could synergistically cause ADM resistance via blocking the autophagy process. Additionally, the down‐regulation of p62 by siRNA attenuated the activation of autophagy and PLAC8 expression in breast cancer cells. Thus, our findings suggest that PLAC8, through the participation of p62, inhibits autophagy and consequently results in ADM resistance in breast cancer. PLAC8/p62 pathway may act as novel therapeutic targets in breast cancer treatment and has potential clinical application in overcoming ADM resistance.

Cleavage of Syndecan-1 Promotes the Proliferation of the Basal-Like Breast Cancer Cell Line BT-549 Via Akt SUMOylation.

Basal-like breast cancer is characterized by an aggressive clinical outcome and presence of metastasis, for which effective therapies are unavailable. We have previously shown that chondroitin 4-O-sulfotransferase-1 (C4ST-1) controls the invasive properties of the basal-like breast cancer cell line BT-549 by inducing matrix metalloproteinase (MMP) expression through the N-cadherin/β-catenin pathway. Here we report that C4ST-1 controls the proliferation of BT-549 cells via the MMP-dependent cleavage of syndecan-1. Syndecan-1 is a membrane-bound proteoglycan associated with an aggressive phenotype and poor prognosis in breast cancer. In addition, the cleavage of syndecan-1 at a specific juxtamembrane cleavage site is implicated in the pathophysiological response in breast cancer. Knockout of C4ST-1 remarkably suppressed both the cleavage of syndecan-1 and proliferation of BT-549 cells. Kinases (AKT1, ERK1/2, PI3K, and STAT3) comprising cancer proliferative pathways are phosphorylated in C4ST-1 knockout cells at a level similar to that in parental BT-549 cells, whereas levels of phosphorylated S6 kinase and SUMOylated AKT (hyperactivated AKT observed in breast cancer) decreased in C4ST-1 knockout cells. An MMP inhibitor, GM6001, suppressed the small ubiquitin-like modifier (SUMO) modification of AKT, suggesting that cleavage of syndecan-1 by MMPs is involved in the SUMO modification of AKT. Forced expression of the cytoplasmic domain of syndecan-1, which is generated by MMP-dependent cleavage, increased the SUMO modification of AKT and global protein SUMOylation. Furthermore, syndecan-1 C-terminal domain-expressing BT-549 cells were more proliferative and sensitive to a potent SUMOylation inhibitor, tannic acid, compared with BT-549 cells transfected with an empty expression vector. These findings assign new functions to the C-terminal fragment of syndecan-1 generated by MMP-dependent proteolysis, thereby broadening our understanding of their physiological importance and implying that the therapeutic inhibition of syndecan-1 cleavage could affect the progression of basal-like breast cancer.

A novel autophagy-related genes prognostic risk model and validation of autophagy-related oncogene VPS35 in breast cancer

BackgroundAccumulating evidence implies that autophagy plays a critical role in breast cancer development and progression. It is crucial to screen out autophagy-related encoding genes (ARGs) with prognostic value in breast cancer and reveal their biological properties in the aggressiveness of breast cancer.MethodsUnivariate and multivariate Cox proportional hazards analyses were used to identify a prognostic risk model of ARGs from The Cancer Genome Atlas (TCGA). Kaplan–Meier analysis, univariate and multivariate Cox regression analyses and receiver operating characteristic (ROC) curve analysis were performed to validate the risk model. Western blot and immunohistochemistry (IHC) were conducted to assess the expression of VPS35 (one of ARGs in risk model). CCK8, Colony formation assay, Transwell migration/invasion assays and autophagy flux assay were used to confirm biological function of VPS35 in breast cancer.ResultsIn this study, the prognostic risk model consisting of six ARGs (VPS35, TRIM21, PRKAB2, RUFY4, MAP1LC3A and LARP1) in breast cancer were identified. The risk model was further verified as a novel independent prognostic factor for breast cancer patients. We also clarified that vacuolar protein sorting-associated protein 35 (VPS35), one of ARGs in the risk model, was upregulated in breast cancer samples and cell lines. VPS35 overexpression was correlated with more aggressive phenotype of breast cancer and indicated worse prognosis in both progression-free survival and overall survival analyses. Meanwhile, VPS35 knockdown inhibited breast cancer cell proliferation, migration and invasion, suggesting that VPS35 promoted the progression of breast cancer. VPS35 silence also influenced autophagy process, indicating that VPS35 was essential for autophagy completion.ConclusionTaken together, the six ARGs risk model has a remarkably prognostic value for breast cancer. Among them, VPS35 might exert as a significant oncogenic and prognostic factor for breast cancer and could be a promising autophagy-related therapeutic target in clinical practice.

SCD5 expression correlates with prognosis and response to neoadjuvant chemotherapy in breast cancer

Neoadjuvant chemotherapy (NACT) represents a standard option for breast cancer. Unfortunately, about 55–80% of breast cancer patients do not have a favorable response to chemotherapy. Highly specific tumor biomarker that can predict the pathological response to neoadjuvant chemotherapy is lacking. Stearoyl-CoA desaturase 5 (SCD5) is an integral membrane protein of the endoplasmic reticulum that participates in lipid metabolism. Previous studies on the role of SCD5 in human cancers drew different conclusions. Therefore, the role of SCD5 in breast cancer remains unclear. Our study aims to understand its expression signature, prognosis value and correlation with pathological response to NACT in breast cancer using bioinformatics from public databases. Analysis of samples from public databases showed that SCD5 expression was down-regulated in some human cancers including breast cancer, and low expression of SCD5 was associated with more aggressive breast cancer phenotypes. Survival analysis revealed that SCD5 expression was related to prognosis in breast cancer. Integrated analysis of multiple public datasets indicated that SCD5 expression signature was associated with pathological response to NACT, particularly in TNBC. Based on functional enrichment analysis, the most affected biological functions in high SCD5-expressing breast cancer tissues were involved in negative regulation of cell cycle. Moreover, a significantly negative correlation between SCD5 expression and several cell cycle regulators was noted. Taken together, SCD5 was involved in the development and progression of breast cancer and might be a predictive biomarker for response to NACT. In conclusion, SCD5 could serve as a predictive biomarker of pathological response to NACT and play a carcinostatic role in breast cancer. These results provided us with clues to better understand SCD5 from the perspective of bioinformatics and highlighted the clinical importance of SCD5 in breast cancer, especially triple negative breast cancer (TNBC).

Expression of adenosine receptors in young patients with breast cancer and its association with high proliferative index

Background: Adenosine is produced in the hypoxic tumor milieu. By stimulating its receptors, it plays an important role not only in evading the body’s immune mechanisms but also in enhancing tumor vasculature and contributing to tumor aggressiveness. Aim: The present study aimed at investigating the immunohistochemical expression of Adenosine receptors (A2A) in breast cancer tissue and its association with different clinico-pathological parameters. Materials and Methods: Thirty formalin-fixed paraffin-embedded (FFPE) breast cancer specimens were immunohistochemically stained using A2AR antibodies. All clinical and pathological data were retrospectively retrieved from the patients’ records. Results: Cytoplasmic expression of A2ARs was noted not only on the tumor immune cells but also on the tumor cells themselves. They were strongly expressed on the tumor cells in 73.3% (n=22) of tumors. Expression was significantly higher in younger aged patients ( 20%) [p=0.018]. No association was observed between A2AR expression and tumor size, type, grade, Lymph node status, percentage of TILs or patient survival after 2 years of follow-up. Conclusion: These findings suggest a possible role for Adenosine in imparting a more aggressive phenotype in breast cancer and that targeting these receptors using Adenosine receptor antagonists could have a potential role in improving the outcome of these patients.

Quercetin blocks the aggressive phenotype of triple-negative breast cancer by inhibiting IGF1/IGF1R-mediated EMT program.

The cancer-preventive activities of quercetin have been extensively studied in invasive breast cancer; however, the role of quercetin on triple-negative breast cancer (TNBC) with overexpression of insulin-like growth factor-1 receptor (IGF1R) has not been resolved. In this article, we demonstrated that quercetin inhibited the activation of IGF1R and its downstream kinases Akt and Erk1/2 in a dose-dependent manner in human MDA-MB-231 breast cancer cells (TNBC cell line). Related to this, quercetin markedly suppressed the metastatic phenotype and epithelial–mesenchymal transition (EMT) of MDA-MB-231 cells by inhibiting the expression of EMT transcription factors Snail and Slug. Quercetin also increased the secretion of IGF-binding protein-3 in the conditioned medium of MDA-MB-231 cells while reducing the secretion of IGF1; thus, quercetin interrupted the autocrine or paracrine loop of IGF1 signaling. In xenograft mouse models, the administration of quercetin blocked the growth of MDA-MB-231 tumor xenografts and their lung metastasis, accompanied by the inactivation of IGF1R and the downregulation of the expression of Snail, Slug, and mesenchymal markers fibronectin and vimentin. These results suggest that quercetin has cancer-preventive value for TNBC by inhibiting IGF1/IGF1R signaling and preventing the consequent EMT and metastasis of TNBC.

Functional cooperation between co-amplified genes promotes aggressive phenotypes of HER2-positive breast cancer

SUMMARYMED1 (mediator subunit 1)co-amplifies with HER2, but its role in HER2-driven mammary tumorigenesis is still unknown. Here, we generate MED1 mammary-specific overexpression mice and cross them with mouse mammary tumor virus (MMTV)-HER2 mice. We observe significantly promoted onset, growth, metastasis, and multiplicity of HER2 tumors by MED1 overexpression. Further studies reveal critical roles for MED1 in epithelial-mesenchymal transition, cancer stem cell formation, and response to anti-HER2 therapy. Mechanistically, RNA sequencing (RNA-seq) transcriptome analyses and clinical sample correlation studies identify Jab1, a component of the COP9 signalosome complex, as the key direct target gene of MED1 contributing to these processes. Further studies reveal that Jab1 can also reciprocally regulate the stability and transcriptional activity of MED1. Together, our findings support a functional cooperation between these co-amplified genes in HER2+ mammary tumorigenesis and their potential usage as therapeutic targets for the treatment of HER2+ breast cancers.

99mTc-Radiolabeled Silica Nanocarriers for Targeted Detection and Treatment of HER2-Positive Breast Cancer.

IntroductionThe overexpression of Human Epidermal Growth Factor Receptor 2 (HER2) is usually associated with aggressive and infiltrating breast cancer (BC) phenotype, and metastases. Functionalized silica-based nanocarriers (SiNPs) can be labeled for in vivo imaging applications and loaded with chemotherapy drugs, making possible the simultaneous noninvasive diagnosis and treatment (theranostic) for HER2-positive BC.MethodsFirstly, FITC-filled SiNPs, were engineered with two different amounts of Hc-TZ (trastuzumab half-chain) per single nanoparticle (1:2 and 1:8, SiNPs to Hc-TZ ratio), which was 99mTc-radiolabeled at histidine residues for ex vivo and in vivo biodistribution evaluations. Secondly, nanoparticles were loaded with DOX and their in vitro and ex vivo/in vivo delivery was assessed, in comparison with liposomal Doxorubicin (Caelyx). Finally, the treatment efficacy of DOX-SiNPs-TZ (1:8 Hc-TZ) was evaluated in vivo by PET and supported by MS-based proteomics profiling of tumors.ResultsSiNPs-TZ (1:8 Hc-TZ) tumor uptake was significantly greater than that of SiNPs-TZ (1:2 Hc-TZ) at 6 hours post-injection (p.i.) in ex vivo biodistribution experiment. At 24 h p.i., radioactivity values remained steady. Fluorescence microscopy, confirmed the presence of radiolabeled SiNPs-TZ (1:8 Hc-TZ) within tumor even at later times. SiNPs-TZ (1:8 Hc-TZ) nanoparticles loaded with Doxorubicin (DOX-SiNPs-TZ) showed a similar DOX delivery capability than Caelyx (at 6 h p.i.), in in vitro and ex vivo assays. Nevertheless, at the end of treatment, tumor volume was significantly reduced by DOX-SiNPs-TZ (1:8 Hc-TZ), compared to Caelyx and DOX-SiNPs treatment. Proteomics study identified 88 high stringent differentially expressed proteins comparing the three treatment groups with controls.ConclusionThese findings demonstrated a promising detection specificity and treatment efficacy for our system (SiNPs-TZ, 1:8 Hc-TZ), encouraging its potential use as a new theranostic agent for HER2-positive BC lesions. In addition, proteomic profile confirmed that a set of proteins, related to tumor aggressiveness, were positively affected by targeted nanoparticles.