bims-merabr 2024-05-26 papers

bims-merabr

Biomed News

on Metabolic rewiring in aggressive breast cancer

Issue of 2024–05–26
thirteen papers selected by
Barbara Mensah Sankofi, University of Oklahoma Health Sciences Center

Pectinose induces cell cycle arrest in luminal A and triple-negative breast cancer cells by promoting autophagy through activation of the p38 MAPK signaling pathway.
Leptin Promotes Vasculogenic Mimicry in Breast Cancer Cells by Regulating Aquaporin-1.
Estrogen Receptor Is Required for Metformin-Induced Apoptosis in Breast Cancer Cells Under Hyperglycemic Conditions.
Genome-wide identification and analysis of epithelial-mesenchymal transition-related RNA-binding proteins and alternative splicing in a human breast cancer cell line.
Fbxo45 facilitates the malignant progression of breast cancer by targeting Bim for ubiquitination and degradation.
MIF as a potential diagnostic and prognostic biomarker for triple-negative breast cancer that correlates with the polarization of M2 macrophages.
The prognostic marker KRT81 is involved in suppressing CD8 + T cells and predicts immunotherapy response for triple-negative breast cancer.
TAZ is involved in breast cancer cell migration via regulating actin dynamics.
Laminin I mediates resistance to lapatinib in HER2-positive brain metastatic breast cancer cells in vitro.
Upregulation of collagen type X alpha 1 promotes the progress of triple-negative breast cancer via Wnt/β-catenin signaling.
BUB1 regulates non-homologous end joining pathway to mediate radioresistance in triple-negative breast cancer.
Tumor-Intrinsic Enhancer of Zeste Homolog 2 Controls Immune Cell Infiltration, Tumor Growth, and Lung Metastasis in a Triple-Negative Breast Cancer Model.
Elucidating the Role of MicroRNA-18a in Propelling a Hybrid Epithelial-Mesenchymal Phenotype and Driving Malignant Progression in ER-Negative Breast Cancer.

BMC Cancer. 2024 May 24. 24(1): 639

Pectinose induces cell cycle arrest in luminal A and triple-negative breast cancer cells by promoting autophagy through activation of the p38 MAPK signaling pathway.

Shilong Yu, Zhaoyi Yue, Qilun Liu.

  Breast cancer patients often have a poor prognosis largely due to lack of effective targeted therapy. It is now well established that monosaccharide enhances growth retardation and chemotherapy sensitivity in tumor cells. However, Pectinose whether has capability to restrict the proliferation of tumor cells remain unclear. Here, we report that Pectinose induced cytotoxicity is modulated by autophagy and p38 MAPK signaling pathway in breast cancer cell lines. The proliferation of cells was dramatically inhibited by Pectinose exposure in a dose-dependent manner, which was relevant to cell cycle arrest, as demonstrated by G2/M cell cycle restriction and ectopic expression of Cyclin A, Cyclin B, p21and p27. Mechanistically, we further identified that Pectinose is positively associated with autophagy and the activation of the p38 MAPK signaling in breast cancer. In contrast, 3-Ma or SB203580, the inhibitor of autophagy or p38 MAPK, reversed the efficacy of Pectinose suppressing on breast cancer cell lines proliferation and cell cycle process. Additionally, Pectinose in vivo treatment could significantly inhibit xenograft growth of breast cancer cells. Taken together, our findings were the first to reveal that Pectinose triggered cell cycle arrest by inducing autophagy through the activation of p38 MAPK signaling pathway in breast cancer cells,especially in luminal A and triple-negative breast cancer.

Keywords:  Autophagy; Breast cancer; Cell cycle arrest; MAPK signaling pathway

DOI:  https://doi.org/10.1186/s12885-024-12293-8
Int J Mol Sci. 2024 May 10. pii: 5215. [Epub ahead of print]25(10):

Leptin Promotes Vasculogenic Mimicry in Breast Cancer Cells by Regulating Aquaporin-1.

Deok-Soo Han, Eun-Ok Lee.

  Leptin is an obesity-related hormone that plays an important role in breast cancer progression. Vasculogenic mimicry (VM) refers to the formation of vascular channels lined by tumor cells. This study aimed to investigate the relationship between leptin and VM in human breast cancer cells. VM was measured by a 3D culture assay. Signal transducers and activators of transcription 3 (STAT3) signaling, aquaporin-1 (AQP1), and the expression of VM-related proteins, including vascular endothelial cadherin (VE-cadherin), twist, matrix metalloproteinase-2 (MMP-2), and laminin subunit 5 gamma-2 (LAMC2), were examined by Western blot. AQP1 mRNA was analyzed by a reverse transcriptase-polymerase chain reaction (RT-PCR). Leptin increased VM and upregulated phospho-STAT3, VE-cadherin, twist, MMP-2, and LAMC2. These effects were inhibited by the leptin receptor-blocking peptide, Ob-R BP, and the STAT3 inhibitor, AG490. A positive correlation between leptin and AQP1 mRNA was observed and was confirmed by RT-PCR. Leptin upregulated AQP1 expression, which was blocked by Ob-R BP and AG490. AQP1 overexpression increased VM and the expression of VM-related proteins. AQP1 silencing inhibited leptin-induced VM and the expression of VM-related proteins. Thus, these results showed that leptin facilitates VM in breast cancer cells via the Ob-R/STAT3 pathway and that AQP1 is a key mediator in leptin-induced VM.

Keywords:  Ob-R; STAT3; aquaporin-1; breast cancer cells; leptin; vasculogenic mimicry

DOI:  https://doi.org/10.3390/ijms25105215
Breast Cancer (Auckl). 2024 ;18 11782234241240173

Estrogen Receptor Is Required for Metformin-Induced Apoptosis in Breast Cancer Cells Under Hyperglycemic Conditions.

Andisyah Putri Sekar, Septia Nurmala, Eiji Matsuura, Xian Wen Tan, Ratika Rahmasari, Rani Sauriasari.

   Backgrounds: About 25% to 30% of estrogen receptor (ER)-positive breast cancer patients develop resistance to endocrine therapy. Human epidermal growth factor receptor 2 (HER2) has been shown to cooperate with several growth factors that regulate cellular energy metabolism, including the insulin-like growth factor 1 receptor (IGF-1R).
Objective: As the first-line therapy for type 2 diabetes mellitus (T2DM) patients, metformin is widely known to inhibit the metabolic reprogramming of cancer cells. This study aims to investigate metformin's efficacy in inhibiting endocrine resistance related to genes regulating energy metabolism in both ER-positive and ER-negative breast cancer cell lines under hyperglycemic conditions.
Design and methods: MDA-MB-361 (ER-positive, HER2-positive) and SKBR3 (ER-negative, HER2-positive) cancer cell lines were used to represent ER status. Cell viability and cell survival rate were measured using the colorimetric assay of Cell Counting Kit-8. All mRNA levels were quantified using real-time quantitative polymerase chain reaction preceded by reverse transcription. A P value of <.05 was considered statistically significant.
Results: Unlike MDA-MB-361, SKBR3 were found to acquire resistance upon metformin treatment in hyperglycemic conditions. Moreover, the mRNA expression of IGF-1R and its downstream signaling, such as the mammalian target of rapamycin (mTOR), was not affected by metformin. Meanwhile, the mRNA expression level of ribosomal S6 kinase 1 (S6K1) was upregulated, whereas forkhead box O1 (FOXO1) was downregulated after metformin treatment in hyperglycemic conditions.
Conclusions: This preliminary study suggests that an alternative pathway of metformin resistance may exist in the absence of ERα. Therefore, relying solely on metformin may be inadequate to inhibit the aggressiveness of breast cancer cells.

Keywords:  FOXO1; IGF-1R; Metformin; breast cancer; estrogen receptor; mTOR

DOI:  https://doi.org/10.1177/11782234241240173
Sci Rep. 2024 05 23. 14(1): 11753

Genome-wide identification and analysis of epithelial-mesenchymal transition-related RNA-binding proteins and alternative splicing in a human breast cancer cell line.

Yin Mi, Meilian Dong, Xiaoxiao Zuo, Qinchen Cao, Xiaobin Gu, Hailong Mi, Fankai Xiao.

  Exploring the mechanism of breast cancer metastasis and searching for new drug therapeutic targets are still the focuses of current research. RNA-binding proteins (RBPs) may affect breast cancer metastasis by regulating alternative splicing (AS) during epithelial-mesenchymal transition (EMT). We hypothesised that during EMT development in breast cancer cells, the expression level of RBPs and the gene AS pattern in the cell were significantly changed on a genome-wide scale. Using GEO database, this study identified differentially expressed RBPs and differential AS events at different stages of EMT in breast cancer cells. By establishing the correlation network of differential RBPs and differential AS events, we found that RBM47, PCBP3, FRG1, SRP72, RBMS3 and other RBPs may regulate the AS of ITGA6, ADGRE5, TNC, COL6A3 and other cell adhesion genes. By further analysing above EMT-related RBPs and AS in breast cancer tissues in TCGA, it was found that the expression levels of ADAT2, C2orf15, SRP72, PAICS, RBMS3, APOBEC3G, NOA1, ACO1 and the AS of TNC and COL6A3 were significantly correlated with the prognosis of breast cancer patients. The expression levels of all 8 RBPs were significantly different in breast cancer tissues without metastasis compared with normal breast tissues. Conclusively, eight RBPs such as RBMS3 and AS of TNC and COL6A3 could be used as predictors of breast cancer prognosis. These findings need to be further explored as possible targets for breast cancer treatment.

Keywords:  Alternative splicing; Breast cancer; Cell adhesion; Epithelial-mesenchymal transition; Immune escape

DOI:  https://doi.org/10.1038/s41598-024-62681-0
BMC Cancer. 2024 May 21. 24(1): 619

Fbxo45 facilitates the malignant progression of breast cancer by targeting Bim for ubiquitination and degradation.

Mengmeng Zheng, Linfeng Wu, Rongyao Xiao, Jiaohao Cai, Weike Chen, Shurong Shen.

   BACKGROUND: Breast cancer is one of the common malignancies in women. Evidence has demonstrated that FBXO45 plays a pivotal role in oncogenesis and progression. However, the role of FBXO45 in breast tumorigenesis remains elusive. Exploration of the regulatory mechanisms of FBXO45 in breast cancer development is pivotal for potential therapeutic interventions in patients with breast cancer.
METHODS: Hence, we used numerous approaches to explore the functions of FBXO45 and its underlaying mechanisms in breast cancer pathogenesis, including CCK-8 assay, EdU assay, colony formation analysis, apoptosis assay, RT-PCR, Western blotting, immunoprecipitation, ubiquitination assay, and cycloheximide chase assay.
RESULTS: We found that downregulation of FBXO45 inhibited cell proliferation, while upregulation of FBXO45 elevated cell proliferation in breast cancer. Silencing of FBXO45 induced cell apoptosis, whereas overexpression of FBXO45 inhibited cell apoptosis in breast cancer. Moreover, FBXO45 interacted with BIM and regulated its ubiquitination and degradation. Furthermore, knockdown of FBXO45 inhibited cell proliferation via regulation of BIM pathway. Notably, overexpression of FBXO45 facilitated tumor growth in mice. Strikingly, FBXO45 expression was associated with poor survival of breast cancer patients.
CONCLUSION: Our study could provide the rational for targeting FBXO45 to obtain benefit for breast cancer patients. Altogether, modulating FBXO45/Bim axis could be a promising strategy for breast cancer therapy.

Keywords:  Apoptosis; Bim; Breast cancer; Fbxo45; Proliferation

DOI:  https://doi.org/10.1186/s12885-024-12382-8
FASEB J. 2024 May 31. 38(10): e23696

MIF as a potential diagnostic and prognostic biomarker for triple-negative breast cancer that correlates with the polarization of M2 macrophages.

Mengting Chen, Hongsen Liu, Bo Hong, Yufei Xiao, Yun Qian.

  Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays a crucial role in antitumor immunity. However, the role of MIF in influencing the tumor microenvironment (TME) and prognosis of triple-negative breast cancer (TNBC) remains to be elucidated. Using R, we analyzed single-cell RNA sequencing (scRNA-seq) data of 41 567 cells from 10 TNBC tumor samples and spatial transcriptomic data from two patients. Relationships between MIF expression and immune cell infiltration, clinicopathological stage, and survival prognosis were determined using samples from The Cancer Genome Atlas (TCGA) and validated in a clinical cohort using immunohistochemistry. Analysis of scRNA-seq data revealed that MIF secreted by epithelial cells in TNBC patients could regulate the polarization of macrophages into the M2 phenotype, which plays a key role in modulating the TME. Spatial transcriptomic data also showed that epithelial cells (tumor cells) and MIF were proximally located. Analysis of TCGA samples confirmed that tumor tissues of patients with high MIF expression were enriched with M2 macrophages and showed a higher T stage. High MIF expression was significantly associated with poor patient prognosis. Immunohistochemical staining showed high MIF expression was associated with younger patients and worse clinicopathological staging. MIF secreted by epithelial cells may represent a potential biomarker for the diagnosis and prognosis of TNBC and may promote TNBC invasion by remodeling the tumor immune microenvironment.

Keywords:  M2 macrophages; MIF; TNBC; immunohistochemistry; prognosis; scRNA‐seq

DOI:  https://doi.org/10.1096/fj.202400578R
Cancer Biol Ther. 2024 Dec 31. 25(1): 2355705

The prognostic marker KRT81 is involved in suppressing CD8 + T cells and predicts immunotherapy response for triple-negative breast cancer.

Zhideng Yan, Zhihui Zhong, Chuanke Shi, Muyin Feng, Xiaoqiang Feng, Tong Liu.

  Triple-negative breast Cancer (TNBC) is an aggressive subtype lacking estrogen, progesterone, and HER2 receptors. Known for limited targeted therapies, it poses challenges and requires personalized treatment strategies. Differential analysis revealed a significant decrease in keratin 81 (KRT81) expression in non-TNBC samples and an increase in TNBC samples, lower KRT81 expression correlated with better TNBC patient outcomes. It emerged as an independent predictive factor for TNBC, with associations found between its expression and clinically relevant features. We further developed a nomogram for survival probability assessment based on Cox regression results, demonstrating its accuracy through calibration curves. Gene annotation analysis indicated that KRT81 is involved in immune-related pathways and tumor cell adhesion. KRT81 is associated with immune cell infiltration of Follicular helper T cells (Tfh) and CD8 + T cells, suggesting its potential impact on the immunological microenvironment. The study delved into KRT81's predictive value for immunotherapy responses, high expression of KRT81 was associated with greater potential for immune evasion. Single-cell RNA sequencing analysis pinpointed KRT81 expression within a specific malignant subtype which was a risk factor for TNBC. Furthermore, KRT81 promoted TNBC cell proliferation, migration, invasion, and adhesion was confirmed by gene knockout or overexpression assay. Co-culture experiments further indicated KRT81's potential role in inhibiting CD8 + T cells, and correlation analysis implied KRT81 was highly correlated with immune checkpoint CD276, providing insights into its involvement in the immune microenvironment via CD276. In conclusion, this comprehensive study positions KRT81 as a promising prognostic marker for predicting tumor progression and immunotherapy responses in TNBC.

Keywords:  CD8 + T cells; Triple-negative breast cancer; immune microenvironment; immunotherapy response; keratin 81; prognostic gene

DOI:  https://doi.org/10.1080/15384047.2024.2355705
Front Oncol. 2024 ;14 1376831

TAZ is involved in breast cancer cell migration via regulating actin dynamics.

Hong Seok Choi, Hyo-Ju Jang, Mathilde K Kristensen, Tae-Hwan Kwon.

   Background: Cancer metastasis is dependent on cell migration. Several mechanisms, including epithelial-to-mesenchymal transition (EMT) and actin fiber formation, could be involved in cancer cell migration. As a downstream effector of the Hippo signaling pathway, transcriptional coactivator with PDZ-binding motif (TAZ) is recognized as a key mediator of the metastatic ability of breast cancer cells. We aimed to examine whether TAZ affects the migration of breast cancer cells through the regulation of EMT or actin cytoskeleton.
Methods: MCF-7 and MDA-MB-231 cells were treated with siRNA to attenuate TAZ abundance. Transwell migration assay and scratch wound healing assay were performed to study the effects of TAZ knockdown on cancer cell migration. Fluorescence microscopy was conducted to examine the vinculin and phalloidin. Semiquantitative immunoblotting and quantitative real-time PCR were performed to study the expression of small GTPases and kinases. Changes in the expression of genes associated with cell migration were examined through next-generation sequencing.
Results: TAZ-siRNA treatment reduced TAZ abundance in MCF-7 and MDA-MB-231 breast cancer cells, which was associated with a significant decrease in cell migration. TAZ knockdown increased the expression of fibronectin, but it did not exhibit the typical pattern of EMT progression. TGF-β treatment in MDA-MB-231 cells resulted in a reduction in TAZ and an increase in fibronectin levels. However, it paradoxically promoted cell migration, suggesting that EMT is unlikely to be involved in the decreased migration of breast cancer cells in response to TAZ suppression. RhoA, a small Rho GTPase protein, was significantly reduced in response to TAZ knockdown. This caused a decrease in the expression of the Rho-dependent downstream pathway, i.e., LIM kinase 1 (LIMK1), phosphorylated LIMK1/2, and phosphorylated cofilin, leading to actin depolymerization. Furthermore, myosin light chain kinase (MLCK) and phosphorylated MLC2 were significantly decreased in MDA-MB-231 cells with TAZ knockdown, inhibiting the assembly of stress fibers and focal adhesions.
Conclusion: TAZ knockdown inhibits the migration of breast cancer cells by regulating the intracellular actin cytoskeletal organization. This is achieved, in part, by reducing the abundance of RhoA and Rho-dependent downstream kinase proteins, which results in actin depolymerization and the disassembly of stress fibers and focal adhesions.

Keywords:  TAZ; actin; breast cancer; cell migration; small GTPase

DOI:  https://doi.org/10.3389/fonc.2024.1376831
Biochem Biophys Res Commun. 2024 May 18. pii: S0006-291X(24)00678-8. [Epub ahead of print]720 150142

Laminin I mediates resistance to lapatinib in HER2-positive brain metastatic breast cancer cells in vitro.

Sumiran Kumar Gurung, Lalita A Shevde, Shreyas S Rao.

  The role of extracellular matrix (ECM) prevalent in the brain metastatic breast cancer (BMBC) niche in mediating cancer cell growth, survival, and response to therapeutic agents is not well understood. Emerging evidence suggests a vital role of ECM of the primary breast tumor microenvironment (TME) in tumor progression and survival. Possibly, the BMBC cells are also similarly influenced by the ECM of the metastatic niche; therefore, understanding the effect of the metastatic ECM on BMBC cells is imperative. Herein, we assessed the impact of various ECM components (i.e., Tenascin C, Laminin I, Collagen I, Collagen IV, and Fibronectin) on brain metastatic human epidermal growth factor receptor 2 (HER2)-positive and triple negative breast cancer (TNBC) cell lines in vitro. The highly aggressive TNBC cell line was minimally affected by ECM components exhibiting no remarkable changes in viability and morphology. On the contrary, amongst various ECM components tested, the HER2-positive cell line was significantly affected by Laminin I with higher viability and demonstrated a distinct spread morphology. In addition, HER2-positive BMBC cells exhibited resistance to Lapatinib in presence of Laminin I. Mechanistically, Laminin I-induced resistance to Lapatinib was mediated in part by phosphorylation of Erk 1/2 and elevated levels of Vimentin. Laminin I also significantly enhanced the migratory potential and replicative viability of HER2-positive BMBC cells. In sum, our findings show that presence of Laminin I in the TME of BMBC cells imparts resistance to targeted therapeutic agent Lapatinib, while increasing the possibility of its dispersal and clonogenic survival.

Keywords:  Brain metastatic breast cancer; Extracellular matrix; HER2; Laminin I

DOI:  https://doi.org/10.1016/j.bbrc.2024.150142
Mol Carcinog. 2024 May 23.

Upregulation of collagen type X alpha 1 promotes the progress of triple-negative breast cancer via Wnt/β-catenin signaling.

Jing Peng, Xiangping Liu, Yan Mao, Meng Lv, Teng Ma, Jiaxiu Liu, Quan Zhou, Yafei Han, Xin Li, Haibo Wang.

  Triple-negative breast cancer (TNBC) is a malignant tumor with high degree of malignancy and lack of effective target treatment. The research aims to explore the role and mechanism of X collagen alpha-1 chain protein (COL10A1 gene) in TNBC. UALCAN and Kaplan-Meier were used to detect the expression of COL10A1 and its role in the prognosis of breast cancer patients. The cells with stably expressing high levels of COL10A1 were obtained by recombinant lentivirus infection. The expression of COL10A1 in cells was temporarily downregulated by siRNA interference fragments. Real-time quantitative polymerase chain reaction and western blot analysis were utilized to detect the changes of COL10A1 mRNA and protein expression. The biological functions of the cells were evaluated by colony formation, cell counting kit-8, cell invasion and wound healing experiments. In addition, the effect of COL10A1 on angiogenesis was investigated by tube formation assay. Xenograft tumor model was used to confirm the effect of COL10A1 on tumorigenicity in vivo and multiplex fluorescent immunohistochemistry to detect multiple proteins simultaneously. The possible molecular mechanism of the function of COL10A1 was speculated through the detection of proteins in functionally related pathways. COL10A1 is highly expressed and is significantly associated with worse overall survival (OS) and recurrence-free survival (RFS) in TNBC. Overexpression of COL10A1 increased the clone formation rate and cell migration capacity of TNBC cells. In the COL10A1 overexpression group, the clone formation rates of MD-MB-231 and BT-549 cells (21.5 ± 0.62, 27.83 ± 3.72)% were significantly higher than those in the control group(15.23 ± 2.79, 19.4 ± 1.47)%, and the relative migration ratio (47.40 ± 3.09, 41.26 ± 4.33)% were higher than those in the control group (34.48 ± 2.03, 21.80 ± 1.03)%. When the expression of COL10A1 was downregulated, the ability of clone formation and wound-healing migration capacity in TNBC cells was weakened. Upregulated COL10A1 in TNBC cells generated more junctions and longer total segments between vascular endothelial cells, and promoted angiogenesis of the cells, and thus enhanced the tumorigenesis. In TNBC, it was found that COL10A1 might affect epithelial-mesenchymal transition (EMT) of the cells through Wnt/β-catenin signaling pathway by the detection of the related pathway proteins. COL10A1 is highly expressed in TNBC, and its high expression leads to poor OS and RFS. COL10A1 may enhance TNBC cell proliferation, migration and tumor-related angiogenesis, and promote tumorigenesis in vivo via Wnt/β-catenin signaling.

Keywords:  COL10A1; EMT; TNBC; angiogenesis; migration; proliferation

DOI:  https://doi.org/10.1002/mc.23747
bioRxiv. 2024 May 10. pii: 2024.05.07.592812. [Epub ahead of print]

BUB1 regulates non-homologous end joining pathway to mediate radioresistance in triple-negative breast cancer.

Sushmitha Sriramulu, Shivani Thoidingjam, Wei-Min Chen, Oudai Hassan, Farzan Siddiqui, Stephen L Brown, Benjamin Movsas, Michael D Green, Anthony J Davis, Corey Speers, Eleanor Walker, Shyam Nyati.

Background: Triple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer subtype often treated with radiotherapy (RT). Due to its intrinsic heterogeneity and lack of effective targets, it is crucial to identify novel molecular targets that would increase RT efficacy. Here we demonstrate the role of BUB1 (cell cycle Ser/Thr kinase) in TNBC radioresistance and offer a novel strategy to improve TNBC treatment.
Methods: Gene expression analysis was performed to look at genes upregulated in TNBC patient samples compared to other subtypes. Cell proliferation and clonogenic survivals assays determined the IC 50 of BUB1 inhibitor (BAY1816032) and radiation enhancement ratio (rER) with pharmacologic and genomic BUB1 inhibition. Mammary fat pad xenografts experiments were performed in CB17/SCID. The mechanism through which BUB1 inhibitor sensitizes TNBC cells to radiotherapy was delineated by γ-H2AX foci assays, BLRR, Immunoblotting, qPCR, CHX chase, and cell fractionation assays.
Results: BUB1 is overexpressed in BC and its expression is considerably elevated in TNBC with poor survival outcomes. Pharmacological or genomic ablation of BUB1 sensitized multiple TNBC cell lines to cell killing by radiation, although breast epithelial cells showed no radiosensitization with BUB1 inhibition. Kinase function of BUB1 is mainly accountable for this radiosensitization phenotype. BUB1 ablation also led to radiosensitization in TNBC tumor xenografts with significantly increased tumor growth delay and overall survival. Mechanistically, BUB1 ablation inhibited the repair of radiation-induced DNA double strand breaks (DSBs). BUB1 ablation stabilized phospho-DNAPKcs (S2056) following RT such that half-lives could not be estimated. In contrast, RT alone caused BUB1 stabilization, but pre-treatment with BUB1 inhibitor prevented stabilization (t 1/2 , ∼8 h). Nuclear and chromatin-enriched fractionations illustrated an increase in recruitment of phospho- and total-DNAPK, and KAP1 to chromatin indicating that BUB1 is indispensable in the activation and recruitment of non-homologous end joining (NHEJ) proteins to DSBs. Additionally, BUB1 staining of TNBC tissue microarrays demonstrated significant correlation of BUB1 protein expression with tumor grade.
Conclusions: BUB1 ablation sensitizes TNBC cell lines and xenografts to RT and BUB1 mediated radiosensitization may occur through NHEJ. Together, these results highlight BUB1 as a novel molecular target for radiosensitization in women with TNBC.

DOI: https://doi.org/10.1101/2024.05.07.592812
Int J Mol Sci. 2024 May 15. pii: 5392. [Epub ahead of print]25(10):

Tumor-Intrinsic Enhancer of Zeste Homolog 2 Controls Immune Cell Infiltration, Tumor Growth, and Lung Metastasis in a Triple-Negative Breast Cancer Model.

Lenore Monterroza, Maria M Parrilla, Sarah G Samaranayake, Dormarie E Rivera-Rodriguez, Sung Bo Yoon, Ramireddy Bommireddy, Justin Hosten, Luisa Cervantes Barragan, Adam Marcus, Brian S Dobosh, Periasamy Selvaraj, Rabindra Tirouvanziam.

  Triple-negative breast cancer (TNBC) is an aggressive and highly metastatic type of tumor. TNBC is often enriched in tumor-infiltrating neutrophils (TINs), which support cancer growth in part by counteracting tumor-infiltrating lymphocytes (TILs). Prior studies identified the enhancer of zeste homolog 2 (EZH2) as a pro-tumor methyltransferase in primary and metastatic TNBCs. We hypothesized that EZH2 inhibition in TNBC cells per se would exert antitumor activity by altering the tumor immune microenvironment. To test this hypothesis, we used CRISPR to generate EZH2 gene knockout (KO) and overexpressing (OE) lines from parent (wild-type-WT) 4T1 cells, an established murine TNBC model, resulting in EZH2 protein KO and OE, respectively. In vitro, EZH2 KO and OE cells showed early, transient changes in replicative capacity and invasiveness, and marked changes in surface marker profile and cytokine/chemokine secretion compared to WT cells. In vivo, EZH2 KO cells showed significantly reduced primary tumor growth and a 10-fold decrease in lung metastasis compared to WT cells, while EZH2 OE cells were unchanged. Compared to WT tumors, TIN:TIL ratios were greatly reduced in EZH2 KO tumors but unchanged in EZH2 OE tumors. Thus, EZH2 is key to 4T1 aggressiveness as its tumor-intrinsic knockout alters their in vitro secretome and in vivo primary tumor growth, TIN/TIL poise, and metastasis.

Keywords:  CD4+ T cell; CD8+ T cell; invasion; myeloid-derived suppressor cell; triple-negative breast cancer; tumor-infiltrating neutrophils

DOI:  https://doi.org/10.3390/ijms25105392
Cells. 2024 May 10. pii: 821. [Epub ahead of print]13(10):

Elucidating the Role of MicroRNA-18a in Propelling a Hybrid Epithelial-Mesenchymal Phenotype and Driving Malignant Progression in ER-Negative Breast Cancer.

Madhumathy G Nair, Apoorva D Mavatkar, Chandrakala M Naidu, Snijesh V P, Anupama C E, Savitha Rajarajan, Sarthak Sahoo, Gayathri Mohan, Vishnu Sunil Jaikumar, Rakesh S Ramesh, Srinath B S, Mohit Kumar Jolly, Tessy Thomas Maliekal, Jyothi S Prabhu.

  Epigenetic alterations that lead to differential expression of microRNAs (miRNAs/miR) are known to regulate tumour cell states, epithelial-mesenchymal transition (EMT) and the progression to metastasis in breast cancer. This study explores the key contribution of miRNA-18a in mediating a hybrid E/M cell state that is pivotal to the malignant transformation and tumour progression in the aggressive ER-negative subtype of breast cancer. The expression status and associated effects of miR-18a were evaluated in patient-derived breast tumour samples in combination with gene expression data from public datasets, and further validated in in vitro and in vivo breast cancer model systems. The clinical relevance of the study findings was corroborated against human breast tumour specimens (n = 446 patients). The down-regulated expression of miR-18a observed in ER-negative tumours was found to drive the enrichment of hybrid epithelial/mesenchymal (E/M) cells with luminal attributes, enhanced traits of migration, stemness, drug-resistance and immunosuppression. Further analysis of the miR-18a targets highlighted possible hypoxia-inducible factor 1-alpha (HIF-1α)-mediated signalling in these tumours. This is a foremost report that validates the dual role of miR-18a in breast cancer that is subtype-specific based on hormone receptor expression. The study also features a novel association of low miR-18a levels and subsequent enrichment of hybrid E/M cells, increased migration and stemness in a subgroup of ER-negative tumours that may be attributed to HIF-1α mediated signalling. The results highlight the possibility of stratifying the ER-negative disease into clinically relevant groups by analysing miRNA signatures.

Keywords:  ER-negative breast cancer; chemoresistance; epithelial–mesenchymal transition; hybrid E/M phenotype; microRNA-18a; stem-like cells

DOI:  https://doi.org/10.3390/cells13100821