Chemotherapy Resistance In Breast Cancer Research Articles

Identification of molecular subtypes based on chromatin regulator-related genes and experimental verification of the role of ASCL1 in conferring chemotherapy resistance to breast cancer.

The aim of this study was to identify the molecular subtypes of breast cancer based on chromatin regulator-related genes. The RNA sequencing data of The Cancer Genome Atlas-Breast Cancer cohort were obtained from the official website, while the single-cell data were downloaded from the Gene Expression Omnibus database (GSE176078). Validation was performed using the Molecular Taxonomy of Breast Cancer International Consortium dataset. Furthermore, the immune characteristics, tumor stemness, heterogeneity, and clinical characteristics of these molecular subtypes were analyzed. The correlation between chromatin regulators and chemotherapy resistance was examined in vitro using the quantitative real-time polymerase chain reaction (qRT-PCR) and Cell Counting Kit-8 (CCK8) assays. This study identified three stable molecular subtypes with different prognostic and pathological features. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and protein-protein interaction analyses revealed that the differentially expressed genes were associated with disease processes, such as mitotic nuclear division, chromosome segregation, condensed chromosome, and specific chromosome region. The T stage and subtypes were correlated with the clinical features. Tumor heterogeneity (mutant-allele tumor heterogeneity, tumor mutational burden, purity, and homologous recombination deficiency) and tumor stemness (RNA expression-based stemness score, epigenetically regulated RNA expression-based stemness score, DNA methylation-based stemness score, and epigenetically regulated DNA methylation-based stemness score) significantly varied between the three subtypes. Furthermore, Western blotting, qRT-PCR, and CCK8 assays demonstrated that the expression of ASCL1 was positively correlated with chemotherapy resistance in breast cancer. This study identified the subtypes of breast cancer based on chromatin regulators and analyzed their clinical features, gene mutation status, immunophenotype, and drug sensitivity. The results of this study provide effective strategies for assessing clinical prognosis and developing personalized treatment strategies.

PFDN4 as a Prognostic Marker Was Associated with Chemotherapy Resistance through CREBP1/AURKA Pathway in Triple-Negative Breast Cancer.

Breast cancer is the most common malignancy and its incidence is increasing. It is currently mainly treated by clinical chemotherapy, but chemoresistance remains poorly understood. Prefolded proteins 4 (PFDN4) are molecular chaperone complexes that bind to newly synthesized polypeptides and allow them to fold correctly to stabilize protein formation. This study aimed to investigate the role of PFDN4 in chemotherapy resistance in breast cancer. Our study found that PFDN4 was highly expressed in breast cancer compared to normal tissues and was statistically significantly associated with stage, nodal status, subclasses (luminal, HER2 positive and triple negative), triple-negative subtype and disease-specific survival by TCGA database analysis. CRISPR knockout of PFDN4 inhibited the growth of 89% of breast cancer cell lines, and the triple-negative cell line exhibited a stronger inhibitory effect than the non-triple-negative cell line. High PFDN4 expression was associated with poor overall survival in chemotherapy and resistance to doxorubicin and paclitaxel through the CREBP1/AURKA pathway in the triple-negative MDAMB231 cell line. This study provides insightful evidence for the value of PFDN4 in poor prognosis and chemotherapy resistance in breast cancer patients.

Correlation between S100A7 and immune characteristics, methylation, tumor stemness and tumor heterogeneity in pan-cancer and its role in chemotherapy resistance in breast cancer.

To explore the relationships between S100A7 and the immune characteristics, tumor heterogeneity, and tumor stemness pan-cancer as well as the effect of S100A7 on chemotherapy sensitivity in breast cancer. TCGA-BRCA and TCGA-PANCANCER RNA-seq data and clinical follow-up survival data were collected from the University of California Santa Cruz database. Survival analyses were performed to explore the relationship between S100A7 expression and pan-cancer prognosis. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, and Gene Set Enrichment Analysis (GSEA) were used to identify the potential pathways related to the differentially expressed genes in breast cancer. Spearman's and Wilcoxon's tests were used to investigate the relationships between S100A7 expression and immune characteristics, methylation, tumor heterogeneity, and tumor stemness. The potential functions of S100A7 and its influence on chemotherapy sensitivity in breast cancer were elucidated using reverse transcription-quantitative PCR, Cell Counting Kit-8 (CCK-8) assay, Transwell assay, and wound healing assay. S100A7 was highly expressed in most types of tumors and was associated with poor prognosis. S100A7 was closely associated with immunomodulators, immune checkpoint and immune cell infiltration. Further, S100A7 was related to tumor mutational burden, tumor heterogeneity, methylation and tumor stemness in breast cancer. High S100A7 expression was associated with the invasiveness, migration, proliferation and chemotherapy resistance of breast cancer cells in vitro experiments. High S100A7 expression was related with poor prognosis and chemotherapy resistance in breast cancer, making it a potential immune and chemotherapy resistance biomarker.

DDX58 deficiency leads to triple negative breast cancer chemotherapy resistance by inhibiting Type I IFN-mediated signalling apoptosis.

Triple-negative breast cancer (TNBC) is characterized by its aggressive nature and absence of specific therapeutic targets, necessitating the reliance on chemotherapy as the primary treatment modality. However, the drug resistance poses a significant challenge in the management of TNBC. In this study, we investigated the role of DDX58 (DExD/H-box helicase 58), also known as RIG-I, in TNBC chemoresistance. The relationship between DDX58 expression and breast cancer prognosis was investigated by online clinical databases and confirmed by immunohistochemistry analysis. DDX58 was knockout by CRISPR-Cas9 system (DDX58-KO), knockdown by DDX58-siRNA (DDX58-KD), and stably over expressed (DDX58-OE) by lentivirus. Western blotting, immunofluorescence and qPCR were used for related molecules detection. Apoptosis was analyzed through flow cytometry (Annexin V/7AAD apoptosis assay) and Caspase 3/7 activity assay. Patients with lower expression of DDX58 led to lower rate of pathological complete response (pCR) and worse prognosis by online databases and hospital clinical data. DDX58-KD cells showed multiple chemo-drugs resistance (paclitaxel, doxorubicin, 5-fluorouracil) in TNBC cell lines. Similarly, DDX58-KO cells also showed multiple chemo-drugs resistance in a dosage-dependent manner. In the CDX model, tumours in the DDX58-KO group had a 25% reduction in the tumour growth inhibition rate (IR) compared to wild-type (WT) group after doxorubicin (Dox) treatment. The depletion of DDX58 inhibited proliferation and promoted the migration and invasion in MDA-MB-231 cells. The findings of our research indicated that DDX58-KO cells exhibit a reduction in Dox-induced apoptosis both in vivo and in vitro. Mechanistically, Dox treatment leads to a significant increase in the expression of double-stranded RNAs (dsRNAs) and activates the DDX58-Type I interferon (IFN) signaling pathway, ultimately promoting apoptosis in TNBC cells. In the process of TNBC chemotherapy, the deficiency of DDX58 can inhibit Dox-induced apoptosis, revealing a new pathway of chemotherapy resistance, and providing a possibility for developing personalized treatment strategies based on DDX58 expression levels.

Correlation between ferroptosis and adriamycin resistance in breast cancer regulated by transferrin receptor and its molecular mechanism.

Breast cancer is the most prevalent malignant tumor in women. Adriamycin (ADR) is a primary chemotherapy drug, but resistance limits its effectiveness. Ferroptosis, a newly identified cell death mechanism, involves the transferrin receptor (TFRC), closely linked with tumor cells. This study aimed to explore TFRC and ferroptosis's role in breast cancer drug resistance. Bioinformatics analysis showed that TFRC was significantly downregulated in drug-resistant cell lines, and patients with low TFRC expression might demonstrate a poor chemotherapeutic response to standard treatment. High expression of TFRC was positively correlated with most of the ferroptosis-related driver genes. The research findings indicate that ferroptosis markers were higher in breast cancer tissues than in normal ones. In chemotherapy-sensitive cases, Ferrous ion (Fe2+ ) and malondialdehyde (MDA) levels were higher than in resistant cases (all p < .05). TFRC expression was higher in breast cancer than in normal tissue, especially in the sensitive group (all p < .05). Cytological experiments showed increased hydrogen peroxide (H2 O2 ) after ADR treatment in both sensitive and resistant cells, with varying MDA changes (all p < .05). Elevating TFRC increased Fe2+ and MDA in ADR-resistant cells, enhancing their sensitivity to ADR. However, TFRC upregulation combined with ADR increased proliferation and invasiveness in resistant cell lines (all p < .05). In conclusion, ADR resistance to breast cancer is related to the regulation of iron ion-mediated ferroptosis by TFRC. Upregulation of TFRC in ADR-resistant breast cancer cells activates ferroptosis and reverses ADR chemotherapy resistance of breast cancer.

CYR61 confers chemoresistance by upregulating survivin expression in triple-negative breast cancer.

Cysteine-rich angiogenic inducer 61 (CYR61) is a protein from the CCN family of matricellular proteins that play diverse regulatory roles in the extracellular matrix. CYR61 is involved in cell adhesion, migration, proliferation, differentiation, apoptosis, and senescence. Here, we show that CYR61 induces chemoresistance in triple-negative breast cancer (TNBC). We observed that CYR61 is overexpressed in TNBC patients, and CYR61 expression correlates negatively with the survival of patients who receive chemotherapy. CYR61 knockdown reduced cell migration, sphere formation, and the cancer stem cell (CSC) population and increased the chemosensitivity of TNBC cells. Mechanistically, CYR61 activated Wnt/β-catenin signaling and increased survivin expression, which are associated with chemoresistance, the epithelial-mesenchymal transition, and CSC-like phenotypes. Altogether, our study demonstrates a novel function of CYR61 in chemotherapy resistance in breast cancer.

Abstract 2467 ZAR1L Protein: Stress Granule Dynamics and Chemotherapy Resistance in Breast Cancer

Abstract 2467 ZAR1L Protein: Stress Granule Dynamics and Chemotherapy Resistance in Breast Cancer

DNAJC12 causes breast cancer chemotherapy resistance by repressing doxorubicin-induced ferroptosis and apoptosis via activation of AKT

BackgroundChemotherapy is a primary treatment for breast cancer (BC), yet many patients develop resistance over time. This study aims to identify critical factors contributing to chemoresistance and their underlying molecular mechanisms, with a focus on reversing this resistance. MethodsWe utilized samples from the Gene Expression Omnibus (GEO) and West China Hospital to identify and validate genes associated with chemoresistance. Functional studies were conducted using MDA-MB-231 and MCF-7 cell lines, involving gain-of-function and loss-of-function approaches. RNA sequencing (RNA-seq) identified potential mechanisms. We examined interactions between DNAJC12, HSP70, and AKT using co-immunoprecipitation (Co-IP) assays and established cell line-derived xenograft (CDX) models for in vivo validations. ResultsBoruta analysis of four GEO datasets identified DNAJC12 as highly significant. Patients with high DNAJC12 expression showed an 8 % pathological complete response (pCR) rate, compared to 38 % in the low expression group. DNAJC12 inhibited doxorubicin (DOX)-induced cell death through both ferroptosis and apoptosis. Combining apoptosis and ferroptosis inhibitors completely reversed DOX resistance caused by DNAJC12 overexpression. RNA-seq suggested that DNAJC12 overexpression activated the PI3K-AKT pathway. Inhibition of AKT reversed the DOX resistance induced by DNAJC12, including reduced apoptosis and ferroptosis, restoration of cleaved caspase 3, and decreased GPX4 and SLC7A11 levels. Additionally, DNAJC12 was found to increase AKT phosphorylation in an HSP70-dependent manner, and inhibiting HSP70 also reversed the DOX resistance. In vivo studies confirmed that AKT inhibition reversed DNAJC12-induced DOX resistance in the CDX model. ConclusionDNAJC12 expression is closely linked to chemoresistance in BC. The DNAJC12-HSP70-AKT signaling axis is crucial in mediating resistance to chemotherapy by suppressing DOX-induced ferroptosis and apoptosis. Our findings suggest that targeting AKT and HSP70 activities may offer new therapeutic strategies to overcome chemoresistance in BC.

Spatiotemporal modeling of chemoresistance evolution in breast tumors uncovers dependencies on SLC38A7 and SLC46A1

In solid tumors, drug concentrations decrease with distance from blood vessels. However, cellular adaptations accompanying the gradated exposure of cancer cells to drugs are largely unknown. Here, we modeled the spatiotemporal changes promoting chemotherapy resistance in breast cancer. Using pairwise cell competition assays at each step during the acquisition of chemoresistance, we reveal an important priming phase that renders cancer cells previously exposed to sublethal drug concentrations refractory to dose escalation. Therapy-resistant cells throughout the concentration gradient display higher expression of the solute carriers SLC38A7 and SLC46A1 and elevated intracellular concentrations of their associated metabolites. Reduced levels of SLC38A7 and SLC46A1 diminish the proliferative potential of cancer cells, and elevated expression of these SLCs in breast tumors from patients correlates with reduced survival. Our work provides mechanistic evidence to support dose-intensive treatment modalities for patients with solid tumors and reveals two members of the SLC family as potential actionable targets.

TRP Channels: The Neglected Culprits in Breast Cancer Chemotherapy Resistance?

Breast cancer is a major health concern worldwide, and resistance to therapies remains a significant challenge in treating this disease. In breast cancer, Transient Receptor Potential (TRP) channels are well studied and constitute key players in nearly all carcinogenesis hallmarks. Recently, they have also emerged as important actors in resistance to therapy by modulating the response to various pharmaceutical agents. Targeting TRP channels may represent a promising approach to overcome resistance to therapies in breast cancer patients.

Quercetin and Morin dual drug loaded nanostructured lipid carriers: formulation and in vitro cytotoxicity study on MCF7 breast cancer cells

The aim of the study was to prepare nanostructured lipid carriers (NLCs) co-encapsulated with Quercetin and Morin and to compare the cytotoxicity of the NLCs with individual drugs as well as with their combination form. The Quercetin and Morin co-encapsulated NLCs were prepared by ultrasonication method. The size of the NLCs particles, the zeta potential value, % of drug entrapment efficiency (% EE), and % of cumulative drug release (% CDR) were estimated. The in vitro cytotoxicity study was carried out in MCF 7 cancer cell. The size of the NLCs particles ranged from 297.6 ± 14.1 to 456.4 ± 14.1 nm. The % EE of Quercetin and Morin in the optimized NLCs formulation (F6) were found to be 84.27 ± 2.1% and 87.11 ± 2.6%, respectively. However, the % CDR of Morin and Quercetin from the F6 formulation were 72.11 ± 3.4% and 81.56 ± 3.6%, respectively. The results of FTIR spectroscopy study indicated that the functional groups of Quercetin and Morin were remained intact in NLCs formulations. The TEM study result revealed that the prepared NLCs were spherical in shape. The in vitro cytotoxicity study result revealed that dual drug loaded NLCs showed higher cytotoxicity as compared to individual drug and their combinations. It was concluded that the Quercetin and Morin co-encapsulated NLCs formulation could be a promising candidate for combating the chemotherapy resistance in breast cancer.

Serum microRNA-210 as a predictor of neoadjuvant chemotherapy resistance in breast cancer

Objectives Breast cancer (BC) is a major global health issue as it is the most common malignancy in women. Despite, the role of neoadjuvant chemotherapy (NAC) in early BC has been established, there is a non-small proportion of patients who might develop chemoresistance. Several studies have investigated the relationship between microRNA-210 (miRNA-210) and neoadjuvant chemoresistance in BC with controversial results. Thus, this study aimed to evaluate the role of miRNA-210 as a predictor for chemoresistance in BC receiving NAC. Material and Methods The study enrolled 15 chemo-sensitive and 15 chemo-resistant patients with BC receiving NAC. In addition, 10 newly-diagnosed BC patients before treatment and 10 healthy women were recruited as controls. Serum samples from all patients and controls were withdrawn and measurements of miRNA-210 levels using quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) were done and compared. Results The median value of miRNA-210 level was 1.53, 0.27, 0.52, and 1.35 in chemo-sensitive, chemo-resistant, newly-diagnosed, and control groups, respectively. A statistically significant difference (Chi square = 9.801, p = 0.020, df = 3) was found in the mean serum miRNA-210 among the four different groups. Using logistic regression model, low serum miRNA-210 expression level was found to be a predictive factor of chemo-resistance with p = 0.038 (OR of 0.103, 95% CI = 0.012 –0.886). Using the receiver operating characteristic curve, it was found that the area under the curve (AUC) was 0.747 (95% CI = 0.550 –0.943). Conclusion Serum miRNA-210 could be an effective predictive biomarker for chemoresistance in BC patients receiving NAC.

Identification of co-regulated genes associated with doxorubicin resistance in the MCF-7/ADR cancer cell line.

The molecular mechanism of chemotherapy resistance in breast cancer is not well understood. The identification of genes associated with chemoresistance is critical for a better understanding of the molecular processes driving resistance. This study used a co-expression network analysis of Adriamycin (or doxorubicin)-resistant MCF-7 (MCF-7/ADR) and its parent MCF-7 cell lines to explore the mechanisms of drug resistance in breast cancer. Genes associated with doxorubicin resistance were extracted from two microarray datasets (GSE24460 and GSE76540) obtained from the Gene Expression Omnibus (GEO) database using the GEO2R web tool. The candidate differentially expressed genes (DEGs) with the highest degree and/or betweenness in the co-expression network were selected for further analysis. The expression of major DEGs was validated experimentally using qRT-PCR. We identified twelve DEGs in MCF-7/ADR compared with its parent MCF-7 cell line, including 10 upregulated and 2 downregulated DEGs. Functional enrichment suggests a key role for RNA binding by IGF2BPs and epithelial-to-mesenchymal transition pathways in drug resistance in breast cancer. Our findings suggested that MMP1, VIM, CNN3, LDHB, NEFH, PLS3, AKAP12, TCEAL2, and ABCB1 genes play an important role in doxorubicin resistance and could be targeted for developing novel therapies by chemical synthesis approaches.

O-GlcNAcylation promotes topoisomerase IIα catalytic activity in breast cancer chemoresistance.

DNA topoisomerase IIα (TOP2A) plays a vital role in replication and cell division by catalytically altering DNA topology. It is a prominent target for anticancer drugs, but clinical efficacy is often compromised due to chemoresistance. In this study, we investigate the role of TOP2A O-GlcNAcylation in breast cancer cells and patient tumor tissues. Our results demonstrate that elevated TOP2A, especially its O-GlcNAcylation, promotes breast cancer malignant progression and resistance to adriamycin (Adm). O-GlcNAcylation at Ser1469 enhances TOP2A chromatin DNA binding and catalytic activity, leading to resistance to Adm in breast cancer cells and xenograft models. Mechanistically, O-GlcNAcylation-modulated interactions between TOP2A and cell cycle regulators influence downstream gene expression and contribute to breast cancer drug resistance. These results reveal a previously unrecognized mechanistic role for TOP2A O-GlcNAcylation in breast cancer chemotherapy resistance and provide support for targeting TOP2A O-GlcNAcylation in cancer therapy.

Much more than hormonal resistance: estrogen receptor activating mutations mediate chemotherapy resistance in breast cancer

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

33P Antitumor activity of TROP2 antibody drug conjugate datopotamab deruxtecan in chemotherapy-resistant breast cancer models

33P Antitumor activity of TROP2 antibody drug conjugate datopotamab deruxtecan in chemotherapy-resistant breast cancer models

IKKα inhibition re-sensitizes acquired adriamycin-resistant triple negative breast cancer cells to chemotherapy-induced apoptosis

IKKα has been shown to be responsible of multiple pro-tumorigenic functions and therapy resistance independent of canonical NF-κB, but its role in acquired chemotherapy resistance in breast cancer remains unclarified. In this study, we obtained pre-treatment biopsy and post-treatment mastectomy specimens from a retrospective cohort of triple-negative breast cancer (TNBC) patients treated with neoadjuvant chemotherapy(NAC) (n = 43). Immunohistochemical methods were used to detect the expression of IKKα before and after NAC, and the relationship between IKKα and the pathologic response to NAC was examined. In addition, we developed a new ADR-resistant MDA-MB-231 cell line(MDA-MB-231/ADR) and analyzed these cells for changes in IKKα expression, the role and mechanisms of the increased IKKα in promoting drug resistance were determined in vitro and in vivo. We demonstrated that the expression of IKKα in residual TNBC tissues after chemotherapy was significantly higher than that before chemotherapy, and was positively correlated with lower pathological reaction. IKKα expression was significantly higher in ADR-resistant TNBC cells than in ADR-sensitive cells, IKKα knockdown results in apoptotic cell death of chemoresistant cells upon drug treatment. Moreover, IKKα knockdown promotes chemotherapeutic drug-induced tumor cell death in an transplanted tumor mouse model. Functionally, we demonstrated that IKKα knockdown significantly upregulated the expression of cleaved caspase 3 and Bax and inhibited the expression of Bcl-2 upon ADR treatment. Our findings highlighted that IKKα exerts an important and previously unknown role in promoting chemoresistance in TNBC, combining IKKα inhibition with chemotherapy may be an effective strategy to improve treatment outcome in chemoresistant TNBC patients.

Abstract 3084: Progesterone receptor mediated crosstalk between cancer associated fibroblasts (CAFs) and ER+/PR+ breast cancer cells through CAF-secreted FGF2

Abstract Late recurring ER+ breast cancer emerges in post-menopausal women despite low/no hormone conditions. Cancer associated fibroblasts (CAFs) represent a major player in the promotion of metastasis, stemness and chemotherapy resistance in breast cancer. Progesterone receptors (PR) are emerging as drivers of stemness and metastasis in ER+ breast cancers. We propose that CAFs provide a mechanism to turn on ligand-independent PR signaling pathways through the secretion of paracrine factors. Methods: Tumorsphere assays were used to measure stem cell expansion. Cell clustering assays were used to measure CAF/tumor cell interactions. ChIP assays were used to measure PR direct binding to stemness gene regulatory elements. Results: Using the ER(+) T47D cell series (i.e., PR-null variants or cells expressing either endogenous PR (T47DCO) or PR-A or PR-B isoforms), we observed that CAF conditioned media (CM) increased tumorsphere formation in PR+ cells relative to PR-null and controls. Similar results were obtained with MCF7L cell models. CAF CM activated MAPK/ERK kinases and induced rapid phosphorylation of PR at Ser294. Physical interaction between CAFs and PR expressing T47D and MCF7L cells in clustering assays demonstrated PR driven co-cluster formation. CAF-derived FGF2 increased PR dependent tumorsphere and co-cluster formation. Blockage of FGF2 with the inhibitor, PD173074, decreased CAF CM-induction of tumorspheres and co-cluster formation. Previous data demonstrated that the cell adhesion molecule, CD44, is implicated in CAF/BC co-cluster formation. Both FGF2 and progestins increased CD44 expression in ER+ breast cancer cell models. Chromatin immunoprecipitation (ChIP) assays demonstrated that both PR isoforms are recruited to PRE-containing regions in the CD44 gene in response to progestin. Finally, we compared the gene expression profiles of breast cancer cells from T47DCO mono-clusters and CAF/T47DCO co-clusters using Single Cell RNA Seq. Among the differentially expressed genes identified were two genes implicated in tamoxifen resistance, BAMBI and NR2F2. Conclusion: We propose a model in which clustering between CAFs and ER+/PR+ breast cancer cells is promoted by the CAF secreted factor, FGF2. FGF2 promotes PR activation and upregulation of CD44 expression, which may further increase physical cell-cell interactions. Importantly, CAF-derived FGF2 can also act through PR to initiate MAPK/ERK signaling pathways that drive stemness and endocrine therapy resistance. Our studies of the interactions between PR+ breast cancer cells with CAFs either in the primary tumor or in the circulation (as CAF/CTC clusters) suggest the need to include anti-progestins as a component of endocrine therapy in late recurring ER+ breast cancer. Citation Format: Angela K. Spartz, Caroline H. Diep, Carol A. Lange, Dorraya El-Ashry. Progesterone receptor mediated crosstalk between cancer associated fibroblasts (CAFs) and ER+/PR+ breast cancer cells through CAF-secreted FGF2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3084.

Abstract 2442: KLF8 and OGT/O-GlcNAcylation regulate stem-like cell properties in breast cancer

Abstract Breast cancer is the most common cancer and the second leading cause of cancer death among women overall. One of the main challenges in fighting breast cancer is the intratumor heterogeneity as they are composed of different subpopulations of cancer cells. This heterogeneity of breast cancer is promoted and maintained by a subpopulation of cancer stem-like cells (CSC). CSC share properties of adult stem cells, capable of self-renewing, differentiating &amp; repopulating a tumor. In addition to CSC role in promoting tumor growth, CSC are involved in metastasis, drug resistance and relapse of breast cancer. Therefore, understanding the mechanisms that drive and maintain CSC will help identify novel therapeutic targets in treating breast cancer. Functional activities of CSC are heavily influenced by modulations in the tumor microenvironment, such as alteration in nutrient status. One key component connecting signaling pathway and cancer cell metabolism is the enzyme O-GlcNAc Transferase (OGT), which utilize UDP-GlcNAc to modify nuclear and cytoplasmic proteins in a process termed O-GlcNAcylation. OGT and O-GlcNAc are upregulated in many cancers. Recently, we showed a direct connection between OGT/O-GlcNAc and CSC in breast cancer, in which OGT/O-GlcNAc is required and sufficient to promote the stemness of breast cancer cells in vitro, as well as tumorigenesis in vivo. Global transcriptomic analysis of CSCs-enriched mammospheres with OGT overexpression revealed Kruppel-like-factor 8 (KLF8) as a downstream target of OGT in CSC. Here, we show that KLF8 expression in breast cancer cells is regulated by OGT at the mRNA and protein level. Knockdown of KLF8 reduced mammosphere forming efficiency (MFE), reduced CSC population, and tumor growth in vivo. In contrast, KLF8 overexpression increased MFE and CSC population. Importantly, KLF8 knockdown blocked the effect of elevated OGT and O-GlcNAcylation in promoting MFE, while KLF8 overexpression rescued OGT inhibition in regulating in breast cancer cells. Consistently, KLF8 knockdown in breast cancer cells significantly reduced expression of stem cells markers at both mRNA and protein level, while KLF8 overexpression increased expression of these CSC factors. Interestingly, KLF8 knockdown in breast cancer cell reduced OGT expression, while KLF8 overexpression increased OGT and O-GlcNAcylation, suggesting a possible feed-forward loop between OGT and KLF8 in promoting CSC. Supporting the idea that KLF8 and OGT are critical for breast cancer progression, high expression of KLF8 and OGT is correlated with poor breast cancer patient outcome. Furthermore, overexpression of KLF8 showed increase in resistance to paclitaxel in triple-negative breast cancer cells in vitro, suggesting a possible role of KLF8 in promoting chemotherapy resistance in breast cancer. Together, our results suggested that KLF8 and OGT may work in concert in promoting breast cancer stem-like cells population. Citation Format: Giang Le Minh, Emily Esquea, Tejsi Dhamelia, Neha Akella, Mauricio J. Reginato. KLF8 and OGT/O-GlcNAcylation regulate stem-like cell properties in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2442.

LncRNA MALAT1 regulates the resistance of breast cancer cells to paclitaxel via the miR-497-5p/SHOC2 axis.

Aim: To explore the roles of lncRNA MALAT1 and SHOC2 in breast cancer, and the potential connections to chemotherapy resistance in breast cancer. Materials & methods: Paclitaxel-resistant breast cancer cells were induced by gradually increasing intermittent doses. Bioinformatic analyses were performed to predict the regulated miRNAs of MALAT1. Results: High expressions of MALAT1 and SHOC2 contribute to paclitaxel resistance in breast cancer cells. MALAT1 sponges miR-497-5penhance SHOC2 expression in paclitaxel-resistant breast cancer cells and contribute to paclitaxel resistance in breast cancer cells. Conclusion: Patients with high expression of MALAT1 and SHOC2 have a poorer response to paclitaxel. Upregulation of miR-497-5p could improve the treatment response to paclitaxel in patients with breast cancer by inhibiting MALAT1 and SHOC2.