Tumor Suppressor In Breast Cancer Research Articles

BRD7 Stabilizes P53 via Dephosphorylation of MDM2 to Inhibit Tumor Growth in Breast Cancer Harboring Wild-type P53.

Bromodomain-containing protein 7 (BRD7) was found to be down-expressed in nasopharyngeal carcinoma as well as breast cancer and to function as a potential tumor suppressor. BRD7 interacts with p53 and is required for p53-dependent oncogene-induced senescence. However, the mechanism how BRD7 functions as tumor suppressor roles in breast cancer remains unclear. MTT, colony formation assay, cell cycle, cell apoptosis, and tumorigenicity assays were performed to evaluate the biological functions of BRD7 in breast cancer cells in vitro and in vivo. Real-time PCR, western blot, luciferase reporter gene assays, and co-immunoprecipitation were used to examine the gene expression, transcription activation and protein-protein interaction. We reported that BRD7 effectively suppressed cell proliferation and tumor growth in vitro and in vivo. In addition, BRD7 increased p53 protein stability through ubiquitin-dependent proteasome pathway and regulated the expression of p53 downstream target genes by activating its transcriptional activity in breast cancers harboring wild-type p53. Mechanistically, BRD7 decreased phosphorylation and activation of MDM2 via inactivating its upstream kinase AKT depending on the bromodomain of BRD7, therefore BRD7 significantly reduced the amounts of phosphorylated MDM2 binding with p53 eventually decreasing ubiquitination level of p53. Furthermore, silencing the expression of p53 at least partly reversed the inhibition effect of BRD7 on cell proliferation and tumor growth in vitro and in vivo. Our studies identify that BRD7 stabilizes p53 by inhibiting the phosphorylation of MDM2 via AKT pathway dependent on its bromodomain to function as a tumor suppressor in breast cancer harboring wild-type p53.

TRIM35 functions as a novel tumor suppressor in breast cancer by inducing cell apoptosis through ubiquitination of PDK1.

Breast cancer is the most common cancer in women. Novel mechanisms and targets are urgently needed to understand and treat this disease due to the complexity of breast cancer. In this study, we evaluated the expression level of tripartite motif-containing (TRIM) 35 in various breast cancer cell lines by qPCR and immunoblot. Cell proliferation assay and flow cytometry were performed upon overexpression and depletion of TRIM35. Xenograft tumor model was applied to validate the findings observed in vitro. The correlation between TRIM35 and outcomes of breast cancer patients was investigated by analyzing The Cancer Genome Atlas database. We observed differential expression of TRIM35 in various breast cancer cell lines. Overexpression of TRIM35 significantly inhibited cell proliferation and promoted cell apoptosis. On the contrary, depletion of TRIM35 exerted the opposite effects on cell proliferation and apoptosis. Mechanistically, TRIM35 reduced PDK1 by ubiquitination, resulting in the degradation of PDK1. Overexpression of TRIM35 significantly suppressed ZR7530 cell line-derived xenograft tumor growth by inducing apoptosis. Finally, a lower level of TRIM35 was associated with a poor prognosis in patients. In conclusion, TRIM35 functions as a tumor suppressor to suppress breast cancer proliferation by inactivating AKT signaling through the increased ubiquitination of PDK1, resulting in the promotion of apoptosis.

Long non-coding RNA CASC7 suppresses malignant behaviors of breast cancer by regulating miR-21-5p/FASLG axis

ABSTRACT Recently, it has been increasingly proved that lncRNAs are functionally involved in a majority of tumor progression. LncRNA CASC7 has also been revealed to participate in the development of several cancers as a tumor promoter or suppressor. Herein, we focus on uncovering the role and underlying molecular mechanism of CASC7 in breast cancer. Tumor tissues and the paired paracancerous tissues from the breast cancer patients were used to evaluate the level of CASC7 in breast cancer. By analyzing the CASC7 expression in breast cancer cell lines, both the expression levels of CASC7 in cancer tissues and cell lines were obviously downregulated compared to those in paired paracancerous tissues and normal human epithelial MCF10A cells. Subsequently, the construction of lentivirus overexpression system (oe-CASC7 and oe-NC) was used to elevate the expression of CASC7. A series of functional experiments were conducted to show that the cell proliferation, migration, and invasion were inhibited when CASC7 overexpressed in breast cancer cells. Meanwhile, the apoptosis of oe-CASC7 cells was induced compared to the oe-NC breast cancer cells. We further confirmed that CASC7 functions by regulating miR-21-5p/FASLG axis. Finally, a xenograft model in nude mice verified that CASC7 was a tumor suppressor in breast cancer. These results suggest that lncRNA CASC7 suppresses to malignant behaviors of breast cancer by modulating miR-21-5p/FASLG axis.AbbreviationslncRNAs: long non-coding RNAs; ceRNA: competing endogenous RNA; CASC7: cancer susceptibility candidate 7; miRNAs: MicroRNAs; MAPK10: mitogen-activated protein kinase 10; FASLG: Tumor Necrosis Factor Ligand Superfamily Member 6; FAS: Tumor Necrosis Factor Receptor Superfamily Member 6

Integral membrane protein 2A enhances sensitivity to chemotherapy via notch signaling pathway in cervical cancer

ABSTRACT As the second most common cancer among women, cervical cancer is a huge threat to their health all over the world. Integral membrane protein 2A (ITM2A), a member of the Type II Integral Membrane protein (ITM2) family, has been reported to act as a tumor suppressor in breast cancer and ovarian cancer. Moreover, the low expression of ITM2A was associated with cervical adenocarcinoma. However, the function of ITM2A in drug resistance in cervical cancer remains unclear. Here, we used bioinformatics methods to screen differentially expressed genes (DEGs) closely related to chemotherapeutic relapse cervical carcinoma. ITM2A is downregulated in cervical tumor tissues and is associated with poor survival. Furthermore, ITM2A is also downregulated in cervical cancer cells with cisplatin resistance. Overexpression of ITM2A increases the cisplatin sensitivity of cervical cancer cells. Mechanically, ITM2A upregulation mediates the sensitivity of cervical cancer cell through Notch signaling pathway. Our study suggests that ITM2A may serve as a target in mediating cisplatin-resistant cervical cancer.

Abstract PO-040: Nischarin is expressed in pancreatic ductal adenocarcinoma and is a potential target for drug repurposing

Abstract The objective of this study was to examine the expression of Nischarin (NISCH) in pancreatic ductal adenocarcinoma (PDAC), and its potential as a target for drug repurposing. NISCH has been described as a tumor suppressor in breast and ovarian cancers, and there are several clinically approved agonists for this receptor. NISCH has also been reported as a scaffolding protein with a role in cell adhesion, invasion and metabolism – aspects of the PDAC biology that are of interest for therapeutical intervention. We examined mRNA and protein expression of NISCH in publicly available datasets, patient tumor samples, representative PDAC cell lines and patient-derived stellate cells. We found that NISCH is a prognostic marker in PDAC patients and that it is expressed in both cancer cells and cancer-associated stroma. Gene set enrichment analysis showed that NISCH expression was associated with the regulation of cell motility, cell cycle and energy metabolism. Indeed, NISCH knockdown in cancer cells induced reorganization of the actin cytoskeleton. Next, we tested the effects of three clinically approved NISCH agonists (rilmenidine, clonidine and moxonidine) on cancer cells and cancer-associated fibroblasts (CAFs). We found that rilmenidine, agonist with the highest affinity for the NISCH receptor, had the most potent effect. Rilmenidine impaired cancer cell adhesion, limited migration and decreased production of pro-metastatic cytokines and extracellular matrix deposition in cancer cell-CAF co-cultures. Our study lays a ground for more extensive examination of the role of NISCH in PDAC and implies that NISCH agonists may be good candidates for drug repurposing in this type of cancer. Citation Format: Jelena Grahovac, Marijana Pavlovic, Marija Ostojic, Kristina Zivic, Daniel Galun, Tatjana Srdic-Rajic. Nischarin is expressed in pancreatic ductal adenocarcinoma and is a potential target for drug repurposing [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-040.

Functional Verification of Two Genes Related to Stripe Rust Resistance in the Wheat-Leymus mollis Introgression Line M8664-3.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most widespread and destructive fungal diseases of wheat worldwide. The cultivation and growth of resistant wheat varieties are the most economical, effective, and environmental friendly methods to control stripe rust. Therefore, it is necessary to use new resistance genes to breed resistant wheat varieties. A single dominant gene temporarily designated as YrM8664-3, from a wheat-Leymus mollis introgression line M8664-3 highly resistant to Chinese predominant Pst races, is a potentially valuable source of stripe rust resistance for breeding. Herein, based on previous YrM8664-3 chromosome location results (bin 4AL13-0.59-0.66 close to 4AL12-0.43-0.59) and expression change information of candidate genes and bioinformatics analysis, several candidate genes with significantly different expression changes were then selected and verified by virus-induced gene silencing (VIGS). Two of the candidate genes temporarily designated as TaFBN [containing plastid lipid-associated proteins (PAP)_fibrillin domain in its protein] and Ta_Pes_BRCT [containing Pescadillo and breast cancer tumour suppressor protein C-terminus (BRCT) domain in its protein], produced the most significant resistance changes in the wheat-Pst interaction system after silencing. These two genes were further verified by Agrobacterium-mediated wheat genetic transformation technology. According to the identification of disease resistance, the resistance function of the candidate gene TaFBN was further verified. Then, the expression of TaFBN under hormone treatment indicated that TaFBN may be related to the salicylic acid (SA) and abscisic acid (ABA) signaling pathways. Combined with the expression of TaFBN in response to environmental stress stimulation, it can be reasonably speculated that TaFBN plays an important role in the resistance of wheat to Pst and is involved in abiotic stress pathways.

DGUOK-AS1 acts as a tumor promoter through regulating miR-204-5p/IL-11 axis in breast cancer

Breast cancer is one of the most lethal malignancies among women; however, the underlying molecular mechanism involved in the progression and metastasis of breast cancer remains unclear. Numerous studies have confirmed that long noncoding RNAs are abnormally expressed in breast cancer and play crucial roles in cell proliferation and metastasis. In the study, we evaluated the functional role and detailed mechanism of DGUOK-AS1 in breast cancer progression and metastasis. DGUOK-AS1 knockdown suppressed proliferation, migration, and invasion of breast cancer cells in vitro and in vivo. Mechanistically, miR-204-5p was identified as an inhibitory target of DGUOK-AS1, which served as a tumor suppressor in breast cancer. Significantly, we found that the ectopic expression of miR-204-5p could counteract DGUOK-AS1-mediated promotion of cell proliferation and metastasis in breast cancer. Moreover, IL-11 was found to be the downstream target of miR-204-5p, and DGUOK-AS1 could protect IL-11 from miR-204-5p-mediated degradation. DGUOK-AS1 overexpression promoted breast cancer cell migration, angiogenesis, and macrophage migration, mediating by the increased secretion of IL-11, which was extremely important for cancer progression. Collectively, our studies reveal that DGUOK-AS1/miR-204-5p/IL-11 axis plays a significant role in the progression and metastasis of breast cancer, and DGUOK-AS1 might be a novel biomarker and therapeutic target for breast cancer.

Interferon-inducible protein, IFIX, has tumor-suppressive effects in oral squamous cell carcinoma

IFIX, a newly discovered member of the interferon-inducible HIN-200 family, has been identified as a tumor suppressor in breast cancer; however, the involvement of IFIX in oral cancer are poorly understood. Here, we demonstrate a relationship between the level of IFIX expression and the invasive or migratory abilities of oral squamous cell carcinoma. Higher IFIX expression significantly correlated with clinicopathological parameters such as the histopathological grade of clinical samples. In vitro, IFIX overexpression suppressed the invasiveness of human tongue squamous cell carcinoma CAL-27 cells, and this inhibitory effect was mediated by stabilization of the cytoskeleton through various cytokeratins along with downregulation of paxillin, an intracellular adaptor protein that promotes tumor invasion. This inhibitory effect does not appear to affect the transformation of cancer stem-like cells in this cell culture model. Altogether, these data provide novel insights into the tumor-suppressive function of IFIX, namely, stabilization of the cancer cell cytoskeleton.

RORα Suppresses Cancer-Associated Inflammation by Repressing Respiratory Complex I-Dependent ROS Generation.

Breast cancer development is associated with macrophage infiltration and differentiation in the tumor microenvironment. Our previous study highlights the crucial function of reactive oxygen species (ROS) in enhancing macrophage infiltration during the disruption of mammary tissue polarity. However, the regulation of ROS and ROS-associated macrophage infiltration in breast cancer has not been fully determined. Previous studies identified retinoid orphan nuclear receptor alpha (RORα) as a potential tumor suppressor in human breast cancer. In the present study, we showed that retinoid orphan nuclear receptor alpha (RORα) significantly decreased ROS levels and inhibited ROS-mediated cytokine expression in breast cancer cells. RORα expression in mammary epithelial cells inhibited macrophage infiltration by repressing ROS generation in the co-culture assay. Using gene co-expression and chromatin immunoprecipitation (ChIP) analyses, we identified complex I subunits NDUFS6 and NDUFA11 as RORα targets that mediated its function in suppressing superoxide generation in mitochondria. Notably, the expression of RORα in 4T1 cells significantly inhibited cancer metastasis, reduced macrophage accumulation, and enhanced M1-like macrophage differentiation in tumor tissue. In addition, reduced RORα expression in breast cancer tissue was associated with an increased incidence of cancer metastasis. These results provide additional insights into cancer-associated inflammation, and identify RORα as a potential target to suppress ROS-induced mammary tumor progression.

Lysophosphatidic acid receptor 6 regulated by miR-27a-3p attenuates tumor proliferation in breast cancer

PurposeLysophosphatidic acid (LPA) is a bioactive molecule which participates in many physical and pathological processes. Although LPA receptor 6 (LPAR6), the last identified LPA receptor, has been reported to have diverse effects in multiple cancers, including breast cancer, its effects and functioning mechanisms are not fully known.MethodsMultiple public databases were used to investigate the mRNA expression of LPAR6, its prognostic value, and potential mechanisms in breast cancer. Western blotting was performed to validate the differential expression of LPAR6 in breast cancer tissues and their adjacent tissues. Furthermore, in vitro experiments were used to explore the effects of LPAR6 on breast cancer. Additionally, TargetScan and miRWalk were used to identify potential upstream regulating miRNAs and validated the relationship between miR-27a-3p and LPAR6 via real-time polymerase chain reaction and an in vitro rescue assay.ResultsLPAR6 was significantly downregulated in breast cancer at transcriptional and translational levels. Decreased LPAR6 expression in breast cancer is significantly correlated with poor overall survival, disease-free survival, and distal metastasis-free survival, particularly for hormone receptor-positive patients, regardless of lymph node metastatic status. In vitro gain and loss-of-function assays indicated that LPAR6 attenuated breast cancer cell proliferation. The analyses of TCGA and METABRIC datasets revealed that LPAR6 may regulate the cell cycle signal pathway. Furthermore, the expression of LPAR6 could be positively regulated by miR-27a-3p. The knockdown of miR-27a-3p increased cell proliferation, and ectopic expression of LPAR6 could partly rescue this phenotype.ConclusionLPAR6 acts as a tumor suppressor in breast cancer and is positively regulated by miR-27a-3p.

EMP3 negatively modulates breast cancer cell DNA replication, DNA damage repair, and stem-like properties

Enhanced DNA damage repair capacity attenuates cell killing of DNA-damaging chemotherapeutic agents. In silico analysis showed that epithelial membrane protein 3 (EMP3) is associated with favorable survival, and negatively regulates cell cycle S-phase. Consistently, loss and gain of function studies demonstrated that EMP3 inhibits breast cancer cell S-phage entry, DNA replication, DNA damage repair, and stem-like properties. Moreover, EMP3 blocks Akt-mTOR signaling activation and induces autophagy. EMP3 negatively modulates BRCA1 and RAD51 expression, indicating EMP3 suppresses homologous recombination repair of DNA double-strand breaks. Accordingly, EMP3 sensitizes breast cancer cells to the DNA-damaging drug Adriamycin. EMP3 downregulates YTHDC1, a RNA-binding protein involved in m6a modification, which at least in part mediates the effects of EMP3 on breast cancer cells. Taken together, these data indicate that EMP3 is a putative tumor suppressor in breast cancer, and EMP3 downregulation may be responsible for breast cancer chemoresistance.

Complement inhibitor CSMD1 modulates epidermal growth factor receptor oncogenic signaling and sensitizes breast cancer cells to chemotherapy

BackgroundHuman CUB and Sushi multiple domains 1 (CSMD1) is a large membrane-bound tumor suppressor in breast cancer. The current study aimed to elucidate the molecular mechanism underlying the effect of CSMD1 in highly invasive triple negative breast cancer (TNBC).MethodsWe examined the antitumor action of CSMD1 in three TNBC cell lines overexpressing CSMD1, MDA-MB-231, BT-20 and MDA-MB-486, in vitro using scanning electron microscopy, proteome array, qRT-PCR, immunoblotting, proximity ligation assay, ELISA, co-immunoprecipitation, immunofluorescence, tumorsphere formation assays and flow cytometric analysis. The mRNA expression pattern and clinical relevance of CSMD1 were evaluated in 3520 breast cancers from a modern population-based cohort.ResultsCSMD1-expressing cells had distinct morphology, with reduced deposition of extracellular matrix components. We found altered expression of several cancer-related molecules, as well as diminished expression of signaling receptors including Epidermal Growth Factor Receptor (EGFR), in CSMD1-expressing cells compared to control cells. A direct interaction of CSMD1 and EGFR was identified, with the EGF-EGFR induced signaling cascade impeded in the presence of CSMD1. Accordingly, we detected increased ubiquitination levels of EGFR upon activation in CSMD1-expressing cells, as well as increased degradation kinetics and chemosensitivity. Accordingly, CSMD1 expression rendered tumorspheres pretreated with gefitinib more sensitive to chemotherapy. In addition, higher mRNA levels of CSMD1 tend to be associated with better outcome of triple negative breast cancer patients treated with chemotherapy.ConclusionsOur results indicate that CSMD1 cross-talks with the EGFR endosomal trafficking cascade in a way that renders highly invasive breast cancer cells sensitive to chemotherapy. Our study unravels one possible underlying molecular mechanism of CSMD1 tumor suppressor function and may provide novel avenues for design of better treatment.

The Impact of Single Nucleotide Polymorphism in the Long Non-coding MEG3 Gene on MicroRNA-182 and MicroRNA-29 Expression Levels in the Development of Breast Cancer in Egyptian Women

Early-stage detection of BC is a critical factor for effective treatment of the disease and can increase the survival rate of BC patients. Long non-coding RNAs can act as miRNA decoys by sequestering miRNAs, thus acting as competing endogenous RNAs and leading to re-expression of miRNA target genes. Maternally expressed 3 (MEG3) is LncRNA and it was reported to be tumor suppressor in breast cancer. The study aims to investigate the effect of MEG3 SNP (rs7158663 G/A) and its association with breast cancer risk in the Egyptian population. In addition, demonstrate the consequence of the MEG3 polymorphism on the expression levels of MEG3, miR-182, and miRNA-29. MEG3 rs7158663 G/A was genotyped and serum MEG3, miRNA-182, and miRNA-29 were measured in 180 breast cancer, 120 FA, and 150 controls by the qPCR. Frequencies of MEG3 rs7158663 GA/AA genotype and A allele were significantly higher in BC patients compared to the controls results showed that serum MEG3 levels were significantly lower, according to the presence of the A allele in different study groups while the expression of miR-182 and miRNA 29 were significantly elevated. MEG3, miR-182, and miRNA-29 are key genes involved in the development of BC, are considered as a novel potential non-invasive diagnostic biomarker for BC.

Reactivation of tumour suppressor in breast cancer by enhancer switching through NamiRNA network

Dysfunction of Tumour Suppressor Genes (TSGs) is a common feature in carcinogenesis. Epigenetic abnormalities including DNA hypermethylation or aberrant histone modifications in promoter regions have been described for interpreting TSG inactivation. However, in many instances, how TSGs are silenced in tumours are largely unknown. Given that miRNA with low expression in tumours is another recognized signature, we hypothesize that low expression of miRNA may reduce the activity of TSG related enhancers and further lead to inactivation of TSG during cancer development. Here, we reported that low expression of miRNA in cancer as a recognized signature leads to loss of function of TSGs in breast cancer. In 157 paired breast cancer and adjacent normal samples, tumour suppressor gene GPER1 and miR-339 are both downregulated in Luminal A/B and Triple Negative Breast Cancer subtypes. Mechanistic investigations revealed that miR-339 upregulates GPER1 expression in breast cancer cells by switching on the GPER1 enhancer, which can be blocked by enhancer deletion through the CRISPR/Cas9 system. Collectively, our findings reveal novel mechanistic insights into TSG dysfunction in cancer development, and provide evidence that reactivation of TSG by enhancer switching may be a promising alternative strategy for clinical breast cancer treatment.

Retraction.

Retraction: "MicroRNA-590-5p functions as a tumor suppressor in breast cancer conferring inhibitory effects on cell migration, invasion, and epithelial-mesenchymal transition by downregulating the Wnt-β-catenin signaling pathway," by Jin Gao, Shao-Rong Yu, Yuan Yuan, Li-Li Zhang, Jian-Wei Lu, Ji-Feng Feng, Sai-Nan Hu, J Cell Physiol. 2019; 1827-1841: The above article, published online on 07 September 2018 in Wiley Online Library (https://onlinelibrary.wiley.com/doi/10.1002/jcp.27056) has been retracted by agreement between the journal's Editor in Chief, Prof. Dr. Gregg Fields, and Wiley Periodicals LLC. The retraction has been agreed following an investigation based on allegations raised by a third party. A detailed investigation revealed that several image elements of the experimental data were published elsewhere in a different scientific context. Thus, the editors consider the conclusions of this article to be invalid.

Abstract 3111: Notch3 functions as a tumor suppressor in ER-positive breast cancer

Abstract The Notch signaling pathway has been implicated in the development as well as tumorigenesis of the mammary gland. Notch3 promotes luminal cell specification and marks a highly clonogenic luminal progenitor population. Aberrant Notch3 activation has been shown to promote the growth of basal breast cancer as well as resistance to hormonal therapy in metastatic luminal breast cancer. Interestingly, recent studies also suggest a tumor-suppressive function of Notch3 in mammary epithelium through regulation of estrogen receptor α (ER). Here we report the expression and functional analysis of Notch3 in the mouse mammary gland. X-gal staining of the Notch3β-Geo/+ mammary gland showed that Notch3 was highly expressed in luminal cells throughout mammary development with exception at the initiation of post-lactational involution, when Notch3 expression was restricted to the basal cells. Deletion of Notch3 caused decreased Notch activation in the CD24HiCD49fLo subpopulation of the pubescent mammary gland, accompanied by a significant decrease in the number of CD24HiCD49fLoCD61+ luminal progenitor cells. Whole-mount preparation of the Notch3 knockout mammary glands showed normal development during puberty, pregnancy, lactation and involution. Surprisingly, parous Notch3 knockout mice developed mammary ductal hyperplasia by 10 months of age, some of which progressed to ductal carcinoma in situ, and ultimately to invasive and metastatic cancer. Parous Notch3 knockout mice exhibited an expansion of the CD24HiCD49fLo subpopulation, and mammary tumors from these mice were composed predominantly of CD24HiCD49fLo cells. The vast majority of these tumors were ER-positive and relatively well differentiated, with a papillary and/or glandular pattern. They expressed the luminal marker cytokeratin 8, and some of them co-expressed cytokeratin 14, a basal marker. All Notch3 knockout mammary tumors showed high level expression of Cyclin D1. These results suggest that Notch3 may prevent ER-positive breast cancer through suppression of CD24HiCD49fLo progenitor cell self-renewal in the postpartum mammary gland. In addition to its impact on mammary epithelium, deletion of Notch3 altered the mammary microenvironment, in particular, brown adipocyte differentiation in the mammary fat pad. Further experiments will be performed to define a potential role for Notch3-regulated brown adipose tissue in breast cancer initiation and progression. Finally, analysis of TCGA and METABRIC human breast cancer data sets revealed a negative correlation between expressions of NOTCH3 and ESR1 (encoding estrogen receptor α), and association of high NOTCH3 expression with enhanced survival of patients with luminal A and luminal B subtype breast tumors. Taken together, Notch3 can act as a tumor suppressor in the mammary epithelium, and possibly in the mammary microenvironment as well, to prevent development and metastasis of ER-positive breast cancer. Citation Format: Wen-Cheng Chung, Sean E. Egan, Keli Xu. Notch3 functions as a tumor suppressor in ER-positive breast cancer [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 3111.

LncRNA NEAT1 promotes the Taxol resistance of breast cancer via sponging the miR-23a-3p-FOXA1 axis.

Breast cancer is the most prevalent malignancy among women worldwide. Paclitaxel (Taxol) is a widely applied chemotherapeutic agent against breast cancer. Although Taxol therapy has achieved improvements recently, development of chemoresistance of breast cancer patients is a major obstacle, leading to therapeutic failure. Long non-coding RNAs (lncRNAs) play pivotal roles in tumorigenesis and progresses of breast cancer. However, the biological roles and molecular targets of lncRNA NEAT1 in Taxol-resistant breast cancer remain unclear. Here, we report that NEAT1 is significantly upregulated in breast tumors and cell lines. In addition, silencing NEAT1 effectively sensitizes breast cancer cells to Taxol. Bioinformatical analysis and luciferase assay demonstrated that miR-23a-3p could be sponged and downregulated by NEAT1. We demonstrated that miR-23a-3p was downregulated and functioned as a tumor suppressor in breast cancer. Furthermore, in the established Taxol-resistant MDA-MB-231 breast cancer cell line, we detected significantly increased NEAT1 expression and downregulated miR-23a-3p expression. Importantly, FOXA1 was identified and validated as a direct target of miR-23a-3p in breast cancer cells. Rescue experiments demonstrated that the restoration of miR-23a-3p in NEAT1-overexpressing Taxol-resistant breast cancer cells successfully overcame the NEAT1-promoted Taxol resistance. Taken together, our results revealed the clinical roles and molecular mechanisms for the NEAT1-mediated chemoresistance, providing new insights into the development of non-coding RNA-based therapeutic strategies for enhancing the anti-cancer effects of traditional chemotherapeutic drugs.

Abstract 2488: Elucidating the role of G0S2 in breast cancer

Abstract Breast cancer has the second-highest cancer mortality rate for women in the United States. There are effective therapies available and a growing list of biomarkers for prognosis. However, new breast cancer targets are critically needed for patients refractory to available therapies. The present study evaluates the role of gap 0 switch 2 (G0S2), in breast cancer. Using online databases, we observed G0S2 expression is downregulated in patients with estrogen receptor-positive (ER+) breast cancer and patients with high G0S2 expression have a lower rate of relapse after treatment. Previously, our lab showed G0S2 overexpression in ER+ breast cancer cell lines resulted in decreased proliferation. Further knockout of G0S2 in murine embryonic fibroblast resulted in higher oncogenic transformation and resistance to mTOR inhibitors. These results suggest that G0S2 has a tumor suppressive function in ER+ breast cancer. To test whether G0S2 has a role in ER-negative breast cancer global knockout of G0S2 was engineered in the ER-negative MMTV-PyMT transgenic mouse model. Slower tumor progression and decreased lung metastasis was observed in G0S2-null transgenic females compared to wild-type transgenic females. These data suggest that the role of G0S2 in breast cancer in dependent on ER-status, where G0S2 functions as a tumor suppressor in ER-positive breast cancer and a tumor promoter in ER-negative breast cancer. Molecular and genetic studies manipulating G0S2 and ER in various breast cancer contexts are ongoing and will help elucidate that precise role of G0S2 in breast cancer and provide clarity on the potential of G0S2 as a novel prognostic marker and therapeutic target. Citation Format: Andrea K. Corbet, Emmanuel Bikorimana, Ratnakar Singh, Zeeshan Fazal, Raya I. Boyd, Sarah Freemantle, Michael J. Spinella. Elucidating the role of G0S2 in breast cancer [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 2488.

Long Noncoding RNA GAS5 in Breast Cancer: Epigenetic Mechanisms and Biological Functions.

Long noncoding RNAs (lncRNAs) have been identified as contributors to the development and progression of cancer through various functions and mechanisms. LncRNA GAS5 is downregulated in multiple cancers and acts as a tumor suppressor in breast cancer. GAS5 interacts with various proteins (e.g., E2F1, EZH2, and YAP), DNA (e.g., the insulin receptor promoter), and various microRNAs (miRNAs). In breast cancer, GAS5 binds with miR-21, miR-222, miR-221-3p, miR-196a-5p, and miR-378a-5p that indicates the presence of several elements for miRNA binding (MREs) in GAS5. Mediated by the listed miRNAs, GAS5 is involved in the upregulation of a number of mRNAs of suppressor proteins such as PTEN, PDCD4, DKK2, FOXO1, and SUFU. Furthermore, the aberrant promoter methylation is involved in the regulation of GAS5 gene expression in triple-negative breast cancer and some other carcinomas. GAS5 can stimulate apoptosis in breast cancer via diverse pathways, including cell death receptors and mitochondrial signaling pathways. GAS5 is also a key player in the regulation of some crucial signal pathways in breast cancer, such as PI3K/AKT/mTOR, Wnt/β-catenin, and NF-κB signaling. Through epigenetic and other mechanisms, GAS5 can increase sensitivity to multiple drugs and improve prognosis. GAS5 is thus a promising target in the treatment of breast cancer patients.

Implications of targeted next-generation sequencing for bladder cancer: report of four cases

BackgroundBladder cancer is considered heterogeneous diseases with two major subgroups: non-muscle- invasive bladder cancer (NMIBC) and muscle invasive bladder cancer (MIBC). It is a major healthcare problem, and it is one of the leading causes of mortality worldwide. Genetic mutations are not only a cause for carcinogenesis but are also a way for treatment strategy. The present study aimed to investigate breast cancer (BRCA genes) tumor suppressor gene mutations in bladder cancer tissue and combined blood samples for patients who developed secondary tumor after or during trimodal therapy. Fresh tissue samples and their matched blood samples were collected from four patients with bladder cancer. The objective regions for the examined genes (BRCA1 and BRCA2) were sequenced using next-generation sequencing (NGS); generated BAM files were uploaded to the cloud-based Ionreporter server, and the Oncomine BRCA-specific plugin was used to analyze the paired normal and tumor sample for each patient using the default plugin parameters. ResultsIntronic BRCA1 mutation c.5050-104 C >T was reported among the four investigated bladder cancer patients, and three somatic mutations were reported as follows: two of them were found to be benign rs1064793056 and rs28897679 on the Clinivar database and one nonsense pathogenic variant rs80357006. BRCA 2 gene mutation reported an exonic synonymous mutation rs397507876 in the tissue and germline DNA. Patients were treated with trimodal; however, three bladder cancer patients who reported BRCA mutations developed secondary tumors. ConclusionIdentification of mutational BRCA changes in bladder cancer is a promising marker for better treatment strategy. Further studies are encouraged on a large cohort of bladder cancer patients to confirm our findings.