Introduction
Triple-negative breast cancer (TNBC), with low or negative ER, PR, or HER2 expression, is biologically heterogeneous, representing 10%-20% of all invasive breast cancers [
1]. TNBC is more aggressive, has more advanced stages, and has higher rates of recurrence and metastasis than non-TNBC subtypes [
1,
2]. Due to the lack of targeted agents, TNBC patient treatment is limited to cytotoxic chemotherapy [
3]. However, patients with TNBCs are unlikely to achieve significant local- and disease-free survival advantages from adjuvant chemotherapy treatment in women [
2,
4,
5]. The therapeutic strategy has recently changed with the advent of poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis) for patients harboring BRCA mutations [
1]. PARPis are thought to function by inhibiting DNA repair and replication in cancer cells deficient in BRCA1/2-dependent homologous recombination (HR) pathways through a process known as synthetic lethality [
6]. Olaparib, a PARPi approved by the US Food and Drug Administration (FDA), selectively binds to and inhibits PARP. BRCA1-associated breast cancer is frequently a TNBC, but approximately 25% of TNBC patients carry a BRCA1 mutation, suggesting the limited application of PARPis [
7]. Although olaparib monotherapy provides better median progression-free survival than single-agent chemotherapy, responses have not been highly durable, even in BRCA-mutant breast cancer patients [
6,
8]. In addition, the development of drug resistance limits the efficacy of PARPis.
A similar situation has also been observed with among patients who received chemotherapy. Chemotherapy leads to an initial substantial response rate, followed by poor outcomes, such as frequent relapses and lower overall survival [
9‐
11]. Cisplatin, which is a first generation platinum-based drug, is used to treat many solid tumors (e.g., lung, breast, and head and neck cancers) [
12]. Platinum derivatives are alkylating agents that exert their effect by binding to DNA and inducing multiple single-strand breaks, resulting in apoptosis or other forms of cell death. Clinical trial data suggested that TNBC or other cancers patients with BRCA mutations exhibit more sensitivity to cisplatin and receive more benefits from cisplatin because of synthetic lethality [
13,
14].
Therapeutic resistance is the main obstacle to TNBC patients experiencing satisfying outcomes. Moreover, the molecular mechanisms of therapeutic resistance are complex and interrelated among genomic and nongenomic factors [
15‐
17]. Compared with ER- or HER2-positive breast cancer cells, TNBC cells display cancer stem-like cell (CSC) signatures at the functional, molecular, and transcriptional levels [
18,
19]. TNBC aggressiveness has been associated, in part, with the breast cancer stem-like cells (ΒCSCs) that mediate tumor metastasis and contribute to the development of treatment resistance and recurrence. The reported molecular mechanisms underlying therapeutic resistance mediated by CSCs include the maintenance or acquisition of stemness and dormancy, increased DNA repair and drug efflux capacity, decreased apoptosis rates, and an interaction between CSCs and their supportive microenvironment, which is called the CSC niche [
17,
20]. Therefore, therapies targeting CSCs are vital for achieving complete therapeutic responses and prolonging patient survival [
19‐
21].
TAB182 was first identified as a novel 182 kDa tankyrase 1-binding protein by Seimiya H and colleagues in 2002 [
22], and it was also named TNKS1BP1. TAB182 can directly bind to tankyrase 1 through its own ankyrin (ANK) domain and is identified by its RXXPDG motif [
22,
23]. TAB182 is located in the nucleus and cytoplasm. Cytoplasmic TAB182 interacts with actin-capping proteins and is a negative regulator of cell motility and invasion [
24]. In addition, TAB182 is a component of a larger mammalian CCR4-NOT protein complex, which can modulate helicase selective recruitment to the complex and shows the potential ability to determine the outcome of the targeted mRNA [
25‐
27]. Additionally, several studies have reported that TAB182 participates in DNA double-strand break (DSB) repair and functions as a potential therapeutic target to increase the radio-/chemosensitivity of various tumors [
28‐
31]. For instance, TAB182 modulates irradiation-induced DNA-PKcs phosphorylation and contributes to DNA DSB repair by regulating PARP-1/DNA-PKcs interaction [
29]. However, the correlation between TAB182 and clinical outcomes is still unclear. The high expression level of TAB182 has been correlated with the poor survival outcomes of patients with lung cancer or esophageal squamous cell carcinoma (ESCC) [
28,
30]. In the context of pancreatic cancer, TAB182 expression was lower in invasive regions than in normal and noninvasive regions [
24]. TAB182 might be a prognostic marker and therapeutic target, but the precise roles of TAB182 in tumorigenesis have not been identified.
In this study, we selected MDA-MB-231 and BT549 cells, which are BRCA wild-type TNBC cells, to identify the functions of TAB182 in the development and progression of TNBC. We found that TAB182 expression was downregulated in TNBC cells, and TAB182 deletion increased the cell proliferation, colony formation, cell migration, and invasion, which suggested that TAB182 might act as a tumor suppressor gene in TNBC cells. Our paper first presents the gene expression profiles regulated by TAB182 in TNBC cells by RNA-seq assay. Both transcriptome analysis and in vitro experiments revealed that TAB182 plays a significant role in the development of cancer stemness in TNBC cells. Furthermore, TAB182 deletion contributes to the resistance of TNBC cells to olaparib and cisplatin by upregulating GLI2. GLI2 is a gene downstream in the Hippo signaling pathway, the most significant CSC-related pathway enriched by TAB182-regulated genes. Our results reveal a novel function of TAB182 as a prospective negative mediator of cancer stemness and resistance to olaparib or cisplatin in TNBC cells.
Materials and methods
Cell lines and treatments
Human breast cancer cell lines, including MCF7, ZR-75–1, MDA-MB-231, and BT549, and the human normal breast cell line MCF10A cell, were obtained from the American Type Culture Collection (ATCC). The MCF7, ZR-75–1, and MDA-MB-231 cells were cultured in DMEM (VCM5313, VIVICUMTM bioscience, Beijing, China) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin–streptomycin (P/S). The BT549 cells were cultured in RPMI-1640 complete medium (PM150110B, Procell, Wuhan, China). The MCF10A cells were cultured in a medium specific for the MCF10A cell line (CM-0525, Procell, Wuhan, China). The cell lines were tested for mycoplasma. The cells were treated with olaparib (S1060, Selleck Chemicals) or cisplatin (S1166, Selleck Chemicals).
shRNA, siRNA, and plasmids
TAB182 shRNA and negative control (NC) shRNA were cloned into the lentivirus vector LV3 (H1/GFP&Puro) (GenePharma, Suzhou, China). TNBC cells were infected with lentivirus harboring two TAB182 shRNAs, #1 and #2, or an NC shRNA, and after infection, the cells were selected after treatment with medium containing 2 μg/ml puromycin for approximately seven days, during which time, stable TAB182 knockdown MDA-MB-231 cells were generated.
TAB182-shRNA#1, sense: 5’-UAUCCAAGCGCUCUUCCCAAACUCC-3’, anti-sense: 5’-GGAGUUUGGGAAGAGCGCUUGGAUA-3’;
TAB182-shRNA#2, sense: 5’-AAGACGAGGAGUAAUCUUCACCCUG-3’, anti-sense: 5’-CAGGGUGAAGAUUACUCCUCGUCUU-3’.
The sequences of siRNA targeting TAB182 were as follows:
sense: 5’- GCCAAGACCAGAGUAAAGUTT-3’,
anti-sense: 5’-ACUUUACUCUGGUCUUGGCTT-3’.
The siRNA sequences targeting GLI2 were as follows:
sense: 5’-GCUUCACAUGACAGAUGUUTT-3’,
anti-sense: 5’-AACAUCUCUCAUCUGAAGCGG-3’.
For siRNA transfection, GP-transfect-Mate (G04009, GenePharma) was used.
To overexpress TAB182, cells were transfected with a pcDNA3.1+-TAB182-expressing vector constructed by GenePharma (Suzhou, China) using GP-transfect-Mate (G04009, GenePharma).
Cell proliferation assay
CCK-8 (CK04, Dojindo Laboratories, Japan) was used to measure cell proliferation according to the manufacturer’s instructions. Cells with or without siRNA transfection for 72 h were seeded in a 96-well plate (1500 cells/well) and cultured for 0 days, 2 days, 3 days, and 4 days. To measure cell viability after olaparib or cisplatin treatment, 2000 cells/well were seeded in a 96-well plate, and after 24 h, they were treated with olaparib or cisplatin for 0 days, 1 day, 2 days, and 3 days. Cell proliferation was measured at the indicated time points by adding 10 µl/well CCK-8 reagent 3 h to the cultures before the measurement was taken. A Tecan Sunrise absorbance microplate reader was used to measure absorbance at 450 nm.
A colony formation assay was performed to assess the cell clonogenic ability. Cells were plated into 6-well plates at 300 cells per well. After 24 h, the cells were treated with the indicated doses of olaparib (DMSO was the control) or cisplatin (ddH2O was the control). After culturing for 14 days, the cell clones were fixed with 4% paraformaldehyde for 15 min, stained with 0.1% crystal violet staining solution for 0.5 h -1 h, washed with PBS and dried. Images were acquired by scanning the plates using a scanner. The colonies (consisting of more than 50 cells) were counted by visual observation. The colony formation rate (%) was calculated according to the following formula: number of colonies per well/number of cells seeded per well × 100%.
Invasion assay
For an invasion assay, Transwell chambers (8.0 μm pore size, Costar 3422, Corning incorporated) were precoated with Matrigel (#356,234, Corning) according to the manufacturer’s protocols. Cells were cultured in serum-starved medium overnight, and then 5 × 104 cells/well were seeded in the upper chamber containing 200 µl serum-free DMEM. The lower chambers were filled with 600 µl DMEM complete medium. After 24 h of incubation at 37 °C, the cancer cells that penetrated the membrane were fixed with 4% paraformaldehyde for 15 min and stained with 0.1% crystal violet staining solution for 0.5 h -1 h. The chamber was washed with PBS solution, and the upper chambers were carefully cleaned with a cotton swab. After the chamber was dried, five random fields in each chamber were observed under a microscope (at 10 × magnification), and the number of invading cells per field was counted under a microscope.
Wound healing assay
Cells were serum-starved for 24 h, trypsinized and seeded into 6-well plates at a density of 6 × 105 cells/well in serum-free medium. After 24 h, a scratch wound was introduced in the across the cell monolayer with a sterilized 200 µl pipette tip. Cells migrating into the wounded area were observed at different time points (0 and 24 h) under an inverted light microscope at a magnification of × 10. In addition, five random fields in each well were observed under a microscope. Triplicate experiments were performed. ImageJ was used to measure the scratching wounds, and the migration rate was calculated according to the following formula: (areas at 0 h—areas at 24 h)/areas at 0 h × 100%.
Five thousand cells were resuspended in serum-free tumorsphere medium (CCM012, StemXVivo, R&D Systems) and then seeded as single cells into each well of a Nunclon Sphera 12-well plate (Thermo Scientific, 12–566-434) with a super low cell attachment surface. After 10–12 days of incubation in a 5% CO2 and 37 °C incubator, five random fields in each well were viewed under a microscope. The experiments were performed in triplicate. Then, the number of mammospheres (at 10 × magnification) greater than 20 μm diameter was counted using ImagJ software, and the quantification data are shown as the number of spheres per 5000 cells.
A soft agar colony formation assay was performed according to a previously published protocol [
32]. A total of 2000 cells were obtained as a single cell in the upper layer of agar of each well in a 6-well plate, and then, the plates were plated into a 37 °C humidified cell culture incubator. Two hundred microliters of culture medium was added to each well every three days to prevent desiccation. After approximately 21 days, images were taken under a microscope at 4 × or 10 × magnification. Colonies containing more than 50 cells were counted under a microscope at 4 × magnification, and the colony formation rate (%) was calculated according to the following formula: number of colonies per well/number of cells seeded per well × 100%.
ALDEFLUOR assay
An ALDEFLUOR kit (#01700, StemCell Technologies, Canada) was used to measure ALDH enzyme activity. Diethylaminobenzaldehyde (DEAB), a specific inhibitor of ALDH, was used as the negative control. However, the TAB182 or control shRNAs used to generate stable TAB182 knockdown cells emitted GFP fluorescence, which overlapped with and interfered with the ALDH-positive fluorescence. Therefore, we used TAB182 siRNA-transfected, or TAB182-overexpressing TNBC cells to perform this assay. TNBC cells were transfected with 100 nM TAB182 siRNA or 2 μg pcDNA3.1+-TAB182-expressing plasmids in one well of a 6-well plate. After 72 h, the cells were processed for ALDEFLUOR assay according to the manufacturer’s protocols and then analyzed by NovoCyte 2060R Flow Cytometer.
Western blotting
Total protein was extracted using M-PER™ Mammalian Protein Extraction Reagent (#78,501, Thermo Scientific). Equal amounts of protein (0.2 μg-1 μg) were loaded into the separation module kit (12–230 kDa or 66–440 kDa) and analyzed using an automated Simple Western system (Protein Simple WES) based on capillary electrophoresis technology to identify and quantify the levels of TAB182 (G-5, sc-514490, Santa Cruz, 1:50), GLI2 (C-10, sc-271786, Santa Cruz, 1:20), SOX2 (D6D9, #3579 s, CST, 1:20), and Slug (ab27568, Abcam, 1:20), according to the manufacturer’s instruction (Protein Simple, USA). Anti-α tubulin antibody (6A204, sc-69969, Santa Cruz, 1:100) or an anti-GAPDH antibody (TA-08, ZSGB-BIO, 1:100) was used as the internal control. Compass software (Protein Simple) was used to present the Western immunoblots.
Quantitative RT‒PCR (qPCR)
Following the manufacturer's procedure, total RNA was extracted using the TRIzol reagent (Invitrogen, CA, USA). One microgram of RNA was reverse transcribed using the HiScript® III RT SuperMix for qPCR (+ gDNA wiper) (R323-01) (Vazyme Biotech, San Diego, USA). qPCR was performed on diluted cDNA with Taq Pro Universal SYBR qPCR Master Mix (Q712-02) (Vazyme Biotech, San Diego, USA). GAPDH was used as a reference gene, and the 2−ΔΔCt formula was used to calculate relative expression. Primer sequences are as follows:
TAB182 forward: 5’- GGCCAGTAAAGTCTCCAGCA-3’;
TAB182 reverse: 5’- GTTGAAGGCCAGGTCGGAAG-3’.
GLI2 forward: 5’-GACATGCGACACCAGGAAGGAAGGT-3’;
GLI2 reverse: 5’-GCCGGATCAAGGAGATGTCAGAGATG-3’.
ALDH1A1 forward: 5’-CCAGGGCCGTACAATACCAA-3’;
ALDH1A1 reverse: 5’- CAGTGCAGGCCCTATCTTCC-3’.
GAPDH forward: 5’-GTCTCCTCTGACTTCAACAGCG-3’;
GAPDH reverse: 5’-ACCACCCTGTTGCTGTAGCCAA-3’.
RNA-seq
RNA-seq experiments were performed in stable TAB182 knockdown cells or control cells. Experiments were performed in triplicate for each condition. LC Sciences (Hangzhou, China) conducted library construction and sequencing. Libraries were sequenced as t paired-end, 2 × 150 bp reads on an Illumina NovaSeq™ 6000 and aligned to the UCSC (
http://genome.ucsc.edu/) Homo sapiens reference genome using the HISAT package. The mapped reads of each sample were assembled using StringTie. After the final transcriptome was generated, StringTie and EdgeR were used to estimate the expression levels of all transcripts. The data presented in this publication have been deposited in the NCBI Gene Expression Omnibus (GEO) database (GSE200038).
Both |fold change (FC)|> 1.5 and
P values < 0.05 were considered to be the threshold to indicate differentially expressed genes for further analysis. Analysis of enrichments of genes in Gene Ontology (biologic processes, cell component, and molecular function) and KEGG pathway [
33] were carried out with the online tool Database for Annotation, Visualization, and Integrated Discovery (DAVID,
https://david.ncifcrf.gov/).
P < 0.05 was considered significant.
Statistical analysis
The data shown are the means with standard deviations (SD) from three independent experiments. An unpaired two-tailed Student’s t test was performed to compare the significance of the differences between the two groups. P < 0.05 was considered statistically significant.
The survival analysis was generated using the KM Plotter online tool (
https://kmplot.com). The hazard ratio with 95% confidence intervals and the log-rank
P value were calculated using Cox proportional hazards regression, and the two groups were separated on the basis of the median as the cutoff. Welch's test was performed to calculate the significance of a global difference between different groups for gene expression in different tissue subtypes using bc-GenExMiner v4.9 (
http://bcgenex.ico.unicancer.fr/BC-GEM/). If a significant global difference was identified (
P < 0.05) and there were more than two groups, Dunnett-Tukey–Kramer's test was computed for each pairwise comparison.
Discussion
To date, the published literature on the roles of TAB182 has been focused mainly on radioresistance driven by TAB182 contributions to DNA repair in various tumors. There is no comprehensive understanding of the functions of TAB182 in tumorigenesis, especially in breast cancer. Although TAB182 has been reported to be associated with tumor aggression and metastasis, reports of its roles in different tumors or cells have been inconsistent [
24,
33]. In this study, we found that downregulation of TAB182 increases the proliferation, colony formation, migration, and invasion of TNBC cells, consistent with the study of T. Ohishi and colleagues [
24], who found a low expression level of TAB182 in pancreatic cancer cells and found that TAB182 deletion played an essential role in cell motility and invasion. However, Gao A et al. found that the downregulation of TAB182 inhibited ESCC cell invasion and migration, and TAB182 was expressed at a high level in ESCC compared to normal cells or tissues [
33]. These contradictory findings suggest that TAB182 may play distinct roles in different types of cancer cells and may be associated with the different basal expression levels of TAB182 in cancer cells compared to that in normal cells or tissues. Therefore, we analyzed the mRNA expression level of TAB182 using online databases. Compared to normal breast tissues or non-TNBC samples, a lower expression level of TAB182 was found in TNBC. Then, we confirmed the downregulation of TAB182 in TNBC cell lines at the protein and mRNA level. Cell migration and invasion are required for cancer cell metastasis, and cancer metastasis is the main reason for mortality in breast cancer patients. These findings suggested that TAB182 may function as a tumor suppressor gene in TNBC cells by inhibiting cell proliferation, colony formation, and cell invasion and migration.
Since the aforementioned results show clear cell phenotypes acquired after TAB182 KD in TNBC cells, the downstream signaling associated with TAB182 deletion was evaluated at the transcriptome level. Our study confirmed the function of TAB182 at the genome level via RNA-seq analysis, which provided information the gene expression profiles modified by TAB182, enabling further study of its regulatory mechanisms. The functional enrichment analysis results revealed that genes upregulated by TAB182 deletion were enriched in cell proliferation and positive regulation of cell migration biological processes, which strongly supports the acquisition of a functional phenotype of TAB182 in TNBC cells. In addition, we found that TAB182 depletion upregulated genes significantly associated with the positive regulation of actin filament polymerization, such as
CCL24 and
CCL26, which play essential roles in cancer cell invasion and migration [
36,
37]. Furthermore, the expression of
ICAM1 or
TGFBI has been shown to be upregulated in TNBC and related to tumor aggressiveness and metastasis [
38‐
40], and the expression of both genes were increased in TAB182 KD cells and participated in the cell adhesion process in the present study. The knockdown of TAB182 inhibited the expression of genes that participate meaningfully in the DNA damage and repair signaling pathways, consistent with the known function of TAB182 in DNA damage repair after ionizing radiation (IR) or adenovirus infection [
28,
31]. The results of the KEGG analysis showed that TAB182-regulated genes participated in the homologous recombination signaling pathway, which is one of the critical pathways involved in the repair of double-strand DNA damage. Moreover, the set of genes downregulated by TAB182 deletion was associated with cell cycle process, which corresponds to a recent study indicating that TAB182 downregulation hindered IR-induced G2/M arrest [
30]. Additionally, our RNA-seq data provide more information to further explore unknown or novel functions of TAB182. For instance, the dysregulation of TAB182 modified the Hippo signaling pathway and the PI3K-Akt signaling pathway, which play critical roles in regulating various cellular functions, including cell growth and proliferation, and their dysregulation has been implicated in several diseases, including cancer [
41,
42].
For TNBC patients, chemotherapy (e.g., cisplatin) has been the main treatment option for a long time. Recently, the therapeutic strategy has changed with the advent of PARP inhibitors (e.g., olaparib) for patients harboring a mutation in the BRCA genes [
7,
13]. Although chemotherapy or PARP inhibitors lead to an initial substantial response, most patients inevitably develop resistance [
9‐
11]. Therapeutic resistance is a significant barrier to complete breast cancer management and is often followed by poor outcomes, such as frequent relapses and lower overall survival [
43]. Dysregulation of the DNA damage repair process is vital to drug sensitivity, including sensitivity to genotoxic agents or DNA-damaging anticancer drugs [
44]. Therefore, we explored the effects of TAB182 on drug sensitivity in the MDA-MB-231 and BT549 cell lines, which are BRCA-wild-type TNBC cell lines, and compared the results to those obtained with BRCA-mutated cells, which exhibit intrinsic resistance to olaparib or cisplatin [
45,
46]. Our study indicates that the overexpression of TAB182 increased the inhibitory effects of olaparib or cisplatin on cell viability more than either treatment alone, which indicates that TAB182 expression negatively regulates therapeutic resistance in TNBC cells. This is inconsistent with the roles of TAB182 in A549 lung cancer cells [
28]. How TAB182 downregulation results in drug resistance in TNBC cells remains to be investigated.
An integrative analysis of the TNBC cell phenotypes and gene expression profiles induced by TAB182 deletion suggested that TAB182 might regulate the formation of CSCs. The downregulation of TAB182 increased cell proliferation, cell invasion, and cell migration and chemoresistance, which are functional outcomes induced by the presence of CSCs. In this study, a KEGG pathway analysis indicated that the expression of gene sets regulated by TAB182 deletion was significantly enriched in cancer stemness-related pathways, namely, the Hippo signaling pathway and the PI3K-AKT signaling pathway. Both of these pathways play vital roles in regulating stemness in various cancers, including TNBC [
15,
47]. According to the literature, the CSCs represent the major sources of malignant progression and poor prognosis of tumors because of their features which differ from those non-CSCs, such as activation or acquisition of self-renewal ability and establishment of a heterogeneous population of tumor cells after treatment [
48]. In our study, the properties of CSCs were examined using in vitro functional experiments. Sphere formation and soft agar colony formation assays demonstrated that TAB182 deregulation increased the tumorigenic and self-renewal abilities of TNBC cells. Furthermore, the percentage of CSCs decreased after TAB182 overexpression. Our study showed that TAB182 plays a considerable role in developing the cancer stem-like properties of TNBC cells.
Various studies have reported that dysregulation of some breast stem cell markers (e.g., ALDH1A1) or signaling pathways (e.g., Hippo/YAP pathway or Hedgehog signaling) relieves drug resistance in different cancers [
17,
49‐
51]. Here, we assumed that TAB182 deletion induced therapy resistance related to cancer stemness. Based on our RNA-seq data, we focused on the Hippo signaling pathway, the most significant pathway enriched by the TAB182-KD-regulated gene set. Among the genes in this gene set, GLI2 was markedly upregulated by TAB182-KD (fold change = 1.93,
P < 0.001), which was verified by Western blot and RT‒qPCR analysis in this study. GLI2 is a downstream target gene of the Hippo/YAP signaling pathway and a transcriptional activator of Hedgehog signaling, and the two aforementioned pathways are essential regulators of CSC maintenance [
52,
53]. GLI2 has been reported to affect stemness and drive chemoresistance in various cancers [
54‐
59]. For instance, in colorectal cancer, the hypoxic tumor microenvironment activates the expression of GLI2 in CSCs, resulting in increased stemness/dedifferentiation and intrinsic resistance to chemotherapy [
54]. In our study, we inhibited GLI2 expression by siRNA, which reversed the increase in the cell proliferation rate that had been induced by TAB182 deletion. In addition, GLI2 deletion inhibited the expression level of ALDH1A1 and the percentage of ALDH-positive cells independent of TAB182 KD. These findings suggest that TAB182 KD promotes CSC development by stimulating GLI2 expression. After olaparib or cisplatin treatment, inhibition of GLI2 overcame cell resistance induced by lower expression of TAB182. Taken together, these results indicate that low expression of TAB182-induced tumorigenesis and therapeutic resistance might be mediated through cancer stemness signaling pathways, and GLI2 shows the potential to be a target and leveraged to reduce cancer stemness in TAB182 low-expression breast cancers.
The limitation of our study is that we explored only the functions of TAB182 via in vitro experiments, and the results need to be validated through in vivo experiments. Additionally, the regulatory effects of TAB182 KD on GLI2 expression need to be further investigated to confirm the specific mechanisms. There is still an urgent need for extensive research on therapy resistance to develop novel biomarkers and therapeutic targets that can predict therapeutic responses or improve the clinical outcomes of TNBC patients. However, the molecular mechanisms of therapeutic resistance are complex and interrelated, involving both genomic and nongenomic factors [
15‐
17]. For the clinical application of TAB182 to be realized, we aim to identify the core mechanisms involved in regulating TAB182 deletion-driven cell stemness and therapy resistance in our further study.
In summary, our results reveal gene expression profiles regulated by TAB182 and identify TAB182 has a possibility to act as a novel negative regulator related to the development of cancer stem-like properties and olaparib/cisplatin resistance that regulates GLI2 expression in the BRCA-proficient TNBC cell lines. Our findings suggest that TAB182 may be a tumor suppressor gene and a potential therapeutic target for TNBC patients.
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