SURVIVIN as a marker for quiescent-breast cancer stem cells-An intermediate, adherent, pre-requisite phase of breast cancer metastasis

A comprehensive review and in silico analysis of the role of survivin (BIRC5) in hepatocellular carcinoma hallmarks: A step toward precision

Hepatocellular carcinoma (HCC) is a complex malignancy driven by the dysregulation of multiple cellular pathways. Survivin, a key member of the inhibitor of apoptosis (IAP) family, plays a central role in HCC tumorigenesis and progression. Despite significant research, a comprehensive understanding of the contributions of survivin to the hallmarks of cancer, its molecular network, and its potential as a therapeutic target remains incomplete. In this review, we integrated bioinformatics analysis with an extensive literature review to provide deeper insights into the role of survivin in HCC. Using bioinformatics tools such as the Human Protein Atlas, GEPIA, STRING, TIMER, and Metascape, we analyzed survivin expression and its functional associations and identified the top 20 coexpressed genes in HCC. These include TK1, SPC25, SGO2, PTTG1, PRR11, PLK1, NCAPH, KPNA2, KIF2C, KIF11, HJURP, GTSE1, FOXM1, CEP55, CENPA, CDCA3, CDC45, CCNB2, CCNB1 and CTD-2510F5.4. Our findings also revealed significant protein-protein interactions among these genes, which were enriched in pathways associated with the FOXM1 oncogenic signaling cascade, and biological processes such as cell cycle regulation, mitotic checkpoints, and diseases such as liver neoplasms. We also discussed the involvement of survivin in key oncogenic pathways, including the PI3K/AKT, WNT/β-catenin, Hippo, and JAK/STAT3 pathways, and its role in modulating cell cycle checkpoints, apoptosis, and autophagy. Furthermore, we explored its interactions with the tumor microenvironment, particularly its impact on immune modulation through myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages, and natural killer cell function in HCC. Additionally, we highlighted its involvement in alkylglycerone phosphate synthase (AGPS)-mediated lipid reprogramming and identified important gaps in the survivin network that warrant further investigation. This review also examined the role of survivin in cancer stemness, inflammation, and virally mediated hepatocarcinogenesis. We evaluated its potential as a diagnostic, prognostic, predictive, and pharmacodynamic biomarker in HCC, emphasizing its relevance in precision medicine. Finally, we summarized emerging survivin-targeted therapeutics and ongoing clinical trials, underscoring the need for novel strategies to effectively target survivin in HCC.

Identification and Pharmacological Targeting of Treatment-Resistant, Stem-like Breast Cancer Cells for Combination Therapy

Tumors frequently harbor isogenic yet epigenetically distinct subpopulations of multi-potent cells with high tumor-initiating potential-often called Cancer Stem-Like Cells (CSLCs). These can display preferential resistance to standard-of-care chemotherapy. Single-cell analyses can help elucidate Master Regulator (MR) proteins responsible for governing the transcriptional state of these cells, thus revealing complementary dependencies that may be leveraged via combination therapy. Interrogation of single-cell RNA sequencing profiles from seven metastatic breast cancer patients, using perturbational profiles of clinically relevant drugs, identified drugs predicted to invert the activity of MR proteins governing the transcriptional state of chemoresistant CSLCs, which were then validated by CROP-seq assays. The top drug, the anthelmintic albendazole, depleted this subpopulation in vivo without noticeable cytotoxicity. Moreover, sequential cycles of albendazole and paclitaxel-a commonly used chemotherapeutic -displayed significant synergy in a patient-derived xenograft (PDX) from a TNBC patient, suggesting that network-based approaches can help develop mechanism-based combinatorial therapies targeting complementary subpopulations.

Statement of significance

Network-based approaches, as shown in a study on metastatic breast cancer, can develop effective combinatorial therapies targeting complementary subpopulations. By analyzing scRNA-seq data and using clinically relevant drugs, researchers identified and depleted chemoresistant Cancer Stem-Like Cells, enhancing the efficacy of standard chemotherapies.

Survivin, β-catenin, and ki-67 immunohistochemical expression in canine perivascular wall tumors: Preliminary assessment of prognostic significance

High survivin expression has been correlated with poor outcomes in several canine tumors but not in soft tissue tumors (STTs). Survivin is a target gene of the Wnt/β-catenin pathway, which is involved in human STT oncogenesis. Immunohistochemistry for survivin, β-catenin, and Ki-67 was performed on 41 canine perivascular wall tumors (cPWTs), and statistical associations of protein expression and histopathologic and clinical variables with clinical outcomes were investigated. Immunohistochemically, there was nuclear positivity (0.9%-12.2% of tumor cells) for survivin in 41/41 (100%), cytoplasmic positivity (0 to > 75% of tumor cells) for survivin in 31/41 (76%), nuclear positivity (2.9%-67.2% of tumor cells) for β-catenin in 24/41 (59%), and cytoplasmic positivity (0% to > 75% of tumor cells) for β-catenin in 23/41 (56%) of cPWTs. All tumors expressed nuclear Ki-67 (2.2%-23.5%). In univariate analysis and multivariate analysis (UA and MA, respectively), every 1% increase of nuclear survivin was associated with an increase of the instantaneous death risk by a factor of 1.15 [hazard ratio (HR) = 1.15; P = .007]. Higher nuclear survivin was associated with grade II/III neoplasms (P = .043). Expression of cytoplasmic survivin, nuclear and cytoplasmic β-catenin, and nuclear Ki-67 were not significantly associated with prognosis in UA nor MA. Tumor size was a significant prognostic factor for local recurrence in UA [subdistribution HR (SDHR) = 1.19; P = .02] and for reduced overall survival time in MA. According to UA and MA, a unitary increase of mitotic count was associated with an increase of the instantaneous death risk by a factor of 1.05 (HR = 1.05; P = .014). Nuclear survivin, mitotic count, and tumor size seem to be potential prognostic factors for cPWTs. In addition, survivin and β-catenin may represent promising therapeutic targets for cPWTs.

Combination of Resveratrol and PARP inhibitor Olaparib efficiently deregulates homologous recombination repair pathway in breast cancer cells through inhibition of TIP60-mediated chromatin relaxation

Recently, we reported that a combination of a natural, bioactive compound Resveratrol (RES) and a PARP inhibitor Olaparib (OLA) deregulated the homologous recombination (HR) pathway, and enhanced apoptosis in BRCA1-wild-type, HR-proficient breast cancer cells. Upon DNA damage, chromatin relaxation takes place, which allows the DNA repair proteins to access the DNA lesion. But whether chromatin remodeling has any role in RES + OLA-mediated HR inhibition is not known. By using in vitro and ex vivo model systems of breast cancer, we have investigated whether RES + OLA inhibits chromatin relaxation and thereby blocks the HR pathway. It was found that RES + OLA inhibited PARP1 activity, terminated PARP1-BRCA1 interaction, and deregulated the HR pathway only in the chromatin fraction of MCF-7 cells. DR-GFP reporter plasmid-based HR assay demonstrated marked reduction in HR efficiency in I-SceI endonuclease-transfected cells treated with OLA. RES + OLA efficiently trapped PARP1 at the DNA damage site in the chromatin of MCF-7 cells. Unaltered expressions of HR proteins were found in the chromatin of PARP1-silenced MCF-7 cells, which confirmed that RES + OLA-mediated DNA damage response was PARP1-dependent. Histone Acetyltransferase (HAT) activity and histone H4 acetylation assays showed reduction in HAT activity and H4 acetylation in RES + OLA-treated chromatin fraction of cells. Western blot analysis showed that the HAT enzyme TIP60, P400 and acetylated H4 were downregulated after RES + OLA exposure. In the co-immunoprecipitation assay, it was observed that RES + OLA caused abolition of PARP1-TIP60-BRCA1 interaction, which suggested the PARP1-dependent TIP60-BRCA1 association. Unaltered expressions of PAR, BRCA1, P400, and acetylated H4 in the chromatin of TIP60-silenced MCF-7 cells further confirmed the role of TIP60 in PARP1-mediated HR activation in the chromatin. Similar results were obtained in ex vivo patient-derived primary breast cancer cells. Thus, the present study revealed that RES + OLA treatment inhibited PARP1 activity in the chromatin, and blocked TIP60-mediated chromatin relaxation, which, in turn, affected PARP1-dependent TIP60-BRCA1 association, resulting in deregulation of HR pathway in breast cancer cells.

Nectin-4 has emerged as a compelling target for breast cancer

The incidence of breast cancer in women has increased year by year, becoming one of the most common malignant tumors in females worldwide. Most patients can be treated with surgery and endocrine drugs, but there are still some patients who lack effective treatment, such as triple-negative breast cancer (TNBC). Nectin-4, a protein encoded by poliovirus receptor-associated protein 4, is a Ca2+-independent immunoglobulin-like protein. It is mainly involved in the adhesion between cells. In recent years, studies have found that Nectin-4 is overexpressed in breast cancer and several other malignancies. Otherwise, several monoclonal antibodies and inhibitors targeting Nectin-4 have shown prosperous outcomes, so Nectin-4 has great potential to be a therapeutic target for breast cancer. The present review systematically describes the significance of Nectin-4 in each aspect of breast cancer, as well as the molecular mechanisms of these aspects mediated by Nectin-4. We further highlight ongoing or proposed therapeutic strategies for breast cancer specific to Nectin-4.

Quinacrine inhibits HIF-1α/VEGF-A mediated angiogenesis by disrupting the interaction between cMET and ABCG2 in patient-derived breast cancer stem cells

BACKGROUND

Breast cancer stem cells (BCSCs) have a critical role in progression of breast cancer by inducing angiogenesis. Several therapeutic strategies have been designed for the treatment of breast cancer by specifically preventing angiogenesis. But there is a dearth of study regarding the treatment procedure which can specifically target and kill the BCSCs and cause lesser harm to healthy cells of the body. A plant-based bioactive compound Quinacrine (QC) specifically kills cancer stem cells (CSCs) without harming healthy cells and also inhibits cancer angiogenesis but the detailed mechanistic study of its anti-CSCs and anti-angiogenic activity is yet to explore.

HYPOTHESIS

Earlier report showed that both cMET and ABCG2 play an essential role in cancer angiogenesis. Both are present on the cell surface of CSCs and share an identical ATP-binding domain. Interestingly, QC a plant based and bioactive compound which was found to inhibit the function of CSCs marker cMET and ABCG2. These relevant evidence led us to hypothesize that cMET and ABCG2 may interact with each other and induce the production of angiogenic factors, resulting in activation of cancer angiogenesis and QC might disrupt the interaction between them to stop this phenomena.

METHODS

Co-immunoprecipitation assay, immunofluorescence assay, and western blotting were performed by using ex vivo patient-derived breast cancer-stem-cells (PDBCSCs) and human umbilical vein endothelial cells (HUVECs). In silico study was carried out to check the interaction between cMET and ABCG2 in presence or absence of QC. Tube formation assay using HUVECs and in ovo Chorioallantoic membrane (CAM) assay using chick fertilized eggs were performed to monitor angiogenesis. In vivo patient-derived xenograft (PDX) mice model was used to validate in silico and ex vivo results.

RESULTS

Data revealed that in a hypoxic tumor microenvironment (TME), cMET and ABCG2 interact with each other and upregulate HIF-1α/VEGF-A axis to induce breast cancer angiogenesis. In silico and ex vivo study showed that QC disrupted the interaction between cMET and ABCG2 to inhibit the angiogenic response in endothelial cells by reducing the secretion of VEGF-A from PDBCSCs within the TME. Knockdown of cMET, ABCG2 or both, significantly downregulated the expression of HIF-1α and reduced the secretion of pro-angiogenic factor VEGF-A in the TME of PDBCSCs. Additionally, when PDBCSCs were treated with QC, similar experimental results were obtained.

CONCLUSION

In silico, in ovo, ex vivo and in vivo data confirmed that QC inhibited the HIF-1α/VEGF-A mediated angiogenesis in breast cancer by disrupting the interaction between cMET and ABCG2.

Quinacrine inhibits cMET-mediated metastasis and angiogenesis in breast cancer stem cells

A trans-membrane receptor tyrosine kinase, cMET, belonging to the MET proto-oncogene family, is responsible for cancer metastasis and angiogenesis. But not much is known about the role of cMET in growth and progression of cancer stem cells (CSCs). Earlier studies have shown that Quinacrine (QC), a bioactive agent, has anti-CSCs activity. Here, the role of QC in deregulation of cMET-mediated metastasis and angiogenesis has been systematically evaluated in vitro in highly metastatic breast CSCs (mBCSCs), ex vivo in patient-derived breast cancer stem cells (PDBCSCs) and in vivo in xenograft mice model systems. Cell proliferation, migration, invasion and representative metastasis markers were upregulated in cMET-overexpressed cells and QC exposure inhibited these processes in both mBCSCs and PDBCSCs. Interestingly, metastasis was significantly inhibited by QC in cMET-overexpressed cells but comparatively lesser significant alteration of the process was noted in cMET-silenced cells. Increase in vascularization (in in ovo CAM assay), and cell-cell tube formation (in HUVECs), and enhanced MMP9 and MMP2 enzymatic activities (in gelatin zymography) were noted after cMET overexpression but these processes got reversed after cMET knockdown or QC treatment in cMET-overexpressed cells. QC inhibited angiogenesis significantly in cMET-overexpressed cells, but lesser significant change was observed in cMET-silenced cells. Reduction in tumor volume and decreased expression of metastatic and angiogenic markers were also noted in xenograft mice after QC treatment. Furthermore, QC inhibited cMET activity by dephosphorylation of its tyrosine residues (Y1234 and Y1356) and downregulation of its downstream cascade. Thus, QC inhibited the cMET-mediated metastasis and angiogenesis in in vitro, in ovo, in vivo and ex vivo model systems. Ligand (HGF) binding leads to receptor dimerization and phosphorylation of tyrosine kinase domain of cMET. This activates the cMET signaling cascade. The representative downstream metastasis and angiogenesis-related proteins get upregulated and induce the metastasis and angiogenesis process. But after the QC treatment, cMET get dephosphorylated and inactivated. As a result, the downstream signaling proteins of cMET along with the other representative metastatic and angiogenic factors get downregulated. These lead to inhibition of cMET-mediated metastasis and angiogenesis. (Created with BioRender.com).

Olaparib enhances the Resveratrol-mediated apoptosis in breast cancer cells by inhibiting the homologous recombination repair pathway

Although sensitization of BRCA-mutated, homologous recombination (HR)-deficient breast cancer cells through PARP inhibitor is widely studied, not much is known about the treatment of BRCA-wild-type, HR-proficient breast cancer. Here, we aim to investigate whether a bioactive compound, Resveratrol (RES), can induce DNA double-strand breaks in HR-proficient breast cancer cells and Olaparib (OLA), a PARP inhibitor, can enhance the RES-mediated apoptosis by deregulating the HR repair pathway. The detailed mechanism of anti-cancer action of RES + OLA combination in breast cancer has been evaluated using in vitro, ex vivo, and in vivo preclinical model systems. OLA increased RES-mediated DNA damage, downregulated the HR pathway proteins, caused a late S/G2 cell cycle arrest, enhanced apoptosis and cell death in RES pre-treated breast cancer cells at much lower concentrations than their individual treatments. Direct measurement of HR pathway activity using a GFP plasmid-based assay demonstrated reduced HR efficiency in I-SceI endonuclease-transfected cells treated with OLA. Moreover, RES + OLA treatment also caused significant reduction in PARP1-mediated PARylation and efficiently trapped PARP1 at the DNA damage site. Upon RES treatment, PARylated PARP1 was found to interact with BRCA1, which then activated other HR pathway proteins. But after addition of OLA in RES pre-treated cells, PARP1 could not interact with BRCA1 due to inhibition of PARylation. This resulted in deregulation of HR pathway. To further confirm the role of BRCA1 in PARP1-mediated HR pathway activation, BRCA1 was knocked down that caused complete inhibition of HR pathway activity, and further enhanced apoptosis after RES + OLA treatment in BRCA1-silenced cells. In agreement with in vitro data, similar experimental results were obtained in ex vivo patient-derived breast cancer cells and in vivo xenograft mice. Thus, RES + OLA combination treatment enhanced breast cancer cell death by causing excessive DNA damage and also simultaneously inhibiting the HR pathway.

Development of a cancer cells self‑activating and miR‑125a‑5p expressing poly‑pharmacological nanodrug for cancer treatment

Cancer cells can acquire resistance to targeted therapeutic agents when the designated targets or their downstream signaling molecules develop protein conformational or activity changes. There is an increasing interest in developing poly-pharmacologic anticancer agents to target multiple oncoproteins or signaling pathways in cancer cells. The microRNA 125a-5p (miR-125a-5p) is a tumor suppressor, and its expression has frequently been downregulated in tumors. By contrast, the anti-apoptotic molecule BIRC5/SURVIVIN is highly expressed in tumors but not in the differentiated normal tissues. In the present study, the development of a BIRC5 gene promoter-driven, miR-125a-5p expressing, poly-L-lysine-conjugated magnetite iron poly-pharmacologic nanodrug (pL-MNP-pSur-125a) was reported. The cancer cells self-activating property and the anticancer effects of this nanodrug were examined in both the multidrug efflux protein ABCB1/MDR1-expressing/-non-expressing cancer cells in vitro and in vivo. It was demonstrated that pL-MNP-pSur-125a decreased the expression of ERBB2/HER2, HDAC5, BIRC5, and SP1, which are hot therapeutic targets for cancer in vitro. Notably, pL-MNP-pSur-125a also downregulated the expression of TDO2 in the human KB cervical carcinoma cells. PL-MNP-pSur-125a decreased the viability of various BIRC5-expressing cancer cells, regardless of the tissue origin or the expression of ABCB1, but not of the human BIRC5-non-expressing HMEC-1 endothelial cells. In vivo, pL-MNP-pSur-125a exhibited potent antitumor growth effects, but without inducing liver toxicity, in various zebrafish human-ABCB1-expressing and ABCB1-non-expressing tumor xenograft models. In conclusion, pL-MNP-pSur-125a is an easy-to-prepare and a promising poly-pharmacological anticancer nanodrug that has the potential to manage numerous malignancies, particularly for patients with BIRC5/ABCB1-related drug resistance after prolonged chemotherapeutic treatments.

Survivin as a biological biomarker for diagnosis and therapy

Introduction: Survivin (SVN) is a member of the inhibitor of apoptosis (IAP) protein family that promotes cellular proliferation and inhibits apoptosis. Overexpression of SVN is associated with autoimmune disease, hyperplasia, and tumors and can be used as a biomarker in these diseases. SVN is widely recognized as a tumor-associated antigen (TAA) and has become an important target for cancer diagnosis and treatment.Areas covered: We reviewed SVN research progress from the PubMed and clinical trials focused on SVN from https://clinicaltrials.gov since 2000 and anticipate future developments in the field. The trials reviewed cover various modalities including diagnostics for early detection and disease progression, small molecule inhibitors of the SVN pathway and immunotherapy targeting SVN epitopes.Expert opinion: The most promising developments involve anti-SVN immunotherapy, with several therapeutic SVN vaccines under evaluation in phase I/II trials. SVN is an important new immune-oncology target that expands the repertoire of individualized combination treatments for cancer.

Mammary cell gene expression atlas links epithelial cell remodeling events to breast carcinogenesis

The female mammary epithelium undergoes reorganization during development, pregnancy, and menopause, linking higher risk with breast cancer development. To characterize these periods of complex remodeling, here we report integrated 50 K mouse and 24 K human mammary epithelial cell atlases obtained by single-cell RNA sequencing, which covers most lifetime stages. Our results indicate a putative trajectory that originates from embryonic mammary stem cells which differentiates into three epithelial lineages (basal, luminal hormone-sensing, and luminal alveolar), presumably arising from unipotent progenitors in postnatal glands. The lineage-specific genes infer cells of origin of breast cancer using The Cancer Genome Atlas data and single-cell RNA sequencing of human breast cancer, as well as the association of gland reorganization to different breast cancer subtypes. This comprehensive mammary cell gene expression atlas ( https://mouse-mammary-epithelium-integrated.cells.ucsc.edu ) presents insights into the impact of the internal and external stimuli on the mammary epithelium at an advanced resolution.

Emerging Importance of Survivin in Stem Cells and Cancer: the Development of New Cancer Therapeutics

Survivin is one of the rare proteins that is differentially expressed in normal and cancer cells and is directly or indirectly involved in numerous pathways required for tumor maintenance. It is expressed in almost all cancers and its expression has been detected at early stages of cancer. These traits make survivin an exceptionally attractive target for cancer therapeutics. Even with these promising features to be an oncotherapeutic target, there has been limited success in the clinical trials targeting survivin. Only recently it has emerged that survivin was not being specifically targeted which could have resulted in the negative clinical outcome. Also, focus of research has now shifted from survivin expression in the overall heterogeneous tumor cell populations to survivin expression in cancer stem cells as these cells have proved to be the major drivers of tumors. Therefore, in this review we have analyzed the expression of survivin in normal and cancer cells with a particular focus on its expression in cancer stem cell compartment. We have discussed the major signaling pathways involved in regulation of survivin. We have explored the current development status of various types of interventions for inhibition of survivin. Furthermore, we have discussed the challenges involving the development of potent and specific survivin inhibitors for cancer therapeutics. Finally we have given insights for some of the promising future anticancer treatments.

E-Cigarettes Promote Macrophage-Tumor Cells Crosstalk: Focus on Breast Carcinoma Progression and Lung Metastasis

Recurrence and metastasis are the foremost causes of morbidity and mortality for breast cancer (BC). Recent studies have highlighted the critical role of the tumor microenvironment, in particular, because it is related to tumor-associated macrophages (TAMs), in metastasis of BC. TAMs are mainly derived from macrophages that are recruited by C-C motif chemokine ligand 5, which are secreted by cancer cells and cancer-related stromal cells. Although E-cigarettes (E-cigs) were originally proposed as a healthy substitute for conventional cigarette smoking, clinical and experimental evidence has highlighted the potentially lethal effects of this alternative. Several studies have illustrated the immune or macrophage activation and DNA damaging effects of E-cigs. However, the potentially pivotal role of TAM-BC crosstalk during BC progression and metastasis for E-cig vaping has not been explored. This review discussed the significant effect that E-cig use had on the BC tumor microenvironment, which ultimately led to enhanced tumor malignancy and metastasis, with an emphasis on the extent that E-cig uses had on the crosstalk between cancer and immune cells, as well as the potential underlying mechanisms that drive this aggressive phenotype of BC. This review advances our understanding of this matter and provides scientific evidence that could highlight risks associated with vaping and suggest a potential intervention for the treatment of aggressive BCs that present an increased risk of metastasis.

Discovering and Characterizing of Survivin Dominant Negative Mutants With Stronger Pro-apoptotic Activity on Cancer Cells and CSCs

Survivin as a member of the inhibitor of apoptosis proteins (IAPs) family is undetectable in normal cells, but highly expressed in cancer cells and cancer stem cells (CSCs) which makes it an attractive target in cancer therapy. Survivin dominant negative mutants have been reported as competitive inhibitors of endogenous survivin protein in cancer cells. However, there is a lack of systematic comparative studies on which mutants have stronger effect on promoting apoptosis in cancer cells, which will hinder the development of novel anti-cancer drugs. Here, based on the previous study of survivin and its analysis of the relationship between structure and function, we designed and constructed a series of different amino acid mutants from survivin (TmSm34, TmSm48, TmSm84, TmSm34/48, TmSm34/84, and TmSm34/48/84) fused cell-permeable peptide TATm at the N-terminus, and a dominant negative mutant TmSm34/84 with stronger pro-apoptotic activity was selected and evaluated systematically in vitro. The double-site mutant of survivin (TmSm34/84) showed more robust pro-apoptotic activity against A549 cells than others, and could reverse the resistance of A549 CSCs to adriamycin (ADM) (reversal index up to 7.01) by decreasing the expression levels of survivin, P-gp, and Bcl-2 while increasing cleaved caspase-3 in CSCs. This study indicated the selected survivin dominant negative mutant TmSm34/84 is promising to be an excellent candidate for recombinant anti-cancer protein by promoting apoptosis of cancer cells and their stem cells and sensitizing chemotherapeutic drugs.

RBBP4 promotes colon cancer malignant progression via regulating Wnt/β-catenin pathway

BACKGROUND

Our previous study demonstrated that RBBP4 was upregulated in colon cancer and correlated with poor prognosis of colon cancer and hepatic metastasis. However, the potential biological function of RBBP4 in colon cancer is still unknown.

AIM

To investigate the biological role and the potential mechanisms of RBBP4 in colon cancer progression.

METHODS

Real-time polymerase chain reaction and western blot analysis were used to detect the expression of RBBP4 in colon cancer cell lines. The cell proliferation and viability of SW620 and HCT116 cells with RBBP4 knockdown was detected by Cell Counting Kit-8 and 5-ethynyl-2’-deoxyuridine staining. The transwell assay was used to detect the invasion and migration capabilities of colon cancer cells with RBBP4 knockdown. Flow cytometry apoptosis assay was used to detect the apoptosis of colon cancer cells. Western blotting analysis was used to detect the expression of epithelial-mesenchymal transition and apoptosis related markers in colon cancer. The nuclear translocation of β-catenin was examined by Western blotting analysis in colon cancer cells with RBBP4 knockdown. The TOPFlash luciferase assay was used to detect the effect of RBBP4 on Wnt/β-catenin activation. The rescue experiments were performed in colon cancer cells treated with Wnt/β-catenin activator LiCl and RBBP4 knockdown.

RESULTS

We found that RBBP4 was highly expressed in colon cancer cell lines. The 5-ethynyl-2’-deoxyuridine assay showed that knockdown of RBBP4 significantly inhibited cell proliferation. RBBP4 inhibition reduced cell invasion and migration via regulating proteins related to epithelial-mesenchymal transition. Knockdown of RBBP4 significantly inhibited survivin-mediated apoptosis. Mechanistically, the TOPFlash assay showed that RBBP4 knockdown increased activity of the Wnt/β-catenin pathway. Meanwhile, RBBP4 knockdown suppressed nuclear translocation of β-catenin. With Wnt/β-catenin activator, rescue experiments suggested that the role of RBBP4 in colon cancer progression was dependent on Wnt/β-catenin pathway.

CONCLUSION

RBBP4 promotes colon cancer development via increasing activity of the Wnt/β-catenin pathway. RBBP4 may serve as a novel therapeutic target in colon cancer.

The Multiple Roles of the IAP Super-family in cancer

The Inhibitor of Apoptosis proteins (IAPs) are a family of proteins that are mainly known for their anti-apoptotic activity and ability to directly bind and inhibit caspases. Recent research has however revealed that they have extensive roles in governing numerous other cellular processes. IAPs are known to modulate ubiquitin (Ub)-dependent signaling pathways through their E3 ligase activity and influence activation of nuclear factor κB (NF-κB). In this review, we discuss the involvement of IAPs in individual hallmarks of cancer and the current status of therapies targeting these critical proteins.

Quinacrine Based Gold Hybrid Nanoparticles Caused Apoptosis through Modulating Replication Fork in Oral Cancer Stem Cells

The presence of cancer stem cells (CSCs) in the tumor microenvironment is responsible for the development of chemoresistance and recurrence of cancer. Our previous investigation revealed the anticancer mechanism of quinacrine-based silver and gold hybrid nanoparticles (QAgNP and QAuNP) in oral cancer cells, but to avoid cancer recurrence, it is important to study the effect of these nanoparticles (NPs) on CSCs. Here, we developed an in vitro CSCs model using SCC-9 oral cancer cells and validated via FACS analysis. Then, 40-60% of cells were found to be CD44+/CD133+ and CD24-. QAuNP showed excellent anti-CSC growth potential against SCC-9-cancer stem like cells (IC₅₀ = 0.4 μg/mL) with the down-regulation of representative CSC markers. Prolonged exposure of QAuNP induced the S-phase arrest and caused re-replication shown by the extended G2/M population and apoptosis to SCC-9-CSC like cells. Up-regulation of BAX, PARP cleavage, and simultaneous down-regulation of Bcl-xL in prolonged treatment to CSCs suggested that the majority of the cells have undergone apoptosis. QAuNP treatment also caused a loss in DNA repair in CSCs. Mostly, the base excision repair (BER) components (Fen-1, DNA ligase-1, Pol-β, RPA, etc.) were significantly down-regulated after QAuNP treatment, which suggested its action against DNA repair machinery. The replication fork maintenance-related proteins, RAD 51 and BRCA-2, were also deregulated. Very surprisingly, depletion of WRN (an interacting partner for Pre-RC and Fen-1) and a significant increase in expression of fork-degrading nuclease MRE-11 in 96 h treated NPs were observed. Results suggest QAuNP treatment caused excessive DNA damage and re-replication mediated replication stress (RS) and stalling of the replication fork. Inhibition of BER components hinders the flap clearance activity of Fen-1, and it further caused RS and stopped DNA synthesis. Overall, QAuNP treatment led to irreparable replication fork movement, and the stalled replication fork might have degraded by MRE-11, which ultimately results in apoptosis and the death of the CSCs.

Inhibition of Wnt signaling by Frizzled7 antibody-coated nanoshells sensitizes triple-negative breast cancer cells to the autophagy regulator chloroquine

Despite improvements in our understanding of the biology behind triple-negative breast cancer (TNBC), it remains a devastating disease due to lack of an effective targeted therapy. Inhibiting Wnt signaling is a promising strategy to combat TNBC because Wnt signaling drives TNBC progression, chemoresistance, and stemness. However, Wnt inhibition can lead to upregulation of autophagy, which confers therapeutic resistance. This provides an opportunity for combination therapy, as autophagy inhibitors applied concurrently with Wnt inhibitors could increase treatment efficacy. Here, we applied the autophagy inhibitor chloroquine (CQ) to TNBC cells in combination with Frizzled7 antibody-coated nanoshells (FZD7-NS) that suppress Wnt signaling by blocking Wnt ligand/FZD7 receptor interactions, and evaluated this dual treatment in vitro. We found that FZD7-NS can inhibit Axin2 and CyclinD1, two targets of canonical Wnt signaling, and increase the expression of LC3, an autophagy marker. When FZD7-NS and CQ are applied together, they reduce the expression of several stemness genes in TNBC cells, leading to inhibition of TNBC cell migration and self-renewal. Notably, co-delivery of FZD7-NS and CQ is more effective than either therapy alone or the combination of CQ with free FZD7 antibodies. This demonstrates that the nanocarrier design is important to its therapeutic utility. Overall, these findings indicate that combined regulation of Wnt signaling and autophagy by FZD7-NS and CQ is a promising strategy to combat TNBC.

Basal-Type Breast Cancer Stem Cells Over-Express Chromosomal Passenger Complex Proteins

(1) Aim: In the present paper we analyzed the transcriptome of CSCs (Cancer Stem Cells), in order to find defining molecular processes of breast cancer. (2) Methods: We performed RNA-Seq from CSCs isolated from the basal cell line MDA-MB-468. Enriched processes and networks were studied using the IPA (Ingenuity Pathway Analysis) tool. Validation was performed with qRT-PCR and the analysis of relevant genes was evaluated by overexpression, flow cytometry and in vivo zebrafish studies. Finally, the clinical relevance of these results was assessed using reported cohorts. (3) Results: We found that CSCs presented marked differences from the non-CSCs, including enrichment in transduction cascades related to stemness, cellular growth, proliferation and apoptosis. Interestingly, CSCs overexpressed a module of co-regulated Chromosomal Passenger Proteins including BIRC5 (survivin), INCENP and AURKB. Overexpression of BIRC5 increased the number of CSCs, as assessed by in vitro and in vivo zebrafish xenotransplant analyses. Analysis of previously published cohorts showed that this co-regulated module was not only overexpressed in basal breast tumors but also associated with relapse-free and overall survival in these patients. (4) Conclusions: These results underline the importance of Cancer Stem Cells in breast cancer progression and point toward the possible use of chromosomal passenger proteins as prognostic factors.

Clinical significance of a pvrl 4 encoded gene Nectin-4 in metastasis and angiogenesis for tumor relapse

PURPOSE

In the present study, we have systematically examined the clinical significance of Nectin-4 (encoded by the PVRL-4 gene), a marker for breast cancer stem cells (CSCs), in cancer metastasis and angiogenesis using a variety of human specimens, including invasive duct carcinoma (IDC) with multiple grades, several types of primary tumors to local and distant relapses, lymph node metastases and circulating tumor cells (CTCs).

METHODS

Nectin-4 was overexpressed in more than 92% of samples with 65.2% Nectin-4-positive cells. The level of expression was increased with increasing tumor grade (GI-III) and size (T1-4) of IDC specimens.

RESULTS

More induction of Nectin-4 was noted in relapsed samples from a variety of tumors (colon, tongue, liver, kidney, ovary, buccal mucosa) in comparison to primary tumors, while paired adjacent normal tissues do not express any Nectin-4. A high expression of Nectin-4 along with other representative markers in CTCs and lymph node metastasis was also observed in cancer specimens. An increased level of Nectin-4 along with representative metastatic (CD-44, Sca1, ALDH1, Nanog) and angiogenic (Ang-I, Ang-II, VEGF) markers were noted in metastatic tumors (local and distant) in comparison to primary tumors that were correlated with different grades of tumor progression. In addition, greater expression of Nectin-4 was observed in secondary tumors (distant metastasis, e.g., breast to liver or stomach to gall bladder) in comparison to primary tumors.

CONCLUSION

Our study demonstrated a significant correlation between Nectin-4 expression and tumor grade as well as stages (p < 0.001), suggesting its association with tumor progression. Nectin-4 was overexpressed at all stages of metastasis and angiogenesis, thus appearing to play a major role in tumor relapse through the PI3K-Akt-NFκβ pathway.

Quinacrine and curcumin synergistically increased the breast cancer stem cells death by inhibiting ABCG2 and modulating DNA damage repair pathway

Cancer stem cell like cells (CSCs) present a challenge in the management of cancers due to their involvement in the development of resistance against various chemotherapeutic agents. Over expression of ABCG2 transporter gene is one of the factors responsible for drug resistance in CSCs, which causes efflux of therapeutic drugs from these cells. The development of inhibitors against CSCs has not achieved any significant success, till date. In this work, we have evaluated the anti-proliferative activity of curcumin (Cur) and quinacrine (QC) against CSCs using in vitro model system. Cur and QC synergistically inhibited the proliferation, migration and invasion of CSCs enriched side population (SP) cells of cigarette smoke condensate induced breast epithelial transformed (MCF-10A-Tr) generated metastatic cells. Cur + QC combination increased the DNA damage and inhibited the DNA repair pathways in SP cells. Uptake of QC increased in Cur pre-treated SP cells and this combination inhibited the ABCG2 activity by the reduction of ATP hydrolysis in cells. In vitro DNA binding reconstitution system suggests that QC specifically binds to DNA and caused DNA damage inside the cell. Decreased level of ABCG2, representative cell survival and DNA repair proteins were noted after Cur + QC treatment in SP cells. The molecular docking studies were performed to examine the binding behaviour of these drugs with ABCG2, which showed that QC (-53.99 kcal/mol) and Cur (-45.90 kcal/mol) occupy a highly overlapping interaction domain. This suggested that in Cur pre-treated cells, the Cur occupied the ligand-binding site in ABCG2, thus making the ligand binding site unavailable for the QC. This causes an increase in the intracellular concentration of QC. The results indicate that Cur + QC combination causes CSCs death by increasing the concentration of QC in the cells and thus causing the DNA damage and inhibiting the DNA repair pathways through modulating the ABCG2 activity.

High Survivin and Low Zinc Finger of the Cerebellum 1 Expression Indicates Poor Prognosis in Triple-negative Breast Carcinoma

Purpose

Triple-negative breast carcinoma (TNBC) is accompanied with high risk of metastasis and recurrence. The present study aimed to explore the clinicopathological and prognostic roles of putative tumor-related genes in patients with TNBC.

Methods

Thirty pairs of frozen-thawed tumors were used to select reliable indicators via real-time quantitative polymerase chain reaction (RT-qPCR). Then, 150 pathology specimens were used to evaluate the expression of proteins in TNBC through immunohistochemistry. In addition, Kaplan-Meier curves and Cox regression analysis were also performed to analyze the overall survival and disease-free survival.

Results

RT-qPCR results indicated that among all the proteins analyzed using fresh-frozen TNBC samples, the expression levels of only Survivin and zinc finger of the cerebellum 1 (ZIC1) were obviously different from those in the corresponding normal tissues. Survivin and ZIC1 expression had opposite effects on the clinicopathological diagnosis and prognostic assessment in TNBC patients. Further, there was a negative correlation between Survivin and ZIC1 expression. In addition, the “Survivin-positive ZIC1-negative group” was associated with histologic grade, lymph node metastasis, and TNM staging (p < 0.001) and this was also an independent factor for evaluating the prognosis of TNBC in patients.

Conclusion

In summary, the expression levels of Survivin and ZIC1 in TNBC are different from those in normal tissues and are negatively correlated mutually. The combined detection of Survivin and ZIC1 expression levels could allow better comprehensive diagnosis and prognostic evaluation for TNBC patients.

Survivin at a glance

Survivin (also known as BIRC5) is an evolutionarily conserved eukaryotic protein that is essential for cell division and can inhibit cell death. Normally it is only expressed in actively proliferating cells, but is upregulated in most, if not all cancers; consequently, it has received significant attention as a potential oncotherapeutic target. In this Cell Science at a Glance article and accompanying poster, we summarise our knowledge of survivin 21 years on from its initial discovery. We describe the structure, expression and function of survivin, highlight its interactome and conclude by describing anti-survivin strategies being trialled.

Yin Yang 1 (YY1): Regulation of Survivin and Its Role In Invasion and Metastasis

Despite significant clinical and basic science advancements, cancer remains a devastating disease that affects people of all ages, races, and backgrounds. The pathogenesis of cancer has recently been described to result from eight biological capabilities or hallmarks and two enabling characteristics. These eight hallmarks are: deregulation of cellular energetics, avoiding immune destruction, enabling replicative immortality, inducing angiogenesis, sustaining proliferative signaling, evading growth suppressors, resisting cell death, and activating invasion and metastasis. The enabling characteristics are: genome instability and mutation and tumor-promoting inflammation. Survivin, the fourth most common transcript found in cancer cells, is a protein that is thought to be involved in the enhanced proliferation, survival, and metastasis and possibly other key hallmarks of cancer cells. Understanding how this gene is turned on and off is vitally important for attempt improving cancer management and therapy. Our work has identified a novel transcriptional regulator of survivin called Yin Yang 1 (YY1), which has been observed to activate some gene promoters and repress others and is gaining increasing interest as a target of cancer therapy. Our work shows for the first time that YY1 represses survivin transcription by physically interacting with the survivin promoter. Furthermore, YY1 appears to contribute to basal survivin transcriptional activity, indicating that disruption of its binding may in part contribute to survivin overexpression after cellular stress events including chemotherapy and radiotherapy.

Nanoquinacrine sensitizes 5-FU-resistant cervical cancer stem-like cells by down-regulating Nectin-4 via ADAM-17 mediated NOTCH deregulation

PURPOSE

Cervical cancer is a major cause of cancer-related death in women world-wide. Although the anti-metabolite 5-FU is widely used for its treatment, its clinical utility is limited due to the frequent occurrence of drug resistance during metastasis. Cancer stem-like cells (CSCs), present in the heterogeneous population of CC cells, are thought to contribute to this resistance. Nectin-4, a CSC marker, is known to play an important role in the cellular aggressiveness associated with metastatic CC. This study was designed to assess the role of Nectin-4 in the acquisition of 5-FU resistance by metastatic CC cells, including its relation to the NOTCH signalling pathway.

METHODS

5FU-resistant CC cell lines were deduced from ME-180 and SiHA cells by continuous exposure to a single concentration of 5-FU. Thymidylate synthase (TS) positive cells were isolated from the 5-FU resistant cells, after which a metastatic model was developed. The role of Nectin-4 in the sensitization of 5-FU resistant metastatic CC cells upon incubation with Nano-formulated Quinacrine (NQC) was investigated using multiple bioassays including MTT, FACS, ELISA, immunoflurescence, Western blotting, comet and in vivo plasmid-based short patch and long patch base excision repair assays.

RESULTS

We found that the expression level of Nectin-4, as well as that of other CSC markers (Oct-4, β-catenin, SOX2) and representative NOTCH signalling components (NOTCH-1, Jagged-1, γ-secretase, ADAM-17) were elevated in the 5-FU resistant metastatic cells compared to those in control cells. Increased nuclear translocation of Nectin-4 and increased proliferation and invasion rates were observed after culturing the metastatic cells under hypoxic conditions. Treatment with NQC inhibited the nuclear translocation of Nectin-4 and decreased the proliferation and invasion rates of the cells by inhibiting the induction of base excision repair (BER) pathway components and ADAM-17 expression levels. After combination treatment of Nectin-4 overexpressing metastatic CC cells with a specific ADAM-17 inhibitor (GW280264) and NQC, a decreased Nectin-4 expression, without alterations in BER and/or other NOTCH pathway components, was noted.

CONCLUSION

Our data indicate that Nectin-4 may play a prominent role in 5-FU resistance of metastatic CC cells and that NQC sensitizes these cells by Nectin-4 deregulation through ADAM-17 inhibition, a major component of the NOTCH signalling pathway.

Breast cancer stem cells: Biology and therapeutic implications

Breast cancer remains to be a dreadful disease even with several advancements in radiation and chemotherapies, owing to the drug resistance and tumor relapse caused by breast cancer stem cells. Cancer stem cells are a minute population of cells of solid tumors which show self-renewal and differentiation properties as well as tumorigenic potential. Several signaling pathways including Notch, Hippo, Wnt and Hedgehog and tumor-stroma exchanges play a critical role in the self-renewal and differentiation of cancer stem cells in breast cancer. Cancer stem cells can grow anchorage-independent manner so they disseminate to different parts of the body to form secondary tumors. Cancer stem cells promote angiogenesis by dedifferentiating to endothelial cells as well as secreting proangiogenic and angiogenic factors. Moreover, multidrug resistance genes and drug efflux transporters expressed in breast cancer stem cells confer resistance to various conventional chemotherapeutic drugs. Indeed, these therapies are recognised to enhance the percent of cancer stem cell population in tumors leading to cancer relapse with increased aggressiveness. Hence, devising the therapeutic interventions to target cancer stem cells would be useful in increasing patients' survival rates. In addition, targeting the self-renewal pathways and tumor-stromal cross-talk helps in eradicating this population. Reversal of the cancer stem cell-mediated drug resistance would increase the sensitivity to various conventional drugs for the effective management of breast cancer. In this review, we have discussed the cancer stem cell origin and their involvement in angiogenesis, metastasis and therapy-resistance. We have also summarized different therapeutic approaches to eradicate the same for the successful treatment of breast cancer.

Unraveling the journey of cancer stem cells from origin to metastasis

Cancer biology research over recent decades has given ample evidence for the existence of self-renewing and drug-resistant populations within heterogeneous tumors, widely recognized as cancer stem cells (CSCs). However, a lack of clear understanding about the origin, existence, maintenance, and metastatic roles of CSCs limit efforts towards the development of CSC-targeted therapy. In this review, we describe novel avenues of current CSC biology. In addition to cell fusion and horizontal gene transfer, CSCs are originated by mutations in somatic or differentiated cancer cells, resulting in de-differentiation and reprogramming. Recent studies also provided evidence for the existence of distinct or heterogeneous CSC populations within a single heterogeneous tumor. Our analysis of the literature also opens the doors for a novel hypothesis that CSC populations with specific phenotypes, metabolic profiles, and clonogenic potential metastasize to specific organs.

An ABCG2 non-substrate anticancer agent FL118 targets drug-resistant cancer stem-like cells and overcomes treatment resistance of human pancreatic cancer

Background

Pancreatic cancer is a deadly disease with a very low 5-year patient survival rate of 6–8%. The major challenges of eliminating pancreatic cancer are treatment resistance and stromal barriers to optimal drug access within the tumor. Therefore, effective molecular targeting drugs with high intra-tumor access and retention are urgently needed for managing this devastating disease in the clinic.

Methods

This study has used the following in vitro and in vivo techniques for the investigation of exceptional anticancer drug FL118’s efficacy in treatment of resistant pancreatic cancer: cell culture; immunoblotting analysis to test protein expression; DNA sub-G1 flow cytometry analyses to test cell death; MTT assay to test cell viability; pancreatic cancer stem cell assays (fluorescence microscopy tracing; matrigel assay; CD44-positive cell colony formation assay); human luciferase-labeled pancreatic tumor orthotopic animal model in vivo imaging; pancreatic cancer patient-derived xenograft (PDX) animal models; and toxicology studies with immune-competent BALB/cj mice and beagle dogs.

Results

Our studies found that FL118 alone preferentially killed cisplatin-resistant cancer cells, while a combination of FL118 with cisplatin synergistically killed resistant pancreatic cancer cells and reduced spheroid formation of treatment-resistant pancreatic cancer stem-like cells. Furthermore, using in vivo-imaging, we found that FL118 in combination with cisplatin strongly inhibited both drug-resistant pancreatic xenograft tumor growth and metastasis. In PDX model, we demonstrated that FL118 alone effectively eliminated PDX tumors, while FL118 in combination with gemcitabine eliminated PDX tumors that showed relative resistance (less sensitivity) to treatment with FL118. These FL118 efficacy results are consistent with our molecular-targeting data showing that FL118 inhibited the expression of multiple antiapoptotic proteins (survivin, Mcl-1, XIAP, cIAP2) and ERCC6, a critical regulator of DNA repair, in treatment-resistant pancreatic stem-like cancer cells. Furthermore, FL118 toxicity studies in BALB/cj mice and beagle dogs indicated that FL118 exhibits favorable hematopoietic and biochemical toxicities.

Conclusion

Together, our studies suggest that FL118 is a promising anticancer drug for further clinical development to effectively treat drug-resistant pancreatic cancer alone or in combination with other pancreatic cancer chemotherapeutic drugs.

microCLIP super learning framework uncovers functional transcriptome-wide miRNA interactions

Argonaute crosslinking and immunoprecipitation (CLIP) experiments are the most widely used high-throughput methodologies for miRNA targetome characterization. The analysis of Photoactivatable Ribonucleoside-Enhanced (PAR) CLIP methodology focuses on sequence clusters containing T-to-C conversions. Here, we demonstrate for the first time that the non-T-to-C clusters, frequently observed in PAR-CLIP experiments, exhibit functional miRNA-binding events and strong RNA accessibility. This discovery is based on the analysis of an extensive compendium of bona fide miRNA-binding events, and is further supported by numerous miRNA perturbation experiments and structural sequencing data. The incorporation of these previously neglected clusters yields an average of 14% increase in miRNA-target interactions per PAR-CLIP library. Our findings are integrated in microCLIP (www.microrna.gr/microCLIP), a cutting-edge framework that combines deep learning classifiers under a super learning scheme. The increased performance of microCLIP in CLIP-Seq-guided detection of miRNA interactions, uncovers previously elusive regulatory events and miRNA-controlled pathways.

AGO-PAR-CLIP is widely used for high-throughput miRNA target characterization. Here, the authors show that the previously neglected non-T-to-C clusters denote functional miRNA binding events, and develop microCLIP, a super learning framework that accurately detects miRNA interactions.

The soluble nectin-4 ecto-domain promotes breast cancer induced angiogenesis via endothelial Integrin-β4

Cancer stem cells secrete diffusible factors into the microenvironment that bind to specific endothelial cell receptors and initiate an angiogenesis cascade. Tumor-induced angiogenesis is an important parameter of tumorigenesis and is critical for tumor growth and metastasis. A pvrl-4 encoded gene, NECTIN-4, has potential roles in cancer cell growth and aggressiveness, and it is only expressed in cancer cells. There is evidence that nectin-4 plays a role in tumorigenesis, but the function of nectin-4 in tumor angiogenesis has lacked thorough evidence of mechanism. Using highly metastatic breast cancer cells and human umbilical vein endothelial cells (HUVECs), we have developed an excellent angiogenesis model and systematically studied the contribution of nectin-4 to angiogenesis. We also provide in-depth in ovo, in vivo and in vivo evidence that nectin-4 causes angiogenesis. Following hypoxia, metastatic breast cancer stem cells (mBCSCs) driven ADAM-17 expression causes the shedding of the ecto-domain of nectin-4 into the microenvironment, which physically interacts with integrin-β4 specifically on endothelial cells. This interaction promotes angiogenesis via the Src, PI3K, AKT, iNOS pathway and not by Phospho-Erk or NF-κβ pathways. In vitro, in ovo and in vivo induction and abrogation of an angiogenesis cascade in the presence and absence of the nectin-4 ecto-domain, respectively, confirms its role in angiogenesis. Thus, disrupting the interaction between nectin-4 ecto-domain and integrin-β4 may provide a means of targeting mBCSC-induced angiogenesis.

Nectin-4 is a breast cancer stem cell marker that induces WNT/β-catenin signaling via Pi3k/Akt axis

Nectin-4 is well known as a junction protein. Recent reports have implicated it in cancer, but there has been little exploration of its functional significance in metastasis and cancer stem cells. Here, using the breast cancer metastasis model system, we report Nectin-4 is a marker for breast cancer stem cells (BCSCs) and provide experimental evidence suggesting that it utilizes WNT/β-Catenin signaling via Pi3k/Akt axis for self renewal of BCSCs. In vitro, in vivo, ex vivo and clinical pathological data showed upregulated Nectin-4 in breast cancer metastasis and WNT/β-Catenin signaling. Nectin-4 depletion inhibited EMT, metastasis, invasion, and the WNT/β-Catenin pathway; conversely, Nectin-4 overexpression in null cells upregulated EMT and metastasis and also induced WNT/β-Catenin signaling via Pi3k/Akt axis, which in turn, controls cancer stem cell proliferation. Induced Nectin-4 was observed in breast tumor patient samples and in breast tumor metastases to axillary lymph nodes, which indicated that Nectin-4 is not only a BCSC marker but also a breast cancer metastasis marker. The current study provides clear evidence that Nectin-4 is a BCSC marker and is responsible for breast cancer metastasis.

Protein Sam68 regulates the alternative splicing of survivin DEx3

Messenger RNA alternative splicing (AS) regulates the expression of a variety of genes involved in both physiological and pathological processes. AS of the anti-apoptotic and proliferation-associated survivin (BIRC5) gene generates six isoforms, which regulate key aspects of cancer initiation and progression. One of the isoforms is survivin DEx3, in which the exclusion of exon 3 generates a unique carboxyl terminus with specific anti-apoptotic functions. This isoform is highly expressed in advanced stages of breast and cervical tumors. Therefore, understanding the mechanisms that regulate survivin DEx3 mRNA AS is clearly important. To this end, we designed a minigene (M), and in combination with a series of deletions and site-directed mutations, we determined that the first 22 bp of exon 3 contain cis-acting elements that enhance the exclusion of exon 3 to generate the survivin DEx3 mRNA isoform. Furthermore, using pulldown assays, we discovered that Sam68 is a possible trans-acting factor that binds to this region and regulates exon 3 splicing. This result was corroborated using a cell line in which the Sam68 binding site in the survivin gene was mutated with the CRISPR/Cas system. This work provides the first clues regarding the regulation of survivin DEx3 mRNA splicing.