Reduced miR-371b-5p expression drives tumor progression via CSDE1/RAC1 regulation in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer; however, specific prognostic biomarkers have not yet been developed. In this study, we identified dysregulated microRNAs (miRNAs) in TNBC by profiling miRNA and mRNA expression. In patients with TNBC, miR-371b-5p expression was reduced, and miR-371b-5p overexpression significantly mitigated TNBC cell growth, migration, and invasion. In addition, we found that expression of cold shock domain-containing protein E1 (CSDE1), a direct target gene of miR-371b-5p, was upregulated in TNBC cells, and inhibition of CSDE1 expression alleviated TNBC cell growth by regulating RAC1 transcription. Mechanistically, CSDE1, phosphorylated C-terminal domain (p-CTD) of RNA polymerase II (RNAPII), and CDK7 form a complex, and downregulation of CSDE1 leads to weak interaction between RNAPII p-CTD and CDK7, resulting in a decrease in RNAPII p-CTD expression to reduce RAC1 transcript levels in CSDE1-deficient TNBC cells. Our data demonstrate that miR-371b-5p is a tumor-suppressive miRNA that regulates the CSDE1/Rac1 axis and could be a potential prognostic biomarker for TNBC.

Crosstalk between WNT and STAT3 is mediated by galectin-3 in tumor progression.

BACKGROUND: Aberrant activation of the WNT/ß-catenin and STAT3 signaling pathways plays a critical role in cancer progression. However, direct targeting of these pathways as an anti-cancer therapeutic approach needs to be reconsidered due to its serious side effects. Here, we demonstrate that overexpression of WNT induces STAT3 activation in a galectin-3-dependent manner. METHODS: We investigated how galectin-3 mediates the crosstalk between WNT/ß-catenin and STAT3 signaling and whether inhibition of galectin-3 can reduce gastric cancer. The molecular mechanisms were analyzed by biochemical assays using cultured gastric cancer cells, patient tissues, and genetically engineered mice. Moreover, we confirm of therapeutic effects of GB1107, a cell-penetrating galectin-3 specific inhibitor, using orthotopic gastric cancer-bearing mice RESULTS: Increased levels of galectin-3 and STAT3 phosphorylation were detected in the stomach tissues of WNT1-overexpressing mouse models. Also, high expression levels and co-localization of ß-catenin, pSTAT3, and galectin-3 in patients with advanced gastric cancer were correlated with a poorer prognosis. Galectin-3 depletion significantly decreased STAT3 Tyr705 phosphorylation, which regulates its nuclear localization and transcriptional activation. A peptide of galectin-3 (Y45-Q48) directly bound to the STAT3 SH2 domain and enhanced its phosphorylation. GB1107, a specific membrane-penetrating inhibitor of galectin-3, significantly reduced the activation of both STAT3 and ß-catenin and inhibited tumor growth in orthotopic gastric cancer-bearing mice. CONCLUSIONS: We propose that galectin-3 mediates the crosstalk between the WNT and STAT3 signaling pathways. Therefore GB1107, a galectin-3-specific inhibitor, maybe a potent agent with anti-gastric cancer activity. Further studies are needed for its clinical application in gastric cancer therapy.

Histone demethylase KDM4C controls tumorigenesis of glioblastoma by epigenetically regulating p53 and c-Myc.

Glioblastoma is the most lethal brain tumor and its pathogenesis remains incompletely understood. KDM4C is a histone H3K9 demethylase that contributes to epigenetic regulation of both oncogene and tumor suppressor genes and is often overexpressed in human tumors, including glioblastoma. However, KDM4C's roles in glioblastoma and the underlying molecular mechanisms remain unclear. Here, we show that KDM4C knockdown significantly represses proliferation and tumorigenesis of glioblastoma cells in vitro and in vivo that are rescued by overexpressing wild-type KDM4C but not a catalytic dead mutant. KDM4C protein expression is upregulated in glioblastoma, and its expression correlates with c-Myc expression. KDM4C also binds to the c-Myc promoter and induces c-Myc expression. Importantly, KDM4C suppresses the pro-apoptotic functions of p53 by demethylating p53K372me1, which is pivotal for the stability of chromatin-bound p53. Conversely, depletion or inhibition of KDM4C promotes p53 target gene expression and induces apoptosis in glioblastoma. KDM4C may serve as an oncogene through the dual functions of inactivation of p53 and activation of c-Myc in glioblastoma. Our study demonstrates KDM4C inhibition as a promising therapeutic strategy for targeting glioblastoma.

Inhibition of Chk1 by miR-320c increases oxaliplatin responsiveness in triple-negative breast cancer.

Checkpoint kinase 1 (Chk1) expression is enhanced in most cancers owing to oncogenic activation and constant replicative stress. Chk1 inactivation is a promising cancer therapy, as its inactivation leads to genomic instability, chromosomal catastrophe, and cancer cell death. Herein, we observed that miR-320c, downregulated in triple-negative breast cancer (TNBC) patients, can target Chk1. In addition, downregulated miR-320c expression was associated with poor overall survival in TNBC patients. As Chk1 was associated with the DNA damage response (DDR), we investigated the effect of miR-320c on DDR in TNBC cells. To induce DNA damage, we used platinum-based drugs, especially oxaliplatin, which is most effective with miR-320c. We observed that overexpression of miR-320c in TNBC regulated the oxaliplatin responsiveness by mediating DNA damage repair through the negative regulation of Chk1 in vitro. Furthermore, using a xenograft model, a combination of miR-320c mimic and oxaliplatin effectively inhibited tumor progression. These investigations indicate the potential of miR-320c as a marker of oxaliplatin responsiveness and a therapeutic target to increase the efficacy of chemotherapy in TNBC.

Synergistic antitumor activity of a DLL4/VEGF bispecific therapeutic antibody in combination with irinotecan in gastric cancer.

Notch signaling has been identified as a critical pathway in gastric cancer (GC) progression and metastasis, and inhibition of Delta-like ligand 4 (DLL4), a Notch ligand, is suggested as a potent therapeutic approach for GC. Expression of both DLL4 and vascular endothelial growth factor receptor 2 (VEGFR2) was similar in the malignant tissues of GC patients. We focused on vascular endothelial growth factor (VEGF), a known angiogenesis regulator and activator of DLL4. Here, we used ABL001, a DLL4/VEGF bispecific therapeutic antibody, and investigated its therapeutic effect in GC. Treatment with human DLL4 therapeutic antibody (anti-hDLL4) or ABL001 slightly reduced GC cell growth in monolayer culture; however, they significantly inhibited cell growth in 3D-culture, suggesting a reduction in the cancer stem cell population. Treatment with anti-hDLL4 or ABL001 also decreased GC cell migration and invasion. Moreover, the combined treatment of irinotecan with anti-hDLL4 or ABL001 showed synergistic antitumor activity. Both combination treatments further reduced cell growth in 3D-culture as well as cell invasion. Interestingly, the combination treatment of ABL001 with irinotecan synergistically reduced the GC burden in both xenograft and orthotopic mouse models. Collectively, DLL4 inhibition significantly decreased cell motility and stem-like phenotype and the combination treatment of DLL4/VEGF bispecific therapeutic antibody with irinotecan synergistically reduced the GC burden in mouse models. Our data suggest that ABL001 potentially represents a potent agent in GC therapy. Further biochemical and pre-clinical studies are needed for its application in the clinic. [BMB Reports 2020; 53(10): 533-538].

HPV-mediated nuclear export of HP1γ drives cervical tumorigenesis by downregulation of p53.

E6 oncoprotein derived from high-risk human papillomavirus (HPV) drives the development of cervical cancer through p53 degradation. Because cervical cancer therapies to inactivate HPV or E6 protein are not available, alternative strategies are required. Here, we show that HPV-mediated nuclear export of human heterochromatin protein 1γ (HP1γ) reduces the stability of p53 through UBE2L3-mediated p53 polyubiquitination during cervical cancer progression. In general, HP1 plays a key role in heterochromatin formation and transcription in the nucleus. However, our immunostaining data showed that the majority of HP1γ is localized in the cytoplasm in HPV-mediated cervical cancer. We found that HPV E6 protein drives unusual nuclear export of HP1γ through the interaction between the NES sequence of HP1γ and exportin-1. The mutation of the NES sequence in HP1γ led to nuclear retention of HP1γ and reduced cervical cancer cell growth and tumor generation. We further discovered that HP1γ directly suppresses the expression of UBE2L3 which drives E6-mediated proteasomal degradation of p53 in cervical cancer. Downregulation of UBE2L3 by overexpression of HP1γ suppressed UBE2L3-dependent p53 degradation-promoting apoptosis of cervical cancer cells. Our findings propose a useful strategy to overcome p53 degradation in cervical cancer through the blockage of nuclear export of HP1γ.

Galectin-3 Interacts with C/EBPß and Upregulates Hyaluronan-Mediated Motility Receptor Expression in Gastric Cancer.

The hyaluronan-mediated motility receptor (HMMR) is overexpressed in gastric cancer; however, the apparent role of HMMR has not been well defined owing to lack of detailed studies on gastric tumorigenesis. Therefore, we elucidated the functional and regulatory mechanisms of HMMR in gastric cancer. Using publicly available data, we confirmed HMMR overexpression in patients with gastric cancer. HMMR silencing decreased proliferation, migration, and invasion of gastric cancer cells, whereas HMMR overexpression reversed these effects. A gastric cancer xenograft mouse model showed statistically significant inhibition of tumor growth upon HMMR depletion. Previous data from cDNA microarray showed reduced HMMR expression upon inhibition of galectin-3. However, overexpression of galectin-3 increased HMMR expression, cell proliferation, and motility in gastric cancer cells, whereas HMMR silencing blocked these effects. Interestingly, galectin-3 interacted directly with C/EBPß and bound to HMMR promoter to drive its transcription, and gastric cancer cell proliferation and motility. Altogether, high expression of HMMR promoted gastric cancer cell proliferation and motility and could be a prognostic factor in gastric cancer. In addition, HMMR expression was regulated by the interaction between C/EBPß and galectin-3. Therefore, targeting HMMR along with galectin-3 and C/EBPß complex could be a potential treatment strategy for inhibiting gastric cancer progression and metastasis. IMPLICATIONS: This study provides evidence that galectin-3 interacts with C/EBPß in gastric cancer, and galectin-3 and C/EBPß complex promotes gastric cancer cell progression and motility through upregulating HMMR expression.

Correction to: Post-translational modification of OCT4 in breast cancer tumorigenesis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

miR-374a-5p promotes tumor progression by targeting ARRB1 in triple negative breast cancer.

Triple negative breast cancer (TNBC) has higher aggressiveness and poorer outcomes compared with other subtypes of breast cancer. However, the genomic and molecular aberrations of TNBC are largely unknown. In this study, miR-374a-5p was discovered as a novel TNBC-specific miRNA and its functions and the molecular mechanisms involved were investigated. Combined gene expression profiling of miRNA-microarray and human transcriptome dataset analysis revealed that miR-374a-5p is specifically upregulated in TNBC patients. Functional studies using in vitro and in vivo models indicated that upregulated miR-374a-5p promotes tumor progression in TNBC. miR-374a-5p was also found to directly target arrestin beta 1 (ARRB1) that is specifically downregulated in TNBC patients in several human genomic datasets. Overexpressed ARRB1 reduced TNBC cell growth and migration, and the ARRB1 expression level is inversely correlated with the histological grade of the breast cancer and positively associated with TNBC patient survival, suggestive of a tumor-suppressive function of ARRB1 in breast cancer. Interestingly, increased ARRB1 activates AMPK in TNBC cells, associated with the expression of miR-374a-5p. Taken together, the findings suggest that miR-374a-5p is a potential prognostic marker of TNBC.

Post-translational modification of OCT4 in breast cancer tumorigenesis.

Recurrence and drug resistance of breast cancer are still the main reasons for breast cancer-associated deaths. Cancer stem cell (CSC) model has been proposed as a hypothesis for the lethality of breast cancer. Molecular mechanisms underlying CSC maintenance are still unclear. In this study, we generated mammospheres derived from breast cancer MDA-MB231 cells and MCF7 cells to enrich CSCs and performed DNA microarray analysis. We found that the expression of carboxy terminus of HSP70-interacting protein (CHIP) E3 ubiquitin ligase was significantly downregulated in breast CSCs. CHIP depletion increased mammosphere formation, whereas CHIP overexpression reversed this effect. We identified interactomes by mass spectrometry and detected CHIP directly interacted with OCT4, a stemness factor. CHIP overexpression decreased OCT4 stability through proteasomal degradation. CHIP induced OCT4 ubiquitination, whereas H260Q, a catalytic CHIP mutant, did not. Interestingly, we determined that OCT4 was ubiquitinated at lysine 284, and CHIP overexpression did not degrade K284R mutant OCT4. CHIP overexpression decreased the proliferation and side population of breast cancer cells, but these were not occurred in K284R mutant OCT4 overexpressed cells. Only 1000 cells showing CHIP depletion or OCT4 overexpression sufficiently generated breast tumors and lung metastases in xenografted mice. Ubiquitination-defective mutant of OCT4(K284R) overexpressed cells drastically generated tumor burdens in mice. Patients with breast cancer who showed low CHIP expression had poor survival probability. Taken together, we suggest that CHIP-induced OCT4 ubiquitination is important in breast CSCs. Regulation of CHIP expression and OCT4 protein stability is a considerable approach for breast cancer therapy.

Galectin-3 supports stemness in ovarian cancer stem cells by activation of the Notch1 intracellular domain.

Ovarian cancer is the most lethal gynecologic disease because usually, it is lately sensed, easily acquires chemoresistance, and has a high recurrence rate. Recent studies suggest that ovarian cancer stem cells (CSCs) are involved in these malignancies. Here, we demonstrated that galectin-3 maintains ovarian CSCs by activating the Notch1 intracellular domain (NICD1). The number and size of ovarian CSCs decreased in the absence of galectin-3, and overexpression of galectin-3 increased them. Overexpression of galectin-3 increased the resistance for cisplatin and paclitaxel-induced cell death. Silencing of galectin-3 decreased the migration and invasion of ovarian cancer cells, and overexpression of galectin-3 reversed these effects. The Notch signaling pathway was strongly activated by galectin-3 overexpression in A2780 cells. Silencing of galectin-3 reduced the levels of cleaved NICD1 and expression of the Notch target genes, Hes1 and Hey1. Overexpression of galectin-3 induced NICD1 cleavage and increased expression of Hes1 and Hey1. Moreover, overexpression of galectin-3 increased the nuclear translocation of NICD1. Interestingly, the carbohydrate recognition domain of galectin-3 interacted with NICD1. Overexpression of galectin-3 increased tumor burden in A2780 ovarian cancer xenografted mice. Increased expression of galectin-3 was detected in advanced stages, compared to stage 1 or 2 in ovarian cancer patients, suggesting that galectin-3 supports stemness of these cells. Based on these results, we suggest that targeting galectin-3 may be a potent approach for improving ovarian cancer therapy.

Epigenetic activation of LY6K predicts the presence of metastasis and poor prognosis in breast carcinoma.

The role of lymphocyte antigen 6 complex, locus K (LY6K) in breast cancer has been studied, whereas the epigenetic control of LY6K transcription is not fully understood. Here, we report that breast cancer patients with increased LY6K expression had shorter disease-free and overall survival than the patients with low levels of LY6K by multivariate analysis. LY6K also was upregulated in breast cancer patients with distant metastases than those without distant metastases, downregulating E-cadherin expression. Furthermore, xenograft tumor volumes from LY6K knockdown nude mice were reduced than those of mice treated with control lentivirus. Interestingly, LY6K has a CpG island (CGI) around the transcription start site and non-CGI in its promoter, called a CGI shore. LY6K expression was inversely correlated with methylation in not only CGI but CGI shore, which are associated with histone modifications. Additionally, LY6K methylation was increased by the PAX3 transcription factor due to the SNP242 mutation in LY6K CGI shore. Taken together, breast cancer risk and metastasis were significantly associated with not only LY6K expression, but also methylation of CGI shore which induced by SNP242 mutation. Our results suggest that an understanding epigenetic mechanism of the LY6K gene may be useful to diagnose carcinogenic risk and predict outcomes of patients with metastatic breast cancer.

Ablation of human telomerase reverse transcriptase (hTERT) induces cellular senescence in gastric cancer through a galectin-3 dependent mechanism.

The human Telomerase Reverse Transcriptase (hTERT) gene encodes a rate-limiting catalytic subunit of telomerase that maintains genomic integrity. Suppression of hTERT expression could induce cellular senescence and is considered a potent approach for gastric cancer therapy. However, control of hTERT expression and function remains poorly understood in gastric cancer. In this study, we demonstrated that high expression levels of hTERT in malignant tissues are correlated with poor survival probability in gastric cancer patients. Knockdown of hTERT expression retarded cell proliferation and cellular senescence, which was confirmed by increased protein expression levels of p21cip1 and p27kip1, and decreased phosphorylation of Rb. In contrast, overexpression of hTERT increased cell proliferation and decreased cellular senescence. Remarkably, the down-regulation of hTERT expression was detected in lgals3-/- mouse embryo fibroblasts (MEFs). Knockdown of galectin-3 decreased the expression of hTERT in gastric cancer cells. Galectin-3 ablation-induced cellular senescence was rescued by concomitant overexpression of hTERT. hTERT ablation-induced cellular senescence and p21cip1 and p27kip1 expression was rescued by concomitant overexpression of galectin-3. The size of tumor burdens was increased in hTERT-overexpressed gastric cancer cells xenografted mice, whereas it was repressed by concomitant depletion of galectin-3. Additionally, we determined that the N-terminal domain of galectin-3 directly interacted with hTERT. The telomeric activity of hTERT was also decreased by galectin-3 ablation. Taken together, ablation of hTERT induces cellular senescence and inhibits the growth of gastric cancer cells, suggesting that it could be a potent target in gastric cancer therapy. We also propose that galectin-3 is an important regulator of hTERT expression and telomeric activity in gastric tumorigenesis.

Tumor Suppressor HIPK2 Regulates Malignant Growth via Phosphorylation of Notch1.

The receptor Notch1 plays an important role in malignant progression of many cancers, but its regulation is not fully understood. In this study, we report that the kinase HIPK2 is responsible for facilitating the Fbw7-dependent proteasomal degradation of Notch1 by phosphorylating its intracellular domain (Notch1-IC) within the Cdc4 phosphodegron motif. Notch1-IC expression was higher in cancer cells than normal cells. Under genotoxic stress, Notch1-IC was phosphorylated constitutively by HIPK2 and was maintained at a low level through proteasomal degradation. HIPK2 phosphorylated the residue T2512 in Notch1-IC. Somatic mutations near this residue rendered Notch1-IC resistant to degradation, as induced either by HIPK2 overexpression or adriamycin treatment. In revealing an important mechanism of Notch1 stability, the results of this study could offer a therapeutic strategy to block Notch1-dependent progression in many types of cancer. Cancer Res; 76(16); 4728-40. ©2016 AACR.

Mitochondrial Sirt3 supports cell proliferation by regulating glutamine-dependent oxidation in renal cell carcinoma.

Clear cell renal carcinoma (RCC), the most common malignancy arising in the adult kidney, exhibits increased aerobic glycolysis and low mitochondrial respiration due to von Hippel-Lindau gene defects and constitutive hypoxia-inducible factor-α expression. Sirt3 is a major mitochondrial deacetylase that mediates various types of energy metabolism. However, the role of Sirt3 as a tumor suppressor or oncogene in cancer depends on cell types. We show increased Sirt3 expression in the mitochondrial fraction of human RCC tissues. Sirt3 depletion by lentiviral short-hairpin RNA, as well as the stable expression of the inactive mutant of Sirt3, inhibited cell proliferation and tumor growth in xenograft nude mice, respectively. Furthermore, mitochondrial pyruvate, which was used for oxidation in RCC, might be derived from glutamine, but not from glucose and cytosolic pyruvate, due to depletion of mitochondrial pyruvate carrier and the relatively high expression of malic enzyme 2. Depletion of Sirt3 suppressed glutamate dehydrogenase activity, leading to impaired mitochondrial oxygen consumption. Our findings suggest that Sirt3 plays a tumor-progressive role in human RCC by regulating glutamine-derived mitochondrial respiration, particularly in cells where mitochondrial usage of cytosolic pyruvate is severely compromised.

A novel miR-34a target, protein kinase D1, stimulates cancer stemness and drug resistance through GSK3/ß-catenin signaling in breast cancer.

One of the properties of human breast cancer cells is cancer stemness, which is characterized by self-renewal capability and drug resistance. Protein kinase D1 (PRKD1) functions as a key regulator of many cellular processes and is downregulated in invasive breast cancer cells. In this study, we found that PRKD1 was upregulated in MCF-7-ADR human breast cancer cells characterized by drug resistance. Additionally, we discovered that PRKD1 expression was negatively regulated by miR-34a binding to the PRKD1 3'-UTR. PRKD1 expression increased following performance of a tumorsphere formation assay in MCF-7-ADR cells. We also found that reduction of PRKD1 by ectopic miR-34a expression or PRKD1 siRNA treatment resulted in suppressed self-renewal ability in breast cancer stem cells. Furthermore, we confirmed that the PRKD1 inhibitor CRT0066101 reduced phosphorylated PKD/PKCµ, leading to suppression of breast cancer stemness through GSK3/ß-catenin signaling. PRKD1 inhibition also influenced apoptosis initiation in MCF-7-ADR cells. Tumors from nude mice treated with miR-34a or CRT0066101 showed suppressed tumor growth, proliferation, and induced apoptosis. These results provide evidence that regulation of PRKD1, a novel miR-34a target, contributes to overcoming cancer stemness and drug resistance in human breast cancer.

Cleaved CD44 intracellular domain supports activation of stemness factors and promotes tumorigenesis of breast cancer.

CD44 plays a role in the progression of tumors and is expressed in cancer stem cells (CSCs). However, the mechanisms underlying the crosstalk of CD44 with stemness genes in CSC maintenance remains unclear. In this study, we demonstrated how the cleaved intracellular domain of CD44 (CD44ICD) activates stemness factors such as Nanog, Sox2 and Oct4, and contributes to the tumorigenesis of breast cancer. We have found that the overexpression of CD44ICD increased mammosphere formation in breast cancer cells. Treatment with a γ-secretase inhibitor (GSI), which blocks the cleavage of CD44ICD, interfered with mammosphere formation. Interestingly, CD44ICD decreased the expression levels and nuclear localization of stemness factors, but overexpression of CD44ICD reversed these effects. In addition, we showed that nuclear localization of CD44ICD is important for transcriptional activation of the stemness factors. Furthermore, CD44ICD-overexpressed cells exhibited strong tumorigenecity and greater metastatic potential than did the control cells or CD44-depleted cells in vivo in mice models. Taken together, it was supposed that CD44 promotes tumorigenesis through the interaction and nuclear-translocation of its intracellular domain and stemness factors. We suggest that the prevention of cleavage and nuclear-translocation of CD44ICD is a potential target in treating breast cancer.

Galectin-3 activates PPARγ and supports white adipose tissue formation and high-fat diet-induced obesity.

Galectin-3, a ß-galactoside-binding lectin, is elevated in obesity and type 2 diabetes mellitus, and metformin treatment reduces these galectin-3 levels. However, the role of galectin-3 in adipogenesis remains controversial. We found that 17-month-old galectin-3-deficient (lgals3(-/-)) mice had decreased body size and epididymal white adipose tissue (eWAT) without related inflammatory diseases when fed normal chow. Galectin-3 knockdown significantly reduced adipocyte differentiation in 3T3-L1 cells and also decreased the expression of peroxisome proliferator-activated receptor (PPAR)-γ, ccaat-enhancer-binding protein α, and ccaat-enhancer-binding protein ß. Endogenous galectin-3 directly interacted with PPARγ, and galectin-3 ablation reduced the nuclear accumulation and transcriptional activation of PPARγ. After a 12-week high-fat diet (60% fat), lgals3(-/-) mice had lower body weight and eWAT mass than lgals3(+/+) mice. Moreover, the expression of PPARγ and other lipogenic genes was drastically decreased in the eWAT and liver of lgals3(-/-) mice. We suggest that galectin-3 directly activates PPARγ and leads to adipocyte differentiation in vitro and in vivo. Furthermore, galectin-3 might be a potential therapeutic target in metabolic syndromes as a PPARγ regulator.

Targeting of miR34a-NOTCH1 axis reduced breast cancer stemness and chemoresistance.

Human breast cancers include cancer stem cell populations as well as nontumorigenic cancer cells. Breast cancer stem cells have self-renewal capability and are resistant to conventional chemotherapy. miRNAs regulate the expression of many target genes; therefore, dysregulation of miRNAs has been associated with the pathogenesis of human diseases, including cancer. However, a role for miRNA dysregulation in stemness and drug resistance has yet to be identified. Members of the miR34 family are reportedly tumor-suppressor miRNAs and are associated with various human cancers. Our results confirm that miR34a expression was downregulated in MCF7/ADR cells compared with MCF7 cells. We hypothesized that this reduction was due to the p53 (TP53) mutation in MCF7/ADR cells. In this study, we found that primary and mature miR34a were suppressed by treatment with p53 RNAi or the dominant-negative p53 mutant in MCF7 cells. Ectopic miR34a expression reduced cancer stem cell properties and increased sensitivity to doxorubicin treatment by directly targeting NOTCH1. Furthermore, tumors from nude mice treated with miR34a were significantly smaller compared with those of mice treated with control lentivirus. Our research suggests that the ectopic expression of miR34a represents a novel therapeutic approach in chemoresistant breast cancer treatment.

Up-regulation of neogenin-1 increases cell proliferation and motility in gastric cancer.

Although elevated expression of neogenin-1 has been detected in human gastric cancer tissue, its role in gastric tumorigenesis remains unclear due to the lack of neogenin-1 studies in cancer. Therefore, we demonstrated here the function and regulatory mechanism of neogenin-1 in gastric cancer. Neogenin-1 ablation decreased proliferation and migration of gastric cancer cells, whereas its over-expression reversed these effects. Xenografted analyses using gastric cancer cells displayed statistically significant inhibition of tumor growth by neogenin-1 depletion. Interestingly, galectin-3 interacted with HSF-1 directly, which facilitated nuclear-localization and binding on neogenin-1 promoter to drive its transcription and gastric cancer cell motility. The galectin-3-increased gastric cancer cell motility was down-regulated by HSF-1 depletion. Moreover, the parallel expression patterns of galectin-3 and neogenin-1, as well as those of HSF-1 and neogenin-1, were detected in the malignant tissues of gastric cancer patients. Taken together, high-expression of neogenin-1 promotes gastric cancer proliferation and motility and its expression is regulated by HSF-1 and galectin-3 interaction. In addition, we propose further studies for neogenin-1 and its associated pathways to provide them as a proper target for gastric cancer therapy.