Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1

Role of microRNA-363 during tumor progression and invasion

Recent progresses in diagnostic and therapeutic methods have significantly improved prognosis in cancer patients. However, cancer is still considered as one of the main causes of human deaths in the world. Late diagnosis in advanced tumor stages can reduce the effectiveness of treatment methods and increase mortality rate of cancer patients. Therefore, investigating the molecular mechanisms of tumor progression can help to introduce the early diagnostic markers in these patients. MicroRNA (miRNAs) has an important role in regulation of pathophysiological cellular processes. Due to their high stability in body fluids, they are always used as the non-invasive markers in cancer patients. Since, miR-363 deregulation has been reported in a wide range of cancers, we discussed the role of miR-363 during tumor progression and metastasis. It has been reported that miR-363 has mainly a tumor suppressor function through the regulation of transcription factors, apoptosis, cell cycle, and structural proteins. MiR-363 also affected the tumor progression via regulation of various signaling pathways such as WNT, MAPK, TGF-β, NOTCH, and PI3K/AKT. Therefore, miR-363 can be introduced as a probable therapeutic target as well as a non-invasive diagnostic marker in cancer patients.

YB-1 Protein in Breast Cancer (Scientific and Personal Meetings with Professor Ovchinnikov)

In the article, the author examines the properties of Y-box-binding protein (YB-1) and expression of the YBX-1 gene in various malignant tumors and provides the data from her own prospective study in breast cancer patients. YB-1 is a member of the highly conserved family of cold shock proteins with multiple functions in the cytoplasm and cell nucleus. YB-1 is involved in embryogenesis; it ensures cell proliferation and protects cell from the action of various aggressive environmental factors. In adult organisms, YB-1 is involved in a variety of cellular functions that regulate malignant phenotype in several types of tumors. YB-1 is a molecular marker of tumor progression that can be used in clinical practice as both prognostic factor and a target for anticancer therapy. Our prospective clinical study showed that expression of YB-1 mRNA is an independent prognostic factor, as breast cancer patients expressing YB-1 have a lower disease-free survival rate, regardless of the tumor stage and biological subtype. We recommend determining the level of YB-1 mRNA expression as a prognostic test in breast cancer patients.

Stress Granules in the Anti-Cancer Medications Mechanism of Action: A Systematic Scoping Review

Stress granule (SG) formation is a well-known cellular mechanism for minimizing stress-related damage and increasing cell survival. In addition to playing a critical role in the stress response, SGs have emerged as critical mediators in human health. It seems logical that SGs play a key role in cancer cell formation, development, and metastasis. Recent studies have shown that many SG components contribute to the anti-cancer medications' responses through tumor-associated signaling pathways and other mechanisms. SG proteins are known for their involvement in the translation process, control of mRNA stability, and capacity to function in both the cytoplasm and nucleus. The current systematic review aimed to include all research on the impact of SGs on the mechanism of action of anti-cancer medications and was conducted using a six-stage methodological framework and the PRISMA guideline. Prior to October 2021, a systematic search of seven databases for eligible articles was performed. Following the review of the publications, the collected data were subjected to quantitative and qualitative analysis. Notably, Bortezomib, Sorafenib, Oxaliplatin, 5-fluorouracil, Cisplatin, and Doxorubicin accounted for the majority of the medications examined in the studies. Overall, this systematic scoping review attempts to demonstrate and give a complete overview of the function of SGs in the mechanism of action of anti-cancer medications by evaluating all research.

Stress Granules Involved in Formation, Progression and Metastasis of Cancer: A Scoping Review

The assembly of stress granules (SGs) is a well-known cellular strategy for reducing stress-related damage and promoting cell survival. SGs have become important players in human health, in addition to their fundamental role in the stress response. The critical role of SGs in cancer cells in formation, progression, and metastasis makes sense. Recent researchers have found that several SG components play a role in tumorigenesis and cancer metastasis via tumor-associated signaling pathways and other mechanisms. Gene-ontology analysis revealed the role of these protein components in the structure of SGs. Involvement in the translation process, regulation of mRNA stability, and action in both the cytoplasm and nucleus are among the main features of SG proteins. The present scoping review aimed to consider all studies on the effect of SGs on cancer formation, proliferation, and metastasis and performed based on a six-stage methodology structure and the PRISMA guideline. A systematic search of seven databases for qualified articles was conducted before July 2021. Publications were screened, and quantitative and qualitative analysis was performed on the extracted data. Go analysis was performed on seventy-one SGs protein components. Remarkably G3BP1, TIA1, TIAR, and YB1 have the largest share among the proteins considered in the studies. Altogether, this scoping review tries to demonstrate and provide a comprehensive summary of the role of SGs in the formation, progression, and metastasis of cancer by reviewing all studies.

The focal adhesion protein Integrin-Linked Kinase (ILK) as an important player in breast cancer pathogenesis

Cell-extracellular matrix interactions, or focal adhesions (FA), are crucial for tissue homeostasis but are also implicated in cancer. Integrin-Linked Kinase (ILK) is an abundantly expressed FA protein involved in multiple signaling pathways. Here, we reviewed the current literature on the role of ILK in breast cancer (BC). Articles included in vitro and in vivo experiments as well as studies in human BC samples. ILK attenuation via silencing or pharmaceutical inhibition, leads to apoptosis or inhibition of epithelial-to-mesenchymal transition, and cell invasion whereas ILK overexpression suppresses anoikis and promotes tumor growth and metastasis. Finally, ILK is upregulated in BC tumors and its expression is associated with grade, and metastasis. Therefore, ILK should be evaluated as a potential anti-cancer pharmaceutical target.

E2F1: Cause and Consequence of DNA Replication Stress

In mammalian cells, cell cycle entry occurs in response to the correct stimuli and is promoted by the transcriptional activity of E2F family members. E2F proteins regulate the transcription of S phase cyclins and genes required for DNA replication, DNA repair, and apoptosis. The activity of E2F1, the archetypal and most heavily studied E2F family member, is tightly controlled by the DNA damage checkpoints to modulate cell cycle progression and initiate programmed cell death, when required. Altered tumor suppressor and oncogenic signaling pathways often result in direct or indirect interference with E2F1 regulation to ensure higher rates of cell proliferation independently of external cues. Despite a clear link between dysregulated E2F1 activity and cancer progression, literature on the contribution of E2F1 to DNA replication stress phenotypes is somewhat scarce. This review discusses how dysfunctional tumor suppressor and oncogenic signaling pathways promote the disruption of E2F1 transcription and hence of its transcriptional targets, and how such events have the potential to drive DNA replication stress. In addition to the involvement of E2F1 upstream of DNA replication stress, this manuscript also considers the role of E2F1 as a downstream effector of the response to this type of cellular stress. Lastly, the review introduces some reflections on how E2F1 activity is integrated with checkpoint control through post-translational regulation, and proposes an exploitable tumor weakness based on this axis.

Long non-coding RNA SNHG5 affects the invasion and apoptosis of renal cell carcinoma by regulating the miR-363-3p-Twist1 interaction

Non-coding RNA dysregulation is associated with many human diseases, including cancer. This study explored the effects of lncRNA SNHG5 on clear cell renal cell carcinoma (ccRCC). We found that lncRNA SNHG5 is upregulated in human ccRCC tissues and that lncRNA SNHG5 inhibition reduced ccRCC cell invasion and promoted apoptosis in vitro. Bioinformatics database searching revealed that lncRNA SNHG5 is predicted to regulate the interaction between miR-363-3p and Twist1. We further verified a ccRCC biomarker panel, which consists of lncRNA SNHG5, miR-363-3p, and Twist1 in ccRCC tissue samples. The direct SNHG5-miR-363-3p and Twist1-miR-363-3p interactions were confirmed via dual-luciferase reporter assays. Additionally, functional assays demonstrated that SNHG5 promotes cell invasion and inhibits apoptosis, while miR-363-3p inhibits cell invasion and promotes apoptosis via an interaction with Twist1. Furthermore, we found that Twist1 promotes tumor metastasis by regulating matrix metalloproteinase (MMP)2 and MMP9 levels. Together, these results suggest that lncRNA SNHG5 may predict ccRCC patient clinical outcome and serve as a novel anti-ccRCC therapeutic target.

Interaction network analysis of YBX1 for identification of therapeutic targets in adenocarcinomas

Human Y-box binding protein-1 (YBX1) is a member of highly conserved cold-shock domain protein family, which is involved in transcriptional as well as translational regulation of many genes. Nuclear localization of YBX1 has been observed in various cancer types and it's overexpression has been linked to adverse clinical outcome and poor therapy response, but no diagnostic or therapeutic correlation has been established so far. This study aimed to identify differentially expressed novel genes among the interactors of YBX1 in different cancer types. Analysis of RNA-Seq data for colorectal, lung, prostate and stomach adenocarcinoma identified 39 unique genes, which are differentially expressed in the four adenocarcinoma types. Gene-enrichment analysis for the differentially expressed genes from individual adenocarcinoma with focus on unique genes resulted in a total of 57 gene sets specific to each adenocarcinoma. Gene ontology for commonly expressed genes suggested the pathways and possible mechanisms through which they affect each adenocarcinoma type considered in the study. Gene regulatory network constructed for the common genes and network topology was analyzed for the central nodes. Here 12 genes were found to play important roles in the network formation; among them, two genes FOXM1 and TOP2A were found to be in central network formation, which makes them a common target for therapeutics. Furthermore, five common differentially expressed genes in all adenocarcinomas were also identified.

Expression and network analysis of YBX1 interactors for identification of new drug targets in lung adenocarcinoma

Y-Box Binding protein 1 (YBX-1) is known to be involved in various types of cancers. It's interactors also play major role in various cellular functions. Present work aimed to study the expression profile of the YBX-1 interactors during lung adenocarcinoma (LUAD). The differential expression analysis involved 57 genes from 95 lung adenocarcinoma samples, construction of gene network and topology analysis. A Total of 43 genes were found to be differentially expressed from which 17 genes were found to be down regulated and 26 genes were up-regulated. We observed that Polyadenylate-binding protein 1 (PABPC1), a protein involved in YBX1 translation, is highly correlated with YBX1. The interaction network analysis for a differentially expressed non-coding RNA Growth Arrest Specific 5 (GAS5) suggests that two proteins namely, Growth Arrest Specific 2 (GAS2) and Peripheral myelin protein 22 (PMP22) are potentially involved in LUAD progression. The network analysis and differential expression suggests that Collagen type 1 alpha 2 (COL1A2) can be potential biomarker and target for LUAD.

Aloe-emodin inhibits HER-2 expression through the downregulation of Y-box binding protein-1 in HER-2-overexpressing human breast cancer cells

Human epidermal growth factor receptor-2 (HER-2)-positive breast cancer tends to be aggressive, highly metastatic, and drug resistant and spreads rapidly. Studies have indicated that emodin inhibits HER-2 expression. This study compared the HER-2-inhibitory effects of two compounds extracted from rhubarb roots: aloe-emodin (AE) and rhein. Our results indicated that AE exerted the most potent inhibitory effect on HER-2 expression. Treatment of HER-2-overexpressing breast cancer cells with AE reduced tumor initiation, cell migration, and cell invasion. AE was able to suppress YB-1 expression, further suppressing downstream HER-2 expression. AE suppressed YB-1 expression through the inhibition of Twist in HER-2-overexpressing breast cancer cells. Our data also found that AE inhibited cancer metastasis and cancer stem cells through the inhibition of EMT. Interestingly, AE suppressed YB-1 expression through the downregulation of the intracellular integrin-linked kinase (ILK)/protein kinase B (Akt)/mTOR signaling pathway in HER-2-overexpressing breast cancer cells. In vivo study showed the positive result of antitumor activity of AE in nude mice injected with human HER-2-overexpressing breast cancer cells. These findings suggest the possible application of AE in the treatment of HER-2-positive breast cancer.

JWA loss promotes cell migration and cytoskeletal rearrangement by affecting HER2 expression and identifies a high-risk subgroup of HER2-positive gastric carcinoma patients

Background and Aims

JWA, a microtubule-associated protein (MAP) involved in apoptosis, has been identified as a suppressor of metastasis, and it affects cell migration in melanoma and its downregulation in tumor is an idependent negative prognostic factor in resectable gastric cancer. HER2 overexpression has been observed in gastric cancer (GC) cells and implicated in the metastatic phenotype. However, the biological role of JWA in migration and its clinical value in HER2-positive GC remain elusive.

Results

JWA suppresses EGF-induced cell migration and actin cytoskeletal rearrangement by abrogating HER2 expression and downstream PI3K/AKT signaling in HER2-overexpressing GC cell lines. The modulation of HER2 by JWA is dependent on ERK activation and consequent PEA3 upregulation and activation. Reduced JWA expression is associated with high HER2 expression and with poor survival in patients with AGC, whereas HER2 expression alone is not associated with survival. However, concomitant low JWA and high HER2 expression is associated with unfavorable outcomes. Additionally, when patients were stratified by JWA expression, those with higher HER2 expression in the low JWA expression subgroup exhibited worse survival.

Methods

The impact of JWA on the EGF-induced migration of HER2-positive GC cells was studied using transwell assays and G-LISA assays. Western blotting, real-time PCR, electrophoretic mobility shift assays and luciferase assays were utilized to investigate the mechanisms by which JWA affects HER2. The association of JWA with HER2 and its clinical value were further analyzed by IHC in 128 pairs of advanced gastric cancer (AGC) and adjacent normal tissue samples.

Conclusions

This study characterizes a novel mechanism for regulating cell motility in HER2-overexpressing GC cells involving JWA-mediated MEK/ERK/PEA3 signaling activation and HER2 downregulation. Furthermore, JWA may be a useful prognostic indicator for advanced GC and may help stratify HER2-positive patient subgroups to better identify unfavorable outcomes.

Targeting integrin-linked kinase to suppress oncogenic KRAS signaling in pancreatic cancer

Although oncogenic KRAS represents a therapeutically relevant target in pancreatic cancer, it is deemed "non-druggable" because of the intrinsic difficulty in designing direct inhibitors of KRAS. Our recent work demonstrated a KRAS-integrin-linked kinase (ILK) regulatory feedback loop that allows pancreatic cancer cells to regulate KRAS expression and to interact with the tumor microenvironment to promote aggressive phenotype. KRAS induces E2F1-mediated transcriptional activation of ILK expression, and ILK, in turn, controls KRAS expression via hnRNPA1, which binds and destabilizes the G-quadruplex in the KRAS promoter. Moreover, ILK inhibition blocked KRAS-driven EMT and growth factor-stimulated KRAS expression. This regulatory loop, however, was not noted in KRAS mutant colorectal and lung cancer cells examined as knockdown of KRAS or ILK did not affect each other's expression, suggesting that this KRAS-ILK feedback regulation is specific for pancreatic cancer. In sum, this regulatory loop provides a strong mechanistic rationale for suppressing oncogenic KRAS signaling through targeting ILK, and this creating a potential new therapeutic strategy for pancreatic cancer.

A novel HIF-1α-integrin-linked kinase regulatory loop that facilitates hypoxia-induced HIF-1α expression and epithelial-mesenchymal transition in cancer cells

Here, we described a novel regulatory feedback loop in which hypoxia induces integrin-linked kinase (ILK) expression through a HIF-1α-dependent mechanism and ILK, in turn, stimulates HIF-1α expression through cell type- and cell context-dependent pathways. HIF-1α increased ILK via transcriptional activation. ILK increased HIF-1α levels by promoting mTOR-mediated translation in PC-3 and MCF-7 cells, and by blocking GSK3β-mediated degradation in LNCaP cells, consistent with the cell line-/cellular context-specific functions of ILK as a Ser473-Akt kinase. We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation. Also, ILK can de-repress HIF-1α signaling through the YB-1-mediated inhibition of Foxo3a expression. In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1. Thus, the ILK-HIF-1α regulatory loop could underlie the maintenance of high HIF-1α expression levels and the promotion of EMT under hypoxic conditions. Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

Function of Integrin-Linked Kinase in Modulating the Stemness of IL-6-Abundant Breast Cancer Cells by Regulating γ-Secretase-Mediated Notch1 Activation in Caveolae

Interleukin-6 (IL-6) and Notch signaling are important regulators of breast cancer stem cells (CSCs), which drive the malignant phenotype through self-renewal, differentiation, and development of therapeutic resistance. We investigated the role of integrin-linked kinase (ILK) in regulating IL-6–driven Notch1 activation and the ability to target breast CSCs through ILK inhibition. Ectopic expression/short hairpin RNA-mediated knockdown of ILK, pharmacological inhibition of ILK with the small molecule T315, Western blot analysis, immunofluorescence, and luciferase reporter assays were used to evaluate the regulation of IL-6–driven Notch1 activation by ILK in IL-6–producing triple-negative breast cancer cell lines (MDA-MB-231, SUM-159) and in MCF-7 and MCF-7^IL-6 cells. The effects of ILK on γ-secretase complex assembly and cellular localization were determined by immunofluorescence, Western blots of membrane fractions, and immunoprecipitation. In vivo effects of T315-induced ILK inhibition on CSCs in SUM-159 xenograft models were assessed by mammosphere assays, flow cytometry, and tumorigenicity assays. Results show that the genetic knockdown or pharmacological inhibition of ILK suppressed Notch1 activation and the abundance of the γ-secretase components presenilin-1, nicastrin, and presenilin enhancer 2 at the posttranscriptional level via inhibition of caveolin-1-dependent membrane assembly of the γ-secretase complex. Accordingly, knockdown of ILK inhibited breast CSC-like properties in vitro and the breast CSC subpopulation in vivo in xenograft tumor models. Based on these findings, we propose a novel function of ILK in regulating γ-secretase–mediated Notch1 activation, which suggests the targeting of ILK as a therapeutic approach to suppress IL-6–induced breast CSCs.

Inhibition of the HER2-YB1-AR axis with Lapatinib synergistically enhances Enzalutamide anti-tumor efficacy in castration resistant prostate cancer

Incurable castration-resistant prostate cancer (CRPC) is driven by androgen receptor (AR) activation. Potent therapies that prevent AR signaling, such as Enzalutamide (ENZ), are mainstay treatments for CRPC; however patients eventually progress with ENZ resistant (ENZR) disease. In this study, we investigated one mechanism of ENZ resistance, and tried to improve therapeutic efficiency of ENZ. We found HER2 expression is increased in ENZR tumors and cell lines, and is induced by ENZ treatment of LNCaP cells. ENZ-induced HER2 overexpression was dependent on AKT-YB1 activation and modulated AR activity. HER2 dependent AR activation in LNCaP and ENZR cells was effectively blocked by treatment with the EGFR/HER2 inhibitor Lapatinib, which reduced cell viability and increased apoptosis. Despite efficacy in vitro, in vivo monotherapy with Lapatinib did not prevent ENZR tumor growth. However, combination treatment of Lapatinib with ENZ most effectively induced cell death in LNCaP cells in vitro and was more effective than ENZ alone in preventing tumor growth in an in vivo model of CRPC. These results suggest that while HER2 overexpression and subsequent AR activation is a targetable mechanism of resistance to ENZ, therapy using Lapatinib is only a rational therapeutic approach when used in combination with ENZ in CRPC.

Integrin-linked kinase as a novel molecular switch of the IL-6-NF-κB signaling loop in breast cancer

Substantial evidence has clearly demonstrated the role of the IL-6-NF-κB signaling loop in promoting aggressive phenotypes in breast cancer. However, the exact mechanism by which this inflammatory loop is regulated remains to be defined. Here, we report that integrin-linked kinase (ILK) acts as a molecular switch for this feedback loop. Specifically, we show that IL-6 induces ILK expression via E2F1 upregulation, which, in turn, activates NF-κB signaling to facilitate IL-6 production. shRNA-mediated knockdown or pharmacological inhibition of ILK disrupted this IL-6-NF-κB signaling loop, and blocked IL-6-induced cancer stem cells in vitro and estrogen-independent tumor growth in vivo Together, these findings establish ILK as an intermediary effector of the IL-6-NF-κB feedback loop and a promising therapeutic target for breast cancer.

Regulation of oncogenic KRAS signaling via a novel KRAS-integrin-linked kinase-hnRNPA1 regulatory loop in human pancreatic cancer cells

Integrin-linked kinase (ILK) is a mediator of aggressive phenotype in pancreatic cancer. On the basis of our finding that knockdown of either KRAS or ILK has a reciprocal effect on the other's expression, we hypothesized the presence of an ILK-KRAS regulatory loop that enables pancreatic cancer cells to regulate KRAS expression. This study aimed to elucidate the mechanism by which this regulatory circuitry is regulated and to investigate the translational potential of targeting ILK to suppress oncogenic KRAS signaling in pancreatic cancer. Interplay between KRAS and ILK and the roles of E2F1, c-Myc and heterogeneous nuclear ribonucleoprotein as intermediary effectors in this feedback loop was interrogated by genetic manipulations through small interfering RNA/short hairpin RNA knockdown and ectopic expression, western blotting, PCR, promoter-luciferase reporter assays, chromatin immunoprecipitation and pull-down analyses. In vivo efficacy of ILK inhibition was evaluated in two murine xenograft models. Our data show that KRAS regulated the expression of ILK through E2F1-mediated transcriptional activation, which, in turn, controlled KRAS gene expression via hnRNPA1-mediated destabilization of the G-quadruplex on the KRAS promoter. Moreover, ILK inhibition blocked KRAS-driven epithelial-mesenchymal transition and growth factor-stimulated KRAS expression. The knockdown or pharmacological inhibition of ILK suppressed pancreatic tumor growth, in part, by suppressing KRAS signaling. These studies suggest that this KRAS-E2F1-ILK-hnRNPA1 regulatory loop enables pancreatic cancer cells to promote oncogenic KRAS signaling and to interact with the tumor microenvironment to promote aggressive phenotypes. This regulatory loop provides a mechanistic rationale for targeting ILK to suppress oncogenic KRAS signaling, which might foster new therapeutic strategies for pancreatic cancer.

Effects of lentivirus-mediated shRNA targeting integrin-linked kinase on oral squamous cell carcinoma in vitro and in vivo

Integrin-linked kinase (ILK), a highly conserved intracellular protein of serine/threonine protein kinase activities, which is associated with the integrin and growth factor receptor signaling pathway, is involved in the regulation of cell proliferation, apoptosis, differentiation, migration and epithelial-mesenchymal transition (EMT). Findings of a previous study showed that ILK overexpression was strongly correlated with a more aggressive tumor phenotype, recurrence and poor survival for oral squamous cell carcinoma (OSCC) patients, as well as some EMT markers. In order to investigate the underlying mechanisms involved, a lentivirus-mediated short hairpin RNA (shRNA) was employed to downregulate ILK. The results showed that the knockdown of ILK inhibited cell growth, adhesion and invasion ability in vitro, and OSCC cells deficient of ILK were blocked in the S phase and underwent apoptosis. Additionally, ILK shRNA inhibited EMT by impairing the expression of Snail, Slug and Twist2 and enhacning E-cadherin expression. ILK shRNA suppressed the phosphorylation of downstream signaling targets Akt and GSk-3β. In addition, the knockdown of ILK inhibited tumor growth, invasion and metastasis of xenograft tumors in vivo. These results suggested that ILK is a promising therapeutic target for the treatment of OSCC.

Epstein-Barr virus latent membrane protein 2A suppresses the expression of HER2 via a pathway involving TWIST and YB-1 in Epstein-Barr virus-associated gastric carcinomas

To explore HER2 expression in Epstein-Barr virus-associated gastric carcinoma (EBVaGC) and the possible mechanisms causing down-regulation of HER2 expression in EBVaGC, we first evaluated HER2 and LMP2A expression on a clinicopathological-features matched cohort including 78 EBVaGC and 216 EBV-negative gastric carcinoma (EBVnGC) cases by immunohistochemistry. Cases with high HER2 expression in EBVaGC were significantly less than in EBVnGC (5.1% versus 23.7%; p<0.001), and none of the 34 LMP2A+ EBVaGC showed high HER2 expression. Further, overexpressing LMP2A in EBV-negative SGC7901 cells significantly decreased HER2, TWIST and YB-1 mRNA by 36.1%±8.1%, 87.6%±14.0% and 83.8%±5.7%, and protein by 44%, 57% and 49%, respectively. Additionally, the nucleus/cytoplasm ratios of TWIST and YB-1 were also decreased by 85% and 80%, respectively. Silencing LMP2A by siRNA in EBV-positive SNU719 cells for 48 h significantly increased HER2, TWIST and YB-1 mRNA to 276.7%±14.6%, 1284.8%±38.2% and 332.0%±15.5% and protein to 212%, 457% and 232%, respectively. The nucleus/cytoplasm ratios of TWIST and YB-1 were up-regulated by 4.00- and 3.57-fold, respectively, following LMP2A down-regulation. Moreover, LMP2A+/HER2^low EBVaGC cases presented the best overall survival compared with LMP2A−/HER2^low and LMP2A−/HER2^high cases (p=0.003, log-rank test). These results suggest that LMP2A may suppress the HER2 expression through the TWIST/YB-1 axis in EBVaGC.

Using Pharmacokinetic Profiles and Digital Quantification of Stained Tissue Microarrays as a Medium-Throughput, Quantitative Method for Measuring the Kinetics of Early Signaling Changes Following Integrin-Linked Kinase Inhibition in an In Vivo Model of Cancer

A small molecule inhibitor (QLT0267) targeting integrin-linked kinase is able to slow breast tumor growth in vivo; however, the mechanism of action remains unknown. Understanding how targeting molecules involved in intersecting signaling pathways impact disease is challenging. To facilitate this understanding, we used tumor tissue microarrays (TMA) and digital image analysis for quantification of immunohistochemistry (IHC) in order to investigate how QLT0267 affects signaling pathways in an orthotopic model of breast cancer over time. Female NCR nude mice were inoculated with luciferase-positive human breast tumor cells (LCC6^Luc) and tumor growth was assessed by bioluminescent imaging (BLI). The plasma levels of QLT0267 were determined by LC-MS/MS methods following oral dosing of QLT0267 (200 mg/kg). A TMA was constructed using tumor tissue collected at 2, 4, 6, 24, 78 and 168 hr after treatment. IHC methods were used to assess changes in ILK-related signaling. The TMA was digitized, and Aperio ScanScope and ImageScope software were used to provide semi-quantitative assessments of staining levels. Using medium-throughput IHC quantitation, we show that ILK targeting by QLT0267 in vivo influences tumor physiology through transient changes in pathways involving AKT, GSK-3 and TWIST accompanied by the translocation of the pro-apoptotic protein BAD and an increase in Caspase-3 activity.

Tamoxifen inhibits ER-negative breast cancer cell invasion and metastasis by accelerating Twist1 degradation

Twist1 is a transcription factor driving epithelial-mesenchymal transition, invasion and metastasis of breast cancer cells. Mice with germ-line Twist1 knockout are embryonic lethal, while adult mice with inducible Twist1 knockout have no obvious health problems, suggesting that Twist1 is a viable therapeutic target for the inhibition of invasion and metastasis of breast cancer in adult patients. In this study, we expressed a luciferase protein or a Twist1-luciferase fusion protein in HeLa cells as part of a high throughput system to screen 1280 compounds in the Library of Pharmacologically Active Compounds (LOPAC) from Sigma-Aldrich for their effects on Twist1 protein expression. One of the most interesting compounds identified is tamoxifen, a selective estrogen receptor (ER) modulator used to treat ER-positive breast cancer. Tamoxifen treatment significantly accelerated Twist1 degradation in multiple cell lines including HEK293 human kidney cells, 4T1 and 168FARN mouse mammary tumor cells with either ectopically or endogenously expressed Twist1. Tamoxifen-induced Twist1 degradation could be blocked by the MG132 proteasome inhibitor, suggesting that tamoxifen induces Twist1 degradation through the ubiquitination-proteasome pathway. However, tamoxifen-induced Twist1 degradation was independent of Twist1 mRNA expression, estrogen signaling and MAPK-mediated Twist1 phosphorylation in these cells. Importantly, tamoxifen also significantly inhibited invasive behavior in Matrigel and lung metastasis in SCID-bg mice of ER-negative 4T1 mammary tumor cells, which depend on endogenous Twist1 to invade and metastasize. These results indicate that tamoxifen can significantly accelerate Twist1 degradation to suppress cancer cell invasion and metastasis, suggesting that tamoxifen can be used not only to treat ER-positive breast cancers but also to reduce Twist1-mediated invasion and metastasis in ER-negative breast cancers.

Integrin-linked kinase links dynactin-1/dynactin-2 with cortical integrin receptors to orient the mitotic spindle relative to the substratum

Cells must divide strictly along a plane to form an epithelial layer parallel to the basal lamina. The axis of cell division is primarily governed by the orientation of the mitotic spindle and spindle misorientation pathways have been implicated in cancer initiation. While β1-Integrin and the Dynein/Dynactin complex are known to be involved, the pathways linking these complexes in positioning mitotic spindles relative to the basal cortex and extracellular matrix remain to be elucidated. Here, we show that Integrin-Linked Kinase (ILK) and α-Parvin regulate mitotic spindle orientation by linking Dynactin-1 and Dynactin-2 subunits of the Dynein/Dynactin complex to Integrin receptors at the basal cortex of mitotic cells. ILK and α-Parvin are required for spindle orientation. ILK interacts with Dynactin-1 and Dynactin-2 and ILK siRNA attenuates Dynactin-2 localization to the basal cortex. Furthermore we show that Dynactin-2 can no longer colocalize or interact with Integrins when ILK is absent, suggesting mechanistically that ILK is acting as a linking protein. Finally we demonstrate that spindle orientation and cell proliferation are disrupted in intestinal epithelial cells in vivo using tissue-specific ILK knockout mice. These data demonstrate that ILK is a linker between Integrin receptors and the Dynactin complex to regulate mitotic spindle orientation.

Inhibition of Integrin-HER2 signaling by Cucurbitacin B leads to in vitro and in vivo breast tumor growth suppression

HER2, an oncogenic receptor is overexpressed in about 25-30% of breast cancer patients. HER2 has been shown to play role in tumor promotion by having cross-talk with multiple oncogenic pathways in cancer cells. Our results show that Cucurbitacin B (CuB), a triterpenoid steroidal compound inhibited the growth of various breast cancer cells with an IC50 ranging from 18-50nM after 48 and 72 h of treatment. Our study also revealed the significant inhibitory effects of CuB on HER2 and integrin signaling in breast cancer. Notably, CuB inhibited ITGA6 and ITGB4 (integrin α6 & integrin β4), which are overexpressed in breast cancer. Furthermore, CuB also induced the expression of major ITGB1and ITGB3, which are known to cause integrin-mediated cell death. In addition, we observed that TGFβ treatment resulted in the increased association of HER2 with ITGA6 and this association was inhibited by CuB treatment. Efficacy of CuB was tested in vivo using two different orthotopic models of breast cancer. MDA-MB-231 and 4T-1 cells were injected orthotopically in the mammary fat pad of female athymic nude mice or BALB/c mice respectively. Our results showed that CuB administration inhibited MDA-MB-231 orthotopic tumors by 55%, and 4T-1 tumors by 40%. The 4T-1 cells represent stage IV breast cancer and form very aggressive tumors. CuB mediated breast tumor growth suppression was associated with the inhibition of HER2/integrin signaling. Our results suggest novel targets of CuB in breast cancer in vitro and in vivo.

The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web

The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies. Despite the advances, cases of drug resistance and recurrence of disease still remain a challenge to overcome. An important aspect for drug resistance is the complexity of the HER2 signaling network. This includes the crosstalk between HER2 and hormone receptors; its function as a transcription factor; the regulation of HER2 by protein-tyrosine phosphatases and a complex network of positive and negative feedback-loops. This review summarises the current knowledge of many different HER2 interactions to illustrate the complexity of the HER2 network from the transcription of HER2 to the effect of its downstream targets. Exploring the novel avenues of the HER2 signaling could yield a better understanding of treatment resistance and give rise to developing new and more effective therapies.

Integrin-linked kinase modulates lipopolysaccharide- and Helicobacter pylori-induced nuclear factor κB-activated tumor necrosis factor-α production via regulation of p65 serine 536 phosphorylation

Integrin-linked kinase (ILK) is a ubiquitously expressed and highly conserved serine-threonine protein kinase that regulates cellular responses to a wide variety of extracellular stimuli. ILK is involved in cell-matrix interactions, cytoskeletal organization, and cell signaling. ILK signaling has also been implicated in oncogenesis and progression of cancers. However, its role in the innate immune system remains unknown. Here, we show that ILK mediates pro-inflammatory signaling in response to lipopolysaccharide (LPS). Pharmacological or genetic inhibition of ILK in mouse embryonic fibroblasts and macrophages selectively blocks LPS-induced production of the pro-inflammatory cytokine tumor necrosis factor α (TNF-α). ILK is required for LPS-induced activation of nuclear factor κB (NF-κB) and transcriptional induction of TNF-α. The modulation of LPS-induced TNF-α synthesis by ILK does not involve the classical NF-κB pathway, because IκB-α degradation and p65 nuclear translocation are both unaffected by ILK inhibition. Instead, ILK is involved in an alternative activation of NF-κB signaling by modulating the phosphorylation of p65 at Ser-536. Furthermore, ILK-mediated alternative NF-κB activation through p65 Ser-536 phosphorylation also occurs during Helicobacter pylori infection in macrophages and gastric cancer cells. Moreover, ILK is required for H. pylori-induced TNF-α secretion in macrophages. Although ILK-mediated phosphorylation of p65 at Ser-536 is independent of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway during LPS stimulation, upon H. pylori infection this event is dependent on the PI3K/Akt pathway. Our findings implicate ILK as a critical regulatory molecule for the NF-κB-mediated pro-inflammatory signaling pathway, which is essential for innate immune responses against pathogenic microorganisms.

Radiation-induced gene signature predicts pathologic complete response to neoadjuvant chemotherapy in breast cancer patients

The identification of biomarkers predictive of neoadjuvant chemotherapy response in breast cancer patients would be an important advancement in personalized cancer therapy. In this study, we hypothesized that due to similarities between radiation- and chemotherapy-induced cellular response mechanisms, radiation-responsive genes may be useful in predicting response to neoadjuvant chemotherapy. Murine p53 null breast cancer cell lines representative of the luminal, basal-like and claudin-low human breast cancer subtypes were irradiated to identify radiation-responsive genes across subtypes. These murine tumor radiation-induced genes were then converted to their human orthologs, and subsequently tested as a predictor of pathologic complete response (pCR), which was validated on two independent published neoadjuvant chemotherapy datasets of genomic data with chemotherapy response. A radiation-induced gene signature consisting of 30 genes was identified on a training set of 337 human primary breast cancer tumor samples that was prognostic for survival. Mean expression of this signature was calculated for individual samples on two independent published datasets and was found to be significantly predictive of pCR. Multivariate logistic regression analysis in both independent datasets showed that this 30 gene signature added significant predictive information independent of that provided by standard clinical predictors and other gene expression-based predictors of pCR. This study provides new information for radiation-induced biology, as well as information regarding response to neoadjuvant chemotherapy and a possible means of improving the prediction of pCR.

Links between the oncoprotein YB-1 and small non-coding RNAs in breast cancer

Background

The nucleic acid-binding protein YB-1, a member of the cold-shock domain protein family, has been implicated in the progression of breast cancer and is associated with poor patient survival. YB-1 has sequence similarity to LIN28, another cold-shock protein family member, which has a role in the regulation of small noncoding RNAs (sncRNAs) including microRNAs (miRNAs). Therefore, to investigate whether there is an association between YB-1 and sncRNAs in breast cancer, we investigated whether sncRNAs were bound by YB-1 in two breast cancer cell lines (luminal A-like and basal cell-like), and whether the abundance of sncRNAs and mRNAs changed in response to experimental reduction of YB-1 expression.

Results

RNA-immunoprecipitation with an anti-YB-1 antibody showed that several sncRNAs are bound by YB-1. Some of these were bound by YB-1 in both breast cancer cell lines; others were cell-line specific. The small RNAs bound by YB-1 were derived from various sncRNA families including miRNAs such as let-7 and miR-320, transfer RNAs, ribosomal RNAs and small nucleolar RNAs (snoRNA). Reducing YB-1 expression altered the abundance of a number of transcripts encoding miRNA biogenesis and processing proteins but did not alter the abundance of mature or precursor miRNAs.

Conclusions

YB-1 binds to specific miRNAs, snoRNAs and tRNA-derived fragments and appears to regulate the expression of miRNA biogenesis and processing machinery. We propose that some of the oncogenic effects of YB-1 in breast cancer may be mediated through its interactions with sncRNAs.

Inducible knockout of Twist1 in young and adult mice prolongs hair growth cycle and has mild effects on general health, supporting Twist1 as a preferential cancer target

Twist1 promotes epithelial-mesenchymal transition, invasion, metastasis, stemness, and chemotherapy resistance in cancer cells and thus is a potential target for cancer therapy. However, Twist1-null mice are embryonic lethal, and people with one Twist1 germline mutant allele develop Saethre-Chotzen syndrome; it is questionable whether Twist1 can be targeted in patients without severe adverse effects. We found that Twist1 is expressed in several tissues, including fibroblasts of the mammary glands and dermal papilla cells of the hair follicles. We developed a tamoxifen-inducible Twist1 knockout mouse model; Twist1 knockout in 6-week-old female mice did not affect mammary gland morphogenesis and function during pregnancy and lactation. In both males and females, the knockout did not influence body weight gain, heart rate, or total lean and fat components. The knockout also did not alter blood pressure in males, although it slightly reduced blood pressure in females. Although Twist1 is not cyclically expressed in dermal papilla cells, knockout of Twist1 at postnatal day 13 (when hair follicles have developed) drastically extended the anagen phase and accelerated hair growth. These results indicate that Twist1 is not essential for maintaining an overall healthy condition in young and adult mice and that loss of function facilitates hair growth in adulthood, supporting Twist1 as a preferential target for cancer therapy.

Mutual regulation between Raf/MEK/ERK signaling and Y-box-binding protein-1 promotes prostate cancer progression

PURPOSE

Y-box-binding protein-1 (YB-1) is known to conduct various functions related to cell proliferation, anti-apoptosis, epithelial-mesenchymal transition, and castration resistance in prostate cancer. However, it is still unknown how YB-1 affects cancer biology, especially its correlations with the mitogen-activated protein kinase (MAPK) signaling pathway. Therefore, we aimed to examine the interaction between YB-1 and the MAPK pathway in prostate cancer.

EXPERIMENTAL DESIGN

Quantitative real-time PCR, Western blotting, and co-immunoprecipitation assay were conducted in prostate cancer cells. YB-1, phosphorylated YB-1 (p-YB-1), and ERK2 protein expressions in 165 clinical specimens of prostate cancer were investigated by immunohistochemistry. YB-1, p-YB-1, and ERK2 nuclear expressions were compared with clinicopathologic characteristics and patient prognoses.

RESULTS

EGF upregulated p-YB-1, whereas MEK inhibitor (U0126, PD98059) decreased p-YB-1. Inversely, silencing of YB-1 using siRNA decreased the expression of ERK2 and phosphorylated MEK, ERK1/2, and RSK. Furthermore, YB-1 interacted with ERK2 and Raf-1 and regulated their expressions, through the proteasomal pathway. Immunohistochemical staining showed a significant correlation among the nuclear expressions of YB-1, p-YB-1, and ERK2. The Cox proportional hazards model revealed that high ERK2 expression was an independent prognostic factor [HR, 7.947; 95% confidence interval (CI), 3.527-20.508; P<0.0001].

CONCLUSION

We revealed the functional relationship between YB-1 and MAPK signaling and its biochemical relevance to the progression of prostate cancer. In addition, ERK2 expression was an independent prognostic factor. These findings suggest that both the ERK pathway and YB-1 may be promising molecular targets for prostate cancer diagnosis and therapeutics.

Sox2 suppresses the invasiveness of breast cancer cells via a mechanism that is dependent on Twist1 and the status of Sox2 transcription activity

Background

Sox2, an embryonic stem cell marker, is aberrantly expressed in a subset of breast cancer (BC). While the aberrant expression of Sox2 has been shown to significantly correlate with a number of clinicopathologic parameters in BC, its biological significance in BC is incompletely understood.

Methods

In-vitro invasion assay was used to evaluate whether the expression of Sox2 is linked to the invasiveness of MCF7 and ZR751 cells. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and/or Western blots were used to assess if Sox2 modulates the expression of factors known to regulate epithelial mesenchymal transition (EMT), such as Twist1. Chromatin immunoprecipitation (ChIP) was used to assess the binding of Sox2 to the promoter region of Twist1.

Results

We found that siRNA knockdown of Sox2 expression significantly increased the invasiveness of MCF7 and ZR751 cells. However, when MCF7 cells were separated into two distinct subsets based on their differential responsiveness to the Sox2 reporter, the Sox2-mediated effects on invasiveness was observed only in ‘reporter un-responsive’ cells (RU cells) but not ‘reporter responsive’ cells (RR cells). Correlating with these findings, siRNA knockdown of Sox2 in RU cells, but not RR cells, dramatically increased the expression of Twist1. Accordingly, using ChIP, we found evidence that Sox2 binds to the promoter region of Twist1 in RU cells only. Lastly, siRNA knockdown of Twist1 largely abrogated the regulatory effect of Sox2 on the invasiveness in RU cells, suggesting that the observed Sox2-mediated effects are Twist1-dependent.

Conclusion

Sox2 regulates the invasiveness of BC cells via a mechanism that is dependent on Twist1 and the transcriptional status of Sox2. Our results have further highlighted a new level of biological complexity and heterogeneity of BC cells that may carry significant clinical implications.

Functional Role of mTORC2 versus Integrin-Linked Kinase in Mediating Ser473-Akt Phosphorylation in PTEN-Negative Prostate and Breast Cancer Cell Lines

Although the rictor-mTOR complex (mTORC2) has been shown to act as phosphoinositide-dependent kinase (PDK)2 in many cell types, other kinases have also been implicated in mediating Ser473-Akt phosphorylation. Here, we demonstrated the cell line specificity of integrin-linked kinase (ILK) versus mTORC2 as PDK2 in LNCaP and PC-3 prostate and MDA-MB-468 breast cancer cells, of which the PTEN-negative status allowed the study of Ser473-Akt phosphorylation independent of external stimulation. PC-3 and MDA-MB-468 cells showed upregulated ILK expression relative to LNCaP cells, which expressed a high abundance of mTOR. Exposure to Ku-0063794, a second-generation mTOR inhibitor, decreased Ser473-Akt phosphorylation in LNCaP cells, but not in PC-3 or MDA-MB-468 cells. In contrast, treatment with T315, a novel ILK inhibitor, reduced the phosphorylation of Ser473-Akt in PC-3 and MDA-MB-468 cells without affecting that in LNCaP cells. This cell line specificity was verified by comparing Ser473-Akt phosphorylation status after genetic knockdown of rictor, ILK, and other putative Ser-473-Akt kinases. Genetic knockdown of rictor, but not ILK or the other kinases examined, inhibited Ser473-Akt phosphorylation in LNCaP cells. Conversely, PC-3 and MDA-MB-468 cells were susceptible to the effect of ILK silencing on Ser473-Akt phosphorylation, while knockdown of rictor or any of the other target kinases had no appreciable effect. Co-immunoprecipitation analysis demonstrated the physical interaction between ILK and Akt in PC-3 cells, and T315 blocked ILK-mediated Ser473 phosphorylation of bacterially expressed Akt. ILK also formed complexes with rictor in PC-3 and MDA-MB-468 cells that were disrupted by T315, but such complexes were not observed in LNCaP cells. In the PTEN-functional MDA-MB-231 cell line, both T315 and Ku-0063794 suppressed EGF-induced Ser473-Akt phosphorylation. Inhibition of ILK by T315 or siRNA-mediated knockdown suppressed epithelial-mesenchymal transition in MDA-MB-468 and PC-3 cells. Thus, we hypothesize that ILK might bestow growth advantage and metastatic potential in the course of tumor progression.

Small interfering RNA targeting ILK inhibits metastasis in human tongue cancer cells through repression of epithelial-to-mesenchymal transition

Integrin-linked kinase (ILK) is a multifunctional serine/threonine kinase. Accumulating evidences suggest that ILK are involved in cell-matrix interactions, cell proliferation, invasion, migration, angiogenesis and Epithelial-mesenchymal transition (EMT). However, the underlying mechanisms remain largely unknown. EMT has been postulated as a prerequisite for metastasis. The reports have demonstrated that EMT was implicated in metastasis of oral squamous cell carcinomas. Therefore, here we further postulate that ILK might participate in EMT of tongue cancer. We showed that ILK siRNA inhibited EMT with low N-cadherin, Vimentin, Snail, Slug and Twist as well as high E-cadherin expression in vivo and in vitro. We found that knockdown of ILK inhibited cell proliferation, migration and invasion as well as changed cell morphology. We also demonstrated that ILK siRNA inhibited phosphorylation of downstream signaling targets Akt and GSK3β as well as reduced expression of MMP2 and MMP9. Furthermore, we found that the tongue tumor with high metastasis capability showed higher ILK, Vimentin, Snail, Slug and Twist as well as lower E-cadherin expression in clinical specimens. Finally, ILK siRNA led to the suppression for tumorigenesis and metastasis in vivo. Our findings suggest that ILK could be a novel diagnostic and therapeutic target for tongue cancer.

YB-1: oncoprotein, prognostic marker and therapeutic target?

Hanahan and Weinberg have proposed the ‘hallmarks of cancer’ to cover the biological changes required for the development and persistence of tumours [Hanahan and Weinberg (2011) Cell 144, 646–674]. We have noted that many of these cancer hallmarks are facilitated by the multifunctional protein YB-1 (Y-box-binding protein 1). In the present review we evaluate the literature and show how YB-1 modulates/regulates cellular signalling pathways within each of these hallmarks. For example, we describe how YB-1 regulates multiple proliferation pathways, overrides cell-cycle check points, promotes replicative immortality and genomic instability, may regulate angiogenesis, has a role in invasion and metastasis, and promotes inflammation. We also argue that there is strong and sufficient evidence to suggest that YB-1 is an excellent molecular marker of cancer progression that could be used in the clinic, and that YB-1 could be a useful target for cancer therapy.

Y-box-binding protein 1 (YB-1) and its functions

This review describes the structure and functions of Y-box binding protein 1 (YB-1) and its homologs. Interactions of YB-1 with DNA, mRNAs, and proteins are considered. Data on the participation of YB-1 in DNA reparation and transcription, mRNA splicing and translation are systematized. Results on interactions of YB-1 with cytoskeleton components and its possible role in mRNA localization are discussed. Data on intracellular distribution of YB-1, its redistribution between the nucleus and the cytoplasm, and its secretion and extracellular functions are summarized. The effect of YB-1 on cell differentiation, its involvement in extra- and intracellular signaling pathways, and its role in early embryogenesis are described. The mechanisms of regulation of YB-1 expression in the cell are presented. Special attention is paid to the involvement of YB-1 in oncogenic cell transformation, multiple drug resistance, and dissemination of tumors. Both the oncogenic and antioncogenic activities of YB-1 are reviewed. The potential use of YB-1 in diagnostics and therapy as an early cancer marker and a molecular target is discussed.

Cold shock Y-box protein-1 participates in signaling circuits with auto-regulatory activities

The cold shock protein Y-box (YB) binding-1 is an example of a highly regulated protein with pleiotropic functions. Besides activities as a transcription factor in the nucleus or regulator of translation in the cytoplasm, recent findings indicate extracellular effects and secretion via a non-classical secretion pathway. This review summarizes regulatory pathways in which YB-1 participates, all iterating auto-regulatory loops. Schematics are developed that elucidate the cold shock protein activities in (i) fine-tuning its own expression level following platelet-derived growth factor-B-, thrombin- or interferon-γ-dependent signaling, (ii) as a component of the messenger ribonucleoprotein (mRNP) complex for interleukin-2 synthesis in T-cell commitment/activation, (iii) pro-fibrogenic cell phenotypic changes mediated by transforming growth factor-β, and (iv) receptor Notch-3 cleavage and signal transduction. Emphasis is put forward on subcellular protein translocation mechanisms and underlying signaling pathways. These have mostly been analysed in cell culture systems and rarely in experimental models. In sum, YB-1 seems to fulfill a pacemaker role in diverse diseases, both inflammatory/pro-fibrogenic as well as tumorigenic. A clue towards potential intervention strategies may reside in the understanding of the outlined auto-regulatory loops and means to interfere with cycling pathways.

Normal and disease-related biological functions of Twist1 and underlying molecular mechanisms

This article reviews the molecular structure, expression pattern, physiological function, pathological roles and molecular mechanisms of Twist1 in development, genetic disease and cancer. Twist1 is a basic helix-loop-helix domain-containing transcription factor. It forms homo- or hetero-dimers in order to bind the Nde1 E-box element and activate or repress its target genes. During development, Twist1 is essential for mesoderm specification and differentiation. Heterozygous loss-of-function mutations of the human Twist1 gene cause several diseases including the Saethre-Chotzen syndrome. The Twist1-null mouse embryos die with unclosed cranial neural tubes and defective head mesenchyme, somites and limb buds. Twist1 is expressed in breast, liver, prostate, gastric and other types of cancers, and its expression is usually associated with invasive and metastatic cancer phenotypes. In cancer cells, Twist1 is upregulated by multiple factors including SRC-1, STAT3, MSX2, HIF-1α, integrin-linked kinase and NF-κB. Twist1 significantly enhances epithelial-mesenchymal transition (EMT) and cancer cell migration and invasion, hence promoting cancer metastasis. Twist1 promotes EMT in part by directly repressing E-cadherin expression by recruiting the nucleosome remodeling and deacetylase complex for gene repression and by upregulating Bmi1, AKT2, YB-1, etc. Emerging evidence also suggests that Twist1 plays a role in expansion and chemotherapeutic resistance of cancer stem cells. Further understanding of the mechanisms by which Twist1 promotes metastasis and identification of Twist1 functional modulators may hold promise for developing new strategies to inhibit EMT and cancer metastasis.

Identification and characterization of a novel integrin-linked kinase inhibitor

Integrin-linked kinase (ILK) represents a relevant target for cancer therapy in light of its role in promoting oncogenesis and tumor progression. Through the screening of an in-house focused compound library, we identified N-methyl-3-(1-(4-(piperazin-1-yl)phenyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-3-yl)propanamide (22) as a novel ILK inhibitor (IC(50), 0.6 μM), which exhibited high in vitro potency against a panel of prostate and breast cancer cell lines (IC(50), 1-2.5 μM), while normal epithelial cells were unaffected. Compound 22 facilitated the dephosphorylation of Akt at Ser-473 and other ILK targets, including glycogen synthase kinase-3β and myosin light chain. Moreover, 22 suppressed the expression of the transcription/translation factor YB-1 and its targets HER2 and EGFR in PC-3 cells, which could be rescued by the stable expression of constitutively active ILK. Evidence indicates that 22 induced autophagy and apoptosis, both of which were integral to its antiproliferative activity. Together, this broad spectrum of mechanisms underlies the therapeutic potential of 22 in cancer treatment, which is manifested by its in vivo efficacy as a single oral agent in suppressing PC-3 xenograft tumor growth.

Y-box binding protein-1 promotes castration-resistant prostate cancer growth via androgen receptor expression

The androgen receptor (AR) is well known to play a central role in the pathogenesis of prostate cancer (PCa). In several studies, AR was overexpressed in castration-resistant PCa (CRPC). However, the mechanism of AR overexpression in CRPC is not fully elucidated. Y-box binding protein-1 (YB-1) is a pleiotropic transcription factor that is upregulated in CPRC. We aimed to elucidate the role of YB-1 in castration resistance of PCa and identify therapeutic potential of targeting YB-1. Using immunohistochemistry, we found that nuclear YB-1 expression significantly correlated with the Gleason score and AR expression in PCa tissues. In PCa cells, YB-1 regulated AR expression at the transcriptional level. Furthermore, YB-1 expression and nuclear localization were upregulated in CRPC cells. Overexpression of AR, as well as YB-1, conferred castration-resistant growth in LNCaP and 22Rv1 cells. Conversely, knocking down YB-1 resulted in suppressed cell growth and induced apoptosis, which was more efficient than knocking down AR in LNCaP cells. In other types of PCa cells, such as CRPC cells, knocking down YB-1 resulted in a significant reduction of cell growth. In conclusion, these findings suggested that YB-1 induces castration resistance in androgen-dependent PCa cells via AR expression. Thus, YB-1 may be a promising therapeutic target for PCa, as well as CRPC.

Small interfering RNA targeting integrin-linked kinase inhibited the growth and induced apoptosis in human bladder cancer cells

Integrin-linked kinase (ILK), an intracellular serine/threonine kinase, is implicated in cell growth and survival, cell-cycle progression, tumor angiogenesis, and cell apoptosis. Recent studies showed that the expression and activity of ILK increased significantly in many types of solid tumors. However, the exact molecular mechanism of ILK underlie tumor has not been fully ascertained. The purpose of our study was to determine whether knockdown of ILK would inhibit cell growth and induce apoptosis in bladder cancer cells using a plasmid vector based small interfering RNA (siRNA). The experiments showed that knockdown of ILK could remarkably inhibit cell proliferation and growth, regulate cell cycle and induce apoptosis of bladder cancer BIU-87 and EJ cells. We demonstrated that knockdown of ILK inhibited phosphorylation of downstream signaling targets protein kinase B/Akt, glycogen synthase kinase 3-beta (GSK-3β), and reduced expression of β-catenin in BIU-87 as well as EJ cells by Western blot and Immunofluorescence analysis. In addition, down-regulation of ILK also could increase expression of Ribonuclease inhibitor (RI), an important acidic cytoplasmic protein with many functions. BALB/C nude mice injected with the BIU-87 cells transfected ILK siRNA showed a significant inhibition of the tumor growth with lighter tumor weight, lower microvessels density and higher apoptosis rate than those in the other two control groups. In conclusion, these results suggest that ILK might be involved in the development of bladder cancer, and could be served as a novel potential therapy target for human bladder cancer. Our study may be of biological and clinical importance.

Impact of oncogenic K-RAS on YB-1 phosphorylation induced by ionizing radiation

Introduction

Expression of Y-box binding protein-1 (YB-1) is associated with tumor progression and drug resistance. Phosphorylation of YB-1 at serine residue 102 (S102) in response to growth factors is required for its transcriptional activity and is thought to be regulated by cytoplasmic signaling phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathways. These pathways can be activated by growth factors and by exposure to ionizing radiation (IR). So far, however, no studies have been conducted on IR-induced YB-1 phosphorylation.

Methods

IR-induced YB-1 phosphorylation in K-RAS wild-type (K-RAS_wt) and K-RAS-mutated (K-RAS_mt) breast cancer cell lines was investigated. Using pharmacological inhibitors, small interfering RNA (siRNA) and plasmid-based overexpression approaches, we analyzed pathways involved in YB-1 phosphorylation by IR. Using γ-H2AX foci and standard colony formation assays, we investigated the function of YB-1 in repair of IR-induced DNA double-stranded breaks (DNA-DSB) and postirradiation survival was investigated.

Results

The average level of phosphorylation of YB-1 in the breast cancer cell lines SKBr3, MCF-7, HBL100 and MDA-MB-231 was significantly higher than that in normal cells. Exposure to IR and stimulation with erbB1 ligands resulted in phosphorylation of YB-1 in K-RAS_wt SKBr3, MCF-7 and HBL100 cells, which was shown to be K-Ras-independent. In contrast, lack of YB-1 phosphorylation after stimulation with either IR or erbB1 ligands was observed in K-RAS_mt MDA-MB-231 cells. Similarly to MDA-MB-231 cells, YB-1 became constitutively phosphorylated in K-RAS_wt cells following the overexpression of mutated K-RAS, and its phosphorylation was not further enhanced by IR. Phosphorylation of YB-1 as a result of irradiation or K-RAS mutation was dependent on erbB1 and its downstream pathways, PI3K and MAPK/ERK. In K-RAS_mt cells K-RAS siRNA as well as YB-1 siRNA blocked repair of DNA-DSB. Likewise, YB-1 siRNA increased radiation sensitivity.

Conclusions

IR induces YB-1 phosphorylation. YB-1 phosphorylation induced by oncogenic K-Ras or IR enhances repair of DNA-DSB and postirradiation survival via erbB1 downstream PI3K/Akt and MAPK/ERK signaling pathways.