miR-145-5p Targets Sp1 in Non-Small Cell Lung Cancer Cells and Links to BMI1 Induced Pemetrexed Resistance and Epithelial-Mesenchymal Transition.

Pemetrexed is a folic acid inhibitor used as a second-line chemotherapeutic agent for the treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC), which accounts for 85% of lung cancers. However, prolonged treatment with pemetrexed may cause cancer cells to develop resistance. In this study, we found increased expressions of BMI1 (B Lymphoma Mo-MLV insertion region 1 homolog) and Sp1 and a decreased expression of miR-145-5p was found in pemetrexed-resistant A400 cells than in A549 cells. Direct Sp1 targeting activity of miR-145-5p was demonstrated by a luciferase based Sp1 3'-UTR reporter. Changed expression of miR-145-5p in A400 or A549 cells by transfection of miR-145-5p mimic or inhibitor affected the sensitivity of the cells to pemetrexed. On the other hand, the overexpression of Sp1 in A549 cells caused the decreased sensitivity to pemetrexed, induced cell migratory capability, and epithelial-mesenchymal transition (EMT) related transcription factors such as Snail Family Transcriptional Repressor 1 and Zinc Finger E-Box Binding Homeobox 1. In addition, the overexpression of BMI1 in the A549 cells resulted in an increase in Sp1 and a decrease in miR-145-5p accompanied by the elevations of cell proliferation and EMT transcription factors, which could be reduced by the overexpression of miR-145-5p or by treatment with the Sp1 inhibitor of mithramycin A. In conclusion, the results of this study suggest that the downregulation of miR-145-5p by BMI1 overexpression could lead to the enhanced expression of Sp1 to induce the EMT process in pemetrexed-resistant NSCLC cells. These results suggest that increasing miR-145-5p expression by delivering RNA drugs may serve as a sensitizing agent for pemetrexed-resistant NSCLC patients.

Disulfiram/Copper Suppresses Cancer Stem Cell Activity in Differentiated Thyroid Cancer Cells by Inhibiting BMI1 Expression.

Differentiated thyroid carcinomas (DTCs), which have papillary and follicular types, are common endocrine malignancies worldwide. Cancer stem cells (CSCs) are a particular type of cancer cells within bulk tumors involved in cancer initiation, drug resistance, and metastasis. Cells with high intracellular aldehyde hydrogenase (ALDH) activity are a population of CSCs in DTCs. Disulfiram (DSF), an ALDH inhibitor used for the treatment of alcoholism, reportedly targets CSCs in various cancers when combined with copper. This study reported for the first time that DSF/copper can inhibit the proliferation of papillary and follicular DTC lines. DSF/copper suppressed thyrosphere formation, indicating the inhibition of CSC activity. Molecular mechanisms of DSF/copper involved downregulating the expression of B lymphoma Mo-MLV insertion region 1 homolog (BMI1) and cell cycle-related proteins, including cyclin B2, cyclin-dependent kinase (CDK) 2, and CDK4, in a dose-dependent manner. BMI1 overexpression diminished the inhibitory effect of DSF/copper in the thyrosphere formation of DTC cells. BMI1 knockdown by RNA interference in DTC cells also suppressed the self-renewal capability. DSF/copper could inhibit the nuclear localization and transcriptional activity of c-Myc and the binding of E2F1 to the BMI1 promoter. Overexpression of c-Myc or E2F1 further abolished the inhibitory effect of DSF/copper on BMI1 expression, suggesting that the suppression of c-Myc and E2F1 by DSF/copper was involved in the downregulation of BMI1 expression. In conclusion, DSF/copper targets CSCs in DTCs by inhibiting c-Myc- or E2F1-mediated BMI1 expression. Therefore, DSF is a potential therapeutic agent for future therapy in DTCs.

L-Type Amino Acid Transporter 1 Regulates Cancer Stemness and the Expression of Programmed Cell Death 1 Ligand 1 in Lung Cancer Cells.

The l-type amino acid transporter 1 (LAT1) is a membranous transporter that transports neutral amino acids for cells and is dysregulated in various types of cancer. Here, we first observed increased LAT1 expression in pemetrexed-resistant non-small cell lung cancer (NSCLC) cells with high cancer stem cell (CSC) activity, and its mRNA expression level was associated with shorter overall survival in the lung adenocarcinoma dataset of the Cancer Genome Atlas database. The inhibition of LAT1 by a small molecule inhibitor, JPH203, or by RNA interference led to a significant reduction in tumorsphere formation and the downregulation of several cancer stemness genes in NSCLC cells through decreased AKT serine/threonine kinase (AKT)/mammalian target of rapamycin (mTOR) activation. The treatment of the cell-permeable leucine derivative promoted AKT/mTOR phosphorylation and reversed the inhibitory effect of JPH203 in the reduction of CSC activity in pemetrexed-resistant lung cancer cells. Furthermore, we observed that LAT1 silencing caused the downregulation of programmed cell death 1 ligand 1 (PD-L1) on lung cancer cells. The PD-L1+/LAT1+ subpopulation of NSCLC cells displayed great CSC activity with increased expression of several cancer stemness genes. These data suggest that LAT1 inhibitors can serve as anti-CSC agents and could be used in combination with immune checkpoint inhibitors in lung cancer therapy.

NAD(P)H:quinone oxidoreductase 1 determines radiosensitivity of triple negative breast cancer cells and is controlled by long non-coding RNA NEAT1.

Radioresistant cells cause recurrence in patients with breast cancer after they undergo radiation therapy. The molecular mechanisms by which cancer cells obtain radioresistance should be understood to develop radiation-sensitizing agents. Results showed that the protein expression and activity of NAD(P)H:quinone oxidoreductase 1 (NQO1) were upregulated in radioresistant MDA-MB-231 triple-negative breast cancer (TNBC) cells. NQO1 knockdown inhibited the proliferation of NQO1 expressing Hs578t TNBC cells or the radioresistant MDA-MB-231 cells, whereas NOQ1 overexpression increased the survival of MDA-MB-231 cells, which lack of NQO1 expression originally, under irradiation. The cytotoxicity of ß-lapachone, an NQO1-dependent bioactivatable compound, was greater in radioresistant MDA-MB-231 cells than in parental cells. ß-lapachone displayed a radiosensitization effect on Hs578t or radioresistant MBDA-MB-231 cells. The expression of the long noncoding RNA NEAT1 positively regulated the NQO1 expression in radioresistant MDA-MB-231 cells at a translational level rather than at a transcription level. The inhibition of the NEAT1 expression through the CRISPR-Cas9 method increased the sensitivity of radioresistant MDA-MB-231 cells to radiation and decreased their proliferation, the activity of cancer stem cells, and the expression of stemness genes, including BMI1, Oct4, and Sox2. In conclusion, the NQO1 expression in triple-negative breast cancer cells determined their radiosensitivity and was controlled by NEAT1. In addition, NOQ1 bioactivatable compounds displayed potential for application in the development of radiation sensitizers in breast cancer.

Effects and mechanisms of betulinic acid on improving EGFR TKI-resistance of lung cancer cells.

Epidermal growth factor receptor (EGFR) mutations have been identified in approximately 55% of lung cancer patients in Taiwan. Gefitinib (Iressa) and Erlotinib (Tarceva) are the first-generation targeting drugs to patients with EGFR gene mutants a work by inhibiting tyrosine kinase activity. However, resistance in EGFR-mutated patients to first-generation tyrosine kinase inhibitor (TKI) therapy after 8-11 months of treatment has occurred. Betulinic acid (BetA) is a pentacyclic triterpenoid natural product derived from widespread plants. BetA has been reported to have a cytotoxic effect in several cancers. The purpose of this study is to investigate the effects and mechanisms of BetA on dampening EGFR TKI-resistance of lung cancer cells. Our study has demonstrated by MTT assay that combining BetA and an EGFR TKI increased the cytotoxicity against EGFR TKI-resistance lung cancer cells. Based on flow cytometry, combination treatments of BetA with an EGFR TKI enhanced Sub-G1 accumulation, induced apoptosis and induced mitochondrial membrane potential loss. Using western blotting, BetA and EGFR TKI combined treatments inhibited cell cycle related protein and triggered apoptosis- and autophagy- related protein expression. Taken together, our data suggests that a target therapy combining BetA with an EGFR TKI improves drug efficacy in EGFR TKI-resistant lung cancer cells.

Chidamide alleviates TGF-ß-induced epithelial-mesenchymal transition in lung cancer cell lines.

Transforming growth factor-ß (TGF-ß)-induced epithelial-mesenchymal transition is a critical process in the initiation of metastasis of various types of cancer. Chidamide is a class I histone deacetylase inhibitor with anti-tumor activity. This study investigated the effects of chidamide on TGF-ß-mediated suppression of E-cadherin expression in adenocarcinomic lung epithelial cells and the molecular mechanisms involved in these effects. Western blot analysis, confocal microscopy, Quantitative methyl-specific PCR and bisulfite sequencing were used to evaluate the effects of different treatments on chidamide ameliorating TGF-ß induced-E-cadherin loss. H3 acetylation binding to the promoter of E-cadherin was detected by chromatin immunoprecipitations (CHIP). We found that chidamide reduced the level of lung cancer cell migration observed using a Boyden chamber assay (as an indicator of metastatic potential). Chidamide inhibited TGF-ß-induced SMAD2 phosphorylation and attenuated TGF-ß-induced loss of E-cadherin expression in lung cancer cells by Western blotting and confocal microscopy, respectively. Quantitative methyl-specific PCR and bisulfite sequencing revealed that TGF-ß-enhanced E-cadherin promoter methylation was ameliorated in cells treated with chidamide. We demonstrated that histone H3 deacetylation within the E-cadherin promoter was required for TGF-ß-induced E-cadherin loss; cell treatment with chidamide increased the H3 acetylation detected by CHIP. Taken together, our results demonstrate that TGF-ß suppressed E-cadherin expression by regulating promoter methylation and histone H3 acetylation. Chidamide significantly enhanced E-cadherin expression in TGF-ß-treated cells and inhibited lung cancer cell migration. These findings indicate that chidamide has a potential therapeutic use due to its capacity to prevent cancer cell metastasis.

Inhibition of Na+/H+ exchanger (NHE) 7 by 5-(N-ethyl-N-isopropyl)-Amiloride displays anti-cancer activity in non-small cell lung cancer by disrupting cancer stem cell activity and downregulating PD-L1 expression.

The alkaline intracellular environment of cancer cells is critical for cell proliferation and controlled by various plasma membrane transporters including Na+/H+ exchangers (NHEs). NHEs can also mediate cell behavior by regulating signaling transduction. In this study, we investigated the role of NHE7 in cancer stem cell (CSC) activity in non-small cell lung cancer (NSCLC) cells and the potential therapeutic implications of targeting NHE7 and the associated immune checkpoint molecule PD-L1. By analyzing the database from The Cancer Genome Atlas, we found a positive correlation between SLC9A7 mRNA levels (the gene encoding NHE7) and poor overall survival in lung adenocarcinoma patients. Using 5-(N-ethyl-N-isopropyl)-Amiloride (EIPA) to inhibit NHE7 activity, we observed disrupted cell cycle progression and suppressed NSCLC cell proliferation without inducing apoptosis. Furthermore, EIPA demonstrated a suppressive effect on CSC activity, evidenced by decreased tumorsphere numbers and inhibition of CSC markers such as ALDH1A2, ABCG2, CD44, and CD133. Flow cytometric analysis revealed that EIPA treatment or NHE7 knockdown in NSCLC cells led to downregulated PD-L1 expression, associated with inhibited STAT3 activity. Interestingly, EIPA's CSC-targeting activity was preferentially observed in NSCLC cells overexpressing BMI1, while increased PD-L1 expression was detected in BMI1-overexpressing NSCLC cells. Our findings suggest that targeting NHE7 with inhibitors like EIPA may have therapeutic potential in NSCLC treatment by disrupting cell cycle progression and suppressing CSC activity. The observed increase in PD-L1 expression in BMI1-overexpressing NSCLC cells upon EIPA treatment highlights the potential benefit of combining NHE7 inhibitors with anti-PD-L1 agents as a promising new therapeutic strategy for NSCLC.

Salmonella inhibits tumor metastasis by downregulating epithelial cell adhesion molecules through the protein kinase-B/mammalian target of rapamycin signaling pathway.

Epithelial cell adhesion molecules (EpCAM) are highly expressed in many carcinomas and regulate the epithelial-mesenchymal transition, which is required for tumor metastasis. Furthermore, EpCAM overexpression induces tumor cells to develop a stem cell-like phenotype and promotes tumor progression. Targeting EpCAM may be a promising approach for inhibiting tumor metastasis and progression. Salmonella treatment suppresses tumor growth and reduces metastatic nodules in tumor-bearing mice. Based on these results, we hypothesized that Salmonella-based treatments could inhibit the expression of metastasis-associated proteins. The dose-dependent Salmonella treatment significantly downregulated the levels of EpCAM and decreased the phosphorylation of protein kinase-B (AKT)/mTOR (mammalian target of rapamycin) pathway, as shown by immunoblotting. In addition, Salmonella treatment increased the levels of epithelial markers and decreased the levels of mesenchymal markers in a dose-dependent manner. Wound-healing and Transwell assays showed that Salmonella treatment significantly reduced tumor cell migration. The mice were intravenously injected with B16F10 and CT26 cells pre-incubated with or without Salmonella, and the survival of tumor-bearing mice in the Salmonella group increased, indicating an antimetastatic effect. Our findings demonstrate that Salmonella plays a role in inhibiting tumor metastasis by downregulating EpCAM via the AKT/mTOR signaling pathway and has great potential for cancer therapy.

Heat-Killed Lactobacilli Preparations Promote Healing in the Experimental Cutaneous Wounds.

Probiotics are defined as microorganisms with beneficial health effects when consumed by humans, being applied mainly to improve allergic or intestinal diseases. Due to the increasing resistance of pathogens to antibiotics, the abuse of antibiotics becomes inefficient in the skin and in systemic infections, and probiotics may also provide the protective effect for repairing the healing of infected cutaneous wounds. Here we selected two Lactobacillus strains, L. plantarum GMNL-6 and L. paracasei GMNL-653, in heat-killed format to examine the beneficial effect in skin wound repair through the selection by promoting collagen synthesis in Hs68 fibroblast cells. The coverage of gels containing heat-killed GMNL-6 or GMNL-653 on the mouse tail with experimental wounds displayed healing promoting effects with promoting of metalloproteinase-1 expression at the early phase and reduced excessive fibrosis accumulation and deposition in the later tail-skin recovery stage. More importantly, lipoteichoic acid, the major component of Lactobacillus cell wall, from GMNL-6/GMNL-653 could achieve the anti-fibrogenic benefit similar to the heat-killed bacteria cells in the TGF-ß stimulated Hs68 fibroblast cell model. Our study offers a new therapeutic potential of the heat-killed format of Lactobacillus as an alternative approach to treating skin healing disorders.

BMI1-Mediated Pemetrexed Resistance in Non-Small Cell Lung Cancer Cells Is Associated with Increased SP1 Activation and Cancer Stemness.

Lung cancer is the leading cause of cancer death worldwide and the therapeutic strategies include surgery, chemotherapy and radiation therapy. Non-small cell lung cancers (NSCLCs) account for around 85% of cases of lung cancers. Pemetrexed is an antifolate agent that is currently used as the second line chemotherapy drug in the treatment of advanced NSCLC patients with a response rate of 20-40%. The search for any combination therapy to improve the efficacy of pemetrexed is required. The existence of cancer stem cells (CSCs) is considered as the main reason for drug resistance of cancers. In this study, we first found that pemetrexed-resistant NSCLC cells derived from A549 cells displayed higher CSC activity in comparison to the parental cells. The expression of CSC related proteins, such as BMI1 or CD44, and the epithelial-mesenchymal transition (EMT) signature was elevated in pemetrexed-resistant NSCLC cells. We next discovered that the overexpression of BMI1 in A549 cells caused the pemetrexed resistance and inhibition of BMI1 by a small molecule inhibitor, PTC-209, or transducing of BMI1-specific shRNAs suppressed cell growth and the expression of thymidylate synthase (TS) in pemetrexed-resistant A549 cells. We further identified that BMI1 positively regulated SP1 expression and treatment of mithramycin A, a SP1 inhibitor, inhibited cell proliferation, as well as TS expression, of pemetrexed-resistant A549 cells. Furthermore, overexpression of BMI1 in A549 cells also caused the activation of EMT in and the enhancement of CSC activity. Finally, we demonstrated that pretreatment of PTC-209 in mice bearing pemetrexed-resistant A549 tumors sensitized them to pemetrexed treatment and the expression of Ki-67, BMI1, and SP1 expression in tumor tissues was observed to be reduced. In conclusion, BMI1 expression level mediates pemetrexed sensitivity of NSCLC cells and the inhibition of BMI1 will be an effective strategy in NSCLC patients when pemetrexed resistance has developed.

Tribbles Pseudokinase 3 Contributes to Cancer Stemness of Endometrial Cancer Cells by Regulating ß-Catenin Expression.

Endometrial cancer (EC) is the second most common gynecological malignancy worldwide. Tribbles pseudokinase 3 (TRIB3) is a scaffolding protein that regulates intracellular signal transduction, and its role in tumor development is controversial. Here, we investigated the biological function of TRIB3 in EC. We found that the messenger RNA (mRNA) expression level of TRIB3 was significantly and positively correlated with shorter overall survival of EC patients in The Cancer Genome Atlas database. The protein expression of TRIB3 was found to be significantly increased in EC cancer stem cells (CSCs) enriched by tumorsphere cultivation. Knockdown of TRIB3 in EC cells suppressed tumorsphere formation, the expression of cancer stemness genes, and the in vivo tumorigenesis. The expression of ß-catenin at both the protein and the mRNA levels was downregulated upon TRIB3 silencing. TRIB3 was found to interact with E74 Like ETS transcription factor 4 (ELF4) in the nucleus and bound to ELF4 consensus sites within the catenin beta 1 (CTNNB1) promoter in EC cell lines. These data indicated that TRIB3 may regulate CTNNB1 transcription by enhancing the recruitment of ELF4 to the CTNNB1 promoter. In conclusion, our results suggest that TRIB3 plays an oncogenic role in EC and positively regulates the self-renewal and tumorigenicity of EC-CSCs. Targeting TRIB3 is considered as a potential therapeutic strategy in future EC therapy.

Reciprocal Regulation Between Indoleamine 2,3-Dioxigenase 1 and Notch1 Involved in Radiation Response of Cervical Cancer Stem Cells.

Cervical cancer is the fourth most common cancer in women around the world. Cancer stem cells (CSCs) are responsible for cancer initiation, as well as resistance to radiation therapy, and are considered as the effective target of cancer therapy. Indoleamine 2,3-dioxygenase 1 (IDO1) mediates tryptophan metabolism and T cell suppression, but the immune-independent function of IDO1 in cancer behavior is not fully understood. Using tumorsphere cultivation for enriched CSCs, we firstly found that IDO1 was increased in HeLa and SiHa cervical cancer cells and in these two cell lines after radiation treatment. The radiosensitivity of HeLa and SiHa tumorsphere cells was increased after the inhibition of IDO1 through RNA interference or by the treatment of INCB-024360, an IDO1 inhibitor. With the treatment of kynurenine, the first breakdown product of the IDO1-mediated tryptophan metabolism, the radiosensitivity of HeLa and SiHa cells decreased. The inhibition of Notch1 by shRNA downregulated IDO1 expression in cervical CSCs and the binding of the intracellular domain of Notch (NICD) on the IDO1 promoter was reduced by Ro-4929097, a γ-secretase inhibitor. Moreover, the knockdown of IDO1 also decreased NICD expression in cervical CSCs, which was correlated with the reduced binding of aryl hydrocarbon receptor nuclear translocator to Notch1 promoter. In vivo treatment of INCB-0234360 sensitized SiHa xenograft tumors to radiation treatment in nude mice through increased DNA damage. Furthermore, kynurenine increased the tumorsphere formation capability and the expression of cancer stemness genes including Oct4 and Sox2. Our data provide a reciprocal regulation mechanism between IDO1 and Notch1 expression in cervical cancer cells and suggest that the IDO1 inhibitors may potentially be used as radiosensitizers.

Chidamide-induced ROS accumulation and miR-129-3p-dependent cell cycle arrest in non-small lung cancer cells.

BACKGROUND: Epigenetic therapy is a promising popular treatment modality for various cancers. Histone modification and miRNA should not be underestimated in lung cancer. This study aimed to investigate whether chidamide, a histone deacetylase inhibitor (HDACi), which inhibits telomerase activity and induces cell cycle arrest, influences ROS and miRNA production in non-small cell lung cancer (NSCLC) cells. METHODS: H1355 and A549 were treated with chidamide. The analysis of DNA content was measured by FACSCalibur equipped with a 488 nm laser. H1355 cells were transfected with miR-129-3p mimic by Lipofectamine2000. Telomerase activity was performed on the telomeric repeat amplification protocol (TRAP) assay. Detection of thymidylate synthase (TS), p21, p53, pRB, and ß-actin, were performed by western blot analysis. RESULTS: Our data showed that expression of TS, p21, and pRB were altered in the presence of chidamide by PCR and western blot. Using BrdU-incorporation analysis, we found that chidamide induced G1 arrest through the regulation of the TS gene by miR-129-3p. Chidamide was shown to suppress telomerase activity in the TRAP assay and reduced the expression of human telomerase reverse transcriptase (hTERT) by PCR and q-PCR in H1355 and A549 cells. Chidamide increased the generation of reactive oxygen species (ROS) by flow cytometry. N-acetyl cysteine (NAC), a ROS scavenger, attenuated chidamide-induced telomerase activity inhibition. CONCLUSION: Chidamide repressed telomerase activity through ROS accumulation and cell cycle arrest by miR-129-3p upregulation in both H1355 and A549 cells. This is the first study to demonstrate that chidamide induces miR-129-3p upregulation and ROS accumulation, leading to cell cycle arrest.

Hinokitiol up-regulates miR-494-3p to suppress BMI1 expression and inhibits self-renewal of breast cancer stem/progenitor cells.

Hinokitiol (ß-thujaplicin) is a tropolone-related compound that has anti-microbe, anti-inflammation, and anti-tumor effects. Cancer stem/progenitor cells (CSCs) are a subpopulation of cancer cells with tumor initiation, chemoresistant, and metastatic properties and have been considered the important therapeutic target in future cancer therapy. Previous studies reported that hinokitiol exhibits an anti-cancer activity against murine tumor cells through the induction of autophagy. The current research revealed that hinokitiol suppressed the self-renewal capabilities of human breast CSCs (BCSCs) and inhibited the expression of BMI1 at protein level without suppressing its mRNA. Treatment of hinokitiol in mammospheres induced the expression of miR-494-3p and inhibition of miR-494-3p expression in BCSCs. This treatment abolished the suppressive effects of hinokitiol in mammosphere formation and BMI1 expression. BMI1 is a target of miR-494-3p by luciferase-based 3'UTR reporter assay. Overexpression of miR-494-3p in BCSCs caused the down-regulation of BMI1 protein, inhibition of mammosphere forming capability, and suppression of their tumorigenicity. Moreover, miR-494-3p expression was significantly and inversely correlated with patient survival in two independent public database sets. Furthermore, treatment of hinokitiol in vivo suppressed the growth of xenograft human breast tumors as well as the expression of BMI1 and ALDH1A1 in xenograft tumors. In conclusion, these data suggest that hinokitiol targets BCSCs through the miR-494-3p-mediated down-modulation of BMI1 expression.

Nuclear ErbB2 enhances translation and cell growth by activating transcription of ribosomal RNA genes.

Aberrant regulation of rRNA synthesis and translation control can facilitate tumorigenesis. The ErbB2 growth factor receptor is overexpressed in many human tumors and has been detected in the nucleus, but the role of nuclear ErbB2 is obscure. In this study, we defined a novel function of nuclear ErbB2 in enhancing rRNA gene transcription by RNA polymerase-I (RNA Pol I). Nuclear ErbB2 physically associates with ß-actin and RNA Pol I, coinciding with active RNA Pol I transcription sites in nucleoli. RNA interference-mediated knockdown of ErbB2 reduced pre-rRNA and protein synthesis. In contrast, wild-type ErbB2 augmented pre-rRNA level, protein production, and cell size/cell growth, but not by an ErbB2 mutant that is defective in nuclear translocation. Chromatin immunoprecipitation assays revealed that ErbB2 enhances binding of RNA Pol I to rDNA. In addition, ErbB2 associated with rDNA, RNA Pol I, and ß-actin, suggesting how it could stimulate rRNA production, protein synthesis, and increased cell size and cell growth. Finally, ErbB2-potentiated RNA Pol I transcription could be stimulated by ligand and was not substantially repressed by inhibition of PI3-K and MEK/ERK (extracellular signal regulated kinase), the main ErbB2 effector signaling pathways. Together, our findings indicate that nuclear ErbB2 functions as a regulator of rRNA synthesis and cellular translation, which may contribute to tumor development and progression.