Tunicamycin inhibits cell proliferation and migration in hepatocellular carcinoma through suppression of CD44s and the ERK1/2 pathway

Effect of Tunicamycin on Viability, Motility, Reactive Oxygen Species, Nitric Oxide, and Lipid Peroxidation in Boar Sperm

Tunicamycin induces endoplasmic reticulum stress in mammalian cells. Our study aimed to investigate the effect of tunicamycin on the motility and viability of sperm, reactive oxygen species, nitric oxide, and lipid peroxidation in boar sperm. We treated 1.0, 2.0, 5.0, and 10 μM of tunicamycin in boar semen, and experimental treatments were performed. The viability (55.44%, 53.20, and 40.00%, p < 0.05) and motility (73.28%, 71.48%, and 54.48%, p < 0.05) of sperm at 2.0, 5.0, and 10.0 μM were decreased by tunicamycin, and the levels of reactive oxygen species and lipid peroxidation in tunicamycin-treated boar semen were increased (p < 0.05). However, the nitric oxide level was not changed by tunicamycin. Based on the results, we indicated that tunicamycin induces cell death by increasing oxidative stress in boar sperm, which may be the cause of decreased sperm viability and motility. Thus, we suggest that tunicamycin may induce cell death due to oxidative stress by reactive oxygen species and lipid peroxidation.

Combination of brefeldin A and tunicamycin induces apoptosis in HepG2 cells through the endoplasmic reticulum stress-activated PERK-eIF2α-ATF4-CHOP signaling pathway

Background and aims

Hepatocellular carcinoma (HCC) is a malignant tumor with a high mortality rate, but there are still no effective treatments. The aim of this study was to investigate the anticancer potential of the combined use of brefeldin A (BFA) and tunicamycin (TM) in HepG2 cells, as well as the underlying mechanisms.

Methods

HepG2 cells were treated with different concentrations of BFA (0.1-2.5 mg/L) and TM (1-5 mg/L) for 24 h. DMSO (0.1 %, v/v) was used as a vehicle control. Cell viability and cell migration were measured using MTT assay and scratch wound assay, respectively. Apoptosis was detected using flow cytometry and acridine orange (AO) staining. The protein and mRNA levels of various factors involved in apoptosis (poly (ADP-ribose) polymerase-1 (PARP-1), caspase-12, caspase-3, and stearoyl-CoA desaturase 1) and endoplasmic reticulum (ER) stress (binding immunoglobulin protein (BiP), protein kinase R-like endoplasmic reticulum kinase (PERK), p-PERK, phosphorylation of eukaryotic translation initiation factor 2alpha (p-eIF2α), activating transcription factor (ATF) 4, and C/EBP homologous protein (CHOP)) were measured using Western blotting and qRT-PCR, respectively.

Results

Both BFA and TM alone significantly reduced the viability of HepG2 cells in a dose-dependent way. The co-incubation with TM (1 mg/L) further significantly reduced the viability of HepG2 cells treated with BFA (0.25 mg/L) alone (P < 0.05). BFA significantly increased the protein and mRNA levels of caspase-3 and PARP-1 (P < 0.05) compared to control and DMSO-treated cells, indicating that BFA induced apoptosis in HepG2 cells by increasing the expression of caspase-3 and PARP-1. The induction of apoptosis by BFA could be further significantly enhanced by co-incubation with TM. In addition, BFA significantly increased the mRNA levels of BiP, PERK and ATF4 (P < 0.05) compared to control and DMSO-treated cells. After co-incubation of BFA and TM, the protein levels of BiP, p-PERK, p-eIF2α and CHOP were significantly increased, indicating that TM could enhance BFA-induced ER stress in HepG2 cells through the PERK-eIF2α-ATF4-CHOP pathway.

Conclusions

BFA could induce apoptosis and ER stress, and TM could enhance the ability of BFA to induce apoptosis and ER stress in HepG2 cells through the PERK-eIF2ɑ-ATF4-CHOP pathway. The findings highlight the therapeutic potential of the combined use of BFA and TM in treating HCC.

Cell surface CD55 traffics to the nucleus leading to cisplatin resistance and stemness by inducing PRC2 and H3K27 trimethylation on chromatin in ovarian cancer

BACKGROUND

Platinum resistance is the primary cause of poor survival in ovarian cancer (OC) patients. Targeted therapies and biomarkers of chemoresistance are critical for the treatment of OC patients. Our previous studies identified cell surface CD55, a member of the complement regulatory proteins, drives chemoresistance and maintenance of cancer stem cells (CSCs). CSCs are implicated in tumor recurrence and metastasis in multiple cancers.

METHODS

Protein localization assays including immunofluorescence and subcellular fractionation were used to identify CD55 at the cell surface and nucleus of cancer cells. Protein half-life determinations were used to compare cell surface and nuclear CD55 stability. CD55 deletion mutants were generated and introduced into cancer cells to identify the nuclear trafficking code, cisplatin sensitivity, and stem cell frequency that were assayed using in vitro and in vivo models. Detection of CD55 binding proteins was analyzed by immunoprecipitation followed by mass spectrometry. Target pathways activated by CD55 were identified by RNA sequencing.

RESULTS

CD55 localizes to the nucleus of a subset of OC specimens, ascites from chemoresistant patients, and enriched in chemoresistant OC cells. We determined that nuclear CD55 is glycosylated and derived from the cell surface pool of CD55. Nuclear localization is driven by a trafficking code containing the serine/threonine (S/T) domain of CD55. Nuclear CD55 is necessary for cisplatin resistance, stemness, and cell proliferation in OC cells. CD55 S/T domain is necessary for nuclear entry and inducing chemoresistance to cisplatin in both in vitro and in vivo models. Deletion of the CD55 S/T domain is sufficient to sensitize chemoresistant OC cells to cisplatin. In the nucleus, CD55 binds and attenuates the epigenetic regulator and tumor suppressor ZMYND8 with a parallel increase in H3K27 trimethylation and members of the Polycomb Repressive Complex 2.

CONCLUSIONS

For the first time, we show CD55 localizes to the nucleus in OC and promotes CSC and chemoresistance. Our studies identify a therapeutic mechanism for treating platinum resistant ovarian cancer by blocking CD55 nuclear entry.

Tumor glucose metabolism and the T cell glycocalyx: implication for T cell function

The T cell is an immune cell subset highly effective in eliminating cancer cells. Cancer immunotherapy empowers T cells and occupies a solid position in cancer treatment. The response rate, however, remains relatively low (<30%). The efficacy of immunotherapy is highly dependent on T cell infiltration into the tumor microenvironment (TME) and the ability of these infiltrated T cells to sustain their function within the TME. A better understanding of the inhibitory impact of the TME on T cells is crucial to improve cancer immunotherapy. Tumor cells are well described for their switch into aerobic glycolysis (Warburg effect), resulting in high glucose consumption and a metabolically distinct TME. Conversely, glycosylation, a predominant posttranslational modification of proteins, also relies on glucose molecules. Proper glycosylation of T cell receptors influences the immunological synapse between T cells and tumor cells, thereby affecting T cell effector functions including their cytolytic and cytostatic activities. This review delves into the complex interplay between tumor glucose metabolism and the glycocalyx of T cells, shedding light on how the TME can induce alterations in the T cell glycocalyx, which can subsequently influence the T cell's ability to target and eliminate tumor cells.

N-glycosylation at N57/100/110 affects CD44s localization, function and stability in hepatocellular carcinoma

The glycosylation levels of proteins in cancer cells are closely related to cancer invasion and migration. CD44 is a transmembrane glycoprotein that is significantly overexpressed in a variety of tumor cells and has been proven to promote the migration and motility of cancer cells, but the effect of its N-glycosylation modification on CD44 protein function in tumors is less studied. Here, we investigated the effect of six N-glycan chains (N25/57/100/110/120/255) on CD44s localization, function and stability in hepatocarcinoma cells. When the six sites were mutated, we found that CD44s lost its membrane localization in Huh7 and MHCC-97H cells. On this basis, we identified three glycosylation sites on CD44s (N57, N100 and N110) that played key roles in intracellular localization. When N57, N100 and N110 were mutated together, CD44 localized to the cytoplasm, while another three-site mutant (N25/N120/N255) was still anchored to the membrane. In addition, the ability of CD44-N57Q/N100Q/N110Q to promote the metastasis and invasion of Huh7 and 97H cells was weakened compared with that of CD44-N25Q/N120Q/N255Q. Furthermore, CD44-N57Q/N100Q/N110Q accumulated abnormally in the ER, and a high level of the ER stress (ERS) marker BiP was detected at the same time compared with wild-type CD44. When the lysosome inhibitor CQ was added, the content of mutant protein that triggered ERS significantly increased, which indicated that the degradation mode of CD44-N57Q/N100Q/N110Q after ERS was mainly through the lysosomal pathway (ERLAD). The results revealed that the N-glycosylation sites N57, N100 and N110 mutated on CD44s affected its function and degraded it by lysosomes after triggering ERS. These findings provide data for new studies on ER-related degradation, further promote the study of the glycan chain function of CD44 and furnish new ideas for the treatment of liver cancer metastasis.

Identification of a Novel Prognostic Signature Based on N-Linked Glycosylation and Its Correlation with Immunotherapy Response in Hepatocellular Carcinoma

Background

The complex tumor microenvironment of hepatocellular carcinoma (HCC) has led to a low response to immune checkpoints inhibitors (ICIs) and a poor prognosis. PD-L1, as one of the indications for ICIs, is rich in glycosylation modifications, which result in untimely ICIs. Our study constructed a prognostic model based on N-linked glycosylation related genes for predicting the prognosis and the response to ICIs.

Methods

The list of N-linked glycosylation related genes is from the AmiGO2 database. The patients in The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) cohorts were enrolled. The Cox regression was performed to develop a prognostic model and patients were divided into a low- and high-risk subgroups. The role of signature in HCC was well investigated by prognostic analysis, gene set enrichment analysis, and immune infiltration analysis. 21 recurrent HCC patients who received postoperative adjuvant ICIs were recruited to evaluate the relationship between immunotherapy response and the signature. In vitro studies were conducted to investigate the oncogenic effects of DDOST, STT3A and TMEM165 in HCC.

Results

59 N-linked glycosylation related differentially expressed genes were screened from HCC and normal tissues in the TCGA cohort. The prognostic model was developed with DDOST, STT3A and TMEM165. The risk score could be an independent prognostic factor. Patients in the high-risk subgroup showed a worse prognosis than patients in the low-risk one. ssGSEA showed that patients in the low-risk subgroup tended to be in the immune-activated state, with higher levels of B cell and macrophage cell infiltrations and lower levels of regulatory T cell (Treg) infiltrations in both TCGC and GEO cohorts. Immunohistochemistry studies showed that DDOST, STT3A and TMEM165 are highly expressed in tumor tissues and patients with a high-risk score correlated with poor progression free survival and worse immunotherapeutic response. Furthermore, the proliferation of HCC cells was reduced after the knockdown of DDOST, as well as upon the knockdown of STT3A and TMEM165.

Conclusion

In this study, we establish that the risk model based on N-linked glycosylation related genes could efficiently predict the prognosis and tumor microenvironment immune state of HCC patients, and the risk score could serve as a novel indicator of immunotherapy.

Nucleotide sugar transporter SLC35A2 is involved in promoting hepatocellular carcinoma metastasis by regulating cellular glycosylation

PURPOSE

Recently, aberrant glycosylation has been recognized to be relate to malignant behaviors of cancer and outcomes of patients with various cancers. SLC35A2 plays an indispensable role on glycosylation as a nucleotide sugar transporter. However, effects of SLC35A2 on malignant behaviors of cancer cells and alteration of cancer cells surface glycosylation profiles are still not fully understood, particularly in hepatocellular carcinoma (HCC). Hence, from a glycosylation perspective, we investigated the effects of SLC35A2 on metastatic behaviors of HCC cells.

METHODS

SLC35A2 expression in clinical samples and HCC cells was examined by immunohistochemical staining or Western blot/quantitative PCR and was regulated by RNA interference or vectors-mediated transfection. Effects of SLC35A2 expression alteration on metastatic behaviors and membrane glycan profile of HCC cells were observed by using respectively invasion, migration, cell adhesion assay, in vivo lung metastatic nude mouse model and lectins microarray. Co-location among proteins in HCC cells was observed by fluorescence microscope and detected by an in vitro co-immunoprecipitation assay.

RESULTS

SLC35A2 was upregulated in HCC tissues, and is associated with poor prognosis of HCC patients. SLC35A2 expression alteration significantly affected the invasion, adhesion, metastasis and membrane glycan profile and led to the dysregulated expressions or glycosylation of cell adhesion-related molecules in HCC cells. Mechanistically, the maintenance of SLC35A2 activity is critical for the recruitment of the key galactosyltransferase B4GalT1, which is responsible for complex glycoconjugate and lactose biosynthesis, to Golgi apparatus in HCC cells.

CONCLUSION

SLC35A2 plays important roles in promoting HCC metastasis by regulating cellular glycosylation modification and inducing the cell adhesive ability of HCC cells.

ER-stress promotes VHL-independent degradation of hypoxia-inducible factors via FBXW1A/βTrCP

Metabolic adaptation and signal integration in response to hypoxic conditions is mainly regulated by hypoxia-inducible factors (HIFs). At the same time, hypoxia induces ROS formation and activates the unfolded protein response (UPR), indicative of endoplasmic reticulum (ER) stress. However, whether ER stress would affect the hypoxia response remains ill-defined. Here we report that feeding mice a high fat diet causes ER stress and attenuates the response to hypoxia. Mechanistically, ER stress promotes HIF-1α and HIF-2α degradation independent of ROS, Ca²⁺, and the von Hippel-Lindau (VHL) pathway, involving GSK3β and the ubiquitin ligase FBXW1A/βTrCP. Thereby, we reveal a previously unknown function of the GSK3β/HIFα/βTrCP1 axis in ER homeostasis and demonstrate that inhibition of the HIF-1 and HIF-2 response and genetic deficiency of GSK3β affects proliferation, migration, and sensitizes cells for ER stress promoted apoptosis. Vice versa, we show that hypoxia affects the ER stress response mainly through the PERK-arm of the UPR. Overall, we discovered previously unrecognized links between the HIF pathway and the ER stress response and uncovered an essential survival pathway for cells under ER stress.

Antitumor effect of 4MU on glioblastoma cells is mediated by senescence induction and CD44, RHAMM and p-ERK modulation

The extracellular matrix plays a key role in cancer progression. Hyaluronan, the main glycosaminoglycan of the extracellular matrix, has been related to several tumor processes. Hyaluronan acts through the interaction with cell membrane receptors as CD44 and RHAMM and triggers signaling pathways as MEK/ERK. 4-methylumbelliferone (4MU), a well-known hyaluronan synthesis inhibitor, is a promising alternative for cancer therapy. 4MU is a coumarin derivative without adverse effects that has been studied in several tumors. However, little is known about its use in glioblastoma (GBM), the most malignant primary brain tumor in adults. Glioblastoma is characterized by fast growth, migration and tissue invasiveness, and a poor median survival of the patients after treatment. Several reports linked glioblastoma progression with HA levels and even with CD44 and RHAMM expression, as well as MEK/ERK activation. Previously, we showed on a murine GBM cell line that HA enhances GBM migration, while 4MU markedly inhibits it. In this work we showed for the first time, that 4MU decreases cell migration and induces senescence in U251 and LN229 human GBM cell lines. Furthermore, we observed that HA promotes GBM cell migration on both cell lines and that such effects depend on CD44 and RHAMM, as well as MEK/ERK signaling pathway. Interestingly, we observed that the exogenous HA failed to counteract the effects of 4MU, indicating that 4MU effects are independent of HA synthesis inhibition. We found that 4MU decreases total CD44 and RHAMM membrane expression, which could explain the effect of 4MU on cell migration. Furthermore, we observed that 4MU increases the levels of RHAMM inside the cell while decreases the nucleus/cytoplasm relation of p-ERK, associated with 4MU effects on cell proliferation and senescence induction. Overall, 4MU should be considered as a promising therapeutic alternative to improve the outcome of patients with GBM.

Upregulation of Rpn10 promotes tumor progression via activation of the NF-κB pathway in clear cell renal cell carcinoma

The ubiquitin-proteasome system (UPS) plays a central role in regulating protein homeostasis in tumor progression. The proteasome subunit Rpn10 is associated with the progression of several tumor types. However, little is known regarding the role of Rpn10 in clear cell renal cell carcinoma (ccRCC). In this study, we found that overexpression of Rpn10 increased ccRCC cell proliferation, migration, and invasion. Silencing Rpn10 expression resulted in decreased cell proli-feration, migration, and invasion in ccRCC cells. Knockdown of Rpn10 inhibits tumor growth and cell proliferation in vivo. Furthermore, we demonstrated that Rpn10 increased cell proliferation, migration, and invasion via regulation of the nuclear factor kappa B (NF-κB) pathway. Rpn10 directly promoted inhibitor of nuclear factor-kappa B alpha (IκBα) degradation through the UPS. Moreover, we observed that upregulation of Rpn10 or downregulation of IκBα in ccRCC was associated with poor prognosis. We found that the combination of these two parameters was a more powerful predictor of poor prognosis than either parameter alone. Collectively, these findings provide evidence that Rpn10 promotes the progression of ccRCC by regulation of the NF-κB pathways and is a prognostic indicator for patients with ccRCC.

Suppressing ERK Pathway Impairs Glycochenodeoxycholate-Mediated Survival and Drug-Resistance in Hepatocellular Carcinoma Cells

Glycochenodeoxycholate (GCDA), a toxic component in bile salts, is involved in carcinogenesis of gastrointestinal tumors. The objective of this research was to study the function of ERK1/2 in the GCDA-mediated survival and drug-resistance in hepatocellular carcinoma cells (HCCs). Firstly, extracellular signal-regulated kinase 1/2 (ERK1/2) was detected extensively expressed in liver cancer cells, and silencing ERK1/2 by RNA interference could suppress GCDA-stimulated survival and promote apoptosis. Furthermore, phosphorylation of endogenous ERK1/2 could be potently stimulated by GCDA in combination with enhanced chemoresistance in QGY-7703 hepatocellular carcinoma cells. The GCDA-mediated proliferation and chemoresistance could be impaired by PD98059, which acted as an inhibitor to block the phosphorylation of ERK1/2. Mechanistically, PD98059 was able to potently suppress GCDA-stimulated nuclear aggregation of ERK1/2 and p-ERK1/2, upregulate pro-survival protein Mcl-1 and downregulate pro-apoptotic protein Bim. The results of this study indicated that disruption of ERK1/2 by blocking phosphorylation or nuclear translocation may put forward new methods for solving the problem of GCDA-related proliferation and drug-resistance in liver cancer treatment.

Dienogest regulates apoptosis, proliferation, and invasiveness of endometriotic cyst stromal cells via endoplasmic reticulum stress induction

Dienogest, a specific progesterone receptor agonist, is used in the treatment of endometriosis. However, it is still unclear as to the mechanisms of therapeutic effects on endometriosis. Our recent study showed that endometriosis may be the result of aberrant endoplasmic reticulum (ER) stress induction due to progesterone resistance. This finding suggests that the regulation of ER stress induction may play a key role in treatment of endometriosis. Therefore, the anti-endometriotic effects of dienogest may be mediated by regulation of ER stress. To test this hypothesis, we elucidate whether dienogest affects endometriotic stromal cell apoptosis, proliferation and invasiveness by modulating ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Specifically, PRKR-like ER kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activating transcription factor 4 (ATF4), inositol-requiring kinase 1 (IRE1)/TNF receptor-associated factor 2 (TRAF2)/apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) signaling, and downstream CHOP were evaluated to determine the involved ER stress-mediated regulation mechanism of CHOP expression. Our results show that progesterone treatment did not have any significant effects on ER stress, apoptosis, proliferation, and invasion in estrogen-treated endometriotic cyst stromal cells (ECSCs). However, dienogest treatment upregulated the induction of ER stress. It also led to increased apoptosis, and decreased proliferation and invasiveness. These dienogest-induced changes in apoptosis, proliferation and invasiveness were reversed by the ER stress inhibitor salubrinal. Furthermore, dienogest-induced ER stress increased CHOP expression through activation of both PERK/elf2α/ATF4 and IRE1/TRAF2/ASK1/JNK signaling. This upregulation was blocked by transfection with PERK and IRE1 siRNA, which decreased apoptosis and increased the proliferation and invasiveness of dienogest-treated ECSCs. Taken together, our findings indicate that dienogest enhances ER stress induction in endometriotic stromal cells, which affects apoptosis, proliferation and invasiveness via CHOP upregulation.

Primary resistance to first-generation EGFR-TKIs induced by MDM2 amplification in NSCLC

Introduction

Targeted therapy for NSCLC is rapidly evolving. EGFR-TKIs benefit NSCLC patients with sensitive EGFR mutations and significantly prolong survival. However, 20–30% of patients demonstrate primary resistance to EGFR-TKIs, which leads to the failure of EGFR-TKI treatment. The mechanisms of primary resistance to EGFR-TKIs require further study.

Methods

Targeted sequencing was used for the detection of genomic alterations among patients in our center. Regular cell culture and transfection with plasmids were used to establish NSCLC cell lines over-expressing MDM2 and vector control. We used the MTT assays to calculate the inhibition rate after exposure to erlotinib. Available datasets were used to determine the role of MDM2 in the prognosis of NSCLC.

Results

Four patients harboring concurrent sensitive EGFR mutations and MDM2 amplifications demonstrated insensitivity to EGFR-TKIs in our center. In vitro experiments suggested that MDM2 amplification induces primary resistance to erlotinib. Over-expressed MDM2 elevated the IC50 value of erlotinib in HCC2279 line and reduced the inhibition rate. In addition, MDM2 amplification predicted a poor prognosis in NSCLC patients and was associated with a short PFS in those treated with EGFR-TKIs. The ERBB2 pathway was identified as a potential pathway activated by MDM2 amplification could be the focus of further research.

Conclusion

MDM2 amplification induces the primary resistance to EGFR-TKIs and predicts poor prognosis in NSCLC patients. MDM2 may serve as a novel biomarker and treatment target for NSCLC. Further studies are needed to confirm the mechanism by which amplified MDM2 leads to primary resistance to EGFR-TKIs.

Tunicamycin induces ER stress and inhibits tumorigenesis of head and neck cancer cells by inhibiting N-glycosylation

Glycosylation plays an important role in the genesis of various cancers. The inhibition of glycosylation disturbs the protein folding machinery, causing the accumulation of unfolded proteins in the cell endoplasmic reticulum (ER) and inducing ER stress. Tunicamycin (TM) is an inhibitor of glycosylation that has shown marked antitumor activity. In this study, we investigated the effect of TM on the tumorigenesis of head and neck cancer cells. The effects of TM on cell proliferation, colony formation and tumorsphere formation in vitro and tumorigenicity in vivo were investigated in head and neck cancer cells. ER stress was determined by the evaluation of PERK, PDI, IRE1-α, BIP, Ero1-Lα and calnexin expression using western blotting and immunofluorescence. We found that TM inhibited colony formation and tumorsphere formation of head and neck cancer cells in vitro and suppressed tumor growth in vivo. After incubation with TM, the expression of the cancer stem cell markers CD44 and Bmi-1 was reduced, and the expression of the ER stress markers BIP, Ero1-Lα and calnexin was elevated. Moreover, the EGFR signaling pathway was inhibited, and nonglycosylated EGFR degradation was accelerated with TM treatment. Our results suggest that inhibition of glycosylation by TM may be a novel treatment strategy for use with HNSCC patients.

Targeting E-cadherin expression with small molecules for digestive cancer treatment

Digestive system cancers, mainly including gastric cancer, hepatocellular carcinoma, pancreatic cancer, and colorectal cancer, are major public health problems and lead to serious cancer-related deaths worldwide. Clinically, treatment strategies of these cancers include surgery, chemotherapy, and immunotherapy. Although successful resection and chemotherapeutic drugs have improved the treatment level, the survival rate of patients with advanced digestive system cancers remains still low primarily due to tumor metastasis. E-cadherin, the prototypical member of the type-1 classical cadherins, has been characrized as an important molecule in epithelial-mesenchymal transition (EMT) process. Loss of E-cadherin is able to induce EMT process, which is associated with cancer stem cells and drug resistance in human cancer. Therefore, restoring E-cadherin could be a useful strategy for reversal of EMT and overcoming drug resistance. In this review, we describe pharmacological small molecules targeting E-cadherin expression for the treatment of digestive system cancers, which have emerged in the recent 5 years. We hope these compounds could be potentially used for treating cancer in the near future.

Proliferation of poorly differentiated endometrial cancer cells through autocrine activation of FGF receptor and HES1 expression

Patients with poorly differentiated endometrial cancer show poor prognosis, and effective molecular target-based therapies are needed. Endometrial cancer cells proliferate depending on the activation of HES1 (hairy and enhancer of split-1), which is induced by several pathways, such as the Notch and fibroblast growth factor receptor (FGFR) signaling pathways. In addition, aberrant, ligand-free activation of the FGFR signaling pathway resulting from mutations in FGFR2 was also reported in endometrial cancer. However, a clinical trial showed that there was no difference in the effectiveness of FGFR inhibitors between patients with and without the FGFR2 mutation, suggesting a presence of another signaling pathway for the FGFR activation. Here, we investigated the signaling pathway regulating the expression of HES1 and proliferation of poorly and well-differentiated endometrial cancer cell lines Ishikawa and HEC-50B, respectively. Whereas Ishikawa cells proliferated and expressed HES1 in a Notch signaling-dependent manner, Notch signaling was not involved in HES1 and proliferation of HEC-50B cells. The FGFR inhibitor, NVP-BGJ398, decreased HES1 expression and proliferation of HEC-50B cells; however, HEC50B cells had no mutations in the FGFR2 gene. Instead, HEC-50B cells highly expressed ligands for FGFR2, suggesting that FGFR2 is activated by an autocrine manner, not by ligand-free activation. This autocrine pathway activated Akt downstream of FGFR for cell proliferation. Our findings suggest the usefulness of HES1 as a marker for the proliferation signaling and that FGFR inhibitor may be effective for poorly differentiated endometrial cancers that harbor wild-type FGFR.

Rpn10 promotes tumor progression by regulating hypoxia-inducible factor 1 alpha through the PTEN/Akt signaling pathway in hepatocellular carcinoma

The ubiquitin-proteasome pathway plays a pivotal role in tumor progression. Rpn10 is the major ubiquitin (Ub) receptor of the 26S proteasome. Mounting evidence shows that Rpn10 is associated with the progression of several tumor types. However, little is known regarding the mechanistic role of Rpn10 in hepatocellular carcinoma (HCC). In this study, we found that the upregulation of Rpn10 in HCC was associated with poor prognosis. The ectopic overexpression of Rpn10 increased HCC cell proliferation, whereas silencing Rpn10 expression resulted in decreased cell proliferation. Furthermore, we demonstrated that knockdown of Rpn10 induced cell cycle arrest at G1 phase in HCC cells. In addition, we found that Rpn10 increased cell proliferation via regulation of the PTEN/Akt pathways. Knockdown of Rpn10 induced suppression of cell proliferation could be reversed by overexpressing active Akt in HCC cells. Rpn10 directly promoted PTEN degradation through the ubiquitin-proteasome system. The transcription factor HIF1α directly bound to the Rpn10 promoter and increased its expression in HCC tissue. Moreover, we observed a significant correlation between HIF1α expression and Rpn10 levels in HCC patients and found that the combination of these two parameters was a more powerful predictor of poor prognosis than either parameter alone. Collectively, these findings highlight the molecular mechanism of Rpn10 expression in HCC and provide valuable information for cancer prognosis and treatment.

Inhibitor of binding/differentiation 2 (Id2) is regulated by CCAAT/enhancer-binding protein-α (C/EBPα) and promotes the proliferation of hepatocellular carcinoma

Inhibitor of DNA binding/differentiation (Id2) is an important regulator involved in the initiation and progression of cancer. However, the function and mechanism of the regulation of Id2 in hepatocellular carcinoma (HCC) was unclear. In the present study, we found that the overexpression of Id2 increased HCC cell proliferation in vitro and in vivo. Knockdown of Id2 inhibited HCC cell proliferation in vitro and in vivo. Furthermore, knockdown of Id2 enhanced sorafenib-induced apoptosis in HCC. Conversely, overexpression of Id2 weakened sorafenib-induced apoptosis in HCC. In addition, the transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα) bound to the Id2 promoter and decreased its expression in HCC cells. Therefore, all results suggest that Id2 promotes the proliferation of HCC cells by inhibiting cell apoptosis. Id2 may serve as a potential target in HCC therapy.

Dendritic cell factor 1 inhibits proliferation and migration and induces apoptosis of neuroblastoma cells by inhibiting the ERK signaling pathway

Neuroblastoma (NB) is the most common extracranial solid tumor that affects mainly children and has extremely high mortality and recurrence rates. A previous study revealed that dendritic cell factor 1 (DCF1), also called transmembrane protein 59, could activate apoptosis in glioma cells. In the present study, we applied immunofluorescence, western blot analysis, flow cytometry and cell tumorigenicity to investigate the DCF1 mechanisms involved in NB apoptosis. DCF1 was overexpressed in Neuro-2a and SK-N-SH cells through instantaneous transfection. The data revealed that overexpression of DCF1 could inhibit cell proliferation, migration, invasion and promote cell apoptosis in vitro, and suppress NB growth in vivo. The ERK1/2 signaling pathway, which promotes cell survival, was the target of DCF1 in neuroblastoma cells. All the results indicated that DCF1 could be a potential therapeutic target for the understanding and treatment of NB.

Tunicamycin inhibits cell proliferation and migration in hepatocellular carcinoma through suppression of CD44s and the ERK1/2 pathway

Tunicamycin (TM) is an N‐linked glycosylation (NLG) inhibitor with strong antitumor activity, the exact underlying molecular mechanism of which remains to be elucidated. In our previous studies, we found that TM reversed drug resistance and improved the efficacy of combination treatments for hepatocellular carcinomas (HCC). Here, we investigated the effects of TM on HCC cell proliferation and migration as well as the mechanism of those effects. Our results showed that TM inhibited cell proliferation and migration as well as induced apoptosis of hepatocellular carcinoma cells. TM inhibited proliferation of HCC cells by inducing cell apoptosis and cell cycle arrest at the G2/M phase. Meanwhile, TM inhibited migration of HCC cells by suppressing CD44s‐mediated epithelial‐mesenchymal transition (EMT). TM inhibited migration and invasion of HCC cells by decreasing CD44 expression and altering its glycosylation. In addition, CD44s is involved in promoting EMT and is associated with a poor prognosis in HCC patients. Overexpression of CD44s promoted tumor migration and activated phosphorylation of ERK1/2 in HCC cells, whereas TM inhibited CD44s overexpression‐associated cell migration. The ability of TM to inhibit cell migration and invasion was enhanced or reversed in CD44s knockdown cells and cells overexpressing CD44s, respectively. The MEK/ERK inhibitor U0126 and TM inhibited hyaluronic acid‐induced cell migration in HCC cells. Furthermore, TM inhibited exogenous transforming growth factor beta (TGF‐β)‐mediated EMT by an ERK1/2‐dependent mechanism and restored the TGF‐β‐mediated loss of E‐cadherin. In summary, our study provides evidence that TM inhibits proliferation and migration of HCC cells through inhibition of CD44s and the ERK1/2 signaling pathway.