ERK and AKT signaling cooperate to translationally regulate survivin expression for metastatic progression of colorectal cancer

Evaluation of spheroid head and neck squamous cell carcinoma cell models in comparison to monolayer cultures

Two-dimensional (2D) monolayer cell culture models are the most common method used to investigate tumor cells in vitro. In the few last decades, a multicellular spheroid model has gained attention due to its adjacency to tumors in vivo. The aim of the present study was to investigate immunohistochemical differences between these two cell culture systems. The FaDu, CAL27 and SCC25 head and neck squamous cell carcinoma (HNSCC) cell lines were seeded out in monolayer and multicellular spheroids. The FaDu and SCC25 cells were treated with increasing doses of cisplatin and irradiation. CAL27 cells were not used in theproliferation experiments, since the spheroids of CAL27 cells were not able to process the reagent in CCK-8 assays. Furthermore, they were stained to present alterations of the following antigens: Ki-67, vascular endothelial growth factor receptor, epithelial growth factor and survivin. Differences in growth rates and expression patterns were detected in certain HNSCC cell lines. The proliferation rates showed a significant divergence of cells grown in the three-dimensional model compared with cells grown in the 2D model. Overall, multicellular spheroids are a promising method to reproduce the immunohistochemical aspects and characteristics of tumor cells, and may show different response rates to therapeutic options.

p70 S6-kinase mediates the cooperation between Akt1 and Mek1 pathways in fibroblast-mediated extracellular matrix remodeling

Previous studies have demonstrated both synergistic and opposing effects of Akt and Mek1/2 in various cell functions and disease states. Furthermore, Akt has been reported to inhibit and activate cRaf/Mek pathway, suggesting that their mutual interaction and cooperation may be cell type, stimuli and/or context specific. While PI3-kinase/Akt and cRaf/Mek pathways have been implicated in the regulation of extracellular matrix (ECM) remodeling, mutual interactions between these two pathways and their specific contributions to the events leading to ECM synthesis and assembly is not clear. We investigated the specific role of Akt1 and Mek1 in ECM synthesis and assembly by NIH 3T3 fibroblasts and how these effects were reconciled to mediate overall ECM remodeling. Our study identified that cooperation between Akt1 and Mek1 is necessary to mediate ECM synthesis. Whereas Akt1 activation resulted in Mek1 activation as evidenced by increased ERK1/2 phosphorylation, Mek1 inhibition using U0126 or DN-Mek1 resulted in enhanced Akt1 phosphorylation. Interestingly, both Akt1 and Mek1 activities were needed for the synthesis and assembly of ECM. The effect of Akt1 and Mek1 on ECM synthesis was reconciled through the activation of p70 S6-kinase via phosphorylation at T421/S424 and S411, respectively. Furthermore, Akt1 and Mek1 cooperated in mediating ECM assembly via activation of integrin β1. Together, we show for the first time that Akt1 and Mek1 pathways cooperate in the regulation of ECM remodeling by the fibroblasts.

Integrin β6 can be translationally regulated by eukaryotic initiation factor 4E: Contributing to colonic tumor malignancy

It is well known that both eukaryotic initiation factor 4E (eIF4E) and integrin αvβ6 can contribute to malignant behavior of colon cancer. We have found that integrin αvβ6 and eIF4E were co-expressed and positively correlated in colon cancer tissues. Recently, deregulation of the protein synthesis apparatus has begun to gain attention as a major participant in cancer development and progression. However, the regulation of integrin β6 expression at translational level has never been investigated before. In present study, gene-silencing technique for eIF4E by small interfering RNA (siRNA) was used in all the subsequent experiments, in order to investigate whether eIF4E could translationally regulate expression of integrin β6 in colon cancer SW480 and HT-29 cell lines. Additionally, the subsequent effects of eIF4E knockdown on cellular malignant behavior were observed. siRNA in SW480 and HT-29 transfectants. Subsequently, protein expression of β6 was markedly suppressed, while mRNA expression of β6 showed no significant variation before and after eIF4E RNA interfering. Therefore, it could be seen that eIF4E could upregulate the expression of β6, without effect on β6 mRNA expression. More importantly, after treated with eIF4E siRNA, cellular migratory capacity on fibronectin of HT-29 and β6-transfected SW480 as well as their survival to 5-FU was decreased distinctly. Expression of integrin β6 could be translationally regulated by eIF4E, which subsequently contributed to tumor malignancy through enhancing cellular migration, survival, anti-apoptosis, and chemoresistance of colon cancer in vitro. Thus, targeting eIF4E in integrin αvβ6 expressing tumors can be a potential therapeutic strategy for patients with colon cancer.

RPL24: a potential therapeutic target whose depletion or acetylation inhibits polysome assembly and cancer cell growth

Partial loss of large ribosomal subunit protein 24 (RPL24) function is known to protect mice against Akt or Myc-driven cancers, in part via translational inhibition of a subset of cap(eIF4E)-dependently translated mRNAs. The role of RPL24 in human malignancies is unknown. By analyzing a public dataset of matched human breast cancers and normal mammary tissue, we found that breast cancers express significantly more RPL24 than matched normal breast samples. Depletion of RPL24 in breast cancer cells by >70% reduced cell viability by 80% and decreased protein expression of the eIF4E-dependently translated proteins cyclin D1 (75%), survivin (46%) and NBS1 (30%) without altering GAPDH or beta-tubulin levels. RPL24 knockdown also reduced 80S subunit levels relative to 40S and 60S levels. These effects on expression of eIF4E-dependent proteins and ribosome assembly were mimicked by 2-24 h treatment with the pan-HDACi, trichostatin A (TSA), which induced acetylation of 15 different polysome-associated proteins including RPL24. Furthermore, HDAC6-selective inhibition or HDAC6 knockdown induced ribosomal protein acetylation. Via mass spectrometry, we found that 60S-associated, but not, polysome-associated, RPL24 undergoes HDACi-induced acetylation on K27. Thus, RPL24 K27 acetylation may play a role in ribosome assembly. These findings point toward a novel acetylation-dependent polysome assembly mechanism regulating tumorigenesis.

So-Cheong-Ryong-Tang induces apoptosis through activation of the intrinsic and extrinsic apoptosis pathways, and inhibition of the PI3K/Akt signaling pathway in non-small-cell lung cancer A549 cells

Background

So-Cheong-Ryong-Tang (SCRT), a traditional Korean medicine containing eight species of medicinal plant, has been used to treat patients with bronchial asthma and allergic rhinitis for hundreds of years; however, its anti-cancer potential is poorly understood. The present study was designed to evaluate the apoptotic effect of SCRT against human non-small-cell lung cancer (NSCLC) A549 cells.

Methods

The effects of SCRT on cell growth and viability were evaluated by trypan blue dye exclusion and 3-(4, 5-dimethyl-thiazol-2-yl)-2, 5-diphenyl tetrazoliumbromide (MTT) assays, respectively. Apoptosis was detected using 4,6-diamidino-2-phenyllindile (DAPI) staining, agarose gel electrophoresis and flow cytometry. The protein levels were determined by Western blot analysis. Caspase activity was measured using a colorimetric assay.

Results

SCRT treatment resulted in significantly decreased A549 cell growth and viability by induction of apoptosis. SCRT induced the translocation of pro-apoptotic Bax to the mitochondria, mitochondrial membrane permeabilization, cytochrome c release from mitochondria to cytosol, and activated caspase-9 and caspase-3. SCRT also increased death receptor-associated ligands and enhanced the activation of caspase-8 and cleavage of its substrate Bid. However, the pan-caspases inhibitor significantly blocked the SCRT-induced apoptosis, suggesting that it is a caspase-dependent pathway. In addition, SCRT suppressed the phosphorylation of phosphoinositide 3-kinase (PI3K) and Akt, and treatment with a potent inhibitor of PI3K further increased the apoptotic activity of SCRT.

Conclusions

These findings suggest that SCRT may play its anti-cancer actions partly through a suppression of the PI3K/Akt signal pathway in A549 cells, and further in vivo studies on the potential of SCRT for prevention and therapy of NSCLCs are warranted.

Ruta graveolens L. induces death of glioblastoma cells and neural progenitors, but not of neurons, via ERK 1/2 and AKT activation

Glioblastoma multiforme is a highly aggressive brain tumor whose prognosis is very poor. Due to early invasion of brain parenchyma, its complete surgical removal is nearly impossible, and even after aggressive combined treatment (association of surgery and chemo- and radio-therapy) five-year survival is only about 10%. Natural products are sources of novel compounds endowed with therapeutic properties in many human diseases, including cancer. Here, we report that the water extract of Ruta graveolens L., commonly known as rue, induces death in different glioblastoma cell lines (U87MG, C6 and U138) widely used to test novel drugs in preclinical studies. Ruta graveolens’ effect was mediated by ERK1/2 and AKT activation, and the inhibition of these pathways, via PD98058 and wortmannin, reverted its antiproliferative activity. Rue extract also affects survival of neural precursor cells (A1) obtained from embryonic mouse CNS. As in the case of glioma cells, rue stimulates the activation of ERK1/2 and AKT in A1 cells, whereas their blockade by pharmacological inhibitors prevents cell death. Interestingly, upon induction of differentiation and cell cycle exit, A1 cells become resistant to rue’s noxious effects but not to those of temozolomide and cisplatin, two alkylating agents widely used in glioblastoma therapy. Finally, rutin, a major component of the Ruta graveolens water extract, failed to cause cell death, suggesting that rutin by itself is not responsible for the observed effects. In conclusion, we report that rue extracts induce glioma cell death, discriminating between proliferating/undifferentiated and non-proliferating/differentiated neurons. Thus, it can be a promising tool to isolate novel drugs and also to discover targets for therapeutic intervention.

Sp1 and c-Myc modulate drug resistance of leukemia stem cells by regulating survivin expression through the ERK-MSK MAPK signaling pathway

BACKGROUND

Acute myeloid leukemia (AML) is initiated and maintained by a subset of self-renewing leukemia stem cells (LSCs), which contribute to the progression, recurrence and therapeutic resistance of leukemia. However, the mechanisms underlying the maintenance of LSCs drug resistance have not been fully defined. In this study, we attempted to elucidate the mechanisms of LSCs drug resistance.

METHODS

We performed reverse phase protein arrays to analyze the expression of anti-apoptotic proteins in the LSC-enriched leukemia cell line KG-1a. Immuno-blotting, cell viability and clinical AML samples were evaluated to verify the micro-assay results. The characteristics and transcriptional regulation of survivin were analyzed with the relative luciferase reporter assay, mutant constructs, chromatin immuno-precipitation (ChIP), quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR), and western blotting. The levels of Sp1, c-Myc, phospho-extracellular signal-regulated kinase (p-ERK), phospho-mitogen and stress-activated protein kinase (p-MSK) were investigated in paired CD34+ and CD34- AML patient samples.

RESULTS

Survivin was highly over-expressed in CD34 + CD38- KG-1a cells and paired CD34+ AML patients compared with their differentiated counterparts. Functionally, survivin contributes to the drug resistance of LSCs, and Sp1 and c-Myc concurrently regulate levels of survivin transcription. Clinically, Sp1 and c-Myc were significantly up-regulated and positively correlated with survivin in CD34+ AML patients. Moreover, Sp1 and c-Myc were further activated by the ERK/MSK mitogen-activated protein kinase (MAPK) signaling pathway, modulating survivin levels.

CONCLUSION

Our findings demonstrated that ERK/MSK/Sp1/c-Myc axis functioned as a critical regulator of survivin expression in LSCs, offering a potential new therapeutic strategy for LSCs therapy.

PAC exhibits potent anti-colon cancer properties through targeting cyclin D1 and suppressing epithelial-to-mesenchymal transition

Colorectal cancer (CRC) is a major cause of cancer morbidity and mortality worldwide. Although response rates and overall survival have been improved in recent years, resistance to multiple drug combinations is inevitable. Therefore, the development of more efficient drugs, with fewer side effects is urgently needed. To this end, we have investigated in the present report the effect of PAC, a novel cucumin analogue, on CRC cells both in vitro and in vivo. We have shown that PAC induces apoptosis, mainly via the internal mitochondrial route, and inhibits cell proliferation through delaying the cell cycle at G2/M phase. Interestingly, the pro-apoptotic effect was mediated through STAT3-dependent down-regulation of cyclin D1 and its downstream target survivin. Indeed, change in the expression level of cyclin D1 modulated the expression of survivin and the response of CRC cells to PAC. Furthermore, using the ChIP assay, we have shown PAC-dependent reduction in the binding of STAT3 to the cyclin D1 promoter in vivo. Additionally, PAC suppressed the epithelial-to-mesenchymal process through down-regulating the mesenchymal markers (N-cadherin, vimentin and Twist1) and inhibiting the invasion/migration abilities of the CRC cells via repressing the pro-migration/invasion protein kinases AKT and ERK1/2. In addition, PAC inhibited tumor growth and repressed the JAK2/STAT3, AKT/mTOR and MEK/ERK pathways as well as their common downstream effectors cyclin D1 and survivin in humanized CRC xenografts. Collectively, these results indicate that PAC has potent anti-CRC effects, and therefore could constitute an effective alternative chemotherapeutic agent, which may consolidate the adjuvant treatment of colon cancer.

E2F-1 overexpression inhibits human gastric cancer MGC-803 cell growth in vivo

AIM: To evaluate the influence of E2F-1 on the growth of human gastric cancer (GC) cells in vivo and the mechanism involved.

METHODS: E2F-1 recombinant lentiviral vectors were injected into xenograft tumors of MGC-803 cells in nude mice, and then tumor growth was investigated. Overexpression of transcription factor E2F-1 was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analysis. Apoptosis rates were determined using a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. Expression levels of certain cell cycle regulators and apoptosis-related proteins, such as Bax, survivin, Bcl-2, cyclin D1, S-phase kinase-associated protein 2, and c-Myc were examined by Western blotting and RT-PCR.

RESULTS: Xenograft tumors of MGC-803 cells in nude mice injected with E2F-1 recombinant lentiviral vectors stably overexpressed the E2F-1 gene as measured by semi-quantitative RT-PCR (relative mRNA expression: 0.10 ± 0.02 vs 0.05 ± 0.02 for control vector and 0.06 ± 0.03 for no infection; both P < 0.01) and Western blotting (relative protein expression: 1.90 ± 0.05 vs 1.10 ± 0.03 in control vector infected and 1.11 ± 0.02 for no infection; both P < 0.01). The growth-curve of tumor volumes revealed that infection with E2F-1 recombinant lentiviral vectors significantly inhibited the growth of human GC xenografts (2.81 ± 1.02 vs 6.18 ± 1.15 in control vector infected and 5.87 ± 1.23 with no infection; both P < 0.05) at 15 d after treatment. TUNEL analysis demonstrated that E2F-1 overexpression promoted tumor cell apoptosis (18.6% ± 2.3% vs 6.7% ± 1.2% in control vector infected 6.3% ± 1.2% for no infection; both P < 0.05). Furthermore, lentiviral vector-mediated E2F-1 overexpression increased the expression of Bax and suppressed survivin, Bcl-2, cyclin D1, Skp2, and c-Myc expression in tumor tissue.

CONCLUSION: E2F-1 inhibits growth of GC cells via regulating multiple signaling pathways, and may play an important role in targeted therapy for GC.

Survivin - The inconvenient IAP

Although technically a member of the Inhibitor of Apoptosis (IAP) gene family, survivin has consistently defied assumptions, refuted predictions and challenged paradigms. Despite its more than 5500 citations currently in Medline, the biology of survivin has remained fascinatingly complex, its exploitation in human disease, most notably cancer, tantalizing, and its regulation of cellular homeostasis unexpectedly far-reaching. An inconvenient outsider that resists schemes and dogmas, survivin continues to hold great promise to unlock fundamental circuitries of cellular functions in health and disease.

New insights into 4E-BP1-regulated translation in cancer progression and metastasis

Remarkable progress has been made highlighting the importance of cap-dependent mRNA translation in cancer progression. 4E-BP1 is a translation initiation repressor by sequestering the mRNA cap-binding protein eIF4E and consequently inhibiting the translation of certain key oncogenic mRNAs encoding proteins for cell proliferation, survival, angiogenesis and malignancy. In most tumors, however, the repressive function of 4E-BP1 is compromised by reduction of its expression or phosphorylation mediated by oncogenic signaling pathways. We recently unveiled that 4E-BP1-regulated cap-dependent translation integrates oncogenic effects of the AKT and ERK signaling pathways on tumor growth and metastatic progression. Mechanistically, we demonstrate that AKT and ERK pathways selectively upregulate survivin expression at the level of translation by convergent activation of the mTORC1/4E-BP1/eIF4E signaling axis. In addition, loss of 4E-BP1 function induces epithelial-mesenchymal transition and increases metastatic capability of cancer cells by translational activation of Snail. Continuous translation of survivin and Snail is important for colorectal cancer progression to metastasis. Herein we discuss our findings concerning deregulation of translation in cancer progression and metastasis and highlight 4E-BP1 as a potential biomarker and therapeutic target.

Silencing of galectin-3 represses osteosarcoma cell migration and invasion through inhibition of FAK/Src/Lyn activation and β-catenin expression and increases susceptibility to chemotherapeutic agents

Galectin-3 is involved in tumor cell proliferation, adhesion, angiogenesis and metastasis. Galectin-3 promotes β-catenin/Wnt signaling, and β-catenin-related oncogenesis has been frequently reported in osteosarcoma. However, the correlation between galectin-3 and β‑catenin signaling in osteosarcoma is poorly defined. We hypothesized that galectin-3 may control the migration and invasion of cancer cells and that silencing of galectin-3 would therefore, suppress motility in osteosarcoma cells. In the present study, we show that galectin-3 silencing in cultured human osteosarcoma cells had decreased cell migration and invasion capabilities; reduced the expression and activation of FAK, Src, Lyn, PI3K/Akt, ERK1/2 and β-catenin, which are key mediators of invasion; inhibited the expression and secretion of VEGF, MCP-1, IL-8, IL-6, MMP2/9 and phospho-Stat3; and potentiated sensitivity to cisplatin. Our results suggest that galectin-3 may be a feasible therapeutic target for osteosarcoma.

Nrdp1 inhibits metastasis of colorectal cancer cells by EGFR signaling-dependent MMP7 modulation

The molecular mechanism underlying cancer invasiveness and metastasis of colorectal cancer (CRC) remains elusive. Here we reported a strong correlation of the levels of neuregulin receptor degradation protein-1 (Nrdp1) and matrix metalloproteinase-7 (MMP7) in CRC from the patients. We then used a human CRC line, Caco-2, to study the underlying molecular basis. We found that Nrdp1 inhibited the phosphorylation of ErB3, a key player in epidermal growth factor receptor (EGFR) signaling in Caco-2 cells, which is required for activation of MMP7 to promote cell invasion. Our findings thus reveal Nrdp1, EGFR signaling, and MMP7 as promising therapeutic targets for preventing the metastasis of CRC.

HMGA2 induces transcription factor Slug expression to promote epithelial-to-mesenchymal transition and contributes to colon cancer progression

Epithelial-to-mesenchymal transition (EMT) is considered to play an essential role in progression and metastasis. This study aims to investigate the expression and underlying molecular targets of high-mobility group AT-hook 2 (HMGA2) in the progression of colon cancer. The expression of HMGA2 is upregulated by both active extracellular signal-regulated kinase (ERK)1/2 and TGF-β signaling in colon cancer cells through a series of lentiviral infection and pharmacological assays. HMGA2 knockdown by specific shRNAs attenuates proliferation, motility and invasion of colon cancer cells in vitro and in vivo. Besides, exogenous HMGA2 expression caused EMT in colon cancer cells, which was confirmed by the downregulation of the epithelial markers and the upregulation of the mesenchymal markers. Moreover, HMGA2 positively regulates the Slug expression by directly binding to the regulatory region in Slug promoter. Importantly, the knockdown of Slug could reverse the HMGA2-induced EMT and decrease the migration and invasion ability of colon cancer cells. Taken together, our results reveal a critical role for HMGA2 in promoting EMT, migration, invasion, and proliferation of colon cancer cells, suggesting HMGA2 as a potential molecular target to prevent colon cancer progression.

Tumor suppressor miR-1 restrains epithelial-mesenchymal transition and metastasis of colorectal carcinoma via the MAPK and PI3K/AKT pathway

Aberrant expression of miR-1 has been implicated in various cancers. However, the mechanisms underlying the role of miR-1 in CRC progression still have not been clarified clearly. Here, we showed the decreased expression of miR-1 in colorectal carcinoma (CRC) tissues and cell lines. Ectopic introduction of miR-1 suppressed cell proliferation and migration, whereas miR-1 inhibitor performed contrary functions in CRC cells. Stable overexpression of miR-1 was sufficient to inhibit tumor growth and homing capacity in vivo. Proteomic analysis revealed that miR-1 modulated the expression of key cellular molecules and involved in the MAPK and PI3K/AKT pathways by inhibiting phosphorylation of ERK and AKT. Meanwhile, miR-1 also reversed epithelial–mesenchymal transition (EMT), which played a pivotal role in the initiation of metastasis. Further studies found that miR-1 can target the 3' untranslated region (3'UTR) of LIM and SH3 protein 1 (LASP1) mRNA and suppress the expression of LASP1, identified as a CRC-associated protein. In contrast to the phenotypes induced by miR-1 restoration, LASP1-induced cell proliferation and migration partly rescued miR-1-mediated biological behaviors. Our results illustrated that miR-1 play a critical role in CRC progression, which suggests its potential role in the molecular therapy of cancer.

Enhanced anti-colorectal cancer effects of carfilzomib combined with CPT-11 via downregulation of nuclear factor-κB in vitro and in vivo

Upregulation of nuclear factor-κB (NF-κB) in colorectal carcinoma (CRC) accelerates tumor growth, whereas, irinotecan (CPT-11)-induced NF-κB activation reduces chemosensitivity and weakens the anti-colorectal cancer function itself, while proteasome inhibitors can inhibit NF-κB and improve the effect of chemotherapy. Carfilzomib (CFZ) is a novel proteasome inhibitor that has been recently approved by the FDA and is in clinical use for the treatment of multiple myeloma, but little is known about its activity against CRC. The aim of the present study was to explore whether CFZ alone or in combination with CPT-11 is effective in CRC treatment. We evaluated the novel therapeutic ability and mechanism of action of CFZ in CRC in vitro and in vivo. SW620 cells were incubated with CFZ alone or in combination with CPT-11. Cell proliferation was assessed by WST-1 and clonogenic assays, the cytotoxic interaction was assessed with a combination index (CI). Cell cycle progression was analysed with flow cytometry. Cell apoptosis was evaluated by detecting the Annexin V/propidium iodide (PI) ratio, caspase 3 and CD95 expression, and with TUNEL staining. Cell migration and invasion was determined with a wound-healing assay and a Transwell matrix penetration assay. A CRC xenograft model was established to monitor tumor growth. EMSA was used to analyse NF-κB activation and western blot analysis was used to detect the protein levels of related signaling factors. CFZ significantly inhibited the growth of SW620 cells, and had synergistic inhibitory effects with CPT-11 on survival and colony formation; possibly by inhibition of NF-κB activation, MEK/ERK and PI3K/AKT pathway factor dephosphorylation and survivin downregulation. Co-administration of CFZ and CPT-11 induced G2/M arrest, increased p21WAF1/CIP, and decreased mutant p53 and cdc25c expression. Induction of apoptosis was accompanied by marked increases in PARP cleavage, caspase 3 activation, an increase of CD95 and p-p38, and ATF3 activation. Combination treatment lowered the invasive and migration ability of SW620 cells, reduced MMP and increased TIMP protein expression. Finally, co-administration of CFZ and CPT-11 suppressed tumor growth and increased apoptosis compared with single-agent treatment in SW620 xenograft models correlated with NF-κB downregulation. Carfilzomib alone or in combination with CPT-11 is effective against colorectal cancer through inhibition of multiple mechanisms related to NF-κB, and could be a potential novel therapy for CRC.

Loss of 4E-BP1 function induces EMT and promotes cancer cell migration and invasion via cap-dependent translational activation of snail

The cap-dependent translation is frequently deregulated in a variety of cancers associated with tumor progression. However, the molecular basis of the translation activation for metastatic progression of cancer remains largely elusive. Here, we demonstrate that activation of cap-dependent translation by silencing the translational repressor 4E-BP1 causes cancer epithelial cells to undergo epithelial-mesenchymal transition (EMT), which is associated with selective upregulation of the EMT inducer Snail followed by repression of E-cadherin expression and promotion of cell migratory and invasive capabilities as well as metastasis. Conversely, inhibition of cap-dependent translation by a dominant active mutant 4E-BP1 effectively downregulates Snail expression and suppresses cell migration and invasion. Furthermore, dephosphorylation of 4E-BP1 by mTORC1 inhibition or directly targeting the translation initiation also profoundly attenuates Snail expression and cell motility, whereas knockdown of 4E-BP1 or overexpression of Snail significantly rescues the inhibitory effects. Importantly, 4E-BP1-regulated Snail expression is not associated with its changes in the level of transcription or protein stability. Together, these findings indicate a novel role of 4E-BP1 in the regulation of EMT and cell motility through translational control of Snail expression and activity, and suggest that targeting cap-dependent translation may provide a promising approach for blocking Snail-mediated metastatic potential of cancer.

Cyr61 promotes growth of pancreatic carcinoma via nuclear exclusion of p27

The molecular regulation of the growth of pancreatic carcinoma (PCC) is complicated and not defined yet. Here we show that the cysteine-rich protein 61 (Cyr61) levels were significantly higher in PCC than in the adjacent nontumor tissues from the same human patient. Overexpression of Cyr61 enhanced the proliferation of PCC cells, while inhibition of Cyr61 decreased the proliferation of PCC cells. Further analysis showed that Cyr61 seemed to activate phosphatidylinositol 3-kinase (PI3K) but not extracellular-related kinase/mitogen-activated protein kinase (ERK/MAPK) signaling pathway in PCC cells, which subsequently induced nuclear exclusion of a major cell cycle inhibitor, p27, to increase cell proliferation. Taken together, these findings reveal the molecular basis underlying Cyr61-regulated PCC proliferation, suggest a potential role of Cyr61 in PCC growth, and highlight Cyr61 as a novel target for PCC therapy.

miR-29b suppresses tumor growth and metastasis in colorectal cancer via downregulating Tiam1 expression and inhibiting epithelial-mesenchymal transition

Recently, the role of miR-29b in colorectal carcinoma (CRC) development appears to be controversial. Until now, the expression and function of miR-29b in CRC have not been clarified clearly. We showed that decreased expression of miR-29b usually occurred in CRC cell lines and tissue samples. Loss- and gain-of-function assays in vitro revealed suppressive effects of miR-29b on cell proliferation and migration. Endogenous overexpression of miR-29b was sufficient to suppress aggressive behavioral phenotypes in mice. Proteomic analysis showed that miR-29b involved in integrate several key biological processes. In addition, miR-29b mediated the inhibition of epithelial-mesenchymal transition (EMT) and the inactivation of mitogen-activated protein kinase and phosphatidylinositol-4,5-bisphosphate 3-kinase/AKT signal transduction pathway. Further studies found that T lymphoma invasion and metastasis 1 (Tiam1) was identified as a direct target of miR-29b. In contrast to the phenotypes induced by miR-29b restoration, Tiam1-induced cell proliferation and migration partly rescued miR-29b-mediated biological behaviors. Our results illustrated that miR-29b as a suppressor has a critical role in CRC progression, which suggests its potential role in the molecular therapy of patients with advanced CRC.

Bortezomib-based chemotherapy regimens can improve response in newly diagnosed multiple myeloma patients with bcl-2 and survivin overexpression

OBJECTIVE

To investigate the relationship between the Bcl-2 and survivin expression and the different regimens therapeutic efficacy newly diagnosed multiple myeloma (NDMM).

METHODS

We retrospectively assessed the association of Bcl-2 and survivin expression with chemotherapeutic efficacy and prognosis in 59 NDMM patients in a single center.

RESULTS

The positive expression rate for survivin and Bcl-2 was 35% and 74%, respectively. Survivin and Bcl-2 protein expression were not associated with clinical stage, suggesting that they are not related to tumor burden in NDMM. Bortezomib-based regimens were more effective in reducing tumor burden and achieving therapeutic (complete and partial) response compared with non-bortezomib-based regimens irrespective of Bcl-2 or survivin expression (P < 0.05). In cases with both negative Bcl-2 and survivin expression (Bcl-2(-)survivin(-)), the response to bortezomib and non-bortezomib-based regimens was similar (p = 0.429). Bcl-2 and survivin expression were not correlated with overall survival (OS); however, Bcl-2-survivin- cases showed a trend towards a longer OS (P = 0.078).

CONCLUSION

We recommend bortezomib-containing regimens for NDMM with single or double-positive Bcl-2 and survivin expression.

Role of H-Ras/ERK signaling in carbon nanotube-induced neoplastic-like transformation of human mesothelial cells

Rapid development and deployment of engineered nanomaterials such as carbon nanotubes (CNTs) in various commercial and biomedical applications have raised concerns about their potential adverse health effects, especially their long-term effects which have not been well addressed. We demonstrated here that prolonged exposure of human mesothelial cells to single-walled CNT (SWCNT) induced neoplastic-like transformation as indicated by anchorage-independent cell growth and increased cell invasiveness. Such transformation was associated with an up-regulation of H-Ras and activation of ERK1/2. Downregulation of H-Ras by siRNA or inactivation of ERK by chemical inhibitor effectively inhibited the aggressive phenotype of SWCNT-exposed cells. Integrin alpha V and cortactin, but not epithelial-mesenchymal transition (EMT) transcriptional regulators, were up-regulated in the SWCNT-exposed cells, suggesting their role in the aggressive phenotype. Cortactin expression was shown to be controlled by the H-Ras/ERK signaling. Thus, our results indicate a novel role of H-Ras/ERK signaling and cortactin in the aggressive transformation of human mesothelial cells by SWCNT.

Nrdp1 inhibits growth of colorectal cancer cells by nuclear retention of p27

The molecular mechanism underlying the proliferation of colorectal cancer (CRC) cells is not completely understood. Here, we found that the level of neuregulin receptor degradation protein-1 (Nrdp1) E3 ubiquitin ligase was significantly decreased in CRC tissues, compared with the adjacent normal tissues from human patients. Knockdown of Nrdp1 enhanced the proliferation of CRC cells, while overexpression of Nrdp1 inhibited the proliferation of CRC cells. Further analysis showed that Nrdp1 may induce degradation of its target ErbB3 to inhibit activation of both ERK/MAPK and PI3K/Akt pathways in CRC cells, which seemed to affect cell proliferation via nuclear retention of a major cell-cycle inhibitor, p27. Taken together, these findings suggest that Nrdp1-mediated ErbB3 degradation suppresses cellular growth of CRC and that Nrdp1 loss in CRC may promote tumor progression, thus highlighting Nrdp1 as a novel target for CRC therapy.

The expression of genes involved in hepatocellular carcinoma chemoresistance is affected by mitochondrial genome depletion

Deletions and mutations in mitochondrial DNA (mtDNA), which are frequent in human tumors, such as hepatocellular carcinoma (HCC), may contribute to enhancing their malignant phenotype. Here we have investigated the effect of mtDNA depletion in the expression of genes accounting for mechanisms of chemoresistance (MOC) in HCC. Using human HCC SK-Hep-1 cells depleted of mtDNA (Rho), changes in gene expression in response to antitumor drugs previously assayed in HCC treatment were analyzed. In Rho cells, a decreased sensitivity to doxorubicin-, SN-38-, cisplatin (CDDP)-, and sorafenib-induced cell death was found. Both constitutive and drug-induced reactive oxygen species generation were decreased. Owing to activation of the NRF2-mediated pathway, MDR1, MRP1, and MRP2 expression was higher in Rho than in wild-type cells. This difference was maintained after further upregulation induced by treatment with doxorubicin, SN-38, or CDDP. Topoisomerase-IIa expression was also enhanced in Rho cells before and after treatment with these drugs. Moreover, the ability of doxorubicin, SN-38 and CDDP to induce proapoptotic signals was weaker in Rho cells, as evidenced by survivin upregulation and reductions in Bax/Bcl-2 expression ratios. Changes in these genes seem to play a minor role in the enhanced resistance of Rho cells to sorafenib, which may be related to an enhanced intracellular ATP content together with the loss of expression of the specific target of sorafenib, tyrosine kinase receptor Kit. In conclusion, these results suggest that mtDNA depletion may activate MOC able to hinder the efficacy of chemotherapy against HCC.

Protein expression of eIF4E and integrin αvβ6 in colon cancer can predict clinical significance, reveal their correlation and imply possible mechanism of interaction

Background

Both eukaryotic translation initiation factor 4E (eIF4E) and integrin αvβ6 play an important role in the development and progression of cancer. The aim of this study was to investigate the expression of eIF4E and Integrin αvβ6, their clinical significance as well as the two proteins’ correlation in colonic carcinoma tissues.

Results

The expression levels of eIF4E and integrin αvβ6 were analyzed in colon cancerous and paraneoplastic tissues of 138 cases via tissue microarray (TMA)- immunohistochemistry. And their clinical significance as well as the two proteins’ correlation was also investigated. The expression of eIF4E was significantly associated with clinical TNM stage (P = 0.009), while T stage (P = 0.011) and TNM stage (P = 0.012) were significantly associated with integrin αvβ6 expression. Moderately weak correlation exists between the two proteins (r =0.299, P <0.001). The survival analysis by Kaplan-Meier and Cox regression model showed that protein expression of high eIF4E and positive integrin αvβ6, as independent prognostic factors (RR = 2.417, P = 0.001 and RR = 2.393, P = 0.001), tended to have a significantly poorer 5-year survival rate (P = 0.013 and 0.025, respectively, the log-rank test).

Conclusion

eIF4E and Integrin αvβ6 were indicators of tumor’s progression and poor prognosis of patients with colon cancer. And the potential signaling loop involving them may provide a helpful therapeutic target in prevention and treatment of colon cancer.

Fragile histidine triad (FHIT) suppresses proliferation and promotes apoptosis in cholangiocarcinoma cells by blocking PI3K-Akt pathway

Fragile histidine triad (FHIT) is a tumor suppressor protein that regulates cancer cell proliferation and apoptosis. However, its exact mechanism of action is poorly understood. Phosphatidylinositol 3-OH kinase (PI3K)-Akt-survivin is an important signaling pathway that was regulated by FHIT in lung cancer cells. To determine whether FHIT can regulate this pathway in cholangiocarcinoma QBC939 cells, we constructed an FHIT expression plasmid and used it to transfect QBC939 cells. Protein and mRNA expression were measured by western blotting and qRT-PCR, respectively. The viability and apoptosis of QBC939 cells were then assessed using MTT assays and flow cytometry. Our results revealed that the expression of survivin and Bcl-2 was downregulated, and caspase 3 was upregulated, in cells overexpressing FHIT. In addition, FHIT suppressed the phosphorylation of Akt. The changes in cell proliferation and apoptosis were obvious in cells overexpressing FHIT which parallels that of treatment with LY294002, a potent inhibitor of phosphoinositide 3-kinases. Treatment with LY294002 further decreased the expression of survivin and Bcl-2 and increased caspase-3 levels. These results suggest that FHIT can block the PI3K-Akt-survivin pathway by suppressing the phosphorylation of Akt and the expression of survivin and Bcl-2 and upregulating caspase 3.

Role of IGF2BP3 in trophoblast cell invasion and migration

The insulin-like growth factor-2 mRNA-binding protein 3 (IGF2BP3) is a member of a highly conserved protein family that is expressed specifically in placenta, testis and various cancers, but is hardly detectable in normal adult tissues. IGF2BP3 has important roles in RNA stabilization and translation, especially during early stages of both human and mouse embryogenesis. Placenta is an indispensable organ in mammalian reproduction that connects developing fetus to the uterine wall, and is responsible for nutrient uptake, waste elimination and gas exchange. Fetus development in the maternal uterine cavity depends on the specialized functional trophoblast. Whether IGF2BP3 plays a role in trophoblast differentiation during placental development has never been examined. The data obtained in this study revealed that IGF2BP3 was highly expressed in human placental villi during early pregnancy, especially in cytotrophoblast cells (CTBs) and trophoblast column, but a much lower level of IGF2BP3 was detected in the third trimester placental villi. Furthermore, the expression level of IGF2BP3 in pre-eclamptic (PE) placentas was significantly lower than the gestational age-matched normal placentas. The role of IGF2BP3 in human trophoblast differentiation was shown by in vitro cell invasion and migration assays and an ex vivo explant culture model. Our data support a role of IGF2BP3 in promoting trophoblast invasion and suggest that abnormal expression of IGF2BP3 might be associated with the etiology of PE.