Targeting Metabolic-Redox Circuits for Cancer Therapy.

Metabolic alterations and elevated levels of reactive oxygen species (ROS) are two characteristics of cancer. The metabolic patterns of cancer cells are elaborately reprogrammed to fulfill the high biomass demands of rapid propagation. ROS, the byproducts of metabolic processes, are accumulated in cancer cells partially due to metabolic abnormalities or oncogenic mutations. To prevent oxidative damage, cancer cells can orchestrate metabolic adaptation to maintain reduction-oxidation (redox) balance by producing reducing equivalents. ROS, acting as second messengers, can in turn manipulate metabolic pathways by directly or indirectly affecting the function of metabolic enzymes. In this review we discuss how cancer cell metabolism and redox signaling are intertwined, with an emphasis on the perspective of targeting metabolic-redox circuits for cancer therapy.

The ROCK-ezrin signaling pathway mediates LPS-induced cytokine production in pulmonary alveolar epithelial cells.

BACKGROUND: Ezrin/radixin/moesin (ERM) proteins are members of the protein 4.1 superfamily and function as linkers that connect the actin cytoskeleton to the plasma membrane of cells. ERM also play critical role in the Lipopolysaccharide (LPS)-induced inflammatory response. However, the signaling mechanisms involved in this process remain unclear. In this study, we aimed to investigate the potential role of the rho-associated coiled-coil containing protein kinase (ROCK) pathway in LPS-induced ezrin phosphorylation and cytokine production in pulmonary alveolar epithelial cells. METHODS: Cultured A549 and HPAEpiC cells were treated with LPS. The expression and localization of ezrin in A549 and HPAEpiC cells were then analyzed by western blotting and immunoflurescence. Activation of RhoA/ROCK was assessed by western blotting and RhoA activity assays. The interaction of ezrin with Syk and myeloid differentiation factor 88 (MyD88)/IL-1R-associated kinase 1 (IRAK-1) was investigated by co-immunoprecipitation. The activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) was measured with electrophoretic mobility shift assays and by western blotting. ELISA and western blotting were performed to detect the levels of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and high mobility group box 1 protein (HMGB1) release into the culture supernatant, and cellular HMGB1 levels. RESULTS: LPS induced ezrin phosphorylation in a concentration- and time-dependent manner. The blockade of RhoA/ROCK inhibited LPS-induced ezrin phosphorylation and its translocation from the cytoplasm to the cell membrane. Co-immunoprecipitation assays further revealed that ezrin associated with Syk constitutively, but only associated with MyD88/IRAK-1 upon LPS challenge. Moreover, LPS-induced p38 and nuclear NF-κB activation was found to be ezrin dependent. The suppression of ezrin by siRNA or the blockade of ROCK activation with Y-27632 reduced the production of TNF-α, IL-1ß, and HMGB1 in response to LPS. CONCLUSIONS: Our findings reveal a novel regulatory mechanism involving ezrin in the LPS-induced production of pro-inflammatory cytokines, and highlight the importance of the RhoA/ROCK-ezrin/Syk-MyD88/IRAK1 axis. Data presented in this manuscript provide novel insights into the signaling pathways activated in pulmonary alveolar epithelial cells by LPS. Video Abstract.

Proline-rich 11 (PRR11) drives F-actin assembly by recruiting the actin-related protein 2/3 complex in human non-small cell lung carcinoma.

The actin cytoskeleton is extremely dynamic and supports diverse cellular functions in many physiological and pathological processes, including tumorigenesis. However, the mechanisms that regulate the actin-related protein 2/3 (ARP2/3) complex and thereby promote actin polymerization and organization in cancer cells are not well-understood. We previously implicated the proline-rich 11 (PRR11) protein in lung cancer development. In this study, using immunofluorescence staining, actin polymerization assays, and siRNA-mediated gene silencing, we uncovered that cytoplasmic PRR11 is involved in F-actin polymerization and organization. We found that dysregulation of PRR11 expression results in F-actin rearrangement and nuclear instability in non-small cell lung cancer cells. Results from molecular mechanistic experiments indicated that PRR11 associates with and recruits the ARP2/3 complex, facilitates F-actin polymerization, and thereby disrupts the F-actin cytoskeleton, leading to abnormal nuclear lamina assembly and chromatin reorganization. Inhibition of the ARP2/3 complex activity abolished irregular F-actin polymerization, lamina assembly, and chromatin reorganization due to PRR11 overexpression. Notably, experiments with truncated PRR11 variants revealed that PRR11 regulates F-actin through different regions. We found that deletion of either the N or C terminus of PRR11 abrogates its effects on F-actin polymerization and nuclear instability and that deletion of amino acid residues 100-184 or 100-200 strongly induces an F-actin structure called the actin comet tail, not observed with WT PRR11. Our findings indicate that cytoplasmic PRR11 plays an essential role in regulating F-actin assembly and nuclear stability by recruiting the ARP2/3 complex in human non-small cell lung carcinoma cells.

Identification and characterization of the promoter of cancer-related gene LOXL2.

Lysyl oxidase like 2, LOXL2, as a member of the lysyl oxidase (LOX) family, has been shown to function similarly to LOX in the extracellular matrix (ECM) by promoting crosslinking of collagen and elastin. LOXL2 is also engaged to transcription regulation, cell signaling transduction and cell adhesion regulation. It has been reported that LOXL2 is highly expressed in several types of tumors and promotes cell proliferation and migration in various cancer cells. However, the regulatory mechanism of LOXL2 expression remains largely unknown. To further investigate its transcriptional regulatory mechanism, LOXL2 promoter region has been cloned and identified in the present study. Chromatin state analysis revealed that LOXL2 gene locus contained an active promoter near its first exon. We then constructed five different LOXL2 gene promoter luciferase reporter constructs covering 1.7 kb upstream of LOXL2 gene transcription initiation site. Series luciferase reporter assay demonstrated that all the five constructs showed notable promoter activity, and LOXL2 core promoter was located in a region of 185 bp near the transcription initiation site. Transcriptional factor binding analysis indicated that, LOXL2 promoter lacked classical TATA box, but contained putative binding sites for classic transcriptional factors such as Sp1 and NF-κB. Ectopic overexpression of Sp1 significantly enhanced LOXL2 promoter activity as well as its endogenous expression in cells. In contrast, mithramycin A (a selective Sp1 inhibitor) treatment repressed LOXL2 promoter as well as its endogenous transcription. Site directed mutagenesis assay further confirmed that the Sp1 binding sites were essential for proximal prompter activity of LOXL2 gene. Chromatin immunoprecipitation (ChIP) assay revealed that Sp1 bound LOXL2 promoter in vivo. Of note, the expression of Sp1 and LOXL2 are positively correlated, and the higher expression of LOXL2 is associated with poor prognosis in colorectal cancer, strongly suggesting the implication of Sp1-mediated LOXL2 transactivation in the pathogenesis of colorectal cancer.

The expression of kappa-opioid receptor promotes the migration of breast cancer cells in vitro.

BACKGROUND: Opioid receptors are implicated in cell proliferation and cancer migration. However, the effects and underlying mechanisms of opioid receptor κ (OPRK1) in breast cancer remain unknown. METHODS: Small interfering RNA (siRNAs) was used to knockdown the expression of OPRK1. Western blot was used to determine the protein expression and reverse transcription-quantitative PCR (RT-qPCR) determined the genes transcription. Cell viability was detected by MTT assay and cell death rates were determined by Annexin V/PI and flow cytometry. Cell migration and invasion were detected by wound healing analysis and transwell assay, respectively. RESULTS: Our research demonstrated that OPRK1 was overexpressed in breast cancer cells compared with the normal human mammary epithelial cells. OPRK1 knockdown could inhibited cell viability and migration in cancer cells, accompanied with the decreased proteins and genes expression of N-cadherin, Snail, MMP2 and Vimentin, while the E-cadherin expression was increased. Additionally, OPRK1 knockdown also promoted PI3K/AKT signaling inactivation. Activation of AKT reversed the OPRK1 knockdown-induced cell viability inhibition and migration suppression, while inhibition of AKT reduced cell viability and promoted cell death. CONCLUSIONS: Our findings illustrated the role of OPRK1 played on promoting migration in vitro, and we also provided the therapeutic research of OPRK1 knockdown combined with AKT inhibition.

Ketoconazole exacerbates mitophagy to induce apoptosis by downregulating cyclooxygenase-2 in hepatocellular carcinoma.

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is a common cancer worldwide and remains a major clinical challenge. Ketoconazole, a traditional antifungal agent, has attracted considerable attention as a therapeutic option for cancer treatment. However, its mechanism of action is still not clearly defined. We aimed to evaluate the effect of ketoconazole on HCC and investigate the underlying mechanisms. METHODS: We examined the antitumor effect of ketoconazole on HCC cells, cell line-derived xenografts, and a patient-derived xenograft (PDX) model. Ketoconazole-induced mitophagy was quantified by immunofluorescence, immunoblotting and transmission electron microscopy analysis. We used mitophagy inhibitors to study the role of mitophagy on HCC cell death induced by ketoconazole. The role of cyclooxygenase-2 (COX-2 [encoded by PTGS2]) on ketoconazole-induced mitophagy was evaluated using gain- and loss-of-function methods. The synergistic effect of ketoconazole with sorafenib on HCC was measured in vivo and in vitro. RESULTS: Ketoconazole stimulated apoptosis in HCC cells by triggering mitophagy in vitro and in vivo. Mechanistically, ketoconazole downregulated COX-2, which led to PINK1 accumulation and subsequent mitochondrial translocation of Parkin (PRKN), and thereby promoted mitophagy-mediated mitochondrial dysfunction. Inhibiting mitophagy alleviated ketoconazole-induced mitochondrial dysfunction and apoptosis, supporting a causal role for mitophagy in the antitumor effect of ketoconazole. In the HCC PDX model, ketoconazole demonstrated a marked antitumor effect characterized by COX-2 downregulation, mitophagy activation, and apoptosis induction. Moreover, ketoconazole acted synergistically with sorafenib to suppress HCC xenograft growth in vivo. CONCLUSION: Our results demonstrate a novel link between ketoconazole and mitophagy machinery, providing preclinical proof of concept for the use of ketoconazole in HCC treatment. LAY SUMMARY: Hepatocellular carcinoma (HCC) is a common malignancy worldwide and remains a major clinical challenge. Our study reveals that ketoconazole, a broad-spectrum antifungal agent, activates PINK1/Parkin-mediated mitophagy by downregulating COX-2, consequently resulting in the acceleration of apoptosis and thereby inhibiting the growth of HCC. Furthermore, ketoconazole acts synergistically with sorafenib in the suppression of HCC growth in vitro and in vivo.

Cell-surface translocation of annexin A2 contributes to bleomycin-induced pulmonary fibrosis by mediating inflammatory response in mice.

Bleomycin, a widely used anti-cancer drug, may give rise to pulmonary fibrosis, a serious side effect which is associated with significant morbidity and mortality. Despite the intensive efforts, the precise pathogenic mechanisms of pulmonary fibrosis still remain to be clarified. Our previous study showed that bleomycin bound directly to annexin A2 (ANXA2, or p36), leading to development of pulmonary fibrosis by impeding transcription factor EB (TFEB)-induced autophagic flux. Here, we demonstrated that ANXA2 also played a critical role in bleomycin-induced inflammation, which represents another major cause of bleomycin-induced pulmonary fibrosis. We found that bleomycin could induce the cell surface translocation of ANXA2 in lung epithelial cells through exosomal secretion, associated with enhanced interaction between ANXA2 and p11. Knockdown of ANXA2 or blocking membrane ANXA2 mitigated bleomycin-induced activation of nuclear factor (NF)-κB pathway and production of pro-inflammatory cytokine IL-6 in lung epithelial cells. ANXA2-deficient (ANXA2-/-) mice treated with bleomycin exhibit reduced pulmonary fibrosis along with decreased cytokine production compared with bleomycin-challenged wild-type mice. Further, the surface ANXA2 inhibitor TM601 could ameliorate fibrotic and inflammatory response in bleomycin-treated mice. Taken together, our results indicated that, in addition to disturbing autophagic flux, ANXA2 can contribute to bleomycin-induced pulmonary fibrosis by mediating inflammatory response.

Redox regulation of inflammation: old elements, a new story.

Inflammation is an essential immune response characterized by pain, swelling, redness, heat, and impaired function. A controlled acute inflammatory response is necessary to fight off infection and overcome injury. However, if the inflammatory process persists and enters into the chronic state, it can lead to local and systemic deleterious effects counterproductive to healing and instead constitutes a new pathology. Typically, inflamed tissues are associated with an elevated level of reactive species (reactive oxygen species (ROS)/reactive nitrogen species (RNS)). These ROS/RNS are generated during the respiratory burst of immune cells and are important factors in defense against invading pathogens. Additionally, reactive species are now known to trigger oxidative/nitrosative modifications of biomolecules. While most of these modifications lead to irreparable damage, some are subtle and fully reversible. The reversible modifications can initiate signaling cascades known as "redox signaling." This redox signaling tightly modulates the inflammatory response. Thus, understanding the complex role of ROS/RNS-induced redox signaling in inflammation will assist in the design of relevant therapeutic intervention strategies for inflammation-associated diseases. This review will highlight the impact of oxidative stress and redox signaling on inflammation and inflammation-associated diseases, with a focus on redox modifications of inflammation-related proteins.

Redox regulation of cancer metastasis: molecular signaling and therapeutic opportunities.

Cancer metastasis is the major cause of cancer-related mortality. Accumulated evidence has shown that high-metastasis potential cancer cells have more reactive oxygen species (ROS) accumulation compared with low-metastasis potential cancer cells. ROS can function as second messengers to regulate multiple cancer metastasis-related signaling pathways via reversible oxidative posttranslational modifications of cysteine in key redox-sensitive proteins, which leads to the structural and functional change of these proteins. Because ROS can promote cancer metastasis, therapeutic strategies aiming at inducing/reducing cellular ROS level or targeting redox sensors involved in metastasis hold great potential in developing new efficient approaches for anticancer therapy. In this review, we summarize recent findings on regulation of tumor metastasis by key redox sensors and describe the potential of targeting redox signaling pathways for cancer therapy.

HIV Infection in gastric epithelial cells.

Many chronic human immunodeficiency virus (HIV) patients suffer from gastric complaints, including gastric tuberculosis and coinfection of other pathogens. Recent work has demonstrated that a variety of nonimmune cells can act as viral reservoirs, even at the early stage of HIV infection. In this study, we detect HIV viral particles, proteins, and nucleic acids in gastric epithelial cells using clinical samples. These observations are further supported by a simian immunodeficiency virus-infected macaque model. Further, the number of HIV-infected gastric epithelial cells is positively associated with blood viral load, and is negatively correlated with CD4 lymphocyte cell counts. We also demonstrate that HIV infection is accompanied by severe inflammatory response in gastric mucosa. Additionally, HIV infection activates signal transducer and activator of transcription 3 and RelA, and enhances the production of interleukin 6 and tumor necrosis factor α in gastric epithelial cells. The present data suggest that the gastric epithelial cells are natural targets of HIV infection, and HIV infection in epithelial cells contributes to HIV-induced gastric mucosal inflammation.

GPR48, a poor prognostic factor, promotes tumor metastasis and activates ß-catenin/TCF signaling in colorectal cancer.

G-protein-coupled receptor 48 (GPR48) is an orphan receptor belonging to the G-protein-coupled receptors family, which plays an important role in the development of various organs and cancer development and progression such as gastric cancer and colorectal cancer (CRC). However, the prognostic value of GPR48 expression in patients with CRC has not been reported. In this study, we observed that GPR48 was overexpressed in primary CRC and metastatic lymph nodes and closely correlated with tumor invasion and metastasis. Multivariate analysis indicated that high GPR48 expression was a poor prognostic factor for overall survival in CRC patients. In vitro and in vivo assays demonstrated that enforced expression of GPR48 contributed to enhance migration and invasion of cancer cells and tumor metastasis. In addition, we found that GPR48 increased nuclear ß-catenin accumulation, T-cell factor 4 (TCF4) transcription activity, and expression of its target genes including Cyclin D1 and c-Myc in CRC cells. Correlation analysis showed that GPR48 expression in CRC tissues was positively associated with ß-catenin expression. Upregulation of GPR48 resulted in increased phosphorylation of glycogen synthase kinase 3ß, Akt and extracellular signal-regulated kinase 1/2 (ERK1/2) in CRC cells, while inhibition of PI3K/Akt and mitogen-activated protein kinase /ERK1/2 pathways was sufficient to abolish the effect of GPR48 on ß-catenin/TCF signaling. Taken together, GPR48 could serve as both a prognostic biomarker and a therapeutic target for resectable CRC patients.

Chemokine CXCL14 is associated with prognosis in patients with colorectal carcinoma after curative resection.

BACKGROUND: The chemokine CXCL14 has been reported to play an important role in the progression of many malignancies such as breast cancer and papillary thyroid carcinoma, but the role of CXCL14 in colorectal carcinoma (CRC) remains to be established. The purpose of this study was to investigate the expression pattern and significance of CXCL14 in CRC progression. METHOD: 265 colorectal carcinoma specimens and 129 matched adjacent normal colorectal mucosa specimens were collected. Expression of CXCL14 in clinical samples was examined by immunostaining. The effect of CXCL14 on colorectal carcinoma cell proliferation was measured by MTT assay, BrdU incorporation assay and colony formation assay. The impact of CXCL14 on migration and invasion of colorectal carcinoma cells was determined by transwell assay and Matrigel invasion assay, respectively. RESULTS: CXCL14 expression was significantly up-regulated in tumor tissues compared with adjacent nontumorous mucosa tissues (P < 0.001). Tumoral CXCL14 expression levels were significantly correlated with TNM (Tumor-node-metastasis) stage, histodifferentiation, and tumor size. In multivariate Cox regression analysis, high CXCL14 expression in tumor specimens (n = 91) from stage I/II patients was associated with increased risk for disease recurrence (risk ratio, 2.92; 95% CI, 1.15-7.40; P = 0.024). Elevated CXCL14 expression in tumor specimens (n = 135) from stage III/IV patients correlated with worse overall survival (risk ratio, 3.087; 95% CI, 1.866-5.107; P < 0.001). Functional studies demonstrated that enforced expression of CXCL14 in SW620 colorectal carcinoma cells resulted in more aggressive phenotypes. In contrast, knockdown of CXCL14 expression could mitigate the proliferative, migratory and invasive potential of HCT116 colorectal carcinoma cells. CONCLUSION: Taken together, CXCL14 might be a potential novel prognostic factor to predict the disease recurrence and overall survival and could be a potential target of postoperative adjuvant therapy in CRC patients.

Proteomics identification of ITGB3 as a key regulator in reactive oxygen species-induced migration and invasion of colorectal cancer cells.

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and second in females worldwide. Unfortunately 40-50% of patients already have metastatic disease at presentation when prognosis is poor with a 5-year survival of <10%. Reactive oxygen species (ROS) have been proposed to play a crucial role in tumor metastasis. We now show that higher levels of ROS accumulation are found in a colorectal cancer-derived metastatic cell line (SW620) compared with a cell line (SW480) derived from the primary lesion from the same patient. In addition, ROS accumulation can affect both the migratory and invasive capacity of SW480 and SW620 cells. To explore the molecular mechanism underlying ROS-induced migration and invasion in CRC, we have compared protein expression patterns between SW480 and SW620 cells using a two-dimensional electrophoresis-based proteomics strategy. A total of 63 altered proteins were identified from tandem MS analysis. Cluster analysis revealed dysregulated expression of multiple redox regulative or ROS responsive proteins, implicating their functional roles in colorectal cancer metastasis. Molecular and pathological validation demonstrated that altered expression of PGAM1, GRB2, DJ-1, ITGB3, SOD-1, and STMN1 was closely correlated with the metastatic potential of CRC. Functional studies showed that ROS markedly up-regulated expression of ITGB3, which in turn promoted an aggressive phenotype in SW480 cells, with concomitant up-regulated expression of STMN1. In contrast, knockdown of ITGB3 expression could mitigate the migratory and invasive potential of SW620 or H(2)O(2)-treated SW480 cells, accompanied by down-regulated expression of STMN1. The function of ITGB3 was dependent on the surface expression of integrin αvß3 heterodimer. Furthermore, STMN1 expression and the PI3K-Akt-mTOR pathway were found to be involved in ROS-induced and ITGB3-mediated migration and invasion of colorectal cancer cells. Taken together, these studies suggest that ITGB3 plays an important role in ROS-induced migration and invasion in CRC.

rRNA-Derived Small RNA rsRNA-28S Regulates the Chemoresistance of Prostate Cancer Cells by Targeting PTGIS.

BACKGROUND: rRNA-derived small RNAs (rsRNAs) represent a novel class of small non-coding RNAs (sncRNAs), produced by the specific cleavage of rRNAs; however, their roles in tumor development are unclear. In the present study, we explored the effect of a kind of rsRNA-28S, which originates from 28S rRNA, on the chemoresistance of prostate cancer cells and the mechanisms underlying its effect. METHODS: Quantitative reverse transcription PCR (RT-PCR) was performed to quantify rsRNA-28S levels in serum samples taken from prostate cancer patients. DU-145R cells, which are resistant to both paclitaxel and docetaxel, were generated from parental DU-145 cells. Northern blot was conducted to detect cellular rsRNA-28S levels following drug treatments. To verify the effect of rsRNAs-28S on chemoresistance, antisense oligonucleotides were utilized to block rsRNA-28S functions, and a series of assays were further performed, such as cell viability, cell proliferation, colony formation and tumor sphere formation. The target gene of rsRNA-28S was explored using dual-luciferase reporter gene assay. RESULTS: The rsRNA-28S level was reduced in the serum samples of patients who received chemotherapy compared to that of patients who did not. Furthermore, the rsRNA-28S level was remarkably declined in DU-145R cells, and drug treatments decreased the levels of rsRNA-28S in DU-145 and DU-145R cells. Moreover, rsRNA-28S inhibition enhanced the chemoresistance of prostate cancer cells as well as their cancer stem cell characteristics. Mechanistically, the prostaglandin I2 synthase (PTGIS) gene transcript was verified as a target of rsRNA-28S, as rsRNA-28S inhibited the translation of PTGIS mRNA by directly binding the 3' untranslated region of PTGIS mRNA. rsRNA-28S inhibition was also found to increase PTGIS abundance, and PTGIS overexpression significantly enhanced prostate cancer cell chemoresistance. CONCLUSIONS: Our findings indicate that rsRNA-28S attenuates prostate cancer cell chemoresistance by downregulating its target gene PTGIS. This study not only greatly contributes to systematic identification and functional elucidation of chemoresistance relevant rsRNAs, but also promotes rsRNA-included combinatorial therapeutic regimens for cancer.

Ciclopirox Olamine Induces Proliferation Inhibition and Protective Autophagy in Hepatocellular Carcinoma.

Hepatocellular carcinoma is one of the most common fatal malignancies worldwide. Thus far, the hepatocellular carcinoma prognosis has been bleak due to deficiencies in the identification and diagnosis of early hepatocellular carcinoma. Ciclopirox olamine (CPX) is a synthetic antifungal agent and has been considered as an anti-cancer candidate drug recently, though the detailed mechanisms related to its anti-cancer effect in hepatocellular carcinoma have not yet been revealed. Here, we found that CPX could inhibit proliferation in HCC cells but not in intrahepatic cholangiocarcinoma cells by arresting the cell cycle. Moreover, the anti-cancer effects of CPX in HCC cells were also attributed to CPX-triggered ROS accumulation and DJ-1 downregulation. Additionally, CPX could promote complete autophagic flux, which alleviated the anti-cancer effect of CPX in HCC cells, whereas the ROS scavenger (NAC) would attenuate CPX-induced protective autophagy. Interestingly, CPX could also induce glycogen clustering in HCC cells. Altogether, this study provides a new insight into the detailed molecular mechanisms of CPX as an anti-cancer therapy and a strategy for treating hepatocellular carcinoma.

Transfer RNA-derived small RNAs (tsRNAs): Versatile regulators in cancer.

tRNA-derived small RNAs (tsRNAs) represent a novel class of regulatory small non-coding RNAs (sncRNAs), produced by the specific cleavage of transfer RNAs (tRNAs). In recent years, pilot studies one after the other have uncovered the critical roles of tsRNAs in various fundamental biological processes as well as in the development of human diseases including cancer. Based on the newly updated hallmarks of cancer, we provide a comprehensive review regarding the dysregulation, functional implications and complicated molecular mechanisms of tsRNAs in cancer. In addition, the potential technical challenges and future prospects in the fields of tsRNA research are discussed in this review.

PRR11 induces filopodia formation and promotes cell motility via recruiting ARP2/3 complex in non-small cell lung cancer cells.

Filopodia, a finger-like structure and actin-rich plasma-membrane protrusion at the leading edge of the cell, has important roles in cell motility. However, the mechanisms of filopodia generation are not well-understood via the actin-related protein 2/3 (ARP2/3) complex in Non-Small Cell Lung Cancer (NSCLC) cells. We previously have demonstrated that PRR11 associates with the ARP2/3 complex to regulate cytoskeleton-nucleoskeleton assembly and chromatin remodeling. In this study, we further demonstrate that PRR11 involves in filopodia formation, focal adhesion turnover and cell motility through ARP2/3 complex. Cell phenotype assays revealed that the silencing of PRR11 increased cellular size and inhibited cell motility in NSCLC cells. Mechanistically, PRR11 recruited and co-localized with Arp2 at the membrane protrusion to promote filopodia formation but not lamellipodia formation. Notably, PRR11 mutant deletion of the proline-rich region 2 (amino acid residues 185-200) abrogated the effect of filopodia formation. In addition, PRR11-depletion inhibited filopodial actin filaments assembly and increased the level of active integrin ß1 in the cell surface, whereas reduced the phosphorylation level of focal adhesion kinase (FAKY397) to repress focal adhesion turnover and cell motility in NSCLC cells. Taken together, our findings indicate that PRR11 has critical roles in controlling filopodia formation, focal adhesion turnover and cell motility by recruiting ARP2/3 complex, thus dysregualted expression of PRR11 potentially facilitates tumor metastasis in NSCLC cells.

ROS generation attenuates the anti-cancer effect of CPX on cervical cancer cells by inducing autophagy and inhibiting glycophagy.

Cervical cancer is one of the most common gynecological malignancies with poor prognosis due to constant chemoresistance and repeated relapse. Ciclopirox olamine (CPX), a synthetic antifungal agent, has recently been identified to be a promising anti-cancer candidate. However, the detailed mechanisms related to its anti-cancer effects remain unclear and need to be further elucidated. In this study, we found that CPX could induce proliferation inhibition in cervical cancer cells by targeting PARK7. Further results demonstrated that CPX could induce cytoprotective autophagy by downregulating the expression of PARK7 to activate PRKAA1 or by PARK7-independent accumulation of ROS to inhibit mTOR signaling. Meanwhile, CPX treatment increased the glycogen clustering and glycophagy in cervical cancer cells. The presence of N-acetyl-l-cysteine (NAC), a ROS scavenger, led to further clustering of glycogen in cells by reducing autophagy and enhancing glycophagy, which promoted CPX-induced inhibition of cervical cancer cell proliferation. Together, our study provides new insights into the molecular mechanisms of CPX in the anti-cancer therapy and opens new avenues for the glycophagy in cancer therapeutics.

Mechanism of cancer cell adaptation to metabolic stress: proteomics identification of a novel thyroid hormone-mediated gastric carcinogenic signaling pathway.

Gastric cancer is the second most common cancer worldwide and has a poor prognosis. To determine the mechanism of adaptation to metabolic stress in cancer cells, we used gastric cancer as a model system to reveal the potential signaling pathways involved. Two-dimensional polyacrylamide gel electrophoresis coupled with ESI-Q-TOF MS/MS analysis was used to identify differentially expressed proteins between gastric tumor tissues and the corresponding noncancerous tissues. In total, 107 spots with significant alteration (+/-over 2-fold, p < 0.05) were positively identified by MS/MS analysis. Altered expression of representative proteins was validated by RT-PCR and Western blotting. Cluster analysis of the changed proteins revealed an interesting group of metabolic proteins, which suggested accumulation of triiodothyronine (T(3); the major functional component of thyroid hormone) and overexpression of hypoxia-induced factor (HIF) in gastric carcinoma. These observations were further confirmed by electrochemiluminescence immunoassay and immunohistochemistry. T(3)-induced expression of HIF1-alpha and vascular endothelial growth factor was further verified using a gastric cancer cell line and in vivo mouse model. Because the early accumulation of HIF1-alpha was found to be independent of de novo transcription, we also found that the cytosolic cascade phosphatidylinositol 3-kinase/Akt pathway sensitive to T(3) stimulus was involved. Furthermore we demonstrated that T(3)-induced overexpression of HIF1-alpha was mediated by fumarate accumulation and could be enhanced by fumarate hydratase inactivation but inhibited by 2-oxoglutarate. These results provide evidence for alteration of metabolic proteins and dysfunction of thyroid hormone regulation in gastric tumors, and a novel thyroid hormone-mediated tumorigenic signaling pathway is proposed. Our findings are considered a significant step toward a better understanding of adaptations to metabolic stress in gastric carcinogenesis.

B-Myb accelerates colorectal cancer progression through reciprocal feed-forward transactivation of E2F2.

B-Myb is an important transcription factor that plays a critical role in gene expression regulation and tumorigenesis. However, its functional implication in colorectal cancer remains elusive. In this study, we found that B-Myb was significantly upregulated at both mRNA and protein levels in colorectal cancer samples compared to non-tumor counterparts. B-Myb overexpression accelerated cell proliferation, cell cycle progression and cell motility in colorectal cancer cells, and promoted tumor growth in orthotopic nude mouse models in vivo. In contrast, B-Myb depletion inhibited these malignant phenotypes. Mechanistic investigations revealed that E2F2 was a novel transcriptional target of B-Myb and is essential to B-Myb-induced malignant phenotypes. Notably, B-Myb and E2F2 exhibited positive expression correlation, and interacted with each other in colorectal cancer cells. In addition to their autoregulatory mechanisms, B-Myb and E2F2 can also directly transactivate each other, thus constituting consolidated reciprocal feed-forward transactivation loops. Moreover, both B-Myb and E2F2 are required for the activation of ERK and AKT signaling pathways in colorectal cancer cells. Taken together, our data clarified a critical role for B-Myb in colorectal cancer and unraveled an exquisite mutual collaboration and reciprocal cross regulation between B-Myb and E2F2 that contribute to the malignant progression of human colorectal cancer.