Antitumor Effect of Regorafenib on MicroRNA Expression in Hepatocellular Carcinoma Cell Lines

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and is one of the leading causes of cancer-related deaths worldwide. Regorafenib, a multi-kinase inhibitor, is used as a second-line treatment for advanced HCC. Here, we aimed to investigate the mechanism of the antitumor effect of regorafenib on HCC and evaluate altered microRNA (miRNA) expression. Cell proliferation was examined in six HCC cell lines (HuH-7, HepG2, HLF, PLC/PRF/5, Hep3B, and Li-7) using the Cell Counting Kit-8 assay. Xenografted mouse models were used to assess the effects of regorafenib in vivo. Cell cycle analysis, western blotting analysis, and miRNA expression analysis were performed to identify the antitumor inhibitory potential of regorafenib on HCC cells. Regorafenib suppressed proliferation in HuH-7 cell and induced G0/G1 cell cycle arrest and cyclin D1 downregulation in regorafenib-sensitive cells. During miRNA analysis, miRNA molecules associated with the antitumor effect of regorafenib were found. Regorafenib suppresses cell proliferation and tumor growth in HCC by decreasing cyclin D1 via alterations in intracellular and exosomal miRNAs in HCC.

Chemopreventive effects of pterostilbene through p53 and cell cycle in mouse lung of squamous cell carcinoma model

Cell proliferation and cell death abnormalities are strongly linked to the development of cancer, including lung cancer. The purpose of this study was to investigate the effect of pterostilbene on cell proliferation and cell death via cell cycle arrest during the transition from G1 to S phase and the p53 pathway. A total of 24 female Balb/C mice were randomly categorized into four groups (n = 6): N-nitroso-tris-chloroethyl urea (NTCU) induced SCC of the lungs, vehicle control, low dose of 10 mg/kg PS + NTCU (PS10), and high dose of 50 mg/kg PS + NTCU (PS50). At week 26, all lungs were harvested for immunohistochemistry and Western blotting analysis. Ki-67 expression is significantly lower, while caspase-3 expression is significantly higher in PS10 and PS50 as compared to the NTCU (p < 0.05). There was a significant decrease in cyclin D1 and cyclin E2 protein expression in PS10 and PS50 when compared to the NTCU (p < 0.05). PS50 significantly increased p53, p21, and p27 protein expression when compared to NTCU (p < 0.05). Pterostilbene is a potential chemoprevention agent for lung SCC as it has the ability to upregulate the p53/p21 pathway, causing cell cycle arrest.

Transcription-coupled structural dynamics of topologically associating domains regulate replication origin efficiency

BACKGROUND

Metazoan cells only utilize a small subset of the potential DNA replication origins to duplicate the whole genome in each cell cycle. Origin choice is linked to cell growth, differentiation, and replication stress. Although various genetic and epigenetic signatures have been linked to the replication efficiency of origins, there is no consensus on how the selection of origins is determined.

RESULTS

We apply dual-color stochastic optical reconstruction microscopy (STORM) super-resolution imaging to map the spatial distribution of origins within individual topologically associating domains (TADs). We find that multiple replication origins initiate separately at the spatial boundary of a TAD at the beginning of the S phase. Intriguingly, while both high-efficiency and low-efficiency origins are distributed homogeneously in the TAD during the G1 phase, high-efficiency origins relocate to the TAD periphery before the S phase. Origin relocalization is dependent on both transcription and CTCF-mediated chromatin structure. Further, we observe that the replication machinery protein PCNA forms immobile clusters around TADs at the G1/S transition, explaining why origins at the TAD periphery are preferentially fired.

CONCLUSION

Our work reveals a new origin selection mechanism that the replication efficiency of origins is determined by their physical distribution in the chromatin domain, which undergoes a transcription-dependent structural re-organization process. Our model explains the complex links between replication origin efficiency and many genetic and epigenetic signatures that mark active transcription. The coordination between DNA replication, transcription, and chromatin organization inside individual TADs also provides new insights into the biological functions of sub-domain chromatin structural dynamics.

PARP14 regulates cyclin D1 expression to promote cell-cycle progression

Cyclin D1 is an essential regulator of the G1-S cell-cycle transition and is overexpressed in many cancers. Expression of cyclin D1 is under tight cellular regulation that is controlled by many signaling pathways. Here we report that PARP14, a member of the poly(ADP-ribose) polymerase (PARP) family, is a regulator of cyclin D1 expression. Depletion of PARP14 leads to decreased cyclin D1 protein levels. In cells with a functional retinoblastoma (RB) protein pathway, this results in G1 cell-cycle arrest and reduced proliferation. Mechanistically, we found that PARP14 controls cyclin D1 mRNA levels. Using luciferase assays, we show that PARP14 specifically regulates cyclin D1 3'UTR mRNA stability. Finally, we also provide evidence that G1 arrest in PARP14-depleted cells is dependent on an intact p53-p21 pathway. Our work uncovers a new role for PARP14 in promoting cell-cycle progression through both cyclin D1 and the p53 pathway.

Momordin Ic induces G0/1 phase arrest and apoptosis in colon cancer cells by suppressing SENP1/c-MYC signaling pathway

Momordin Ic (MI) is a natural pentacyclic triterpenoid enriched in various Chinese natural medicines such as the fruit of Kochia scoparia (L.) Schrad. Studies have shown that MI presents antitumor properties in liver and prostate cancers. However, the activity and potential mechanisms of MI against colorectal cancer remain elusive. Here, we showed that MI inhibited cell proliferation with G0/1 phase cell cycle arrest in colon cancer cells. Moreover, it was observed that MI increased apoptosis compared to untreated cells. Further investigation showed that the SUMOylation of c-Myc was enhanced by MI and led to the down-regulated protein level of c-Myc, which is involved in regulating cell proliferation and apoptosis. SENP1 has been demonstrated to be critical for the SUMOylation of c-Myc. Meanwhile, knockdown of SENP1 by siRNA abolished the effects of MI on c-Myc level and cell viability in colon cancer cells. Together, these results revealed that MI exerted an anti-tumor activity in colon cancer cells via SENP1/c-Myc signaling pathway. These finding provide an insight into the potential of MI for colon cancer therapy.

Lamin B1 acetylation slows the G1 to S cell cycle transition through inhibition of DNA repair

The integrity and regulation of the nuclear lamina is essential for nuclear organization and chromatin stability, with its dysregulation being linked to laminopathy diseases and cancer. Although numerous posttranslational modifications have been identified on lamins, few have been ascribed a regulatory function. Here, we establish that lamin B1 (LMNB1) acetylation at K134 is a molecular toggle that controls nuclear periphery stability, cell cycle progression, and DNA repair. LMNB1 acetylation prevents lamina disruption during herpesvirus type 1 (HSV-1) infection, thereby inhibiting virus production. We also demonstrate the broad impact of this site on laminar processes in uninfected cells. LMNB1 acetylation negatively regulates canonical nonhomologous end joining by impairing the recruitment of 53BP1 to damaged DNA. This defect causes a delay in DNA damage resolution and a persistent activation of the G1/S checkpoint. Altogether, we reveal LMNB1 acetylation as a mechanism for controlling DNA repair pathway choice and stabilizing the nuclear periphery.

ZNF674-AS1 antagonizes miR-423-3p to induce G0/G1 cell cycle arrest in non-small cell lung cancer cells

BACKGROUND

ZNF674-AS1, a recently characterized long noncoding RNA, shows prognostic significance in hepatocellular carcinoma and glioma. However, the expression and function of ZNF674-AS1 in non-small cell lung cancer (NSCLC) are unclear.

METHODS

In this work, we investigated the expression of ZNF674-AS1 in 83 pairs of NSCLC specimens and adjacent noncancerous lung tissues. The clinical significance of ZNF674-AS1 in NSCLC was analyzed. The role of ZNF674-AS1 in NSCLC growth and cell cycle progression was explored.

RESULTS

Our data show that ZNF674-AS1 expression is decreased in NSCLC compared to normal tissues. ZNF674-AS1 downregulation is significantly correlated with advanced TNM stage and decreased overall survival of NSCLC patients. Overexpression of ZNF674-AS1 inhibits NSCLC cell proliferation, colony formation, and tumorigenesis, which is accompanied by a G0/G1 cell cycle arrest. Conversely, knockdown of ZNF674-AS1 enhances the proliferation and colony formation of NSCLC cells. Biochemically, ZNF674-AS1 overexpression increases the expression of p21 through downregulation of miR-423-3p. Knockdown of p21 or overexpression of miR-423-3p blocks ZNF674-AS1-mediated growth suppression and G0/G1 cell cycle arrest. In addition, ZNF674-AS1 expression is negatively correlated with miR-423-3p in NSCLC specimens.

CONCLUSIONS

ZNF674-AS1 suppresses NSCLC growth by downregulating miR-423-3p and inducing p21. This work suggests the therapeutic potential of ZNF674-AS1 in the treatment of NSCLC.

Overexpressed CA12 has prognostic value in pancreatic cancer and promotes tumor cell apoptosis via NF-κB signaling

INTRODUCTION

Pancreatic adenocarcinoma (PAAD) is among the deadliest forms of cancer globally. Carbonic anhydrase 12 (CA12) is known to play central roles in regulating many cancers, but its function in the context of PAAD is rarely discussed. This study was, therefore, designed to assess the expression of CA12 in PAAD and to explore its underlying mechanistic role in this cancer type.

METHODS

Immunohistochemical staining was used to measure CA12 expression in PAAD samples. The functionality of pancreatic cancer cells expressing varying levels of CA12 was assessed through wound healing, Transwell, and CCK-8 assays. In addition, flow cytometry was used to measure apoptosis and cell cycle progression in these same cells, while Western blotting was used to analyze the expression of proteins associated with the NF-κB signaling pathway.

RESULTS

PAAD tissue samples exhibited significant CA12 downregulation (P < 0.001), and lower CA12 expression was, in turn, associated with poorer overall survival (P < 0.001). CA12 overexpression significantly impaired the proliferation of PAAD cell lines, instead inducing their apoptotic death and G0/G1 phase cell cycle arrest (P < 0.05). We additionally found that CA12 may exert its tumor suppressive roles via modulating the NF-κB signaling pathway.

CONCLUSION

These results indicate that CA12 functions as a tumor suppressor in PAAD and may thus be a novel therapeutic target that can be used to guide PAAD patient treatment.

Upregulation of Metallothionein-1G Accelerates G1/S Transition in the Growth Phase of Acute Promyelocytic Leukemia NB4 Cells

Downregulation of the myeloid master regulator Spi1/PU.1 plays a pivotal role in leukemogenesis, and we previously showed that Spi1/PU.1 directly represses metallothionein (MT)-1G through the epigenetic activity of PU.1. Furthermore, we recently demonstrated that overexpression of MT-1G inhibits retinoic acid-induced differentiation of acute promyelocytic leukemia NB4 cells. As PU.1 is a master regulator of growth and differentiation in myeloid cells, we examined its effects on cell proliferation of MT-1G-overexpressing NB4 (NB4MTOE) cells in the present study. Although there were no significant differences in total viable cell numbers between NB4MTOE cells and control cells during the time course examined, the proportion of S-phase cells was obviously increased in all NB4MTOE cells at 16-24 h after serum stimulation. Consistent with these findings, real-time PCR analyses revealed marked increases in the expression of cyclin E (G1/S-phase cyclin) and cyclin A (S-phase cyclin) in NB4MTOE cells during the same time period. Furthermore, NB4MTOE cells were significantly resistant to cytosine arabinoside (Ara-C), an S-phase-specific chemotherapeutic drug. Collectively, these findings suggest a role for MT-1G in G1/S transition during the growth phase of NB4 cells.

Lysine 164 is critical for SARS-CoV-2 Nsp1 inhibition of host gene expression

The emerging pathogen severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused social and economic disruption worldwide, infecting over 9.0 million people and killing over 469 000 by 24 June 2020. Unfortunately, no vaccine or antiviral drug that completely eliminates the transmissible disease coronavirus disease 2019 (COVID-19) has been developed to date. Given that coronavirus nonstructural protein 1 (nsp1) is a good target for attenuated vaccines, it is of great significance to explore the detailed characteristics of SARS-CoV-2 nsp1. Here, we first confirmed that SARS-CoV-2 nsp1 had a conserved function similar to that of SARS-CoV nsp1 in inhibiting host-protein synthesis and showed greater inhibition efficiency, as revealed by ribopuromycylation and Renilla luciferase (Rluc) reporter assays. Specifically, bioinformatics and biochemical experiments showed that by interacting with 40S ribosomal subunit, the lysine located at amino acid 164 (K164) was the key residue that enabled SARS-CoV-2 nsp1 to suppress host gene expression. Furthermore, as an inhibitor of host-protein expression, SARS-CoV-2 nsp1 contributed to cell-cycle arrest in G0/G1 phase, which might provide a favourable environment for virus production. Taken together, this research uncovered the detailed mechanism by which SARS-CoV-2 nsp1 K164 inhibited host gene expression, laying the foundation for the development of attenuated vaccines based on nsp1 modification.

The Insulin Receptor Adaptor IRS2 is an APC/C Substrate That Promotes Cell Cycle Protein Expression and a Robust Spindle Assembly Checkpoint

Insulin receptor substrate 2 (IRS2) is an essential adaptor that mediates signaling downstream of the insulin receptor and other receptor tyrosine kinases. Transduction through IRS2-dependent pathways is important for coordinating metabolic homeostasis, and dysregulation of IRS2 causes systemic insulin signaling defects. Despite the importance of maintaining proper IRS2 abundance, little is known about what factors mediate its protein stability. We conducted an unbiased proteomic screen to uncover novel substrates of the Anaphase Promoting Complex/Cyclosome (APC/C), a ubiquitin ligase that controls the abundance of key cell cycle regulators. We found that IRS2 levels are regulated by APC/C activity and that IRS2 is a direct APC/C target in G1 Consistent with the APC/C's role in degrading cell cycle regulators, quantitative proteomic analysis of IRS2-null cells revealed a deficiency in proteins involved in cell cycle progression. We further show that cells lacking IRS2 display a weakened spindle assembly checkpoint in cells treated with microtubule inhibitors. Together, these findings reveal a new pathway for IRS2 turnover and indicate that IRS2 is a component of the cell cycle control system in addition to acting as an essential metabolic regulator.

RASA1 inhibits the progression of renal cell carcinoma by decreasing the expression of miR-223-3p and promoting the expression of FBXW7

RAS p21 protein activator 1 (RASA1), also known as p120-RasGAP, is a RasGAP protein that functions as a signaling scaffold protein, regulating pivotal signal cascades. However, its biological mechanism in renal cell carcinoma (RCC) remains unknown. In the present study, RASA1, F-box/WD repeat-containing protein 7 (FBXW7), and miR-223-3p expression were assessed via quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. Then, the targeted correlations of miR-223-3p with FBXW7 and RASA1 were verified via a dual-luciferase reporter gene assay. CCK-8, flow cytometry, and Transwell assays were implemented independently to explore the impact of RASA1 on cell proliferation, apoptosis, migration, and cell cycle progression. Finally, the influence of RASA1 on tumor formation in RCC was assessed in vivo through the analysis of tumor growth in nude mice. Results showed that FBXW7 and RASA1 expression were decreased in RCC tissues and cell lines, while miR-223-3p was expressed at a higher level. Additionally, FBXW7 and RASA1 inhibited cell proliferation but facilitated the population of RCC cells in the G0/G1 phase. Altogether, RASA1 may play a key role in the progression of RCC by decreasing miR-223-3p and subsequently increasing FBXW7 expression.

Loss of ZC4H2 and RNF220 Inhibits Neural Stem Cell Proliferation and Promotes Neuronal Differentiation

The ubiquitin E3 ligase RNF220 and its co-factor ZC4H2 are required for multiple neural developmental processes through different targets, including spinal cord patterning and the development of the cerebellum and the locus coeruleus. Here, we explored the effects of loss of ZC4H2 and RNF220 on the proliferation and differentiation of neural stem cells (NSCs) derived from mouse embryonic cortex. We showed that loss of either ZC4H2 or RNF220 inhibits the proliferation and promotes the differentiation abilities of NSCs in vitro. RNA-Seq profiling revealed 132 and 433 differentially expressed genes in the ZC4H2^−/− and RNF220^−/− NSCs, compared to wild type (WT) NSCs, respectively. Specifically, Cend1, a key regulator of cell cycle exit and differentiation of neuronal precursors, was found to be upregulated in both ZC4H2^−/− and RNF220^−/− NSCs at the mRNA and protein levels. The targets of Cend1, such as CyclinD1, Notch1 and Hes1, were downregulated both in ZC4H2^−/− and RNF220^−/− NSCs, whereas p53 and p21 were elevated. ZC4H2^−/− and RNF220^−/− NSCs showed G0/G1 phase arrest compared to WT NSCs in cell cycle analysis. These results suggested that ZC4H2 and RNF220 are likely involved in the regulation of neural stem cell proliferation and differentiation through Cend1.

Genome Maintenance by DNA Helicase B

DNA Helicase B (HELB) is a conserved helicase in higher eukaryotes with roles in the initiation of DNA replication and in the DNA damage and replication stress responses. HELB is a predominately nuclear protein in G1 phase where it is involved in initiation of DNA replication through interactions with DNA topoisomerase 2-binding protein 1 (TOPBP1), cell division control protein 45 (CDC45), and DNA polymerase α-primase. HELB also inhibits homologous recombination by reducing long-range end resection. After phosphorylation by cyclin-dependent kinase 2 (CDK2) at the G1 to S transition, HELB is predominately localized to the cytosol. However, this cytosolic localization in S phase is not exclusive. HELB has been reported to localize to chromatin in response to replication stress and to localize to the common fragile sites 16D (FRA16D) and 3B (FRA3B) and the rare fragile site XA (FRAXA) in S phase. In addition, HELB is phosphorylated in response to ionizing radiation and has been shown to localize to chromatin in response to various types of DNA damage, suggesting it has a role in the DNA damage response.

Broussoflavonol B from Broussonetia kazinoki Siebold Exerts Anti-Pancreatic Cancer Activity through Downregulating FoxM1

Pancreatic cancer has a high mortality rate due to poor rates of early diagnosis. One tumor suppressor gene in particular, p53, is frequently mutated in pancreatic cancer, and mutations in p53 can inactivate normal wild type p53 activity and increase expression of transcription factor forkhead box M1 (FoxM1). Overexpression of FoxM1 accelerates cellular proliferation and cancer progression. Therefore, inhibition of FoxM1 represents a therapeutic strategy for treating pancreatic cancer. Broussoflavonol B (BF-B), isolated from the stem bark of Broussonetia kazinoki Siebold has previously been shown to inhibit the growth of breast cancer cells. This study aimed to investigate whether BF-B exhibits anti-pancreatic cancer activity and if so, identify the underlying mechanism. BF-B reduced cell proliferation, induced cell cycle arrest, and inhibited cell migration and invasion of human pancreatic cancer PANC-1 cells (p53 mutated). Interestingly, BF-B down-regulated FoxM1 expression at both the mRNA and protein level. It also suppressed the expression of FoxM1 downstream target genes, such as cyclin D1, cyclin B1, and survivin. Cell cycle analysis showed that BF-B induced the arrest of G0/G1 phase. BF-B reduced the phosphorylation of extracellular signal-regulated kinase ½ (ERK½) and expression of ERK½ downstream effector c-Myc, which regulates cell proliferation. Furthermore, BF-B inhibited cell migration and invasion, which are downstream functional properties of FoxM1. These results suggested that BF-B could repress pancreatic cancer cell proliferation by inactivation of the ERK/c-Myc/FoxM1 signaling pathway. Broussoflavonol B from Broussonetia kazinoki Siebold may represent a novel chemo-therapeutic agent for pancreatic cancer.

Trichothecin Inhibits Cancer-Related Features in Colorectal Cancer Development by Targeting STAT3

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that contributes to cancer progression through multiple processes of cancer development, which makes it an attractive target for cancer therapy. The IL-6/STAT3 pathway is associated with an advanced stage in colorectal cancer patients. In this study, we identified trichothecin (TCN) as a novel STAT3 inhibitor. TCN was found to bind to the SH2 domain of STAT3 and inhibit STAT3 activation and dimerization, thereby blocking STAT3 nuclear translocation and transcriptional activity. TCN did not affect phosphorylation levels of STAT1. TCN significantly inhibited cell growth, arrested cell cycle at the G0/G1 phase, and induced apoptosis in HCT 116 cells. In addition, the capacities of colony formation, migration, and invasion of HCT 116 cells were impaired upon exposure to TCN with or without IL-6 stimulation. In addition, TCN treatment abolished the tube formation of HUVEC cells in vitro. Taken together, these results highlight that TCN inhibits various cancer-related features in colorectal cancer development in vitro by targeting STAT3, indicating that TCN is a promising STAT3 inhibitor that deserves further exploration in the future.

Highly Expressed FOXF1 Inhibit Non-Small-Cell Lung Cancer Growth via Inducing Tumor Suppressor and G1-Phase Cell-Cycle Arrest

Cancer pathogenesis results from genetic alteration-induced high or low transcriptional programs, which become highly dependent on regulators of gene expression. However, their role in progressive regulation of non-small-cell lung cancer (NSCLC) and how these dependencies may offer opportunities for novel therapeutic options remain to be understood. Previously, we identified forkhead box F1 (FOXF1) as a reprogramming mediator which leads to stemnesss when mesenchymal stem cells fuse with lung cancer cells, and we now examine its effect on lung cancer through establishing lowly and highly expressing FOXF1 NSCLC engineered cell lines. Higher expression of FOXF1 was enabled in cell lines through lentiviral transduction, and their viability, proliferation, and anchorage-dependent growth was assessed. Flow cytometry and Western blot were used to analyze cellular percentage in cell-cycle phases and levels of cellular cyclins, respectively. In mice, tumorigenic behavior of FOXF1 was investigated. We found that FOXF1 was downregulated in lung cancer tissues and cancer cell lines. Cell proliferation and ability of migration, anchorage-independent growth, and transformation were inhibited in H441-FOXF1^H and H1299-FOXF1^H, with upregulated tumor suppressor p21 and suppressed cellular cyclins, leading to cell-cycle arrest at the gap 1 (G1) phase. H441-FOXF1^H and H1299-FOXF1^H injected mice showed reduced tumor size. Conclusively, highly expressing FOXF1 inhibited NSCLC growth via activating tumor suppressor p21 and G1 cell-cycle arrest, thus offering a potentially novel therapeutic strategy for lung cancer.

Cell adhesion molecule 4 suppresses cell growth and metastasis by inhibiting the Akt signaling pathway in non-small cell lung cancer

Cell adhesion molecule 4 (CADM4) is downregulated in many human cancers. However, CADM4 expression levels in human non-small cell lung cancer (NSCLC) tissues and its roles in NSCLC progression remain unknown. Our study aims to address these issues. We examined CADM4 levels in NSCLC tissues using real-time PCR and western blot. A549 and NCI-H1299 cells were then transfected with pcDNA3.1-CADM4 plasmid or siCADM4 to overexpress or knock down CADM4. Cell proliferation, cell cycle distribution, migration, and invasion were evaluated. NSCLC cells transfected with pcDNA3.1-CADM4 plasmid or siCADM4 were treated with SC79 or LY294002, respectively, to investigate the involvement of the Akt signaling pathway. Male nude mice were subcutaneously injected with stably transfected cells (1 × 10⁶ cells/mice) to observe tumor growth. Stable transfectants were injected into nude mice (1 × 10⁶ cells/mice) via tail vein to observe tumor metastasis. The results showed that CADM4 gene and protein levels in NSCLC tissues were significantly lower than those in corresponding adjacent tissues. CADM4 overexpression markedly inhibited cell proliferation, migration, and invasion. We also found that matrix metalloproteinase 9 (MMP-9) and MMP-2 activities were reduced. Moreover, CADM4 overexpression arrested the cell cycle at G1 phase, with the changes in expression of cell cycle regulators. The Akt signaling pathway was inhibited by CADM4 overexpression. In contrast, CADM4 knockdown showed the opposite effects. Additionally, SC79 and LY294002 reversed the effects of CADM4 overexpression and CADM4 knockdown in vitro, respectively. In xenograft models, CAMD4 overexpression suppressed, while CADM4 knockdown promoted tumor growth, accompanied by changes in Ki67 expression. In in vivo metastasis assay, CADM4 overexpression decreased, while CADM4 knockdown increased numbers of metastatic nodules in lung and liver. These evidences suggest that CADM4 may regulate NSCLC progression via the Akt signaling pathway. CADM4 may be a potential therapeutic target for NSCLC.

Colocalization of MID1IP1 and c-Myc is Critically Involved in Liver Cancer Growth via Regulation of Ribosomal Protein L5 and L11 and CNOT2

Though midline1 interacting protein 1 (MID1IP1) was known as one of the glucose-responsive genes regulated by carbohydrate response element binding protein (ChREBP), the underlying mechanisms for its oncogenic role were never explored. Thus, in the present study, the underlying molecular mechanism of MID1P1 was elucidated mainly in HepG2 and Huh7 hepatocellular carcinoma cells (HCCs). MID1IP1 was highly expressed in HepG2, Huh7, SK-Hep1, PLC/PRF5, and immortalized hepatocyte LX-2 cells more than in normal hepatocyte AML-12 cells. MID1IP1 depletion reduced the viability and the number of colonies and also increased sub G1 population and the number of TUNEL-positive cells in HepG2 and Huh7 cells. Consistently, MID1IP1 depletion attenuated pro-poly (ADP-ribose) polymerase (pro-PARP), c-Myc and activated p21, while MID1IP1 overexpression activated c-Myc and reduced p21. Furthermore, MID1IP1 depletion synergistically attenuated c-Myc stability in HepG2 and Huh7 cells. Of note, MID1IP1 depletion upregulated the expression of ribosomal protein L5 or L11, while loss of L5 or L11 rescued c-Myc in MID1IP1 depleted HepG2 and Huh7 cells. Interestingly, tissue array showed that the overexpression of MID1IP1 was colocalized with c-Myc in human HCC tissues, which was verified in HepG2 and Huh7 cells by Immunofluorescence. Notably, depletion of CCR4-NOT2 (CNOT2) with adipogenic activity enhanced the antitumor effect of MID1IP1 depletion to reduce c-Myc, procaspase 3 and pro-PARP in HepG2, Huh7 and HCT116 cells. Overall, these findings provide novel insight that MID1IP1 promotes the growth of liver cancer via colocalization with c-Myc mediated by ribosomal proteins L5 and L11 and CNOT2 as a potent oncogenic molecule.

Heterochromatin loss as a determinant of progerin-induced DNA damage in Hutchinson-Gilford Progeria

Hutchinson-Gilford progeria is a premature aging syndrome caused by a truncated form of lamin A called progerin. Progerin expression results in a variety of cellular defects including heterochromatin loss, DNA damage, impaired proliferation and premature senescence. It remains unclear how these different progerin-induced phenotypes are temporally and mechanistically linked. To address these questions, we use a doxycycline-inducible system to restrict progerin expression to different stages of the cell cycle. We find that progerin expression leads to rapid and widespread loss of heterochromatin in G1-arrested cells, without causing DNA damage. In contrast, progerin triggers DNA damage exclusively during late stages of DNA replication, when heterochromatin is normally replicated, and preferentially in cells that have lost heterochromatin. Importantly, removal of progerin from G1-arrested cells restores heterochromatin levels and results in no permanent proliferative impediment. Taken together, these results delineate the chain of events that starts with progerin expression and ultimately results in premature senescence. Moreover, they provide a proof of principle that removal of progerin from quiescent cells restores heterochromatin levels and their proliferative capacity to normal levels.

Cytotoxic Activity of Organotin(IV) Derivatives with Triazolopyrimidine Containing Exocyclic Oxygen Atoms

In this study cytotoxicity of organotin(IV) compounds with 1,2,4-triazolo[1,5-a]pyrimidines, Me3Sn(5tpO) (1), n-Bu3Sn(5tpO) (2), Me3Sn(mtpO) (3), n-Bu3Sn(mtpO) (4), n-Bu3Sn(HtpO2) (5), Ph3Sn(HtpO2) (6) where 5HtpO = 4,5-dihydro-5-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, HmtpO = 4,7-dihydro-5-methyl-7-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, and H2tpO2 = 4,5,6,7-tetrahydro-5,7- dioxo-[1,2,4]triazolo-[1,5-a]-pyrimidine, was assessed on three different human tumor cell lines: HCT-116 (colorectal carcinoma), HepG2 (hepatocarcinoma) and MCF-7 (breast cancer). While 1 and 3 were inactive, compounds 2, 4, 5 and 6 inhibited the growth of the three tumor cell lines with IC50 values in the submicromolar range and showed high selectivity indexes towards the tumor cells (SI > 90). The mechanism of cell death triggered by the organotin(IV) derivatives, investigated on HCT-116 cells, was apoptotic, as evident from the externalization of phosphatidylserine to the cell surface, and occurred via the intrinsic pathway with fall of mitochondrial inner membrane potential and production of reactive oxygen species. While compound 6 arrested the cell progression in the G2/M cell cycle phase and increased p53 and p21 levels, compounds 2, 4 and 5 blocked cell duplication in the G1 phase without affecting the expression of either of the two tumor suppressor proteins. Compounds 1 and 2 were also investigated using single crystal X-ray diffraction and found to be, in both cases, coordination polymers forming 1 D chains based on metal-ligand interactions. Interestingly, for n-Bu3Sn(5tpO)(2) H-bonding interactions between 5tpO- ligands belonging to adjacent chains were also detected that resemble the "base-pairing" assembly and could be responsible for the higher biological activity compared to compound 1. In addition, they are the first example of bidentate N(3), O coordination for the 5HtpO ligand on two adjacent metal atoms.

PIR promotes tumorigenesis of breast cancer by upregulating cell cycle activator E2F1

Pirin (PIR) protein belongs to the superfamily of cupin and is highly conserved between eukaryotic and prokaryotic organisms. It has been reported that PIR is upregulated in various tumors and involved in tumorigenesis. However, its biological functions particularly in promoting tumorigenesis are, to date, poorly characterized. Here we report that knockdown of PIR in MCF7 and MDA-MB-231 cell lines causes a dramatic decrease in cell proliferation and xenograft tumor growth in mice. Mechanistically, the cell cycle activator E2F1 and its target genes cdk4, cdk6, cycE, cycD and DDR1 are remarkably downregulated in PIR depleted cells, leading to G1/S phase arrest. Luciferase reporter assay and chromatin immunoprecipitation assay indicate that PIR can activate E2F1 transcription by binding to its promoter region. Consistent with the observation in PIR knockdown cells, PIR inhibitors markedly inhibit the proliferation of both cell lines. Furthermore, knockdown of PIR significantly decreases the abilities of MCF7 cells for mobility and invasion in vitro and their metastasis in mice, which may be attributed to the decrease of DDR1. In conclusion, PIR stimulates tumorigenesis and progression by activating E2F1 and its target genes. Our finding thus suggests PIR as a potential druggable target for the therapy of cancers with high expression level of PIR.

Differential scaling between G1 protein production and cell size dynamics promotes commitment to the cell division cycle in budding yeast

In the unicellular eukaryote Saccharomyces cerevisiae, Cln3-cyclin-dependent kinase activity enables Start, the irreversible commitment to the cell division cycle. However, the concentration of Cln3 has been paradoxically considered to remain constant during G1, due to the presumed scaling of its production rate with cell size dynamics. Measuring metabolic and biosynthetic activity during cell cycle progression in single cells, we found that cells exhibit pulses in their protein production rate. Rather than scaling with cell size dynamics, these pulses follow the intrinsic metabolic dynamics, peaking around Start. Using a viral-based bicistronic construct and targeted proteomics to measure Cln3 at the single-cell and population levels, we show that the differential scaling between protein production and cell size leads to a temporal increase in Cln3 concentration, and passage through Start. This differential scaling causes Start in both daughter and mother cells across growth conditions. Thus, uncoupling between two fundamental physiological parameters drives cell cycle commitment.

Ribosomal mistranslation leads to silencing of the unfolded protein response and increased mitochondrial biogenesis

Translation fidelity is the limiting factor in the accuracy of gene expression. With an estimated frequency of 10-4, errors in mRNA decoding occur in a mostly stochastic manner. Little is known about the response of higher eukaryotes to chronic loss of ribosomal accuracy as per an increase in the random error rate of mRNA decoding. Here, we present a global and comprehensive picture of the cellular changes in response to translational accuracy in mammalian ribosomes impaired by genetic manipulation. In addition to affecting established protein quality control pathways, such as elevated transcript levels for cytosolic chaperones, activation of the ubiquitin-proteasome system, and translational slowdown, ribosomal mistranslation led to unexpected responses. In particular, we observed increased mitochondrial biogenesis associated with import of misfolded proteins into the mitochondria and silencing of the unfolded protein response in the endoplasmic reticulum.

MicroRNA-194 inactivates hepatic stellate cells and alleviates liver fibrosis by inhibiting AKT2

BACKGROUND

Activation of hepatic stellate cells (HSCs) is a pivotal event in the onset and progression of liver fibrosis. Loss of microRNA-194 (miR-194) has been reported in activated HSCs, but the actual role of miR-194 in liver fibrosis remains uncertain.

AIM

To explore the role and potential mechanism of miR-194-mediated regulation of liver fibrosis in vitro and in vivo.

METHODS

The expression of miR-194 was examined in human fibrotic liver tissues, activated HSCs, and a carbon tetrachloride (CCl₄) mouse model by qPCR. The effects of AKT2 regulation by miR-194 on the activation and proliferation of HSCs were assessed in vitro. For in vivo experiments, we reintroduced miR-194 in mice using a miR-194 agomir to investigate the functions of miR-194 in liver fibrosis.

RESULTS

MiR-194 expression was notably lacking in activated HSCs from both humans and mice. Overexpression of miR-194 (OV-miR-194) inhibited α-smooth muscle actin (α-SMA) and type I collagen (Col I) expression and suppressed cell proliferation in HSCs by causing cell cycle arrest in G0/G1 phase. AKT2 was predicted to be a target of miR-194. Notably, the effects of miR-194 knockdown in HSCs were almost blocked by AKT2 deletion, indicating that miR-194 plays a role in HSCs via regulation of AKT2. Finally, miR-194 agomir treatment dramatically ameliorated liver fibrosis in CCl₄-treated mice.

CONCLUSION

We revealed that miR-194 plays a protective role by inhibiting the activation and proliferation of HSCs via AKT2 suppression. Our results further propose miR-194 as a potential therapeutic target for liver fibrosis.

ESRP1 Induces Cervical Cancer Cell G1-Phase Arrest Via Regulating Cyclin A2 mRNA Stability

Accumulating evidence indicates that epithelial splicing regulatory protein 1 (ESRP1) can inhibit the epithelial-to-mesenchymal transition (EMT), thus playing a central role in regulating the metastatic progression of tumors. However, it is still not clear whether ESRP1 directly influences the cell cycle, or what the possible underlying molecular mechanisms are. In this study, we showed that ESRP1 protein levels were significantly correlated with the Ki-67 proliferative index (r = −0.521; p < 0.01), and that ESRP1 overexpression can significantly inhibit cervical carcinoma cell proliferation and induced G1-phase arrest by downregulating cyclin A2 expression. Importantly, ESRP1 can bind to GGUGGU sequence in the 3′UTR of the cyclin A2 mRNA, and ESRP1 overexpression significantly decreases the stability of the cyclin A2 mRNA. In addition, our experimental results confirm that ESRP1 overexpression results in enhanced CDC20 expression, which is known to be responsible for cyclin A2 degradation. This study provides the first evidence that ESRP1 overexpression induces G1-phase cell cycle arrest via reducing the stability of the cyclin A2 mRNA, and inhibits cervical carcinoma cell proliferation. The findings suggest that the ESRP1/cyclin A2 regulatory axis may be essential as a regulator of cell proliferation, and may thus represent an attractive target for cervical cancer prevention and treatment.

Supraphysiological androgens suppress prostate cancer growth through androgen receptor-mediated DNA damage

Prostate cancer (PC) is initially dependent on androgen receptor (AR) signaling for survival and growth. Therapeutics designed to suppress AR activity serve as the primary intervention for advanced disease. However, supraphysiological androgen (SPA) concentrations can produce paradoxical responses leading to PC growth inhibition. We sought to discern the mechanisms by which SPA inhibits PC and to determine if molecular context associates with anti-tumor activity. SPA produced an AR-mediated, dose-dependent induction of DNA double-strand breaks (DSBs), G0/G1 cell cycle arrest and cellular senescence. SPA repressed genes involved in DNA repair and delayed the restoration of damaged DNA which was augmented by PARP1 inhibition. SPA-induced DSBs were accentuated in BRCA2-deficient PCs, and combining SPA with PARP or DNA-PKcs inhibition further repressed growth. Next-generation sequencing was performed on biospecimens from PC patients receiving SPA as part of ongoing Phase II clinical trials. Patients with mutations in genes mediating homology-directed DNA repair were more likely to exhibit clinical responses to SPA. These results provide a mechanistic rationale for directing SPA therapy to PCs with AR amplification or DNA repair deficiency, and for combining SPA therapy with PARP inhibition.

Knockdown of FAM64A suppresses proliferation and migration of breast cancer cells

BACKGROUND

FAM64A is a mitotic regulator promoting cell metaphase-anaphase transition, and it is frequently reported to be highly expressed in cancer cells. However, the role of FAM64A in human breast cancer (BrC) is poorly studied.

METHODS

The expression of FAM64A mRNA in BrC samples was determined by RT-qPCR assay and TCGA database mining. Kaplan-Meier plotter was used to analyze whether FAM64A expression impacted prognosis. Then, the expression of FAM64A was silenced using RNA interference. Cell-counting assay, colony formation assay and flow cytometry assay were conducted to detect proliferation; transwell migration assay, EMT-related proteins expression (E-cadherin, N-cadherin and vimentin), and EMT-related transcription factors mRNA expression (Snail, Twist, Slug) were conducted to evaluate the migration ability.

RESULTS

FAM64A was highly expressed in human BrC samples, which was negatively associated with poor survival time. Analysis of FAM64A expression in BrC cell lines demonstrated that the expression of FAM64A was significantly correlated with the proliferation rate and migration ability of BrC cells. Indeed, knockdown of FAM64A suppressed the proliferation of MDA-MB-231 and MCF-7 cells. Importantly, we also found that silencing of FAM64A inhibited the migration of BrC cells via impeding epithelial-mesenchymal transition.

CONCLUSIONS

Our findings suggest that FAM64A plays an important role in the proliferation and migration of BrC cells, which might serve as a potential target for BrC treatment.

8:2 Fluorotelomer alcohol causes G1 cell cycle arrest and blocks granulocytic differentiation in HL-60 cells

Fluorotelomer alcohols (FTOHs) are fluorinated intermediates used in manufacturing specialty polymer and surfactants, with 8:2 FTOH the homologue of largest production. FTOHs were found to pose acute toxicity, hepatotoxicity, nephrotoxicity, developmental toxicity and endocrine-disrupting risks, whereas research regarding immunotoxicity and its underlying mechanism, especially on specific immune cells is limited. Here, we investigated the immunotoxicity of 8:2 FTOH on immature immune cells in an in vitro system. We observed that exposure of HL-60 cells, a human promyelocytic leukemic cell line, to 8:2 FTOH reduced cell viability in a dose- and time-dependent manner. In addition, 8:2 FTOH exposure caused G1 cell cycle arrest in HL-60 cells, while it showed no effect on apoptosis. Exposure to 8:2 FTOH inhibited the mRNA expression of cell cycle-related genes, including CCNA1, CCNA2, CCND1, and CCNE2. Moreover, exposure to 8:2 FTOH inhibited the mRNA expression of granulocytic differentiation-related genes of CD11b, CSF3R, PU.1, and C/EPBε in HL-60 cells . Furthermore, 8:2 FTOH exhibited no effect on intracellular ROS level, while hydralazine hydrochloride (Hyd), one reactive carbonyl species (RCS) scavenger, partially blocked 8:2 FTOH-caused cytotoxicity in HL-60 cells. Overall, the results obtained in the study show that 8:2 FTOH poses immunotoxicity in immature immune cells and RCS may partially underline its mechanism.

KLF1 mutation E325K induces cell cycle arrest in erythroid cells differentiated from congenital dyserythropoietic anemia patient-specific induced pluripotent stem cells

Krüppel-like factor 1 (KLF1), a transcription factor controlling definitive erythropoiesis, is involved in sequential control of terminal cell division and enucleation via fine regulation of key cell cycle regulator gene expression in erythroid lineage cells. Type IV congenital dyserythropoietic anemia (CDA) is caused by a monoallelic mutation at the second zinc finger of KLF1 (c.973G>A, p.E325K). We recently diagnosed a female patient with type IV CDA with the identical missense mutation. To understand the mechanism underlying the dyserythropoiesis caused by the mutation, we generated induced pluripotent stem cells (iPSCs) from the CDA patient (CDA-iPSCs). The erythroid cells that differentiated from CDA-iPSCs (CDA-erythroid cells) displayed multinucleated morphology, absence of CD44, and dysregulation of the KLF1 target gene expression. In addition, uptake of bromodeoxyuridine by CDA-erythroid cells was significantly decreased at the CD235a⁺/CD71⁺ stage, and microarray analysis revealed that cell cycle regulator genes were dysregulated, with increased expression of negative regulators such as CDKN2C and CDKN2A. Furthermore, inducible expression of the KLF1 E325K, but not the wild-type KLF1, caused a cell cycle arrest at the G1 phase in CDA-erythroid cells. Microarray analysis of CDA-erythroid cells and real-time polymerase chain reaction analysis of the KLF1 E325K inducible expression system also revealed altered expression of several KLF1 target genes including erythrocyte membrane protein band 4.1 (EPB41), EPB42, glutathione disulfide reductase (GSR), glucose phosphate isomerase (GPI), and ATPase phospholipid transporting 8A1 (ATP8A1). Our data indicate that the E325K mutation in KLF1 is associated with disruption of transcriptional control of cell cycle regulators in association with erythroid membrane or enzyme abnormalities, leading to dyserythropoiesis.

MicroRNA-29c induces G1 arrest of melanoma by targeting CDK6

PURPOSE

Melanoma is a malignant skin tumor that can easily metastasize, while no effective treatment exists for this disease. This study explored the mechanism of microRNA-29c in inhibiting melanoma cell growth.

METHODS

Bioinformatics analysis and polymerase chain reaction (PCR) experiments were performed to analyze the expression of microRNA-29c in various samples. The Cell Counting Kit-8 (CCK-8) experiment was used to detect cell viability. The mimic and inhibitor of microRNA-29c were transfected into melanoma cells to achieve microRNA-29c overexpression or knockdown so as to observe the biological effect on the melanoma cells. Flow cytometry was used to detect cell cycle, while the luciferase reporter gene assay was used for predicting microRNA-29c target genes. Western blot was performed to determine the cellular protein expression.

RESULTS

microRNA-29c was highly expressed in melanoma cells. Overexpression of microRNA-29c inhibited cell viability and induced G1 cell cycle arrest. Conversely, cell proliferation and cycle progression were promoted by transfection of microRNA-29c inhibitor in melanoma cells. In addition, CDK6 served as a microRNA-29c target gene. G1 phase of melanoma cells was blocked by knockdown of CDK6.

CONCLUSIONS

microRNA-29c can inhibit the growth of melanoma cells by targeting CDK6, which could trigger G1 arrest of melanoma cells.

DNA Binding and Molecular Dynamic Studies of Polycyclic Tetramate Macrolactams (PTM) with Potential Anticancer Activity Isolated from a Sponge-Associated Streptomyces zhaozhouensis subsp. mycale subsp. nov

A sponge-associated actinomycete (strain MCCB267) was isolated from a marine sponge Mycale sp. collected in the Indian Ocean off the Southeast coast of India. Phylogenetic studies of this strain using 16S rRNA gene sequencing showed high sequence similarity to Streptomyces zhaozhouensis. However, strain MCCB267 showed distinct physiological and biochemical characteristic features and was thus designated as S. zhaozhouensis subsp. mycale. subsp. nov. A cytotoxicity-guided fractionation of the crude ethyl acetate extract of strain MCCB267 culture medium yielded four pure compounds belonging to the polycyclic tetramate macrolactam (PTM) family of natural products: ikarugamycin (IK) (1), clifednamide A (CF) (2), 30-oxo-28-N-methylikarugamycin (OI) (3), and 28-N-methylikarugamycin (MI) (4). The four compounds exhibited promising cytotoxic activity against NCI-H460 lung carcinoma cells in vitro, by inducing cell death via apoptosis. Flow cytometric analysis revealed that 1, 3, and 4 induced cell cycle arrest during G1 phase in the NCI-H460 cell line, whereas 2 induced cell arrest in the S phase. A concentration-dependent accumulation of cells in the sub-G1 phase was also detected upon treatment of the cancer cell line with compounds 1-4. The in vitro cytotoxicity studies were supported by molecular docking and molecular dynamic simulation analyses. An in silico study revealed that the PTMs can bind to the minor groove of DNA and subsequently induce the apoptotic stimuli leading to cell death. The characterization of the isolated actinomycete, the study of the mode of action of the four PTMs, 1-4, and the molecular docking and molecular dynamic simulations analyses are herein described.

B-cell translocation gene 3 overexpression inhibits proliferation and invasion of colorectal cancer SW480 cells via Wnt/β-catenin signaling pathway

Increasing evidences have shown that B-cell translocation gene 3 (BTG3) inhibits metastasis of multiple cancer cells. However, the role of BTG3 in colorectal cancer (CRC) and its possible mechanism have not yet been reported. In our study, we evaluated BTG3 expression in several CRC cell lines. Then, pcDNA3.1-BTG3 was transfected into SW480 cells. We found that BTG3 was upregulated in SW480 cells after overexpression plasmid transfection. BTG3 overexpression significantly inhibited cell growth and decreased PCNA (proliferating cell nuclear antigen) and Ki67 levels. BTG3 overexpression markedly downregulated Cyclin D1 and Cyclin E1 levels, whereas elevated p27. Overexpression of BTG3 arrested the cell cycle at G1 phase, which was abrogated by p27 silencing. Furthermore, migration, invasion and EMT of SW480 cells were significantly suppressed by BTG3 overexpression. Further investigations showed the inhibition of Wnt/β-catenin signaling pathway. We then used GSK3β specific inhibitor SB-216763 to activate the Wnt/β-catenin signaling pathway. We found that Wnt/β-catenin signaling pathway activation reversed the effect of BTG3 overexpression on cell proliferation, cell cycle progression, invasion and EMT. In conclusion, BTG3 overexpression inhibited cell growth, induced cell cycle arrest and suppressed the metastasis of SW480 cells via the Wnt/β-catenin signaling pathway. BTG3 may be considered as a therapeutic target in CRC treatment.

Telomere Loop Dynamics in Chromosome End Protection

Telomeres regulate DNA damage response (DDR) and DNA repair activity at chromosome ends. How telomere macromolecular structure contributes to ATM regulation and its potential dissociation from control over non-homologous end joining (NHEJ)-dependent telomere fusion is of central importance to telomere-dependent cell aging and tumor suppression. Using super-resolution microscopy, we identify that ATM activation at mammalian telomeres with reduced TRF2 or at human telomeres during mitotic arrest occurs specifically with a structural change from telomere loops (t-loops) to linearized telomeres. Additionally, we find the TRFH domain of TRF2 regulates t-loop formation while suppressing ATM activity. Notably, we demonstrate that ATM activation and telomere linearity occur separately from telomere fusion via NHEJ and that linear DDR-positive telomeres can remain resistant to fusion, even during an extended G1 arrest, when NHEJ is most active. Collectively, these results suggest t-loops act as conformational switches that specifically regulate ATM activation independent of telomere mechanisms to inhibit NHEJ.

Genomic and Transcriptomic Analysis Reveals Incremental Disruption of Key Signaling Pathways during Melanoma Evolution

We elucidated genomic and transcriptomic changes that accompany the evolution of melanoma from pre-malignant lesions by sequencing DNA and RNA from primary melanomas and their adjacent precursors, as well as matched primary tumors and regional metastases. In total, we analyzed 230 histopathologically distinct areas of melanocytic neoplasia from 82 patients. Somatic alterations sequentially induced mitogen-activated protein kinase (MAPK) pathway activation, upregulation of telomerase, modulation of the chromatin landscape, G1/S checkpoint override, ramp-up of MAPK signaling, disruption of the p53 pathway, and activation of the PI3K pathway; no mutations were specifically associated with metastatic progression, as these pathways were perturbed during the evolution of primary melanomas. UV radiation-induced point mutations steadily increased until melanoma invasion, at which point copy-number alterations also became prevalent.

RASSF7 promotes cell proliferation through activating MEK1/2-ERK1/2 signaling pathway in hepatocellular carcinoma

The Ras-association domain family (RASSF) proteins have been involved in many important biological processes. RASSF7 is recently reported to be up-regulated in several types of cancer. However, the function of RASSF7 remain unknown in human cancers. To explore the role of RASSF7 in hepatocellular carcinoma (HCC) cells proliferation and molecular mechanism. RASSF7 expression was examined using public database TCGA, qRT-PCR and Western blot. The correlation between RASSF7 and clinicopathological features was measured. Overexpression and silencing of RASSF7 were performed to measure the impact on HCC cell proliferation, cell cycle and apoptosis. Futhermore, the molecular mechanism of MEK1/2-ERK1/2 signaling pathway regulation by RASSF7 was explored. RASSF7 was significantly up-regulated in HCC tissues and cell lines, and correlated with AFP, poor tumor histology and T stage. Overexpression of RASSF7 promoted HCC cell proliferation, drived G1-S phase cell cycle transition and inhibited apoptosis. Knockdown of RASSF7 suppressed cell growth, induced G1-S phase cell cycle arrest and cell apoptosis. Furthermore, our findings also demonstrated that RASSF7 promoted HCC cell proliferation through activating MEK1/2-ERK1/2 signaling pathway. Taken together, this study provides a novel evidence for clinical significance of RASSF7 as a potential biomarker, and demonstrates that RASSF7- MEK1/2-ERK1/2 signaling pathway might be a novel pathway involved in HCC progression.

CREBRF promotes the proliferation of human gastric cancer cells via the AKT signaling pathway

Gastric cancer (GC) is one of the most common malignant cancer around the world, however the mechanisms is still unclear. In the present study, we investigated the function of CREB3 regulatory factor (CREBRF) in human GC and explored its relevant molecular mechanism. We found that CREBRF was highly expressed in primary GC tissues and the expression level was associated with the clinicopathologic characteristics of GC. CREBRF silencing inhibited GC cell proliferation and induced G1/G0 to S phase cell cycle arrest through regulating Cyclin A, Cyclin D1 and CDK2 expressions. Furthermore, the results showed that knockdown of CREBRF suppressed the activation of AKT signaling pathway. We further discovered that activating of AKT rescued the effect of CREBRF silencing on cell growth and drove cell re-enter into the S phase of the cell cycle with SC79 (a AKT activator). Taken together, our study demonstrated that CREBRF might promote GC cell proliferation and induce G1-S phase transition through activating AKT signaling pathway. These findings suggest that CREBRF acts as a novel oncogene and may be a potential therapeutic target in therapy of GC.

Upregulation of CDCA5 promotes gastric cancer malignant progression via influencing cyclin E1

The cell division cycle associated 5(CDCA5) was reported to be associated with progression of several human cancers, however, its clinical significance and biological role still remain unknown in gastric cancer(GC). By analyzing The Cancer Genome Atlas(TCGA), we found CDCA5 was significantly upregulated in GC tissues compared to adjacent normal tissues. Tissue microarray(TMA) indicated upregulation of CDCA5 was significantly correlated with more advanced clinicopathological features, and acts as an independent risk factor for worse overall survival(OS) in GC patients. Moreover, silence of CDCA5 suppresses proliferation of GC cells by inducing G1-phase arrest via downregulating Cyclin E1(CCNE1). Our results demonstrate upregulation of CDCA5 promotes GC malignant progression, which may offer a potential prognostic and therapeutic strategy.

[miR-503-5p inhibits the proliferation of T24 and EJ bladder cancer cells by interfering with the Rb/E2F signaling pathway]

Objective To observe the effect of microRNA-503-5p (miR-503-5p) on the growth of T24 and EJ bladder cancer cells, and explore the possible molecular mechanism. Methods The miR-504-5p mimics or miR-NC was transfected into T24 and EJ cells. The target gene of miR-503-5p was predicted by bioinformatics. The expressions of E2F transcription factor 3 (E2F3) mRNA and Rb/E2F signaling pathway mRNA were detected by the real-time quantitative PCR (qPCR). The expressions of Rb/E2F signal pathway proteins E2F3, cyclin E, CDK2, Rb and p-Rb were detected by Western blotting. The cell cycle of bladder cancer cell lines was determined by flow cytometry. MTT assay and plate cloning assay were performed to observe the proliferation ability of bladder cancer cells. Results After miR-503-5p mimics transfection, the expression of miR-503-5p in bladder cancer cells significantly increased. The increased expression of miR-503-5p significantly reduced the expressions of E2F3 mRNA and Rb/E2F signaling pathway mRNA in bladder cancer cells. What's more, the expressions of Rb/E2F signal pathway proteins were down-regulated. The bladder cancer cells were arrested in G0/G1 phase, and their growth was significantly inhibited by miR-503-5p. Conclusion The miR-503-5p over-expression can inhibit the growth of bladder cancer cell lines T24 and EJ by down-regulating the expression of the Rb/E2F signaling pathway.

DNA damage and senescence in osteoprogenitors expressing Osx1 may cause their decrease with age

Age-related bone loss in mice results from a decrease in bone formation and an increase in cortical bone resorption. The former is accounted by a decrease in the number of postmitotic osteoblasts which synthesize the bone matrix and is thought to be the consequence of age-dependent changes in mesenchymal osteoblast progenitors. However, there are no specific markers for these progenitors, and conclusions rely on results from in vitro cultures of mixed cell populations. Moreover, the culprits of such changes remain unknown. Here, we have used Osx1-Cre;TdRFP mice in which osteoprogenitors express the TdRFP fluorescent protein. We report that the number of TdRFP-Osx1 cells, freshly isolated from the bone marrow, declines by more than 50% between 6 and 24 months of age in both female and male mice. Moreover, TdRFP-Osx1 cells from old mice exhibited markers of DNA damage and senescence, such as γH2AX foci, G1 cell cycle arrest, phosphorylation of p53, increased p21CIP1 levels, as well as increased levels of GATA4 and activation of NF-κB - two major stimulators of the senescence-associated secretory phenotype (SASP). Bone marrow stromal cells from old mice also exhibited elevated expression of SASP genes, including several pro-osteoclastogenic cytokines, and increased capacity to support osteoclast formation. These changes were greatly attenuated by the senolytic drug ABT263. Together, these findings suggest that the decline in bone mass with age is the result of intrinsic defects in osteoprogenitor cells, leading to decreased osteoblast numbers and increased support of osteoclast formation.

Downstream targets of GWAS-detected genes for breast, lung, and prostate and colon cancer converge to G1/S transition pathway

Genome-wide association studies (GWASs) identified over 500 single nucleotide polymorphisms (SNPs) influencing cancer risk. It is logical to expect the cancer-associated genes to cluster in pathways directly involved in carcinogenesis, e.g. cell cycle. Nevertheless, analyses of the GWAS-detected cancer risk genes usually show no or weak enrichment by known cancer genes.We hypothesized that GWAS-detected cancer risk-associated genes function as upstream regulators of the genes directly involved in carcinogenesis. We have analyzed four common cancers: breast, colon, lung, and prostate. To identify downstream targets of GWAS-detected cancer risk genes we used MedScan, which is a text mining tool offered by PathwayStudio. We also used data on protein/protein interactions reported by BioGRID database. Among all identified targets we have selected common downstream targets. A gene was considered a common downstream target if it was a downstream target for at least three GWAS-detected genes for a given cancer type. Common downstream targets were identified separately for each cancer type. We found that common downstream targets for all four cancer types were enriched by cell cycle genes, more specifically, the genes involved in G1/S transition. Common downstream targets for bipolar disorder, Crohn's disease, and type 2 diabetes did not show G1/S transition enrichment.The results of this analysis suggest that many cancer risk genes function as upstream regulators of the genes directly involved in G1/S transition and exert their risk effects by reducing threshold for G1/S transition, elevating the background level of cell proliferation and cancer risk.

Down-regulation of long non-coding RNA RP11-708H21.4 is associated with poor prognosis for colorectal cancer and promotes tumorigenesis through regulating AKT/mTOR pathway

Long non-coding RNAs (lncRNAs) serve critical roles in cancer development and progression. Herein, through next generation RNA sequencing and experimental validations, we determined the expression status of RP11-708H21.4 in colorectal cancer (CRC) and explored its clinical significance and biological functions in CRC. Differentially expressed lncRNAs from CRC samples and corresponding normal mucosa tissues was screened through RNA sequencing, and RP11-708H21.4 was selected for further experimental validation. The expression levels of RP11-708H21.4 in CRC tissues and cell lines were determined using qRT-PCR. Also, the relationship between the clinicopathological features and RP11-708H21.4 expression was analyzed. Cell viability was examined by CCK-8 and colony assays; cell migration and invasion were detected by transwell assays; cell cycle and cell apoptosis were analyzed by flow cytometry. The chemosensitivity of CRC cells to 5-Fluorouracil (5-FU) was also determined using CCK-8 assay. CRC xenograft tumor models were established to determine the biological functions of RP11-708H21.4 in vivo. Levels of cell cycle-related proteins and AKT/mTOR pathway-related proteins were detected by western blot assay. RP11-708H21.4 expression was aberrantly decreased in CRC, and its expression was closely associated with aggressive clinicopathologic features and unfavorable prognosis of CRC patients. Overexpressed RP11-708H21.4 suppresses CRC cell proliferation through inducing G1 arrest. Moreover, up-regulation of RP11-708H21.4 inhibits cell migration and invasion, causes cell apoptosis, and enhances 5-FU sensitivity of CRC cells. Finally, increased RP11-708H21.4 expression blocked AKT/mTOR pathway, and repressed in vivo CRC xenograft tumor growth. The results indicated that RP11-708H21.4 might have potential roles as a biomarker and a therapeutic target for CRC.

The Concerted Action of Type 2 and Type 3 Deiodinases Regulates the Cell Cycle and Survival of Basal Cell Carcinoma Cells

BACKGROUND

Thyroid hormones (THs) mediate pleiotropic cellular processes involved in metabolism, cellular proliferation, and differentiation. The intracellular hormonal environment can be tailored by the type 1 and 2 deiodinase enzymes D2 and D3, which catalyze TH activation and inactivation respectively. In many cellular systems, THs exert well-documented stimulatory or inhibitory effects on cell proliferation; however, the molecular mechanisms by which they control rates of cell cycle progression have not yet been entirely clarified. We previously showed that D3 depletion or TH treatment influences the proliferation and survival of basal cell carcinoma (BCC) cells. Surprisingly, we also found that BCC cells express not only sustained levels of D3 but also robust levels of D2. The aim of the present study was to dissect the contribution of D2 to TH metabolism in the BCC context, and to identify the molecular changes associated with cell proliferation and survival induced by TH and mediated by D2 and D3.

METHODS

We used the CRISPR/Cas9 technology to genetically deplete D2 and D3 in BCC cells and studied the consequences of depletion on cell cycle progression and on cell death. Cell cycle progression was analyzed by fluorescence activated cell sorting analysis of synchronized cells, and the apoptosis rate by annexin V incorporation.

RESULTS

Mechanistic investigations revealed that D2 inactivation accelerates cell cycle progression thereby enhancing the proportion of S-phase cells and cyclin D1 expression. Conversely, D3 mutagenesis drastically suppressed cell proliferation and enhanced apoptosis of BCC cells. Furthermore, the basal apoptotic rate was oppositely regulated in D2- and D3-depleted cells.

CONCLUSION

Our results indicate that BCC cells constitute an example in which the TH signal is finely tuned by the concerted expression of opposite-acting deiodinases. The dual regulation of D2 and D3 expression plays a critical role in cell cycle progression and cell death by influencing cyclin D1-mediated entry into the G1-S phase. These findings reinforce the concept that TH is a potential therapeutic target in human BCC.

A TLR9-dependent checkpoint governs B cell responses to DNA-containing antigens

Mature B cell pools retain a substantial proportion of polyreactive and self-reactive clonotypes, suggesting that activation checkpoints exist to reduce the initiation of autoreactive B cell responses. Here, we have described a relationship among the B cell receptor (BCR), TLR9, and cytokine signals that regulate B cell responses to DNA-containing antigens. In both mouse and human B cells, BCR ligands that deliver a TLR9 agonist induce an initial proliferative burst that is followed by apoptotic death. The latter mechanism involves p38-dependent G1 cell-cycle arrest and subsequent intrinsic mitochondrial apoptosis and is shared by all preimmune murine B cell subsets and CD27- human B cells. Survival or costimulatory signals rescue B cells from this fate, but the outcome varies depending on the signals involved. B lymphocyte stimulator (BLyS) engenders survival and antibody secretion, whereas CD40 costimulation with IL-21 or IFN-γ promotes a T-bet+ B cell phenotype. Finally, in vivo immunization studies revealed that when protein antigens are conjugated with DNA, the humoral immune response is blunted and acquires features associated with T-bet+ B cell differentiation. We propose that this mechanism integrating BCR, TLR9, and cytokine signals provides a peripheral checkpoint for DNA-containing antigens that, if circumvented by survival and differentiative cues, yields B cells with the autoimmune-associated T-bet+ phenotype.

Inhibitory effects of miR-101 overexpression on cervical cancer SiHa cells

PURPOSE OF INVESTIGATION

microRNAs (miRNAs), which can regulate cell biological behaviors such as proliferation and apoptosis as oncogenes or anti-oncogenes, are closely associated with cancer onset and progression. The aim of this study was to detect the expres- sion changes of miR-101 in cervical cancer tissues and the effects on the biological functions of cervical cancer SiHa cells.

MATERIALS AND METHODS

Through transient transfection of SiHa cells with mature miR-101 sequences, the effects on apoptosis, proliferation, and cell cycle were evaluated by real-time PCR, CCK-8 assay, and flow cytometry.

RESULTS

Significantly less miR-101 was expressed in cervical cancer tissues than that in normal cervical tissues. miR-101 was overexpressed in SiHa cells through transient transfection of miR-101 mimics. CCK-8 assay and flow cytometry showed that miR-101 overexpression significantly inhibited cell proliferation, pro- moted apoptosis, and arrested them in the G(l)/S phase. Real-time PCR exhibited that Mcl-i and c-Fos mRNA expressions significantly decreased.

CONCLUSION

miR-101 significantly reduced the viability of SiHa cells as a potential anti-oncogene.

Knockdown of HMGB1 inhibits cell proliferation and induces apoptosis in hemangioma via downregulation of AKT pathway

The high mobility group box 1 (HMGB1) as a conserved non-histone nuclear protein has been involved in a variety of biological processes of cancer, such as cell proliferation, apoptosis, angiogenesis and metastasis. Despite the increased expression of HMGB1 in many malignant tumors, the functions and molecular mechanisms by which HMGB1 contributes to the formation of hemangioma (HA) remain unclear. In the present study, immunohistochemistry was used to detect the expression levels of HMGB1 in different phases of human HAs. Cell function experiments, including MTT, cell colony formation and flow cytometry analysis were performed to evaluate the effects of HMGB1 knockdown on cell proliferation and apoptosis in HA CRL-2586 EOMA cells. As a consequence, we found that HMGB1 expression was significantly increased in proliferating phase HAs compared with the involuting phase HAs and normal skin tissues (P less than 0.01). Moreover, knockdown of HMGB1 gene in vitro suppressed EOMA cell proliferation and colony formation and induced cell apoptosis and cycle arrest at G0/G1 phase by downregulation of PCNA, CyclinD1, p-AKT and upregulation of p53 and cleaved PARP. Taken together, our findings demonstrate that HMGB1 may be implicated in the formation of HA through upregulation of AKT pathway, and represent a potential therapeutic target for treating HA.

A Novel Role of Dickkopf-Related Protein 3 in Macropinocytosis in Human Bladder Cancer T24 Cells

Dickkopf-related protein 3 (Dkk-3) is a potential tumor suppressor reported in various cancer entities. However, we found that Dkk-3 was exceptionally upregulated in bladder cancer T24 cells. To validate the biological role of Dkk-3 other than a tumor suppressor, we examined the function of Dkk-3 in T24 cells. Gene silencing of Dkk-3 inhibited cell growth through inducing G₀/G₁ cell-cycle arrest. Furthermore, Dkk-3 knock-down caused macropinocytosis accompanied by autophagy, which were canceled in part by their inhibitors 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and 3-methyladenine (3-MA). The macropinocytosis was induced by the Dkk-3 knock-down when there were sufficient extracellular nutrients. On the other hand, when the nutritional condition was poor, the autophagy was mainly induced by the Dkk-3 knock-down. These data indicated that Dkk-3 has a role in modulating macropinocytotic and autophagic pathways, a distinct function other than a Wnt antagonist.

The phytoestrogenic Cyclopia extract, SM6Met, increases median tumor free survival and reduces tumor mass and volume in chemically induced rat mammary gland carcinogenesis

SM6Met, a phytoestrogenic extract of Cyclopia subternata indigenous to the Western Cape province of South Africa, displays estrogenic attributes with potential for breast cancer chemoprevention. In this study, we report that SM6Met, in the presence of estradiol, induces a significant cell cycle G0/G1 phase arrest similar to the selective estrogen receptor modulator, tamoxifen. Furthermore, as a proof of concept, in the N-Methyl-N-nitrosourea induced rat mammary gland carcinogenesis model, SM6Met increases tumor latency by 7days and median tumor free survival by 42 days, while decreasing palpable tumor frequency by 32%, tumor mass by 40%, and tumor volume by 53%. Therefore, the current study provides proof of concept that SM6Met has definite potential as a chemopreventative agent against the development and progression of breast cancer.

Construction of recombinant adenovirus Ad-rat PLCγ2 and its effects on apoptosis of rat liver cell BRL-3A in vitro

Although the role of PLCγ2 in apoptotic response has been reported, too little is known about whether PLCγ2 induces liver cell apoptosis during liver regeneration. Therefore, this study firstly packaged Ad-PLCγ2 recombinant adenovirus and primarily evaluated its effect on apoptosis of rat liver cell BRL-3A in vitro. Following ten days of co-transfection of pHBAd-MCMV-GFP-PLCγ2 and pHBAd-BHG into HEK293 cells, viral cytopathic effect (CPE) was apparent. Following three rounds of amplification, tissue culture infectious dose 50 (TCID50) assay showed that the titer value reached 1×1010 PFU/mL. After 24 h of transfection of recombinant adenovirus into BRL-3A cells, transfection efficiency of adenovirus into BRL-3A cells was above 90% when obsereved under fluorescent microscopy. qRT-PCR and Western blot assays showed mRNA and protein levels of PLCγ2 were significantly elevated in the transfected BRL-3A cells. Flow cytometric analysis showed that, compared with the control and Ad-GFP groups, cell apoptosis rate of Ad-PLCγ2 group were significantly increased (P<0.01), and the cell cycle in Ad-PLCγ2 group was arrested at G1 phase which was manifested by a marked increase (P<0.01) in the percentage of G1 phase cells and a great decrease (P<0.01) in the percentage of S and G2/M phase cells. It was concluded from above results that recombinant adenovirus Ad-PLCγ2 was packaged successfully, and could promote cell apoptosis by arresting the transition from G1 to S phase of BRL-3A cells.

MiR-26a and miR-138 block the G1/S transition by targeting the cell cycle regulating network in prostate cancer cells

PURPOSE

The tumor-suppressive microRNAs miR-26a and miR-138 are significantly down-regulated in prostate cancer (PCa) and have been identified as direct regulators of enhancer of zeste homolog 2 (EZH2), which is a known oncogene in PCa. In the present study, the influence of miR-26a and miR-138 on EZH2 and cellular function including the impact on the cell cycle regulating network was evaluated in PCa cells.

METHODS

PC-3 and DU-145 PCa cells were transfected with 100 nM of miRNA mimics, siRNA against EZH2 (siR-EZH2) or control constructs for 4 h. Analyses of gene expression and cellular function were conducted 48 h after transfection.

RESULTS

Both miRNAs influenced the EZH2 expression and activity only marginally, whereas siR-EZH2 led to a notable decrease of the EZH2 expression and activity. Both miRNAs inhibited short- and/or long-term proliferation of PCa cells but showed no effect on viability and apoptosis. In PC-3 cells, miR-26a and miR-138 caused a significant surplus of cells in the G0/G1 phase of 6 and 12 %, respectively, thus blocking the G1/S-phase transition. Treatment with siR-EZH2 was without substantial influence on cellular function and cell cycle. Therefore, alternative target genes involved in cell cycle regulation were identified in silico. MiR-26a significantly diminished the expression of its targets CCNE1, CCNE2 and CDK6, whereas CCND1, CCND3 and CDK6 were suppressed by their regulator miR-138.

CONCLUSIONS

The present findings suggest an anti-proliferative role for miR-26a and miR-138 in PCa by blocking the G1/S-phase transition independent of EZH2 but via a concerted inhibition of crucial cell cycle regulators.