Cyclin A accumulates at the onset of S phase, remains high during G(2) and early mitosis and is degraded at prometaphase. Here, we report that the acetyltransferase P/CAF directly interacts with cyclin A that as a consequence becomes acetylated at lysines 54, 68, 95 and 112. Maximal acetylation occurs simultaneously to ubiquitylation at mitosis, indicating importance of acetylation on cyclin A stability. This was further confirmed by the observation that the pseudoacetylated cyclin A mutant can be ubiquitylated whereas the nonacetylatable mutant cannot. The nonacetylatable mutant is more stable than cyclin A WT (cycA WT) and arrests cell cycle at mitosis. Moreover, in cells treated with histone deacetylase inhibitors cyclin A acetylation increases and its stability decreases, thus supporting the function of acetylation on cyclin A degradation. Although the nonacetylatable mutant cannot be ubiquitylated, it interacts with the proteins needed for its degradation (cdks, Cks, Cdc20, Cdh1 and APC/C). In fact, its association with cdks is increased and its complexes with these kinases display higher activity than control cycA WT-cdk complexes. All these results indicate that cyclin A acetylation at specific lysines is crucial for cyclin A stability and also has a function in the regulation of cycA-cdk activity.

BACKGROUND

About 20% of colorectal cancer (CRC) patients show some kind of familiarity, which might be caused by yet unknown combinations of low penetrance susceptibility genes. We aimed to identify genetic factors for familial CRC (fCRC) in a unique study design that includes phenotypic extremes as represented by fCRC cases and 'hyper-normal' controls without CRC history and no adenomatous polyps on colonoscopy.

METHODS

Candidate gene variants were determined by allele-specific amplification (SLC10A2 c.169C>T and c.171G>T) and restriction fragment length polymorphism assays (CCND1 c.870A>G; CDH1 -160C>A; TP53 R72P; VDR T2M). In total, 98 patients with fCRC, 96 patients with sporadic CRC, and 220 hyper-normal controls were included.

RESULTS

The minor allele of the CDH1 -160C>A polymorphism occurred significantly more often in controls compared to fCRC cases (OR = 0.664; p = 0.042). Homozygosity of the minor allele was significantly associated with affiliation to the control group (OR = 0.577; p = 0.029), indicating that both heterozygous and homozygous carriers of the common allele are at-risk for CRC. With respect to the CCND1 c.870A>G mutation, comparison of fCRC and sporadic CRC cases showed that A/A homozygosity was more common than G/G homozygosity among fCRC patients compared to controls (OR = 2.119; p = 0.045). However, no differences in allele or genotype frequencies were detected between sporadic CRC cases and controls, and no associations were observed for SLC10A2, TP53, and VDR polymorphisms.

CONCLUSIONS

We report a potential association of variants in the CCND1 and CDH1 genes with fCRC using a unique study design with phenotypic extremes.

We reported here an efficient and generally applicable genomic analysis that uses transcriptional profiling to identify candidate substrates of regulatory enzymes, such as kinases and ubiquitin ligases. We applied this strategy to the anaphase-promoting complex/cyclosome (APC/C), a ubiquitin ligase that controls sister chromatid separation and exit from mitosis. We found that a microtubule-associated protein, CKAP2, is a substrate of APC/C and demonstrated that ubiquitination and degradation of CKAP2 in vitro require a KEN-box and is mediated by Cdh1, an activator of APC/C. We showed that the levels of CKAP2 fluctuated across the cell cycle in culture cells, high in mitosis and low during mitotic exit. Overexpression of Cdh1 reduced the levels of CKAP2 in a KEN-box-dependent manner, while knockdown of Cdh1 increased the half-life of CKAP2. CKAP2 associated with centrosomal microtubules in late G(2), but only after the separation of the duplicated centrosomes. During mitosis, CKAP2 associated with spindle poles and with spindle microtubules from prophase through anaphase and dis-appeared from microtubules during cytokinesis. The function of CKAP2 during mitosis does not seem essential, as efficient knockdown of CKAP2 neither altered the cell cycle distribution of the cells, nor generated observable mitotic defects. On the other hand, ectopic expression of either the wild-type or a non-degradable CKAP2 led to a mitotic arrest with monopolar spindles containing highly bundled microtubules. We concluded that CKAP2 is a physiological substrate of APC/C during mitotic exit and that a tight regulation of the CKAP2 protein level is critical for the normal mitotic progression.

BACKGROUND

The loss of E-cadherin (ECAD) protein expression has been linked to aggressive head and neck squamous cell carcinoma (HNSCC). Promoter hypermethylation of the cadherin 1, type 1 (CDH1) gene (encoding ECAD) is 1 mechanism by which this protein can be inactivated, although this epigenetic alteration of the gene has not been linked conclusively to poorer patient outcome and, in fact, may be associated with better patient prognosis.

METHODS

The authors investigated the prevalence of CDH1 promoter hypermethylation in a population-based case series of 340 primary HNSCC tumors using methylation-specific polymerase chain reaction. They also studied the association between CDH1 hypermethylation and patient demographic characteristics using multivariate analysis and examined the impact of CDH1 hypermethylation on patient survival using both univariate and multivariate methods.

RESULTS

Hypermethylation of CDH1 was significantly more prevalent (P < .03) among individuals with a low smoking history independent of whether they were seropositive for human papillomavirus type 16 (HPV-16). Patients who had tumors with CDH1 hypermethylation had significantly better overall survival compared with patients who had tumors without hypermethylation (P < .02; log-rank test). This effect was independent of HPV-16 status and demonstrated a significant hazard ratio of 0.5 (95% confidence interval, 0.3-0.9) in a model that controlled for HPV-16 serology, age, sex, and tumor stage.

CONCLUSIONS

The current results suggested that hypermethylation of CDH1 occurs more commonly in patients with HNSCC who are low smokers, suggesting that an additional factor may be driving this epigenetic alteration. Clinically, CDH1 hypermethylation may hold powerful prognostic potential in addition to that observed with HPV serology, and the authors concluded that it should be pursued in additional studies.

Microtubule targeting drugs are successful in chemotherapy because they indefinitely activate the spindle assembly checkpoint. The spindle assembly checkpoint monitors proper attachment of all kinetochores to microtubules and tension between the kinetochores of sister chromatids to prevent premature anaphase entry. To this end, the activated spindle assembly checkpoint suppresses the E3 ubiquitin ligase activity of the anaphase-promoting complex (APC). In the continued presence of conditions that activate the spindle assembly checkpoint, cells eventually escape from mitosis by "slippage". It has not been directly tested whether APC activation accompanies slippage. Using cells blocked in mitosis with the microtubule assembly inhibitor nocodazole, we show that mitotic APC substrates are degraded upon mitotic slippage. To confirm that APC is normally activated upon mitotic slippage we have found that knockdown of Cdc20 and Cdh1, two mitotic activators of APC, prevents the degradation of APC substrates during mitotic slippage. We provide the first direct demonstration that despite conditions that activate the spindle checkpoint, APC is indeed activated upon mitotic slippage of cells to interphase cells. Activation of the spindle checkpoint by microtubule targeting drugs used in chemotherapy may not indefinitely prevent APC activation.

Cervical cancer is the principal cause of death due to cancer in women. Five-year survival rate ranges from 15-80%, depending on the extent of the disease. New predictive markers for relapse may increase survival rates by improving treatment of patients at high risk for relapse. The gene products of <em>CDH1</em> and <em>CDH1</em>3, namely E-cadherin and H-cadherin, play a key role in cell-cell adhesion. Inactivation of the cadherin-mediated cell adhesion system, caused by aberrant methylation, is a common finding in human cancers. To test the hypothesis that <em>CDH1</em>/<em>CDH1</em>3 methylation is a prognostic marker in cervical cancer we determined the methylation status of <em>CDH1</em>/<em>CDH1</em>3 in serum samples from 93 cervical cancer patients. Methylation analysis was carried out using MethyLight. Aberrant methylation of the 5'-region of <em>CDH1</em> or <em>CDH1</em>3 was observed in 43% (40 of 93) of the patients. Cervical cancer patients with unmethylated <em>CDH1</em>/<em>CDH1</em>3 in serum samples showed significantly better disease-free survival in univariate and multivariate analysis. Median disease-free survival for <em>CDH1</em>/<em>CDH1</em>3 methylation negative and positive patients was 4.3 years and 1.2 years, respectively. Our results suggest that detection of aberrant methylation of <em>CDH1</em>/<em>CDH1</em>3 may be of potential use as a marker for selecting cervical cancer patients at high risk for relapse who could benefit from additional systemic therapy.

WNTs (Wingless-type MMTV integration site family member) are involved in critical developmental and growth processes in animals. These studies investigated WNT pathways in the ovine uterus and conceptus during the periimplantation period of pregnancy. WNT2 and WNT2B mRNAs were detected in endometrial stroma. WNT5A and WNT5B mRNAs were most abundant in the stroma and less so in the luminal epithelium, whereas WNT11 mRNA was detected primarily in the glands. WNT7A mRNA was present in the luminal epithelium on d 10, absent on d 12 and 14, and increased between d 16 and 20. Only WNT2, WNT2B, and WNT4 were detected in conceptus trophectoderm. FZD6/8 (frizzled receptor) and GSK3B (glycogen synthase kinase 3beta) mRNAs were detected primarily in endometrial epithelia and conceptus trophectoderm, whereas the LRP5/6 (low-density lipoprotein receptor-related proteins 5 and 6) coreceptor was present in all endometrial cells and the trophectoderm. DKK1 (Dickkopf), a WNT signaling inhibitor, increased in the endometrium from d 16-20. CTNNB1 [catenin (cadherin associated protein) beta1] and CDH1 (E-cadherin) mRNAs were most abundant in the endometrial epithelia and trophectoderm. LEF1 (lymphoid enhancer-binding factor 1) mRNA was expressed primarily in uterine epithelia, whereas TCF7L2 [(transcription factor 7-like 2 (T-cell specific, HMG-box)] was primarily in the conceptus. CTNNB1 and TCF7L2 proteins were both abundant in the nuclei of trophoblast giant binucleate cells. WNT7A stimulated a TCF/LEF-luciferase reporter activity in ovine trophectoderm cells that was inhibited by dominant-negative TCF and Sfrp2 (secreted FZD-related protein 2). WNT7A increased trophectoderm cell proliferation as well as MSX2 (msh homeobox 2) and MYC (myelocytomatosis oncogene) mRNA levels. Wnt5a increased trophectoderm cell migration in a Rho kinase-dependent manner. These results support the hypotheses that canonical and noncanonical WNT signaling pathways are conserved regulators of conceptus-endometrial interactions in mammals and regulate periimplantation ovine conceptus development.

In recent years, diverse and unexpected neurobiological functions have been uncovered for the major cell cycle-regulated ubiquitin ligase, the anaphase-promoting complex (APC). Functions of the APC in the nervous system range from orchestrating neuronal morphogenesis and synapse development to the regulation of neuronal differentiation, survival, and metabolism. The APC acts together with the coactivating proteins Cdh1 and Cdc20 in neural cells to target specific substrates for ubiquitination and consequent degradation by the proteasome. As we continue to unravel APC functions and mechanisms in neurobiology, these studies should advance our understanding of the molecular mechanisms of neuronal connectivity, with important implications for the study of brain development and disease.

F-box proteins are the substrate recognition subunits of SCF (Skp1, Cul1, F-box protein) ubiquitin ligase complexes. Skp2 is a nuclear F-box protein that targets the CDK inhibitor p27 for ubiquitin- and proteasome-dependent degradation. In G(0) and during the G(1) phase of the cell cycle, Skp2 is degraded via the APC/C(Cdh1) ubiquitin ligase to allow stabilization of p27 and inhibition of CDKs, facilitating the maintenance of the G(0)/G(1) state. APC/C(Cdh1) binds Skp2 through an N-terminal domain (amino acids 46-94 in human Skp2). It has been shown that phosphorylation of Ser64 and Ser72 in this domain dissociates Skp2 from APC/C. More recently, it has instead been proposed that phosphorylation of Skp2 on Ser72 by Akt/PKB allows Skp2 binding to Skp1, promoting the assembly of an active SCF(Skp2) ubiquitin ligase, and Skp2 relocalization/retention into the cytoplasm, promoting cell migration via an unknown mechanism. According to these reports, a Skp2 mutant in which Ser72 is substituted with Ala is unable to promote cell proliferation and loses its oncogenic potential. Given the contrasting reports, we revisited these results and conclude that phosphorylation of Skp2 on Ser72 does not control Skp2 binding to Skp1 and Cul1, has no influence on SCF(Skp2) ubiquitin ligase activity, and does not affect the subcellular localization of Skp2.

BACKGROUND

The follicle cells of the Drosophila egg chamber provide an excellent model in which to study modulation of the cell cycle. During mid-oogenesis, the follicle cells undergo a variation of the cell cycle, endocycle, in which the cells replicate their DNA, but do not go through mitosis. Previously, we showed that Notch signaling is required for the mitotic-to-endocycle transition, through downregulating String/Cdc25, and Dacapo/p21 and upregulating Fizzy-related/Cdh1.

RESULTS

In this paper, we show that Notch signaling is modulated by Shaggy and temporally induced by the ligand Delta, at the mitotic-to-endocycle transition. In addition, a downstream target of Notch, tramtrack, acts at the mitotic-to-endocycle transition. We also demonstrate that the JNK pathway is required to promote mitosis prior to the transition, independent of the cell cycle components acted on by the Notch pathway.

CONCLUSIONS

This work reveals new insights into the regulation of Notch-dependent mitotic-to-endocycle switch.

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) exhibits heterogeneous clinical features and a marked variable response to treatment.

METHODS

We investigated the prognostic significance of the methylation status of DAPK, GSTP1, P14, P15, P16, P33, RB1, SHP1, CDH1, APC, BLU, VHL, TIMP3, and RASSF1A genes in 46 DLBCL specimens from Tunisian patients. Methylation status of each gene was correlated with clinicopathological parameters including the International Prognostic Index (IPI), the germinal center immunophenotype, and response to treatment and survival. Overall survival (OS) and disease-free survival (DFS) rates were calculated by the Kaplan-Meier method and differences were compared with the log-rank test.

RESULTS

Hypermethylation of SHP1 was associated with elevated lactate dehydrogenase level (P = 0.031). P16 and VHL were frequently hypermethylated in patients with high IPI scores (P = 0.006 and 0.004) and a performance status of two or more (P = 0.007 and 0.047). In addition, hypermethylation of P16 was significantly associated with advanced clinical stages and B symptoms (P = 0.041 and 0.012). Interestingly, hypermethylation of DAPK was significantly correlated with resistance to treatment (P = 0.023). With regard to survival rates, promoter hypermethylation of DAPK, P16, and VHL were significantly associated with shortened OS (P = 0.003, 0.001, and 0.017, respectively) and DFS (P = 0.006, 0.003, and 0.046, respectively). In multivariate analysis, hypermethylation of DAPK remains an independent prognostic factor in predicting shortened OS (P = 0.001) and DFS (P = 0.024), as well as the IPI and the germinal center status.

CONCLUSIONS

This study demonstrates that DLBCLs with hypermethylated P16, VHL, DAPK, and SHP1 commonly show a biologically aggressive phenotype and worse prognosis. Interestingly, hypermethylation of DAPK was found to be an independent prognostic factor that may be used in conjunction with the conventional prognostic factors such as the IPI and the germinal center status.

Shugoshin 1 (Sgo1) protects centromeric sister-chromatid cohesion in early mitosis and, thus, prevents premature sister-chromatid separation. The protein level of Sgo1 is regulated during the cell cycle; it peaks in mitosis and is down-regulated in G1/S. Here we show that Sgo1 is degraded during the exit from mitosis, and its degradation depends on the anaphase-promoting complex/cyclosome (APC/C). Overexpression of Cdh1 reduces the protein levels of ectopically expressed Sgo1 in human cells. Sgo1 is ubiquitinated by APC/C bound to Cdh1 (APC/C(Cdh1)) in vitro. We have further identified two functional degradation motifs in Sgo1; that is, a KEN (Lys-Glu-Asn) box and a destruction box (D box). Although removal of either motif is not sufficient to stabilize Sgo1, Sgo1 with both KEN box and D box deleted is stable in cells. Surprisingly, mitosis progresses normally in the presence of non-degradable Sgo1, indicating that degradation of Sgo1 is not required for sister-chromatid separation or mitotic exit. Finally, we show that the spindle checkpoint kinase Bub1 contributes to the maintenance of Sgo1 steady-state protein levels in an APC/C-independent mechanism.

Ubiquitin-dependent degradation of Cdc25A is a major mechanism for damage-induced S-phase checkpoint. Two ubiquitin ligases, the Skp1-cullin-beta-TrCP (SCFbeta-TrCP) complex and the anaphase-promoting complex (APCCdh1), are involved in Cdc25A degradation. Here we demonstrate that the transforming growth factor beta (TGF-beta)-Smad3 pathway promotes SCF(beta-TrCP)-mediated Cdc25A ubiquitination. Cells treated with TGF-beta, as well as cells transfected with Smad3 or a constitutively active type I TGF-beta receptor, exhibit increased ubiquitination and markedly shortened half-lives of Cdc25A. Furthermore, Cdc25A is stabilized in cells transfected with Smad3 small interfering RNA (siRNA) and cells from Smad3-null mice. TGF-beta-induced ubiquitination is associated with Cdc25A phosphorylation at the beta-TrCP docking site (DS82G motif) and physical association of Cdc25A with Smad3 and beta-TrCP. Cdc25A mutant proteins deficient in DS82G phosphorylation are resistant to TGF-beta-Smad3-induced degradation, whereas a Cdc25A mutant protein defective in APCCdh1 recognition undergoes efficient degradation. Smad3 siRNA inhibits beta-TrCP-Cdc25A interaction and Cdc25A degradation in response to TGF-beta. beta-TrCP2 siRNA also inhibits Smad3-induced Cdc25A degradation. In contrast, Cdh1 siRNA had no effect on Cdc25A down-regulation by Smad3. These data suggest that Smad3 plays a key role in the regulation of Cdc25A ubiquitination by SCFbeta-TrCP and that Cdc25A stabilization observed in various cancers could be associated with defects in the TGF-beta-Smad3 pathway.

OBJECTIVE

E-cadherin, a M(r) 120,000 transmembrane glycoprotein, mediates calcium-dependent intercellular adhesion that is essential for normal tissue homeostasis. Loss of E-cadherin occurs in a variety of epithelial tumors and is correlated with invasion and metastasis. In esophageal adenocarcinoma, reduction of E-cadherin expression has been demonstrated previously, but mutations of the gene (CDH1) are rare.

METHODS

In this study, we used a nested PCR approach to examine the methylation status of the 5' CpG island of E-cadherin in esophageal specimens obtained from individuals with and without a history of esophageal cancer.

RESULTS

In four individuals without esophageal cancer, E-cadherin was completely unmethylated in normal squamous cell-lined esophageal mucosa. In contrast, in patients with esophageal adenocarcinoma, E-cadherin was methylated in 26 of 31 (84%) tumor specimens. In the majority of cases, matched normal tissue (esophagus or stomach) from each patient was completely unmethylated. By immunostaining, methylated tumor samples demonstrated heterogeneously decreased membranous E-cadherin staining.

CONCLUSIONS

These data suggest that epigenetic silencing via aberrant methylation of the E-cadherin promoter is a common cause of inactivation of this gene in esophageal adenocarcinoma.

The ability of eukaryotes to alter chromatin structure and function is modulated, in part, by histone-modifying enzymes and the post-translational modifications they create. One of these enzymes, PR-Set7/Set8/KMT5a, is the sole histone methyltransferase responsible for the monomethylation of histone H4 lysine 20 (H4K20me1) in higher eukaryotes. Both PR-Set7 and H4K20me1 were previously found to be tightly cell cycle regulated suggesting that they play an important, although unknown, role in cell cycle progression. Several recent reports reveal that PR-Set7 abundance is dynamically regulated during different cell cycle phases by distinct enzymes including cdk1/cyclinB, Cdc14, SCF(Skp2), CRL4(cdt2) and APC(cdh1). Importantly, these reports demonstrate that inappropriate levels of PR-Set7 result in profound cell cycle defects including the inability to initiate S phase, the re-replication of DNA and the improper timing of mitotic progression. Here, we summarize the significance of these new findings, raise some important questions that require further investigation and explore several possibilities of how PR-Set7 and methylated H4K20 may likely function as novel regulators of the cell cycle.

OBJECTIVE

Hyperactivation of the RAS-RAF signaling pathway in colorectal tumors is associated with metastasis and poor outcomes of patients. Little is known about how RAS-RAF signaling is turned off once activated. We investigated how the pH domain and leucine-rich repeat protein phosphatases (PHLPPs) control RAS-RAF signaling and colorectal cancer (CRC) development.

METHODS

We used co-immunoprecipitation assays to identify substrates of PHLPP1 and PHLPP2. We studied phosphorylation of RAF1 in CRC cells that express exogenous PHLPP1 or PHLPP2, or lentiviral-based small hairpin RNAs against their transcripts; we measured effects on cell motility, migration, and invasion in vitro. Tumor progression and survival were analyzed in Phlpp1(-/-) Apc(Min) and Apc(Min)/Phlpp1(-/-) mice. Microarray datasets of colorectal tumor and nontumor tissues were analyzed for PHLPP gene expression.

RESULTS

PHLPP1 and 2 were found to dephosphorylate RAF1 at S338, inhibiting its kinase activity in vitro and in CRC cells. In cells, knockdown of PHLPP1 or PHLPP2 increased the amplitude and duration of RAF-MEK-ERK signaling downstream of epidermal growth factor receptor and KRAS, whereas overexpression had the opposite effect. In addition, knockdown of PHLPP1 or PHLPP2 caused CRC cells to express markers of the epithelial-mesenchymal transition, and increased cell migration and invasion. Apc(Min)/Phlpp1(-/-) mice had decreased survival and developed larger intestinal and colon tumors compared to Apc(Min) mice. Whereas Apc(Min) mice developed mostly low-grade adenomas, 20% of the tumors that developed in Apc(Min)/Phlpp1(-/-) mice were invasive adenocarcinomas. Normal villi and adenomas of Apc(Min)/Phlpp1(-/-) mice had significantly fewer apoptotic cells than Apc(Min) mice. Human CRC patient microarray data revealed that the expression of PHLPP1 or PHLPP2 is positively correlated with CDH1.

CONCLUSIONS

PHLPP1 and PHLPP2 dephosphorylate RAF1 to reduce its signaling, increase the invasive and migratory activities of CRC cells, and activate the epithelial-mesenchymal transition. In Apc(Min) mice, loss of PHLPP1 promotes tumor progression.

Pancreatic cancer with liver metastases has a poor prognosis and the molecular mechanisms remain unclear. In this study, SW1990HM, a highly metastatic human pancreatic carcinoma line was subcloned from SW1990 by intrasplenic injection. In vivo and in vitro tumorigenicity, metastatic potential, in vitro invasion, cell growth curves, plate efficiency and S-phase cell numbers were higher in SW1990HM cells. Gene expression profiles of SW1990HM and SW1990 cells showed 40 metastasis-related genes expressed with a 3-fold difference. Thirteen of these 32.5% (13/40) were adhesion and extracellular-matrix related and twelve 30% (12/40) were cell growth and proliferation related, such as MMP10, MMP9, MMP7, CDH1, MGAT5, CTNNA1, IGF1, IL8RB, ITGA7, MDM2, MET, SSTR2 and VEGF, which were related to the onset and progression of tumor metastasis. Thus, SW1990HM is an attractive model to study metastasis and identify potential therapeutic targets.

Hereditary diffuse gastric cancer (HDGC) is a relatively rare disorder, with a mutated CDH1 gene as the only known cause. Carriers of a germline mutation in CDH1 have a lifetime risk of >80% of developing diffuse gastric cancer. As periodic gastric surveillance is of limited value in detecting early stages of HDGC, prophylactic gastrectomy is advised for this patient group. Little is known about other types of familial gastric cancer. The Dutch working group on hereditary gastric cancer has formulated guidelines for various aspects of medical management for families and individuals at high risk of developing gastric cancer, including criteria for referral, classification, diagnostics, and periodic gastric surveillance. These guidelines are not limited to HDGC and are therefore partially complementary to the guidelines on hereditary diffuse gastric cancer of the international gastric cancer linkage consortium (IGCLC 2010). In order to optimize the care and increase the knowledge on hereditary gastric cancer it is important to centralize medical care for these patients. National and international collaboration is warranted to improve the quality of research by increasing the size of study cohorts.

OBJECTIVE

The mechanisms of hepatocarcinogenesis induced by hepatitis C virus remain unclear. Our aim was to investigate the effect of the HCV core protein on the promoter methylation status of selected genes potentially involved in the hepatocellular carcinoma (HCC).

METHODS

We evaluated the promoter methylation levels of the E-cadherin (CDH1), the glutathione S-transferase p1 (GSTP1), adenomatosis polyposis coli (APC), tissue inhibitor of metalloproteinase 3 (TIMP3), catenin (cadherin-associated protein) beta 1 (CNNTB1) genes by a quantitative methylation-specific polymerase chain reaction (QMSP) in the in vitro model of Huh-7 cells expressing the HCV core protein of genotype 1b.

RESULTS

We found that CDH1 promoter was hypermethylated in genotype 1b HCV core protein-positive cells as compared to control cells expressing the GFP protein alone (HCV core 1b vs GFP p=0.00; HCV core 1b vs Huh-7 p=0.03). This resulted in reduced levels of CDH1 protein as evaluated by immunoblot and by immunofluorescence. On the other hand no significant changes were observed for the other genes investigated. Furthermore, we present evidence that genotype 1b HCV core protein expression induces SIRT1 upregulation and that treatment with SIRT1 inhibitor sirtinol decreases the methylation levels of CDH1 promoter (1b+sirtinol vs 1b p=0.05; 1b+sirtinol vs GFP+sirtinol p=NS) resulting in 1.7-fold increased CDH1 mRNA expression (1b+sirtinol vs 1b p=0.05).

CONCLUSIONS

Our findings suggest that HCV core protein could play a role in HCC at least in part by altering the methylation status of CDH1 promoter. These findings could also suggest a novel therapeutic approach for HCC.

Aurora A kinase (AURKA) is overexpressed in 96% of human cancers and is considered an independent marker of poor prognosis. While the majority of tumors have elevated levels of AURKA protein, few have AURKA gene amplification, implying that posttranscriptional mechanisms regulating AURKA protein levels are significant. Here, we show that NEDD9, a known activator of AURKA, is directly involved in AURKA stability. Analysis of a comprehensive breast cancer tissue microarray revealed a tight correlation between the expression of both proteins, significantly corresponding with increased prognostic value. A decrease in AURKA, concomitant with increased ubiquitination and proteasome-dependent degradation, occurs due to depletion or knockout of NEDD9. Reexpression of wild-type NEDD9 was sufficient to rescue the observed phenomenon. Binding of NEDD9 to AURKA is critical for AURKA stabilization, as mutation of S296E was sufficient to disrupt binding and led to reduced AURKA protein levels. NEDD9 confers AURKA stability by limiting the binding of the cdh1-substrate recognition subunit of APC/C ubiquitin ligase to AURKA. Depletion of NEDD9 in tumor cells increases sensitivity to AURKA inhibitors. Combination therapy with NEDD9 short hairpin RNAs and AURKA inhibitors impairs tumor growth and distant metastasis in mice harboring xenografts of breast tumors. Collectively, our findings provide rationale for the use of AURKA inhibitors in treatment of metastatic tumors and predict the sensitivity of the patients to AURKA inhibitors based on NEDD9 expression.

Interactions between neurons and glia are a key feature during the assembly of the nervous system. During development, glial cells often follow extending axons, implying that axonal outgrowth and glial migration are precisely coordinated. We found that the anaphase-promoting complex/cyclosome (APC/C) co-activator fizzy-related/Cdh1 (Fzr/Cdh1) is involved in the non-autonomous control of peripheral glial migration in postmitotic Drosophila neurons. APC/C(Fzr/Cdh1) is a cell-cycle regulator that targets proteins that are required for G1 arrest for ubiquitination and subsequent degradation. We found that Fzr/Cdh1 function is mediated by the immunoglobulin superfamily cell adhesion molecule Fasciclin2 (Fas2). In motor neurons Fzr/Cdh1 is crucial for the establishment of a graded axonal distribution of Fas2. Axonal Fas2 interacts homophilically with a glial isoform of Fas2. Glial migration is initiated along axonal segments that have low levels of Fas2 but stalls in axonal domains with high levels of Fas2 on their surfaces. This represents a simple mechanism by which a subcellular gradient of adhesiveness can coordinate glial migration with axonal growth.

The ZEB1 transcription factor is best known as an inducer of epithelial-mesenchymal transitions (EMT) in cancer metastasis, acting through transcriptional repression of CDH1 (encoding E-cadherin) and the EMT-suppressing microRNA-200s (miR-200s). Here we analyze roles of the ZEB1 zebrafish orthologs, Zeb1a and Zeb1b, and of miR-200s in control of cell adhesion and morphogenesis during gastrulation and segmentation stages. Loss and gain of function analyses revealed that Zeb1 represses cdh1 expression to fine-tune adhesiveness of migrating deep blastodermal cells. Furthermore, Zeb1 acts as a repressor of epcam in the deep cells of the blastoderm and may contribute to control of epithelial integrity of enveloping layer cells, the outermost cells of the blastoderm. We found a similar ZEB1-dependent repression of EPCAM expression in human pancreatic and breast cancer cell lines, mediated through direct binding of ZEB1 to the EPCAM promoter. Thus, Zeb1 proteins employ several evolutionary conserved mechanisms to regulate cell-cell adhesion during development and cancer.

Epithelial to mesenchymal transition (EMT) involves loss of an epithelial phenotype and activation of a mesenchymal one. Enhanced expression of genes associated with a mesenchymal transition includes ZEB1/2, TWIST, and FOXC1. miRNAs are known regulators of gene expression and altered miRNA expression is known to enhance EMT in breast cancer. Here we demonstrate that the tumor suppressive miRNA family, miR-200, is not expressed in triple negative breast cancer (TNBC) cell lines and that miR-200b-3p over-expression represses EMT, which is evident through decreased migration and increased CDH1 expression. Despite the loss of migratory capacity following re-expression of miR-200b-3p, no subsequent loss of the conventional miR-200 family targets and EMT markers ZEB1/2 was observed. Next generation RNA-sequencing analysis showed that enhanced expression of pri-miR-200b lead to ectopic expression of both miR-200b-3p and miR-200b-5p with multiple isomiRs expressed for each of these miRNAs. Furthermore, miR-200b-5p was expressed in the receptor positive, epithelial breast cancer cell lines but not in the TNBC (mesenchymal) cell lines. In addition, a compensatory mechanism for miR-200b-3p/200b-5p targeting, where both miRNAs target the RHOGDI pathway leading to non-canonical repression of EMT, was demonstrated. Collectively, these data are the first to demonstrate dual targeting by miR-200b-3p and miR-200b-5p and a previously undescribed role for microRNA processing and strand expression in EMT and TNBC, the most aggressive breast cancer subtype.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial-to-mesenchymal transition (EMT) is a key contributor in the metastatic process. We previously showed the pan-deacetylase inhibitor LBH589 induces CDH1 expression in TNBC cells, suggesting regulation of EMT. The purpose of this study was to examine the effects of LBH589 on the metastatic qualities of TNBC cells and the role of EMT in this process. A panel of breast cancer cell lines (MCF-7, MDA-MB-231, and BT-549), drugged with LBH589, was examined for changes in cell morphology, migration, and invasion in vitro. The effect on in vivo metastasis was examined using immunofluorescent staining of lung sections. EMT gene expression profiling was used to determine LBH589-induced changes in TNBC cells. ZEB overexpression studies were conducted to validate requirement of ZEB in LBH589-mediated proliferation and tumorigenesis. Our results indicate a reversal of EMT by LBH589 as demonstrated by altered morphology and altered gene expression in TNBC. LBH589 was shown to be a more potent inhibitor of EMT than other HDAC inhibitors, SAHA and TMP269. Additionally, we found that LBH589 inhibits metastasis of MDA-MB-231 cells in vivo. These effects of LBH589 were mediated in part by inhibition of ZEB, as overexpression of ZEB1 or ZEB2 mitigated the effects of LBH589 on MDA-MB-231 EMT-associated gene expression, migration, invasion, CDH1 expression, and tumorigenesis. These data indicate therapeutic potential of LBH589 in targeting EMT and metastasis of TNBC.