RAD52-dependent mitotic DNA synthesis is required for genome stability in Cyclin E1-overexpressing cells

Overexpression of Cyclin E1 perturbs DNA replication, resulting in DNA lesions and genomic instability. Consequently, Cyclin E1-overexpressing cancer cells increasingly rely on DNA repair, including RAD52-mediated break-induced replication during interphase. We show that not all DNA lesions induced by Cyclin E1 overexpression are resolved during interphase. While DNA lesions upon Cyclin E1 overexpression are induced in S phase, a significant fraction of these lesions is transmitted into mitosis. Cyclin E1 overexpression triggers mitotic DNA synthesis (MiDAS) in a RAD52-dependent fashion. Chemical or genetic inactivation of MiDAS enhances mitotic aberrations and persistent DNA damage. Mitosis-specific degradation of RAD52 prevents Cyclin E1-induced MiDAS and reduces the viability of Cyclin E1-overexpressing cells, underscoring the relevance of RAD52 during mitosis to maintain genomic integrity. Finally, analysis of breast cancer samples reveals a positive correlation between Cyclin E1 amplification and RAD52 expression. These findings demonstrate the importance of suppressing mitotic defects in Cyclin E1-overexpressing cells through RAD52.

CircROR1 upregulates CCNE1 expression to promote melanoma invasion and metastasis by recruiting KAT2A

Circular RNAs (circRNAs) play important roles in cancer occurrence and progression. To explore and elucidate the clinical significance of specific circular RNA in melanoma and its potential molecular mechanism. CircROR1 expression in melanoma cells and tissues was confirmed by qRT-PCR and ISH. qRT-PCR and Western blotting were performed to measure the levels of CCNE1, KAT2A, MMP9 and TIMP2. MTT, Transwell and wound healing assays were performed to evaluate cell proliferation, invasion and metastasis. A xenograft mouse model was established to further verify the CircROR1/CCNE1 axis in vivo. RNA pull-down and RIP assays were performed to detect the direct interaction KAT2A and CircROR1. A ChIP assay was used to investigate the enrichment of H3K9ac acetylation in the CCNE1 promoter. CircROR1 was significantly upregulated in metastatic melanoma cells and tissues, promoting proliferation, invasion and metastasis in vitro and tumour growth in vivo. CircROR1 overexpression increased CCNE1 and MMP9 protein expression and decreased TIMP2 protein expression. Functional rescue assays demonstrated that CircROR1 played a role in promoting malignant progression through CCNE1. CircROR1 specifically bound to the KAT2A protein without affecting its expression. CircROR1 overexpression increased the level of H3K9ac modification in the CCNE1 promoter region by recruiting KAT2A, thus upregulating CCNE1 expression. CircROR1 upregulates CCNE1 expression through KAT2A-mediated histone acetylation. Our research confirms the critical role of CircROR1 in melanoma invasion and metastasis, and CircROR1 could serve as a potential therapeutic target for melanoma treatment.

PPM1D activity promotes the replication stress caused by cyclin E1 overexpression

Oncogene-induced replication stress has been recognized as a major cause of genome instability in cancer cells. Increased expression of cyclin E1 caused by amplification of the CCNE1 gene is a common cause of replication stress in various cancers. Protein phosphatase magnesium-dependent 1 delta (PPM1D) is a negative regulator of p53 and has been implicated in termination of the cell cycle checkpoint. Amplification of the PPM1D gene or frameshift mutations in its final exon promote tumorigenesis. Here, we show that PPM1D activity further increases the replication stress caused by overexpression of cyclin E1. In particular, we demonstrate that cells expressing a truncated mutant of PPM1D progress faster from G1 to S phase and fail to complete licensing of the replication origins. In addition, we show that transcription-replication collisions and replication fork slowing caused by CCNE1 overexpression are exaggerated in cells expressing the truncated PPM1D. Finally, replication speed and accumulation of focal DNA copy number alterations caused by induction of CCNE1 expression was rescued by pharmacological inhibition of PPM1D. We propose that increased activity of PPM1D suppresses the checkpoint function of p53 and thus promotes genome instability in cells expressing the CCNE1 oncogene.

Regulation of Interferon-β-Modified Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes in Proliferation and Apoptosis of Prostate Cancer Cells

Prostate cancer (PCa) poses a serious burden to men. Interferon-β (IFN-β) is implicated in cancer cell growth. This study hence explored the regulation of IFN-β-modified human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-Exos) in PCa cells. In vitro-cultured hUCMSCs were transfected with pcDNA3.1-IFN-β plasmid or IFN-β siRNA. hUCMSC-Exos were extracted by ultracentrifugation and identified. PCa cells (PC3 and LNCap) were treated with Exos. Cellular internalization of Exos by cells was detected by uptake assay. Cell proliferation, cycle, and apoptosis were evaluated by CCK-8, EdU staining, and flow cytometry. Levels of cell cycle-related proteins (cyclin D/cyclin E) were determined by Western blot. The effect of IFN-β-modified hUCMSC-Exos in vivo was analyzed. IFN-β-modified hUCMSC-Exos (Exooe-IFN-β or Exosi-IFN-β) were successfully isolated. IFN-β was encapsulated in Exos, and PCa cells could uptake Exos. After treating with Exooe-IFN-β, PCa cell proliferation was impeded, the percentage of cells in the G0/G1 phase, cyclin D/cyclin E levels, and cell apoptotic rate were elevated, while cells treated with Exooe-IFN-β exhibited contrary trends. IFN-β-modified hUCMSC-Exos reduced PCa tumor size and weight in vivo. Conjointly, IFN-β-modified hUCMSC-Exos suppress PCa cell proliferation and facilitate apoptosis.

FBXL12 degrades FANCD2 to regulate replication recovery and promote cancer cell survival under conditions of replication stress

Fanconi anemia (FA) signaling, a key genomic maintenance pathway, is activated in response to replication stress. Here, we report that phosphorylation of the pivotal pathway protein FANCD2 by CHK1 triggers its FBXL12-dependent proteasomal degradation, facilitating FANCD2 clearance at stalled replication forks. This promotes efficient DNA replication under conditions of CYCLIN E- and drug-induced replication stress. Reconstituting FANCD2-deficient fibroblasts with phosphodegron mutants failed to re-establish fork progression. In the absence of FBXL12, FANCD2 becomes trapped on chromatin, leading to replication stress and excessive DNA damage. In human cancers, FBXL12, CYCLIN E, and FA signaling are positively correlated, and FBXL12 upregulation is linked to reduced survival in patients with high CYCLIN E-expressing breast tumors. Finally, depletion of FBXL12 exacerbated oncogene-induced replication stress and sensitized cancer cells to drug-induced replication stress by WEE1 inhibition. Collectively, our results indicate that FBXL12 constitutes a vulnerability and a potential therapeutic target in CYCLIN E-overexpressing cancers.

PKMYT1: A Potential Target for CCNE1 Amplificated Colorectal Tumors

Colorectal cancer is a malignant tumor with higher morbidity and mortality. The purpose of this study is to investigate whether inhibition of Protein Kinase, Membrane Associated Tyrosine/Threonine 1 (PKMYT1) affects tumor cell proliferation, survival and migration in colon tumors with high Cyclin E1 (CCNE1) expression. PcDNA3.1-CCNE1 vector and si-PKMYT1 were transfected in SW480 cells by Lipofectamine 2000. Q-PCR and western blot assay were processed to detect the expression. Transwell assay and Edu assay were undertaken to verify the migration and proliferation. CCNE1 promotes the proliferation and migration of SW480. Silencing of PKMYT1 inhibited the proliferation of tumor cells. Silencing the expression of PKMYT1 under the premise of overexpression of CCNE1, the level of Cyclin Dependent Kinase 1 (CDK1)-PT14 was reduced, indicating that the cell cycle was blocked. The expression of γH2AX increased significantly, indicating that the DDR pathway of tumor cells was activated and DNA damage accumulated. The results of immunofluorescence microscopy showed significantly increased expression of DNA damage-associated marker (γH2AX: H2AX Variant Histone). In CCNE1 amplificated colorectal tumor cells, knockdown of PKMYT1 reduced cells in S phase, inhibited cell proliferation and promoted cell apoptosis, confirming that PKMYT1 was a potential therapeutic target for colorectal tumor. This study may verify a potential therapeutic target and provide a new idea for the treatment of colorectal cancer in the future.

Cyclin E/CDK2 and feedback from soluble histone protein regulate the S phase burst of histone biosynthesis

Faithful DNA replication requires that cells fine-tune their histone pool in coordination with cell-cycle progression. Replication-dependent histone biosynthesis is initiated at a low level upon cell-cycle commitment, followed by a burst at the G1/S transition, but it remains unclear how exactly the cell regulates this burst in histone biosynthesis as DNA replication begins. Here, we use single-cell time-lapse imaging to elucidate the mechanisms by which cells modulate histone production during different phases of the cell cycle. We find that CDK2-mediated phosphorylation of NPAT at the restriction point triggers histone transcription, which results in a burst of histone mRNA precisely at the G1/S phase boundary. Excess soluble histone protein further modulates histone abundance by promoting the degradation of histone mRNA for the duration of S phase. Thus, cells regulate their histone production in strict coordination with cell-cycle progression by two distinct mechanisms acting in concert.

Pers reverse angiotensin II -induced vascular smooth muscle cell proliferation by targeting cyclin E expression via inhibition of the MAPK signaling pathway

The circadian rhythm of blood pressure (BP) is believed to be regulated by the clock system, which is closely linked to levels of angiotensin II (Ang II). This study aimed to investigate whether Ang II mediates the proliferation of vascular smooth muscle cells (VSMCs) through the interaction between the clock system and the mitogen-activated protein kinase (MAPK) signaling pathway. Primary rat aortic VSMCs were treated with Ang II, with or without MAPK inhibitors. VSMC proliferation, expression of clock genes, CYCLIN E, and MAPK pathways were assessed. Ang II treatment resulted in increased VSMC proliferation and rapid upregulation of clock gene Periods (Pers) expression. Compared to the non-diseased control (NC) group, VSMCs incubated with Ang II displayed a noticeable delay in the G1/S phase transition and downregulation of CYCLIN E upon silencing of Per1 and Per2 genes. Importantly, silencing Per1 or Per2 in VSMCs led to decreased expression of key MAPK pathway proteins, including RAS, phosphorylated mitogen-activated protein kinase (P-MEK), and phosphorylated extracellular signal-regulated protein kinase (P-ERK). Moreover, the MEK and ERK inhibitors, U0126 and SCH772986, significantly attenuated the Ang II-induced proliferation of VSMCs, as evidenced by an increased G1/S phase transition and decreased CYCLIN E expression. The MAPK pathway plays a critical role in regulating VSMC proliferation in response to Ang II stimulation. This regulation is controlled by the expression of circadian clock genes involved in the cell cycle. These findings provide novel insights for further research on diseases associated with abnormal VSMC proliferation.

Spatiotemporal Epigenetic Control of the Histone Gene Chromatin Landscape during the Cell Cycle

Higher-order genomic organization supports the activation of histone genes in response to cell cycle regulatory cues that epigenetically mediates stringent control of transcription at the G1/S-phase transition. Histone locus bodies (HLBs) are dynamic, non-membranous, phase-separated nuclear domains where the regulatory machinery for histone gene expression is organized and assembled to support spatiotemporal epigenetic control of histone genes. HLBs provide molecular hubs that support synthesis and processing of DNA replication-dependent histone mRNAs. These regulatory microenvironments support long-range genomic interactions among non-contiguous histone genes within a single topologically associating domain (TAD). HLBs respond to activation of the cyclin E/CDK2/NPAT/HINFP pathway at the G1/S transition. HINFP and its coactivator NPAT form a complex within HLBs that controls histone mRNA transcription to support histone protein synthesis and packaging of newly replicated DNA. Loss of HINFP compromises H4 gene expression and chromatin formation, which may result in DNA damage and impede cell cycle progression. HLBs provide a paradigm for higher-order genomic organization of a subnuclear domain that executes an obligatory cell cycle-controlled function in response to cyclin E/CDK2 signaling. Understanding the coordinately and spatiotemporally organized regulatory programs in focally defined nuclear domains provides insight into molecular infrastructure for responsiveness to cell signaling pathways that mediate biological control of growth, differentiation phenotype, and are compromised in cancer.

Cullin 3 mutant causing familial hyperkalemic hypertension lacks normal activity in the kidney

Mutations in the ubiquitin ligase scaffold protein cullin 3 (CUL3) cause the disease familial hyperkalemic hypertension (FHHt). We recently reported that in the kidney, aberrant mutant CUL3 (CUL3-Δ9) activity lowers the abundance of CUL3-Δ9 and Kelch-like 3, the CUL3 substrate adaptor for with-no-lysine kinase 4 (WNK4) and that this is mechanistically important. However, whether CUL3-Δ9 exerts additional effects on other targets that may alter renal function is unclear. Here, we sought to determine 1) whether CUL3-Δ9 expression can rescue the phenotype of renal tubule-specific Cul3 knockout mice, and 2) whether CUL3-Δ9 expression affects other CUL3 substrates. Using an inducible renal tubule-specific system, we studied two CUL3-Δ9-expressing mouse models: Cul3 knockout (Cul3-/-/Δ9) and Cul3 heterozygous background (Cul3+/-/Δ9, FHHt model). The effects of CUL3-Δ9 in these mice were compared with Cul3-/- and Cul3+/- mice. Similar to Cul3-/- mice, Cul3-/-/Δ9 mice displayed polyuria with loss of aquaporin 2 and collecting duct injury; proximal tubule injury also occurred. CUL3-Δ9 did not promote degradation of two CUL3 targets that accumulate in the Cul3-/- kidney: high-molecular-weight (HMW) cyclin E and NAD(P)H:quinone oxidoreductase 1 (NQO1) [a surrogate for the CUL3-Kelch-like ECH-associated protein 1 (KEAP1) substrate nuclear factor erythroid-2-related factor 2]. Since CUL3-Δ9 expression cannot rescue the Cul3-/- phenotype, our data suggest that CUL3-Δ9 cannot normally function in ubiquitin ligase complexes. In Cul3+/-/Δ9 mice, KEAP1 abundance did not differ but NQO1 abundance was higher, suggesting adaptor sequestration by CUL3-Δ9 in vivo. Together, our results provide evidence that in the kidney, CUL3-Δ9 completely lacks normal activity and can trap CUL3 substrate adaptors in inactive complexes.NEW & NOTEWORTHY CUL3 mutation (CUL3-Δ9) causes familial hyperkalemic hypertension (FHHt) by reducing adaptor KLHL3, impairing substrate WNK4 degradation. Whether CUL3-Δ9 affects other targets in kidneys remains unclear. We found that CUL3-Δ9 cannot degrade two CUL3 targets, cyclin E and nuclear factor erythroid-2-related factor 2 (NRF2; using a surrogate marker NQO1), or rescue injury or polyuria caused by Cul3 disruption. In an FHHt model, CUL3-Δ9 impaired NRF2 degradation without reduction of its adaptor KEAP1. Our data provide additional insights into CUL3-Δ9 function in the kidney.

Nuclear Prospero allows one-division potential to neural precursors and post-mitotic status to neurons via opposite regulation of Cyclin E

In Drosophila embryonic CNS, the multipotential stem cells called neuroblasts (NBs) divide by self-renewing asymmetric division and generate bipotential precursors called ganglion mother cells (GMCs). GMCs divide only once to generate two distinct post-mitotic neurons. The genes and the pathways that confer a single division potential to precursor cells or how neurons become post-mitotic are unknown. It has been suggested that the homeodomain protein Prospero (Pros) when localized to the nucleus, limits the stem-cell potential of precursors. Here we show that nuclear Prospero is phosphorylated, where it binds to chromatin. In NB lineages such as MP2, or GMC lineages such as GMC4-2a, Pros allows the one-division potential, as well as the post-mitotic status of progeny neurons. These events are mediated by augmenting the expression of Cyclin E in the precursor and repressing the expression in post-mitotic neurons. Thus, in the absence of Pros, Cyclin E is downregulated in the MP2 cell. Consequently, MP2 fails to divide, instead, it differentiates into one of the two progeny neurons. In progeny cells, Pros reverses its role and augments the downregulation of Cyclin E, allowing neurons to exit the cell cycle. Thus, in older pros mutant embryos Cyclin E is upregulated in progeny cells. These results elucidate a long-standing problem of division potential of precursors and post-mitotic status of progeny cells and how fine-tuning cyclin E expression in the opposite direction controls these fundamental cellular events. This work also sheds light on the post-translational modification of Pros that determines its cytoplasmic versus nuclear localization.

Chloroquine regulates the proliferation and apoptosis of palate development on mice embryo by activating P53 through blocking autophagy in vitro

Cleft lip and palate is one of the most frequent congenital developmental defects. Autophagy is a highly conserved process of cell self-degradation in eukaryotes, involving multiple biological processes in which chloroquine (CQ) is the most common inhibitor. However, whether CQ affects and how it affects palate development is unknown. Mouse embryonic palatal cells (MEPCs) were treated with CQ to observe cell viability, apoptosis, migration, osteogenic differentiation by cell proliferation assay, flow cytometric analysis, scratch assay, and alizarin red staining. PI staining was used to measure cell cycle distribution. Immunofluorescence (IF) assay and transmission electron microscopy were used to detect autophagosomes. The autophagy-related factors (LC3 and P62), apoptosis-related markers (P53, caspase-3 cleaved caspase-3, BAX, and BCL-2), and cell cycle-related proteins (P21, CDK2, CDK4, cyclin D1, and cyclin E) were all measured by western blot. CQ inhibited the proliferation of MEPCs by arresting the G0/G1 phase of the cell cycle in a concentration- and time-dependent manner with cell cycle-related proteins P21 upregulated and CDK2, CDK4, cyclin D1, and cyclin E downregulated. Then we detected CQ also induced cell apoptosis in a dose-dependent manner by decreasing the BCL-2/BAX ratio and increasing cleaved caspase-3. Next, it was investigated that migration and osteogenesis of MEPCs decreased with CQ treatment in a dose-dependent manner. Meanwhile, CQ blocked the autophagy pathway by upregulating LC3II and P62 expressions which activated the P53 pathway. CQ activates P53 which affects MEPC biological characteristics by changing the proliferation and apoptosis of MEPCs through inhibiting autophagy.

The Potential Key Role of the NRF2/NQO1 Pathway in the Health Effects of Arsenic Pollution on SCC

Arsenic is widely present in nature and is a common environmental poison that seriously damages human health. Chronic exposure to arsenic is a major environmental poisoning factor that promotes cell proliferation and leads to malignant transformation. However, its molecular mechanism remains unclear. In this study, we found that arsenite can promote the transformation of immortalized human keratinocyte cells (HaCaT) from the G0/G1 phase to S phase and demonstrated malignant phenotypes. This phenomenon is accompanied by obviously elevated levels of NRF2, NQO1, Cyclin E, and Cyclin-dependent kinase 2 (CDK2). Silencing the NRF2 expression with small interfering RNA (siRNA) in arsenite-transformed (T-HaCaT) cells was shown to reverse the malignant phenotype. Furthermore, the siRNA silencing of NQO1 significantly decreased the levels of the cyclin E-CDK2 complex, inhibiting the G0/G1 to S phase cell cycle progression and transformation to the T-HaCaT phenotypes. Thus, we hypothesized that the NRF2/NQO1 pathway played a key role in the arsenite-induced malignancy of HaCaT cells. By increasing the expression of Cyclin E-CDK2, the NRF2/NQO1 pathway can affect cell cycle progression and cell proliferation. A new common health effect mechanism of arsenic carcinogenesis has been identified; thus, it would contribute to the development of novel treatments to prevent and treat skin cancer caused by arsenic.

High cyclin E1 protein, but not gene amplification, is prognostic for basal-like breast cancer

Basal-like breast cancer (BLBC) has a greater overlap in molecular features with high-grade serous ovarian cancer (HGSOC) than with other breast cancer subtypes. Similarities include BRCA1 mutation, high frequency of TP53 mutation, and amplification of CCNE1 (encoding the cyclin E1 protein) in 6-34% of cases, and these features can be used to group patients for targeted therapies in clinical trials. In HGSOC, we previously reported two subsets with high levels of cyclin E1: those in which CCNE1 is amplified, have intact homologous recombination (HR), and very poor prognosis; and a CCNE1 non-amplified subset, with more prevalent HR defects. Here, we investigate whether similar subsets are identifiable in BLBC that may allow alignment of patient grouping in clinical trials of agents targeting cyclin E1 overexpression. We examined cyclin E1 protein and CCNE1 amplification in a cohort of 76 BLBCs and validated the findings in additional breast cancer datasets. Compared to HGSOC, CCNE1 amplified BLBC had a lower level of amplification (3.5 versus 5.2 copies) and lower relative cyclin E1 protein, a lack of correlation of amplification with expression, and no association with polyploidy. BLBC with elevated cyclin E1 protein also had prevalent HR defects, and high-level expression of the cyclin E1 deubiquitinase ubiquitin-specific protease 28 (USP28). Using a meta-analysis across multiple studies, we determined that cyclin E1 protein overexpression but not amplification is prognostic in BLBC, while both cyclin E1 overexpression and amplification are prognostic in HGSOC. Overall CCNE1 gene amplification is not equivalent between BLBC and HGSOC. However, high cyclin E1 protein expression can co-occur with HR defects in both BLBC and HGSOC, and is associated with poor prognosis in BLBC.

CCNE1 Amplification and PKMYT1 Inhibition Are Synthetic Lethal

Using a genome-wide screen, PKMYT1 inhibition was found to be synthetic lethal with CCNE1 amplification.

G6PD upregulates Cyclin E1 and MMP9 to promote clear cell renal cell carcinoma progression

Background: Clear cell renal cell carcinoma (ccRCC) is a cell metabolic disease with high metastasis rate and poor prognosis. Our previous studies demonstrate that glucose-6-phosphate dehydrogenase (G6PD), the first and rate-limiting enzyme of the pentose phosphate pathway, is highly expressed in ccRCC and predicts poor outcomes of ccRCC patients. The aims of this study were to confirm the oncogenic role of G6PD in ccRCC and unravels novel mechanisms involving Cyclin E1 and MMP9 in G6PD-mediated ccRCC progression. Methods: Real-time RT-PCR, Western blot and immunohistochemistry were used to determine the expression patterns of G6PD, Cyclin E1 and MMP9 in ccRCC. TCGA dataset mining was used to identify Cyclin E1 and MMP9 correlations with G6PD expression, relationships between clinicopathological characteristics of ccRCC and the genes of interest, as well as the prognosis of ccRCC patients. The role of G6PD in ccRCC progression and the regulatory effect of G6PD on Cyclin E1 and MMP9 expression were investigated by using a series of cytological function assays in vitro. To verify this mechanism in vivo, xenografted mice models were established. Results: G6PD, Cyclin E1 and MMP9 were overexpressed and positively correlated in ccRCC, and they were associated with poor prognosis of ccRCC patients. Moreover, G6PD changed cell cycle dynamics, facilitated cells proliferation, promoted migration in vitro, and enhanced ccRCC development in vivo, more likely through enhancing Cyclin E1 and MMP9 expression. Conclusion: These findings present G6PD, Cyclin E1 and MMP9, which contribute to ccRCC progression, as novel biomarkers and potential therapeutic targets for ccRCC treatment.

Fine-tuned repression of Drp1-driven mitochondrial fission primes a 'stem/progenitor-like state' to support neoplastic transformation

Gene knockout of the master regulator of mitochondrial fission, Drp1, prevents neoplastic transformation. Also, mitochondrial fission and its opposing process of mitochondrial fusion are emerging as crucial regulators of stemness. Intriguingly, stem/progenitor cells maintaining repressed mitochondrial fission are primed for self-renewal and proliferation. Using our newly derived carcinogen transformed human cell model, we demonstrate that fine-tuned Drp1 repression primes a slow cycling 'stem/progenitor-like state', which is characterized by small networks of fused mitochondria and a gene-expression profile with elevated functional stem/progenitor markers (Krt15, Sox2 etc) and their regulators (Cyclin E). Fine tuning Drp1 protein by reducing its activating phosphorylation sustains the neoplastic stem/progenitor cell markers. Whereas, fine-tuned reduction of Drp1 protein maintains the characteristic mitochondrial shape and gene-expression of the primed 'stem/progenitor-like state' to accelerate neoplastic transformation, and more complete reduction of Drp1 protein prevents it. Therefore, our data highlights a 'goldilocks' level of Drp1 repression supporting stem/progenitor state dependent neoplastic transformation.

Clinical significance of CCNE1 copy number gain in acral melanoma patients

Copy number variations are frequently observed in cell cycle-related genes in acral melanoma. However, the clinical significance of copy number gain of CCNE1 in acral melanoma has not been fully elucidated. In this study, 490 acral melanoma samples were examined for CCNE1 copy number using the QuantiGenePlex DNA Assay. Correlation between CCNE1 copy number and acral melanoma patients' clinicopathologic features were analyzed using Chi-squared test. The impact of CCNE1 copy number on patients' progression-free survival (PFS) and overall survival (OS) probability were analyzed using Kaplan-Meier analysis. The impact of CCNE1 copy number on patients' median PFS after receiving chemotherapy was also evaluated. The results showed that CCNE1 copy number gain was observed in 28.30% of patients, with 3.16% of patients carrying both CCNE1 copy number gain and BRAF mutation and 4.34% of patients carrying both CCNE1 copy number gain and NRAS mutation. The median PFS time for patients with CCNE1 copy number gain was shorter than that of patients without CCNE1 copy number gain (17.0 vs. 27.0 months, P = 0.002).In the cohort that received chemotherapy (n = 82), the median PFS time for patients with CCNE1 copy number gain was shorter than that of patients without CCNE1 copy number gain (4.8 vs. 7.4 months, P = 00.006). CCNE1 copy number gain was an independent prognostic marker for acral melanoma patients' PFS. Our study indicates that CCNE1 copy number gain is frequent in acral melanoma and may be a biomarker to predict acral melanoma patients' outcomes after receiving chemotherapy.

Cytoplasmic Cyclin E Expression Predicts for Response to Neoadjuvant Chemotherapy in Breast Cancer

BACKGROUND

Pathologic complete response (pCR) has been shown to be associated with favorable outcomes in breast cancer. Predictors of pCR could be useful in guiding treatment decisions regarding neoadjuvant therapy. The objective of this study was to evaluate cyclin E as a predictor of response to neoadjuvant chemotherapy in breast cancer.

METHODS

Patients (n = 285) with stage II-III breast cancer were enrolled in a prospective study and received neoadjuvant chemotherapy with anthracyclines, taxanes, or combination of the two. Pretreatment biopsies from 190 patients and surgical specimens following chemotherapy from 192 patients were available for immunohistochemical analysis. Clinical and pathologic responses were recorded and associated with presence of tumor infiltrating lymphocytes, cyclin E, adipophilin, programmed cell death-ligand 1, and elastase staining and other patient, tumor and treatment characteristics.

RESULTS

The pCR rate was significantly lower in patients with cytoplasmic cyclin E staining compared with those who had no cyclin E expression (16.1% vs 38.9%, P = 0.0005). In multivariable logistic regression analysis, the odds of pCR for patients who had cytoplasmic negative tumors was 9.35 times (P value < 0.0001) that compared with patients with cytoplasmic positive tumors after adjusting for ER, PR, and HER2 status. Cytoplasmic cyclin E expression also predicts long-term outcome and is associated with reduced disease free, recurrence free, and overall survival rates, independent of increased pretreatment tumor infiltrating lymphocytes.

CONCLUSIONS

Cyclin E independently predicted response to neoadjuvant chemotherapy. Hence, its routine immunohistochemical analysis could be used clinically to identify those breast cancer patients expected to have a poor response to anthracycline/taxane-based chemotherapy.

Targeting cell-cycle machinery in cancer

Abnormal activity of the core cell-cycle machinery is seen in essentially all tumor types and represents a driving force of tumorigenesis. Recent studies revealed that cell-cycle proteins regulate a wide range of cellular functions, in addition to promoting cell division. With the clinical success of CDK4/6 inhibitors, it is becoming increasingly clear that targeting individual cell-cycle components may represent an effective anti-cancer strategy. Here, we discuss the potential of inhibiting different cell-cycle proteins for cancer therapy.

PRMT5 Promotes Cyclin E1 and Cell Cycle Progression in CD4 Th1 Cells and Correlates With EAE Severity

Multiple Sclerosis (MS) is a debilitating central nervous system disorder associated with inflammatory T cells. Activation and expansion of inflammatory T cells is thought to be behind MS relapses and influence disease severity. Protein arginine N-methyltransferase 5 (PRMT5) is a T cell activation-induced enzyme that symmetrically dimethylates proteins and promotes T cell proliferation. However, the mechanism behind PRMT5-mediated control of T cell proliferation and whether PRMT5 contributes to diseases severity is unclear. Here, we evaluated the role of PRMT5 on cyclin/cdk pairs and cell cycle progression, as well as PRMT5's link to disease severity in an animal model of relapsing-remitting MS. Treatment of T helper 1 (mTh1) cells with the selective PRMT5 inhibitor, HLCL65, arrested activation-induced T cell proliferation at the G1 stage of the cell cycle, suggesting PRMT5 promotes cell cycle progression in CD4+ T cells. The Cyclin E1/Cdk2 pair promoting G1/S progression was also decreased after PRMT5 inhibition, as was the phosphorylation of retinoblastoma. In the SJL mouse relapsing-remitting model of MS, the highest PRMT5 expression in central nervous system-infiltrating cells corresponded to peak and relapse timepoints. PRMT5 expression also positively correlated with increasing CD4 Th cell composition, disease severity and Cyclin E1 expression. These data indicate that PRMT5 promotes G1/S cell cycle progression and suggest that this effect influences disease severity and/or progression in the animal model of MS. Modulating PRMT5 levels may be useful for controlling T cell expansion in T cell-mediated diseases including MS.

CCNE1 Is a Putative Therapeutic Target for ARID1A-Mutated Ovarian Clear Cell Carcinoma

Background: Ovarian clear cell carcinoma (OCCC) is resistant to platinum chemotherapy and is characterized by poor prognosis. Today, the use of poly (ADP-ribose) polymerase (PARP) inhibitor, which is based on synthetic lethality strategy and characterized by cancer selectivity, is widely used for new types of molecular-targeted treatment of relapsed platinum-sensitive ovarian cancer. However, it is less effective against OCCC. Methods: We conducted siRNA screening to identify synthetic lethal candidates for the ARID1A mutation; as a result, we identified Cyclin-E1 (CCNE1) as a potential target that affects cell viability. To further clarify the effects of CCNE1, human OCCC cell lines, namely TOV-21G and KOC7c (ARID1A mutant lines), and RMG-I and ES2 (ARID1A wild type lines) were transfected with siRNA targeting CCNE1 or a control vector. Results: Loss of CCNE1 reduced proliferation of the TOV-21G and KOC7c cells but not of the RMG-I and ES2 cells. Furthermore, in vivo interference of CCNE1 effectively inhibited tumor cell proliferation in a xenograft mouse model. Conclusion: This study showed for the first time that CCNE1 is a synthetic lethal target gene to ARID1A-mutated OCCC. Targeting this gene may represent a putative, novel, anticancer strategy in OCCC treatment.

Discriminative SKP2 Interactions with CDK-Cyclin Complexes Support a Cyclin A-Specific Role in p27KIP1 Degradation

The SCFSKP2 ubiquitin ligase relieves G1 checkpoint control of CDK-cyclin complexes by promoting p27KIP1 degradation. We describe reconstitution of stable complexes containing SKP1-SKP2 and CDK1-cyclin B or CDK2-cyclin A/E, mediated by the CDK regulatory subunit CKS1. We further show that a direct interaction between a SKP2 N-terminal motif and cyclin A can stabilize SKP1-SKP2-CDK2-cyclin A complexes in the absence of CKS1. We identify the SKP2 binding site on cyclin A and demonstrate the site is not present in cyclin B or cyclin E. This site is distinct from but overlapping with features that mediate binding of p27KIP1 and other G1 cyclin regulators to cyclin A. We propose that the capacity of SKP2 to engage with CDK2-cyclin A by more than one structural mechanism provides a way to fine tune the degradation of p27KIP1 and distinguishes cyclin A from other G1 cyclins to ensure orderly cell cycle progression.

Potential use of kiwifruit extract for treatment of melanoma

Skin cancers are the most common cancers in the world and among the different types of skin cancers, melanoma is the deadliest and incidence is rising. Previous studies have shown promising in vitro and human evidence of kiwifruit exhibiting anti-cancer effects. This study was designed to investigate if kiwifruit extract (KE) has any effect on CRL-11147 melanoma cancer cells and to investigate the possible mechanisms behind the results. The effects of KE on CRL-11147 melanoma cell survival, proliferation, and apoptosis was investigated using clonogenic survival assay, cell proliferation, and caspase-3 activity kits. Potential anti-tumor molecular mechanisms were elucidated using RT-PCR and IHC. Addition of KE decreased CRL-11147 cell colonies percentages indicated by a decreased optical density value of cancer cells when compared to control. Furthermore, treatment with KE increased relative caspase-3 activity in cancer cells, which indicated increased apoptosis of cancer cells. The anti-proliferative effect of KE on cancer cells corresponded with decreased expression of the pro-proliferative molecule Cyclin E and CDK4, while increased expression of the pro-apoptotic molecule TRAILR1 corresponded with the pro-apoptotic effect. KE decreases CRL-11147 melanoma cell growth via downregulation of Cyclin E and CDK4 and upregulation in TRAILR1. Our study suggests a potential use for KE in treatment of melanoma.

Ubiquitin ligation to F-box protein targets by SCF-RBR E3-E3 super-assembly

E3 ligases are typically classified by hallmark domains such as RING and RBR, which are thought to specify unique catalytic mechanisms of ubiquitin transfer to recruited substrates1,2. However, rather than functioning individually, many neddylated cullin-RING E3 ligases (CRLs) and RBR-type E3 ligases in the ARIH family-which together account for nearly half of all ubiquitin ligases in humans-form E3-E3 super-assemblies3-7. Here, by studying CRLs in the SKP1-CUL1-F-box (SCF) family, we show how neddylated SCF ligases and ARIH1 (an RBR-type E3 ligase) co-evolved to ubiquitylate diverse substrates presented on various F-box proteins. We developed activity-based chemical probes that enabled cryo-electron microscopy visualization of steps in E3-E3 ubiquitylation, initiating with ubiquitin linked to the E2 enzyme UBE2L3, then transferred to the catalytic cysteine of ARIH1, and culminating in ubiquitin linkage to a substrate bound to the SCF E3 ligase. The E3-E3 mechanism places the ubiquitin-linked active site of ARIH1 adjacent to substrates bound to F-box proteins (for example, substrates with folded structures or limited length) that are incompatible with previously described conventional RING E3-only mechanisms. The versatile E3-E3 super-assembly may therefore underlie widespread ubiquitylation.

LncRNA TTN-AS1 intensifies sorafenib resistance in hepatocellular carcinoma by sponging miR-16-5p and upregulation of cyclin E1

Drug resistance has always been an important problem affecting the therapeutic effect of hepatocellular carcinoma (HCC). To investigate the potential role of lncRNA TTN-AS1 in HCC cells with sorafenib (SOR) resistance, and explore the underlying pathways, quantitative real time polymerase chain reaction (qRT-PCR) was used to test the expression of TTN-AS1 in HCC tissues and cells. Then, the expression of TTN-AS1 was down-regulated by shRNA, the activity changes, apoptosis and related protein expression in HCC cells with/without SOR treatment were observed in succession. Expression levels of the downstream target of TTN-AS1, miR-16-5p were studied by dual-luciferase binding assay, cell proliferation, and western blotting analysis. Nude mice models of human HCC with TTN-AS1 gene knockdown were established to observe the tumor growth. As the results revealed, TTN-AS1 silencing in HCC cells induced apoptosis by enhancing the sensitivity of cells to SOR, and the tumor in nude mice became smaller. The mechanism study showed that miR-16-5p was affected by TTN-AS1 sponge, up-regulated cyclin E1 expression, and regulated PTEN/Akt signaling pathway, thereby significantly alleviating the inhibition of apoptosis of HCC cells induced by TTN-AS1 gene. Collectively, our results provided TTN-AS1 as a potential therapeutic target for sorafenib resistance in HCC.

Garcinone C suppresses colon tumorigenesis through the Gli1-dependent hedgehog signaling pathway

BACKGROUND

Although garcinone C, a natural xanthone derivative identified in the pericarp of Garcinia mangostana, has been demonstrated to exert different health beneficial activities in oxidative stress and β-amyloid aggregation, the role of garcinone C in colon tumorigenesis has not been investigated. In addition, aberrant Hedgehog (Hh) signaling activation is associated with tumorigenesis including colon cancer. Here, we hypothesized that garcinone C can prevent colon tumorigenesis through regulating the Hh signaling pathway.

METHOD

Colony formation assay and flow cytometry were used to evaluate the effect of garcinone C on the proliferation and cell cycle progression of colon cancer cells. Protein expression of cell cycle related markers and Hh/Gli1 signaling mediators were determined. The regulatory effect of orally administered garcinone C on the Hh/Gli1 signaling pathway and colon tumorigenesis was evaluated in an azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon cancer animal model.

RESULTS

Garcinone C suppressed the proliferation of colon cancer cells, induced G0/G1 cell cycle arrest, as well as regulated the expression of cell cycle-related markers such as cyclin D1, cyclin E, CDK6, and p21. Garcinone C inhibited the expression of Gli1, a key mediator of Hedgehog signaling, and protein kinase B (AKT) phosphorylation in Smo-independent colon cancer cells. In the AOM/DSS-induced colon tumorigenesis model, garcinone C significantly inhibited tumor development, regulated the expression of cell cycle markers and Gli1, and reduced AKT phosphorylation in colon tumor tissues, which is consistent with our in vitro results.

CONCLUSION

Garcinone C can suppress colon tumorigenesis in vitro and in vivo through Gli1-dependent non-canonical Hedgehog signaling, suggesting that it may serve as a potent chemopreventive agent against colon tumorigenesis.

Lowered Cyclin E levels increase the efficiency and the specificity of capsaicin against cancerous cells of mesothelium

Capsaicin is one of the most extensively studied phytochemicals and its cytotoxicity on various types of cancer has been demonstrated both in vitro and in vivo. The evaluation of its effect on mesothelioma, however, has remained quite limited. In this study, we investigated the anti-mesothelioma potential of capsaicin by observing its cytotoxicity on healthy, immortalized and cancerous cells of mesothelium in vitro and how this potential be affected by lowered Cyclin E levels, a key regulator of G1/S transition of cell cycle. For this purpose, we determined and compared the IC50 values of capsaicin in both FBS (Fetal Bovine Serum) containing and FBS-deprived medium of each cell population studied. Additionally, we examined the changes in both protein and mRNA levels of caspase-3 upon capsaicin exposure as well as conducted a series of experiments through which the relatively long term effect of capsaicin on the growth rate of the cells was assessed. As a result, the reduced Cyclin E obtained through the absence of FBS in growth medium was found not only to decrease IC50 values for all cell types dramatically (p&lt;0.05) but also to cause a considerable difference between the values determined for cancerous and non-cancerous populations (p&lt;0.05), which had not been observed in regular medium. Moreover, along with the fact that capsaicin exposure did not have an impact on the cell growth in long term in most cases, caspase-3 levels also remained the same when exposed to capsaicin, suggesting a mechanism of cell death independent of caspases.

Mutual antagonism between Hippo signaling and cyclin E drives intracellular pattern formation

Not much is known about how organelles organize into patterns. In ciliates, the cortical pattern is propagated during "tandem duplication," a cell division that remodels the parental cell into two daughter cells. A key step is the formation of the division boundary along the cell's equator. In Tetrahymena thermophila, the cdaA alleles prevent the formation of the division boundary. We find that the CDAA gene encodes a cyclin E that accumulates in the posterior cell half, concurrently with accumulation of CdaI, a Hippo/Mst kinase, in the anterior cell half. The division boundary forms between the margins of expression of CdaI and CdaA, which exclude each other from their own cortical domains. The activities of CdaA and CdaI must be balanced to initiate the division boundary and to position it along the cell's equator. CdaA and CdaI cooperate to position organelles near the new cell ends. Our data point to an intracellular positioning mechanism involving antagonistic Hippo signaling and cyclin E.

Emulsifying Properties of an Homologous Series of Medium- and Long-Chain d-Maltotriose Esters and their Impacts on the Viabilities of Selected Cell Lines

The development of functional as well as nutritional surfactants for the food industry remains a matter of great interest. In the present study, a series of 6″-O-acylmaltotriose monoesters bearing alkyl side chains of 10-18 carbons was prepared by enzymatic means. The emulsions derived from those monoesters incorporating palmitoyl, stearoyl, and oleoyl side chains generally displayed advantageous shelf-lives, superior resistance to environmental variations, and more favorable droplet size distributions as well as stronger cytotoxic effects against various cancer cell lines. Ester 6 was shown to significantly inhibit the proliferation of MCF-7 breast cancer cells by inducing G1 phase arrest. Specifically, the levels of the G1 phase-related markers cyclin D1 and cyclin E as well as the cycle-dependent kinase 4 were suppressed by this particular ester. This study thus reveals that maltotriose esters can not only serve as novel functional food emulsifiers but also act, in vitro, as notable cytotoxic agents through a well-defined mechanism-of-action.

PD173074 blocks G1/S transition via CUL3-mediated ubiquitin protease in HepG2 and Hep3B cells

Fibroblast growth factor receptors (FGFRs) are frequently altered in a variety of human cancer cells and are overexpressed in hepatocellular carcinoma (HCC). Several literatures have proven that they are efficacious for HCC therapy, however, the underlying mechanism remains unclear. Here, we found FGFR4 was overexpressed in HCC cell lines HepG2 and Hep3B and we used PD173074, an FGFR4 inhibitor, to explore the role of FGFR4 and its underlying mechanism in these cell lines. The results showed that PD173074 significantly arrested HepG2 and Hep3B cells in G1 phase and inhibited cell proliferation. Furthermore, Western blot analysis revealed that PD173074 decreased the levels of P-FRS2α, P-ERK, CDK2, cyclin E and NF-κB (p65) in the nucleus while it increased the levels of ubiquitin and CUL3, an E3 ubiquitin ligase which involves in cyclin E degradation. Meanwhile, the data from RT-qPCR showed that PD173074 also decreased miR-141 level. In conclusion, these results suggest that FGFR4 is involved in HCC by ERK/CUL3/cyclin E signaling pathway, and the finding may provide a potential theoretical basis for treatment by targeting FGFR4 in HCC.

Decyl caffeic acid inhibits the proliferation of colorectal cancer cells in an autophagy-dependent manner in vitro and in vivo

The treatment of human colorectal cancer (CRC) cells through suppressing the abnormal survival signaling pathways has recently become a significant area of focus. In this study, our results demonstrated that decyl caffeic acid (DC), one of the novel caffeic acid derivatives, remarkedly suppressed the growth of CRC cells both in vitro and in vivo. The inhibitory effects of DC on CRC cells were investigated in an in vitro cell model and in vivo using a xenograft mouse model. CRC cells were treated with DC at various dosages (0, 10, 20 and 40 μM), and cell survival, the apoptotic index and the autophagy level were measured using an MTT assay and flow cytometry analysis, respectively. The signaling cascades in CRC were examined by Western blot assay. The anti-cancer effects of DC on tumor growth were examined by using CRC HCT-116 cells implanted in an animal model. Our results indicated that DC differentially suppressed the growth of CRC HT-29 and HCT-116 cells through an enhancement of cell-cycle arrest at the S phase. DC inhibited the expression of cell-cycle regulators, which include cyclin E and cyclin A proteins. The molecular mechanisms of action were correlated to the blockade of the STAT3 and Akt signaling cascades. Strikingly, a high dosage of DC prompted a self-protection action through inducing cell-dependent autophagy in HCT-116 cells. Suppression of autophagy induced cell death in the treatment of DC in HCT-116 cells. DC seemed to inhibit cell proliferation of CRC differentially, and the therapeutic advantage appeared to be autophagy dependent. Moreover, consumption of DC blocked the tumor growth of colorectal adenocarcinoma in an experimental animal model. In conclusion, our results suggested that DC could act as a therapeutic agent through the significant suppression of tumor growth of human CRC cells.

Coimmunoprecipitation with MYR1 Identifies Three Additional Proteins within the Toxoplasma gondii Parasitophorous Vacuole Required for Translocation of Dense Granule Effectors into Host Cells

Toxoplasma gondii is a ubiquitous, intracellular protozoan that extensively modifies infected host cells through secreted effector proteins. Many such effectors must be translocated across the parasitophorous vacuole (PV), in which the parasites replicate, ultimately ending up in the host cytosol or nucleus. This translocation has previously been shown to be dependent on five parasite proteins: MYR1, MYR2, MYR3, ROP17, and ASP5. We report here the identification of several MYR1-interacting and novel PV-localized proteins via affinity purification of MYR1, including TGGT1_211460 (dubbed MYR4), TGGT1_204340 (dubbed GRA54), and TGGT1_270320 (PPM3C). Further, we show that three of the MYR1-interacting proteins, GRA44, GRA45, and MYR4, are essential for the translocation of the Toxoplasma effector protein GRA16 and for the upregulation of human c-Myc and cyclin E1 in infected cells. GRA44 and GRA45 contain ASP5 processing motifs, but like MYR1, processing at these sites appears to be nonessential for their role in protein translocation. These results expand our understanding of the mechanism of effector translocation in Toxoplasma and indicate that the process is highly complex and dependent on at least eight discrete proteins.IMPORTANCEToxoplasma is an extremely successful intracellular parasite and important human pathogen. Upon infection of a new cell, Toxoplasma establishes a replicative vacuole and translocates parasite effectors across this vacuole to function from the host cytosol and nucleus. These effectors play a key role in parasite virulence. The work reported here newly identifies three parasite proteins that are necessary for protein translocation into the host cell. These results significantly increase our knowledge of the molecular players involved in protein translocation in Toxoplasma-infected cells and provide additional potential drug targets.

Overexpression of tripartite motif containing 26 inhibits non-small cell lung cancer cell growth by suppressing PI3K/AKT signaling

It has been reported that tripartite motif containing 26 (TRIM26) is involved in the tumorigenesis of some cancers, but its function in non-small cell lung cancer (NSCLC) is still unclear. In this study, we found that TRIM26 was markedly down-regulated in both of NSCLC tumor tissues and cell lines. Additionally, high expression of TRIM26 in NSCLC patients predicted a positive index for patients' overall survival. What is more, overexpression of TRIM26 significantly suppressed NSCLC cell growth. Our further studies indicated that overexpression of TRIM26 inhibited the phosphorylation of PI3K p85 and AKT. And overexpressed TRIM26 regulated cell cycle-related genes' expression, including downregulating CDK4, Cyclin A, Cyclin D1, Cyclin D3, and Cyclin E, and upregulating p27 expression. Finally, we found that TRIM26 up-regulated PTEN expression by stabilizing PTEN protein in NSCLC cells. Collectively, our present study indicated that TRIM26 was decreased in NSCLC and overexpression of TRIM26 inhibited NSCLC cell growth by suppressing PI3K/AKT pathway, which suggested that TRIM26 could be as a potential target for the treatment of NSCLC in the future.

The Antiproliferative Activity of Oxypeucedanin via Induction of G2/M Phase Cell Cycle Arrest and p53-Dependent MDM2/p21 Expression in Human Hepatoma Cells

Oxypeucedanin (OPD), a furocoumarin compound from Angelica dahurica (Umbelliferae), exhibits potential antiproliferative activities in human cancer cells. However, the underlying molecular mechanisms of OPD as an anticancer agent in human hepatocellular cancer cells have not been fully elucidated. Therefore, the present study investigated the antiproliferative effect of OPD in SK-Hep-1 human hepatoma cells. OPD effectively inhibited the growth of SK-Hep-1 cells. Flow cytometric analysis revealed that OPD was able to induce G₂/M phase cell cycle arrest in cells. The G₂/M phase cell cycle arrest by OPD was associated with the downregulation of the checkpoint proteins cyclin B1, cyclin E, cdc2, and cdc25c, and the up-regulation of p-chk1 (Ser345) expression. The growth-inhibitory activity of OPD against hepatoma cells was found to be p53-dependent. The p53-expressing cells (SK-Hep-1 and HepG2) were sensitive, but p53-null cells (Hep3B) were insensitive to the antiproliferative activity of OPD. OPD also activated the expression of p53, and thus leading to the induction of MDM2 and p21, which indicates that the antiproliferative activity of OPD is in part correlated with the modulation of p53 in cancer cells. In addition, the combination of OPD with gemcitabine showed synergistic growth-inhibitory activity in SK-Hep-1 cells. These findings suggest that the anti-proliferative activity of OPD may be highly associated with the induction of G₂/M phase cell cycle arrest and upregulation of the p53/MDM2/p21 axis in SK-HEP-1 hepatoma cells.

TUG1 Is a Regulator of AFP and Serves as Prognostic Marker in Non-Hepatitis B Non-Hepatitis C Hepatocellular Carcinoma

Thyroid hormone (T₃) and its receptor (TR) are involved in cell metabolism and cancer progression. Hypothyroidism is associated with significantly elevated risk of hepatocellular carcinoma (HCC). Levels of the glycoprotein alpha-fetoprotein (AFP) are increased in the majority of patients with HCC and may be useful in diagnosis and follow-up. However, the relationship between T₃/TR and AFP levels in HCC is currently unclear. The expression profiles of long non-coding RNAs (lncRNAs) were compared in microarrays of HepG2-TRα1 cells treated with/without T₃ and HCC specimens. The effects of T₃ on taurine upregulated gene 1 (TUG1) and AFP expression were validated using qRT-PCR. A correlation between TUG1 and AFP was confirmed via RNAi and clustered regularly interspaced short palindromic repeats (CRISPR) strategies. Finally, overall and recurrence-free survival rates were analyzed using the Kaplan–Meier method and confirmed in online datasets. T₃/TR treatment reduced TUG1 expression in vitro, resulting in the downregulation of AFP mRNA. Knockdown of TUG1 suppressed cell cycle progression and soft agar colony formation and induced cellular senescence. Our data support the involvement of TUG1 in the T₃/TR-mediated suppression of cell growth. AFP mRNA levels showed strong positive correlations with TUG1 and unfavorable prognosis in patients with non-hepatitis B/non-hepatitis C HCC (NBNC-HCC). T₃/TR, TUG1, and AFP may potentially serve as effective prognostic markers for NBNC-HCC.

Cul3 regulates cyclin E1 protein abundance via a degron located within the N-terminal region of cyclin E

Cyclin E and its binding partner Cdk2 control the G1/S transition in mammalian cells. Increased levels of cyclin E are found in some cancers. Additionally, proteolytic removal of the cyclin E N-terminus occurs in some cancers and is associated with increased cyclin E-Cdk2 activity and poor clinical prognosis. Cyclin E levels are tightly regulated and controlled in part through ubiquitin-mediated degradation initiated by one of two E3 ligases, Cul1 and Cul3. Cul1 ubiquitylates phosphorylated cyclin E, but the mechanism through which Cul3 ubiquitylates cyclin E is poorly understood. In experiments to ascertain how Cul3 mediates cyclin E destruction, we identified a degron on cyclin E that Cul3 targets for ubiquitylation. Recognition of the degron and binding of Cul3 does not require a BTB domain-containing adaptor protein. Additionally, this degron is lacking in N-terminally truncated cyclin E. Our results describe a mechanism whereby N-terminally truncated cyclin E can avoid the Cul3-mediated degradation pathway. This mechanism helps to explain the increased activity that is associated with the truncated cyclin E variants that occurs in some cancers.

Knockdown of E2F8 Suppresses Cell Proliferation in Colon Cancer Cells by Modulating the NF-κB Pathway

OBJECTIVE

E2F8, one of the E2F transcription factor family members, has been demonstrated to be involved in the development and progression of several human cancers; however, the physiological and functional roles of E2F8 in colorectal cancer are not fully elucidated.

METHODS

In vitro experiments were performed using multiple human colon cancer cells lines and generating cell knockdown E2F8 using viral vectors. The expression of mRNA and proteins were measured by quantitative reverse transcription PCR and western blotting.

RESULTS

Our results suggest that E2F8 expression is induced in several colon cancer cell lines. The forced downregulation of E2F8 expression inhibits the growth of colon cancer cells. Our findings indicate that knocking down E2F8 can suppress nuclear factor kappa B (NF-κB) activation. We further determine that knocking down E2F8 decreased the expression of cell cycle regulators.

CONCLUSIONS

These results demonstrate that E2F8 modulates the growth of human colon cancer cells through promoting the NF-κB pathway.

The Regulatory Effects of CDKN1A on Relevant Genes in Kaposi's Sarcoma Cells

The cyclin-dependent kinase inhibitor 1A (CDKN1A) gene plays important roles in different types of cancer; however, its mechanism in Kaposi's Sarcoma (KS) is far less known. The aim of this study is to investigate the regulatory effects of CDKN1A on relevant genes in KS cells, and ultimately determine the role of CDKN1A in KS. In the study, the CDKN1A overexpression group, or siRNA group, was transfected into KS cells, respectively. Western-Blot (WB) and quantitative real-time polymerase chain reactions (q-PCR) were performed to detect the expression of cell cycle protein D1 (CyclinD1) and cell cycle protein E (CyclinE). Q-PCR was performed to determine the expression of kshv-mir-k12-1-5p. The results prove that CDKN1A negatively regulates the expression of CyclinD1, CyclinE, and kshv-mir-k1-2-1-5p. Therefore, CDKN1A may be involved in the formation and development of KS through the regulation of kshv-mir-k12-1-5p, CyclinD1, and CyclinE. CDKN1A may become a new choice for targeted therapy in KS.

Shaping of Drosophila Neural Cell Lineages Through Coordination of Cell Proliferation and Cell Fate by the BTB-ZF Transcription Factor Tramtrack-69

Cell diversity in multicellular organisms relies on coordination between cell proliferation and the acquisition of cell identity. The equilibrium between these two processes is essential to assure the correct number of determined cells at a given time at a given place. Using genetic approaches and correlative microscopy, we show that Tramtrack-69 (Ttk69, a Broad-complex, Tramtrack and Bric-à-brac - Zinc Finger (BTB-ZF) transcription factor ortholog of the human promyelocytic leukemia zinc finger factor) plays an essential role in controlling this balance. In the Drosophila bristle cell lineage, which produces the external sensory organs composed by a neuron and accessory cells, we show that ttk69 loss-of-function leads to supplementary neural-type cells at the expense of accessory cells. Our data indicate that Ttk69 (1) promotes cell cycle exit of newborn terminal cells by downregulating CycE, the principal cyclin involved in S-phase entry, and (2) regulates cell-fate acquisition and terminal differentiation, by downregulating the expression of hamlet and upregulating that of Suppressor of Hairless, two transcription factors involved in neural-fate acquisition and accessory cell differentiation, respectively. Thus, Ttk69 plays a central role in shaping neural cell lineages by integrating molecular mechanisms that regulate progenitor cell cycle exit and cell-fate commitment.

Diamond Nanoparticles Downregulate Expression of CycD and CycE in Glioma Cells

Our previous studies have shown that diamond nanoparticles (NDs) exhibited antiangiogenic and proapoptotic properties in vitro in glioblastoma multiforme (GBM) cells and in tumors in vivo. Moreover, NDs inhibited adhesion, leading to the suppression of migration and invasion of GBM. In the present study, we hypothesized that the NDs might also inhibit proliferation and cell cycle in glioma cells. Experiments were performed in vitro with the U87 and U118 lines of GBM cells, and for comparison, the Hs5 line of stromal cells (normal cells) after 24 h and 72 h of treatment. The analyses included cell morphology, cell death, viability, and cell cycle analysis, double timing assay, and gene expression (Rb, E2F1, CycA, CycB, CycD, CycE, PTEN, Ki-67). After 72 h of ND treatment, the expression level of Rb, CycD, and CycE in the U118 cells, and E2F1, CycD, and CycE in the U87 cells were significantly lower in comparison to those in the control group. We observed that decreased expression of cyclins inhibited the G1/S phase transition, arresting the cell cycle in the G0/G1 phase in glioma cells. The NDs did not affect the cell cycle as well as PTEN and Ki-67 expression in normal cells (Hs5), although it can be assumed that the NDs reduced proliferation and altered the cell cycle in fast dividing cells.

MiR-15b regulates cell differentiation and survival by targeting CCNE1 in APL cell lines

MicroRNAs have been shown to be involved in various cell processes, including proliferation, apoptosis and differentiation. However, little is known about their function in granulopoiesis. In the present study, overexpression and knockdown experiments revealed that miR-15b was required to block the proliferation of NB4 and HL60 cells and induce them differentiated to granulocyte lineage. Moreover, we identified CCNE1 as a direct target of miR-15b, and demonstrated that CCNE1 was involved in cell differentiation and proliferation in acute promyelocytic leukemia cells. In addition, we demonstrated a novel pathway in which miR-15b regulated cells arrested in the G0/G1 phase and promoted terminal differentiation of cells by targeting CCNE1, which could modulate the cell cycle effort pRb in APL cells. These events blocked cell proliferation and promoted granulocyte differentiation. In conclusion, our data highlighted, for the first time, the important role of miR-15b in myeloid differentiation and suggested the potential role of miR-15b in cancer therapy.

The PERK-EIF2α-ATF4 signaling branch regulates osteoblast differentiation and proliferation by PTH

Parathyroid hormone (PTH) and its related peptide (PTH-related peptide 1-34) are two of the Food and Drug Administration-approved bone-promoting drugs for age-related osteoporosis. Treatment with PTH stimulates bone formation. However, the molecular mechanisms of PTH-mediated osteoblast differentiation and cell proliferation are still not completely understood. In this study, we showed that PTH induced endoplasmic reticulum (ER) stress in osteoblasts through the PKR-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor 2α (EIF2α)-activating transcription factor 4 (ATF4)-signaling pathway. After separately blocking PERK-EIF2α-ATF4 signaling with two different inhibitors [AMG'44 and integrated stress response inhibitor (ISRIB)] or specific small interfering RNA for PERK and ATF4, the following targets were all downregulated: expression of osteoblast differentiation markers [runt-related transcription factor 2 (Runx2), alkaline phosphatase (Alp), type I collagen (Col1a1), and osteocalcin (Ocn)], cell proliferation markers (CyclinE, CyclinD, and CDC2), amino acid import (Glyt1), and metabolism-related genes (Asns). Additionally, Alp-positive staining cells, Alp activity, matrix mineralization, Ocn secretion, and cell proliferation indexes were inhibited. Interestingly, we found that salubrinal enhanced PTH-induced osteoblast differentiation and proliferation by maintenance of phosphorylation of EIF2α. Furthermore, we observed that PTH increased the association between heat shock protein 90 (HSP90) and PERK and maintained PERK protein stabilization in the early stages of PTH-induced ER stress. Treatment of MC3T3-E1 cells with geldanamycin, an HSP90 inhibitor, decreased PERK protein expression and inhibited osteoblast differentiation and cell proliferation upon PTH treatment. Taken together, our data demonstrate that PTH regulates osteoblast differentiation and cell proliferation, partly by activating the HSP90-dependent PERK-EIF2α-ATF4 signaling pathway.

Bergapten induces G1 arrest and pro-apoptotic cascade in colorectal cancer cells associating with p53/p21/PTEN axis

Bergapten is a natural compound and has potent anticancer activities. In this study, we explored the cytotoxicity of bergapten on colorectal cancer (CRC) cell DLD-1 and LoVo and its underlying mechanisms. We observed that bergapten (30 and 50 μM) decreased the viability of the CRC cells and induced the G0/G1 and sub-G1 phase arrest. Furthermore, immunoblotting results indicated that bergapten increased p53, phospho-p53(Ser-46), p21, PUMA, Bax, PTEN, and the caspase-9 and caspase-3 cleavage, but decreased cyclin E, CDK2, and phosphor-AKT(Ser-473) in the CRC cells. Inhibition of p53 by pifithrin-α reversed the bergapten-induced p53-mediated apoptotic cascade and restored the survival signaling and cell viability. Collectively, our findings reveal that bergapten decrease the cell viability and induce cell cycle arrest in the CRC cells, which may be attributed to p53-mediated apoptotic cascade, upregulation of p21 and PTEN, and inhibition of AKT.

Rosmarinic Acid, a Component of Rosemary Tea, Induced the Cell Cycle Arrest and Apoptosis through Modulation of HDAC2 Expression in Prostate Cancer Cell Lines

Rosmarinic acid (RA), a main phenolic compound contained in rosemary which is used as tea, oil, medicine and so on, has been known to present anti-inflammatory, anti-oxidant and anti-cancer effects. Histone deacetylases (HDACs) are enzymes that play important roles in gene expression by removing the acetyl group from histone. The aberrant expression of HDAC in human tumors is related with the onset of human cancer. Especially, HDAC2, which belongs to HDAC class I composed of HDAC 1, 2, 3 and 8, has been reported to be highly expressed in prostate cancer (PCa) where it downregulates the expression of p53, resulting in an inhibition of apoptosis. The purpose of this study is to investigate the effect of RA in comparison with suberoylanilide hydroxamic acid (SAHA), an HDAC inhibitor used as an anti-cancer agent, on survival and apoptosis of PCa cell lines, PC-3 and DU145, and the expression of HDAC. RA decreased the cell proliferation in cell viability assay, and inhibited the colony formation and tumor spheroid formation. Additionally, RA induced early- and late-stage apoptosis of PC-3 and DU145 cells in Annexin V assay and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, respectively. In western blot analysis, RA inhibited the expression of HDAC2, as SAHA did. Proliferating cell nuclear antigen (PCNA), cyclin D1 and cyclin E1 were downregulated by RA, whereas p21 was upregulated. In addition, RA modulated the protein expression of intrinsic mitochondrial apoptotic pathway-related genes, such as Bax, Bcl-2, caspase-3 and poly (ADP-ribose) polymerase 1 (PARP-1) (cleaved) via the upregulation of p53 derived from HDAC2 downregulation, leading to the increased apoptosis of PC-3 and DU145 cells. Taken together, treatment of RA to PCa cell lines inhibits the cell survival and induces cell apoptosis, and it can be used as a novel therapeutic agent toward PCa.

Functional Interactions Between rsks-1/S6K, glp-1/Notch, and Regulators of Caenorhabditis elegans Fertility and Germline Stem Cell Maintenance

The proper accumulation and maintenance of stem cells is critical for organ development and homeostasis. The Notch signaling pathway maintains stem cells in diverse organisms and organ systems. In Caenorhabditis elegans, GLP-1/Notch activity prevents germline stem cell (GSC) differentiation. Other signaling mechanisms also influence the maintenance of GSCs, including the highly-conserved TOR substrate ribosomal protein S6 kinase (S6K). Although C. elegans bearing either a null mutation in rsks-1/S6K or a reduction-of-function (rf) mutation in glp-1/Notch produce half the normal number of adult germline progenitors, virtually all these single mutant animals are fertile. However, glp-1(rf) rsks-1(null) double mutant animals are all sterile, and in about half of their gonads, all GSCs differentiate, a distinctive phenotype associated with a significant reduction or loss of GLP-1 signaling. How rsks-1/S6K promotes GSC fate is unknown. Here, we determine that rsks-1/S6K acts germline-autonomously to maintain GSCs, and that it does not act through Cyclin-E or MAP kinase in this role. We found that interfering with translation also enhances glp-1(rf), but that regulation through rsks-1 cannot fully account for this effect. In a genome-scale RNAi screen for genes that act similarly to rsks-1/S6K, we identified 56 RNAi enhancers of glp-1(rf) sterility, many of which were previously not known to interact functionally with Notch. Further investigation revealed at least six candidates that, by genetic criteria, act linearly with rsks-1/S6K. These include genes encoding translation-related proteins, cacn-1/Cactin, an RNA exosome component, and a Hedgehog-related ligand. We found that additional Hedgehog-related ligands may share functional relationships with glp-1/Notch and rsks-1/S6K in maintaining germline progenitors.

Low-Molecular-Weight Cyclin E in Human Cancer: Cellular Consequences and Opportunities for Targeted Therapies

Cyclin E, a regulatory subunit of cyclin-dependent kinase 2 (CDK2), is central to the initiation of DNA replication at the G1/S checkpoint. Tight temporal control of cyclin E is essential to the coordination of cell-cycle processes and the maintenance of genome integrity. Overexpression of cyclin E in human tumors was first observed in the 1990s and led to the identification of oncogenic roles for deregulated cyclin E in experimental models. A decade later, low-molecular-weight cyclin E (LMW-E) isoforms were observed in aggressive tumor subtypes. Compared with full-length cyclin E, LMW-E hyperactivates CDK2 through increased complex stability and resistance to the endogenous inhibitors p21CIP1 and p27KIP1 LMW-E is predominantly generated by neutrophil elastase-mediated proteolytic cleavage, which eliminates the N-terminal cyclin E nuclear localization signal and promotes cyclin E's accumulation in the cytoplasm. Compared with full-length cyclin E, the aberrant localization and unique stereochemistry of LMW-E dramatically alters the substrate specificity and selectivity of CDK2, increasing tumorigenicity in experimental models. Cytoplasmic LMW-E, which can be assessed by IHC, is prognostic of poor survival and predicts resistance to standard therapies in patients with cancer. These patients may benefit from therapeutic modalities targeting the altered biochemistry of LMW-E or its associated vulnerabilities. Cancer Res; 78(19); 5481-91. ©2018 AACR.

Down-Regulated LncRNA-HOTAIR Suppressed Colorectal Cancer Cell Proliferation, Invasion, and Migration by Mediating p21

BACKGROUND AND AIM

HOX transcript antisense intergenic RNA (HOTAIR) is a relatively well-understood RNA, which plays a central role in the pathogenesis of various tumors. The aim of the present study was to investigate the effect by which HOTAIR acts to influence the biological processes of colorectal cancer (CRC) through p21.

METHODS

Reverse transcription quantitative polymerase chain reaction and Western blot methods were employed to provide verification regarding the changes in HOTAIR, PCNA, Ki67, p21, cyclin E, and CDK2 among the CRC tissues and cells. The correlation between the clinicopathological characteristics of patients and expression of HOTAIR and p21 was subsequently evaluated, followed by an analysis into the effects of HOTAIR on the biological processes of M5 cells.

RESULTS

HOTAIR was found to be expressed at high levels, while p21 was determined to be at a low level among both the CRC tissues and the CRC cell lines. The expressions of HOTAIR and p21 were determined to be related to lymph node metastasis, tumor node metastasis, Dukes staging, distant metastases, histological types, and the degree of differentiation. Cells transfected with HOTAIR siRNA displayed inhibited rates of proliferation, invasion, and migration, as well as decreased cyclin E and CDK2, while apoptosis and p21 were increased.

CONCLUSION

The principal findings demonstrated that down-regulation of HOTAIR elicits an inhibitory effect on proliferation, invasion, and migration, while promoting the apoptosis of CRC cells through the up-regulation of p21. We believe that HOTAIR could represent a novel target for the treatment of CRC.

The dNTP triphosphohydrolase activity of SAMHD1 persists during S-phase when the enzyme is phosphorylated at T592

SAMHD1 is the major catabolic enzyme regulating the intracellular concentrations of DNA precursors (dNTPs). The S-phase kinase CDK2-cyclinA phosphorylates SAMHD1 at Thr-592. How this modification affects SAMHD1 function is highly debated. We investigated the role of endogenous SAMHD1 phosphorylation during the cell cycle. Thr-592 phosphorylation occurs first at the G1/S border and is removed during mitotic exit parallel with Thr-phosphorylations of most CDK1 targets. Differential sensitivity to the phosphatase inhibitor okadaic acid suggested different involvement of the PP1 and PP2 families dependent upon the time of the cell cycle. SAMHD1 turn-over indicates that Thr-592 phosphorylation does not cause rapid protein degradation. Furthermore, SAMHD1 influenced the size of the four dNTP pools independently of its phosphorylation. Our findings reveal that SAMHD1 is active during the entire cell cycle and performs an important regulatory role during S-phase by contributing with ribonucleotide reductase to maintain dNTP pool balance for proper DNA replication.

Lycopene treatment inhibits activation of Jak1/Stat3 and Wnt/β-catenin signaling and attenuates hyperproliferation in gastric epithelial cells

Helicobacter pylori (H pylori) colonizes the human stomach and increases the risk of gastric diseases including gastric cancer. H pylori increases reactive oxygen species (ROS), which activate Janus-activator kinase 1 (Jak1)/signal transducers and activators of transcription 3 (Stat3) in gastric epithelial cells. ROS mediate hyperproliferation, a hallmark of carcinogenesis, by activating Wnt/β-catenin signaling in various cells. Lycopene is a potent antioxidant exhibiting anticancer effects. We hypothesized that lycopene may inhibit H pylori-induced hyperproliferation by suppressing ROS-mediated activation of Jak1/Stat3 and Wnt/β-catenin signaling, and β-catenin target gene expression in gastric epithelial cells. We determined cell viability, ROS levels, and the protein levels of phospho- and total Jak1/Stat3, Wnt/β-catenin signaling molecules, Wnt-1, lipoprotein-related protein 5, and β-catenin target oncogenes (c-Myc and cyclin E) in H pylori-infected gastric epithelial AGS cells. The Jak1/Stat3 inhibitor AG490 served as the control treatment. The significance of the differences among groups was calculated using the 1-way analysis of variance followed by Newman-Keuls post hoc tests. The results show that lycopene reduced ROS levels and inhibited Jak1/Stat3 activation, alteration of Wnt/β-catenin multiprotein complex molecules, expression of c-Myc and cyclin E, and cell proliferation in H pylori-infected AGS cells. AG490 similarly inhibited H pylori-induced cell proliferation, alteration of Wnt/β-catenin multiprotein complex molecules, and oncogene expression. H pylori increased the levels of Wnt-1 and its receptor lipoprotein-related protein 5; this increase was inhibited by either lycopene or AG490 in AGS cells. In conclusion, lycopene inhibits ROS-mediated activation of Jak1/Stat3 and Wnt/β-catenin signaling and, thus, oncogene expression in relation to hyperproliferation in H pylori-infected gastric epithelial cells. Lycopene might be a potential and promising nutrient for preventing H pylori-associated gastric diseases including gastric cancer.