KIF18b-dependent hypomethylation of PARPBP gene promoter enhances oxaliplatin resistance in colorectal cancer.

As the new platinum drug oxaliplatin has been widely used in clinical treatment of colorectal cancer (CRC), oxaliplatin resistance has become a burning problem. In this study, higher expression of PARP-1 binding protein (PARPBP) was detected in oxaliplatin-resistant CRC (OR-CRC) cells than in non-resistant cells. Further research showed that kinesin family member 18 b (KIF18b) induced the overexpression of PARPBP, sustaining oxaliplatin resistance in OR-CRC cells. Through exploring the PARPBP gene promoter, we found that SP1-recruited DNMT3b methylated PARPBP promoter to suppress transcription in CRC cells, and increased KIF18b attenuated the recruitment of DNMT3b to PARPBP promoter by directly interacting with SP1 in OR-CRC cells. Clinical analysis suggested a positive relationship between KIF18b and PARPBP in CRC tissues and indicated poor prognosis in CRC patients with high level of KIF18b or PARPBP. In summary, KIF18b-induced PARPBP contributes to the resistant phenotype of OR-CRC.

E2F1 promotes cell cycle progression by stabilizing spindle fiber in colorectal cancer cells.

BACKGROUND: E2F1 is a transcription factor that regulates cell cycle progression. It is highly expressed in most cancer cells and activates transcription of cell cycle-related kinases. Stathmin1 and transforming acidic coiled-coil-containing protein 3 (TACC3) are factors that enhance the stability of spindle fiber. METHODS: The E2F1-mediated transcription of transforming acidic coiled-coil-containing protein 3 (TACC3) and stathmin1 was examined using the Cancer Genome Atlas (TCGA) analysis, quantitative polymerase chain reaction (qPCR), immunoblotting, chromatin immunoprecipitation (ChIP), and luciferase reporter. Protein-protein interaction was studied using co-IP. The spindle structure was shown by immunofluorescence. Phenotype experiments were performed through MTS assay, flow cytometry, and tumor xenografts. Clinical colorectal cancer (CRC) specimens were analyzed based on immunohistochemistry. RESULTS: The present study showed that E2F1 expression correlates positively with the expression levels of stathmin1 and TACC3 in colorectal cancer (CRC) tissues, and that E2F1 transactivates stathmin1 and TACC3 in CRC cells. Furthermore, protein kinase A (PKA)-mediated phosphorylation of stathmin1 at Ser16 is essential to the phosphorylation of TACC3 at Ser558, facilitating the assembly of TACC3/clathrin/α-tubulin complexes during spindle formation. Overexpression of Ser16-mutated stathmin1, as well as knockdown of stathmin1 or TACC3, lead to ectopic spindle poles including disorganized and multipolar spindles. Overexpression of wild-type but not Ser16-mutated stathmin1 promotes cell proliferation in vitro and tumor growth in vivo. Consistently, a high level of E2F1, stathmin1, or TACC3 not only associates with tumor size, lymph node metastasis, TNM stage, and distant metastasis, but predicts poor survival in CRC patients. CONCLUSIONS: E2F1 drives the cell cycle of CRC by promoting spindle assembly, in which E2F1-induced stathmin1 and TACC3 enhance the stability of spindle fiber.

Lipid metabolic features of T cells in the Tumor Microenvironment.

The tumor microenvironment (TME) is characterized by discrete changes in metabolic features of cancer and immune cells, with various implications. Cancer cells take up most of the available glucose to support their growth, thereby leaving immune cells with insufficient nutrients to expand. In the relative absence of glucose, T cells switch the metabolic program to lipid-based sources, which is pivotal to T-cell differentiation and activation in nutrient-stressed TME. Although consumption of lipids should provide an alternative energy source to starving T cells, a literature survey has revealed that it may not necessarily lead to antitumor responses. Different subtypes of T cells behave differently in various lipid overload states, which widely depends upon the kind of free fatty acids (FFA) engulfed. Key lipid metabolic genes provide cytotoxic T cells with necessary nutrients for proliferation in the absence of glucose, thereby favoring antitumor immunity, but the same genes cause immune evasion in Tmem and Treg. This review aims to detail the complexity of differential lipid metabolism in distinct subtypes of T cells that drive the antitumor or pro-tumor immunity in specific TME states. We have identified key drug targets related to lipid metabolic rewiring in TME.

IL-6-induced acetylation of E2F1 aggravates oxidative damage of retinal pigment epithelial cell line.

Oxidative damage in retinal pigment epithelial cells (RPE) is considered to be a crucial pathogenesis of age-related macular degeneration (AMD). Although dysregulation of the DNA repair system has been found in RPE cells of AMD patients, the detailed molecular mechanisms of this dysregulation and their relationship with the intraocular microenvironment of AMD patients remain unclear. Here, we established an RPE model of H2O2-induced oxidative stress and found that Sirtuin 1 (Sirt1)-mediated deacetylation of E2F transcription factor 1 (E2F1) was required for oxidation resistance in RPE cells. Moreover, E2F1 induced the expression of the chromatin-binding protein, high mobility group AT-Hook 1 (HMGA1), which promoted the transcription of glucose 6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway, to increase NADPH level for antioxidant defense. Interrupting the E2F1/HMGA1/G6PD regulatory axis increased reactive oxygen species (ROS) levels, DNA damage, and apoptosis in RPE cells under oxidative stress. Notably, interleukin 6 (IL-6), an inflammatory cytokine that is known to be upregulated in the intraocular fluid of AMD patients, induced phosphorylation (S47) of Sirt1 by activating PI3K/AKT/mTOR signaling, thereby inhibiting Sirt1 activity and increasing the acetylation of E2F1. Specific inhibitors of PI3K/AKT/mTOR signaling decreased DNA damage and ROS while increasing NADPH in RPE cells. Collectively, our findings demonstrate that IL-6-induced acetylation of E2F1 impairs the antioxidant capacity of RPE cells by disturbing the pentose phosphate pathway, which elucidates a relationship between the intraocular microenvironment and RPE oxidative damage in AMD and provides a possible therapeutic target for AMD.

Histone deacetylase 5 promotes the migration and invasion of hepatocellular carcinoma via increasing the transcription of hypoxia-inducible factor-1α under hypoxia condition.

Hypoxia plays a critical role in the progression and metastasis of hepatocellular carcinoma by activating the key transcription factor, hypoxia-inducible factor-1. This study aims to identify the novel mechanisms underlying the dysregulation of hypoxia-inducible factor-1α in hepatocellular carcinoma. We found that histone deacetylase 5, a highly expressed histone deacetylase in hepatocellular carcinoma, strengthened the migration and invasion of hepatocellular carcinoma cells under hypoxia but not normoxia condition. Furthermore, histone deacetylase 5 induced the transcription of hypoxia-inducible factor-1α by silencing homeodomain-interacting protein kinase-2 expression, which was also dependent on hypoxia. And then knockdown of hypoxia-inducible factor-1α decreased the expressions of mesenchymal markers, N-cadherin, and Vimentin, as well as matrix metalloproteinases, MMP7 and MMP9; however, the epithelial marker, E-cadherin, increased. Phenotype experiments showed that the migration and invasion of hepatocellular carcinoma cells were impaired by knockdown of histone deacetylase 5 or hypoxia-inducible factor-1α but rescued when eliminating homeodomain-interacting protein kinase-2 in hepatocellular carcinoma cells, which suggested the critical role of histone deacetylase 5-homeodomain-interacting protein kinase-2-hypoxia-inducible factor-1α pathway in hypoxia-induced metastasis. Finally, clinical analysis confirmed the positive correlation between histone deacetylase 5 and hypoxia-inducible factor-1α in hepatocellular carcinoma specimens and a relatively poor prognosis for the patients with high levels of histone deacetylase 5 and hypoxia-inducible factor-1α. Taken together, our findings demonstrated a novel mechanism underlying the crosstalk between histone deacetylase 5 and hypoxia-inducible factor-1 in hepatocellular carcinoma.

Ribonucleotide reductase large subunit M1 plays a different role in the invasion and metastasis of papillary thyroid carcinoma and undifferentiated thyroid carcinoma.

Ribonucleotide reductase (RR) has been reported to be associated with several types of cancer while the expression and role of RR in thyroid carcinoma (TC) has not been investigated. Here, we first examined the expression level of three RR subunit proteins (RRM1, RRM2, and RRM2B) in papillary thyroid carcinoma (PTC) and undifferentiated thyroid carcinoma (UTC) patient samples by immunohistochemistry. The results showed that RRM1 was higher expressed in 95.2 % cancer tissues compared with their adjacent normal tissues in 146 PTC samples. The expression level of RRM1 was positively correlated with T stage, lymph node metastasis (LNM), extrathyroidal invasion (ETI), and TNM stage in PTC patients. However, in 12 UTC samples, RRM1 expression was negatively expressed in six cases. To further determine the biological role of RRM1 in TC, ectopic expression or siRNA-mediated knockdown of RRM1 were carried out in the high-differentiated thyroid carcinoma cell line TPC-1 and the poor-differentiated thyroid carcinoma cell line SW579, respectively. In TPC-1 and SW579 cells, overexpression and siRNA knockdown of RRM1 demonstrated that RRM1 promoted DNA synthesis and proliferation in both cell lines as shown by EdU incorporation and cell viability assays. However, RRM1 enhanced cell migration and invasion in TPC-1 cells but inhibited that in SW579 cells as shown by wound healing and transwell assays. Moreover, we also found that RRM1 promoted PTEN expression and reduced Akt phosphorylation in a RR-activity-independent manner in the low-differentiated TC cells but not in the high-differentiated TC cells. In contrast, RRM2 expression was higher expressed in both PTC and UTC patient samples, consisting with its oncogenic role in other cancers. Therefore, we suggest that RRM1 promotes thyroid carcinoma proliferation as a component of RR but may play a different role in the invasion and metastasis of differently differentiated thyroid carcinomas through a non-RR pathway, which could be meaningful to precision treatment of thyroid carcinoma with RR inhibitors.

E2F1 promote the aggressiveness of human colorectal cancer by activating the ribonucleotide reductase small subunit M2.

As the ribonucleotide reductase small subunit, the high expression of ribonucleotide reductase small subunit M2 (RRM2) induces cancer and contributes to tumor growth and invasion. In several colorectal cancer (CRC) cell lines, we found that the expression levels of RRM2 were closely related to the transcription factor E2F1. Mechanistic studies were conducted to determine the molecular basis. Ectopic overexpression of E2F1 promoted RRM2 transactivation while knockdown of E2F1 reduced the levels of RRM2 mRNA and protein. To further investigate the roles of RRM2 which was activated by E2F1 in CRC, CCK-8 assay and EdU incorporation assay were performed. Overexpression of E2F1 promoted cell proliferation in CRC cells, which was blocked by RRM2 knockdown attenuation. In the migration and invasion tests, overexpression of E2F1 enhanced the migration and invasion of CRC cells which was abrogated by silencing RRM2. Besides, overexpression of RRM2 reversed the effects of E2F1 knockdown partially in CRC cells. Examination of clinical CRC specimens demonstrated that both RRM2 and E2F1 were elevated in most cancer tissues compared to the paired normal tissues. Further analysis showed that the protein expression levels of E2F1 and RRM2 were parallel with each other and positively correlated with lymph node metastasis (LNM), TNM stage and distant metastasis. Consistently, the patients with low E2F1 and RRM2 levels have a better prognosis than those with high levels. Therefore, we suggest that E2F1 can promote CRC proliferation, migration, invasion and metastasis by regulating RRM2 transactivation. Understanding the role of E2F1 in activating RRM2 transcription will help to explain the relationship between E2F1 and RRM2 in CRC and provide a novel predictive marker for diagnosis and prognosis of the disease.

E2F1 modulates RCCD1 expression to participate in the initiation and progression of EMT in colorectal cancer.

OBJECTIVE: Metastases in the advanced stages of colorectal cancer (CRC) present a major challenge to its treatment. Epithelial-Mesenchymal Transition (EMT) plays a crucial role in enhancing the metastasis and invasion ability of cancer cells. However, the progress of E2F transcription factor 1 (E2F1) and Regulator of chromatin condensation 1 (RCCD1) in CRC on EMT has not been studied. METHODS: The CRC differential expression data from The Cancer Genome Atlas database were analyzed by Gene Set Enrichment Analysis to verify the difference in expression of E2F1 and RCCD1 in cancerous and para-cancerous tissues.DNA-pull down and dual luciferase experiments confirmed that E2F1 regulates RCCD1. Western-blot and q-PCR experiments confirmed that E2F1 regulates RCCD1 and participates in the EMT-related progress of CRC.EDU, Wound healing and Transwell experiments verified the effects of regulation of E2F1 and RCCD1 on the proliferation, migration and invasion of CRC cells. RESULTS: E2F1 and RCCD1 are highly expressed in cancer tissues and cancer cells. E2F1 binds to the upstream promoter of RCCD1 to regulate RCCD1 and affect the expression of EMT-related targets in CRC cells. It also affects the proliferation, migration and invasion of CRC cells. CONCLUSIONS: E2F1 regulates the involvement of RCCD1 in CRC EMT and affects the proliferation, migration and invasion ability of CRC cells.

HDAC5 deacetylates c-Myc and facilitates cell cycle progression in hepatocellular carcinoma cells.

Histone deacetylase 5 (HDAC5) is an enzyme that deacetylates lysine residues on the N-terminal of histones and other proteins. It has been reported that HDAC5 deacetylates p53, the critical factor regulating cell cycle, in response to cellular stress, but the transcriptional products haven't been identified. Herein, we used p53 signaling pathway qPCR-chip to determine how HDAC5-mediated deacetylation of p53 affects cell cycle. However, validation using immunoblotting analysis revealed that acetylation of p53 at K120 impacted little to the expression of the genes identified using the qPCR-chip, indicating HDAC5 might deacetylate some other proteins to facilitate cell cycle via transactivating the differentially expressed genes determined by the qPCR-chip. The subsequent assays demonstrated that HDAC5 deacetylated c-Myc at K143 and K157 to facilitate the transactivation of CDK1, CDK4, and CDC25C, promoting cell cycle progression of hepatocellular carcinoma (HCC). This study shows that HDAC5 plays important roles in modulating deacetylation of c-Myc and regulating cell cycle progression, and it proves that LMK-235, the inhibitor targeting HDAC5 potentially serves as a drug for combating HCC via promoting acetylation of c-Myc at K143 and K157.

Bioinformatics analysis and experimental validation identified HMGA2/microRNA-200c-3p/LSAMP/Wnt axis as an immunological factor of patients with colorectal cancer.

Colorectal cancer (CRC) is one of the most common malignant cancers. The tumor microenvironment (TME) plays an important role in tumor progression and affects the prognosis of CRC patients. However, the TME has been poorly characterized and studies aiming to identify the biomarkers or combined risk scores of CRC patients are limited. Here, we overlapped differentially expressed genes and stromal/immune-score-related modules to identify immune- and stromal-related genes in CRC patients. These genes were fed into the LASSO-Cox regression analysis for dimensionality reduction to establish a TME-associated risk model. A high TME-associated risk score was identified as an unfavorable prognostic factor in The Cancer Genome Atlas and Gene Expression Omnibus datasets, as well as in a subgroup analysis, stratified by gender, age, microsatellite instability, and tumor lymph node metastasis stage. Ten genes were mutated more frequently in the high TME-associated risk score group; these mutations may be related to changes in the TME and the response to immunotherapy. Thus, a lower TME-associated risk score may indicate a better response to immunotherapy and longer overall survival. Experimental validation demonstrated that LSAMP, a novel TME-associated-risk-score-related gene, increased sensitivity of CRC to CD8+-T-cell-mediated cytotoxicity. A mechanistic investigation showed that the HMGA2/microRNA-200c-3p/LSAMP/Wnt axis was an immunological factor in CRC patients. To conclusion, we demonstrated that the TME-associated risk score model could be a reliable prognostic biomarker for CRC patients and highlighted the significance of the HMGA2/microRNA-200c-3p/LSAMP/Wnt axis in the oncoimmunology of CRC.

TRIM55 inhibits colorectal cancer development via enhancing protein degradation of c-Myc.

BACKGROUND: Colorectal cancer (CRC) is one of the most common and lethal malignancies which including colon and rectum cancer. Tripartite motif containing 55 (TRIM55) is an E3 ubiquitin ligase belonging to the TRIM family. Although the aberrant TRIM55 expression has been implicated in several tumors, its functional role, and molecular mechanisms in CRC remain unknown. METHODS: Immunohistochemical studies, qRT-PCR, and Western blot were performed to analyze the expression of TRIM55 in CRC patients and cell lines. TRIM55 expression and its relevance to clinical traits and prognosis were further explored in the TCGA database, and in our 87 clinical samples. Subsequently, we performed a series of functional assays to explore the effect of TRIM55 on CRC progression. Finally, the molecular mechanism of TRIM55 was investigated by immunoprecipitation and ubiquitination analyses. RESULTS: Here, we demonstrated that TRIM55 was markedly downregulated in CRC cell lines and tumors from CRC patients. Moreover, overexpression of TRIM55 could suppress CRC cell growth in vitro and inhibit CRC xenograft tumor development in vivo. Additionally, TRIM55 overexpression dampened CRC cell migration and invasion. Further bioinformatics analysis indicated that TRIM55 suppressed cyclin D1 and c-Myc expression. Mechanistically, co-immunoprecipitation assay revealed that TRIM55 directly interacted with c-Myc and down-regulated its protein expression level via protein ubiquitination. Intriguingly, c-Myc overexpression partially antagonized the function of TRIM55 overexpression. CONCLUSIONS: Taken together, our findings suggest that TRIM55 inhibits CRC tumor development via, at least in part, enhancing protein degradation of c-Myc. Targeting TRIM55 could provide a new therapeutic approach for CRC patients.

E2F8 exerts cancer-promoting effects by transcriptionally activating RRM2 and E2F8 knockdown synergizes with WEE1 inhibition in suppressing lung adenocarcinoma.

Ribonucleotide reductase (RR) is a rate-limiting enzyme that facilitates DNA replication and repair by reducing nucleotide diphosphates (NDPs) to deoxyribonucleotide diphosphates (dNDPs) and is thereby crucial for cell proliferation and cancer development. The E2F family of transcription factors includes key regulators of gene expression involved in cell cycle control. In this study, E2F8 expression was significantly increased in most cancer tissues of lung adenocarcinoma (LUAD) patients and was correlated with the expression of RRM2 through database and clinical samples analysis. The protein expression of E2F8 and RRM2 were positively correlated with tumor-node-metastasis (TNM) pathological stage, and high expression of E2F8 and RRM2 predicted a low 5-year overall survival rate in LUAD patients. Overexpression and knockdown experiments showed that E2F8 was essential for LUAD cell proliferation, DNA synthesis, and cell cycle progression, which were RRM2-dependent. Reporter gene, ChIP-qPCR, and DNA pulldown-Western blot assays indicated that E2F8 activated the transcription of the RRM2 gene by directly binding with the RRM2 promoter in LUAD cells. Previous studies indicated that inhibition of WEE1 kinase can suppress the phosphorylation of CDK1/2 and promote the degradation of RRM2. We further showed here that the combination of E2F8 knockdown with MK-1775, an inhibitor of WEE1 being evaluated in clinical trials, synergistically suppressed proliferation and promoted apoptosis of LUAD cells in vitro and in vivo. Thus, this study reveals a novel role of E2F8 as a proto-oncogenic transcription activator by activating RRM2 expression in LUAD, and targeting both the transcription and degradation mechanisms of RRM2 could produce a synergistic inhibitory effect for LUAD treatment in addition to conventional inhibition of RR enzyme activity.

TOPBP1 regulates resistance of gastric cancer to oxaliplatin by promoting transcription of PARP1.

Gastric cancer (GC) is the third leading cause of cancer-associated mortality worldwide. The platinum derivative oxaliplatin is widely applied in standard GC chemotherapy but recurrence and metastasis are common in advanced GC cases due to intrinsic or induced chemoresistance. Poly(ADP-Ribose) polymerase 1 (PARP1) is an enzyme crucial for repairing DNA damage induced by platinum compounds, which undermines the effectiveness of platinum-based chemotherapy. Data from the current study showed that topoisomerase IIß binding protein 1 (TOPBP1), an interacting partner of topoisomerase IIß, is highly expressed in oxaliplatin-resistant GC (OR-GC) cells and promotes PARP1 transcription through direct binding to its proximal promoter region. Furthermore, AKT-mediated phosphorylation of TOPBP1 at Ser1159 was indispensable for inducing PARP1 expression in OR-GC cells. Disruption of the TOPBP1/PARP1 regulatory pathway decreased cell viability and augmented apoptosis of OR-GC cells. The positive correlation between TOPBP1 and PARP1 was confirmed using both the TCGA database and immunohistochemical analysis of GC tissues. In GC patients receiving oxaliplatin treatment, high expression of TOPBP1 or PARP1 was associated with poor prognosis. Our finding that the TOPBP1/PARP1 pathway facilitates acquisition of oxaliplatin resistance uncovers a novel mechanism underlying platinum-based chemotherapy resistance in gastric cancer that may be utilized for developing effective therapeutic strategies.

Development and experimental verification of C-arm camera shooting locator.

This study aimed to develop a self-made C-arm camera shooting locator and verify its accuracy and advantages. A total of 60 physicians and nurses from the Surgical System of Sanmen People's Hospital, Zhejiang Province, China, were randomly selected as filming operators. The C-arm machine with a self-made locator and a C-arm machine without a locator were used to measure the center of the circular plate. The iron nails were used to shoot. The distance between the iron nail and the center point of the circular display area on display was defined as the shooting deviation. When it was less than 3 cm, the shooting was stopped. The number of shots, total shooting time, and first-shot deviation in the C-arm camera shooting groups with and without the locator were statistically analyzed, and the advantages and disadvantages of the two were compared. The average number of shots, average total shooting time, and average first-shot deviation of the C-arm camera using the locator were significantly better than those in the group without the locator, and the differences were statistically significant. When the shooting distance (X) was equal to 30 cm and the shooting angle (Y) was equal to 0°, the average number of shots, average total shooting time, and average first-shot deviation were optimal. The C-arm camera shooting locator can improve the shooting accuracy of the C-arm camera and effectively reduce the number of shots and total shooting time. Hence, it can be applied in clinical and surgical practice.

Insights Into the Function and Clinical Application of HDAC5 in Cancer Management.

Histone deacetylase 5 (HDAC5) is a class II HDAC. Aberrant expression of HDAC5 has been observed in multiple cancer types, and its functions in cell proliferation and invasion, the immune response, and maintenance of stemness have been widely studied. HDAC5 is considered as a reliable therapeutic target for anticancer drugs. In light of recent findings regarding the role of epigenetic reprogramming in tumorigenesis, in this review, we provide an overview of the expression, biological functions, regulatory mechanisms, and clinical significance of HDAC5 in cancer.

A comprehensive review of the roles of E2F1 in colon cancer.

E2F transcription factor 1 (E2F1) is a member of the E2F family of transcription factors. E2F1 binds to DNA with dimerization partner (DP) proteins through an E2 recognition site. The dissociation of E2F1 from retinoblastoma (Rb) protein recovers its transcriptional activity, which drives the cell cycle from the G1 to S phase. E2F1 has been shown to be involved in cellular proliferation, differentiation, and apoptosis in colon cancer. It was recently found that E2F1 also participates in the metastasis and chemoresistance of colon cancer. There are abundant experimental data regarding the actions of E2F1, which can be grouped as either pro-tumorigenic or pro-apoptotic. Despite a growing interest and plentiful data, there is currently no review that focuses on the role of E2F1 in colon cancer. Research on E2F1 and colon cancer has been scattered over various genes and microRNAs (miRNAs) that affect E2F1 expression. Here, we provide the first review that aims to consider and dissect all of the elucidated complex behaviors of E2F1 in colon cancer. This review also provides an analysis and conclusion regarding the current understanding of E2F1 in colon cancer in order to facilitate the direction of future research.

Multi-omics analysis to identify driving factors in colorectal cancer.

Aim: We aim to identify driving genes of colorectal cancer (CRC) through multi-omics analysis. Materials & methods: We downloaded multi-omics data of CRC from The Cancer Genome Atlas dataset. Integrative analysis of single-nucleotide variants, copy number variations, DNA methylation and differentially expressed genes identified candidate genes that carry CRC risk. Kernal genes were extracted from the weighted gene co-expression network analysis. A competing endogenous RNA network composed of CRC-related genes was constructed. Biological roles of genes were further investigated in vitro. Results: We identified LRRC26 and REP15 as novel prognosis-related driving genes for CRC. LRRC26 hindered tumorigenesis of CRC in vitro. Conclusion: Our study identified novel driving genes and may provide new insights into the molecular mechanisms of CRC.

The TGFß1-FOXM1-HMGA1-TGFß1 positive feedback loop increases the cisplatin resistance of non-small cell lung cancer by inducing G6PD expression.

Platinum-based chemotherapy is still widely applied for the treatment of advanced non-small cell lung cancer (NSCLC). However, acquired chemoresistance compromises the curative effect of this drug. In this study, we found that glucose-6-phosphate dehydrogenase (G6PD), a critical enzyme of the pentose phosphate pathway, contributed to cisplatin resistance in NSCLC. The experimental results showed that transforming growth factor beta 1 (TGFß1) increased the expression of G6PD by activating the forkhead box protein M1-high mobility group AT-hook 1-G6PD (FOXM1-HMGA1-G6PD) transcriptional regulatory pathway, in which TGFß1 inhibited the ubiquitination and degradation of FOXM1 protein. Additionally, HMGA1 induced TGFß1 expression, and neutralized TGFß1 in the culture medium downregulated HMGA1 levels, suggesting the existence of a TGFß1-FOXM1-HMGA1-TGFß1 positive feedback loop and its role in maintaining G6PD expression. Further investigations showed that exogenous TGFß1 enhanced the cisplatin resistance of NSCLC cells, while disrupting the FOXM1-HMGA1-G6PD pathway, thereby sensitizing the cells to cisplatin. Consistently, the TGFß1-FOXM1-HMGA1-G6PD axis was confirmed in NSCLC tissues, and overactivation of this axis predicted poor survival in NSCLC patients. Collectively, the results of this study demonstrate that the TGFß1-FOXM1-HMGA1-TGFß1 positive feedback loop plays a crucial role in the cisplatin resistance of NSCLC by upregulating the expression of G6PD, providing a potential therapeutic target to restore chemosensitivity in cisplatin-resistant NSCLC.

E2F1 transactivates IQGAP3 and promotes proliferation of hepatocellular carcinoma cells through IQGAP3-mediated PKC-alpha activation.

For decades, E2F1 has been recognized as a retinoblastoma protein (RB) binding transcription factor that regulates the cell cycle. E2F1 binds preferentially to RB and accelerates the cell cycle in most cancer cells. However, it is thought that E2F1 modulates cell proliferation in other ways as well. Herein, it has been discovered that in pathological tissues derived from hepatocellular carcinoma (HCC) patients, E2F1 correlates positively with IQGAP3 and that both of these factors are highly expressed (N = 164, R = 0.6716). In addition, a high level of E2F1 or IQGAP3 predicted poor survival in HCC patients. Further study determined that E2F1 transactivates IQGAP3, the GTPase binding protein in MHCC-97H cells. Co-immunoprecipitation analysis indicated that IQGAP3 interacts with PKCδ and competitively inhibits the interaction between PKCδ and PKCα, resulting in phosphorylation of PKCα activation and promotion of cell proliferation. This study reveals that highly expressed E2F1 not only transactivates cell-cycle-related factors but also promotes HCC proliferation by activating the phosphorylation of PKCα.

YY1 promotes colorectal cancer proliferation through the miR-526b-3p/E2F1 axis.

We previously reported that E2F1 expression is up-regulated and positively correlated with the malignant phenotypes of colorectal cancer (CRC). However, the underlying mechanisms leading to the aberrant up-regulation of E2F1 in CRC have not been clarified. In this study, we observed that miR-526b-3p directly targets the 3'UTR of E2f1 mRNA, leading to reduced E2F1 expression. Overexpression of miR-526b-3p inhibited the proliferation of CRC cells by decreasing the level of E2F1. We also found that the Ying Yang 1 (YY1)-dependent transcriptional suppression of miR-526b-3p is responsible for the up-regulation of E2F1 in CRC, in which YY1 binds to the promoter of miR-526b gene and recruits histone deacetylase (HDAC). Knockdown of YY1 led to cell cycle arrest and diminished colony formation in CRC cells partly through relieving the miR-526b-3p suppression. Clinical analysis showed that YY1 and E2F1 were negatively correlated with miR-526b-3p in CRC tissues. Moreover, a high level of YY1 and E2F1, or a low level of miR-526b-3p, predicted poor survival of CRC patients. In conclusion, our findings highlight the dysregulation of the YY1/miR-526b-3p/E2F1 axis in CRC development, implicating a novel regulatory pathway for E2F1 as a potential therapeutic target in CRC.