Upregulation of E3 Ubiquitin Ligase CBLC Enhances EGFR Dysregulation and Signaling in Lung Adenocarcinoma

CBLC promotes the development of colorectal cancer by promoting ABI1 degradation to activate the ERK signaling pathway

CBLC (CBL proto-oncogene C) is an E3 ubiquitin protein ligase that plays a key role in cancers. However, the function and mechanism of CBLC in colorectal cancer (CRC) has not been fully elucidated. The aim of this study was to investigate the function of CBLC in CRC and its underlying molecular mechanism. High CBLC levels were certified in tumor tissues of CRC patients, and its expression was positively associated with TNM stage. Next, we explored the role of CBLC in CRC using gain or loss of function. For biological function analysis, CCK-8 cell proliferation, colony formation, flow cytometry, scratch, and transwell assays collectively suggested that CBLC overexpression promoted cell proliferation, cell cycle progression, migration and invasion. As observed, CBLC knockdown exhibited exactly opposite effects, resulting in impaired tumorigenicity in vitro. Xenograft studies displayed that CBLC overexpression accelerated tumor growth and promoted tumor metastasis to the lung, while the inhibitory effects of CBLC knockdown on tumorigenicity and metastasis ability of CRC cells was also confirmed. Furthermore, the molecular mechanism of CBLC in CRC was explored. CBLC induced the activation of ERK signaling pathway, further leading to its pro-tumor role. Notably, CBLC decreased ABI1 (Abelson interactor protein-1, a candidate tumor suppressor) protein levels through its ubiquitin ligase activity, while ABI1 upregulation abolished the effects of CBLC on the tumorigenesis of CRC. Taken together, these results demonstrate that CBLC acts as a tumor promoter in CRC through triggering the ubiquitination and degradation of ABI1 and activating the ERK signaling pathway. CBLC may be a potential novel target for CRC.

E3 ubiquitin ligases in lung cancer: Emerging insights and therapeutic opportunities

Aim In this review, we have attempted to provide the readers with an updated account of the role of a family of proteins known as E3 ligases in different aspects of lung cancer progression, along with insights into the deregulation of expression of these proteins during lung cancer. A detailed account of the therapeutic strategies involving E3 ligases that have been developed or currently under development has also been provided in this review. MATERIALS AND METHODS: The review article employs extensive literature search, along with differential gene expression analysis of lung cancer associated E3 ligases using the DESeq2 package in R, and the Gene Expression Profiling Interactive Analysis (GEPIA) database (http://gepia.cancer-pku.cn/). Protein expression analysis of CPTAC lung cancer samples was carried out using the UALCAN webtool (https://ualcan.path.uab.edu/index.html). Assessment of patient overall survival (OS) in response to high and low expression of selected E3 ligases was performed using the online Kaplan-Meier plotter (https://kmplot.com/analysis/index.php?p=background). KEY FINDINGS: SIGNIFICANCE: The review provides an in-depth understanding of the role of E3 ligases in lung cancer progression and an up-to-date account of the different therapeutic strategies targeting oncogenic E3 ligases for improved lung cancer management.

Recruitment of hexahydroquinoline as anticancer scaffold targeting inhibition of wild and mutants EGFR (EGFRWT, EGFRT790M, and EGFRL858R)

Hexahydroquinoline (HHQ) scaffold was constructed and recruited for development of new series of anticancer agents. Thirty-two new compounds were synthesised where x-ray crystallography was performed to confirm enantiomerism. Thirteen compounds showed moderate to good activity against NCI 60 cancer cell lines, with GI % mean up to 74% for 10c. Expending erlotinib as a reference drug, target compounds were verified for their inhibiting activities against EGFRWT, EGFRT790M, and EGFRL858R where compound 10d was the best inhibitor with IC50 = 0.097, 0.280, and 0.051 µM, respectively, compared to erlotinib (IC50 = 0.082 µM, 0.342 µM, and 0.055 µM, respectively). Safety profile was validated using normal human lung (IMR-90) cells. 10c and 10d disrupted cell cycle at pre-G1 and G2/M phases in lung cancer, HOP-92, and cell line. Molecular docking study was achieved to understand the potential binding interactions and affinities in the active sites of three versions of EGFRs.

Methylation of the epigenetic JMJD2D protein by SET7/9 promotes prostate tumorigenesis

How the function of the JMJD2D epigenetic regulator is regulated or whether it plays a role in prostate cancer has remained elusive. We found that JMJD2D was overexpressed in prostate tumors, stimulated prostate cancer cell growth and became methylated by SET7/9 on K427. Mutation of this lysine residue in JMJD2D reduced the ability of DU145 prostate cancer cells to grow, invade and form tumors and elicited extensive transcriptomic changes. This included downregulation of CBLC, a ubiquitin ligase gene with hitherto unknown functions in prostate cancer, and upregulation of PLAGL1, a transcription factor with reported tumor suppressive characteristics in the prostate. Bioinformatic analyses indicated that CBLC expression was elevated in prostate tumors. Further, downregulation of CBLC largely phenocopied the effects of the K427 mutation on DU145 cells. In sum, these data have unveiled a novel mode of regulation of JMJD2D through lysine methylation, illustrated how this can affect oncogenic properties by influencing expression of the CBLC gene, and established a pro-tumorigenic role for CBLC in the prostate. A corollary is that JMJD2D and CBLC inhibitors could have therapeutic benefits in the treatment of prostate and possibly other cancers.

JAC4 Inhibits EGFR-Driven Lung Adenocarcinoma Growth and Metastasis through CTBP1-Mediated JWA/AMPK/NEDD4L/EGFR Axis

Lung adenocarcinoma (LUAD) is the most common lung cancer, with high mortality. As a tumor-suppressor gene, JWA plays an important role in blocking pan-tumor progression. JAC4, a small molecular-compound agonist, transcriptionally activates JWA expression both in vivo and in vitro. However, the direct target and the anticancer mechanism of JAC4 in LUAD have not been elucidated. Public transcriptome and proteome data sets were used to analyze the relationship between JWA expression and patient survival in LUAD. The anticancer activities of JAC4 were determined through in vitro and in vivo assays. The molecular mechanism of JAC4 was assessed by Western blot, quantitative real-time PCR (qRT-PCR), immunofluorescence (IF), ubiquitination assay, co-immunoprecipitation, and mass spectrometry (MS). Cellular thermal shift and molecule-docking assays were used for confirmation of the interactions between JAC4/CTBP1 and AMPK/NEDD4L. JWA was downregulated in LUAD tissues. Higher expression of JWA was associated with a better prognosis of LUAD. JAC4 inhibited LUAD cell proliferation and migration in both in-vitro and in-vivo models. Mechanistically, JAC4 increased the stability of NEDD4L through AMPK-mediated phosphorylation at Thr367. The WW domain of NEDD4L, an E3 ubiquitin ligase, interacted with EGFR, thus promoting ubiquitination at K716 and the subsequent degradation of EGFR. Importantly, the combination of JAC4 and AZD9191 synergistically inhibited the growth and metastasis of EGFR-mutant lung cancer in both subcutaneous and orthotopic NSCLC xenografts. Furthermore, direct binding of JAC4 to CTBP1 blocked nuclear translocation of CTBP1 and then removed its transcriptional suppression on the JWA gene. The small-molecule JWA agonist JAC4 plays a therapeutic role in EGFR-driven LUAD growth and metastasis through the CTBP1-mediated JWA/AMPK/NEDD4L/EGFR axis.

Hsa-miR-22-3p inhibits liver cancer cell EMT and cell migration/ invasion by indirectly regulating SPRY2

The general mechanism for microRNAs to play biological function is through their inhibition on the expression of their target genes. In cancer, microRNAs may accelerate cell senescence, block angiogenesis, decrease energy supplies, repress tumor cell cycle and promote apoptosis to function as the tumor repressors. On the other hand, microRNAs can modulate tumor suppressor molecules to activate oncogene relevant signaling pathway to initiate tumorigenesis and promote tumor progression. By targeting different genes, miR-22 can function as either a tumor suppressor or a tumor promoter in different types of cancer. In liver cancer, miR-22 mainly functions as a tumor suppressor via its regulation on different genes. In this study, we demonstrated that miR-22 indirectly regulates SPRY2 by inhibiting CBL, an E3 ligase for SPRY2 that has been confirmed. As one of the modulators of the MAPK (mitogen-activated protein kinase)/ERK (extracellular signal-regulated kinase) signaling pathway, SPRY2 plays important roles in many developmental and physiological processes, and its deregulation has been reported in different types of cancer and shown to affect cancer development, progression, and metastasis. By inhibiting the expression of CBL, which stabilizes SPRY2, miR-22 indirectly upregulates SPRY2, thereby suppressing the epithelial-mesenchymal transition (EMT), cell migration, and invasion and decreasing the expression of liver cancer stem cell (CSC) marker genes. The inhibitory effects of miR-22 on EMT, cell migration, and invasion can be blocked by the knockdown of SPRY2 expression in miR-22 overexpressing cells. Additionally, we demonstrated that miR-22 expression inhibits the ERK signaling pathway and that this effect is due to its upregulation of SPRY2. Overall, our study revealed a novel miR-22-3p/CBL/SPRY2/ERK axis that plays an important role in EMT, cell migration, and invasion of liver cancer cells.

Cadmium Activates EGFR/STAT5 Signaling to Overcome Calcium Chelation and Promote Epithelial to Mesenchymal Transition

Cadmium (Cd) is a heavy metal found in cigarette smoke, as well as in air and drinking water due to agricultural and industrial activities, and it poses a health risk to the general population. Prolonged low-dose Cd exposure via inhalation or ingestion causes lung and kidney cancers in humans and in animal models. While high doses of Cd exposure are correlated with the occupational setting and are cytotoxic, low doses of Cd are mainly correlated with exposure in the general population and induce carcinogenesis. The mechanism by which Cd-exposed cells overcome calcium chelation and induce malignant transformation remains unclear. This study examines how cells exposed to low doses of Cd survive loss of E-cadherin cell-cell adhesion via activation of the epidermal growth factor receptor (EGFR) and signal transducer and activator of transcription 5 (STAT5), which work to upregulate genes associated with survival and proliferation. To demonstrate the role of Cd in EGFR/STAT5 activation, we exposed two epithelial cell lines, BEAS-2B and HEK293, to two different doses (0.4 µM and 1.6 µM) of Cadmium chloride hemipentahydrate (CdCl₂·2.5H₂O) that are environmentally relevant to levels of Cd found in food and cigarettes for 24 h (hours) and 9 weeks (wks). When comparing cells treated with Cd with control cells, the Cd treated cells exhibited faster proliferation; therefore, we studied activation of EGFR via the STAT5 pathway using immunofluorescence (IF) for protein expression and localization and, in addition, RT-qPCR to examine changes in EGFR/STAT5 inducible genes. Our results showed an increase in EGFR and phosphorylated EGFR (p-EGFR) protein, with 1.6 µM of Cadmium having the highest expression at both 24-hour (hr) and 9-week (wk) exposures. Moreover, the IF analysis also demonstrated an increase of STAT5 and phosphorylated STAT5 (pSTAT5) in both short-term and long-term exposure, with 0.4 µM having the highest expression at 24 h. Finally, via Western blot analysis, we showed that there was a dose-dependent decrease in E-cadherin protein expression and increased N-cadherin in cells treated with low doses of Cd. These data demonstrate that epithelial cells can overcome Cd-mediated toxicity via activation of EGFR pathway to induce cell proliferation and survival and promote epithelial to mesenchymal transition.

Emerging Roles of Non-proteolytic Ubiquitination in Tumorigenesis

Ubiquitination is a critical type of protein post-translational modification playing an essential role in many cellular processes. To date, more than eight types of ubiquitination exist, all of which are involved in distinct cellular processes based on their structural differences. Studies have indicated that activation of the ubiquitination pathway is tightly connected with inflammation-related diseases as well as cancer, especially in the non-proteolytic canonical pathway, highlighting the vital roles of ubiquitination in metabolic programming. Studies relating degradable ubiquitination through lys48 or lys11-linked pathways to cellular signaling have been well-characterized. However, emerging evidence shows that non-degradable ubiquitination (linked to lys6, lys27, lys29, lys33, lys63, and Met1) remains to be defined. In this review, we summarize the non-proteolytic ubiquitination involved in tumorigenesis and related signaling pathways, with the aim of providing a reference for future exploration of ubiquitination and the potential targets for cancer therapies.

The functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination

Ubiquitination of substrates usually have two fates: one is degraded by 26S proteasome, and the other is non-degradative ubiquitination modification which is associated with cell cycle regulation, chromosome inactivation, protein transportation, tumorigenesis, achondroplasia, and neurological diseases. Cullin3 (CUL3), a scaffold protein, binding with the Bric-a-Brac-Tramtrack-Broad-complex (BTB) domain of substrates recognition adaptor and RING-finger protein 1 (RBX1) form ubiquitin ligases (E3). Based on the current researches, this review has summarized the functions and effects of CUL3-E3 ligases mediated non-degradative ubiquitination.

Identifying General Tumor and Specific Lung Cancer Biomarkers by Transcriptomic Analysis

The bioinformatic pipeline previously developed in our research laboratory is used to identify potential general and specific deregulated tumor genes and transcription factors related to the establishment and progression of tumoral diseases, now comparing lung cancer with other two types of cancer. Twenty microarray datasets were selected and analyzed separately to identify hub differentiated expressed genes and compared to identify all the deregulated genes and transcription factors in common between the three types of cancer and those unique to lung cancer. The winning DEGs analysis allowed to identify an important number of TFs deregulated in the majority of microarray datasets, which can become key biomarkers of general tumors and specific to lung cancer. A coexpression network was constructed for every dataset with all deregulated genes associated with lung cancer, according to DAVID’s tool enrichment analysis, and transcription factors capable of regulating them, according to oPOSSUM´s tool. Several genes and transcription factors are coexpressed in the networks, suggesting that they could be related to the establishment or progression of the tumoral pathology in any tissue and specifically in the lung. The comparison of the coexpression networks of lung cancer and other types of cancer allowed the identification of common connectivity patterns with deregulated genes and transcription factors correlated to important tumoral processes and signaling pathways that have not been studied yet to experimentally validate their role in lung cancer. The Kaplan–Meier estimator determined the association of thirteen deregulated top winning transcription factors with the survival of lung cancer patients. The coregulatory analysis identified two top winning transcription factors networks related to the regulatory control of gene expression in lung and breast cancer. Our transcriptomic analysis suggests that cancer has an important coregulatory network of transcription factors related to the acquisition of the hallmarks of cancer. Moreover, lung cancer has a group of genes and transcription factors unique to pulmonary tissue that are coexpressed during tumorigenesis and must be studied experimentally to fully understand their role in the pathogenesis within its very complex transcriptomic scenario. Therefore, the downstream bioinformatic analysis developed was able to identify a coregulatory metafirm of cancer in general and specific to lung cancer taking into account the great heterogeneity of the tumoral process at cellular and population levels.

CancerOmicsNet: a multi-omics network-based approach to anti-cancer drug profiling

Development of novel anti-cancer treatments requires not only a comprehensive knowledge of cancer processes and drug mechanisms of action, but also the ability to accurately predict the response of various cancer cell lines to therapeutics. Numerous computational methods have been developed to address this issue, including algorithms employing supervised machine learning. Nonetheless, high prediction accuracies reported for many of these techniques may result from a significant overlap among training, validation, and testing sets, making existing predictors inapplicable to new data. To address these issues, we developed CancerOmicsNet, a graph neural network with sophisticated attention propagation mechanisms to predict the therapeutic effects of kinase inhibitors across various tumors. Emphasizing on the system-level complexity of cancer, CancerOmicsNet integrates multiple heterogeneous data, such as biological networks, genomics, inhibitor profiling, and gene-disease associations, into a unified graph structure. The performance of CancerOmicsNet, properly cross-validated at the tissue level, is 0.83 in terms of the area under the receiver operating characteristics, which is notably higher than those measured for other approaches. CancerOmicsNet generalizes well to unseen data, i.e., it can predict therapeutic effects across a variety of cancer cell lines and inhibitors. CancerOmicsNet is freely available to the academic community at https://github.com/pulimeng/CancerOmicsNet.

PSMA5 contributes to progression of lung adenocarcinoma in association with the JAK/STAT pathway

Proteasome dysregulation is a common feature of cancer and a critical risk for tumorigenesis. However, the characteristics of proteasome components in tumor development and metastasis are poorly understood. PSMA5, an α5 subunit of the 20S core proteasome, is associated with the degradation of intracellular proteins. Increasing evidence indicated it is involved in tumor development, but the underlying mechanism has remained unknown. Here, we show that PSMA5 is up-regulated in lung adenocarcinoma (LUAD) cells and clinical LUAD tissues. Moreover, its up-regulation is positively associated with lymph node metastasis and the poor prognosis of LUAD patients. PSMA5 knockdown inhibited the proliferation, invasion and metastasis of LUAD cells in vitro and in vivo, induced apoptosis of LUAD cells and sensitized LUAD cells to cisplatin. Further investigations revealed that PSMA5 overexpression inhibited cell apoptosis by activating the janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway in LUAD cells. In total, our results demonstrate that PSMA5 may function as a prognostic factor in LUAD. In addition, PSMA5 is a promising therapeutic target for LUAD, as its depletion induces cell apoptosis by inhibiting the JAK/STAT pathway.

Novel cell lines derived from Chinese hamster kidney tissue

Immortalized kidney cell lines are widely used in basic and applied research such as cell permeability tests and drug screening. Although many cell lines have been established from kidney tissues, the immortalization process has not been clarified in these cell lines. In this study, we analyzed the phenotypic changes that occurred during the immortalization of kidney cells derived from Chinese hamster tissue in terms of karyotype and gene expression profiles. In the newly established cell line, designated as CHK-Q, gene expression profiles at each stage of the immortalization process and during the adaptation to serum-free conditions were analyzed by DNA microarray. Renal stem cell markers CD24 and CD133 were expressed in CHK-Q cells, suggesting that CHK-Q cells were transformed from renal stem cells. Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis to identify the pathways of upregulated and downregulated genes revealed that the immortalization of CHK-Q cells was associated with increased fluctuations in the expression of specific proto-oncogenes. Karyotype analysis of spontaneously immortalized CHK-Q cells indicated that CHK-Q chromosomes had a typical modal number of 23 but possessed slight chromosomal abnormalities. In this study, we investigated the mechanism of cell environmental adaptation by analyzing gene expression behavior during the immortalization process and serum-free adaptation. CHK-Q cells are applicable to the fields of biotechnology and biomedical science by utilizing their characteristics as kidney-derived cells.

TGFα-EGFR pathway in breast carcinogenesis, association with WWOX expression and estrogen activation

WWOX is a tumor-suppressive steroid dehydrogenase, which relationship with hormone receptors was shown both in animal models and breast cancer patients. Herein, through nAnT-iCAGE high-throughput gene expression profiling, we studied the interplay of estrogen receptors and the WWOX in breast cancer cell lines (MCF7, T47D, MDA-MB-231, BT20) under estrogen stimulation and either introduction of the WWOX gene by retroviral transfection (MDA-MB-231, T47D) or silenced with shRNA (MCF7, BT20). Additionally, we evaluated the consequent biological characteristics by proliferation, apoptosis, invasion, and adhesion assays. TGFα-EGFR signaling was found to be significantly affected in all examined breast cancer cell lines in response to estrogen and strongly associated with the level of WWOX expression, especially in ER-positive MCF7 cells. Under the influence of 17β-estradiol presence, biological characteristics of the cell lines were also delineated. The study revealed modulation of adhesion, invasion, and apoptosis. The obtained results point at a complex role of the WWOX gene in the carcinogenesis of the breast tissue, which seems to be closely related to the presence of estrogen α and/or β receptors.

Stabilization of AURKA by the E3 ubiquitin ligase CBLC in lung adenocarcinoma

CBL family proteins (CBL, CBLB and CBLC in mammals) are E3 ubiquitin ligases of protein tyrosine kinases. CBL mediates the lysosomal degradation of activated EGFR through K63-linked ubiquitination, while CBLC has an oncogenic function by positively regulating EGFR activation through K6 and K11-linked ubiquitination in EGFR mutant lung adenocarcinoma (LAD). Here, we used immunoprecipitation and mass spectrometry to study the CBLC interactome, and found that CBLC is also involved in cell cycle regulation by stabilizing Aurora kinase A (AURKA). CBLC interacted with the kinase domain of AURKA and positively regulated the stability of AURKA by conjugating monoubiquitination and K11/K63-linked polyubiquitination, which are protective from degrading K11/K48 polyubiquitination. CBLC depletion markedly decreased the half-life of AURKA in cycloheximide-treated LAD cells. When LAD cells were synchronized with double thymidine block at the G1/S boundary and then released into mitotic arrest, CBLC depletion delayed the accumulation and activation of AURKA and prevented cancer cells from entering mitosis. CBLC deficiency significantly delayed cell cycle progression, reduced the mitotic population, and increased apoptosis of LAD cells. Targeting CBLC inhibited tumor growth of LAD cells and enhanced their sensitivity to paclitaxel in xenograft models. Immunohistochemical staining of the tissue microarray also revealed a positive correlation between the expression of CBLC and AURKA in normal and LAD tissues, further supporting the positive regulation of AURKA expression by CBLC. In summary, these findings indicate that the oncogenic E3 ligase CBLC plays a role in mitotic entry by stabilizing AURKA via ubiquitination in LAD. This work demonstrates that targeting CBLC combined with paclitaxel might be a potential option for the treatment of LAD patients who have no available targeted therapies.

Non-proteolytic ubiquitylation in cellular signaling and human disease

Ubiquitylation is one of the most common post-translational modifications (PTMs) of proteins that frequently targets substrates for proteasomal degradation. However it can also result in non-proteolytic events which play important functions in cellular processes such as intracellular signaling, membrane trafficking, DNA repair and cell cycle. Emerging evidence demonstrates that dysfunction of non-proteolytic ubiquitylation is associated with the development of multiple human diseases. In this review, we summarize the current knowledge and the latest concepts on how non-proteolytic ubiquitylation pathways are involved in cellular signaling and in disease-mediating processes. Our review, may advance our understanding of the non-degradative ubiquitylation process.

Evanthia Pangou and co-authors review recent insights into the important roles of non-proteolytic ubiquitylation in cellular signaling as well as in physiology and disease.

Downregulation of NEDD4L by EGFR signaling promotes the development of lung adenocarcinoma

Cumulative evidence indicates that the abnormal regulation of the NEDD4 family of E3-ubiquitin ligases participates in the tumorigenesis and development of cancer. However, their role in lung adenocarcinoma (LUAD) remains unclear. This study comprehensively analyzed the NEDD4 family in LUAD data sets from public databases and found only NEDD4L was associated with the overall survival of LUAD patients. Gene set enrichment analysis (GSEA) indicated that NEDD4L might be involved in the regulation of mTORC1 pathway. Both cytological and clinical assays showed that NEDD4L inhibited the activity of the mTOR signaling pathway. In vivo and in vitro experiments showed that NEDD4L could significantly inhibit the proliferation of LUAD cells. In addition, this study also found that the expression of NEDD4L was regulated by EGFR signaling. These findings firstly revealed that NEDD4L mediates an interplay between EGFR and mTOR pathways in LUAD, and suggest that NEDD4L held great potential as a novel biomarker and therapeutic target for LUAD.

Comprehensive Analysis of E3 Ubiquitin Ligases Reveals Ring Finger Protein 223 as a Novel Oncogene Activated by KLF4 in Pancreatic Cancer

Pancreatic cancer is one of the major malignancies and causes of mortality worldwide. E3 ubiquitin-protein ligases transfer activated ubiquitin from ubiquitin-conjugating enzymes to protein substrates and confer substrate specificity in cancer. In this study, we first downloaded data from The Cancer Genome Atlas pancreatic adenocarcinoma dataset, acquired all 27 differentially expressed genes (DEGs), and identified genomic alterations. Then, the prognostic significance of DEGs was analyzed, and eight DEGs (MECOM, CBLC, MARCHF4, RNF166, TRIM46, LONRF3, RNF39, and RNF223) and two clinical parameters (pathological N stage and T stage) exhibited prognostic significance. RNF223 showed independent significance as an unfavorable prognostic marker and was chosen for subsequent analysis. Next, the function of RNF223 in the pancreatic cancer cell lines ASPC-1 and PANC-1 was investigated, and RNF223 silencing promoted pancreatic cancer growth and migration. To explore the potential targets and pathways of RNF223 in pancreatic cancer, quantitative proteomics was applied to analyze differentially expressed proteins, and metabolism-related pathways were primarily enriched. Finally, the reason for the elevated expression of RNF223 was analyzed, and KLF4 was shown to contribute to the increased expression of RNF233. In conclusion, this study comprehensively analyzed the clinical significance of E3 ligases. Functional assays revealed that RNF223 promotes cancer by regulating cell metabolism. Finally, the elevated expression of RNF223 was attributed to KLF4-mediated transcriptional activation. This study broadens our knowledge regarding E3 ubiquitin ligases and signal transduction and provides novel markers and therapeutic targets in pancreatic cancer.

Sleeping Beauty Transposon Mutagenesis Identifies Genes Driving the Initiation and Metastasis of Uterine Leiomyosarcoma

Uterine leiomyosarcoma (ULMS) is a malignancy, which arises from the uterine smooth muscle. Because of its rarity, aggressive nature, and extremely poor prognosis, the molecular mechanisms driving ULMS remain elusive. To identify candidate cancer genes (CCG) driving ULMS, we conducted an in vivo Sleeping Beauty (SB) transposon mutagenesis screen in uterine myometrium-specific, PTEN knockout, KRAS mutant (PTEN KO/KRAS) mice. ULMS quickly developed in SB PTEN KO/KRAS mice, but not in PTEN KO/KRAS mice, demonstrating the critical importance of SB mutagenesis for driving ULMS in this model. Subsequent sequencing of SB insertion sites in these tumors identified 19 ULMS CCGs that were significantly enriched in known cancer genes. Among them, Zfp217 and Sfmbt2 functioned at early stages of tumor initiation and appeared to be oncogenes. Expression of ZNF217, the human homolog of ZFP217, was shown to be elevated in human ULMS compared with paired normal uterine smooth muscle, where it negatively correlated with patient prognosis. Inhibition of ZNF217 suppressed, whereas overexpression induced, proliferation, survival, migration, and stemness of human ULMS. In a second ex vivo ULMS SB metastasis screen, three CCGs were identified that may drive ULMS metastasis to the lung. One of these CCGs, Nrd1 (NRDC in humans), showed stronger expression in human metastatic tumors compared with primary ULMS and negatively associated with patient survival. NRDC knockdown impaired migration and adhesion without affecting cell proliferation, whereas overexpression had the opposite effect. Together, these results reveal novel mechanism driving ULMS tumorigenesis and metastasis and identify ZNF217 and NRDC as potential targets for ULMS therapy. SIGNIFICANCE: An in vivo Sleeping Beauty transposon mutagenesis screen identifies candidate cancer genes that drive initiation and progression of uterine leiomyosarcoma and may serve as therapeutic targets.

The immune microenvironment in EGFR- and ERBB2-mutated lung adenocarcinoma

Background

Targeted therapies have improved survival and quality of life for patients with non-small-cell lung cancer with actionable driver mutations. However, epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 gene (HER2, also known as ERBB2) exon 20 insertions (Ex20mut) are characterized by a poor response to currently approved tyrosine kinase inhibitors and immunotherapies. The underlying immune biology is not well understood.

Materials and methods

We carried out messenger RNA expression profiling of lung adenocarcinomas (ADCs) with ERBB2 (n = 19) and EGFR exon 20-insertion mutations (n = 13) and compared these to tumors with classical EGFR mutations (n = 40, affecting EGFR exons 18, 19 or 21) and EGFR/ERBB2 mutation-negative lung ADC (EGFR/ERBB2wt, n = 26) focusing on immunologically relevant transcripts. Tumor-infiltrating immune cells were estimated from gene expression profiles.

Results

Cytotoxic cells were significantly lower in EGFR-mutated tumors regardless of the affected exon, while Th1 cells were significantly lower in EGFR-Ex20mut compared to EGFR/ERBB2wt tumors. We assessed the differentially expressed genes of ERBB2-Ex20mut and EGFR-Ex20mut tumors compared to EGFR-Ex18/19/21mut and EGFR/ERBB2wt tumors. Of these, the genes GUSB, HDAC11, IFNGR2, PUM1, RASGRF1 and RBL2 were up-regulated, while a lower expression of CBLC, GBP1, GBP2, GBP4 and MYC was observed in all three comparison groups. The omnibus test revealed 185 significantly (FDR = 5%) differentially expressed genes and we found these four most significant gene expression changes in the study cohort: VHL and JAK1 were overexpressed in ERBB2-Ex20mut and EGFR-Ex20mut tumors compared to both EGFR-Ex18/19/21mut and EGFR/ERBB2wt tumors. RIPK1 and STK11IP showed the highest expression in ERBB2-Ex20mut tumors.

Conclusions

Targeted gene expression profiling is a promising tool to read out the characteristics of the tumor microenvironment from routine diagnostic lung cancer biopsies. Significant immune reactivity and specific immunosuppressive characteristics in ERBB2-Ex20mut and EGFR-Ex20mut lung ADC with at least some degree of immune infiltration support further clinical evaluation of immune-modulators as partners of immune checkpoint inhibitors in such tumors.

•

Gene expression profiling to characterize the tumor microenvironment is feasible using diagnostic lung cancer biopsies.

•

EGFR exon 20-mutated tumors show a higher expression of VHL and an immunologic ‘colder’ phenotype than EGFR/ERBB2wt tumors.

•

ERBB2 exon 20-mutated tumors show an overexpression of RIPK1 and STK11IP and a reduction of cytotoxic natural killer cells.

•

Drugs targeting these alterations are potential partners of checkpoint blockade in exon 20-mutated non-small-cell lung cancer.

The Ubiquitin System: An Emerging Therapeutic Target for Lung Cancer

The ubiquitin system, present in all eukaryotes, contributes to regulating multiple types of cellular protein processes such as cell signaling, cell cycle, and receptor trafficking, and it affects the immune response. In most types of cancer, unusual events in ubiquitin-mediated signaling pathway modulation can lead to a variety of clinical outcomes, including tumor formation and metastasis. Similarly, ubiquitination acts as a core component, which contributes to the alteration of cell signaling activity, dictating biosignal turnover and protein fates. As lung cancer acquires the most commonly mutated proteins, changes in the ubiquitination of the proteins contribute to the development of lung cancer. Various inhibitors targeting the ubiquitin system have been developed for clinical applications in lung cancer treatment. In this review, we summarize the current research advances in therapeutics for lung cancer by targeting the ubiquitin system.

[6]-Paradol suppresses proliferation and metastases of pancreatic cancer by decreasing EGFR and inactivating PI3K/AKT signaling

Background

The underlying mechanism behind the tumorigenesis and progression of pancreatic cancer is not clear, and treatment failure is generally caused by early metastasis, recurrence, drug resistance and vascular invasion. Exploring novel therapeutic regimens is necessary to overcome drug resistance and improve patients outcomes.

Methods

Functional assays were performed to investigate the role of [6]-Paradol (6-P) in proliferation and metastasis of pancreatic cancer in vitro and in vivo. The interaction between EGFR and 6-P was tested by KEGG enrichment analysis and molecular docking analysis. qRT-PCR was performed to detect the mRNA expression of EGFR in 6-P treated groups. Involvement of the PI3K/AKT pathway was measured by western blotting.

Results

6-P significantly suppressed pancreatic cancer cell proliferation and metastasis. KEGG enrichment analysis and molecular docking analysis suggested that there existed certain interaction between EGFR and 6-P. In addition, 6-P obviously decreased EGFR protein expression level but did not change the mRNA expression level of EGFR. 6-P could induce degradation of EGFR through decreasing the protein stability of EGFR and enhancing the ubiquitin-mediated proteasome-dependent degradation, 6-P-mediated EGFR degradation led to inactivation of PI3K/AKT signaling pathway. However, ectopic expression of EGFR protein resulted in resistance to 6-P-mediated inactivity of PI3K/AKT signaling and inhibition of malignant phenotype of pancreatic cancer. Inversely, erlotinib could enhance the 6-P-mediated anticancer activity.

Conclusion

Our data indicated that 6-P/EGFR/PI3K/AKT signaling axis might become one of the potential therapies for the treatment of pancreatic cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02118-0.

Risk of lung cancer due to external environmental factor and epidemiological data analysis

Lung cancer is a cancer with the fastest growth in the incidence and mortality all over the world, which is an extremely serious threat to human's life and health. Evidences reveal that external environmental factors are the key drivers of lung cancer, such as smoking, radiation exposure and so on. Therefore, it is urgent to explain the mechanism of lung cancer risk due to external environmental factors experimentally and theoretically. However, it is still an open issue regarding how external environment factors affect lung cancer risk. In this paper, we summarize the main mathematical models involved the gene mutations for cancers, and review the application of the models to analyze the mechanism of lung cancer and the risk of lung cancer due to external environmental exposure. In addition, we apply the model described and the epidemiological data to analyze the influence of external environmental factors on lung cancer risk. The result indicates that radiation can cause significantly an increase in the mutation rate of cells, in particular the mutation in stability gene that leads to genomic instability. These studies not only can offer insights into the relationship between external environmental factors and human lung cancer risk, but also can provide theoretical guidance for the prevention and control of lung cancer.

Beyond K48 and K63: non-canonical protein ubiquitination

Protein ubiquitination has become one of the most extensively studied post-translational modifications. Originally discovered as a critical element in highly regulated proteolysis, ubiquitination is now regarded as essential for many other cellular processes. This results from the unique features of ubiquitin (Ub) and its ability to form various homo- and heterotypic linkage types involving one of the seven different lysine residues or the free amino group located at its N-terminus. While K48- and K63-linked chains are broadly covered in the literature, the other types of chains assembled through K6, K11, K27, K29, and K33 residues deserve equal attention in the light of the latest discoveries. Here, we provide a concise summary of recent advances in the field of these poorly understood Ub linkages and their possible roles in vivo.

A novel risk score system of immune genes associated with prognosis in endometrial cancer

Background

Endometrial cancer was the commonest gynecological malignancy in developed countries. Despite striking advances in multimodality management, however, for patients in advanced stage, targeted therapy still remained a challenge. Our study aimed to investigate new biomarkers for endometrial cancer and establish a novel risk score system of immune genes in endometrial cancer.

Methods

The clinicopathological characteristics and gene expression data were downloaded from The Cancer Genome Atlas (TCGA) database. Differentially expressed genes (DEGs) of immune genes between tumors and normal tissues were identified. Protein–protein interaction (PPI) network of immune genes and transcriptional factors was integrated and visualized in Cytoscape. Univariate and multivariate analysis were employed for key genes to establish a new risk score system. Receiver operating characteristic (ROC) curve and survival analysis were performed to investigate the prognostic value of the model. Association between clinical characteristics and the model was analyzed by logistic regression. For validation, we identified 34 patients with endometrial cancer from Fudan University Shanghai Cancer Center (FUSCC). We detected 14-genes mRNA expression and calculated the risk scores of each patients and we performed survival analysis between the high-risk group and the low-risk group.

Results

23 normal tissues and 552 tumor tissues were obtained from TCGA database. 410 immune-related DEGs was identified by difference analysis and correlation analysis. KEGG and GO analysis revealed these DEGs were enriched in cell adhesion, chemotaxis, MAPK pathways and PI3K-Akt signaling pathway, which might regulate tumor progression and migration. All genes were screened for risk model construction and 14 hub immune-related genes (HTR3E, CBLC, TNF, PSMC4, TRAV30, PDIA3, FGF8, PDGFRA, ESRRA, SBDS, CRHR1, LTA, NR2F1, TNFRSF18) were prognostic in endometrial cancer. The area under the curve (AUC) was 0.787 and the high-risk group estimated by the model possessed worse outcome (P < 0.001). Multivariate analysis suggested that the model was indeed an independent prognostic factor (high-risk vs. low-risk, HR = 1.14, P < 0.001). Meanwhile, the high-risk group was prone to have higher grade (P = 0.002) and advanced clinical stage (P = 0.018). In FUSCC validation set, the high-risk group had worse survival than the low-risk group (P < 0.001).

Conclusions

In conclusion, the novel risk model of immune genes had some merits in predicting the prognosis of endometrial cancer and had strong correlation with clinical outcomes. Furthermore, it might provide new biomarkers for targeted therapy in endometrial cancer.

RNF115-mediated ubiquitination of p53 regulates lung adenocarcinoma proliferation

Lung adenocarcinoma (LAC) represents approximately 40% of all lung cancer cases and is the leading cause of cancer-associated mortality worldwide. Although combined treatment, including radiotherapy, chemotherapy, surgical treatment and immunotherapy, has been used in treating LAC, the five-year survival rate of patients with LAC has not significantly improved. Therefore, it is vital for cancer research to investigate novel prognostic markers and new targets for molecular targeted therapy in LAC. TP53 is an important tumor suppressor gene and is frequently inactivated in lung cancer, thus upregulation or activation of p53 may be a novel targeted therapy for LAC. The present study found that RNF115 mediates ubiquitination of p53 and predicts poor prognosis of patients with LAC. Functionally, it was demonstrated that disruption of RNF115 significantly inhibited cell viability in vitro through inducing G1 phase arrest of LAC cells, which reduced tumor growth in an xenograft model. Taken together, these results suggest that RNF115 could be a novel prognostic biomarker and the RNF115-p53 axis may be a potential target for LAC therapy.

UBE2I promotes metastasis and correlates with poor prognosis in hepatocellular carcinoma

Background

A comprehensive investigation of ubiquitin-conjugating enzyme E2I (UBE2I) in cancer is still insufficiency. In this study, we aimed to analyze its role and mechanism in cancer by combination of bioinformatic analysis and experimental validation.

Methods

The expression profile of UBE2I in human cancers were obtained using GEPIA. Kaplan–Meier plotter was used to assess the prognostic values of UBE2I in diverse types of cancer. ROC curve analysis was employed to determine the diagnostic role of UBE2I in hepatocellular carcinoma (HCC). The expression differences based on various clinicopathological features was evaluated by UALCAN. Wound healing assay and transwell invasion assay were used to detected the effects of UBE2I on migration and invasion of HCC cells, respectively. The miRNA regulatory mechanism of UBE2I was successively investigated by binding prediction, expression analysis, survival analysis and dual-luciferase reporter assay. The correlation of UBE2I mRNA expression and UBE2I promoter methylation level was assessed using cBioPortal. STRING was finally introduced to perform co-expression analysis and enrichment analysis for UBE2I.

Results

UBE2I was upregulated in HCC, correlated with cancer progression and poor prognosis of HCC. We also found a significant diagnostic value of UBE2I in HCC. Functional experiments revealed that knockdown of UBE2I significantly inhibited HCC migration and invasion. Further research on mechanism suggested that loss of inhibition of hsa-miR-195-3p and dysregulation of UBE2I promoter methylation might account for UBE2I overexpression in HCC. Analysis of UBE2I-invovled regulatory network identified six key genes (NSMCE2, SAE1, UBA2, RANGAP1, SUMO1 and SUMO2) whose expression linked to poor prognosis in HCC.

Conclusions

In conclusion, UBE2I may be a promising therapeutic target and biomarker in cancer, especially HCC.

Identification of High-Frequency Methylation Sites in RNF180 Promoter Region Affecting Expression and Their Relationship with Prognosis of Gastric Cancer

Background

Ring finger protein 180 (RNF180) is a tumor suppressor gene regulated by promoter methylation. We previously demonstrated that the RNF180 promoter methylation could be a risk factor for gastric cancer (GC); and eight high-frequency hypermethylated CpG sites were associated with GC. However, it is not clear whether these key sites can affect gene expression and involve in prognosis. The aim of this study was to investigate the effects of above CpG sites on the gene expression and prognosis of GC.

Patients and Methods

A total of 164 GC tissues were enrolled and followed up. Tissue samples were used for DNA and RNA isolation. Methylation status of RNF180 was detected using bisulfite sequencing PCR (BSP). Expression levels of RNF180 were detected using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). JASPAR and PROMO databases were used to predict the transcription factors (TFs) binding to the CpG site.

Results

The methylation in RNF180 promoter region increased and mRNA expression decreased in GC tissue. Correlation analysis revealed that the average methylation rate (AMR) and four CpG sites methylation rate were negatively related to RNF180 expression, including M3(−165)(Chr5:64165942), M5(−148)(Chr5:64,165,959), M7(−133)(Chr5:64,165,974) and M8(−130)(Chr5:64,165,977). Furthermore, the methylation rate of M5(−148)(Chr5:64,165,959) and M27(−26)(Chr5:64,166,081) above 0.3 indicated poor prognosis (P_M5 = 0.008, P_M27 = 0.003, HR_M5(−148) = 2.000 (1.201,3.332), HR_M27(−26)=2.389 (1.336,4.271)), which could be independent factors of prognosis.

Conclusion

By focusing on the methylation sites in the RNF180 promoter region, we identified two high-frequency methylation sites, M5(−148)(Chr5:64,165,959) and M27(−26)(Chr5:64,166,081), which could affect gene expression and predict the prognosis of GC. In the future, the possible molecular mechanism involved needs to be further studied.

High Expression of Krüppel-like Factor 7 Indicates Unfavorable Clinical Outcomes in Patients with Lung Adenocarcinoma

BACKGROUND

Krüppel-like factor 7 (KLF7), which belongs to the KLF family of zinc finger transcription factors, plays a critical role in regulating gene expression. It was reported that KLF7 overexpression was closely related to the progression of gastric cancer. However, the role of KLF7 in lung adenocarcinoma (LAC) has not been elucidated. The aim of our study is to investigate the expression pattern of KLF7 and explore whether the KLF7 expression is correlated with unfavorable clinical outcome of patients with LAC.

MATERIALS AND METHODS

The protein and mRNA levels of KLF7 were examined in LAC tissues by using immunohistochemistry staining and quantitative reverse transcription polymerase chain reaction, respectively. The prognostic role of KLF7 in patients with LAC was assessed using univariate and multivariate analyses. Clinical outcomes were evaluated by Kaplan-Meier analysis and logrank test. The effects of KLF7 on lung cancer cells were investigated through cellular experiments.

RESULTS

KLF7 expression was elevated in LAC tissues compared with adjacent normal tissues. High protein level of KLF7 was correlated with larger tumor size, positive lymph node metastasis, and advanced TNM stage. Moreover, patients with LAC with higher expression level of KLF7 had poorer overall survival, and KLF7 was identified as an unfavorable independent prognosis factor. Knockdown of KLF7 can suppress the proliferation and invasion abilities of cancer cells.

CONCLUSIONS

Our studies revealed that high KLF7 expression level was significantly associated with the poorer clinical outcomes of patients with LAC, indicating the potential role of KLF7 as a novel prognostic biomarker and therapeutic target.

Emerging Roles and Research Tools of Atypical Ubiquitination

Ubiquitination is a posttranslational modification characterized by the covalent attachment of ubiquitin molecules to protein substrates. The ubiquitination modification process is reversible, dynamic, and involved in the regulation of various biological processes, such as autophagy, inflammatory responses, and DNA damage responses. The forms of ubiquitin modification are very diverse, incorporating either a single ubiquitin molecule or a complicated ubiquitin polymer, and different types of ubiquitination usually elicit corresponding cellular responses. The development of research tools and strategies has afforded more detailed insight into atypical ubiquitin signaling pathways that were previously poorly understood. Here, an update on the understanding of atypical ubiquitin chain signaling pathways is provided and the recent development of representative research tools for ubiquitin systems is discussed. In addition, the future challenges in ubiquitin research are reflected on and summarized.

The ubiquitin system: orchestrating cellular signals in non-small-cell lung cancer

The ubiquitin system, known as a common feature in eukaryotes, participates in multiple cellular processes, such as signal transduction, cell-cycle progression, receptor trafficking and endocytosis, and even the immune response. In lung cancer, evidence has revealed that aberrant events in ubiquitin-mediated processes can cause a variety of pathological outcomes including tumorigenesis and metastasis. Likewise, ubiquitination on the core components contributing to the activity of cell signaling controls bio-signal turnover and cell final destination. Given this, inhibitors targeting the ubiquitin system have been developed for lung cancer therapies and have shown great prospects for clinical application. However, the exact biological effects and physiological role of the drugs used in lung cancer therapies are still not clearly elucidated, which might seriously impede the progress of treatment. In this work, we summarize current research advances in cell signal regulation processes mediated through the ubiquitin system during the development of lung cancer, with the hope of improving the therapeutic effects by means of aiming at efficient targets.

Cell signaling and cancer: a mechanistic insight into drug resistance

Drug resistance is a major setback for advanced therapeutics in multiple cancers. The increasing prevalence of this resistance is a growing concern and bitter headache for the researchers since a decade. Hence, it is essential to revalidate the existing strategies available for cancer treatment and to look after a novel therapeutic approach for target based killing of cancer cells at the genetic level. This review outlines the different mechanisms enabling resistance including drug efflux, drug target alternation, alternative splicing, the release of the extracellular vesicle, tumor heterogeneity, epithelial-mesenchymal transition, tumor microenvironment, the secondary mutation in the receptor, epigenetic alternation, heterodimerization of receptors, amplification of target and amplification of components rather than the target. Furthermore, existing evidence and the role of various signaling pathways like EGFR, Ras, PI3K/Akt, Wnt, Notch, TGF-β, Integrin-ECM signaling in drug resistance are explained. Lastly, the prevention of this resistance by a contemporary therapeutic strategy, i.e., a combination of specific signaling pathway inhibitors and the cocktail of a cancer drug is summarized showing the new treatment strategies.