p14ARFPrevents Proliferation of Aneuploid Cells by Inducing p53-Dependent Apoptosis

CRISPR/Cas9-mediated knockout of the ubiquitin variant UbKEKS reveals a role in regulating nucleolar structures and composition

Ubiquitination is a post-translational modification responsible for one of the most complex multilayered communication and regulation systems in the cell. Over the past decades, new ubiquitin variants and ubiquitin-like proteins arose to further enrich this mechanism. Recently discovered ubiquitin variant UbKEKS can specifically target several proteins and yet, functional consequences of this new modification remain unknown. Depletion of UbKEKS induces accumulation of lamin A in the nucleoli, highlighting the need for deeper investigations about protein composition and functions regulation of this highly dynamic and membrane-less compartment. Using data-independent acquisition mass spectrometry and microscopy, we show that despite not impacting protein stability, UbKEKS is required to maintain a normal nucleolar organization. The absence of UbKEKS increases nucleoli's size and accentuate their circularity while disrupting dense fibrillar component and fibrillar centre structures. Moreover, depletion of UbKEKS leads to distinct changes in nucleolar composition. Lack of UbKEKS favours nucleolar sequestration of known apoptotic regulators such as IFI16 or p14ARF, resulting in an increase of apoptosis observed by flow cytometry and real-time monitoring. Overall, these results identify the first cellular functions of the UbKEKS variant and lay the foundation stone to establish UbKEKS as a new universal layer of regulation in the ubiquitination system.

The role of BMI1 in endometrial cancer and other cancers

Endometrial cancer (EC) is the third leading gynecological malignancy, and its treatment remains challenging. B cell-specific Moloney murine leukemia virus integration site-1 (BMI1) is one of the core members of the polycomb group (PcG) family, which plays a promoting role in the occurrence and development of various tumors. Notably, BMI1 has been found to be frequently upregulated in endometrial cancer (EC) and promote the occurrence of EC through promoting epithelial-mesenchymal transition (EMT) and AKT/PI3K pathways. This review summarizes the structure and upstream regulatory mechanisms of BMI1 and its role in EC. In addition, we focused on the role of BMI1 in chemoradiotherapy resistance and summarized the current drugs that target BMI1.

Losing DNA methylation at repetitive elements and breaking bad

Background

DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome.

Main body

Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually methylated to maintain a heterochromatic, repressed state. Notably, there is increasing evidence showing that repetitive elements (satellites, long interspersed nuclear elements (LINEs), Alus) are frequently hypomethylated in various of human pathologies, from cancer to psychiatric disorders. Repetitive sequences’ hypomethylation correlates with chromatin relaxation and unscheduled transcription. If these alterations are directly involved in human diseases aetiology and how, is still under investigation.

Conclusions

Hypomethylation of different families of repetitive sequences is recurrent in many different human diseases, suggesting that the methylation status of these elements can be involved in preservation of human health. This provides a promising point of view towards the research of therapeutic strategies focused on specifically tuning DNA methylation of DNA repeats.

Pyrazole[3,4-d]pyrimidine derivatives loaded into halloysite as potential CDK inhibitors

Uncontrolled cell proliferation is a hallmark of cancer as a result of rapid and deregulated progression through the cell cycle. The inhibition of cyclin-dependent kinases (CDKs) activities is a promising therapeutic strategy to block cell cycle of tumor cells. In this work we reported a new example of nanocomposites based on halloysite nanotubes (HNTs)/pyrazolo[3,4-d]pyrimidine derivatives (Si306 and Si113) as anticancer agents and CDK inhibitors. HNTs/Si306 and HNTs/Si113 nanocomposites were synthesized and characterized. The release kinetics were also investigated. Antitumoral activity was evaluated on three cancer cell lines (HeLa, MDA-MB-231 and HCT116) and the effects on cell cycle arrest in HCT116 cells were evaluated. Finally, molecular dynamics simulations were performed of the complexes between Si113 or Si306 and the active site of both CDK 1 and 2.

P14ARF: The Absence that Makes the Difference

P14^ARF is a tumor suppressor encoded by the CDKN2a locus that is frequently inactivated in human tumors. P14^ARF protein quenches oncogene stimuli by inhibiting cell cycle progression and inducing apoptosis. P14^ARF functions can be played through interactions with several proteins. However, the majority of its activities are notoriously mediated by the p53 protein. Interestingly, recent studies suggest a new role of p14^ARF in the maintenance of chromosome stability. Here, we deepened this new facet of p14^ARF which we believe is relevant to its tumor suppressive role in the cell. To this aim, we generated a monoclonal HCT116 cell line expressing the p14^ARF cDNA cloned in the piggyback vector and then induced aneuploidy by treating HCT116 cells with the CENP-E inhibitor GSK923295. P14^ARF ectopic re-expression restored the near-diploid phenotype of HCT116 cells, confirming that p14^ARF counteracts aneuploid cell generation/proliferation.

Investigating REPAIRv2 as a Tool to Edit CFTR mRNA with Premature Stop Codons

Cystic fibrosis (CF) is caused by mutations in the gene encoding the transmembrane conductance regulator (CFTR) protein. Some CF patients are compound heterozygous or homozygous for nonsense mutations in the CFTR gene. This implies the presence in the transcript of premature termination codons (PTCs) responsible for a truncated CFTR protein and a more severe form of the disease. Aminoglycoside and PTC124 derivatives have been used for the read-through of PTCs to restore the full-length CFTR protein. However, in a precision medicine framework, the CRISPR/dCas13b-based molecular tool “REPAIRv2” (RNA Editing for Programmable A to I Replacement, version 2) could be a good alternative to restore the full-length CFTR protein. This RNA editing approach is based on the targeting of the deaminase domain of the hADAR2 enzyme fused to the dCas13b protein to a specific adenosine to be edited to inosine in the mutant mRNA. Targeting specificity is allowed by a guide RNA (gRNA) complementarily to the target region and recognized by the dCas13b protein. Here, we used the REPAIRv2 platform to edit the UGA PTC to UGG in different cell types, namely IB3-1 cells, HeLa, and FRT cells engineered to express H2BGFP^opal and CFTR^W1282X, respectively.

DNA Replication Stress and Chromosomal Instability: Dangerous Liaisons

Chromosomal instability (CIN) is associated with many human diseases, including neurodevelopmental or neurodegenerative conditions, age-related disorders and cancer, and is a key driver for disease initiation and progression. A major source of structural chromosome instability (s-CIN) leading to structural chromosome aberrations is "replication stress", a condition in which stalled or slowly progressing replication forks interfere with timely and error-free completion of the S phase. On the other hand, mitotic errors that result in chromosome mis-segregation are the cause of numerical chromosome instability (n-CIN) and aneuploidy. In this review, we will discuss recent evidence showing that these two forms of chromosomal instability can be mechanistically interlinked. We first summarize how replication stress causes structural and numerical CIN, focusing on mechanisms such as mitotic rescue of replication stress (MRRS) and centriole disengagement, which prevent or contribute to specific types of structural chromosome aberrations and segregation errors. We describe the main outcomes of segregation errors and how micronucleation and aneuploidy can be the key stimuli promoting inflammation, senescence, or chromothripsis. At the end, we discuss how CIN can reduce cellular fitness and may behave as an anticancer barrier in noncancerous cells or precancerous lesions, whereas it fuels genomic instability in the context of cancer, and how our current knowledge may be exploited for developing cancer therapies.

Aneuploid IMR90 cells induced by depletion of pRB, DNMT1 and MAD2 show a common gene expression signature

Chromosome segregation defects lead to aneuploidy which is a major feature of solid tumors. How diploid cells face chromosome mis-segregation and how aneuploidy is tolerated in tumor cells are not completely defined yet. Thus, an important goal of cancer genetics is to identify gene networks that underlie aneuploidy and are involved in its tolerance. To this aim, we induced aneuploidy in IMR90 human primary cells by depleting pRB, DNMT1 and MAD2 and analyzed their gene expression profiles by microarray analysis. Bioinformatic analysis revealed a common gene expression profile of IMR90 cells that became aneuploid. Gene Set Enrichment Analysis (GSEA) also revealed gene-sets/pathways that are shared by aneuploid IMR90 cells that may be exploited for novel therapeutic approaches in cancer. Furthermore, Protein-Protein Interaction (PPI) network analysis identified TOP2A and KIF4A as hub genes that may be important for aneuploidy establishment.

Low-grade serous ovarian carcinoma: an evolution toward targeted therapy

Low-grade serous ovarian carcinoma and its high-grade serous ovarian carcinoma counterpart differ in their precursor lesions, molecular profile, natural history, and response to therapies. As such, low-grade serous ovarian carcinoma needs to be studied separately from high-grade serous ovarian carcinoma, despite challenges stemming from its rarity. A deeper understanding of the pathogenesis of low-grade serous ovarian carcinoma and the most common molecular defects and pathways involved in the carcinogenesis of the ovarian epithelium from normal to serous borderline ovarian tumors to low-grade serous ovarian carcinoma will help develop better therapies. By adopting targeted approaches there may be an opportunity to integrate novel therapies without the need for robust numbers in clinical trials. This manuscript will discuss low-grade serous ovarian carcinoma and focus on the arising treatments being developed with an improved understanding of the pathogenesis of this disease.

The expression profile of p14, p53 and p21 in tumour cells is associated with disease-specific survival and the outcome of postoperative chemotherapy treatment in muscle-invasive bladder cancer

PURPOSE

We investigated the effects of alterations in the biological markers p14, p53, p21, and p16 in relation to tumour cell proliferation, T-category, N- category, lymphovascular invasion, and the ability to predict prognosis in patients with muscle-invasive bladder cancer (MIBC) treated with cystectomy and, if applicable, chemotherapy.

MATERIALS AND METHODS

We prospectively studied patients with urinary bladder cancer pathological stage pT1 to pT4 treated with cystectomy, pelvic lymph node dissection and postoperative chemotherapy. Tissue microarrays from paraffin-embedded cystectomy tumour samples were examined for expression of immunostaining of p14, p53, p21, p16 and Ki-67 in relation to other clinical and pathological factors as well as cancer-specific survival.

RESULTS

The median age of the 110 patients was 70 years (range 51-87 years), and 85 (77%) were male. Pathological staging was pT1 to pT2 (organ-confined) in 28 (25%) patients and pT3 to pT4 (non-organ-confined) in 82 (75%) patients. Lymph node metastases were found in 47 patients (43%). P14 expression was more common in tumours with higher T-stages (P = 0.05). The expression of p14 in p53 negative tumours was associated with a significantly shorter survival time (P=0.003). Independently of p53 expression, p14 expression was associated with an impaired response to chemotherapy (P=0.001). The expression of p21 in p53 negative tumours was associated with significantly decrease levels of tumour cell proliferation detected as Ki-67 expression (P=0.03).

CONCLUSIONS

The simultaneous expression of the senescence markers involved in the p53-pathway shows a more relevant correlation to the pathological outcome of MIBC than each protein separately. P14 expression in tumours with non-altered (p53-) tumours is associated with poor prognosis. P14 expression is associated with impaired response to chemotherapy. P21 expression is related to decreased tumour cell proliferation.

Proliferation of aneuploid cells induced by CENP-E depletion is counteracted by the p14ARF tumor suppressor

The spindle assembly checkpoint (SAC) is a cellular surveillance mechanism that ensures the fidelity of chromosomes segregation. Reduced expression of some of its components weakens the SAC and induces chromosome instability and aneuploidy, which are both well-known hallmarks of cancer cells. Centromere protein-E (CENP-E) is a crucial component of the SAC and its function is to facilitate kinetochore microtubule attachment required to achieve and maintain chromosome alignment. The present study investigates the possible role of p14^ARF as a controller of aneuploid cells proliferation. We used RNA interference to induce aneuploidy by partial depletion of CENP-E in human primary fibroblasts (IMR90) and in near diploid tumor cells (HCT116). In contrast to IMR90 aneuploid cell number, which was drastically reduced and leaned towards the WT condition, HCT116 aneuploid cell numbers were slightly decreased at later time points. This euploidy restoration was accompanied by increased p14^ARF expression in IMR90 cells and followed ectopic p14^ARF re-expression in p14^ARF-null HCT116 cells. Collectively, our results suggest that hampering proliferation of aneuploid cells could be an additional role of the p14^ARF tumor suppressor.