LINC01021 Attenuates Expression and Affects Alternative Splicing of a Subset of p53-Regulated Genes.

BACKGROUND: Loss of the p53-inducible LINC01021 in p53-proficient CRC cell lines results in increased sensitivity to DNA-damaging chemotherapeutics. Here, we comprehensively analyze how LINC01021 affects the p53-induced transcriptional program. METHODS: Using a CRISPR/Cas9-approach, we deleted the p53 binding site in the LINC01021 promoter of SW480 colorectal cancer cells and subjected them to RNA-Seq analysis after the activation of ectopic p53. RNA affinity purification followed by mass spectrometry was used to identify proteins associated with LINC01021. RESULTS: Loss of the p53-inducibility of LINC01021 resulted in an ~1.8-fold increase in the number of significantly regulated mRNAs compared to LINC01021 wild-type cells after ectopic activation of p53. A subset of direct p53 target genes, such as NOXA and FAS, displayed significantly stronger induction when the p53-inducibility of LINC01021 was abrogated. Loss of the p53-inducibility of LINC01021 resulted in alternative splicing of a small number of mRNAs, such as ARHGAP12, HSF2, and LYN. Several RNA binding proteins involved in pre-mRNA splicing were identified as interaction partners of LINC01021 by mass spectrometry. CONCLUSIONS: Our results suggest that LINC01021 may restrict the extent and strength of p53-mediated transcriptional changes via context-dependent regulation of the expression and splicing of a subset of p53-regulated genes.

A comparative analysis of transcriptomics of newly diagnosed multiple myeloma: exploring drug repurposing.

Multiple myeloma (MM) is an incurable malignant plasma cell disorder characterized by the infiltration of clonal plasma cells in the bone marrow compartment. Gene Expression Profiling (GEP) has emerged as a powerful investigation tool in modern myeloma research enabling the dissection of the molecular background of MM and allowing the identification of gene products that could potentially serve as targets for therapeutic intervention. In this study we investigated shared transcriptomic abnormalities across newly diagnosed multiple myeloma (NDMM) patient cohorts. In total, publicly available transcriptomic data of 7 studies from CD138+ cells from 281 NDMM patients and 44 healthy individuals were integrated and analyzed. Overall, we identified 28 genes that were consistently differentially expressed (DE) between NDMM patients and healthy donors (HD) across various studies. Of those, 9 genes were over/under-expressed in more than 75% of NDMM patients. In addition, we identified 4 genes (MT1F, PURPL, LINC01239 and LINC01480) that were not previously considered to participate in MM pathogenesis. Meanwhile, by mining three drug databases (ChEMBL, IUPHAR/BPS and DrugBank) we identified 31 FDA-approved and 144 experimental drugs that target 8 of these 28 over/under-expressed MM genes. Taken together, our study offers new insights in MM pathogenesis and importantly, it reveals potential new treatment options that need to be further investigated in future studies.

PURPL and NEAT1 Long Non-Coding RNAs Are Modulated in Vascular Smooth Muscle Cell Replicative Senescence.

Cellular senescence is characterized by proliferation and migration exhaustion, senescence-associated secretory phenotype (SASP), and oxidative stress. Senescent vascular smooth muscle cells (VSMCs) contribute to cardiovascular diseases and atherosclerotic plaque instability. Since there are no unanimously agreed senescence markers in human VSMCs, to improve our knowledge, we looked for new possible senescence markers. To this end, we first established and characterized a model of replicative senescence (RS) in human aortic VSMCs. Old cells displayed several established senescence-associated markers. They stained positive for the senescence-associated ß-galactosidase, showed a deranged proliferation rate, a dramatically reduced expression of PCNA, an altered migratory activity, increased levels of TP53 and cell-cycle inhibitors p21/p16, and accumulated in the G1 phase. Old cells showed an altered cellular and nuclear morphology, downregulation of the expression of LMNB1 and HMGB1, and increased expression of SASP molecules (IL1ß, IL6, IL8, and MMP3). In these senescent VSMCs, among a set of 12 manually selected long non-coding RNAs (lncRNAs), we detected significant upregulation of PURPL and NEAT1. We observed also, for the first time, increased levels of RRAD mRNA. The detection of modulated levels of RRAD, PURPL, and NEAT1 during VSMC senescence could be helpful for future studies on potential anti-aging factors.

Abnormal expressions of PURPL, miR-363-3p and ADAM10 predicted poor prognosis for patients with ovarian serous cystadenocarcinoma.

Objective: This study aimed to elucidate the prognostic implications of deviant expressions of long non-coding RNA (lncRNA) p53 upregulated regulator of p53 levels (PURPL), microRNA-363-3p (miR-363-3p), and ADAM metallopeptidase domain 10 (ADAM10) in patients diagnosed with ovarian serous cystadenocarcinoma (OSC). Methods: To predict and refine the targeted miRNAs and downstream target genes for PURPL, we utilized open medical databases. Through the employment of real-time RT-PCR, we conducted tissue analysis to discern the expressions of PURPL, miR-363-3p, and ADAM10 in both OSC and control tissues. The pathological correlations in the clinic and the prognostic implications of deviant expressions of PURPL, miR-363-3p, and ADAM10 in OSC patients were analyzed independently. Results: Database inquiries revealed that PURPL might target miR-363-3p, and in turn, miR-363-3p could target ADAM10. Differential expression of PURPL, miR-363-3p, and ADAM10 was observed between OSC and paired tissues. The premature version of miR-363-3p, miR-363, correlated with overall survival (OS), while ADAM10 corresponded with progression-free survival (PFS) in ovarian cancer patients. Tissue detection displayed significantly elevated expressions of PURPL and ADAM10, and conspicuously diminished expressions of miR-363-3p in OSC tissues compared to the control tissues (P<0.05). A negative correlation was observed between the expressions of PURPL and miR-363-3p, and miR-363-3p and ADAM10, while a positive correlation was found between PURPL and ADAM10 in different ovarian tissues (P<0.05). In OSC tissues, upregulation of PURPL was associated with an advanced clinical stage, TP53 mutation, and lymph node metastasis (P<0.05), downregulation of miR-363-3p was associated with a more advanced clinical stage and lymph node metastasis (P<0.05), and overexpression of ADAM10 correlated with a more advanced FIGO stage. High expressions of PURPL and ADAM10, and low expression of miR-363-3p, were linked with poor PFS and OS in OSC patients, respectively (P<0.05). In addition, OSC patients with elevated PURPL and reduced miR-363-3p, patients with elevated PURPL and ADAM10, and patients with reduced miR-363-3p and elevated ADAM10 also demonstrated worse PFS and OS, respectively (P<0.05). Conclusions: The anomalous expressions of PURPL, miR-363-3p, and ADAM10 might contribute to the pathogenesis of OSC via up-down stream regulation, and these abnormal expressions could serve as potential prognostic indicators for OSC patients.

Long non-coding RNA p53 upregulated regulator of p53 levels (PURPL) promotes the development of gastric cancer.

Gastric cancer (GC), one of the most prevalent malignancies across the world, has an increasing incidence rate. Long non-coding RNA (lncRNA) PURPL (also referred to as LINC01021) has been demonstrated to influence malignant GC behaviors and partake in other cancers. Notwithstanding, reports pertaining to the underlying mechanism of PURPL in GC haven't been rarely seen. Presently, in-vivo and ex-vivo experiments were implemented to examine the PURPL-miR-137-ZBTB7A-PI3K-AKT-NF-κB regulatory axis in GC. Our statistics revealed that PURPL presented a high expression in GC tissues and cell lines. PURPL overexpression remarkably exacerbated colony formation, migration, and invasion and repressed apoptosis in GC cells (AGS and MNK-45). In-vivo experiments also corroborated that cell growth was boosted by PURPL up-regulation. Mechanistic investigations verified that PURPL interacted with miR-137 and lowered its profile in GC cell lines. miR-137 overexpression or ZBTB7A knockdown upended the oncogenic function mediated by PURPL. PURPL initiated the PI3K/AKT/NF-κB pathway. PI3K and NF-κB inhibition impaired the promoting impact on GC cells elicited by PURPL overexpression and contributed to PURPL down-regulation. These findings disclosed that PURPL serves as an oncogene in the context of GC via miR-137-ZBTB7A-PI3K-AKT-NF-κB axis modulation.

Context-Dependent Function of Long Noncoding RNA PURPL in Transcriptome Regulation during p53 Activation.

PURPL is a p53-induced lncRNA that suppresses basal p53 levels. Here, we investigated PURPL upon p53 activation in liver cancer cells, where it is expressed at significantly higher levels than other cell types. Using isoform sequencing, we discovered novel PURPL transcripts that have a retained intron and/or previously unannotated exons. To determine PURPL function upon p53 activation, we performed transcriptome sequencing (RNA-Seq) after depleting PURPL using CRISPR interference (CRISPRi), followed by Nutlin treatment to induce p53. Strikingly, although loss of PURPL in untreated cells altered the expression of only 7 genes, loss of PURPL resulted in altered expression of ~800 genes upon p53 activation, revealing a context-dependent function of PURPL. Pathway analysis suggested that PURPL is important for fine-tuning the expression of specific genes required for mitosis. Consistent with these results, we observed a significant decrease in the percentage of mitotic cells upon PURPL depletion. Collectively, these data identify novel transcripts from the PURPL locus and suggest that PURPL delicately moderates the expression of mitotic genes in the context of p53 activation to control cell cycle arrest.

Disregulations of PURPL and MiR-338-3p Could Serve As Prognosis Biomarkers for Epithelial Ovarian Cancer.

Objective: The present study aimed to explore the expressions of long noncoding RNA (lncRNA) p53 upregulated regulator of p53 levels (PURPL) in different ovarian tissues, and to evaluate the significance of disregulations of PURPL and microRNA-338-3p (miR-338-3p) in epithelial ovarian cancer (EOC). Methods: The expressions of PURPL in ovarian cancer, the relations between PURPL and the prognosis of ovarian cancer, and the relation between PURPL and miR-338-3p were queried in multiple biomedical databases. Real-time PCR was performed to detect the expressions of PURPL in different ovarian tissues. Logistic regression analysis was used to analyze the risk factors of recurrence and death. Kaplan-Meier analysis was implemented to evaluate the relations between PURPL and miR-338-3p expressions and the survival of ovarian cancer. Results: PURPL could target miR-338-3p, PURPL were upregulated in ovarian cancer tissues, upregulation of PURPL in ovarian cancer was negatively related with the recurrence free survival (RFS) and overall survival (OS), which were indicated by biomedical databases query. Our data showed upregulations of PURPL were noted in ovarian cancer tissues. Higher expressions of PURPL were associated with more advanced FIGO stage and developed lymph node metastasis in epithelial ovarian cancer. Upregulation of PURPL was related with the recurrence (P=0.002, OR=21.482, 95%CI: 3.457~94.251) and death (P=0.004, OR=35.643, 95%CI: 2.453~84.359) of ovarian cancer patient. PURPL expressions were negatively correlated to miR-338-3p expressions in different ovarian tissues (r = -0.968, P<0.0001). Poor RFS (χ2=19.410, P=0.0002) and OS (χ2=17.600, P=0.0005) were found in patients with high level PURPL and low level miR-338-3p expressions. Conclusions: Upregulation of PURPL and downregulation of miR-338-3p were related with the poor RFS and OS of ovarian cancer, which indicated disregulations of PURPL and miR-338-3p could serve as prognosis biomarkers for epithelial ovarian cancer.

Overexpression of PURPL and downregulation of NONHSAT062994 as potential biomarkers in gastric cancer.

AIMS: Long non-coding RNAs (LncRNAs) play central roles in the formation and development of gastric cancer (GC). The aim of this study was to evaluate the expression of PURPL and NONHSAT062994 and the relationship between their expressions with clinical characteristics in GC. MAIN METHODS: PURPL and NONHSAT062994 LncRNAs and p53 gene expression levels were analyzed both in 50 pairs of cancerous and adjacent noncancerous tissue samples in GC patients using qRT-PCR and in four sets of data obtained from Gene Expression Omnibus (GEO) database. Chi-square (χ2) test was used to determine the relationship between PURPL, NONHSAT062994 RNA levels and the clinicopathological characteristics of GC. Receiver operating characteristic (ROC) curves were drawn to represent sensitivity and specificity of PURPL and NONHSAT062994 expression as markers of GC. KEY FINDINGS: Expression of PURPL was significantly upregulated in 50 GC samples as well as in GC tissues from GSE13911 and GSE27342 datasets. Our results demonstrated that PURPL RNA level in GC was significantly related to tumor size and histopathological grade. p53 expression at both protein and mRNA levels were significantly decreased in GC tissues compared to adjacent control samples. NONHSAT062994 expression was downregulated in 50-pair GC and GC tissues from GSE13915 dataset. However, NONHSAT062994 showed no consistently differential expression in GSE2637dataset. NONHSAT062994 was significantly associated with histological grade and tumor size. SIGNIFICANCE: Overall, these results suggest that PURPL and NONHSAT062994 may play critical roles in the progression of GC and therefore might be considered as candidate tumor markers for therapeutic goals.

Long Noncoding RNA PURPL Suppresses Basal p53 Levels and Promotes Tumorigenicity in Colorectal Cancer.

Basal p53 levels are tightly suppressed under normal conditions. Disrupting this regulation results in elevated p53 levels to induce cell cycle arrest, apoptosis, and tumor suppression. Here, we report the suppression of basal p53 levels by a nuclear, p53-regulated long noncoding RNA that we termed PURPL (p53 upregulated regulator of p53 levels). Targeted depletion of PURPL in colorectal cancer cells results in elevated basal p53 levels and induces growth defects in cell culture and in mouse xenografts. PURPL associates with MYBBP1A, a protein that binds to and stabilizes p53, and inhibits the formation of the p53-MYBBP1A complex. In the absence of PURPL, MYBBP1A interacts with and stabilizes p53. Silencing MYBBP1A significantly rescues basal p53 levels and proliferation in PURPL-deficient cells, suggesting that MYBBP1A mediates the effect of PURPL in regulating p53. These results reveal a p53-PURPL auto-regulatory feedback loop and demonstrate a role for PURPL in maintaining basal p53 levels.