Ribonucleotide reductase M2 subunit silencing suppresses tumorigenesis in pancreatic cancer via inactivation of PI3K/AKT/mTOR pathway

Study on the effects and mechanism of RRM2 on three gynecological malignancies

Cervical cancer, endometrial cancer, and ovarian cancer are the three most common gynecological malignancies. Their occurrence seriously affects women's health and life. Despite aggressive treatments, some patients still find it difficult to benefit from available therapies. Ribonucleic acid reductase subunit M2 (RRM2) is a limiting RNR enzyme involved in DNA synthesis and damage repair and plays a crucial role in many key cellular processes such as cell proliferation, migration, invasion, and senescence. Many studies have also shown that RRM2 also has a significant impact on tumor progression. However, the role of RRM2 in gynecological tumors has not been systematically studied. Our bioinformatics analysis of datasets related to cervical, endometrial, and ovarian cancers revealed that RRM2 is a significantly differentially expressed gene common to these cancers. We found that RRM2 was significantly overexpressed in cervical, endometrial, and ovarian cancer tissues and cells, exhibiting overall pro-oncogenic effects. RRM2 promoted cell proliferation, migration invasion, angiogenesis, and cell cycle in gynecological tumors while inhibiting apoptosis. The potential oncogenic effects of RRM2 in gynecologic tumor cell lines were further demonstrated using the RRM2 inhibitor Triapine (3-AP). These pro-tumorigenic effects may then be mediated through the involvement of RRM2 in the p53 and Akt/mTOR signaling pathways, altering the expression of p53 and Akt/mTOR. Thus, RRM2 is potentially a candidate gene for the unified diagnosis of cervical, endometrial, and ovarian cancers.

Indirect targeting of MYC and direct targeting in combination with chemotherapies are more effective than direct mono-targeting in triple negative breast cancer

MYC amplification is disproportionally elevated in triple-negative breast cancer (TNBC) compared to other subtypes of breast cancer. Indeed, MYC has long been considered an undruggable oncogene using conventional drug design strategies or small molecules. We hypothesized that targeting MYC using asymmetric siRNA (asiRNA) alone or in combination with chemotherapeutic agents or indirectly via BRD4 and RRM2, may curb its oncogenic behavior. We developed paclitaxel-, doxorubicin-, and cisplatin-resistant MDA-MB-231 cells to study MYC's role in upregulating DNA repair genes during drug resistance development. Our results showed that the knockdown of either MYC or RRM2 downregulated both RAD51 and PARP1 but increased γH2AX. The cytotoxic effect of RRM2 knockdown was significantly (p < 0.05) higher than that of direct MYC knockdown. The knockdown of BRD4 was more effective than the direct knockdown of MYC in downregulating MYC protein. The combined use of asiRNA-VP (Vinylphosphonate) with dacomitinib or talazoparib was synthetic lethal in TNBC cell lines. Compared to chemotherapy-sensitive cells, resistant cells showed overexpression of MYC, RRM2, RAD51, and PARP1 proteins upon chemotherapy treatment, but downregulated in cells treated with asiRNA-VP combination. We confirmed that MYC knockdown upregulated cFLIP, BCL2, STAT1, pSTAT1, STAT2, and cleaved saspase-3 in both TNBC and non-small cell lung cancer (NSCLC) cell lines. Finally, we recommend a combination treatment approach that synergizes with MYC inhibition rather than monotherapy or indirect targeting via upstream regulators such as the BRD4 and RRM2 genes or selective modulation at the protein level to suppress anti-apoptotic genes (cFLIP and BCL2) at the same time.

The SAGA acetyltransferase module is required for the maintenance of MAF and MYC oncogenic gene expression programs in multiple myeloma

Despite recent advances in therapeutic treatments, multiple myeloma (MM) remains an incurable malignancy. Epigenetic factors contribute to the initiation, progression, relapse, and clonal heterogeneity in MM, but our knowledge on epigenetic mechanisms underlying MM development is far from complete. The SAGA complex serves as a coactivator in transcription and catalyzes acetylation and deubiquitylation. Analyses of data sets in the Cancer Dependency Map Project revealed that many SAGA components are selective dependencies in MM. To define SAGA-specific functions, we focused on ADA2B, the only subunit in the lysine acetyltransferase (KAT) module that specifically functions in SAGA. Integration of RNA sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), and cleavage under targets and release using nuclease assay (CUT&RUN) results identified pathways directly regulated by ADA2B including MTORC1 signaling and oncogenic programs driven by MYC, E2F, and MM-specific MAF. We discovered that ADA2B is recruited to MAF and MYC gene targets, and that MAF shares a majority of its targets with MYC in MM cells. Furthermore, we found that the SANT domain of ADA2B is required for interaction with both GCN5 and PCAF acetyltransferases, incorporation into SAGA, and ADA2B protein stability. Our findings uncover previously unknown SAGA KAT module-dependent mechanisms controlling MM cell growth, revealing a vulnerability that might be exploited for future development of MM therapy.

The SAGA acetyltransferase module is required for the maintenance of MAF and MYC oncogenic gene expression programs in multiple myeloma

Despite recent advances in therapeutic treatments, multiple myeloma (MM) remains an incurable malignancy. Epigenetic factors contribute to the initiation, progression, relapse, and clonal heterogeneity in MM, but our knowledge on epigenetic mechanisms underlying MM development is far from complete. The SAGA complex serves as a coactivator in transcription and catalyzes acetylation and deubiquitylation. Analyses of datasets in the Cancer Dependency Map Project revealed many SAGA components are selective dependencies in MM. To define SAGA-specific functions, we focused on ADA2B, the only subunit in the lysine acetyltransferase (KAT) module that specifically functions in SAGA. Integration of RNA-seq, ATAC-seq, and CUT&RUN results identified pathways directly regulated by ADA2B include MTORC1 signaling, MYC, E2F, and MM-specific MAF oncogenic programs. We discovered that ADA2B is recruited to MAF and MYC gene targets, and that MAF shares a majority of its targets with MYC in MM cells. Furthermore, we found the SANT domain of ADA2B is required for interaction with both GCN5 and PCAF acetyltransferases, incorporation into SAGA, and ADA2B protein stability. Our findings uncover previously unknown SAGA KAT module-dependent mechanisms controlling MM cell growth, revealing a vulnerability that might be exploited for future development of MM therapy.

Altered CELF4 splicing factor enhances pancreatic neuroendocrine tumors aggressiveness influencing mTOR and everolimus response

Pancreatic neuroendocrine tumors (PanNETs) comprise a heterogeneous group of tumors with growing incidence. Recent molecular analyses provided a precise picture of their genomic and epigenomic landscape. Splicing dysregulation is increasingly regarded as a novel cancer hallmark influencing key tumor features. We have previously demonstrated that splicing machinery is markedly dysregulated in PanNETs. Here, we aimed to elucidate the molecular and functional implications of CUGBP ELAV-like family member 4 (CELF4), one of the most altered splicing factors in PanNETs. CELF4 expression was determined in 20 PanNETs, comparing tumor and non-tumoral adjacent tissue. An RNA sequencing (RNA-seq) dataset was analyzed to explore CELF4-linked interrelations among clinical features, gene expression, and splicing events. Two PanNET cell lines were employed to assess CELF4 function in vitro and in vivo. PanNETs display markedly upregulated CELF4 expression, which is closely associated with malignancy features, altered expression of key tumor players, and distinct splicing event profiles. Modulation of CELF4 influenced proliferation in vitro and reduced in vivo xenograft tumor growth. Interestingly, functional assays and RNA-seq analysis revealed that CELF4 silencing altered mTOR signaling pathway, enhancing the effect of everolimus. We demonstrate that CELF4 is dysregulated in PanNETs, where it influences tumor development and aggressiveness, likely by modulating the mTOR pathway, suggesting its potential as therapeutic target.

RRM2‑mediated Wnt/β‑catenin signaling pathway activation in lung adenocarcinoma: A potential prognostic biomarker

The present study aimed to investigate the role and mechanism of action of ribonucleotide reductase M2 (RRM2) in lung adenocarcinoma and its potential as a therapeutic target. Data of patients with lung adenocarcinoma from The Cancer Genome Atlas database were collected and analyzed to evaluate the potential of RRM2 as a biomarker. The expression of RRM2 was evaluated in the A549 cell line and its cisplatin-resistant A549/DDP cell line derivative by western blot and reverse transcription-quantitative PCR. The study also investigated cell proliferation and the mechanism by which RRM2 controls cellular cisplatin resistance using CCK-8 and colony-formation assays. In addition, cell migration was assessed using Transwell assays, and the cell cycle and apoptosis were examined using flow cytometry. RRM2 was highly expressed in lung adenocarcinoma and was associated with the clinical TMN stage. Functional enrichment analysis showed that RRM2 was enriched in the cell cycle. Immune cell infiltration analysis identified 12 types of immune cell that exhibited differences between patients expressing different levels of RRM2. Cellular assays revealed higher levels of RRM2 expression in A549/DDP cells than A549 cells, and its expression was induced by cisplatin. RRM2 knockdown decreased cell proliferation and migration, accelerated apoptosis and caused cell cycle arrest in the S-phase, increasing the sensitivity of A549 and A549/DDP cells to cisplatin through the Wnt/β-catenin signaling pathway. Overexpression of β-catenin reduced the effects of RRM2 knockdown on A549 cells. Lung adenocarcinoma growth may be influenced by RRM2 through the Wnt/β-catenin signaling pathway, suggesting a potential pathway for cancer progression.

RRM2 as a novel prognostic and therapeutic target of NF1-associated MPNST

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas that typically develop in the setting of neurofibromatosis type 1 (NF1) and cause significant morbidity. Conventional therapies are often ineffective for MPNSTs. Ribonucleotide reductase subunit M2 (RRM2) is involved in DNA synthesis and repair, and is overexpressed in multiple cancers. However, its role in NF1-associated MPNSTs remains unknown. Our objective was to determine the therapeutic and prognostic potential of RRM2 in NF1-associated MPNSTs.

METHODS

Identification of hub genes was performed by using NF1-associated MPNST microarray datasets. We detected RRM2 expression by immunochemical staining in an MPNST tissue microarray, and assessed the clinical and prognostic significance of RRM2 in an MPNST cohort. RRM2 knockdown and the RRM2 inhibitor Triapine were used to assess cell proliferation and apoptosis in NF1-associated MPNST cells in vitro and in vivo. The underlying mechanism of RRM2 in NF1-associated MPNST was revealed by transcriptome analysis.

RESULTS

RRM2 is a key hub gene and its expression is significantly elevated in NF1-associated MPNST. We revealed that high RRM2 expression accounted for a larger proportion of NF1-associated MPNSTs and confirmed the correlation of high RRM2 expression with poor overall survival. Knockdown of RRM2 inhibited NF1-associated MPNST cell proliferation and promoted apoptosis and S-phase arrest. The RRM2 inhibitor Triapine displayed dose-dependent inhibitory effects in vitro and induced significant tumor growth reduction in vivo in NF1-associated MPNST. Analysis of transcriptomic changes induced by RRM2 knockdown revealed suppression of the AKT-mTOR signaling pathway. Overexpression of RRM2 activates the AKT pathway to promote NF1-associated MPNST cell proliferation.

CONCLUSIONS

RRM2 expression is significantly elevated in NF1-associated MPNST and that high RRM2 expression correlates with poorer outcomes. RRM2 acts as an integral part in the promotion of NF1-associated MPNST cell proliferation via the AKT-mTOR signaling pathway. Inhibition of RRM2 may be a promising therapeutic strategy for NF1-associated MPNST.

Regulatory Role of Ribonucleotide Reductase Subunit M2 in Hepatocyte Growth and Pathogenesis of Hepatitis C Virus

Hepatitis C virus (HCV) frequently causes chronic infection in the human liver, which may progress to advanced hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. HCV primarily infects highly differentiated quiescent hepatocytes and can modulate cell cycle-regulatory genes and proliferation pathways, which ultimately contribute to persistent infection and pathogenesis. On the other hand, several studies have shown differential regulation of HCV RNA and viral protein expression levels, depending on the proliferation state of hepatocytes and the phase of the cell cycle. HCV typically requires factors provided by host cells for efficient and persistent viral replication. Previously, we found that HCV infection upregulates the expression of ribonucleotide reductase subunit M2 (RRM2) in quiescent hepatocytes. RRM2 is a rate-limiting protein that catalyzes de novo synthesis of deoxyribonucleotide triphosphates, and its expression is highly regulated during various phases of the cell cycle. RRM2 functions as a pro-viral factor essential for HCV RNA synthesis, but its functional role in HCV-induced liver diseases remains unknown. Here, we present a comprehensive review of the role of the hepatocyte cell cycle, in correlation with RRM2 expression, in the regulation of HCV replication. We also discuss the potential relevance of this protein in the pathogenesis of HCV, particularly in the development of hepatocellular carcinoma.

A Novel Cuproptosis-Associated Gene Signature to Predict Prognosis in Patients with Pancreatic Cancer

Background

Pancreatic cancer (PAAD) is a malignant tumor with a poor prognosis and lacks sensitive biomarkers for diagnosis and targeted therapy. Cuproptosis, a recently proposed form of cell death based on cellular copper ion concentration, plays a key role in cancer biology. This study is aimed at constructing a risk model for predicting the prognosis of PAAD patients based on cuproptosis-related genes.

Methods

Pancreatic-related data from UCSC-TCGA and UCSC-GTEx databases were extracted for analysis, and TCGA-PAAD samples were randomly divided into the training and validation groups. Pearson correlation analysis was used to obtain cuproptosis-related genes coexpressed with 19 copper death genes. Univariate Cox and Lasso regression analyses were used to obtain cuproptosis-related prognostic genes. Multivariate Cox regression analysis was used to construct the final prognostic risk model. The risk score curve, Kaplan-Meier survival curves, and ROC curve were used to evaluate the predictive ability of the Cox risk model. Finally, the functional annotation of the risk model was obtained through enrichment analysis.

Results

The Cox risk model has an eight prognostic cuproptosis-related gene signature. Kaplan-Meier survival curves demonstrated that the high-risk group had a shorter survival time. The ROC curve of the risk score was well created to predict one-, three-, and five-year survival rates, and AUC of the risk score was higher than other clinical characteristics. Cox regression analysis revealed that the risk score has an independent prognostic value for PAAD. GSEA reveals specific tumor pathways associated with the risk model (Myc targets v1, mTORC1 signaling, and E2F targets).

Conclusions

We constructed a prognostic model containing eight cuproptosis-related genes (AKR1B10, KLHL29, PROM2, PIP5K1C, KIF18B, AMIGO2, MRPL3, and PI4KB) that can accurately predict the prognosis of PAAD patients. The results will provide new perspectives for individualized outcome prediction and new therapy development for PAAD patients.