METTL3 facilitates tumor progression via an m6A-IGF2BP2-dependent mechanism in colorectal carcinoma.

BACKGROUND: Colorectal carcinoma (CRC) is one of the most common malignant tumors, and its main cause of death is tumor metastasis. RNA N6-methyladenosine (m6A) is an emerging regulatory mechanism for gene expression and methyltransferase-like 3 (METTL3) participates in tumor progression in several cancer types. However, its role in CRC remains unexplored. METHODS: Western blot, quantitative real-time PCR (RT-qPCR) and immunohistochemical (IHC) were used to detect METTL3 expression in cell lines and patient tissues. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and transcriptomic RNA sequencing (RNA-seq) were used to screen the target genes of METTL3. The biological functions of METTL3 were investigated in vitro and in vivo. RNA pull-down and RNA immunoprecipitation assays were conducted to explore the specific binding of target genes. RNA stability assay was used to detect the half-lives of the downstream genes of METTL3. RESULTS: Using TCGA database, higher METTL3 expression was found in CRC metastatic tissues and was associated with a poor prognosis. MeRIP-seq revealed that SRY (sex determining region Y)-box 2 (SOX2) was the downstream gene of METTL3. METTL3 knockdown in CRC cells drastically inhibited cell self-renewal, stem cell frequency and migration in vitro and suppressed CRC tumorigenesis and metastasis in both cell-based models and PDX models. Mechanistically, methylated SOX2 transcripts, specifically the coding sequence (CDS) regions, were subsequently recognized by the specific m6A "reader", insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), to prevent SOX2 mRNA degradation. Further, SOX2 expression positively correlated with METTL3 and IGF2BP2 in CRC tissues. The combined IHC panel, including "writer", "reader", and "target", exhibited a better prognostic value for CRC patients than any of these components individually. CONCLUSIONS: Overall, our study revealed that METTL3, acting as an oncogene, maintained SOX2 expression through an m6A-IGF2BP2-dependent mechanism in CRC cells, and indicated a potential biomarker panel for prognostic prediction in CRC.

Identification of surrogate endpoints in patients with locoregionally advanced nasopharyngeal carcinoma receiving neoadjuvant chemotherapy plus concurrent chemoradiotherapy versus concurrent chemoradiotherapy alone.

BACKGROUND: In the era of intensity-modulated radiotherapy (IMRT), the efficacy of additional neoadjuvant chemotherapy (NACT) to concurrent chemoradiotherapy (CCRT) in locoregionally advanced nasopharyngeal carcinoma (NPC) is currently being investigated in ongoing trials. Overall survival (OS) is the gold standard endpoint in NPC trials. We performed this analysis to identify surrogate endpoints for OS, which could shorten follow-up duration and speed up assessment of treatment effects. METHODS: We retrospectively analysed 208 matched-pair patients with locoregionally advanced NPC receiving NACT+CCRT or CCRT. Progression-free survival (PFS), failure-free survival (FFS), distant failure-free survival (D-FFS) and locoregional failure-free survival (LR-FFS) at 2 and 3 years were assessed as surrogates for 5-year OS according to Prentice's criteria. The strength of the associations were assessed using Spearman's rank correlation coefficient. RESULTS: No significant differences were observed between treatment arms for any surrogate endpoint at 2 years, which rejected Prentice's second criterion. In contrast, 3-year LR-FFS, PFS, FFS and D-FFS were consistent with all four of Prentice's criteria; the rank correlation coefficient (0.730) between 3-year PFS and 5-year OS was highest. CONCLUSIONS: 3-year PFS, FFS and D-FFS could be valid surrogate endpoints for 5-year OS; 3-year PFS may be the most accurate.

High expression of Talin-1 is associated with poor prognosis in patients with nasopharyngeal carcinoma.

BACKGROUND: Talin-1 is a cytoskeletal protein that plays an important role in tumourgenesis, migration and metastasis in several malignant tumors. The aim of this study was to evaluate the expression and prognostic value of Talin-1 in nasopharyngeal carcinoma (NPC). METHODS: Talin-1 mRNA and protein expression were examined in NPC cell lines and clinical nasopharyngeal tissues by quantitative RT-PCR, agarose gel electrophoresis and western blotting. The expression of Talin-1 was analyzed by immunohistochemical staining in 233 paraffin-embedded NPC specimens with clinical follow-up data and cox regression analysis was used to identify independent prognostic factors. The functional role of Talin-1 in NPC cell lines was evaluated by small interfering RNA-mediated depletion of the protein followed by the wound healing and transwell invasion assays. RESULTS: The expression of Talin-1 was significantly upregulated in most NPC cell lines and clinical tissues at both the mRNA and protein levels. High expression of Talin-1 was significantly associated with distant metastasis (P = 0.001) and patient death (P = 0.001). In addition, high expression of Talin-1 was associated with significantly poorer overall survival (OS: HR, 2.15; 95% CI, 1.28-3.63; P = 0.003) and poorer distant metastasis-free survival (DMFS: HR, 2.39; 95% CI, 1.38-4.15; P = 0.001). Cox regression analysis indicated that high expression of Talin-1 and TNM stage were independent prognostic indicators (both P < 0.05). Stratified analysis demonstrated that high expression of Talin-1 was associated with significantly poorer survival in patients with advanced stage disease (stage III-IV, HR, 1.91; 95% CI, 1.09-3.35; P = 0.02 for OS and HR, 2.22; 95% CI, 1.24-3.99; P = 0.006 for DMFS). Furthermore, the depletion of Talin-1 suppressed the migratory and invasive ability of NPC cells in vitro. CONCLUSIONS: Our data demonstrate that high expression of Talin-1 is associated with significantly poorer OS and poorer DMFS in NPC and depletion of Talin-1 expression inhibited NPC cell migration and invasion. Talin-1 may serve as novel prognostic biomarker in NPC.

Overexpression of CIP2A is an independent prognostic indicator in nasopharyngeal carcinoma and its depletion suppresses cell proliferation and tumor growth.

BACKGROUND: Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncoprotein that acts as a prognostic marker for several human malignancies. In this study, we investigated the clinical significance of CIP2A and its function in nasopharyngeal carcinoma (NPC). METHODS: Quantitative RT-PCR, western blot, and immunohistochemistry analyses were used to quantify CIP2A expression in NPC cell lines and clinical samples. Kaplan-Meier curves were used to estimate the association between CIP2A expression and patient survival. The functional role of CIP2A in NPC cell lines was evaluated by small interfering RNA-mediated depletion of the protein followed by analyses of cell proliferation and xenograft growth. RESULTS: CIP2A levels were upregulated in NPC cell lines and clinical samples at both the mRNA and protein levels (P < 0.01). Patients with high CIP2A expression had poorer overall survival (HR, 1.98; 95% CI, 1.16-3.34; P = 0.01) and poorer disease-free survival (HR, 1.68; 95% CI, 1.07-2.62; P = 0.02) rates than patients with low CIP2A expression. In addition, CIP2A expression status was an independent prognostic indicator for NPC patients. The depletion of CIP2A expression inhibited c-Myc protein expression in NPC cell lines, suppressed cell viability, colony formation, and anchorage-independent growth in vitro, and inhibited xenograft tumor growth in vivo. CONCLUSIONS: Our data demonstrate that high CIP2A expression in patients was associated with poor survival in NPC, and depletion of CIP2A expression inhibited NPC cell proliferation and tumor growth. Thus, these results warrant further investigation of CIP2A as a novel therapeutic target for the treatment of NPC.

Overexpression of paxillin induced by miR-137 suppression promotes tumor progression and metastasis in colorectal cancer.

The deregulation of paxillin (PXN) has been involved in the progression and metastasis of different malignancies including colorectal cancer (CRC). miR-137 is frequently suppressed in CRC. PXN is predicted to be a direct target of miR-137 in CRC cells. On this basis, we hypothesized that overexpression of PXN induced by suppression of miR-137 may promote tumor progression and metastasis and predicts poor prognosis. We detected the expression of PXN and miR-137 in clinical tumor tissues by immunohistochemical analysis and real-time PCR, positive PXN staining was observed in 198 of the 247 (80.1%) cases, whereas no or weak PXN staining was observed in the adjacent non-cancerous area. Higher level of PXN messenger RNA (mRNA) and lower level of miR-137 was observed in cancer tissues than adjacent non-cancerous tissues. High expression of PXN and low expression of miR-137 was associated with aggressive tumor phenotype and adverse prognosis. Moreover, the expression of PXN was negatively correlated with miR-137 expression. A dual-luciferase reporter gene assay validated that PXN was a direct target of miR-137. The use of miR-137 mimics or inhibitor could decrease or increase PXN mRNA and protein levels in CRC cell lines. Knockdown of PXN or ectopic expression of miR-137 could markedly inhibit cell proliferation, migration and invasion in vitro and repress tumor growth and metastasis in vivo. Taken together, these results demonstrated that overexpression of PXN induced by suppression of miR-137 promotes tumor progression and metastasis and could serve as an independent prognostic indicator in CRC patients.

Evolutionary route of nasopharyngeal carcinoma metastasis and its clinical significance.

It is critical to understand factors associated with nasopharyngeal carcinoma (NPC) metastasis. To track the evolutionary route of metastasis, here we perform an integrative genomic analysis of 163 matched blood and primary, regional lymph node metastasis and distant metastasis tumour samples, combined with single-cell RNA-seq on 11 samples from two patients. The mutation burden, gene mutation frequency, mutation signature, and copy number frequency are similar between metastatic tumours and primary and regional lymph node tumours. There are two distinct evolutionary routes of metastasis, including metastases evolved from regional lymph nodes (lymphatic route, 61.5%, 8/13) and from primary tumours (hematogenous route, 38.5%, 5/13). The hematogenous route is characterised by higher IFN-γ response gene expression and a higher fraction of exhausted CD8+ T cells. Based on a radiomics model, we find that the hematogenous group has significantly better progression-free survival and PD-1 immunotherapy response, while the lymphatic group has a better response to locoregional radiotherapy.

As an independent unfavorable prognostic factor, IL-8 promotes metastasis of nasopharyngeal carcinoma through induction of epithelial-mesenchymal transition and activation of AKT signaling.

Nasopharyngeal carcinoma (NPC) has the highest metastatic potential among head and neck cancers. Distant metastasis is the major cause of treatment failure. The role of interleukin-8 (IL-8) in NPC progression remains unknown. Our multivariate survival analyses of 255 patients with NPC revealed that higher IL-8 expression in primary NPC tissue was an independent prognostic factor for overall survival, disease-free survival, and distant metastasis-free survival of the patients. In vitro study revealed that IL-8 was highly expressed in the established high-metastasis NPC clone S18 relative to the low-metastasis cells. Suppression of IL-8 by short-hairpin RNA reduced the expression of IL-8 in S18 cells and subsequently inhibited migration, invasion, and hepatic metastasis of the cells without influencing cellular growth. Overexpression of IL-8 in S26 cells resulted in increased migration, invasion, and metastasis capabilities of the cells without affecting cellular growth. Exogenous IL-8 enhanced the migration and invasion of low-metastasis CNE-2 cells in a dose-dependent manner. An epithelial-mesenchymal transition (EMT) could be induced by IL-8 in various NPC cell lines. The high level of phosphorylated AKT in S18 cells could be suppressed by knocking down IL-8 expression. Further, IL-8-promoted migration and invasion could be abolished by either the application of the phosphoinositide-3-kinase inhibitor LY294002 or the knock down of AKT expression by using small-interfering RNA. In summary, IL-8 serves as an independent prognostic indicator of overall survival, disease-free survival, and metastasis-free survival for patients with NPC. IL-8 promotes NPC metastasis via autocrine and paracrine means, involving activation of AKT signaling and inducing EMT in NPC cells.

Skp2 expression unfavorably impacts survival in resectable esophageal squamous cell carcinoma.

BACKGROUND: The correlation of S-phase kinase-associated protein 2 (Skp2) with metastasis and prognosis in esophageal squamous cell carcinoma (ESCC) is controversial. The purpose of this study was to explore whether there was a correlation between the expression of Skp2 evaluated by immunohistochemistry and the clinical outcome of patients with operable ESCC, and to further determine the possible mechanism of the impact of Skp2 on survival. METHODS: Tissue microarrays that included 157 surgically resected ESCC specimens was successfully generated for immunohistochemical evaluation. The clinical/prognostic significance of Skp2 expression was analyzed. Kaplan-Meier analysis was used to compare the postoperative survival between groups. The prognostic impact of clinicopathologic variables and Skp2 expression was evaluated using a Cox proportional hazards model. A cell proliferation assay and a colony formation assay were performed in ESCC cell lines to determine the function of Skp2 on the progression of ESCC in vitro. RESULTS: Skp2 expression correlated closely with the T category (p = 0.035) and the pathological tumor-node-metastasis (TNM) stage (p = 0.027). High expression of Skp2 was associated with poor overall survival in resectable ESCC (p = 0.01). The multivariate Cox regression analysis demonstrated that pathological T category, pathological N category, cell differentiation, and negative Skp2 expression were independent factors for better overall survival. In vitro assays of ESCC cell lines demonstrated that Skp2 promoted the proliferative and colony-forming capacity of ESCCs. CONCLUSIONS: Negative Skp2 expression in primary resected ESCC is an independent factor for better survival. Skp2 may play a pro-proliferative role in ESCC cells.

Correlation of Skp2 overexpression to prognosis of patients with nasopharyngeal carcinoma from South China.

S-phase kinase-associated protein 2 (Skp2), which plays a role in cell cycle regulation, is commonly overexpressed in a variety of human cancers and associated with poor prognosis. However, its role in nasopharyngeal carcinoma (NPC) is not well understood. In this study, we examined the clinical significance of Skp2, with a particular emphasis on overall survival (OS) and disease-free survival (DFS), in NPC cases in South China, where NPC is an epidemic. Additionally, we explored the function of Skp2 in maintaining a cancer stem cell-like phenotype in NPC cell lines. Skp2 expression was assessed for 127 NPC patients using tissue microarrays and immunohistochemistry and analyzed together with clinicopathologic features, OS, and DFS. Skp2 expression was detectable, or positive, in 75.6% of patients. Although there was no correlation between Skp2 and any clinicopathologic factor, Skp2 expression significantly portended inferior OS (P = 0.013) and DFS (P = 0.012). In the multivariate model, Skp2 expression remained significantly predictive of poor OS [P = 0.009, risk ratio (RR) = 4.06] and DFS (P = 0.008, RR = 3.56), and this was also true for clinical stage (P = 0.012 and RR=3.201 for OS; P = 0.002 and RR=1.94 for DFS) and sex (P = 0.016 and RR=0.31 for OS; P = 0.006 and RR = 0.27 for DFS). After Skp2 knockdown, a colony formation assay was used to evaluate the self-renewal property of stem-like cells in the NPC cell lines CNE-1 and CNE-2. The colony formation efficiency in CNE-1 and CNE-2 cells was decreased. In Skp2-transfected CNE-1 and CNE-2 cells, side population (SP) proportion was increased as detected by flow cytometry. Skp2 is an independent prognostic marker for OS and DFS in NPC. Skp2 may play a role in maintaining the cancer stem cell-like phenotype of NPC cell lines.

Erratum: Oncogenic roles of carbonic anhydrase IX in human nasopharyngeal carcinoma.

[This corrects the article on p. 2942 in vol. 7, PMID: 25031713.].

BRD2 induces drug resistance through activation of the RasGRP1/Ras/ERK signaling pathway in adult T-cell lymphoblastic lymphoma.

BACKGROUND: Adult patients with T-cell lymphoblastic lymphoma (T-LBL) are treated with high-intensity chemotherapy regimens, but the response rate is still unsatisfactory because of frequent drug resistance. We aimed to investigate the potential mechanisms of drug resistance in adults with T-LBL. METHODS: Gene expression microarray was used to identify differential mRNA expression profiles between chemotherapy-resistant and chemotherapy-sensitive adult T-LBL tissues. Real-time PCR and immunohistochemistry were performed to detect the expression of bromodomain-containing protein 2 (BRD2) and c-Myc in fresh-frozen T-LBL tissues from 85 adult patients. The Ras pull-down assay was performed to monitor Ras activation. Chromatin immunoprecipitation assays were used to analyze the binding of E2F transcription factor 1 (E2F1)/BRD2 to the RAS guanyl releasing protein 1 (RasGRP1) promoter region. The drug resistance effect and mechanism of BRD2 were determined by both in vivo and in vitro studies. RESULTS: A total of 86 chemotherapy resistance-related genes in adult T-LBL were identified by gene expression microarray. Among them, BRD2 was upregulated in chemotherapy-resistant adult T-LBL tissues and associated with worse progression-free survival and overall survival of 85 adult T-LBL patients. Furthermore, BRD2 suppressed doxorubicin (Dox)-induced cell apoptosis both in vitro and in vivo. The activation of RasGRP1/Ras/ERK signaling might contribute to the Dox resistance effect of BRD2. Besides, OTX015, a bromodomain and extra-terminal (BET) inhibitor, reversed the Dox resistance effect of BRD2. Patient-derived tumor xenograft demonstrated that the sequential use of OTX015 after Dox showed superior therapeutic effects. CONCLUSIONS: Our data showed that BRD2 promotes drug resistance in adult T-LBL through the RasGRP1/Ras/ERK signaling pathway. Targeting BRD2 may be a novel strategy to improve the therapeutic efficacy and prolong survival of adults with T-LBL.

Suppression of fumarate hydratase activity increases the efficacy of cisplatin-mediated chemotherapy in gastric cancer.

Gastric cancer (GC) is one of the most common malignancies worldwide. Due to the low rate of early detection, most GC patients were diagnosed as advance stages and had poor response to chemotherapy. Some studies found that Fumarate hydratase (FH) participated in the DNA damage response and its deficiency was associated with tumorigenesis in some cancers. In this study, we investigated the relationship between FH and cisplatin (CDDP) sensitivity in GC cell lines. We found that FH was the most significant gene which induced by CDDP treatment and the suppression of FH could enhance the cytotoxicity of CDDP. Miconazole Nitrate (MN) could inhibit FH activity and enhance the effect of CDDP in vitro and in vivo. We also investigated the significance of expression of FH in GC tissues. The FH expression, which was higher in GC tissues than in noncancerous tissues, was negatively associated with the prognosis of patients. Together, these results revealed that FH is a reliable indicator for response to CDDP treatment in GC and the inhibition of FH may be a potential strategy to improve the effects of CDDP-based chemotherapy.

Clonal Mutations Activate the NF-κB Pathway to Promote Recurrence of Nasopharyngeal Carcinoma.

The genetic events occurring in recurrent nasopharyngeal carcinoma (rNPC) are poorly understood. Here, we performed whole-genome and whole-exome sequencing in 55 patients with rNPC and 44 primarily diagnosed NPC (pNPC), with 7 patients having paired rNPC and pNPC samples. Previously published pNPC exome data were integrated for analysis. rNPC and pNPC tissues had similar mutational burdens, however, the number of clonal mutations was increased in rNPC samples. TP53 and three NF-κB pathway components (TRAF3, CYLD, and NFKBIA) were significantly mutated in both pNPC and rNPC. Notably, mutations in TRAF3, CYLD, and NFKBIA were all clonal in rNPC, however, 55.6% to 57.9% of them were clonal in pNPC. In general, the number of clonal mutations in NF-κB pathway-associated genes was significantly higher in rNPC than in pNPC. The NF-κB mutational clonality was selected and/or enriched during NPC recurrence. The amount of NF-κB translocated to the nucleus in samples with clonal NF-κB mutants was significantly higher than that in samples with subclonal NF-κB mutants. Moreover, the nuclear abundance of NF-κB protein was significantly greater in pNPC samples with locoregional relapse than in those without relapse. Furthermore, high nuclear NF-κB levels were an independent negative prognostic marker for locoregional relapse-free survival in pNPC. Finally, inhibition of NF-κB enhanced both radiosensitivity and chemosensitivity in vitro and in vivo. In conclusion, NF-κB pathway activation by clonal mutations plays an important role in promoting the recurrence of NPC. Moreover, nuclear accumulation of NF-κB is a prominent biomarker for predicting locoregional relapse-free survival. SIGNIFICANCE: This study uncovers genetic events that promote the progression and recurrence of nasopharyngeal carcinoma and has potential prognostic and therapeutic implications.See related commentary by Sehgal and Barbie, p. 5915.

A Prognostic Bio-Model Based on SQSTM1 and N-Stage Identifies Nasopharyngeal Carcinoma Patients at High Risk of Metastasis for Additional Induction Chemotherapy.

Purpose: Metastasis is one of the most important causes of treatment failure in nasopharyngeal carcinoma (NPC). In T4 or N2-3 patients at high-risk of metastasis, concurrent chemoradiotherapy (CCRT) is inadequate and additional induction chemotherapy (IC) is controversial. There is a critical need to develop a better patient stratification to efficiently identify patients at high-risk of metastasis for additional IC. Recently, Sequestosome 1 (SQSTM1)/p62, an autophagy adaptor protein, was identified as one of the metastasis-related proteins in NPC. However, the mechanism by which SQSTM1 is involved in NPC metastasis was not investigated.Experimental Design: The effect of SQSTM1 on cell migration and invasion was examined in vitro and in vivo SQSTM1 expression was analyzed in clinical NPC samples using IHC. Luciferase reporter analyses were conducted to identify the effects of SQSTM1 on NF-κB transcriptional activity. A prediction bio-model was constructed by Cox analysis. Retrospective and prospective randomized clinical data were adopted to build and test the model, respectively.Results: SQSTM1 mediated epithelial to mesenchymal transition (EMT) through the NF-κB pathway to promote NPC metastasis. Inhibiting SQSTM1 enhanced sensitivity to cisplatin in NPC cells. In NPC patients, high SQSTM1 expression was associated with increased risk of distant metastasis. Furthermore, we propose a prognostic bio-model based on SQSTM1 and N-stage to predict NPC metastasis. Most importantly, our prospective randomized study suggested that IC is beneficial for NPC patients with high metastasis risk.Conclusions: The prognostic bio-model identifies NPC patients at high-risk of metastasis for additional IC. Clin Cancer Res; 24(3); 648-58. ©2017 AACR.

The CXCL5/CXCR2 axis contributes to the epithelial-mesenchymal transition of nasopharyngeal carcinoma cells by activating ERK/GSK-3ß/snail signalling.

BACKGROUND: Distant metastasis is the major cause of treatment failure in patients with nasopharyngeal carcinoma (NPC). Although several biomarkers correlate with metastasis and prognosis, the molecular mechanisms of NPC development and progression remain unclear. METHODS: Quantitative RT-PCR (qRT-PCR), western blotting, cell growth, foci formation, migration and invasion assays, and xenograft mouse models were utilized to examine the expression levels and functions of the CXCL5/CXCR2 axis in NPC. A luciferase reporter assay, western blotting, immunofluorescence, and migration and invasion assays were used to identify and verify the ERK/GSK-3ß/Snail signalling pathway. RESULTS: CXCL5 was significantly increased in the sera of NPC patients, and high expression levels of CXCL5/CXCR2 in NPC primary tissues indicated poor survival. CXCL5 and CXCR2 were upregulated in NPC cell lines. Ectopic expression of the CXCL5/CXCR2 axis promoted NPC cell migration and invasion in vitro and the formation of lung metastases in vivo. Mechanistically, the dual overexpression of CXCL5 and CXCR2 promoted cell spreading by inducing the epithelial-mesenchymal transition (EMT) through the activation of the ERK/GSK-3ß/Snail signalling pathway. CONCLUSION: The CXCL5/CXCR2 axis contributes to the EMT of NPC cells by activating ERK/GSK-3ß/Snail signalling, and this axis may be a potential diagnostic marker and therapeutic target for patients with NPC.

CSTF2-Induced Shortening of the RAC1 3'UTR Promotes the Pathogenesis of Urothelial Carcinoma of the Bladder.

Shortening of the 3' untranslated regions (3'UTR) of mRNA is an important mechanism for oncogene activation. However, 3'UTR alteration events, their pathologic functions, and underlying mechanisms in human urothelial carcinoma of the bladder (UCB) are not clear. Here, we combine RNA sequencing, bioinformatics, and clinical studies in two independent cohorts of patients with UCB to identify a novel RAC1 shorter 3'UTR isoform that is frequently expressed in UCB and is critical in the tumorigenesis and acquisition of a poor prognostic phenotype in patients. Short 3'UTR isoform of RAC1 substantially upregulated RAC1 expression by escaping from miRNA-targeted repression and played an essential oncogenic role in UCB pathogenesis. An important cleavage/polyadenylation factor, cleavage stimulation factor 2 (CSTF2), induced 3'UTR shortening of RAC1 in UCB by mediating slow transcriptional elongation at RAC1 Cotranscriptional recruitment of CSTF2 on the GUAAU motif at proximal polyadenylation site of RAC1 attenuated the recruitment of two transcription factors AFF1 and AFF4, causing the defects in elongation. CSTF2 regulated the tumorigenic functions of the shorter RAC1 isoform in UCB cells, enhancing cell proliferation, migration, and invasion. The combination of high expression of CSTF2 and high usage of RAC1 short-3'UTR isoform may be used as a powerful biomarker to predict poor prognosis in UCB. Our findings also suggest a CSTF2-regulated RAC1-3'UTR shortening program as an exploitable therapeutic strategy for patients with UCB.Significance: These findings demonstrate that the short isoform of RAC1 is critical in UCB tumorigenesis and may have implications for developing new therapeutic strategies to treat this disease. Cancer Res; 78(20); 5848-62. ©2018 AACR.

Structure of Schlafen13 reveals a new class of tRNA/rRNA- targeting RNase engaged in translational control.

Cleavage of transfer (t)RNA and ribosomal (r)RNA are critical and conserved steps of translational control for cells to overcome varied environmental stresses. However, enzymes that are responsible for this event have not been fully identified in high eukaryotes. Here, we report a mammalian tRNA/rRNA-targeting endoribonuclease: SLFN13, a member of the Schlafen family. Structural study reveals a unique pseudo-dimeric U-pillow-shaped architecture of the SLFN13 N'-domain that may clamp base-paired RNAs. SLFN13 is able to digest tRNAs and rRNAs in vitro, and the endonucleolytic cleavage dissevers 11 nucleotides from the 3'-terminus of tRNA at the acceptor stem. The cytoplasmically localised SLFN13 inhibits protein synthesis in 293T cells. Moreover, SLFN13 restricts HIV replication in a nucleolytic activity-dependent manner. According to these observations, we term SLFN13 RNase S13. Our study provides insights into the modulation of translational machinery in high eukaryotes, and sheds light on the functional mechanisms of the Schlafen family.

CPT1A-mediated fatty acid oxidation promotes colorectal cancer cell metastasis by inhibiting anoikis.

Anoikis is a critical obstacle to cancer metastasis. Colorectal cancer (CRC) exhibits a high rate of metastasis, leading to death, and the mechanisms involved in anoikis resistance are still unclear. We identified that the fatty acid oxidation (FAO) pathway was activated in detached CRC cells. Multiple genes in the FAO pathway, specifically the rate-limiting enzyme CPT1A, were upregulated in CRC cells grown in suspension. Reactive oxygen species elimination mediated by CPT1A in CRC cells was vital to anoikis resistance. In vivo experiments showed that CPT1A-suppressed CRC cells colonized the lung at a much lower rate than normal CRC cells, suggesting that CPT1A-mediated FAO activation increased metastatic capacity. In clinical tissue specimens from CRC patients, elevated expression of CPT1A was observed in metastatic sites compared with primary sites. Our results demonstrate that CPT1A-mediated FAO activation induces CRC cells to resist anoikis, suggesting that CPT1A is an attractive target for treating metastatic CRC.

Prognostic value of wait time in nasopharyngeal carcinoma treated with intensity modulated radiotherapy: a propensity matched analysis.

The aim of this study was to determine the prognostic value of wait time from histological diagnosis to primary treatmen for nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT). Between October 2009 and February 2012, a total of 1672 NPC patients were retrospectively analyzed. A cutoff value of > 4 weeks was used to define prolonged wait time. Matched patients according to the wait time were identified using propensity score matching (PSM), which was also used to identify matched patients for subsequent stratified analyses. Differences in progression-free survival (PFS), overall survival (OS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRFS) were estimated using the Kaplan-Meier method and Cox proportional hazards models. In total, 407 pairs of NPC patients were selected by PSM. The 3-year PFS rate was significantly lower for patients with a prolonged wait time (> 4 weeks) than for those with an acceptable wait time (P = 0.035). Stratified analyses revealed that the negative effects of a prolonged wait time occurred primarily in patients with advanced NPC without neoadjuvant chemotherapy (NACT; PFS:P = 0.040; DMFS:P = 0.028). In multivariate analysis, a prolonged wait time was found to be an independent unfavorable prognostic factor for PFS and DMFS in advanced-staged patients without NACT. These results suggest that a prolonged time (> 4 weeks) between diagnosis and primary radical radiotherapy is a disadvantage for NPC patients, particularly those with advanced disease receiving no NACT. Thus, it is necessary to optimize resources for decreasing this wait time, although additional studies are warranted to further clarify our findings.