The Association of R-Loop Binding Proteins Subtypes with CIN Implicates Therapeutic Strategies in Colorectal Cancer.

Chromosomal instability (CIN) covers approximately 65 to 70% of colorectal cancer patients and plays an essential role in cancer progression. However, the molecular features and therapeutic strategies related to those patients are still controversial. R-loop binding proteins (RLBPs) exert significant roles in transcription and replication. Here, integrative colorectal cancer proteogenomic analysis identified two RLBPs subtypes correlated with distinct prognoses. Cluster I (CI), represented by high expression of RLBPs, was associated with the CIN phenotype. While Cluster II (CII) with the worst prognosis and low expression of RLBPs was composed of a high percentage of patients with mucinous adenocarcinoma or right-sided colon cancer. The molecular feature analysis revealed that the active RNA processing, ribosome synthesis, and aberrant DNA damage repair were shown in CI, a high inflammatory signaling pathway, and lymphocyte infiltration was enriched in CII. In addition, we revealed 42 tumor-associated RLBPs proteins. The CI with high expression of tumor-associated proteins was sensitive to drugs targeting genome integrity and EGFR in both cell and organoid models. Thus, our study unveils a significant molecular association of the CIN phenotype with RLBPs, and also provides a powerful resource for further functional exploration of RLBPs in cancer progression and therapeutic application.

Asparagine synthetase regulates lung-cancer metastasis by stabilizing the ß-catenin complex and modulating mitochondrial response.

The availability of asparagine is the limitation of cell growth and metastasis. Asparagine synthetase (ASNS) was an essential enzyme for endogenous asparagine products. In our study, ASNS-induced asparagine products were essential to maintain tumor growth and colony formations in vitro. But mutated ASNS which defected endogenous asparagine products still upregulated cell invasiveness, which indicated that ASNS promoted invasiveness by alternative pathways. Mechanically, ASNS modulated Wnt signal transduction by promoting GSK3ß phosphorylation on ser9 and stabilizing the ß-catenin complex, as result, ASNS could promote more ß-catenin translocation into nucleus independent of endogenous asparagine. At the same time, ASNS modulated mitochondrial response to Wnt stimuli with increased mitochondrial potential and membrane fusion. In summary, ASNS promoted metastasis depending on Wnt pathway and mitochondrial functions even without endogenous asparagine products.

Fatty acid oxidation fuels glioblastoma radioresistance with CD47-mediated immune evasion.

Glioblastoma multiforme (GBM) remains the top challenge to radiotherapy with only 25% one-year survival after diagnosis. Here, we reveal that co-enhancement of mitochondrial fatty acid oxidation (FAO) enzymes (CPT1A, CPT2 and ACAD9) and immune checkpoint CD47 is dominant in recurrent GBM patients with poor prognosis. A glycolysis-to-FAO metabolic rewiring is associated with CD47 anti-phagocytosis in radioresistant GBM cells and regrown GBM after radiation in syngeneic mice. Inhibition of FAO by CPT1 inhibitor etomoxir or CRISPR-generated CPT1A-/-, CPT2-/-, ACAD9-/- cells demonstrate that FAO-derived acetyl-CoA upregulates CD47 transcription via NF-κB/RelA acetylation. Blocking FAO impairs tumor growth and reduces CD47 anti-phagocytosis. Etomoxir combined with anti-CD47 antibody synergizes radiation control of regrown tumors with boosted macrophage phagocytosis. These results demonstrate that enhanced fat acid metabolism promotes aggressive growth of GBM with CD47-mediated immune evasion. The FAO-CD47 axis may be targeted to improve GBM control by eliminating the radioresistant phagocytosis-proofing tumor cells in GBM radioimmunotherapy.

The Roles of RNA Helicases in DNA Damage Repair and Tumorigenesis Reveal Precision Therapeutic Strategies.

DEAD-box RNA helicases belong to a large group of RNA-processing factors and play vital roles unwinding RNA helices and in ribosomal RNA biogenesis. Emerging evidence indicates that RNA helicases are associated with genome stability, yet the mechanisms behind this association remain poorly understood. In this study, we performed a comprehensive analysis of RNA helicases using multiplatform proteogenomic databases. More than 50% (28/49) of detected RNA helicases were highly expressed in multiple tumor tissues, and more than 60% (17/28) of tumor-associated members were directly involved in DNA damage repair (DDR). Analysis of repair dynamics revealed that these RNA helicases are engaged in an extensively broad range of DDR pathways. Among these factors is DDX21, which was prominently upregulated in colorectal cancer. The high expression of DDX21 gave rise to frequent chromosome exchange and increased genome fragmentation. Mechanistically, aberrantly high expression of DDX21 triggered inappropriate repair processes by delaying homologous recombination repair and increasing replication stress, leading to genome instability and tumorigenesis. Treatment with distinct chemotherapeutic drugs caused higher lethality to cancer cells with genome fragility induced by DDX21, providing a perspective for treatment of tumors with high DDX21 expression. This study revealed the role of RNA helicases in DNA damage and their associations with cancer, which could expand therapeutic strategies and improve precision treatments for cancer patients with high expression of RNA helicases. SIGNIFICANCE: The involvement of the majority of tumor-associated RNA helicases in the DNA damage repair process suggests a new mechanism of tumorigenesis and offers potential alternative therapeutic strategies for cancer.

Low Expression of ECT2 Confers Radiation Therapy Resistance Through Transcription Coupled Nucleolar DNA Damage Repair.

PURPOSE: Radioresistance contributes to poor clinical therapeutic efficacy in most cancers. Emerging evidence shows that aberrant DNA damage repair is involved in radioresistance. This study aimed to elucidate the mechanism for radioresistance and explore the precise treatment to sensitize the radioresistant tumors. METHODS AND MATERIALS: Real-time polymerase chain reaction and Western blot were used to confirm the differential expression of epithelial cell transforming 2 (ECT2) in irradiation-resistant and sensitive cell lines. Laser microirradiation was used to examine the ribosome DNA (rDNA) damage response of ECT2. Biotin-identification, in vivo, in vitro binding assay, and dot blotting were used to confirm the interaction of ECT2 and PARP1. The xenograft mouse model and cell survival assay were used to assess the irradiation sensitivity with or without PARP1 inhibitor. RESULTS: We found the expression of ECT2 correlates with sensitivity to radiation therapy in both lung cancer and nasopharyngeal carcinoma. We demonstrated that low expression of ECT2 causes radioresistance, mainly by protecting rDNA in nucleoli from persistent irradiation exposure through transcriptional recovery prevention. ECT2 is recruited to the rDNA damage site in an ataxia-telangiectasia-mutated RNA polymerase I dependent manner. The recruited ECT2 interacts with PARP1 and facilitates the disassociation of PARP1 from rDNA in nucleoli. Thus, ECT2 deficiency results in sustained activation of PARP1, which subsequently inhibits nucleolar transcription and results in a low frequency of rDNA exposure under DNA damage. PARP inhibition synergized with irradiation can sensitize radioresistant tumors with low ECT2 expression. CONCLUSIONS: Our study provides a potential perspective for the application of PARP inhibitor to sensitize low-ECT2 expressing tumors to radiation therapy.

Paradoxical effects of DNA tumor virus oncogenes on epithelium-derived tumor cell fate during tumor progression and chemotherapy response.

Epstein-Barr virus (EBV) and human papillomavirus (HPV) infection is the risk factors for nasopharyngeal carcinoma and cervical carcinoma, respectively. However, clinical analyses demonstrate that EBV or HPV is associated with improved response of patients, although underlying mechanism remains unclear. Here, we reported that the oncoproteins of DNA viruses, such as LMP1 of EBV and E7 of HPV, inhibit PERK activity in cancer cells via the interaction of the viral oncoproteins with PERK through a conserved motif. Inhibition of PERK led to increased level of reactive oxygen species (ROS) that promoted tumor and enhanced the efficacy of chemotherapy in vivo. Consistently, disruption of viral oncoprotein-PERK interactions attenuated tumor growth and chemotherapy in both cancer cells and tumor-bearing mouse models. Our findings uncovered a paradoxical effect of DNA tumor virus oncoproteins on tumors and highlighted that targeting PERK might be an attractive strategy for the treatment of NPC and cervical carcinoma.

DIAPH3 promotes pancreatic cancer progression by activating selenoprotein TrxR1-mediated antioxidant effects.

Pancreatic cancer is a highly malignant tumour of the digestive tract which is difficult to diagnose and treat. Approximately 90% of cases arise from ductal adenocarcinoma of the glandular epithelium. The morbidity and mortality of the disease have increased significantly in recent years. Its 5-year survival rate is <1% and has one of the worst prognoses amongst malignant tumours. Pancreatic cancer has a low rate of early-stage diagnosis, high surgical mortality and low cure rate. Selenium compounds produced by selenoamino acid metabolism may promote a large amount of oxidative stress and subsequent unfolded reactions and endoplasmic reticulum stress by consuming the NADPH in cells, and eventually lead to apoptosis, necrosis or necrotic cell death. In this study, we first identified DIAPH3 as a highly expressed protein in the tissues of patients with pancreatic cancer, and confirmed that DIAPH3 promoted the proliferation, anchorage-independent growth and invasion of pancreatic cancer cells using overexpression and interference experiments. Secondly, bioinformatics data mining showed that the potential proteins interacted with DIAPH3 were involved in selenoamino acid metabolism regulation. Selenium may be incorporated into selenoprotein synthesis such as TrxR1 and GPX4, which direct reduction of hydroperoxides or resist ferroptosis, respectively. Our following validation confirmed that DIAPH3 promoted selenium content and interacted with the selenoprotein RPL6, a ribosome protein subunit involved in selenoamino acid metabolism. In addition, we verified that DIAPH3 could down-regulate cellular ROS level via up-regulating TrxR1 expression. Finally, nude mice xenograft model experimental results demonstrate DIAPH3 knock down could decrease tumour growth and TrxR1 expression and ROS levels in vivo. Collectively, our observations indicate DIAPH3 could promote pancreatic cancer progression by activating selenoprotein TrxR1-mediated antioxidant effects.

STARD4 promotes breast cancer cell malignancy.

Breast cancer (BRCA) is one of the most common malignancies encountered in women worldwide. Lipid metabolism has been found to be involved in cancer progression. Steroidogenic acute regulatory protein­related lipid transfer 4 (STARD4) is an important cholesterol transporter involved in the regulatory mechanism of intracellular cholesterol homeostasis. However, to the best of our knowledge, the molecular functions of STARD4 in BRCA are unclear. Immunohistochemical staining and public dataset analysis were performed to investigate the expression levels of STARD4 in BRCA. In the present study, high expression of STARD4 was identified in BRCA samples and higher STARD4 expression was significantly associated with shorter distant metastasis­free survival time in patients with BRCA, which indicated that STARD4 may be associated with BRCA progression. Cell cytometry system Celigo® analysis, Cell Counting K­8 assays, flow cytometry, wound healing assays and transwell assays were used to investigate the effects of STARD4 knockdown on proliferation, cell cycle, apoptosis and migration in BRCA cells. Loss­of­function assays demonstrated that STARD4 acted as an oncogene to promote proliferation and cell cycle progression, while suppressing apoptosis in BRCA cells in vitro and in vivo. Furthermore, knockdown of STARD4 significantly suppressed BRCA metastasis. To assess the mechanism of action of STARD4, microarray analysis was performed following STARD4 knockdown in MDA­MB­231 cells. The data were analyzed in detail using bioinformatics, and a series of genes, including E74 like ETS transcription factor 1, cAMP responsive element binding protein 1 and p21 (RAC1) activated kinase 2, which have been previously reported to be crucial genes implicated in the malignant phenotype of cancer cells, were identified to be regulated by STARD4. Loss­of function assays demonstrated that knockdown of STARD4 suppressed BRCA proliferation and migration. These findings suggested that STARD4 had an oncogenic effect in human BRCA progression.

Dual blockade of CD47 and HER2 eliminates radioresistant breast cancer cells.

Although the efficacy of cancer radiotherapy (RT) can be enhanced by targeted immunotherapy, the immunosuppressive factors induced by radiation on tumor cells remain to be identified. Here, we report that CD47-mediated anti-phagocytosis is concurrently upregulated with HER2 in radioresistant breast cancer (BC) cells and RT-treated mouse syngeneic BC. Co-expression of both receptors is more frequently detected in recurrent BC patients with poor prognosis. CD47 is upregulated preferentially in HER2-expressing cells, and blocking CD47 or HER2 reduces both receptors with diminished clonogenicity and augmented phagocytosis. CRISPR-mediated CD47 and HER2 dual knockouts not only inhibit clonogenicity but also enhance macrophage-mediated attack. Dual antibody of both receptors synergizes with RT in control of syngeneic mouse breast tumor. These results provide the evidence that aggressive behavior of radioresistant BC is caused by CD47-mediated anti-phagocytosis conjugated with HER2-prompted proliferation. Dual blockade of CD47 and HER2 is suggested to eliminate resistant cancer cells in BC radiotherapy.

Establishment of a pattern recognition metabolomics model for the diagnosis of hepatocellular carcinoma.

BACKGROUND: Early diagnosis of hepatocellular carcinoma may help to ensure that patients have a chance for long-term survival; however, currently available biomarkers lack sensitivity and specificity. AIM: To characterize the serum metabolome of hepatocellular carcinoma in order to develop a new metabolomics diagnostic model and identifying novel biomarkers for screening hepatocellular carcinoma based on the pattern recognition method. METHODS: Ultra-performance liquid chromatography-mass spectroscopy was used to characterize the serum metabolome of hepatocellular carcinoma (n = 30) and cirrhosis (n = 29) patients, followed by sequential feature selection combined with linear discriminant analysis to process the multivariate data. RESULTS: The concentrations of most metabolites, including proline, were lower in patients with hepatocellular carcinoma, whereas the hydroxypurine levels were higher in these patients. As ordinary analysis models failed to discriminate hepatocellular carcinoma from cirrhosis, pattern recognition analysis was used to establish a pattern recognition model that included hydroxypurine and proline. The leave-one-out cross-validation accuracy and area under the receiver operating characteristic curve analysis were 95.00% and 0.90 [95% Confidence Interval (CI): 0.81-0.99] for the training set, respectively, and 78.95% and 0.84 (95%CI: 0.67-1.00) for the validation set, respectively. In contrast, for α-fetoprotein, the accuracy and area under the receiver operating characteristic curve were 65.00% and 0.69 (95%CI: 0.52-0.86) for the training set, respectively, and 68.42% and 0.68 (95%CI: 0.41-0.94) for the validation set, respectively. The Z test revealed that the area under the curve of the linear discriminant analysis model was significantly higher than the area under the curve of α-fetoprotein (P < 0.05) in both the training and validation sets. CONCLUSION: Hydroxypurine and proline might be novel biomarkers for hepatocellular carcinoma, and this disease could be diagnosed by the metabolomics model based on pattern recognition.

m6A Reader YTHDC2 Promotes Radiotherapy Resistance of Nasopharyngeal Carcinoma via Activating IGF1R/AKT/S6 Signaling Axis.

N6-methyladenosine (m6A) modification has been reported as a critical regulator of gene transcript expression. Although m6A modification plays important roles in tumor development, its role in therapeutic resistance remains unknown. In this study, we aimed to examine the expression level of m6A-modification related proteins and elucidate the effect of m6A-related proteins on radiation response in nasopharyngeal carcinoma (NPC). Among the genes that participated in m6A modification, YTHDC2, a m6A reader, was found to be consistently highly expressed in radioresistant NPC cells. Knocking down of YTHDC2 expression in radioresistant NPC cells improved the therapeutic effect of radiotherapy in vitro and in vivo, whereas overexpression of YTHDC2 in radiosensitive NPC cells exerted an opposite effect. Bioinformatics and mechanistic studies revealed that YTHDC2 could physically bound to insulin-like growth factor 1 receptor (IGF1R) messenger RNA and promoted translation initiation of IGF1R mRNA, which in turn activated the IGF1R-AKT/S6 signaling pathway. Thus, the present study suggests that YTHDC2 promotes radiotherapy resistance of NPC cells by activating the IGF1R/ATK/S6 signaling axis and may serve as a potential therapeutic target in radiosensitization of NPC cells.

Radiation-Enhanced Expression of CCL22 in Nasopharyngeal Carcinoma is Associated With CCR4+ CD8 T Cell Recruitment.

PURPOSE: Radiation therapy elicits profound alterations in gene expression in tumor cells. This study aims to determine the dynamic changes in the expression of immunity-associated genes in nasopharyngeal carcinoma (NPC) cells upon radiation therapy. METHODS AND MATERIALS: The study was performed using NPC patient-derived tumor xenograft tumors, cell lines, CCR4+ CD8 T cells sorted from peripheral blood mononuclear cells of healthy volunteers, and TCGA-derived bulk RNA-seq or single-cell RNA-seq (scRNA-seq) data sets. Patient-derived tumor xenograft tumors or cell lines were irradiated and collected for bulk RNA sequencing or for CCL22 expression and release detection. Malignant phenotypes and radiosensitivity were assessed in cells with or without overexpression of CCL22 or recombinant CCL22 treatment in the presence or absence of irradiation. TCGA data sets were used for uncovering CCR4 status in subtypes of T cells. CCL22 in supernatants, cell lysates, or serum samples was measured with enzyme-linked immunosorbent assay. RESULTS: CCL22 was significantly increased in the irradiated patient-derived tumor xenograft tumors, the supernatants and cell lysates collected from irradiated NPC cell lines, and the serum of patients who received radiation therapy. No alterations of malignant phenotypes were found in tumor cells with CCL22 overexpression or recombinant CCL22 treatment. Kaplan-Meier analysis revealed that CCL22 or its receptor CCR4 positively correlated with cytotoxic T lymphocyte signatures, and high expression of CCL22 or CCR4 was associated with better prognosis for patients with NPC. scRNA-seq data set-based analysis demonstrated that CCR4 was expressed in multiple subtypes of T cells, including effector CD8 T cells. Chemotaxis assay indicated that CCR4+ CD8 T cells could be recruited by CCL22 treatment. CONCLUSION: The radiation-enhanced release of CCL22 from NPC cells promotes migration of CCR4 + effector CD8 T cells, which might partially be associated with radiation therapy-mediated antitumor immunity.

Rab25-Mediated EGFR Recycling Causes Tumor Acquired Radioresistance.

Tumor acquired radioresistance remains as the major limit in cancer radiotherapy (RT). Rab25, a receptor recycling protein, has been reported to be enhanced in tumors with aggressive phenotype and chemotherapy resistance. In this study, elevated Rab25 expression was identified in an array of radioresistant human cancer cell lines, in vivo radioresistant xenograft tumors. Clinical investigation confirmed that Rab25 expression was also associated with a worse prognosis in patients with lung adenocarcinoma (LUAD) and nasopharyngeal carcinoma (NPC). Enhanced activities of EGFR were observed in both NPC and LUAD radioresistant cells. Rab25 interacts with EGFR to enhance EGFR recycling to cell surface and to decrease degradation in cytoplasm. Inhibition of Rab25 showed synergized radiosensitivity with reduced aggressive phenotype. This study provides the clinical and experimental evidence that Rab25 is a potential therapeutic target to alleviate the hyperactive EGFR signaling and to prevent RT-acquired tumor resistance in patients with LUAD and NPC.

Cathepsin L interacts with CDK2-AP1 as a potential predictor of prognosis in patients with breast cancer.

Cathepsin L (CTSL) is a lysosomal acid cysteine protease that has been implicated in tumorigenesis and malignant progression. In the present study, the role of CTSL in tumorigenesis and prognosis of breast cancer was evaluated. The prognostic value of CTSL was analyzed using immunohistochemistry in patients with breast cancer, as well as online microarray datasets. CTSL expression was knocked down in the breast cancer cell line T-47D using RNA interference. MTT and colony formation assays were performed to assess the role of CTSL in the proliferation of breast cancer cells. Cell cycle progression and apoptosis were measured using flow cytometry. A physical interaction of CTSL and cyclin dependent kinase 2 associated protein 1 (CDK2-AP1) was determined using a glutathione S-transferase pull-down assay. Endogenous CTSL expression was high in breast cancer cells and exhibited an inverse association with CDK2-AP1 expression; aberrant expression of CTSL in breast cancer tissues predicted an improved clinical outcome and prognosis. In addition, CTSL knockdown decelerated the progression of breast cancer cells by arresting cell cycle progression and increasing apoptosis. Thus, CTSL may be a potential therapeutic target for treating patients with breast cancer.

Glutamine synthetase facilitates cancer cells to recover from irradiation-induced G2/M arrest.

Resistance to radiation of cancer cells can be either intrinsic or acquired, leading to treatment failure. In response to DNA damage caused by IR, cancer cells are arrested in cell cycle showing limited proliferation and increased apoptosis. However, radiation-resistant cells are able to overcome the cell cycle block and proceed to proliferation, for which the detailed mechanism remains to be elucidated. In the present study, we showed that radioresistant cells exhibited a recoverable G2/M phase during prolonged cell cycle and manifested lower apoptosis rate and more colony formation. RNA-seq analysis revealed that glutamine synthetase (GS, GLUL) gene was highly expressed in radioresistant cancer cells in comparison with the parental cells, which was in accordance with the G2/M arrest after ionizing radiation. Knocking out of GS in radioresistant cells resulted in a delayed G2/M recovery and lowered proliferation rate after ionizing radiation treatment, which was accompanied with increased inhibitory phosphorylation of CDK1 at Y15 and downregulated Cdc25B, a dual specific phosphatase of CDK1. Moreover, there was an enhanced complex formation of CDK1 and Cyclin B1 when the cells were rescued by re-introducing GS. In vivo, knocking down of GS significantly sensitized CNE2-R xenografts to RT in mice. In this study, we demonstrate a novel role of glutamine synthetase independent of metabolic function in promoting recovery from G2/M arrest caused by ionizing radiation, thus, causing cancer cell resistance to radiotherapy.

MTMR3 is upregulated in patients with breast cancer and regulates proliferation, cell cycle progression and autophagy in breast cancer cells.

As a member of the myotubularin family, myotubularin related protein 3 (MTMR3) has been demonstrated to participate in tumor development, including oral and colon cancer. However, little is known about its functional roles in breast cancer. In the present study, the expression of MTMR3 in breast cancer was evaluated by immunohistochemical staining of tumor tissues from 172 patients. Online data was then used for survival analysis from the PROGgeneV2 database. In vitro, MTMR3 expression was silenced in MDA­MB­231 cells via lentiviral shRNA transduction. MTT, colony formation and flow cytometry assays were performed in the control and MTMR3­silenced cells to evaluate the cell growth, proliferation and cell cycle phase distribution, respectively. Western blotting was used to evaluate the protein expression levels of autophagy­related markers. The results demonstrated that the expression of MTMR3 in breast cancer tissues was significantly increased compared with adjacent normal tissues. MTMR3 was highly expressed in triple­negative breast cancer and was associated with disease recurrence. MTMR3 knockdown in MDA­MB­231 cells inhibited cell proliferation and induced cell cycle arrest and autophagy. The present results indicated that MTMR3 may have an important role in promoting the progression of breast cancer, and its inhibition may serve as a promising therapeutic target for breast cancer treatment.

Glutamine Synthetase Promotes Radiation Resistance via Facilitating Nucleotide Metabolism and Subsequent DNA Damage Repair.

Radiation resistance is a critical problem in radiotherapy for cancer. Radiation kills tumor cells mainly through causing DNA damage. Thus, efficiency of DNA damage repair is one of the most important factors that limits radiotherapy efficacy. Glutamine physiologically functions to generate protein and nucleotides. Here, we study the impact of glutamine metabolism on cancer therapeutic responses, in particular under irradiation-induced stress. We show that radiation-resistant cells possessed low glycolysis, mitochondrial respiration, and TCA cycle but high glutamine anabolism. Transcriptome analyses revealed that glutamine synthetase (GS), an enzyme catalyzing glutamate and ammonia to glutamine, was responsible for the metabolic alteration. ChIP and luciferase reporter assays revealed that GS could be transcriptionally regulated by STAT5. Knockdown of GS delayed DNA repair, weakened nucleotide metabolism, and enhanced radiosensitivity both in vitro and in vivo. Our data show that GS links glutamine metabolism to radiotherapy response through fueling nucleotide synthesis and accelerating DNA repair.

RIG-I promotes IFN/JAK2 expression and the endoplasmic reticulum stress response to inhibit chemoradiation resistance in nasopharyngeal carcinoma.

RIG-I is associated with the occurrence and development of many tumors. However, the role of RIG-I in radiotherapy and chemotherapy in NPC has not been reported to date. In our study, RIG-I expression was significantly reduced in chemoradiotherapy-resistant NPC tissues and cells compared with that in therapy-sensitive tissues and cells. RIG-I expression increased in nonresistant NPC cells, including CNE1 and CNE2, in a dose-dependent manner with increasing chemotherapy drug concentration or radiotherapy dose. RIG-I overexpression promoted radiotherapy and chemotherapy sensitivity in NPC cells, leading to cellular apoptosis and increased expression of the proapoptotic factors BAX and caspase-3. Similarly, RIG-I knockdown in NPC cells promoted chemoradiotherapy resistance and reduced apoptosis. Analysis of microarray data indicated that the expression of IFN/JAK2 and endoplasmic reticulum (ER) stress response markers, such as JAK2, STAT1, IRF9, IFNB1, IRF3, p-IRF3, XBP1, ATF6, IFIT2, and ISG15, was inhibited in chemoradiotherapy-resistant cells compared with that in sensitive cells. Conversely, activation of IFN/JAK2 and ER stress response pathways in NPC cells reduced paclitaxel resistance and increased apoptosis. RIG-I promotes IFN/JAK2 and ER stress response-mediated apoptosis to inhibit chemoradiation resistance in nasopharyngeal carcinoma.

EIF2A promotes cell survival during paclitaxel treatment in vitro and in vivo.

The integrated stress response (ISR) is critical for cancer cell survival during stress stimuli and has been implicated in the resistance to cancer therapeutics, in which the mechanism, however, is poorly understood. Here, we showed that paclitaxel, the major chemotherapy drug for breast cancer, induced ISR and phosphorylated ser51 residue of EIF2S1 by EIF2AK3 and EIF2AK4. When exposed to paclitaxel, cancer cells activated the EIF2AK3/EIF2AK4-pEIF2S1-ATF4 axis and maintained redox homoeostasis by inducing expression of the major antioxidant enzymes HMOX1, SHMT2 and SLC7A11. Paclitaxel-mediated cell death was significantly increased following loss of ISR or ATF4 expression. This sensitizing effect could be partially rescued by Trolox, a ROS scavenger. We demonstrated that the alternative initiation factor EIF2A was essential for cancer cell survival after paclitaxel-mediated ISR both in vitro and in vivo. Moreover, patients with breast cancer exhibited higher ISR after chemotherapy, and the elevated mRNA levels of HMOX1, SHMT2 and EIF2A were correlated with poor prognosis. Collectively, our findings reveal a novel mechanism for paclitaxel resistance and suggest that targeting EIF2A combined with ISR agonist may be a potential treatment regimen to overcome drug resistance for breast cancer.

Downregulation of Fat Mass and Obesity Associated (FTO) Promotes the Progression of Intrahepatic Cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (ICC) ranks as the second most malignant type of primary liver cancer with a high degree of incidence and a very poor prognosis. Fat mass and obesity-associated protein (FTO) functions as an eraser of the RNA m6A modification, but its roles in ICC tumorigenesis and development remain unknown. We showed here that the protein level of FTO was downregulated in clinical ICC samples and cell lines and that FTO expression was inversely correlated with the expression of CA19-9 and micro-vessel density (MVD). A Kaplan-Meier survival analysis showed that a low expression of FTO predicted poor prognosis in ICC. in vitro, decreased endogenous expression of FTO obviously reduced apoptosis of ICC cells. Moreover, FTO suppressed the anchorage-independent growth and mobility of ICC cells. Through mining the database, FTO was found to regulate the integrin signaling pathway, inflammation signaling pathway, epidermal growth factor receptor (EGFR) signaling pathway, angiogenesis, and the pyrimidine metabolism pathway. RNA decay assay showed that oncogene TEAD2 mRNA stability was impaired by FTO. In addition, the overexpression of FTO suppressed tumor growth in vivo. In conclusion, our study demonstrated the critical roles of FTO in ICC.