Reduced RKIP enhances nasopharyngeal carcinoma radioresistance by increasing ERK and AKT activity

Targeting the RAS/RAF/MAPK pathway for cancer therapy: from mechanism to clinical studies

Metastatic dissemination of solid tumors, a leading cause of cancer-related mortality, underscores the urgent need for enhanced insights into the molecular and cellular mechanisms underlying metastasis, chemoresistance, and the mechanistic backgrounds of individuals whose cancers are prone to migration. The most prevalent signaling cascade governed by multi-kinase inhibitors is the mitogen-activated protein kinase (MAPK) pathway, encompassing the RAS-RAF-MAPK kinase (MEK)-extracellular signal-related kinase (ERK) pathway. RAF kinase is a primary mediator of the MAPK pathway, responsible for the sequential activation of downstream targets, such as MEK and the transcription factor ERK, which control numerous cellular and physiological processes, including organism development, cell cycle control, cell proliferation and differentiation, cell survival, and death. Defects in this signaling cascade are associated with diseases such as cancer. RAF inhibitors (RAFi) combined with MEK blockers represent an FDA-approved therapeutic strategy for numerous RAF-mutant cancers, including melanoma, non-small cell lung carcinoma, and thyroid cancer. However, the development of therapy resistance by cancer cells remains an important barrier. Autophagy, an intracellular lysosome-dependent catabolic recycling process, plays a critical role in the development of RAFi resistance in cancer. Thus, targeting RAF and autophagy could be novel treatment strategies for RAF-mutant cancers. In this review, we delve deeper into the mechanistic insights surrounding RAF kinase signaling in tumorigenesis and RAFi-resistance. Furthermore, we explore and discuss the ongoing development of next-generation RAF inhibitors with enhanced therapeutic profiles. Additionally, this review sheds light on the functional interplay between RAF-targeted therapies and autophagy in cancer.

Raf kinase inhibitor protein combined with phosphorylated extracellular signal-regulated kinase offers valuable prognosis in gastrointestinal stromal tumor

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Tyrosine kinase inhibitors, such as imatinib, have been used as first-line therapy for the treatment of GISTs. Although these drugs have achieved considerable efficacy in some patients, reports of resistance and recurrence have emerged. Extracellular signal-regulated kinase 1/2 (ERK1/2) protein, as a member of the mitogen-activated protein kinase (MAPK) family, is a core molecule of this signaling pathway. Nowadays, research reports on the important clinical and prognostic value of phosphorylated-ERK (P-ERK) and phosphorylated-MAPK/ERK kinase (P-MEK) proteins closely related to raf kinase inhibitor protein (RKIP) have gradually emerged in digestive tract tumors such as gastric cancer, colon cancer, and pancreatic cancer. However, literature on the expression of these downstream proteins combined with RKIP in GIST is scarce. This study will focus on this aspect and search for answers to the problem.

AIM

To detect the expression of RKIP, P-ERK, and P-MEK protein in GIST and to analyze their relationship with clinicopathological characteristics and prognosis of this disease. Try to establish a new prognosis evaluation model using RKIP and P-ERK in combination with analysis and its prognosis evaluation efficacy.

METHODS

The research object of our experiment was 66 pathologically diagnosed GIST patients with complete clinical and follow-up information. These patients received surgical treatment at China Medical University Affiliated Hospital from January 2015 to January 2020. Immunohistochemical method was used to detect the expression of RKIP, P-ERK, and P-MEK proteins in GIST tissue samples from these patients. Kaplan-Meier method was used to calculate the survival rate of 63 patients with complete follow-up data. A Nomogram was used to represent the new prognostic evaluation model. The Cox multivariate regression analysis was conducted separately for each set of risk evaluation factors, based on two risk classification systems [the new risk grade model vs the modified National Institutes of Health (NIH) 2008 risk classification system]. Receiver operating characteristic (ROC) curves were used for evaluating the accuracy and efficiency of the two prognostic evaluation systems.

RESULTS

In GIST tissues, RKIP protein showed positive expression in the cytoplasm and cell membrane, appearing as brownish-yellow or brown granules. The expression of RKIP was related to GIST tumor size, NIH grade, and mucosal invasion. P-ERK protein exhibited heterogeneous distribution in GIST cells, mainly in the cytoplasm, with occasional presence in the nucleus, and appeared as brownish-yellow granules, and the expression of P-ERK protein was associated with GIST tumor size, mitotic count, mucosal invasion, and NIH grade. Meanwhile, RKIP protein expression was negatively correlated with P-ERK expression. The results in COX multivariate regression analysis showed that RKIP protein expression was not an independent risk factor for tumor prognosis. However, RKIP combined with P-ERK protein expression were identified as independent risk factors for prognosis with statistical significance. Furthermore, we establish a new prognosis evaluation model using RKIP and P-ERK in combination and obtained the nomogram of the new prognosis evaluation model. ROC curve analysis also showed that the new evaluation model had better prognostic performance than the modified NIH 2008 risk classification system.

CONCLUSION

Our experimental results showed that the expression of RKIP and P-ERK proteins in GIST was associated with tumor size, NIH 2008 staging, and tumor invasion, and P-ERK expression was also related to mitotic count. The expression of the two proteins had a certain negative correlation. The combined expression of RKIP and P-ERK proteins can serve as an independent risk factor for predicting the prognosis of GIST patients. The new risk assessment model incorporating RKIP and P-ERK has superior evaluation efficacy and is worth further practical application to validate.

Tumor-suppressive E3 ubiquitin ligase CHIP inhibits the PBK/ERK axis to repress stem cell properties and radioresistance in non-small cell lung cancer

Recently, radioresistant cancer cells surviving radiotherapy have been suggested to show more aggressive phenotypes than parental cells, and the underlying mechanisms may be associated with cancer stem cells. This study provided novel mechanistic insights for E3 ubiquitin ligase CHIP in stem cell properties and radioresistance of non-small cell lung cancer (NSCLC). After bioinformatic prediction for key genes involved, NSCLC tissues and cells were collected to measure the expression of CHIP and PBK. E3 ubiquitin ligase CHIP was poorly expressed, while PBK was highly expressed in NSCLC tissues and cells. CHIP reduced the protein stability of PBK through the ubiquitin-protease pathway to repress the activation of ERK pathway. Based on the gain- or loss-of-function experiments, it was noted that restoration of CHIP curtailed stem cell properties and radioresistance in NSCLC, as manifested by inhibited sphere formation and cell proliferation, decreased number of CD133⁺CD44⁺ cells and expression of OCT4, SOX2, and NANOG, as well as facilitated apoptosis of NSCLC cells. Besides, in vivo animal experiments further confirmed that CHIP restrained tumorigenic ability and improved radiosensitivity of NSCLC cells by inhibiting PBK/ERK axis. Collectively, CHIP suppressed stem cell properties and radioresistance of NSCLC cells by inhibiting PBK/ERK axis, therefore offering a potential therapeutic target for enhancing efficacy of radiotherapy.

Regulation on tumor metastasis by Raf kinase inhibitory protein: New insight with reactive oxygen species signaling

Targeted therapy aiming at the metastatic signal pathway, such as that triggered by receptor tyrosine kinase (RTK), for the prevention of tumor progression is promising. However, RTK-based targeted therapy frequently suffered from drug resistance due to the co-expression of multiple growth factor receptors that may raise compensatory secondary signaling and acquired mutations after treatment. One alternative strategy is to manipulate the common negative regulators of the RTK signaling. Among them, Raf kinase inhibitory protein (RKIP) is highlighted and focused on this review. RKIP can associate with Raf-1, thus suppressing the downstream mitogen-activated protein kinase (MAPK) cascade. RKIP also negatively regulates other metastatic signal molecules including NF-κB, STAT3, and NOTCH1. In general, RKIP achieves this task via associating and blocking the activity of the critical molecules on upstream of the aforementioned pathways. One novel RKIP-related signaling involves reactive oxygen species (ROS). In our recent report, we found that PKCδ-mediated ROS generation may interfere with the association of RKIP with heat shock protein 60 (HSP60)/MAPK complex via oxidation of HSP60 triggered by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. The departure of RKIP may impact the downstream MAPK in two aspects. One is to trigger the Mt→cytosol translocation of HSP60 coupled with MAPKs. The other is to change the conformation of HSP60, favoring more efficient activation of the associated MAPK by upstream kinases in cytosol. It is worthy of investigating whether various RTKs capable of generating ROS can drive metastatic signaling via affecting RKIP in the same manner.

Investigation of Marine-Derived Natural Products as Raf Kinase Inhibitory Protein (RKIP)-Binding Ligands

Raf kinase inhibitory protein (RKIP) is an essential regulator of the Ras/Raf-1/MEK/ERK signaling cascade and functions by directly interacting with the Raf-1 kinase. The abnormal expression of RKIP is linked with numerous diseases including cancers, Alzheimer's and diabetic nephropathy. Interestingly, RKIP also plays an indispensable role as a tumor suppressor, thus making it an attractive therapeutic target. To date, only a few small molecules have been reported to modulate the activity of RKIP, and there is a need to explore additional scaffolds. In order to achieve this objective, a pharmacophore model was generated that explores the features of locostatin, the most potent RKIP modulator. Correspondingly, the developed model was subjected to screening, and the mapped compounds from Marine Natural Products (MNP) library were retrieved. The mapped MNPs after ensuing drug-likeness filtration were escalated for molecular docking, where locostatin was regarded as a reference. The MNPs exhibiting higher docking scores than locostatin were considered for molecular dynamics simulations, and their binding affinity towards RKIP was computed via MM/PBSA. A total of five molecules revealed significantly better binding free energy scores than compared to locostatin and, therefore, were reckoned as hits. The hits from the present in silico investigation could act as potent RKIP modulators and disrupt interactions of RKIP with its binding proteins. Furthermore, the identification of potent modulators from marine natural habitat can act as a future drug-discovery source.

AKR1B10 confers resistance to radiotherapy via FFA/TLR4/NF-κB axis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is one kind of human head and neck cancers with high incidence in Southern China, Southeast Asia and North Africa. In spite of great innovations in radiation and chemotherapy treatments, the 5-year survival rate is not satisfactory. One of the main reasons is resistance to radiotherapy which leads to therapy failure and recurrence of NPC. The mechanism underlying remains to be fully elucidated. Aldo-keto reductase B10 (AKR1B10) plays a role in the formation and development of carcinomas. However, its role in resistance to radiotherapy of NPC is not clear. In this research, the relationships between AKR1B10 expression and the treatment effect of NPC patients, NPC cell survival, cell apoptosis, and DNA damage repair, as well as the effect and mechanism of AKR1B10 expression on NPC radioresistance were explored. A total of 58 paraffin tissues of NPC patients received radiotherapy were collected including 30 patients with radiosensitivity and 28 patients with radioresistance. The relationships between AKR1B10 expression and the treatment effect as well as clinical characteristics were analyzed by immuno-histochemical experiments, and the roles of AKR1B10 in cell survival, apoptosis and DNA damage repair were detected using the AKR1B10 overexpressed cell models. Furthermore the mechanism of AKR1B10 in NPC radioresistance was explored. Finally, the radioresistance effect of AKR1B10 expression was evaluated by the tumor xenograft model of nude mice and the method of radiotherapy. The results showed AKR1B10 expression level was correlated with radiotherapy resistance, and AKR1B10 overexpression promoted proliferation of NPC cells, reduced apoptosis and decreased cellular DNA damage after radiotherapy. The probable molecular mechanism is that AKR1B10 expression activated FFA/TLR4/NF-κB axis in NPC cells. This was validated by using the TLR4 inhibitor TAK242 to treat NPC cells with AKR1B10 expression, which reduced the phosphorylation of NF-κB. This study suggests that AKR1B10 can induce radiotherapy resistance and promote cell survival via FFA/TLR4/NF-κB axis in NPC, which may provide a novel target to fight against radiotherapy resistance of NPC.

GPR120 promotes radiation resistance in esophageal cancer via regulating AKT and apoptosis pathway

The aim of the study is to investigate the role of GPR120 on the biological behavior of esophageal cancer cells in the setting of radiation and explore the mechanism. GPR120 knockdown was fulfilled by siRNA-mediated effects in two esophageal cancer cell lines Eca109 and EC9706. Colony formation, survival fraction calculation, viable cell evaluation by cell counting kit-8 assay and cell apoptosis analysis by phycoerythrin annexin V and 7-amino-actinomycin (7-AAD) staining and the flow cytometry examination was evaluated in Eca109 and EC9706 under the treatment of different radiation dosage. The mechanisms were explored by the evaluation of the Akt pathway and apoptosis protein level. Significantly decreased GPR120 mRNA and protein after GPR120 siRNA treatment compared to control siRNA treatment. Significantly decreased colony formation was found in GPR120 siRNA-treated Eca109 and EC9706 cells compared to control siRNA-treated cells at the radiation dosage of 2, 4, 6 and 8 Gy. Moreover, decreased survival fraction number with increased sensitive enhancing ratio was also found in GPR120 siRNA-treated Eca109 and EC9706 cells compared to control siRNA-treated cells. Decreased cell viability and increased cell apoptosis in GPR120 siRNA-treated esophageal cancer cells. GPR120 siRNA decreased the Akt phosphorylation and anti-apoptotic Bcl-2 expression level, but increased pro-apoptotic Bim expression level in esophageal cancer cell lines. GPR120 regulated the biological behavior of the esophageal cancer cells via affecting Akt pathway and apoptosis molecules. Moreover, GPR120 siRNA combined radiation treatment could be a therapeutic choice for esophageal cancer.

Label-free quantitative mass spectrometry from formalin-fixed paraffin-embedded samples of nasopharyngeal carcinoma: Preliminary results from a non-endemic European cohort of patients

Aim

Report our results of biomarker discovery in formalin-fixed paraffin-embedded (FFPE) nasopharyngeal carcinoma (NPC) via proteomic analysis.

Background

Nasopharyngeal carcinoma (NPC) is a rare cancer in Western countries. Proteomic analysis have already been reported as a useful tool to provide biomarkers. Formalin-fixed paraffin-embedded (FFPE) samples, despite largely underused, can provide invaluable information for biomarker research via proteomic analysis.

Methods

FFPE samples of NPC were submitted to protein extraction followed by FASP-digestion and label-free quantitative mass spectrometry (MS). Patients' received concurrent chemoradiation with or without adjuvant chemotherapy as per Intergroup 0099 trial. IMRT was delivered following the RTOG0615 specifications. Toxicity was scored using the CTCAE 4.03 tables. Survival was estimated using Kaplan-Meier curves. Log-rank was used to detect differences. KEGG ontology graphics were generated.

Results

28 FFPE samples from NPC patients were used. Patients were: 79% male, 97% Caucasians, 86% WHO type 3, 40% T1, 10% T2, 25% T3, and 25% T4. With a median follow up of 37 months, local control was 83 (T1, 100% T2, T3 and T4), overall survival was 84%, and six patients developed distant metastases. All five patients that died were due to metastatic disease. Tumor samples contained a median of 75% of tumor material. We found Epstein-Barr (EBV) and Herpes simplex (HSV) viruses' related proteins significantly present in early-stage primary NPC (T1 and T2, p < 0.01). A pool of 10 proteins was statistically up-regulated in the metastatic group of patients (p < 0.01). Median survival from this M1 group was <1 year (p < 0.001).

Conclusions

FFPE samples yielded adequate material for MS analysis. We found EBV and HSV related proteins on early-stage NPC, and proteomic profiling associated with distant metastases, potential candidates of disease biomarkers. Validation is needed.

Downregulation of RKIP promotes radioresistance of nasopharyngeal carcinoma by activating NRF2/NQO1 axis via downregulating miR-450b-5p

Dysregulation of RKIP and NRF2 has been widely involved in the therapy resistance of multiple malignances, however, their relation and the corresponding mechanisms, especially in radiation response, have not been elucidated. In this study, we revealed that RKIP could negatively regulate the expression of NRF2 in nasopharyngeal carcinoma (NPC) cells. Depletion or ectopic expression of NRF2 countered the pro- or anti- radioresistant effects of RKIP knockdown or overexpression on NPC cells, respectively, both in vitro and in vivo. Furthermore, our results indicated that NQO1 was positively regulated by NRF2 and served as the downstream effector of RKIP/NRF2 axis in regulation of NPC radioresistance. Mechanistically, miR-450b-5p, being positively regulated by RKIP in NPC cells, could sensitize NPC cells to irradiation by directly targeting and suppressing the level of NRF2. Besides, we analyzed the level of aforementioned molecules in NPC tissues. The results indicated that RKIP was significantly downregulated, NRF2 and NQO1 were notably upregulated in NPC tissues compared with in normal nasopharyngeal mucosa (NNM) tissues. Furthermore, RKIP and miR-450b-5p were remarkably lower, yet NRF2 and NQO1 were notably higher, in radioresistant NPC tissues relative to in radiosensitive NPC tissues. Consistent with the pattern in NPC cells, the RKIP/miR-450b-5p/NRF2/NQO1 axis was significantly correlated in NPC tissues. Downregulation of RKIP and miR-450b-5p, and upregulation of NRF2 and NQO1, positively correlated to malignant pathological parameters such as primary T stage, Lymph node (N) metastasis, and TNM stage. Finally, RKIP and miR-450b-5p served as favorable prognostic indicators, and NRF2 and NQO1 acted as unfavorable prognostic biomarkers in patients with NPC. Collectively, our outcomes reveal that RKIP downregulation promotes radioresistance of NPC by downregulating miR-450b-5p and subsequently upregulating and activating NRF2 and NQO1, highlighting RKIP/miR-450b-5p/NRF2/NQO1 axis as a potential therapeutic target for improving the radiosensitivity of NPC.

Multiple Mechanisms Involving in Radioresistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is the malignant tumor with ethnic and geographical distribution preference. Although intensity-modulated radiotherapy (IMRT)-based radiotherapy combined with chemotherapy and targeted therapy has dramatically improved the overall survival of NPC patients, there are still some patients suffering from recurrent tumors and the prognosis is poor. Multiple mechanisms may be responsible for radioresistance of NPC, such as cancer stem cells (CSCs) existence, gene mutation or aberrant expression of genes, epigenetic modification of genes, abnormal activation of certain signaling pathways, alteration of tumor microenvironment, stress granules (SGs) formation, etc. We conduct a comprehensive review of the published literatures focusing on the causes of radioresistance, retrospect the regulation mechanisms following radiation, and discuss future directions of overcoming the resistance to radiation.

Elevated IL18 levels in Nasopharyngeal carcinoma induced PD-1 expression on NK cells in TILS leading to poor prognosis

OBJECTIVES

Characterisation of tumor-infiltrating lymphocytes (TILS) population for cancer prognostication has enabled deeper understanding of tumor immune interactions in cancer immunology. We aim to examine the significance of both the density and functional status of NK cells in a cohort of Epstein Barr Virus (EBV) associated Nasopharyngeal Cancer (NPC) patients.

METHODS

NK TILS of 50 NPC samples were quantified on immunohistochemistry and the density of NK TILS was correlated with clinical outcomes. Next, NK cells and a panel of cytokines of 10 newly diagnosed NPC patients were characterized in both NPC tissue and peripheral circulation. Exhausted NK cells were identified using co-expression of PD-1 and/or Tim-3. Comparison of percentage of NK cells in NPC and healthy controls was performed using student t-test for two groups; and a p value of less than 0.05 values was considered significant.

RESULTS

NK TILS exhibited a bimodal distribution; with the NK^high cohort demonstrating a poorer 2-year overall survival rate (p < 0.035). In-vitro studies revealed a higher proportion of infiltrated NK cells in the NK^high cohort co-expressed PD-1. Additionally, IL-18 levels in NPC tissue were significantly higher than in healthy nasopharynx; and IL-18 alone induced PD-1 expression on NK cells. Expectedly, plasma IL-18 concentration and percentage of circulating PD-1-expressing NK cells were similar among NPC patients and healthy controls.

CONCLUSION

The cytotoxic function of NK TILS is mitigated by an elevated IL-18 levels within the NPC microenvironment. Hence, the functional status, and the density of NK cells in TILS should be considered when prognosticating NPC.

miR-181a Upregulation Promotes Radioresistance of Nasopharyngeal Carcinoma by Targeting RKIP

Background

Radioresistance is the leading cause of treatment failure for nasopharyngeal carcinoma (NPC). Therefore, screening the critical regulators in radioresistance and revealing the underlying mechanisms is imperative for improvement of therapeutical efficacy in NPC.

Materials and methods

Our previous study has proved that miR-181a may serve as a pro-radioresistant miRNA. In this study, we explored the expression of miR-181a in NPC, especially in radioresistant NPC samples, by qPCR. Moreover, the clinical significance of miR-181a level was also analyzed. Furthermore, the functions of miR-181a, both in vitro and in vivo, were detected via a serial of assays such as CCK-8, plate clone survival, apoptosis, and xenograft tumor model. The downstream target of miR-181a was also validated by dual luciferase reporter assay and the roles of miR-181a’s target in the regulation of NPC radioresistance were investigated.

Results

The results revealed that miR-181a was significantly upregulated in NPC, especially in radioresistant NPC. MiR-181a level is positively correlated to lymph node metastasis and advanced TNM stages and negatively associated with overall survival rate in NPC. Ectopic expression of miR-181a in radiosensitive NPC cells, or overexpression of miR-181a inhibitor in radioresistant NPC cells, could enhance or impair the radioresistance of NPC cells supported by the results from both in vitro and in vivo, respectively. Mechanistically, dual luciferase report assay indicated that miR-181a could directly target RKIP. Moreover, both in vitro and in vivo experimental outcomes indicated that RKIP restoration and knockdown could antagonize the effects of miR-181a and miR-181a inhibitor in the regulation of NPC radioresistance.

Conclusion

Collectively, the findings of this study proved that miR-181a is upregulated and promotes radioresistance by targeting RKIP in NPC. Targeting miR-181a/RKIP axis may be a valid path for reinforcing radiosensitivity and eventually improving the outcomes of clinical treatment in NPC.

IGF-1R Inhibition Suppresses Cell Proliferation and Increases Radiosensitivity in Nasopharyngeal Carcinoma Cells

Although ionizing radiation (IR) has provided considerable improvements in nasopharyngeal carcinoma (NPC) treatment, radioresistance is still a major threat for some subsets of patients. The insulin-like growth factor-1 receptor (IGF-1R) signaling pathway is tightly regulated and plays critical roles in mediating cell proliferation, growth, and survival. Thus, IGF-1R may be a potential therapeutic target for patients with different malignancies. However, its mechanism in NPC is not fully investigated. Linsitinib is an oral small molecule and is a tyrosine kinase inhibitor (TKI) of IGF-1R, which has been known for antitumor effects used widely. Here, we evaluated the proliferation and radiosensitivity of NPC cell lines (CNE-2 and SUNE-1) after linsitinib treatment. We found that linsitinib suppresses IGF-1-induced cell proliferation through inhibiting Akt and ERK phosphorylation. Moreover, linsitinib further boosted IR-induced DNA damage, G2-M cell cycle delay, and apoptosis in NPC cells. Finally, linsitinib reversed radioresistant NPC cells by decreasing the phosphorylation of IGF-1R. Our data indicated that the combination of linsitinib and IR and targeting IGF-1R by linsitinib could be a promising therapeutic strategy for NPC.

Differential Activation of ERK Signaling in HPV-Related Oropharyngeal Squamous Cell Carcinoma

Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC) forms a distinct tumor entity with better survival clinical outcome. Numerous underlying molecular mechanisms have been postulated for differences in treatment response, but the impact of MEK/ERK signaling, a main driver of carcinogenesis in various cancers including OPSCC and key player mediating therapy resistance remains elusive. In a retrospective experimental cohort study, primary tumor samples from OPSCC patients (n = 124) were available on tissue microarrays (TMAs) and expression levels of phosphorylated ERK1/2 (pERK1/2) were detected by immunohistochemical staining. Correlations of pERK1/2 expression patterns with clinicopathological features and clinical outcome were evaluated by statistical analysis. A low pERK1/2 expression was strongly associated with HPV-related OPSCC, while primary tumors with high pERK1/2 staining showed a distinctly worse survival outcome and were associated with higher cellular differentiation. Co-activation of both ERK1/2 and AKT was a common event and was associated with unfavorable prognosis in our cohort. However, the combinatorial analysis of pAKT (Ser473) and pERK1/2 did not strengthen the predictive power of pERK1/2, suggesting that pERK1/2 plays a more significant function in OPSCC. In summary, our data provide a compelling experimental and statistical evidence that low levels of tumor cell intrinsic ERK1/2 activation contribute at least in part to the favorable outcome of HPV-related OPSCC. On the other hand, presented findings indicate that non-HPV-related OPSCC with elevated ERK phosphorylation are at high risk for treatment failure and might benefit from targeted therapy of MEK/ERK signaling.

miRNA-17 promotes nasopharyngeal carcinoma radioresistance by targeting PTEN/AKT

Radioresistance remains a challenge during nasopharyngeal carcinoma (NPC) radiotherapy. Numerous studies suggest that the miRNAs may play important roles in the regulation of radioresistance. miRNA-17-5p, which is located within the miR-17-92a cluster, could modulate tumor progression in different tissues by targeting multiple tumor associated genes. However, whether it is correlated with the radioresistance of tumor cells has not yet been elucidated. In our study, we have observed increasing miR-17-5p expression in radioresistant NPC tissues. The functional experiments suggested that miR-17-5p could clearly promote NPC cell proliferation and the cell cycle even after X-ray irradiation. Irradiation leads to tumor cell damage and death via ROS generation. The overexpression of miR-17-5p could protect NPC cells from apoptosis induced by irradiation. In addition, an in vivo experiment indicated that miR-17-5p promoted tumor growth with radiotherapy using the xenograft tumor model. A bioinformatics analysis and reporter assay were carried out to demonstrate that PTEN, which is a key regulator of AKT phosphorylation, is a target of miR-17-5p. The overexpression of miR-17-5p directly suppresses the mRNA and protein expression of PTEN. In addition, the rescue experiments showed that the AKT inhibitor can diminish the proliferation, promotion, and apoptosis inhibition effects on radioresistant NPC cells mediated by miR-17-5p. In conclusion, our findings demonstrated that miR-17-5p can enhance the radioresistance of NPC through the PTEN/AKT pathway, which is a biomarker of radioresistant NPC and a potential target for new therapeutic strategies.

RNA binding motif protein 3 (RBM3) drives radioresistance in nasopharyngeal carcinoma by reducing apoptosis via the PI3K/AKT/Bcl-2 signaling pathway

Radioresistance is an important obstacle to nasopharyngeal carcinoma (NPC) therapy. In this study, we explored the role of RNA-binding motif protein 3 (RBM3) in the radioresistance of NPC and its underlying mechanism. We measured the expression of RBM3 in 20 clinical NPC tissues and in NPC cell lines. We found that RBM3 was upregulated in radioresistant NPC tissues and cells. Radioresistant NPC cells (CNE1/IR) and parental NPC cells (CNE1) were subjected to RBM3-shRNA knockdown and RBM3 overexpression, respectively. RBM3 depletion in CNE1/IR cells sensitized cells to radiotherapy, increased DNA damage, and accelerated the rate of apoptosis. In contrast, RBM3 overexpression in CNE1 cells significantly enhanced radioresistance and reduced the rate of apoptosis. Additionally, radioresistance conferred by RBM3 was attributed to the activation of the AKT/Bcl-2 signaling pathway and reduction of caspase 3. Inhibition of AKT signaling attenuated RBM3-mediated radioresistance. Furthermore, RBM3 directly interacted with PI3K subunit p85 in NPC cell lines. Altogether, our data demonstrate that RBM3 enhances radioresistance by inhibiting the apoptotic response to radiotherapy through the PI3K/AKT/Bcl-2 signaling pathway. RBM3 may serve as a novel factor for predicting radioresistance and as a molecular target in the treatment of NPC.

CAV3.1 knockdown suppresses cell proliferation, migration and invasion of prostate cancer cells by inhibiting AKT

Background

Aberrant expression of CAV3.1, one of T-type Ca²⁺ channels, is reported to exert important functions in pathological processes, including carcinogenesis. However, its expression pattern and function in prostate cancer (PCa) remains unclear.

Materials and methods

The expression pattern of CAV3.1 was analyzed in multiple ways, including online analysis in Oncomine database, experimental analyses in cell lines, and collected clinical specimens using immunohistochemistry, quantitative reverse transcription polymerase chain reaction, and Western blot. Then, CAV3.1 was downregulated in PCa cells to explore its functions.

Results

Upregulated CAV3.1 in PCa tissues and cells was confirmed by analyzing mRNA expression datasets from Oncomine and quantitative reverse transcription polymerase chain reaction detection, respectively. Accordingly, significantly higher CAV3.1 protein level in PCa tissues specimens than that in benign prostatic hyperplasia tissues was indicated by immunohistochemical staining. In addition, CAV3.1 upregulation was positively associated with metastasis. Depletion of CAV3.1 impaired the proliferation, migration, and invasion ability of PCa cells demonstrating by cell functional experiments, such as CCK-8, cell cycle distribution, plate clone formation, scratch wound healing, and transwell invasion assays. Mechanistically, due to constrained Akt activity, CAV3.1 knockdown resulted in decreased level of CCND1, N-cadherin, and Vimentin, and increased level of E-cadherin whose expressions could be reversed by ectopic Akt expression. Similarly, ectopic Akt expression also rescued the inhibitory effects of CAV3.1 knockdown on cell functions like proliferation and migration in PCa cells.

Conclusion

Upregulated CAV3.1 is positively associated with the development of PCa. CAV3.1 knockdown can inhibit PCa cell proliferation, migration, and invasion by suppressing AKT activity.

RKIP: A Key Regulator in Tumor Metastasis Initiation and Resistance to Apoptosis: Therapeutic Targeting and Impact

RAF-kinase inhibitor protein (RKIP) is a well-established tumor suppressor that is frequently downregulated in a plethora of solid and hematological malignancies. RKIP exerts antimetastatic and pro-apoptotic properties in cancer cells, via modulation of signaling pathways and gene products involved in tumor survival and spread. Here we review the contribution of RKIP in the regulation of early metastatic steps such as epithelial–mesenchymal transition (EMT), migration, and invasion, as well as in tumor sensitivity to conventional therapeutics and immuno-mediated cytotoxicity. We further provide updated justification for targeting RKIP as a strategy to overcome tumor chemo/immuno-resistance and suppress metastasis, through the use of agents able to modulate RKIP expression in cancer cells.

MIIP gene expression is associated with radiosensitivity in human nasopharyngeal carcinoma cells

The present study aims to investigate the radiosensitization effect of the migration and invasion inhibitory protein (MIIP) gene on nasopharyngeal carcinoma (NPC) cells. The MIIP gene was transfected into NPC 5-8F and CNE2 cells. The level of MIIP was analyzed by quantitative reverse transcription-polymerase chain reaction analysis and western blot. The changes in radiosensitivity of the cells were analyzed by colony formation assay. The changes in cell apoptosis and cycle distribution following irradiation were detected by flow cytometry. The expression of BCL2 associated X, apoptosis regulator/B-cell lymphoma 2 was evaluated using western blot. DNA damage was analyzed by counting γ-H2AX foci. The expression levels of γ-H2AX were evaluated by immunofluorescence and western blot. In a previous study by the authors, the results indicated that the expression of MIIP gene evidently increased in MIIP-transfected 5-8F (5-8F OE) and MIIP-transfected CNE2 (CNE2 OE) cells compared with the parental or negative control cells. In the present study, the survival rate of 5-8F OE and CNE2 OE cells markedly decreased following irradiation (0, 2, 4, 6 and 8 Gy) compared with the negative control (5-8F NC and CNE2 NC) and the untreated (5-8F and CNE2) groups. The expression of MIIP was able to increase apoptosis, which resulted in G2/M cell cycle arrest and DNA damage repair was attenuated in 5-8F and CNE2 cells following irradiation as measured by the accumulation of γ-H2AX. It was indicated that MIIP expression is associated with the radiosensitivity of NPC cells and has a significant role in regulating cell radiosensitivity.

Cofilin-2 Acts as a Marker for Predicting Radiotherapy Response and Is a Potential Therapeutic Target in Nasopharyngeal Carcinoma

Background

The purpose of this study was to determine whether cofilin-2 could serve as a protein marker for predicting radiotherapy response and as a potential therapeutic target in nasopharyngeal carcinoma (NPC).

Material/Methods

Cofilin-2 protein levels in serum and tissue samples from patients with NPC were assessed by sandwich ELISA and IHC. In vitro, cofilin-2 levels in CNE-2R cells were significantly higher than those of CNE-2 cells. Meanwhile, CNE-2R cells were silenced for cofilin-2 to obtain a stable cofilin-2-RNAi-LV3 cell line. Then, cell proliferation, radiosensitivity, invasion and migration abilities, cell cycle, and apoptosis were evaluated by Cell Counting Kit 8 assay (CCK-8), flow cytometry (FCM), clone formation assay, and in vitro.

Results

The secreted levels of the cofilin-2 protein in radioresistant NPC patients were significantly higher than those of radiosensitive cases. After cofilin-2 knockdown in nasopharyngeal carcinoma CNE-2R cells, proliferation was decreased, while apoptosis and radiosensitivity were enhanced; cell cycle distribution was altered, and the transplanted tumors in nude mice grew significantly less.

Conclusions

Overall, our findings suggest that cofilin-2 acts as a marker for predicting radiotherapy response and is a potential therapeutic target in nasopharyngeal carcinoma.

Sphingosine kinase 1 is a potential therapeutic target for nasopharyngeal carcinoma

Sphingosine kinase 1 (SPHK1) has been shown to be involved in the progression of various types of human cancers. We previously demonstrated that SPHK1 is overexpressed and associated with clinical stage, locoregional recurrence, distant metastasis and poor prognosis in nasopharyngeal carcinoma (NPC). However, the biological roles involving SPHK1 and its potential usefulness as a therapeutic target in NPC remain unknown. In this study, Blocking SPHK1 using siRNA or FTY720 (a SPHK1 inhibitor) significantly reduced proliferation and migration and increased cell cycle arrest and apoptosis in NPC cells. FTY720 also decreased SPHK1 activity, and overexpressing SPHK1 abrogated the FTY720-induced effects on cell viability. In addition, FTY720 sensitized NPC cells to radiotherapy by inhibiting SPHK1 activity in vitro and in vivo. Furthermore, high SPHK1 expression was associated with increased Ki-67 and p-Akt and decreased caspase-3 expression in human NPC specimens. These data suggest that SPHK1 might be a potential therapeutic target for NPC.

Long non-coding RNA PVT1 predicts poor prognosis and induces radioresistance by regulating DNA repair and cell apoptosis in nasopharyngeal carcinoma

The long non-coding RNA, plasmacytoma variant translocation 1 (PVT1), is highly expressed in a variety of tumors, and is believed to be a potential oncogene. However, the role and mechanism of action of PVT1 in the carcinogenesis and progression of nasopharyngeal carcinomas (NPCs) remains unclear. In this study, for the first time, we have discovered that PVT1 shows higher expression in NPCs than in normal nasopharyngeal epithelial tissue, and patients with NPCs who show higher expression of PVT1 have worse progression-free and overall survivals. Additionally, we observed that the proliferation of NPC cells decreased, and their rate of apoptosis increased; these results indicated that the knockdown of PVT1 expression in the NPC cells induced radiosensitivity. Further, we have shown that the knockdown of PVT1 expression can induce apoptosis in the NPC cells by influencing the DNA damage repair pathway after radiotherapy. In general, our study shows that PVT1 may be a novel biomarker for prognosis and a new target for the treatment of NPCs. Additionally, targeting PVT1 may be a potential strategy for the clinical management of NPC and for the improvement of the curative effect of radiation in NPCs.

RKIP reduction enhances radioresistance by activating the Shh signaling pathway in non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) is exceptionally deadly because the tumors lack sensitive early-stage diagnostic biomarkers and are resistant to radiation and chemotherapy. Here, we investigated the role and mechanism of Raf kinase inhibitory protein (RKIP) in NSCLC radioresistance. The clinical data showed that the RKIP expression level was generally lower in radioresistant NSCLC tissues than in radiosensitive tissues. Reduced RKIP expression was related to NSCLC radioresistance and poor prognosis. In vitro experiments showed that RKIP knockdown increased radioresistance and metastatic ability in NSCLC cell lines. Mechanistically, RKIP reduction activated the Shh signaling pathway by derepressing Smoothened (Smo) and initiating glioma-associated oncogene-1 (Gli1)-mediated transcription in NSCLC. In addition, the inappropriately activated Shh–Gli1 signaling pathway then enhanced cancer stem cell (CSC) expression in the cell lines. The increasing quantity of CSCs in the tumor ultimately promotes the radiation resistance of NSCLC. Together, these results suggest that RKIP plays a vital role in radiation response and metastasis in NSCLC. RKIP reduction enhances radioresistance by activating the Shh signaling pathway and initiating functional CSCs. This role makes it a promising therapeutic target for improving the efficacy of NSCLC radiation treatment.

Inhibition of HSP90 sensitizes a novel Raf/ERK dual inhibitor CY-9d in triple-negative breast cancer cells

Raf and extracellular signal-regulated kinases (ERK) are both important therapeutic targets in the mitogen-activated protein kinase (MAPK) pathway, and play crucial roles in the apoptosis resistance of breast cancer cells. In the present study, cytotoxic and apoptosis-inducing activities of the Raf/ERK dual inhibitor CY-9d were found to be restricted in triple negative breast cancer (TNBC) cells compared with ER/PR-positive cells. Based on the analysis of differentially expressed proteins using a quantitative proteomic iTRAQ method and bioinformatics analysis, HSP90 was found to identify as a potential mediator between Raf and ERK in TNBC cells. Western blotting and RNA interference suggested that down-regulated IQGAP1 can attenuate the routine Raf/MEK/ERK cascade and recruit HSP90 as a bypass pathway. Simultaneous treatment with the HSP90 inhibitor and CY-9d at sub-therapeutic doses was found to produce synergistic therapeutic and apoptosis-inducing effects in TNBC cells. Moreover, CY-9d was also found to suppress breast cancer growth, inhibit the activation of Raf/ERK, and induce mitochondrial apoptosis in vivo without remarkable toxicity. These results support the combination of HSP90 and Raf/ERK inhibitors as a potential target therapeutic strategy with enhanced tumor growth suppression, downstream pathway blockade, and greater induction of apoptosis.

Derlin-1 is a target to improve radiotherapy effect of esophageal squamous cell carcinoma

Radiotherapy is widely used for treatment of esophageal squamous cell carcinoma (ESCC). This study aimed to explore the role of Derlin-1 on the sensitivity of ESCC to radiotherapy and its underlying mechanism. We examined the clinical significance of Derlin-1 in 125 ESCC tissues. We found that Derlin-1 protein was higher in ESCC tissues than that in normal esophageal epithelial tissues. Derlin-1 overexpression was correlated with chemoradiotherapy resistance in ESCC patients and served an independent predictor for short overall survival. siRNA knockdown and plasmid transfection were carried out in ESCC cell lines. Derlin-1 depletion inhibited cell growth while its overexpression facilitated cell growth. Derlin-1 overexpression in Eca-109 cells dramatically enhanced its resistance to radiotherapy with decreased apoptosis rate. On the contrary, Derlin-1 depletion in TE-1 cell line showed the opposite effects. In addition, radioresistance conferred by Derlin-1 was attributed to its role of activating AKT/Bcl-2 signaling pathway and reducing caspase3 cleavage. Blockage of AKT signaling attenuated the role of Derlin-1 on radioresistance. Furthermore, Derlin-1 could interact with PI3K p110α in ESCC cell lines. Taken together, Our data demonstrate that Derlin-1 overexpression predicts poor prognosis and protects ESCC from irradiation induced apoptosis through PI3K/AKT/Bcl-2 signaling pathway. Derlin-1 may serve as a novel predictor for radiosentivity and a molecular target for ESCC.

EMP2 re-expression inhibits growth and enhances radiosensitivity in nasopharyngeal carcinoma

Although radiation therapy is the primary treatment for nasopharyngeal carcinoma, radioresistance remains a major obstacle to successful treatment in many cases, and the exact underlying molecular mechanisms are still ill-defined. EMP2, epithelial membrane protein-2, was a recently identified potential oncogene involved in multiple biological processes including cell migration and cell proliferation. This study was to explore the potential relationship between EMP2 expression, nasopharyngeal carcinoma genesis, and radioresistance. EMP2 expression status in 98 nasopharyngeal carcinoma clinical samples was examined by immunohistochemical staining. As a result, most of the nasopharyngeal carcinoma tumor samples were weakly or negatively stained, while paired adjacent normal tissues were moderately or strongly stained. Moreover, patients with higher expression of EMP2 had significant longer survival times. EMP2 re-expression suppresses cell growth, induces S-phase cell cycle arrest, and promotes radiosensitivity and apoptosis in nasopharyngeal carcinoma cells. These results support that loss of EMP2 is common, and its re-expression may serve as an approach to enhance radiation sensitivity in nasopharyngeal carcinoma.

Serum CD166: A novel biomarker for predicting nasopharyngeal carcinoma response to radiotherapy

The present study aimed to identify whether CD166 can be used as a biomarker for predicting the response of nasopharyngeal carcinoma (NPC) to radiotherapy. The serum concentration of CD166 in patients with NPC were detected by enzyme-linked immunosorbent assay. The secreted level of CD166 with radioresistant NPC was significantly higher than that with radiosensitive NPC. In vitro, the CD166 positive rate in the CNE2 cell membrane was significantly lower than that in the CNE2R cell membrane. The magnetic-activated cell sorting technology was used to obtain CNE-2R-CD166(+) and CNE-2R-CD166(−) cell lines. Then radiosensitivity, cell proliferation, and apoptosis were assessed using colony formation assay, cell counting kit 8 assay (CCK-8), and flow cytometry, respectively. The radiation sensitivity ratio was 1.28, indicating that the CNE2R-CD166(−) cells had a stronger radiation sensitivity. The result of CCK-8 assay indicated that the survival fraction of CNE2R-CD166(+) cells was significantly higher than that of CNE2R-CD166(−) cells. The apoptotic rate of CNE2R-CD166(+) cells was significantly lower than that of CNE2R-CD166(−) cells. Our data demonstrate that the secreted protein CD166 may be can used as a biomarker for predicting the response of NPC to radiotherapy.

SIX1 overexpression predicts poor prognosis and induces radioresistance through AKT signaling in esophageal squamous cell carcinoma

The Sineoculis homeobox homolog 1 (SIX1) protein has been found to be overexpressed in several human cancers. However, its expression pattern and biological roles in esophageal squamous cell carcinoma (ESCC) remain unexplored. This study examined the clinical significance of SIX1 in 119 ESCC tissues. It was found that SIX1 protein was upregulated in 36.9% (44/119) cases. SIX1 overexpression was an independent predictor for short survival of ESCC patients. siRNA knockdown and plasmid transfection were carried out in ESCC cell lines. SIX1 depletion inhibited cell growth, invasion, and colony formation, whereas its overexpression facilitated in vivo and in vitro cell growth, invasion, and colony formation. The apoptosis rate induced by X-ray irradiation was substantially increased by SIX1 knockdown in Eca-109 cells. Ectopic overexpression of SIX1 in TE-1 cells dramatically enhanced resistance to irradiation. Western blot analysis showed that SIX1 depletion downregulated cyclin E, matrix metalloproteinase-2 (MMP-2), Bcl-2 expression and upregulated Bim expression. SIX1 overexpression exhibited the opposite effect on these proteins. In addition, it was found that SIX1 could positively regulate extracellular signal-regulated kinase (ERK) and AKT signaling pathway. ERK inhibitor abolished the effect of SIX1 on MMP-2 expression. AKT inhibitor treatment blocked the role of SIX1 on anti-apoptotic protein Bcl-2. In conclusion, this study demonstrates that SIX1 overexpression predicts poor survival in ESCC patients and confers radioresistance through activation of AKT signaling pathways.