RACK1 promotes radiation resistance in esophageal cancer via regulating AKT pathway and Bcl-2 expression

RACK1 facilitates breast cancer progression by competitively inhibiting the binding of β-catenin to PSMD2 and enhancing the stability of β-catenin

The receptor for activated C kinase 1 (RACK1) is a key scaffolding protein with multifunctional and multifaceted properties. By mediating protein-protein interactions, RACK1 integrates multiple intracellular signals involved in the regulation of various physiological and pathological processes. Dysregulation of RACK1 has been implicated in the initiation and progression of many tumors. However, the exact function of RACK1 in cancer cellular processes, especially in proliferation, remains controversial. Here, we show that RACK1 is required for breast cancer cell proliferation in vitro and tumor growth in vivo. This effect of RACK1 is associated with its ability to enhance β-catenin stability and activate the canonical WNT signaling pathway in breast cancer cells. We identified PSMD2, a key component of the proteasome, as a novel binding partner for RACK1 and β-catenin. Interestingly, although there is no interaction between RACK1 and β-catenin, RACK1 binds PSMD2 competitively with β-catenin. Moreover, RACK1 prevents ubiquitinated β-catenin from binding to PSMD2, thereby protecting β-catenin from proteasomal degradation. Collectively, our findings uncover a novel mechanism by which RACK1 increases β-catenin stability and promotes breast cancer proliferation.

Stabilization of CCDC102B by Loss of RACK1 Through the CMA Pathway Promotes Breast Cancer Metastasis via Activation of the NF-κB Pathway

Background

Breast cancer is one of the leading causes of cancer-related death among women, and the pathological status of axillary lymph nodes is an important predictor of prognosis. However, the mechanism involved in this early stage of metastasis remains largely unknown.

Methods

Microarray analysis was used to carry out differential genomics analyses between matched pairs of metastatic sentinel lymph node tissues and breast primary tumors. The CRISPR/Cas9 gene editing system was used for in vivo screening by transplanting a loss-of-function cell pool into immunocompromised mice. MAGeCK was used to analyze the screening results. Survival analysis was performed via the Kaplan–Meier method. Cell proliferation, wound healing, migration and invasion assays were performed to confirm the phenotype. A tail vein model and subcutaneous xenotransplanted tumor model were used for the in vivo study. The relationship between coiled-coil domain containing 102B (CCDC102B) and receptor for activated C kinase 1 (RACK1) was examined using coimmunoprecipitation, mass spectrometry, nuclear protein extraction and immunofluorescence assays. The primary biological functions and pathways related to CCDC102B were enriched by RNA sequencing.

Results

We identified CCDC102B through screening and found that it was significantly upregulated in metastatic lesions in lymph nodes compared to matched primary tumors. Increased expression of CCDC102B promoted breast cancer metastasis in vitro and in vivo. Additionally, high expression of CCDC102B was correlated with poor clinical outcomes in breast cancer patients. We further identified that CCDC102B was stabilized by the loss of RACK1, a protein negatively correlated with breast cancer metastasis. Mechanistically, we found that RACK1 promoted CCDC102B lysosomal degradation by mediating chaperone-mediated autophagy (CMA). The aggressive behavior of CCDC102B in breast cancer cells could be reversed by the expression of RACK1. Moreover, CCDC102B was correlated with the significant enrichment of NF-κB pathway components. Overexpressing CCDC102B led to less interaction between RACK1 and IKKa. Thus, CCDC102B positively regulates the NF−κB pathway by interacting with RACK1.

Conclusion

Taken together, our findings uncover a novel role of CCDC102B in breast cancer metastasis. CCDC102B serves as a potential metastasis promoter by regulating the activation of the NF-κB pathway and can be degraded by RACK1 via CMA.

miR-498/DNMT3b Axis Mediates Resistance to Radiotherapy in Esophageal Cancer Cells

Objective: To explore the role of miR-498 in the radiotherapy resistance of esophageal cancer (EC) and its underlying mechanism. Methods: In vivo models of EC tissues with radioresistance or radiosensitivity were isolated from 72 EC patients who received radiotherapy. In vitro models were established after irradiation of KYSE30 cells. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were employed to measure the expression levels of miR-498 and DNMT3b in EC cells sensitive or resistant to irradiation. Then, protein expression of DNMT3b was verified by immunohistochemistry. The cell viability, colony formation rate, and cell apoptotic rate of EC were correspondingly assessed by CCK-8, colony formation assay, and Annexin V/PI (propidium iodide) double staining. Western blot was utilized to perform the expression levels of PI3K, p-PI3K, AKT, and p-AKT in EC cell lines after irradiation. Results: Highly expressed DNMT3b and lowly expressed miR-498 were found in EC tissues. EC tissues with radiosensitivity had higher miR-498 level and lower DNMT3b expression than EC tissues with radioresistance. Overexpression of miR-498 or knockdown of DNMT3b enhanced the radiosensitivity of EC cells. DNMT3b was a target gene of miR-498. DNMT3b diminished the radiosensitization of miR-498 in EC cells. Conclusions: MiR-498 enhances the sensitivity of EC cells to radiation by DNMT3b inhibition, and exerts biological functions by inactivating the PI3K/AKT signaling pathway.

Cellular fractionation reveals transcriptome responses of human fibroblasts to UV-C irradiation

While cells activate a multifaceted DNA damage response to remove transcription-blocking DNA lesions, mechanisms to regulate genome-wide reduction of RNA synthesis and the paradoxical continuous loading of RNAP II at initiation sites are still poorly understood. Uncovering how dramatic changes to the transcriptional program contribute to TC-NER (transcription-coupled nucleotide excision repair) is important in DNA repair research. However, the functional significance of transcriptome dynamics and the mechanisms of chromatin attachment for thousands of unstudied human lncRNAs remain unclear. To address these questions, we examined UV-induced gene expression regulation in human fibroblasts by performing RNA-seq with fractionated chromatin-associated and cytoplasmic transcripts. This approach allowed us to separate the synthesis of nascent transcripts from the accumulation of mature RNAs. In addition to documenting the subcellular locations of coding transcripts, our results also provide a high-resolution view of the transcription activities of noncoding RNAs in response to cellular stress. At the same time, the data showed that vast majority of genes exhibit large changes in chromatin-associated nascent transcripts without corresponding changes in cytoplasmic mRNA levels. Distinct from protein-coding genes that transcripts with shorter length prefer to be recovered first, repression of lncRNA transcription after UV exposure is inactivated first on noncoding transcripts with longer length. This work provides an updated framework for cellular RNA organization in response to stress and may provide useful information in understanding how cells respond to transcription-blocking DNA damage.

Radiosensitization of HER2-positive esophageal cancer cells by pyrotinib

Radiation therapy is a widely used treatment for esophageal cancer. However, radiation resistance might result in a poor prognosis. Overexpression of HER2 has been related to adaptive radiation resistance. Pyrotinib is a HER2 inhibitor that shows an anti-tumor effect in breast cancer. The present study aims to explore the influence of pyrotinib combined with radiotherapy on HER2-positive esophageal cancer cells and explore the underlying mechanism. We screened two cell lines (TE-1 and KYSE30) that highly express HER2 from several human esophageal cancer cell lines. Cells were treated with pyrotinib or/and radiation. Cell proliferation, cell cycle distribution, and cell migration were measured. The protein levels involved in cell cycle and DNA repair were measured by Western blot. Results showed that pyrotinib inhibited HER2 activation and exerted an anti-proliferative effect in TE-1 and KYSE30 cells. Furthermore, it enhanced the anti-proliferative effect of radiation in these two cell lines. These effects might be via inhibiting HER2 phosphorylation, inducing G0/G1 arrest, and reducing EMT and DNA repair. Our results indicated that pyrotinib sensitivitied HER2 positive esophageal cancer cells to radiation treatment through various mechanisms. These findings may provide a new therapeutic strategy for treating HER2 positive esophageal cancer.

STING Mediates Lupus via the Activation of Conventional Dendritic Cell Maturation and Plasmacytoid Dendritic Cell Differentiation

Signaling through stimulator of interferon genes (STING) leads to the production of type I interferons (IFN-Is) and inflammatory cytokines. A gain-of-function mutation in STING was identified in an autoinflammatory disease (STING-associated vasculopathy with onset in infancy; SAVI). The expression of cyclic GMP-AMP, DNA-activated cGAS-STING pathway, increased in a proportion of patients with SLE. The STING signaling pathway may be a candidate for targeted therapy in SLE. Here, we demonstrated that disruption of STING signaling ameliorated lupus development in Fcgr2b-deficient mice. Activation of STING promoted maturation of conventional dendritic cells and differentiation of plasmacytoid dendritic cells via LYN interaction and phosphorylation. The inhibition of LYN decreased the differentiation of STING-activated dendritic cells. Adoptive transfer of STING-activated bone marrow-derived dendritic cells into the FCGR2B and STING double-deficiency mice restored lupus phenotypes. These findings provide evidence that the inhibition of STING signaling may be a candidate targeted treatment for a subset of patients with SLE.

Isocitrate dehydrogenase 2 contributes to radiation resistance of oesophageal squamous cell carcinoma via regulating mitochondrial function and ROS/pAKT signalling

Background

Antioxidase alleviates the accumulation of radiation-induced reactive oxygen species (ROS) and therefore has strong connections with radioresistance. Isocitrate dehydrogenase 2 (IDH2) facilitates the turnover of antioxidase, but its role in radiotherapeutic efficiency in oesophageal squamous cell carcinoma (ESCC) still remains elusive.

Methods

The involvement of IDH2 in radiotherapeutic efficacy in ESCC was investigated in vitro and vivo by IDH2 knockdown. IDH2 expression in biopsy specimens of 141 patients was identified to evaluate its clinical significance.

Results

We found that Kyse510 and Kyse140 cells were more radioresistant and had higher IDH2 expression. In these two cell lines, IDH2 knockdown intensified the radiation-induced ROS overload and oxidative damage on lipid, protein, and nucleic acids. In addition, IDH2 silencing aggravated the radiation-induced mitochondrial dysfunction and cell apoptosis and ultimately promoted radiosensitisation via inhibiting AKT phosphorylation in a ROS-dependent manner. Furthermore, IDH2 depletion facilitated the radiation-induced growth inhibition and cell apoptosis in murine xenografts. Finally, IDH2 expression was correlated with definite chemoradiotherapy (dCRT) efficacy and served as an independent prognostic factor for survival of ESCC patients.

Conclusions

IDH2 plays a key role in the radioresistance of ESCC. Targeting IDH2 could be a promising regimen to improve radiotherapeutic efficiency in ESCC patients.

Rack1 mediates tyrosine phosphorylation of Anxa2 by Src and promotes invasion and metastasis in drug-resistant breast cancer cells

Background

Acquirement of resistance is always associated with a highly aggressive phenotype of tumor cells. Recent studies have revealed that Annexin A2 (Anxa2) is a key protein that links drug resistance and cancer metastasis. A high level of Anxa2 in cancer tissues is correlated to a highly aggressive phenotype. Increased Anxa2 expression appears to be specific in many drug-resistant cancer cells. The functional activity of Anxa2 is regulated by tyrosine phosphorylation at the Tyr23 site. Nevertheless, the accurate molecular mechanisms underlying the regulation of Anxa2 tyrosine phosphorylation and whether phosphorylation is necessary for the enhanced invasive phenotype of drug-resistant cells remain unknown.

Methods

Small interfering RNAs, small molecule inhibitors, overexpression, loss of function or gain of function, rescue experiments, Western blot, wound healing assays, transwell assays, and in vivo metastasis mice models were used to investigate the functional effects of Rack1 and Src on the tyrosine phosphorylation of Anxa2 and the invasion and metastatic potential of drug-resistant breast cancer cells. The interaction among Rack1, Src, and Anxa2 in drug-resistant cells was verified by co-immunoprecipitation assay.

Results

We demonstrated that Anxa2 Tyr23 phosphorylation is necessary for multidrug-resistant breast cancer invasion and metastasis. Rack1 is required for the invasive and metastatic potential of drug-resistant breast cancer cells through modulating Anxa2 phosphorylation. We provided evidence that Rack1 acts as a signal hub and mediates the interaction between Src and Anxa2, thereby facilitating Anxa2 phosphorylation by Src kinase.

Conclusions

Our findings suggest a convergence point role of Rack1/Src/Anxa2 complex in the crosstalk between drug resistance and cancer aggressiveness. The interaction between Anxa2 and Rack1/Src is responsible for the association between drug resistance and invasive/metastatic potential in breast cancer cells. Thus, our findings provide novel insights on the mechanism underlying the functional linkage between drug resistance and cancer aggressiveness.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1147-7) contains supplementary material, which is available to authorized users.

MicroRNA-153-3p enhances cell radiosensitivity by targeting BCL2 in human glioma

Background

Glioma is the most prevalent malignant tumor in human central nervous systems. Recently, the development of resistance to radiotherapy in glioma patients markedly vitiates the therapy outcome. MiR-153-3p has been reported to be closely correlated with tumor progression, but its effect and molecular mechanism underlying radioresistance remains unclear in glioma.

Methods

The expression of miR-153-3p was determined in radioresistant glioma clinical specimens as well as glioma cell lines exposed to irradiation (IR) using quantitative real-time PCR. Cell viability, proliferation and apoptosis were then evaluated by MTT assay, colony formation assay, Flow cytometry analysis and caspase-3 activity assay in glioma cells (U87 and U251). Tumor forming was evaluated by nude mice model in vivo. TUNEL staining was used to detect cell apoptosis in nude mice model. The target genes of miR-153-3p were predicted and validated using integrated bioinformatics analysis and a luciferase reporter assay.

Results

Here, we found that miR-153-3p was down-regulated in radioresistant glioma clinical specimens as well as glioma cell lines (U87 and U251) exposed to IR. Enhanced expression of miR-153-3p promoted the radiosensitivity, promoted apoptosis and elevated caspase-3 activity in glioma cells in vitro, as well as the radiosensitivity in U251 cell mouse xenografs in vivo. Mechanically, B cell lymphoma-2 gene (BCL2) was identified as the direct and functional target of miR-153-3p. Moreover, restoration of BCL2 expression reversed miR-153-3p-induced increase of radiosensitivity, apoptosis and caspase-3 activity in U251 cells in vitro. In addition, clinical data indicated that the expression of miR-153-3p was significantly negatively associated with BCL2 in radioresistance of glioma samples.

Conclusions

Our findings suggest that miR-153-3p is a potential target to enhance the effect of radiosensitivity on glioma cells, thus representing a new potential therapeutic target for glioma.

Role of RACK1 on cell proliferation, adhesion, and bortezomib-induced apoptosis in multiple myeloma

Receptor for activated C kinase 1 (RACK1), a scaffold protein, plays a crucial role in the progression of various cancers. However, the biological function and underlying mechanism of RACK1 in multiple myeloma (MM) cells remain unclear. The present study aimed to explore the function of RACK1 on the cell proliferation, adhesion, and bortezomib-induced apoptosis in MM. We found that RACK1 was significantly overexpressed in myeloma cell lines and primary myeloma cells compared with normal bone marrow plasma cells. Moreover, immunofluorescence revealed that RACK1 was primarily expressed in the cytoplasm of MM cells. Knockdown of RACK1 impaired growth of MM cells, blocked entry into the S-phase of the cell cycle, and resulted in reduced cell adhesion rates. More importantly, knockdown of RACK1 decreased the proliferation of MM cells by activating P-P38 and P-ERK in the MAPK/ERK signaling pathway. We also found that altered expression of RACK1 is associated with bortezomib-mediated MM cell apoptosis. In summary, these results may provide a possible target for therapy in MM.

Inhalation treatment of primary lung cancer using liposomal curcumin dry powder inhalers

Lung cancer is the leading cause of cancer-related deaths. Traditional chemotherapy causes serious toxicity due to the wide bodily distribution of these drugs. Curcumin is a potential anticancer agent but its low water solubility, poor bioavailability and rapid metabolism significantly limits clinical applications. Here we developed a liposomal curcumin dry powder inhaler (LCD) for inhalation treatment of primary lung cancer. LCDs were obtained from curcumin liposomes after freeze-drying. The LCDs had a mass mean aerodynamic diameter of 5.81 μm and a fine particle fraction of 46.71%, suitable for pulmonary delivery. The uptake of curcumin liposomes by human lung cancer A549 cells was markedly greater and faster than that of free curcumin. The high cytotoxicity on A549 cells and the low cytotoxicity of curcumin liposomes on normal human bronchial BEAS-2B epithelial cells yielded a high selection index partly due to increased cell apoptosis. Curcumin powders, LCDs and gemcitabine were directly sprayed into the lungs of rats with lung cancer through the trachea. LCDs showed higher anticancer effects than the other two medications with regard to pathology and the expression of many cancer-related markers including VEGF, malondialdehyde, TNF-α, caspase-3 and BCL-2. LCDs are a promising medication for inhalation treatment of lung cancer with high therapeutic efficiency.

The receptor for activated protein kinase C promotes cell growth, invasion and migration in cervical cancer

Cervical cancer is one of the most common malignant tumors in women all over the world. However, the exact etiology of cervical cancer remains unclear. The receptor for activated protein kinase C (RACK1) is reported to be involved in tumorigenesis and tumor progression. Besides, the prognostic value of RACK1 in several kinds of tumors has been identified. However, there are limited studies on the functional role of RACK1 in cervical cancer. In this study, we tested the expression level of RACK1 by immunohistochemistry and western blot technologies and find that it is upregulated in cervical cancer. Colony formation and CCK8 assays indicate that RACK1 promotes cell proliferation in CaSki cervical cancer cells. While the silence of RACK1 decreases the cell proliferation in CCK8 analysis. β-galactosidase staining suggests that RACK1 decreases cell senescence in cervical cancer cells. Invasion and migration assay show that RACK1 promotes the invasion and migration of cervical cancer cells. Also, when RACK1 was silenced, it exerts the opposite result. Furthermore, the mRNA expression levels of MMP‑3, MMP‑9 and MMP‑10 were upregulated in RACK1‑overexpressed CaSki cells by qPCR analysis. RACK1 also induces S phase accumulation in cell cycle analysis and suppresses cell apoptosis in cervical cancer cells. Flow cytometry analysis of mitochondria functions suggests that RACK1 increases the mitochondrial membrane potential (Δψm) levels to prevent mitochondrial apoptosis in cervical cancer cells. To explore the possible mechanism of RACK1, we tested and found that RACK1 upregulates the expression of NF-κB, cyclin D1 and CDK4 and downregulates the expression of p53, p38, p21 and STAT1 in cervical cancer cells. These results suggest that RACK1 promotes cell growth and invasion and inhibits the senescence and apoptosis in cervical cancer cells probably by affecting the p53 pathway.