The synergistic anticancer effect of the bromodomain inhibitor OTX015 and histone deacetylase 6 inhibitor WT-161 in osteosarcoma.

BACKGROUND: Osteosarcoma (OS) is a tumour with a high malignancy level and a poor prognosis. First-line chemotherapy for OS has not been improved for many decades. Bromodomain and extraterminal domain (BET) and histone deacetylases (HDACs) regulate histone acetylation in tandem, and BET and HDACs have emerged as potential cancer therapeutic targets. METHODS: Cell proliferation, migration, invasion, colony formation, and sphere-forming assays were performed with the two inhibitors alone or in combination to evaluate their suppressive effect on the malignant properties of OS cells. Apoptosis and the cell cycle profile were measured by flow cytometry. The synergistic inhibitory effect of OTX015/WT-161 on tumours was also examined in a nude mouse xenograft model. RESULTS: The combined therapy of OTX015/WT-161 synergistically inhibited growth, migration, and invasion and induced apoptosis, resulting in G1/S arrest of OS cells. Additionally, OTX015/WT-161 inhibited the self-renewal ability of OS stem cells (OSCs) in a synergistic manner. Further mechanistic exploration revealed that the synergistic downregulation of ß-catenin by OTX015-mediated suppression of FZD2 and WT-161-mediated upregulation of PTEN may be critical for the synergistic effect. Finally, the results of an in vivo assay showed that tumour xenografts were significantly decreased after treatment with the OTX015/WT-161 combination compared with OTX015 or WT-161 alone. CONCLUSIONS: Our findings in this study demonstrated that OTX015 and WT-161 had synergistic anticancer efficacy against OS, and their combination might be a promising therapeutic strategy for OS.

The novel prognostic risk factor STC2 can regulate the occurrence and progression of osteosarcoma via the glycolytic pathway.

Osteosarcoma, a highly aggressive malignant tumor of the bone, usually occurs in children and young adults. However, although the considerable achievement in the clinical treatment of osteosarcoma recent years, the overall survival of osteosarcoma patients has not been obviously improved. Cancer cells preferentially use glycolysis instead of oxidative phosphorylation to meet their increased energetic and biosynthetic demands, a phenomenon known as the Warburg effect. Glycolysis is a driving factor in multiple cancers and is emerging as a new cancer target treatment. In the present study, we established a model to screen for glycolysis-associated genes in osteosarcoma. This risk score of the model were correlated with clinical characteristics osteosarcoma patients. Besides, a functional assay identified that STC2 enhanced the glycolysis of osteosarcoma cells. Modulation of STC2 changes glucose consumption and lactate production as well as GLUT1 expression in osteosarcoma. Furthermore, we identified that change in the expression levels of STC2 affected the proliferation, invasion, and migration of osteosarcoma cells. Our findings showed STC2 as a new tumor-promoting factor of osteosarcoma cells through enhancing glycolysis.

Role of LncRNAs in regulating cancer amino acid metabolism.

The metabolic change of tumor cells is an extremely complicated process that involves the intersection and integration of various signal pathways. Compared with normal tissues, cancer cells show distinguished metabolic characteristics called metabolic reprogramming, which has been considered as a sign of cancer occurrence. With the deepening of tumor research in recent years, people gradually found that amino acid metabolism played crucial roles in cancer progression. Long non-coding RNAs (lncRNAs), which are implicated in many important biological processes, were firstly discovered dysregulating in cancer tissues and participating in extensive regulation of tumorigenesis. This review focuses on the reprogramming of amino acid metabolism in cancers and how lncRNAs participate in the regulatory network by interacting with other macromolecular substances. Understanding the functions of lncRNA in amino acid reprogramming in tumors might provide a new vision on the mechanisms of tumorigenesis and the development of new approaches for cancer therapy.

LncRNA GSEC promotes the proliferation, migration and invasion by sponging miR-588/ EIF5A2 axis in osteosarcoma.

BACKGROUND: Long noncoding RNAs (LncRNAs) show dysregulation in a variety of cancers. However, the function and specific mechanism of LncRNA GSEC in the progression of osteosarcoma remain mostly unknown. In this study, we sought to elucidate the role and mechanism of LncRNA GSEC in the occurrence and progression of osteosarcoma. METHODS: we examined the expression of LncRNA GSEC in osteosarcoma cell lines by quantitative real time PCR. In vitro experiments, including transwell assays, cck8 assays, and flow cytometry analysis have biologically demonstrated the effect of LncRNA GSEC on the proliferation and migration of osteosarcoma cell lines. Furthermore, the regulation of miR-588 by LncRNA GSEC was determined by luciferase reporter assay and quantitative real time PCR. What's more, subcutaneous tumor formation was performed in nude mice to monitor the growth of the tumor in vivo. RESULTS: We found that the expression of LncRNA GSEC was up-regulated in osteosarcoma cell lines. Overexpression of LncRNA GSEC promoted the proliferating and migratory capacity, and inhibited the apoptosis of osteosarcoma cells. Conversely, knockdown of LncRNA GSEC resulted in the opposite effect. Mechanistically, we identified LncRNA GSEC functioned as the sponge of miR-588, thus inhibiting the miR-588/EIF5A2 signal pathway. In addition, the expression of miR-588 was negatively correlated with LncRNA GSEC, and the effect by silencing or overexpressing LncRNA GSEC could be rescued by the introduction of miR-588 mimics or inhibitors, respectively. CONCLUSIONS: In summary, this study shows that LncRNA GSEC promotes the proliferation and invasion of OS through the regulation of miR-588/EIF5A2 pathway, which might provide a new strategy for the treatment of osteosarcoma in the future.

The decade of exosomal long RNA species: an emerging cancer antagonist.

Exosomes have emerged as a novel approach for the treatment and diagnosis of cancer after RNA content was discovered in exosomes in 2007. As important meditators of intercellular communication, exosomes have become a strong focus of investigation for researchers in the past decade, as witnessed through the exponential increase of research on exosomes. The capability of exosomes to transfer functionally active cargo highlights their importance as promising biomarkers and diagnostic molecules, as well as prospective drug delivery systems. The accessibility of exosomes in nearly all biofluids additionally alludes to its unprecedented ability in various types of cancers due to its extensive impact on tumor formation and progression. This review analyzes the role of exosomal long RNA species, which is comprised of mRNA, lncRNA, and circRNA, in tumor formation and progression, with an emphasis on their potential as future diagnostic biomarkers and treatment vectors in cancer biology. Their alignment with the development of exosomal databases is further examined in this review, in view of the accumulation of studies published on exosomes in the past decade.

LncRNA SNHG5 promotes the progression of osteosarcoma by sponging the miR-212-3p/SGK3 axis.

BACKGROUND: Long non-coding RNA (lncRNA) SNHG5 has been found to play an important role in tumors. Nevertheless, the function and mechanism of lncRNA SNHG5 in osteosarcoma (OS) remains unclear. The purpose of this study was to investigate whether lncRNA SNHG5 can regulate the occurrence and development of OS cells. METHODS: We performed quantitative real time PCR to detect the expression of lncRNA SNHG5 in OS cells. 143B, MG63 (knockdown) and U2OS, U2R (overexpression) cell lines were chosen for the function study of SNHG5. The effect of SNHG5, miR-212-3p, and SGK3 in OS cells was explored by MTT assays, clony formation, flow cytometry, transwell assays, wound healing assays, and cell spreading assays. Quantitative real-time PCR, Western blot analysis and luciferase assays were used to detect the interaction between lncRNA SNHG5 and miR-212-3p. RESULTS: In this study, knockdown of lncRNA SNHG5 suppressed the growth and metastasis of OS cells, whereas the overexpression of SNHG5 produced an opposite result. Mechanistically, lncRNA SNHG5 functions as a sponger against miR-212-3p and suppresses the miR-212-3p/SGK3 signaling pathway. Introduction of miR-212-3p mimics or inhibitors reverses SNHG5 overexpression or silences the exerted tumor promoting or suppressing effect. In addition, our results showed that the function of SNHG5 can be rescued by miR-212-3p and can regulate the growth and metastasis of OS cells via SGK3, the downstream target of miR-212-3p. CONCLUSIONS: In summary, our study demonstrated that lncRNA SNHG5 can regulate the proliferation and metastasis of OS cells through the miR-212-3p/SGK3 axis. This axis may provide a new target for future clinical treatment.

The overexpression of hypomethylated miR-663 induces chemotherapy resistance in human breast cancer cells by targeting heparin sulfate proteoglycan 2 (HSPG2).

MicroRNAs are involved in regulating the biology of cancer cells, but their involvement in chemoresistance is not fully understood. We found that miR-663 was up-regulated in our induced multidrug-resistant MDA-MB-231/ADM cell line and that this up-regulation was closely related to chemosensitivity. In the present study, we aimed to clarify the role of miR-663 in regulating the chemoresistance of breast cancer. MicroRNA microarray and quantitative RT-PCR assays were used to identify differentially expressed microRNAs. Cell apoptosis was evaluated by annexin V/propidium iodide staining, TUNEL, and reactive oxygen species generation analysis. The expression of miR-663 and HSPG2 in breast cancer tissues was detected by in situ hybridization and immunohistochemistry. The potential targets of miR-663 were defined by a luciferase reporter assay. Bisulfite sequencing PCR was used to analyze the methylation status. We found that miR-663 was significantly elevated in MDA-MB-231/ADM cells, and the down-regulation of miR-663 sensitized MDA-MB-231/ADM cells to both cyclophosphamide and docetaxel. The overexpression of miR-663 in breast tumor tissues was associated with chemoresistance; in MDA-MB-231 cells, this chemoresistance was accompanied by the down-regulation of HSPG2, which was identified as a target of miR-663. MDA-MB-231/ADM contained fewer methylated CpG sites than its parental cell line, and miR-663 expression in MDA-MB-231 cells was reactivated by 5-aza-29-deoxycytidine treatment, indicating that DNA methylation may play a functional role in the expression of miR-663. Our findings suggest that the overexpression of hypomethylated miR-663 induced chemoresistance in breast cancer cells by down-regulating HSPG2, thus providing a potential target for the development of an microRNA-based approach for breast cancer therapy.

MiR-92a mediates AZD6244 induced apoptosis and G1-phase arrest of lymphoma cells by targeting Bim.

AZD6244, an ATP-uncompetitive inhibitor of mitogen-activated protein kinase 1/2 (MEK1/2), has shown activity in several malignant tumours. However, whether AZD6244 has a function in lymphoma cells is not known. We report that AZD6244 treatment represses the growth of Raji and MOLT4 cells by inducing apoptosis and G1-phase arrest. Using miRNAs array and quantitative RT-PCR, miR-92a was downregulated byAZD6244 treatment through the ERK1/2-AP1 signalling pathway. Overexpression of miR-92a abrogated AZD6244-induced apoptosis and G1-phase arrest, indicating that it is involved in the cytotoxicity of AZD6244 in lymphoma cells. A luciferase reporter assay showed that miR-92a directly targetsthe 3'-UTRs of Bim. Overexpression of miR-92a mimics downregulated Bim mRNA and protein expression level, indicating that miR-92a negatively regulates its expression at both levels. Silencing Bim decreases AZD6244-induced apoptosis and G1-phase arrest, suggesting that Bim contributes to the growth arrest. Thus, miR-92a mediates AZD6244-induced cytotoxicity of lymphoma cells by targeting Bim. Downregulation of miR-92a by AZD6244 is mediated by the ERK1/2-AP1 signalling pathway.

UCA1 Inhibits NKG2D-mediated Cytotoxicity of NK Cells to Breast Cancer.

BACKGROUND: Natural killer cells play important roles in tumor immune surveillance, and cancer cells must resist this surveillance in order to progress and metastasise. INTRODUCTION: The study aimed to explore the mechanism of how breast cancer cells become resistant to the cytotoxicity of NK cells. METHODS: We established NK-resistant breast cancer cells by exposing MDA-MB-231 cells and MCF-7 cells to NK92 cells. Profiles of lncRNA were compared between the NK-resistant and parental cell lines. Primary NK cells were isolated by MACS, and the NK attacking effect was tested by non-radioactive cytotoxicity. The change in lncRNAs was analyzed by Gene-chip. The interaction between lncRNA and miRNA was displayed by Luciferase assay. The regulation of the gene was verified by QRT-PCR and WB. The clinical indicators were detected by ISH, IH, and ELISA, respectively. RESULTS: UCA1 was found to be significantly up-regulated in both NK-resistant cell lines, and we confirmed such up-regulation on its own to be sufficient to render parental cell lines resistant to NK92 cells. We found that UCA1 up-regulated ULBP2 via the transcription factor CREB1, while it up-regulated ADAM17 by "sponging" the miR-26b-5p. ADAM17 facilitated the shedding of soluble ULBP2 from the surface of breast cancer cells, rendering them resistant to killing by NK cells. UCA1, ADAM17, and ULBP2 were found to be expressed at higher levels in bone metastases of breast cancer than in primary tumors. CONCLUSION: Our data strongly suggest that UCA1 up-regulates ULBP2 expression and shedding, rendering breast cancer cells resistant to killing by NK cells.

Solute carrier family 35 member A2 regulates mitophagy through the PI3K/AKT/mTOR axis, promoting the proliferation, migration, and invasion of osteosarcoma cells.

The treatment of osteosarcoma patients exhibits individual variability, underscoring the critical importance of targeted therapy. Although (Solute carrier family 35 member A2) SLC35A2's role in the progression of various cancers has been extensively investigated, its specific implications in osteosarcoma remain unexplored. Leveraging data from the (The Cancer Genome Atlas) TCGA and (Genotype-Tissue Expression) GTEx databases, we have discerned that SLC35A2 is notably upregulated in osteosarcoma and correlates with the prognosis of osteosarcoma patients. Consequently, it becomes imperative to delve into the role of SLC35A2 in the context of osteosarcoma. Our research substantiates that SLC35A2 exerts a notable influence on mitochondrial autophagy in osteosarcoma, thereby exerting cascading effects on the proliferation, migration, invasion, and apoptosis of osteosarcoma cells. Mechanistically, SLC35A2 orchestrates mitochondrial autophagy via the PI3K/AKT/mTOR signaling pathway. Moreover, we have conducted rigorous animal experiments to further corroborate the repercussions of SLC35A2 on osteosarcoma growth. In summation, our study elucidates that SLC35A2's modulation of mitochondrial autophagy through the PI3K/AKT/mTOR signaling pathway constitutes a pivotal factor in the malignant progression of osteosarcoma, unveiling promising therapeutic targets for patients grappling with this condition.

MicroRNA 34c gene down-regulation via DNA methylation promotes self-renewal and epithelial-mesenchymal transition in breast tumor-initiating cells.

Tumor-initiating cells (T-ICs), a subpopulation of cancer cells with stem cell-like properties, are related to tumor relapse and metastasis. Our previous studies identified a distinct profile of microRNA (miRNA) expression in breast T-ICs (BT-ICs), and the dysregulated miRNAs contribute to the self-renewal and tumorigenesis of these cells. However, the underlying mechanisms for miRNA dysregulation in BT-ICs remain obscure. In the present study, we demonstrated that the expression and function of miR-34c were reduced in the BT-ICs of MCF-7 and SK-3rd cells, a breast cancer cell line enriched for BT-ICs. Ectopic expression of miR-34c reduced the self-renewal of BT-ICs, inhibited epithelial-mesenchymal transition, and suppressed migration of the tumor cells via silencing target gene Notch4. Furthermore, we identified a single hypermethylated CpG site in the promoter region of miR-34c gene that contributed to transcriptional repression of miR-34c in BT-ICs by reducing DNA binding activities of Sp1. Therefore, miR-34c reduction in BT-ICs induced by a single hypermethylated CpG site in the promoter region promotes self-renewal and epithelial-mesenchymal transition of BT-ICs.

Downregulation of miRNA-128 sensitises breast cancer cell to chemodrugs by targeting Bax.

miR-128 is more highly expressed in drug-resistant breast cancer samples than in drug-sensitive samples. We have confirmed that Bax is the target of miR-128 by negative post-transcriptional regulation. miR-128 and Bax were detected in the breast cancer cell line, MDA-MB-231, which was then transfected with miR-128 MIMIC (precursor of miR-128) or AMO (antisense-miR-128 oligonucleotides). After transfection, the chemosensitivity of MDA-MB-231 cell was up-regulated with increasing of Bax and inhibition of miR-128.

Indirect bilirubin impairs invasion of osteosarcoma cells via inhibiting the PI3K/AKT/MMP-2 signaling pathway by suppressing intracellular ROS.

Background: Osteosarcoma is most prevalently found primary malignant bone tumors, with primary metastatic patients accounting for approximately 25% of all osteosarcoma patients, yet their 5-year OS remains below 30%. Bilirubin plays a key role in oxidative stress-associated events, including malignancies, making the regulation of its serum levels a potential anti-tumor strategy. Herein, we investigated the association of osteosarcoma prognosis with serum levels of TBIL, IBIL and DBIL, and further explored the mechanisms by which bilirubin affects tumor invasion and migration. Methods: ROC curve was plotted to assess survival conditions based on the determined optimal cut-off values and the AUC. Then, Kaplan-Meier curves, along with Cox proportional hazards model, was applied for survival analysis. Inhibitory function of IBIL on the malignant properties of osteosarcoma cells was examined using the qRT-PCR, transwell assays, western blotting, and flow cytometry. Results: We found that, versus osteosarcoma patients with pre-operative higher IBIL (>8.9 µmol/L), those with low IBIL (≤8.9 µmol/L) had shorter OS and PFS. As indicated by the Cox proportional hazards model, pre-operative IBIL functioned as an independent prognostic factor for OS and PFS in total and gender-stratified osteosarcoma patients (P < 0.05 for all). In vitro experiments further confirmed that IBIL inhibits PI3K/AKT phosphorylation and downregulates MMP-2 expression via reducing intracellular ROS, thereby decreasing the invasion of osteosarcoma cells. Conclusions: IBIL may serve as an independent prognostic predictor for osteosarcoma patients. IBIL impairs invasion of osteosarcoma cells through repressing the PI3K/AKT/MMP-2 pathway by suppressing intracellular ROS, thus inhibiting its metastatic potential.

LncRNA LBX2-AS1 impacts osteosarcoma sensitivity to JQ-1 by sequestering miR-597-3p away from BRD4.

Objective: Recent knowledge concerning the significance of long non-coding RNA (lncRNA)-mediated ceRNA networks provides new insight into their possible roles as specific biomarkers for the treatment of osteosarcoma (OS). Thus, this study aims to clarify the functional relevance and mechanistic actions of lncRNA LBX2-AS1 in OS. Methods: Differential analysis was performed by integrating the TCGA and GTEx databases. Cox regression analysis was then employed to assess the prognostic value of the model. The expression of lncRNA LBX2-AS1 and miR-597-3p was quantified in OS cell lines by qRT-PCR. The proliferation, migration, invasion, and apoptosis of OS cell lines in response to manipulated lncRNA LBX2-AS1 were evaluated by MTT, colony formation, transwell, Western blot, and flow cytometry assays. Luciferase activity was assayed to validate the reciprocal regulation between lncRNA LBX2-AS1 and miR-597-3p. The protein levels of BRD4 and EMT-related factors were examined by Western blot assay. Finally, tumor growth in response to LBX2-AS1 knockdown was evaluated in xenograft-bearing nude mice. Results: By integrating the GTEx and TCGA databases, we identified 153 differentially expressed lncRNAs. Among them, 5 lncRNAs, RP11-535M15.1, AC002398.12, RP3-355L5.4, LBX2-AS1, and RP11.47A8.5, were selected to establish a model, which predicted the prognosis of OS. Higher lncRNA LBX2-AS1 expression was noted in OS tissues relative to that in normal tissues. Silencing lncRNA LBX2-AS1 facilitated apoptosis and curtailed proliferative, migratory, and invasive capacities of OS cells. Mechanistically, lncRNA LBX2-AS1 could elevate the expression of BRD4, an oncogene, by competitively binding to miR-597-3p. More importantly, knockdown of lncRNA LBX2-AS1 increased the sensitivity of OS cells to the BRD4 inhibitor JQ-1. Finally, the tumor growth of OS cell xenografts was constrained in vivo in the presence of lncRNA LBX2-AS1 knockdown. Conclusion: In conclusion, lncRNA LBX2-AS1 promotes the growth of OS and represses the sensitivity to JQ-1 by sponging miR-597-3p to elevate the expression of BRD4.

FKBP11 improves the malignant property of osteosarcoma cells and acts as a prognostic factor of osteosarcoma.

BACKGROUND: Osteosarcoma has become the most common bone malignancy in adolescents. Although the clinical treatment of osteosarcoma has advanced considerably in recent years, the 5-year survival rate has not improved significantly. Recently, many studies have shown that mRNA has unique advantages as a target for drug therapy. Therefore, this study aimed to identify a new prognostic factor and provide a new target for the treatment of osteosarcoma to improve the prognosis of patients. METHODS AND RESULTS: We selected prognostic genes that are closely associated with osteosarcoma clinical features by obtaining osteosarcoma patient information from the GTEx and TARGET databases, and then we developed a risk model. We detected the expression of FKBP11 in osteosarcoma by qRT-PCR, western blotting, and immunohistochemistry and performed CCK-8, Transwell, colony formation, and flow cytometry assays to reveal the regulatory role of FKBP11. We found that FKBP11 was highly expressed in osteosarcoma; silencing FKBP11 expression suppressed the invasion and migration of osteosarcoma cells, slowed cell proliferation, and promoted apoptosis. We also found that silencing the expression of FKBP11 led to inhibition of MEK/ERK phosphorylation. CONCLUSIONS: In conclusion, we validated that the prognostic factor FKBP11 is closely associated with osteosarcoma. Additionally, we identified a novel mechanism by which FKBP11 ameliorates the malignant properties of osteosarcoma cells through the MAPK pathway and serves as a prognostic factor in osteosarcoma. This study provides a new method for the treatment of osteosarcoma.

Long non-coding RNA MIR17HG sponges microRNA-21 to upregulate PTEN and regulate homoharringtonine-based chemoresistance of acute myeloid leukemia cells.

Long non-coding (lnc)RNA MIR17HG has been identified as a oncogene whose roles in acute myeloid leukemia (AML) remain unclear. The present study aimed to investigate the role of lncRNA MIR17HG in AML. Differential expression of MIR17HG in AML was determined by reverse transcription-quantitative PCR. Overexpression assays and dual luciferase reporter assays were performed to determine the relationship between MIR17HG and microRNA (miR)-21, and apoptosis was analyzed by using an apoptosis assay. The results showed that the expression of MIR17HG was decreased in AML, which was further decreased following homoharringtonine (HHT)-based chemotherapy. Bioinformatics analysis predicted that miR-21 could bind with MIR17HG. However, miR-21 overexpression had no effect on the expression level of MIR17HG. Dual luciferase reporter assays were performed to verify the direct interaction between miR-21 and MIR17HG. In addition, overexpression of MIR17HG and miR-21 in AML cell lines up- and downregulated the expression level of PTEN, respectively. Furthermore, cell apoptosis showed that MIR17HG and PTEN overexpression enhanced cell apoptosis following cell treatment with HTT. However, miR-21 overexpression exerted the opposite effect, since it reversed the effects of MIR17HG and PTEN overexpression in AML cell apoptosis. In conclusion, the current study suggested that MIR17HG could regulate the miR-21/PTEN axis to modulate the chemoresistance of AML cells.

Stabilization of SAMHD1 by NONO is crucial for Ara-C resistance in AML.

Cytarabine (Ara-C) is the first-line drug for the treatment of acute myelogenous leukemia (AML). However, resistance eventually develops, decreasing the efficacy of Ara-C in AML patients. The expression of SAMHD1, a deoxynucleoside triphosphate (dNTP) triphosphohydrolase, has been reported to be elevated in Ara-C-resistant AML patients and to play a crucial role in mediating Ara-C resistance in AML. However, the mechanism by which SAMHD1 is upregulated in resistant AML remains unknown. In this study, NONO interacted with and stabilized SAMHD1 by inhibiting DCAF1-mediated ubiquitination/degradation of SAMHD1. Overexpression of NONO increased SAMHD1 expression and reduced the sensitivity of AML cells to Ara-C, and downregulation of NONO had the opposite effects. In addition, the DNA-damaging agents DDP and adriamycin (ADM) reduced NONO/SAMHD1 expression and sensitized AML cells to Ara-C. More importantly, NONO was upregulated in Ara-C-resistant AML cells, resulting in increased SAMHD1 expression in resistant AML cells, and DDP and ADM treatment resensitized resistant AML cells to Ara-C. This study revealed the mechanism by which SAMHD1 is upregulated in Ara-C-resistant AML cells and provided novel therapeutic strategies for Ara-C-resistant AML.

Mitochondrial fission induces immunoescape in solid tumors through decreasing MHC-I surface expression.

Mitochondrial dynamics can regulate Major Histocompatibility Complex (MHC)-I antigen expression by cancer cells and their immunogenicity in mice and in patients with malignancies. A crucial role in the mitochondrial fragmentation connection with immunogenicity is played by the IRE1α-XBP-1s axis. XBP-1s is a transcription factor for aminopeptidase TPP2, which inhibits MHC-I complex cell surface expression likely by degrading tumor antigen peptides. Mitochondrial fission inhibition with Mdivi-1 upregulates MHC-I expression on cancer cells and enhances the efficacy of adoptive T cell therapy in patient-derived tumor models. Therefore mitochondrial fission inhibition might provide an approach to enhance the efficacy of T cell-based immunotherapy.

Damaged DNA-binding protein 1 (DDB1) interacts with Cdh1 and modulates the function of APC/CCdh1.

APC/C(Cdh1) plays a key role in mitotic exit and has essential targets in the G(1) phase; however, these mechanisms are poorly understood. In this report, we provide evidence that damaged DNA-binding protein 1 (DDB1) is capable of binding the WD40 domains of Cdh1, but not of Cdc20, through its BPA and BPC domains. Moreover, cells lacking DDB1 exhibit markedly elevated levels of the protein substrates of APC/C(Cdh1). Depletion of DDB1 in mitotic cells significantly delays mitotic exit, which demonstrates that the interaction between DDB1 and Cdh1 plays a critical role in regulating APC/C(Cdh1) activity. However, cells depleted of Cdh1 demonstrated no change in the UV-induced degradation of Cdt1, the main function of DDB1 as an E3 ligase. Strikingly, the APC/C(Cdh1) substrate levels are normal in cell knockdowns of Cul4A and Cul4B, which, along with DDB1, form an E3 ligase complex. This finding indicates that DDB1 modulates the function of APC/C(Cdh1) in a manner independent on the Cul4-DDB1 complex. Our results suggest that DDB1 may functionally regulate mitotic exit by modulating APC/C(Cdh1) activity. This study reveals that there may be cross-talk among DDB1, Cdh1, and Skp2 in the control of cell cycle division.

miR-124 suppresses multiple steps of breast cancer metastasis by targeting a cohort of pro-metastatic genes in vitro.

Metastasis is a multistep process involving modification of morphology to suit migration, reduction of tumor cell adhesion to the extracellular matrix, increase of cell mobility, tumor cell resistance to anoikis, and other steps. MicroRNAs are well-suited to regulate tumor metastasis due to their capacity to repress numerous target genes in a coordinated manner, thereby enabling their intervention at multiple steps of the invasion-metastasis cascade. In this study, we identified a microRNA exemplifying these attributes, miR-124, whose expression was reduced in aggressive MDA-MB-231 and SK-3rd breast cancer cells. Down-regulation of miR-124 expression in highly aggressive breast cancer cells contributed in part to DNA hypermethylation around the promoters of the three genes encoding miR-124. Ectopic expression of miR-124 in MDA-MB-231 cells suppressed metastasis-related traits including formation of spindle-like morphology, migratory capacity, adhesion to fibronectin, and anoikis. These findings indicate that miR-124 suppresses multiple steps of metastasis by diverse mechanisms in breast cancer cells and suggest a potential application of miR-124 in breast cancer treatment.