Regulation of F-box proteins by noncoding RNAs in human cancers

FBXO22 promotes glioblastoma malignant progression by mediating VHL ubiquitination and degradation

Glioblastoma (GBM) is the most common malignant primary brain tumor. Despite comprehensive treatment with traditional surgery, radiotherapy, and chemotherapy, the median survival rate is <14.6% and the 5-year survival rate is only 5%. FBXO22, a substrate receptor of the SCF ubiquitin ligases, has been reported to play a promoting role in melanoma, liver cancer, cervical cancer, and other cancers. However, the function of FBXO22 in GBM has not been reported. In the present study, we demonstrate that FBXO22 is highly expressed in glioma and is positively correlated with worse pathological features and shorter survival of GBM patients. We revealed that FBXO22 promotes GBM cell proliferation, angiogenesis, migration, and tumorigenesis in vitro and in vivo. In terms of mechanism, we reveal that FBXO22 decreases VHL expression by directly mediating VHL ubiquitination degradation, which ultimately increases HIF-1α and VEGFA expression. In addition, our data confirm that there are positive correlations among FBXO22, HIF-1α, and VEGFA expression, and there is a negative correlation between FBXO22 and VHL protein expression in glioma patients. Our study strongly indicates that FBXO22 is a promising diagnostic marker and therapeutic target for glioma patients.

SKping cell cycle regulation: role of ubiquitin ligase SKP2 in hematological malignancies

SKP2 (S-phase kinase-associated protein 2) is a member of the F-box family of substrate-recognition subunits in the SCF ubiquitin-protein ligase complexes. It is associated with ubiquitin-mediated degradation in the mammalian cell cycle components and other target proteins involved in cell cycle progression, signal transduction, and transcription. Being an oncogene in solid tumors and hematological malignancies, it is frequently associated with drug resistance and poor disease outcomes. In the current review, we discussed the novel role of SKP2 in different hematological malignancies. Further, we performed a limited in-silico analysis to establish the involvement of SKP2 in a few publicly available cancer datasets. Interestingly, our study identified Skp2 expression to be altered in a cancer-specific manner. While it was found to be overexpressed in several cancer types, few cancer showed a down-regulation in SKP2. Our review provides evidence for developing novel SKP2 inhibitors in hematological malignancies. We also investigated the effect of SKP2 status on survival and disease progression. In addition, the role of miRNA and its associated families in regulating Skp2 expression was explored. Subsequently, we predicted common miRNAs against Skp2 genes by using miRNA-predication tools. Finally, we discussed current approaches and future prospective approaches to target the Skp2 gene by using different drugs and miRNA-based therapeutics applications in translational research.

Long noncoding RNAs regulate intrauterine adhesion and cervical cancer development and progression

Intrauterine adhesion, one of reproductive system diseases in females, is developed due to endometrial injury, such as infection, trauma, uterine congenital abnormalities and uterine curettage. Intrauterine adhesion affects female infertility and causes several complications, including amenorrhoea, hypomenorrhoea, and recurrent abortion. Cervical cancer is one of the common gynecological tumors and the fourth leading cancer-related death in women worldwide. Although the treatments of cervical cancer have been improved, the advanced cervical cancer patients have a low survival rate due to tumor recurrence and metastasis. The molecular mechanisms of intrauterine adhesion and cervical tumorigenesis have not been fully elucidated. In recent years, long noncoding RNAs (lncRNAs) have been known to participate in intrauterine adhesion and cervical carcinogenesis. Therefore, in this review, we will summarize the role of lncRNAs in regulation of intrauterine adhesion development and progression. Moreover, we will discuss the several lncRNAs in control of cervical oncogenesis and progression. Furthermore, we highlight that targeting lncRNAs could be used for treatment of intrauterine adhesion and cervical cancer.

FBXW7 and human tumors: mechanisms of drug resistance and potential therapeutic strategies

Drug therapy, including chemotherapy, targeted therapy, immunotherapy, and endocrine therapy, stands as the foremost therapeutic approach for contemporary human malignancies. However, increasing drug resistance during antineoplastic therapy has become a substantial barrier to favorable outcomes in cancer patients. To enhance the effectiveness of different cancer therapies, an in-depth understanding of the unique mechanisms underlying tumor drug resistance and the subsequent surmounting of antitumor drug resistance is required. Recently, F-box and WD Repeat Domain-containing-7 (FBXW7), a recognized tumor suppressor, has been found to be highly associated with tumor therapy resistance. This review provides a comprehensive summary of the underlying mechanisms through which FBXW7 facilitates the development of drug resistance in cancer. Additionally, this review elucidates the role of FBXW7 in therapeutic resistance of various types of human tumors. The strategies and challenges implicated in overcoming tumor therapy resistance by targeting FBXW7 are also discussed.

MiR-217 regulates autophagy through OPG/RANKL/RANK in giant cell tumors

BACKGROUND

Increasing evidence suggests that microRNAs (miRNAs) play a crucial role in cancer development and progression. Our previous study showed remarkably lower levels of miR-217 in GCT cells and tissues, and miR-217 re-expression inhibited the occurrence and development of GCT in vitro; however, the associated mechanisms remain unknown. Thus, this study aimed to explore the mechanisms underlying the proliferation inhibitory effect of miR-217 in GCT cells.

METHODS

The proliferative potential of the GCT cells was measured with an MTT assay and BrdU straining. Changes in GCT cell migration and invasion was assessed by a transwell assay. Finally, Western blot and RT-PCR assays were employed to evaluate OPG/RANKL/RANK signaling pathway-related protein expression.

RESULTS

The excessive upregulation of miR-217 markedly suppressed GCT cell proliferation and tumorigenesis both in vitro and in vivo. miR-217 overexpression could inhibit the OPG/RANKL/RANK signaling pathway in vitro and in vivo. Furthermore, ALP activity was significantly decreased in GCT cells following miR-217 treatment. Importantly, miR-217 could inhibit autophagy-related protein expression and autophagosome/autolysosome formation in GCT cells and tissues.

CONCLUSION

These results suggest that miR-217 upregulation could inhibit the occurrence and development of GCT by blocking autophagy. These findings offer an effective therapeutic target to improve the survival rates of patients with CGT in the future.

The role of E3 ubiquitin ligases and deubiquitinases in bladder cancer development and immunotherapy

Bladder cancer is one of the common malignant urothelial tumors. Post-translational modification (PTMs), including ubiquitination, acetylation, methylation, and phosphorylation, have been revealed to participate in bladder cancer initiation and progression. Ubiquitination is the common PTM, which is conducted by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin-protein ligase. E3 ubiquitin ligases play a key role in bladder oncogenesis and progression and drug resistance in bladder cancer. Therefore, in this review, we summarize current knowledge regarding the functions of E3 ubiquitin ligases in bladder cancer development. Moreover, we provide the evidence of E3 ubiquitin ligases in regulation of immunotherapy in bladder cancer. Furthermore, we mention the multiple compounds that target E3 ubiquitin ligases to improve the therapy efficacy of bladder cancer. We hope our review can stimulate researchers and clinicians to investigate whether and how targeting E3 ubiquitin ligases acts a novel strategy for bladder cancer therapy.

FBXW7 attenuates tumor drug resistance and enhances the efficacy of immunotherapy

FBXW7 (F-box and WD repeat domain containing 7) is a critical subunit of the Skp1-Cullin1-F-box protein (SCF), acting as an E3 ubiquitin ligase by ubiquitinating targeted protein. Through degradation of its substrates, FBXW7 plays a pivotal role in drug resistance in tumor cells and shows the potential to rescue the sensitivity of cancer cells to drug treatment. This explains why patients with higher FBXW7 levels exhibit higher survival times and more favorable prognosis. Furthermore, FBXW7 has been demonstrated to enhance the efficacy of immunotherapy by targeting the degradation of specific proteins, as compared to the inactivated form of FBXW7. Additionally, other F-box proteins have also shown the ability to conquer drug resistance in certain cancers. Overall, this review aims to explore the function of FBXW7 and its specific effects on drug resistance in cancer cells.

The E3 ubiquitin ligases regulate PD-1/PD-L1 protein levels in tumor microenvironment to improve immunotherapy

The tumor microenvironment (TME) is the tumor surrounding environment, which is critical for tumor development and progression. TME is also involved in clinical intervention and treatment outcomes. Modulation of TME is useful for improving therapy strategies. PD-L1 protein on tumor cells interacts with PD-1 protein on T cells, contributing to T cell dysfunction and exhaustion, blockage of the immune response. Evidence has demonstrated that the expression of PD-1/PD-L1 is associated with clinical response to anti-PD-1/PD-L1 therapy in cancer patients. It is important to discuss the regulatory machinery how PD-1/PD-L1 protein is finely regulated in tumor cells. In recent years, studies have demonstrated that PD-1/PD-L1 expression was governed by various E3 ubiquitin ligases in TME, contributing to resistance of anti-PD-1/PD-L1 therapy in human cancers. In this review, we will discuss the role and molecular mechanisms of E3 ligases-mediated regulation of PD-1 and PD-L1 in TME. Moreover, we will describe how E3 ligases-involved PD-1/PD-L1 regulation alters anti-PD-1/PD-L1 efficacy. Altogether, targeting E3 ubiquitin ligases to control the PD-1/PD-L1 protein levels could be a potential strategy to potentiate immunotherapeutic effects in cancer patients.

Fbxo45 promotes the malignant development of esophageal squamous cell carcinoma by targeting GGNBP2 for ubiquitination and degradation

Esophageal squamous cell carcinoma (ESCC) is one of the most common and deadly cancers. Fbxo45, a substrate recognition subunit of E3 ligase, is critically involved in tumorigenesis and tumor progression. However, the function of Fbxo45 and the underlying mechanisms have not been elucidated in ESCC. We used cellular and molecular methods to explore the molecular basis of Fbxo45-mediated ESCC development. We found that ectopic overexpression of Fbxo45 promoted the growth of Kyse-150, Kyse30 and ECA-109 cells and inhibited the apoptosis. Moreover, overexpression of Fbxo45 promoted the migration and invasion of ESCC cells. Consistently, knockdown of Fbxo45 exhibited the opposite effects on ESCC cells. Mechanistically, we observed that Fbxo45 binds to GGNBP2 via its SPRY domain and targets GGNBP2 for ubiquitination and degradation. GGNBP2 overexpression exhibited anticancer activity in ESCC cells. Furthermore, Fbxo45 exerted its functions by regulating GGNBP2 stability in ESCC cells. Notably, overexpression of Fbxo45 facilitated tumor growth in mice. Strikingly, Fbxo45 was highly expressed in ESCC tissues, and GGNBP2 had a lower expression in ESCC specimens. High expression of Fbxo45 and low expression of GGNBP2 were associated with poor prognosis in ESCC patients. Fbxo45 was negatively correlated with GGNBP2 expression in ESCC tissues. Therefore, Fbxo45 serves as an oncoprotein to promote ESCC tumorigenesis by targeting the stability of the tumor suppressor GGNBP2 in ESCC.

Fbxo22 promotes cervical cancer progression via targeting p57Kip2 for ubiquitination and degradation

F-box only protein 22 (FBXO22) is a key subunit of the Skp1-Cullin 1-F-box protein (SCF) E3 ubiquitin ligase complex. Little is known regarding its biological function and underlying molecular mechanisms in regulating cervical cancer (CC) progression. In this study, we aim to explore the role and mechanism of FBXO22 in CC progression. The correlation between FBXO22 and clinicopathological characteristics of CC was analyzed by tissue microarray. MTT, colony formation, flow cytometry, Western blotting, qRT-PCR, protein half-life, co-immunoprecipitation, ubiquitination, and xenograft experiments were performed to assess the functions of FBXO22 and potential molecular mechanisms of FBXO22-mediated malignant progression in CC. The expression of FBXO22 protein in CC tissues was higher than that in adjacent non-tumor cervical tissues. Notably, high expression of FBXO22 was significantly associated with high histology grades, positive lymph node metastasis, and poor outcomes in CC patients. Functionally, ectopic expression of FBXO22 promoted cell viability in vitro and induced tumor growth in vivo, while knockdown of FBXO22 exhibited opposite effects. In addition, overexpression of FBXO22 promoted G1/S phase progression and inhibited apoptosis in CC cells. Mechanistically, FBXO22 physically interacted with the cyclin-dependent kinase inhibitor p57Kip2 and subsequently mediated its ubiquitination and proteasomal degradation leading to tumor progression. FBXO22 protein level was found negatively associated with p57Kip2 protein levels in patient CC samples. FBXO22 promotes CC progression partly through regulating the ubiquitination and proteasomal degradation of p57Kip2. Our study indicates that FBXO22 might be a novel prognostic biomarker and therapeutic target for CC.

CACNA1C-AS2 inhibits cell proliferation and suppresses cell migration and invasion via targeting FBXO45 and PI3K/AKT/mTOR pathways in glioma

Glioma is the most common brain cancer with a poor prognosis, and its underlying molecular mechanisms still needs to be further explored. In the current study, we discovered that an antisense lncRNA, CACNA1C-AS2, suppressed growth, migration and invasion of glioma cells, suggesting that CACNA1C-AS2 functions as a tumor suppressor. Furthermore, we found that CACNA1C-AS2 negatively regulated Fbxo45 protein expression in glioma cells. Impressively, extensive experimental results revealed that Fbxo45 accelerated growth, migration and invasion of glioma cells. Clinically, increased Fbxo45 expression was observed in 75 human glioma tissue samples. Moreover, in vivo experiments also demonstrated that Fbxo45 overexpression enhanced tumor growth in mice. Especially, we further identified that Fbxo45 activated mTORC1 rather than mTORC2 through PI3K/AKT signaling to promote cell growth and motility in glioma cells. Rescue experiments also exhibited that CACNA1C-AS2 inhibited cell growth and motility partly through down-regulating Fbxo45 expression in glioma. Our results provide the novel insights into the critical role of CACNA1C-AS2/Fbxo45/mTOR axis involved in regulating glioma tumorigenesis and progression, and further indicate that CACNA1C-AS2 and Fbxo45 may be the potential biomarkers and therapeutic targets for glioma.

The functions of lncRNAs in the HPV-negative cervical cancer compared with HPV-positive cervical cancer

Cervical cancer is one of the most common female malignancies. Human papillomaviruses (HPV) are the main causative agents of virtually all cervical carcinomas. Nevertheless, emerging evidence has demonstrated that a small proportion of cervical cancer patients are HPV negative. Long noncoding RNAs (lncRNAs) have been identified to play a crucial role in cervical cancer development. Here, this review describes the incidence and development of HPV-negative cervical cancer. Moreover, HPV-negative cervical cancers are more likely diagnosed at non-squamous type, older ages, more advanced stage and metastases, and associated with poorer prognosis as compared to HPV-positive cervical cancer. Furthermore, the significant role and functions of lncRNAs underlying HPV-negative cervical cancer is clarified.

LncRNA SCAMP1 disrupts the balance between miR-26a-5p and ZEB2 to promote osteosarcoma cell viability and invasion

Osteosarcoma often occurs in children and adolescents and affects their health. The survival rate of osteosarcoma patients is unsatisfactory due to the lack of early detection and metastasis development and drug resistance. Hence, dissection of molecular insight into osteosarcoma initiation and progression is pivotal to provide the new therapeutic strategy. In recent years, long noncoding RNAs (lncRNAs) have burst into stage in osteosarcoma development and malignant behaviors. LncRNA SCAMP1 has been discovered to play an essential role in carcinogenesis and progression. However, the mechanisms of lncRNA SCAMP1-involved tumorigenesis have not been reported in human osteosarcoma. In this study, we utilized multiple cellular biological approaches to determine the function of lncRNA SCAMP1 in osteosarcoma cells. Moreover, we performed several molecular biological approaches to define the mechanism by which lncRNA SCAMP1 regulated cell viability and invasion in osteosarcoma. We dissected that lncRNA SCAMP1 promoted progression of osteosarcoma via modulation of miR-26a-5p/ZEB2 axis. In conclusion, targeting lncRNA SCAMP1 and its downstream targets, miR-26a-5p and ZEB2, might be a useful approach for osteosarcoma therapy.

The functions of long noncoding RNAs on regulation of F-box proteins in tumorigenesis and progression

Accumulated evidence has revealed that F-box protein, a subunit of SCF E3 ubiquitin ligase complexes, participates in carcinogenesis and tumor progression via targeting its substrates for ubiquitination and degradation. F-box proteins could be regulated by cellular signaling pathways and noncoding RNAs in tumorigenesis. Long noncoding RNA (lncRNA), one type of noncoding RNAs, has been identified to modulate the expression of F-box proteins and contribute to oncogenesis. In this review, we summarize the role and mechanisms of multiple lncRNAs in regulating F-box proteins in tumorigenesis, including lncRNAs SLC7A11-AS1, MT1JP, TUG1, FER1L4, TTN-AS1, CASC2, MALAT1, TINCR, PCGEM1, linc01436, linc00494, GATA6-AS1, and ODIR1. Moreover, we discuss that targeting these lncRNAs could be helpful for treating cancer via modulating F-box protein expression. We hope our review can stimulate the research on exploration of molecular insight into how F-box proteins are governed in carcinogenesis. Therefore, modulation of lncRNAs is a potential therapeutic strategy for cancer therapy via regulation of F-box proteins.

Targeting matrix metalloproteinases by E3 ubiquitin ligases as a way to regulate the tumor microenvironment for cancer therapy

The tumor microenvironment (TME) plays an important role in neoplastic development. Matrix metalloproteinases (MMPs) are critically involved in tumorigenesis by modulation of the TME and degradation of the extracellular matrix (ECM) in a large variety of malignancies. Evidence has revealed that dysregulated MMPs can lead to ECM damage, the promotion of cell migration and tumor metastasis. The expression and activities of MMPs can be tightly regulated by TIMPs, multiple signaling pathways and noncoding RNAs. MMPs are also finely controlled by E3 ubiquitin ligases. The current review focuses on the molecular mechanism by which MMPs are governed by E3 ubiquitin ligases in carcinogenesis. Due to the essential role of MMPs in oncogenesis, they have been considered the attractive targets for antitumor treatment. Several strategies that target MMPs have been discovered, including the use of small-molecule inhibitors, peptides, inhibitory antibodies, natural compounds with anti-MMP activity, and RNAi therapeutics. However, these molecules have multiple disadvantages, such as poor solubility, severe side-effects and low oral bioavailability. Therefore, it is necessary to discover the novel inhibitors that suppress MMPs for cancer therapy. Here, we discuss the therapeutic potential of targeting E3 ubiquitin ligases to inhibit MMPs. We hope this review will stimulate the discovery of novel therapeutics for the MMP-targeted treatment of a variety of human cancers.

Clinical significance of FBXW7 loss of function in human cancers

FBXW7 (F-Box and WD Repeat Domain Containing 7) (also referred to as FBW7 or hCDC4) is a component of the Skp1-Cdc53 / Cullin-F-box-protein complex (SCF/β-TrCP). As a member of the F-box protein family, FBXW7 serves a role in phosphorylation-dependent ubiquitination and proteasome degradation of oncoproteins that play critical role(s) in oncogenesis. FBXW7 affects many regulatory functions involved in cell survival, cell proliferation, tumor invasion, DNA damage repair, genomic instability and telomere biology. This thorough review of current literature details how FBXW7 expression and functions are regulated through multiple mechanisms and how that ultimately drives tumorigenesis in a wide array of cell types. The clinical significance of FBXW7 is highlighted by the fact that FBXW7 is frequently inactivated in human lung, colon, and hematopoietic cancers. The loss of FBXW7 can serve as an independent prognostic marker and is significantly correlated with the resistance of tumor cells to chemotherapeutic agents and poorer disease outcomes. Recent evidence shows that genetic mutation of FBXW7 differentially affects the degradation of specific cellular targets resulting in a distinct and specific pattern of activation/inactivation of cell signaling pathways. The clinical significance of FBXW7 mutations in the context of tumor development, progression, and resistance to therapies as well as opportunities for targeted therapies is discussed.

Robust Prediction of Prognosis and Immunotherapeutic Response for Clear Cell Renal Cell Carcinoma Through Deep Learning Algorithm

It is of great urgency to explore useful prognostic markers and develop a robust prognostic model for patients with clear-cell renal cell carcinoma (ccRCC). Three independent patient cohorts were included in this study. We applied a high-level neural network based on TensorFlow to construct the robust model by using the deep learning algorithm. The deep learning-based model (FB-risk) could perform well in predicting the survival status in the 5-year follow-up, which could also significantly distinguish the patients with high overall survival risk in three independent patient cohorts of ccRCC and a pan-cancer cohort. High FB-risk was found to be partially associated with negative regulation of the immune system. In addition, the novel phenotyping of ccRCC based on the F-box gene family could robustly stratify patients with different survival risks. The different mutation landscapes and immune characteristics were also found among different clusters. Furthermore, the novel phenotyping of ccRCC based on the F-box gene family could perform well in the robust stratification of survival and immune response in ccRCC, which might have potential for application in clinical practices.

Diverse Roles of F-BoxProtein3 in Regulation of Various Cellular Functions

Accumulated evidence shows that the F-box protein 3 (FBXO3) has multiple biological functions, including regulation of immune pathologies, neuropathic diseases and antiviral response. In this review article, we focus on the role of FBXO3 in inflammatory disorders and human malignancies. We also describe the substrates of FBXO3, which contribute to inflammatory disorders and cancers. We highlight that the high expression of FBXO3 is frequently observed in rheumatoid arthritis, leukemia, pituitary adenoma, and oral squamous cell carcinoma. Moreover, we discuss the regulation of FBXO3 by both carcinogens and cancer preventive agents. Our review provides a comprehensive understanding of the role of FBXO3 in various biological systems and elucidates how FBXO3 regulates substrate ubiquitination and degradation during various physiological and pathological processes. Therefore, FBXO3 can be a novel target in the treatment of human diseases including carcinomas.

FBXO17 Inhibits the Wnt/β-Catenin Pathway and Proliferation of Ishikawa Cells

Uterine corpus endometrial carcinoma (UCEC) is one of the most common types of cancer in women, and the incidence is rapidly increasing. Studies have shown that various signaling pathways serve crucial roles in the tumorigenesis of UCEC, amongst which the Wnt/β-catenin pathway is of great interest due to its crucial role in cell proliferation and the huge potential as a therapeutic target. In the present study, it was shown that FBXO17, which is a member of the F-box family, is abnormally downregulated in UCEC tissues compared with non-tumor endometrial tissues, and this was significantly associated with the clinical histological grade, as well as the abnormal proliferation of the UCEC cell line, Ishikawa, both in vitro and in vivo. Besides, the results suggested that FBXO17 may inhibit the Wnt/β-catenin signaling pathway and influence the expression of adhesion molecules, such as E-cadherin and N-cadherin in Ishikawa cells. In conclusion, these findings indicate that FBXO17 is a novel inhibitor of endometrial tumor development and it likely exerts effects via regulation of the Wnt signaling pathway.

F-box proteins in cancer stemness: An emerging prognostic and therapeutic target

Cancer is a complex heterogenic disease with significant therapeutic challenges. The presence of cancer stem cells (CSCs) in cancer tissue orchestrates tumor growth, progression, and metastasis, the tumor heterogeneity, disease relapse, and therapeutic resistance. Hence, it is imperative to explore how progenitor or cancer-initiating cells acquire stemness features and reprogram different biological mechanisms to maintain their sustained oncogenicity. Interestingly, deregulation of F-box proteins (FBPs) is crucial for cancer stemness features, including drug resistance and disease relapse. In this review, we highlight recent updates on the clinical significance of targeting FBPs in cancer therapy, with emphasis on eliminating CSCs and associated therapeutic challenges. Moreover, we also discuss novel strategies for the selective elimination of CSCs by targeting FBPs.

MicroRNA-221 Promotes Cell Proliferation and Inhibits Apoptosis in Osteosarcoma Cells by Directly Targeting FBXW11 and Regulating Wnt Signaling

BACKGROUND AND OBJECTIVES

MicroRNAs play a crucial role in the progression of various cancers, and microRNA-221 (miR-221) has been observed to be significantly overexpressed in osteosarcoma (OS) cells. FBXW11, a vital F-box protein of the ubiquitin-proteasome system, mediates the proliferation and survival of cancer cells by targeting multiple substrates for degradation. FBXW11 inhibits OS growth and metastasis by antagonizing the β-catenin/Wnt signaling pathway. Therefore, we hypothesized that miR-221 targets FBXW11 to mediate Wnt signaling and promote OS proliferation.

METHODS

In this study, we demonstrated the increased expression of miR-221 and FBXW11 in OS tissues and cell lines by real-time polymerase chain reaction (RT-PCR). Moreover, to elucidate the regulatory mechanism(s) of miR-221 and FBXW11 in progression, cell viability and apoptosis were analyzed by the MTT assay and flow cytometry, respectively.

RESULTS

The results showed that the overexpression of miR-221 in OS cells dramatically promoted cell growth and cell cycle progression, and inhibited apoptosis, whereas miR-221 inhibitors conversely inhibited proliferation and promoted apoptosis in OS cells. The data also showed that FBXW11 directly targeted miR-221 and miR-221 regulated OS cell proliferation and apoptosis by binding to FBXW11. We further confirmed that miR-221 targeted FBXW11 to promote proliferation and inhibit apoptosis in OS cell lines by inhibiting Wnt signaling.

INTERPRETATION AND CONCLUSIONS

Overall, our study revealed a functional mechanism for miR-221 in OS. Further studies will elucidate its role in the progression of OS and inhibiting miR-221 may represent a useful treatment strategy.

The characteristics and roles of β-TrCP1/2 in carcinogenesis

β-transducin repeat-containing protein (β-TrCP), one of the well-characterized F-box proteins, acts as a substrate receptor and constitutes an active SCF^β-TrCP E3 ligase with a scaffold protein CUL1, a RING protein RBX1, and an adaptor protein SKP1. β-TrCP plays a critical role in the regulation of various physiological and pathological processes, including signal transduction, cell cycle progression, cell migration, DNA damage response, and tumorigenesis, by governing burgeoning amounts of key regulators for ubiquitination and proteasomal degradation. Given that a variety of β-TrCP substrates are well-known oncoproteins and tumor suppressors, and dysregulation of β-TrCP is frequently identified in human cancers, β-TrCP plays a vital role in carcinogenesis. In this review, we first briefly introduce the characteristics of β-TrCP1, β-TrCP2, and SCF^β-TrCP ubiquitin ligase, and then discuss SCF^β-TrCP ubiquitin ligase regulated biological processes by targeting its substrates for degradation. Moreover, we summarize the regulation of β-TrCP1 and β-TrCP2 at multiple layers and further discuss the various roles of β-TrCP1 and β-TrCP2 in human cancer, functioning as either an oncoprotein or a tumor suppressor in a manner dependent of cellular context. Finally, we provide novel insights for future perspectives on the potential of targeting β-TrCP1 and β-TrCP2 for cancer therapy.

FBXO45 is a potential therapeutic target for cancer therapy

FBXO protein 45 (FBXO45), a substrate-recognition subunit of E3 ligases, has been characterised to have pivotal roles in many human diseases, including nervous system diseases, inflammatory diseases and human malignancies. In this article, we describe the expression of FBXO45 in several types of human tumour specimens and highlight the downstream substrates of FBXO45. Moreover, the biological functions of FBXO45 in the regulation of proliferation, apoptosis, the cell cycle and metastasis are mentioned. Furthermore, we describe that the expression level of FBXO45 is regulated by several upstream factors such as miR-27a, Hey1, m6A and the lncRNA RP11. As FBXO45 has a critical role in tumorigenesis and progression, FBXO45 might be a novel therapeutic target for cancer treatment.