F-box protein FBXW7 inhibits cancer metastasis in a non-cell-autonomous manner

Identification of effective CCR2 inhibitors for cancer therapy using humanized mice

C-C chemokine receptor type 2 (CCR2) is the receptor for C-C motif chemokine 2 (CCL2) and is associated with various inflammatory diseases and cancer metastasis. Although many inhibitors for CCR2 have been developed, it remains unresolved which inhibitors are the most effective in the clinical setting. In the present study, we compared 10 existing human CCR2 antagonists in a calcium influx assay using human monocytic leukemia cells. Among them, MK0812 was found to be the most potent inhibitor of human CCR2. Furthermore, we generated a human CCR2B knock-in mouse model to test the efficacy of MK0812 against a lung metastasis model of breast cancer. Oral administration of MK0812 to humanized mice did indeed reduce the number of monocytic myeloid-derived suppressor cells and the rate of lung metastasis. These results suggest that MK0812 is the most promising candidate among the commercially available CCR2 inhibitors. We propose that combining these two screening methods may provide an excellent experimental method for identifying effective drugs that inhibit human CCR2.

Role of the ubiquitin-proteasome system on macrophages in the tumor microenvironment

Tumor-associated macrophages (TAMs) are key components of the tumor microenvironment, and their different polarization states play multiple roles in tumors by secreting cytokines, chemokines, and so on, which are closely related to tumor development. In addition, the enrichment of TAMs is often associated with poor prognosis of tumors. Thus, targeting TAMs is a potential tumor treatment strategy, in which therapeutic approaches such as reducing TAMs numbers, remodeling TAMs phenotypes, and altering their functions are being extensively investigated. Meanwhile, the ubiquitin-proteasome system (UPS), an important mechanism of protein hydrolysis in eukaryotic cells, participates in cellular processes by regulating the activity and stability of key proteins. Interestingly, UPS plays a dual role in the process of tumor development, and its role in TAMs deserve to be investigated in depth. This review builds on this foundation to further explore the multiple roles of UPS on TAMs and identifies a promising approach to treat tumors by targeting TAMs with UPS.

KPNA2 Silencing, Regulated by E3 Ubiquitin Ligase FBXW7, Alleviates Endothelial Dysfunction and Inflammation Through Inhibiting the Nuclear Translocation of p65 and IRF3: A Possible Therapeutic Approach for Atherosclerosis

Atherosclerosis (AS), characterized by a maladaptive inflammatory response, is one of the most common causes of death among the elderly. Karyopherin subunit alpha 2 (KPNA2), a member of the nuclear transport protein family, has been reported to play a pro-inflammatory role in various pathological processes by regulating the nuclear translocation of pro-inflammatory transcription factors. However, the function of KPNA2 in AS remains unknown. ApoE-/- mice were fed high-fat diets for 12 weeks to establish an AS mice model. Human umbilical vein endothelial cells (HUVECs) were treated with lipopolysaccharide (LPS) to establish an AS cell model. We found that KPNA2 was upregulated in the aortic roots of atherosclerotic mice and LPS-stimulated cells. KPNA2 knockdown inhibited LPS-induced secretion of pro-inflammatory factors and monocyte-endothelial adhesion in HUVECs, whereas KPNA2 overexpression exerted the opposite effects. p65 and interferon regulatory factor 3 (IRF3), the transcription factors known to regulate the transcription of pro-inflammatory genes, interacted with KPNA2, and their nuclear translocations were blocked following KPNA2 silencing. Furthermore, we found that KPNA2 protein level was decreased by E3 ubiquitin ligase F-box and WD repeat domain containing 7 (FBXW7), which was downregulated in the atherosclerotic mice. FBXW7 overexpression induced ubiquitination with subsequent proteasomal degradation of KPNA2. Meanwhile, the effects of KPNA2 deficiency on atherosclerotic lesions were further confirmed by in vivo experiments. Taken together, our study indicates that KPNA2 downregulation, regulated by FBXW7, may alleviate endothelial dysfunction and related inflammation in the progression of AS by suppressing the nuclear translocation of p65 and IRF3.

The role of germanium in diseases: exploring its important biological effects

With the development of organic germanium and nanotechnology, germanium serves multiple biological functions, and its potential value in biochemistry and medicine has increasingly captured the attention of researchers. In recent years, germanium has gradually gained significance as a material in the field of biomedicine and shows promising application prospects. However, there has been a limited amount of research conducted on the biological effects and mechanisms of germanium, and a systematic evaluation is still lacking. Therefore, the aim of this review is to systematically examine the application of germanium in the field of biomedicine and contribute new insights for future research on the functions and mechanisms of germanium in disease treatment. By conducting a comprehensive search on MEDLINE, EMBASE, and Web of Science databases, we systematically reviewed the relevant literature on the relationship between germanium and biomedicine. In this review, we will describe the biological activities of germanium in inflammation, immunity, and antioxidation. Furthermore, we will discuss its role in the treatment of neuroscience and oncology-related conditions. This comprehensive exploration of germanium provides a valuable foundation for the future application of this element in disease intervention, diagnosis, and prevention.

Nanocarrier-based targeting of metabolic pathways for endometrial cancer: Status and future perspectives

Cancer is the second-most lethal global disease, as per health reports, and is responsible for around 70% of deaths in low- and middle-income countries. Endometrial cancer is one of the emerging malignancies and has been predicted as a public health challenge for the future. Insulin resistance, obesity, and diabetes mellitus are the key metabolic factors that promote risks for the development of endometrial cancer. Various signaling pathways and associated genes are involved in the genesis of endometrial cancer, and any mutation or deletion in such related factors leads to the induction of endometrial cancer. The conventional way of drug delivery has been used for ages but is associated with poor management of cancer due to non-targeting of the endometrial cancer cells, low efficacy of the therapy, and toxicity issues as well. In this context, nanocarrier-based therapy for the management of endometrial cancer is an effective alternate choice that overcomes the problems associated with conventional therapy. In this review article, we highlighted the nanocarrier-based targeting of endometrial cancer, with a special focus on targeting various metabolic signaling pathways. Furthermore, the future perspectives of nanocarrier-based targeting of metabolic pathways in endometrial cancer were also underpinned. It is concluded that targeting metabolic signaling pathways in endometrial cancer via nanocarrier scaffolds is the future of pharmaceutical design for the significant management and treatment of endometrial cancer.

InDEP: an interpretable machine learning approach to predict cancer driver genes from multi-omics data

Cancer driver genes are critical in driving tumor cell growth, and precisely identifying these genes is crucial in advancing our understanding of cancer pathogenesis and developing targeted cancer drugs. Despite the current methods for discovering cancer driver genes that mainly rely on integrating multi-omics data, many existing models are overly complex, and it is difficult to interpret the results accurately. This study aims to address this issue by introducing InDEP, an interpretable machine learning framework based on cascade forests. InDEP is designed with easy-to-interpret features, cascade forests based on decision trees and a KernelSHAP module that enables fine-grained post-hoc interpretation. Integrating multi-omics data, InDEP can identify essential features of classified driver genes at both the gene and cancer-type levels. The framework accurately identifies driver genes, discovers new patterns that make genes as driver genes and refines the cancer driver gene catalog. In comparison with state-of-the-art methods, InDEP proved to be more accurate on the test set and identified reliable candidate driver genes. Mutational features were the primary drivers for InDEP's identifying driver genes, with other omics features also contributing. At the gene level, the framework concluded that substitution-type mutations were the main reason most genes were identified as driver genes. InDEP's ability to identify reliable candidate driver genes opens up new avenues for precision oncology and discovering new biomedical knowledge. This framework can help advance cancer research by providing an interpretable method for identifying cancer driver genes and their contribution to cancer pathogenesis, facilitating the development of targeted cancer drugs.

FBXW7 in breast cancer: mechanism of action and therapeutic potential

Breast cancer is one of the frequent tumors that seriously endanger the physical and mental well-being in women. F-box and WD repeat domain-containing 7 (FBXW7) is a neoplastic repressor. Serving as a substrate recognition element for ubiquitin ligase, FBXW7 participates in the ubiquitin-proteasome system and is typically in charge of the ubiquitination and destruction of crucial oncogenic proteins, further performing a paramount role in cell differentiation, apoptosis and metabolic processes. Low levels of FBXW7 cause abnormal stability of pertinent substrates, mutations and/or deletions in the FBXW7 gene have been reported to correlate with breast cancer malignant progression and chemoresistance. Given the lack of an effective solution to breast cancer's clinical drug resistance dilemma, elucidating FBXW7's mechanism of action could provide a theoretical basis for targeted drug exploration. Therefore, in this review, we focused on FBXW7's role in a range of breast cancer malignant behaviors and summarized the pertinent cellular targets, signaling pathways, as well as the mechanisms regulating FBXW7 expression. We also proposed novel perspectives for the exploitation of alternative therapies and specific tumor markers for breast cancer by therapeutic strategies aiming at FBXW7.

The chemokine monocyte chemoattractant protein-1/CCL2 is a promoter of breast cancer metastasis

Breast cancer is the most prevalent cancer worldwide, and metastasis is the leading cause of death in cancer patients. Human monocyte chemoattractant protein-1 (MCP-1/CCL2) was isolated from the culture supernatants of not only mitogen-activated peripheral blood mononuclear leukocytes but also malignant glioma cells based on its in vitro chemotactic activity toward human monocytes. MCP-1 was subsequently found to be identical to a previously described tumor cell-derived chemotactic factor thought to be responsible for the accumulation of tumor-associated macrophages (TAMs), and it became a candidate target of clinical intervention; however, the role of TAMs in cancer development was still controversial at the time of the discovery of MCP-1. The in vivo role of MCP-1 in cancer progression was first evaluated by examining human cancer tissues, including breast cancers. Positive correlations between the level of MCP-1 production in tumors and the degree of TAM infiltration and cancer progression were established. The contribution of MCP-1 to the growth of primary tumors and metastasis to the lung, bone, and brain was examined in mouse breast cancer models. The results of these studies strongly suggested that MCP-1 is a promoter of breast cancer metastasis to the lung and brain but not bone. Potential mechanisms of MCP-1 production in the breast cancer microenvironment have also been reported. In the present manuscript, we review studies in which the role of MCP-1 in breast cancer development and progression and the mechanisms of its production were examined and attempt to draw a consensus and discuss the potential use of MCP-1 as a biomarker for diagnosis.

The Role of FBXW7 in Gynecologic Malignancies

The F-Box and WD Repeat Domain Containing 7 (FBXW7) protein has been shown to regulate cellular growth and act as a tumor suppressor. This protein, also known as FBW7, hCDC4, SEL10 or hAGO, is encoded by the gene FBXW7. It is a crucial component of the Skp1-Cullin1-F-box (SCF) complex, which is a ubiquitin ligase. This complex aids in the degradation of many oncoproteins, such as cyclin E, c-JUN, c-MYC, NOTCH, and MCL1, via the ubiquitin-proteasome system (UPS). The FBXW7 gene is commonly mutated or deleted in numerous types of cancer, including gynecologic cancers (GCs). Such FBXW7 mutations are linked to a poor prognosis due to increased treatment resistance. Hence, detection of the FBXW7 mutation may possibly be an appropriate diagnostic and prognostic biomarker that plays a central role in determining suitable individualized management. Recent studies also suggest that, under specific circumstances, FBXW7 may act as an oncogene. There is mounting evidence indicating that the aberrant expression of FBXW7 is involved in the development of GCs. The aim of this review is to give an update on the role of FBXW7 as a potential biomarker and also as a therapeutic target for novel treatments, particularly in the management of GCs.

Epigenetic status of FBXW7 gene and its role in Ovarian cancer pathogenesis

BACKGROUND

Chromatin immunoprecipitation (ChIP) analysis revealed that the FBXW7 gene and the long non-coding RNA (LINC01588) are potential candidates in epithelial ovarian cancer (EOC) pathogenesis. However, their exact role in EOC is not yet known. Thus, the present study sheds light on the impact of the mutations/ methylation status of the FBXW7 gene.

MATERIALS AND METHODS

We used public databases to assess the correlation between mutations/ methylation status and the FBXW7 expression. Furthermore, we performed Pearson's correlation analysis between the FBXW7 gene and LINC01588. We performed gene panel exome sequencing and Methylation-specific PCR (MSP) in HOSE 6-3, MCAS, OVSAHO, and eight EOC patients' samples to validate the bioinformatics results.

RESULTS

The FBXW7 gene was less expressed in EOC, particularly in stages III and IV, compared to healthy tissues. Furthermore, bioinformatics analysis, gene panel exome sequencing, and MSP revealed that the FBXW7 gene is neither mutated nor methylated in EOC cell lines and tissues, suggesting alternative mechanisms for FBXW7 gene regulation. Interestingly, Pearson's correlation analysis showed an inverse, significant correlation between the FBXW7 gene and LINC01588  expression, suggesting a potential regulatory role of LINC01588.

CONCLUSION

Neither mutations nor methylation is the causative mechanism for the FBXW7 downregulation in EOC, suggesting alternative means involving the lncRNA LINC01588.

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.

Depletion of tumor-associated macrophages inhibits lung cancer growth and enhances the antitumor effect of cisplatin

In lung cancer, tumor-associated macrophages (TAMs), especially M2-like TAMs, represent the main tumor progression components in the tumor microenvironment (TME). Therefore, M2-like TAMs may serve as a therapeutic target. The purpose of this study was to investigate the effect of M2-like TAM depletion in the TME on tumor growth and chemotherapy response in lung cancer. The levels of secreted monocyte chemoattractant protein (MCP-1) and prostaglandin E2 (PGE2) in the supernatants of lung cancer cell lines A549 and LLC were evaluated via ELISA. Cell migration assays were performed to assess the recruitment ability of macrophage cell lines THP-1 and J774-1 cells. Differentiation of macrophages was assessed via flow cytometry. Immunohistochemical staining was performed to visualize M2-like TAMs in transplanted lung cancer in mouse. We used the COX-2 inhibitor nimesulide to inhibit the secretion of MCP-1 and PGE2, which promotes macrophage migration and M2-like differentiation. Nimesulide treatment decreased the secretion of MCP-1 and PGE2 from lung cancer cells. Nimesulide treatment suppressed the migration of macrophages by blocking MCP-1. Lung cancer supernatant induced the differentiation of macrophages toward the M2-like phenotype, and nimesulide treatment inhibited M2-like differentiation by blocking MCP-1 and PGE2. In the lung cancer mouse model, treatment with nimesulide depleted M2-like TAMs in the TME and enhanced the tumor inhibitory effect of cisplatin. Our results indicated that blocking the secretion of MCP-1 and PGE2 from tumor cells depleted M2-like TAMs in the TME and the combination therapy with cisplatin considerably suppressed tumor growth in the LLC mouse model.

Disruption of SLFN11 Deficiency-Induced CCL2 Signaling and Macrophage M2 Polarization Potentiates Anti-PD-1 Therapy Efficacy in Hepatocellular Carcinoma

BACKGROUND & AIMS

The therapeutic effect of immune checkpoint inhibitors (ICIs) is poor in hepatocellular carcinoma (HCC) and varies greatly among individuals. Schlafen (SLFN) family members have important functions in immunity and oncology, but their roles in cancer immunobiology remain unclear. We aimed to investigate the role of the SLFN family in immune responses against HCC.

METHODS

Transcriptome analysis was performed in human HCC tissues with or without response to ICIs. A humanized orthotopic HCC mouse model and a co-culture system were constructed, and cytometry by time-of-flight technology was used to explore the function and mechanism of SLFN11 in the immune context of HCC.

RESULTS

SLFN11 was significantly up-regulated in tumors that responded to ICIs. Tumor-specific SLFN11 deficiency increased the infiltration of immunosuppressive macrophages and aggravated HCC progression. HCC cells with SLFN11 knockdown promoted macrophage migration and M2-like polarization in a C-C motif chemokine ligand 2-dependent manner, which in turn elevated their own PD-L1 expression by activating the nuclear factor-κB pathway. Mechanistically, SLFN11 suppressed the Notch pathway and C-C motif chemokine ligand 2 transcription by binding competitively with tripartite motif containing 21 to the RNA recognition motif 2 domain of RBM10, thereby inhibiting tripartite motif containing 21-mediated RBM10 degradation to stabilize RBM10 and promote NUMB exon 9 skipping. Pharmacologic antagonism of C-C motif chemokine receptor 2 potentiated the antitumor effect of anti-PD-1 in humanized mice bearing SLFN11 knockdown tumors. ICIs were more effective in patients with HCC with high serum SLFN11 levels.

CONCLUSIONS

SLFN11 serves as a critical regulator of microenvironmental immune properties and an effective predictive biomarker of ICIs response in HCC. Blockade of C-C motif chemokine ligand 2/C-C motif chemokine receptor 2 signaling sensitized SLFN11^low HCC patients to ICI treatment.

Pre-metastatic niche: from revealing the molecular and cellular mechanisms to the clinical applications in breast cancer metastasis

Breast cancer (BC) is one of the most commonly diagnosed cancers and the leading cause of cancer-related deaths in women worldwide. Metastasis is a major contributor to high cancer mortality and is usually the endpoint of a series of sequential and dynamic events. One of the critical events is forming a pre-metastatic niche (PMN) that occurs before macroscopic tumor cell invasion and provides a suitable environment for tumor cells to colonize and progress into metastases. Due to the unique characteristics of PMN in cancer metastasis, developing therapies to target PMN may bring new advantages in preventing cancer metastasis at an early stage. Various biological molecules, cells, and signaling pathways are altered in BC, regulating the functions of distinctive immune cells and stromal remodeling, inducing angiogenesis, and effect metabolic reprogramming and organotropism to promote PMN formation. In this review, we elucidate the multifaceted mechanisms contributing to the development of PMN in BC, discuss the characteristics of PMN, and highlight the significance of PMN in providing potential diagnostic and therapeutic strategies for BC metastasis, which may bring promising insights and foundations for future studies.

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.

Recent Insight on Regulations of FBXW7 and Its Role in Immunotherapy

SCF^FBXW7 E3 ubiquitin ligase complex is a crucial enzyme of the ubiquitin proteasome system that participates in variant activities of cell process, and its component FBXW7 (F-box and WD repeat domain–containing 7) is responsible for recognizing and binding to substrates. The expression of FBXW7 is controlled by multiple pathways at different levels. FBXW7 facilitates the maturity and function maintenance of immune cells via functioning as a mediator of ubiquitination-dependent degradation of substrate proteins. FBXW7 deficiency or mutation results in the growth disturbance and dysfunction of immune cell, leads to the resistance against immunotherapy, and participates in multiple illnesses. It is likely that FBXW7 coordinating with its regulators and substrates could offer potential targets to improve the sensitivity and effects of immunotherapy. Here, we review the mechanisms of the regulation on FBXW7 and its tumor suppression role in immune filed among various diseases (mostly cancers) to explore novel immune targets and treatments.

Tumor-Associated Macrophages Regulate PD-1/PD-L1 Immunosuppression

Anti-programmed cell death 1 (PD-1) or anti-PD-ligand (L) 1 drugs, as classic immune checkpoint inhibitors, are considered promising treatment strategies for tumors. In clinical practice, some cancer patients experience drug resistance and disease progression in the process of anti-PD-1/PD-L1 immunotherapy. Tumor-associated macrophages (TAMs) play key roles in regulating PD-1/PD-L1 immunosuppression by inhibiting the recruitment and function of T cells through cytokines, superficial immune checkpoint ligands, and exosomes. There are several therapies available to recover the anticancer efficacy of PD-1/PD-L1 inhibitors by targeting TAMs, including the inhibition of TAM differentiation and re-education of TAM activation. In this review, we will summarize the roles and mechanisms of TAMs in PD-1/PD-L1 blocker resistance. Furthermore, we will discuss the therapies that were designed to deplete TAMs, re-educate TAMs, and intervene with chemokines secreted by TAMs and exosomes from M1 macrophages, providing more potential options to improve the efficacy of PD-1/PD-L1 inhibitors.

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.

Global and context-specific transcriptional consequences of oncogenic Fbw7 mutations

The Fbw7 ubiquitin ligase targets many proteins for proteasomal degradation, which include oncogenic transcription factors (TFs) (e.g., c-Myc, c-Jun, and Notch). Fbw7 is a tumor suppressor and tumors often contain mutations in FBXW7, the gene that encodes Fbw7. The complexity of its substrate network has obscured the mechanisms of Fbw7-associated tumorigenesis, yet this understanding is needed for developing therapies. We used an integrated approach employing RNA-Seq and high-resolution mapping (cleavage under target and release using nuclease) of histone modifications and TF occupancy (c-Jun and c-Myc) to examine the combinatorial effects of misregulated Fbw7 substrates in colorectal cancer (CRC) cells with engineered tumor-associated FBXW7 null or missense mutations. Both Fbw7 mutations caused widespread transcriptional changes associated with active chromatin and altered TF occupancy: some were common to both Fbw7 mutant cell lines, whereas others were mutation specific. We identified loci where both Jun and Myc were coregulated by Fbw7, suggesting that substrates may have synergistic effects. One coregulated gene was CIITA, the master regulator of MHC Class II gene expression. Fbw7 loss increased MHC Class II expression and Fbw7 mutations were correlated with increased CIITA expression in TCGA colorectal tumors and cell lines, which may have immunotherapeutic implications for Fbw7-associated cancers. Analogous studies in neural stem cells in which FBXW7 had been acutely deleted closely mirrored the results in CRC cells. Gene set enrichment analyses revealed Fbw7-associated pathways that were conserved across both cell types that may reflect fundamental Fbw7 functions. These analyses provide a framework for understanding normal and neoplastic context-specific Fbw7 functions.

Targeting Oncogenic Pathways in the Era of Personalized Oncology: A Systemic Analysis Reveals Highly Mutated Signaling Pathways in Cancer Patients and Potential Therapeutic Targets

Cancer is the second leading cause of death globally. One of the main hallmarks in cancer is the functional deregulation of crucial molecular pathways via driver genetic events that lead to abnormal gene expression, giving cells a selective growth advantage. Driver events are defined as mutations, fusions and copy number alterations that are causally implicated in oncogenesis. Molecular analysis on tissues that have originated from a wide range of anatomical areas has shown that mutations in different members of several pathways are implicated in different cancer types. In recent decades, significant efforts have been made to incorporate this knowledge into daily medical practice, providing substantial insight towards clinical diagnosis and personalized therapies. However, since there is still a strong need for more effective drug development, a deep understanding of the involved signaling mechanisms and the interconnections between these pathways is highly anticipated. Here, we perform a systemic analysis on cancer patients included in the Pan-Cancer Atlas project, with the aim to select the ten most highly mutated signaling pathways (p53, RTK-RAS, lipids metabolism, PI-3-Kinase/Akt, ubiquitination, b-catenin/Wnt, Notch, cell cycle, homology directed repair (HDR) and splicing) and to provide a detailed description of each pathway, along with the corresponding therapeutic applications currently being developed or applied. The ultimate scope is to review the current knowledge on highly mutated pathways and to address the attractive perspectives arising from ongoing experimental studies for the clinical implementation of personalized medicine.

F-box and WD repeat domain-containing 7 (FBXW7) mediates the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect hypoxic-ischemic brain damage in neonatal rats

The aim of this study was to determine whether F-box and WD repeat domain-containing 7 (FBXW7) can mediate the hypoxia inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) signaling pathway to affect neonatal hypoxic-ischemic brain damage (HIBD) in neonatal rats. HIBD rats were treated with LV-shFBXW7. Cerebral infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining, while microvessel density (MVD) was evaluated by immunohistochemistry. Learning and memory were tested using the Morris water maze (MWM) test. FBXW7 and HIF-1α/VEGF signaling pathway proteins were measured by Western blotting. Brain microvascular endothelial cells (BMECs) were isolated to establish an oxygen-glucose deprivation (OGD) model to evaluate treatment with FBXW7 siRNA. Cell viability was detected using a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay, while cell migration was evaluated using a wound healing assay. The tube formation of BMECs was also assessed. The results demonstrated that HIBD rats exhibited increased protein expression of FBXW7, HIF-1α, and VEGF. HIBD rats also displayed increased cerebral infarct size, prolonged escape latency and a decreased number of platform crossings. However, HIBD rats treated with LV-shFBXW7 exhibited reversal of these changes. In vitro experiments showed that BMECs in the OGD group had significantly decreased cell viability, shorter vascular lumen length, and shorter migration distance than cells in the control group. Moreover, silencing FBXW7 promoted proliferation, tube formation and migration of BMECs. Taken together, silencing FBXW7 upregulates the HIF-1α/VEGF signaling pathway to promote the angiogenesis of neonatal HIBD rats after brain injury, reducing infarct volume and improving recovery of nerve function in HIBD rats.

Immune Effect of Active Components of Traditional Chinese Medicine on Triple-Negative Breast Cancer

Triple-negative breast cancers are heterogeneous, poorly prognostic, and metastatic malignancies that result in a high risk of death for patients. Targeted therapy for triple-negative breast cancer has been extremely challenging due to the lack of expression of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Clinical treatment regimens for triple-negative breast cancer are often based on paclitaxel and platinum drugs, but drug resistance and side effects from the drugs frequently lead to treatment failure, thus requiring the development of new therapeutic platforms. In recent years, research on traditional Chinese medicine in modulating the immune function of the body has shown that it has the potential to be an effective treatment option against triple-negative breast cancer. Active components of herbal medicines such as alkaloids, flavonoids, polyphenols, saponins, and polysaccharides have been shown to inhibit cancer cell proliferation and metastasis by activating inflammatory immune responses and can modulate tumor-related signaling pathways to further inhibit the invasion of triple-negative breast cancer. This paper reviews the immunomodulatory mechanisms of different herbal active ingredients against triple-negative breast cancer and provides an outlook on the challenges and directions of development for the treatment of triple-negative breast cancer with herbal active ingredients.

FBXW7alpha Promotes the Recovery of Traumatic Spinal Cord

BACKGROUND

White matter damage and neuronal cell death are incurred by spinal cord injury (SCI). FBXW7α, an important mediator of cell division and growth was investigated to explore its role in repairing the traumatic spinal cord in rats. Underlying mechanisms such as oxidative stress and inflammasomes signaling were also studied.

METHODS

Spinal cord injury in rats was established by longitudinal surgical incision from the lower to mid-thoracic vertebrae on the backside, followed by 20-g weight placed on the exposed Th12 surface for 30 min. AAV-delivered FBXW7α and -sh-FBXW7α were intrathecally injected into the rat spinal cord. Indices of oxidation, neurotrophic factors, and pyroptosis were measured by Western blot, Elisa, and RT-PCR.

RESULTS

We found the overexpression of FBXW7α in spinal cord rescue neuronal death triggered by the injury. Specifically, the nutritional condition, oxidative stress, and pyroptosis were improved. A synchronization of BNDF and GDNF expression patterns in various groups indicated the secretion of neurotrophic factors affect the outcome of SCI. The SOD1, CAT, and GSH-px were suppressed after trauma but all restored in response to FBXW7α overexpression. Inflammasomes-activated pyroptosis was incurred after the injury, and relevant biomarkers such as GSDMD, caspase-1, caspase- 11, IL-1β, and IL-18 were down-regulated after the introduction of FBXW7α into the injured cord. Additionally, up-regulating FBXW7α also repaired the mitochondria dysfunction.

CONCLUSION

Our data indicate FBXW7α probably serves as an important molecular target for the therapy of spinal cord injury.

The Role of Macrophages in Cancer Development and Therapy

Macrophages are critical mediators of tissue homeostasis and influence various aspects of immunity. Tumor-associated macrophages are one of the main cellular components of the tumor microenvironment. Depending on their activation status, macrophages can exert a dual influence on tumorigenesis by either antagonizing the cytotoxic activity of immune cells or, less frequently, by enhancing antitumor responses. In most situations, TAMs suppress T cell recruitment and function or regulate other aspects of tumor immunity. The importance of TAMs targeting in cancer therapy is derived from the strong association between the high infiltration of TAMs in the tumor tissue with poor patient prognosis. Several macrophage-targeting approaches in anticancer therapy are developed, including TAM depletion, inhibition of new TAM differentiation, or re-education of TAM activation for cancer cell phagocytosis. In this review, we will describe the role of TAMs in tumor development, including such aspects as protumorigenic inflammation, immune suppression, neoangiogenesis, and enhancement of tissue invasion and distant metastasis. Furthermore, we will discuss therapeutic approaches that aim to deplete TAMs or, on the contrary, re-educate TAMs for cancer cell phagocytosis and antitumor immunity.

The FBXW7-NOTCH interactome: A ubiquitin proteasomal system-induced crosstalk modulating oncogenic transformation in human tissues

BACKGROUND

Ubiquitin ligases or E3 ligases are well programmed to regulate molecular interactions that operate at a post-translational level. Skp, Cullin, F-box containing complex (or SCF complex) is a multidomain E3 ligase known to mediate the degradation of a wide range of proteins through the proteasomal pathway. The three-dimensional domain architecture of SCF family proteins suggests that it operates through a novel and adaptable "super-enzymatic" process that might respond to targeted therapeutic modalities in cancer.

RECENT FINDINGS

Several F-box containing proteins have been characterized either as tumor suppressors (FBXW8, FBXL3, FBXW8, FBXL3, FBXO1, FBXO4, and FBXO18) or as oncogenes (FBXO5, FBXO9, and SKP2). Besides, F-box members like βTrcP1 and βTrcP2, the ones with context-dependent functionality, have also been studied and reported. FBXW7 is a well-studied F-box protein and is a tumor suppressor. FBXW7 regulates the activity of a range of substrates, such as c-Myc, cyclin E, mTOR, c-Jun, NOTCH, myeloid cell leukemia sequence-1 (MCL1), AURKA, NOTCH through the well-known ubiquitin-proteasome system (UPS)-mediated degradation pathway. NOTCH signaling is a primitive pathway that plays a crucial role in maintaining normal tissue homeostasis. FBXW7 regulates NOTCH protein activity by controlling its half-life, thereby maintaining optimum protein levels in tissue. However, aberrations in the FBXW7 or NOTCH expression levels can lead to poor prognosis and detrimental outcomes in patients. Therefore, the FBXW7-NOTCH axis has been a subject of intense study and research over the years, especially around the interactome's role in driving cancer development and progression. Several studies have reported the effect of FBXW7 and NOTCH mutations on normal tissue behavior. The current review attempts to critically analyze these mutations prognostic value in a wide range of tumors. Furthermore, the review summarizes the recent findings pertaining to the FBXW7 and NOTCH interactome and its involvement in phosphorylation-related events, cell cycle, proliferation, apoptosis, and metastasis.

CONCLUSION

The review concludes by positioning FBXW7 as an effective diagnostic marker in tumors and by listing out recent advancements made in cancer therapeutics in identifying protocols targeting the FBXW7-NOTCH aberrations in tumors.

Postoperative elevation in the plasma CCL2 level is a predictive biomarker of colorectal cancer recurrence

PURPOSE

There is currently no adequate biomarker for predicting colorectal cancer (CRC) recurrence. Chemokine (C-C motif) ligand 2 (CCL2) induces macrophages and fibroblasts to occupy metastatic niches in distant organs. The purpose of this study was to examine CCL2 as a potential predictive biomarker for CRC recurrence.

METHODS

Plasma samples (n = 402) were collected from 80 stage II/III/IV CRC cases and the relationship between CCL2 profiles and recurrence was investigated. The tumor immune response genes associated with CCL2 mRNA expression in a subgroup of 8 stage I/II CRC cases with 12 recurrent sites and The Cancer Genome Atlas database were also analyzed retrospectively.

RESULTS

Sixteen stage II/III/IV postoperative recurrent CRC cases experienced a significant increase in plasma CCL2 levels 6 months after surgery and continuously increased even after R0-1 resection. The 6-month postoperative CCL2 levels in recurrent cases of ≥ 1 year were significantly higher than in non-recurrent cases and recurrent cases of < 1 year. The CCL2 level in the primary tumor cases significantly correlated with the cytolytic activity, thus indicating a tumor immune response from the CD163-expressing macrophages.

CONCLUSION

Plasma CCL2 was found to be a predictive biomarker of postoperative CRC recurrence. CCL2 in metastatic sites derives from metastatic niches that surpass the host immune response.

MicroRNA-874-3p/ADAM (A Disintegrin and Metalloprotease) 19 Mediates Macrophage Activation and Renal Fibrosis After Acute Kidney Injury

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STYX/FBXW7 axis participates in the development of endometrial cancer cell via Notch-mTOR signaling pathway

Endometrial cancer (EC) is the most common gynecologic malignancy in world. It has been reported that the mutation rate of FBXW7 is frequent in EC, but the specific functions of FBXW7 remain unknown in EC. In the present study, we revealed the role and mechanism of FBXW7 in EC cells. Compared with adjacent nontumor tissues, the FBXW7 expression level was lower in EC tissues. However, the level of STYX was in contrast with the expression of FBXW7 in EC tissues. And STYX interacted with FBXW7 and then down-regulated its expression level in EC. Over-expression of FBXW7 inhibited cell proliferation and facilitated apoptosis in EC cells, whereas silencing FBXW7 acted an opposite effect on EC cells. And the process of FBXW7 participated the proliferation and apoptosis in EC was regulated by STYX. FBXW7 suppressed the expression of Notch pathway related protein, and further inhibited the phosphorylation of mTOR. In addition, we also found that mTOR activitor (MHY1485) and Notch activator (Jagged-1) reversed the effect of over-expressing FBXW7 on cell proliferation and cell apoptosis. And Notch inhibitor (DAPT) counteracted the impact of over-expressing STYX on cell proliferation and cell apoptosis. Collectively, the present study verified that STYX inhibited the expression level of FBXW7 in EC, and then promoted cell proliferation but suppressed apoptosis through Notch–mTOR signaling pathway, which promoted carcinogenesis and progression of EC.

FBW7 suppresses ovarian cancer development by targeting the N6-methyladenosine binding protein YTHDF2

Background

The tumor suppressor FBW7 is the substrate recognition component of the SCF E3-ubiquitin ligase complex that mediates proteolytic degradation of various oncogenic proteins. However, the role of FBW7 in ovarian cancer progression remains inadequately understood.

Methods

IP-MASS, co-IP, immunohistochemistry, and western blotting were used to identify the potential substrate of FBW7 in ovarian cancer. The biological effects of FBW7 were investigated using in vitro and in vivo models. LC/MS was used to detect the m⁶A levels in ovarian cancer tissues. MeRIP-Seq and RNA-Seq were used to assess the downstream targets of YTHDF2.

Results

We unveil that FBW7 is markedly down-regulated in ovarian cancer tissues and its high expression is associated with favorable prognosis and elevated m⁶A modification levels. Consistently, ectopic FBW7 inhibits ovarian cancer cell survival and proliferation in vitro and in vivo, while ablation of FBW7 empowers propagation of ovarian cancer cells. In addition, the m⁶A reader protein, YTHDF2, is identified as a novel substrate for FBW7. FBW7 counteracts the tumor-promoting effect of YTHDF2 by inducing proteasomal degradation of the latter in ovarian cancer. Furthermore, YTHDF2 globally regulates the turnover of m⁶A-modified mRNAs, including the pro-apoptotic gene BMF.

Conclusions

Our study has demonstrated that FBW7 suppresses tumor growth and progression via antagonizing YTHDF2-mediated BMF mRNA decay in ovarian cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01340-8.

Regulation of Notch signaling by E3 ubiquitin ligases

Notch signaling is an evolutionarily conserved pathway that is widely used for multiple cellular events during development. Activation of the Notch pathway occurs when the ligand from a neighboring cell binds to the Notch receptor and induces cleavage of the intracellular domain of Notch, which further translocates into the nucleus to activate its downstream genes. The involvement of the Notch pathway in diverse biological events is possible due to the complexity in its regulation. In order to maintain tight spatiotemporal regulation, the Notch receptor, as well as its ligand, undergoes a series of physical and biochemical modifications that, in turn, helps in proper maintenance and fine-tuning of the signaling outcome. Ubiquitination is the post-translational addition of a ubiquitin molecule to a substrate protein, and the process is regulated by E3 ubiquitin ligases. The present review describes the involvement of different E3 ubiquitin ligases that play an important role in the regulation and maintenance of proper Notch signaling and how perturbation in ubiquitination results in abnormal Notch signaling leading to a number of human diseases.

Characteristics of pre-metastatic niche: the landscape of molecular and cellular pathways

Metastasis is a major contributor to cancer-associated deaths. It involves complex interactions between primary tumorigenic sites and future metastatic sites. Accumulation studies have revealed that tumour metastasis is not a disorderly spontaneous incident but the climax of a series of sequential and dynamic events including the development of a pre-metastatic niche (PMN) suitable for a subpopulation of tumour cells to colonize and develop into metastases. A deep understanding of the formation, characteristics and function of the PMN is required for developing new therapeutic strategies to treat tumour patients. It is rapidly becoming evident that therapies targeting PMN may be successful in averting tumour metastasis at an early stage. This review highlights the key components and main characteristics of the PMN and describes potential therapeutic strategies, providing a promising foundation for future studies.

CREBBP/EP300 mutations promoted tumor progression in diffuse large B-cell lymphoma through altering tumor-associated macrophage polarization via FBXW7-NOTCH-CCL2/CSF1 axis

Epigenetic alterations play an important role in tumor progression of diffuse large B-cell lymphoma (DLBCL). However, the biological relevance of epigenetic gene mutations on tumor microenvironment remains to be determined. The core set of genes relating to histone methylation (KMT2D, KMT2C, EZH2), histone acetylation (CREBBP, EP300), DNA methylation (TET2), and chromatin remodeling (ARID1A) were detected in the training cohort of 316 patients by whole-genome/exome sequencing (WGS/WES) and in the validation cohort of 303 patients with newly diagnosed DLBCL by targeted sequencing. Their correlation with peripheral blood immune cells and clinical outcomes were assessed. Underlying mechanisms on tumor microenvironment were investigated both in vitro and in vivo. Among all 619 DLBCL patients, somatic mutations in KMT2D (19.5%) were most frequently observed, followed by mutations in ARID1A (8.7%), CREBBP (8.4%), KMT2C (8.2%), TET2 (7.8%), EP300 (6.8%), and EZH2 (2.9%). Among them, CREBBP/EP300 mutations were significantly associated with decreased peripheral blood absolute lymphocyte-to-monocyte ratios, as well as inferior progression-free and overall survival. In B-lymphoma cells, the mutation or knockdown of CREBBP or EP300 inhibited H3K27 acetylation, downregulated FBXW7 expression, activated the NOTCH pathway, and downstream CCL2/CSF1 expression, resulting in tumor-associated macrophage polarization to M2 phenotype and tumor cell proliferation. In B-lymphoma murine models, xenografted tumors bearing CREBBP/EP300 mutation presented lower H3K27 acetylation, higher M2 macrophage recruitment, and more rapid tumor growth than those with CREBBP/EP300 wild-type control via FBXW7-NOTCH-CCL2/CSF1 axis. Our work thus contributed to the understanding of aberrant histone acetylation regulation on tumor microenvironment as an alternative mechanism of tumor progression in DLBCL.

E3 ligase FBXW7 restricts M2-like tumor-associated macrophage polarization by targeting c-Myc

FBXW7 functions as an E3 ubiquitin ligase to mediate oncoprotein degradation via the ubiquitin-proteasome system in cancer cells, effectively inhibiting the growth and survival of tumor cells. However, little is known about the functions of FBXW7 in macrophages and the tumor immune microenvironment. In this study, we find that FBXW7 suppresses M2-like tumor-associated macrophage (TAM) polarization to limit tumor progression. We identified a significant increase in the proportion of M2-like TAMs and aggravated tumor growth in mice with myeloid FBXW7 deficiency by subcutaneous inoculation with Lewis lung carcinoma cells (LLCs). When stimulated with LLCs supernatant in vitro, FBXW7-knockout macrophages displayed increased M2 macrophage polarization and enhanced ability of supporting cancer cells growth. In mechanism, we confirmed that FBXW7 inhibited M2-like TAM polarization by mediating c-Myc degradation via the ubiquitin-proteasome system. These findings highlight the role of FBXW7 in M2-like TAM polarization and provide new insights into the potential targets for cancer immunotherapies.

Isoform specific FBXW7 mediates NOTCH1 Abruptex mutation C1133Y deregulation in oral squamous cell carcinoma

Our group previously identified that the NOTCH1 Abruptex domain contains the most mutations in Chinese OSCC patients, including a hotspot mutation (C1133Y). FBXW7 is an E3 ubiquitin ligase that regulates a network of proteins, including NOTCH1, via degradation. In this study, we first described the co-localization of isoform specific FBXW7-FBXW7β and NOTCH1^C1133Y mutation in the same cytoplasmic sites. Gain- and loss-of-function assays were performed to examine the tumor suppressor role of FBXW7β in the proliferation and invasion of OSCC cells. The co-expression of NOTCH1^C1133Y and FBXW7β significantly attenuated tumor growth. Meanwhile, FBXW7β reversed the oncogenic phenotype and the activation of the AKT/ERK/NFκB pathway induced by NOTCH1^C1133Y mutation. FBXW7β downregulated the stability of NOTCH1^C1133Y protein and promoted protein ubiquitination. This was the first time that we selected a NOTCH1 hotspot mutation detected in clinical samples and identified the function of FBXW7β that mediated NOTCH1 mutation degradation in OSCC. The newly identified interaction between FBXW7β and NOTCH1^C1133Y protein provides new insights into the progression of OSCC, especially regarding Abruptex domain mutations, and represents a valuable target for OSCC therapy.

Notch-Inflammation Networks in Regulation of Breast Cancer Progression

Members of the Notch family and chronic inflammation were each separately demonstrated to have prominent malignancy-supporting roles in breast cancer. Recent investigations indicate that bi-directional interactions that exist between these two pathways promote the malignancy phenotype of breast tumor cells and of their tumor microenvironment. In this review article, we demonstrate the importance of Notch-inflammation interplays in malignancy by describing three key networks that act in breast cancer and their impacts on functions that contribute to disease progression: (1) Cross-talks of the Notch pathway with myeloid cells that are important players in cancer-related inflammation, focusing mainly on macrophages; (2) Cross-talks of the Notch pathway with pro-inflammatory factors, exemplified mainly by Notch interactions with interleukin 6 and its downstream pathways (STAT3); (3) Cross-talks of the Notch pathway with typical inflammatory transcription factors, primarily NF-κB. These three networks enhance tumor-promoting functions in different breast tumor subtypes and act in reciprocal manners, whereby Notch family members activate inflammatory elements and vice versa. These characteristics illustrate the fundamental roles played by Notch-inflammation interactions in elevating breast cancer progression and propose that joint targeting of both pathways together may provide more effective and less toxic treatment approaches in this disease.

Function and regulation of F-box/WD repeat-containing protein 7

The ubiquitin-proteasome system is an important post-translational modification system involved in numerous biological processes, such as cell cycle regulation, gene transcription, signal transduction, apoptosis, differentiation and development. F-box/WD repeat-containing protein 7 (FBXW7) is one of the most studied F-box (FBX) proteins, serving as substrate recognition component of S phase kinase-associated protein 1-Cullin 1-FBX protein complexes. As a tumor suppressor, FBXW7 recognizes numerous proto-oncoproteins and promotes their ubiquitination and subsequent proteasomal degradation. FBXW7 is regulated at different levels, leading to tunable and specific control of the activity and abundance of its substrates. Therefore, genetic mutations or decreases in its expression serve an important biological role in tumor development. In-depth studies and identification of additional substrates targeted by FBXW7 have suggested a signaling network regulated by FBXW7, including its tumor-inhibitory role. The present review focused on the role of FBXW7 in tumor suppression and its application in cancer therapy.

Macrophage correlates with immunophenotype and predicts anti-PD-L1 response of urothelial cancer

Immune-checkpoint blockades (ICBs) have been routinely implemented to treat metastatic urothelial cancer (mUC), whereas robust biomarkers are urgently warranted. Herein, we explored latent promising biomarkers based on 348 pretreatment mUC samples from IMvigor210. Methods: The genome, transcriptome, immunome, and metabolome were systemically analyzed using the external TCGA dataset for validation. Kaplan-Meier and ROC curve analyses were performed to estimate the predictive capacity of M1-macrophage infiltration. Chi-square/Spearman/Mann Whitney U test are used to determine its correlation to genetic, biochemical, and clinicopathological parameters. Results: M1 frequency is a robust biomarker for predicting the prognosis and response to ICBs, which is non-inferior to tumor mutation burden (TMB) or tumor neoantigen burden (TNB), and exceeds CD8 T cells, T cell inflamed gene expression profile (GEP), and PD-L1 expression. Moreover, M1 infiltration is associated with immune phenotypes (AUC = 0.785) and is negatively correlated with immune exclusion. Additionally, transcriptomic analysis showed immune activation in the high-M1 subgroup, whereas it showed steroid and drug metabolism reprograming in the M1-deficient subset, which characterized the limited sensitivity to ICB therapy. Notably, investigation of the corresponding intrinsic genomic profiles highlighted the significance of TP53 and FGFR alterations. Conclusions: M1 infiltration is a robust biomarker for immunotherapeutic response and immunophenotype determination in an mUC setting. Innate immunity activation involving macrophage polarization remodeling and anti-FGFR mutations may be promising strategies for synergy with anti-PD-L1 treatments and may help prolong the clinical survival of patients with mUC.

F-Box Proteins and Cancer

Controlled protein degradation is essential for the operation of a variety of cellular processes including cell division, growth, and differentiation. Identification of the relations between ubiquitin ligases and their substrates is key to understanding the molecular basis of cancer development and to the discovery of novel targets for cancer therapeutics. F-box proteins function as the substrate recognition subunits of S-phase kinase-associated protein 1 (SKP1)−Cullin1 (CUL1)−F-box protein (SCF) ubiquitin ligase complexes. Here, we summarize the roles of specific F-box proteins that have been shown to function as tumor promoters or suppressors. We also highlight proto-oncoproteins that are targeted for ubiquitylation by multiple F-box proteins, and discuss how these F-box proteins are deployed to regulate their cognate substrates in various situations.

Recent insight into the role of FBXW7 as a tumor suppressor

FBXW7 (also known as Fbw7, Sel10, hCDC4, or hAgo) is a tumor suppressor and the most frequently mutated member of the F-box protein family in human cancers. FBXW7 functions as the substrate recognition component of an SCF-type E3 ubiquitin ligase. It specifically controls the proteasome-mediated degradation of many oncoproteins such as c-MYC, NOTCH, KLF5, cyclin E, c-JUN, and MCL1. In this review, we summarize the molecular and biological features of FBXW7 and its substrates as well as the impact of mutations of FBXW7 on cancer development. We also address the clinical potential of anticancer therapy targeting FBXW7.

Phase I dose-escalation trial to repurpose propagermanium, an oral CCL2 inhibitor, in patients with breast cancer

The formation of premetastatic niches creates a fertile environment for the seeding of disseminated cancer cells in selected secondary organs. This is crucial for the development of metastasis in various malignancies, including breast cancer (BC). We previously reported that the loss of FBXW7 in bone marrow‐derived stromal cells promoted cancer metastasis by increasing the production of the chemokine CCL2, which attracts myeloid‐derived suppressor cells and macrophages to the premetastatic niche. Furthermore, treatment with the CCL2 inhibitor propagermanium (PG), which has been used in Japan as a therapeutic agent against chronic hepatitis B, was shown to block the enhancement of metastasis in FBXW7‐deficient mice through inhibiting the formation of premetastatic niches. Here, we describe a phase I dose‐escalation study of PG used as an antimetastatic drug for perioperative patients with primary BC. The primary end‐point was the percentage of patients who experience dose‐limiting toxicity. Twelve patients were enrolled in the study. Dose‐limiting toxicity was not observed, and the maximum dose was determined to be 90 mg/body/day. The serum concentrations of PG were nearly within the normal range in all observation days. We observed an inverse correlation between FBXW7 mRNA levels in blood and the serum concentrations of CCL2 and interleukin (IL)‐6, in agreement with our previous mouse model. Also, IL‐6 was downregulated in a PG dose‐dependent manner, as observed in mice. Thus, PG was given safely and it is expected to have antimetastatic potential in BC. This trial is registered in the UMIN Clinical Trials Registry as UMIN000022494.

Drug repositioning in cancer: The current situation in Japan

Cancer is a leading cause of death worldwide, and the incidence continues to increase. Despite major research aimed at discovering and developing novel and effective anticancer drugs, oncology drug development is a lengthy and costly process, with high attrition rates. Drug repositioning (DR, also referred to as drug repurposing), the process of finding new uses for approved noncancer drugs, has been gaining popularity in the past decade. DR has become a powerful alternative strategy for discovering and developing novel anticancer drug candidates from the existing approved drug space. Indeed, the availability of several large established libraries of clinical drugs and rapid advances in disease biology, genomics/transcriptomics/proteomics and bioinformatics has accelerated the pace of activity‐based, literature‐based and in silico DR, thereby improving safety and reducing costs. However, DR still faces financial obstacles in clinical trials, which could limit its practical use in the clinic. Here, we provide a brief review of DR in cancer and discuss difficulties in the development of DR for clinical use. Furthermore, we introduce some promising DR candidates for anticancer therapy in Japan.

Higher prevalence of homologous recombination deficiency in tumors from African Americans versus European Americans

To improve our understanding of longstanding disparities in incidence and mortality in lung cancer across ancestry, we performed a systematic comparative analysis of molecular features in tumors from African Americans (AAs) and European Americans (EAs). We find that lung squamous cell carcinoma tumors from AAs exhibit higher genomic instability-the proportion of non-diploid genome-aggressive molecular features such as chromothripsis and higher homologous recombination deficiency (HRD). In The Cancer Genome Atlas, we demonstrate that high genomic instability, HRD and chromothripsis among tumors from AAs is found across many cancer types. The prevalence of germline HRD (that is, the total number of pathogenic variants in homologous recombination genes) is higher in tumors from AAs, suggesting that the somatic differences observed have genetic ancestry origins. We also identify AA-specific copy-number-based arm-, focal- and gene-level recurrent features in lung cancer, including higher frequencies of PTEN deletion and KRAS amplification. These results highlight the importance of including under-represented populations in genomics research.

Knockout Mouse Models Provide Insight into the Biological Functions of CRL1 Components

The CRL1 complex, also known as the SCF complex, is a ubiquitin ligase that in mammals consists of an adaptor protein (SKP1), a scaffold protein (CUL1), a RING finger protein (RBX1, also known as ROC1), and one of about 70 F-box proteins. Given that the F-box proteins determine the substrate specificity of the CRL1 complex, the variety of these proteins allows the generation of a large number of ubiquitin ligases that promote the degradation or regulate the function of many substrate proteins and thereby control numerous key cellular processes. The physiological and pathological functions of these many CRL1 ubiquitin ligases have been studied by the generation and characterization of knockout mouse models that lack specific CRL1 components. In this chapter, we provide a comprehensive overview of these mouse models and discuss the role of each CRL1 component in mouse physiology and pathology.

Fbxw7 and Skp2 Regulate Stem Cell Switch between Quiescence and Mitotic Division in Lung Adenocarcinoma

BACKGROUND/AIMS

The molecular mechanism of dormancy initiation of cancer stem cells (CSCs) is not clear. This study was to explore the molecular mechanism by which CSCs switch from mitotic division to quiescence.

METHODS

MTT assays, flow cytometry, Western blotting, qRT-PCR, and immunofluorescence staining were used to test cell viability, cell cycle and expression of F-box and WD repeat domain-containing 7 (Fbxw7), c-myc, S phase kinase associated protein-2 (Skp2), cyclin-dependent kinase inhibitor 1B (p27), octamer-binding transcription factor 3/4 (Oct3/4), and β catenin gene in 5-fluorouracil (5-FU)-treated A549 cells. Lung adenocarcinoma xenograft models were employed to detect the effects of Fbxw7 on tumor growth.

RESULTS

5-FU inhibited the proliferation of A549 cells, with a median inhibitory concentration (IC50) of 200 μg/ml after 24 h treatment. 5-FU treatment increased the expressions of Oct3/4, Fbxw7, and p27 and increased the number of A549 cells at G0/G1. 5-FU treatment triggered nuclear translocation of β-catenin, decreased the expression levels of c-myc and Skp2, and decreased the number of A549 cells at S phase. Release from 5-FU decreased the expressions of Oct3/4, Fbxw7 and p27; decreased the percentage of cells in the G0/G1 phase; increased the expressions of Skp2 and c-myc; and increased the proportion of cells in S phase. 5-FU treatment led to high expressions of Oct3/4, c-myc, and p27, with low expressions of Fbxw7 and Skp2. Knockdown of Fbxw7 augmented the expression of c-myc and decreased the proportion of A549 cells in Go/G1 phase. Skp2 siRNA increased the expression of p27 and the percentage of G0/G1 phase cells and reduced the proportion of S phase cells. Fbxw7 overexpression inhibited tumor growth in mouse lung adenocarcinoma xenograft models. When Fbxw7 expression was low, Skp2 expression was higher in lung adenocarcinoma tissues and associated with the differentiation of lung adenocarcinoma.

CONCLUSION

5-FU enriches the CSCs in lung adenocarcinoma cells via increasing Fbxw7 and decreasing Skp2 expression, followed by downregulation of c-myc and upregulation of p27, which switches cells to quiescence.

Potentials of C-C motif chemokine 2-C-C chemokine receptor type 2 blockers including propagermanium as anticancer agents

Inflammation plays an essential role in the development and progression of most cancers. Chemokine C‐C motif chemokine 2 (CCL2) and its receptor C‐C chemokine receptor type 2 (CCR2) constitute a key signaling axis in inflammation that has recently attracted much interest on the basis of evidence showing its association with cancer progression. Propagermanium (3‐oxygermylpropionic acid polymer) is an organogermanium compound that is given for the treatment of hepatitis B in Japan and which inhibits the CCL2‐CCR2 signaling pathway. Herein, we review the importance of the CCL2‐CCR2 axis as a target in cancer treatment as shown by studies in mice and humans with pharmacological agents including propagermanium.

Regulation of Fn14 stability by SCFFbxw7α during septic acute kidney injury

Acute kidney injury (AKI) initiated by sepsis remains a thorny problem despite recent advancements in its clinical management. Having been found to be activated during AKI, fibroblast growth factor-inducible molecule 14 (Fn14) may be a potential therapeutic target because of its involvement in the molecular basis of injury. Here, we report that LPS induces apoptosis of mouse cortical tubule cells mediated by Fn14, for which simultaneous Toll-like receptor (TLR)4 activation is required. Mechanistically, TLR4 activation by lipopolysaccharide, through disassociating E3 ligase SCFFbxw7α from Fn14, dismantles Lys48-linked polyubiquitination of Fn14 and stabilizes it. Pharmacological deactivation of Fn14 with monoclonal antibody ITEM-2 provides effective protection against lethal sepsis and AKI in mice. Our study underscores an adaptive mechanism whereby TLR4 regulates SCFFbxw7α-dependent Fn14 stabilization during inflammatory tubular damage and further supports investigation of targeting Fn14 in clinical trials of patients with septic AKI.

Molecular-targeted therapies and precision medicine for endometrial cancer

The overall survival rate of patients with early-stage endometrial cancer is relatively high; however, there are few treatment options for patients with advanced or recurrent endometrial cancer, and the prognosis of such patients remains poor. Recent progress in molecular-targeted therapies demonstrated that they have the potential to improve the long-term survival of cancer patients with appropriate biomarkers. However, the median progression-free survival of patients who received single-agent molecular-targeted therapy was <5 months, and the development of molecular-targeted therapies for endometrial cancer patients is urgently needed. This review highlights the previous efforts, including antiangiogenesis therapy, PI3K/AKT/mTOR pathway inhibitor treatment and epidermal growth factor receptor inhibitor treatment and reports on ongoing phase 2 clinical trials, including immune checkpoint inhibitor and PARP inhibitor. We also summarized the genetic background of endometrial cancer according to The Cancer Genome Atlas data and considered the theoretical background for future efforts to prolong the survival of patients with refractory endometrial cancer and for other interesting challenges.

Prevention of cancer dormancy by Fbxw7 ablation eradicates disseminated tumor cells

Dormant cancer cells known as disseminated tumor cells (DTCs) are often present in bone marrow of breast cancer patients. These DTCs are thought to be responsible for the incurable recurrence of breast cancer. The mechanism underlying the long-term maintenance of DTCs remains unclear, however. Here, we show that Fbxw7 is essential for the maintenance of breast cancer dormancy. Genetic ablation of Fbxw7 in breast cancer cells disrupted the quiescence of DTCs, rendering them proliferative, in mouse xenograft and allograft models. Fbxw7-deficient DTCs were significantly depleted by treatment with paclitaxel, suggesting that cell proliferation induced by Fbxw7 ablation sensitized DTCs to chemotherapy. The combination of Fbxw7 ablation and chemotherapy reduced the number of DTCs even when applied after tumor cell dissemination. Mice injected with Fbxw7-deficient cancer cells survived longer after tumor resection and subsequent chemotherapy than did those injected with wild-type cells. Furthermore, database analysis revealed that breast cancer patients whose tumors expressed FBXW7 at a high level had a poorer prognosis than did those with a low FBXW7 expression level. Our results suggest that a wake-up strategy for DTCs based on Fbxw7 inhibition might be of value in combination with conventional chemotherapy for the treatment of breast cancer.

FBXW7 in Cancer: What Has Been Unraveled Thus Far?

: The FBXW7 (F-box with 7 tandem WD40) protein encoded by the gene FBXW7 is one of the crucial components of ubiquitin ligase called Skp1-Cullin1-F-box (SCF) complex that aids in the degradation of many oncoproteins via the ubiquitin-proteasome system (UPS) thus regulating cellular growth. FBXW7 is considered as a potent tumor suppressor as most of its target substrates can function as potential growth promoters, including c-Myc, Notch, cyclin E, c-JUN, and KLF5. Its regulators include p53, C/EBP-δ, Numb, microRNAs, Pin 1, Hes-5, BMI1, Ebp2. Mounting evidence has indicated the involvement of aberrant expression of FBXW7 for tumorigenesis. Moreover, numerous studies have also shown its role in cancer cell chemosensitization, thereby demonstrating the importance of FBXW7 in the development of curative cancer therapy. This comprehensive review emphasizes on the targets, functions, regulators and expression of FBXW7 in different cancers and its involvement in sensitizing cancer cells to chemotherapeutic drugs.