TRAF2 Cooperates with Focal Adhesion Signaling to Regulate Cancer Cell Susceptibility to Anoikis

Oncogenic KEAP1 mutations activate TRAF2-NFκB signaling to prevent apoptosis in lung cancer cells

The Kelch-like ECH-associated protein 1 (KEAP1) - Nuclear factor erythroid 2 -related factor 2 (NRF2) pathway is the major transcriptional stress response system in cells against oxidative and electrophilic stress. NRF2 is frequently constitutively active in many cancers, rendering the cells resistant to chemo- and radiotherapy. Loss-of-function (LOF) mutations in the repressor protein KEAP1 are common in non-small cell lung cancer, particularly adenocarcinoma. While the mutations can occur throughout the gene, they are enriched in certain areas, indicating that these may have unique functional importance. In this study, we show that in the GSEA analysis of TCGA lung adenocarcinoma RNA-seq data, the KEAP1 mutations in R320 and R470 were associated with enhanced Tumor Necrosis Factor alpha (TNFα) - Nuclear Factor kappa subunit B (NFκB) signaling as well as MYC and MTORC1 pathways. To address the functional role of these hotspot mutations, affinity purification and mass spectrometry (AP-MS) analysis of wild type (wt) KEAP1 and its mutation forms, R320Q and R470C were employed to interrogate differences in the protein interactome. We identified TNF receptor associated factor 2 (TRAF2) as a putative protein interaction partner. Both mutant KEAP1 forms showed increased interaction with TRAF2 and other anti-apoptotic proteins, suggesting that apoptosis signalling could be affected by the protein interactions. A549 lung adenocarcinoma cells overexpressing mutant KEAP1 showed high TRAF2-mediated NFκB activity and increased protection against apoptosis, XIAP being one of the key proteins involved in anti-apoptotic signalling. To conclude, KEAP1 R320Q and R470C and its interaction with TRAF2 leads to activation of NFκB pathway, thereby protecting against apoptosis.

Molecular and functional insight into focal adhesion kinases: Therapeutic implications for oral malignancies

Oral carcinoma is the sixth most common cancer globally, with one death occurring every hour. Focal adhesion kinase (FAK) is an intercellular protein tyrosine kinase, a key indicator of the development of oral cancer. FAK overexpression leads to the initiation and significant progression of metastasis in head and neck cancers, indicating its vital role in cancer progression and potential as a biomarker for early oral malignant transformation. The present review elaborates on FAK's function in oral malignancies since it could serve as a biomarker of the initial stages of oral malignant transformation and a possible predictive factor for risk assessment.

Focal adhesion kinase: from biological functions to therapeutic strategies

Focal adhesion kinase (FAK), a nonreceptor cytoplasmic tyrosine kinase, is a vital participant in primary cellular functions, such as proliferation, survival, migration, and invasion. In addition, FAK regulates cancer stem cell activities and contributes to the formation of the tumor microenvironment (TME). Importantly, increased FAK expression and activity are strongly associated with unfavorable clinical outcomes and metastatic characteristics in numerous tumors. In vitro and in vivo studies have demonstrated that modulating FAK activity by application of FAK inhibitors alone or in combination treatment regimens could be effective for cancer therapy. Based on these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. This article briefly describes the structure and function of FAK, as well as research progress on FAK inhibitors in combination therapies. We also discuss the challenges and future directions regarding anti-FAK combination therapies.

Anoikis resistance--protagonists of breast cancer cells survive and metastasize after ECM detachment

Breast cancer exhibits the highest global incidence among all tumor types. Regardless of the type of breast cancer, metastasis is a crucial cause of poor prognosis. Anoikis, a form of apoptosis initiated by cell detachment from the native environment, is an outside-in process commencing with the disruption of cytosolic connectors such as integrin-ECM and cadherin-cell. This disruption subsequently leads to intracellular cytoskeletal and signaling pathway alterations, ultimately activating caspases and initiating programmed cell death. Development of an anoikis-resistant phenotype is a critical initial step in tumor metastasis. Breast cancer employs a series of stromal alterations to suppress anoikis in cancer cells. Comprehensive investigation of anoikis resistance mechanisms can inform strategies for preventing and regressing metastatic breast cancer. The present review first outlines the physiological mechanisms of anoikis, elucidating the alterations in signaling pathways, cytoskeleton, and protein targets that transpire from the outside in upon adhesion loss in normal breast cells. The specific anoikis resistance mechanisms induced by pathological changes in various spatial structures during breast cancer development are also discussed. Additionally, the genetic loci of targets altered in the development of anoikis resistance in breast cancer, are summarized. Finally, the micro-RNAs and targeted drugs reported in the literature concerning anoikis are compiled, with keratocin being the most functionally comprehensive. Video Abstract.

Understanding and targeting anoikis in metastasis for cancer therapies

The development of effective treatments for cancers requires investigations for a more detailed and comprehensive understanding of the basic cellular mechanisms involved in carcinogenesis, cancer progression, and metastasis. One of those driving mechanisms is anoikis, a special type of apoptosis, which is induced by losing anchorage from the extracellular matrix (ECM). In other words, resisting death in detached cells (cells without ECM) forms an anoikis-resistant phenotype. Since the anoikis-resistance state compensates for the initial steps of cancer metastasis, this review aimed to discuss mechanisms of gaining anoikis/anoikis resistance phenotype in tumor cells. Finally, we highlighted the significance of anoikis in malignancies so as to provide clear insight into cancer diagnosis and therapy development.

The multi-omics analysis identifies a novel cuproptosis-anoikis-related gene signature in prognosis and immune infiltration characterization of lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD) has emerged as one of the most aggressive lethal cancers. Anoikis serves as programmed apoptosis initiated by the detachment of cells from the extracel-lular matrix. Cuproptosis is distinct from traditional cell death modalities. The above two modes are both closely related to tumor progression, prognosis, and treatment. However, whether they have synergistic effects in LUAD deserves further investigation.

Methods

The anoikis-related prognostic genes (ANRGs) co-expressed with cuproptosis-associated genes (CAGs) were screened using correlation analysis, analysis of variance, least absolute shrinkage, and selection operator (LASSO), and COX regression followed by functional analysis, and then LUAD risk score model was constructed. Using consensus clustering, the relationship between different subtypes and clinicopathological features, immune infiltration characteristics, and somatic mutations was analyzed. A nomogram was developed by incorporating clinical information, which provided a prediction of the survival of patients. Finally, a comprehensive analysis of ANRGs was performed and verified by the HPA database.

Results

A total of 27 ANRGs associated with cuproptosis were obtained. On this basis, three distinct ANRGs subtypes were identified, and the differences between clinical prognosis and immune infiltration were observed. A risk score model has been constructed by incorporating seven ANRGs signatures (EIF2AK3, IKZF3, ITGAV, OGT, PLK1, TRAF2, XRCC5). A highly reliable nomogram was developed to help formulate treatment strategies based on risk score and the clinicopathological features of LUAD. The seven-gene signature was turned out to be strongly linked to immune cells and validated in single-cell data. Immunohistochemistry proved that all of them are highly expressed in LUAD tissues.

Conclusion

This study reveals the potential relationship between cuproptosis-related ANRGs and clinicopathological features, tumor microenvironment (TME), and mutation characteristics, which can be applied for predicting the prognosis of LUAD and help develop individualized treatment strategies.

Uncovering the potential functions of lymph node metastasis-associated aberrant methylation differentially expressed genes and their association with the immune infiltration and prognosis in bladder urothelial carcinoma

Background

Bladder urothelial carcinoma (BLCA) is a malignant tumor of the urinary system. This study aimed to explore the potential role of lymph node metastasis-associated aberrant methylation differentially expressed genes (DEGs) in BLCA.

Methods

CHAMP and limma packages were used to identify lymph node metastasis-associated aberrant methylation DEGs. Univariate Cox analysis and Lasso analysis were performed to identify the signature genes, and multivariate Cox analysis was used to construct the risk score. Subsequently, the molecular characteristics of the signature genes and the relationship between risk score and prognosis, clinical characteristics and immune cell infiltration were analyzed. The signature gene AKAP7 was selected for functional verification.

Results

A novel risk score model was constructed based on 12 signature genes. The risk score had a good ability to predict overall survival (OS). The nomogram constructed based on age, N stage and risk score had a higher value in predicting the prognosis of patients. It was also found that stromal activation in TIME may inhibit the antitumor effects of immune cells. Functional enrichment analysis revealed that ECM receptor interaction and focal adhesion were two important pathways involved in the regulation of BLCA. Immunohistochemistry showed that AKAP7 may be associated with the occurrence, clinical stages and grades, and lymph node metastasis of BLCA. In vitro cell experiments showed that the migration and invasion ability of EJ cells was significantly inhibited after AKAP7 overexpression, while the migration and invasion ability of T24 cells was significantly promoted after AKAP7 knockdown.

Conclusion

The risk score model based on lymph node metastasis-associated aberrant methylation DEGs has a good ability to predict OS and is an independent prognostic factor for BLCA. It was also found that stromal activation in TIME may inhibit the antitumor effects of immune cells. This implicates aberrant methylation modifications as an important factor contributing to the heterogeneity and complexity of individual tumor microenvironments. Functional enrichment analysis revealed that ECM receptor interaction and focal adhesion were two important pathways involved in the regulation of BLCA, which contributed to the exploration of the pathological mechanism of BLCA. In addition, immunohistochemistry showed that AKAP7 may be associated with the occurrence, progression and lymph node metastasis of BLCA. In vitro cell experiments showed that AKAP7 could also inhibit the migration and invasion of cancer cells.

TNF Receptor Associated Factor 2 (TRAF2) Signaling in Cancer

Simple Summary

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) is an intracellular adapter protein with E3 ligase activity, which interacts with a plethora of other signaling proteins, including plasma membrane receptors, kinases, phosphatases, other E3 ligases, and deubiquitinases. TRAF2 is involved in various cancer-relevant cellular processes, such as the activation of transcription factors of the NFκB family, stimulation of mitogen-activated protein (MAP) kinase cascades, endoplasmic reticulum (ER) stress signaling, autophagy, and the control of cell death programs. In a context-dependent manner, TRAF2 promotes tumor development but it can also act as a tumor suppressor. Based on a general description, how TRAF2 in concert with TRAF2-interacting proteins and other TRAF proteins act at the molecular level is discussed for its importance for tumor development and its potential usefulness as a therapeutic target in cancer therapy.

Abstract

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) has been originally identified as a protein interacting with TNF receptor 2 (TNFR2) but also binds to several other receptors of the TNF receptor superfamily (TNFRSF). TRAF2, often in concert with other members of the TRAF protein family, is involved in the activation of the classical NFκB pathway and the stimulation of various mitogen-activated protein (MAP) kinase cascades by TNFRSF receptors (TNFRs), but is also required to inhibit the alternative NFκB pathway. TRAF2 has also been implicated in endoplasmic reticulum (ER) stress signaling, the regulation of autophagy, and the control of cell death programs. TRAF2 fulfills its functions by acting as a scaffold, bringing together the E3 ligase cellular inhibitor of apoptosis-1 (cIAP1) and cIAP2 with their substrates and various regulatory proteins, e.g., deubiquitinases. Furthermore, TRAF2 can act as an E3 ligase by help of its N-terminal really interesting new gene (RING) domain. The finding that TRAF2 (but also several other members of the TRAF family) interacts with the latent membrane protein 1 (LMP1) oncogene of the Epstein–Barr virus (EBV) indicated early on that TRAF2 could play a role in the oncogenesis of B-cell malignancies and EBV-associated non-keratinizing nasopharyngeal carcinoma (NPC). TRAF2 can also act as an oncogene in solid tumors, e.g., in colon cancer by promoting Wnt/β-catenin signaling. Moreover, tumor cell-expressed TRAF2 has been identified as a major factor-limiting cancer cell killing by cytotoxic T-cells after immune checkpoint blockade. However, TRAF2 can also be context-dependent as a tumor suppressor, presumably by virtue of its inhibitory effect on the alternative NFκB pathway. For example, inactivating mutations of TRAF2 have been associated with tumor development, e.g., in multiple myeloma and mantle cell lymphoma. In this review, we summarize the various TRAF2-related signaling pathways and their relevance for the oncogenic and tumor suppressive activities of TRAF2. Particularly, we discuss currently emerging concepts to target TRAF2 for therapeutic purposes.

FAK in Cancer: From Mechanisms to Therapeutic Strategies

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, is overexpressed and activated in many cancer types. FAK regulates diverse cellular processes, including growth factor signaling, cell cycle progression, cell survival, cell motility, angiogenesis, and the establishment of immunosuppressive tumor microenvironments through kinase-dependent and kinase-independent scaffolding functions in the cytoplasm and nucleus. Mounting evidence has indicated that targeting FAK, either alone or in combination with other agents, may represent a promising therapeutic strategy for various cancers. In this review, we summarize the mechanisms underlying FAK-mediated signaling networks during tumor development. We also summarize the recent progress of FAK-targeted small-molecule compounds for anticancer activity from preclinical and clinical evidence.

Regulation of Cancer Metastasis by TRAIL/Death Receptor Signaling

Death ligands such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; TNFSF10) and their corresponding death receptors (e.g., DR5) not only initiate apoptosis through activation of the extrinsic apoptotic pathway but also exert non-apoptotic biological functions such as regulation of inflammation and cancer metastasis. The involvement of the TRAIL/death receptor signaling pathway in the regulation of cancer invasion and metastasis is complex as both positive and negative roles have been reported. The underlying molecular mechanisms are even more complicated. This review will focus on discussing current knowledge in our understanding of the involvement of TRAIL/death receptor-mediated signaling in the regulation of cancer cell invasion and metastasis.

Focal Adhesion Kinase Fine Tunes Multifaced Signals toward Breast Cancer Progression

Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.

3,3'-diindolylmethane exerts antiproliferation and apoptosis induction by TRAF2-p38 axis in gastric cancer

3,3'-diindolylmethane (DIM), an active phytochemical derivative extracted from cruciferous vegetables, possesses anticancer effects. However, the underlying anticancer mechanism of DIM in gastric cancer remains unknown. Tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2), one of the signal transduction proteins, plays critical role in proliferation and apoptosis of human gastric cancer cells, but there are still lack of practical pharmacological modulators for potential clinical application. Here, we further explored the role of TRAF2 in inhibiting cell proliferation and inducing apoptosis by DIM in human gastric cancer BGC-823 and SGC-7901 cells. After treating BGC-823 and SGC-7901 cells with DIM for 24 h, cell proliferation, apoptosis and TRAF2-related protein were measured. Our findings showed that DIM inhibited the expressions of TRAF2, activated p-p38 and its downstream protein p-p53, which were paralleled with DIM-triggered cells proliferation, inhibition and apoptosis induction. These effects of DIM were reversed by TRAF2 overexpression or p38 mitogen-activated protein kinase (MAPK)-specific inhibitor (SB203580). Taken together, our data suggest that regulating TRAF2/p38 MAPK signaling pathway is essential for inhibiting gastric cancer proliferation and inducing apoptosis by DIM. These findings broaden the understanding of the pharmacological mechanism of DIM's action as a new modulator of TRAF2, and provide a new therapeutic target for human gastric cancer.

Collagen production and niche engineering: A novel strategy for cancer cells to survive acidosis in DCIS and evolve

Growing tumors are dynamic and nonlinear ecosystems, wherein cancer cells adapt to their local microenvironment, and these adaptations further modify the environment, inducing more changes. From nascent intraductal neoplasms to disseminated metastatic disease, several levels of evolutionary adaptations and selections occur. Here, we focus on one example of such an adaptation mechanism, namely, "niche construction" promoted by adaptation to acidosis, which is a metabolic adaptation to the early harsh environment in intraductal neoplasms. The avascular characteristics of ductal carcinoma in situ (DCIS) make the periluminal volume profoundly acidic, and cancer cells must adapt to this to survive. Based on discovery proteomics, we hypothesized that a component of acid adaptation involves production of collagen by pre-cancer cells that remodels the extracellular matrix (ECM) and stabilizes cells under acid stress. The proteomic data were surprising as collagen production and deposition are commonly believed to be the responsibility of mesenchymally derived fibroblasts, and not cells of epithelial origin. Subsequent experiments in 3D culture, spinning disk and second harmonic generation microscopy of DCIS lesions in patients' samples are concordant. Collagen production assay by acid-adapted cells in vitro demonstrated that the mechanism of induction involves the RAS and SMAD pathways. Secretome analyses show upregulation of ECM remodeling enzymes such as TGM2 and LOXL2 that are collagen crosslinkers. These data strongly indicate that acidosis in incipient cancers induces collagen production by cancer cells and support the hypothesis that this adaptation initiates a tumor-permissive microenvironment promoting survival and growth of nascent cancers.

Roles of TRAFs in Ischemia-Reperfusion Injury

Tumor necrosis factor receptor-associated factor (TRAF) proteins are a family of signaling molecules that function downstream of multiple receptor signaling pathways, and they play a pivotal role in the regulation of intracellular biological progresses. These TRAF-dependent signaling pathways and physiological functions have been involved in the occurrence and progression of ischemia-reperfusion injury (IRI), which is a common pathophysiological process that occurs in a wide variety of clinical events, including ischemic shock, organ transplantation, and thrombolytic therapy, resulting in a poor prognosis and high mortality. IRI occurs in multiple organs, including liver, kidney, heart, lung, brain, intestine, and retina. In recent years, mounting compelling evidence has confirmed that the genetic alterations of TRAFs can cause subversive phenotype changes during IRI of those organs. In this review, based on current knowledge, we summarized and analyzed the regulatory effect of TRAFs on the IRI of various organs, providing clear direction and a firm theoretical basis for the development of treatment strategies to manipulate TRAF proteins or TRAF-dependent signaling pathways in IRI-related diseases.

Caveolin1 Tyrosine-14 Phosphorylation: Role in Cellular Responsiveness to Mechanical Cues

The plasma membrane is a dynamic lipid bilayer that engages with the extracellular microenvironment and intracellular cytoskeleton. Caveolae are distinct plasma membrane invaginations lined by integral membrane proteins Caveolin1, 2, and 3. Caveolae formation and stability is further supported by additional proteins including Cavin1, EHD2, Pacsin2 and ROR1. The lipid composition of caveolar membranes, rich in cholesterol and phosphatidylserine, actively contributes to caveolae formation and function. Post-translational modifications of Cav1, including its phosphorylation of the tyrosine-14 residue (pY14Cav1) are vital to its function in and out of caveolae. Cells that experience significant mechanical stress are seen to have abundant caveolae. They play a vital role in regulating cellular signaling and endocytosis, which could further affect the abundance and distribution of caveolae at the PM, contributing to sensing and/or buffering mechanical stress. Changes in membrane tension in cells responding to multiple mechanical stimuli affects the organization and function of caveolae. These mechanical cues regulate pY14Cav1 levels and function in caveolae and focal adhesions. This review, along with looking at the mechanosensitive nature of caveolae, focuses on the role of pY14Cav1 in regulating cellular mechanotransduction.

Role of Focal Adhesion Kinase in Head and Neck Squamous Cell Carcinoma and Its Therapeutic Prospect

Head and neck cancers are one of the most prevalent cancers globally. Among them, head and neck squamous cell carcinoma (HNSCC) accounts for approximately 90% of head and neck cancers, which occurs in the oral cavity, oral pharynx, hypopharynx and larynx. The 5-year survival rate of HNSCC patients is only 63%, mainly because about 80–90% of patients with advanced HNSCC tend to suffer from local recurrence or even distant metastasis. Despite the more in-depth understanding of the molecular mechanisms underlying the occurrence and progression of HNSCC in recent years, effective targeted therapies are unavailable for HNSCC, which emphasize the urgent demand for studies in this area. Focal adhesion kinase (FAK) is an intracellular non-receptor tyrosine kinase that contributes to oncogenesis and tumor progression by its significant function in cell survival, proliferation, adhesion, invasion and migration. In addition, FAK exerts an effect on the tumor microenvironment, epithelial–mesenchymal transition, radiation (chemotherapy) resistance, tumor stem cells and regulation of inflammatory factors. Moreover, the overexpression and activation of FAK are detected in multiple types of tumors, including HNSCC. FAK inhibition can induce cell cycle arrest and apoptosis, significantly decrease cell growth, invasion and migration in HNSCC cell lines. In this article, we mainly review the research progress of FAK in the occurrence, development and metastasis of HNSCC, and put forward the prospects for the therapeutic targets of HNSCC.