A novel gain-of-function mutation of TGF-β receptor II promotes cancer progression via delayed receptor internalization in oral squamous cell carcinoma

Expanding the Chemical Space of Transforming Growth Factor-β (TGFβ) Receptor Type II Degraders with 3,4-Disubstituted Indole Derivatives

The TGFβ type II receptor (TβRII) is a central player in all TGFβ signaling downstream events, has been linked to cancer progression, and thus, has emerged as an auspicious anti-TGFβ strategy. Especially its targeted degradation presents an excellent goal for effective TGFβ pathway inhibition. Here, cellular structure-activity relationship (SAR) data from the TβRII degrader chemotype 1 was successfully transformed into predictive ligand-based pharmacophore models that allowed scaffold hopping. Two distinct 3,4-disubstituted indoles were identified from virtual screening: tetrahydro-4-oxo-indole 2 and indole-3-acetate 3. Design, synthesis, and screening of focused amide libraries confirmed 2r and 3n as potent TGFβ inhibitors. They were validated to fully recapitulate the ability of 1 to selectively degrade TβRII, without affecting TβRI. Consequently, 2r and 3n efficiently blocked endothelial-to-mesenchymal transition and cell migration in different cancer cell lines while not perturbing the microtubule network. Hence, 2 and 3 present novel TβRII degrader chemotypes that will (1) aid target deconvolution efforts and (2) accelerate proof-of-concept studies for small-molecule-driven TβRII degradation in vivo.

Tumor-Suppressive and Immunomodulating Activity of miR-30a-3p and miR-30e-3p in HNSCC Cells and Tumoroids

Head and neck squamous cell carcinomas (HNSCCs) are heterogeneous tumors, well known for their frequent relapsing nature. To counter recurrence, biomarkers for early diagnosis, prognosis, or treatment response prediction are urgently needed. miRNAs can profoundly impact normal physiology and enhance oncogenesis. Among all of the miRNAs, the miR-30 family is frequently downregulated in HNSCC. Here, we determined how levels of the 3p passenger strands of miR-30a and miR-30e affect tumor behavior and clarified their functional role in LA-HNSCC. In a retrospective study, levels of miR-30a-3p and miR-30e-3p were determined in 110 patients and correlated to overall survival, locoregional relapse, and distant metastasis. miR-30a/e-3p were expressed in HNSCC cell lines and HNSCC patient-derived tumoroids (PDTs) to investigate their effect on tumor cells and their microenvironment. Both miRNAs were found to have a prognosis value since low miR-30a/e-3p expression correlates to adverse prognosis and reduces overall survival. Low expression of miR-30a/e-3p is associated with a shorter time until locoregional relapse and a shorter time until metastasis, respectively. miR-30a/e-3p expression downregulates both TGF-βR1 and BMPR2 and attenuates the survival and motility of HNSCC. Results were confirmed in PDTs. Finally, secretomes of miR-30a/e-3p-transfected HNSCC activate M1-type macrophages, which exert stronger phagocytic activities toward tumor cells. miR-30a/e-3p expression can discriminate subgroups of LA-HNSCC patients with different prognosis, making them good candidates as prognostic biomarkers. Furthermore, by targeting members of the TGF-β family and generating an immune-permissive microenvironment, they may emerge as an alternative to anti-TGF-β drugs to use in combination with immune checkpoint inhibitors.

Mutational drivers of cancer cell migration and invasion

Genomic instability and mutations underlie the hallmarks of cancer-genetic alterations determine cancer cell fate by affecting cell proliferation, apoptosis and immune response, and increasing data show that mutations are involved in metastasis, a crucial event in cancer progression and a life-threatening problem in cancer patients. Invasion is the first step in the metastatic cascade, when tumour cells acquire the ability to move, penetrate into the surrounding tissue and enter lymphatic and blood vessels in order to disseminate. A role for genetic alterations in invasion is not universally accepted, with sceptics arguing that cellular motility is related only to external factors such as hypoxia, chemoattractants and the rigidity of the extracellular matrix. However, increasing evidence shows that mutations might trigger and accelerate the migration and invasion of different types of cancer cells. In this review, we summarise data from published literature on the effect of chromosomal instability and genetic mutations on cancer cell migration and invasion.

A novel TGF-β receptor II mutation (I227T/N236D) promotes aggressive phenotype of oral squamous cell carcinoma via enhanced EGFR signaling

Background

Transforming growth factor-β (TGF-β) signaling is a double-edged sword in cancer development and progression. TGF-β signaling plays a tumor suppressive role during the early stages of tumor development but promotes tumor progression in later stages. We have previously identified various mutations of TGF-β receptor II (TβRII) in human oral squamous cell carcinoma (OSCC) samples. In the present study we analyzed I227T/N236D mutation of TβRII, which was detected in the metastatic lymph node of an OSCC patient.

Methods

The effect of I227T/N236D TβRII mutation on transcriptional activities was measured using DR26 cells, which lack functional TβRII. HSC2 human OSCC cells stably expressing wild-type and I227T/N236D mutant TβRII were generated and used to examine the effect of I227T/N236D TβRII mutation on xenograft tumor growth, in vitro cell proliferation, apoptosis, migration, and invasion.

Results

The I227T/N236D mutation of TβRII upregulated TGF-β signaling and promoted xenograft tumor growth when compared with the wild-type, without affecting the in vitro proliferative capacities. To delineate the differences in proliferative capacities in vivo and in vitro, the apoptotic and survival signals were analyzed following curcumin treatment. Concomitant with apoptotic induction, epidermal growth factor receptor (EGFR) activation was observed upon curcumin treatment, which was further activated in I227T/N236D mutant transfectant cells when compared with wild-type cells. Enhanced EGFR activation correlated with cell survival and apoptotic resistance. Enhanced migratory and invasive capabilities of I227T/N236D mutant cells also depended on EGFR signaling.

Conclusions

These results suggest that enhanced EGFR signaling via upregulated TGF-β signaling shifted the balance toward survival and promoted cell migration and invasion in I227T/N236D mutant cells, elucidating the role of I227T/N236D mutation of TβRII in OSCC progression.

Roles of Myosin-Mediated Membrane Trafficking in TGF-β Signaling

Recent findings have revealed the role of membrane traffic in the signaling of transforming growth factor-β (TGF-β). These findings originate from the pivotal function of TGF-β in development, cell proliferation, tumor metastasis, and many other processes essential in malignancy. Actin and unconventional myosin have crucial roles in subcellular trafficking of receptors; research has also revealed a growing number of unconventional myosins that have crucial roles in TGF-β signaling. Unconventional myosins modulate the spatial organization of endocytic trafficking and tether membranes or transport them along the actin cytoskeletons. Current models do not fully explain how membrane traffic forms a bridge between TGF-β and the downstream effectors that produce its functional responsiveness, such as cell migration. In this review, we present a brief overview of the current knowledge of the TGF-β signaling pathway and the molecular components that comprise the core pathway as follows: ligands, receptors, and Smad mediators. Second, we highlight key role(s) of myosin motor-mediated protein trafficking and membrane domain segregation in the modulation of the TGF-β signaling pathway. Finally, we review future challenges and provide future prospects in this field.

Targeted sequencing of cancer-related genes in nasopharyngeal carcinoma identifies mutations in the TGF-β pathway

Approximately, 25% of nasopharyngeal carcinoma (NPC) patients develop recurrent disease. NPC may involve relatively few genomic alterations compared to other cancers due to its association with Epstein‐Barr virus (EBV). We envisioned that in‐depth sequencing of tumor tissues might provide new insights into the genetic alterations of this cancer. Thirty‐three NPC paired tumor/adjacent normal or peripheral blood mononuclear cell samples were deep‐sequenced (>1000×) with respect to a panel of 409 cancer‐related genes. Newly identified mutations and its correlation with clinical outcomes were evaluated. Profiling of somatic mutations and copy number variations (CNV) in NPC tumors identified alterations in RTK/RAS/PI3K, NOTCH, DNA repair, chromatin remodeling, cell cycle, NF‐κB, and TGF‐β pathways. In addition, patients harbored CNV among 409 cancer‐related genes and missense mutations in TGF‐β/SMAD signaling were associated with poor overall survival and poor recurrence‐free survival, respectively. The CNV events were correlated with plasma EBV copies, while mutations in TGFBR2 and SMAD4 abrogate SMAD‐dependent TGF‐β signaling. Functional analysis revealed that the new TGFBR2 kinase domain mutants were incapable of transducing the signal, leading to failure of phosphorylation of SMAD2/3 and activation of downstream TGF‐β‐mediated cell growth arrest. This study provides evidence supporting CNV and dysregulated TGF‐β signaling contributes to exacerbating the NPC pathogenesis.

Naturally occurring and synthetic constitutive-active cytokine receptors in disease and therapy

Cytokines control immune related events and are critically involved in a plethora of patho-physiological processes including autoimmunity and cancer development. Mutations which cause ligand-independent, constitutive activation of cytokine receptors are quite frequently found in diseases. Many constitutive-active cytokine receptor variants have been directly connected to disease development and mechanistically analyzed. Nature's solutions to generate constitutive cytokine receptors has been recently adopted by synthetic cytokine receptor biology, with the goal to optimize immune therapeutics. Here, CAR T cell immmunotherapy represents the first example to combine synthetic biology with genetic engineering during therapy. Hence, constitutive-active cytokine receptors are therapeutic targets, but also emerging tools to improve or modulate immunotherapeutic strategies. This review gives a comprehensive insight into the field of naturally occurring and synthetic constitutive-active cytokine receptors.

Intracellular trafficking of transforming growth factor β receptors

Transforming growth factor β (TGFβ) family members signal via heterotetrameric complexes of type I (TβRI) and type II (TβRII) dual specificity kinase receptors. The availability of the receptors on the cell surface is controlled by several mechanisms. Newly synthesized TβRI and TβRII are delivered from the Golgi apparatus to the cell surface via separate routes. On the cell surface, TGFβ receptors are distributed between different microdomains of the plasma membrane and can be internalized via clathrin- and caveolae-mediated endocytic mechanisms. Although receptor endocytosis is not essential for TGFβ signaling, localization of the activated receptor complexes on the early endosomes promotes TGFβ-induced Smad activation. Caveolae-mediated endocytosis, which is widely regarded as a mechanism that facilitates the degradation of TGFβ receptors, has been shown to be required for TGFβ signaling via non-Smad pathways. The importance of proper control of TGFβ receptor intracellular trafficking is emphasized by clinical data, as mislocalization of receptors has been described in connection with several human diseases. Thus, control of intracellular trafficking of the TGFβ receptors together with the regulation of their expression, posttranslational modifications and down-regulation, ensure proper regulation of TGFβ signaling.

Paradoxical roles of TGF-β signaling in suppressing and promoting squamous cell carcinoma

Transforming growth factor β (TGF-β) signaling either promotes or inhibits tumor formation and/or progression of many cancer types including squamous cell carcinoma (SCC). Canonical TGF-β signaling is mediated by a number of downstream proteins including Smad family proteins. Alterations in either TGF-β or Smad signaling can impact cancer. For instance, defects in TGF-β type I and type II receptors (TGF-βRI and TGF-βRII) and in Smad2/3/4 could promote tumor development. Conversely, increased TGF-β1 and activated TGF-βRI and Smad3 have all been shown to have tumor-promoting effects in experimental systems of human and mouse SCCs. Among TGF-β/Smad signaling, only TGF-βRII or Smad4 deletion in mouse epithelium causes spontaneous SCC in the mouse model, highlighting the critical roles of TGF-βRII and Smad4 in tumor suppression. Herein, we review the dual roles of the TGF-β/Smad signaling pathway and related mechanisms in SCC, highlighting the potential benefits and challenges of TGF-β/Smad-targeted therapies.

Tumor exome sequencing and copy number alterations reveal potential predictors of intrinsic resistance to multi-targeted tyrosine kinase inhibitors

Multi-targeted tyrosine kinase inhibitors (TKIs) have broad efficacy and similar FDA-approved indications, suggesting shared molecular drug targets across cancer types. Irrespective of tumor type, 20-30% of patients treated with multi-targeted TKIs demonstrate intrinsic resistance, with progressive disease as a best response. We conducted a retrospective cohort study to identify tumor (somatic) point mutations, insertion/deletions, and copy number alterations (CNA) associated with intrinsic resistance to multi-targeted TKIs. Using a candidate gene approach (n=243), tumor next-generation sequencing and CNA data was associated with resistant and non-resistant outcomes. Resistant individuals (n=11) more commonly harbored somatic point mutations in NTRK1, KDR, TGFBR2, and PTPN11 and CNA in CDK4, CDKN2B, and ERBB2 compared to non-resistant (n=26, p<0.01). Using a random forest classification model for variable reduction and a decision tree classification model, we were able to differentiate intrinsically resistant from non-resistant patients. CNA in CDK4 and CDKN2B were the most important analytical features, implicating the cyclin D pathway as a potentially important factor in resistance to multi-targeted TKIs. Replication of these results in a larger, independent patient cohort has potential to inform personalized prescribing of these widely utilized agents.

Follistatin N terminus differentially regulates muscle size and fat in vivo

Delivery of follistatin (FST) represents a promising strategy for both muscular dystrophies and diabetes, as FST is a robust antagonist of myostatin and activin, which are critical regulators of skeletal muscle and adipose tissues. FST is a multi-domain protein, and deciphering the function of different domains will facilitate novel designs for FST-based therapy. Our study aims to investigate the role of the N-terminal domain (ND) of FST in regulating muscle and fat mass in vivo. Different FST constructs were created and packaged into the adeno-associated viral vector (AAV). Overexpression of wild-type FST in normal mice greatly increased muscle mass while decreasing fat accumulation, whereas overexpression of an N terminus mutant or N terminus-deleted FST had no effect on muscle mass but moderately decreased fat mass. In contrast, FST-I-I containing the complete N terminus and double domain I without domain II and III had no effect on fat but increased skeletal muscle mass. The effects of different constructs on differentiated C2C12 myotubes were consistent with the in vivo finding. We hypothesized that ND was critical for myostatin blockade, mediating the increase in muscle mass, and was less pivotal for activin binding, which accounts for the decrease in the fat tissue. An in vitro TGF-beta1-responsive reporter assay revealed that FST-I-I and N terminus-mutated or -deleted FST showed differential responses to blockade of activin and myostatin. Our study provided direct in vivo evidence for a role of the ND of FST, shedding light on future potential molecular designs for FST-based gene therapy.

TRAIL, Wnt, Sonic Hedgehog, TGFβ, and miRNA Signalings Are Potential Targets for Oral Cancer Therapy

Clinical studies and cancer cell models emphasize the importance of targeting therapies for oral cancer. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is highly expressed in cancer, and is a selective killing ligand for oral cancer. Signaling proteins in the wingless-type mouse mammary tumor virus (MMTV) integration site family (Wnt), Sonic hedgehog (SHH), and transforming growth factor β (TGFβ) pathways may regulate cell proliferation, migration, and apoptosis. Accordingly, the genes encoding these signaling proteins are potential targets for oral cancer therapy. In this review, we focus on recent advances in targeting therapies for oral cancer and discuss the gene targets within TRAIL, Wnt, SHH, and TGFβ signaling for oral cancer therapies. Oncogenic microRNAs (miRNAs) and tumor suppressor miRNAs targeting the genes encoding these signaling proteins are summarized, and the interactions between Wnt, SHH, TGFβ, and miRNAs are interpreted. With suitable combination treatments, synergistic effects are expected to improve targeting therapies for oral cancer.

Mechanobiology of cell migration in the context of dynamic two-way cell-matrix interactions

Migration of cells is integral in various physiological processes in all facets of life. These range from embryonic development, morphogenesis, and wound healing, to disease pathology such as cancer metastasis. While cell migratory behavior has been traditionally studied using simple assays on culture dishes, in recent years it has been increasingly realized that the physical, mechanical, and chemical aspects of the matrix are key determinants of the migration mechanism. In this paper, we will describe the mechanobiological changes that accompany the dynamic cell-matrix interactions during cell migration. Furthermore, we will review what is to date known about how these changes feed back to the dynamics and biomechanical properties of the cell and the matrix. Elucidating the role of these intimate cell-matrix interactions will provide not only a better multi-scale understanding of cell motility in its physiological context, but also a more holistic perspective for designing approaches to regulate cell behavior.

The role of endocytic Rab GTPases in regulation of growth factor signaling and the migration and invasion of tumor cells

Metastasis is characterized pathologically by uncontrolled cell invasion, proliferation, migration and angiogenesis. It is a multistep process that encompasses the modulation of membrane permeability and invasion, cell spreading, cell migration and proliferation of the extracellular matrix, increase in cell adhesion molecules and interaction, decrease in cell attachment and induced survival signals and propagation of nutrient supplies (blood vessels). In cancer, a solid tumor cannot expand and spread without a series of synchronized events. Changes in cell adhesion receptor molecules (e.g., integrins, cadherin-catenins) and protease expressions have been linked to tumor invasion and metastasis. It has also been determined that ligand-growth factor receptor interactions have been associated with cancer development and metastasis via the endocytic pathway. Specifically, growth factors, which include IGF-1 and IGF-2 therapy, have been associated with most if not all of the features of metastasis. In this review, we will revisit some of the key findings on perhaps one of the most important hallmarks of cancer metastasis: cell migration and cell invasion and the role of the endocytic pathway in mediating this phenomenon.

Lipid raft regulates the initial spreading of melanoma A375 cells by modulating β1 integrin clustering

Cell adhesion and spreading require integrins-mediated cell-extracellular matrix interaction. Integrins function through binding to extracellular matrix and subsequent clustering to initiate focal adhesion formation and actin cytoskeleton rearrangement. Lipid raft, a liquid ordered plasma membrane microdomain, has been reported to play major roles in membrane motility by regulating cell surface receptor function. Here, we identified that lipid raft integrity was required for β1 integrin-mediated initial spreading of melanoma A375 cells on fibronectin. We found that lipid raft disruption with methyl-β-cyclodextrin led to the inability of focal adhesion formation and actin cytoskeleton rearrangement by preventing β1 integrin clustering. Furthermore, we explored the possible mechanism by which lipid raft regulates β1 integrin clustering and demonstrated that intact lipid raft could recruit and modify some adaptor proteins, such as talin, α-actinin, vinculin, paxillin and FAK. Lipid raft could regulate the location of these proteins in lipid raft fractions and facilitate their binding to β1 integrin, which may be crucial for β1 integrin clustering. We also showed that lipid raft disruption impaired A375 cell migration in both transwell and wound healing models. Together, these findings provide a new insight for the relationship between lipid raft and the regulation of integrins.

The role of endosomal signaling triggered by metastatic growth factors in tumor progression

Within tumor microenvironment, a lot of growth factors such as hepatocyte growth factor and epidermal growth factor may induce similar signal cascade downstream of receptor tyrosine kinase (RTK) and trigger tumor metastasis synergistically. In the past decades, the intimate relationship of RTK-mediated receptor endocytosis with signal transduction was well established. In general, most RTK undergoes clathrin-dependent endocytosis and/or clathrin-independent endocytosis. The internalized receptors may sustain the signaling within early endosome, recycling to plasma membrane for subsequent ligand engagement or sorting to late endosomes/lysosome for receptor degradation. Moreover, receptor endocytosis influences signal transduction in a temporal and spatial manner for periodical and polarized cellular processes such as cell migration. The endosomal signalings triggered by various metastatic factors are quite similar in some critical points, which are essential for triggering cell migration and tumor progression. There are common regulators for receptor endocytosis including dynamin, Rab4, Rab5, Rab11 and Cbl. Moreover, many critical regulators within the RTK signal pathway such as Grb2, p38, PKC and Src were also modulators of endocytosis. In the future, these may constitute a new category of targets for prevention of tumor metastasis.

βarrestin2 interacts with TβRII to regulate Smad-dependent and Smad-independent signal transduction

The Transforming Growth Factor beta (TGFβ) signaling pathway is necessary for a variety of normal cellular processes. However, the distinct mechanisms involved in TGFβ receptor turnover and the effect on signal transduction have yet to be fully elucidated. We have previously shown that TβRIII is able to interact with the TβRII/TβRI complex to increase clathrin-dependent endocytosis and receptor half-life. Others have shown that βarrestin2 binds TβRIII to mediate TβRII/TβRIII endocytosis. To further understand the mechanism regulating TGFβ receptor signaling, we evaluated the role of βarrestin2 in TGFβ receptor signal transduction, half-life and trafficking. We have found that TβRII binds βarrestin2 in the absence of TβRIII. Furthermore, using immunofluorescence microscopy we show that βarrestin2 traffics to the early endosome with TβRII. We investigated the effect of loss of βarrestin2 on TβRII dynamics and found that loss of βarrestin2 increases steady-state levels of TβRII at the cell surface. The interaction of TβRII with βarrestin2 is involved in modulating TGFβ signal transduction, as loss of βarrestin2 increases the phosphorylation of p38 and modestly affects pSmad levels. Using a luciferase assay to assess TGFβ-dependent transcription we show that loss of βarrestin2 decreases Smad-dependent TGFβ-stimulated transcription. Furthermore, loss of βarrestin2 increases p38 signal transduction, which correlated with increased cell death via apoptosis. Overall, our results suggest a role for βarrestin2 in the regulation of Smad-dependent and independent TGFβ pathways.