Induction of fibroblast senescence generates a non-fibrogenic myofibroblast phenotype that differentially impacts on cancer prognosis

Celastrol mediates CAV1 to attenuate pro-tumorigenic effects of senescent cells

BACKGROUND

Cellular senescence is an emerging hallmark of cancers, primarily fuels cancer progression by expressing senescence-associated secretory phenotype (SASP). Caveolin-1 (CAV1) is a key mediator of cell senescence. Previous studies from our group have evidenced that the expression of CAV1 is downregulated by Celastrol (CeT).

PURPOSE

To investigate the impact of CeT on cellular senescence and its subsequent influence on post-senescence-driven invasion, migration, and stemness of clear cell renal cell carcinoma (ccRCC).

STUDY DESIGN AND METHODS

The expression levels of CAV1, canonical senescence markers, and markers associated with epithelial-mesenchymal transition (EMT) and stemness in clinical samples were assessed through Pearson correlation analysis. Senescent cell models were induced using DOX, and their impact on migration, invasion, and stemness was evaluated. The effects of CeT treatment on senescent cells and their pro-tumorigenic effects were examined. Subsequently, the underlying mechanism of CeT were explored using lentivirus transfection and CRISPR/Cas9 technology to silence CAV1.

RESULTS

In human ccRCC clinical samples, the expression of the canonical senescence markers p53, p21, and p16 are associated with ccRCC progression. Senescent cells facilitated migration, invasion, and enhanced stemness in both ccRCC cells and ccRCC tumor-bearing mice. As expected, CeT treatment reduced senescence markers (p16, p53, p21, SA-β-gal) and SASP factors (IL6, IL8, CXCL12), alleviating cell cycle arrest. However, it did not restore the proliferation of senescent cells. Additionally, CeT suppressed senescence-driven migration, invasion, and stemness. Further investigations into the underlying mechanism demonstrated that CAV1 is a critical mediator of cell senescence and represents a potential target for CeT to attenuate cellular senescence.

CONCLUSIONS

This study presents a pioneering investigation into the intricate interplay between cellular senescence and ccRCC progression. We unveil a novel mechanism of CeT to mitigate cellular senescence by downregulating CAV1, thereby inhibiting the migration, invasion and stemness of ccRCC driven by senescent cells. These findings provide valuable insights into the underlying mechanisms of CeT and its potential as a targeted therapeutic approach for alleviating the aggressive phenotypes associated with senescent cells in ccRCC.

Fibroblast senescence-associated extracellular matrix promotes heterogeneous lung niche

Senescent cell accumulation in the pulmonary niche is associated with heightened susceptibility to age-related disease, tissue alterations, and ultimately a decline in lung function. Our current knowledge of senescent cell-extracellular matrix (ECM) dynamics is limited, and our understanding of how senescent cells influence spatial ECM architecture changes over time is incomplete. Herein is the design of an in vitro model of senescence-associated extracellular matrix (SA-ECM) remodeling using a senescent lung fibroblast-derived matrix that captures the spatiotemporal dynamics of an evolving senescent ECM architecture. Multiphoton second-harmonic generation microscopy was utilized to examine the spatial and temporal dynamics of fibroblast SA-ECM remodeling, which revealed a biphasic process that established a disordered and heterogeneous architecture. Additionally, we observed that inhibition of transforming growth factor-β signaling during SA-ECM remodeling led to improved local collagen fiber organization. Finally, we examined patient samples diagnosed with pulmonary fibrosis to further tie our results of the in vitro model to clinical outcomes. Moreover, we observed that the senescence marker p16 is correlated with local collagen fiber disorder. By elucidating the temporal dynamics of SA-ECM remodeling, we provide further insight on the role of senescent cells and their contributions to pathological ECM remodeling.

Fibroblasts from HPV-negative oropharynx squamous cell carcinomas stimulate the release of osteopontin from cancer cells via the release of IL-6

Introduction

HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) shows distinct biological and clinical behaviour when compared to HPV-negative OPSCC. The overall role of the tumour microenvironment (TME) in head and neck cancer progression and metastasis has been studied intensively, but differences in HPV-negative and HPV-positive OPSCCs are less understood.

Objective

To investigate the role of cancer-associated fibroblasts (CAFs) and the functional interactions of normal tonsil fibroblasts (NTFs) and OP CAFs with HPV+ and HPV- OPSCC cells and explore novel candidates in tumour-fibroblast crosstalk.

Materials and methods

A retrospective cohort of 143 primary OPSCCs was characterised using HPV16/18 RNAScope assay, p16 IHC and ɑ-SMA. Four OPSCC, three NTF and 2 new OPSCC CAF cultures were used to assess the cytokine-based interactions using cytokine arrays on conditioned media (CM), followed by co-culture approaches to identify the role of individual cell types and the role of OPN (SPP1) and IL-6 in SCC/fibroblast communication.

Results

HPV status was associated with better overall survival. Although ɑ-SMA expression was observed in both OPSCC subtypes, it provided survival stratification only in the HPV-positive group (Log-Rank p = 0.02). Three normal tonsillar fibroblast cultures (NTFs) were characterised by induction of myofibroblastic and senescent phenotypes with similar reactivity to our published NOF phenotype. The OPSCC-derived CAF cultures were characterised and their baseline myofibroblastic and senescence phenotypes varied. Cytokine array analysis of CM to identify novel candidates in the crosstalk between OPSCC tumour cells and NTFs/CAFs identified differences in the cytokine profiles on comparison of HPV+ and HPV- OPSCC cells. Osteopontin (OPN/SPP1) was identified, particularly in HPV-negative OPSCC cell analyses. We have demonstrated that OPN was produced by the OPSCC cells and revealed an associated upregulation of IL-6 in fibroblasts. Treatment of NTFs with rOPN showed alteration in phenotype, including increased contraction and IL-6 production. Antibody-mediated inhibition of CD44v6 attenuated the production of IL-6 by OPN in NTFs.

Conclusion

This investigation with OPSCC fibroblasts provides novel insights into the role of CAFs in OPSCC mediated by IL-6 stimulated release of OPN from HPV negative OPSCC cells. The details of HPV-positive SCC cell/fibroblast cytokine crosstalk remain elusive.

Rosarugosides A and D from Rosa rugosa Flower Buds: Their Potential Anti-Skin-Aging Effects in TNF-α-Induced Human Dermal Fibroblasts

This present study investigated the anti-skin-aging properties of Rosa rugosa. Initially, phenolic compounds were isolated from a hot water extract of Rosa rugosa's flower buds. Through repeated chromatography (column chromatography, MPLC, and prep HPLC), we identified nine phenolic compounds (1-9), including a previously undescribed depside, rosarugoside D (1). The chemical structure of 1 was elucidated via NMR, HR-MS, UV, and hydrolysis. Next, in order to identify bioactive compounds that are effective against TNF-α-induced NHDF cells, we measured intracellular ROS production in samples treated with each of the isolated compounds (1-9). All isolates reduced the level of ROS at a concentration of 10 μM. Particularly, two depsides-rosarugosides A and D (2 and 1)-significantly inhibited ROS expression in TNF-α-induced NHDFs compared to the other phenolic compounds. Subsequently, the production of MMP-1 and procollagen type Ι α1 by these two depsides was examined. Remarkably, rosarugoside A (2) significantly decreased MMP-1 secretion at all concentrations. In contrast, rosarugoside D (1) regulated the expression of procollagen type Ι α1. These findings collectively suggest that Rosa rugosa extracts and their isolated compounds, rosarugosides A (2) and D (1), hold significant potential for protecting against aging and skin damage. Overall, these findings suggest that Rosa rugosa extracts and their isolated compounds, rosarugosides A (2) and D (1), have the potential to prevent and protect against aging and skin damage, although more specific quantitative analysis is needed.

Emerging Role of Fibroblasts in Vitiligo: A Formerly Underestimated Rising Star

Vitiligo is a disfiguring depigmentation disorder characterized by loss of melanocytes. Although numerous studies have been conducted on the pathogenesis of vitiligo, the underlying mechanisms remain unclear. Although most studies have focused on melanocytes and keratinocytes, growing evidence suggests the involvement of dermal fibroblasts, residing deeper in the skin. This review aims to elucidate the role of fibroblasts in both the physiological regulation of skin pigmentation and their pathological contribution to depigmentation, with the goal of shedding light on the involvement of fibroblasts in vitiligo. The topics covered in this review include alterations in the secretome, premature senescence, autophagy dysfunction, abnormal extracellular matrix, autoimmunity, and metabolic changes.

Mutual regulation of TGFβ-induced oncogenic EMT, cell cycle progression and the DDR

TGFβ signaling and the DNA damage response (DDR) are two cellular toolboxes with a strong impact on cancer biology. While TGFβ as a pleiotropic cytokine affects essentially all hallmarks of cancer, the multifunctional DDR mostly orchestrates cell cycle progression, DNA repair, chromatin remodeling and cell death. One oncogenic effect of TGFβ is the partial activation of epithelial-to-mesenchymal transition (EMT), conferring invasiveness, cellular plasticity and resistance to various noxae. Several reports show that both individual networks as well as their interface affect chemo-/radiotherapies. However, the underlying mechanisms remain poorly resolved. EMT often correlates with TGFβ-induced slowing of proliferation, yet numerous studies demonstrate that particularly the co-activated EMT transcription factors counteract anti-proliferative signaling in a partially non-redundant manner. Collectively, evidence piled up over decades underscore a multifaceted, reciprocal inter-connection of TGFβ signaling / EMT with the DDR / cell cycle progression, which we will discuss here. Altogether, we conclude that full cell cycle arrest is barely compatible with the propagation of oncogenic EMT traits and further propose that 'EMT-linked DDR plasticity' is a crucial, yet intricate facet of malignancy, decisively affecting metastasis formation and therapy resistance.

Aging and oral squamous cell carcinoma development: the role of cellular senescence

The gradual accumulation and inadequate renewal of senescent cells over time drive organismal aging. Senescent cells undergo altered gene expression and release inflammatory mediators collectively termed the senescence-associated secretory phenotype (SASP), which significantly contributes to a spectrum of age-related disorders, including cancer. In the context of carcinogenesis, the SASP produced by senescent cells has been implicated in the promotion of epithelial cancers, including oral squamous cell carcinoma (OSCC), the most common form of oral cancer. Senescent cells within the tumor microenvironment release factors that amplify the growth and invasiveness of neighboring cancer cells. Senotherapeutics, including senolytics and senomorphics, emerge as promising modalities to target senescent cells and their associated inflammatory factors, thereby opening novel avenues for augmenting the efficacy of cancer treatments. Here, we review the general aspects of cellular senescence, focusing on the relation between senescence-related inflammation with cancer development. We also analyze the available evidence linking cellular senescence with OSCC, highlighting possible clinical applications.

Mapping Cell-in-Cell Structures in Oral Squamous Cell Carcinoma

Cell-in-cell (CIC) structures contribute to tumor aggressiveness and poor prognosis in oral squamous cell carcinoma (OSCC). In vitro 3D models may contribute to the understanding of the underlying molecular mechanisms of these events. We employed a spheroid model to study the CIC structures in OSCC. Spheroids were obtained from OSCC (HSC3) and cancer-associated fibroblast (CAF) lines using the Nanoshuttle-PLTM bioprinting system (Greiner Bio-One). Spheroid form, size, and reproducibility were evaluated over time (EvosTM XL; ImageJ version 1.8). Slides were assembled, stained (hematoxylin and eosin), and scanned (Axio Imager Z2/VSLIDE) using the OlyVIA System (Olympus Life Science) and ImageJ software (NIH) for cellular morphology and tumor zone formation (hypoxia and/or proliferative zones) analysis. CIC occurrence, complexity, and morphology were assessed considering the spheroid regions. Well-formed spheroids were observed within 6 h of incubation, showing the morphological aspects of the tumor microenvironment, such as hypoxic (core) and proliferative zone (periphery) formation. CIC structures were found in both homotypic and heterotypic groups, predominantly in the proliferative zone of the mixed HSC3/CAF spheroids. "Complex cannibalism" events were also noted. These results showcase the potential of this model in further studies on CIC morphology, formation, and relationship with tumor prognosis.

Cancer-associated fibroblasts: Mediators of head and neck tumor microenvironment remodeling

Cancer-associated fibroblasts (CAFs) are involved in critical aspects of head and neck squamous cell carcinoma (HNSCC) pathogenesis, such as the formation of a tumor-permissive extracellular matrix structure, angiogenesis, or immune and metabolic reprogramming of the tumor microenvironment (TME), with implications for metastasis and resistance to radiotherapy and chemotherapy. The pleiotropic effect of CAFs in TME is likely to reflect the heterogeneity and plasticity of their population, with context-dependent effects on carcinogenesis. The specific properties of CAFs provide many targetable molecules that could play an important role in the future therapy of HNSCC. In this review article, we will focus on the role of CAFs in the TME of HNSCC tumors. We will also discuss clinically relevant agents targeting CAFs, their signals, and signaling pathways, which are activated by CAFs in cancer cells, with the potential for repurposing for HNSCC therapy.

Identification of AOC3 and LRRC17 as Colonic Fibroblast Activation Markers and Their Potential Roles in Colorectal Cancer Progression

BACKGROUND

Accumulation of cancer-associated fibroblasts (CAFs) in the tumor stroma is linked to poor prognosis in colorectal cancer (CRC). CAF-cancer cell interplay, facilitated by secretomes including transforming growth factor-beta 1 (TGF-β1), supports fibroblast activation, drives colorectal carcinogenesis, and contributes to CRC aggressive phenotypes. Although widely used, traditional CAF biomarkers are found to have heterogeneous and non-specific expression. Amine oxidase copper containing 3 (AOC3) and leucine-rich repeat-containing 17 (LRRC17) have been reported to be emerging markers of myofibroblasts.

AIM

Our objective was to investigate the potential of AOC3 and LRRC17 as biomarkers for fibroblast activation thus predicting their roles in CRC progression.

METHODS

Immunofluorescence (IF) staining of AOC3 and LRRC17 was performed on myofibroblast line (CCD-112CoN), primary fibroblasts from colorectal tumor (CAFs), and adjacent normal tissue (normal fibroblasts-NFs). SW620 (epithelial CRC cell line) was used as a control.  Conventional CAF biomarker (alpha-smooth muscle actin - α-SMA) was included in the IF analysis. Fluorescence intensity was compared between groups using ImageJ software. Proliferation and contractility of treated cells were assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and collagen gel contraction assays, respectively. Fibroblast contraction under TGF-β1 treatment was compared to those treated with complete medium (addition of 10% serum) and serum free (SF) medium.

RESULTS

Positive AOC3, LRRC17, and α-SMA expression were observed in colonic fibroblasts, more prominent in CAFs, whereas negative staining was found in SW620. Significant downregulation of AOC3, and upregulations in LRRC17 and α-SMA expression was found in TGF-β1-treated fibroblasts compared to SF medium treatment (p-value<0.05). All fibroblasts exhibited higher proliferation in complete medium and under treatment with conditioned medium from SW620 than SF medium. Significant contraction of NFs was recorded in complete medium and TGF-β1 (p-value<0.01).

CONCLUSION

Our results demonstrate AOC3 and LRRC17 as the potential markers of CAF activation which promote CRC progression.

The plasticity of fibroblasts: A forgotten player in the aging process

Tissue-resident fibroblasts are mesenchymal cells which possess an impressive plasticity in their ability to modify their properties according to the requirements of the microenvironment. There are diverse subgroups of fibroblast phenotypes associated with different tissue pathological conditions, e.g., cancers, wound healing, and many fibrotic and inflammatory conditions. The heterogeneous phenotypes can be subdivided into fibrogenic and non-fibrogenic, inflammatory and immunosuppressive subtypes as well as cellular senescent subsets. A major hallmark of activated fibroblasts is that they contain different amounts of stress fibers combined with α-smooth muscle actin (α-SMA) protein, i.e., commonly this phenotype has been called the myofibroblast. Interestingly, several stresses associated with the aging process are potent inducers of myofibroblast differentiation, e.g., oxidative and endoplasmic reticulum stresses, extracellular matrix (ECM) disorders, inflammatory mediators, and telomere shortening. Accordingly, anti-aging treatments with metformin and rapamycin inhibited the differentiation of myofibroblasts in tissues. There is evidence that the senescent phenotype induced in cultured fibroblasts does not represent the phenotype of fibroblasts in aged tissues. Considering the versatile plasticity of fibroblasts as well as their frequency and structural importance in tissues, it does seem that fibroblasts are overlooked players in the aging process.

Reshaping of the tumor microenvironment by cellular senescence: An opportunity for senotherapies

Cellular senescence is a stress response associated with aging and disease, including cancer. Senescent cells undergo a stable cell cycle arrest, undergo a change in morphology and metabolic reprogramming, and produce a bioactive secretome termed the senescence-associated secretory phenotype (SASP). In cancer, senescence is an important barrier to tumor progression. Induction of senescence in preneoplastic cells limits cancer initiation, and many cancer therapies act in part by inducing senescence in cancer cells. Paradoxically, senescent cells lingering in the tumor microenvironment (TME) can contribute to tumor progression, metastasis, and therapy resistance. In this review, we discuss the different types of senescent cells present in the TME and how these senescent cells and their SASP reshape the TME, affect immune responses, and influence cancer progression. Furthermore, we will highlight the importance of senotherapies, including senolytic drugs that eliminate senescent cells and impede tumor progression and metastasis by restoring anti-tumor immune responses and influencing the TME.

Senescent Stromal Cells in the Tumor Microenvironment: Victims or Accomplices?

Cellular senescence is a unique cellular state. Senescent cells enter a non-proliferative phase, and the cell cycle is arrested. However, senescence is essentially an active cellular phenotype, with senescent cells affecting themselves and neighboring cells via autocrine and paracrine patterns. A growing body of research suggests that the dysregulation of senescent stromal cells in the microenvironment is tightly associated with the development of a variety of complex cancers. The role of senescent stromal cells in impacting the cancer cell and tumor microenvironment has also attracted the attention of researchers. In this review, we summarize the generation of senescent stromal cells in the tumor microenvironment and their specific biological functions. By concluding the signaling pathways and regulatory mechanisms by which senescent stromal cells promote tumor progression, distant metastasis, immune infiltration, and therapy resistance, this paper suggests that senescent stromal cells may serve as potential targets for drug therapy, thus providing new clues for future related research.

Pericentromeric satellite lncRNAs are induced in cancer-associated fibroblasts and regulate their functions in lung tumorigenesis

The abnormal tumor microenvironment (TME) often dictates the therapeutic response of cancer to chemo- and immuno-therapy. Aberrant expression of pericentromeric satellite repeats has been reported for epithelial cancers, including lung cancer. However, the transcription of tandemly repetitive elements in stromal cells of the TME has been unappreciated, limiting the optimal use of satellite transcripts as biomarkers or anti-cancer targets. We found that transcription of pericentromeric satellite DNA (satDNA) in mouse and human lung adenocarcinoma was observed in cancer-associated fibroblasts (CAFs). In vivo, lung fibroblasts expressed pericentromeric satellite repeats HS2/HS3 specifically in tumors. In vitro, transcription of satDNA was induced in lung fibroblasts in response to TGFβ, IL1α, matrix stiffness, direct contact with tumor cells and treatment with chemotherapeutic drugs. Single-cell transcriptome analysis of human lung adenocarcinoma confirmed that CAFs were the cell type with the highest number of satellite transcripts. Human HS2/HS3 pericentromeric transcripts were detected in the nucleus, cytoplasm, extracellularly and co-localized with extracellular vesicles in situ in human biopsies and activated fibroblasts in vitro. The transcripts were transmitted into recipient cells and entered their nuclei. Knock-down of satellite transcripts in human lung fibroblasts attenuated cellular senescence and blocked the formation of an inflammatory CAFs phenotype which resulted in the inhibition of their pro-tumorigenic functions. In sum, our data suggest that satellite long non-coding (lnc) RNAs are induced in CAFs, regulate expression of inflammatory genes and can be secreted from the cells, which potentially might present a new element of cell-cell communication in the TME.

Heart Disease and Ageing: The Roles of Senescence, Mitochondria, and Telomerase in Cardiovascular Disease

During ageing molecular damage leads to the accumulation of several hallmarks of ageing including mitochondrial dysfunction, cellular senescence, genetic instability and chronic inflammation, which contribute to the development and progression of ageing-associated diseases including cardiovascular disease. Consequently, understanding how these hallmarks of biological ageing interact with the cardiovascular system and each other is fundamental to the pursuit of improving cardiovascular health globally. This review provides an overview of our current understanding of how candidate hallmarks contribute to cardiovascular diseases such as atherosclerosis, coronary artery disease and subsequent myocardial infarction, and age-related heart failure. Further, we consider the evidence that, even in the absence of chronological age, acute cellular stress leading to accelerated biological ageing expedites cardiovascular dysfunction and impacts on cardiovascular health. Finally, we consider the opportunities that modulating hallmarks of ageing offer for the development of novel cardiovascular therapeutics.

Cancer-Associated Fibroblast Heterogeneity, Activation and Function: Implications for Prostate Cancer

The continuous remodeling of the tumor microenvironment (TME) during prostate tumorigenesis is emerging as a critical event that facilitates cancer growth, progression and drug-resistance. Recent advances have identified extensive communication networks that enable tumor-stroma cross-talk, and emphasized the functional importance of diverse, heterogeneous stromal fibroblast populations during malignant growth. Cancer-associated fibroblasts (CAFs) are a vital component of the TME, which mediate key oncogenic events including angiogenesis, immunosuppression, metastatic progression and therapeutic resistance, thus presenting an attractive therapeutic target. Nevertheless, how fibroblast heterogeneity, recruitment, cell-of-origin and differential functions contribute to prostate cancer remains to be fully delineated. Developing our molecular understanding of these processes is fundamental to developing new therapies and biomarkers that can ultimately improve clinical outcomes. In this review, we explore the current challenges surrounding fibroblast identification, discuss new mechanistic insights into fibroblast functions during normal prostate tissue homeostasis and tumorigenesis, and illustrate the diverse nature of fibroblast recruitment and CAF generation. We also highlight the promise of CAF-targeted therapies for the treatment of prostate cancer.

ATM Regulates Differentiation of Myofibroblastic Cancer-Associated Fibroblasts and Can Be Targeted to Overcome Immunotherapy Resistance

Myofibroblastic cancer-associated fibroblast (myoCAF)-rich tumors generally contain few T cells and respond poorly to immune-checkpoint blockade. Although myoCAFs are associated with poor outcome in most solid tumors, the molecular mechanisms regulating myoCAF accumulation remain unclear, limiting the potential for therapeutic intervention. Here, we identify ataxia-telangiectasia mutated (ATM) as a central regulator of the myoCAF phenotype. Differentiating myofibroblasts in vitro and myoCAFs cultured ex vivo display activated ATM signaling, and targeting ATM genetically or pharmacologically could suppress and reverse differentiation. ATM activation was regulated by the reactive oxygen species-producing enzyme NOX4, both through DNA damage and increased oxidative stress. Targeting fibroblast ATM in vivo suppressed myoCAF-rich tumor growth, promoted intratumoral CD8 T-cell infiltration, and potentiated the response to anti-PD-1 blockade and antitumor vaccination. This work identifies a novel pathway regulating myoCAF differentiation and provides a rationale for using ATM inhibitors to overcome CAF-mediated immunotherapy resistance.

SIGNIFICANCE

ATM signaling supports the differentiation of myoCAFs to suppress T-cell infiltration and antitumor immunity, supporting the potential clinical use of ATM inhibitors in combination with checkpoint inhibition in myoCAF-rich, immune-cold tumors.

Therapy-Induced Stromal Senescence Promoting Aggressiveness of Prostate and Ovarian Cancer

Cancer progression is supported by the cross-talk between tumor cells and the surrounding stroma. In this context, senescent cells in the tumor microenvironment contribute to the development of a pro-inflammatory milieu and the acquisition of aggressive traits by cancer cells. Anticancer treatments induce cellular senescence (therapy-induced senescence, TIS) in both tumor and non-cancerous cells, contributing to many detrimental side effects of therapies. Thus, we focused on the effects of chemotherapy on the stromal compartment of prostate and ovarian cancer. We demonstrated that anticancer chemotherapeutics, regardless of their specific mechanism of action, promote a senescent phenotype in stromal fibroblasts, resulting in metabolic alterations and secretion of paracrine factors, sustaining the invasive and clonogenic potential of both prostate and ovarian cancer cells. The clearance of senescent stromal cells, through senolytic drug treatment, reverts the malignant phenotype of tumor cells. The clinical relevance of TIS was validated in ovarian and prostate cancer patients, highlighting increased accumulation of lipofuscin aggregates, a marker of the senescent phenotype, in the stromal compartment of tissues from chemotherapy-treated patients. These data provide new insights into the potential efficacy of combining traditional anticancer strategies with innovative senotherapy to potentiate anticancer treatments and overcome the adverse effects of chemotherapy.

Tumour: Fibroblast Interactions Promote Invadopodia-Mediated Migration and Invasion in Oral Squamous Cell Carcinoma

OBJECTIVES

In the progression of cancer, interactions between cancer cells and cancer-associated fibroblasts (CAFs) play important roles. Cancer cell invasion is facilitated by filamentous actin (F-actin)-rich membrane protrusions called invadopodia, and the relationship between CAFs and invadopodia has been unclear. We used oral squamous cell carcinoma (OSCC) to investigate CAFs' effects on the formation of invadopodia, and we assessed the expressions of invadopodia markers and CAF markers ex vivo and their relationship with clinical parameters and survival.

MATERIALS AND METHODS

We examined the effect of culture with normal oral fibroblast (NOF)-derived and CAF-derived conditioned medium on the migration and invasion of two OSCC-derived cell lines using Transwells in the absence/presence of Matrigel. Immunoblotting and immunocytochemistry were conducted to assess the expressions of the invadopodia markers tyrosine kinase substrate 5 (Tks5) and membrane type 1 matrix metalloproteinase (MT1-MMP). We also used immunohistochemistry to examine patients with OSCC for an evaluation of the relationship between the CAF marker alpha smooth muscle actin (αSMA) and the expression of Tks5. The patients' survival was also assessed.

RESULTS

Compared to the use of culture medium alone, NOF-CM and CAF-CM both significantly increased the OSCC cells' migration and invasion (p < 0.05), and they significantly increased the expressions of both Tks5 and MT1-MMP. After the depletion of Tks5, the OSCC cells' migration and invasion abilities decreased. The expression of Tks5 and that of αSMA were correlated with poor survival, and a high expression of both markers was associated with an especially poor prognosis.

CONCLUSIONS

These results indicate that the formation of invadopodia is (i) important for OSCC cells' migration and invasion and (ii) regulated by the interaction of OSCC cells and stromal fibroblasts.

Tumor-stroma ratio can predict lymph-node metastasis in cT1/2N0 oral tongue squamous cell carcinoma independent of tumor budding grade

BACKGROUND

cT1/2 oral tongue squamous cell carcinoma (OTSCC) often metastasizes to cervical lymph nodes. However, predicting neck lymph-node metastasis (NLM) remains challenging. Pathomorphological evaluation of tumor budding grade (TBG) and tumor-stroma ratio (TSR) reportedly can predict lymph-node metastases. Hence, this study aimed to evaluate TBG and TSR in OTSCC and investigate their relationship to occult NLM and cancer relapse.

METHODS

Clinicopathological data of patients with cT1/2N0 OTSCC treated at the University of Tokyo Hospital between 2007 and 2017 were collected. TBG and TSR were evaluated using hematoxylin-eosin staining and cytokeratin AE1/AE3 immunostaining.

RESULTS

Out of 70 patients, 16 underwent elective neck dissection in addition to primary-tumor resection, whereas 54 did not. During follow-up, NLM was found in 35 patients. NLM correlated with the pathological depth of invasion (pDOI) (p < 0.001), TBG (p = 0.008), and TSR (p < 0.001) in univariate analysis and pDOI (p = 0.01) and TSR (p = 0.02) in multivariate analysis. The 5-year recurrence-free survival rate (RFS) was 78% for patients with a pDOI ≤ 5 mm and stroma-poor tumors and 33% for patients with a pDOI > 5 mm and stroma-rich tumors.

CONCLUSION

Patients with a pDOI > 5 mm and stroma-rich tumors have a high risk for cancer relapse. TSR and pDOI may be promising NLM predictors in cT1/2N0 OTSCC.

Transcriptional Heterogeneity of Cellular Senescence in Cancer

Cellular senescence plays a paradoxical role in tumorigenesis through the expression of diverse senescence-associated (SA) secretory phenotypes (SASPs). The heterogeneity of SA gene expression in cancer cells not only promotes cancer stemness but also protects these cells from chemotherapy. Despite the potential correlation between cancer and SA biomarkers, many transcriptional changes across distinct cell populations remain largely unknown. During the past decade, single-cell RNA sequencing (scRNA-seq) technologies have emerged as powerful experimental and analytical tools to dissect such diverse senescence-derived transcriptional changes. Here, we review the recent sequencing efforts that successfully characterized scRNA-seq data obtained from diverse cancer cells and elucidated the role of senescent cells in tumor malignancy. We further highlight the functional implications of SA genes expressed specifically in cancer and stromal cell populations in the tumor microenvironment. Translational research leveraging scRNA-seq profiling of SA genes will facilitate the identification of novel expression patterns underlying cancer susceptibility, providing new therapeutic opportunities in the era of precision medicine.

The extracellular matrix alteration, implication in modulation of drug resistance mechanism: friends or foes?

The extracellular matrix (ECM) is an important component of the tumor microenvironment (TME), having several important roles related to the hallmarks of cancer. In cancer, multiple components of the ECM have been shown to be altered. Although most of these alterations are represented by the increased or decreased quantity of the ECM components, changes regarding the functional alteration of a particular ECM component or of the ECM as a whole have been described. These alterations can be induced by the cancer cells directly or by the TME cells, with cancer-associated fibroblasts being of particular interest in this regard. Because the ECM has this wide array of functions in the tumor, preclinical and clinical studies have assessed the possibility of targeting the ECM, with some of them showing encouraging results. In the present review, we will highlight the most relevant ECM components presenting a comprehensive description of their physical, cellular and molecular properties which can alter the therapy response of the tumor cells. Lastly, some evidences regarding important biological processes were discussed, offering a more detailed understanding of how to modulate altered signalling pathways and to counteract drug resistance mechanisms in tumor cells.

Targeting Cellular Components of the Tumor Microenvironment in Solid Malignancies

Simple Summary

The tumor microenvironment comprises numerous different cellular players that engage transformed cancer cells and may exert pro- vs anti-tumor functions. Their crosstalk, functionality, as well as cell recruitment to cancer lesions, is chiefly dictated by cytokines/chemokines-receptor pairs and these axes can represent therapeutic vulnerabilities—as for immune checkpoint blockers. In this review, we recapitulate the main drivers of cellular TME dynamics, interactions, and functionality, mainly focusing on T lymphocytes, macrophages and cancer associated fibroblasts, also providing an outlook on state-of-the-art TME-targeting agents.

Abstract

Cancers are composed of transformed cells, characterized by aberrant growth and invasiveness, in close relationship with non-transformed healthy cells and stromal tissue. The latter two comprise the so-called tumor microenvironment (TME), which plays a key role in tumorigenesis, cancer progression, metastatic seeding, and therapy resistance. In these regards, cancer-TME interactions are complex and dynamic, with malignant cells actively imposing an immune-suppressive and tumor-promoting state on surrounding, non-transformed, cells. Immune cells (both lymphoid and myeloid) can be recruited from the circulation and/or bone marrow by means of chemotactic signals, and their functionality is hijacked upon arrival at tumor sites. Molecular characterization of tumor-TME interactions led to the introduction of novel anti-cancer therapies targeting specific components of the TME, such as immune checkpoint blockers (ICB) (i.e., anti-programmed death 1, anti-PD1; anti-Cytotoxic T-Lymphocyte Antigen 4, anti-CTLA4). However, ICB resistance often develops and, despite the introduction of newer technologies able to study the TME at the single-cell level, a detailed understanding of all tumor-TME connections is still largely lacking. In this work, we highlight the main cellular and extracellular components of the TME, discuss their dynamics and functionality, and provide an outlook on the most relevant clinical data obtained with novel TME-targeting agents, with a focus on T lymphocytes, macrophages, and cancer-associated fibroblasts.

Dose-dependent dominance: How cell densities design stromal cell functions during soft tissue healing

Regular soft tissue healing relies on the well-organized interaction of different stromal cell types with endothelial cells. However, spatiotemporal conditions might provoke high densities of one special stromal cell type, potentially leading to impaired healing. Detailed knowledge of the functions of rivaling stromal cell types aiming for tissue contraction and stabilization as well as vascular support is mandatory. By the application of an in vitro approach comprising the evaluation of cell proliferation, cell morphology, myofibroblastoid differentiation, and cytokine release, we verified a density-dependent modulation of these functions among juvenile and adult fibroblasts, pericytes, and adipose-derived stem cells during their interaction with microvascular endothelial cells in cocultures. Results indicate that juvenile fibroblasts rather support angiogenesis via paracrine regulation at the early stage of healing, a role potentially compromised in adult fibroblasts. In contrast, pericytes showed a more versatile character aiming at angiogenesis, vessel stabilization, and tissue contraction. Such a universal character was even more pronounced among adipose-derived stem cells. The explicit knowledge of the characteristic functions of stromal cell types is a prerequisite for the development of new analytical and therapeutic approaches for impaired soft tissue healing. The present study delivers new considerations concerning the roles of rivaling stromal cell types within a granulation tissue, pointing to extraordinary properties of pericytes and adipose-derived stem cells.

Focus on the Contribution of Oxidative Stress in Skin Aging

Skin aging is one of the most evident signs of human aging. Modification of the skin during the life span is characterized by fine lines and wrinkling, loss of elasticity and volume, laxity, rough-textured appearance, and pallor. In contrast, photoaged skin is associated with uneven pigmentation (age spot) and is markedly wrinkled. At the cellular and molecular level, it consists of multiple interconnected processes based on biochemical reactions, genetic programs, and occurrence of external stimulation. The principal cellular perturbation in the skin driving senescence is the alteration of oxidative balance. In chronological aging, reactive oxygen species (ROS) are produced mainly through cellular oxidative metabolism during adenosine triphosphate (ATP) generation from glucose and mitochondrial dysfunction, whereas in extrinsic aging, loss of redox equilibrium is caused by environmental factors, such as ultraviolet radiation, pollution, cigarette smoking, and inadequate nutrition. During the aging process, oxidative stress is attributed to both augmented ROS production and reduced levels of enzymatic and non-enzymatic protectors. Apart from the evident appearance of structural change, throughout aging, the skin gradually loses its natural functional characteristics and regenerative potential. With aging, the skin immune system also undergoes functional senescence manifested as a reduced ability to counteract infections and augmented frequency of autoimmune and neoplastic diseases. This review proposes an update on the role of oxidative stress in the appearance of the clinical manifestation of skin aging, as well as of the molecular mechanisms that underline this natural phenomenon sometimes accelerated by external factors.

The Outside-In Journey of Tissue Transglutaminase in Cancer

Tissue transglutaminase (TG2) is a member of the transglutaminase family that catalyzes Ca²⁺-dependent protein crosslinks and hydrolyzes guanosine 5′-triphosphate (GTP). The conformation and functions of TG2 are regulated by Ca²⁺ and GTP levels; the TG2 enzymatically active open conformation is modulated by high Ca²⁺ concentrations, while high intracellular GTP promotes the closed conformation, with inhibition of the TG-ase activity. TG2’s unique characteristics and its ubiquitous distribution in the intracellular compartment, coupled with its secretion in the extracellular matrix, contribute to modulate the functions of the protein. Its aberrant expression has been observed in several cancer types where it was linked to metastatic progression, resistance to chemotherapy, stemness, and worse clinical outcomes. The N-terminal domain of TG2 binds to the 42 kDa gelatin-binding domain of fibronectin with high affinity, facilitating the formation of a complex with β-integrins, essential for cellular adhesion to the matrix. This mechanism allows TG2 to interact with key matrix proteins and to regulate epithelial to mesenchymal transition and stemness. Here, we highlight the current knowledge on TG2 involvement in cancer, focusing on its roles translating extracellular cues into activation of oncogenic programs. Improved understanding of these mechanisms could lead to new therapeutic strategies targeting this multi-functional protein.

iTRAQ proteomics of sentinel lymph nodes for identification of extracellular matrix proteins to flag metastasis in early breast cancer

Patients with early breast cancer are affected by metastasis to axillary lymph nodes. Metastasis to these nodes is crucial for staging and quality of surgery. Sentinel Lymph Node Biopsy that is currently used to assess lymph node metastasis is not effective. This necessitates identification of biomarkers that can flag metastasis. Early stage breast cancer patients were recruited. Surgical resection of breast was followed by identification of sentinel lymph nodes. Fresh frozen section biopsy was used to assign metastatic and non-metastatic sentinel lymph nodes. Discovery phase included iTRAQ proteomics coupled with mass spectrometric analysis to identify differentially expressed proteins. Data is available via ProteomeXchange with identifier PXD027668. Validation was done by bioinformatic analysis and ELISA. There were 2398 unique protein groups and 109 differentially expressed proteins comparing metastatic and non-metastatic lymph nodes. Forty nine proteins were up-regulated, and sixty proteins that were down regulated in metastatic group. Bioinformatic analysis showed ECM-receptor interaction pathways to be implicated in lymph node metastasis. ELISA confirmed up-regulation of ECM proteins in metastatic lymph nodes. ECM proteins have requisite parameters to be developed as a diagnostic tool to assess status of sentinel lymph nodes to guide surgical intervention in early breast cancer.

Dynamic regulation of myofibroblast phenotype in cellular senescence

Cellular senescence is an antiproliferative response with a critical role in the control of cellular balance in diverse physiological and pathological settings. Here, we set to study the impact of senescence on the regulation of cell plasticity, focusing on the regulation of the myofibroblastic phenotype in primary fibroblasts. Myofibroblasts are contractile, highly fibrogenic cells with key roles in wound healing and fibrosis. Using cellular models of fibroblast senescence, we find a consistent loss of myofibroblastic markers and functional features upon senescence implementation. This phenotype can be transmitted in a paracrine manner, most likely through soluble secreted factors. A dynamic transcriptomic analysis during paracrine senescence confirmed the non-cell-autonomous transmission of this phenotype. Moreover, gene expression data combined with pharmacological and genetic manipulations of the major SASP signaling pathways suggest that the changes in myofibroblast phenotype are mainly mediated by the Notch/TGF-β axis, involving a dynamic switch in the TGF-β pathway. Our results reveal a novel link between senescence and myofibroblastic differentiation with potential implications in the physiological and pathological functions of myofibroblasts.

Oral Senescence: From Molecular Biology to Clinical Research

Cellular senescence is an irreversible cell cycle arrest occurring following multiple rounds of cell division (replicative senescence) or in response to cellular stresses such as ionizing radiation, signaling imbalances and oxidative damage (stress-induced premature senescence). Even very small numbers of senescent cells can be deleterious and there is evidence that senescent cells are instrumental in a number of oral pathologies including cancer, oral sub mucous fibrosis and the side effects of cancer therapy. In addition, senescent cells are present and possibly important in periodontal disease and other chronic inflammatory conditions of the oral cavity. However, senescence is a double-edged sword because although it operates as a suppressor of malignancy in pre-malignant epithelia, senescent cells in the neoplastic environment promote tumor growth and progression. Many of the effects of senescent cells are dependent on the secretion of an array of diverse therapeutically targetable proteins known as the senescence-associated secretory phenotype. However, as senescence may have beneficial roles in wound repair, preventing fibrosis and stem cell activation the clinical exploitation of senescent cells is not straightforward. Here, we discuss biological mechanisms of senescence and we review the current approaches to target senescent cells therapeutically, including senostatics and senolytics which are entering clinical trials.

The functional multipotency of transforming growth factor β signaling at the intersection of senescence and cancer

The transforming growth factor β (TGF-β) family of cytokines comprises a group of proteins, their receptors, and effector molecules that, in a coordinated manner, modulate a plethora of physiological and pathophysiological processes. TGF-β1 is the best known and plausibly most active representative of this group. It acts as an immunosuppressant, contributes to extracellular matrix remodeling, and stimulates tissue fibrosis, differentiation, angiogenesis, and epithelial-mesenchymal transition. In recent years, this cytokine has been established as a vital regulator of organismal aging and cellular senescence. Finally, the role of TGF-β1 in cancer progression is no longer in question. Because this protein is involved in so many, often overlapping phenomena, the question arises whether it can be considered a molecular bridge linking some of these phenomena together and governing their reciprocal interactions. In this study, we reviewed the literature from the perspective of the role of various TGF-β family members as regulators of a complex mutual interplay between senescence and cancer. These aspects are then considered in a broader context of remaining TGF-β-related functions and coexisting processes. The main narrative axis in this work is centered around the interaction between the senescence of normal peritoneal cells and ovarian cancer cells. The discussion also includes examples of TGF-β activity at the interface of other normal and cancer cell types.

Novel insights from a multiomics dissection of the hayflick limit

The process wherein dividing cells exhaust proliferative capacity and enter into replicative senescence has become a prominent model for cellular aging in vitro. Despite decades of study, this cellular state is not fully understood in culture and even much less so during aging. Here, we revisit Leonard Hayflick’s original observation of replicative senescence in WI-38 human lung fibroblasts equipped with a battery of modern techniques including RNA-seq, single-cell RNA-seq, proteomics, metabolomics, and ATAC-seq. We find evidence that the transition to a senescent state manifests early, increases gradually, and corresponds to a concomitant global increase in DNA accessibility in nucleolar and lamin associated domains. Furthermore, we demonstrate that senescent WI-38 cells acquire a striking resemblance to myofibroblasts in a process similar to the epithelial to mesenchymal transition (EMT) that is regulated by t YAP1/TEAD1 and TGF-β2. Lastly, we show that verteporfin inhibition of YAP1/TEAD1 activity in aged WI-38 cells robustly attenuates this gene expression program.

Studying Activated Fibroblast Phenotypes and Fibrosis-Linked Mechanosensing Using 3D Biomimetic Models

Fibrosis and solid tumor progression are closely related, with both involving pathways associated with chronic wound dysregulation. Fibroblasts contribute to extracellular matrix (ECM) remodeling in these processes, a crucial step in scarring, organ failure, and tumor growth, but little is known about the biophysical evolution of remodeling regulation during the development and progression of matrix-related diseases including fibrosis and cancer. A 3D collagen-based scaffold model is employed here to mimic mechanical changes in normal (2 kPa, soft) versus advanced pathological (12 kPa, stiff) tissues. Activated fibroblasts grown on stiff scaffolds show lower migration and increased cell circularity compared to those on soft scaffolds. This is reflected in gene expression profiles, with cells cultured on stiff scaffolds showing upregulated DNA replication, DNA repair, and chromosome organization gene clusters, and a concomitant loss of ability to remodel and deposit ECM. Soft scaffolds can reproduce biophysically meaningful microenvironments to investigate early stage processes in wound healing and tumor niche formation, while stiff scaffolds can mimic advanced fibrotic and cancer stages. These results establish the need for tunable, affordable 3D scaffolds as platforms for aberrant stroma research and reveal the contribution of physiological and pathological microenvironment biomechanics to gene expression changes in the stromal compartment.

Extracellular citrate and metabolic adaptations of cancer cells

It is well established that cancer cells acquire energy via the Warburg effect and oxidative phosphorylation. Citrate is considered to play a crucial role in cancer metabolism by virtue of its production in the reverse Krebs cycle from glutamine. Here, we review the evidence that extracellular citrate is one of the key metabolites of the metabolic pathways present in cancer cells. We review the different mechanisms by which pathways involved in keeping redox balance respond to the need of intracellular citrate synthesis under different extracellular metabolic conditions. In this context, we further discuss the hypothesis that extracellular citrate plays a role in switching between oxidative phosphorylation and the Warburg effect while citrate uptake enhances metastatic activities and therapy resistance. We also present the possibility that organs rich in citrate such as the liver, brain and bones might form a perfect niche for the secondary tumour growth and improve survival of colonising cancer cells. Consistently, metabolic support provided by cancer-associated and senescent cells is also discussed. Finally, we highlight evidence on the role of citrate on immune cells and its potential to modulate the biological functions of pro- and anti-tumour immune cells in the tumour microenvironment. Collectively, we review intriguing evidence supporting the potential role of extracellular citrate in the regulation of the overall cancer metabolism and metastatic activity.

Senescence and Immunoregulation in the Tumor Microenvironment

Immunotherapies have revolutionized cancer treatment, but despite the many lives that have been extended by these therapies many patients do not respond for reasons that are not well understood. The tumor microenvironment (TME) is comprised of heterogeneous cells that regulate tumor immune responses and likely influence immunotherapy response. Senescent (e.g., aged) stroma within the TME, and its expression of the senescence-associated secretory phenotype induces chronic inflammation that encourages tumor development and disease progression. Senescent environments also regulate the function of immune cells in ways that are decidedly protumorigenic. Here we discuss recent developments in senescence biology and the immunoregulatory functions of senescent stroma. Understanding the multitude of cell types present in the TME, including senescent stroma, will aid in the development of combinatorial therapeutic strategies to increase immunotherapy efficacy.

Intratumoral follicular regulatory T cells curtail anti-PD-1 treatment efficacy

Immune-checkpoint blockade (ICB) has shown remarkable clinical success in boosting antitumor immunity. However, the breadth of its cellular targets and specific mode of action remain elusive. We find that tumor-infiltrating follicular regulatory T (TFR) cells are prevalent in tumor tissues of several cancer types. They are primarily located within tertiary lymphoid structures and exhibit superior suppressive capacity and in vivo persistence as compared with regulatory T cells, with which they share a clonal and developmental relationship. In syngeneic tumor models, anti-PD-1 treatment increases the number of tumor-infiltrating TFR cells. Both TFR cell deficiency and the depletion of TFR cells with anti-CTLA-4 before anti-PD-1 treatment improve tumor control in mice. Notably, in a cohort of 271 patients with melanoma, treatment with anti-CTLA-4 followed by anti-PD-1 at progression was associated with better a survival outcome than monotherapy with anti-PD-1 or anti-CTLA-4, anti-PD-1 followed by anti-CTLA-4 at progression or concomitant combination therapy.

Profiling Cancer-Associated Fibroblasts in Melanoma

Solid tumors are complex systems characterized by dynamic interactions between neoplastic cells, non-tumoral cells, and extracellular components. Among all the stromal cells that populate tumor microenvironment, fibroblasts are the most abundant elements and are critically involved in disease progression. Cancer-associated fibroblasts (CAFs) have pleiotropic functions in tumor growth and extracellular matrix remodeling implicated in local invasion and distant metastasis. CAFs additionally participate in the inflammatory response of the tumor site by releasing a variety of chemokines and cytokines. It is becoming clear that understanding the dynamic, mutual melanoma-fibroblast relationship would enable treatment options to be amplified. To better characterize melanoma-associated fibroblasts, here we analyzed low-passage primary CAFs derived from advanced-stage primary skin melanomas, focusing on the immuno-phenotype. Furthermore, we assessed the expression of several CAF markers and the production of growth factors. To deepen the study of CAF-melanoma cell crosstalk, we employed CAF-derived supernatants and trans-well co-culture systems to evaluate the influences of CAFs on (i) the motogenic ability of melanoma cells, (ii) the chemotherapy-induced cytotoxicity, and (iii) the release of mediators active in modulating tumor growth and spread.

Cancer-Associated Fibroblasts in Oral Cancer: A Current Perspective on Function and Potential for Therapeutic Targeting

The role of the tumour microenvironement (TME) in cancer progression and resistance to therapies is now widely recognized. The most prominent non-immune cell type in the microenvironment of oral cancer (OSCC) is cancer-associated fibroblasts (CAF). Although CAF are a poorly characterised and heterogenous cell population, those with an "activated" myofibroblastic phenotype have been shown to support OSCC progression, promoting growth, invasion and numerous other "hallmarks of malignancy." CAF also confer broad resistance to different types of therapy, including chemo/radiotherapy and EGFR inhibitors; consistent with this, CAF-rich OSCC are associated with poor prognosis. In recent years, much CAF research has focused on their immunological role in the tumour microenvironment, showing that CAF shield tumours from immune attack through multiple mechanisms, and particularly on their role in promoting resistance to anti-PD-1/PD-L1 checkpoint inhibitors, an exciting development for the treatment of recurrent/metastatic oral cancer, but which fails in most patients. This review summarises our current understanding of CAF subtypes and function in OSCC and discusses the potential for targeting these cells therapeutically.

The Effects of Chemotherapeutics on the Ovarian Cancer Microenvironment

High-grade serous ovarian cancer (HGSOC) is characterized by a complex and dynamic tumor microenvironment (TME) composed of cancer-associated fibroblasts (CAFs), immune cells, endothelial cells, and adipocytes. Although most approved therapies target cancer cells, a growing body of evidence suggests that chemotherapeutic agents have an important role in regulating the biology of the diverse cells that compose the TME. Understanding how non-transformed cells respond and adapt to established therapeutics is necessary to completely comprehend their action and develop novel therapeutics that interrupt undesired tumor-stroma interactions. Here, we review the effects of chemotherapeutic agents on normal cellular components of the host-derived TME focusing on CAFs. We concentrate on therapies used in the treatment of HGSOC and synthesize findings from studies focusing on other cancer types and benign tissues. Agents such as platinum derivatives, taxanes, and PARP inhibitors broadly affect the TME and promote or inhibit the pro-tumorigenic roles of CAFs by modifying the bidirectional cross-talk between tumor and stromal cells in the tumor organ. While most chemotherapy research focuses on cancer cells, these studies emphasize the need to consider all cell types within the tumor organ when evaluating chemotherapeutics.

The Biological and Biomechanical Role of Transglutaminase-2 in the Tumour Microenvironment

Transglutaminase-2 (TG2) is the most highly and ubiquitously expressed member of the transglutaminase enzyme family and is primarily involved in protein cross-linking. TG2 has been implicated in the development and progression of numerous cancers, with a direct role in multiple cellular processes and pathways linked to apoptosis, chemoresistance, epithelial-mesenchymal transition, and stem cell phenotype. The tumour microenvironment (TME) is critical in the formation, progression, and eventual metastasis of cancer, and increasing evidence points to a role for TG2 in matrix remodelling, modulation of biomechanical properties, cell adhesion, motility, and invasion. There is growing interest in targeting the TME therapeutically in response to advances in the understanding of its critical role in disease progression, and a number of approaches targeting biophysical properties and biomechanical signalling are beginning to show clinical promise. In this review we aim to highlight the wide array of processes in which TG2 influences the TME, focussing on its potential role in the dynamic tissue remodelling and biomechanical events increasingly linked to invasive and aggressive behaviour. Drug development efforts have yielded a range of TG2 inhibitors, and ongoing clinical trials may inform strategies for targeting the biomolecular and biomechanical function of TG2 in the TME.

Cancer-associated cells release citrate to support tumour metastatic progression

Citrate is important for lipid synthesis and epigenetic regulation in addition to ATP production. We have previously reported that cancer cells import extracellular citrate via the pmCiC transporter to support their metabolism. Here, we show for the first time that citrate is supplied to cancer by cancer-associated stroma (CAS) and also that citrate synthesis and release is one of the latter's major metabolic tasks. Citrate release from CAS is controlled by cancer cells through cross-cellular communication. The availability of citrate from CAS regulated the cytokine profile, metabolism and features of cellular invasion. Moreover, citrate released by CAS is involved in inducing cancer progression especially enhancing invasiveness and organ colonisation. In line with the in vitro observations, we show that depriving cancer cells of citrate using gluconate, a specific inhibitor of pmCiC, significantly reduced the growth and metastatic spread of human pancreatic cancer cells in vivo and muted stromal activation and angiogenesis. We conclude that citrate is supplied to tumour cells by CAS and citrate uptake plays a significant role in cancer metastatic progression.

Autophagy is deregulated in cancer-associated fibroblasts from oral cancer and is stimulated during the induction of fibroblast senescence by TGF-β1

Many of the characteristics ascribed to cancer-associated fibroblasts (CAFs) are shared by activated, autophagic and senescent fibroblasts. Whilst most oral squamous cell carcinomas (OSCCs) are genetically unstable (GU-OSCC), genetically stable variants (GS-OSCC) have been described and, notably, CAF activation (myofibroblast differentiation) and senescence are characteristics particularly associated with GU-OSCCs. However, it is not known whether autophagy is disrupted in these cells or whether autophagy regulates the development of the myofibroblast and senescent phenotypes. In this study, we show that senescent CAFs from GU-OSCCs contained more autophagosomes than normal human oral fibroblasts (NHOFs) and CAFs from GS-OSCCs possibly due to autophagic impairment. Further, we show that deregulation of autophagy in normal fibroblasts, either by inhibition with autophagy inhibitor, SAR405, or activation with TGF-β1, induced fibroblast activation and senescence: In response to TGF-β1, autophagy was induced prior to the development of the activated and senescent phenotypes. Lastly, we show that both SAR405- and TGF-β1-treated NHOFs enhance OSCC cell migration but only TGF-β1-treated cells increase OSCC invasion through Matrigel, indicating that TGF-β1 has additional effects that are independent of fibroblast activation/senescence. These results suggest a functional role for autophagy in the development of myofibroblast and CAF phenotypes.

Determination of Senescent Myofibroblasts in Precision-Cut Lung Slices

Fibroblast-to-myofibroblast transdifferentiation and the acquisition of a senescent phenotype are hallmarks of fibrotic diseases. The study of the localization of senescent myofibroblasts as well as their interactions with other cell types in the fibrotic tissue has been hindered by the lack of methods to detect these cells in vivo. Here, we describe methods to detect tissue localization of senescent myofibroblasts in precision-cut lung slices (PCLS) by combining β-galactosidase staining with immunofluorescence techniques.

Extracellular Citrate Fuels Cancer Cell Metabolism and Growth

Cancer cells need excess energy and essential nutrients/metabolites not only to divide and proliferate but also to migrate and invade distant organs for metastasis. Fatty acid and cholesterol synthesis, considered a hallmark of cancer for anabolism and membrane biogenesis, requires citrate. We review here potential pathways in which citrate is synthesized and/or supplied to cancer cells and the impact of extracellular citrate on cancer cell metabolism and growth. Cancer cells employ different mechanisms to support mitochondrial activity and citrate synthesis when some of the necessary substrates are missing in the extracellular space. We also discuss the different transport mechanisms available for the entry of extracellular citrate into cancer cells and how citrate as a master metabolite enhances ATP production and fuels anabolic pathways. The available literature suggests that cancer cells show an increased metabolic flexibility with which they tackle changing environmental conditions, a phenomenon crucial for cancer cell proliferation and metastasis.

Fibroblast Senescence in Idiopathic Pulmonary Fibrosis

Aging is an inevitable and complex natural phenomenon due to the increase in age. Cellular senescence means a non-proliferative but viable cellular physiological state. It is the basis of aging, and it exists in the body at any time point. Idiopathic pulmonary fibrosis (IPF) is an interstitial fibrous lung disease with unknown etiology, characterized by irreversible destruction of lung structure and function. Aging is one of the most critical risk factors for IPF, and extensive epidemiological data confirms IPF as an aging-related disease. Senescent fibroblasts in IPF show abnormal activation, telomere shortening, metabolic reprogramming, mitochondrial dysfunction, apoptosis resistance, autophagy deficiency, and senescence-associated secretory phenotypes (SASP). These characteristics of senescent fibroblasts establish a close link between cellular senescence and IPF. The treatment of senescence-related molecules and pathways is continually emerging, and using senolytics eliminating senescent fibroblasts is also actively tried as a new therapy for IPF. In this review, we discuss the roles of aging and cellular senescence in IPF. In particular, we summarize the signaling pathways through which senescent fibroblasts influence the occurrence and development of IPF. On this basis, we further talk about the current treatment ideas, hoping this paper can be used as a helpful reference for future researches.

A Framework of Major Tumor-Promoting Signal Transduction Pathways Implicated in Melanoma-Fibroblast Dialogue

Simple Summary

Melanoma cells reside in a complex stromal microenvironment, which is a critical component of disease onset and progression. Mesenchymal or fibroblastic cell type are the most abundant cellular element of tumor stroma. Factors secreted by melanoma cells can activate non-malignant associated fibroblasts to become melanoma associate fibroblasts (MAFs). MAFs promote tumorigenic features by remodeling the extracellular matrix, supporting tumor cells proliferation, neo-angiogenesis and drug resistance. Additionally, environmental factors may contribute to the acquisition of pro-tumorigenic phenotype of fibroblasts. Overall, in melanoma, perturbed tissue homeostasis contributes to modulation of major oncogenic intracellular signaling pathways not only in tumor cells but also in neighboring cells. Thus, targeted molecular therapies need to be considered from the reciprocal point of view of melanoma and stromal cells.

Abstract

The development of a modified stromal microenvironment in response to neoplastic onset is a common feature of many tumors including cutaneous melanoma. At all stages, melanoma cells are embedded in a complex tissue composed by extracellular matrix components and several different cell populations. Thus, melanomagenesis is not only driven by malignant melanocytes, but also by the altered communication between melanocytes and non-malignant cell populations, including fibroblasts, endothelial and immune cells. In particular, cancer-associated fibroblasts (CAFs), also referred as melanoma-associated fibroblasts (MAFs) in the case of melanoma, are the most abundant stromal cells and play a significant contextual role in melanoma initiation, progression and metastasis. As a result of dynamic intercellular molecular dialogue between tumor and the stroma, non-neoplastic cells gain specific phenotypes and functions that are pro-tumorigenic. Targeting MAFs is thus considered a promising avenue to improve melanoma therapy. Growing evidence demonstrates that aberrant regulation of oncogenic signaling is not restricted to transformed cells but also occurs in MAFs. However, in some cases, signaling pathways present opposite regulation in melanoma and surrounding area, suggesting that therapeutic strategies need to carefully consider the tumor–stroma equilibrium. In this novel review, we analyze four major signaling pathways implicated in melanomagenesis, TGF-β, MAPK, Wnt/β-catenin and Hyppo signaling, from the complementary point of view of tumor cells and the microenvironment.

Tumor-Resident Stromal Cells Promote Breast Cancer Invasion through Regulation of the Basal Phenotype

Collective invasion can be led by breast cancer cells expressing basal epithelial markers, typified by keratin-14 (KRT14). We analyzed gene expression data from The Cancer Genome Atlas and demonstrated a significant correlation between a KRT14+ invasion signature and a stromal-mediated extracellular matrix (ECM) organization module. We then developed a novel coculture model of tumor organoids with autologous stromal cells. Coculture significantly increased KRT14 expression and invasion of organoids from both luminal and basal murine breast cancer models. However, stromal cell conditioned medium induced invasion but not KRT14 expression. Cancer cells released TGFβ and that signaling pathway was required for stromal cell-induced invasion and KRT14 expression. Mechanistically, TGFβ induced NOX4 expression in stromal cells and NOX4 inhibition reduced invasion and KRT14 expression. In summary, we developed a novel coculture model and revealed dynamic molecular interactions between stromal cells and cancer cells that regulate both basal gene expression and invasive behavior. IMPLICATIONS: Fibroblasts within mammary tumors can regulate the molecular phenotype and invasive behavior of breast cancer cells. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/18/11/1615/F1.large.jpg.

Portrait of a CAF: The story of cancer-associated fibroblasts in head and neck cancer

Complex interactions take place during cancer formation and progression. In this regard, there has been increasing focus on the non-malignant cells that make up the tumour microenvironment (TME), and how they interact with malignant tumour cells. TME is highly heterogeneous and has a major influence on tumour behaviour and therapy response. Cancer-associated fibroblasts (CAFs), one of the main components of the TME, establish dangerous liaisons with cancer cells and other components of the TME to shape a tumour-supportive environment in many types of cancer. Head and neck squamous cell carcinoma (HNSCC) encompass the malignant neoplasms arising from the mucosal lining of the oral cavity, pharynx and larynx. The TME of HNSCC contributes to tumour progression and this stromal compartment may be an interesting target for treatment. There is an emerging picture of the behaviour of CAFs in HNSCC; how they affect and are affected by the TME. We aim to summarise and discuss the current understanding of CAFs in head and neck cancer, exploring CAF activation and heterogeneity, and interaction with cancer cells and other cells within the TME.

Eukaryotic translation elongation factor 1δ, N-terminal propeptide of type I collagen and cancer-associated fibroblasts are prognostic markers of oral squamous cell carcinoma patients

OBJECTIVE

Identifying markers that influence oral squamous cell carcinoma (OSCC) prognosis is a fundamental strategy to improve the overall survival of patients. Markers such as eukaryotic translation elongation factor 1δ (EEF1D), fascin, N-terminal propeptide of type I collagen (PINP), and cancer-associated fibroblasts (CAFs) have been noticed in OSCCs and their levels are closely related to the prognosis of tumors. Our aim was to confirm the role of those markers in OSCC prognosis.

STUDY DESIGN

Immunohistochemistry was performed in 90 OSCC specimens. The associations between clinicopathologic features and expression of markers were assessed by χ² test. Kaplan-Meier curves and univariate and multivariate Cox regression models were used for survival analysis. Markers were analyzed individually and in combination.

RESULTS

High expression of EEF1D (P = .017) and PINP (P = .02) and abundant density of CAFs in tumor stroma (P = .005) predicted significantly poor survival in OSCC patients. Multivariate analysis revealed that all 3 parameters are individually independent prognostic factors of OSCC patients, and their combination improved the discrimination of patients at high risk for poor survival.

CONCLUSIONS

Our results suggested that the expression of EEF1D and PINP and the density of CAFs might influence the survival of patients with OSCC.

Cancer-associated fibroblasts of colorectal cancer and their markers: updates, challenges and translational outlook

Accumulation of cancer-associated fibroblasts (CAFs) in the tumor microenvironment is associated with poor prognosis and recurrence of colorectal cancer (CRC). Despite their prominent roles in colorectal carcinogenesis, there is a lack of robust and specific markers to classify the heterogeneous and highly complex CAF populations. This has resulted in confusing and misleading definitions of CAFs in cancer niche. Advancements in molecular biology approaches have open doors to reliable CAF marker detection methods in various solid tumors. These discoveries would contribute to more efficient screening, monitoring and targeted therapy of CRC thus potentially will reduce cancer morbidity and mortality rates. This review highlights current scenarios, dilemma, translational potentials of CAF biomarker and future therapeutic applications involving CAF marker identification in CRC.