Cancer Stromal Cells Research Articles

Cutting the Brakes on Ras-Cytoplasmic GAPs as Targets of Inactivation in Cancer.

Simple SummaryGTPase-Activating Proteins (RasGAPs) are a group of structurally related proteins with a fundamental role in controlling the activity of Ras in normal and cancer cells. In particular, loss of function of RasGAPs may contribute to aberrant Ras activation in cancer. Here we review the multiple molecular mechanisms and factors that are involved in downregulating RasGAPs expression and functions in cancer. Additionally, we discuss how extracellular stimuli from the tumor microenvironment can control RasGAPs expression and activity in cancer cells and stromal cells, indirectly affecting Ras activation, with implications for cancer development and progression.The Ras pathway is frequently deregulated in cancer, actively contributing to tumor development and progression. Oncogenic activation of the Ras pathway is commonly due to point mutation of one of the three Ras genes, which occurs in almost one third of human cancers. In the absence of Ras mutation, the pathway is frequently activated by alternative means, including the loss of function of Ras inhibitors. Among Ras inhibitors, the GTPase-Activating Proteins (RasGAPs) are major players, given their ability to modulate multiple cancer-related pathways. In fact, most RasGAPs also have a multi-domain structure that allows them to act as scaffold or adaptor proteins, affecting additional oncogenic cascades. In cancer cells, various mechanisms can cause the loss of function of Ras inhibitors; here, we review the available evidence of RasGAP inactivation in cancer, with a specific focus on the mechanisms. We also consider extracellular inputs that can affect RasGAP levels and functions, implicating that specific conditions in the tumor microenvironment can foster or counteract Ras signaling through negative or positive modulation of RasGAPs. A better understanding of these conditions might have relevant clinical repercussions, since treatments to restore or enhance the function of RasGAPs in cancer would help circumvent the intrinsic difficulty of directly targeting the Ras protein.

Tumor Microenvironment Sensitive Nanocarriers for Bioimaging and Therapeutics.

The tumor microenvironment (TME), which is composed of cancer cells, stromal cells, immune cells, and extracellular matrices, plays an important role in tumor growth and progression. Thus, targeting the TME using a well-designed nano-drug delivery system is emerging as a promising strategy for the treatment of solid tumors. Compared to normal tissues, the TME presents several distinguishable physiological features such as mildly acidic pH, hypoxia, high level of reactive oxygen species, and overexpression of specific enzymes, that are exploited as stimuli to induce specific changes in the nanocarrier structures, and thereby facilitates target-specific delivery of imaging or chemotherapeutic agents for the early diagnosis or effective treatment, respectively. Recently, smart nanocarriers that respond to more than one stimulus in the TME have also been designed to elicit a more desirable spatiotemporally controlled drug release. This review highlights the recent progress in TME-sensitive nanocarriers designed for more efficient tumor therapy and imaging. In particular, the design strategies, challenges, and critical considerations involved in the fabrication of TME-sensitive nanocarriers, along with their in vitro and in vivo evaluations are discussed.

Crosstalk Between Cancer Associated Fibroblasts and Cancer Cells in Scirrhous Type Gastric Cancer.

Gastric cancer (GC) is the third leading cause among all cancer deaths globally. Although the treatment outcome of GC has improved, the survival of patients with GC at stages III and IV remains unsatisfactory. Among several types of GC, scirrhous type GC (SGC) shows highly aggressive growth and invasive activity, leading to frequent peritoneal metastasis. SGC is well known to accompany abundant stromal cells that compose the tumor microenvironment (TME) along with the produced extracellular matrix (ECM) and secreted factors. One of the main stromal components is cancer associated fibroblast (CAF). In the SGC microenvironment, CAFs are a source of various secreted factors, including fibroblast growth factors (FGFs), which mediate prominent tumor-stimulating activity. In turn, cancer cells also secrete numerous factors, which can activate and educate CAFs. Current findings suggest that cancer cells and stromal cells communicate interactively via the soluble factors, the ECM, and likely also by exosomes. In this review, we focus on the soluble factors mediating communication between cancer cells and CAFs in SGC, and consider how they are related to the modulation of TME and the high rate of peritoneal metastasis. At last, we discuss the perspectives on targeting these communication pathways for improved future treatment.

A versatile system to record cell-cell interactions.

Cell-cell interactions influence all aspects of development, homeostasis, and disease. In cancer, interactions between cancer cells and stromal cells play a major role in nearly every step of carcinogenesis. Thus, the ability to record cell-cell interactions would facilitate mechanistic delineation of the role of the cancer microenvironment. Here, we describe GFP-based Touching Nexus (G-baToN) which relies upon nanobody-directed fluorescent protein transfer to enable sensitive and specific labeling of cells after cell-cell interactions. G-baToN is a generalizable system that enables physical contact-based labeling between various human and mouse cell types, including endothelial cell-pericyte, neuron-astrocyte, and diverse cancer-stromal cell pairs. A suite of orthogonal baToN tools enables reciprocal cell-cell labeling, interaction-dependent cargo transfer, and the identification of higher order cell-cell interactions across a wide range of cell types. The ability to track physically interacting cells with these simple and sensitive systems will greatly accelerate our understanding of the outputs of cell-cell interactions in cancer as well as across many biological processes.

Single-cell transcriptome atlas of lung adenocarcinoma featured with ground glass nodules

As an early type of lung adenocarcinoma, ground glass nodule (GGN) has been detected increasingly and now accounts for most lung cancer outpatients. GGN has a satisfactory prognosis and its characteristics are quite different from solid adenocarcinoma (SADC). We compared the GGN adenocarcinoma (GGN-ADC) with SADC using the single-cell RNA sequencing (scRNA-seq) to fully understand GGNs. The tumor samples of five patients with lung GGN-ADCs and five with SADCs underwent surgery were digested to a single-cell suspension and analyzed using 10× Genomic scRNA-seq techniques. We obtained 60,459 cells and then classified them as eight cell types, including cancer cells, endothelial cells, fibroblasts, T cells, B cells, Nature killer cells, mast cells, and myeloid cells. We provided a comprehensive description of the cancer cells and stromal cells. We found that the signaling pathways related to cell proliferation were downregulated in GGN-ADC cancer cells, and stromal cells had different effects in GGN-ADC and SADC based on the analyses of scRNA-seq results. In GGN-ADC, the signaling pathways of angiogenesis were downregulated, fibroblasts expressed low levels of some collagens, and immune cells were more activated. Furthermore, we used flow cytometry to isolate the cancer cells and T cells in 12 GGN-ADC samples and in an equal number of SADC samples, including CD4+ T and CD8+ T cells, and validated the expression of key molecules by quantitative real-time polymerase chain reaction analyses. Through comprehensive analyses of cell phenotypes in GGNs, we provide deep insights into lung carcinogenesis that will be beneficial in lung cancer prevention and therapy.

Resveratrol Suppresses Cross-Talk between Colorectal Cancer Cells and Stromal Cells in Multicellular Tumor Microenvironment: A Bridge between In Vitro and In Vivo Tumor Microenvironment Study.

The interaction between tumor cells and the tumor microenvironment (TME) is an important process for the development of tumor malignancy. Modulation of paracrine cross-talk could be a promising strategy for tumor control within the TME. The exact mechanisms of multi-targeted compound resveratrol are not yet fully understood. Whether resveratrol can modulate paracrine signal transduction-induced malignancy in the multicellular-TME of colorectal cancer cells (CRC) was investigated. An in vitro model with 3D-alginate HCT116 cells in multicellular-TME cultures (fibroblast cells, T-lymphocytes) was used to elucidate the role of TNF-β, Sirt1-ASO and/or resveratrol in the proliferation, invasion and cancer stem cells (CSC) of CRC cells. We found that multicellular-TME, similar to TNF-β-TME, promoted proliferation, colony formation, invasion of CRC cells and enabled activation of CSCs. However, after co-treatment with resveratrol, the malignancy of multicellular-TME reversed to HCT116. In addition, resveratrol reduced the secretion of T-lymphocyte/fibroblast (TNF-β, TGF-β3) proteins, antagonized the T-lymphocyte/fibroblast-promoting NF-κB activation, NF-κB nuclear translocation and thus the expression of NF-κB-promoting biomarkers, associated with proliferation, invasion and survival of CSCs in 3D-alginate cultures of HCT116 cells induced by TNF-β- or multicellular-TME, but not by Sirt1-ASO, indicating the central role of this enzyme in the anti-tumor function of resveratrol. Our results suggest that in vitro multicellular-TME promotes crosstalk between CRC and stromal cells to increase survival, migration of HCT116 and the resveratrol/Sirt1 axis suppresses this loop by modulating paracrine agent secretion and NF-κB signaling. Fibroblasts and T-lymphocytes are promising targets for resveratrol in the prevention of CRC metastasis.

Microenvironmental modulation of the developing tumour: an immune-stromal dialogue.

Successful establishment of a tumour relies on a cascade of interactions between cancer cells and stromal cells within an evolving microenvironment. Both immune and nonimmune cellular components are key factors in this process, and the individual players may change their role from tumour elimination to tumour promotion as the microenvironment develops. While the tumour-stroma crosstalk present in an established tumour is well-studied, aspects in the early tumour or premalignant microenvironment have received less attention. This is in part due to the challenges in studying this process in the clinic or in mouse models. Here, we review the key anti- and pro-tumour factors in the early microenvironment and discuss how understanding this process may be exploited in the clinic.

Proteoglycans in the Pathogenesis of Hormone-Dependent Cancers: Mediators and Effectors.

Hormone-dependent cancers exhibit high morbidity and mortality. In spite of advances in therapy, the treatment of hormone-dependent cancers remains an unmet health need. The tumor microenvironment (TME) exhibits unique characteristics that differ among various tumor types. It is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded and supported by components of the extracellular matrix (ECM). Therefore, the interactions among cancer cells, stromal cells, and components of the ECM determine cancer progression and response to therapy. Proteoglycans (PGs), hybrid molecules consisting of a protein core to which sulfated glycosaminoglycan chains are bound, are significant components of the ECM that are implicated in all phases of tumorigenesis. These molecules, secreted by both the stroma and cancer cells, are crucial signaling mediators that modulate the vital cellular pathways implicated in gene expression, phenotypic versatility, and response to therapy in specific tumor types. A plethora of deregulated signaling pathways contributes to the growth, dissemination, and angiogenesis of hormone-dependent cancers. Specific inputs from the endocrine and immune systems are some of the characteristics of hormone-dependent cancer pathogenesis. Importantly, the mechanisms involved in various aspects of cancer progression are executed in the ECM niche of the TME, and the PG components crucially mediate these processes. Here, we comprehensively discuss the mechanisms through which PGs affect the multifaceted aspects of hormone-dependent cancer development and progression, including cancer metastasis, angiogenesis, immunobiology, autophagy, and response to therapy.

Abstract 5098: Cues from extracellular matrix produced by fibroblasts prime lung cancer cells for distant dissemination

Abstract Extracellular matrix (ECM) plays a crucial role in the regulation of tumor growth and progression. In the lungs, fibroblasts are involved in ECM homeostasis and are therefore crucial in lung tissue repair and remodeling. These activities are exploited by cancer cells during tumor growth by reprogramming fibroblast towards a tumor supportive phenotype including regulation of ECM-related proteins. We previously identified the nuclear transported XPO1 as a master regulator of fibroblast metabolic reprogramming. How cues from ECM can regulate the fate of cells disseminating from primary tumors is however poorly understood. To investigate the relevance of ECM remodeling during tumor development, primary lung fibroblasts were treated with TGF-β to mimic signals in the tumor microenvironment and Real-Time PCR was then performed to evaluate expression levels of ECM-related genes. Co-cultures and experiments with fibroblast conditioned medium or fibroblast-derived decellularized extracellular matrix (dECM) were performed with lung cancer cells and modulation of stemness phenotype evaluated by increase of CD133+ cancer stem cells. dECM from patient-derived fibroblast cultures was used in subcutaneous co-injections experiments with lung cancer cell lines in immunocompromised mice and dissemination to the lungs evaluated by flow-cytometry. Treatment with TGF-β induced over-expression of ECM-related genes (including COL1A and SPARC) which could be prevented by pharmacological inhibition of XPO1. Primary tumor growth was increased by dECM obtained from cultures of cancer associated fibroblasts. Interestingly analysis of tumors obtained by co-injection with different ECMs showed acquisition of specific phenotypes at late time points including relative content of CD133+ cancer stem cells and regulation of ECM-related genes in both cancer cells and stromal cells. Primary tumor microenvironments with high content of COL1A and COL6A3 were conductive to dissemination to distant sites which was associated by a local reduction of NK cells and an increase in macrophages. In vitro XPO1 inhibition prevented the ability of activated fibroblasts to stimulate migration of lung cancer cell lines and to increase the frequency of CD133+ cancer stem cells thereby reducing their pro-tumorigenic activity in vivo. Taken together these results reveal the activity of lung fibroblasts in dictating the metastatic phenotype by an ECM-regulated niche at the primary tumor site and suggest potential therapeutic value of pharmacological interventions blocking tumor-stroma interactions. Citation Format: Giuliana Pollaci, Francesca Giovinazzo, Ornella Rondinone, Antonina Bruccoleri, Federica Facchinetti, Monica Tortoreto, Ugo Pastorino, Giulia Bertolini, Gabriella Sozzi, Luca Roz. Cues from extracellular matrix produced by fibroblasts prime lung cancer cells for distant dissemination [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5098.

Report of the use of patient-derived xenograft models in the development of anticancer drugs in Japan.

Cell line‐derived xenograft (CDX) models created by implanting cancer cell lines into immunodeficient mice have contributed largely to the development of cancer drug therapies. However, cell lines often lose their original biological characteristics through many passages and cancer tissues in CDX models have many cancer cells and few cancer stromal cells, therefore CDX models are currently considered not suitable for predicting the results of clinical studies. Conversely, patient‐derived xenograft (PDX) models are gaining importance, as human cancer biological characteristics and microenvironments are recreated by implanting tumor tissue into immunodeficient mice. These highly expected, evidently beneficial PDX models have been used in some basic research and are becoming more generalized. However, quality control and quality assurance criteria have not been established for them, and challenges and problems in the utilization of valuable PDX models in drug development have yet to be clarified. In this report, we conducted a questionnaire survey among researchers in Japanese academic institutions and pharmaceutical companies to understand the current status of PDX models in Japan. Based on the questionnaire results, we summarized the situations surrounding respondent's utilization and quality control in the development of anticancer drugs and proposed several measures to facilitate the utilization of PDX models in the development of anticancer drugs.

Prognostic Value of CXCR2 in Breast Cancer.

The tumor microenvironment appears essential in cancer progression and chemokines are mediators of the communication between cancer cells and stromal cells. We have previously shown that the ligands of the chemokine receptor CXCR2 were expressed at higher levels in triple-negative breast cancers (TNBC). Our hypothesis was that CXCR2 expression could also be altered in breast cancer. Here, we have analyzed the potential role of CXCR2 in breast cancer in a retrospective cohort of 105 breast cancer patients. Expression of CXCR2, CD11b (a marker of granulocytes) and CD66b (a marker of neutrophils) was analyzed by immunohistochemistry on tumor samples. We demonstrated that CXCR2 stained mainly stromal cells and in particular neutrophils. CXCR2, CD11b and CD66b expression were correlated with high grade breast cancers. Moreover, TNBC displayed a higher expression of CXCR2, CD11b and CD66b than hormone receptor positive or Her2 positive tumors. High levels of CXCR2 and CD11b, but not CD66b, were associated with a higher infiltration of T lymphocytes and B lymphocytes. We also observed a correlation between CXCR2 and AP-1 activity. In univariate analyses, CXCR2, but not CD11b or CD66b, was associated with a lower risk of relapse; CXCR2 remained significant in multivariate analysis. Our data suggest that CXCR2 is a stromal marker of TNBC. However, higher levels of CXCR2 predicted a lower risk of relapse.

Cancer-associated fibroblasts mediate cancer progression and remodel the tumouroid stroma

BackgroundCancer-associated fibroblasts (CAFs) are highly differentiated and heterogeneous cancer-stromal cells that promote tumour growth, angiogenesis and matrix remodelling.MethodsWe utilised an adapted version of a previously developed 3D in vitro model of colorectal cancer, composed of a cancer mass and the surrounding stromal compartment. We compared cancer invasion with an acellular stromal surround, a “healthy” or normal cellular stroma and a cancerous stroma. For the cancerous stroma, we incorporated six patient-derived CAF samples to study their differential effects on cancer growth, vascular network formation and remodelling.ResultsCAFs enhanced the distance and surface area of the invasive cancer mass whilst inhibiting vascular-like network formation. These processes correlated with the upregulation of hepatocyte growth factor (HGF), metallopeptidase inhibitor 1 (TIMP1) and fibulin-5 (FBLN5). Vascular remodelling of previously formed endothelial structures occurred through the disruption of complex networks, and was associated with the upregulation of vascular endothelial growth factor (VEGFA) and downregulation in vascular endothelial cadherin (VE-Cadherin).ConclusionsThese results support, within a biomimetic 3D, in vitro framework, the direct role of CAFs in promoting cancer invasion, and their key function in driving vasculogenesis and angiogenesis.

D2-40/podoplanin expression in cancer stroma by immunohistochemical staining is associated with poor prognosis in bladder cancer patients after radical cystectomy

ObjectivesWe assessed whether D2-40/podoplanin (PDPN) could be used to identify bladder cancer patients with a higher probability of benefiting from cisplatin-based combination chemotherapy. Patients and methodsWe investigated PDPN expression by immunohistochemical analysis of cystectomy specimens from 96 bladder cancer patients who had undergone radical cystectomy without neoadjuvant or adjuvant cisplatin-based combination chemotherapy until recurrence. We classified the cases into 2 groups according to the achievement of 2-year recurrence-free survival (RFS) and evaluated whether PDPN expression was associated with patient prognosis. We also classified the 96 cases into 3 groups according to the possible need for perioperative chemotherapy based on the response to chemotherapy after recurrence as “unnecessary” (achieving 2-year RFS), “responder” (recurring within 2 years and responding to chemotherapy after recurrence), and “non-responder” (not responding chemotherapy following recurrence) and compared PDPN expression between these groups. ResultsAmong 13 cases diagnosed with clinically <T2 disease, all 13 cases achieved 2-year RFS. Only 6 (8.7%) and 9 cases (13.0%) were classified as “responders” and “non-responders,” respectively, out of 69 cases with clinical T2 or higher disease who received cisplatin-based chemotherapy after recurrence. We identified PDPN expression in cancer stroma cells were morphologically fibroblasts, but not in cancer cells. Cases with <1% PDPN staining positivity ratios showed significantly better prognosis compared to that in cases with ≧1% (log-rank tests). Moreover, the positive predictive value and specificity of a <1% PDPN positive staining ratio were 89.5% and 86.7%, respectively, for “unnecessary” perioperative chemotherapy in the 69 cases. ConclusionOur results confirmed that cisplatin-based perioperative chemotherapy is unnecessary in many cases requiring radical cystectomy. To our knowledge, this is the first report of PDPN expression in bladder cancer stroma cells that are morphologically fibroblasts. Although PDPN expression might be associated with poor prognosis after surgery, we did not find that it helped to predict chemotherapy response. Whether PDPN expression by fibroblasts in high-risk bladder cancer cases is a marker for prognosis after radical cystectomy and response to perioperative cisplatin-based chemotherapy to avoid unnecessary chemotherapy warrants further investigation.

Expressions of extracellular matrix‐remodeling factors in lymph nodes from oral cancer patients

Most malignant tumors require remodeling extracellular matrices (ECMs) for invasive growth and metastasis. Cancer cells and stromal cells remodel ECM. We investigated the relationship between regional lymph node (LN) metastasis and expression of ECM-remodeling factors in oral squamous cell carcinoma (OSCC). Using primary OSCC and cervical LNs obtained surgically, we performed immunohistochemical evaluation of the ECM-remodeling factors, lysyl oxidase (LOX), MT1-MMP, S100A8, and TIMP-1 in primary tumor and marginal sinus histiocytosis (MSH) in LNs, and determined the statistical significance of the positive rates between metastatic and metastasis-free groups. Marginal sinus histiocytosis was more frequently formed in the metastatic group compared to the metastasis-free group. Lymphatic metastasis correlated with the immunopositivity rates of tumor cells expressing LOX, MT1-MMP, and TIMP-1, and of stromal cells expressing TIMP-1. The case rates of MSH containing macrophages positive for LOX and MT1-MMP in the metastasis group were significantly higher than in the metastasis-free group. ECM-remodeling-associated macrophages accumulate in marginal sinus in conjunction with lymphatic metastasis. Expression of LOX, MT1-MMP, and TIMP-1 in the parenchyma, and stromal expression of TIMP-1 in primary tumor may predict lymphatic metastasis. LOX and MT1-MMP have a possibility to participate in formation of pre-metastatic niche in LNs.

Geospatial immune variability illuminates differential evolution of lung adenocarcinoma.

Remarkable progress in molecular analyses has improved our understanding of the evolution of cancer cells toward immune escape1-5. However, the spatial configurations of immune and stromal cells, which may shed light on the evolution of immune escape across tumor geographical locations, remain unaddressed. We integrated multiregion exome and RNA-sequencing (RNA-seq) data with spatial histology mapped by deep learning in 100 patients with non-small cell lung cancer from the TRACERx cohort6. Cancer subclones derived from immune cold regions were more closely related in mutation space, diversifying more recently than subclones from immune hot regions. In TRACERx and in an independent multisample cohort of 970 patients with lung adenocarcinoma, tumors with more than one immune cold region had a higher risk of relapse, independently of tumor size, stage and number of samples per patient. In lung adenocarcinoma, but not lung squamous cell carcinoma, geometrical irregularity and complexity of the cancer-stromal cell interface significantly increased in tumor regions without disruption of antigen presentation. Decreased lymphocyte accumulation in adjacent stroma was observed in tumors with low clonal neoantigen burden. Collectively, immune geospatial variability elucidates tumor ecological constraints that may shape the emergence of immune-evading subclones and aggressive clinical phenotypes.

The Autonomic Regulation of Tumor Growth and the Missing Links.

Accumulating evidence now indicates that peripheral nerves and solid tumors mutually support the growth of each other. Tumor-derived molecular cues guide nerve infiltration to the tumor milieu, while the tumor-infiltrating nerves provide molecular support to promote tumor growth and dissemination. In this mini-review, we discuss the unique roles of sympathetic and parasympathetic nerves in promoting tumor growth and metastasis. The contribution of adrenergic and cholinergic signals, the specific receptors involved, and the downstream molecular links in both cancer cells and stromal cells are discussed for their intrinsic capacity to modulate tumor growth. We identified unappreciated niche areas in the field, an investigation of which are critical to filling the knowledge gap in understanding the biology of neuromodulation of cancers.

Investigating Tunneling Nanotubes in Cancer Cells: Guidelines for Structural and Functional Studies through Cell Imaging.

By allowing insured communication between cancer cells themselves and with the neighboring stromal cells, tunneling nanotubes (TNTs) are involved in the multistep process of cancer development from tumorigenesis to the treatment resistance. However, despite their critical role in the biology of cancer, the study of the TNTs has been announced challenging due to not only the absence of a specific biomarker but also the fragile and transitory nature of their structure and the fact that they are hovering freely above the substratum. Here, we proposed to review guidelines to follow for studying the structure and functionality of TNTs in tumoral neuroendocrine cells (PC12) and nontumorigenic human bronchial epithelial cells (HBEC-3, H28). In particular, we reported how crucial is it (i) to consider the culture conditions (culture surface, cell density), (ii) to visualize the formation of TNTs in living cells (mechanisms of formation, 3D representation), and (iii) to identify the cytoskeleton components and the associated elements (categories, origin, tip, and formation/transport) in the TNTs. We also focused on the input of high-resolution cell imaging approaches including Stimulated Emission Depletion (STED) nanoscopy, Transmitted and Scanning Electron Microscopies (TEM and SEM). In addition, we underlined the important role of the organelles in the mechanisms of TNT formation and transfer between the cancer cells. Finally, new biological models for the identification of the TNTs between cancer cells and stromal cells (liquid air interface, ex vivo, in vivo) and the clinical considerations will also be discussed.

Three-dimensional models of breast cancer-fibroblasts interactions.

Tumor stroma plays an important role in progression of cancers to a fatal metastatic disease. Modern treatment strategies are considering targeting tumor stroma to improve outcomes for cancer patients. A current challenge to develop stroma-targeting therapeutics is the lack of preclinical physiologic tumor models. Animal models widely used in cancer research lack human stroma and are not amenable to screening of chemical compounds for cancer drug discovery. In this review, we outline in vitro three-dimensional tumor models that we have developed to study the interactions among cancer cells and stromal cells. We describe development of the tumor models in a modular fashion, from a spheroid model to a sophisticated organotypic model, and discuss the importance of using correct physiologic models to recapitulate tumor-stromal signaling. These biomimetic tumor models will facilitate understanding of tumor-stromal signaling biology and provide a scalable approach for testing and discovery of cancer drugs.

Targeting the HGF/c-MET pathway in advanced pancreatic cancer: a key element of treatment that limits primary tumour growth and eliminates metastasis

BackgroundStromal–tumour interactions facilitate pancreatic cancer (PC) progression. The hepatocyte growth factor (HGF)/c-MET pathway is upregulated in PC and mediates the interaction between cancer cells and stromal pancreatic stellate cells (PSCs). This study assessed the effect of HGF/c-MET inhibition plus gemcitabine (G) on the progression of advanced PC.MethodsOrthotopic PC was produced by implantation of luciferase-tagged human cancer cells + human PSCs into mouse pancreas. Tumours were allowed to develop without treatment for 4 weeks. Mice were then treated for 6 weeks with one of the following: IgG, G, HGF inhibitor (Hi), c-MET inhibitor (Ci), Hi + Ci, Hi + G, Ci + G, or Hi + Ci + G.ResultsBioluminescence imaging showed similar tumour sizes in all mice at the initiation of treatments. Triple therapy (Hi + Ci + G): (1) completely eliminated metastasis; (2) significantly reduced tumour size as assessed by bioluminescence and at necropsy; (3) significantly reduced proliferating cancer cell density and stem cell marker DCLK1 expression in tumours. In vitro 3D culture studies supported our in vivo findings.ConclusionEven at an advanced disease stage, a two-pronged approach, targeting (a) HGF/c-MET with relevant inhibitors and (b) cancer cells with chemotherapy, completely eliminated metastasis and significantly decreased tumour growth, suggesting that this is a promising treatment approach for PC.

Taking a Full Snapshot of Cancer Biology: Deciphering the Tumor Microenvironment for Effective Cancer Therapy in the Oncology Clinic.

A bottleneck that is hindering therapeutics innovation in cancers is the current lack of integration of what we have learned in tumor biology as well as the tumor microenvironment (TME). This is because tumors are complex tissues composed of cancer cells, stromal cells, and the extracellular matrix (ECM). Although genetic alterations might cause the initial uncontrolled growth, resistance to apoptosis in cancer cells and stromal cells play additional key roles within the TME and thus influence tumor initiation, progression, therapy resistance, and metastasis. Therapies targeting cancer cells are usually insufficient when the stromal component of the TME causes therapy resistance. For innovation in cancer treatment and to take a full snapshot of cancer biology, anticancer drug design must, therefore, target both cancer cells and the stromal component. This expert review critically examines the TME components such as cancer-associated fibroblasts and ECM that can be reprogrammed to create a tumor-suppressive environment, thereby aiding in tumor treatment. Better cancer experimental models that mimic the TME such as tumor spheroids, microfluidics, three dimensional (3D) bioprinted models, and organoids will allow deeper investigations of the TME complexity and can lead to the translation of basic tumor biology to effective cancer treatments. Ultimately, innovative cancer treatments and, by extension, improvement in cancer patients' outcomes will emerge from combinatorial drug development strategies targeting both cancer cells and stromal components of the TME. Combinatorial treatment strategies can take the form of chemotherapy and radiotherapy (targeting tumor cells and stromal components) and immunotherapy that is able to regulate immune responses against tumor cells. This expert review thus addresses a previously neglected knowledge gap in cancer drug design and development by broadening the focus in cancer biology to TME so as to empower disruptive health care innovations in the oncology clinic.