Human gastrointestinal neoplasia-associated myofibroblasts can develop from bone marrow-derived cells following allogeneic stem cell transplantation

Impact of STAT-signaling pathway on cancer-associated fibroblasts in colorectal cancer and its role in immunosuppression

Colorectal cancer (CRC) remains one of the most commonly diagnosed and deadliest types of cancer worldwide. CRC displays a desmoplastic reaction (DR) that has been inversely associated with poor prognosis; less DR is associated with a better prognosis. This reaction generates excessive connective tissue, in which cancer-associated fibroblasts (CAFs) are critical cells that form a part of the tumor microenvironment. CAFs are directly involved in tumorigenesis through different mechanisms. However, their role in immunosuppression in CRC is not well understood, and the precise role of signal transducers and activators of transcription (STATs) in mediating CAF activity in CRC remains unclear. Among the myriad chemical and biological factors that affect CAFs, different cytokines mediate their function by activating STAT signaling pathways. Thus, the harmful effects of CAFs in favoring tumor growth and invasion may be modulated using STAT inhibitors. Here, we analyze the impact of different STATs on CAF activity and their immunoregulatory role.

Targeting the devil: Strategies against cancer-associated fibroblasts in colorectal cancer

Cancer-associated fibroblasts (CAFs), as significant constituents of the tumor microenvironment (TME), play a pivotal role in the progression of cancers, including colorectal cancer (CRC). In this comprehensive review, we presented the origins and activation mechanisms of CAFs in CRC, elaborating on how CAFs drive tumor progression through their interactions with CRC cells, immune cells, vascular endothelial cells, and the extracellular matrix within the TME. We systematically outline the intricate web of interactions among CAFs, tumor cells, and other TME components, and based on this complex interplay, we summarize various therapeutic strategies designed to target CAFs in CRC. It is also essential to recognize that CAFs represent a highly heterogeneous group, encompassing various subtypes such as myofibroblastic CAF (myCAF), inflammatory CAF (iCAF), antigen-presenting CAF (apCAF), vessel-associated CAF (vCAF). Herein, we provide a summary of studies investigating the heterogeneity of CAFs in CRC and the characteristic expression patterns of each subtype. While the majority of CAFs contribute to the exacerbation of CRC malignancy, recent findings have revealed specific subtypes that exert inhibitory effects on CRC progression. Nevertheless, the comprehensive landscape of CAF heterogeneity still awaits exploration. We also highlight pivotal unanswered questions that need to be addressed before CAFs can be recognized as feasible targets for cancer treatment. In conclusion, the aim of our review is to elucidate the significance and challenges of advancing in-depth research on CAFs, while outlining the pathway to uncover the complex roles of CAFs in CRC and underscore their significant potential as therapeutic targets.

Recovery of Therapeutically Ablated Engineered Blood-Vessel Networks on a Plug-and-Play Platform

Limiting the availability of key angiogenesis-promoting factors is a successful strategy to ablate tumor-supplying blood vessels or to reduce excessive vasculature in diabetic retinopathy. However, the efficacy of such anti-angiogenic therapies (AATs) varies with tumor type, and regrowth of vessels is observed upon termination of treatment. The ability to understand and develop AATs remains limited by a lack of robust in vitro systems for modeling the recovery of vascular networks. Here, complex 3D micro-capillary networks are engineered by sequentially seeding human bone marrow-derived mesenchymal stromal cells and human umbilical vein endothelial cells (ECs) on a previously established, synthetic plug-and-play hydrogel platform. In the tightly interconnected vascular networks that form this way, the two cell types share a basement membrane-like layer and can be maintained for several days of co-culture. Pre-formed networks degrade in the presence of bevacizumab. Upon treatment termination, vessel structures grow back to their original positions after replenishment with new ECs, which also integrate into unperturbed established networks. The data suggest that this plug-and-play platform enables the screening of drugs with blood-vessel inhibiting functions. It is believed that this platform could be of particular interest in studying resistance or recovery mechanisms to AAT treatment.

Role of cancer-educated mesenchymal stromal cells on tumor progression

The malignant tumor is the main cause of human deaths worldwide. Current therapies focusing on the tumor itself have achieved unprecedented benefits. Various pro-tumorigenic factors in the tumor microenvironment (TME) could abolish the effect of cancer therapy. Mesenchymal stromal cells (MSCs) are one of the substantial components in the tumor microenvironment, contributing to tumor progression. However, MSCs are not inherently tumor-promoting. Indeed, they acquire pro-tumorigenic properties under the education of the TME. We herein review how various elements in the TME including tumor cells, immune cells, pro-inflammatory factors, hypoxia, and extracellular matrix influence the biological characteristics of MSCs through complex interactions and demonstrate the underlying mechanisms. We also highlight the importance of tumor-associated mesenchymal stromal cells (TA-MSCs) in promoting tumor progression. Our review gives a new insight into the TA-MSCs as a potential tumor therapeutic target. It is anticipated that subverting MSCs education will facilitate the outbreak of therapeutic strategies against tumors.

The Origin, Differentiation, and Functions of Cancer-Associated Fibroblasts in Gastrointestinal Cancer

Emerging evidence has shown the importance of the tumor microenvironment in tumorigenesis and progression. Cancer-associated fibroblasts (CAFs) are one of the most infiltrated stroma cells of the tumor microenvironment in gastrointestinal tumors. CAFs play crucial roles in tumor development and therapeutic response by biologically secreting soluble factors or structurally remodeling the extracellular matrix. Conceivably, CAFs may become excellent targets for tumor prevention and treatment. However, the limited knowledge of the heterogeneity of CAFs represents a huge challenge for clinically targeting CAFs. In this review, we summarize the newest understanding of gastrointestinal CAFs, with a special focus on their origin, differentiation, and function. We also discuss the current understanding of CAF subpopulations as shown by single-cell technologies.

Cancer-associated fibroblasts: from basic science to anticancer therapy

Cancer-associated fibroblasts (CAFs), as a central component of the tumor microenvironment in primary and metastatic tumors, profoundly influence the behavior of cancer cells and are involved in cancer progression through extensive interactions with cancer cells and other stromal cells. Furthermore, the innate versatility and plasticity of CAFs allow their education by cancer cells, resulting in dynamic alterations in stromal fibroblast populations in a context-dependent manner, which highlights the importance of precise assessment of CAF phenotypical and functional heterogeneity. In this review, we summarize the proposed origins and heterogeneity of CAFs as well as the molecular mechanisms regulating the diversity of CAF subpopulations. We also discuss current strategies to selectively target tumor-promoting CAFs, providing insights and perspectives for future research and clinical studies involving stromal targeting.

Neural induction drives body axis formation during embryogenesis, but a neural induction-like process drives tumorigenesis in postnatal animals

Characterization of cancer cells and neural stem cells indicates that tumorigenicity and pluripotency are coupled cell properties determined by neural stemness, and tumorigenesis represents a process of progressive loss of original cell identity and gain of neural stemness. This reminds of a most fundamental process required for the development of the nervous system and body axis during embryogenesis, i.e., embryonic neural induction. Neural induction is that, in response to extracellular signals that are secreted by the Spemann-Mangold organizer in amphibians or the node in mammals and inhibit epidermal fate in ectoderm, the ectodermal cells lose their epidermal fate and assume the neural default fate and consequently, turn into neuroectodermal cells. They further differentiate into the nervous system and also some non-neural cells via interaction with adjacent tissues. Failure in neural induction leads to failure of embryogenesis, and ectopic neural induction due to ectopic organizer or node activity or activation of embryonic neural genes causes a formation of secondary body axis or a conjoined twin. During tumorigenesis, cells progressively lose their original cell identity and gain of neural stemness, and consequently, gain of tumorigenicity and pluripotency, due to various intra-/extracellular insults in cells of a postnatal animal. Tumorigenic cells can be induced to differentiation into normal cells and integrate into normal embryonic development within an embryo. However, they form tumors and cannot integrate into animal tissues/organs in a postnatal animal because of lack of embryonic inducing signals. Combination of studies of developmental and cancer biology indicates that neural induction drives embryogenesis in gastrulating embryos but a similar process drives tumorigenesis in a postnatal animal. Tumorigenicity is by nature the manifestation of aberrant occurrence of pluripotent state in a postnatal animal. Pluripotency and tumorigenicity are both but different manifestations of neural stemness in pre- and postnatal stages of animal life, respectively. Based on these findings, I discuss about some confusion in cancer research, propose to distinguish the causality and associations and discriminate causal and supporting factors involved in tumorigenesis, and suggest revisiting the focus of cancer research.

Dual Role of Fibroblasts Educated by Tumour in Cancer Behavior and Therapeutic Perspectives

Tumours are complex systems with dynamic interactions between tumour cells, non-tumour cells, and extracellular components that comprise the tumour microenvironment (TME). The majority of TME's cells are cancer-associated fibroblasts (CAFs), which are crucial in extracellular matrix (ECM) construction, tumour metabolism, immunology, adaptive chemoresistance, and tumour cell motility. CAF subtypes have been identified based on the expression of protein markers. CAFs may act as promoters or suppressors in tumour cells depending on a variety of factors, including cancer stage. Indeed, CAFs have been shown to promote tumour growth, survival and spread, and secretome changes, but they can also slow tumourigenesis at an early stage through mechanisms that are still poorly understood. Stromal-cancer interactions are governed by a variety of soluble factors that determine the outcome of the tumourigenic process. Cancer cells release factors that enhance the ability of fibroblasts to secrete multiple tumour-promoting chemokines, acting on malignant cells to promote proliferation, migration, and invasion. This crosstalk between CAFs and tumour cells has given new prominence to the stromal cells, from being considered as mere physical support to becoming key players in the tumour process. Here, we focus on the concept of cancer as a non-healing wound and the relevance of chronic inflammation to tumour initiation. In addition, we review CAFs heterogeneous origins and markers together with the potential therapeutic implications of CAFs "re-education" and/or targeting tumour progression inhibition.

Identification and characterization of FGFR2+ hematopoietic stem cell-derived fibrocytes as precursors of cancer-associated fibroblasts induced by esophageal squamous cell carcinoma

Background

Cancer-associated fibroblast (CAF) is an ideal target for cancer treatment. Recent studies have focused on eliminating CAFs and their effects by targeting their markers or blocking individual CAF-secreted factors. However, these strategies have been limited by their specificity for targeting CAFs and effectiveness in blocking widespread influence of CAFs. To optimize CAF-targeted therapeutic strategies, we tried to explore the molecular mechanisms of CAF generation in this study.

Methods

Using FGFR2 as a tracing marker, we identified a novel origin of CAFs in esophageal squamous cell carcinoma (ESCC). Furthermore, we successfully isolated CAF precursors from peripheral blood of ESCC patients and explored the mechanisms underlying their expansion, recruitment, and differentiation via RNA-sequencing and bioinformatics analysis. The mechanisms were further verified by using different models both in vitro and in vivo.

Results

We found that FGFR2⁺ hematopoietic stem cell (HSC)-derived fibrocytes could be induced by ESCC cells, recruited into tumor xenografts, and differentiated into functional CAFs. They were mobilized by cancer-secreted FGF2 and recruited into tumor sites via the CXCL12/CXCR4 axis. Moreover, they differentiated into CAFs through the activation of YAP-TEAD complex, which is triggered by directly contracting with tumor cells. FGF2 and CXCR4 neutralizing antibodies could effectively block the mobilization and recruitment process of FGFR2⁺ CAFs. The YAP-TEAD complex-based mechanism hold promise for locally activation of genetically encoded therapeutic payloads at tumor sites.

Conclusions

We identified a novel CAF origin and systematically studied the process of mobilization, recruitment, and maturation of CAFs in ESCC under the guidance of tumor cells. These findings give rise to new approaches that target CAFs before their incorporation into tumor stroma and use CAF-precursors as cellular vehicles to target tumor cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02435-w.

The Origin and Contribution of Cancer-Associated Fibroblasts in Colorectal Carcinogenesis

BACKGROUND & AIMS

Cancer-associated fibroblasts (CAFs) play an important role in colorectal cancer (CRC) progression and predict poor prognosis in CRC patients. However, the cellular origins of CAFs remain unknown, making it challenging to therapeutically target these cells. Here, we aimed to identify the origins and contribution of colorectal CAFs associated with poor prognosis.

METHODS

To elucidate CAF origins, we used a colitis-associated CRC mouse model in 5 different fate-mapping mouse lines with 5-bromodeoxyuridine dosing. RNA sequencing of fluorescence-activated cell sorting-purified CRC CAFs was performed to identify a potential therapeutic target in CAFs. To examine the prognostic significance of the stromal target, CRC patient RNA sequencing data and tissue microarray were used. CRC organoids were injected into the colons of knockout mice to assess the mechanism by which the stromal gene contributes to colorectal tumorigenesis.

RESULTS

Our lineage-tracing studies revealed that in CRC, many ACTA2⁺ CAFs emerge through proliferation from intestinal pericryptal leptin receptor (Lepr)⁺ cells. These Lepr-lineage CAFs, in turn, express melanoma cell adhesion molecule (MCAM), a CRC stroma-specific marker that we identified with the use of RNA sequencing. High MCAM expression induced by transforming growth factor β was inversely associated with patient survival in human CRC. In mice, stromal Mcam knockout attenuated orthotopically injected colorectal tumoroid growth and improved survival through decreased tumor-associated macrophage recruitment. Mechanistically, fibroblast MCAM interacted with interleukin-1 receptor 1 to augment nuclear factor κB-IL34/CCL8 signaling that promotes macrophage chemotaxis.

CONCLUSIONS

In colorectal carcinogenesis, pericryptal Lepr-lineage cells proliferate to generate MCAM⁺ CAFs that shape the tumor-promoting immune microenvironment. Preventing the expansion/differentiation of Lepr-lineage CAFs or inhibiting MCAM activity could be effective therapeutic approaches for CRC.

Contributing factors common to COVID‑19 and gastrointestinal cancer

The devastating complications of coronavirus disease 2019 (COVID-19) result from the dysfunctional immune response of an individual following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events, ultimately leading to COVID-19. The authors have previously identified a number of contributing factors (CFs) common to myriad chronic diseases. Based on these observations, it was hypothesized that there may be a significant overlap between CFs associated with COVID-19 and gastrointestinal cancer (GIC). Thus, in the present study, a streamlined dot-product approach was used initially to identify potential CFs that affect COVID-19 and GIC directly (i.e., the simultaneous occurrence of CFs and disease in the same article). The nascent character of the COVID-19 core literature (~1-year-old) did not allow sufficient time for the direct effects of numerous CFs on COVID-19 to emerge from laboratory experiments and epidemiological studies. Therefore, a literature-related discovery approach was used to augment the COVID-19 core literature-based ‘direct impact’ CFs with discovery-based ‘indirect impact’ CFs [CFs were identified in the non-COVID-19 biomedical literature that had the same biomarker impact pattern (e.g., hyperinflammation, hypercoagulation, hypoxia, etc.) as was shown in the COVID-19 literature]. Approximately 2,250 candidate direct impact CFs in common between GIC and COVID-19 were identified, albeit some being variants of the same concept. As commonality proof of concept, 75 potential CFs that appeared promising were selected, and 63 overlapping COVID-19/GIC potential/candidate CFs were validated with biological plausibility. In total, 42 of the 63 were overlapping direct impact COVID-19/GIC CFs, and the remaining 21 were candidate GIC CFs that overlapped with indirect impact COVID-19 CFs. On the whole, the present study demonstrates that COVID-19 and GIC share a number of common risk/CFs, including behaviors and toxic exposures, that impair immune function. A key component of immune system health is the removal of those factors that contribute to immune system dysfunction in the first place. This requires a paradigm shift from traditional Western medicine, which often focuses on treatment, rather than prevention.

N-cadherin mediates the migration of bone marrow-derived mesenchymal stem cells toward breast tumor cells

Rationale: Bone marrow-derived mesenchymal stem cells (BM-MSCs) recruited into breast tumors regulate the behavior of tumor cells via various mechanisms and affect clinical outcomes. Although signaling molecules, such as transforming growth factor β (TGF-β), are known to transmit signals between BM-MSCs and breast tumor cells for recruiting BM-MSCs, it is unclear which specific intrinsic molecules involved in cell motility mediate the migration of BM-MSCs into breast tumor. It is also unclear as to how specific intrinsic molecules contribute to the migration. Methods: Conditioned medium (CM) from breast tumor cells (MCF-7 and MDA-MB-231) that simulates breast tumor secreting TGF-β was used to examine the migration of BM-MSCs into breast tumors. A three-dimensional migration assay was performed to investigate the collective migration of BM-MSCs, maintaining cell-cell adhesion, toward breast tumor cells. Results: N-cadherin formed adherens junction-like structures on the intercellular borders of BM-MSCs, and TGF-β increased the expression of N-cadherin on these borders. Knockdown of Smad4 impaired the TGF-β-mediated increase in N-cadherin expression in BM-MSCs, but inhibitors of non-canonical TGF-β pathways, such as extracellular signal-regulated kinases, Akt, and p38, did not affect it. siRNA-mediated knockdown of N-cadherin and Smad4 impaired the migration of BM-MSCs in response to TGF-β. Conditioned medium from breast tumor cells also enhanced the expression of N-cadherin in BM-MSCs, but inactivation of TGF-β type 1 receptor (TGFBR1) with SB505124 and TGFBR1 knockdown abolished the increase in N-cadherin expression. BM-MSCs collectively migrated toward CM from MDA-MB-231 in vitro while maintaining cell-cell adhesion through N-cadherin. Knockdown of N-cadherin abolished the migration of BM-MSCs toward the CM from breast tumor cells. Conclusion: In the present study, we identified N-cadherin, an intrinsic transmembrane molecule in adherens junction-like structures, on BM-MSCs as a mediator for the migration of these cells toward breast tumor. The expression of N-cadherin increases on the intercellular borders of BM-MSCs through the TGF-β canonical signaling and they collectively migrate in response to breast tumor cells expressing TGF-β via N-cadherin-dependent cell-cell adhesion. We, herein, introduce a novel promising strategy for controlling and re-engineering the breast tumor microenvironment.

Embryonic protein NODAL regulates the breast tumor microenvironment by reprogramming cancer-derived secretomes

The tumor microenvironment (TME) is an important mediator of breast cancer progression. Cancer-associated fibroblasts constitute a major component of the TME and may originate from tissue-associated fibroblasts or infiltrating mesenchymal stromal cells (MSCs). The mechanisms by which cancer cells activate fibroblasts and recruit MSCs to the TME are largely unknown, but likely include deposition of a pro-tumorigenic secretome. The secreted embryonic protein NODAL is clinically associated with breast cancer stage and promotes tumor growth, metastasis, and vascularization. Herein, we show that NODAL expression correlates with the presence of activated fibroblasts in human triple-negative breast cancers and that it directly induces Cancer-associated fibroblasts phenotypes. We further show that NODAL reprograms cancer cell secretomes by simultaneously altering levels of chemokines (e.g., CXCL1), cytokines (e.g., IL-6) and growth factors (e.g., PDGFRA), leading to alterations in MSC chemotaxis. We therefore demonstrate a hitherto unappreciated mechanism underlying the dynamic regulation of the TME.

Role of Cancer-Associated Fibroblast in Gastric Cancer Progression and Resistance to Treatments

Although the survival of gastric cancer (GC) patients has gradually improved, the outcomes of advanced GC patients remain unsatisfactory despite standard treatment with conventional chemotherapy or targeted agents. Several studies have shown that cancer-associated fibroblasts (CAFs), a major component of tumor stroma in GC, may have significant roles in GC progression and resistance to treatments. CAFs are a major source of various secreted molecules in the tumor microenvironment, which stimulate cancer cells and other noncancerous components of GC. Surprisingly, these factors could be involved in gastric carcinogenesis. Cytokines, including interleukin-6 and interleukin-11, or growth factors, such as fibroblast growth factor produced from CAFs, can directly activate GC cells and consequently lead to the development of an aggressive phenotype. Galectin-1 or hepatocyte growth factor can be involved in CAF-derived neovascularization in GC. In addition, recent studies showed that CAFs can affect tumor immunity through M2 polarization of tumor-associated macrophages. Finally, the current study aimed to introduce several inhibitory agents and evaluate their suppressive effects on CAFs in patients with GC progression. However, further studies are required to evaluate their safety and select appropriate patients for application in clinical settings.

Cancer-associated fibroblasts in gastrointestinal cancer

The tumour microenvironment, also termed the tumour stroma or tumour mesenchyme, includes fibroblasts, immune cells, blood vessels and the extracellular matrix and substantially influences the initiation, growth and dissemination of gastrointestinal cancer. Cancer-associated fibroblasts (CAFs) are one of the critical components of the tumour mesenchyme and not only provide physical support for epithelial cells but also are key functional regulators in cancer, promoting and retarding tumorigenesis in a context-dependent manner. In this Review, we outline the emerging understanding of gastrointestinal CAFs with a particular emphasis on their origin and heterogeneity, as well as their function in cancer cell proliferation, tumour immunity, angiogenesis, extracellular matrix remodelling and drug resistance. Moreover, we discuss the clinical implications of CAFs as biomarkers and potential targets for prevention and treatment of patients with gastrointestinal cancer.

Bone marrow-derived mesenchymal stem cells promote colorectal cancer progression via CCR5

Mesenchymal stem cells (MSCs) are recruited from BM to the stroma of developing tumors, where they serve as critical components of the tumor microenvironment by secreting growth factors, cytokines, and chemokines. The role of MSCs in colorectal cancer (CRC) progression was controversial. In this study, we found that C-C chemokine receptor type 5 (CCR5) ligands (i.e., C-C motif chemokine ligand 3 (CCL3), CCL4, and CCL5) were highly produced from MSCs using a chemokine array screening with conditioned media from the cultured human MSCs. A relatively strong CCR5 expression could be detected within the cytoplasm of several CRC cell lines. Regarding the effect of MSC, we found that the xenografts in which CCR5-overexpressing HCT116 cells were inoculated into immunocompromised mice were highly promoted in vivo by a mixture with MSCs. Notably, the CCR5 inhibitor, maraviroc, significantly abolished the MSC-induced tumor growth in vivo. In human clinical specimens (n = 89), 20 cases (29%) were high for CCR5, whereas 69 cases (71%) were low. Statistical analyses indicated that CCR5 expression in primary CRC was associated with CRC patients’ prognosis. Especially, stage III/IV patients with CCR5-high CRCs exhibited a significantly poorer prognosis than those with CCR5-low CRCs. Furthermore, we investigated the effects of preoperative serum CCR5 ligands on patients’ prognosis (n = 114), and found that CRC patients with high serum levels of CCL3 and CCL4 exhibited a poorer prognosis compared to those with low levels of CCL3 and CCL4, while there was no association between CCL5 and prognosis. These results suggest that the inhibition of MSC–CRC interaction by a CCR5 inhibitor could provide the possibility of a novel therapeutic strategy for CRC, and that serum levels of CCL3 and CCL4 could be predictive biomarkers for the prognosis of CRC patients.

Mesenchymal Stem Cells: Miraculous Healers or Dormant Killers?

Mesenchymal Stem Cells (MSCs) are a heterogeneous population of fibroblast-like cells which maintain self-renewability and pluripotency to differentiate into mesodermal cell lineages. The use of MSCs in clinical settings began with high enthusiasm and the number of MSC-based clinical trials has been rising ever since. However; the very unique characteristics of MSCs that made them suitable to for therapeutic use, might give rise to unwanted outcomes, including tumor formation and progression. In this paper, we present a model of carcinogenesis initiated by MSCs, which chains together the tissue organization field theory, the stem cell theory, and the inflammation-cancer chain. We believe that some tissue resident stem cells could be leaked cells from bone marrow MSC pool to various injured tissue, which consequently transform and integrate in the host tissue. If the injury persists or chronic inflammation develops, as a consequence of recurring exposure to growth factors, cytokines, etc. the newly formed tissue from MSCs, which still has conserved their mesenchymal and stemness features, go through rapid population expansion, and nullify their tumor suppressor genes, and hence give rise to neoplastic cell (carcinomas, sarcomas, and carcino-sarcomas). Considering the probability of this hypothesis being true, the clinical and therapeutic use of MSCs should be with caution, and the recipients' long term follow-up seems to be insightful.

Bone marrow-derived epithelial cells and hair follicle stem cells contribute to development of chronic cutaneous neoplasms

We used allogeneic bone marrow transplantation (BMT) and a mouse multistage cutaneous carcinogenesis model to probe recruitment of bone marrow-derived epithelial cells (BMDECs) in skin tumors initiated with the carcinogen, dimethylbenz[a]anthracene (DMBA), and promoted with 12-O-tetradecanolyphorbol-13-acetate (TPA). BMDECs clustered in the lesional epithelium, expressed cytokeratins, proliferated, and stratified. We detected cytokeratin induction in plastic-adherent bone marrow cells (BMCs) cultured in the presence of filter-separated keratinocytes (KCs) and bone morphogenetic protein 5 (BMP5). Lineage-depleted BMCs migrated towards High Mobility Group Box 1 (HMGB1) protein and epidermal KCs in ex vivo invasion assays. Naive female mice receiving BMTs from DMBA-treated donors developed benign and malignant lesions after TPA promotion alone. We conclude that BMDECs contribute to the development of papillomas and dysplasia, demonstrating a systemic contribution to these lesions. Furthermore, carcinogen-exposed BMCs can initiate benign and malignant lesions upon tumor promotion. Ultimately, these findings may suggest targets for treatment of non-melanoma skin cancers.

Origin of cancer-associated fibroblasts and tumor-associated macrophages in humans after sex-mismatched bone marrow transplantation

Cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) in tumor stroma play a key role in disease progression. Recent studies using mice models suggest that CAFs are partly derived from bone marrow and TAMs primarily originate from bone marrow-derived inflammatory monocytes. However, the origin of these cells in humans remains unclear. Hence, we investigated their human origin, using specimens from human secondary tumors that developed after sex-mismatched bone marrow transplantation, by modified immunofluorescent in situ hybridization analysis and triple immunostaining. We observed that most of the α-smooth muscle actin (αSMA)-positive CAFs in the mammary gland, liver, and oral mucosa specimens obtained 3-19 years after bone marrow transplantation are recipient-derived cells. In contrast, the majority of the peritumoral αSMA-negative fibroblast-like cells are actually bone marrow-derived HLA-DR-positive myeloid cells, such as macrophages and dendritic cells. Furthermore, almost all CD163-positive TAMs and macrophages present in the non-tumor areas are derived from bone marrow.

Microenvironmental Signals and Biochemical Information Processing: Cooperative Determinants of Intratumoral Plasticity and Heterogeneity

Intra-tumor cellular heterogeneity is a major challenge in cancer therapy. Tumors are composed of multiple phenotypic subpopulations that vary in their ability to initiate metastatic tumors and in their sensitivity to chemotherapy. In many cases, cells can transition between these subpopulations, not by genetic mutation, but instead through reversible changes in signal transduction or gene expression programs. This plasticity begins at the level of the microenvironment where local autocrine and paracrine signals, exosomes, tumor–stroma interactions, and extracellular matrix (ECM) composition create a signaling landscape that varies over space and time. The integration of this complex array of signals engages signaling pathways that control gene expression. The resulting modulation of gene expression programs causes individual cells to sample a wide array of phenotypic states that support tumor growth, dissemination, and therapeutic resistance. In this review, we discuss how information flows dynamically within the microenvironmental landscape to inform cell state decisions and to create intra-tumoral heterogeneity. We address the role of plasticity in the acquisition of transient and prolonged drug resistant states and discuss how targeted pharmacological modification of the signaling landscape may be able to constrain phenotypic plasticity, leading to improved treatment responses.

Drug targeting to myofibroblasts: Implications for fibrosis and cancer

Myofibroblasts are the key players in extracellular matrix remodeling, a core phenomenon in numerous devastating fibrotic diseases. Not only in organ fibrosis, but also the pivotal role of myofibroblasts in tumor progression, invasion and metastasis has recently been highlighted. Myofibroblast targeting has gained tremendous attention in order to inhibit the progression of incurable fibrotic diseases, or to limit the myofibroblast-induced tumor progression and metastasis. In this review, we outline the origin of myofibroblasts, their general characteristics and functions during fibrosis progression in three major organs: liver, kidneys and lungs as well as in cancer. We will then discuss the state-of-the art drug targeting technologies to myofibroblasts in context of the above-mentioned organs and tumor microenvironment. The overall objective of this review is therefore to advance our understanding in drug targeting to myofibroblasts, and concurrently identify opportunities and challenges for designing new strategies to develop novel diagnostics and therapeutics against fibrosis and cancer.

Tumor-educated mesenchymal stem cells promote pro-metastatic phenotype

Multipotent mesenchymal stem cells (MSCs) are recruited into tumor microenvironment in response to multiple signals produced by cancer cells. Molecules involved in their homing to tumors are the same inflammatory mediators produced by injured tissues: chemokines, cytokines and growth factors. When MSCs arrive into the tumor microenvironment these are “educated” to have pro-metastatic behaviour. Firstly, they promote cancer immunosuppression modulating both innate and adaptive immune systems. Moreover, tumor associated-MSCs trans-differentiating into cancer-associated fibroblasts can induce epithelial-mesenchymal-transition program in tumor cells. This process determinates a more aggressive phenotype of cancer cells by increasing their motility and invasiveness and favoring their dissemination to distant sites. In addition, MSCs are involved in the formation and modelling of pre-metastatic niches creating a supportive environment for colonization of circulating tumor cells.

The development of novel therapeutic approaches targeting the different functions of MSCs in promoting tumor progression as well as the mechanisms underlying their activities could enhance the efficacy of conventional and immune anti-cancer therapies.

Furthermore, many studies report the use of MSCs engineered to express different genes or as vehicle to specifically deliver novel drugs to tumors exploiting their strong tropism. Importantly, this approach can enhance local therapeutic efficacy and reduce the risk of systemic side effects.

A unified model of the hierarchical and stochastic theories of gastric cancer

Gastric cancer (GC) is a life-threatening disease worldwide. Despite remarkable advances in treatments for GC, it is still fatal to many patients due to cancer progression, recurrence and metastasis. Regarding the development of novel therapeutic techniques, many studies have focused on the biological mechanisms that initiate tumours and cause treatment resistance. Tumours have traditionally been considered to result from somatic mutations, either via clonal evolution or through a stochastic model. However, emerging evidence has characterised tumours using a hierarchical organisational structure, with cancer stem cells (CSCs) at the apex. Both stochastic and hierarchical models are reasonable systems that have been hypothesised to describe tumour heterogeneity. Although each model alone inadequately explains tumour diversity, the two models can be integrated to provide a more comprehensive explanation. In this review, we discuss existing evidence supporting a unified model of gastric CSCs, including the regulatory mechanisms of this unified model in addition to the current status of stemness-related targeted therapy in GC patients.

Mesenchymal Cells in Colon Cancer

Mesenchymal cells in the intestine comprise a variety of cell types of diverse origins, functions, and molecular markers. They provide mechanical and structural support and have important functions during intestinal organogenesis, morphogenesis, and homeostasis. Recent studies of the human transcriptome have revealed their importance in the development of colorectal cancer, and studies from animal models have provided evidence for their roles in the pathogenesis of colitis-associated cancer and sporadic colorectal cancer. Mesenchymal cells in tumors, called cancer-associated fibroblasts, arise via activation of resident mesenchymal cell populations and the recruitment of bone marrow-derived mesenchymal stem cells and fibrocytes. Cancer-associated fibroblasts have a variety of activities that promote colon tumor development and progression; these include regulation of intestinal inflammation, epithelial proliferation, stem cell maintenance, angiogenesis, extracellular matrix remodeling, and metastasis. We review the intestinal mesenchymal cell-specific pathways that regulate these processes, with a focus on their roles in mediating interactions between inflammation and carcinogenesis. We also discuss how increasing our understanding of intestinal mesenchymal cell biology and function could lead to new strategies to identify and treat colitis-associated cancers.

Paradigm Shift from Stem Cells to Cell-Free Regenerative Endodontic Procedures: A Critical Review

Regenerative endodontic procedures of immature teeth with necrotic pulp have become a part of therapeutic endodontic spectrum and are considered as an alternative to calcium hydroxide or mineral trioxide aggregate apexification. In last decade, numerous case reports and series with usage of cell-free approaches known as revascularization, revitalization, or maturogenesis have been published. This cell-free approach prevails in clinical regenerative endodontics because of its relative ease of performance, lower financial demands, and absence of complications such as tumorigenesis of used stem cells. In this article, the integral steps of cell-free treatment approaches such as source of stem cells, possible endogenous scaffolds, sources of growth factors, and width of apical foramen in the context of sufficient disinfection of root canal system and outcome of treatment are discussed. Despite not being a fully established treatment protocol, the achieved outcomes are promising regardless of it having a reparative character than a regenerative one.

Tumour-associated mesenchymal stem/stromal cells: emerging therapeutic targets

Mesenchymal stem cells, also known as mesenchymal stromal cells (MSCs), exist in many tissues and are known to actively migrate to sites of tissue injury, where they participate in wound repair. Tumours can be considered "wounds that never heal" and, in response to cues from a tumour, MSCs are continuously recruited to and become integral components of the tumour microenvironment. Recently, it has become apparent that such tumour-associated MSCs (TA-MSCs) have an active role in tumour initiation, promotion, progression and metastasis. In this Review, we discuss recent advances in our understanding of the pathogenic role of TA-MSCs in regulating the survival, proliferation, migration and drug resistance of tumour cells, as well as the influence of MSCs on the immune status of the tumour microenvironment. Moreover, we discuss therapeutic approaches that target TA-MSC upstream or downstream modulators or use MSCs as vehicles for the delivery of tumoricidal agents. It is anticipated that new insights into the functions of TA-MSCs will lead to the development of novel therapeutic strategies against tumours.

Differentiation and transdifferentiation potentials of cancer stem cells

Tumor cells actively contribute to constructing their own microenvironment during tumorigenesis and tumor progression. The tumor microenvironment contains multiple types of stromal cells that work together with the extracellular matrix and local and systemic factors to coordinately contribute to tumor initiation and progression. Tumor cells and their stromal compartments acquire many genetic and/or epigenetic alternations to facilitate tumor growth and metastasis. The cancer stem cell (CSC) concept has been widely applied to interpreting tumor initiation, growth, metastasis, dormancy and relapse. CSCs have differentiation abilities to generate the original lineage cells that are similar to their normal stem cell counterparts. Interestingly, recent evidence demonstrates that CSCs also have the potential to transdifferentiate into vascular endothelial cells and pericytes, indicating that CSCs can transdifferentiate into other lineage cells for promoting tumor growth and metastasis in some tissue contexts instead of only recruiting stromal cells from local or distant tissues. Although the transdifferentiation of CSCs into tumor stromal cells provides a new dimension that explains tumor heterogeneity, many aspects of CSC transdifferentiation remain elusive. In this review, we summarize the multi-lineage differentiation and transdifferentiation potentials of CSCs as well as discuss their potential contributions to tumor heterogeneity and tumor microenvironment in tumor progression.

Concise Review: Pancreatic Cancer and Bone Marrow-Derived Stem Cells

Pancreatic adenocarcinoma remains one of the most challenging diseases of modern gastroenterology, and, even though considerable effort has been put into understanding its pathogenesis, the exact molecular mechanisms underlying the development and/or systemic progression of this malignancy still remain unclear. Recently, much attention has been paid to the potential role of bone marrow-derived stem cells (BMSCs) in this malignancy. Hence, herein, we comprehensively review the most recent discoveries and current achievements and concepts in this field. Specifically, we discuss the significance of identifying pancreatic cancer stem cells and novel therapeutic approaches involving molecular interference of their metabolism. We also describe advances in the current understanding of the biochemical and molecular mechanisms responsible for BMSC mobilization during pancreatic cancer development and systemic spread. Finally, we summarize experimental, translational, and/or clinical evidence regarding the contribution of bone marrow-derived mesenchymal stem cells, endothelial progenitor cells, hematopoietic stem/progenitor cells, and pancreatic stellate cells in pancreatic cancer development/progression. We also present their potential therapeutic value for the treatment of this deadly malignancy in humans.

SIGNIFICANCE

Different bone marrow-derived stem cell populations contribute to the development and/or progression of pancreatic cancer, and they might also be a promising "weapon" that can be used for anticancer treatments in humans. Even though the exact role of these stem cells in pancreatic cancer development and/or progression in humans still remains unclear, this concept continues to drive a completely novel scientific avenue in pancreatic cancer research and gives rise to innovative ideas regarding novel therapeutic modalities that can be safely offered to patients.

Rapid selection of mesenchymal stem and progenitor cells in primary prostate stromal cultures

BACKGROUND

Carcinoma-associated fibroblasts (CAFs) are a dominant component of the tumor microenvironment with pro-tumorigenic properties. Despite this knowledge, their physiologic origins remain poorly understood. Mesenchymal stem cells (MSCs) can be recruited from the bone marrow to areas of tissue damage and inflammation, including prostate cancer. MSCs can generate and have many overlapping properties with CAFs in preclinical models.

METHODS

Multiparameter flow cytometry and multipotent differentiation assays used to define MSCs in primary prostate stromal cultures derived from young (<25 yrs) organ donors and prostate cancer patients compared with bone marrow-derived stromal cultures. Population doubling times, population doublings, cell size, and differentiation potential determined under multiple culture conditions, including normoxia, hypoxia, and a variety of media. TGF-β measured by ELISA.

RESULTS

MSCs and stromal progenitors are not only present in normal and malignant prostate tissue, but are quickly selected for in primary stromal cultures derived from these tissues; becoming the dominant population within just a few passages. Growth potential inversely associated with TGF-β concentrations. All conditions generated populations with an average cell diameter >15 µm. All cultures tested had the ability to undergo osteogenic and chondrogenic differentiation, but unlike bone marrow-derived MSCs, primary stromal cultures derived from normal prostate tissue lack adipogenic differentiation potential. In contrast, a subset of stromal cultures derived from prostate cancer patients retain the ability to differentiate into adipocytes; a property that is significantly suppressed under hypoxic conditions in both bone marrow- and prostate-derived MSCs.

CONCLUSIONS

Primary prostate stromal cultures are highly enriched in cells with an MSC or stromal progenitor phenotype. The use of primary cultures such as these to study CAFs raises interesting implications when considering their overlapping properties. The lack of adipogenesis in stromal cultures derived from normal prostates suggests they have a lineage-restricted progenitor phenotype. The retention of adipogenic differentiation in cultures from a subset of prostate cancer patients suggests the active recruitment of less committed progenitors or MSCs from the bone marrow as a function of disease progression. This recruitment can potentially be exploited for prognostic purposes or a cell-based platform for the systemic delivery of cytotoxic agents to sites of prostate cancer.

Mesenchymal stem cells promote epithelial to mesenchymal transition and metastasis in gastric cancer though paracrine cues and close physical contact

Mesenchymal stem cells (MSCs) have been shown to integrate into the tumor stroma; however, the precise mechanisms of this process are still elusive. In this study, the EMT phenotype and the enhanced metastatic ability of tumor cells were observed using transwell and trans-endothelial migration assays, respectively, as well as by using electron and laser confocal microscopy. Critical genes were screened and validated using gene arrays and clinical samples, and the changes at the protein level were examined both in vitro and in vivo. Cancer cells acquired an "activated" carcinoma-associated fibroblasts (CAFs) phenotype after being in close contact with MSCs and enhancing tumor metastasis and growth in vivo. Paracrine signals also induced EMT and promoted transwell and trans-endothelial migration, the changes were dependent on β-catenin, MMP-16, snail and twist. Notably, the higher expression levels of β-catenin and MMP-16 were correlated with tumor invasion and distant organ and lymph node metastases in intestinal type gastric cancer. MSCs within the tumor niche significantly facilitated tumor growth and metastasis by paracrine cues and close physical connection. This occurred partly through snail, twist and its downstream targets, specifically β-catenin/MMP-16.

Peripheral trafficking of bone-marrow-derived stem cells in patients with different types of gastric neoplasms

Recently, there has been a growing interest in the importance of stem cells (SCs) in the development/progression of gastric neoplasms. In this study, we performed a comprehensive analysis of different populations of bone-marrow-derived stem cells (BMSCs) in patients with various types of gastric malignancies, including gastric cancer, gastrointestinal stromal tumors (GISTs), neuroendocrine neoplasms (NENs), and lymphomas. We found significantly lower numbers of circulating Lin-/CD45 +/ CD133 + hematopoietic stem/progenitor cells (HSPCs), and intensified peripheral trafficking of both Lin-/CD45-/CXCR4+/CD34+/CD133+ very small embryonic/epiblast-like stem cells (VSELs) and CD105 + /STRO-1 +/ CD45- mesenchymal SCs (MSCs) in patients with gastric cancer, but not in those with other types of gastric neoplasms. No significant differences in the absolute numbers of circulating CD34 +/ KDR +/ CD31 +/ CD45- endothelial progenitor cells (EPCs) were observed between the groups. This abnormal balance in the peripheral trafficking of BMSCs in patients with gastric cancer was neither associated with clinical stage of the disease nor with systemic levels of stromal-derived factor-1 (SDF-1), as these were comparable to the values observed in control individuals. Interestingly, the absolute numbers of circulating BMSCs correlated with the concentrations of complement cascade-derived anaphylatoxins/molecules (mainly C5b-9/membrane attack complex-MAC) and sphingosine-1-phosphate (S1P). In summary, our translational study revealed that abnormal peripheral trafficking of BMSCs occurs in patients with gastric cancer, but not in those with other types of gastric neoplasms. Further, our findings indicate that highlighted complement cascade-derived molecules and S1P, but not SDF-1, are significant players associated with this phenomenon.

Expression of cancer-associated fibroblast-related proteins in adipose stroma of breast cancer

Cancer-associated fibroblasts (CAFs) play key roles in tumor microenvironment; they are thought to originate from adipocytes. This study aimed to evaluate CAF-related protein expression and its implications in breast cancer. Of the 939 enrolled breast cancer patients, 642 had fibrous and 297 had adipose stroma. The status of estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER-2), Ki-67, podoplanin, prolyl 4-hydroxylase, fibroblast activation protein α (FAPα), S100A4, platelet-derived growth factor receptor α (PDGFRα), PDGFRβ, and chondroitin sulfate proteoglycan (NG2) was evaluated via tissue microarrays. Tumors were divided into luminal A, luminal B, HER-2, or triple-negative breast cancer subtypes according to their molecular status. Luminal A subtype was more prevalent in breast cancer of adipose stroma type, whereas other molecular subtypes were more common in fibrous stroma type (p < 0.001). Tumor cell expression of podoplanin and FAPα was higher in adipose stroma type, while higher expression of prolyl 4-hydroxylase and PDGFRα was observed in fibrous stroma type. Furthermore, adipose stroma type exhibited higher stromal expression of podoplanin, FAPα, PDGFRβ, and NG2, whereas fibrous stroma type had higher prolyl 4-hydroxylase and S100A4 expression. In adipose stroma type, tumor positivity (p = 0.034) and stromal positivity (p = 0.005) of prolyl 4-hydroxylase were associated with shorter disease-free survival, and stromal prolyl 4-hydroxylase positivity was with shorter overall survival (p < 0.001). In conclusion, expression of CAF-related proteins was observed in breast cancer, with different profiles between adipose and fibrous stroma types. Prolyl 4-hydrolase status might be of prognostic value in adipose stroma type.

[Advancement of phenotype transformation of cancer-associated fibroblasts: from genetic alterations to epigenetic modification]

In the field of human cancer research, even though the vast majority attentions were paid to tumor cells as "the seeds", the roles of tumor microenvironments as "the soil" are gradually explored in recent years. As a dominant compartment of tumor microenvironments, cancer-associated fibroblasts (CAFs) were discovered to correlated with tumorigenesis, tumor progression and prognosis. And the exploration of the mechanisms of CAF phenotype transformation would conducive to the further understand of the CAFs function in human cancers. As we known that CAFs have four main origins, including epithelial cells, endothelial cells, mesenchymal stem cells (MSCs) and local mesenchymal cells. However, researchers found that all these origins finally conduct similiar phenotypes from intrinsic to extrinsic ones. Thus, what and how a mechanism can conduct the phenotype transformation of CAFs with different origins? Two viewpoints are proposed to try to answer the quetsion, involving genetic alterations and epigenetic modifications. This review will systematically summarize the advancement of mechanisms of CAF phenotype transformations in the aspect of genentic and epigenetic modifications.

Evidence of cell fusion in carcinogen-induced mice gastric carcinoma. Tumour Biol. 2015;36:5089-5094. [PMID: 25656611 DOI: 10.1007/s13277-015-3160-5]

The role of bone marrow-derived cells in gastric cancer formation was not fully understood. In this study, bone marrow from female green fluorescent protein transgenic mice was transplanted into male wild-type mice to generate sex-mismatched chimeric mice. The chimeric mice were treated with carcinogen to induce gastric cancer. At time of sacrifice, 18.2 % (2/11) of mice showed severe dysplasia and 25 % (3/12) of mice successfully induced with cancer. Fluorescence in situ hybridization results showed that bone marrow-derived cells participated in renewal of gastric mucosa and cell fusion was observed in both precancerous lesions and adenocarcinoma, but no sign of fusion was observed in squamous cell carcinoma. Our findings suggest that bone marrow-derived cells participate in renewal of gastric mucosa during chronic damage and might have acquired the phenotype of gastric epithelial cells through cell fusion. Fusion between gastric epithelial cells and bone marrow-derived cells was involved in increased carcinogenesis.

Interaction between gastric cancer stem cells and the tumor microenvironment

Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are selectively capable of tumor initiation and are implicated in tumor relapse and metastasis, thus, governing the prognosis of GC patients. Stromal cells and extracellular matrix adjacent to cancer cells are known to form a supportive environment for cancer progression. CSC properties are also regulated by their microenvironment through cell signaling and related factors. This review presents the current findings regarding the influence of the tumor microenvironment on GC stem cells, which will support the development of novel therapeutic strategies for patients with GC.

Role of the tumor microenvironment in the pathogenesis of gastric carcinoma

Gastric carcinoma (GC) is the 4^th most prevalent cancer and has the 2^nd highest cancer-related mortality rate worldwide. Despite the incidence of GC has decreased over the past few decades, it is still a serious health problem. Chronic inflammatory status of the stomach, caused by the infection of Helicobacter pylori (H. pylori) and through the production of inflammatory mediators within the parenchyma is suspected to play an important role in the initiation and progression of GC. In this review, the correlation between chronic inflammation and H. pylori infection as an important factor for the development of GC will be discussed. Major components, including tumor-associated macrophages, lymphocytes, cancer-associated fibroblasts, angiogenic factors, cytokines, and chemokines of GC microenvironment and their mechanism of action on signaling pathways will also be discussed. Increasing our understanding of how the components of the tumor microenviroment interact with GC cells and the signaling pathways involved could help identify new therapeutic and chemopreventive targets.

To grab the stroma by the horns: from biology to cancer therapy with mesenchymal stem cells

Mesenchymal stem or stromal cells (MSCs) are precursor cells that play important roles in tumorigenesis. MSCs are recruited to tumors from local and distant sources to form part of the tumor microenvironment. MSCs influence tumor progression by interacting with cancer cells, endothelial cells, immune cells, and cancer stem cells, in a context-dependent network. This review aims to synthesize this emerging yet controversial field to identify key questions regarding the mechanisms of MSC mobilization and survival in blood; homing to tumors, metastases, and premetastatic sites; spatiotemporal organization and differentiation; and interaction with immune cells and cancer stem cells. Understanding the fundamental biology underlying mesenchymal stem cell and tumor interactions has the potential to inform our knowledge of cancer initiation and progression as well as lead to novel therapeutics for cancer. Furthermore, knowledge of endogenous mechanisms can be used to “program” exogenous MSCs for targeted chemotherapeutic delivery to tumors and metastases. Emerging studies will provide crucial insight into the mechanisms of tumor interactions with the whole organism including MSCs.

Is carcinoma a mesenchymal disease? The role of the stromal microenvironment in carcinogenesis

Most research into the biology of carcinoma has focused on the epithelial cells therein; the inherent assumption has been that the tumour arises from epithelial cells 'gone bad', and that the surrounding stroma is simply an 'innocent bystander'. However, there is increasing evidence that there is a complex interplay between tumour cells and their surrounding microenvironment, and that the latter may be just as important in determining the development and clinical behaviour of a given tumour. Similarly, traditional oncological practice has been predominantly aimed at a perceived ideal goal of killing all the tumour epithelial cells, with only a few recently developed therapies seeking to affect other components (such as tumour vasculature); but identifying stromal factors involved in tumour growth and survival may well lead to the development of novel therapies. This review examines current understanding of the interplay between tumour epithelial cells and their microenvironment, and enumerates various stromal factors which appear to play a role in tumour progression and/or metastasis.

Bone marrow-derived myofibroblasts promote colon tumorigenesis through the IL-6/JAK2/STAT3 pathway

Bone marrow-derived myofibroblasts (BMFs) have been shown to promote tumor growth. Here, we found that BMFs or BMF conditioned medium (BMF-CM) induced cancer stem cell-like sphere formation of colon cancer cells. The co-cultured BMFs, but not co-cultured cancer cells, expressed higher levels of IL-6 than BMFs or cancer cells cultured alone. Anti-mouse IL-6 neutralizing antibody, JAK2 inhibitors and STAT3 knockdown in mouse cancer cells reduced BMF- and BMF-CM-induced sphere formation of colon cancer cells. When co-injected, BMFs significantly enhanced tumorigenesis of colon cancer cells in mice. Our results demonstrate that BMFs promote tumorigenesis via the activation of the IL-6/JAK2/STAT3 pathway.

Bone marrow-derived mesenchymal stem cells favor the immunosuppressive T cells skewing in a Helicobacter pylori model of gastric cancer

Bone marrow-derived mesenchymal stem cells (BM-MSCs) play an important role in Helicobacter pylori-induced gastric carcinogenesis. While the mechanism is not well understood, BM-MSCs have been shown to contribute to the immunosuppressive response found in a number of diseases. Here, BM-MSCs were transplanted into the stomach of mice with a 44-week mouse-adapted H. pylori infection. At day 28 post-transplantation, BM-MSCs migrated from the subserosal to the mucosal layer of the stomach. The grafted BM-MSCs significantly stimulated systemic and local interleukin-10 (IL-10)-secreting T cell and regulatory T cell (Treg) functions. This observation was correlated with an increased percentage of CD4⁺IL-10⁺ cells and CD4⁺CD25⁺FoxP3⁺ cells in splenic mononuclear cells compared with H. pylori-infected mice not receiving BM-MSCs. Moreover, inhibitory cytokines IL-10 and transforming growth factor-β1 increased in the gastric tissue, while there was a decrease in inflammatory interferon-γ (IFN-γ). BM-MSC-transplanted mice also developed elevated IL-10/IFN-γ secreting and Treg/Th17 ratios. A coculture system in the presence or absence of BM-MSCs was also established to evaluate the immune responses in vitro. An increase in IL-10-secreting T cells and Tregs, associated with increased expression of Gata-3 and FoxP3, generation of IL-10 in the supernatant, and proliferation of gastric epithelial cells (GECs) was observed. These findings demonstrate that transplantation of BM-MSCs into a chronic H. pylori-infected mouse model results in the generation of an immunosuppressive environment. The local and systemic immunosuppression mediated by BM-MSCs likely contributed to an environment that is compatible with the development of H. pylori-induced gastric cancer.

Cancer stem cells: the 'heartbeat' of gastric cancer

Gastric cancer (GC) remains one of the most common cancers worldwide. Its prevalence is still on the rise in the developing countries due to the ageing population. The cancer stem cell (CSC) theory provides a new insight into the interpretation of tumor initiation, aggressive growth, recurrence, and metastasis of cancer, as well as the development of new strategies for cancer treatment. This review will focus on the progress of biomarkers and signaling pathways of CSCs, the complex crosstalk networks between the microenvironment and CSCs, and the development of therapeutic approaches against CSCs, predominantly focusing on GC.

Dentin and dental pulp regeneration by the patient's endogenous cells

The goal of regenerative endodontics is to restore the functions of the dental pulp-dentin complex. Two approaches are being applied toward dental pulp-dentin regeneration: cell transplantation and cell homing. The majority of previous approaches are based on cell transplantation by delivering ex vivo cultivated cells toward dental pulp or dentin regeneration. Many hurdles limit the clinical translation of cell transplantation such as the difficulty of acquiring and isolating viable cells, uncertainty of what cells or what fractions of cells to use, excessive cost of cell manipulation and transportation, and the risk of immune rejection, pathogen transmission, and tumorigenesis in associated with ex vivo cell manipulation. In contrast, cell homing relies on induced chemotaxis of endogenous cells and therefore circumvents many of the difficulties that are associated with cell transplantation. An array of proteins, peptides, and chemical compounds that are yet to be identified may orchestrate endogenous cells to regenerate dental pulp-dentin complex. Both cell transplantation and cell homing are scientifically valid approaches; however, cell homing offers a number of advantages that are compatible with the development of clinical therapies for dental pulp-dentin regeneration.

'Cancer associated fibroblasts'--more than meets the eye

Cancer associated fibroblasts (CAFs) are a subpopulation of cells that reside within the tumor microenvironment and promotes the transformation process by encouraging tumor growth, angiogenesis, inflammation, and metastasis. CAF-specific proteins serve as both prognostic markers and targets for anticancer drugs. With the growing interest in CAFs, several controversial issues have been raised, including the genomic landscape of these cells, the identity of specific markers, and their cell of origin. Here, we tackle these debated issues and put forward a new definition for 'CAF' as a cell 'state' rather than a cell type. We hope this conceptualization can resolve the ongoing discrepancies revolving around CAF research and aid in designing better anti-cancer treatment strategies.