Mesenchymal stem cells regulate epithelial-mesenchymal transition and tumor progression of pancreatic cancer cells

Decoding secret role of mesenchymal stem cells in regulating cancer stem cells and drug resistance

Drug resistance caused by the efflux of chemotherapeutic drugs is one of the most challenging obstacles to successful cancer therapy. Several efflux transporters have been identified since the discovery of the P-gp/ABCB1 transporter in 1976. Over the last four decades, researchers have focused on developing efflux transporter inhibitors to overcome drug resistance. However, even with the third-generation inhibitors available, we are still far from effectively inhibiting the efflux transporters. Additionally, Cancer stem cells (CSCs) pose another significant challenge, contributing to cancer recurrence even after successful treatment. The ability of CSCs to enter dormancy and evade detection makes them almost invulnerable to chemotherapeutic drug treatment. In this review, we discuss how Mesenchymal stem cells (MSCs), one of the key components of the Tumor Microenvironment (TME), regulate both the CSCs and efflux transporters. We propose a new approach focusing on MSCs, which can be crucial to successfully address CSCs and efflux transporters.

Mesenchymal stromal cells as cancer promoters

Mesenchymal stromal cells (MSCs) are important cellular constituents of tumor stroma that play an active role in tumor development. Complex interactions between MSCs and cancer promote tumor progression by creating a favorable milieu for tumor cell proliferation, angiogenesis, motility, invasion, and metastasis. The cellular heterogeneity, source of origin, diversity in isolation methods, culture techniques and model systems of MSCs, together with the different tumor subtypes, add to the complexity of MSC-tumor interactions. In this review, we discuss the mechanisms of MSC-mediated tumor promotion and evaluate cell-stromal interactions between cancer cells, MSCs, cells of the tumor microenvironment (TME), and the extracellular matrix (ECM). A more thorough understanding of tumor-MSC interactions is likely to lead to better cancer management.

The cross-talk between the macro and micro-environment in precursor lesions of pancreatic cancer leads to new and promising circulating biomarkers

Pancreatic cancer (PC) is a clinically challenging tumor to combat due to its advanced stage at diagnosis as well as its resistance to currently available therapies. The absence of early symptoms and known detectable biomarkers renders this disease incredibly difficult to detect/manage. Recent advances in the understanding of PC biology have highlighted the importance of cancer-immune cell interactions, not only in the tumor micro-environment but also in distant systemic sites, like the bone marrow, spleen and circulating immune cells, the so-called macro-environment. The response of the macro-environment is emerging as a determining factor in tumor development by contributing to the formation of an increasingly immunogenic micro-environment promoting tumor homeostasis and progression. We will summarize the key events associated with the feedback loop between the tumor immune micro-environment (TIME) and the tumor immune macroenvironment (TIMaE) in pancreatic precancerous lesions along with how it regulates disease development and progression. In addition, liquid biopsy biomarkers capable of diagnosing PC at an early stage of onset will also be discussed. A clearer understanding of the early crosstalk between micro-environment and macro-environment could contribute to identifying new molecular therapeutic targets and biomarkers, consequently improving early PC diagnosis and treatment.

Pancreatic cancer cell- and cancer-associated fibroblast-derived exosomes in disease progression, metastasis, and therapy

Exosomes play a crucial role in the progression and spread of pancreatic cancer, serving not only as promoters of tumor growth and organ-specific metastasis but also as promising biomarkers and targets for treatment. These nano vesicles enhance intercellular communication by transferring bioactive molecules, such as proteins and RNAs, between cells. This process significantly affects cancer cell dynamics, including their proliferation, migration, and invasion, while also contributing to drug resistance. Our review focuses on the crucial interactions between cancer cells and fibroblasts mediated by exosomes within the pancreatic cancer microenvironment. We delve into how exosomes from both cancer-associated fibroblasts and the cancer cells themselves drive tumor progression through various mechanisms, such as epithelial-mesenchymal transition and facilitating metastasis to specific organs like the lungs and liver. The potential of leveraging exosomes for therapeutic interventions is also explored, highlighting the importance of understanding their role in cell communication as a step forward in developing more effective pancreatic cancer treatments.

Adenosine increases PD-L1 expression in mesenchymal stromal cells derived from cervical cancer through its interaction with A2AR/A2BR and the production of TGF-β1

Mesenchymal stromal cells (MSCs) together with malignant cells present in the tumor microenvironment (TME), participate in the suppression of the antitumor immune response through the production of immunosuppressive factors, such as transforming growth factor beta 1 (TGF-β1). In previous studies, we reported that adenosine (Ado), generated by the adenosinergic activity of cervical cancer (CeCa) cells, induces the production of TGF-β1 by interacting with A2AR/A2BR. In the present study, we provide evidence that Ado induces the production of TGF-β1 in MSCs derived from CeCa tumors (CeCa-MSCs) by interacting with both receptors and that TGF-β1 acts in an autocrine manner to induce the expression of programmed death ligand 1 (PD-L1) in CeCa-MSCs, resulting in an increase in their immunosuppressive capacity on activated CD8+ T lymphocytes. The addition of the antagonists ZM241385 and MRS1754, specific for A2AR and A2BR, respectively, or SB-505124, a selective TGF-β1 receptor inhibitor, in CeCa-MSC cultures significantly inhibited the expression of PD-L1. Compared with CeCa-MSCs, MSCs derived from normal cervical tissue (NCx-MSCs), used as a control and induced with Ado to express PD-L1, showed a lower response to TGF-β1 to increase PD-L1 expression. Those results strongly suggest the presence of a feedback mechanism among the adenosinergic pathway, the production of TGF-β1, and the induction of PD-L1 in CeCa-MSCs to suppress the antitumor response of CD8+ T lymphocytes. The findings of this study suggest that this pathway may have clinical importance as a therapeutic target.

Extracellular vesicle-mediated communication between CD8+ cytotoxic T cells and tumor cells

Tumors pose a significant global public health challenge, resulting in numerous fatalities annually. CD8+ T cells play a crucial role in combating tumors; however, their effectiveness is compromised by the tumor itself and the tumor microenvironment (TME), resulting in reduced efficacy of immunotherapy. In this dynamic interplay, extracellular vesicles (EVs) have emerged as pivotal mediators, facilitating direct and indirect communication between tumors and CD8+ T cells. In this article, we provide an overview of how tumor-derived EVs directly regulate CD8+ T cell function by carrying bioactive molecules they carry internally and on their surface. Simultaneously, these EVs modulate the TME, indirectly influencing the efficiency of CD8+ T cell responses. Furthermore, EVs derived from CD8+ T cells exhibit a dual role: they promote tumor immune evasion while also enhancing antitumor activity. Finally, we briefly discuss current prevailing approaches that utilize functionalized EVs based on tumor-targeted therapy and tumor immunotherapy. These approaches aim to present novel perspectives for EV-based tumor treatment strategies, demonstrating potential for advancements in the field.

Biology and Therapeutic Properties of Mesenchymal Stem Cells in Leukemia

This comprehensive review delves into the multifaceted roles of mesenchymal stem cells (MSCs) in leukemia, focusing on their interactions within the bone marrow microenvironment and their impact on leukemia pathogenesis, progression, and treatment resistance. MSCs, characterized by their ability to differentiate into various cell types and modulate the immune system, are integral to the BM niche, influencing hematopoietic stem cell maintenance and functionality. This review extensively explores the intricate relationship between MSCs and leukemic cells in acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, and chronic lymphocytic leukemia. This review also addresses the potential clinical applications of MSCs in leukemia treatment. MSCs' role in hematopoietic stem cell transplantation, their antitumor effects, and strategies to disrupt chemo-resistance are discussed. Despite their therapeutic potential, the dual nature of MSCs in promoting and inhibiting tumor growth poses significant challenges. Further research is needed to understand MSCs' biological mechanisms in hematologic malignancies and develop targeted therapeutic strategies. This in-depth exploration of MSCs in leukemia provides crucial insights for advancing treatment modalities and improving patient outcomes in hematologic malignancies.

A novel PDPN antagonist peptide CY12-RP2 inhibits melanoma growth via Wnt/β-catenin and modulates the immune cells

BACKGROUND

Podoplanin (PDPN) is a highly conserved, mucin-type protein specific to the lymphatic system. Overexpression of PDPN is associated with the progression of various solid tumors, and plays an important roles in the tumor microenvironment by regulating the immune system. However, the role of PDPN-mediated signal activation in the progression of melanoma is still unknown.

METHODS

PDPN expression was first analyzed in 112 human melanoma tissue microarrays and melanoma cell lines. Functional experiments including proliferation, clone formation, migration, and metastasis were utilized to identify the suppressive effects of PDPN. The Ph.D.TM-12 Phage Display Peptide Library was used to obtain a PDPN antagonist peptide, named CY12-RP2. The immunofluorescence, SPR assay, and flow cytometry were used to identify the binding specificity of CY12-RP2 with PDPN in melanoma cells. Functional and mechanistic assays in vivo and in vitro were performed for discriminating the antitumor and immune activation effects of CY12-RP2.

RESULTS

PDPN was overexpressed in melanoma tissue and cells, and inhibited melanoma cells proliferation, migration, and metastasis by blocking the EMT and Wnt/β-catenin pathway. PDPN antagonistic peptide, CY12-RP2, could specifically bind with PDPN, suppressing melanoma various functions inducing apoptosis in both melanoma cells and 3D spheroids. CY12-RP2 also enhanced the anti-tumor capacity of PBMC, and inhibited melanoma cells growth both in xenografts and allogeneic mice model. Moreover, CY12-RP2 could inhibit melanoma lung metastasis, and abrogated the immunosuppressive effects of PDPN by increasing the proportion of CD3 + CD4 + T cells, CD3 + CD8 + T cells, CD49b + Granzyme B + NK cells, and CD11b + CD86 + M1-like macrophages and the levels of IL-1β, TNF-α, and IFN-γ.

CONCLUSIONS

This study has demonstrated the important role of PDPN in the progression of melanoma and formation of immunosuppressive environment, and provided a potential approach of treating melanoma using the novel CY12-RP2 peptide. In melanoma, PDPN is overexpressed in the cancer cells, and promotes melanoma cells growth and metastasis through activating the Wnt/β-catenin pathway. Treatment with the PDPN antagonistic peptide CY12-RP2 could not only inhibit the melanoma growth and metastasis both in vitro and in vivo through Wnt/β-catenin pathway blockade, but also abrogate the immunosuppressive effects of PDPN through modulating immune cells.

Cancer-associated mesenchymal stem/stromal cells: role in progression and potential targets for therapeutic approaches

Malignancies contain a relatively small number of Mesenchymal stem/stromal cells (MSCs), constituting a crucial tumor microenvironment (TME) component. These cells comprise approximately 0.01-5% of the total TME cell population. MSC differentiation potential and their interaction with the tumor environment enable these cells to affect tumor cells' growth, immune evasion, metastasis, drug resistance, and angiogenesis. This type of MSC, known as cancer-associated mesenchymal stem/stromal cells (CA-MSCs (interacts with tumor/non-tumor cells in the TME and affects their function by producing cytokines, chemokines, and various growth factors to facilitate tumor cell migration, survival, proliferation, and tumor progression. Considering that the effect of different cells on each other in the TME is a multi-faceted relationship, it is essential to discover the role of these relationships for targeting in tumor therapy. Due to the immunomodulatory role and the tissue repair characteristic of MSCs, these cells can help tumor growth from different aspects. CA-MSCs indirectly suppress antitumor immune response through several mechanisms, including decreasing dendritic cells (DCs) antigen presentation potential, disrupting natural killer (NK) cell differentiation, inducing immunoinhibitory subsets like tumor-associated macrophages (TAMs) and Treg cells, and immune checkpoint expression to reduce effector T cell antitumor responses. Therefore, if these cells can be targeted for treatment so that their population decreases, we can hope for the treatment and improvement of the tumor conditions. Also, various studies show that CA-MSCs in the TME can affect other vital aspects of a tumor, including cell proliferation, drug resistance, angiogenesis, and tumor cell invasion and metastasis. In this review article, we will discuss in detail some of the mechanisms by which CA-MSCs suppress the innate and adaptive immune systems and other mechanisms related to tumor progression.

The Dual Role of Mesenchymal Stem Cells in Cancer Pathophysiology: Pro-Tumorigenic Effects versus Therapeutic Potential

Mesenchymal stem/stromal cells (MSCs) are multipotent cells involved in numerous physiological events, including organogenesis, the maintenance of tissue homeostasis, regeneration, or tissue repair. MSCs are increasingly recognized as playing a major, dual, and complex role in cancer pathophysiology through their ability to limit or promote tumor progression. Indeed, these cells are known to interact with the tumor microenvironment, modulate the behavior of tumor cells, influence their functions, and promote distant metastasis formation through the secretion of mediators, the regulation of cell-cell interactions, and the modulation of the immune response. This dynamic network can lead to the establishment of immunoprivileged tissue niches or the formation of new tumors through the proliferation/differentiation of MSCs into cancer-associated fibroblasts as well as cancer stem cells. However, MSCs exhibit also therapeutic effects including anti-tumor, anti-proliferative, anti-inflammatory, or anti-oxidative effects. The therapeutic interest in MSCs is currently growing, mainly due to their ability to selectively migrate and penetrate tumor sites, which would make them relevant as vectors for advanced therapies. Therefore, this review aims to provide an overview of the double-edged sword implications of MSCs in tumor processes. The therapeutic potential of MSCs will be reviewed in melanoma and lung cancers.

The effects of mesenchymal stem cells on the chemotherapy of colorectal cancer

Colorectal cancer (CRC) has been the third commonest cancer in the world. The prognosis of patients with CRC is related to the molecular subtypes and gene mutations, which is prone to recurrence, metastasis, and drug resistance. Mesenchymal stem cells (MSCs) are a group of progenitor ones with the capabilities of self-renewal， multi-directional differentiation, and tissue re-population, which could be isolated from various kinds of tissues and be differentiated into diverse cell types. In recent years, MSCs are applied for mechanisms study of tissue repairing, graft-versus-host disease (GVHD) and autoimmune-related disease, and tumor development, with the advantages of anti-inflammation, multi-lineage differentiation, and homing capability. Integrating the chemotherapy and MSCs therapy might provide a novel treatment approach for CRC patients. In this review, we summarize the current progress in the integrated treatment of integrating the MSCs and chemotherapy for CRC.

Mesenchymal Stromal Cell-Based Targeted Therapy Pancreatic Cancer: Progress and Challenges

Pancreatic cancer is an aggressive malignancy with high mortality rates and poor prognoses. Despite rapid progress in the diagnosis and treatment of pancreatic cancer, the efficacy of current therapeutic strategies remains limited. Hence, better alternative therapeutic options for treating pancreatic cancer need to be urgently explored. Mesenchymal stromal cells (MSCs) have recently received much attention as a potential therapy for pancreatic cancer owing to their tumor-homing properties. However, the specific antitumor effect of MSCs is still controversial. To this end, we aimed to focus on the potential anti-cancer treatment prospects of the MSC-based approach and summarize current challenges in the clinical application of MSCs to treat pancreatic cancer.

Cold atmospheric plasma: Novel opportunities for tumor microenvironment targeting

With mounting preclinical and clinical evidences on the prominent roles of the tumor microenvironment (TME) played during carcinogenesis, the TME has been recognized and used as an important onco-therapeutic target during the past decade. Delineating our current knowledge on TME components and their functionalities can help us recognize novel onco-therapeutic opportunities and establish treatment modalities towards desirable anti-cancer outcome. By identifying and focusing on primary cellular components in the TME, that is, tumor-infiltrating lymphocytes, tumor-associated macrophages, cancer-associated fibroblasts and mesenchymal stem cells, we decomposed their primary functionalities during carcinogenesis, categorized current therapeutic approaches utilizing traits of these components, and forecasted possible benefits that cold atmospheric plasma, a redox modulating tool with selectivity against cancer cells, may convey by targeting the TME. Our insights may open a novel therapeutic avenue for cancer control taking advantages of redox homeostasis and immunostasis.

Cancer-Associated Fibroblasts: The Origin, Biological Characteristics and Role in Cancer-A Glance on Colorectal Cancer

Simple Summary

Tumor microenvironment is a major contributor to tumor growth, metastasis and resistance to therapy. It consists of many cancer-associated fibroblasts (CAFs), which derive from different types of cells. CAFs detected in different tumor types are linked to poor prognosis, as in the case of colorectal cancer. Although their functions differ according to their subtype, their detection is not easy, and there are no established markers for such detection. They are possible targets for therapeutic treatment. Many trials are ongoing for their use as a prognostic factor and as a treatment target. More research remains to be carried out to establish their role in prognosis and treatment.

Abstract

The therapeutic approaches to cancer remain a considerable target for all scientists around the world. Although new cancer treatments are an everyday phenomenon, cancer still remains one of the leading mortality causes. Colorectal cancer (CRC) remains in this category, although patients with CRC may have better survival compared with other malignancies. Not only the tumor but also its environment, what we call the tumor microenvironment (TME), seem to contribute to cancer progression and resistance to therapy. TME consists of different molecules and cells. Cancer-associated fibroblasts are a major component. They arise from normal fibroblasts and other normal cells through various pathways. Their role seems to contribute to cancer promotion, participating in tumorigenesis, proliferation, growth, invasion, metastasis and resistance to treatment. Different markers, such as a-SMA, FAP, PDGFR-β, periostin, have been used for the detection of cancer-associated fibroblasts (CAFs). Their detection is important for two main reasons; research has shown that their existence is correlated with prognosis, and they are already under evaluation as a possible target for treatment. However, extensive research is warranted.

Pancreatic cancer growth promoted by bone marrow mesenchymal stromal cell-derived IL-6 is reversed predominantly by IL-6 blockade

Pancreatic cancer is a highly lethal cancer characterized by local invasiveness, early metastasis, recurrence and high resistance to current therapies. Extensive stroma or desmoplasia is a key histological feature of the disease, and interactions between cancer and stromal cells are critical for pancreatic cancer development and progression. Mesenchymal stromal cells [MSCs] exhibit preferential tropism to primary and metastatic tumor sites and may either suppress or support tumor growth. Although MSCs represent a potential source of pancreatic cancer stroma, their contribution to pancreatic tumor growth remains poorly known. Here, we show that bone marrow MSCs significantly contribute to pancreatic cancer growth in vitro and in vivo. Furthermore, MSCs create a pro-carcinogenic microenvironment through the release of key factors mediating growth and angiogenesis, including interleukin (IL)-6, IL-8, vascular endothelial growth factor and activation of STAT3 signaling in tumor cells. IL-6 released by MSCs was largely responsible for the pro-tumorigenic effects of MSCs. Knockdown of IL-6 expression in MSCs by small interfering RNA (siRNA) abolished the MSC growth-promoting effect in vitro, reducing tumor cell proliferation and clonogenic potential. In addition, in a heterotopic nude mouse model of human pancreatic tumor xenografts, blockade of IL-6 with the anti-IL-6 receptor antibody, tocilizumab, or of its downstream effector STAT3 with the small molecule STAT3 inhibitor S3I-201, abrogated MSC-mediated tumor promotion and delayed tumor formation significantly. Our data demonstrate that MSCs promote pancreatic cancer growth, with IL-6 produced by MSCs playing a pivotal role.

Human amniotic fluid mesenchymal stem cells attenuate pancreatic cancer cell proliferation and tumor growth in an orthotopic xenograft mouse model

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a malignant cancer and chemotherapy ineffectively treats PDAC, leading to the requirement for alternative tumor-targeted treatment. Human amniotic fluid mesenchymal stem cells (hAFMSCs) have been revealed to suppress tumor growth in various cancers and they are a strong candidate for treating PDAC.

METHODS

To evaluate the effects of hAFMSCs on human pancreatic carcinoma cells (PANC1, AsPC1 and BxPC3 cell lines) and the possible mechanism involved, an in vitro cell coculture system was used. A PANC1 orthotopic xenograft mouse model was established and hAFMSCs were injected intravenously at 4 weeks post-xenograft.

RESULTS

An in vitro coculture assay showed that hAFMSCs inhibited PANC1 cell proliferation by inducing S phase cell cycle arrest and increased cell apoptosis in a time-dependent manner. In PANC1 cells, hAFMSCs caused the downregulation of Cyclin A and Cyclin B1 as well as the upregulation of p21 (CDKN1A) at 24 h post coculture. The upregulation of pro-apoptotic factors Caspase-3/-8 and Bax at 24 h post coculture reduced the migration and invasion ability of PANC1 cells through inhibiting the epithelial-mesenchymal transition (EMT) process. In a PANC1 orthotopic xenograft mouse model, a single injection of hAFMSCs showed significant tumor growth inhibition with evidence of the modulation of cell cycle and pro-apoptotic regulatory genes and various genes involved in matrix metallopeptidase 7 (MMP7) signaling-triggered EMT process. Histopathological staining showed lower Ki67 levels in tumors from hAFMSCs-treated mice.

CONCLUSIONS

Our data demonstrated that hAFMSCs strongly inhibit PDAC cell proliferation, tumor growth and invasion, possibly by altering cell cycle arrest and MMP7 signaling-triggered EMT.

[Research Progress of Mesenchymal Stem Cells and Their Exosomes on Tumors]

In China, malignant tumor is the main cause of death in both urban and rural areas. Mesenchymal stem cells (MSCs) have multidirectional differentiation potential, self-renewal ability and good immunomodulatory properties. Exosomes, as important paracrine substances of MSCs, mediate information exchange and transmission between cells in tumor microenvironment and influence the occurrence and development of tumors. Recently, conflicting findings have been reported on the effects of MSCs and their exosomes on tumors. On the one hand, MSCs and their exosomes are tumorigenic and can target specific sites to inhibit tumor growth; On the other hand, there is also evidence that MSCs could affect tumor growth and migration as part of the tumor microenvironment. In this paper, we will review the relationship between MSCs and exosomes and tumorgenesis and development, as well as how MSCs and exosomes play different roles in tumorgenesis and development, in order to provide beneficial help for tumor diagnosis, prognosis and precise treatment.
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The Roles of Mesenchymal Stem Cells in Gastrointestinal Cancers

Mesenchymal stem cells (MSCs) were reported to have strong immunomodulatory ability, and inhibit the proliferation of T cells and their immune response through cell-to-cell interactions and the generation of cytokines. With high differentiation potential and self-renewal ability, MSCs are considered to function in alleviating inflammatory responses, promoting tissue regeneration and inhibiting tissue fibrosis formation. As the most common malignancies, gastrointestinal (GI) cancers have high incidence and mortality. The accurate diagnosis, exact prognosis and treatment of GI cancers have always been a hot topic. Therefore, the potential applications of MSCs in terms of GI cancers are receiving more and more attention. Recently, there is increasing evidence that MSCs may serve as a key point in the growth, metastasis, inhibition, treatment and prognosis of GI cancers. In this review, we summarized the roles of MSCs in GI cancers, mainly focusing on esophageal cancer (EC), gastric cancer (GC), liver cancer (LC), colorectal cancer (CRC) and pancreatic cancer. Besides, we proposed MSCs as potential targets and treatment strategies for the effective treatment of GI cancers, which may provide better guidance for the clinical treatment of GI cancers.

The Role of Mesenchymal Stem Cells in the Induction of Cancer-Stem Cell Phenotype

Cancer stem cells (CSCs) modify and form their microenvironment by recruiting and activating specific cell types such as mesenchymal stem cells (MSCs). Tumor-infiltrating MSCs help to establish a suitable tumor microenvironment for the restoration of CSCs and tumor progression. In addition, crosstalk between cancer cells and MSCs in the microenvironment induces a CSC phenotype in cancer cells. Many mechanisms are involved in crosstalk between CSCs/cancer cells and MSCs including cell-cell interaction, secretion of exosomes, and paracrine secretion of several molecules including inflammatory mediators, cytokines, and growth factors. Since this crosstalk may contribute to drug resistance, metastasis, and tumor growth, it is suggested that blockade of the crosstalk between MSCs and CSCs/cancer cells can provide a new avenue to improving the cancer therapeutic tools. In this review, we will discuss the role of MSCs in the induction of cancer stem cell phenotype and the restoration of CSCs. We also discuss targeting the crosstalk between MSCs and CSCs/cancer cells as a therapeutic strategy.

Mesenchymal stem cell-derived exosomes for gastrointestinal cancer

Gastrointestinal (GI) malignancies, a series of malignant conditions originating from the digestive system, include gastric cancer, hepatocellular carcinoma, pancreatic cancer, and colorectal cancer. GI cancers have been regarded as the leading cancer-related cause of death in recent years. Therefore, it is essential to develop effective treatment strategies for GI malignancies. Mesenchymal stem cells (MSCs), a type of distinct non-hematopoietic stem cells and an important component of the tumor microenvironment, play important roles in regulating GI cancer development and progression through multiple mechanisms, such as secreting cytokines and direct interactions. Currently, studies are focusing on the anti-cancer effect of MSCs on GI malignancies. However, the effects and functional mechanisms of MSC-derived exosomes on GI cancer are less studied. MSC-derived exosomes can regulate GI tumor growth, drug response, metastasis, and invasion through transplanting proteins and miRNA to tumor cells to activate the specific signal pathway. Besides, the MSC-derived exosomes are also seen as an important drug delivery system and have shown potential in anti-cancer treatment. This study aims to summarize the effect and biological functions of MSC-derived exosomes on the development of GI cancers and discuss their possible clinical applications for the treatment of GI malignancies.

The Versatile Roles of Cancer-Associated Fibroblasts in Colorectal Cancer and Therapeutic Implications

The tumor microenvironment (TME) is populated by abundant cancer-associated fibroblasts (CAFs) that radically influence the disease progression across many cancers, including the colorectal cancer (CRC). In theory, targeting CAFs holds great potential in optimizing CRC treatment. However, attempts to translate the therapeutic benefit of CAFs into clinic practice face many obstacles, largely due to our limited understanding of the heterogeneity in their origins, functions, and mechanisms. In recent years, accumulating evidence has uncovered some cellular precursors and molecular markers of CAFs and also revealed their versatility in impacting various hallmarks of CRC, together helping us to better define the population of CAFs and also paving the way toward their future therapeutic targeting for CRC treatment. In this review, we outline the emerging concept of CAFs in CRC, with an emphasis on their origins, biomarkers, prognostic significance, as well as their functional roles and underlying mechanisms in CRC biology. At last, we discuss the prospect of harnessing CAFs as promising therapeutic targets for the treatment of patients with CRC.

Mesenchymal stem cells in cancer therapy; the art of harnessing a foe to a friend

For a long time, mesenchymal stem cells (MSCs) were discussed only as stem cells which could give rise to different types of cells. However, when it became clear that their presence in the tumor microenvironment (TME) was like a green light for tumorigenesis, they emerged from the ashes. This review was arranged to provide a comprehensive and precise description of MSCs' role in regulating tumorigenesis and to discuss the dark and the bright sides of cancer treatment strategies using MSCs. To gather the details about MSCs, we made an intensive literature review using keywords, including MSCs, tumor microenvironment, tumorigenesis, and targeted therapy. Through transferring cytokines, growth factors, and microRNAs, MSCs maintain the cancer stem cell population, increase angiogenesis, provide a facility for cancer metastasis, and shut down the anti-tumor activity of the immune system. Although MSCs progress tumorigenesis, there is a consensus that these cells could be used as a vehicle to transfer anti-cancer agents into the tumor milieu. This feature opened a new chapter in MSCs biology, this time from the therapeutic perspective. Although the data are not sufficient, the advent of new genetic engineering methods might make it possible to engage these cells as Trojan horses to eliminate the malignant population. So many years of investigation showed that MSCs are an important group of cells, residing in the TME, studying the function of which not only could add a delicate series of information to the process of tumorigenesis but also could revolutionize cancer treatment strategies.

Pathology and Molecular Characteristics of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. However, it should be kept in mind that there are other pancreatic cancers that are classified by their cellular lineage: acinar cell carcinomas (acinar differentiation), neuroendocrine neoplasms (arising from the islets), solid-pseudopapillary neoplasms (showing no discernible cell lineage), and pancreatoblastomas (characterized by multiphenotypic differentiation, including acinar endocrine and ductal). This article focuses on the molecular and pathology alterations in PDAC.

The Extracellular Matrix in Pancreatic Cancer: Description of a Complex Network and Promising Therapeutic Options

The stroma is a relevant player in driving and supporting the progression of pancreatic ductal adenocarcinoma (PDAC), and a large body of evidence highlights its role in hindering the efficacy of current therapies. In fact, the dense extracellular matrix (ECM) characterizing this tumor acts as a natural physical barrier, impairing drug penetration. Consequently, all of the approaches combining stroma-targeting and anticancer therapy constitute an appealing option for improving drug penetration. Several strategies have been adopted in order to target the PDAC stroma, such as the depletion of ECM components and the targeting of cancer-associated fibroblasts (CAFs), which are responsible for the increased matrix deposition in cancer. Additionally, the leaky and collapsing blood vessels characterizing the tumor might be normalized, thus restoring blood perfusion and allowing drug penetration. Even though many stroma-targeting strategies have reported disappointing results in clinical trials, the ECM offers a wide range of potential therapeutic targets that are now being investigated. The dense ECM might be bypassed by implementing nanoparticle-based systems or by using mesenchymal stem cells as drug carriers. The present review aims to provide an overview of the principal mechanisms involved in the ECM remodeling and of new promising therapeutic strategies for PDAC.

Identification of a Hematopoietic Cell Population Emerging From Mouse Bone Marrow With Proliferative Potential In Vitro and Immunomodulatory Capacity

There is continuing interest in therapeutic applications of bone marrow-derived mesenchymal stromal cells (MSC). Unlike human counterparts, mouse MSC are difficult to propagate in vitro due to their contamination with adherent hematopoietic cells that overgrow the cultures. Here we investigated the properties of these contaminating cells, referred to as bone marrow-derived proliferating hematopoietic cells (BM-PHC). The results showed that both BM-PHC and MSC had strong immunomodulatory properties on T cells in vitro, with PGE2 and NO involved in this mechanism. However, BM-PHC were stronger immunomodulators than MSC, with CCL-6 identified as putative molecule responsible for superior effects. In vivo studies showed that, in contrast to BM-PHC, MSC endorsed a more rapid xenograft tumor rejection, thus indicating a particular context in which only MSC therapy would produce positive outcomes. In conclusion, bone marrow contains two cell populations with immunomodulatory properties, which are valuable sources for therapeutic studies in specific disease-relevant contexts.

SEMA4D Knockdown Attenuates β-Catenin-Dependent Tumor Progression in Colorectal Cancer

Semaphorin 4D (SEMA4D), a protein originally demonstrated to regulate the immune system and axonal growth cone collapse in the developing central nervous system, is overexpressed in various human malignancies, including colorectal cancer (CRC). This investigation was undertaken to examine the effects of SEMA4D silencing on the biological properties of the CRC cell line. SW48 cells were transfected with a siRNA-targeting SEMA4D. The mRNA expression of underlying pro- and antiapoptotic proteins including Bax, Bcl-2, P53, and caspase-3, cancer stem cell (CSC) markers, epithelial-mesenchymal transition (EMT) markers, MMP-2, and MMP-9 was examined using qRT-PCR. Further, the protein expression of E-cadherin and β-catenin was confirmed by Western blot. SW48 cell migration and MMP activity were detected using scratch and zymography analysis, respectively. Finally, the apoptosis rate was assessed via the flowcytometry test. SEMA4D knock-down was associated with a considerable suppression of in vitro cell viability, EMT-related genes, CSC markers, β-catenin signaling pathway, sphere-forming, cell migration, and MMP-2 activity as well as induction of apoptosis. This study identifies the inhibitory effects of SEMA4D gene silencing on tumor progression. Thereby, this might conclude a possible alternative to cancer therapy by targeting several prominent pathways involved in cancer through SEMA4D suppression.

Fas-threshold signalling in MSCs promotes pancreatic cancer progression and metastasis

Mesenchymal stem cells (MSCs) belong to the tumour microenvironment and have been implicated in tumour progression. We found that the number of MSCs significantly increased in tumour-burdened mice driven by Fas-threshold signalling. Consequently, MSCs lacking Fas lost their ability to induce metastasis development in a pancreatic cancer model. Mixing of MSCs with pancreatic cancer cells led to sustained production of the pro-metastatic cytokines CCL2 and IL6 by the stem cells. The levels of these cytokines were dependent on the number of MSCs, linking Fas-mediated MSC-proliferation to their capacity to promote tumour progression. Furthermore, we discovered that CCL2 and IL6 were induced by pancreatic cancer cell-derived IL1. Importantly, analysis of patient transcriptomic data revealed that high FasL expression correlates with high levels of MSC markers as well as increased IL6 and CCL2 levels in pancreatic tumours. Moreover, both FasL and CCL2 are linked to elevated levels of markers specific for monocytes known to possess further pro-metastatic activities. These results confirm our experimental findings of a FasL-MSC-IL1-CCL2/IL6 axis in pancreatic cancer and highlights the role of MSCs in tumour progression.

Cell-derived biomimetic nanocarriers for targeted cancer therapy: cell membranes and extracellular vesicles

Nanotechnology provides synthetic carriers for cancer drug delivery that protect cargos from degradation, control drug release and increase local accumulation at tumors. However, these non-natural vehicles display poor tumor targeting and potential toxicity and are eliminated by the immune system. Recently, biomimetic nanocarriers have been widely developed based on the concept of ‘mimicking nature.’ Among them, cell-derived biomimetic vehicles have become the focus of bionics research because of their multiple natural functions, such as low immunogenicity, long circulation time and targeting ability. Cell membrane-coated carriers and extracellular vesicles are two widely used cell-based biomimetic materials. Here, this review summarizes the latest progress in the application of these two biomimetic carriers in targeted cancer therapy. Their properties and performance are compared, and their future challenges and development prospects are discussed.

Application of mesenchymal stem cell therapy for aging frailty: from mechanisms to therapeutics

Aging frailty is a complex geriatric syndrome that becomes more prevalent with advancing age. It constitutes a major health problem due to frequent adverse outcomes. Frailty is characterized by disruption of physiological homeostasis and progressive decline of health status. Multiple factors contribute to development of frailty with advancing age, including genome instability, DNA damage, epigenetic alternations, stem cell exhaustion, among others. These interrelated factors comprehensively result in loss of tissue homeostasis and diminished reserve capacity in frailty. Therefore, the aged organism gradually represents symptoms of frailty with decline in physiological functions of organs. Notably, the brain, cardiovascular system, skeletal muscle, and endocrine system are intrinsically interrelated to frailty. The patients with frailty may display the diminished reserves capacity of organ systems. Due to the complex pathophysiology, no specific treatments have been approved for prevention of this syndrome. At such, effective strategies for intervening in pathogenic process to improve health status of frail patients are highly needed. Recent progress in cell-based therapy has greatly contributed to the amelioration of degenerative diseases related to age. Mesenchymal stem cells (MSCs) can exert regenerative effects and possess anti-inflammatory properties. Transplantation of MSCs represents as a promising therapeutic strategy to address the pathophysiologic problems of frail syndrome. Currently, MSC therapy have undergone the phase I and II trials in human subjects that have endorsed the safety and efficacy of MSCs for aging frailty. However, despite these positive results, caution is still needed with regard to potential to form tumors, and further large-scale studies are warranted to confirm the therapeutic efficacy of MSC therapy.

In-Depth Characterization of Stromal Cells within the Tumor Microenvironment Yields Novel Therapeutic Targets

Simple Summary

This up-to-date and in-depth review describes fibroblast-derived cells and their role within the tumor microenvironment for tumor progression. Moreover, targets for future antitumor therapies are summarized and potential aspects for future translational research are outlined. Furthermore, this review discusses the challenges and possible obstacles related to certain treatment targets.

Abstract

Cells within the tumor stroma are essential for tumor progression. In particular, cancer-associated fibroblasts (CAF) and CAF precursor cells (resident fibroblasts and mesenchymal stromal cells) are responsible for the formation of the extracellular matrix in tumor tissue. Consequently, CAFs directly and indirectly mediate inflammation, metastasis, immunomodulation, angiogenesis, and the development of tumor chemoresistance, which is orchestrated by complex intercellular cytokine-mediated crosstalk. CAFs represent a strategic target in antitumor therapy but their heterogeneity hinders effective treatment regimes. In-depth understanding of CAF subpopulations and knowledge of specific functions in tumor progression will ultimately result in more specific and effective cancer treatments. This review provides a detailed description of CAFs and CAF precursor cells and summarizes possible treatment strategies as well as molecular targets of these cells in antitumor therapies.

Mesenchymal stem cells as a double-edged sword in tumor growth: focusing on MSC-derived cytokines

Mesenchymal stem cells (MSCs) show homing capacity towards tumor sites. Numerous reports indicate that they are involved in multiple tumor-promoting processes through several mechanisms, including immunosuppression; stimulation of angiogenesis; transition to cancer-associated fibroblasts; inhibition of cancer cell apoptosis; induction of epithelial-mesenchymal transition (EMT); and increase metastasis and chemoresistance. However, other studies have shown that MSCs suppress tumor growth by suppressing angiogenesis, incrementing inflammatory infiltration, apoptosis and cell cycle arrest, and inhibiting the AKT and Wnt signaling pathways. In this review, we discuss the supportive and suppressive impacts of MSCs on tumor progression and metastasis. We also discuss MSC-based therapeutic strategies for cancer based on their potential for homing to tumor sites.

Pancreatic cancer-targeting exosomes for enhancing immunotherapy and reprogramming tumor microenvironment

Immunotherapy has gained increasing focus in treating pancreatic ductal adenocarcinoma (PDAC), since conventional therapies like chemotherapy could not provide satisfactory improvement in overall survival outcome of PDAC patients. However, it is still not the game changing solution due to the unique tumor microenvironment and low cancer immunogenicity of PDAC. Thus, inducing more intratumoral effector immune cells as well as reversing immunosuppression is the core of PDAC treatment. Herein, we demonstrate an exosome-based dual delivery biosystem for enhancing PDAC immunotherapy as well as reversing tumor immunosuppression of M2-like tumor associated macrophages (M2-TAMs) upon disruption of galectin-9/dectin 1 axis. The deliver system is constructed from bone marrow mesenchymal stem cell (BM-MSC) exosomes, electroporation-loaded galectin-9 siRNA, and surficially modified with oxaliplatin (OXA) prodrug as an immunogenic cell death (ICD)-trigger. The use of biomaterials, BM-MSC exosomes, can significantly improve tumor targeting efficacy, thus increasing drug accumulation in the tumor site. The combined therapy (iEXO-OXA) elicits anti-tumor immunity through tumor-suppressive macrophage polarization, cytotoxic T lymphocytes recruitment and Tregs downregulation, and achieves significant therapeutic efficacy in cancer treatment.

Tumor resistance mechanisms and their consequences on γδ T cell activation

Human γδ T lymphocytes are predominated by two major subsets, defined by the variable domain of the δ chain. Both, Vδ1 and Vδ2 T cells infiltrate in tumors and have been implicated in cancer immunosurveillance. Since the localization and distribution of tumor-infiltrating γδ T cell subsets and their impact on survival of cancer patients are not completely defined, this review summarizes the current knowledge about this issue. Different intrinsic tumor resistance mechanisms and immunosuppressive molecules of immune cells in the tumor microenvironment have been reported to negatively influence functional properties of γδ T cell subsets. Here, we focus on selected tumor resistance mechanisms including overexpression of cyclooxygenase (COX)-2 and indolamine-2,3-dioxygenase (IDO)-1/2, regulation by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL-R4 pathway and the release of galectins. These inhibitory mechanisms play important roles in the cross-talk of γδ T cell subsets and tumor cells, thereby influencing cytotoxicity or proliferation of γδ T cells and limiting a successful γδ T cell-based immunotherapy. Possible future directions of a combined therapy of adoptively transferred γδ T cells together with γδ-targeting bispecific T cell engagers and COX-2 or IDO-1/2 inhibitors or targeting sialoglycan-Siglec pathways will be discussed and considered as attractive therapeutic options to overcome the immunosuppressive tumor microenvironment.

Bone marrow mesenchymal stem cells-derived exosomes for penetrating and targeted chemotherapy of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most intractable malignancy, with an only 6% 5-year relative survival rate. The dismal therapeutic effect is attributed to the chemotherapy resistance and unique pathophysiology with abundant inflammatory cytokines and abnormal hyperplasia of extracellular matrix (ECM). Based on the theory that bone marrow mesenchymal stem cells (BM-MSCs) can influence the tumorous microenvironment and malignant growth of PDAC, we employed exosomes (Exos) derived from BM-MSCs as PDAC-homing vehicles to surpass the restrictions of pathological ECM and increase the accumulation of therapeutics in tumor site. To overcome chemoresistance of PDAC, paclitaxel (PTX) and gemcitabine monophosphate (GEMP)-an intermediate product of gemcitabine metabolism-were loaded in/on the purified Exos. In this work, the Exo delivery platform showed superiorities in homing and penetrating abilities, which were performed on tumor spheroids and PDAC orthotopic models. Meanwhile, the favorable anti-tumor efficacy in vivo and in vitro, plus relatively mild systemic toxicity, was found. Loading GEMP and PTX, benefitting from the naturally PDAC selectivity, the Exo platform we constructed performs combined functions on excellent penetrating, anti-matrix and overcoming chemoresistance (Scheme 1). Worth expectantly, the Exo platform may provide a prospective approach for targeted therapies of PDAC.

Inflammatory Mediators in Glioma Microenvironment Play a Dual Role in Gliomagenesis and Mesenchymal Stem Cell Homing: Implication for Cellular Therapy

Glioblastoma is the most aggressive malignant primary brain tumor, with a dismal prognosis and a devastating overall survival. Despite aggressive surgical resection and adjuvant treatment, average survival remains approximately 14.6 months. The brain tumor microenvironment is heterogeneous, comprising multiple populations of tumor, stromal, and immune cells. Tumor cells evade the immune system by suppressing several immune functions to enable survival. Gliomas release immunosuppressive and tumor-supportive soluble factors into the microenvironment, leading to accelerated cancer proliferation, invasion, and immune escape. Mesenchymal stem cells (MSCs) isolated from bone marrow, adipose tissue, or umbilical cord are a promising tool for cell-based therapies. One crucial mechanism mediating the therapeutic outcomes often seen in MSC application is their tropism to sites of injury. Furthermore, MSCs interact with host immune cells to regulate the inflammatory response, and data points to the possibility of using MSCs to achieve immunomodulation in solid tumors. Interleukin 1β, interleukin 6, tumor necrosis factor α, transforming growth factor β, and stromal cell-derived factor 1 are notably up-regulated in glioblastoma and dually promote immune and MSC trafficking. Mesenchymal stem cells have widely been regarded as hypoimmunogenic, enabling this cell-based administration across major histocompatibility barriers. In this review, we will highlight (1) the bidirectional communication of glioma cells and tumor-associated immune cells, (2) the inflammatory mediators enabling leukocytes and transplantable MSC migration, and (3) review preclinical and human clinical trials using MSCs as delivery vehicles. Mesenchymal stem cells possess innate abilities to migrate great distances, cross the blood-brain barrier, and communicate with surrounding cells, all of which make them desirable "Trojan horses" for brain cancer therapy.

Evaluation of the expression of bone marrow-derived mesenchymal stem cells and cancer-associated fibroblasts in the stroma of gastric cancer tissue

AIM

Cancer-associated fibroblasts (CAFs) generated by bone marrow-derived mesenchymal stem cells (BM-MSCs) play an important role in cancer progression. In this study, we investigated the relationships of BM-MSCs and CAFs in resected gastric cancers with the clinicopathological factors of patients.

METHODS

We analyzed 120 gastric cancer patients who underwent gastrectomy. Immunostaining was performed with an anti-CD271 antibody (BM-MSCs) and anti-α-smooth muscle actin (αSMA) antibody (CAFs). Staining intensity was used to divide patients into low and high expression groups. Observation sites in cancer tissues were invasive, central, and whole portions.

RESULTS

Expression of αSMA was significantly related to depth of tumor invasion (T), lymph node metastasis (N), lymphatic invasion (ly), venous invasion (v), and stage. Expression of CD271 was significantly related to v, stage, stromal volume, and tumor infiltration pattern (INF). Overall survival (OS) of the high expression group was significantly lower than that of the low expression group for both αSMA and CD271. Multivariate analysis showed that N, αSMA (whole), and CD271 (invasive) were independent prognostic factors.

CONCLUSIONS

Cancer-associated fibroblasts and BM-MSCs are related to the progression, invasion, and prognosis of gastric cancer and may be therapeutic targets of gastric cancer.

Association of Jagged1 expression with malignancy and prognosis in human pancreatic cancer

PURPOSE

Pancreatic cancer is one of the most aggressive cancers. Preclinical and clinical data indicate that Notch 1 ligand jagged1 (JAG1) plays a pro-oncogenic role in several malignant cancers. As yet, however, the role of JAG1 in pancreatic cancer is poorly understood. The objective of the present study was to investigate JAG1 as a therapeutic target in human pancreatic cancer.

METHODS

Expression levels of Notch signaling molecules were assessed using GEO datasets and Western blot analysis, respectively. Anti-tumor effects following JAG1 silencing were evaluated using in vitro and in vivo assays. Prognostic implications were assessed using GEO datasets.

RESULTS

Using GEO datasets and Western blot analysis we detected significantly higher JAG1 mRNA and protein expression levels in pancreatic cancer compared to normal pancreatic tissues. JAG1 silencing significantly restrained the growth, migration and invasion of pancreatic cancer cells through the induction of apoptosis and blockade of various kinases independent of the Notch1 pathway. Combined JAG1 silencing and gemcitabine treatment showed synergistic anti-viability effects in human pancreatic cancer cells. JAG1 silencing also resulted in significant anti-cancer effects in vivo and high JAG1 expression was found to be associated with an adverse prognosis in pancreatic cancer patients.

CONCLUSIONS

From our data we conclude that JAG1 may be a promising therapeutic target in pancreatic cancer.

Interplay between mesenchymal stem cell and tumor and potential application

Mesenchymal stem cells (MSCs) possess the capabilities of self-renewal and multipotent differentiation. Firstly isolated from bone marrow, MSCs are subsequently identified from various post-natal tissue types. Based the differentiation into tissue-specific cells, MSCs were capable of replacing damaged and diseased tissues. In addition, MSCs have been demonstrated to possess important immunomodulatory properties. Increasing data showed that MSCs exhibited tropism for sites of the tumor microenvironment and interacted with tumor cells closely through paracrine signaling. Therefore, better understanding of crosstalk between MSCs and tumor cells will be able to develop potential strategies in the treatment of tumors in the future. Herein, we summarize the research progress of the influence of MSCs on tumor cells and the prospect of their application in tumor therapy in this review.

Activation PDGFR-α/AKT Mediated Signaling Pathways in Oral Squamous Cell Carcinoma by Mesenchymal Stem/Stromal Cells Promotes Anti-apoptosis and Decreased Sensitivity to Cisplatin

Desmoplasia, a hallmark of a head and neck cancer, has both biologic and physiologic effects on cancer progression and chemotherapeutic response. Mesenchymal stem/stromal cells (MSCs), also known as mesenchymal stromal progenitor cells, have been shown to play a role in cancer progression, alter apoptotic responses, and confer resistance to chemotherapy in various carcinomas. The pathophysiology of MSCs with respect to tumorigenesis is widely reported in other cancers and is sparsely reported in oral squamous cell carcinomas (OSCCs). We previously reported paracrine mediated PDGF-AA/PDGFR-α signaling to underlie MSCs chemotaxis in OSCC. Given the poor clinical response to primary chemotherapy, we hypothesized that MSCs may alter cancer cell sensitivity to cisplatin through activation of PDGFR-α mediated signaling pathways. Co-culture of MSCs with human derived OSCC cell lines, JHU-012 and −019, resulted in a significant increase in the production of PDGF-AA and MCP-1 compared to cancer cells grown alone (p < 0.005) and was accompanied by an increase in the phosphorylation state of PDGFR-α (p < 0.02) and downstream target AKT at S473 (p < 0.025) and T308 (p < 0.02). JHU-012 and −019 cancer cells grown in co-culture were significantly less apoptotic (p < 0.001), expressed significantly higher levels of Bcl-2 (p < 0.04) with a concomitant significant decrease in bid expression (p < 0.001) compared to cancer cells grown alone. There was a significant increase in the cisplatin dose response curve in cancer cell clones derived from JHU-012 and 019 cancer cells grown in co-culture with MSCs compared to clones derived from cancer cells grown alone (p < 0.001). Moreover clones derived from JHU-012 cells grown in co-culture with MSCs were significantly more susceptible to cisplatin following pretreatment with, crenolanib, a PDGFR inhibitor, compared to cancer cells grown alone or in co-culture with MSCs (p < 0.0001). These findings suggest that crosstalk between cancer cells and MSCs is mediated, at least in part, by activation of autocrine PDGF-AA/PDGFR-α loop driving AKT-mediated signaling pathways, resulting in reduced cancer cell sensitivity to cisplatin through alterations in apoptosis.

Mesenchymal Stem Cells in the Tumor Microenvironment

The interactions between tumor cells and the non-malignant stromal and immune cells that make up the tumor microenvironment (TME) are critical to the pathophysiology of cancer. Mesenchymal stem cells (MSCs) are multipotent stromal stem cells found within most cancers and play a critical role influencing the formation and function of the TME. MSCs have been reported to support tumor growth through a variety of mechanisms including (i) differentiation into other pro-tumorigenic stromal components, (ii) suppression of the immune response, (iii) promotion of angiogenesis, (iv) enhancement of an epithelial-mesenchymal transition (EMT), (v) enrichment of cancer stem-like cells (CSC), (vi) increase in tumor cell survival, and (vii) promotion of tumor metastasis. In contrast, MSCs have also been reported to have antitumorigenic functions including (i) enhancement of the immune response, (ii) inhibition of angiogenesis, (iii) regulation of cellular signaling, and (iv) induction of tumor cell apoptosis. Although literature supporting both arguments exists, most studies point to MSCs acting in a cancer supporting role within the confines of the TME. Tumor-suppressive effects are observed when MSCs are used in higher ratios to tumor cells. Additionally, MSC function appears to be tissue type dependent and may rely on cancer education to reprogram a naïve MSC with antitumor effects into a cancer-educated or cancer-associated MSC (CA-MSC) which develops pro-tumorigenic function. Further work is required to delineate the complex crosstalk between MSCs and other components of the TME to accurately assess the impact of MSCs on cancer initiation, growth, and spread.

Potentials of "stem cell-therapy" in pancreatic cancer: An update

In recent times, cell-therapies like T-activated cells, dendritic cells and natural killer cells have shown increasing promise in treating cancers as evidenced by both animal and human studies in the literature. In addition, stem cells are also being considered as potent anti-cancer agents since they act through multi-pronged approaches (chemokines, cytokines, paracrine action). In this review, we have attempted to discuss the inferences of studies that have used different sub-types of stem cells namely mesenchymal stem cells (MSCs), hematopoietic stem cells (HSCs) and neural stem cells (NSCs) in in-vitro/in-vivo mice and/or human studies as a treatment modality for pancreatic cancer. Pancreatic cancers are diagnosed in late/metastatic stages hence limiting its progress to partial/disease-free status. Recent literature supports evidences of stem cell therapy in pancreatic cancer with promising results; yet their impact remains inconclusive due to limited studies in human subjects. With reference to the treatment options for pancreatic cancer, the most studied sub-type of stem cells was HSCs as evident from the available clinical trials. The suggested mechanism of the HSC-transplantation is presumably via the graft-versus-tumor effect that elicits an anti-tumor immune response activated by the T-cell repertoires. On the other hand, the property of MSCs like tropism, migration to tumor site and activation of host immune cells by its secretome, appear to be able to regulate pancreatic tumor microenvironment. Further, drug delivery potential could be mediated via engineered MSCs to enhance the bioavailability of drug/prodrug at tumor site. Conclusively, stem cells have shown great potentials as next-generation therapeutic options.

Biophysical Characterization and Drug Delivery Potential of Exosomes from Human Wharton's Jelly-Derived Mesenchymal Stem Cells

Cell-derived exosomes (30-200 nm) as biological "nanocarriers" have attracted a great deal of interest for therapeutic applications due to their ability to internalize in in vivo biological systems (i.e., cells). Although they can be harvested from various sources including stem cells, yet an appropriate isolation and characterization protocol to obtain "pure" exosomal population is needed. For potential clinical applications, understanding the functional ability of exosomes and their purity, that is, free from microvesicles, apoptotic bodies, and protein aggregates, is a pre-requisite. To achieve high purity and yield of exosomes from human Wharton's jelly-derived mesenchymal stem cells (hWJ-MSCs) in the size range of 30-200 nm, we have performed and compared three isolation procedures: ultracentrifugation (UC), sucrose cushion (SC), and commercially available reagent (CR). The isolated exosomes were characterized using nanoparticle tracking analysis (NTA), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). Furthermore, to understand the therapeutic potential of the hWJ-MSC-derived exosomes (hWJ-ME) to target pancreatic tumor cells, the internalization efficacy has been evaluated on the MiaPaCa-2 cell lines using confocal microscopy and flow cytometry. The NTA results showed sucrose cushion to be an optimal method for exosome isolation with high purity (86.8%), as compared to UC (40.5%; p = 0.050) and CR (38%; p = 0.050). Optical analysis by FESEM and AFM revealed that SC-isolated exosomes presented a spherical morphology, whereas UC- and CR-isolated exosomes exhibited an uneven morphology. Furthermore, the data from confocal images and flow cytometry showed that hWJ-ME were internalized by MiaPaCa-2, demonstrating the feasibility of exosomes as a "potential nanocarrier". Thus, our study suggests that a combination of NTA (yield), AFM (dimensions), and FESEM (morphology and topography) could provide sensitive biophysical characterization of hWJ-ME. In the future, enriched exosomes could be used as a delivery vehicle to transport target-specific drugs or gene-silencing constructs to tumors.

Targeting the Interplay Between Cancer Fibroblasts, Mesenchymal Stem Cells, and Cancer Stem Cells in Desmoplastic Cancers

Malignant tumors are highly heterogeneous and likely contain a subset of cancer cells termed cancer stem cells (CSCs). CSCs exist in a dynamic equilibrium with their microenvironments and the CSC phenotype is tightly regulated by both cell-intrinsic and cell-extrinsic factors including those derived from their surrounding cells or stroma. Many human solid tumors like breast, lung, colorectal and pancreatic cancers are characterized by a pronounced stromal reaction termed “the desmoplastic response.” Carcinoma-associated fibroblasts (CAFs) derived either from resident fibroblasts or tumor-infiltrating mesenchymal stem cells (MSCs) are a major component of the stroma in desmoplastic cancers. Recent studies identified subpopulations of CAFs proficient in secreting a plethora of factors to foster CSCs, tumor growth, and invasion. In addition, cytotoxic therapy can lead to the enrichment of functionally perturbed CAFs, which are endowed with additional capabilities to enhance cancer stemness, leading to treatment resistance and tumor aggressiveness. When recruited into the tumor stroma, bone-marrow-derived MSCs can promote cancer stemness by secreting a specific set of paracrine factors or converting into pro-stemness CAFs. Thus, blockade of the crosstalk of pro-stemness CAFs and MSCs with CSCs may provide a new avenue to improving the therapeutic outcome of desmoplastic tumors. This up-to-date, in-depth and balanced review describes the recent progress in understanding the pro-stemness roles of CAFs and tumor-infiltrating MSCs and the associated paracrine signaling processes. We emphasize the effects of systemic chemotherapy on the CAF/MSC–CSC interplay. We summarize various promising and novel approaches in mitigating the stimulatory effect of CAFs or MSCs on CSCs that have shown efficacies in preclinical models of desmoplastic tumors and highlight the unique advantages of CAF- or MSC-targeted therapies. We also discuss potential challenges in the clinical development of CSC- or MSC-targeted therapies and propose CAF-related biomarkers that can guide the next-generation clinical studies.

The multifaceted role of mesenchymal stem cells in cancer

Mesenchymal stem cells (MSCs) are multipotent stem cells derived from the mesoderm that give rise to several mesenchymal lineages, including osteoblasts, adipocytes, chondrocytes and myocytes. Their potent ability to home to tumors coupled with their differentiation potential and immunosuppressive function positions MSCs as key regulators of tumor fate. Here we review the existing knowledge on the involvement of MSCs in multiple tumor-promoting processes, including angiogenesis, epithelial-mesenchymal transition, metastasis, immunosuppression and therapy resistance. We also discuss the clinical potential of MSC-based therapy for cancer.

Anti-tumor Drug THZ1 Suppresses TGFβ2-mediated EMT in Lens Epithelial Cells via Notch and TGFβ/Smad Signaling Pathway

Selective covalent CDK7 inhibitor THZ1 is a promising potential anti-tumor drug in many kinds of cancers. Epithelial-mesenchymal Transition (EMT) is highly related to cancer initiation, development, invasion and metastasis and other pathogenesis processes. We treated cancer cell line Hela229 and three retinoblastoma cell lines so-RB50, WERI-Rb-1, Y79 with gradient concentration of THZ1, and found that THZ1 could inhibit cell viability and EMT, suggesting that THZ1 may be a promising drug for human cervical cancer and retinoblastoma treatment. Our results verified the role of THZ1 in EMT for the first time, however, the mechanism needs further study. Here we report that THZ1 suppresses the TGFβ2 induced EMT in human SRA01/04 lens epithelial cells (LECs), rabbit primary lens epithelial cells, and whole rat lens culture semi-in vivo model. RNA-sequencing and KEGG analysis revealed that the THZ1 inhibits EMT by down-regulating phosphorylate Smad2 and Notch signaling pathway. On the other hand, we found that THZ1 could strongly inhibit LECs proliferation through G2/M phase arrest as well as attenuating of MAPK, PI3K/AKT signaling pathway. Our results uncovered the function and underlying mechanism of THZ1 in regulation of EMT, which provides a new perspective of the anti-tumor effect by THZ1 and may offer a novel treatment for PCO.

Human mesenchymal stem cells promote tumor growth via MAPK pathway and metastasis by epithelial mesenchymal transition and integrin α5 in hepatocellular carcinoma

Mesenchymal stem cells (MSCs) appear to be a potential vehicle for anticancer drugs due to their excellent tumor tropism ability. However, the interactions between MSCs and hepatocellular carcinoma (HCC) are quite controversial and the underlying mechanisms are ambiguous. In this study, an investigation was conducted into the effect of human MSCs (hMSCs) on tumor proliferation and metastasis both in xenograft and orthotopic models. It was discovered that hMSCs could promote tumor growth though activating mitogen-activated protein kinase (MAPK) signaling pathway and promote metastasis by epithelial mesenchymal transition (EMT) in vivo. To test whether hMSCs could induce immunosuppressive effects, the expression of the Natural killer (NK) cell marker CD56 was measured by immunohistochemical staining and the expression of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured by qRT-PCR. It was found out that CD56 expression significantly decreased, while TNF-α and IL-6 expression increased in the hMSCs-treated tissues. Mechanistically, RNA sequencing was performed, which led to a discovery that integrin α5 (ITGA5) was over-expressed in hMSCs-treated HCC. ITGA5 siRNAs blocked the hMSCs-induced migration and invasion of HCC, while over-expression of ITGA5 promoted the migration and invasion ability in HCC-hMSCs, indicating that the expression of ITGA5 is associated with hMSCs-induced tumor metastasis. These findings suggest that hMSCs may play a vital role in HCC proliferation and metastasis and could be identified as a putative therapeutic target in HCC.

Next Viable Routes to Targeting Pancreatic Cancer Stemness: Learning from Clinical Setbacks

Pancreatic ductal adenocarcinoma (PDAC) is a devastating and highly aggressive malignancy. Existing therapeutic strategies only provide a small survival benefit in patients with PDAC. Laboratory and clinical research have identified various populations of stem-cell-like cancer cells or cancer stem cells (CSCs) as the driving force of PDAC progression, treatment-resistance, and metastasis. Whilst a number of therapeutics aiming at inhibiting or killing CSCs have been developed over the past decade, a series of notable clinical trial setbacks have led to their deprioritization from the pipelines, triggering efforts to refine the current CSC model and exploit alternative therapeutic strategies. This review describes the current and the evolving models of pancreatic CSCs (panCSCs) and the potential factors that hamper the clinical development of panCSC-targeted therapies, emphasizing the heterogeneity, the plasticity, and the non-binary pattern of cancer stemness, as well as the desmoplastic stroma impeding drug penetration. We summarized novel and promising therapeutic strategies implicated by the works of our groups and others' that may overcome these hurdles and have shown efficacies in preclinical models of PDAC, emphasizing the unique advantages of targeting the stroma-engendered panCSC-niches and metronomic chemotherapy. Finally, we proposed feasible clinical trial strategies and biomarkers that can guide the next-generation clinical trials.

Extracellular S100A11 Plays a Critical Role in Spread of the Fibroblast Population in Pancreatic Cancers

The fertile stroma in pancreatic ductal adenocarcinomas (PDACs) has been suspected to greatly contribute to PDAC progression. Since the main cell constituents of the stroma are fibroblasts, there is crosstalking(s) between PDAC cells and surrounding fibroblasts in the stroma, which induces a fibroblast proliferation burst. We have reported that several malignant cancer cells including PDAC cells secrete a pronounced level of S100A11, which in turn stimulates proliferation of cancer cells via the receptor for advanced glycation end products (RAGE) in an autocrine manner. Owing to the RAGE⁺ expression in fibroblasts, the extracellular abundant S100A11 will affect adjacent fibroblasts. In this study, we investigated the significance of the paracrine axis of S100A11-RAGE in fibroblasts for their proliferation activity. In in vitro settings, extracellular S100A11 induced upregulation of fibroblast proliferation. Our mechanistic studies revealed that the induction is through RAGE-MyD88-mTOR-p70 S6 kinase upon S100A11 stimulation. The paracrine effect on fibroblasts is linked mainly to triggering growth but not cellular motility. Thus, the identified pathway might become a potential therapeutic target to suppress PDAC progression through preventing PDAC-associated fibroblast proliferation.