Intratumoral macrophages contribute to epithelial-mesenchymal transition in solid tumors

Microenvironment in metastasis: roadblocks and supportive niches

In many cancers, malignant cells can spread from the primary tumor through blood circulation and initiate metastasis in secondary organs. Metastatic colonization may depend not only on inherent properties of cancer cells, but also on suitable microenvironments in distant sites. Increasing evidence suggests that the nature of the microenvironment may determine the fate of disseminated cancer cells, providing either hindrance or support for cancer cell propagation. This can result in strong selective pressure where the vast majority of cancer cells, invading a secondary organ, are either eliminated or maintained in a dormant state. The ability of cancer cells to fend off or circumvent anti-metastatic signals from the stroma and the capacity to manipulate the local microenvironment towards a supporting environment, a metastatic niche, may be essential for metastatic growth. The molecular interactions between cancer cells and the stroma are still enigmatic, but recent studies are beginning to reveal their nature. Here, we discuss the interactive relationship between metastatic cancer cells and host stroma, involving selection and adaptation of metastasis-initiating cells and host tissue remodeling. Understanding the dynamic and continuously evolving cross talk between metastatic cancer cells and the stroma may be crucial when developing cancer treatments.

IL-8, a novel messenger to cross-link inflammation and tumor EMT via autocrine and paracrine pathways (Review)

The epithelial-mesenchymal transition (EMT) is a process through which epithelial cells trans-differentiate and acquire an aggressive mesenchymal phenotype. In tumor cells, EMT is a vital step of tumor progression and metastasis. Amid the increasing interest in tumor EMT, only a few studies focused on the soluble mediators secreted by tumor cells passing through this phenotypic switch. In this review, we focus on the essential role of interleukin-8 (IL-8) signaling for the acquisition and maintenance of tumor EMT via direct and indirect mechanisms. Besides the autocrine loop between IL-8 and tumor cells that have gone through EMT, IL-8 could potentiate adjacent epithelial tumor cells into a mesenchymal phenotype via a paracrine mode. Moreover, understanding the role of IL-8 in EMT will provide insight into the pathogenesis of tumor progression and may facilitate the development of an effective strategy for the prevention and treatment of metastatic cancer.

Melanoma-initiating cells exploit M2 macrophage TGFβ and arginase pathway for survival and proliferation

M2 macrophages promote tumor growth and metastasis, but their interactions with specific tumor cell populations are poorly characterized. Using a mouse model of spontaneous melanoma, we showed that CD34⁻ but not CD34⁺ tumor-initiating cells (TICs) depend on M2 macrophages for survival and proliferation. Tumor-associated macrophages (TAMs) and macrophage-conditioned media protected CD34⁻ TICs from chemotherapy in vitro. In vivo, while inhibition of CD115 suppressed the macrophage-dependent CD34⁻ TIC population, chemotherapy accelerated its development. The ability of TICs to respond to TAMs was acquired during melanoma progression and immediately preceded a surge in metastatic outgrowth. TAM-derived transforming growth factor-β (TGFβ) and polyamines produced via the Arginase pathway were critical for stimulation of TICs and synergized to promote their growth.

Regulation of epithelial-mesenchymal transition by tumor-associated macrophages in cancer

It should be urgently better understood of the mechanism that contributes cancer aggressiveness. Epithelial-mesenchymal transition (EMT) plays a fundamental role in tumor progression and metastasis formation by invasion, resistance to cell death and senescence, resistance to chemotherapy and immunotherapy, immune surveillance, immunosuppression and inflammation, confers stem cell properties. Tumor-associated macrophages (TAMs) are key orchestrators and a set of macrophages in tumor microenvironment. They are major players in the connection between inflammation and cancer. TAMs could promote proliferation, invasion and metastasis of tumor cells, stimulate tumor angiogenesis, and inhibit anti-tumor immune response mediated by T cell followed by promoting tumor progression. Recently, studies showed that TAMs played critical role in the regulation of EMT in cancer, although the underlying mechanism of TAMs-mediated acquisition of EMT has been largely unclear. This review will discuss recent advances in our understanding of the role of TAMs in the regulation of EMT during tumorigenesis and summarize the recent ongoing experimental and pre-clinical TAMs targeted studies.

Gene expression profile in the activation of subperitoneal fibroblasts reflects prognosis of patients with colon cancer

Tumors can create a heterogenetic tumor microenvironment. We recently identified the pathologically unique cancer microenvironment formed by peritoneal invasion (CMPI), and revealed that subperitoneal fibroblasts (SPFs) within peritoneal tissue play a crucial role in tumor progression through their interaction with cancer cells. Therefore, the genes in SPFs altered by cancer stimulation may include some biologically important factors associated with patient prognosis. In this study, we aimed to identify new biomarkers using genes specifically upregulated in SPFs by cancer-cell-conditioned medium (CCCM) stimulation (SPFs CCCM response genes; SCR genes) in colon cancer (CC). We constructed two frameworks using SCR gene data: a publicly released microarray dataset, and validation cases with freshly frozen CC samples to identify genes related to short recurrence-free survival (RFS). In the first framework, we selected differentially expressed genes between the high and low SCR gene expression groups. In the second framework, genes significantly related to short RFS were selected by univariate analysis using all SCR genes, and multivariate analysis was performed to select robust genes associated with short RFS. We identified CTGF, CALD1, INHBA and TAGLN in the first framework, and PDLIM5, MAGI1, SPTBN1 and TAGLN in the second framework. Among these seven genes, high expression of three genes (CALD1, TAGLN and SPTBN1) showed a poor prognosis in our validation cases. In a public microarray dataset, SCR gene expression was associated with the expression of ECM component, EMT, and M2-macrophage associated genes, which was concordant with the pathological features of CMPI. Thus, we successfully identified new prognostic factors.

Tumor-induced myeloid deviation: when myeloid-derived suppressor cells meet tumor-associated macrophages

The generation of an inflammatory environment is favorable and often decisive for the growth of both primary tumors and metastases. Tumor cells either express membrane molecules or release tumor-derived soluble factors able to alter myelopoiesis. Tumor-reprogrammed myeloid cells not only create a tolerogenic environment by blocking T cell functions and proliferation, but also directly drive tumor growth by promoting cancer stemness, angiogenesis, stroma deposition, epithelial-to-mesenchymal transition, and metastasis formation. In this Review, we discuss the interplay between immunosuppressive and protumoral myeloid cells and detail their immune-regulatory mechanisms, the molecular pathways involved in their differentiation, as well as their potential role as prognostic and diagnostic biomarkers and prospective targets for innovative approaches to treat tumor-bearing hosts.

Macrophage-tumor cell fusions from peripheral blood of melanoma patients

Background

While the morbidity and mortality from cancer are largely attributable to its metastatic dissemination, the integral features of the cascade are not well understood. The widely accepted hypothesis is that the primary tumor microenvironment induces the epithelial-to-mesenchymal transition in cancer cells, facilitating their escape into the bloodstream, possibly accompanied by cancer stem cells. An alternative theory for metastasis involves fusion of macrophages with tumor cells (MTFs). Here we culture and characterize apparent MTFs from blood of melanoma patients.

Methods

We isolated enriched CTC populations from peripheral blood samples from melanoma patients, and cultured them. We interrogated these cultured cells for characteristic BRAF mutations, and used confocal microscopy for immunophenotyping, motility, DNA content and chromatin texture analyses, and then conducted xenograft studies using nude mice.

Findings

Morphologically, the cultured MTFs were generally large with many pseudopod extensions and lamellipodia. Ultrastructurally, the cultured MTFs appeared to be macrophages. They were rich in mitochondria and lysosomes, as well as apparent melanosomes. The cultured MTF populations were all heterogeneous with regard to DNA content, containing aneuploid and/or high-ploidy cells, and they typically showed large sheets (and/or clumps) of cytoplasmic chromatin. This cytoplasmic DNA was found within heterogeneously-sized autophagic vacuoles, which prominently contained chromatin and micronuclei. Cultured MTFs uniformly expressed pan-macrophage markers (CD14, CD68) and macrophage markers indicative of M2 polarization (CD163, CD204, CD206). They also expressed melanocyte-specific markers (ALCAM, MLANA), epithelial biomarkers (KRT, EpCAM), as well as the pro-carcinogenic cytokine MIF along with functionally related stem cell markers (CXCR4, CD44). MTF cultures from individual patients (5 of 8) contained melanoma-specific BRAF activating mutations. Chromatin texture analysis of deconvoluted images showed condensed DNA (DAPI-intense) regions similar to focal regions described in stem cell fusions. MTFs were readily apparent in vivo in all human melanomas examined, often exhibiting even higher DNA content than the cultured MTFs. When cultured MTFs were transplanted subcutaneously in nude mice, they disseminated and produced metastatic lesions at distant sites.

Conclusions and Hypothesis

Apparent MTFs are present in peripheral blood of patients with cutaneous melanomas, and they possess the ability to form metastatic lesions when transplanted into mice. We hypothesize that these MTFs arise at the periphery of primary tumors in vivo, that they readily enter the bloodstream and invade distant tissues, secreting cytokines (such as MIF) to prepare “niches” for colonization by metastasis initiating cells.

Epithelial-mesenchymal transition and drug resistance in breast cancer (Review)

Breast cancer is the leading cause of cancer death in women worldwide. Insensitivity of tumor cells to drug therapies is an essential reason arousing such high mortality. Epithelial-mesenchymal transition (EMT) is defined by the loss of epithelial characteristics and the acquisition of a mesenchymal phenotype. It is well known that EMT plays an important role in breast cancer progression. Recently, mounting evidence has demonstrated involvement of EMT in antagonizing chemotherapy in breast cancer. Here, we discuss the biological significance and clinical implications of these findings, with an emphasis on novel approaches that effectively target EMT to increase the efficacy of anticancer therapies.

Prognostic value of tumor-associated macrophages according to histologic locations and hormone receptor status in breast cancer

Tumor-associated macrophages (TAMs) are involved in tumor progression by promoting epithelial-mesenchymal transition (EMT), tumor cell invasion, migration and angiogenesis. However, in breast cancer, the clinical relevance of the TAM infiltration according to distinct histologic locations (intratumoral vs. stromal) and hormone receptor status is unclear. We investigated the significance of the levels of TAM infiltration in distinct histologic locations in invasive breast cancer. We also examined the relationship of the TAM levels with the clinicopathologic features of tumors, expression of EMT markers, and clinical outcomes. Finally, we analyzed the prognostic value of TAM levels according to hormone receptor status. High levels of infiltration of intratumoral, stromal and total TAMs were associated with high histologic grade, p53 overexpression, high Ki-67 proliferation index and negative hormone receptor status. Infiltration of TAMs was also correlated with overexpression of vimentin, smooth muscle actin and alteration of β-catenin. Overall, a high level of infiltration of intratumoral TAMs was associated with poor disease-free survival, and was found to be an independent prognostic factor. In subgroup analyses by hormone receptor status, a high level of infiltration of intratumoral TAM was an independent prognostic factor in the hormone receptor-positive subgroup, but not in the hormone-receptor negative subgroup. Our findings suggest that intratumoral TAMs play an important role in tumor progression in breast cancer, especially in the hormone receptor-positive group, and the level of TAM infiltration may be used as a prognostic factor and even a therapeutic target in breast cancer.

Immunotherapy for lung cancer: for whom the bell tolls?

Lung cancer is the leading cause of cancer-related death and accounts for approximately 30% of all cancer deaths. Despite the recent developments in personalized therapy, the prognosis in lung cancer is still very poor. Immunotherapy is now emerging as a new hope for patients with lung cancer. It is well known that standard chemotherapeutic regimens have devastating effects for the patient's immune system. Therefore, the aim of immunotherapy is to specifically enhance the immune response against the tumour. Recently, many trials addressed the role of such therapies for metastatic non-small cell lung cancer (NSCLC) treatment: ipilimumab, tremelimumab, nivolumab and pembrolizumab are immunotherapeutic agents of high relevance in this field. Anti-tumour vaccines, as well as dendritic cell-based therapies, have emerged as potent inducers of immune response against the tumour. Herein, we will review some of the most promising cancer immunotherapies, highlighting their advantages and try to understand, in an immunological perspective, the missteps associated with the current treatments for cancer.

Alternatively activated (M2) macrophages promote tumour growth and invasiveness in hepatocellular carcinoma

BACKGROUND & AIMS

The roles of alternatively activated (M2) macrophages on pro-tumour phenotypes have been well documented in many cancers except hepatocellular carcinoma (HCC). Considering their close relationship with chronic tissue injuries as well as enhanced tumour invasiveness and growth, we aimed to investigate the direct effects of M2 macrophages on HCC.

METHODS

M2 macrophages in 95 HCC clinical specimens were quantified using immunohistochemistry and quantitative PCR. The pro-tumour functions and the underlying molecular mechanisms of M2 macrophages in HCC were investigated in vivo and in an in vitro co-culture system.

RESULTS

In the clinical study, high M2-specific CD163 (hazard ratio=2.693; p=0.043) and scavenger receptor A (hazard ratio=3.563; p=0.044) levels indicated poor prognosis and correlated with increased tumour nodules and venous infiltration in HCC patients. In an orthotopic model, the liver tumour volume was increased 3.26-fold (1.27 cm3±0.36) after M2 macrophage injection compared with the control (0.39 cm3±0.05) (p=0.032). An increased rate of lung metastasis was also found in the treatment group. In vitro, co-cultivation with M2 macrophages elevated the number of HCC cells (MHCC97L) and migration events by 1.3-fold and 3.2-fold, respectively (p<0.05). Strongly induced by MHCC97L, M2 macrophage-derived CCL22 was proven to enhance tumour migration capacities and correlate with venous infiltration in HCC patients. Increased epithelial-mesenchymal transition (EMT) via Snail activation in MHCC97L was found to be promoted by M2 macrophages and CCL22.

CONCLUSIONS

M2 macrophages contribute to poor prognosis in HCC and promote tumour invasiveness through CCL22-induced EMT.

NG2 proteoglycan-dependent recruitment of tumor macrophages promotes pericyte-endothelial cell interactions required for brain tumor vascularization

Early stage growth of intracranial B16F10 tumors is reduced by 87% in myeloid-specific NG2 null (Mac-NG2ko) mice and by 77% in pericyte-specific NG2 null (PC-NG2ko) mice, demonstrating the importance of the NG2 proteoglycan in each of these stromal compartments. In both genotypes, loss of pericyte-endothelial cell interaction results in numerous structural defects in tumor blood vessels, including decreased formation of endothelial cell junctions and decreased assembly of the vascular basal lamina. All vascular deficits are larger in Mac-NG2ko mice than in PC-NG2ko mice, correlating with the greater decrease in pericyte-endothelial cell interaction in Mac-NG2ko animals. Accordingly, tumor vessels in Mac-NG2ko mice have a smaller diameter, lower degree of patency, and higher degree of leakiness than tumor vessels in PC-NG2ko mice, leading to less efficient tumor blood flow and to increased intratumoral hypoxia. While reduced pericyte interaction with endothelial cells in PC-NG2ko mice is caused by loss of NG2-dependent pericyte activation of β1 integrin signaling in endothelial cells, reduced pericyte-endothelial cell interaction in Mac-NG2ko mice is due to a 90% reduction in NG2-dependent macrophage recruitment to tumors. The absence of a macrophage-derived signal(s) in Mac-NG2ko mice results in the loss of pericyte ability to associate with endothelial cells, possibly due to reduced expression of N-cadherin by both pericytes and endothelial cells.

CD4+ T cells potently induce epithelial-mesenchymal-transition in premalignant and malignant pancreatic ductal epithelial cells-novel implications of CD4+ T cells in pancreatic cancer development

Chronic pancreatitis (CP) is a risk factor of pancreatic ductal adenocarcinoma (PDAC) and characterized by a pronounced desmoplastic reaction with CD4⁺ T cells accounting for the majority of the stromal T cell infiltrate. Epithelial-mesenchymal-transition (EMT) is a critical process for metastasis by which epithelial/carcinoma cells become enabled to disseminate probably prior to tumor formation. To investigate whether CD4⁺ T cells induce EMT in human pancreatic ductal epithelial cells, premalignant H6c7 cells were mono- or co-cultured with human CD4⁺CD25⁺CD127^-CD49d^- regulatory T cells (T-regs) or CD4⁺CD25^- T-effector cells (T-effs) being isolated by negative magnetic bead separation from blood of healthy donors. Particularly in the presence of activated T-effs, H6c7 cells acquired a spindle-shaped morphology, reduced E-cadherin expression, and elevated expression of the mesenchymal proteins vimentin, L1CAM, and ZEB-1. This was accompanied by an increased invasive behavior. Moreover, activated T-effs exerted similar effects in the PDAC cell line T3M4. Blocking of TNF-α and IL-6 being released at greater amounts into supernatants during co-cultures with activated T-effs attenuated the EMT-associated alterations in H6c7 cells. Supporting these findings, EMT-associated alterations (exemplified by reduced E-cadherin expression and enhanced expression of vimentin and L1CAM) were predominantly detected in ductal epithelium of CP tissues surrounded by a dense stroma enriched with CD4⁺ T cells. Overall this study points to a novel role of CD4⁺ T cells beyond their immune function in pancreatic tumorigenesis and underscores the view that EMT induction in pancreatic ductal epithelial cells represents an early event in PDAC development being essentially promoted by inflammatory processes.

ISG15 is a critical microenvironmental factor for pancreatic cancer stem cells

Cancer stem cells (CSC) are thought to play a major role in the development and metastatic progression of pancreatic ductal adenocarcinoma (PDAC), one of the deadliest solid tumors. Likewise, the tumor microenvironment contributes critical support in this setting, including from tumor stromal cells and tumor-associated macrophages (TAM) that contribute structural and paracrine-mediated supports, respectively. Here, we show that TAMs secrete the IFN-stimulated factor ISG15, which enhances CSC phenotypes in PDAC in vitro and in vivo. ISG15 was preferentially and highly expressed by TAM present in primary PDAC tumors resected from patients. ISG15 was secreted by macrophages in response to secretion of IFNβ by CSC, thereby reinforcing CSC self-renewal, invasive capacity, and tumorigenic potential. Overall, our work demonstrates that ISG15 is a previously unrecognized support factor for CSC in the PDAC microenvironment with a key role in pathogenesis and progression.

Tumor necrosis factor-alpha-converting enzyme activities and tumor-associated macrophages in breast cancer

The role of the tumor microenvironment especially of tumor-associated macrophages (TAMs) in the progression and metastatic spread of breast cancer is well established. TAMs have primarily a M2 (wound-healing) phenotype with minimal cytotoxic activities. The mechanisms by which tumor cells influence TAMs to display a pro-tumor phenotype are still debated although the key roles of immunomodulatory cytokines released by tumor cells, including colony-stimulating factor 1, tumor necrosis factor (TNF) and soluble TNF receptors 1/2, soluble vascular cell adhesion molecule 1, soluble interleukin 6 receptor and amphiregulin, have been demonstrated. Importantly, these factors are released through ectodomain shedding by the activities of the tumor necrosis factor-alpha-converting enzyme (TACE/ADAM17). The role of TACE activation leading to autocrine effects on tumor progression has been extensively studied. In contrast, limited information is available on the role of tumor cell TACE activities on TAMs in breast cancer. TACE inhibitors, currently in clinical trials, will certainly affect TAMs and subsequently treatment outcomes based on the substrates it releases. Furthermore, whether targeting a subset of the molecules shed by TACE, specifically those leading to TAMs with altered functions and phenotype, holds greater therapeutic promises than past clinical trials of TACE antagonists' remains to be determined. Here, the potential roles of TACE ectodomain shedding in the breast tumor microenvironment are reviewed with a focus on the release of tumor-derived immunomodulatory factors shed by TACE that directs TAM phenotypes and functions.

Tumor infiltrating lymphocytes (TIL) and prognosis in oral cavity squamous carcinoma: a preliminary study

OBJECTIVES

Tumor infiltrating lymphocytes (TILs) in the microenvironment reflect may tumor biology and predict outcome. We previously demonstrated that infiltrates of CD4, CD8, and FoxP3 positive lymphocytes were associated with HPV-status and survival in oropharyngeal cancers. To determine if TILs were of prognostic importance in oral cancer, TIL levels were evaluated retrospectively in 52 oral cancer patients treated with surgery and correlations with outcome determined.

METHODS

Complete TIL and clinical data were available for 39 patients. Levels of CD4, CD8, FoxP3 (Treg), CD68 and NK cells were assessed by immunohistochemistry in tumor cores on a tissue microarray. Associations with clinical variables, tobacco and alcohol use and histologic features were assessed using Spearman correlation coefficient and the non-parametric Kruskal-Wallis testing. Time-to-event outcomes were determined using univariate and multivariate Cox models. Median follow up was 60 months.

RESULTS

The ratio of CD4/CD8 (p=.01) and CD8 infiltrates (p=.05) were associated with tumor recurrence but not overall survival. Lower CD4 infiltrates were associated with alcohol use (p=.005) and poor tumor differentiation (p=.02). Interestingly, higher levels of CD68+ macrophages were found associated with positive nodes (p=.06) and poorer overall survival (p=.07). Overall and DSS survival were significantly shorter for patients with positive nodes, extracapsular spread, or perineural invasion.

CONCLUSION

Infiltrating immune cell levels in oral cavity cancer appear influenced by health behaviors and tumor characteristics. In contrast to oropharynx cancer, infiltrates of CD68 positive tumor associated macrophages may contribute to metastatic behavior and outcome in advanced oral cavity carcinoma.

Neurotensin, a Novel Messenger to Cross-Link Inflammation and Tumor Invasion via Epithelial-Mesenchymal Transition Pathway

Multiple cytokines and growth factors are critical for the prognosis of cancer which has been regarded as a worldwide health problem. Recently, neuropeptides, soluble factors regulating a series of functions in the central nervous system, have also been demonstrated to stimulate the proliferation and migration of tumor cells. Among these signaling peptides, the role of neurotensin (NTS) on malignancy procession has become a hot topic. The effects of NTS on tumor growth and its antiapoptosis role have already been identified. Subsequently, studies demonstrated the impact of NTS on the migration and invasion, but the molecular mechanisms involved are still unclear at present. Recently, some reports indicated that NTS could induce expression and secretion of interleukin-8 (IL-8) to promote local imflammatory response which might participate in epithelial-mesenchymal transition (EMT)-related tumor migration. In present review, we highlight the process of tumor EMT induced by NTS through stimulating IL-8 and the significance of NTS/IL-8 pathway in clinical application prospect.

miRNA expression in anaplastic thyroid carcinomas

Anaplastic thyroid carcinoma (ATC) is the most lethal form of thyroid neoplasia and represents an end stage of thyroid tumor progression. No effective treatment exists so far. In this study, we analyzed the miRNA expression profiles of 11 ATC by microarrays and their relationship with the mRNA expression profiles of the same 11 ATC samples. ATC show distinct miRNA expression profiles compared to other less aggressive thyroid tumor types. ATC show 18 commonly deregulated miRNA compared to normal thyroid tissue (17 downregulated and 1 upregulated miRNA). First, the analysis of a combined approach of the mRNA gene expression and of the bioinformatically predicted mRNA targets of the deregulated miRNA suggested a role for these regulations in the epithelial to mesenchymal transition (EMT) process in ATC. Second, the direct interaction between one of the upregulated mRNA target, the LOX gene which is an EMT key player, and a downregulated miRNA, the miR-29a, was experimentally validated by a luciferase assay in HEK cell. Third, we confirmed that the ATC tissue is composed of about 50% of tumor associated macrophages (TAM) and suggested, by taking into account our data and published data, their most likely direct or paracrine intercommunication between them and the thyroid tumor cells, amplifying the tumor aggressiveness. Finally, we demonstrated by in situ hybridization a specific thyrocyte localization of 3 of the deregulated miRNA: let-7g, miR-29a and miR-30e and we pointed out the importance of identifying the cell type localization before drawing any conclusion on the physiopathological role of a given gene.

Tumor-associated macrophages: from mechanisms to therapy

The tumor microenvironment is a complex ecology of cells that evolves with and provides support to tumor cells during the transition to malignancy. Among the innate and adaptive immune cells recruited to the tumor site, macrophages are particularly abundant and are present at all stages of tumor progression. Clinical studies and experimental mouse models indicate that these macrophages generally play a protumoral role. In the primary tumor, macrophages can stimulate angiogenesis and enhance tumor cell invasion, motility, and intravasation. During monocytes and/or metastasis, macrophages prime the premetastatic site and promote tumor cell extravasation, survival, and persistent growth. Macrophages are also immunosuppressive, preventing tumor cell attack by natural killer and T cells during tumor progression and after recovery from chemo- or immunotherapy. Therapeutic success in targeting these protumoral roles in preclinical models and in early clinical trials suggests that macrophages are attractive targets as part of combination therapy in cancer treatment.

Tumor-associated macrophages: from mechanisms to therapy

The tumor microenvironment is a complex ecology of cells that evolves with and provides support to tumor cells during the transition to malignancy. Among the innate and adaptive immune cells recruited to the tumor site, macrophages are particularly abundant and are present at all stages of tumor progression. Clinical studies and experimental mouse models indicate that these macrophages generally play a protumoral role. In the primary tumor, macrophages can stimulate angiogenesis and enhance tumor cell invasion, motility, and intravasation. During monocytes and/or metastasis, macrophages prime the premetastatic site and promote tumor cell extravasation, survival, and persistent growth. Macrophages are also immunosuppressive, preventing tumor cell attack by natural killer and T cells during tumor progression and after recovery from chemo- or immunotherapy. Therapeutic success in targeting these protumoral roles in preclinical models and in early clinical trials suggests that macrophages are attractive targets as part of combination therapy in cancer treatment.

MicroRNA-26b inhibits epithelial-mesenchymal transition in hepatocellular carcinoma by targeting USP9X

BACKGROUND

Metastasis is responsible for the rapid recurrence and poor survival of malignancies. Epithelial-mesenchymal transition (EMT) has a critical role in metastasis. Increasing evidence indicates that EMT can be regulated by microRNAs (miRNAs). The aim of this study was to investigate the role of miR-26b in modulating epithelial-mesenchymal transition (EMT) in hepatocellular carcinoma (HCC), as well as to identify its underlying mechanism of action.

METHODS

The expression level of miR-26b was assessed in multiple HCC cell lines (HepG2, MHCC97H, Hep3B, MHCC97L, HCCC9810, BEL-7402, Huh7 and QGY-7703), as well as in liver tissue from patients with HCC. Follow-up studies examined the effects of a miR-26b mimic (increased expression) and a miR-26b inhibitor (decreased expression) on markers of EMT, wound healing and cell migration. The molecular target of miR-26b was also identified using a computer algorithm and confirmed experimentally.

RESULTS

MiR-26b expression was decreased in HCC cell lines and was inversely correlated with the grade of HCC. Increased expression of miR-26b inhibited the migration and invasiveness of HCC cell lines, which was accompanied by decreased expression of the epithelial marker E-cadherin and increased expression of the mesenchymal marker vimentin, at both the mRNA and protein expression levels. A binding site for miR-26b was theoretically identified in the 3'UTR of USP9X. Further studies revealed that overexpression of miR-26b repressed the endogenous level of USP9X protein expression. Overexpression of miR-26b also repressed Smad4 expression, whereas its inhibition elevated Smad4 expression.

CONCLUSIONS

Taken together, our results indicate that miR-26b were inhibited in HCC. In HCC cell lines, miR-26b targeted the 3'UTR of USP9X, which in turn affects EMT through Smad4 and the TGF-β signaling pathway. Our analysis of clinical HCC samples verifies that miR-26b also targets USP9X expression to inhibit the EMT of hepatocytes. Thus, miR-26b may have some effects on the EMT of HCC cells.

Tumor-associated macrophages promote cancer stem cell-like properties via transforming growth factor-beta1-induced epithelial-mesenchymal transition in hepatocellular carcinoma

Tumor-associated macrophages (TAMs), a crucial component of immune cells infiltrated in tumor microenvironment, have been found to be associated with progression and metastasis of hepatocellular carcinoma (HCC). In this study, we aimed to clarify the mechanism underlying the crosstalk between TAMs and cancer stem cells (CSCs) in HCC. Mouse macrophage cell line RAW264.7 cells were used to investigate the effects of TAMs on mouse hepatoma cell line Hepa1-6 cells in vivo and vitro. A total of 90 clinical samples had pathology-proven HCC were used to evaluate the distribution of TAMs and CSCs and analyze their value in predicting the prognosis. In the study, we have found that the number of TAMs has a positive correlation with the density of CSCs in the marginal of human HCC. Our results show that, cocultured with TAM-conditioned medium (CM) promoted CSC-like properties in Hepa1-6 cells, which underwent EMT and gained higher invasive capability. TAMs secreted more transforming growth factor- beta1 (TGF-beta1) than other phenotypes of macrophage. Furthermore, depletion of TGF-beta1 blocked acquisition of CSC-like properties by inhibition of TGF-beta1-induced EMT. High expression of CD68 in the EpCAM positive expression HCC tissues was strongly associated with both poor cancer-free survival and overall survival in patients. Our results indicate that the TAMs promote CSC-like properties via TGF-beta1-induced EMT and they may contribute to investigate the prognosis of HCC.

Macrophage-targeted delivery systems for nucleic acid therapy of inflammatory diseases

Inflammation is an immune response that marks several pathophysiological conditions in our body. Though adaptive immune cells play a major role in the progression of the disease, components of innate immune system, mainly monocytes and macrophages play the central role in onset of inflammation. Tissue-associated macrophages are widely distributed in the body showing tremendous anatomical and functional diversity and are actively involved in maintaining the homeostasis. They exhibit different phenotypes depending on their residing tissue microenvironment and the two major functional phenotypes are classically activated M1 phenotype showing pro-inflammatory characteristics and alternatively activated M2 phenotype demonstrating anti-inflammatory nature. Several cytokines, chemokines and other regulatory mediators delicately govern the balance of the two phenotypes in a tissue. This balance, however, is subverted during infection, injury or autoimmune response leading to increased population of M1 phenotype and subsequent chronic inflammatory disease states. This review underlines the role of macrophages in inflammatory diseases with an insight into potential molecular targets for nucleic acid therapy. Finally, some recent nanotechnology-based approaches to devise macrophage-specific targeted therapy have been highlighted.

Consideration of the cellular microenvironment: physiologically relevant co-culture systems in drug discovery

There is renewed interest in phenotypic approaches to drug discovery, using cell-based assays to select new drugs, with the goal of improving pharmaceutical success. Assays that are more predictive of human biology can help researchers achieve this goal. Primary cells are more physiologically relevant to human biology and advances are being made in methods to expand the available cell types and improve the potential clinical translation of these assays through the use of co-cultures or three-dimensional (3D) technologies. Of particular interest are assays that may be suitable for industrial scale drug discovery. Here we review the use of primary human cells and co-cultures in drug discovery and describe the characteristics of co-culture models for inflammation biology (BioMAP systems), neo-vascularization and tumor microenvironments. Finally we briefly describe technical trends that may enable and impact the development of physiologically relevant co-culture assays in the near future.

Tumor-induced STAT3 activation in monocytic myeloid-derived suppressor cells enhances stemness and mesenchymal properties in human pancreatic cancer

Pancreatic cancer (PC) mobilizes myeloid cells from the bone marrow to the tumor where they promote tumor growth and proliferation. Cancer stem cells (CSCs) are a population of tumor cells that are responsible for tumor initiation. Aldehyde dehydrogenase-1 activity in PC identifies CSCs, and its activity has been correlated with poor overall prognosis in human PC. Myeloid cells have been shown to impact tumor stemness, but the impact of immunosuppressive tumor-infiltrating granulocytic and monocytic myeloid-derived suppressor cells (Mo-MDSC) on ALDH1^Bright CSCs and epithelial to mesenchymal transition is not well understood. In this study, we demonstrate that Mo-MDSC (CD11b⁺/Gr1⁺/Ly6G⁻/Ly6C^hi) significantly increase the frequency of ALDH1^Bright CSCs in a mouse model of PC. Additionally, there was significant upregulation of genes associated with epithelial to mesenchymal transition. We also found that human PC converts CD14⁺ peripheral blood monocytes into Mo-MDSC (CD14⁺/HLA-DR^low/−) in vitro, and this transformation is dependent on the activation of the STAT3 pathway. In turn, these Mo-MDSC increase the frequency of ALDH1^Bright CSCs and promote mesenchymal features of tumor cells. Finally, blockade of STAT3 activation reversed the increase in ALDH1^Bright CSCs. These data suggest that the PC tumor microenvironment transforms monocytes to Mo-MDSC by STAT3 activation, and these cells increase the frequency of ALDH1^Bright CSCs. Therefore, targeting STAT3 activation may be an effective therapeutic strategy in targeting CSCs in PC.

Tumor microenvironment in head and neck squamous cell carcinoma

The tumor microenvironment (TME) of head and neck squamous cell carcinoma (HNSCC) is comprised of cancer-associated fibroblasts (CAFs), immune cells, and other supporting cells. Genetic changes in the carcinoma cells, such as alterations to TP53, NOTCH1, and specific gene expression profiles, contribute to derangements in cancer and microenvironment cells such as increased ROS, overproduction of cytokines, and epithelial to mesenchymal transition (EMT). CAFs are among the most critical elements of the TME contributing to proliferation, invasion, and metastasis. The adaptive immune response is suppressed in HNSCC through overexpression of cytokines, triggered apoptosis of T cells, and alterations in antigen processing machinery. Overexpression of critical cytokines, such as transforming growth factor-β (TGF-β), contributes to EMT, immune suppression, and evolution of CAFs. Inflammation and hypoxia are driving forces in angiogenesis and altered metabolism. HNSCC utilizes glycolytic and oxidative metabolism to fuel tumorigenesis via coupled mechanisms between cancer cell regions and cells of the TME. Increased understanding of the TME in HNSCC illustrates that the long-held notion of "condemned mucosa" reflects a process that extends beyond the epithelial cells to the entire tissue comprised of each of these elements.

Tumor-associated macrophages exhibit pro- and anti-inflammatory properties by which they impact on pancreatic tumorigenesis

Pancreatic ductal adenocarcinoma (PDAC) still ranking 4th in the order of fatal tumor diseases is characterized by a profound tumor stroma with high numbers of tumor-associated macrophages (TAMs). Driven by environmental factors, monocytes differentiate into M1- or M2-macrophages, the latter commonly regarded as being protumorigenic. Because a detailed analysis of TAMs in human PDAC development is still lacking, freshly isolated PDAC-derived TAMs were analyzed for their phenotype and impact on epithelial-mesenchymal-transition (EMT) of benign (H6c7) and malignant (Colo357) pancreatic ductal epithelial cells. TAMs exhibited characteristics of M1-macrophages (expression of HLA-DR, IL-1β, or TNF-α) and M2-macrophages (expression of CD163 and IL-10). In the presence of TAMs, H6c7, and Colo357 cells showed an elongated cell shape along with an increased expression of mesenchymal markers such as vimentin and reduced expression of epithelial E-cadherin. Similar to TAMs, in vitro generated M1- and M2-macrophages both mediated EMT in H6c7 and Colo357 cells. M1-macrophages acquired M2-characteristics during coculture that could be prevented by GM-CSF treatment. However, M1-macrophages still potently induced EMT in H6c7 and Colo357 cells although lacking M2-characteristics. Overall, these data demonstrate that TAMs exhibit anti- as well as proinflammatory properties that equally contribute to EMT induction in PDAC initiation and development.

Chronic Inflammation: Synergistic Interactions of Recruiting Macrophages (TAMs) and Eosinophils (Eos) with Host Mast Cells (MCs) and Tumorigenesis in CALTs. M-CSF, Suitable Biomarker for Cancer Diagnosis!

Ongoing debates, misunderstandings and controversies on the role of inflammation in cancer have been extremely costly for taxpayers and cancer patients for over four decades. A reason for repeated failed clinical trials (90% ± 5 failure rates) is heavy investment on numerous genetic mutations (molecular false-flags) in the chaotic molecular landscape of site-specific cancers which are used for "targeted" therapies or "personalized" medicine. Recently, unresolved/chronic inflammation was defined as loss of balance between two tightly regulated and biologically opposing arms of acute inflammation ("Yin"-"Yang" or immune surveillance). Chronic inflammation could differentially erode architectural integrities in host immune-privileged or immune-responsive tissues as a common denominator in initiation and progression of nearly all age-associated neurodegenerative and autoimmune diseases and/or cancer. Analyses of data on our "accidental" discoveries in 1980s on models of acute and chronic inflammatory diseases in conjunctival-associated lymphoid tissues (CALTs) demonstrated at least three stages of interactions between resident (host) and recruited immune cells: (a), acute phase; activation of mast cells (MCs), IgE Abs, histamine and prostaglandin synthesis; (b), intermediate phase; down-regulation phenomenon, exhausted/degranulated MCs, heavy eosinophils (Eos) infiltrations into epithelia and goblet cells (GCs), tissue hypertrophy and neovascularization; and (c), chronic phase; induction of lymphoid hyperplasia, activated macrophages (Mfs), increased (irregular size) B and plasma cells, loss of integrity of lymphoid tissue capsular membrane, presence of histiocytes, follicular and germinal center formation, increased ratios of local IgG1/IgG2, epithelial thickening (growth) and/or thinning (necrosis) and angiogenesis. Results are suggestive of first evidence for direct association between inflammation and identifiable phases of immune dysfunction in the direction of tumorigenesis. Activated MFs (TAMs or M2) and Eos that are recruited by tissues (e.g., conjunctiva or perhaps lung airways) whose principal resident immune cells are MCs and lymphocytes are suggested to play crucial synergistic roles in enhancing growth promoting capacities of host toward tumorigenesis. Under oxidative stress, M-CSF may produce signals that are cumulative/synergistic with host mediators (e.g., low levels of histamine), facilitating tumor-directed expression of decoy receptors and immune suppressive factors (e.g., dTNFR, IL-5, IL-10, TGF-b, PGE2). M-CSF, possessing superior sensitivity and specificity, compared with conventional markers (e.g., CA-125, CA-19-9) is potentially a suitable biomarker for cancer diagnosis and technology development. Systematic monitoring of interactions between resident and recruited cells should provide key information not only about early events in loss of immune surveillance, but it would help making informed decisions for balancing the inherent tumoricidal (Yin) and tumorigenic (Yang) properties of immune system and effective preventive and therapeutic approaches and accurate risk assessment toward improvement of public health.

Microenvironmental regulation of tumor progression and metastasis

Cancers develop in complex tissue environments, which they depend on for sustained growth, invasion and metastasis. Unlike tumor cells, stromal cell types within the tumor microenvironment (TME) are genetically stable and thus represent an attractive therapeutic target with reduced risk of resistance and tumor recurrence. However, specifically disrupting the pro-tumorigenic TME is a challenging undertaking, as the TME has diverse capacities to induce both beneficial and adverse consequences for tumorigenesis. Furthermore, many studies have shown that the microenvironment is capable of normalizing tumor cells, suggesting that re-education of stromal cells, rather than targeted ablation per se, may be an effective strategy for treating cancer. Here we discuss the paradoxical roles of the TME during specific stages of cancer progression and metastasis, as well as recent therapeutic attempts to re-educate stromal cells within the TME to have anti-tumorigenic effects.

Positive and negative influence of the matrix architecture on antitumor immune surveillance

The migration of T cells and access to tumor antigens is of utmost importance for the induction of protective anti-tumor immunity. Once having entered a malignant site, T cells encounter a complex environment composed of non-tumor cells along with the extracellular matrix (ECM). It is now well accepted that a deregulated ECM favors tumor progression and metastasis. Recent progress in imaging technologies has also highlighted the impact of the matrix architecture found in solid tumor on immune cells and especially T cells. In this review, we argue that the ability of T cells to mount an antitumor response is dependent on the matrix structure, more precisely on the balance between pro-migratory reticular fiber networks and unfavorable migration zones composed of dense and aligned ECM structures. Thus, the matrix architecture, that has long been considered to merely provide the structural framework of connective tissues, can play a key role in facilitating or suppressing the antitumor immune surveillance. A new challenge in cancer therapy will be to develop approaches aimed at altering the architecture of the tumor stroma, rendering it more permissive to antitumor T cells.

Pushing tumor cells towards a malignant phenotype: stimuli from the microenvironment, intercellular communications and alternative roads

The tumor microenvironment produces different types of stimuli capable of endowing tumor cells with an aggressive behavior that is characterized by increased motility, invasiveness and propensity to metastasize, gain of a tumor-initiating phenotype, and drug resistance. The following classes of stimuli have been reported to promote such a malignant phenotype: (i) solid- or fluid-induced stress; (ii) altered composition of the extracellular matrix; (iii) hypoxia and low pH; (iv) innate and adaptive immune responses; (v) antitumor drugs. The simultaneous presence of more than one of these stimuli, as likely occurs in vivo, may lead to synergistic interactions in the induction of malignant traits. In many cases, the gain of a malignant phenotype is not the result of a direct effect of the stimuli on tumor cells but, rather, a stimulus-promoted cross-talk between tumor cells and other cell types within the tumor microenvironment. This cross-talk is mainly mediated by two classes of molecules: paracrine factors and adhesion receptors. Stimuli that promote a malignant phenotype can promote additional outcomes in tumor cells, including autophagy and cell death. We summarize here the available evidence about the variables that induce tumor cells to take one or the other of these roads in response to the same stimuli. At the end of this review, we address some unanswered questions in this domain and indicate future directions of research.

The epigenetics of epithelial-mesenchymal plasticity in cancer

During the course of malignant cancer progression, neoplastic cells undergo dynamic and reversible transitions between multiple phenotypic states, the extremes of which are defined by the expression of epithelial and mesenchymal phenotypes. This plasticity is enabled by underlying shifts in epigenetic regulation. A small cohort of pleiotropically acting transcription factors is widely recognized to effect these shifts by controlling the expression of a constituency of key target genes. These master regulators depend on complex epigenetic regulatory mechanisms, notably the induction of changes in the modifications of chromatin-associated histones, in order to achieve the widespread changes in gene expression observed during epithelial-mesenchymal transitions (EMTs). These associations indicate that an understanding of the functional interactions between such EMT-inducing transcription factors and the modulators of chromatin configuration will provide crucial insights into the fundamental mechanisms underlying cancer progression and may, in the longer term, generate new diagnostic and therapeutic modalities for treating high-grade malignancies.

Autocrine HBEGF expression promotes breast cancer intravasation, metastasis and macrophage-independent invasion in vivo

Increased expression of HBEGF in ER negative breast tumors is correlated with enhanced metastasis to distant organ sites and more rapid disease recurrence upon removal of the primary tumor. Our previous work has demonstrated a paracrine loop between breast cancer cells and macrophages in which the tumor cells are capable of stimulating macrophages through the secretion of CSF-1 while the tumor associated macrophages (TAMs) in turn aid in tumor cell invasion by secreting EGF. To determine how the autocrine expression of EGFR ligands by carcinoma cells would affect this paracrine loop mechanism, and in particular whether tumor cell invasion depends on spatial ligand gradients generated by TAMs, we generated cell lines with increased HBEGF expression. We find that autocrine HBEGF expression enhanced in vivo intravasation and metastasis, and resulted in a novel phenomenon in which macrophages were no longer required for in vivo invasion of breast cancer cells. In vitro studies revealed that expression of HBEGF enhanced invadopodium formation, thus providing a mechanism for cell autonomous invasion. The increased invadopodium formation was directly dependent on EGFR signaling, as demonstrated by a rapid decrease in invadopodia upon inhibition of autocrine HBEGF/EGFR signaling as well as inhibition of signaling downstream of EGFR activation. HBEGF expression also resulted in enhanced invadopodium function via upregulation of MMP2 and MMP9 expression. We conclude that high levels of HBEGF expression can short-circuit the tumor cell/macrophage paracrine invasion loop, resulting in enhanced tumor invasion that is independent of macrophage signaling.

Strategies to increase drug penetration in solid tumors

Despite significant improvement in modalities for treatment of cancer that led to a longer survival period, the death rate of patients with solid tumors has not changed during the last decades. Emerging studies have identified several physical barriers that limit the therapeutic efficacy of cancer therapeutic agents such as monoclonal antibodies, chemotherapeutic agents, anti-tumor immune cells, and gene therapeutics. Most solid tumors are of epithelial origin and, although malignant cells are de-differentiated, they maintain intercellular junctions, a key feature of epithelial cells, both in the primary tumor as well as in metastatic lesions. Furthermore, nests of malignant epithelial tumor cells are shielded by layers of extracellular matrix (ECM) proteins (e.g., collagen, elastin, fibronectin, laminin) whereby tumor vasculature rarely penetrates into the tumor nests. In this chapter, we will review potential strategies to modulate the ECM and epithelial junctions to enhance the intratumoral diffusion and/or to remove physical masking of target receptors on malignant cells. We will focus on peptides that bind to the junction protein desmoglein 2 and trigger intracellular signaling, resulting in the transient opening of intercellular junctions. Intravenous injection of these junction openers increased the efficacy and safety of therapies with monoclonal antibodies, chemotherapeutics, and T cells in mouse tumor models and was safe in non-human primates. Furthermore, we will summarize approaches to transiently degrade ECM proteins or downregulate their expression. Among these approaches is the intratumoral expression of relaxin or decorin after adenovirus- or stem cell-mediated gene transfer. We will provide examples that relaxin-based approaches increase the anti-tumor efficacy of oncolytic viruses, monoclonal antibodies, and T cells.

[Epithelial-mesenchymal transition in non-small cell lung cancer]

Non-small cell lung carcinoma (NSCLC) is a highly fibrotic malignancy, which exhibits a prominent desmoplastic stroma. Epithelial-mesenchymal transition (EMT) is one of the main modes of carcinoma invasion. We identified the stromal N-glycoprotein periostin by mass spectrometry of lung adenocarcinoma pleural effusions. Validation on a NSCLC tissue microarray and on tumor whole sections by immunohistochemistry indicated that periostin is strongly upregulated at the invasive front in both tumor epithelia and the surrounding matricellular space. In comparison to collagen, elastin and vimentin, periostin was found to be most closely associated with parameters of tumor progression such as larger size and higher stage, with the squamous cell histotype, and with decreased survival. An association with decreased survival was also found for the cell adhesion molecule L1CAM. In conclusion, enlargement of NSCLC tumors is associated with an increase of desmoplastic stroma and concomitant upregulation of EMT markers at the invasive front. The tumor-stroma interface may be a candidate topographic region for stroma- or EMT-directed therapy.

Osteopontin up-regulates critical epithelial-mesenchymal transition transcription factors to induce an aggressive breast cancer phenotype

BACKGROUND

Tumor cells undergoing epithelial-mesenchymal transition (EMT) develop cellular properties leading to stroma invasion and intravasation. We have previously shown in a xenograft breast cancer model that blocking osteopontin (OPN), a secreted phosphoprotein, decreases EMT. This study examines OPN's role in EMT initiation through its regulation of EMT transcription factors (TFs) Snail, Slug, and Twist. OPN's role in Twist activation is examined through immunoprecipitation and Western blot.

STUDY DESIGN

MDA-MB-231 breast cancer cells secreting high levels of OPN were treated with OPN aptamer (APT) or mutant APT. Osteopontin APT binds to and inhibits extracellular OPN. Low-OPN-secreting breast cancer cells, MCF-7, were treated with OPN, OPN+APT, or OPN+mutant APT. Twist was isolated in MDA-MB-231 with immunoprecipitation. Phospho-serine antibody detected activated Twist in Western blot. Activation of Twist was confirmed by chromatin immunoprecipitation.

RESULTS

Analysis through quantitative polymerase chain reaction demonstrated APT inhibition of OPN in MDA-MB-231 cells caused a decrease in EMT-TF expression (MDA-MB-231 vs MDA-MB-231+APT: *Twist ΔΔCT: 1.0 vs 0.07; *Snail ΔΔCT: 1.0 vs 0.11; *Slug ΔΔCT: 1.0 vs 0.11; *p < 0.001). Mutant APT did not change EMT-TF expression (NS). Treatment of MCF-7 cells with OPN caused an increase in EMT-TF expression (MCF-7 vs MCF-7+OPN: Twist ΔΔCT: 1.0 vs 9.1; *Snail ΔΔCT: 1.0 vs 11.2; *Slug ΔΔCT: 1.0 vs 10.9; *p < 0.001). The EMT-TF expression in MCF-7 treated with OPN+APT did not differ significantly from MCF-7 alone. Phosphorylated Twist protein was reduced 2-fold with APT in MDA-MB-231 compared with MDA-MB-231 and MDA-MB-231+mutant APT. Twist phorphorylation induced binding to the promoter regions of Twist-regulated gene, B lymphoma Mo-MLV insertion region 1 homolog, a critical protein for EMT progression.

CONCLUSIONS

This study shows that OPN is critical in EMT initiation through activation of Twist via serine phosphorylation. These unique observations indicate that OPN APT can serve a clinical role as a novel therapeutic agent by diminishing breast cancer oncogenesis.

Nichotherapy for stem cells: there goes the neighborhood

Stem cells and their malignant counterparts require the support of a specific microenvironment or "niche". While various anti-cancer therapies have been broadly successful, there are growing opportunities to target the environment in which these cells reside to further improve therapeutic efficacy and outcome. This is particularly true when the aim is to target normal or malignant stem cells. The field aiming to target or use the niches that harbor, protect, and support stem cells could be designated as "nichotherapy". In this essay, we provide a few examples of nichotherapies. Some have been employed for decades, such as hematopoietic stem cell mobilization, whereas others are emerging, such as chemosensitization of leukemia stem cells by targeting their niche.

Epithelial mesenchymal transition in drug resistance and metastasis of lung cancer

Among all types of cancer, incidence of lung cancer remains the highest with regard to cancer-related mortality. Problems contributing to recurrence of the disease include metastasis and drug resistance. Mounting evidence has demonstrated involvement of epithelial mesenchymal transition (EMT) in cancer progression. EMT is a critical mechanism ensuring tissue remodeling during morphogenesis of multicellular organisms. Therefore, understanding of the biology of this process for identification of potential EMT-targeted therapeutic strategies for the benefit cancer patients is necessary. This review describes recent evidence of EMT involvement in drug resistance and metastasis of cancers, with an emphasis on lung cancer.

Microenvironmental regulation of epithelial-mesenchymal transitions in cancer

The evolution of the cancer cell into a metastatic entity is the major cause of death in patients with cancer. Activation of the epithelial-to-mesenchymal transition (EMT) endows invasive and metastatic properties upon cancer cells that favor successful colonization of distal target organs. The observation that in many cancers distant metastases resemble the epithelial phenotype of primary tumors has led to speculation that the disseminated tumor cells recruited to the target organs undergo mesenchymal-to-epithelial transition (MET). However, the MET cascade has not been recapitulated in vivo, and the cellular and molecular regulators that promote MET remain unknown. In a recent report, using a model of spontaneous breast cancer, we have shown that bone marrow-derived myeloid progenitor cells in the premetastatic lung secrete the proteoglycan versican, which induces MET of metastatic tumor cells and accelerates metastases. This review summarizes recent progress in MET research, outlines a unique paracrine cross-talk between the microenvironment and the cancer cells, which promotes tumor outgrowth in the metastatic organ, and discusses opportunities for novel antimetastatic approaches for cancer therapy.

Immune microenvironment in tumor progression: characteristics and challenges for therapy

The tumor microenvironment plays a critical role in cancer development, progression, and control. The molecular and cellular nature of the tumor immune microenvironment influences disease outcome by altering the balance of suppressive versus cytotoxic responses in the vicinity of the tumor. Recent developments in systems biology have improved our understanding of the complex interactions between tumors and their immunological microenvironment in various human cancers. Effective tumor surveillance by the host immune system protects against disease, but chronic inflammation and tumor “immunoediting” have also been implicated in disease development and progression. Accordingly, reactivation and maintenance of appropriate antitumor responses within the tumor microenvironment correlate with a good prognosis in cancer patients. Improved understanding of the factors that shape the tumor microenvironment will be critical for the development of effective future strategies for disease management. The manipulation of these microenvironmental factors is already emerging as a promising tool for novel cancer treatments. In this paper, we summarize the various roles of the tumor microenvironment in cancer, focusing on immunological mediators of tumor progression and control, as well as the significant challenges for future therapies.

TGF-β-induced epithelial-mesenchymal transition: a link between cancer and inflammation

Metastatic spread of tumor cells to vital organs is the major cause of death in cancer. Accumulating data support an important role of infiltrating immune cells in promoting carcinoma progression into metastatic disease. Tumor-infiltrating immune cells produce and secrete cytokines, growth factors and proteases that re-activate latent developmental processes including epithelial-mesenchymal transition (EMT). EMT provides tumor cells with invasive, migratory and stem cell properties allowing them to disseminate and propagate at distant sites. Induction of EMT requires two criteria to be fulfilled: (i) cells are competent to undergo EMT (ii) an EMT-permissive microenvironment exists. The cytokine TGF-β, which is expressed by tumor-infiltrating immune cells, stands out as a master regulator of the pro-invasive tumor microenvironment. TGF-β cooperates with stem cell pathways, such as Wnt and Ras signaling, to induce EMT. In addition, TGF-β contributes to an EMT-permissive microenvironment by switching the phenotypes of tumor-infiltrating immune cells, which thereby mount pro-invasive and pro-metastatic immune responses. In this review, we discuss the role of TGF-β-induced EMT as a link between cancer and inflammation in the context of questions, which from our point of view are key to answer in order to understand the functionality of EMT in tumors.

Selection of Mesenchymal-Like Metastatic Cells in Primary Tumors - An in silico Investigation

In order to metastasize, cancer cells must undergo phenotypic transition from an anchorage-dependent form to a motile form via a process referred to as epithelial to mesenchymal transition. It is currently unclear whether metastatic cells emerge late during tumor progression by successive accumulation of mutations, or whether they derive from distinct cell populations already present during the early stages of tumorigenesis. Similarly, the selective pressures that drive metastasis are poorly understood. Selection of cancer cells with increased proliferative capacity and enhanced survival characteristics may explain how some transformations promote a metastatic phenotype. However, it is difficult to explain how cancer cells that disseminate can emerge due to such selective pressure, since these cells usually remain dormant for prolonged periods of time. In the current study, we have used in silico modeling and simulation to investigate the hypothesis that mesenchymal-like cancer cells evolve during the early stages of primary tumor development, and that these cells exhibit survival and proliferative advantages within the tumor microenvironment. In an agent-based tumor microenvironment model, cancer cell agents with distinct sets of attributes governing nutrient consumption, proliferation, apoptosis, random motility, and cell adhesion were allowed to compete for space and nutrients. These simulation data indicated that mesenchymal-like cancer cells displaying high motility and low adhesion proliferate more rapidly and display a survival advantage over epithelial-like cancer cells. Furthermore, the presence of mesenchymal-like cells within the primary tumor influences the macroscopic properties, emergent morphology, and growth rate of tumors.

Isolation and characterization of Pseudomonas aeruginosa PAO mutant that produces altered elastase

Triple-negative breast cancer (TNBC) is cancer that tested as negative for estrogen receptors (ER), progesterone receptors (PR), and excess human epidermal growth factor receptor 2 (HER2) protein which accounts for 15%–20% of all breast cancer cases. TNBC is considered to be a poorer prognosis than other types of breast cancer, mainly because it involves more aggressive phenotypes that are similar to stem cell–like cancer cells (cancer stem cell, CSC). Thus, targeted treatment of TNBC remains a major challenge in clinical practice. This review article surveys the latest evidence concerning the role of genomic alteration in current TNBC treatment responses, current clinical trials and potential targeting sites, CSC and drug resistance, and potential strategies targeting CSCs in TNBC. Furthermore, the role of insulin-like growth factor 1 receptor (IGF-1R) and nicotinic acetylcholine receptors (nAChR) in stemness expression, chemoresistance, and metastasis in TNBC and their relevance to potential treatments are also discussed and highlighted.