Stem cell plasticity and tumour formation

Mesenchymal stem cell transplantation improves chronic colitis-associated complications through inhibiting the activity of toll-like receptor-4 in mice

BACKGROUND

A variety of extra-intestinal manifestations (EIMs), including hepatobiliary complications, are associated with inflammatory bowel disease (IBD). Mesenchymal stem cells (MSCs) have been shown to play a potential role in the therapy of IBD. This study was designed to investigate the effect and mechanism of MSCs on chronic colitis-associated hepatobiliary complications using mouse chronic colitis models induced by dextran sulfate sodium (DSS).

METHODS

DSS-induced mouse chronic colitis models were established and treated with MSCs. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW), colon length and histopathology. Serum lipopolysaccharide (LPS) levels were detected by limulus amebocyte lysate test (LAL-test). Histology and liver function of the mice were checked correspondingly. Serum LPS levels and bacterial translocation of mesenteric lymph nodes (MLN) were detected. Pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-17A (IL-17A), Toll receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6) and nuclear factor kappa B (NF-κB) were detected by immunohistochemical staining, western blot analysis and real-time PCR, respectively.

RESULTS

The DSS-induced chronic colitis model was characterized by reduced BW, high DAI, worsened histologic inflammation, and high levels of LPS and E. coli. Liver histopathological lesions, impaired liver function, enhanced proteins and mRNA levels of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB were observed after DSS administration. MSCs transplantation markedly ameliorated the pathology of colon and liver by reduction of LPS levels and proteins and mRNA expressions of TNF-α, IFN-γ, IL-1β, IL-17A, TLR4, TRAF6 and NF-κB.

CONCLUSIONS

MSCs can improve chronic colitis-associated hepatobiliary complications, probably by inhibition of enterogenous endotoxemia and hepatic inflammation through LPS/TLR4 pathway. MSCs may represent a novel therapeutic approach for chronic colitis-associated hepatobiliary complications.

Contribution of bone marrow derived cells to the pancreatic tumor microenvironment

Pancreatic cancer is a complex, aggressive, and heterogeneous malignancy driven by the multifaceted interactions within the tumor microenvironment. While it is known that the tumor microenvironment accommodates many cell types, each playing a key role in tumorigenesis, the major source of these stromal cells is not well-understood. This review examines the contribution of bone marrow-derived cells (BMDC) to pancreatic carcinogenesis, with respect to their role in constituting the tumor microenvironment. In particular, their role in supporting fibrosis, immunosuppression, and neovascularization will be discussed.

Recruitment and activation of pancreatic stellate cells from the bone marrow in pancreatic cancer: a model of tumor-host interaction

BACKGROUND AND AIMS

Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas.

METHODS

Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation.

RESULTS

GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3.

CONCLUSIONS

This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis.

Expression analysis of putative stem cell markers in human benign and malignant prostate

BACKGROUND

Stem cells were suggested to be present in human prostate cancer as a small population of distinct cells, which may contribute to carcinogenesis, tumor recurrence, and chemoresistance. To identify potential prostatic stem cells, we analyzed the expression of several potential stem cell markers in benign prostate and prostatic adenocarcinoma.

METHODS

CD44, CD133, Oct4, SOX2, and EZH2 expression was detected by immunohistochemical (IHC) staining using tissue microarray assays (TMA) composed of benign (non-neoplastic) prostatic tissue, high grade prostatic intraepithelial neoplasia (HGPIN), and prostatic adenocarcinoma. Positive staining was defined as 1+ (<10%), 2+ (10-50%), or 3+ (>50%).

RESULTS

We found CD44 staining in 97% and 72% of benign + HGPIN and malignant lesions, respectively. CD133 staining was detected in a small fraction (4 of 67) of prostate carcinomas. We found that Oct4 nuclear expression was strongly associated with benign lesions and HGPIN but not prostate cancer (P < 0.05). In most cases, nuclear expression of EZH2 and SOX2 was detected in less than 10% of cells in non-neoplastic prostate glands, HGPINs or prostate adenocarcinomas. Moreover, 27 of 33 SOX2 1+ prostate cancers were also EZH2 1+, whereas all 33 of these cases were CD44+.

CONCLUSIONS

Expression of CD44 and Oct4 identified large populations of benign and malignant cells in the prostate, which did not fit the definition of stem cells as a small fraction of the total cell population. Our results suggest that combined expression of embryonic stem cell markers EZH2 and SOX2 might identify potential cancer stem cells as a minor (<10%) subgroup in CD44+ prostatic adenocarcinoma.

Bone marrow contributes to the population of pancreatic stellate cells in mice

Activated pancreatic stellate cells (PSCs) play a pivotal role in the development of pancreatic fibrosis. The origin of activated PSCs has been thought to be transformation of quiescent PSCs residing locally in the pancreas. Recent studies have suggested that bone marrow (BM)-derived cells participate in regeneration processes in various organs. This study aimed to clarify the contribution of BM-derived cells to the population of PSCs in mice. We transplanted BM cells from male enhanced green fluorescent protein transgenic mice into female C57BL/6 mice after lethal irradiation. Eight weeks after BM transplantation, chronic pancreatitis was induced by administration of six intra-abdominal injections of cerulein (50 microg/kg body wt) at 1-h intervals, 3 days per week, for the total of 6 wk. BM-derived cells were tracked by green fluorescent protein expression and in situ hybridization for the Y-chromosome. Eight weeks after BM transplantation, BM-derived cells accounted for 8.7% of the desmin (a marker of PSCs)-positive cells in the pancreas. We could isolate BM-derived cells, which contained lipid droplets and expressed desmin. They could be transformed to myofibroblast-like cells by culture in vitro, further supporting that BM contributed to the population of quiescent PSCs. After induction of pancreatic fibrosis, BM-derived cells accounted for 20.2% of alpha-smooth muscle actin-positive activated PSCs. The contribution of BM-derived cells to pancreatic ductal cells (positive for cytokeratin-19) was rare and less than 1%. In conclusion, our results suggested that BM-derived cells contributed to the population of PSCs in mice.

Bone marrow mesenchymal stem cells reduce intestinal ischemia/reperfusion injuries in rats

BACKGROUND

Adult stem cells are promising novel therapies in regenerative medicine. We investigated effects of bone marrow-derived mesenchymal stem cells (MSCs) on intestinal mucosal permeability impaired by ischemia/reperfusion (I/R).

METHODS

We used a common I/R model in rats to induce intestinal injury by clamping and unclamping the superior mesenteric artery (SMA) in female Sprague-Dawley rats. MSCs were directly injected into the small intestinal submucosa of the syngenic female rats. Control group were injected with the same volume of 0.9% sodium chloride. Small intestine samples were examined for the engraftment of donor-derived mesenchymal stem cells (MSCs) by Y chromosome in situ hybridization analysis. The small intestinal permeability and histomorphologic alternations were measured to evaluate the therapeutic effect of MSCs transplantation.

RESULTS

Small intestinal permeability and villi injuries were significantly reduced in the MSCs administrated group compared with control group. MSCs administration accelerated the recovery of the intestinal barrier dysfunction.

CONCLUSION

We concluded that submucosal infusion of MSCs might exert protective effects on the integrity of intestinal barrier.

Bone marrow-derived cells and epithelial tumours: more than just an inflammatory relationship

PURPOSE OF REVIEW

Cancer-associated fibroblasts/myofibroblasts and inflammatory cells produce a vast array of growth factors, chemokines and extracellular matrix (ECM) components that facilitate cancer progression, invasion/metastasis and neovascularization. This review highlights some surprisingly novel mechanisms of this paracrine relationship.

RECENT FINDINGS

Mesenchymal stem/stromal cells (MSCs) are known for their tropism towards certain tumours, but now we find that cross-talk between tumours and MSCs leads to greater tumour motility and metastasis. Two closely related populations of immature myeloid cells, so-called 'cap cells' and myeloid-derived suppressor cells (MDSCs) also cross-talk with tumour cells, promoting invasion and metastasis through matrix metalloproteinase (MMP) secretion, as well as contributing to neovascularization and T-cell tolerance. The contribution of bone marrow-derived cells (BMDCs) to tumour neovascularization is controversial, but BMD--endothelial progenitor cells (EPCs)--are strongly implicated in the angiogenic switch in a mouse model. BMDCs are also credited with the creation of premetastatic niches to which metastatic cells adhere via integrins.

SUMMARY

There is no doubt that BMDCs are not simply bystanders in the tumour battleground. The mechanisms through which they aid tumour progression are numerous; effective treatments that combat BMDC-tumour cross-talk are surely on the way.

"Cancer stem cells"-lessons from Hercules to fight the Hydra

Following the initial identification of hematopoietic tumor stem cells, such cells were also found in several solid tumor types. In urology, cancer stem cells have only been found in prostate tumors so far. The concept and detection of tumor stem cells rely heavily on findings derived from stem cell research. Therefore, in addition to identifying and characterizing urologic tumor stem cells, research in uro-oncology should also aim at better understanding the stem-cell biology of urologic organs. Insights in similarities and differences gleaned from these studies could be used to develop strategies for targeted destruction of tumor stem cells while sparing the physiological stem cells. The main target of future curative therapies in uro-oncology must therefore be the central, immortal head of the Hydra, the tumor stem cell.

Effects of transplanted bone marrow mesenchymal stem cells on the irradiated intestine of mice

We investigated the potency of exogenous bone marrow mesenchymal stem cells (MSCs) to engraft into irradiated intestine, as well as these cells' effects on radiation-induced enteric injury. MSCs from beta-Gal-transgenic mice were transplanted into C57BL/6J recipient mice that received abdominal irradiation (13 Gy). At different time points, recipient intestines were examined for the engraftment of donor-derived cells by immunofluorescence analysis. Additionally, the expression status of chemokines induced by radiation injury was analyzed in the irradiated intestine. Next, MSCs were transduced with an adenoviral vector encoding a certain chemokine receptor gene in order to promote the engraftment rate via chemotaxis. The intestinal permeability and histomorphological alterations were measured to evaluate the therapeutic effect of MSC transplantation. The results demonstrated that infused MSCs possessed the potency to engraft into irradiated enteric mucosa, but the engraftment rate was too low to produce a therapeutic effect. The expression of stromal cell-derived factor-1 (SDF-1) was up-regulated in irradiated intestine. MSCs genetically modified by CXCR4 (the receptor for SDF-1) engrafted into irradiated intestine at a significantly elevated level and ameliorated the intestinal permeability and histopathological damage.

Plasticity after allogeneic hematopoietic stem cell transplantation

The postulated almost unlimited potential of transplanted hematopoietic stem cells (HSCs) to transdifferentiate into cell types that do not belong to the hematopoietic system denotes a complete paradigm shift of the hierarchical hemopoietic tree. In several studies during the last few years, donor cells have been identified in almost all recipient tissues after allogeneic HSC transplantation (HSCT), supporting the theory that any failing organ could be accessible to regenerative cell therapy. However, the putative potential ability of the stem cells to cross beyond lineage barriers has been questioned by other studies which suggest that hematopoietic cells might fuse with non-hematopoietic cells and mimic the appearance of transdifferentiation. Proof that HSCs have preserved the capacity to transdifferentiate into other cell types remains to be demonstrated. In this review, we focus mainly on clinical studies addressing plasticity in humans who underwent allogeneic HSCT. We summarize the published data on non-hematopoietic chimerism, donor cell contribution to tissue repair, the controversies related to the methods used to detect donor-derived non-hematopoietic cells and the functional impact of this phenomenon in diverse specific target tissues and organs.

Fusion of tumour cells with bone marrow-derived cells: a unifying explanation for metastasis

The causes of metastasis remain elusive despite vast information on cancer cells. We posit that cancer cell fusion with macrophages or other migratory bone marrow-derived cells (BMDCs) provides an explanation. BMDC-tumour hybrids have been detected in numerous animal models and recently in human cancer. Molecular studies indicate that gene expression in such hybrids reflects a metastatic phenotype. Should BMDC-tumour fusion be found to underlie invasion and metastasis in human cancer, new approaches for therapy would surely follow.

Defining the steps that lead to cancer: replicative telomere erosion, aneuploidy and an epigenetic maturation arrest of tissue stem cells

Recently, an influential sequencing study found that more than 1700 genes had non-silent mutations in either a breast or colorectal cancer, out of just 11 breast and 11 colorectal tumor samples. This is not surprising given the fact that genomic instability is the hallmark of cancer cells. The plethora of genomic alterations found in every carcinoma does not obey the 'law of genotype-phenotype correlation', since the same histological subtype of cancer harbors different gene mutations and chromosomal aberrations in every patient. In an attempt to make sense out of the observed genetic and chromosomal chaos in cancer, I propose a cascade model. According to this model, tissue regeneration depends on the proliferation and serial activation of stem cells. Replicative telomere erosion limits the proliferative life span of adult stem cells and results in the Hayflick limit (M1). However, local tissue exhaustion or old age might promote the activation of M1-deficient tissue stem cells. Extended proliferation of these cells leads to telomere-driven chromosomal instability and aneuploidy (abnormal balance of chromosomes and/or chromosome material). Several of the aforementioned steps have been already described in the literature. However, in contrast to common theories, it is proposed here that the genomic damage blocks the epigenetic differentiation switch. As a result of aneuploidy, differentiation-specific genes cannot be activated by modification of methylation patterns. Consequently, the phenotype of cancer tissue is largely determined by the epigenetic maturation arrest of tissue stem cells, which in addition enables a fraction of cancer cells to proliferate, invade and metastasize, as normal adult stem cells do. The new model combines genetic and epigenetic alterations of cancer cells in one causative cascade and offers an explanation for why identical histologic cancer types harbor a confusing variety of chromosomal and gene aberrations. The Viennese Cascade, as presented here, may end the debate on if and how 'tumor-unspecific' aneuploidy leads to cancer.

The role of bone marrow-derived cells in fibrosis

There is a growing realization that bone marrow-derived cells (BMDCs) are a potential therapy for many diseases including ischemic heart disease, arterial stenosis and osteogenesis imperfecta. On the other hand, the fact that BMDCs may also contribute to fibrosis in many solid organs as well as to fibrosis surrounding tumours suggests that BMDCs are also involved in disease progression. This review focuses on the contribution of bone marrow cells to organ and tumour fibrosis, noting the utility of BMDCs as a potential new portal through which to direct anti-tumour therapies. Conversely, bone marrow cell therapy has been claimed to reduce fibrosis in some organs, highlighting a seemingly beneficial as opposed to a detrimental effect of BMDCs on organ fibrosis.

Stem cells and cancer: a deadly mix

Stem cells and cancer are inextricably linked; the process of carcinogenesis initially affects normal stem cells or their closely related progenitors and then, at some point, neoplastic stem cells are generated that propagate and ultimately maintain the process. Many, if not all, cancers contain a minority population of self-renewing stem cells, "cancer stem cells", that are entirely responsible for sustaining the tumour and for giving rise to proliferating but progressively differentiating cells that contribute to the cellular heterogeneity typical of many solid tumours. Thus, the bulk of the tumour is often not the clinical problem, and so the identification of cancer stem cells and the factors that regulate their behaviour are likely to have an enormous bearing on the way that we treat neoplastic disease in the future. This review summarises (1) our knowledge of the origins of some cancers from normal stem cells and (2) the evidence for the existence of cancer stem cells; it also illustrates some of the stem cell renewal pathways that are frequently aberrant in cancer and that may represent druggable targets.

'Open minded' cells: how cells can change fate

It has long intrigued researchers why some but not all organisms can regenerate missing body parts. Plants are remarkable in that they can regenerate the entire organism from a small piece of tissue, or even a single cell. Epigenetic mechanisms that control chromatin organization are now known to regulate the cellular plasticity and reprogramming necessary for regeneration. Interestingly, although animals and plants have evolved different strategies and mechanisms to control developmental processes, they have maintained many similarities in the way they regulate chromatin organization. Given that plants can rapidly switch fate, we propose that an understanding of the mechanisms regulating this process in plant cells could provide a new perspective on cellular dedifferentiation in animals.