Bone marrow-derived progenitor cells could modulate pancreatic cancer tumorigenesis via peritumoral microenvironment in a rat model

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

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

SIGNIFICANCE

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

Key players in pancreatic cancer-stroma interaction: Cancer-associated fibroblasts, endothelial and inflammatory cells

Pancreatic cancer (PC) is the most aggressive type of common cancers, and in 2014, nearly 40000 patients died from the disease in the United States. Pancreatic ductal adenocarcinoma, which accounts for the majority of PC cases, is characterized by an intense stromal desmoplastic reaction surrounding the cancer cells. Cancer-associated fibroblasts (CAFs) are the main effector cells in the desmoplastic reaction, and pancreatic stellate cells are the most important source of CAFs. However, other important components of the PC stroma are inflammatory cells and endothelial cells. The aim of this review is to describe the complex interplay between PC cells and the cellular and non-cellular components of the tumour stroma. Published data have indicated that the desmoplastic stroma protects PC cells against chemotherapy and radiation therapy and that it might promote the proliferation and migration of PC cells. However, in animal studies, experimental depletion of the desmoplastic stroma and CAFs has led to more aggressive cancers. Hence, the precise role of the tumour stroma in PC remains to be elucidated. However, it is likely that a context-dependent therapeutic modification, rather than pure depletion, of the PC stroma holds potential for the development of new treatment strategies for PC patients.

An intensified systemic trafficking of bone marrow-derived stem/progenitor cells in patients with pancreatic cancer

Various experimental studies indicate potential involvement of bone marrow (BM)-derived stem cells (SCs) in malignancy development and progression. In this study, we comprehensively analysed systemic trafficking of various populations of BM-derived SCs (BMSCs), i.e., mesenchymal, haematopoietic, endothelial stem/progenitor cells (MSCs, HSCs, EPCs respectively), and of recently discovered population of very small embryonic/epiblast-like SCs (VSELs) in pancreatic cancer patients. Circulating CD133⁺/Lin⁻/CD45⁻/CD34⁺ cells enriched for HSCs, CD105⁺/STRO-1⁺/CD45⁻ cells enriched for MSCs, CD34⁺/KDR⁺/CD31⁺/CD45⁻ cells enriched for EPCs and small CXCR4⁺CD34⁺CD133⁺ subsets of Lin⁻CD45⁻ cells that correspond to VSELs were enumerated and sorted from blood samples derived from 29 patients with pancreatic cancer, and 19 healthy controls. In addition, plasma levels of stromal-derived factor-1 (SDF-1), growth/inhibitory factors and sphingosine-1-phosphate (S1P; chemoattractants for SCs), as well as, of complement cascade (CC) molecules (C3a, C5a and C5b-9/membrane attack complex – MAC) were measured. Higher numbers of circulating VSELs and MSCs were detected in pancreatic cancer patients (P < 0.05 and 0.01 respectively). This trafficking of BMSCs was associated with significantly elevated C5a (P < 0.05) and C5b-9/MAC (P < 0.005) levels together with S1P concentrations detected in plasma of cancer patients, and seemed to be executed in a SDF-1 independent manner. In conclusion, we demonstrated that in patients with pancreatic cancer, intensified peripheral trafficking of selected populations of BMSCs occurs. This phenomenon seems to correlate with systemic activation of the CC, hepatocyte growth factor and S1P levels. In contrast to previous studies, we demonstrate herein that systemic SDF-1 levels do not seem to be linked with increased mobilization of stem cells in patients with pancreatic cancer.

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.

Mesenchymal Stem Cells Restore Lung Function by Recruiting Resident and Nonresident Proteins

Because human lungs are unlikely to repair or regenerate beyond the cellular level, cell therapy has not previously been considered for chronic irreversible obstructive lung diseases. To explore whether cell therapy can restore lung function, we administered allogenic intratracheal mesenchymal stem cells (MSCs) in the trachea of rats with chronic thromboembolic pulmonary hypertension (CTEPH), a disease characterized by single or recurrent pulmonary thromboembolic obliteration and progressive pulmonary vascular remodeling. MSCs were retrieved only in high pressure-exposed lungs recruited via a homing stromal derived factor-1α/ CXCR4 pathway. After MSC administration, a marked and long-lasting improvement of all clinical parameters and a significant change of the proteome level were detected. Beside a variation of liver proteome, such as caspase-3, NF-κB, collagen1A1, and α-SMA, we also identified more than 300 resident and nonresident lung proteins [e.g., myosin light chain 3 (P16409) or mitochondrial ATP synthase subunit alpha (P15999)]. These results suggest that cell therapy restores lung function and the therapeutic effects of MSCs may be related to protein-based tissue reconstituting effects.

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.

Interaction of stellate cells with pancreatic carcinoma cells

Pancreatic cancer is characterized by its late detection, aggressive growth, intense infiltration into adjacent tissue, early metastasis, resistance to chemo- and radiotherapy and a strong “desmoplastic reaction”. The dense stroma surrounding carcinoma cells is composed of fibroblasts, activated stellate cells (myofibroblast-like cells), various inflammatory cells, proliferating vascular structures, collagens and fibronectin. In particular the cellular components of the stroma produce the tumor microenvironment, which plays a critical role in tumor growth, invasion, spreading, metastasis, angiogenesis, inhibition of anoikis, and chemoresistance. Fibroblasts, myofibroblasts and activated stellate cells produce the extracellular matrix components and are thought to interact actively with tumor cells, thereby promoting cancer progression. In this review, we discuss our current understanding of the role of pancreatic stellate cells (PSC) in the desmoplastic response of pancreas cancer and the effects of PSC on tumor progression, metastasis and drug resistance. Finally we present some novel ideas for tumor therapy by interfering with the cancer cell-host interaction.