Cancer evolution is predominantly studied by focusing on differences in the genetic characteristics of malignant cells within tumors. However, the spatiotemporal dynamics of clonal outgrowth that ...underlie evolutionary trajectories remain largely unresolved. Here, we sought to unravel the clonal dynamics of colorectal cancer (CRC) expansion in space and time by using a color-based clonal tracing method. This method involves lentiviral red-green-blue (RGB) marking of cell populations, which enabled us to track individual cells and their clonal outgrowth during tumor initiation and growth in a xenograft model. We found that clonal expansion largely depends on the location of a clone, as small clones reside in the center and large clones mostly drive tumor growth at the border. These dynamics are recapitulated in a computational model, which confirms that the clone position within a tumor rather than cell-intrinsic features, is crucial for clonal outgrowth. We also found that no significant clonal loss occurs during tumor growth and clonal dispersal is limited in most models. Our results imply that, in addition to molecular features of clones such as (epi-)genetic differences between cells, clone location and the geometry of tumor growth are crucial for clonal expansion. Our findings suggest that either microenvironmental signals on the tumor border or differences in physical properties within the tumor, are major contributors to explain heterogeneous clonal expansion. Thus, this study provides further insights into the dynamics of solid tumor growth and progression, as well as the origins of tumor cell heterogeneity in a relevant model system.
Solid malignancies have been speculated to depend on cancer stem cells (CSCs) for expansion and relapse after therapy. Here we report on quantitative analyses of lineage tracing data from primary ...colon cancer xenograft tissue to assess CSC functionality in a human solid malignancy. The temporally obtained clone size distribution data support a model in which stem cell function in established cancers is not intrinsically, but is entirely spatiotemporally orchestrated. Functional stem cells that drive tumour expansion predominantly reside at the tumour edge, close to cancer-associated fibroblasts. Hence, stem cell properties change in time depending on the cell location. Furthermore, although chemotherapy enriches for cells with a CSC phenotype, in this context functional stem cell properties are also fully defined by the microenvironment. To conclude, we identified osteopontin as a key cancer-associated fibroblast-produced factor that drives in situ clonogenicity in colon cancer.
The tissue dynamics that govern maintenance and regeneration of the pancreas remain largely unknown. In particular, the presence and nature of a cellular hierarchy remains a topic of debate. Previous ...lineage tracing strategies in the pancreas relied on specific marker genes for clonal labeling, which left other populations untested and failed to account for potential widespread phenotypical plasticity. Here we employed a tracing system that depends on replication-induced clonal marks. We found that, in homeostasis, steady acinar replacement events characterize tissue dynamics, to which all acinar cells have an equal ability to contribute. Similarly, regeneration following pancreatitis was best characterized by an acinar self-replication model because no evidence of a cellular hierarchy was detected. In particular, rapid regeneration in the pancreas was found to be driven by an accelerated rate of acinar fission-like events. These results provide a comprehensive and quantitative model of cell dynamics in the exocrine pancreas.
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•All acinar cells have an equal probability to contribute to tissue renewal•All acinar cells function as bona fide progenitor cells during homeostasis•Acinar fission-like events underlie pancreas regeneration
The dynamics of tissue maintenance in the adult exocrine pancreas are largely unknown. In this study, Lodestijn et al. use a combination of experimental and computational methods to reveal that there is no hierarchy in the adult exocrine pancreas and that all cells can act as bona fide progenitors.
Effective treatments for pancreatic ductal adenocarcinoma (PDAC) are lacking, and targeted agents have demonstrated limited efficacy. It has been speculated that a rare population of cancer stem ...cells (CSCs) drives growth, therapy resistance, and rapid metastatic progression in PDAC. These CSCs demonstrate high clonogenicity in vitro and tumorigenic potential in vivo. However, their relevance in established PDAC tissue has not been determined. Here, we use marker-independent stochastic clonal labeling, combined with quantitative modeling of tumor expansion, to uncover PDAC tissue growth dynamics. We find that in contrast to the CSC model, all PDAC cells display clonogenic potential in situ. Furthermore, the proximity to activated cancer-associated fibroblasts determines tumor cell clonogenicity. This means that the microenvironment is dominant in defining the clonogenic activity of PDAC cells. Indeed, manipulating the stroma by Hedgehog pathway inhibition alters the tumor growth mode, revealing that tumor-stroma crosstalk shapes tumor growth dynamics and clonal architecture.
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•Marker-free lineage tracing and modeling reveal pancreatic cancer growth dynamics•Clonogenicity of pancreatic cancer cells is fully defined by the microenvironment•Stromal Hh inhibition impacts on clonal dynamics, but not pancreatic tumor growth
Lodestijn et al. employ marker-free lineage tracing in pancreatic cancer xenograft models to demonstrate that clonogenic capacity of tumor cells is fully defined by the microenvironment and not by tumor-cell-intrinsic features. Consequently, targeting the stroma using Hedgehog inhibition alters clonal dynamics but does not limit tumor growth.
Pancreatic acinar cells have high plasticity and can transdifferentiate into ductal‐like cells. This acinar‐to‐ductal metaplasia (ADM) contributes to tissue maintenance but may also contribute to the ...premalignant transformation that can eventually progress to pancreatic ductal adenocarcinoma (PDAC). Macrophages are key players in ADM, and macrophage‐secreted matrix metalloproteinase (MMP)‐9 induces ADM through yet unknown mechanisms. As we previously identified MMP9 as a novel agonist of protease‐activated receptor 1 (PAR1), a receptor that is known to orchestrate the cross‐talk between macrophages and tumor cells in PDAC, we here assessed the contribution of PAR1 to pancreatic cell fates. We found that genetic deficiency for PAR1 increases acinar gene expression programs in the healthy pancreas and that PAR1 deficiency limits ductal transdifferentiation in experimental systems for ADM. Moreover, PAR1 silencing in PDAC cells increases acinar marker expression. Changes in PDAC cell lines were associated with a downregulation of known Myc‐target genes, and Myc inhibition mimics PAR1 deficiency in enhancing acinar programs in healthy organoids and PDAC cells. Overall, we identify the PAR1‐Myc axis as a driver of ductal cell fates in premalignant pancreas and PDAC. Moreover, we show that cellular plasticity is not unique to acinar cells and that ductal regeneration into acinar‐like cells is possible even in the context of oncogenic KRAS activation.
Using healthy pancreatic tissue, premalignant transdifferentiation, and ductal carcinoma models, we demonstrated that protease‐activated receptor 1 (PAR1) drives ductal cell fate. PAR1 deficiency prevented ductal transdifferentiation in models for acinar‐to‐ductal metaplasia. We demonstrated that downstream of PAR1 activation, Myc activity drives ductal differentiation programs which goes in line with the known effector functions of Myc in pancreatic ductal adenocarcinoma.
Cell generation and renewal are essential processes to develop, maintain, and regenerate tissues. New cells can be generated from immature cell types, such as stem-like cells, or originate from more ...differentiated pre-existing cells that self-renew or transdifferentiate. The adult pancreas is a dormant organ with limited regeneration capacity, which complicates studying these processes. As a result, there is still discussion about the existence of stem cells in the adult pancreas. Interestingly, in contrast to the classical stem cell concept, stem cell properties seem to be plastic, and, in circumstances of injury, differentiated cells can revert back to a more immature cellular state. Importantly, deregulation of the balance between cellular proliferation and differentiation can lead to disease initiation, in particular to cancer formation. Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with a 5-year survival rate of only ~9%. Unfortunately, metastasis formation often occurs prior to diagnosis, and most tumors are resistant to current treatment strategies. It has been proposed that a specific subpopulation of cells, i.e., cancer stem cells (CSCs), are responsible for tumor expansion, metastasis formation, and therapy resistance. Understanding the underlying mechanisms of pancreatic stem cells during homeostasis and injury might lead to new insights to understand the role of CSCs in PDAC. Therefore, in this review, we present an overview of the current literature regarding the stem cell dynamics in the pancreas during health and disease. Furthermore, we highlight the influence of the tumor microenvironment on the growth behavior of PDAC.
Pancreatic ductal adenocarcinoma (PDAC) is characterized by abundant stroma, the main cellular constituents of which are cancer‐associated fibroblasts (CAFs). Stroma‐targeting agents have been ...proposed to improve the poor outcome of current treatments. However, clinical trials using these agents showed disappointing results. Heterogeneity in the PDAC CAF population was recently delineated demonstrating that both tumor‐promoting and tumor‐suppressive activities co‐exist in the stroma. Here, we aimed to identify biomarkers for the CAF population that contribute to a favorable outcome. RNA‐sequencing reads from patient‐derived xenografts (PDXs) were mapped to the human and mouse genome to allocate the expression of genes to the tumor or stroma. Survival meta‐analysis for stromal genes was performed and applied to human protein atlas data to identify circulating biomarkers. The candidate protein was perturbed in co‐cultures and assessed in existing and novel single‐cell gene expression analysis from control, pancreatitis, pancreatitis‐recovered and PDAC mouse models. Serum levels of the candidate biomarker were measured in two independent cohorts totaling 148 PDAC patients and related them to overall survival. Osteoglycin (OGN) was identified as a candidate serum prognostic marker. Single‐cell analysis indicated that Ogn is derived from a subgroup of inflammatory CAFs. Ogn‐expressing fibroblasts are distinct from resident healthy pancreatic stellate cells and arise during pancreatitis. Serum OGN levels were prognostic for favorable overall survival in two independent PDAC cohorts (HR = 0.47, P = .042 and HR = 0.53, P = .006). Altogether, we conclude that high circulating OGN levels inform on a previously unrecognized subgroup of CAFs and predict favorable outcomes in resectable PDAC.
What's new?
The heterogeneity of cancer‐associated fibroblasts (CAFs) in pancreatic ductal adenocarcinoma (PDAC) with both tumor‐promoting and tumor‐suppressive properties has recently been recognized. Our study identifies osteoglycin as a distinct marker for an inflammatory and tumor‐suppressive CAF subpopulation. The favorable prognostic significance of high serum osteoglycin levels was observed in a cohort of 40 patients with resected PDAC and further validated in a nationwide multicenter cohort of 108 patients. The findings point to osteoglycin as a potential noninvasive biomarker that not only predicts favorable clinical outcomes but also distinguishes a novel CAFs subtype.
Cancer stem cells: here, there, and everywhere Lodestijn, Sophie C.; Lenos, Kristiaan J.; Miedema, Daniël M. ...
Molecular & Cellular Oncology,
01/2019, Letnik:
6, Številka:
1
Journal Article
Odprti dostop
By using marker-free lineage tracing in combination with quantitative analysis, we recently revealed cancer stem cell functionality in established human colon cancer is not intrinsically defined, but ...fully spatiotemporally regulated.
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