Spatiotemporal regulation of clonogenicity in colorectal cancer xenografts

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

Health care utilisation and problems in accessing health care of female undocumented immigrants in the Netherlands

Contains fulltext : 88419.pdf (publisher's version ) (Closed access)OBJECTIVE: To obtain information about the actual use of health care facilities by undocumented women and to identify obstacles they experience in accessing health care facilities. METHODS: A mixed methods study, with structured questionnaires and semi-structured interviews, was chosen to obtain a complete understanding. One-hundred undocumented women were recruited. Diversity was sought according to age, origin and reason for being undocumented. RESULTS: Undocumented female immigrants have unmet health care needs (56%) and low health care utilisation. Sixty-nine per cent of the women reported obstacles in accessing health care facilities. These included many personal obstacles such as shame, fear and/or lack of information. Poor language proficiency (OR 0.28;. CI 0.09-0.90) reduces utilisation of primary health care services. CONCLUSION: Health care utilisation of undocumented women is low. Undocumented women refrain from seeking health care because of personal obstacles. These women need to be identified and informed about their rights, the health care system and the duty of professional confidentiality of doctors. Finally, institutional obstacles to access care should be removed since they strengthen reluctance to seek help.1 oktober 201

Stem cells in homeostasis and cancer of the gut

Abstract The intestinal epithelial lining is one of the most rapidly renewing cell populations in the body. As a result, the gut has been an attractive model to resolve key mechanisms in epithelial homeostasis. In particular the role of intestinal stem cells (ISCs) in the renewal process has been intensely studied. Interestingly, as opposed to the traditional stem cell theory, the ISC is not a static population but displays significant plasticity and in situations of tissue regeneration more differentiated cells can revert back to a stem cell state upon exposure to extracellular signals. Importantly, normal intestinal homeostasis provides important insight into mechanisms that drive colorectal cancer (CRC) development and growth. Specifically, the dynamics of cancer stem cells bear important resemblance to ISC functionality. In this review we present an overview of the current knowledge on ISCs in homeostasis and their role in malignant transformation. Also, we discuss the existence of stem cells in intestinal adenomas and CRC and how these cells contribute to (pre-)malignant growth. Furthermore, we will focus on new paradigms in the field of dynamical cellular hierarchies in CRC and the intimate relationship between tumor cells and their niche

Stem Cells: All that Is Solid Melts into Air

The intestinal epithelium displays great resilience, as several cell populations can replenish the stem cell pool upon damage. Two studies in Cell Stem Cell extend this capacity to enteroendocrine cells, addressing the molecular basis underlying cellular plasticity observed in the intestine and the identities of putative reserve stem cell

GPs’ perspectives on colorectal cancer screening and their potential influence on FIT-positive patients: an exploratory qualitative study from a Dutch context

Background: In the Dutch colorectal cancer (CRC) screening programme, individuals receive a faecal immunochemical test (FIT) to do at home. After a positive FIT result, a follow-up colonoscopy is recommended to identify CRC or advanced adenomas (AA). GPs may influence their patients’ decisions on adherence to follow-up by colonoscopy. Aim: To explore GPs’ perspectives on the CRC screening programme and their potential influence on FIT-positive patients to follow up with the recommended colonoscopy. Design & setting: Semi-structured interviews among GPs in Amsterdam, the Netherlands. Method: GPs were approached using purposive sampling. Analysis was performed on 11 interviews using open coding and constant comparison. Results: All interviewed GPs would recommend FIT-positive patients without obvious contraindications to adhere to a follow-up colonoscopy. If patients were likely to be distressed by a positive FIT result, most GPs described using reassurance strategies emphasising a low cancer probability. Most GPs stressed the probability of false-positive FIT results. Some described taking a positive screening result in CRC screening less seriously than one in breast cancer screening. Most GPs underestimated CRC and AA probabilities after a positive FIT result. When told the actual probabilities, some stated that this knowledge might change the way they would inform patients. Conclusion: These results imply that some of the interviewed GPs have too low a perception of the risk associated with a positive FIT result, which might influence their patients’ decision-making. Simply informing GPs about the actual rates of CRC and AA found in the screening programme might improve this risk perception

The "evidence-based practice inventory" : reliability and validity was demonstrated for a novel instrument to identify barriers and facilitators for Evidence Based Practice in health care

OBJECTIVES: To design and validate a practical questionnaire for clinicians, to identify barriers and facilitators for evidence-based practice (EBP), that is, the use of research evidence in patient care. The inventory is ultimately intended for departments to assess local conditions for EBP, to aim and evaluate efforts at improving or maximizing EBP. STUDY DESIGN AND SETTING: We derived candidate items from existing EBP scales, psychology, and behavioral economics. In an online Delphi study, 537 international expert clinicians, researchers, teachers, and policymakers interested in EBP identified items with sufficient face and content validity. We piloted and validated the resulting draft inventory among 127 clinicians from various specialties and career stages. RESULTS: The Delphi study started with 114 items and resulted in a draft inventory with 29 items in five dimensions. During the pilot, the inventory was easy to complete within 15 minutes and the items showed sufficient response variation. In four of five dimensions, test-retest reliability was substantial to almost perfect and the power to discriminate between groups with different expertise was adequate, whereas internal consistency showed that the items generally measured the same construct. On the basis of internal consistency and factor analysis, we excluded three items. The final EBP inventory consists of 26 items in five dimensions: decision making, subjective norm, attitude, perceived behavior control, and intention and behavior. DISCUSSION AND CONCLUSION: The EBP inventory was developed with support of EBP experts and validated among various academic clinicians. It shows adequate face and content validity, internal consistency, test-retest reliability, discriminative power, and completion will take <15 minutes. We recommend further evaluation of its value in field trials

Defining Stem Cell Dynamics in Models of Intestinal Tumor Initiation

Cancer is a disease in which cells accumulate genetic aberrations that are believed to confer a clonal advantage over cells in the surrounding tissue. However, the quantitative benefit of frequently occurring mutations during tumor development remains unknown. We quantified the competitive advantage of Apc loss, Kras activation, and P53 mutations in the mouse intestine. Our findings indicate that the fate conferred by these mutations is not deterministic, and many mutated stem cells are replaced by wild-type stem cells after biased, but still stochastic events. Furthermore, P53 mutations display a condition-dependent advantage, and especially in colitis-affected intestines, clones harboring mutations in this gene are favored. Our work confirms the previously theoretical notion that the tissue architecture of the intestine suppresses the accumulation of mutated lineage

Continuous Clonal Labeling Reveals Small Numbers of Functional Stem Cells in Intestinal Crypts and Adenomas

Lineage-tracing approaches, widely used to characterize stem cell populations, rely on the specificity and stability of individual markers for accurate results. We present a method in which genetic labeling in the intestinal epithelium is acquired as a mutation-induced clonal mark during DNA replication. By determining the rate of mutation in vivo and combining this data with the known neutral-drift dynamics that describe intestinal stem cell replacement, we quantify the number of functional stem cells in crypts and adenomas. Contrary to previous reports, we find that significantly lower numbers of "working" stem cells are present in the intestinal epithelium (five to seven per crypt) and in adenomas (nine per gland), and that those stem cells are also replaced at a significantly lower rate. These findings suggest that the bulk of tumor stem cell divisions serve only to replace stem cell loss, with rare clonal victors driving gland repopulation and tumor growt