癌症生物学

The extracellular matrix (ECM) is a non-cellular network of macromolecules, which provides cells and tissues with structural support and biomechanical feedback to regulate cellular function, tissue tension, and homeostasis. Even subtle changes to ECM abundance, architecture, and organization can affect downstream biological pathways, thereby influencing normal cell and tissue function and also driving disease conditions. For example, in cancer, the ECM is well known to provide both biophysical and biochemical cues that influence cancer initiation, progression, and metastasis, highlighting the need to better understand cell–ECM interactions in cancer and other ECM-enriched diseases. Initial cell-derived matrix (CDM) models were used as an in vitro system to mimic and assess the physiologically relevant three-dimensional (3D) cell–ECM interactions. Here, we describe an expansion to these initial CDM models generated by fibroblasts to assess the effect of genetic or pharmacological intervention on fibroblast-mediated matrix production and organization. Additionally, we highlight current methodologies to quantify changes in the ultrastructure and isotropy of the resulting ECM and also provide protocols for assessing cancer cell interaction with CDMs. Understanding the nature and influence of these complex and heterogeneous processes can offer insights into the biomechanical and biochemical mechanisms, which drive cancer development and metastasis, and how we can target them to improve cancer outcomes.

Bone is the most frequently affected organ by metastases of breast cancer and prostate cancer. Our knowledge on bone metastasis is extremely limited due to the lack of potent and efficient experimental models. We developed the “Bone-In-Culture Array (BICA)” platform to model the bone colonization of cancer cells in ex vivo cultures. The use of the BICA platform will facilitate in-depth mechanistic studies and high-throughput screening of drugs for bone metastasis.

Bone is one of common metastasis sites for many types of cancer. In bone metastatic microenvironment, tumor-bone interactions play a significant role in the regulation of osteolytic or osteoblastic bone metastasis. In order to investigate the direct interaction between tumor cells and bone tissue, it is essential to generate appropriate animal models that mimic the behavior of tumor cells in bone metastatic lesions. Calvarial implantation model (bone invasion model) is a newly-established animal model that accurately recapitulates the behavior of tumor cells in the tumor-bone microenvironment. The surgical technique for tumor cell implantation is simpler than intracardiac, intra-arterial, or intraosseous injection techniques. This model can be useful for the identification of key factors driving tumor-induced osteolytic or osteoblastic changes.

We have developed a 3D co-culture system composed of fibroblasts and colorectal cancer cells that enables us to study the desmoplastic reaction. This method also enables us to study the influence of the desmoplastic reaction on the migration of colorectal cancer cells through the surrounding stroma. This protocol has been previously published (Coulson-Thomas et al., 2011) and is described here in more detail.

We have developed a 2D heterotypic co-culture technique between fibroblasts and cancer cells that enables the study of the stromal reaction. For such, stromal cells are seeded and cultured immediately around a tumour cell line, and the cells establish cell-cell contacts, as well as a gradient of soluble factors throughout the stromal cells, similar to that found in tissues. Thus, this system also enables the researcher to distinguish between events that are caused by direct cell-cell contact and secreted factors.

Cancer tissue is composed of cancer cells and a large number of stromal cells including fibroblasts. In order to understand the relationship between fibroblasts and cancer cells during invasion of the stroma, 3D gel invasion assay is useful. Most tumors are associated with a biologically active type of fibroblasts known as cancer-associated fibroblasts (CAFs), which promote the invasion of cancer cells. Here, we describe the method of imaging the invasion by fluorescently labeled CAFs and gastric cancer cells in gels containing extracellular matrix. For two-color fluorescence labeling of living cells, long-chain dialkylcarbocyanines, DiO and DiI were used. This method is also applicable for studying invasion by other stromal cells and cancer cells, and for evaluation of drugs targeting cancer stromal cells.

Tumors are comprised of heterogeneous subpopulations that may exhibit differing capacity for differentiation, self-renewal, and tumorigenicity. In vivo lineage-tracing studies are a powerful tool for defining the role of tumor subpopulations in tumor growth and as targets for therapeutic agents. This protocol describes using a neuroblastoma cancer cell line transduced with two different fluorescent proteins (GFP and tdTomato) to track the specific contributions of cells expressing the GCSF receptor (CD114⁺) or not (CD114^-) on tumor growth in vivo.

Tumour microenvironment and cancer-associated fibroblasts in particular exhibit tumour promoting abilities that are not present in their normal counterparts (Calvo et al., 2013; Hanahan and Coussens, 2012). Therefore, functional and molecular characterization of the modifications occurring in fibroblasts during tumour progression is essential to fully understand their role in tumour progression. Previous studies have addressed this issue using human fibroblasts and comparing normal and adjacent fibroblasts to tumour-associated fibroblasts (Kalluri and Zeisberg, 2006). However, these studies are hampered by the intrinsic variability of human samples (e.g. pairing, age, genomic landscape, etc). In order to overcome these issues, we used a fully characterised mouse breast cancer model, MMTV-PyMT (Guy et al., 1992; Lin et al., 2003). MMTV-PyMT transgenic mice express the Polyoma Virus middle T antigen under the direction of the mouse mammary tumor virus promoter/enhancer. This is a multifocal luminal breast cancer model that goes through well defined and characterised stages (namely, hyperplasia, adenoma, carcinoma and invasive carcinoma). Interestingly, this model has a 100% incidence, is very desmoplastic (presenting high concentration of fibroblasts) and gives raise to spontaneous metastasis in the lung with 80-94% incidence. Importantly, at least for the inguinal mammary glands (glands 4 and 9), the different tumoral stages are well correlated to the age of the mouse: hyperplasia arising at 6 weeks of age, adenoma between 6-8 weeks of age, carcinoma and invasive carcinoma from 8 weeks onwards. This model allowed us to confidently isolate fibroblasts from different tumoral stages and carefully characterise their functional and molecular properties (Calvo et al., 2013).