癌症生物学

Metastasis accounts for the majority of cancer related deaths. The genetically engineered mouse (GEM) models and cell line-based subcutaneous and orthotopic mouse xenografts have been developed to study the metastatic process. By using lung cancer cell line A549 as an example, we present a modified protocol to establish the cell line-based xenograft. Our protocol ensures sufficient establishment of the mouse xenografts and allows us to monitor tumor growth and spontaneous metastasis. This protocol could be adapted to other types of established cancer cell lines or primary cancer cells to study the mechanism of metastatic process as well as to test the effect of the potential anti-cancer agents on tumor growth and metastatic capacity.

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).

Developing cancer therapeutics requires the ability to investigate their effects using in vitro models of a specific type of tumor. This protocol provides a method for the isolation and adoption to growth in culture of cells from primary tumors. This is particularly valuable for studying mouse models where original tumor cells can be evaluated, for example for gene modifications, and subsequently injected back to the same background mice to create more tumors for in vivo efficacy studies.