Invasiveness of human pleural mesothelioma cells is influenced in vitro by the three-dimensional structure of the ECM and its composition

Cell and extracellular matrix interaction models in benign mesothelial and malignant pleural mesothelioma cells in 2D and 3D in-vitro

Malignant pleural mesothelioma (MPM) is an aggressive tumour that grows in the pleural cavity. MPM spheroids released in the pleural fluid can form new tumour foci. Cell-cell, cell-extracellular matrix (ECM) interactions in 2D and 3D impact malignant cell behaviour during cell adhesion, migration, proliferation and epithelial-mesenchymal transition (EMT). In this study, epithelioid, biphasic and sarcomatoid MPM cell types as well as benign mesothelial cells were tested with regards to the above phenotypes. Fibronectin (FN) and homologous cell-derived extracellular matrix (hcd-ECM) treated substratum differentially affected the above phenotypes. 3D MPM spheroid invasion was higher in FN-collagen matrices in the epithelioid and biphasic cells, while 3D cell cultures of epithelioid and sarcomatoid MPM cells in FN-collagen showed a higher contractility compared to hcd-ECM-collagen. Cell aggregates demonstrated invasive behaviour in hcd-ECM matrices alone. Our results suggest that ECM and the dimensionality affect malignant cell behaviour during cell culture studies.

c-Myb regulates matrix metalloproteinases 1/9, and cathepsin D: implications for matrix-dependent breast cancer cell invasion and metastasis

Background

The c-Myb transcription factor is essential for the maintenance of stem-progenitor cells in bone marrow, colon epithelia, and neurogenic niches. c-Myb malfunction contributes to several types of malignancies including breast cancer. However, the function of c-Myb in the metastatic spread of breast tumors remains unexplored. In this study, we report a novel role of c-Myb in the control of specific proteases that regulate the matrix-dependent invasion of breast cancer cells.

Results

Ectopically expressed c-Myb enhanced migration and ability of human MDA-MB-231 and mouse 4T1 mammary cancer cells to invade Matrigel but not the collagen I matrix in vitro. c-Myb strongly increased the expression/activity of cathepsin D and matrix metalloproteinase (MMP) 9 and significantly downregulated MMP1. The gene coding for cathepsin D was suggested as the c-Myb-responsive gene and downstream effector of the migration-promoting function of c-Myb. Finally, we demonstrated that c-Myb delayed the growth of mammary tumors in BALB/c mice and affected the metastatic potential of breast cancer cells in an organ-specific manner.

Conclusions

This study identified c-Myb as a matrix-dependent regulator of invasive behavior of breast cancer cells.

Monitoring of lung tumour cell growth in artificial membranes

Morbidity of many tumour types is associated with invasion of tumour cells through the basement membrane and subsequent metastasis to vital organs. Tumour invasion is frequently detected late on as many patients present with advanced disease. The method of detecting invasion is through conventional histological staining techniques, which are time consuming and require processing of the sample. This can affect interpretation of the results. In this study, a new imaging technique, optical coherence tomography (OCT), was used to monitor lung tumour cell growth in two artificial membranes composed of either collagen type I or Matrigel. In parallel, standard histological section analysis was performed to validate the accuracy of the monitoring by OCT. Cross-sectional images from OCT revealed that lung tumour cells infiltrated only when low cell seeding density (5 x 10(5)) and low collagen concentration (1.5 mg/ml) were combined. The cells could be easily differentiated from the artificial membranes and appeared as either a brighter layer on the top of the membrane or brighter foci embedded within the darker membrane. These cell-membrane morphologies matched remarkably to the standard histological section images. Our results suggest that OCT has a great potential to become a useful tool for fast and robust imaging of cell growth in vivo and as a potential assessment of cell invasion.

Study of tumor cell invasion by Fourier transform infrared microspectroscopy

Lung cancer is usually fatal once it becomes metastatic. However, in order to develop metastases, a tumor usually invades the basal membrane and enters the vascular or lymphatic system. In this study, a three-dimensional artificial membrane using collagen type I, one of the main components of basal membranes, was established in order to investigate tumor cell invasion. Lung cancer cell line CALU-1 was seeded on this artificial membrane and cell invasion was studied using the Fourier transform infrared (FTIR) imaging technique. This approach allowed identification of tumor cells invading the collagen type I membrane by means of their infrared spectra and images. The mapping images obtained with FTIR microspectroscopy were validated with standard histological section analysis. The FTIR image produced using a single wavenumber at 1080 cm(-1), corresponding to PO2- groups in DNA from cells, correlated well with the histological section, which clearly revealed a cell layer and invading cells within the membrane. Furthermore, the peaks corresponding to amide A, I, and II in the spectra of the invading cells shifted compared to the noninvading cells, which may relate to the changes in conformation and/or heterogeneity in the phenotype of the cells. The data presented in this study demonstrate that FTIR microspectroscopy can be a fast and reliable technique to assess tumor invasion in vitro.

Cell protection, resistance and invasiveness of two malignant mesotheliomas as assessed by 10K-microarray

Malignant pleural mesothelioma (MPM) is an aggressive serosal tumor, strongly associated with former exposure to asbestos fibers and for which there is currently no effective treatment available. In human, MPM is characterized by a high local invasiveness, poor prognosis and therapeutic outcomes. In order to assess molecular changes that specify this phenotype, we performed a global gene expression profiling of human MPM. Using a 10,000-element microarray, we analyzed mRNA relative gene expression levels by comparing a mesothelioma cell line to either a pleural cell line or tumor specimens. To analyze these gene expression data, we used various bioinformatics softwares. Hierarchical clustering methods were used to group genes and samples with similar expression in an unsupervised mode. Genes of known function were further sorted by enzyme, function and pathway clusters using a supervised software (IncyteGenomics). Taken together, these data defined a molecular fingerprint of human MPM with more than 700 up- or down-regulated genes related to several traits of the malignant phenotype, specially associated with MPM invasiveness, protection and resistance to anticancer defenses. This portrait is meaningful in disease classification and management, and relevant in finding new specific markers of MPM. These molecular markers should improve the accuracy of mesothelioma diagnosis, prognosis and therapy.