Proteomic analysis of the effects of cell culture density on the metastasis of breast cancer cells.

Cancer cell progression and proliferation increase cell density, resulting in changes to the tumour site, including the microenvironment. What is not known is if increased cell density influences the aggressiveness of cancer cells, especially their proliferation, migration, and invasion capabilities. In this study, we found that dense cell culture enhances the aggressiveness of the metastatic cancer cell lines, 4T1 and ZR-75-30, by increasing their proliferation, migration, and invasion capabilities. However, a less metastatic cell line, MCF-7, did not show an increase in aggressiveness, following dense cell culture conditions. We conducted a differential proteomic analysis on 4T1 cells cultured under dense or sparse conditions and identified an increase in expression for proteins involved in migration, including focal adhesion, cytoskeletal reorganization, and transendothelial migration. In contrast, 4T1 cells grown under sparse conditions had higher expression levels for proteins involved in metabolism, including lipid and phospholipid binding, lipid and cholesterol transporter activity, and protein binding. These results suggest that the high-density tumour microenvironment can cause a change in cellular behaviour, leading towards more aggressive cancers. SIGNIFICANCE OF THE STUDY: Metastasis of cancer cells is an obstacle to the clinical treatment of cancer. We found that dense cultures made metastatic cancer cells more potent in terms of proliferation, migration, and invasion. The proteomic and bioinformatic analyses provided some valuable clues for further intensive studies about the effects of cell density on cancer cell aggressiveness, which were associated with events such as pre-mRNA splicing and RNA transport, focal adhesion and cytoskeleton reorganization, ribosome biogenesis, and transendothelial migration, or associated with proteins, such as JAM-1 and S100A11. This investigation gives us new perspectives to investigate the metastasis mechanisms related to the microenvironment of tumour sites.

[Correlation between lymph-node metastasis and combined expression of Hpa and C-erbB-2 of invasive ductal breast carcinoma].

OBJECTIVE: This study is to learn the correlation between lymph-node metastasis and the combined expression of Heparanase (Hpa) and C-erbB-2. METHODS: The expressions of Hpa and C-erbB-2 were examined in 81 human invasive ductal breast carcinomas ( IDBC ) and 14 fibroadenomas by SP immunohistochemistry analysis. We analyzed the expressions of two factors in two groups, in which their correlation with lymph-node metastasis in IDBC was also studied. RESULTS: (1) Positive expressions of Hpa and C-erbB-2 in IDBC tissue were 59 (72.84%) and 29(35. 80%) respectively, in which the positive expression rates were significantly higher than those in fibroadenomas (P = 0.0000, 0.0177). (2) The expression of C-erbB-2 was correlated with Hpa expression (r = 0.668, P < 0.01). (3) When Hpa expression was combined with the status of C-erbB-2 expression, the lymph node metastasis with positive-Hpa and positive-C-erbB-2 expressions occurred significantly higher in patients with IDBC (all P < 0.01). CONCLUSION: Hpa may up-regulate the expression of C-erbB-2. Furthermore, as co-expression, Hpa and C-erbB-2 work together, which would take the possession of stronger role in the procedure of growth, invasion and metastasis of IDBC.