Figure 4.

(A) Measured expression patterns of human and mouse genes by cross-species hybridization with human and mouse RNA microarray slides. The data are presented in matrix format in which rows represent individual gene and columns represent each hybridization event. Each cell in the matrix represents the expression level of a gene feature in an individual hybridization. The red in cells reflects measured expression levels, and intensity of color represents the magnitude of expression (log₂-transformed scale). These results confirm the specificity of the analyses. (B) Expression patterns of human genes in MDA-MB-231 and PC14Br₄ cocultured with murine astrocytes or 3T3 cells. We identified genes whose expression patterns were altered on interaction with astrocytes in each cell line by applying two-sample t tests (P <.001). In MDA-MB-231 and PC14Br₄ cells, 1069 and 594 genes, respectively, were differentially expressed. The expression of 205 genes was altered in both cell lines. Of these, several are related to antiapoptosis and cell survival. (C) Validation of microarray by Western blot analysis. Protein was extracted from MDA-MB-231 and PC14Br₄ cells after they were cultured alone or with or murine astrocytes. The expression of the antiapoptotic survival genes BCL2L1, TWIST1, and GSTA was upregulated in MDA-MB-231 and PC14Br₄ cells cocultured with murine astrocytes. (D) Expression of BCL2L1, TWIST1, and GSTA5 in clinical specimen of breast cancer and lung cancer metastasis in the brain and breast cancer in the brain and lung. BCL2L1, TWIST1, and GSTA5 were highly expressed (green) on tumor cells. Nuclei were stained with 4′,6-diamidino-2-phenylindole (blue). Tumor cells in clinical specimen of breast cancer metastases to the lung were negative for expression of these genes, whereas low expression of these genes was detected in normal alveolar epithelial cells and alveolar macrophages.