Using a xenograft model of human breast cancer metastasis to find genes associated with clinically aggressive disease.

Metastasis is the primary cause of death from breast cancer. A xenograft model was used to identify genes potentially involved with metastasis, comparing expression in the poorly metastatic GI101A human breast cancer cell line and a highly metastatic variant, GILM2. cDNA microarray analyses of these isogenic variants were done using 16K Operon 70-mer oligonucleotide microarray slides. Differentially expressed genes were identified by ANOVA, and differences of > or =2.5-fold were found for 106 genes. Changes in protein or RNA expression were confirmed for 10 of 12 genes. Three markers, heat shock protein 70 (HSP-70), chemokine (C-X-C motif) ligand 1 (CXCL-1), and secreted leukocyte protease inhibitor (SLPI), were studied further with breast cancer tissue microarrays using a novel method of automated quantitative analysis. This uses cytokeratin to define pixels as breast cancer (tumor mask) within the tissue array spot and then measures intensity of marker expression using a cyanine 5-conjugated antibody within the mask. Scores were correlated with clinicopathologic variables. High HSP-70 expression and high nuclear CXCL-1 expression in primary tumors were both associated with decreased survival (P = 0.05 and 0.027, respectively). Expression of each marker was strongly associated with lymph node involvement (P = 0.0002, 0.008, 0.0012, and 0.012 for HSP-70, nuclear CXCL-1, cytoplasmic CXCL-1, and SLPI, respectively). Identification of genes associated with metastasis in experimental models may have clinical implications for the management of breast cancer, because some of these are associated with lymph node metastasis and survival and might be useful as prognostic markers or molecular targets for novel therapies.

Different signalling pathways regulate VEGF and IL-8 expression in breast cancer: implications for therapy.

Elevated expression of pro-angiogenic cytokines is associated with aggressive tumour growth and decreased survival of patients with breast cancer. In general, the breast cancer cell lines with high vascular endothelial growth factor (VEGF) expression also express high levels of interleukin-8 (IL-8). The consequence of inhibiting mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K), both implicated in regulation of these cytokines, was examined in four cell lines. Treatment with the mitogen-activated protein kinase/extracellular signal-related kinase (MEK) inhibitor U0126 reduced expression of VEGF and IL-8 in MDA-MB-231 cells, partially inhibited expression in MDA-MB-468 and Hs578T cells, with minimal effects in GI101A cells. Treatment with LY294002 reduced cytokine expression in GI101A and MDA-MB-468 cells, with partial reduction in Hs578T and less effect in MDA-MB-231 cells. Thus, IL-8 and VEGF were regulated by different signalling pathways in different cell lines; this suggests that inhibition of the dominantly active pathway can downregulate both angiogenic cytokines. Recognising which signalling pathway is active may identify targets for anti-angiogenic therapy of breast cancer.

alphaB-crystallin as a marker of lymph node involvement in breast carcinoma.

BACKGROUND: It was found previously that alphaB-crystallin, a small heat-shock protein, was overexpressed in a metastatic variant of the GI101A human breast carcinoma cell line. The objective of the current study was to determine whether the expression of alphaB-crystallin in primary breast carcinomas was associated with lymph node metastasis and survival. METHODS: Expression of alphaB-crystallin was measured in human breast carcinoma cell lines by immunoblotting. Expression in human breast carcinomas was evaluated by immunohistochemical staining of tissue microarrays that contained samples from 317 patients with lymph node-negative breast carcinoma and 291 patients with lymph node-positive breast carcinoma. RESULTS: It was found that alphaB-crystallin was expressed constitutively in certain breast carcinoma cell lines, including those that were capable of metastasizing in immunodeficient mice. Expression of alphaB-crystallin in human tissue samples was associated strongly with lymph node involvement (P < 0.0001; chi-square test) and, to a lesser degree, with high nuclear grade (P = 0.05). Increased intensity of expression was correlated with shorter survival (P = 0.0091; log-rank test). Multivariate analysis indicated that alphaB-crystallin expression was not independent of lymph node status as a predictor of survival. CONCLUSIONS: The data obtained in the current study revealed a strong association between high expression levels of alphaB-crystallin in primary breast carcinoma specimens and lymph node involvement. Further studies will be needed to prospectively elucidate the role of this novel tumor marker as a clinical prognostic marker in local and locally advanced breast carcinoma as well as its potential status as a new target for therapy in patients with breast carcinoma.

Therapeutic intervention with breast cancer metastasis.

Metastatic disease, mainly to the lungs, liver, bone, and brain, is the most common cause of death from breast cancer, despite advances in surgical and clinical management. Two basic principles govern the process of metastasis. First, that tumors are heterogeneous populations of cells, and second, that the process is a sequence of events that depends on tumor cell properties and interactions with the microenvironment at the site of metastasis. Inhibitors targeted at any of these different steps have the potential to inhibit metastatic progression, and examples of key therapeutic targets include overexpression of growth factor receptors, angiogenic factors, matrix metalloproteases, and integrin receptors. The identification of molecular targets for therapy of breast cancer metastasis will be accelerated by DNA array technology, and their selection for use should include evaluation of interactions between tumor cells and normal tissue components. These sorts of inhibitors are likely to target both cancer and normal cell functions, for example, inhibitors of matrix metalloproteases that can potentially inhibit both tumor cell invasion and angiogenesis. The use of appropriate animal models will be necessary to determine the impact of targeted inhibitors on the growth and development of breast cancer metastasis.