ABSTRACT: Breast cancer metastasizes to bone, visceral organs, and/or brain depending on the subtypes. Various cell line models have been used to develop gene expression signatures unique to cancer cells that have metastasized to specific organs, although these efforts were not in a uniform setting. In this study, we compared gene expression pattern in MDA-MB-231 cells and its mammary fat pad tumor (TMD-231), lung metastasis (LMD-231), bone metastasis (BMD-231), adrenal metastasis (ADMD-231) and brain metastasis (231-BR) variants grown under the same growth condition. When gene expression differences between metasteses (p value of <0.01) were compared, 231-BR cells showed the highest gene expression difference (633 genes) followed by ADMD-231 (196 genes), LMD-231 (79 genes), and BMD-231 cells (60 genes) compared with other metastatic cells. 231-BR cells specifically overexpressed neuronal transmembrane proteins SLITRK2, TMEM47, and LYPD1 by more than five fold compared with cells isolated from other sites of metastasis. Ingenuity pathway analysis of differentially expressed genes revealed activation of pathways that would enable cancer cells to adapt to organs of metastasis such as drug detoxification/oxidative stress response/semaphorin neuronal pathway in 231-BR cells, Notch/orphan nuclear receptor signals involved in steroidogenesis in ADMD-231, acute phase response in LMD-231, and cytokine/hematopoietic stem cell signaling in BMD-231 cells. Only NF-κB signaling pathway activation was common to all metastatic cells except BMD-231.To test this possibility, we compared gene expression pattern in MDA-MB-231 cells and its mammary fat pad tumor (TMD-231), lung-metastasis (LMD-231), bone-metastasis (BMD-231), adrenal-metastasis (ADMD-231) and brain-metastasis (231-BR) variants. Between metastatic cells, 231-BR cells showed the highest gene expression difference followed by ADMD-231, LMD-231, and BMD-231 cells. 231-BR cells specifically overexpressed neuronal transmembrane proteins SLITRK2, TMEM47, and LYPD1. pathways that would enable cancer cells to adapt to organs of metastasis such as drug detoxification/oxidative stress response/semaphorin neuronal pathway in 231-BR cells, Notch/orphan nuclear receptor signals involved in steroidogenesis in ADMD-231, acute phase response in LMD-231, and cytokine/hematopoietic stem cell signaling in BMD-231 cells. Only NF-κB signaling pathway activation was common to all metastatic cells except BMD-231. Cells were maintained in MEM with 10% fetal calf serum. RNA was prepared exponentially growing cells using RNeasy kit (Qiagen, Valencia, CA, USA) Microarray with biological triplicates was performed using Illumina HumanHT-12 V4 expression beadchip. Probe profile data was imported into partek genomics suite. Genes that showed statistically insignificant signals in majority of samples were removed from the microarray data, and only those probes that showed statistically significant signal in at least half of samples of at least one group were retained. Differential expression analysis was performed using ANOVA.
