The red bone marrow (BM) is an important indicator organ of hematogenous micrometastatic spread of carcinomas. Characterization of biological properties specific for BM micrometastatic cells, however, is technically challenging due to the limited number of target cells usually available for the purpose. This report provides referrals to qualitative gene expression profiling of BM micrometastatic cells enriched by immunomagnetic selection. First, an experimental strategy was used to study regulatory mechanisms involved when BM micrometastatic cells colonize distant organs. The MA-11 cells, originating from BM micrometastases in a breast cancer patient clinically devoid of overt metastatic disease, were injected into immunodeficient rats. Metastatic MA-11 cells were subsequently immunoselected from the resulting in vivo lesions. The selected cell populations were compared to the injected cells by differential display analysis, and several genes possibly involved in tumor cell invasion and proliferation were confirmed as differentially expressed among the various MA-11 cell populations. A direct approach to qualitative gene expression profiling of BM micrometastatic cells was also explored. Carcinoma cells were immunoselected from BM and axillary lymph nodes obtained from breast cancer patients, and the isolated cell populations were compared by differential display analysis. Two candidate genes, identified as factors involved in cellular growth control, appeared as differentially expressed by the target cells from BM. Our study provides detailed information on how to combine an immunomagnetic selection procedure and differential display analysis to reveal gene expression profiles that may characterize BM micrometastatic cells. © 2002 Wiley-Liss, Inc.
Key words: bone marrow; micrometastasis; breast cancer; immunomagnetic cell preparation; differential cloningClinical and experimental evidence suggests that epithelial tumor cells are able to disseminate to secondary organs at an early stage of primary tumor development. The red bone marrow (BM) compartment represents an important indicator organ of hematogenous micrometastatic spread of carcinomas. According to current concepts, however, disseminated tumor cells detected in the BM are not able to grow as distant metastatic lesions unless they possess certain biological characteristics, among which the ability of invasion into and proliferation within the target organ is considered highly significant. [1][2][3] The classical, experimental works on mechanisms of tumor metastasis demonstrated that only a small subset of cells within the parental population is capable of metastasizing 4 and that the cellular composition of secondary tumors differs from that of the primaries. 5 Subsequent reports introduced the concept of dynamic heterogeneity, which argues that although the metastatic phenotype is a genetically controlled trait, it is inherently unstable. 6 Indeed, cellular properties that are crucial for initiation of distant tumor growth may be obscured by the heterog...