Lymphatic metastasis of breast cancer cells is associated with differential gene expression profiles that predict cancer stem cell-like properties and the ability to survive, establish and grow in a foreign environment.

Although lymphatic dissemination is a major route for breast cancer metastasis, there has been little work to determine what factors control the ability of tumor cells to survive, establish and show progressive growth in a lymph node environment. This information is of particular relevance now, in the era of sentinel lymph node biopsy, where smaller intranodal tumor deposits are being detected earlier in the course of disease, the clinical relevance of which is uncertain. In this study, we compared differentially expressed genes in cell lines of high (468LN) vs. low (468GFP) lymphatic metastatic ability, and related these to clinical literature on genes associated with lymphatic metastatic ability and prognosis, to identify genes of potential clinical relevance. This approach revealed differential expression of a set of genes associated with 'cancer stem cell-like' properties, as well as networks of genes potentially associated with survival and autonomous growth. We explored these differences functionally and found that 468LN cells have a higher proportion of cells with a cancer stem cell-like (CD44+/CD24-) phenotype, have a higher clonogenic potential and a greater ability to survive, establish and grow in a foreign (lymph node and 3D Matrigel) microenvironment, relative to 468GFP cells. Differentially expressed genes which reflect these functions provide candidates for investigation as potential targets for therapy directed against early lymphatic metastasis.

Recombinant human erythropoietin in combination with chemotherapy increases breast cancer metastasis in preclinical mouse models.

PURPOSE: Erythropoiesis-stimulating agents (ESA) are used clinically for treating cancer-related anemia. Recent clinical trials have reported increased adverse events and reduced survival in ESA-treated breast cancer patients receiving chemotherapy, potentially related to erythropoietin (EPO)-induced cancer progression. However, minimal preclinical data are available about the impact of EPO on metastatic cell behavior and/or the metastatic process, and this was the goal of our study. EXPERIMENTAL DESIGN: Breast cancer cell lines were treated with recombinant human EPO (rHuEPO) and screened for expression of EPO receptors (EPOR). MDA-MB-231 and MDA-MB-435 cell lines were used for functional assays in vitro (two-dimensional/three-dimensional growth and survival) and in vivo (tumorigenicity and metastasis), in the presence or absence of EPO and/or cytotoxic agents. RESULTS: A large variation in EPOR expression across cell lines was observed. In vitro, rHuEPO had a protective effect on radiation-treated MDA-MB-435 cells (P < 0.05); however, rHuEPO treatment alone or combined with chemotherapy or hypoxia did not influence cell survival. In vivo, rHuEPO increased lung metastases in immunocompromised mice injected with MDA-MB-231 or MDA-MB-435 cells and treated with chemotherapy relative to mice treated with chemotherapy alone (P < 0.05). CONCLUSIONS: The lack of an in vitro effect of rHuEPO highlights the importance of in vivo studies to delineate the effects of EPO on the metastatic process. These studies may begin to uncover the underlying functional explanation for the observed EPO-related adverse events and decreased survival in ESA-treated metastatic breast cancer patients undergoing chemotherapy.