Chemokine receptor CXCR4 expression in breast cancer as a potential predictive marker of isolated tumor cells in bone marrow

Interactions between the CXCR4 chemokine receptor in breast cancer cells and the ligand CXCL12/SDF-1alpha are thought to play an important role in breast cancer metastases. In this pilot study, CXCR4 expression along with other biomarkers including HER2-neu and EGFR, were measured in primary tumor samples of patients with operable breast cancer to test whether any of these biomarkers alone and in combination could indicate breast cancer with high likelihood of metastasizing to bone marrow. Cytokeratin (CK) positive cells in bone marrow were identified by flow-cytometry following enrichment with CK 7/8 antibody-coupled magnetic beads. Primary tumors (n = 18) were stained with specific antibodies for CXCR4, HER2-neu, EGFR, and PCNA using an indirect avidin-biotin horseradish peroxidase method. The majority of the patients had T2/T3 tumors (72%), or lymph node involvement (67%) as pathologic characteristics that were more indicative of high-risk breast cancer. High CXCR4 cytoplasmic expression was found in 7 of 18 patients (39%), whereas 6 of 18 patients (33%) were found to have CK positivity in bone marrow. The median number of CK(+) cells was 236 (range, 20-847) per 5 x 10(4) enriched BM cells. The presence of CK(+) cells in bone marrow was found to be associated with increased expression of CXCR4 alone or in addition to EGFR and/or HER2-neu expression (P = 0.013, P = 0.005, and P = 0.025, respectively) in primary tumors. Furthermore, three patients with high CK positivity (>236 CK(+) per 5 x 10(4) enriched bone marrow cells) in bone marrow exclusively expressed high levels of CXCR4 with EGFR/HER2-neu (P = 0.001). Our data suggest that high CXCR4 expression in breast cancer may be a potential marker in predicting isolated tumor cells in bone marrow. CXCR4 coexpression with EGFR/HER2-neu might further predict a particular subset of patients with high CK positivity in bone marrow.

An ultrasensitive tumor enriched flow-cytometric assay for detection of isolated tumor cells in bone marrow of patients with breast cancer

BACKGROUND

An ultrasensitive tumor enriched flow-cytometric assay was used to determine its feasibility in detection of isolated tumor cells (ITC) in bone marrow (BM) of patients with breast cancer.

METHODS

Epithelial cells were removed by magnetic microbeads conjugated with an anti-cytokeratin 7/8 monoclonal antibody to enrich tumor cells in BM samples. A specific gate for MCF-7 breast cancer cells (gate(MCF-7 cells)) was also taken into consideration in addition to a gate including all enriched BM cells (gate(enriched BM cells)) in flow-cytometric analysis to enhance the specificity of the method.

RESULTS

Nineteen patients with stage I/II were evaluated. Ten patients (53%) were found to have cytokeratin positive (CK(+)) cells according to the gate(enriched BM cells) whereas 6 patients (32%) had CK(+) cells when the gate(MCF-7 cells) was taken into account.

CONCLUSIONS

New strategies in nonmorphological ultrasensitive techniques might be useful to categorize patients with ITCs having different tumor morphology and characteristics.