CD44/CD24, ABCG2 and CXCR4 as Markers of Tumor Stem Cells in Locally Advanced Breast Cancer

INTRODUCTION: the expressions of CD44/CD24, CXCR4 and ABCG2 have been reported as potential breast cancer stem-like cell (CSLC) markers. The association between the quantity of CSLCs and the response to neoadjuvant chemotherapy (NACT) remains unclear. METHODS: we prospectively analyzed the expression of CD44/CD24, CXCR4 and ABCG2 in 36 patients with locally advanced or metastatic (LAMBC) invasive ductal carcinomas of the breast subjected to NACT. The mammosphere assay (Mammocult®) was studied in 21 samples. Patients’ mean age was 53.1 ± 9.5 yo. According to clinical stage (CS), 7 patients were IIb, 1 - IIIc, 9 - IIIa, 1- IIA, 6 – Iib, 11- IIIb and 7 - IV. The mean clinical tumor diameter was 6.2 ± 3.6 cm. The ER, PgR and HER2 positive expression rates were 63%, 55% and 52%, respectively. Eighteen patients were treated with EC-T, thirteen were treated with EC-TH (HER2+) and five were treated with FEC75 combination as NACT. The median percentage CD44+/CD24-, CXCR4+, ABCG2+ and ESA+ cells within Lincells were determined by flow cytometry in fresh sampled tumors after tissue digestion. The relationship between flow cytometry analyses and clinical and pathological response to therapy was analyzed. RESULTS: complete pathological response (pCR) was observed in 8 (22.2%) patients. According to IHC, we observed a higher pCR rate among patients with ER negative and HER2 positive tumors but not statistically significant (p= 0.09 and p= 0.1, respectively). According to flow cytometry analyses, we observed no association between the pCR with the percentage of CD44+/CD24-, CXCR4+ and ABCG2+ cells within the tumor and with the number of mammospheres formation. The median percentage of ESA+/ABCG2+ cells within the tumor in pCR patients was 1.2% and 3.9% in patients with no pCR (p= 0.2). The median number of sphere formation was 1.2/1000 cells and 4/1000 cells in pCR and non-pCR patients, respectively (p= 0.1). Interestingly, there was a positive correlation between ABCG2 expression and the number of mammosfere formation (r= 0.64; p= 0.002). This correlation was not significant comparing to CD44+/CD24- cells or CXCR4. CONCLUSIONS: the percentage of CD44+/CD24-, CXCR4+ and ABCG2+ cancer cells within the tumor and the number of mammosphere formation are not predictive factors for pCR in LAMBC patients subjected to NACT. The strong correlation between ABCG2 expression and the capacity to form spheres