Molecular characterization of circulating tumor cells identifies predictive markers for outcome in triple-negative breast cancer patients

Background:

Circulating Tumor Cells (CTCs) present in each subtype may represent distinct metabolic profiles for survival, metastatic spread and therapy resistance. Using a multi-marker gene panel for the characterization of CTCs, we here compared the genetic profiles of CTCs in triple-negative BC (TNBC) and non-TNBC patients (pts).

Methods:

52 TNBC and non-TNBC pts. (41 = HER2-/HR+; 11 = HER2+/HR-) before and/or after neoadjuvant therapy were analyzed for CTCs, applying positive immunomagnetic selection targeting EpCAM, EGFR and HER2 using the AdnaTest EMT-2/Stem Cell Select (QIAGEN, Hilden, Germany). Subsequently, cDNA was gene specifically pre-amplified using TaqMan PreAmp Master Mix according to in house designed assays. Multiplex RT-qPCR was performed for 19 genes, GAPDH and CD45 served as reference genes. The cutoff was calculated as Ct(cutoff)-Ct(sample)-[Ct(CD45cutoff)-Ct(CD45sample)], taking into account the false positive rate in healthy donors.

Results:

In TNBC pts, all the different genes were expressed, representing the most heterogeneous CTC population. HER2+/HER3+CTCs were found at both time points in more than 20% of the pts. Before therapy, the androgen receptor (AR) and EGFR were present in CTCs of 35% and 23% of the pts. 67% of the genes were expressed before and after therapy (mainly ERBB-family and PI3K pathway). A reduced DFS in TNBC pts seems to be related to the presence of HER2+/HER3+/EGFR+CTCs before and after therapy and to platinum-based-therapy, which induced PI3K expression in CTCs after therapy, resulting in the expression of genes related to resistance.

Conclusion:

This knowledge might efficiently help to predict a personalized targeted therapy for these pts in the future.