Molecular characterization and heterogeneity of circulating tumor cells in breast cancer

Introduction

This study analyzes peripheral blood samples from breast cancer (BC) patients. CTCs from peripheral blood were enriched by size-based separation and were then cultivated in vitro. The primary aim of this study was to demonstrate the antigen independent CTC separation method with high CTC recovery. Subsequently, CTCs enriched several times during the treatment were characterized molecularly.

Methods

Patients with different stages of BC (N = 167) were included into the study. All patients were candidates for surgery, surgical diagnostics, or were undergoing chemotherapy. In parallel, 20 patients were monitored regularly and in addition to CTC presence, also CTC character was examined by qPCR, with special focus on HER2 and ESR status.

Results

CTC positivity in the cohort was 76%. There was no significant difference between the tested groups, but the highest CTC occurrence was identified in the group undergoing surgery and similarly in the group before the start of neoadjuvant treatment. On the other hand, the lowest CTC frequencies were observed in the menopausal patient group (56%), ESR+ patient group (60%), and DCIS group (44.4%). It is worth noting that after completion of neoadjuvant therapy (NACT) CTCs were present in 77.7% of cases. On the other hand, patients under hormonal treatment were CTC positive only in 52% of cases.

Discussions

Interestingly, HER2 and ESR status of CTCs differs from the status of primary tumor. In 50% of patients HER2 status on CTCs changed not only from HER2+ to HER2−, but also from HER2– to HER2+ (33%). ESR status in CTCs changed only in one direction from ESR+ to ESR−.

Conclusions

Data obtained from the present study suggest that BC is a heterogeneous disease but CTCs may be detected independently of the disease characteristics in 76% of patients at any time point during the course of the disease. This relatively high CTC occurrence in BC should be considered when planning the long-term patient monitoring.

Characterization of circulating tumor cells in early breast cancer patients receiving neoadjuvant chemotherapy

Background and Aims:

The aim of this study was to characterize circulating tumor cells (CTCs) during neoadjuvant chemotherapy (NACT) in early and locally advanced breast cancer (LABC) patients. Using ultrasound, tumor volume measurement was compared with the presence and the molecular nature of CTCs over multiple time intervals corresponding to treatment periods.

Methods:

A total of 20 patients diagnosed with breast cancer (BC) of different histotypes were monitored during the NACT period and in the follow-up period (~5 years). Peripheral blood for CTCs (n = 115) was taken prior to NACT, after two to three chemotherapy cycles, after the completion of NACT (before surgery) and at some time points during adjuvant therapy. CTCs were enriched using a size-based filtration method (MetaCell®) capturing viable cells, which enabled vital fluorescence microscopy. A set of tumor-associated (TA) genes and chemoresistance-associated (CA) genes was analyzed by qPCR in the enriched CTC fractions.

Results:

The analysis of tumor volume reduction after administration of anthracyclines (AC) and taxanes (TAX) during NACT showed that AC therapy was responsive in 60% (12/20) of tumors, whereas TAX therapy was responsive in 30% (6/20; n.s.). After NACT, CTCs were still present in 70.5% (12/17) of patients (responders versus non-responders, 61.5% versus 100%; not significant).

In triple-negative BC (TNBC) patients (n = 8), tumor volume reduction was observed in 75% cases. CTCs were significantly reduced in 42.9% of all HER2-negative BC patients. In HER2+ tumors, CTC reduction was reported in 16.6% only. Relapses were also more prevalent in the HER2-positive patient group (28.5 versus 66.6%).

During NACT, the presence of CTCs (three tests for each patient) identified patients with relapses and indicated significantly shorter progression-free survival (PFS) rates (p = 0.03). Differentiation between progressive disease and non-progressive disease was obtained when the occurrence of excessive expression for CA genes in CTCs was compared (p = 0.024). Absence of tumor volume reduction was also significantly indicative for progressive disease (p = 0.0224).

Disseminated CTCs in HER2-negative tumors expressed HER2 in 29% of samples collected during the overall follow-up period (16/55), and in 32% of samples during the follow-up of NACT (10/31). The change accounted for 78.5% of HER2-negative patients (11/14) in total, and 63.6% of the conversion cases occurred during NACT (7/11). For the remaining four patients (36.3%), conversion to HER2+ CTCs occurred later during adjuvant therapy. We believe there is the possibility of preventing further progression by identifying less responsive tumors during NACT using CTC monitoring, which could also be used effectively during adjuvant therapy.

Molecular characterization of circulating tumor cells in ovarian cancer

The main focus of the study was to detect circulating tumor cells (CTCs) in ovarian cancer (OC) patients using a new methodological approach (MetaCell(TM)) which is based on size-dependent separation of CTCs and subsequent cytomorphological evaluation. Cytomorphological evaluation using vital fluorescence microscopy approach enables to use the captured cells for further RNA/DNA analysis. The cytomorphological analysis is then completed by gene expression analysis (GEA). GEA showed that relative expression of EPCAM is elevated in CTC-enriched fractions in comparison to the whole peripheral blood sample and that the expression grows with in vitro cultivation time. Comparison of the relative gene expression level in the group of peripheral blood samples and CTC-fraction samples confirmed a statistically significant difference for the following genes (p < 0.02): KRT7, WT1, EPCAM, MUC16, MUC1, KRT18 and KRT19. Thus, we suggest that the combination of the above listed genes could confirm CTCs presence in OC patients with higher specificity than when GEA tests are performed for one marker only. The GEA revealed two separate clusters identifying patients with or without CTCs.

The added value of circulating tumor cells examination in ovarian cancer staging

Delayed diagnosis of ovarian cancer (OC) is usually a cause of its high mortality. OC counts for one of the most aggressive gynecological malignancies. Noninvasive biomarkers may be used to help with diagnostic and treatment decisions in OC management. The incidence and clinical significance of occult OC cells (circulating tumor cells-CTCs) in the peripheral blood of patients with newly diagnosed or nondiagnosed OC at the time of surgical intervention were examined in our study. The objective of the study was to isolate and cultivate CTCs in OC patients (mainly stage IIIB-C) by a recently introduced size-based separation method (MetaCell(®)). CTCs were successfully isolated in patients with OC capturing cells with proliferation potential. The cells were enriched in good fitness, which enabled the short term in vitro culture of the CTCs. The CTCs may be used for further downstream applications (e.g. gene expression analysis) even if in the majority of the in vitro CTC cultures no confluence was reached. The CTCs were detected in 77 out of 118 patients (65.2%). CTC positivity was given to the relationship with different disease stage parameters with special focus on CA125 marker levels. The results show that the information on CTC presence may provide new and independent prognosis staging information to the patient description. Several interesting relationships of CA125, age and ascites presence are reported. As shown in our patient sample, patients with ascites tend to have higher CA125 levels, even if the CTCs were not found in the peripheral blood. It suggests that hematogenous dissemination is fully represented by the CTCs while lymphogenic dissemination is represented by elevated CA125. In this context, easy access to CTCs provided by the method applied in our study, both at the time of diagnosis and relapse, may become an increasingly valuable tool in future. This methodology may provide an opportunity for more personalized medicine where treatment for OC may be guided by information from an individual's CTC molecular profile.