Tracking metastatic breast cancer: the future of biology in biosensors

Circulating Tumor Cells in Breast Cancer Patients: A Balancing Act between Stemness, EMT Features and DNA Damage Responses

Circulating tumor cells (CTCs) traverse vessels to travel from the primary tumor to distant organs where they adhere, transmigrate, and seed metastases. To cope with these challenges, CTCs have reached maximal flexibility to change their differentiation status, morphology, migratory capacity, and their responses to genotoxic stress caused by metabolic changes, hormones, the inflammatory environment, or cytostatic treatment. A significant percentage of breast cancer cells are defective in homologous recombination repair and other mechanisms that protect the integrity of the replication fork. To prevent cell death caused by broken forks, alternative, mutagenic repair, and bypass pathways are engaged but these increase genomic instability. CTCs, arising from such breast tumors, are endowed with an even larger toolbox of escape mechanisms that can be switched on and off at different stages during their journey according to the stress stimulus. Accumulating evidence suggests that DNA damage responses, DNA repair, and replication are integral parts of a regulatory network orchestrating the plasticity of stemness features and transitions between epithelial and mesenchymal states in CTCs. This review summarizes the published information on these regulatory circuits of relevance for the design of biomarkers reflecting CTC functions in real-time to monitor therapeutic responses and detect evolving chemoresistance mechanisms.

PPFIA1 is upregulated in liver metastasis of breast cancer and is a potential poor prognostic indicator of metastatic relapse

Although the oncogenic role of PPFIA1 (liprin-α1) in breast cancer has been reported, whether its dysregulation is associated with metastasis risk or survival outcomes in breast cancer patients is not clear. Our primary data showed that PPFIA1 expression was significantly higher in liver metastatic breast tumors than in the primary tumors. Then, we tried to pool previous annotated genomic data to assess the prognostic value of PPFIA1 in distant metastasis-free survival, the risk of metastatic relapse, and metastatic relapse-free survival in breast cancer patients by data mining in two large databases, Kaplan-Meier plotter and bc-GenExMiner 4.0. Results from Kaplan-Meier plotter showed that although high PPFIA1 expression was generally associated with decreased distant metastasis-free survival in estrogen receptor+ patients, subgroup analysis only confirmed significant association in estrogen receptor+/N- (nodal negative) group (median survival, high PPFIA1 group vs low PPFIA1 cohort: 191.21 vs 236.22 months; hazard ratio: 2.23, 95% confidence interval: 1.42-3.5, p < 0.001), but not in estrogen receptor+/N+ (nodal positive) group (hazard ratio: 1.63, 95% confidence interval: 0.88-3.03, p = 0.12). In estrogen receptor- patients, there was no association between PPFIA1 expression and distant metastasis-free survival, no matter in Nm (nodal status mixed), N-, or N+ subgroups. In bc-GenExMiner 4.0, Nottingham Prognostic Index- and Adjuvant! Online-adjusted analysis validated the independent prognostic value of PPFIA1 in metastatic risks in estrogen receptor+/N- patients. Based on these findings, we infer that high PPFIA1 expression might be an independent prognostic indicator of increased metastatic relapse risk in patients with estrogen receptor+/N- breast cancer, but not in estrogen receptor+/N+ or estrogen receptor- patients.

HET0016 decreases lung metastasis from breast cancer in immune-competent mouse model

Distant metastasis is the primary cause of death in the majority of the cancer types. Recently, much importance has been given to tumor microenvironment (TME) in the development of invasive malignant tumors, as well as the metastasis potential. The ability of tumor cells to modulate TME and to escape immune-mediated attack by releasing immunosuppressive cytokines has become a hallmark of breast cancer. Our study shows the effect of IV formulation of HET0016 (HPßCD-HET0016) a selective inhibitor of 20-HETE synthesis, administered intravenously in immune-competent in vivo mouse model of murine breast cancer. 4T1 luciferase positive cells were implanted to the mammary fat pad in Balb/c mice. Treatment started on day 15, and was administered for 5 days a week for 3 weeks. The development of metastasis was detected via optical imaging. Blood, spleen, lungs, bone marrow and tumor were collected for flow cytometry, to investigate changes in myeloid-derived suppressive cells (MDSCs) populations and endothelial phenotype. Tumor and lungs were collected for protein analysis. Our results show that HPßCD-HET0016: (1) decreased tumor volume and lung metastasis compared to the vehicle group; (2) reduced migration and invasion of tumor cells and levels of metalloproteinases in the lungs of animals treated with HPßCD-HET0016 via PI3K/AKT pathway; and (3) decreased expression of pro-inflammatory cytokines, growth factors and granulocytic MDSCs population in the lung microenvironment in treated animals. Thus, HPßCD-HET0016 showed potential in treating lung metastasis in a preclinical mouse model and needs further investigations on TME.

Identification of high independent prognostic value of nanotechnology based circulating tumor cell enumeration in first-line chemotherapy for metastatic breast cancer patients

Enumeration of circulating tumor cells (CTCs) is a promising tool in the management of metastatic breast cancer (MBC). This study investigated the capturing efficiency and prognostic value of our previously reported peptide-based nanomagnetic CTC isolation system (Pep@MNPs). We counted CTCs in blood samples taken at baseline (n = 102) and later at patients' first clinical evaluation after starting firstline chemotherapy (n = 72) in a cohort of women treated for MBC. Their median follow-up was 16.3 months (range: 9.0-31.0 months). The CTC detection rate was 69.6 % for the baseline samples. Patients with ≤2 CTC/2 ml at baseline had longer median progression-free survival (PFS) than did those with >2 CTC/2 ml (17.0 months vs. 8.0 months; P = 0.002). Patients with ≤2 CTC/2 ml both at baseline and first clinical evaluation had longest PFS (18.2 months) among all patient groups (P = 0.004). Particularly, among patients with stable disease (SD; per imaging evaluation) our assay could identify those with longer PFS (P < 0.001). Patients with >2 CTC/2 ml at baseline were also significantly more likely to suffer liver metastasis (P = 0.010). This study confirmed the prognostic value of Pep@MNPs assays for MBC patients who undergo firstline chemotherapy, and offered extra stratification regarding PFS for patients with SD, and a possible indicator for patients at risk for liver metastasis.