Circulating tumor cells (CTCs) bearing phenotypes related to cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT) have been identified in breast cancer; however, their clinical significance is not clear. In the current study, we investigated the prognostic relevance of single CSC+/partial-EMT+ CTCs in patients with metastatic breast cancer and the effect of first-line chemotherapy on their incidence. For this purpose, triple immunofluorescence against cytokeratin, ALDH1, and TWIST1 was performed in peripheral blood mononuclear cell (PBMC) cytospins from 130 patients before and after first-line chemotherapy. CSC+/partial-EMT+ CTCs were characterized as cells co-expressing cytokeratin, high levels of ALDH1, and nuclear TWIST1. CSC+/partial-EMT+ CTCs were evident in 27.7% of patients at baseline and were correlated to lung metastases (P = 0.010) and decreased progression-free survival [PFS; median 10.2 (8.9–11.6) vs. 13.5 (11.3–15.7) months; P = 0.024]. Their detection was an independent factor predicting for increased risk of relapse [multivariate analysis; HR (95% confidence interval (CI)): 1.785 (1.171–2.720); P = 0.007]. In HER-2–negative patients, CSC+/partial-EMT+ CTCs were additionally associated with reduced overall survival (OS) [median 39 (26.2–51.9) vs. 51 (15.7–86.4) months; P = 0.020] and increased risk of death [multivariate analysis; HR (95% CI): 2.228 (1.066–4.655); P = 0.033]. Chemotherapy resulted in a significant increase in the incidence of CSC+/partial-EMT+ CTCs (mean CTC% per patient: 59.4% post vs. 39.5% pre; P = 0.018), which was subsequently confirmed only in HER2-negative patients (P = 0.040) and in non-responders at the end of treatment (P = 0.020). In conclusion, CSC+/partial-EMT+ CTCs represent a chemoresistant subpopulation, which independently predicts for unfavorable outcome in metastatic breast cancer. Efficient targeting of these CTCs could potentially increase patient survival.

Background: In primary breast cancer metastases frequently arise from a state of dormancy that may persist for extended periods of time. We investigated the efficacy of plasma micro-RNA (miR)-21, miR-23b, miR-190, miR-200b and miR-200c, related to dormancy and metastasis, to predict the outcome of patients with early breast cancer. Methods: miRNAs were evaluated by RT-qPCR in plasma obtained before adjuvant chemotherapy. miRNA expression, classified as high or low according to median values, correlated with relapse and survival. Receiver operating characteristic (ROC) curves were constructed to determine miRNA sensitivity and specificity. Results: miR-21 (p < 0.001), miR-23b (p = 0.028) and miR-200c (p < 0.001) expression were higher and miR-190 was lower (p = 0.013) in relapsed (n = 49), compared to non-relapsed patients (n = 84). Interestingly, miR-190 was lower (p = 0.0032) in patients with early relapse (at < 3 years; n = 23) compared to those without early relapse (n = 110). On the other hand, miR-21 and miR-200c were higher (p = 0.015 and p < 0.001, respectively) in patients with late relapse (relapse at ≥ 5 years; n = 20) as compared to non-relapsed patients. High miR-200c was associated with shorter disease-free survival (DFS) (p = 0.005) and high miR-21 with both shorter DFS and overall survival (OS) (p < 0.001 and p = 0.033, respectively) compared to low expression. ROC curve analysis revealed that miR-21, miR-23b, miR-190 and miR-200c discriminated relapsed from non-relapsed patients. A combination of of miR-21, miR-23b and miR-190 showed higher sensitivity and specificity in ROC analyses compared to each miRNA alone; accuracy was further improved by adding lymph node infiltration and tumor grade to the panel of three miRs (AUC 0.873). Furthermore, the combination of miR-200c, lymph node infiltration, tumor grade and estrogen receptor predicted late relapse (AUC 0.890). Conclusions: Circulating miRNAs are differentially expressed among relapsed and non-relapsed patients with early breast cancer and predict recurrence many years before its clinical detection. Our results suggest that miRNAs represent potential circulating biomarkers in early breast cancer.

Novel therapies have significantly improved survival for non-metastatic non-small cell lung cancer (NSCLC), however recurrence remains a challenge. Current treatment and surveillance strategies rely on imaging and clinical assessments with limited sensitivity in early detection of disease progression. Liquid biopsy-mediated detection of minimal residual disease (MRD) allows monitoring of tumor activity at the molecular level before clinical and radiologic progression. Here, we review the current evidence for MRD in the adaptive management and surveillance of non-metastatic NSCLC, focusing on the missing links that prevent its widespread clinical adoption.

Circulating miRNAs as a marker of metastatic disease and prognostic factor in metastatic breast cancer Circulating miRNAs as a marker of metastatic disease and prognostic factor in metastatic breast cancer

The role of the microbiome in cancer and its crosstalk with the tumor microenvironment (TME) has been extensively studied and characterized. An emerging field in the cancer microbiome research is the concept of the intratumoral microbiome, which refers to the microbiome residing within the tumor. This microbiome primarily originates from the local microbiome of the tumor-bearing tissue or from translocating microbiome from distant sites, such as the gut. Despite the increasing number of studies on intratumoral microbiome, it remains unclear whether it is a driver or a bystander of oncogenesis and tumor progression. This review aims to elucidate the intricate role of the intratumoral microbiome in tumor development by exploring its effects on reshaping the multileveled ecosystem in which tumors thrive, the TME. To dissect the complexity and the multitude of layers within the TME, we distinguish six specialized tumor microenvironments, namely, the immune, metabolic, hypoxic, acidic, mechanical and innervated microenvironments. Accordingly, we attempt to decipher the effects of the intratumoral microbiome on each specialized microenvironment and ultimately decode its tumor-promoting or tumor-suppressive impact. Additionally, we portray the intratumoral microbiome as an orchestrator in the tumor milieu, fine-tuning the responses in distinct, specialized microenvironments and remodeling the TME in a multileveled and multifaceted manner.