Microfluidic Chip-Based Cancer Diagnosis and Prediction of Relapse by Detecting Circulating Tumor Cells and Circulating Cancer Stem Cells

SIMPLE SUMMARY: Metastasis is the main cause of cancer-related death. Circulating cancer stem cells have recently attracted attention because they have higher tumorigenicity than non-stem-like circulating tumor cells. Despite the strong scientific evidence for circulating cancer stem cells and secondary tumor formation, the exact mechanisms behind the generation and characteristics of circulating cancer stem cells are not yet fully understood because of their extreme scarcity. This review aims to introduce the recent advances in the detection and analysis of circulating tumor cells and circulating cancer stem cells. ABSTRACT: Detecting circulating tumor cells (CTCs) has been considered one of the best biomarkers in liquid biopsy for early diagnosis and prognosis monitoring in cancer. A major challenge of using CTCs is detecting extremely low-concentrated targets in the presence of high noise factors such as serum and hematopoietic cells. This review provides a selective overview of the recent progress in the design of microfluidic devices with optical sensing tools and their application in the detection and analysis of CTCs and their small malignant subset, circulating cancer stem cells (CCSCs). Moreover, discussion of novel strategies to analyze the differentiation of circulating cancer stem cells will contribute to an understanding of metastatic cancer, which can help clinicians to make a better assessment. We believe that the topic discussed in this review can provide brief guideline for the development of microfluidic-based optical biosensors in cancer prognosis monitoring and clinical applications.