Hypoxia stimulates CTC-platelet cluster formation to promote breast cancer metastasis
Circulating tumor cell clusters/micro-emboli (CTM) possess greater metastatic capacity and survival advantage compared to individual circulating tumor cell (CTCs). However, the formation of CTM subtypes and their role in tumor metastasis remain unclear. In this study, we used a microfluidic Cluster-chip with easy operation and high efficiency to isolate CTM from peripheral blood, which confirmed their correlation with clinicopathological features and identified the critical role of CTC-platelet clusters in BC metastasis. The correlation between platelets and CTM function was further confirmed in a mouse model and RNA-seq of CTM identified high-expressed genes related to hypoxia stimulation and platelet activation which possibly suggested the correlation of hypoxia and CTC-platelet cluster formation.  In conclusion, we successfully developed the Cluster-chip platform to realize the clinical capture of CTMs and analyze the biological properties of CTC-platelet clusters, which could benefit the design of potential treatment regimens to prevent CTM-mediated metastasis and tumor malignant progression. Overall design: In order to  further understand the mechanism of CTM hematogenous metastasis, examination of the molecular characteristics of CTM can aid in elucidating the mechanism of CTM-mediated hematogenous metastasis. For this purpose, we used the Cluster-chip to recover CTM in mice with lung metastasis secondary to breast cancer for RNA sequencing to investigate the biological characteristics of hematogenous metastasis with a control group comprised of the 4T1 cell line.