title: Circulating tumour cells--a bona fide cause of metastatic cancer.
abstract: Circulating tumour cells (CTCs) are emerging as important prognostic markers and have potential clinical utility as tumour biomarkers for targeted cancer therapy. Although CTCs were proposed more than 100 years ago as potential precursors that may form metastatic lesions, formal evidence that CTCs are indeed capable of initiating metastases is limited. Moreover, the process of CTCs shedding into the circulation, relocating to distant organ sites and initiating metastatic foci is complex and intrinsically inefficient. To partially explain the metastatic process, the concepts of CTCs as metastatic precursors or pre-metastatic conditioners have been proposed; however, it is questionable as to whether these are both variable pathways to metastasis or just markers of metastatic burden. This review explores the evidence for CTCs in the initiation and progression of metastatic cancer and the data supporting these different concepts in an attempt to better understand the role of CTCs in metastasis. A greater understanding of the metastatic potential of CTCs will open new avenues for therapeutic interventions in the future.
authors.affiliation: South West Sydney Translational Cancer Research Unit, Ingham Institute for Applied Medical Research, Liverpool Hospital, Liverpool, NSW, 2170, Australia, nicole.caixeiro@sswahs.nsw.gov.au.
authors.forename: N J
authors.initials: NJ
authors.lastname: Caixeiro
authors.forename: N
authors.initials: N
authors.lastname: Kienzle
authors.forename: S H
authors.initials: SH
authors.lastname: Lim
authors.forename: K J
authors.initials: KJ
authors.lastname: Spring
authors.forename: A
authors.initials: A
authors.lastname: Tognela
authors.forename: K F
authors.initials: KF
authors.lastname: Scott
authors.forename: P
authors.initials: P
authors.lastname: de Souza
authors.forename: T M
authors.initials: TM
authors.lastname: Becker
mesh_terms: D000818:Animals; D006801:Humans; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D009360:Neoplastic Cells, Circulating; D059016:Tumor Microenvironment