RNA sequencing of pancreatic circulating tumour cells implicates WNT signaling in metastasis

Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, Massachusetts 02114, USA.
Nature (Impact Factor: 41.46). 07/2012; 487(7408):510-3. DOI: 10.1038/nature11217
Source: PubMed


Circulating tumour cells (CTCs) shed into blood from primary cancers include putative precursors that initiate distal metastases. Although these cells are extraordinarily rare, they may identify cellular pathways contributing to the blood-borne dissemination of cancer. Here, we adapted a microfluidic device for efficient capture of CTCs from an endogenous mouse pancreatic cancer model and subjected CTCs to single-molecule RNA sequencing, identifying Wnt2 as a candidate gene enriched in CTCs. Expression of WNT2 in pancreatic cancer cells suppresses anoikis, enhances anchorage-independent sphere formation, and increases metastatic propensity in vivo. This effect is correlated with fibronectin upregulation and suppressed by inhibition of MAP3K7 (also known as TAK1) kinase. In humans, formation of non-adherent tumour spheres by pancreatic cancer cells is associated with upregulation of multiple WNT genes, and pancreatic CTCs revealed enrichment for WNT signalling in 5 out of 11 cases. Thus, molecular analysis of CTCs may identify candidate therapeutic targets to prevent the distal spread of cancer.

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Available from: Shannon L Stott
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    • "As well, new technologies allowing the detection of circulating tumor cells (CTCs; Ramskold et al., 2012) may allow for the interrogation of the circulation survival step in the metastasis cascade. Although this has initially been performed, for example in pancreatic cancer, the use of an endothelial marker (cytokeratin) for CTC detection may exclude cells that have undergone EMT (Yu et al., 2012). Finally, our initial glimpse into the vastness of non-coding RNA transcription was greatly facilitated by the advent of improved whole transcriptome analysis techniques, such as RNA sequencing. "
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    • "Therefore, elucidating the mechanisms involved in this process is crucial. Metastasis is considered to begin with epithelial-to-mesenchymal transition (EMT), a cascade of events during which tumor cells lose their epithelial characteristics and acquire mesenchymal cell characteristics (1). The change in the tumor cells is accompanied by an increase in motility and matrix invasion. "
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    ABSTRACT: Metastasis, a cascade of events beginning with epithelial-to-mesenchymal transition (EMT), is the main cause of cancer-related mortality. EMT endows circulating cancer cells (CTCs) with invasive and anti-apoptotic properties. These transitioning cells leave the primary tumor site and travel through the circulation to populate remote organs, even prior to the onset of clinical symptoms. During this journey, CTCs activate platelets, which in turn secrete α-granules. These α-granules contain high levels of transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF), both considered to be powerful activators of EMT. Recently, regular aspirin use was associated with a reduced risk of cancer metastasis. However, the molecular mechanism underlying the chemotherapeutic effects of aspirin on metastasis has not been fully elucidated. As platelets lack a nucleus, regular aspirin use may exert long-lasting effects on irreversible inhibition of cyclooxygenase (COX)-1 and, subsequently, the secretion of α-granules, which contributes to the maintenance of the EMT state of CTCs. Thus, we hypothesized that the inhibition of platelet-induced EMT of CTCs through the COX-1 signaling pathway may contribute to the intriguing antimetastatic potential of aspirin.
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    • "This will ultimately help us to better understand, prevent and eventually cure the disease efficiently [10,53]. For example, screening cancer by analyzing Circulating Tumor Cells (CTCs) from peripheral blood [64] will enable the understanding of the mechanism of carcinogenesis in terms of transformation, lineage structure and clonal evolution [2]. Additionally, such single-cell screening will potentially allow for detection of genetic mutations or chromosome abnormalities in an embryo or fetus with a single or a few nucleated red blood cells (nRBC) enriched from the peripheral blood of the mother (non-invasive prenatal diagnosis)[65], or with a blastomere isolated from an in vitro fertilized embryo (preimplantation genetic diagnosis, or screening) [2,65-67]. "
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