| 1. |
- Olmeda, David, et al.
(författare)
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Whole-body imaging of lymphovascular niches identifies pre-metastatic roles of midkine
- 2017
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 546:7660, s. 676-680
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Tidskriftsartikel (refereegranskat)abstract
- Cutaneous melanoma is a type of cancer with an inherent potential for lymph node colonization, which is generally preceded by neolymphangiogenesis(1-3). However, sentinel lymph node removal does not necessarily extend the overall survival of patients with melanoma(4,5). Moreover, lymphatic vessels collapse and become dysfunctional as melanomas progress(6,7). Therefore, it is unclear whether (and how) lymphangiogenesis contributes to visceral metastasis. Soluble and vesicle-associated proteins secreted by tumours and/or their stroma have been proposed to condition pre-metastatic sites in patients with melanoma(8-14). Still, the identities and prognostic value of lymphangiogenic mediators remain unclear(2,14). Moreover, our understanding of lymphangiogenesis (in melanomas and other tumour types) is limited by the paucity of mouse models for live imaging of distal pre-metastatic niches(15). Injectable lymphatic tracers have been developed(7), but their limited diffusion precludes whole-body imaging at visceral sites(16). Vascular endothelial growth factor receptor 3 (VEGFR3) is an attractive 'lymphoreporter' 17 because its expression is strongly downregulated in normal adult lymphatic endothelial cells, but is activated in pathological situations such as inflammation and cancer(17,18). Here, we exploit this inducibility of VEGFR3 to engineer mouse melanoma models for whole-body imaging of metastasis generated by human cells, clinical biopsies or endogenously deregulated oncogenic pathways. This strategy revealed early induction of distal pre-metastatic niches uncoupled from lymphangiogenesis at primary lesions. Analyses of the melanoma secretome and validation in clinical specimens showed that the heparin-binding factor midkine is a systemic inducer of neo-lymphangiogenesis that defines patient prognosis. This role of midkine was linked to a paracrine activation of the mTOR pathway in lymphatic endothelial cells. These data support the use of VEGFR3 reporter mice as a 'MetAlert' discovery platform for drivers and inhibitors of metastasis.
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| 2. |
- Zhao, Ziran, et al.
(författare)
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PPP2R2A prostate cancer haploinsufficiency is associated with worse prognosis and a high vulnerability to B55 alpha/PP2A reconstitution that triggers centrosome destabilization
- 2019
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Ingår i: Oncogenesis. - : NATURE PUBLISHING GROUP. - 2157-9024. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The PPP2R2A gene encodes the B55 alpha regulatory subunit of PP2A. Here, we report that PPP2R2A is hemizygously lost in similar to 42% of prostate adenocarcinomas, correlating with reduced expression, poorer prognosis, and an increased incidence of hemizygous loss (>75%) in metastatic disease. Of note, PPP2R2A homozygous loss is less common (5%) and not increased at later tumor stages. Reduced expression of B55 alpha is also seen in prostate tumor tissue and cell lines. Consistent with the possibility that complete loss of PPP2R2A is detrimental in prostate tumors, PPP2R2A deletion in cells with reduced but present B55 alpha reduces cell proliferation by slowing progression through the cell cycle. Remarkably, B55 alpha-low cells also appear addicted to lower B55 alpha expression, as even moderate increases in B55 alpha expression are toxic. Reconstitution of B55 alpha expression in prostate cancer (PCa) cell lines with low B55 alpha expression reduces proliferation, inhibits transformation and blocks xenograft tumorigenicity. Mechanistically, we show B55 alpha reconstitution reduces phosphorylation of proteins essential for centrosomal maintenance, and induces centrosome collapse and chromosome segregation failure; a first reported link between B55 alpha/PP2A and the vertebrate centrosome. These effects are dependent on a prolonged metaphase/anaphase checkpoint and are lethal to PCa cells addicted to low levels of B55 alpha. Thus, we propose the reduction in B55 alpha levels associated with hemizygous loss is necessary for centrosomal integrity in PCa cells, leading to selective lethality of B55 alpha reconstitution. Such a vulnerability could be targeted therapeutically in the large pool of patients with hemizygous PPP2R2A deletions, using pharmacologic approaches that enhance PP2A/B55 alpha activity.
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