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ORAL 25 - Biology and Other Issues in SCLC (ID 125)
- Event: WCLC 2015
- Type: Oral Session
- Track: Small Cell Lung Cancer
- Presentations: 1
ORAL25.02 - Vasculogenic Mimicry in Small Cell Lung Cancer (ID 2654)
10:45 - 12:15 | Author(s): F. Trapani
Small cell lung cancer (SCLC) accounts for 15-20% of lung cancer cases worldwide and is characterised by early dissemination. Despite initial responses to chemotherapy, most patients relapse with drug resistant disease and long term survival is rare. Targeting tumour vasculature in SCLC with anti-angiogenic drugs produced disappointing results. However, angiogenesis-independent tumour vascularisation including vasculogenic mimicry (VM), warrant further investigation. VM describes the ability of aggressive tumour cells with ‘stem-like’ plasticity to adopt endothelial characteristics and form fluid conducting channel-like structures independent of host vasculature. We sought to determine the prevalence of VM in SCLC and explore associations of VM with chemotherapy sensitivity and patient outcomes. We investigated the role of a VM-associated protein, VE-Cadherin in vitro and in vivo and in SCLC CTCs. We are testing the hypothesis that VM may contribute to the high prevalence of CTCs in SCLC and components of the VM pathway may be targets for SCLC therapeutics.
VM was evaluated using CD31/periodic acid-Schiff (PAS) staining in a tissue micro-array (TMA) from 41 limited stage SCLC chemo-naive patients and in tumours from 11 Circulating Tumour Cell (CTC) Derived Explant (CDX) models (Hodgkinson et al Nature Medicine, 2014). The relative abundance of VM channels (CD31-ve/PAS+ve) compared to host derived blood vessels (CD31+ve/PAS+ve), (VM/total vessels) in the TMA was compared to patient overall survival (OS). VM was evaluated in vitro by network formation in Matrigel (Hendrix et al., PNAS 2001) in a panel of SCLC cells lines and in H446 cells where VE-Cadherin was knocked down with shRNA. H446 cells +/- VE-Cadherin were grown in vivo as xenografts and evaluated for VM. ISET filtered, DAPI stained CTCs were immune-stained for CD45, cytokeratin and VE-cadherin and a VM score was generated.
In the TMA, a VM/Total Vessels score >10% was a poor prognostic factor for OS by univariate (p=0.011) and multivariate (p=0.014) analyses. VM was present in all CDX models provide surrogate tissues in which to study VM. Of 12 SCLC cell lines studied, H446 showed significant VE-Cadherin expression and formed networks in Matrigel; VE-Cadherin shRNA abrogated this network formation. Similarly, a pilot in vivo study demonstrated that there were fewer VM vessels when VE-Cadherin was reduced. In CTC samples 37/38 chemonaive SCLC patients contained a sub-population of VE-Cadherin expressing CTCs where the VM score ranged from 0 – 100% (median 11%, mean 21%).
We present the first evidence of VM in SCLC which correlates with poor OS consistent with findings in other cancer types. VE-Cadherin is required in SCLC for VM network formation in vitro and preliminary data indicate that VE-Cadherin influences VM in vivo. Furthermore, VE-Cadherin and pan-cytokeratin co-expression was found in SCLC CTC sub-populations. We are investigating the role of VE-Cadherin in VM in SCLC and are exploring the hypotheses that VE-cadherin and VM may play a role in drug delivery and/or sensitivity and may represent an aggressive, ‘stem-like’ population that may contribute to dissemination and relapse in this highly aggressive disease.
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