Abstract 77: bcl-xL protein overexpression enhances tumor progression of human melanoma cells in zebrafish xenograft model: Involvement of CXCL8 chemokine
Authors: Gabellini Chiara , Gómez Elena , Oliveira Sofia de , Bufalo Donatella Del , Mulero Victoriano 
Published: May 2015

The anti-apoptotic protein bcl-xL, whose expression is associated with melanoma progression, enhances metastatic potential in different tumor hystotypes and promotes tumor angiogenesis through enhancing pro-inflammatory chemokine interleukin 8 (CXCL8) expression. Using the derivative clones of human melanoma M14 cell line stably overexpressing bcl-xL protein, we evaluated the impact of bcl-xL/CXCL8 axis in promoting melanoma angiogenesis and aggressiveness in vivo using zebrafish as experimental model. Implantation of M14 trasfectants overexpressing bcl-xL protein into the yolk sac of 2 days post-fertilization (dpf) zebrafish embryos resulted in higher significant dissemination from primary site of injection and metastatization to distal parts of the larvae when compared to control cell line. Since the enhanced invasiveness showed by bcl-xL overexpressing cells might be due to their enhanced CXCL8 protein secretion, we tested the capability of human recombinant CXCL8 protein to induce angiogenesis in zebrafish. When injected in the yolk sac of 2dpf transgenic fli1:EGFP embryos, increasing doses of human CXCL8 protein induced a significant increased percentage of larvae positive for subintestinal veins (SIVs) sprouting at 24 hours post-injection (hpi). Moreover, while the proinflammatory activity of CXCL8 is conserved between humans and zebrafish, there are no evidences that this chemokine elicits pro-angiogenic activity in zebrafish. To this aim, we injected zebrafish recombinant Cxcl8-L2 in the yolk sac of 2dpf transgenic fli1:EGFP zebrafish embryos, demonstrating that it is able to induce SIVs sprouting at 24hpi, but at a lesser extent than human CXCL8. However when comparing the capability of human and zebrafish CXCL8 to induce neutrophils recruitment after injection in the yolk sac, we found that human CXCL8 is not able to induce the recruitment to the zebrafish compartment, in contrast to its zebrafish homologue. Next, through the use of morpholino-mediated depletion, we will investigated the involvement of CXCL8 receptors Cxcr1 and Cxcr2, highly conserved between humans and zebrafish, in the capability of bcl-xL protein to enhance melanoma cell invasion in zebrafish larvae and with the aim of elucidating the signaling pathways involved in the proangiogenic activity of human CXCL8 chemokine in zebrafish.

These data elucidate the involvement of CXCL8 signalling in bcl-xL-induced melanoma progression, supporting future studies for developing new therapeutic approaches for tumors characterized by high bcl-xL expression. Moreover the conservation of pro-angiogenic activity of CXCL8 molecule in zebrafish establishes the possible use of this experimental model to study the efficacy of novel compounds inhibiting CXCL8 axis to counteract tumor progression.

Note: This abstract was not presented at the meeting.

Citation Format: Chiara Gabellini, Elena Gómez, Sofia de Oliveira, Donatella Del Bufalo, Victoriano Mulero. bcl-xL protein overexpression enhances tumor progression of human melanoma cells in zebrafish xenograft model: Involvement of CXCL8 chemokine. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 77. doi:10.1158/1538-7445.AM2014-77