CXCL4L1-fibstatin cooperation inhibits tumor angiogenesis, lymphangiogenesis and metastasis.

Anti-angiogenic and anti-lymphangiogenic drugs slow tumor progression and dissemination. However, an important difficulty is that a tumor reacts and compensates to obtain the blood supply needed for tumor growth and lymphatic vessels to escape to distant loci. Therefore, there is a growing consensus on the requirement of multiple anti-(lymph)angiogenic molecules to stop cell invasion efficiently. Here we studied the cooperation between endogenous anti-angiogenic molecules, endostatin and fibstatin, and a chemokine, the Platelet Factor-4 variant 1, CXCL4L1. Anti-angiogenic factors were co-expressed by IRES-based bicistronic vectors and their cooperation was analyzed either by local delivery following transduction of pancreatic adenocarcinoma cells with lentivectors, or by distant delivery resulting from intramuscular administration in vivo of adeno-associated virus derived vectors followed by tumor subcutaneous injection. In this study, fibstatin and CXCL4L1 cooperate to inhibit endothelial cell proliferation, migration and tubulogenesis in vitro. No synergistic effect was found for fibstatin-endostatin combination. Importantly, we demonstrated for the first time that fibstatin and CXCL4L1 not only inhibit in vivo angiogenesis, but also lymphangiogenesis and tumor spread to the lymph nodes, whereas no beneficial effect was found on tumor growth inhibition using molecule combinations compared to molecules alone. These data reveal the synergy of CXCL4L1 and fibstatin in inhibition of tumor angiogenesis, lymphangiogenesis and metastasis and highlight the potential of IRES-based vectors to develop anti-metastasis combined gene therapies.

The p53 isoform, Δ133p53α, stimulates angiogenesis and tumour progression.

The tumour suppressor p53, involved in DNA repair, cell cycle arrest and apoptosis, also inhibits blood vessel formation, that is, angiogenesis, a process strongly contributing to tumour development. The p53 gene expresses 12 different proteins (isoforms), including TAp53 (p53 (or p53α), p53ß and p53γ) and Δ133p53 isoforms (Δ133p53α, Δ133p53ß and Δ133p53γ). The Δ133p53α isoform was shown to modulate p53 transcriptional activity and is overexpressed in various human tumours. However, its role in tumour progression is still unexplored. In the present study, we examined the involvement of Δ133p53 isoforms in tumoural angiogenesis and tumour growth in the highly angiogenic human glioblastoma U87. Our data show that conditioned media from U87 cells depleted for Δ133p53 isoforms block endothelial cell migration and tubulogenesis without affecting endothelial cell proliferation in vitro. The Δ133p53 depletion in U2OS osteosarcoma cells resulted in a similar angiogenesis blockade. Furthermore, using conditioned media from U87 cells ectopically expressing each Δ133p53 isoform, we determined that Δ133p53α and Δ133p53γ but not Δ133p53ß, stimulate angiogenesis. Our in vivo data using the chicken chorio-allantoic membrane and mice xenografts establish that angiogenesis and growth of glioblastoma U87 tumours are inhibited upon depletion of Δ133p53 isoforms. By TaqMan low-density array, we show that alteration of expression ratio of Δ133p53 and TAp53 isoforms differentially regulates angiogenic gene expression with Δ133p53 isoforms inducing pro-angiogenic gene expression and repressing anti-angiogenic gene expression.