The tumour suppressor ING1 shares many biological functions with p53, such as cell cycle arrest, DNA repair, apoptosis, and chemosensitivity. Since p53 inhibits invasion and angiogenesis of melanoma cells, we sought to investigate if p33ING1 (one of ING1 isoforms) is also involved in these biological processes. We first overexpressed p33ING1 in melanoma cells and assessed the protein levels in MMP-1, MMP-2, and MMP-9. Results from Western blot analysis showed no significant difference in these matrix metalloproteinase levels between cells transfected with vector, p33ING1, and antisense p33ING1. Wound healing assay was performed to examine if p33ING1 plays a role in migration and invasion. Results showed that there was no difference between vector, p33ING1, and antisense p33ING1 groups in melanoma cell migration across the wound. Western blot analysis also indicated that there is no difference in the levels of proteins which are directly involved in angiogenesis, such as VEGF, Flt-1, and Flk-1, between cells transfected with vector, p33ING1, and antisense p33ING1. Furthermore, functional studies indicated that cultured medium derived from p33ING1-transfected melanoma cells did not stimulate the growth of HUVEC cells, compared to controls, providing support to the lack of functional role of p33ING1 in angiogenesis. In conclusion, we demonstrate in vitro that p33ING1, unlike p53, does not play a role in angiogenesis and migration in melanoma cells.

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