These findings are supported by several direct facts, including the following: (i) CD9P-1 expression correlated with the metastatic status of hLT and was inversely proportional to CD9 expression; (ii) the truncated form of CD9P-1, GS-168AT2, was rapidly internalised by tumour cells correlating with its interaction with both CD9 and CD81; and most importantly, (iii) treatments of hLT-xenografted Nude mice with GS-168AT2 led to a drastic inhibition of hLT growth that was associated with an important in vivo downregulation of CD9 in the tumour core, but not in CD81. This evidence concerns the gene PTGFRN and neoplasm.