For skin, I'm sorry, I've never immortalized this kind of cells...but probably it can be done by serial replating of cells (Immortalization by serial passage)...
Thanks for your answers. I actually was thinking to SV40 immortalization (with Lenti-SV40) that seems to be more reliable or hTERT immortalization but, having never tried these protocols, I would like to know if they are really better than Epstein Barr. Regarding serial replating (immortalization by serial passages) are there articles or review articles that compare it with other methods? Or this protocol is used when viruses fail?