I dont think the cas9 is causing the off target mutations according to those papers, it's more potentially selecting for cells with already dysfunctional p53 in

I dont think the cas9 is causing the off target mutations according to those papers, it's more potentially selecting for cells with already dysfunctional p53 in those few cell lines by inducing a p53 mediated dna damage response. It's in cells that arent going to go near humans and are pretty different in form and function than those used in trials, and while it's a risk to consider (not trying to downplay potential risks here- all new medicine and biology must be thoroughly evaluated for safety and risk), it's nowhere near a show-stopping demonstration that CAS9 mediated editing causes cancer and hasn't stopped clinical trials from moving forward