In tumors, hypoxia in the center leads to high autophagy activity, and genetically ablating autophagy in tumors results in a 'hollow tumor' because cells in the hypoxic center do not survive.

“and in fact one of the first things we did was when we looked at tumors tumors are well known to have hypoxia in the centre when we engineered tumor cells to be genetically deficient for our Tophet a and you look at them they're completely Hollow I mean they may have no organelles nothing not the cells are hollow the tumor is hollow oh wow the further the cells get from a blood supply meaning the more susceptible they are to hypoxia they're dead right so if you take a tumor if the middle is hypoxic that's where your top of G is most active and if you genetically a blade on top of G in the tumor you end up with a hollow tumor because the tumor cells in the middle don't survive”