I’m glad you pointed to this article. This is one of my favorite quotes:
“‘We know the [niacin/butyrate GPR109A] receptor is silenced in cancer but it’s not like the gene goes away,’ says Dr. Vadivel Ganapathy, corresponding author and chair of the Department of Biochemistry and Molecular Biology in the MCG School of Medicine.”

For instance: 
“GPR109A expression is silenced in breast cancer”
https://www.researchgate.net/figure/GPR109A-expression-is-silenced-in-breast-cancer-A-and-B-expression-of-GPR109A-and_fig5_259473949

Butyrate was likely not getting into the colon properly for many without many/all of these other essential nutrients now per the two videos recouped yet. Perhaps the pancreas was getting it then for those with tumors developing there? Butyrate we know is an essential immune fuel, so I would say it plays a role everywhere, and this is why I have brought it back in (to be recouped if needed, which is for many after COVID / as they age, even still trying to endogenously restore it, a little boost now for everyone will be big, and I think for pretty much every cancer, with full protocol, should be huge in curing – via getting that GPR109A re-upregulated/modulated for niacin to crush)