Allow me to clarify then...
It would seem that the exact pathway is still an unknown.
Is there a specific animal protein based benzene/amine sequence processed by the human gut and passed to our cells that can trigger cancerous mutation? It would “seem” that such a pathway exists in other species... But it is still an unknown for us...
My Uncle was a bio-chem scientist who lost a two year battle with pancreatic cancer. It’s given me a renewed interest in the topic.
Judging by the physical structure of heterocyclic amines, I would hypothesize that the carcinogenic properties result from their ability to intercalate with DNA (that is, they stick themselves between the base-pairs). This causes deformation of the DNA, which affects the ability of DNA replication and repair enzymes to properly bind to and act on DNA.
Since some essential nutrients are also heterocyclic amines, I would also hypothesize that the carcinogenic heterocyclic amines are resistant to enzyme action that would normally shunt them into various metabolic pathways for further processing.
I also happen to be a biochemist, PhD type.