Aspartame Is a Possible Cause of Cancer in Humans, a WHO Agency Says

Well, we do know that it's during cellular reproduction when DNA is copied, that genetic mutations most often happen. So in theory, anything that our body can metabolize, is carcinogenic in the sense that energy intake fuels cell growth/reproduction. In other words, eating causes cellular growth -> which causes DNA to be copied -> which increases the chances of mutations occurring from DNA replication -> which increases the chances of cancer occurring. Aspartame is broken down to aspartic acid and phenylalanine which your body does metabolize so yes, it could theoretically increase the chances of cancer occurring in this way.

But then again, almost everything is carcinogenic in this sense - even breathing oxygen. Perhaps it would be helpful if we start considering what substances are more or less carcinogenic, rather than merely asking whether they are carcinogenic at all. Along that thinking, I'd wager that aspartame is probably less carcinogenic than say, sugar.

Everything is a chemical. Table salt is NaCl, Sugar is C12O1H22, water is H2O, ...

Aspartame is made of two amino acids. The amino acids are the parts of the protein, like the proteins in meat. So aspartame is just a "short protein" of length 2, but biologist have and arbitrary threshold of 50 or 100 to call it a protein.

It's one of the mot innocent looking artificial sweeteners because it has no weird parts that are not in normal food. Saccharin is weird and IIRC it's not part of normal food. If you me the formula of Sucralose, I would guess it's an insecticide instead of a sweetener.