Lead is a toxic heavy metal and is not known to be used in any biological processes.
Yet some organisms do possess genes, but moreso for detoxification and sequestration of lead, humans included.
However, polymorphic forms of preexisting genes could potentially affect: polymorphic forms of the delta-aminolevulinic acid dehydratase gene (ALAD), which is involved in the heme biosynthesis pathway, has actually been shown to affect blood and bone lead levels.
So, if say, increased expression of both polymorphic forms of the gene, or a gain of function mutation that allows for constitutive expression via pluripotency and morphogenic redifferentiation (somehow).
There's also the vitamin D receptor VDR gene, which polymorphic forms could also influence accumulation of lead in bone.
This could also potentially explain why the Engine's effects didn't work on everyone: Polymorphisms are variants of alleles (alternate versions of genes) that only some proportion of the population posseses.
Unsure % of population that possess these polymorphisms, though, since you do see massive phenotypical changes in most Variants' cases.
It could be that the nanofactory (expression of lead tumors) part did work (for some) but the control part didn't (but that's kind of out of my realm of understanding).
But that would also mean heavy external lead influence (ie, Murkoff treating victims with lead).
tl;dr. Amendment to my "it's most likely iron based tumors" comment on my last post— it possibly could be lead, but still unlikely as we don't actually use lead in biological processes, unlike iron.
(Based off A O Onalaja et al. 2000, Genetic Susceptibility to Lead Poisoning)



















