The subject of "might underlie"

In the sentence "It seems reversible changes to the DNA scaffold might underlie drug resistance in some cancer cells", the subject for the predicate "might underlie" is "reversible changes to the DNA scaffold"?


Context:

Drug-resistant cancer might forget how to fight
 10 April 2010
DRUG-resistant tumours might be made vulnerable again. It seems reversible changes to the DNA scaffold might underlie drug resistance in some cancer cells.
Jeffrey Settleman of the Massachusetts General Hospital Cancer Center in Charlestown and his colleagues treated tumour cells with cancer drugs. A small subset survived. But placing these "resistant" cells temporarily in a drug-free environment was enough to reverse the resistance: "offspring" of these cells were once again killed by the drugs.