Could the An-225 use Trent 500 engines?
There have been various proposals to use Western engines on new versions of the An-124:

An-124-200: Proposed version with General Electric CF6-80C2 engines, each rated at 59,200 lbf (263 kN)
An-124-210: Joint proposal with Air Foyle to meet UK's Short Term Strategic Airlifter (STSA) requirement, with Rolls-Royce RB211-524H-T engines, each rated 60,600 lbf (264 kN) and Honeywell avionics—STSA competition abandoned in August 1999, reinstated, and won by the Boeing C-17A.

Antonov fell victim to the fall of the Soviet Union: its HQ is in independent Ukraine which doesn't have the best relations with Moscow, so Antonov's sales cratered and left them with no development funds for new versions of the An-124. Western-engined versions were proposed to generate some sales in the West, but potential buyers were scared off by having to buy a paper project (and having to pay for development of the new version).

Along with the modest improvements to the An-124 being considered for new production of the aircraft, the Antonov organization has also investigating a more ambitious cargolifter, an improved hybrid of the An-124 and An-225 called the &quot;An-124-300&quot;. It would feature the fuselage of the An-124 and the extended wing of the An-225, kitted up with modern avionics and engines. Since more powerful engines are now available, only four would be needed instead of six. The cargo floor would be extended, and a palletized loading system would be installed. It would have a maximum range of 11,500 kilometers (7,145 miles) with a 100-tonne (110-ton) cargo. Development costs were cited as less than a billion USD.
Given that the relationship between Ukraine and Russia is antagonistic, the Antonov organization is very interested in &quot;Westernizing&quot; the An-124 and any follow-ons -- using Western avionics and systems at the very least, and possibly re-engining the aircraft with Western turbofans.