Change employers , group co after i-140 approval

[psani]

I have completed my 6 years on H1 B visa. My i-140 has been approved and am waiting for PD to get current to file I-485. Can I take up a new job with a group company, I believe AC 21 portability cannot be applied since I-485 has not been applied?? If so, 2nd option - can my application continue with the existing company and the new group company sub contracts this position with them? Any risks associated with this?

Thanks ,
PS.