Here you go....
Here is a chat from Murthy
Chat User : Hi. My I-140 and I-485 have been pending for more than 10 months. I am currently working on my EAD for another employer. What happens if my I-140 is revoked before it is approved? Will my I-485 application stand good?
Attorney Murthy : As repeatedly mentioned before in MurthyChat sessions, and as stated by the USCIS in their August 2003 Headquarters policy Memo on AC21, if the employer revokes the I-140 petition before it is approved, the I-485 cannot stand and may be denied by the USCIS. Both of the following conditions have to be satisfied for the person to enjoy I-485 portability: first, the I-140 has to be approved; second, the I-485 has to be pending in excess of 180 days; and third, the employee needs to show that the new job is in the same or similar field for the GC to be portable to the new employer.