If the I-140 has been approved for at least 180 days, it may remain valid for certain purposes even if the employer withdraws it, particularly regarding priority date retention. However, if the I-485 has not yet been filed or has not been pending long enough for portability, the green card process may be disrupted.

If the employer withdraws it before 180 days after approval, the employee may lose the green card process and priority date. But if it is after 180 days, there should be no issue