Switching from Cap Exempt Employer to Cap Subject Employer

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I have been on H1-B for a little over 6 years. The first 3 years I worked for Cap-Subject employer A, after which I switched to a cap-exempt employer B. Employer B filed my PERM and I-140. Now I have an offer from employer C, which is a cap-subject employer. Is it possible to transfer my H1 from cap-exempt employer B to cap-subject employer C based on the fact that I have already been through the lottery once? 

My I-140 is through cap exempt employer B for a job that is significantly different from the job that I have been offered at cap subject employer C. If I can switch, I will start my PERM process again with employer C. But does my current I-140 limit my ability to transfer to a job that is of significantly different responsibility with a cap subject employer.