The estate of Lehman Brothers Holdings sued JP Morgan Chase, alleging that the firm helped drive Lehman into bankruptcy by forcing it to give up billions of dollars in cash reserves that it otherwise could have used to stay afloat. The suit, filed Wednesday, says JP Morgan forced the now-failed bank to put up collateral in the days before it collapsed that sapped Lehman of cash that, at the least, would have enabled it to wind down operations in an orderly process.