AMERICAN EXPRESS <AXP> TO DISCUSS SHEARSON DEAL American Express Co's board of directors Monday will discuss the company's arrangement to sell 13 pct of Shearson Lehman Brothers Inc to Nippon Life Insurance Co, a company spokesman said. The spokesman would not say whether the board is planning to vote on the understanding between American Express and Nippon Life. The Shearson stake is to be sold for 530 mln dlrs, American Express has said. The spokesman also would not comment on speculation that the board was to discuss a sale of securities to the public. Monday's board meeting is a regular monthly meeting. The plan to sell part of Shearson to Nippon Life must be approved by the American Express board and Japan's Ministry of Finance. Earlier, American Express and Shearson said they were subpoenaed by the Securities and Exchange Commission. American Express said it was subpoenaed for documents pertaining to securities transactions of American Express and Fireman's Fund. Shearson was subpoenaed for documents related to transactions with Jefferies and Co and others. The American Express spokesman said he could not comment on whether any officials of the firm were subpoenaed.