Sharon Disney Lund, a daughter of Walt Disney, died yesterday of complications from cancer. She was 56.Lund died at 9:30 a.m. at St. John’s Hospital and Health Center, said Dick Lippin, a spokesman for the family. She was a director of the Walt Disney Co. since 1984 and was an officer of Retlaw Enterprises Inc., a successor to the corporation her father organized in 1952 for certain personal business ventures. She also was a trustee of the California Institute of the Arts, the Marianne Frostig Center of Educational Therapy, and the Curtis School Foundation. She was also active with the Los Angeles County Music Center. Lund is survived by her mother, Lillian Disney, daughters Victoria and Michelle, son Brad and sister Diane Disney Miller. Her first husband, Robert Brown, died. She was divorced from her second husband, Bill Lund.