Chicago--Citing a drop in revenue, The Tribune Co. on Thursday lowered its second-quarter earnings forecast and announced that it will cut 6% of its workforce, or 2000 jobs, through the end of the year. Most of the cuts will come from the company's publishing unit. The media conglomerate, which operates 21 daily newspapers, including the Chicago Tribune and Los Angeles Times, said it expects to report second-quarter earnings of 22 cents a share, excluding non-operating items. Analysts had predicted second-quarter earnings of 28 cents a share. Tribune also said it's launched a voluntary retirement program, which is expected to reduce the work force by 3%, mainly in the company's publishing unit. The company also plans additional cuts within the publishing unit that will reduce the staff another 3%.