March 2 (Reuters) - Union Pacific Corp's Chief Executive Officer James Young, 59, is taking a medical leave of absence for pancreatic cancer treatment, the largest publicly held U.S. railroad company said on Friday.
John Koraleski, executive vice president of marketing and sales, will step up as acting president and CEO of the Omaha, Nebraska-based company.
Young will remain chairman of the board during his leave, which a spokesman said is effectively immediately.
Young, who joined the company in 1978, was elected chairman in January 2007 and president and CEO in 2005. He is also on the boards of the FXE Railroad in Mexico, the University of Nebraska Medical Center, Joslyn Art Museum Foundation, Creighton University and Boys Town, according to Union Pacific's website.
Koraleski has held his position since 1999 and in that role has been responsible for the company's six major business units -- agriculture, chemicals, energy, industrial products and intermodal -- that account for nearly $16 billion in annual revenue. He joined the company in 1972.
Union Pacific's shares were up 0.2 percent in early trading at $111.72 on the New York Stock Exchange and are up 5.5 percent so far this year. The Dow Jones Transportation average has risen 3.7 percent in that time.