LAS VEGAS, Nev. (AP) _ Entertainment columnist Forrest Duke, whose ''Duke of Las Vegas'' column once ran in 21 newspapers nationwide, died Wednesday following a long bout with emphysema.

He was 69.

''He was very powerful in show business circles, but he was very careful how he used that power and how he spoke about entertainers,'' said Jim Seagrave, publicity director at the Frontier Hotel. ''He was on a first-name basis with every big name in the business, but he always took time out to cover the newcomers. So many times it was his mention of these newcomers that gave them their first big break.''

Duke was the entertainment columnist for the Las Vegas Review-Journal until his retirement in April 1986. He was honored shortly after his retirement in a farewell gala hosted by more than two dozen entertainment personalities as well as fellow journalists and hotel executives.

Duke, who wrote a column for 28 years, died at Desert Springs Hospital.

Duke is survived by his wife, Florence; two sons; three grandchildren; a niece and three nephews.