** Regional lender Pacific Premier Bancorp's PPBI.O shares rise 1.7% to $20.46 in early trading
** Umpqua Bank-parent Columbia Banking System COLB.O will buy PPBI in a $2 billion all-stock deal, the companies announced late Wednesday
** COLB shares fall 3.6% to $22.68
** Deal values PPBI at $20.83 per share, implying a 3.6% upside to stock's last close
** Transaction, expected to close in the second half of 2025, will create a combined bank with about $70 billion in assets and bolster COLB's presence in Western U.S.
** Umpqua Bank plans to change its name to Columbia Bank later this year to "ensure brand clarity" as it deepens its expansion throughout the West
** PPBI stock has fallen 17.7% YTD while COLB is down 16% YTD
(Reporting by Arasu Kannagi Basil in Bengaluru)
((ArasuKannagi.Basil@thomsonreuters.com;))