BUZZ-PrivateBancorp Inc: Set for best day ever on CIBC's buyout deal
** Bank holding company's shares up 26.5 pct at $45.46 premarket, set for best day ever
** Canadian Imperial Bank of Commerce to buy company in cash-and-stock deal valued at about $3.8 bln
** Up to Tuesday's close, PrivateBancorp's shares had fallen 12.4 pct this year
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