Sony Pictures says to lay off 450 workers

* Sony Pictures laying off 6.5 pct of workers

* Move to offset falling DVD sales and box office

LOS ANGELES Feb 1 (Reuters) - Sony Pictures plans to lay off 450 employees, or 6.5 percent of its workforce, in coming weeks to combat falling DVD sales, online piracy and other factors hurting long-term box office and sales growth.

Sony Pictures Entertainment, a division of Sony Corp (6758.T), said on Monday most of the layoff notifications will be completed by the first week of March.

"We are going through a painful time now, and the next couple of months are going to be challenging for everybody," Amy Pascal, co-chairman of Sony Pictures Entertainment, said in a video message to employees.

Sony Pictures last week restructured its home entertainment division, shuffling the executive team for that unit. Aside from laying off 450 employees, Sony Pictures also said it plans to close 100 open positions.

In a memo to employees, Pascal and Michael Lynton, Chairman and CEO of Sony Pictures, said Sony was adjusting to the growth of online piracy, the effects of online social media on box office performance, and changes in DVD buying habits.

"The business is going through a rough period of trial and transition, and we have an obligation to take the steps necessary to get through it," the memo said. (Reporting by Alex Dobuzinskis: Editing by Bernard Orr)