SAN FRANCISCO, March 22 (Reuters) - Instagram is expected to announce on Wednesday that it has reached more than 1 million monthly active advertisers, as the Facebook Inc-owned FB.O photo-sharing app tries to become a center of online commerce.

The number of advertisers has grown five-fold from 200,000 a year ago, Instagram's vice president for business, James Quarles, said in a phone interview this week. He called the 1 million number a "milestone."

Facebook bought Instagram for $1 billion in 2012, and initially, the app had limited advertising with only a handful of well-known brands.

Last year, Instagram began pushing businesses that had created standard profiles to adopt business-specific profiles, and 8 million businesses have done so, Quarles said. Instagram is able to use Facebook's ad technology to target specific audiences.

Facebook's apps compete against rivals such as Snap Inc SNAP.N , Alphabet Inc's GOOGL.O Google and Twitter Inc TWTR.N for slices of digital advertising spending.

Quarles declined to give projections for further growth. He said there was "tremendous upside" and added: "This is about getting as many businesses as we can to have pages."





(Reporting by David Ingram; Editing by Peter Cooney) ((David.Ingram@thomsonreuters.com; +1 415 344 4938; Reuters Messaging: David.Ingram.thomsonreuters.com@reuters.net))