It isn't possible I don't think. I bought NBA 2K10, 11 and 12 all 3 Retail DVD versions here in the UK.
None of them CD Keys activated for me on Steam!
Only Retail DVD games that are Steamworks activate on Steam.
Plus there isn't any real advantage getting the Steam version as it doesn't support Steam achievements anyway. If your concern is that you want to chat with friends, organize clan/leagues then you can download Xfire for that matter. Xfire would do the exact same job if not better than Steam.
Otherwise there isn't any other particular advantage with the Steam version. Unless you don't have a DVD drive.

I am gonna buy the Retail version this Friday official UK release. You won't lose anything. I always like to keep a collection of my PC games physically!
Plus you get a manual booklet with instructions for the game, which is handy unlike the Steam version.