You can and it wouldn't hurt the speaker but I would advise against it and it isn't because of the shape of the cabinet. The speakers response profile particularly the horizontal and vertical off-axis are designed for the speaker to be orientated vertically.

Placing the speaker horizontally will be specifically detrimental to the horizontal off-axis response and IMO a very bad trade-off. Keep it vertical!

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne