Can polar and brown bears interbreed?

Yes, there is one known specimen of the Grizzly Bear that Bred with a Polar Bear and unfortunately the way they got the specimen was by that of a taxidermist that was not able to put the skin of the bear on either one of those models (this was a young bear) and the hunter that shot and killed the bear was so proud to have the only known specimen in which the blood was tested later in a laboratory to reveal the two sets of DNA from both types of Bears.