Comcast is moving forward with plans to spin off its NBCUniversal cable television networks including MSNBC and CNBC, sources say, shedding a once core part of the business that has been a casualty of the streaming video revolution.

In a move that could portend more changes in the declining business of traditional television, Comcast, the parent company of NBC, announced plans on Wednesday morning to break off several of its cable channels and put them into a separate company.

Comcast is spinning off into a new company many of its cable television networks that were once at the heart of the entertainment giant, as consumers increasingly swap out their cable TV subscriptions