In span of 14 verses, the gospel of Jesus Christ is equated with the gospel of God. Aristotelian logic: Things equal to the same thing are equal to one another.
Don’t neglect such connections when you are talking to Jehovah’s Witnesses and other groups who deny the deity of Christ. There are hundreds of these kind of passages in the New Testament. Hunt them down and use them as you defend with gentleness what the Scripture teaches about our great God.