Yes - mating large dogs will make more large dogs, and mating two especially large dogs may concentrate the traits that make dogs large. By the way, timber wolves can weigh as much as 200 pounds - more than nearly any domestic dog.

I don't know if you can genetically engineer one individual dog to start to grow bigger. But you could artificially select a dog breed and make it bigger. People have done this many times. If you constantly breed dogs and only let the largest of the puppies breed with each other, slowly, over many generations, the next generation of dogs will likely become bigger.