Place the brisket in a stainless steel or glass container. In a small bowl, stir together broth soy sauce, lemon juice, and liquid smoke; pour over brisket. Place in refrigerator and marinate overnight.
Preheat oven to 325 degrees F (165 degrees C). Remove brisket from marinade and place in a 9x13 inch baking dish. Bake in a preheated oven for 6 hours or until tender.
For the sauce, in a small bowl combine the softened cream cheese and horseradish. Whisk together thoroughly.
