Not unless you want really fast breaks and really slow DNB, usually theres about 30bpm difference between the two styles, 145bpm for breaks and 175bpm for dnb, so if you try mixing them one after the other it will sound terrible.
you could use a break down into a different tempo to add drama to your mix, or you could do it gradually, working from breaks into some jungle around 160bpm, and work up to full tempo drum & bass, but probably going to take about 20 mins to make a smooth transition between the styles