Running (as in distance mode) is something I've been using to cut the fat down and I'm now at the crossroads of continuing and losing more body fat or stop now and return to resistance training as the primary mode.
Here's my understanding:
Running primarily uses slow twitch muscle fibre and resistance training primarily uses fast twitch muscle fibres. It is true that both types of muscle fibres are used in all exercise and movement to some degree, but generally speaking, when you run, you're using more of the slow types because the muscle contraction over a lengthy period requires oxygen, and slow twitch fibres are the ones that use oxygen to release energy within the muscle.
Basically it all comes down to specificity - what you do you become and what you use more often, you develop more of... lol.. so if you run far more than resistance train, you'll get far more type 1 (slow twitch) fibres.
A lot of what you 'get' in way of dominance of fast and slow muscle fibre types (yes...you have both) is determined genetically, and in the early years of life - according to the experts.
So To get back to your question, I think you'll find that yes, it is possible to continue to gain, yet it is difficult if you're doing more running than resistance training. My guess would be a 30:70 ratio to guarantee gains. (running:resistance).
It's worthwhile noting though, all training needs to recruit both types of fibres - even more so when it comes to running. To be an effective runner you need leg speed (power) training, lactic acid tolerance training, and neuromuscular training.
All in all, you'll only know what suites you when you get out there and give it a go. You'll soon know to taper back the running if you're just not gaining.