For short term cultivation periods, this should be no problem. I did some of my MM6 experiments in DMEM as well and it worked. I never checked, if they could grow for a long time in DMEM. MAybe you could do this.
According to the original publication of Ziegler-Heitbrock, MM6 cells needed, in addition to the supplements all cells need, oxalacetate and pyruvate. If you observe some cultivation problems, you could try to add these 2 compounds to the DMEM basic medium. I was always using OPI supplement from Sigma.