Excitotoxins have been found to dramatically promote cancer growth and metastasis. In fact, one aspartame researcher noticed that, when cancer cells were exposed to aspartame, they became more mobile, and you see the same effect with MSG. It also causes a cancer cell to become more mobile, and that enhances metastasis, or spread. These MSG-exposed cancer cells developed all of these pseudopodians and started moving through tissues, which is one of the earlier observations from cancer.
When you increase the glutamate level, cancer just grows like wildfire, and then when you block glutamate, it dramatically slows the growth of the cancer.