This study grafted malignant gliomas cells (which are one of the most common types of primary brain tumors) into rat brains to see if nicotinic acid administration would help regulate the implanted tumor. ~70% of the allografted rats that were continuously administered with nicotinic acid were still alive on day 58. 100% of control group died by day 24. Biopsy showed much less tumor spread in nicotinic acid rats. Their results suggest that niacin the helps prevent the invasion of other kinds of malignant cells such as melanoma ( skin cancer ) cells and that this points to a general role of nicotinic acid in regulating tumor invasion.