Researchers claim that blackberries may be among the most potent cancer-fighting fruits. Blackberries are rich in substances that may have cancer-protective properties. According to studies, Cyanidin 3-glucoside, (which is in blackberries) has chemotherapeutic and chemo-protective activity. Ellagic, another substance in blackberries, has been shown to inhibit cancer cells from forming. These properties in blackberries may effectively prevent cancer, according to scientists.