(-)-Oleocanthal (oleocanthal) is a phenolic compound found in varying concentrations in extra virgin olive oil oleocanthal has been shown to be active physiologically, benefiting several diseased states by conferring anti-inflammatory and neuroprotective benefits. Recently, we and other groups have demonstrated its specific and selective toxicity toward cancer cells; however, the mechanism leading to cancer cell death is still disputed. The current study demonstrates that oleocanthal, as well as naturally oleocanthal-rich extra virgin olive oils, induced damage to cancer cells’ lysosomes leading to cellular toxicity in vitro and in vivo . Lysosomal membrane permeabilization following oleocanthal treatment in various cell lines was assayed via three complementary methods. Additionally, we found oleocanthal treatment reduced tumor burden and extended lifespan of mice engineered to develop pancreatic neuroendocrine tumors. Finally, following-up on numerous correlative studies demonstrating consumption of olive oil reduces cancer incidence and morbidity, we observed that extra virgin olive oils naturally rich in oleocanthal sharply reduced cancer cell viability and induced lysosomal membrane permeabilization while oleocanthal-poor oils did not. Our results are especially encouraging since tumor cells often have larger and more numerous lysosomes, making them especially vulnerable to lysosomotropic agents such as oleocanthal.

Prostate cells are hormonally driven to grow and divide. Typical treatments for prostate cancer involve blocking activation of the androgen receptor by androgens. Androgen deprivation therapy can lead to the selection of cancer cells that grow and divide independently of androgen receptor activation. Prostate cancer cells that are insensitive to androgens commonly display metastatic phenotypes and reduced long-term survival of patients. In this study we provide evidence that androgen-insensitive prostate cancer cells have elevated PLD activity relative to the androgen-sensitive prostate cancer cells. PLD activity has been linked with promoting survival in many human cancer cell lines; and consistent with the previous studies, suppression of PLD activity in the prostate cancer cells resulted in apoptotic cell death. Of significance, suppressing the elevated PLD activity in androgen resistant prostate cancer lines also blocked the ability of these cells to migrate and invade Matrigel™. Since survival signals are generally an early event in tumorigenesis, the apparent coupling of survival and metastatic phenotypes implies that metastasis is an earlier event in malignant prostate cancer than generally thought. This finding has implications for screening strategies designed to identify prostate cancers before dissemination.