ABSTRACT
Proanthocyanidins, compounds highly concentrated in dietary fruits, such as cranberries and grapes, demonstrate significant cancer prevention potential against many types of cancer. The objective of this study was to evaluate cranberry and grape seed extracts to quantitate and compare their anti-proliferative effects on the most common type of oral cancer, oral squamous cell carcinoma. Using two well-characterized oral squamous cell carcinoma cell lines, CAL27 and SCC25, assays were performed to evaluate the effects of cranberry and grape seed extract on phenotypic behaviors of these oral cancers. The proliferation of both oral cancer cell lines was significantly inhibited by the administration of cranberry and grape seed extracts, in a dose-dependent manner. In addition, key regulators of apoptosis, caspase-2 and caspase-8, were concomitantly up-regulated by these treatments. However, cranberry and grape seed extracts elicited differential effects on cell adhesion, cell morphology, and cell cycle regulatory pathways. This study represents one of the first comparative investigations of cranberry and grape seed extracts and their anti-proliferative effects on oral cancers. Previous findings using purified proanthocyanidin from grape seed extract demonstrated more prominent growth inhibition, as well as apoptosis-inducing, properties on CAL27 cells. These observations provide evidence that cranberry and grape seed extracts not only inhibit oral cancer proliferation but also that the mechanism of this inhibition may function by triggering key apoptotic regulators in these cell lines. This information will be of benefit to researchers interested in elucidating which dietary components are central to mechanisms involved in the mediation of oral carcinogenesis and progression.
ABSTRACT
BACKGROUND: Approximately 30,000 people are diagnosed with oral cancer annually in the United States. Recent evidence suggests that nutrition may play a more complex role in the prevention of oral cancers than previously believed. Proanthocyanidins (PACs) are a class of compounds found in normal dietary foods that exhibit chemopreventive properties and chemotherapeutic potential. Recently preliminary evidence suggests that PACs inhibit the proliferation of oral cancer cell lines. The primary goal of this study was to elucidate the mechanisms responsible for previous observations that grape seed-derived PACs significantly inhibited oral cancer proliferation. METHODS: Using the well-characterized oral squamous cell carcinoma cell lines, CAL27 and SCC25, as well as nontumorigenic cell lines, a series of in vitro assays was performed to quantify the temporal and dose-specific growth inhibitory properties of PAC on oral cancers. In addition, quantitative analysis of mRNA from key intracellular signaling pathway molecules, involved in both cell-cycle control and apoptosis, were analyzed using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). RESULTS: This study found that oral cancer proliferation was inhibited by 24 hours in the PAC concentration range of 50-70 µg/mL with concomitant decreases in mRNA expression of specific cell-cycle regulators, and increases in the expression of apoptosis-specific molecules, such as caspase-2 and caspase-8. CONCLUSION: These results may represent the first demonstration of simultaneous, temporal inhibition of cell-cycle signaling pathways with the activation of specific apoptosis-related signaling pathways within oral cancers in response to PAC, lending further support to the concept that PACs may be promising candidates for adjuvant or complementary therapies for oral cancer patients.
