Differential effects of 1,25-dihydroxyvitamin D3 on oral squamous cell carcinomas in vitro.

OBJECTIVE: The inverse association between vitamin D and cancer risk is well-established, but the relationship with oral cancer is less well-understood. To further the understanding of these relationships, this study sought to evaluate any growth-inhibiting effects of vitamin D on well-characterized oral cancers. METHODS: This study utilized 1,25-dihydroxy Vitamin D3 to evaluate any changes in growth using CAL27, SCC15, and SCC25 oral cancer cell lines at physiological and supraphysiological concentrations. RESULTS: These assays revealed that the growth of all three cancer cell lines was significantly reduced by vitamin D administration, with maximal inhibition in SCC15 of -6.8% at 50 nmol, -19.7% in CAL27, and -43.6% in SCC25 at 100 nmol (p < .05). In addition, the observed decreases in growth were associated with significant decreases in viability (ranging from -18% in SCC15, -23% in CAL27, and -47% in SCC25 cells), as well as activation of two key apoptotic pathways (caspase and bcl:bax). CONCLUSION: The results of this study demonstrate the growth-inhibitory effects of vitamin D administration in specific oral cancer cell lines, which will enhance the understanding of oral oncologists and oral health researchers in developing standards for generalizing the health-protective effects of diet and dietary supplements as treatment options for patients with oral cancer.

Folic acid supplementation increases survival and modulates high risk HPV-induced phenotypes in oral squamous cell carcinoma cells and correlates with p53 mRNA transcriptional down-regulation.

BACKGROUND: Although the primary risk factors for developing oral cancers are well understood, less is known about the relationship among the secondary factors that may modulate the progression of oral cancers, such as high-risk human papillomavirus (HPV) infection and folic acid (FA) supplementation. This study examined high-risk HPV and FA supplementation effects, both singly and in combination, to modulate the proliferative phenotypes of the oral cancer cell lines CAL27, SCC25 and SCC15. RESULTS: Using a comprehensive series of integrated in vitro assays, distinct effects of HPV infection and FA supplementation were observed. Both high-risk HPV strains 16 and 18 induced robust growth-stimulating effects in CAL27 and normal HGF-1 cells, although strain-specific responses were observed in SCC25 and SCC15 cells. Differential effects were also observed with FA administration, which significantly altered the growth rate of the oral cancer cell lines CAL27, SCC15, and SCC25, but not HGF-1 cells. Unlike HPV, FA administration induced broad, general increases in cell viability among all cell lines that were associated with p53 mRNA transcriptional down-regulation. None of these cell lines were found to harbor the common C677T mutation in methylenetetrahydrofolate reductase (MTHFR), which can reduce FA availability and may increase oral cancer risk. CONCLUSION: Increased FA utilization and DNA hypermethylation are common features of oral cancers, and in these cell lines, specifically. The results of this study provide further evidence that FA antimetabolites, such as Fluorouracil (f5U or 5-FU) and Raltitrexed, may be alternative therapies for tumors resistant to other therapies. Moreover, since the incidence of oral HPV infection has been increasing, and can influence oral cancer growth, the relationship between FA bioavailability and concomitant HPV infection must be elucidated. This study is among the first pre-clinical studies to evaluate FA- and HPV-induced effects in oral cancers, both separately and in combination, which provides additional rationale for clinical screening of HPV infection prior to treatment.

Soy protein extract (SPE) exhibits differential in vitro cell proliferation effects in oral cancer and normal cell lines.

Prior research has demonstrated that specific isoflavones derived from soy may exhibit antitumor effects against many cancers, including oral cancer. Most of this prior research involved isolation and testing of individual soy components, such as genistein, daidzein, and glycitein, which exhibit cytotoxicity against cancerous cells but may also have residual cytotoxic effects on normal cells. Few studies have evaluated whole soy extract, containing a combination of these isoflavones, and other bioreactive compounds, which may function synergistically and more effectively against oral cancers. This study compared the antiproliferative effects of whole soy protein extract (SPE) on CAL 27 and SCC25 oral cancer cell lines in vitro. Administration of SPE significantly inhibited oral cancer growth and exerted these effects at lower concentrations compared with another class of flavonoids (proanthocyanidins) that were previously tested on these cell lines. This SPE-induced growth inhibition correlated with down-regulated mRNA expression in the oral cancer cell-cycle promoter ornithine decarboxylase (ODC), as well as upregulation of caspase-2 and caspase-8, initiators and effectors of apoptosis. These results suggest that SPE may represent a potential chemopreventive or chemotherapeutic option for oral cancer. Moreover, SPE may be more effective than other flavonoids currently used and may be effective at lower concentrations that approximate physiologic serum levels (0-2 µmol/l). This study may help to explain why diets rich in fruits, vegetables, and soy protein are associated with protection against development and progression of oral cancers, although further study is needed to develop specific public health recommendations for oral cancer treatment and prevention.

Folate supplementation induces differential dose-dependent modulation of proliferative phenotypes among cancerous and noncancerous oral cell lines in vitro.

Sufficient folate intake confers positive health benefits, while deficiency is linked with many health problems. Although the US policy of dietary folic acid fortification has reduced the incidence of these deficiency-related health problems, recent evidence has demonstrated an association between folic acid supplementation and increased colorectal cancer incidence. Few studies have explored the possibility that folate affects other slowly developing cancers. This study sought to determine whether folic acid supplementation is sufficient to alter the growth and development of existing oral cancers. A series of in vitro growth, viability, and adhesion assays were performed using the well-characterized human oral squamous cell carcinoma cell lines, CAL27 and SCC25, to determine the effects of folic acid supplementation. Folic acid administration significantly stimulated CAL27 and SCC25 proliferation in a dose-dependent manner, but it was not sufficient to increase proliferation at any concentration tested in the normal control cell line, HGF-1. Neither oral cancer cell line harbored the common C677T DNA polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene, which might reduce folate bioavailability. Overexpression of p53 mRNA was observed in both cancerous cell lines, but it was differentially altered by folic acid administration in only SCC25 cells. These findings suggest folic acid administration may significantly alter growth of oral cancers in vitro via p53-dependent and p53-independent pathways. As oral cancer rates continue to rise in specific geographic areas, and among specific subsets of the US population, understanding environmental mediators, such as folic acid supplementation, becomes increasingly important for nutrition and public health scientists.