Citrus flavone tangeretin inhibits leukaemic HL-60 cell growth partially through induction of apoptosis with less cytotoxicity on normal lymphocytes.
British Journal of Cancer. 1995 December;72(6):1380-8
Antitumor agents can induce apoptosis in tumour cells, but they may also be toxic to normal cells such as myelocytes and immunocytes. The aim of this study wa to investigate the cytotoxic effects of tangeretin on human leukaemia cells and blood mononuclear cells. The presence of tangeretin resulted in apoptosis of only the tumour cells. This effect was significantly attenuated in the presence of zink ions, suggesting that protein synthesis is required for tangeretin-induced apoptosis. The study concluded that tangeretin has antitumor activity by inhibiting growth of the human leukemia cells in vitro without causing serious side effects on immune cells.
Flavonoids (apigenin, tangeretin) counteract tumor promoter-induced inhibition of intercellular communication of rat liver epithelial cells.
Cancer Letters. 1997 March 19;114(1-2):207-10
Connexins or gap junction proteins are proteins that assemble to form vertebrate gap junctions. These junctions are essential for many physiological processes an intercellular communication. This study investigated the influence of apigenin and tangeretin on the gap junctional intercellular communication in rat liver epithelial cells. The researchers found that these two phytochemicals antagonized the inhibition of gap junctional intercellular communication induced by chemical tumor promoters. Other flavonoids including naringenin, myricetin, catechin and chrysin did not show such effect.
Inhibition of bacterial mutagenesis by Citrus flavonoids.
Planta Medica. 1996 Jun;62(3):222-6
This study investigated the anti-mutagenicity of the phytochemicals naringin, hesperidin, nobiletin and tangeretin. The researchers used the Ames test to determined influence of these phytochemicals on the mutagenic effect of the mutagens benzo-a-pyrene, 2-aminofluorene, quercetin and nitroquinoline-N-oxide. The anti-oxidant quercetin has been show to possess mutagenic properties but the intake of food containing quercetin is considered safe because this foods contains other anti-mutagenic phytochemicals and quercetin can also act as anti-mutagen. The researchers found that both naringin and hesperidin showed a weak anti-mutagenic activity against benzo-a-pyrene only. Tangeretin was anti-mutagenic against all tested mutagens. Nobiletin acted as an anti-mutagen against quercetin and benzo-a-pyrene but enhanced the mutagenicity of 2-aminofluorene. The study concluded that citrus flavonoids naringin, hesperidin, nobiletin and tangeretin might play a role in the chemoprevention of cancer.
Antiproliferative effects of citrus flavonoids on a human squamous cell carcinoma in vitro.
Cancer Letters. 1991 February;56(2):147-52
Kandaswami C and his colleagues looked at the effect of the four flavonoids quercetin, taxifolin, nobiletin and tangeretin on the viability of cultured human skin cancer cells. The two polymethoxylated flavonoids nobiletin and tangeretin significantly inhibited cell growth whereas quercetin and taxifolin showed no significant effect. inhibition at any of the concentrations tested. The researchers speculated that the hydrophobic methoxyl groups increase membrane uptake of these flavonoids.
Tangeretin and nobiletin induce G1 cell cycle arrest but not apoptosis in human breast and colon cancer cells.
Cancer Letters. 2007 June 18;251(1):168-78
In vitro and in vivo studies have shown that the two citrus flavonoids tangeretin and nobiletin have antitumor activity because they inhibit growth of cancer cells. This study investigated this inhibitory effect on human breast cancer cells and human colon cancer cells. Morley and his colleagues found that both phytochemicals inhibited the cell proliferation by stopping the cell cycle progression at the G1 phase but did not cause cell death, even at high concentrations. When the treatment of cancer cells with the flavonoids were stopped the cells continued to grow normally, indicating that their effect is only cytostatic. The use of tangeretin and nobiletin as anticancer agents looks promising because they restrict cell proliferation without cytotoxic effects.
Treatment of metastatic melanoma B16F10 by the flavonoids tangeretin, rutin, and diosmin.
Journal of Agriculture and Food Chemistry. 2005 August 24;53(17):6791-7
Melanoma cancer can easily spread to other organs. The aim of this in vitro study was to examine the effect of the flavonoids tangeretin, rutin and diosmin on the formation of metastatic nodules. The researchers found that all three phytochemicals, but especially diosmin reduced the formation of metastatic nodules.
Tangeretin induces cell-cycle G1 arrest through inhibiting cyclin-dependent kinases 2 and 4 activities as well as elevating Cdk inhibitors p21 and p27 in human colorectal carcinoma cells.
Carcinogenesis. 2002 October;23(10):1677-84
Epidemiological studies have shown that the intake of foods containing flavonoids can help to prevent cancer. Tangeretin is a flavonoid mainly found in the peel of citrus fruits, where it probably acts as an antifungal agent. The peel of Dancy tangerins contains 5x higher levels of tangeretin than oranges. Previous studies have shown that tangeretin enhances gap junctional intracellular communication and inhibits cancer cell growth. The aim of this study was to determine the effects of tangeretin and other flavonoids on the growth of colon cancer cells. The researchers measured cyclin levels, p53 protein levels, phosphorylation state of Rb and the activities of some kinases. They found that mainly tangeretin, but also luteolin and nobiletin inhibited colon cancer cell growth. The results indicate that tangeretin inhibits cell growth of colon cancer cells by increasing levels of cyclin-dependent kinases inhibitory units and decreasing the activity of cyclin-dependent kinases.
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