Functional analysis of flavonoid 3',5'-hydroxylase from tea plant (Camellia sinensis): critical role in the accumulation of catechins.

BACKGROUND: Flavonoid 3',5'-hydroxylase (F3'5'H), an important branch point enzyme in tea plant flavan-3-ol synthesis, belongs to the CYP75A subfamily and catalyzes the conversion of flavones, flavanones, dihydroflavonols and flavonols into 3',4',5'-hydroxylated derivatives. However, whether B-ring hydroxylation occurs at the level of flavanones and/or dihydroflavonols, in vivo remains unknown. RESULTS: The Camellia sinensis F3'5'H (CsF3'5'H) gene was isolated from tea cDNA library. Expression pattern analysis revealed that CsF3'5'H expression was tissue specific, very high in the buds and extremely low in the roots. CsF3'5'H expression was enhanced by light and sucrose. Over-expression of CsF3'5'H produced new-delphinidin derivatives, and increased the cyanidin derivative content of corollas of transgenic tobacco plants, resulting in the deeper transgenic plant flower color. Heterologous expressions of CsF3'5'H in yeast were carried out to demonstrate the function of CsF3'5'H enzyme in vitro. Heterologous expression of the modified CsF3'5'H (CsF3'5'H gene fused with Vitis vinifera signal peptide, FSI) revealed that 4'-hydroxylated flavanone (naringenin, N) is the optimum substrate for CsF3'5'H, and was efficiently converted into both 3'4'- and 3'4'5'-forms. The ratio of 3'4'5'- to 3'4'-hydroxylated products in FSI transgenic cells was significantly higher than VvF3'5'H cells. CONCLUSIONS: CsF3'5'H is a key controller of tri-hydroxyl flavan-3-ol synthesis in tea plants, which can effectively convert 4'-hydroxylated flavanone into 3'4'5'- and/or 3'4'-hydroxylated products. These findings provide animportant basis for further studies of flavonoid biosynthesis in tea plants. Such studies would help accelerate flavonoid metabolic engineering in order to increase B-ring tri-hydroxyl product yields.

Regulatory T cells are associated with post-cryoablation prognosis in patients with hepatitis B virus-related hepatocellular carcinoma.

BACKGROUND: We carried out this study to evaluate the association between regulatory T cells (Treg) and prognosis and progression after cryoablation in patients with hepatitis-B virus-related hepatocellular carcinoma. METHODS: Peripheral Treg frequency in 111 patients with hepatocellular carcinoma (HCC) was detected by flow cytometry. Treg frequency and function were re-examined during patient follow up. A possible association between Treg and α-fetoprotein (AFP) was also analyzed, and the distribution of resident CD4(+) and CD8(+) T cells and FoxP3(+) T cells in the liver tissue of patients with HCC was examined by immunohistochemistry. RESULTS: Treg frequency significantly increased with disease progression. Our longitudinal study showed that Treg frequency had significantly decreased in 17 patients with HCC regression following cryoablation, but the frequency had dramatically increased in 14 patients with HCC recurrence or progression. Furthermore, AFP levels varied in a way comparable with Treg frequency in patients with elevated AFP recorded before therapy. Significantly increased suppressive effects of Treg on proliferation and cytokine secretion of CD8(+) and CD4(+) T cells were observed during follow up in patients with tumor progression, but not in patients with tumor response. Moreover, the numbers of CD8(+), CD4(+), and FoxP3(+) cells infiltrating the tumors around the cryotherapeutic zones were significantly decreased after argon-helium cryoablation, and this was associated with a reduction in the FoxP3/CD8 ratio. Importantly,increased quantities of circulating CD4(+)CD25(+)FoxP3(+) Treg and tumor infiltrating FoxP3(+) cells before cryoablation were associated with high recurrence or risk of progression in HCC patients after cryoablation. CONCLUSIONS: Treg variation is associated with tumor regression or progression in HCC following cryoablation and may be used as a marker to estimate HCC progression.

Efficacy of argon-helium cryosurgical ablation on primary hepatocellular carcinoma: a pilot clinical study.

BACKGROUND AND OBJECTIVE: Recent years, great progression has been made in treating primary hepatocellular carcinoma (HCC) with argon-helium cryosurgical ablation. This study was to evaluate its efficacy on unresectable primary HCC. METHODS: A total of 124 primary HCC patients were divided into early stage, middle stage and advanced stage groups according to BCLC staging classification. Clinical symptoms, tumor size, serum level of alpha-fetoprotein (AFP), complications, and survival time were analyzed. RESULTS: After cryoablation of the tumors, serum level of AFP was reduced in 76 (82.6%) patients, 205 (92.3%) of the 222 tumor lesions were diminished or unchanged. Untill April 2008, 14 patients survived and 110 died. The median survival time was 31.25 months in early stage group, 17.41 months in middle stage group and 6.82 months in advanced stage group. CONCLUSION: For the patients with unresectable HCC, argon-helium cryosurgical ablation has the advantages of few complications and certain efficacy.