Huanyu Jin

Cancer prevention by tea: Evidence from laboratory studies.

The cancer preventive activities of tea (Camellia sinensis Theaceae) have been studied extensively. Inhibition of tumorigenesis by green tea extracts and tea polyphenols has been demonstrated in different animal models, including those for cancers of the skin, lung, oral cavity, esophagus, stomach, small intestine, colon, bladder, liver, pancreas, prostate, and mammary glands. Many studies in cell lines have demonstrated the modulation of signal transduction and metabolic pathways by (-)-epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea. These molecular events can result in cellular changes, such as enhancement of apoptosis, suppression of cell proliferation, and inhibition of angiogenesis. Nevertheless, the molecular mechanisms of inhibition of carcinogenesis in animals and humans remain to be further investigated. Future research directions in this area are discussed.

Curcumin Induces the Differentiation of Myeloid-Derived Suppressor Cells and Inhibits Their Interaction with Cancer Cells and Related Tumor Growth

Myeloid-derived suppressor cells (MDSC) accumulate in the spleen and tumors and contribute to tumor growth, angiogenesis, and progression. In this study, we examined the effects of curcumin on the activation and differentiation of MDSCs, their interaction with human cancer cells, and related tumor growth. Treatment with curcumin in the diet or by intraperitoneal injection significantly inhibited tumorigenicity and tumor growth, decreased the percentages of MDSCs in the spleen, blood, and tumor tissues, reduced interleukin (IL)-6 levels in the serum and tumor tissues in a human gastric cancer xenograft model and a mouse colon cancer allograft model. Curcumin treatment significantly inhibited cell proliferation and colony formation of cancer cells and decreased the secretion of murine IL-6 by MDSCs in a coculture system. Curcumin treatment inhibited the expansion of MDSCs, the activation of Stat3 and NF-κB in MDSCs, and the secretion of IL-6 by MDSCs, when MDSCs were cultured in the presence of IL-1β, or with cancer cell- or myofibroblast-conditioned medium. Furthermore, curcumin treatment polarized MDSCs toward a M1-like phenotype with an increased expression of CCR7 and decreased expression of dectin 1 in vivo and in vitro. Our results show that curcumin inhibits the accumulation of MDSCs and their interaction with cancer cells and induces the differentiation of MDSCs. The induction of MDSC differentiation and inhibition of the interaction of MDSCs with cancer cells are potential strategies for cancer prevention and therapy. Cancer Prev Res; 5(2); 205–15. ©2011 AACR.

Synergistic Actions of Atorvastatin with γ-Tocotrienol and Celecoxib against Human Colon Cancer HT29 and HCT116 Cells

The synergistic actions of atorvastatin (ATST) with γ‐tocotrienol (γ‐TT) and celecoxib (CXIB) were studied in human colon cancer cell lines HT29 and HCT116. The synergistic inhibition of cell growth by ATST and γ‐TT was demonstrated by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and isobologram analysis. δ‐TT exhibited a similar inhibitory action when combined with ATST. Mevalonate and geranylgeranyl pyrophosphate eliminated most of the growth inhibitory effect of ATST, but only marginally decreased that of γ‐TT; whereas farnesyl pyrophosphate and squalene exhibited little effect on the inhibitory action of ATST and γ‐TT, indicating protein geranylgeranylation, but not farnesylation are involved in the inhibition of colon cancer cell growth. Both mevalonate and squalene restored the cellular cholesterol level that was reduced by ATST treatment, but only mevalonate eliminated the cell growth inhibitory effect, suggesting that the cholesterol level in cells does not play an essential role in inhibiting cancer cell growth. Protein level of HMG‐CoA reductase increased after ATST treatment, and the presence of γ‐TT attenuated the elevated level of HMG‐CoA reductase. ATST also decreased membrane‐bound RhoA, possibly due to a reduced level of protein geranylgeranylation; addition of γ‐TT enhanced this effect. The mediation of HMG‐CoA reductase and RhoA provides a possible mechanism for the synergistic action of ATST and γ‐TT. The triple combination of ATST, γ‐TT and CXIB showed a synergistic inhibition of cancer cell growth in MTT assays. The synergistic action of these three compounds was also illustrated by their induction of G0/G1 phase cell cycle arrest and apoptosis.

Synergistic Inhibition of Lung Tumorigenesis by a Combination of Green Tea Polyphenols and Atorvastatin

Purpose: The present study investigated the possible synergistic inhibitory effect of a novel combination of polyphenon E (PPE, a standardized green tea polyphenol preparation) and atorvastatin (trade name Lipitor) in a mouse tumorigenesis model and in human lung cancer H1299 and H460 cell lines. Experimental Design: Female A/J mice were given two weekly i.p. injections of 4-(methylnitrosaminao)-1-(3-pyridyl)-1-butanone (150 mg/kg total dose); 1 week later, mice were treated with PPE (0.25% or 0.5% in drinking fluid), atorvastatin (200 or 400 ppm in diet), or PPE (0.25%) plus atorvastatin (200 ppm) for 16 weeks. The interaction of these two agents was also studied in human lung cancer H1299 and H460 cells. Results: The individual agents, PPE or atorvastatin, were not effective in inhibiting lung tumorigenesis. The low-dose combination of PPE and atorvastatin, however, significantly reduced both the tumor multiplicity and tumor burden (by 56% and 55%, respectively, P < 0.05). Isobologram analysis of the interaction of the two agents indicated that the combination synergistically decreased tumor multiplicity (P = 0.0006) and tumor burden (P = 0.0009). The inhibition was associated with enhanced apoptosis and suppressed myeloid cell leukemia 1 (Mcl-1) level in adenoma as determined by immunohistochemistry and Western blots. Treatment with combinations of PPE and atorvastatin also synergistically decreased the number of viable H1299 and H460 cells as determined by isobologram analysis. This synergistic effect was associated with increased apoptosis as determined by the terminal deoxyribonucleotide transferase–mediated nick-end labeling assay. The combination of PPE and atorvastatin was more efficient in reducing the antiapoptotic protein Mcl-1 level and increasing the cleaved caspase-3 and cleaved poly(ADP)-ribose polymerase level than the single-agent treatment. Conclusions: The present work showed that PPE and atorvastatin synergistically inhibited 4-(methylnitrosaminao)-1-(3-pyridyl)-1-butanone–induced lung tumorigenesis in mice and the growth of lung cancer H1299 and H460 cells, possibly through enhanced apoptosis. The results provide leads for future research on the application of this combination for the prevention and treatment of lung cancer.

Bone marrow-derived myofibroblasts promote colon tumorigenesis through the IL-6/JAK2/STAT3 pathway

Bone marrow-derived myofibroblasts (BMFs) have been shown to promote tumor growth. Here, we found that BMFs or BMF conditioned medium (BMF-CM) induced cancer stem cell-like sphere formation of colon cancer cells. The co-cultured BMFs, but not co-cultured cancer cells, expressed higher levels of IL-6 than BMFs or cancer cells cultured alone. Anti-mouse IL-6 neutralizing antibody, JAK2 inhibitors and STAT3 knockdown in mouse cancer cells reduced BMF- and BMF-CM-induced sphere formation of colon cancer cells. When co-injected, BMFs significantly enhanced tumorigenesis of colon cancer cells in mice. Our results demonstrate that BMFs promote tumorigenesis via the activation of the IL-6/JAK2/STAT3 pathway.

NNK-Induced DNA Methyltransferase 1 in Lung Tumorigenesis in A/J Mice and Inhibitory Effects of (−)-Epigallocatechin-3-Gallate

DNA methyltransferase 1 (DNMT1), a key enzyme mediating DNA methylation, is known to be elevated in various cancers, including the mouse lung tumors induced by the tobacco-specific carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). However, it is not known whether DNMT1 expression is induced right after NNK treatment and how DNMT1 expression varies throughout lung tumorigenesis. In the present study, we found that administration of NNK to A/J mice caused elevation of DNMT1 in bronchial epithelial cells at Days 1, 3, and 14 after NNK treatment. DNMT1 elevation at Day 1 was accompanied by an increase in phospho-histone H2AX (γ-H2AX) and phospho-AKT (p-AKT). At Weeks 5 to 20, NNK-induced DNMT1 in lung tissues was in lower levels than the early stages, but was highly elevated in lung tumors at Week 20. In addition, the early induction of p-AKT and γ-H2AX as well as cleaved caspase-3 in NNK-treated lung tissues was not detected at Weeks 5 to 20 but was elevated in lung tumors. In concordance with DNMT1 elevation, promoter hypermethylation of tumor suppressor genes Cdh13, Prdm2, and Runx3 was observed in lung tissues at Day 3 and in lung tumors. Treatment by EGCG attenuated DNMT1, p-AKT, and γ-H2AX inductions at Days 1 and 3 and inhibited lung tumorigenesis.

Abstract A45: Hydroxylated polymethoxyflavones: a novel class of agents for colon cancer prevention

A45 Orange peels have been used as flavoring and traditional Chinese medicine for many centuries. Polymethoxyflavones (PMFs) are a unique class of flavonoids, and almost exclusively exist in the citrus genus, particularly in the peels of sweet oranges (Citrus senensis) and mandarin oranges (Citrus reticulata). Major PMFs are permethoxylated PMFs (Me-PMFs) such as nobiletin, 3,5,6,7,8,3’,4’-heptamethoxyflavone (HMF), and tangeretin, which have been shown to inhibit cancer cell growth in vitro and in vivo. Recently, we have isolated a class of novel PMFs, namely hydroxylated PMFs (OH-PMFs), from sweet orange peel. These OH-PMFs can be formed from their corresponding Me-PMFs counterparts by hydrolysis naturally. Herein, we studied the effects of three major OH-PMFs, namely 5-hydroxy-6,7,8,3’,4’-pentamethoxyflavone (5HPMF), 5-hydroxy-3,6,7,8,3’,4’-hexamethoxyflavone (5HHMF), and 5-hydroxy-6,7,8,4’-tetramethoxyflavone (5HTMF), on colon cancer cells, and compared their effects with their corresponding Me-PMFs counterparts, namely nobiletin, HMF, and tangeretin, respectively. Our results showed that OH-PMFs significantly inhibited colon cancer cell (HCT116 and HT29) growth in a dose dependent fashion, and these effects were much stronger than those produced by their corresponding Me-PMFs counterparts. Cell cycle analysis by flow cytometry demonstrated that at 24 h, 5HPMF caused cell cycle arrest at G2/M phase, while 5HHMF resulted in arrest at G0/G1 phase. In contrast, at much lower concentration, 5HTMF significantly increased the sub-G0/G1 cell population, indicating possible DNA degradation due to cell death. Annexin V/PI co-staining assay was used to detect possible apoptosis after treatments with OH-PMFs for 48 h. It was found that all three OH-PMFs increased the apoptotic cell population, but 5HTMF showed a much stronger pro-apoptotic effect at much lower concentration in comparison to 5HPMF and 5HHMF. The distinct effects of these three OH-PMFs on cell cycle and apoptosis of colon cancer cells suggest that each OH-PMFs may have different molecular targets in the cancer cells. Moreover, three OH-PMFs profoundly modulated proteins related to cell proliferation and apoptosis. OH-PMFs, namely 5HPMF and 5HHMF, produced profound tumor-suppressive changes on these proteins, while their corresponding Me-PMFs, namely nobiletin or HMF did not cause any noticeable change on the same proteins tested. On the other hand, tangeretin caused various tumor-suppressive changes on the proteins tested, however, its effects were either similar or to less extent than those produced by 5HTMF at much lower concentrations. Overall, at 48 h, three OH-PMFs decreased the level of K-RAS and phosphorylation of AKT, increased the level of p16, and activated caspase cascade, while 5HTMP also increased the level of p16 and decreased the level of Mcl-1. Our results demonstrated that OH-PMFs are promising novel agents for colon cancer prevention. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A45.