Thomas Jefferson University, Department of Pathology, Anatomy and Cell Biology, Oral Administration of Apigenin Inhibits Metastasis through AKT/P70S6K1/MMP-9 Pathway in Orthotopic Ovarian Tumor Model.

Apigenin, a flavonoid commonly present in the daily diet, is known for its potential anti-tumor properties. However, the effect of apigenin via oral administration on tumor growth and metastasis remains unknown. In this study we developed an orthotopic ovarian tumor model in nude mice to test the effect of apigenin oral administration, and showed that apigenin inhibited the micrometastasis of cancer cells in the animal tumor model. To understand the mechanism of apigenin in inhibiting metastasis, we found that apigenin greatly inhibited MMP-9 expression and p-AKT and p-p70S6K1 levels in the tumor tissues compared to the control group. We further demonstrated that the downregulation of MMP-9 by apigenin was mediated by the AKT/p70S6K1 pathway. These findings help to address the question with common interests to the public of whether oral uptake of flavonoids is effective in preventing cancer. Our results demonstrate for the first time that oral uptake of apigenin can inhibit tumor metastasis through MMP-9 expression using the orthotopic ovarian tumor model

MiR-21 induced angiogenesis through AKT and ERK activation and HIF-1α expression.

MicroRNAs (miRNAs) are endogenous, small noncoding RNAs that play important roles in various cellular functions and tumor development. Recent studies have indicated that miR-21 is one of the important miRNAs associated with tumor growth and metastasis, but the role and molecular mechanism of miR-21 in regulating tumor angiogenesis remain to be elucidated. In this study, miR-21 was overexpressed by transfecting pre-miR-21 into human prostate cancer cells and tumor angiogenesis was assayed using chicken chorioallantoic membrane (CAM). We found that overexpression of miR-21 in DU145 cells increased the expression of HIF-1α and VEGF, and induced tumor angiogenesis. AKT and extracellular regulated kinases (ERK) 1/2 are activated by miR-21. Inhibition of miR-21 by the antigomir blocked this process. Overexpression of the miR-21 target, PTEN, also inhibited tumor angiogenesis by partially inactivating AKT and ERK and decreasing the expression of HIF-1 and VEGF. The AKT and ERK inhibitors, LY294002 and U0126, suppressed HIF-1α and VEGF expression and angiogenesis. Moreover, inhibition of HIF-1α expression alone abolished miR-21-inducing tumor angiogenesis, indicating that HIF-1α is required for miR-21-upregulated angiogenesis. Therefore, we demonstrate that miR-21 induces tumor angiogenesis through targeting PTEN, leading to activate AKT and ERK1/2 signaling pathways, and thereby enhancing HIF-1α and VEGF expression; HIF-1α is a key downstream target of miR-21 in regulating tumor angiogenesis

miR-21 induced angiogenesis through mediating AKT and ERK1/2 activation.

<p>(A) DU145 cells were transfected with pre-miR-21. After transfection for 36 h, the cells were trypsinized, mixed with 15 µl Matrigel in the presence or absence of 10 µM of LY294002 or U0126. Representative plugs from DMSO control, LY294002, and U0126 treatment groups were shown. <i>Scale,</i> 2 mm. (B) The number of blood vessels were counted from 8 replicate experiments, and normalized to that of the pre-miR-21 group as relative angiogenesis. ^##, indicates the significant decrease when compared to that of pre-miR-21 treatment group (<i>p</i><0.01).</p

HIF-1α expression is required in miR-21 inducing VEGF expression and tumor angiogenesis.

<p>(A) DU145 cells were transfected with pre-miR-21. After 24 h incubation, cells were infected with adenovirus carrying GFP (Ad-SCR) or siRNA against HIF-1α (Ad-siHIF-1α) at 20 MOI for 24 h. The total proteins were analyzed by immunoblotting. (B–C) The expression levels of VEGF and GAPDH mRNA were analyzed by RT-PCR (B), and by real-time RT-PCR (C). (D) After DU145 cells were transfected with pre-miR-21 for 24 h, the cells were infected with Ad-GFP or Ad-siHIF-1α at 20 MOI for 24 h. Then the cells were used to perform angiogenesis assay as described above. The picture showed the representative plugs from Ad-GFP and Ad-siHIF-1α treatment groups. <i>Scale</i>, 2 mm. (E) The number of blood vessels were counted from replicate experiments, and normalized to that of the Ad-siSCR group as relative angiogenesis. The data are mean ± SD from 6 replicate experiments. ##, indicates the significant difference when compared to that of the Ad-siSCR group (<i>p</i><0.01).</p

miR-21 induced the activation of AKT and ERK1/2, and the expression of HIF-1α and VEGF.

<p>(A) DU145 cells were seeded into 60 mm dishes. When cells were 60% confluence, cells were transfected with pre-miRNA negative control or pre-miR-21 as described above. Total proteins were extracted 36 h after the transfection, and analyzed for the expression of phospho-AKT (p-AKT), total AKT, phospho-ERK1/2 (p-ERK), and ERK2 by immunoblotting. (B) DU145 cells were transfected with pre-miR-21 precursor as described above. After the transfection for 36 h, the cells were treated with solvent alone, 10 µM of LY294002, or 10 µM of U0126 for 6 h. The expression levels of p-AKT, total AKT, p-ERK, ERK2, HIF-1α and HIF-1β were analyzed by immunoblotting. (C-D) After the transfection of cells with pre-miR-21, the cells were cultured for 36 h, then treated with solvent alone, 10 µM of LY294002, or 10 µM of U0126 for 12 h. VEGF mRNA expression was analyzed by RT-PCR (C), and by real-time RT-PCR (D). ##, indicates the significant decrease when compared to that of the control (<i>p</i><0.01).</p

PTEN was the downstream target of miR-21 in inducing angiogenesis.

<p>(A) DU145 cells were infected with adenovirus carrying GFP (Ad-GFP) or PTEN (Ad-PTEN). After 24 h, cells were transfected with pre-miR-21 or scrambled control. The next day, cells were trypsinized and angiogenesis assay was performed as above. The representative plugs from treatments of Ad-GFP plus scrambled control, Ad-GFP plus pre-miR-21, and Ad-PTEN plus pre-miR-21 were shown in the picture. <i>Scale</i>, 2 mm. (B) The relative angiogenesis was showed in the bar graph. Results from each group are presented as mean ±SD of 6 samples. * indicates the significant increase when compared to the Ad-GFP plus scrambled control group (<i>p</i><0.05). ^#, indicates the significant decrease when compared to Ad-GFP plus miR-21 group (<i>p</i><0.05).</p

MicroRNA miR-21 overexpression increased HIF-1α and VEGF expression and induced tumor angiogenesis.

<p>(A) Human prostate cancer cells DU145 were transfected with pre-miRNA negative control or pre-miR-21 at 25 nM. After the transfection for 36 h, cells were collected and subjected to qRT-PCR for miR-21 expression. (B) DU145 cells were treated as in <i>A</i>, the total protein was extracted and subjected to Western blotting assay. (C–D) DU145 cells were collected after the transfection for 36 h. Total RNAs were extracted and analyzed for VEGF and GAPDH mRNA expression by RT-PCR analysis (C), and by real-time RT-PCR (D). (E) DU145 cells were transfected as above. After 24 h, cells (2×10⁶cells, 15 µl) were mixed with 15 µl Matrigel. The cell mixture was implanted onto the CAM of a 9-day old chicken embryo. After 4 days of implantation, the CAM was cut off, and the amount of blood vessels on the CAM induced by the DU145 plugs was determined from eight different replicated experiments. Representative plugs from negative control and miR-21 treatment groups were shown. <i>Scale</i>, 2 mm. (F) The number of blood vessels were counted from replicate experiments, and normalized to that of the negative control group as relative angiogenesis. The data are mean±SD from 6 replicates. ** indicates the significant increase when compared to the pre-miRNA negative control (<i>p</i><0.01).</p

The inhibitor of miR-21 inhibited miR-21-inducing expression of HIF-1α and VEGF, activation of AKT and ERK1/2, and angiogenesis.

<p>(A) The total proteins were prepared 36 h after transfection, and analyzed by immunoblotting for the expression of PTEN, β-actin, p-AKT, AKT, p-ERK1/2, ERK2, HIF-1α, and HIF-1β. (B–C) The expression levels of VEGF in the cells described as above were analyzed by RT-PCR (B), and by real-time RT-PCR (C). (D) The cells above were used for angiogenesis assay. Representative plugs from the negative control and miR-21 inhibitor treated groups were shown. <i>Scale</i>, 2 mm. (E) The number of blood vessels were counted from replicate experiments, and normalized to that of the control group as relative angiogenesis. The data are the mean ±SD from 6 replicate experiments. ##, indicates the significant decrease when compared to that of the control (<i>p</i><0.01).</p