kava and Urinary-Bladder-Neoplasms

Flavokawain A (FKA) is the predominant chalcone identified from the kava plant. We have previously shown that FKA preferentially inhibits the growth of p53 defective bladder cancer cell lines. Here, we examined whether FKA could inhibit bladder cancer development and progression in vivo in the UPII-SV40T transgenic model that resembles human urothelial cell carcinoma (UCC) with defects in the p53 and the retinoblastoma (Rb) protein pathways. Genotyped UPII-SV40T mice were fed orally with vehicle control (AIN-93M) or FKA (6 g/kg food; 0.6%) for 318 days starting at 28 days of age. More than 64% of the male mice fed with FKA-containing food survived beyond 318 days of age, whereas only about 38% of the male mice fed with vehicle control food survived to that age (P = 0.0383). The mean bladder weights of surviving male transgenic mice with the control diet versus the FKA diet were 234.6 ± 72.5 versus 96.1 ± 69.4 mg (P = 0.0002). FKA was excreted primarily through the urinary tract and concentrated in the urine up to 8.4 μmol/L, averaging about 38 times (males) and 15 times (females) more concentrated than in the plasma (P = 0.0001). FKA treatment inhibited the occurrence of high-grade papillary UCC, a precursor to invasive urothelial cancer, by 42.1%. A decreased expression of Ki67, survivin, and X-linked inhibitor of apoptotic proteins (XIAP) and increased expression of p27 and DR5, and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive apoptotic cells were observed in the urothelial tissue of FKA-fed mice. These results suggest a potential of FKA in preventing the recurrence and progression of non-muscle-invasive UCC.

Topics: Animals; Antigens, Polyomavirus Transforming; Apoptosis; Blotting, Southern; Blotting, Western; Cell Proliferation; Cell Transformation, Neoplastic; Chalcone; Chromatography, Liquid; Disease Models, Animal; Female; Humans; Immunoenzyme Techniques; Kava; Male; Mice; Mice, Transgenic; Tandem Mass Spectrometry; Urinary Bladder Neoplasms; Uroplakin II

Flavokawain A is the predominant chalcone from kava extract. We have assessed the mechanisms of flavokawain A's action on cell cycle regulation. In a p53 wild-type, low-grade, and papillary bladder cancer cell line (RT4), flavokawain A increased p21/WAF1 and p27/KIP1, which resulted in a decrease in cyclin-dependent kinase-2 (CDK2) kinase activity and subsequent G(1) arrest. The increase of p21/WAF1 protein corresponded to an increased mRNA level, whereas p27/KIP1 accumulation was associated with the down-regulation of SKP2, which then increased the stability of the p27/KIP1 protein. The accumulation of p21/WAF1 and p27/KIP1 was independent of cell cycle position and thus not a result of the cell cycle arrest. In contrast, flavokawain A induced a G(2)-M arrest in six p53 mutant-type, high-grade bladder cancer cell lines (T24, UMUC3, TCCSUP, 5637, HT1376, and HT1197). Flavokawain A significantly reduced the expression of CDK1-inhibitory kinases, Myt1 and Wee1, and caused cyclin B1 protein accumulation leading to CDK1 activation in T24 cells. Suppression of p53 expression by small interfering RNA in RT4 cells restored Cdc25C expression and down-regulated p21/WAF1 expression, which allowed Cdc25C and CDK1 activation, which then led to a G(2)-M arrest and an enhanced growth-inhibitory effect by flavokawain A. Consistently, flavokawain A also caused a pronounced CDK1 activation and G(2)-M arrest in p53 knockout but not in p53 wild-type HCT116 cells. This selectivity of flavokawain A for inducing a G(2)-M arrest in p53-defective cells deserves further investigation as a new mechanism for the prevention and treatment of bladder cancer.

Topics: Animals; Antineoplastic Agents; Carcinoma, Papillary; Cell Cycle; Cell Line, Tumor; Chalcone; Chalcones; Drug Resistance, Neoplasm; Genes, p53; HCT116 Cells; Humans; Kava; Mice; Mice, Nude; Mutant Proteins; Urinary Bladder Neoplasms; Xenograft Model Antitumor Assays

Consumption of the traditional kava preparation was reported to correlate with low and uncustomary gender ratios (more cancer in women than men) of cancer incidences in three kava-drinking countries: Fiji, Vanuatu, and Western Samoa. We have identified flavokawain A, B, and C but not the major kavalactone, kawain, in kava extracts as causing strong antiproliferative and apoptotic effect in human bladder cancer cells. Flavokawain A results in a significant loss of mitochondrial membrane potential and release of cytochrome c into the cytosol in an invasive bladder cancer cell line T24. These effects of flavokawain A are accompanied by a time-dependent decrease in Bcl-x(L), a decrease in the association of Bcl-x(L) to Bax, and an increase in the active form of Bax protein. Using the primary mouse embryo fibroblasts Bax knockout and wild-type cells as well as a Bax inhibitor peptide derived from the Bax-binding domain of Ku70, we showed that Bax protein was, at least in part, required for the apoptotic effect of flavokawain A. In addition, flavokawain A down-regulates the expression of X-linked inhibitor of apoptosis and survivin. Because both X-linked inhibitor of apoptosis and survivin are main factors for apoptosis resistance and are overexpressed in bladder tumors, our data suggest that flavokawain A may have a dual efficacy in induction of apoptosis preferentially in bladder tumors. Finally, the anticarcinogenic effect of flavokawain A was evident in its inhibitory growth of bladder tumor cells in a nude mice model (57% of inhibition) and in soft agar.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Carcinoma, Transitional Cell; Caspase 3; Caspase 9; Caspases; Cell Growth Processes; Chalcone; Cytochromes c; Flavonoids; Humans; Inhibitor of Apoptosis Proteins; Kava; Membrane Potentials; Mice; Mice, Nude; Microtubule-Associated Proteins; Mitochondria; Neoplasm Proteins; Plant Extracts; Poly(ADP-ribose) Polymerases; Proteins; Proto-Oncogene Proteins c-bcl-2; Survivin; Urinary Bladder Neoplasms; X-Linked Inhibitor of Apoptosis Protein; Xenograft Model Antitumor Assays