Agent identification and preclinical testing

Comparison of pharmacokinetic and pharmacodynamic profiles of aspirin following oral gavage and diet dosing in rats

Aspirin is one of the oldest drugs and has been purported to have multiple beneficial effects, including prevention of cardiovascular disease and cancer, in addition to its original indication for treatment of inflammation, fever and pain. In cancer chemoprevention studies using animal models, two methods of aspirin administration have been employed: oral gavage and diet. The untested assumption was that exposure and the resultant pharmacological effects are similar for these two administration methods when dosing is normalized on the basis of mg/kg body weight/day. This study examined and compared time-dependent plasma and colon mucosal concentrations of aspirin metabolite salicylate (aspirin concentrations were below level of quantification), plasma thromboxane B(2) concentrations, and colon mucosal prostaglandin E(2) concentration following these two different dosing paradigms in rats. Diet dosing yielded relatively constant plasma and colon salicylate concentration vs. time profiles. On the other hand, oral gavage dosing led to a rapid peak followed by a fast decline in salicylate concentration in both plasma and colon. Nevertheless, the exposure as measured by the area under plasma or colon concentration-time curve of salicylate was linearly related to dose irrespective of the dosing method. Linear relationships were also observed between colon and plasma salicylate areas under the curve and between colon prostaglandin E(2) and plasma thromboxane B(2) areas under the curve. Therefore, more easily accessible plasma salicylate and thromboxane B(2) concentrations were representative of the salicylate exposure and prostaglandin E(2) pharmacodynamic biomarker in the target colon, respectively.

A novel anti-cancer effect of genistein: reversal of epithelial mesenchymal transition in prostate cancer cells

AIM

The aim of the present study was to investigate whether low dose genistein affects the invasion and epithelial mesenchymal transition (EMT) of prostate cancer (PCa) cells.

METHODS

Human PCa cell lines, IA8-ARCaP and LNCaP/ HIF-1a, were used in this study. The cell lines were found to process EMT in our previous study. The PCa cells were treated with increasing concentrations, from 0.1 to 75 micromol/L. Proliferation was assessed with 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay. EMT was proven by cell morphological transition and the expression changes of EMT-related markers, which were confirmed by RT-PCR, Western blotting, and indirect immunofluorescence labeling. Transwell invasion assay was used to analyze the invasive potency.

RESULTS

The addition of genistein to the medium reduced the IA8-ARCaP and LNCaP/HIF-1a viable cell number in a dose-dependent manner (with increasing concentrations from 15 to 75 micromol/L). Less than 15 micromol/L genistein was selected as the low dose concentration, which did not affect cell proliferation. The treatment of cells with low-dose genistein induced the reversal of EMT, which was confirmed by cell morphological transition and the expression changes of EMT-related markers. The reversal of EMT in the PCa cells by low-dose genistein was in a dose-dependent manner. Moreover, low-dose genistein effectively inhibited invasion of the PCa cells in vitro.

CONCLUSION

These results showed that treatment with low-dose genistein may be a potential strategy for the suppression of invasive growth through the reversal of EMT in cancer cells, which justifies the potential use of soybean foods as a practical chemopreventive approach for patients with PCa.

Effects of oral dosing paradigms (gavage versus diet) on pharmacokinetics and pharmacodynamics

In cancer chemopreventive studies, test agents are typically administered via diet, while the preclinical safety studies normally employ oral gavage dosing. Correspondence in pharmacokinetic and pharmacodynamic profiles between the two dosing approaches cannot be assumed a priori. Sulindac, a non-steroidal anti-inflammatory agent with potential chemopreventive activity, was used to assess effects of the two oral dosing paradigms on its pharmacokinetics and pharmacodynamics. Time-dependent concentrations of sulindac and its sulfone metabolite were determined in plasma and potential target organ, mammary gland. Prostaglandin E(2) was used as a pharmacodynamic biomarker and measured in mammary gland. An inverse linear relationship was detected between pharmacodynamic and pharmacokinetic markers, area under the curve for prostaglandin E(2) levels and sulindac sulfone concentrations, respectively, in the mammary tissue. Marked differences in pharmacokinetics and pharmacodynamics were observed after administration of sulindac by the two oral dosing paradigms. In general, oral gavage resulted in higher peak and lower trough concentrations of sulindac in plasma and mammary tissue, higher area under concentration-time curve in plasma and mammary tissue, and greater effect on prostaglandin E(2) levels than the corresponding diet dosing. This study illustrates potential pitfalls and limitations in trying to generalize based on data obtained with different oral dosing schemes and their extrapolation to potential efficacy and health risks in humans.

Genistein inhibits p38 map kinase activation, matrix metalloproteinase type 2, and cell invasion in human prostate epithelial cells

Epidemiologic studies associate consumption of genistein, in the form of dietary soy, with lower rates of metastatic prostate cancer. We have previously shown that genistein inhibits prostate cancer cell detachment in vitro, that it is well tolerated in an older cohort of men with prostate cancer, and that it alters cell signaling in that same cohort. We have also shown that p38 mitogen-activated protein kinase (MAPK) is necessary for transforming growth factor beta (TGF-beta)-mediated increases in prostate cancer adhesion. Although cell invasion is closely linked to metastatic behavior, little is known about how this process is regulated in prostate cancer or what effect, if any, genistein has on associated processes. We now show that genistein inhibits matrix metalloproteinase type 2 (MMP-2) activity in six of seven prostate cell lines tested, blocks MMP-2 induction by TGF-beta, and inhibits cell invasion. Efficacy was seen at low nanomolar concentrations, corresponding to blood concentrations of free genistein attained after dietary consumption. Inhibition of p38 MAPK by either SB203580 or dominant-negative construct blocked induction of MMP-2 and cell invasion by TGF-beta. Genistein exerted similar effects and was found to block activation of p38 MAPK by TGF-beta. This study shows that p38 MAPK is necessary for TGF-beta-mediated induction of MMP-2 and cell invasion in prostate cancer and that genistein blocks activation of p38 MAPK, thereby inhibiting processes closely linked to metastasis, and does so at concentrations associated with dietary consumption. Any potential causal link to epidemiologic findings will require further investigation.