Mechanism of action of, and combination chemotherapy with isoprenoids perillyl alcohol, farnesol, and geraniol in in vitro and in vivo models of human pancreatic adenocarcinoma
Abstract
The isoprenoid compounds Farnesol (FOH), Geraniol (GOH), and Perillyl Alcohol (POH) have demonstrated anticancer activity in vitro and in vivo in a number of models of human cancer, including pancreatic adenocarcinoma. POH has shown promise in human Phase II clinical trials, while FOH and GOH are currently undergoing pre-clinical evaluation. In the process of characterizing the in vitro mechanism of action of these three isoprenoids in MIA PaCa-2 and BxPC-3 human pancreatic adenocarcinoma cells, we determined that all three induce a cell-cycle arrest in G0/G1-phase occurring as early as 9 hours following onset of exposure. Associated with arrest was a dose-dependent upregulation of cyclin-dependent kinase inhibitor (CKI) proteins p21Cip1 and p27Kip1, with a simultaneous decrease in cyclin A, cyclin B1, and CDK2 proteins. Following exposure to isoprenoids, both p21 Cip1 and p27Kip1 were increasingly associated with CDK2, and CDK2 kinase activity toward histone H1 decreased. siRNA-induced downregulation of p21Cip1 and p27Kip1 demonstrated that the antiproliferative effect of isoprenoids is mediated by these CKIs at relatively lower effective doses (<600 >μM POH, <400 >μM GOH, <60 >μM FOH). However, at higher doses, the antiproliferative effect is independent of p21Cip1 and p27Kip1. Preliminary data using cDNA microarray analysis showed transcriptional downregulation CDK2, CDK3, CDK4, and CDC2 following 8 hours of exposure to either 500 μM POH, 400 μM GOH, or 60 μM FOH. We evaluated the combinatorial potential of isoprenoids with established anticancer agents gemcitabine (dFdC), taxol (TAX), doxorubicin (DOX), and camptothecin (CPT) in vitro and the combination of POH and dFdC in vivo. While combinations of dFdC demonstrated superadditive antiproliferative activity with POH, it was determined that POH could protect MIA PaCa-2 cells from dFdC cytotoxicity. Combinations with other agents either provided insignificant benefit or proved antagonistic. Similar conclusions were found in vivo, using a Syrian golden hamster model of pancreatic ductal adenocarcinoma. However, the studies were hampered by technical issues of previously unseen toxicity and weight loss which adversely affected the data. In conclusion, isoprenoids remain promising agents in both chemopreventive and chemotherapeutic avenues, though additional evaluation is needed in order to identify ideal methods of use.
Degree
Ph.D.
Advisors
Crowell, Purdue University.
Subject Area
Pharmacology|Oncology|Radiology|Molecular biology
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