Abstract 4407: Synergistic inhibition of prostate cancer cell (PC3) growth in vitro with low dose combinations of simvastatin and alendronate
Authors: Rogers Mailien R. , Kalra Sumit , Moukharskaya Julia , Lightner Janet , Phillip Henry , Niyazi Maximilian , Ramsauer Victoria , Krishnan Koyamangalath 
Published: June 2012

The mevalonate pathway plays an important role in cancer biology and has been targeted previously with farnesyl transferase inhibitors, although their efficacy is limited due to significant adverse effects. We hypothesize that combination of Simvastatin with Alendronate may have significant synergistic anti-carcinogenic potential in prostate cancer due to sequential blockade in the mevalonate pathway and will serve as a safer and better tolerated alternative than previously tried drugs. Simvastatin and alendronate sequentially inhibit HMG Co-A reductase and farnesyl pyrophosphate synthase enzymes respectively in the mevalonate pathway. This inhibition subsequently reduces isoprenoid synthesis including farnesyl pyrophosphate and geranylgeranylpyrophosphate. Prenylation (isoprenoid attachment) of G protein subunits and nuclear laminins help facilitate protein interactions in addition to termination of small GTPases’ activity. These proteins have important biological roles, including transmembrane signal transduction (RAS), cytoskeletal reorganization (RHO), gene expression (RAS), microtubule organization and nucleocytoplasmic transport. Inhibiting this pathway may have important anti-oncogenic effects through inhibition of processes such as tumor cell adhesion, migration, invasion, proliferation and induction of apoptosis.

To test the hypothesis, we plated a predetermined number of 5000 PC3 cells into a 96 well plate and allowed them to adhere to the wells for an initial 24 hour incubation period using standard color free medium. Simvastatin and alendronate were prepared in various dose concentrations (simvastatin; 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, and 5.0µM and alendronate: 1, 2.0, 5.0. 10.0. 20.0, and 40.0µM). The cells were treated with simvastatin or alendronate alone, and then in various dose combinations. The cells with drug free medium were used as control. After 96 hour incubation, the quantity of living cells were determined via standard MTT assay and spectrophotometric analysis at 570nm and compared to the control group. Significant inhibition of PC3 cell growth was observed using simvastatin and alendronate alone as well as in combinations at low doses. Isobologram analysis was utilized as visual assessment of the drugs’ interaction with independent statistical analysis from calculations using total dose in a fixed-ratio combination and with calculated additive total dose for the same effect. Our results demonstrate synergistic inhibition of PC3 cell growth in vitro at various low dose combinations of simvastatin with alendronate. The fact that both of these drugs are commonly used in the population with no reported severe adverse effects from their combination offers a safe, effective and synergistic treatment option in the future treatment of prostate cancer. In vivo studies must be undertaken to explore these effects further.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4407. doi:10.1158/1538-7445.AM2011-4407