Mitochondrial and mTOR pathway inhibition synergise to block pancreatic adenocarcinoma development (#111)
Pancreatic ductal adenocarcinoma
(PDAC) is the fourth leading cause of death by cancer
in Western countries, with very little improvement in survival rate over the
last 40 years. Studies of PDAC tumour metabolism demonstrated that
activation of specific glycolytic metabolic switches is of strong relevance [1].
We previously showed that the tumour metabolism inhibitor, PENAO, has strong in vitro and in vivo inhibitory activity against PDAC [2]. PENAO is a novel
compound that targets mitochondrial function by inhibiting adenine nucleotide translocase.
Given that mTOR signaling pathway, notably mTORC1, is critical for maintaining
the glycolytic metabolism of pancreatic cancer cells [3], we combined PENAO
with mTOR inhibitors in an attempt to further interfere with the proliferation
of PDAC cells. PENAO was combined with three mTORC1 inhibitors (temsirolimus,
everolimus and deforolimus) on four KRAS- mutated PDAC cell lines: MIA PaCa-2,
AsPC-1, Panc-1 and Capan-1. Clear synergism of proliferation arrest measured by
endpoint and real time proliferation assays (CI 0.59 - 0.82) was observed with all
mTORC1 inhibitors. In a subcutaneous xenograft model of PDAC in mice, the
combination of PENAO (0.25mg/kg/day) + everolimus (5mg/kg/day) was significantly
more potent than single treatments at inhibiting tumour growth: growth delays
were 4.2, 7.0 and 17.8 days for PENAO, everolimus and combination treatments,
respectively. Tumour regression was observed when a stronger regimen was
employed. This regression was consistent with a significant (2.1 fold, p<0.01)
increase of necrotic regions in tumour sections from treated animals. There
were no macroscopic signs of toxicity. Our findings demonstrate the potential
of dual metabolism targeting in PDAC and warrants further investigations. Considering
that both PENAO and mTOR inhibitors are currently being tested in clinical
trials, a quick translation of this study to the clinic is realistic.
- Guillaumond F. et al. (2014). Pancreatic tumor cell metabolism: focus on glycolysis and its connected metabolic pathways. Arch Biochem Biophys, 545, 69-73.
- Dilda P.J. et al. (2009). Optimization of the anti-tumor efficacy of a mitochondrial toxin by increasing the residence time in the cytosol. J Med Chem, 52, 6209-6216
- Liu L. et al. (2013). Glycolysis in Panc-1 human pancreatic cancer cells is inhibited by everolimus. Exp Therap Med, 5, 338-42