Poster Presentation 26th Lorne Cancer Conference 2014

Elucidating the mechanism by which novel anti-tropomyosin compounds induce neuroblastoma cell death (#130)

Melissa Desouza 1 , Teresa Bonello 1 , Alyce Nehme 1 , Peter Gunning 1 , Justine Stehn 1
  1. University of New South Wales, Sydney, NSW, Australia

Neuroblastoma is a childhood cancer with poor patient prognosis due to limited treatment options and increased resistance in high risk patients. The actin cytoskeleton represents an attractive cancer target however the indiscriminate targeting of actin results in unwanted cytotoxicity. To circumvent this problem we have designed a novel class of compounds that target the second core polymer of the actin cytoskeleton, tropomyosin, which allows us to specifically target actin filaments that are required for tumour cell survival. Using biochemical assays, we have demonstrated that our lead compound TR100 increased actin depolymerisation in the presence of tropomyosin, suggesting that TR100 destabilises actin filaments. Treatment of neuroblastoma SH-EP and melanoma SK-MEL-28 cells with TR100 disrupted actin cytoskeleton morphology at low micro-molar doses and triggered mitochondrial-dependent apoptosis (measured by annexin V/propidium iodide co-staining, caspase-3 activity and TMRE staining for detection of mitochondrial permeabilisation). A new generation compound, TR200 was also demonstrated to disrupt the actin cytoskeleton inducing mitochondrial-dependent apoptosis in SH-EP and SK-MEL-28 cells. We now aim to elucidate the molecular mechanism by which anti-tropomyosin compounds target the actin cytoskeleton and induce tumour cell death. To delineate the signalling pathways leading to apoptosis after treatment with anti-tropomyosin compounds, a Kinexus phospho-array was conducted using SH-EP cells treated with TR200 for 8 and 24hr. TR200 treatment activated key stress/apoptosis pathways including JNK and DAPK and simultaneously reduced the activity of essential survival pathways including MEK/ERK, p90RSK and PI3K/Akt. Validation of these results in-house, using Western blotting revealed a significant reduction in Akt and JNK expression after 24hr treatment. To summarise, anti-tropomyosin compounds induce tumour cell apoptosis by impacting multiple signalling pathways essential to tumour cell survival such as Akt, JNK and MEK/ERK. Elucidating the signalling pathways involved in the mechanism of action of anti-tropomyosin compounds will allow us to better understand how these compounds may act in combination with current chemotherapeutics to improve patient outcome.