Oral Presentation ESA-SRB-AOTA 2019

Aurora Kinases Regulate Telomerase in Thyroid Cancer (#153)

Grace Lim 1 2 , Martyn Bullock 1 2 , Eugene Choi 3 , Hilda Pickett 3 , Roger Reddel 4 , Roderick Clifton-Bligh 1 2 5
  1. Cancer Genetics, Kolling Institute of Medical Research , St Leonards , NSW , Australia
  2. University of Sydney , Sydney , NSW, Australia
  3. Telomere Length Regulation Unit, Childrens' Medical Research Institute, University of Sydney , Westmead, NSW, Australia
  4. Cancer Research Unit, Childrens' Medical Research Institute, University of Sydney , Westmead, NSW, Australia
  5. Endocrinology , Royal North Shore Hospital , St Leonards, NSW , Australia

Current Tyrosine Kinase Inhibitor (TKI) therapies for advanced thyroid cancer (TC) only modestly improves progression-free survival and the discovery of novel therapeutic targets is a high clinical priority. Activation of telomere maintenance mechanisms (e.g. Telomerase) is critical for cancer cells to acquire the replicative immortality necessary for sustained tumour growth. Telomerase activation can occur via Telomerase Reverse Transcriptase promoter (TERTp) mutations, which arise frequently in TC and strongly correlate with poor clinical outcome. We recently screened a drug library for TERTp inhibitors and discovered that Aurora Kinases (AURKs), positively regulate the TERTp in TC cells. In this study, we investigated the underlying regulatory mechanism and evaluate the therapeutic potential of AURK inhibitors (AURKi).

The dose- and time-dependent changes in TERTp activity following AURKi versus TKI treatments (Heperadin and ENMD-2076 versus Sorafenib) was assayed in SW1736, C643, TPC1 TC cell-lines transfected with WT/C228T-TERTp luciferase-reporters. TERT expression was quantified by qRT-PCR with RNA harvested from similarly treated cells, or from cells transfected with AURKB-targeting shRNA. Telomerase activity was assessed in TC cells treated for 5 days with the IC50 dose of AURKi. Phospho-blots (p-WB) of lysates isolated from treated TC cells were performed to assess kinase pathway activity.

AURKi treated TC cells had suppressed WT/C228T-TERTp activity (6-fold p<0.005, 4-fold p<0.0001 respectively). Similarly, AURK inhibition by AURKi and AURKB-shRNA led to a decrease in TERT expression (8-fold p<0.001, 4-fold respectively), which was not evident in Sorafenib treated cells. Furthermore, telomerase activity was significantly suppressed (6-fold p<0.01) and p-WB revealed a significant inhibition of pERK and pAKT (>95%, p<0.001) but no significant effect on pS6 levels.

We have discovered that AURKi treatment downregulates telomerase in TC cells via TERTp inhibition, and this previously unrealised regulatory action of AURKs identifies them as a potential therapeutic target for treating TERTp positive TC.