B61
TRAIL-R1-specific therapeutic agents in combination with Doxorubicin selectively target primary breast tumour cells for apoptosis
Shambhavi Naik1, Davina Twiddy1, Roshna Mistry1, Jennifer Edwards1, Gerald M. Cohen2, Rosemary A. Walker1, Marion MacFarlane1
1MRC Toxicology Unit, Leicester, UK, 2Cancer Studies & Molecular Medicine, University of Leicester, UK
Background
Breast cancer is the most common cancer in the UK. Although the majority of breast cancer cell lines are sensitive to the death-inducing ligand and potential cancer biotherapeutic, TNF-Related Apoptosis-Inducing Ligand (TRAIL), most primary tumours are TRAIL-resistant. Doxorubicin, a chemotherapeutic agent commonly used in breast cancer, has been shown to sensitise TRAIL-resistant breast cancer cell lines to TRAIL. Furthermore, using ligands (generated in-house)/mAbs specific for the TRAIL death receptors, TRAIL-R1/TRAIL-R2, we have previously shown that primary Chronic Lymphocytic Leukaemia (CLL) cells can be sensitised to apoptosis by combining an HDACi with a TRAIL-R1-specific form of TRAIL/TRAIL-R1 mAb.
Aim
To examine the potency of TRAIL-R1/R2-specfic ligands/mAbs in breast cancer, by employing the TRAIL-resistant breast cancer cell line, T47D, and a novel approach of culturing primary breast tumour explants in vitro, thus providing a clinically relevant tumour model.
Method and Results
Studies were carried out either in the cell line T47D or in primary breast tumour explants cultured on 0.4 m inserts to maintain their 3D architecture. Despite expressing the death receptors, TRAIL-R1/R2, the cell line T47D requires initial sensitisation by doxorubicin and exhibits selectivity towards apoptosis induced by a TRAIL-R1-selective TRAIL/TRAIL-R1 mAb. Importantly, we show that doxorubicin also sensitises TRAIL-resistant primary breast tumour explants to TRAIL-induced apoptosis, while having no effect on normal breast tissue. In this ex-vivo model, TRAIL combined with doxorubicin again induces significantly more apoptosis via TRAIL-R1 than TRAIL-R2. Using the cell line T47D, we provide evidence that doxorubicin enhances TRAIL Death-Inducing Signalling Complex (DISC) formation, which may be the key mechanism of sensitisation.
Conclusion
Our results have important implications in the treatment of breast cancer, as using a TRAIL-R1-specific ligand/mAb combined with sub-toxic concentrations of doxorubicin could prevent potential side-effects, such as triggering of TRAIL-induced pro-survival pathways or cardiotoxicity induced by higher concentrations of doxorubicin used in monotherapy.
