Community Research and Development Information Service - CORDIS


TRIPLE-BC Report Summary

Project ID: 322737
Funded under: FP7-IDEAS-ERC
Country: Netherlands

Mid-Term Report Summary - TRIPLE-BC (Identification and functional validation of drugable targets/pathways for triple negative breast cancer)

Patients suffering from triple-negative breast cancer (TNBC) have a poor prognosis as these tumors frequently confer resistance against chemotherapeutic agents, and lack the known drug targets estrogen receptor, progesterone receptor and epidermal growth factor receptor-2. Insufficient knowledge on the tumor biology of this specific heterogeneous breast tumor type hinders the identification of potential novel drug targets. Lethality enhancer screening is an ideal approach to identify new drug targets in tumors with specific genetic aberrations. We have used this concept of synthetic lethality anticipating that while TNBC cells confer resistance to available anticancer drugs, specific knock down of particular genes by RNA-interference (RNAi) results in synergistic cell killing. In the initial stage of our work, a panel of TNBC cell lines representative for distinct molecular subtypes of TNBC were characterized for sensitivity to a panel of commonly-used classic and new anticancer drugs. These experiments revealed that TNBC cell lines responded differently to the EGFR-targeting drug lapatinib and the mTOR-targeting drug rapamycin, the focus drugs of the first screens. For the actual screening we selected two drug-resistant cell lines and drug-sensitive cell lines. To obtain a prioritized list of candidate genes for the screens, bioinformatic modelling approaches were used to select genes for the primary siRNA drug-enhancer screens. The screen for lapatinib resistance revealed 16 genes that were essential for growth/survival of three TNBC cell lines tested. However, no synergy with lapatinib was observed and as an alternative approach we performed a kinase inhibitor screen (273 kinase inhibitors targeting >40 kinases) to identify kinase inhibitors that would act in synergy with the EGFR inhibitor lapatinib nor with mTOR-targeting drugs in the lapatinib-resistant and rapamycin-resistant cell lines. We identified a variety of compounds that strongly enhanced the response of resistant TNBC cell lines to lapatinib. Furthermore, we observed a synergistic effect of lapatinib with a dual Cdk7/Cdk9 inhibitor in dramatic reduction of cell proliferation and induction of apoptosis in all lapatinib-resistant TNBC cell lines. Given the success of the unbiased kinase screen, we are currently performing a lethality enhancer screen using a kinase-wide siRNA library targeting 720 kinases/genes. So far the experiments have been carried out with 2D cultures, and as a next step in our project we plan to translate our results also to 3D conditions. This will include both 3D cultures of TNBC cell lines, similar to the once used in our experiments so far, as well as cultures of patient-derived xenografts. We will expand our drug-enhancer screening efforts with respect to resistance to additional drugs using a selection of TNBC cell lines with a different molecular subtype. The most effective combinations for each TNBC subtype will be functionally investigated in vitro and in vivo to unravel the molecular nature of the synthetic lethality. Translational studies will subsequently be performed to assess the potential clinical relevance of the identified targets/pathways in large numbers of human TNBC and non-TNBC tumors on tissue microarrays, which already have been prepared. Ultimately, it is expected that the established newly designed (combination) therapies will result in a decline in TNBC mortality and a reduction in costs of healthcare.

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