Medizinische Universität Graz - Research portal
Selected Publication:
Haas, D.
Modelling and overcoming clinically relevant resistance mechanisms to CDK4/6i-based therapy in hormone receptor-positive breast cancer cells.
[ Diplomarbeit/Master Thesis (UNI) ] TU Graz; 2023.
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- Authors Med Uni Graz:
- Advisor:
- Hrzenjak Andelko
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- Abstract:
- Breast cancer is the most common cause of cancer-related death in women. It is a heterogeneous disease and occurs in many forms with different histological and biological characteristics. Dysregulation of the cell cycle is a hallmark of cancer. In hormone receptor-positive (HR+) breast cancer, aberrant proliferation is driven by the female sex hormones estrogen and progesterone. In addition to endocrine therapy to target hormone-dependent tumour growth, cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have become the standard of care for patients with advanced HR+ breast cancer. CDK4/6i directly target the cell cycle regulation and induce cell cycle arrest, resulting in reduced proliferation of cancer cells. However, resistance to CDK4/6i is frequently observed in the clinic and new treatment strategies are needed. For example, BH3-mimetics are a class of drugs that target and antagonize pro-survival proteins (e.g., MCL-1), and shown to be able to sensitize drug resistant cancer cells in different pre-clinical models. The aim of this master thesis was to model clinically relevant molecular mechanisms of CDK4/6i resistance in breast cancer cell lines in vitro using CRISPR/Cas9 genome engineering and to explore new treatment strategies to overcome resistance. We focused on mutations detected in patients resistant to CDK4/6i, such as fibroblast growth factor receptor 1 (FGFR1) amplification, and loss of breast cancer gene 2 (BRCA2). Loss of the retinoblastoma protein 1 (RB1) is associated with strong resistance to CDK4/6i and was used as a positive control. The MCL-1 inhibitor (MCL-1i) S63845 was used to investigate the efficacy of BH3-mimetics on CDK4/6i resistant cells. BRCA2 and RB1 knockouts as well as FGFR1 overexpression were successfully introduced in several breast cancer cell lines. As expected, loss of RB1 enhanced tumour cell growth and induced strong resistance to CDK4/6i. However, contrary to our expectations, FGFR1 overexpression had no effect on cell cycle and CDK4/6i sensitivity in our assays. Interestingly, BRCA2 deficient cells showed reduced growth rates. No changes in cell viability were observed when CDK4/6i-resistant RB1 knockout cells were treated with MCL-1i. We have developed a workflow to efficiently model clinically relevant mutations in breast cancer cells. This platform can now be used to rapidly explore treatment strategies to overcome resistance observed in patients.