Using Caspase-3 activation as a potential indicator to assess the systemic toxicity of chemotherapy in breast cancer patients

• Main Author: Song, Kai
• Other Authors: Luo Qian, Kathy
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/65224
• Institution: Nanyang Technological University

Background: Among many kinds of side effects associated with cancer chemotherapy, the most potentially severe and common one is neutropenia, which usually leave cancer patients fragile to life-threatening infections. Currently, in clinical practice, the method using for neutropenia management is to monitor the decrease of white blood cells (WBC) count (especially neutrophil count) and their graded scales. However, by the time the fall of WBC is detected, nothing can be done besides administering granulocyte-colony stimulating factor (G-CSF) to boost the production of WBCs. Also, patients should be treated with empirical antibiotics if fever is present as well. Since different individuals experience different level of myelotoxicity under the exposure on similar dose anticancer drug treatment, such variation among people demands a reliable mean of predicting future toxicity and tailoring the chemotherapy in the early stage of chemotherapy. Hypothesis: After the commencement of chemotherapy, the rate of normal cell death would outweigh the WBCs’ ability to remove the apoptotic bodies because of the myelosuppression effects of these drugs. Besides, the decrease of WBCs triggered by chemotherapy could worsen this situation. Caspase-3s, which are pro-enzymes present in most body cells, are activated during apoptosis triggered by anti-cancer drugs. If the apoptotic bodies are not effectively removed by phagocytosis executed by WBCs, capase-3 will be released into blood plasma. Hence, it is proposed that caspase-3 activity can serve as a direct measure of chemotoxicity and may also act as an early indicator of predicting the development of neutropenia. Method: The preliminary result had shown a good correlation between neutrophil count and caspase-3 activity, which was measured by the commercialized caspase-3 assay on first 20 patients using the substrate Ac-DEVD-AMC. In order to increase the sensitivity of caspase-3 detection and screen more background noises, a novel FRET substrate named sensor C3, a complex of protein CFP-DEVD-YFP, was developed in this project. Result: The blood plasma of all 39 patients receiving different chemotherapy regimens were measured using commercialized substrate first. The results agree with our hypothesis well: caspase-3 in plasma increased during the course of chemotherapy, and its activity has a reverse correlation with absolute neutrophil count and WBC count, although the data interpretation is confounded by G-CSF administration sometimes. Anthracycline-based (AC) regimens produced more marked increases in caspase-3 activity levels compared with non-anthracycline ones since anthracyclines can induce a more profound myelosuppression from clinical observation. The liability test of novel substrate shows that it has a large potential to act as a high sensitivity casapse-3 assay, which could benefit a lot for the clinical study. It is expected that the result of this project will provide clinicians a guide on personalized dosing schedule according to each individual’s sensitivity to the anti-cancer drugs, generating preventive means to reduce neutropenia events.