The article explores the mechanisms of drug resistance in cancer cells, focusing on the development of resistance to cisplatin. The authors used four different cancer cell lines (A549, U1810, SKOV3, and SW620) to study the mechanisms of chemoresistance. They employed a pulse-selection approach to create cisplatin-resistant cell lines and used various methods to assess the resistance mechanisms, including MTS assays, LIVE/DEAD assays, clonogenic assays, metabolic assays, and Western blotting. Key findings include: 1. **Cisplatin Resistance Mechanisms**: - **SW620**: Developed resistance by avoiding cell death, as indicated by reduced apoptosis and increased survival rates. - **U1810, A549, SKOV3**: Developed resistance by modulating cell proliferation to avoid the cytostatic effects of cisplatin. 2. **Biochemical Analysis**: - **SW620**: Showed increased accumulation of p89 PARP and active caspase-3, indicating apoptosis induction. - **U1810, A549, SKOV3**: Decreased levels of phosphorylated histone H2AX, suggesting reduced DNA damage and increased resistance to cytotoxic effects. - **SKOV3**: Increased expression of GPX4, potentially contributing to ferroptosis. 3. **Metabolic Changes**: - **SW620**: Maintained metabolic activity despite cisplatin treatment. - **U1810, A549, SKOV3**: Showed significant decreases in mitochondrial respiration, indicating metabolic changes during resistance development. The authors conclude that the mechanisms of resistance vary among the cell lines, with SW620 primarily avoiding cell death, while U1810, A549, and SKOV3 modulate proliferation to avoid cytostatic effects. They recommend a combination of methods, including MTS and LIVE/DEAD assays, clonogenic assays, and Western blotting, to comprehensively evaluate resistance mechanisms.The article explores the mechanisms of drug resistance in cancer cells, focusing on the development of resistance to cisplatin. The authors used four different cancer cell lines (A549, U1810, SKOV3, and SW620) to study the mechanisms of chemoresistance. They employed a pulse-selection approach to create cisplatin-resistant cell lines and used various methods to assess the resistance mechanisms, including MTS assays, LIVE/DEAD assays, clonogenic assays, metabolic assays, and Western blotting. Key findings include: 1. **Cisplatin Resistance Mechanisms**: - **SW620**: Developed resistance by avoiding cell death, as indicated by reduced apoptosis and increased survival rates. - **U1810, A549, SKOV3**: Developed resistance by modulating cell proliferation to avoid the cytostatic effects of cisplatin. 2. **Biochemical Analysis**: - **SW620**: Showed increased accumulation of p89 PARP and active caspase-3, indicating apoptosis induction. - **U1810, A549, SKOV3**: Decreased levels of phosphorylated histone H2AX, suggesting reduced DNA damage and increased resistance to cytotoxic effects. - **SKOV3**: Increased expression of GPX4, potentially contributing to ferroptosis. 3. **Metabolic Changes**: - **SW620**: Maintained metabolic activity despite cisplatin treatment. - **U1810, A549, SKOV3**: Showed significant decreases in mitochondrial respiration, indicating metabolic changes during resistance development. The authors conclude that the mechanisms of resistance vary among the cell lines, with SW620 primarily avoiding cell death, while U1810, A549, and SKOV3 modulate proliferation to avoid cytostatic effects. They recommend a combination of methods, including MTS and LIVE/DEAD assays, clonogenic assays, and Western blotting, to comprehensively evaluate resistance mechanisms.