The study investigates the role of autophagy in the survival and tumorigenesis of cells expressing activated Ras oncogenes. Key findings include: 1. **Autophagy Upregulation in Ras-Expressing Cells**: Expression of H-rasV12 or K-rasV12 oncogenes upregulates basal autophagy, which is essential for tumor cell survival under starvation conditions and in tumorigenesis. 2. **Autophagy Defects in Mitochondrial Function**: In Ras-expressing cells, defective autophagosome formation or cargo delivery leads to the accumulation of abnormal mitochondria and reduced oxygen consumption. Autophagy defects also result in tricarboxylic acid (TCA) cycle metabolite and energy depletion during starvation. 3. **Role of Mitochondria in Cell Viability**: Mitochondria are crucial for sustaining viability in Ras-expressing cells under starvation conditions. Autophagy is necessary to maintain the pool of functional mitochondria, which is essential for supporting the growth of Ras-driven tumors. 4. **High Basal Autophagy in Human Cancer Cell Lines**: Human cancer cell lines with activating Ras mutations often have high levels of basal autophagy. Down-regulation of essential autophagy proteins impairs cell growth in these cells. 5. **Autophagy Addiction in Aggressive Cancers**: The high basal autophagy in human cancer cell lines with Ras mutations suggests that targeting autophagy and mitochondrial metabolism may be valuable approaches to treat these aggressive cancers. 6. **Mechanism of Autophagy-Dependent Survival**: Autophagy deficiency in Ras-expressing cells impairs mitophagy, leading to reduced mitochondrial function and energy levels. This results in an acute energy crisis and cell death. 7. **Clinical Implications**: The findings highlight the potential for autophagy inhibition as a therapeutic strategy in cancers with activating Ras mutations, particularly in pancreatic, lung, and colorectal cancers. Overall, the study demonstrates that autophagy is essential for maintaining mitochondrial metabolic function and energy levels in Ras-driven tumors, suggesting a "autophagy addiction" that could be exploited for therapeutic intervention.The study investigates the role of autophagy in the survival and tumorigenesis of cells expressing activated Ras oncogenes. Key findings include: 1. **Autophagy Upregulation in Ras-Expressing Cells**: Expression of H-rasV12 or K-rasV12 oncogenes upregulates basal autophagy, which is essential for tumor cell survival under starvation conditions and in tumorigenesis. 2. **Autophagy Defects in Mitochondrial Function**: In Ras-expressing cells, defective autophagosome formation or cargo delivery leads to the accumulation of abnormal mitochondria and reduced oxygen consumption. Autophagy defects also result in tricarboxylic acid (TCA) cycle metabolite and energy depletion during starvation. 3. **Role of Mitochondria in Cell Viability**: Mitochondria are crucial for sustaining viability in Ras-expressing cells under starvation conditions. Autophagy is necessary to maintain the pool of functional mitochondria, which is essential for supporting the growth of Ras-driven tumors. 4. **High Basal Autophagy in Human Cancer Cell Lines**: Human cancer cell lines with activating Ras mutations often have high levels of basal autophagy. Down-regulation of essential autophagy proteins impairs cell growth in these cells. 5. **Autophagy Addiction in Aggressive Cancers**: The high basal autophagy in human cancer cell lines with Ras mutations suggests that targeting autophagy and mitochondrial metabolism may be valuable approaches to treat these aggressive cancers. 6. **Mechanism of Autophagy-Dependent Survival**: Autophagy deficiency in Ras-expressing cells impairs mitophagy, leading to reduced mitochondrial function and energy levels. This results in an acute energy crisis and cell death. 7. **Clinical Implications**: The findings highlight the potential for autophagy inhibition as a therapeutic strategy in cancers with activating Ras mutations, particularly in pancreatic, lung, and colorectal cancers. Overall, the study demonstrates that autophagy is essential for maintaining mitochondrial metabolic function and energy levels in Ras-driven tumors, suggesting a "autophagy addiction" that could be exploited for therapeutic intervention.