ATG4B and osteosarcoma: In addition, osteosarcoma Saos-2 cells lacking ATG4B failed to grow as a xenograft in nude mice due to a defective in autophagy activity [65].The expression of ATG4B was increased significantly in human epidermal growth factor receptor 2 (HER2) positive breast cancer cells and ATG4B was required for these cells to survive under stressful conditions, implying that this subtype of breast cancers is suitable for employing ATG4B inhibition strategies [32].