WIPI1 and osteosarcoma: However, it was recently reported that intracellular agr-positive S. aureus was efficiently entrapped in WIPI-1 positive autophagosome-like vesicles and targeted for lysosomal degradation in non-professional phagocytic cells (human osteosarcoma U2OS cells, ATCC) [9], indicating that agr-positive S. aureus is eliminated by the autophagy system followed by degradation in the lysosome.