PCNA and osteosarcoma: As shown in Fig 6A, in comparison with that in the Control group of tumors, ultrasound, but not 5-ALA, treatment significantly reduced the frequency of anti-PCNA positively stained proliferative osteosarcoma cells (p<0.05) and ALA-SDT further reduced the percentages of proliferative osteosarcoma cells (p<0.01).