To further confirm the role of Siglec-15-induced autophagy in osteosarcoma cell metastasis, KHOS cells were transfected with a Beclin-1 overexpression vector, and Beclin-1 overexpression increased MMP-9 expression levels and promoted EMT, as shown by Western blotting (Fig. 6a). The gene discussed is MMP9; the disease is osteosarcoma.