The expression of P62 and proliferating cell nuclear antigen (PCNA) in DM1-03 (Fig. 5d, e) and DM1-13-3 SSCs (Fig. 5i, j) increased after mTOR overexpression, but was still lower than that in DM1-04 SSCs (Fig. 5k, l). Here, PCNA is linked to myotonic dystrophy type 1.