PCNA and colorectal carcinoma: Consistent with the above findings, in the IHC staining analysis of xenograft tumors, the restoration of HSPB1 expression in SW620 MSI2 knockdown cells markedly reduced the expression of ACSL4, but the expression of PCNA and Ki67 was increased (Fig. 7 M and S3B), indicating that HSPB1 could inhibit ferroptosis and promote CRC proliferation.