Cd20 expression down-regulated by SOX2 induces rituximab resistance in diffuse large b-cell lymphoma / 肿瘤

ABSTRACT

Objective: To explore the molecular mechanism of resistance to rituximab in diffuse large B-cell lymphoma (DLBCL) during treatment with R-CHOP (rituximab+cyclophosphamide+ doxorubicin+vincristine+prednisone). Methods: FCM was used to detect the expression level of CD20 and the three membrane complement regulatory proteins CD46, CD55 and CD59 in parental cells LY8 [germinal center B-cell-like (GCB) subtype] and NU-DUL-1 [activated B-cell-like (ABC) subtype], rituximab (R) resistance cells LY8-R and NU-DUL-1-R, chemotherapy drug cyclophosphamide+doxorubicin+ vincristine (CHO) resistance cells LY8-CHO and NU-DUL-1-CHO, and rituximab combined with CHO resistance (RCHO) LY8-RCHO and NU-DUL-1-RCHO cells. The expression level of CD20 protein and mRNA were detected by Western blotting and real-time fluorescent quantitative PCR, respectively. The expression levels of CD20, CD46, CD55 and CD59 in SRY (sex determining region Y)-box 2 (SOX2) overexpression of parental LY8 and NU-DUL-1 cells as well as SOX2 gene silencing of LY8-RCHO and NU-DUL-1-RCHO cells were detected by FCM method. Furthermore, in tumor tissues of clinical 25 DLBCL patients with at least 6 circles of R-CHOP regimen treatment, immunohistochemical were used to detect the expression levels of CD20 and SOX2 before and after the treatment. Results: Compared with the parental cells, in the LY8-R, LY8-RCHO and NU-DUL-1-R and NU-DUL-1-RCHO cells that developed rituximab resistance, not in LY8-CHO and NU-DUL-1-CHO cells which resistant to chemotherapy, the expression level of CD20 was significantly reduced (all P < 0.001), while the expression levels of CD46, CD55 and CD59 were also decreased (all P < 0.05). The expression level of CD20 protein and mRNA were significantly reduced (P < 0.001and P < 0.01). Furthermore, in the parental LY8 and NU-DUL-1 cells, overexpression of SOX2 significantly reduced the expression level of CD20 (P < 0.000 1), while knockdown of SOX2 in LY8-RCHO and NU-DUL-1-RCHO cells significantly increased the expression level of CD20 (P < 0.0001). It was further found that the expression level of CD20 in tumor tissues of DLBCL patients was significantly decreased after R-CHOP treatments (P < 0.01), and the expression level of SOX2 was significantly increased (P < 0.001). After comprehensive analysis, it was found that there was a negative correlation between CD20 and SOX2 expression in tumor tissues (P < 0.000 1). Conclusion: SOX2 induces DLBCL resistance to rituximab by reducing the expression level of CD20.