Knockout Tumor Microenvironment HO-1 Enhances the Therapeutic Effect of Histone Deacetylase Inhibitor (RGFP966) on B Cell Lymphoma

Objection: Histone deacetylase inhibitor has been approved for the treatment of cutaneous manifestations of cutaneous T cell lymphoma (CTCL). RGFP966 is an HDAC3 targeting inhibitor has also shown its anticancer activity about hematological and solid malignancies, but few studies have been reported in B cell lymphoma. HO-1 is well known as a rate-limiting enzyme that catalyze the degradation of heme, moreover HO-1 shown effects of cytoprotective and drug resistance in various tumors as well as B cell lymphoma. This study investigate the effect of histone deacetylase inhibitor (RGFP966) combined with HO-1 knockout on apoptosis of malignant B-cell lymphoma cells.

Methods: C57/BL6 (HO-1 knockout) mouse were radiation with 6.5GY once in a row to repress residual immunity. Malignant B-cell lymphoma A20 cells respectively (1×10⁷ cells) per animal were injected subcutaneously into the right abdomen. After tumor formation, Q-PCR, Western blot and immunoprecipitation (CO-IP) were used to detect the expression of HO-1, HDAC3, STAT3 and MCL-1 mRNA and protein expression. The expression of MHCII, CD40 and CD80 on the surface of malignant B cells was detected by cell membrane protein staining. Cell staining data were collected by flow cytometry.

Results: The expression of HO-1 gene knockout combined with histone deacetylase inhibitor (RGFP966) could significantly decrease the expression of STAT3 and MCL-1 mRNA and protein. Compared with chemotherapy alone, HO-1 gene knockout combination Histone deacetylase inhibitor (RGFP966) significantly increased the expression of MHC, CD40 and CD80 in A20 cells, and the difference was statistically significant (P <0.01).

Conclusion: Based on the HO-1 knockout mouse model combined with inhibition of histone deacetylase 3 can enhance the expression of molecules that determine the immunogenicity of malignant B cells and increase cell apoptosis.