Ro 08-2750 increases radiation-induced cytotoxicity in DLBCL by dysregulating the DNA damage response

PURPOSE: Current research aims to increase treatment efficacy in diffuse large B‑cell lymphoma (DLBCL). Recently, Musashi‑2 (MSI-2) was identified as a negative prognostic marker and potential therapeutic target in DLBCL. Here, we evaluated the effect of the MSI‑2 inhibitor Ro 08-2750 in DLBCL cells. METHODS: First, we established the effects of Ro 08-2750 on DLBCL in cell viability and clonogenicity assays. Changes in cell cycle and apoptosis were analyzed flow cytometrically. We then evaluated modifications in DLBCL treatment response when combining radiation treatment or chemotherapy with Ro 08-2750. Following confirmation of a Ro 08-2750-associated increase in radiation-induced DNA damage via a γH2AX assay, an immunoblot-based assay was used to detect changes in radiation-induced DNA damage repair protein activation. To understand Ro 08-2750-induced modifications in gene expression and protein abundance, we performed RT-qPCR, bulk mRNA-sequencing, western blotting, and quantitative mass spectrometry-based proteomic analyses. RESULTS: Ro 08-2750 reduced cell viability and proliferation in DLBCL. Functionally, Ro 08-2750 induced cell cycle arrest in the S phase, where the DNA synthesis rate was attenuated. Additionally, apoptosis was increased. Ro 08-2750 also sensitized DLBCL cell lines to irradiation but not to chemotherapy, and it increased irradiation-induced DNA double-strand breaks. Transcriptome and proteome analyses showed changes in various tumor-associated signaling pathways, primarily associating Ro 08-2750 with compromised DNA repair, cell cycle, and cell division. CONCLUSION: We identified Ro 08-2750 as a radiosensitizer in DLBCL. Our results suggest that the combination of Ro 08-2750 with radiation therapy may enhance treatment efficacy.