PIM1 mutation drives ANXA2 membrane relocalization and promotes lymphomagenesis through PI3K/AKT/mTOR pathway in DLBCL Free

：Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma and we have observed high mutation rates of the PIM1 gene in DLBCL patients with inferior outcomes previously. However, the molecular genetic mechanisms contributing to lymphomagenesis are currently unknown.

Methods：In our cohort, we found that PIM1 mutation significantly associated with poor prognosis. We also screened various lymphoma cohorts from public databases and predict prognosis according to the mutational sites of PIM1 gene. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis combined with Co-IP was used to identify proteins interacting with PIM1. A high-throughput drug screening platform was leveraged to find potential therapeutic vulnerabilities unique to PlM1 mutant cells. The antiproliferative effects of PlM1 and Pl3K inhibitor were evaluated in DLBCL cell lines and further validated in NSG mouse xenograft models.

Results：We identified that PIM1 mutations, specifically P81S, E135K, L184F, and S97N, as frequently occurring variants, with the former three significantly associated with poor outcome. In particular, the PIM1^L184F mutation promoted cell proliferation and was resistant to doxorubicin in vitro and showed faster tumor growth in vivo. Mechanistically, the PIM1^L184F mutation was found to interact with the annexin A2 (ANXA2) gene, activating it through phosphorylation of serine 26. The activated ANXA2 gene then translocated from the cytoplasm to the cell membrane, binding with the Toll-like receptor 4 (TLR4) gene and recruiting BCAP to the cell membrane to interact with p85α further activating the PI3K/AKT/mTOR signaling pathway. Additionally, the high-throughput drug screening demonstrated that the PIM1^L184F mutated cells were more sensitive to the PI3K inhibitor YY20394. PIM1 inhibitor SMI-4a combined with YY20394 showed synergistic antitumor effects both in vitro and in vivo.

Conclusions：Taken together, these findings not only shed light on an innovative regulatory mechanism for how PIM1^L184F mutation contributes to the pathogenesis of DLBCL but also provide a potential therapeutic strategy for effectively managing DLBCL patients harboring PIM1^L184F mutation.

PIM1, Mutation, ANXA2, Diffuse large B-cell lymphoma, Targeted therapy