Up-regulation of the PI3K/AKT and RHO/RAC/PAK signalling pathways in CHK1 inhibitor resistant E\ub5-Myc lymphoma cells

\ua9 2022 The Author(s). The development of resistance and the activation of bypass pathway signalling represents a major problem for the clinical application of protein kinase inhibitors. While investigating the effect of either a c-Rel deletion or RelAT505A phosphosite knockin on the E\ub5-Myc mouse model of B-cell lymphoma, we discovered that both NF-κB subunit mutations resulted in CHK1 inhibitor resistance, arising from either loss or alteration of CHK1 activity, respectively. However, since E\ub5-Myc lymphomas depend on CHK1 activity to cope with high levels of DNA replication stress and consequent genomic instability, it was not clear how these mutant NF-κB subunit lymphomas were able to survive. To understand these survival mechanisms and to identify potential compensatory bypass signalling pathways in these lymphomas, we applied a multi-omics strategy. With c-Rel-/- E\ub5-Myc lymphomas we observed high levels of Phosphatidyl-inositol 3-kinase (PI3K) and AKT pathway activation. Moreover, treatment with the PI3K inhibitor Pictilisib (GDC-0941) selectively inhibited the growth of reimplanted c-Rel-/- and RelAT505A, but not wild type (WT) E\ub5-Myc lymphomas. We also observed up-regulation of a RHO/RAC pathway gene expression signature in both E\ub5-Myc NF-κB subunit mutation models. Further investigation demonstrated activation of the RHO/RAC effector p21-activated kinase (PAK) 2. Here, the PAK inhibitor, PF-3758309 successfully overcame resistance of RelAT505A but not WT lymphomas. These findings demonstrate that up-regulation of multiple bypass pathways occurs in CHK1 inhibitor resistant E\ub5-Myc lymphomas. Consequently, drugs targeting these pathways could potentially be used as either second line or combinatorial therapies to aid the successful clinical application of CHK1 inhibitors

Genetic variability associates with ancestry, age at disease onset, organ involvement and disease severity in juvenile-onset systemic lupus erythematosus

\ua9 2025 The Author(s). Juvenile-onset systemic lupus erythematosus (jSLE) is a complex autoimmune/inflammatory disease in which genetic factors likely contribute to pathophysiology and clinical expression. This study explored associations between general (alternate allele counts; AAC) and gene-specific (alternate allele scores; GAAS) sequence variability, age at onset, sex, ancestry, disease activity/severity, organ involvement and treatments in jSLE. 289 participants from the UK JSLE Cohort Study underwent panel sequencing of 62 genes/genomic regions. Weighted AAC and GAAS were calculated. Correlation analyses and generalized linear models assessed associations between genetic burden, ancestry, age at diagnosis and clinical variables. AAC inversely correlated with age at diagnosis (R = -0.15, p = 0.01), primarily driven by South Asians (R = -0.28, p < 0.001). African/Caribbean patients exhibited higher AAC (p < 0.001). Clinical variables, including severity of renal involvement (ACP5, ITGAM, LYN, p < 0.001; TNFAIP3, p = 0.007), associated with GAAS. Genetic variability likely contributes to early disease expression and severity in jSLE, supporting patient stratification and personalised care