No abstract

Approximately 20% of newly diagnosed multiple myeloma (NDMM) patients harbor t (11;14), a marker of inferior prognosis, resulting in up-regulation of CCND1. These patients respond to BCL2 inhibitor experimental drug venetoclax. Furthermore, t(11;14) is reported to be associated with increased BCL2/MCL1 ratio. We investigated the use of venetoclax (400 mg daily) in a cohort of 25 multiple myeloma (MM) and ALamyloidosis patients harboring t(11;14) and assessed safety and efficacy. Efficacy was assessed by response rate (RR) and time on treatment. Furthermore, immunohistochemistry (IHC), for BCL2 family member expression was assessed at diagnosis and relapse in the venetoclax-treated group and analyzed for correlation with clinical RR. Additionally, patient material from venetoclax non-treated group including non-t(11;14) diagnosis (n = 27), t(11;14) diagnosis (n = 17), t(11;14) relapse (n = 7), hyperdiploidy (n = 6) and hyperdiploidy + t(11;14) (n = 6) was used for RNA sequencing (RNASeq) and validation by qPCR. Venetoclax treatment in t(11;14) patients demonstrated manageable safety and promising efficacy. Partial responses or better were observed in eleven patients (44%). Responding patients had significantly higher BCL2/MCL1 (p = 0.031) as well as BCL2/BCL-XL (p = 0.021) ratio, regardless of time of measurement before venetoclax treatment. Furthermore, an IRF5 motif was enriched (p < .001) in the downregulated genes in t(11;14) relapses vs diagnoses. The RR with single agent venetoclax was 71% in AL-amyloidosis and 33% in MM, and IHC proved useful in prediction of treatment outcome. We could also demonstrate possible resistance mechanisms of t(11;14), downregulation of IRF5 targeted genes, which can be exploited for therapeutic advantages.

One-carbon (1C) metabolism has a key role in metabolic programming with both mitochondrial (m1C) and cytoplasmic (c1C) components. Here we show that activating transcription factor 4 (ATF4) exclusively activates gene expression involved in m1C, but not the c1C cycle in prostate cancer cells. This includes activation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) expression, the central player in the m1C cycle. Consistent with the key role of m1C cycle in prostate cancer, MTHFD2 knockdown inhibited prostate cancer cell growth, prostatosphere formation, and growth of patient-derived xenograft organoids. In addition, therapeutic silencing of MTHFD2 by systemically administered nanoliposomal siRNA profoundly inhibited tumor growth in preclinical prostate cancer mouse models. Consistently, MTHFD2 expression is significantly increased in human prostate cancer, and a gene expression signature based on the m1C cycle has significant prognostic value. Furthermore, MTHFD2 expression is coordinately regulated by ATF4 and the oncoprotein c-MYC, which has been implicated in prostate cancer. These data suggest that the m1C cycle is essential for prostate cancer progression and may serve as a novel biomarker and therapeutic target. Significance: These findings demonstrate that the mitochondrial, but not cytoplasmic, one-carbon cycle has a key role in prostate cancer cell growth and survival and may serve as a biomarker and/or therapeutic target.

The development of B cells relies on an intricate network of transcription factors critical for developmental progression and lineage commitment. In the B cell developmental trajectory, a temporal switch from predominant Foxo3 to Foxo1 expression occurs at the CLP stage. Utilizing VAV-iCre mediated conditional deletion, we found that the loss of FOXO3 impaired B cell development from LMPP down to B cell precursors, while the loss of FOXO1 impaired B cell commitment and resulted in a complete developmental block at the CD25 negative proB cell stage. Strikingly, the combined loss of FOXO1 and FOXO3 resulted in the failure to restrict the myeloid potential of CLPs and the complete loss of the B cell lineage. This is underpinned by the failure to enforce the early B-lineage gene regulatory circuitry upon a predominantly pre-established open chromatin landscape. Altogether, this demonstrates that FOXO3 and FOXO1 cooperatively govern early lineage restriction and initiation of B-lineage commitment in CLPs.

Natural killer (NK) cells play roles in viral clearance and early surveillance against malignant transformation, yet our knowledge of the underlying mechanisms controlling their development and functions remain incomplete. To reveal cell fate-determining pathways in NK cell progenitors (NKP), we utilized an unbiased approach and generated comprehensive gene expression profiles of NK cell progenitors. We found that the NK cell program was gradually established in the CLP to preNKP and preNKP to rNKP transitions. In line with FOXO1 and FOXO3 being co-expressed through the NK developmental trajectory, the loss of both perturbed the establishment of the NK cell program and caused stalling in both NK cell development and maturation. In addition, we found that the combined loss of FOXO1 and FOXO3 caused specific changes to the composition of the non-cytotoxic innate lymphoid cell (ILC) subsets in bone marrow, spleen, and thymus. By combining transcriptome and chromatin profiling, we revealed that FOXO TFs ensure proper NK cell development at various lineage-commitment stages through orchestrating distinct molecular mechanisms. Combined FOXO1 and FOXO3 deficiency in common and innate lymphoid cell progenitors resulted in reduced expression of genes associated with NK cell development including ETS-1 and their downstream target genes. Lastly, we found that FOXO1 and FOXO3 controlled the survival of committed NK cells via gene regulation of IL-15Rβ (CD122) on rNKPs and bone marrow NK cells. Overall, we revealed that FOXO1 and FOXO3 function in a coordinated manner to regulate essential developmental genes at multiple stages during murine NK cell and ILC lineage commitment.