Circadian clocks are encoded by a transcription-translation feedback loop that aligns energetic processes with the solar cycle. We show that genetic disruption of the clock activator BMAL1 in skeletal myotubes and fibroblasts increased levels of the hypoxia-inducible factor 1α (HIF1α) under hypoxic conditions. Bmal1−/− myotubes displayed reduced anaerobic glycolysis, mitochondrial respiration with glycolytic fuel, and transcription of HIF1α targets Phd3, Vegfa, Mct4, Pk-m, and Ldha, whereas abrogation of the clock repressors CRY1/2 stabilized HIF1α in response to hypoxia. HIF1α bound directly to core clock gene promoters, and, when co-expressed with BMAL1, led to transactivation of PER2-LUC and HRE-LUC reporters. Further, genetic stabilization of HIF1α in Vhl−/− cells altered circadian transcription. Finally, induction of clock and HIF1α target genes in response to strenuous exercise varied according to the time of day in wild-type mice. Collectively, our results reveal bidirectional interactions between circadian and HIF pathways that influence metabolic adaptation to hypoxia.
Pigment epithelial-derived factor (PEDF), an angiogenesis inhibitor with neurotrophic properties, balances angiogenesis in the eye and blocks tumor progression. Its neurotrophic function and the ability to block vascular leakage is replicated by the PEDF 44-mer peptide (residues 58-101). We analyzed PEDFs' three-dimensional structure and identified a potential receptor-binding surface. Seeking PEDF-based antiangiogenic agents we generated and tested peptides representing the middle and lower regions of this surface. We identified previously unknown antiangiogenic epitopes consisting of the 34-mer (residues 24-57) and a shorter proximal peptide (TGA, residues 16-26) with the critical stretch L19VEEED24 and a fragment within the 44-mer (ERT, residues 78-94), which retained neurotrophic activity. The 34-mer and TGA, but not the 44-mer reproduced PEDF angioinhibitory signals hinged on c-jun-NH2-kinase-dependent nuclear factor of activated T cell deactivation and caused apoptosis. Conversely, the ERT, but not the 34-mer/TGA induced neuronal differentiation. For the 44-mer/ERT, we showed a novel ability to cause neuroendocrine differentiation in prostate cancer cells. PEDF and the peptides bound endothelial and PC-3 prostate cancer cells. Bound peptides were displaced by PEDF, but not by each other, suggesting multiple receptors. PEDF and its active fragments blocked tumor formation when conditionally expressed by PC-3 cells. The 34- and 44-mer used distinct mechanisms: the 34-mer acted on endothelial cells, blocked angiogenesis, and induced apoptosis whereas 44-mer prompted neuroendocrine differentiation in cancer cells. Our results map active regions for the two PEDF functions, signaling via distinct receptors, identify candidate peptides, and provide their mechanism of action for future development of PEDF-based tumor therapies.
Effective targeting of cancer stem cells (CSCs) requires neutralization of self-renewal and chemoresistance, but these phenotypes are often regulated by distinct molecular mechanisms. Here we report the ability to target both of these phenotypes via CD55, an intrinsic cell surface complement inhibitor, which was identified in a comparative analysis between CSCs and nonCSCs in endometrioid cancer models. In this context, CD55 functions in a complement-independent manner and required lipid raft localization for CSC maintenance and cisplatin resistance. CD55 regulated self-renewal and core pluripotency genes via ROR2/JNK signaling and in parallel cisplatin resistance via lymphocyte-specific protein tyrosine kinase (LCK) signaling, which induced DNA repair genes. Targeting LCK signaling via saracatinib, an inhibitor currently undergoing clinical evaluation, sensitized chemoresistant cells to cisplatin. Collectively, our findings identify CD55 as a unique signaling node that drives self-renewal and therapeutic resistance through a bifurcating signaling axis and provides an opportunity to target both signaling pathways in endometrioid tumors.
Menin inhibitors (MENINi) show promise for relapsed or refractory (R/R) acute myeloid leukemia (AML) with KMT2A rearrangements (KMT2Ar) and NPM1 mutations (NPM1c). Outcomes after MENINi failure are poorly understood. To characterize the mutational landscape and subsequent outcomes, we conducted a multicenter retrospective study of adults from 4 U.S. centers with R/R AML after MENINi failure (relapse after response or primary refractory). The 84 patients (63% KMT2Ar, n=53; 23% NPM1c, n=19) who received MENINi were heavily pre-treated: 86% (n=72) had prior intensive chemotherapy (IC), 77% venetoclax (VEN, n=67), and 38% (n=32) allogeneic stem cell transplantation. After MENINi failure, 40% of patients (n=34) received supportive care. Of the 60% (n=50) that were treated, common regimens were hypomethylating agent (HMA)/VEN (26%, n=13), clinical trial (26%, n=13), and gilteritinib-based therapy (18%, n=9). The CR/CRi rate for non-trial therapies was 19% (n=7); ORR was 32% (n=12). All CR/CRi occurred with HMA/VEN (n=2, 15%), IC+VEN (n=4, 67%), or MENINi switching (bleximenib to revumenib, n=1, 50%). No FLT3-mutant patients responded to gilteritinib (0/6 gilteritinib-naïve). Median overall survival (mOS) from start of next therapy was 4.4 months; patients who achieved CR/CRi had mOS of 15.4 vs 3.4 months for non-responders (p=0.048). Outcomes after MENINi failure are poor, but responses occur with VEN-based regimens or MENINi switching. FLT3-ITD, WT1, and MEN1 mutations are associated with resistance.
