Glutamoptosis is the induction of apoptotic cell death as a consequence of the aberrant activation of glutaminolysis and mTORC1 signaling during nutritional imbalance in proliferating cells. The role of the bioenergetic sensor AMPK during glutamoptosis is not defined yet. Here, we show that AMPK reactivation blocks both the glutamine-dependent activation of mTORC1 and glutamoptosis in vitro and in vivo. We also show that glutamine is used for asparagine synthesis and the GABA shunt to produce ATP and to inhibit AMPK, independently of glutaminolysis. Overall, our results indicate that glutamine metabolism is connected with mTORC1 activation through two parallel pathways: an acute alpha-ketoglutarate-dependent pathway; and a secondary ATP/AMPK-dependent pathway. This dual metabolic connection between glutamine and mTORC1 must be considered for the future design of therapeutic strategies to prevent cell growth in diseases such as cancer.

G-quadruplex ligands exert their antiproliferative effects through telomere-dependent and telomere-independent mechanisms, but the inter-relationships among autophagy, cell growth arrest and cell death induced by these ligands remain largely unexplored. Here, we demonstrate that the G-quadruplex ligand 20A causes growth arrest of cancer cells in culture and in a HeLa cell xenografted mouse model. This response is associated with the induction of senescence and apoptosis. Transcriptomic analysis of 20A treated cells reveals a significant functional enrichment of biological pathways related to growth arrest, DNA damage response and the lysosomal pathway. 20A elicits global DNA damage but not telomeric damage and activates the ATM and autophagy pathways. Loss of ATM following 20A treatment inhibits both autophagy and senescence and sensitizes cells to death. Moreover, disruption of autophagy by deletion of two essential autophagy genes ATG5 and ATG7 leads to failure of CHK1 activation by 20A and subsequently increased cell death. Our results, therefore, identify the activation of ATM by 20A as a critical player in the balance between senescence and apoptosis and autophagy as one of the key mediators of such regulation. Thus, targeting the ATM/autophagy pathway might be a promising strategy to achieve the maximal anticancer effect of this compound.

Patients with deficiency in ferrochelatase (FECH), the last enzyme of the heme biosynthetic pathway, experience a painful type of skin photosensitivity called erythropoietic protoporphyria (EPP), which is caused by the excessive production of protoporphyrin IX (PPIX) by erythrocytes. Controversial results have been reported regarding hematologic status and iron status of patients with EPP. We thoroughly explored these parameters in Fech^m1Pas mutant mice of 3 different genetic backgrounds. FECH deficiency induced microcytic hypochromic anemia without ringed sideroblasts, little or no hemolysis, and no erythroid hyperplasia. Serum iron, ferritin, hepcidin mRNA, and Dcytb levels were normal. The homozygous Fech^m1Pas mutant involved no tissue iron deficiency but showed a clear-cut redistribution of iron stores from peripheral tissues to the spleen, with a concomitant 2- to 3-fold increase in transferrin expression at the mRNA and the protein levels. Erythrocyte PPIX levels strongly correlated with serum transferrin levels. At all stages of differentiation in our study, transferrin receptor expression in bone marrow erythroid cells in Fech^m1Pas was normal in mutant mice but not in patients with iron-deficiency anemia. Based on these observations, we suggest that oral iron therapy is not the therapy of choice for patients with EPP and that the PPIX–liver transferrin pathway plays a role in the orchestration of iron distribution between peripheral iron stores, the spleen, and the bone marrow.

Purpose: Activating missense mutations of KRAS are the most frequent oncogenic driver events in lung adenocarcinoma (LUAD). However, KRAS isoforms are highly heterogeneous, and data on the potential isoform-dependent therapeutic vulnerabilities are still lacking. Experimental Design: We developed an isogenic cell-based platform to compare the oncogenic properties and specific therapeutic actionability of KRAS-mutant isoforms. In parallel, we analyzed clinicopathologic and genomic data from 3,560 patients with non–small cell lung cancer (NSCLC) to survey allele-specific features associated with oncogenic KRAS mutations. Results: In isogenic cell lines expressing different mutant KRAS isoforms, we identified isoform-specific biochemical, biological, and oncogenic properties both in vitro and in vivo. These exclusive features correlated with different therapeutic responses to MEK inhibitors, with KRAS G12C and Q61H mutants being more sensitive compared with other isoforms. In vivo, combined KRAS G12C and MEK inhibition was more effective than either drug alone. Among patients with NSCLCs that underwent comprehensive tumor genomic profiling, STK11 and ATM mutations were significantly enriched among tumors harboring KRAS G12C, G12A, and G12V mutations. KEAP1 mutation was significantly enriched among KRAS G12C and KRAS G13X LUADs. KRAS G13X-mutated tumors had the highest frequency of concurrent STK11 and KEAP1 mutations. Transcriptomic profiling revealed unique patterns of gene expression in each KRAS isoform, compared with KRAS wild-type tumors. Conclusions: This study demonstrates that KRAS isoforms are highly heterogeneous in terms of concurrent genomic alterations and gene-expression profiles, and that stratification based on KRAS alleles should be considered in the design of future clinical trials.