ABSTRACT
Cancer cells consume glucose and secrete lactate in culture. It is unknown whether lactate contributes to energy metabolism in living tumors. We previously reported that human non-small-cell lung cancers (NSCLCs) oxidize glucose in the tricarboxylic acid (TCA) cycle. Here, we show that lactate is also a TCA cycle carbon source for NSCLC. In human NSCLC, evidence of lactate utilization was most apparent in tumors with high 18fluorodeoxyglucose uptake and aggressive oncological behavior. Infusing human NSCLC patients with 13C-lactate revealed extensive labeling of TCA cycle metabolites. In mice, deleting monocarboxylate transporter-1 (MCT1) from tumor cells eliminated lactate-dependent metabolite labeling, confirming tumor-cell-autonomous lactate uptake. Strikingly, directly comparing lactate and glucose metabolism in vivo indicated that lactate's contribution to the TCA cycle predominates. The data indicate that tumors, including bona fide human NSCLC, can use lactate as a fuel in vivo.
Subject(s)
Carcinoma, Non-Small-Cell Lung/metabolism , Lactic Acid/metabolism , Lung Neoplasms/metabolism , Animals , Blood Chemical Analysis , Cell Line, Tumor , Citric Acid Cycle , Disease Models, Animal , Female , Glyceric Acids/metabolism , Heterografts , Humans , Male , Mice , Monocarboxylic Acid Transporters/genetics , Monocarboxylic Acid Transporters/metabolism , Neoplasm Transplantation , Symporters/genetics , Symporters/metabolismABSTRACT
Membrane-bound cGMP-dependent protein kinase (PKG) II is a key regulator of bone growth, renin secretion, and memory formation. Despite its crucial physiological roles, little is known about its cyclic nucleotide selectivity mechanism due to a lack of structural information. Here, we find that the C-terminal cyclic nucleotide binding (CNB-B) domain of PKG II binds cGMP with higher affinity and selectivity when compared with its N-terminal CNB (CNB-A) domain. To understand the structural basis of cGMP selectivity, we solved co-crystal structures of the CNB domains with cyclic nucleotides. Our structures combined with mutagenesis demonstrate that the guanine-specific contacts at Asp-412 and Arg-415 of the αC-helix of CNB-B are crucial for cGMP selectivity and activation of PKG II. Structural comparison with the cGMP selective CNB domains of human PKG I and Plasmodium falciparum PKG (PfPKG) shows different contacts with the guanine moiety, revealing a unique cGMP selectivity mechanism for PKG II.
Subject(s)
Cyclic GMP-Dependent Protein Kinase Type II/chemistry , Cyclic GMP-Dependent Protein Kinase Type II/metabolism , Cyclic GMP/metabolism , Allosteric Regulation , Animals , COS Cells , Chlorocebus aethiops , Crystallography, X-Ray , Cyclic AMP/metabolism , HEK293 Cells , Humans , Models, Molecular , Protein Structure, Tertiary , Substrate SpecificityABSTRACT
BACKGROUND: Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) can significantly improve the survival in selected patients with peritoneal carcinomatosis. This study aims to identify perioperative patient characteristics predictive of failure to rescue (FTR), mortality following postoperative complications from CRS/HIPEC. METHODS: Patients suffering a complication following CRS/HIPEC between 2005 and 2013 were identified in the American College of Surgeons National Surgical Quality Improvement Program data set. FTR was defined as 30-d mortality in the setting of a complication. Patients who suffered FTR were compared against those who survived a complication (non-FTR). Predictors of FTR were identified using a multivariable logistic regression model. RESULTS: A total of 915 eligible CRS/HIPEC cases were identified. In all, 382 patients (42%) developed ≥1 postoperative complication, and 88 patients (10%) suffered ≥1 major complication. Seventeen patients died following a complication, amounting to an FTR rate of 4%. FTR patients were more likely than non-FTR patients to have dependent functional status (18% versus 2%, P = 0.01), have American Society of Anesthesiologists (ASA) class 4 status (29% versus 8%, P = 0.01), develop ≥3 complications (65% versus 24%, P < 0.01), and suffer a major complication (94% versus 20%, P < 0.01). The following were independently associated with FTR: ASA class 4 (odds ratio [OR]: 13.4, 95% confidence interval [CI], 1.2-146.8) and major complications (OR: 66.0, 95% CI, 8.4-516.6). CONCLUSIONS: ASA class 4, major morbidity, and likely dependent functional status are independent predictors of FTR following CRS/HIPEC to treat peritoneal carcinomatosis. Therefore, ASA class 4 and dependent functional status should be considered as contraindications for CRS/HIPEC and only offered in highly selective cases.