Characterizing Metabolic Heterogeneity of Hepatocellular Carcinoma with Hyperpolarized 13C Pyruvate MRI and Mass Spectrometry.

Purpose To characterize the metabolomic profiles of two hepatocellular carcinoma (HCC) rat models, track evolution of these profiles to a stimulated tumor state, and assess their effect on lactate flux with hyperpolarized (HP) carbon 13 (13C) MRI. Materials and Methods Forty-three female adult Fischer rats were implanted with N1S1 or McA-RH7777 HCC tumors. In vivo lactate-to-pyruvate ratio (LPR) was measured with HP 13C MRI at 9.4 T. Ex vivo mass spectrometry was used to measure intratumoral metabolites, and Ki67 labeling was used to quantify proliferation. Tumors were first compared with three normal liver controls. The tumors were then compared with stimulated variants via off-target hepatic thermal ablation treatment. All comparisons were made using the Mann-Whitney test. Results HP 13C pyruvate MRI showed greater LPR in N1S1 tumors compared with normal liver (mean [SD], 0.564 ± 0.194 vs 0.311 ± 0.057; P < .001 [n = 9]), but not for McA-RH7777 (P = .44 [n = 8]). Mass spectrometry confirmed that the glycolysis pathway was increased in N1S1 tumors and decreased in McA-RH7777 tumors. The pentose phosphate pathway was also decreased only in McA-RH7777 tumors. Increased proliferation in stimulated N1S1 tumors corresponded to a net increase in LPR (six stimulated vs six nonstimulated, 0.269 ± 0.148 vs 0.027 ± 0.08; P = .009), but not in McA-RH7777 (eight stimulated vs six nonstimulated, P = .13), despite increased proliferation and metastases. Mass spectrometry demonstrated relatively increased lactate production with stimulation in N1S1 tumors only. Conclusion Two HCC subtypes showed divergent glycolytic dependency at baseline and during transformation to a high proliferation state. This metabolic heterogeneity in HCC should be considered with use of HP 13C MRI for diagnosis and tracking. Keywords: Molecular Imaging-Probe Development, Liver, Abdomen/GI, Oncology, Hepatocellular Carcinoma © RSNA, 2024 See also commentary by Ohliger in this issue.

Combined thermal ablation and liposomal granulocyte-macrophage colony stimulation factor increases immune cell trafficking in a small animal tumor model.

PURPOSE: To characterize intratumoral immune cell trafficking in ablated and synchronous tumors following combined radiofrequency ablation (RFA) and systemic liposomal granulocyte-macrophage colony stimulation factor (lip-GM-CSF). METHODS: Phase I, 72 rats with single subcutaneous R3230 adenocarcinoma were randomized to 6 groups: a) sham; b&c) free or liposomal GM-CSF alone; d) RFA alone; or e&f) combined with blank liposomes or lip-GM-CSF. Animals were sacrificed 3 and 7 days post-RFA. Outcomes included immunohistochemistry of dendritic cells (DCs), M1 and M2 macrophages, T-helper cells (Th1) (CD4+), cytotoxic T- lymphocytes (CTL) (CD8+), T-regulator cells (T-reg) (FoxP3+) and Fas Ligand activated CTLs (Fas-L+) in the periablational rim and untreated index tumor. M1/M2, CD4+/CD8+ and CD8+/FoxP3+ ratios were calculated. Phase II, 40 rats with double tumors were randomized to 4 groups: a) sham, b) RFA, c) RFA-BL and d) RFA-lip-GM-CSF. Synchronous untreated tumors collected at 7d were analyzed similarly. RESULTS: RFA-lip-GMCSF increased periablational M1, CTL and CD8+/FoxP3+ ratio at 3 and 7d, and activated CTLs 7d post-RFA (p<0.05). RFA-lip-GMSCF also increased M2, T-reg, and reduced CD4+/CD8+ 3 and 7d post-RFA respectively (p<0.05). In untreated index tumor, RFA-lip-GMCSF improved DCs, M1, CTLs and activated CTL 7d post-RFA (p<0.05). Furthermore, RFA-lip-GMSCF increased M2 at 3 and 7d, and T-reg 7d post-RFA (p<0.05). In synchronous tumors, RFA-BL and RFA-lip-GM-CSF improved DC, Th1 and CTL infiltration 7d post-RFA. CONCLUSION: Systemic liposomal GM-CSF combined with RFA improves intratumoral immune cell trafficking, specifically populations initiating (DC, M1) and executing (CTL, FasL+) anti-tumor immunity. Moreover, liposomes influence synchronous untreated metastases increasing Th1, CTL and DCs infiltration.

PFKFB3-mediated Pro-glycolytic Shift in Hepatocellular Carcinoma Proliferation.

BACKGROUND & AIMS: Metabolic reprogramming, in particular, glycolytic regulation, supports abnormal survival and growth of hepatocellular carcinoma (HCC) and could serve as a therapeutic target. In this study, we sought to identify glycolytic regulators in HCC that could be inhibited to prevent tumor progression and could also be monitored in vivo, with the goal of providing a theragnostic alternative to existing therapies. METHODS: An orthotopic HCC rat model was used. Tumors were stimulated into a high-proliferation state by use of off-target liver ablation and were compared with lower-proliferating controls. We measured in vivo metabolic alteration in tumors before and after stimulation, and between stimulated tumors and control tumors using hyperpolarized 13C magnetic resonance imaging (MRI) (h13C MRI). We compared metabolic alterations detected by h13C MRI to metabolite levels from ex vivo mass spectrometry, mRNA levels of key glycolytic regulators, and histopathology. RESULTS: Glycolytic lactate flux increased within HCC tumors 3 days after tumor stimulation, correlating positively with tumor proliferation as measured with Ki67. This was associated with a shift towards aerobic glycolysis and downregulation of the pentose phosphate pathway detected by mass spectrometry. MRI-measured lactate flux was most closely coupled with PFKFB3 expression and was suppressed with direct inhibition using PFK15. CONCLUSIONS: Inhibition of PFKFB3 prevents glycolytic-mediated HCC proliferation, trackable by in vivo h13C MRI.

Redox regulation by TXNRD3 during epididymal maturation underlies capacitation-associated mitochondrial activity and sperm motility in mice.

During epididymal transit, redox remodeling protects mammalian spermatozoa, preparing them for survival in the subsequent journey to fertilization. However, molecular mechanisms of redox regulation in sperm development and maturation remain largely elusive. In this study, we report that thioredoxin-glutathione reductase (TXNRD3), a thioredoxin reductase family member particularly abundant in elongating spermatids at the site of mitochondrial sheath formation, regulates redox homeostasis to support male fertility. Using Txnrd3-/- mice, our biochemical, ultrastructural, and live cell imaging analyses revealed impairments in sperm morphology and motility under conditions of TXNRD3 deficiency. We find that mitochondria develop more defined cristae during capacitation in wildtype sperm. Furthermore, we show that absence of TXNRD3 alters thiol redox status in both the head and tail during sperm maturation and capacitation, resulting in defective mitochondrial ultrastructure and activity under capacitating conditions. These findings provide insights into molecular mechanisms of redox homeostasis and bioenergetics during sperm maturation, capacitation, and fertilization.

Selenoprotein TXNRD3 supports male fertility via the redox regulation of spermatogenesis.

Thioredoxin/glutathione reductase (TXNRD3) is a selenoprotein composed of thioredoxin reductase and glutaredoxin domains. This NADPH-dependent thiol oxidoreductase evolved through gene duplication within the Txnrd family, is expressed in the testes, and can reduce both thioredoxin and glutathione in vitro; however, the function of this enzyme remains unknown. To characterize the function of TXNRD3 in vivo, we generated a strain of mice bearing deletion of Txnrd3 gene. We show that these Txnrd3 knockout mice are viable and without discernable gross phenotypes, and also that TXNRD3 deficiency leads to fertility impairment in male mice. We found that Txnrd3 knockout animals exhibited a lower fertilization rate in vitro, a sperm movement phenotype, and an altered thiol redox status in sperm cells. Proteomic analyses further revealed a broad range of substrates reduced by TXNRD3 during sperm maturation, presumably as a part of sperm quality control. Taken together, these results show that TXNRD3 plays a critical role in male reproduction via the thiol redox control of spermatogenesis.

Beaver and Naked Mole Rat Genomes Reveal Common Paths to Longevity.

Long-lived rodents have become an attractive model for the studies on aging. To understand evolutionary paths to long life, we prepare chromosome-level genome assemblies of the two longest-lived rodents, Canadian beaver (Castor canadensis) and naked mole rat (NMR, Heterocephalus glaber), which were scaffolded with in vitro proximity ligation and chromosome conformation capture data and complemented with long-read sequencing. Our comparative genomic analyses reveal that amino acid substitutions at "disease-causing" sites are widespread in the rodent genomes and that identical substitutions in long-lived rodents are associated with common adaptive phenotypes, e.g., enhanced resistance to DNA damage and cellular stress. By employing a newly developed substitution model and likelihood ratio test, we find that energy and fatty acid metabolism pathways are enriched for signals of positive selection in both long-lived rodents. Thus, the high-quality genome resource of long-lived rodents can assist in the discovery of genetic factors that control longevity and adaptive evolution.

Mitochondrial redox sensing by the kinase ATM maintains cellular antioxidant capacity.

Mitochondria are integral to cellular energy metabolism and ATP production and are involved in regulating many cellular processes. Mitochondria produce reactive oxygen species (ROS), which not only can damage cellular components but also participate in signal transduction. The kinase ATM, which is mutated in the neurodegenerative, autosomal recessive disease ataxia-telangiectasia (A-T), is a key player in the nuclear DNA damage response. However, ATM also performs a redox-sensing function mediated through formation of ROS-dependent disulfide-linked dimers. We found that mitochondria-derived hydrogen peroxide promoted ATM dimerization. In HeLa cells, ATM dimers were localized to the nucleus and inhibited by the redox regulatory protein thioredoxin 1 (TRX1), suggesting the existence of a ROS-mediated, stress-signaling relay from mitochondria to the nucleus. ATM dimer formation did not affect its association with chromatin in the absence or presence of nuclear DNA damage, consistent with the separation of its redox and DNA damage signaling functions. Comparative analysis of U2OS cells expressing either wild-type ATM or the redox sensing-deficient C2991L mutant revealed that one function of ATM redox sensing is to promote glucose flux through the pentose phosphate pathway (PPP) by increasing the abundance and activity of glucose-6-phosphate dehydrogenase (G6PD), thereby increasing cellular antioxidant capacity. The PPP produces the coenzyme NADPH needed for a robust antioxidant response, including the regeneration of TRX1, indicating the existence of a regulatory feedback loop involving ATM and TRX1. We propose that loss of the mitochondrial ROS-sensing function of ATM may cause cellular ROS accumulation and oxidative stress in A-T.

Population genomics of finless porpoises reveal an incipient cetacean species adapted to freshwater.

Cetaceans (whales, dolphins, and porpoises) are a group of mammals adapted to various aquatic habitats, from oceans to freshwater rivers. We report the sequencing, de novo assembly and analysis of a finless porpoise genome, and the re-sequencing of an additional 48 finless porpoise individuals. We use these data to reconstruct the demographic history of finless porpoises from their origin to the occupation into the Yangtze River. Analyses of selection between marine and freshwater porpoises identify genes associated with renal water homeostasis and urea cycle, such as urea transporter 2 and angiotensin I-converting enzyme 2, which are likely adaptations associated with the difference in osmotic stress between ocean and rivers. Our results strongly suggest that the critically endangered Yangtze finless porpoises are reproductively isolated from other porpoise populations and harbor unique genetic adaptations, supporting that they should be considered a unique incipient species.

Ivermectin induces PAK1-mediated cytostatic autophagy in breast cancer.

Ivermectin is a broad-spectrum antiparasitic drug that has recently been demonstrated to exhibit potent anticancer activity against colon cancer, ovarian cancer, melanoma and leukemia. However, the molecular mechanism underlying this anticancer effect remains poorly understood. We recently found that ivermectin markedly inhibits the growth of breast cancer cells by stimulating cytostatic macroautophagy/autophagy in vitro and in vivo. Ivermectin inhibits the AKT-MTOR signaling pathway by promoting ubiquitination-mediated degradation of PAK1 (p21 [RAC1] activated kinase 1), leading to increased autophagic flux. Together, our work unravels the molecular mechanism underpinning ivermectin-induced cytostatic autophagy in breast cancer, and characterizes ivermectin as a potential therapeutic option for breast cancer treatment.

Ivermectin Induces Cytostatic Autophagy by Blocking the PAK1/Akt Axis in Breast Cancer.

Breast cancer is the most common cancer among women worldwide, yet successful treatment remains a clinical challenge. Ivermectin, a broad-spectrum antiparasitic drug, has recently been characterized as a potential anticancer agent due to observed antitumor effects. However, the molecular mechanisms involved remain poorly understood. Here, we report a role for ivermectin in breast cancer suppression by activating cytostatic autophagy both in vitro and in vivo Mechanistically, ivermectin-induced autophagy in breast cancer cells is associated with decreased P21-activated kinase 1 (PAK1) expression via the ubiquitination-mediated degradation pathway. The inhibition of PAK1 decreases the phosphorylation level of Akt, resulting in the blockade of the Akt/mTOR signaling pathway. In breast cancer xenografts, the ivermectin-induced cytostatic autophagy leads to suppression of tumor growth. Together, our results provide a molecular basis for the use of ivermectin to inhibit the proliferation of breast cancer cells and indicate that ivermectin is a potential option for the treatment of breast cancer. Cancer Res; 76(15); 4457-69. ©2016 AACR.

PDLIM1 Stabilizes the E-Cadherin/ß-Catenin Complex to Prevent Epithelial-Mesenchymal Transition and Metastatic Potential of Colorectal Cancer Cells.

Metastasis is a major cause of death in patients with colorectal cancer, and increasing evidence supports the contribution of the epithelial-mesenchymal transition (EMT) to cancer progression. The dissociation of the E-cadherin/ß-catenin adhesion complex represents a key step in EMT and promotes cancer invasion and metastasis, but the upstream signaling pathways regulating this interaction are poorly understood. Here, we show that PDLIM1, a member of the PDZ and LIM protein family, was downregulated in highly metastatic colorectal cancer cells and liver metastases from colorectal cancer patients. We found that loss of PDLIM1 promoted the expression of EMT markers and increased the invasive and migratory properties of multiple colorectal cancer cell lines. Furthermore, PDLIM1 knockdown increased colon-derived liver metastasis in an orthotopic colorectal cancer model and promoted distant metastatic colonization in an experimental lung metastasis model. Mechanistic investigations revealed that PDLIM1 interacted with and stabilized the E-cadherin/ß-catenin complex, thereby inhibiting the transcriptional activity of ß-catenin and preventing EMT. Accordingly, PDLIM1 overexpression attenuated EMT of colorectal cancer cells. Moreover, the downregulation of PDLIM1 in colorectal cancer samples correlated with reduced E-cadherin and membrane ß-catenin levels, and was associated with shorter overall survival. In conclusion, our study demonstrates that PDLIM1 suppresses EMT and metastatic potential of colorectal cancer cells by stabilizing ß-catenin at cell-cell junctions, and its loss in metastatic tissues may represent a potential prognostic marker of aggressive disease.

Thiol-based redox proteomics in cancer research.

Cancer cells maintain their intracellular ROS concentrations at required levels for their survival. Changes in ROS concentrations can regulate biochemical signaling mechanisms that control cell function. It has been demonstrated that ROS regulate the cellular events through redox regulation of redox-sensitive proteins (redox sensors). Upon oxidative stress, redox sensors undergo redox modifications that cause the allosteric changes of these proteins and endow them with different functions. Understanding the altered functions of redox sensors and the underlying mechanisms is critical for the development of novel cancer therapeutics. Recently, a series of high-throughput proteomics approaches have been developed for screening redox processes. In this manuscript, we review these methodologies and discuss the important redox sensors recently identified that are related to cancer.