Abstract 4840: Dysregulation of mitochondrial function by PLK1-mediated PDHA1 phosphorylation promotes Cr(VI)-associated lung cancer progression

Hexavalent chromium (Cr(VI)), an class I environmental carcinogen, not only induces lung epithelial cell transformation but also promotes lung cancer progression by alterations of the cell cycle and cellular energy metabolism. Using Cr(VI)-transformed (CrT) bronchial epithelial cells (BEAS-2B) and parental BEAS-2B cells, we demonstrate that the level of polo-like kinase 1 (PLK1) is highly upregulated in CrT cells, which blocks mitochondrial function, and further promotes cell proliferation both in vitro and in vivo. Cells expressing a high level of PLK1 exhibited repressed mitochondrial activity due to defective modulation of pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1), which facilitates the carbon influx to TCA cycle via catalyzing pyruvate/Acetyl-CoA conversion. Mechanistically, we show that PDHA1 can be directly phosphorylated by PLK1 at T57, which triggers collapse of E1 and PDHA1 degradation via activation of mitophagy. These defects resulted in the inhibition of oxidative phosphorylation and reduction of mitochondrial reactive oxygen species (ROS) generation, eventually inhibiting mitochondrial-mediated apoptotic response. Defining the role of PLK1 in metabolic reprogramming in Cr(VI)-associated cancer progression may give us a new perspective and a target to inhibit Cr(VI)-induced cancer development. In addition, PLK1 inhibitors may be used to increase the chemo-sensitivity of cancer cells by restoring the normal function of mitochondria, thus alleviating the drug resistance caused by dysfunction and hyperpolarization of mitochondria.

Citation Format: Qiongsi Zhang, Zhiguo Li, Xiongjian Rao, Derek B. Allison, Qi Qiao, Zhuangzhuang Zhang, Yifan Kong, Ruixin Wang, Teresa W. Fan, Richard M. Higashi, Andrew N. Lane, Xiaoqi Liu. Dysregulation of mitochondrial function by PLK1-mediated PDHA1 phosphorylation promotes Cr(VI)-associated lung cancer progression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4840.

[Chi-liang Kwei and an unfulfilled plan of establishing a modern psychiatric hospital in China]

Church General Hospital in Wuchang, China planned to establish a psychiatric hospital in 1930. Chi-liang Kwei, received his PhD at Johns Hopkins Medical School of America and was appointed to be in charge of the preparation. After working out a draft plan for the hospital, Dr. Kwei applied for the Henderson Research Scholarship on Mental Diseases. She planned to study under the guidance of Dr. D.K. Henderson in the Glasgow Mental Royal Hospital for a full year in preparation for the establishment of the hospital. By drawing on the correspondence files of Chi-liang Kwei and psychiatrists Adolf Meyer and David Kennedy Henderson, the paper describes the background conditions and planning for the hospital establishment and interprets the significance and value of Chi-liang Kwei's efforts to establish a psychiatric hospital from the perspective of the historic development of modern psychiatry in China.

Abstract 5028: Mapping metabolic networks and drug resistance in 3D spheroids using stable isotope-resolved metabolomics (SIRM)

Introduction: 2D cells lack cell-cell and cell-extracellular matrix interactions, critical for regulating cell functions. 3D cells in matrigel, hydrogels, hanging drops, and micropatterned plates can overcome these drawbacks but suffer from long spheroid formation times with variable efficiency. Magnetic 3D bioprinting (M3DB) can circumvent these issues by utilizing nanoparticles-magnetized cells for spheroid formation. M3DB spheroids can emulate tissue microenvironments and exhibit higher resistance to toxic agents than their 2D counterparts. It is, however, unclear how M3DB spheroids influence toxic responses in cells via metabolic perturbations. We employed Stable Isotope-Resolved Metabolomics (SIRM) with 13C6-glucose to map metabolic networks in 2D cells and M3DB spheroids formed from lung (A549) and pancreatic (PANC1) adenocarcinoma cells ± anti-cancer Na2SeO3.

Experimental: A549 and PANC1 cells were grown in 2D culture in DMEM to ca. 70% confluence for loading with magnetic nanoparticles (Nanoshuttle, N3D Biosciences), detached, and placed in cell repellent plates for spheroid formation. Spheroids were then treated in [U-13C]-glucose ± Na2SeO3 for 24 h. Metabolites were extracted in cold 70% methanol and analyzed by IC-FTMS and NMR 1,2 to determine the 13C isotopologue and isotopomer distributions for reconstructing metabolic networks.

Findings: We found that spheroids remained metabolically active in 10-day cultures. 13C label incorporation into glycolytic, Krebs cycle, and nucleotide metabolites was similar between spheroids and their 2D counterparts. The exceptions were higher 13C-ribose incorporation into uracil nucleotides in 2D than M3DB cultures of A549 cells and activation of gluconeogenesis in PANC1 M3DB spheroids. Selenite inhibited these pathways less in spheroids than 2D counterparts for both cell lines, consistent with the growth changes. Thus, the increased resistance of cancer spheroids to selenite may be mediated by these metabolic pathways central to growth and survival.

Conclusions: 3D spheroids offer convenient models with more relevant 3-D architectures for preclinical studies on metabolic reprogramming and drug response of human cancer cells and cancer-stromal cell co-cultures. Spheroid formation in the M3DB system is fast, high throughput without matrix interferences for metabolic analyses.

Supported by NCI P01CA163223-01A1, P30 CA177558 and NIDDK 1U24DK097215-01A1

1. Sun RC, Fan TW-M, Deng P, et al. Liquid diet delivery of stable isotopes into PDX mice for deep metabolic pathway tracing. Nat. Commun. 2017;9:1646.

2. Fan TW-M, Warmoes MO, Sun Q, et al. Distinctly perturbed metabolic networks underlie differential tumor tissue damages induced by immune modulator β-glucan in a two-case ex vivo non-small cell lung cancer study. CSH Molec Case Studies 2016;2:a000893.

Citation Format: Teresa W. Fan, Salim S. El-Amouri, Jessica K. Macedo, Qiushi Sun, Andrew N. Lane. Mapping metabolic networks and drug resistance in 3D spheroids using stable isotope-resolved metabolomics (SIRM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5028.

Abstract 452: Activation of Akt pathway and autophagy promotes resistance to FASN inhibition in colorectal cancer patient-derived xenograft models

Fatty Acid Synthase (FASN), a key enzyme of de novo lipogenesis, is upregulated in many cancers including colorectal cancer (CRC); increased FASN expression is associated with poor prognosis. Potent FASN inhibitors developed by 3-V Biosciences demonstrate anti-tumor activity in vitro and in vivo and a favorable tolerability profile in a Phase I clinical trial in solid tumor patients. However, CRC characteristics associated with responsiveness to FASN inhibition are not fully understood. The purpose of our study was: (i) to determine the effect of FASN inhibition on tumor growth in CRC patient-derived xenografts (PDXs); (ii) to identify potential biomarkers associated with CRC responsiveness to FASN inhibition; and (iii) to explore new combination strategies with FASN inhibitors. METHODS. Tumor growth was assessed in 9 PDXs established in NSG mice using freshly resected specimens. Once the xenografts grew to ~100 mm3, mice were randomized into two groups (n=5) to receive either vehicle or TVB-3664 or four groups (n=10) for TVB-3664 treatment in combination with either MK2206 or Chloroquine (CQ). Tumor volume and animal weights were measured weekly. Western blot analysis and immunohistochemistry staining were used to identify FASN-mediated changes in signaling pathways. Changes in metabolites and lipids were analyzed by nuclear magnetic resonance and mass spectrometry in plasma and tumor tissues. Next Generation Sequencing was used to assess the mutation profile of 198 oncogenes in patient tumors and PDXs. RESULTS. PDXs showed a wide range of sensitivity to FASN inhibition: TVB-3664 treatment attained significant response (reduced tumor volume) in 3 PDXs, significant response followed by developed resistance in one PDX, and no response in 5 PDXs. Activation of Akt and AMPK pathways was associated with resistance to FASN inhibition and combination of TVB-3664 with either MK2206 or CQ led to a significant reduction in tumor volume as compared to either drug alone. Moreover, TVB-3664 treatment significantly decreased the total palmitate level in plasma and the levels of triglycerides, diglycerides, phosphatidylserines, phosphatidylethanolamines, and phosphatidylcholines in tumor tissues. Furthermore, a significant decrease in the levels of AXP-1, AXP-2 and myo-Inositol-2 was observed in tumors responsive to FASN inhibition. CONCLUSIONS. Our studies demonstrate that TVB-3664 shows anti-tumor activity in CRC. Importantly, our results suggest that activation of Akt and autophagy are major mechanisms of resistance to FASN inhibition and demonstrate that combine inhibition of these pathways and FASN may be a new therapeutic approach in CRC. Ongoing studies of correlation between mutation and metabolic profiles of tumors and tumor response to FASN inhibition aim to identify a subset of CRC patients that are likely to respond to FASN-targeted therapy.

Citation Format: Yekaterina Y. Zaytseva, Piotr G. Rychahou, Anh-Thu Le, Robert M. Flight, Timothy L. Scott, Jennifer W. Harris, Sally Hodges, Brent J. Hallahan, Dana L. Napier, Jinpeng Liu, Chi Wang, Manjula Sunkara, Andrew Morris, Ji Tae Kim, Sivakumaran Theru Arumugam, Andrew Lane, Teresa W. Fan, Hunter Moseley, Tianyan Gao, Eun Y. Lee, Heidi L. Weiss, Timothy S. Heuer, George Kemble, B Mark Evers. Activation of Akt pathway and autophagy promotes resistance to FASN inhibition in colorectal cancer patient-derived xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 452. doi:10.1158/1538-7445.AM2017-452

Abstract 2501: Assessing metabolic activity of patient-derived models of non-small cell lung cancer using stable isotope resolved metabolomics (SIRM)

Stable Isotope-Resolved Metabolomics (SIRM) has been a useful tool in interrogating metabolic reprogramming in cancer. We have recently published several protocols using SIRM in patient-derived models of non-small cell lung cancer (NSCLC)1. In this case study, we compared central metabolic activity in three different model systems, all derived from the same patient. Slices from the human tumor (Warburg slices 2,3), slices from an NSG mouse bearing the human tumor 4, and the patient-derived cell culture were incubated in [U-13C]-glucose or [U-13C,15N]-glutamine for 24 hours. Samples were then harvested and analyzed by gas-chromatography-mass spectrometry and NMR. All three models displayed similar levels of fractional enrichment after 24 hours, making metabolic comparison possible, despite their very different 3D architectures. Glucose metabolism in particular, showed consistent labeling patterns of metabolites in glycolysis and the Krebs cycle. Glutamine metabolism, however, was distinct in the cell culture, with a pattern that indicated upregulation of anaplerotic glutaminolysis. Activation of glutaminolysis may be an important transformative step in the establishment of a viable cell culture. We are also in the process of validating the present finding by comparing multiple patient-derived models of NSCLC and tracking the evolution of their metabolic activity.

1 Lane, A. N., Higashi, R. M. & Fan, T. W.-M. Preclinical models for interrogating drug action in human cancers using Stable Isotope Resolved Metabolomics (SIRM) Metabolomics 12, 1-15 (2016).

2 Fan, T. W.-M. et al. Distinctly perturbed metabolic networks underlie differential tumor tissue damages induced by immune modulator β-glucan in a two-case ex vivo non-small cell lung cancer study. CSH Molec. Case Studies J. 2, a00083, (2016).

3 Fan, T. W.-M., Lane, A. N. & Higashi, R. M. Stable Isotope Resolved Metabolomics Studies in ex vivo Tissue Slices. Bio-protocol 6, e1730 (2016).

4 Lane, A. N., Yan, J. & Fan, T. W.-M. 13C Tracer Studies of Metabolism in Mouse Tumor Xenografts. Bio-protocol 5, e1650 (2015).

Citation Format: Connor J. Kinslow, Jinlian Tan, Yihua Cai, Jun Yan, Richard M. Higashi, Andrew N. Lane, Teresa W. Fan. Assessing metabolic activity of patient-derived models of non-small cell lung cancer using stable isotope resolved metabolomics (SIRM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2501. doi:10.1158/1538-7445.AM2017-2501

Abstract SY02-02: Exploring the lung cancer metabolome, in vivo and ex vivo, for individualized medicine

Lung cancer is a leading cause of cancer death worldwide. This disease is of serious concern in Kentucky, which leads the nation in both lung cancer incidence and mortality. The past decade of research in cancer metabolism reveals the untapped value of exploring human metabolome for the discovery of novel therapeutic and diagnostic biomarkers for human cancers and other diseases. To better understand metabolic reprogramming in individual tumors of lung cancer patients, we have developed stable isotope tracers (e.g., [13C6]-glucose) coupled with NMR and MS-based stable isotope-resolved metabolomics (SIRM) analysis directly in patient and in patient-derived ex vivo and in vivo models. In the in vivo patient study, we mapped differential metabolic network between paired cancerous (CA) and noncancerous (NC) tissues procured from non–small cell lung cancer (NSCLC) patients infused with [13C6]-glucose and snap-frozen immediately after resection (1). In particular, we uncovered elevated anaplerotic pyruvate carboxylase (PC) activity in CA versus paired NC tissues. Proliferating cancer cells require active Krebs cycle for generating anabolic precursors, in addition to energy production. Diversion of the Krebs cycle intermediates to meet anabolic demands cannot be sustained without anaplerosis. Pyruvate carboxylation represents one of the two major anaplerotic pathways that replenish the Krebs cycle intermediates; the other involves glutaminolysis initiated by glutaminase (GLS). We also found that PC but not GLS protein was overexpressed (median 8-10 fold; n=86) in CA tissues relative to paired NC tissues and that PC expression was functionally important to NSCLC cell growth both in vitro and in vivo (1). We also utilize the “Warburg slice” concept to systematically define metabolic distinctions between thinly sliced paired CA versus NC lung tissues freshly resected from individual NSCLC patients and cultured in stable isotope tracers. This ex vivo tissue slice culture system is excellently suited for delineating reprogrammed metabolic pathways in CA tissues without systemic interferences (2-4). These lung tissue slices were metabolically viable for up to 72 hr, while maintaining their 3D architecture and microenvironment (4). We found that the reprogrammed metabolic network in the cultured human tissue slices recapitulated that in vivo (1). These advantages make the ex vivo human tissue slice systems a unique preclinical model for exploring human target tissue metabolism and how it underlies the response to anticancer agents such as chemopreventive Se compounds, enzyme inhibitors (5), and the immune modular β-glucan (4). We found that selenite blocked PC anaplerosis and elicited massive necrosis in CA but not in NC lung tissues. CA lung tissue slices also responded to β-glucan with perturbed metabolic activity and histopathologic changes, which were consistent with polarization towards M1-type macrophages. We were intrigued to find that the metabolism and histopathology of these CA lung tissue slices from different patients responded distinctly to these anticancer agents, which could be translated into individual patients' response to drugs. Furthermore, to delineate systemic and microenvironmental influences on cancer metabolism, we compared and found that the ex vivo tissue slice cultures incorporated to a higher extent 13C from [13C6]-glucose into glycolytic, PPP, and purine nucleotide products than the corresponding mouse PDX in vivo, illustrating the high metabolic viability of the ex vivo tissue slice cultures. These new developments in preclinical models and mechanistic metabolic interrogations promise to provide rigorous prediction for individual patients' response to therapeutics while revealing new and exciting targets for the next generation of personalized therapeutics. Supported by 1R01CA118434-01A2, 1P01CA163223-01A1, 1R01ES022191-01, 3R01ES022191-04S1, 3R01CA118434-02S1, 1U24DK097215-01A1, P30CA177558; KLCRP, and the KY Challenge for Excellence.

References

1. Sellers K, Fox MP, Bousamra M II, Slone SP, Higashi RM, Mille, DM, et al. Pyruvate carboxylase is critical for non-small-cell lung cancer proliferation. J Clin Invest 2015;125:687-98.

2. Fan TW, Lane AN, Higashi RM. (2016) Stable isotope resolved metabolomics Studies in ex vivo tissue slices. Bio-protocol 2016;6:e1730.

3. Lane AN, Higashi RM, Fan TWM. (2016) Preclinical models for interrogating drug action in human cancers using Stable Isotope Resolved Metabolomics (SIRM). Metabolomics 2016;12:1-15.

4. Fan TW, Warmoes MO, Sun Q, Song H, Turchan-Cholewo J, Martin JT, et al. Distinctly perturbed metabolic networks underlie differential tumor tissue damages induced by immune modulator beta-glucan in a two-case ex vivo non-small-cell lung cancer study. Cold Spring Harb Mol Case Stud 2016;2:a000893.

5. Xie H, Hanai JI, Ren JG, Kats L, Burgess K, Bhargava P, et al. (2014) Targeting lactate dehydrogenase-A inhibits tumorigenesis and tumor progression in mouse models of lung cancer and impacts tumor-initiating cells. Cell Metab 2014;19:1-15.

Citation Format: Teresa W. Fan, Ramon Sun, Marc Warmoes, Qiushi Sun, Huan Song, Angela Mahan, Jeremiah Martin, RICHARD M. Higashi, Andrew N. Lane. Exploring the lung cancer metabolome, in vivo and ex vivo, for individualized medicine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr SY02-02. doi:10.1158/1538-7445.AM2017-SY02-02

Abstract 1424: Enhanced pyruvate carboxylation is crucial to non-small cell lung cancer proliferation and anabolism

Proliferating cancer cells require an active Krebs cycle for generating anabolic precursors, in addition to energy production. Diversion of the Krebs cycle intermediates to meet anabolic demands cannot be sustained without anaplerosis. The two major anaplerotic pathways are the deamidation of glutamine to form glutamate catalyzed by glutaminase (GLS) or glutaminolysis, and the carboxylation of pyruvate to oxaloacetate by pyruvate carboxylase (PC).

We determined the expression of PC and GLS proteins in fresh tumor tissue and paired adjacent benign tissue from 86 human NSCLC patients. PC was elevated (median 8-10 fold) in 94% of the tumor tissues, whereas GLS expression did not differ significantly between tumor and paired non tumorous lung tissue. Using 13C6 glucose as tracer and stable isotope-resolved metabolomics (SIRM), we also observed elevated PC activity in vivo in human patients with early stage NSCLC. To examine the importance of PC in the growth and survival of NSCLC, 5 NSCLC cell lines were transduced with a lentiviral vector containing an shRNA against PC. PC knockdown slowed proliferation, induced multinucleation, and reduced colony formation in soft agar. To validate attenuated PC activity and to profile the metabolic effect of PC knockdown, A549 cells were grown in 13C6 glucose or 13C5 glutamine and the incorporation of 13C into various metabolic pathways was measured by NMR and MS by SIRM. We found reduced entry of both glucose and glutamine carbon into the Krebs cycle metabolites, fatty acyl chains of lipids, and nucleotides, suggesting that both energy production and anabolic pathways were hindered and blocking the PC pathway was not compensated by GLS activity. In addition, glutathione biosynthesis and homeostasis were perturbed by PC suppression, leading to compromised anti-oxidation capacity. We further found that PC knockdown in A549 cells reduced their growth rate in mouse xenografts, and recapitulate the metabolic perturbations seen both in cell culture and in human patients. Together, these results suggest that PC is indispensible for the growth and anabolism of NSCLC.

This work was funded by 5P20RR018733, 1R01CA118434-01A2, 1P01CA163223-01A1, 1R01ES022191-01, and 3R01CA118434-02S1; and the KLCRP, CTSPGP, and the KY Challenge for Excellence.

Citation Format: Katherine E. Sellers, Matthew P. Fox, Michael Bousamra, Jun Yan, Mariia Yuneva, Richard M. Higashi, Andrew N. Lane, Teresa WM Fan. Enhanced pyruvate carboxylation is crucial to non-small cell lung cancer proliferation and anabolism. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1424. doi:10.1158/1538-7445.AM2014-1424

Sodium arsenite ± hyperthermia sensitizes p53-expressing human ovarian cancer cells to cisplatin by modulating platinum-DNA damage responses

Epithelial ovarian cancer (EOC) is the leading cause of gynecological cancer death in the United States. Cisplatin is a DNA damaging agent initially effective against EOC but limited by resistance. P53 plays a critical role in cellular response to DNA damage and has been implicated in EOC response to platinum chemotherapy. In this study, we examined the role of p53 status in EOC response to a novel combination of cisplatin, sodium arsenite, and hyperthermia. Human EOC cells were treated with cisplatin ± 20μM sodium arsenite at 37°C or 39°C for 1 h. Sodium arsenite ± hyperthermia sensitized wild-type p53-expressing (A2780, A2780/CP70, OVCA 420, OVCA 429, and OVCA 433) EOC cells to cisplatin. Hyperthermia sensitized p53-null SKOV-3 and p53-mutant (OVCA 432 and OVCAR-3) cells to cisplatin. P53 small interfering RNA (siRNA) transfection abrogated sodium arsenite sensitization effect. XPC, a critical DNA damage recognition protein in global genome repair pathway, was induced by cisplatin only in wild-type p53-expressing cells. Cotreatment with sodium arsenite ± hyperthermia attenuated cisplatin-induced XPC in wild-type p53-expressing cells. XPC siRNA transfection sensitized wild-type p53-expressing cells to cisplatin, suggesting that sodium arsenite ± hyperthermia attenuation of XPC is a mechanism by which wild-type p53-expressing cells are sensitized to cisplatin. Hyperthermia ± sodium arsenite enhanced cellular and DNA accumulation of platinum in wild-type p53-expressing cells. Only hyperthermia enhanced platinum accumulation in p53-null cells. In conclusion, sodium arsenite ± hyperthermia sensitizes wild-type p53-expressing EOC cells to cisplatin by suppressing DNA repair protein XPC and increasing cellular and DNA platinum accumulation.

Enzyme replacement therapy for mucopolysaccharidosis VI (Maroteaux-Lamy syndrome): experience in Hong Kong

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) is a very rare inherited lysosomal storage disease. We evaluated the efficacy and safety of weekly infusions of recombinant human arylsulfatase B as enzyme replacement therapy for two patients in whom this condition was advanced. The primary outcome variables were the distance walked in a 6-minute walk test, forced vital capacity, and ejection fraction. The secondary outcome variables were the number of stairs climbed in a 3-minute stair climbing test, joint mobility, urinary glycosaminoglycan excretion, auto-continuous positive airway pressure study and liver size. After 24 weeks of treatment, patient A walked 40 m (36%) and patient B walked 66 m (58%) more in the walk test than at baseline. After 48 weeks, in patient A the corresponding improvements were 142 m (129%) in the walk test and 33 stairs (60%) in the 3-minute stair climbing test, and in patient B the respective improvements were 198 m (174%) and 77 stairs (140%). There was a significant decline in urinary glycosaminoglycan excretion and improvement in range of motion of joints in both patients. The auto-continuous positive airway pressure study revealed improvements in patient A, while other efficacy variables remained static. There were no drug-related adverse events or allergic reactions reported during and after the infusions of recombinant human arylsulfatase B. Recombinant human arylsulfatase B significantly improves endurance and reduces urinary glycosaminoglycan excretion. The drug is generally safe and well tolerated.

Sodium arsenite and hyperthermia modulate cisplatin-DNA damage responses and enhance platinum accumulation in murine metastatic ovarian cancer xenograft after hyperthermic intraperitoneal chemotherapy (HIPEC)

BACKGROUND

Epithelial ovarian cancer (EOC) is the leading cause of gynecologic cancer death in the USA. Recurrence rates are high after front-line therapy and most patients eventually die from platinum (Pt) - resistant disease. Cisplatin resistance is associated with increased nucleotide excision repair (NER), decreased mismatch repair (MMR) and decreased platinum uptake. The objective of this study is to investigate how a novel combination of sodium arsenite (NaAsO2) and hyperthermia (43°C) affect mechanisms of cisplatin resistance in ovarian cancer.

METHODS

We established a murine model of metastatic EOC by intraperitoneal injection of A2780/CP70 human ovarian cancer cells into nude mice. We developed a murine hyperthermic intraperitoneal chemotherapy model to treat the mice. Mice with peritoneal metastasis were perfused for 1 h with 3 mg/kg cisplatin ± 26 mg/kg NaAsO2 at 37 or 43°C. Tumors and tissues were collected at 0 and 24 h after treatment.

RESULTS

Western blot analysis of p53 and key NER proteins (ERCC1, XPC and XPA) and MMR protein (MSH2) suggested that cisplatin induced p53, XPC and XPA and suppressed MSH2 consistent with resistant phenotype. Hyperthermia suppressed cisplatin-induced XPC and prevented the induction of XPA by cisplatin, but it had no effect on Pt uptake or retention in tumors. NaAsO2 prevented XPC induction by cisplatin; it maintained higher levels of MSH2 in tumors and enhanced initial accumulation of Pt in tumors. Combined NaAsO2 and hyperthermia decreased cisplatin-induced XPC 24 h after perfusion, maintained higher levels of MSH2 in tumors and significantly increased initial accumulation of Pt in tumors. ERCC1 levels were generally low except for NaAsO2 co-treatment with cisplatin. Systemic Pt and arsenic accumulation for all treatment conditions were in the order: kidney > liver = spleen > heart > brain and liver > kidney = spleen > heart > brain respectively. Metal levels generally decreased in systemic tissues within 24 h after treatment.

CONCLUSION

NaAsO2 and/or hyperthermia have the potential to sensitize tumors to cisplatin by inhibiting NER, maintaining functional MMR and enhancing tumor platinum uptake.

Ruptured adrenocortical carcinoma as a cause of paediatric acute abdomen

Adrenocortical carcinoma (ACC) is rare in children. Its presentation is usually related to hormonal activity of the tumour. We report a case of childhood ACC that presented as an acute abdomen due to tumour rupture. This is the first reported case of a ruptured ACC as a cause of paediatric acute abdomen.

Phytosiderophores influence on cadmium mobilization and uptake by wheat and barley plants

A constant anthropogenic release of cadmium to the environment has resulted in a continuous buildup of Cd in soils. Uptake and accumulation of Cd in plant tissue and in grains may lead to food chain transfer to humans. Application of synthetic chelates was suggested to increase metal mobilization and facilitate phytoextraction as a means for the remediation of metal-polluted soils. However, most of the chelate-extracted metal may be leached rather than mobilized to plant roots. In contrast to the synthetic chelates added to soils, plant-produced chelators called phytosiderophores (PS) are excreted directly to the rhizosphere. Previous studies have shown that PS facilitate uptake of Zn and Fe by graminaceous plants. In this study, a two-step PS mediation of Cd uptake was hypothesized: (i) extraction and chelation in the soil solution, and (ii) delivery of the chelated Cd to the uptake system of the plant. We examined Cd extraction by PS, the synthetic chelate HEDTA [N-(2-hydroxyethyl)-ethylenediaminetriacetic acid], and a fungal siderophore rhizoferrin from solid-phase Cd phosphate at pH 7.3 with and without Fe competition in the presence of Ca and Mg as additional competing metals. While rhizoferrin did not extract Cd, PS and HEDTA did extract Cd even in the presence of Fe. Yet, uptake of Cd by wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) plants was not significantly influenced by Fe stress, but instead was controlled primarily by Cd2+ activity in solution. These results suggest that even though Cd may be mobilized by PS, there is no significant uptake of the Cd-PS complex by the plant roots.

Comprehensive chemical profiling of gramineous plant root exudates using high-resolution NMR and MS

Root exudates released into soil have important functions in mobilizing metal micronutrients and for causing selective enrichment of plant beneficial soil micro-organisms that colonize the rhizosphere. Analysis of plant root exudates typically has involved chromatographic methods that rely on a priori knowledge of which compounds might be present. In the research reported here, the combination of multinuclear and 2-D NMR with GC-MS and high-resolution MS provided de novo identification of a number of components directly in crude root exudates of different plant types. This approach was applied to examine the role of exudate metal ion ligands (MIL) in the acquisition of Cd and transition metals by barley and wheat. The exudation of mugineic acids and malate was enhanced by Fe deficiency. which in turn led to an increase in the tissue content of Cu, Mn, and Zn. The presence of elevated Cd maintained at a free activity pCd of 8.8 (10(-8.8) M), resulted in reduced phytosiderophore production by Fe deficient plants. The buffer morpholinoethane sulfonate (MES), which is commonly used in chelator-buffering nutrient solutions, was detected in the root exudate mixture, suggesting uptake and re-secretion of this compound by the roots. The ability to detect this compound in complex mixtures containing organic acids, amino acids, and other substances suggests that the analytical methods used here provide an unbiased method for simultaneous detection of all major components contained in root exudates.

Testicular volume of boys after inguinal herniotomy: combined clinical and radiological follow-up

A total of 173 boys aged 10 to 179 months with previous unilateral inguinal herniotomy were called back for follow-up. Clinical and ultrasound examinations of the scrotum were performed. The interval between operation and follow-up was 6 to 123 months (mean 31.68 months). One boy (0.58%) had a more than 50% and 10 (5.8%) had a more than 25% decrease in testicular volume on the operated side when compared with the non-operated side.

Analysis of phosphorylated metabolites in crayfish extracts by two-dimensional 1H-31P NMR heteronuclear total correlation spectroscopy (heteroTOCSY)

In vivo and extract analyses by one-dimensional 31P NMR have been a key tool in investigating energy-related metabolism. Although many phosphorylated metabolites have been observed, many of them have yet to be identified. This reflects the difficulty in identifying them using 31P NMR alone. Two-dimensional 1H-31P correlation experiments have been shown to be useful for assigning phosphorylated metabolites. To obtain better sensitivity and structure information, 1H-detected 31P-1H heteronuclear total correlation spectroscopy (heteroTOCSY) was implemented and a complete chemical shift assignment for a number of phosphorylated standards was made. The time courses of 1D heteroTOCSY signal intensity versus spin-locking time were established for these standards to aid the optimization of the 2D experiment. This method was applied to crayfish extracts for the assignment of glucose 6-phosphate, alpha-glycerophosphate, ribose 5-phosphate, fructose 1,6-bisphosphate, phosphocholine, phosphoethanolamine, glucose 1-phosphate, glycerophosphoethanolamine, glycerophosphocholine, ATP, ADP, and AMP. An alkyl phosphate, a hexose 1-phosphate, and a UDP-hexose were also observed. These assignments allowed the identification of many changes in the 31P NMR spectra of crayfish extracts elicited by treatment with the organophosphate pesticide chlorpyrifos. The assignment of an in vivo 31P spectrum of a live crayfish was also made based on the extract assignment. This approach should be a powerful tool for examining stress-associated changes in the metabolism of phosphorylated compounds.

Comprehensive analysis of organic ligands in whole root exudates using nuclear magnetic resonance and gas chromatography-mass spectrometry

Root exudates in the rhizosphere are vital to the normal life cycle of plants. A key factor is phytometallophores, which function in the nutritional acquisition of iron and zinc and are likely to be important in the uptake of pollutant metals by plants. Unraveling the biochemistry of these compounds is tedious using traditional analyses, which also fall short in providing the overall chemical composition or in detecting unknown or unexpected organic ligands in the exudates. Here, we demonstrate a comprehensive analysis of the exudate composition directly by 1H and 13C multidimensional NMR and silylation GC-MS. The advantages are (a) minimal sample preparation, with no loss of unknown compounds, and reduced net analysis time; (b) structure-based analysis for universal detection and identification; and (c) simultaneous analysis of a large number of constituents in a complex mixture. Using barley root exudates, a large number of common organic and amino acids were identified. Three derivatives of mugineic acid phytosiderophores were also determined, the major one being 3-epihydroxymugineic acid, for which complete 1H and 13C NMR assignments were obtained. Quantification of all major components using these methods revealed a sevenfold increase in total exudation under moderate iron deficiency, with 3-epihydroxymugineic acid comprising approximately 22% of the exudate mixture. As iron deficiency increased, total quantities of exudate per gram of root remained unchanged, but the relative quantity of carbon allocated to phytosiderophore increased to approximately 50% of the total exudate in response to severe iron deficiency.

In vivo 13C NMR analysis of acyl chain composition and organization of perirenal triacylglycerides in rats fed vegetable and fish oils

Lipid composition of body fat can be a key indicator of nutritional status and a number of human disorders. In vivo 13C NMR provides for repeated, noninvasive analysis of fatty acyl chain composition on individuals, which circumvents classical problems of individual variation and repetitive invasive sampling. It also offers a unique opportunity to examine acyl chain organization in situ. This approach was used to examine the fatty acyl chain composition in the perirenal fat pads of rats fed olive, safflower, and menhaden oil-containing diets. These changes were then monitored during a diet switch between olive and menhaden oil-fed rats. The fatty acid composition of perirenal fat pads and livers was also analyzed using gas chromatography for comparison with the in vivo NMR analysis. Both tissues assumed the general characteristics of diet fatty acyl chain and fatty acid composition and the diet switch induced a switchover of the perirenal composition in 30-45 days. These results indicate that a large portion of the diet fatty acyl chains were incorporated directly into adipose and liver tissues although some were also metabolized, particularly in menhaden oil-fed rats. Furthermore, changes in the in vivo spin-lattice relaxation times (T1) of fatty acyl carbons in the perirenal fat pads and their lipid extracts were followed and effective correlation times (tau eff) were calculated from the T1 data. The result indicated that the in vivo segmental mobility of acyl carbons was sensitive to changes in diet-derived fatty acyl chain composition and that the central region of the acyl chain was more sensitive to these changes. There was a qualitative similarity but quantitative differences in the tau eff of acyl carbons acquired in vivo and from extracts. These results suggest that adipose triacylglycerides experience an overall liquid-like microenvironment in vivo but with more restriction in their mobility, and that different factors may exist in governing their organization in situ versus in extracts.

Electrophoretic separation, characterization, and quantification of biologically active lignin-derived macromolecules

Degraded macromolecular lignin, which was isolated from the effluents of commercial pulp processing and known to inhibit early development in marine organisms, was separated and characterized using several polyacrylamide gel electrophoresis (PAGE) techniques. This lignin-derived macromolecule (LDM), when subjected to native PAGE and stained with alcian blue, appeared as a single band. On sodium dodecyl sulfate (SDS)-PAGE, LDM appeared to consist of two subcomponents with apparent molecular weights of 11 and < 1 kDa. When subjected to isoelectrofocusing--PAGE of pH 3-9, LDM consisted of two major bands in the basic region of the gel, with less distinct banding in the more acidic region. Two-dimensional PAGE of LDM indicated that the higher molecular weight subcomponent corresponded to the more basic constituents, while the lower molecular weight subcomponent corresponded to acidic constituents. When the two subcomponents of LDM were isolated from SDS gels by electroelution and assessed for their effects on successful fertilization and early development, the higher molecular weight subcomponent possessed most of the inhibitory activity. This is the first report of the application of a variety of electrophoretic techniques to both structurally and biologically characterize lignin-derived macromolecules.

Determination of metabolites by 1H NMR and GC: analysis for organic osmolytes in crude tissue extracts

World-wide salinity and drought problems necessitate the understanding of biological adaptation to water deficit. Osmotic adjustment via organic solutes is a common strategy for organisms to deal with water deficit problems. Numerous water-soluble organic metabolites across several chemical classes are commonly utilized as osmolytes, including betaines, sulfonium and sulfonate compounds, amino acids, carbohydrates, and polyols. To deal with the complexity and variability in osmolyte composition, we have devised an analytical approach that combines high-resolution 1H NMR and GLC to provide both structure identification and quantification of a broad spectrum of compounds. This combined approach also facilitated direct analyses of crude tissue extracts without extensive sample preparation, making it well-suited for a convenient screening of potential osmolytes. The structures of known osmolytes were confirmed from two-dimensional total correlation 1H NMR spectra, which also yielded structural information about unknown compounds. Five each terrestrial plant and marine animal species were examined for 41 metabolites, including osmolyte candidates glycinebetaine, dimethylsulfoniopropionate, taurine, proline, glycine, asparagine, alanine, glutamine, glucose, and sucrose. The osmotic function of glycinebetaine, proline, asparagine, glutamine, glucose, and sucrose was also demonstrated in leaves of Distichlis spicata under different salinity treatments.

Identification of glycerophosphorylcholine in mussel ovarian extracts by two-dimensional nuclear magnetic resonance

The abundance of the "phosphodiester" peak in differentiating or proliferating tissues, including reproductive organs and tumors, warrants further investigations of its metabolic role(s), which would require a rigorous confirmation of its identity. The assignment of this peak to glycerophosphorylcholine in 31P NMR spectra of biological samples has been largely based on chemical shift, which can result in ambiguities. We employed a combination of two-dimensional 31P-1H heteronuclear shift correlation and 1H total correlation spectroscopies to trace the spin connectivities of glycerophosphorylcholine and thus to identify its structure directly from crude ovarian extracts of mussels without ambiguities and the need for extensive purification. This approach can be applied generally to the identification of molecules containing heteroatoms in crude tissue extracts.

Temperature dependence of arginine kinase reaction in the tail muscle of live Sycionia ingentis as measured in vivo by 31P-NMR driven saturation transfer

We have employed the driven 31P-NMR saturation transfer method to measure in vivo the temperature dependence of the forward and reverse unidirectional fluxes of the arginine kinase reaction in the tail muscle of a live shrimp, Sycionia ingentis. Our results indicated that neither the forward nor the reverse rate constants of this reaction were significantly temperature-dependent between 8 and 16 degrees C, in contrast to the kinetic characteristics of isolated arginine kinases.

Hypoxia does not affect rate of ATP synthesis and energy metabolism in rice shoot tips as measured by 31P NMR in vivo

The cytoplasmic pH, concentrations of phosphate metabolites, and rate of ATP synthesis were measured in vivo in excised rice shoot tips under normoxic and hypoxic conditions using 31P NMR. When supplied with glucose, the shoot tips grew rapidly and were relatively unaffected by hypoxia. The cytoplasmic pH decreased transiently by only 0.2 units during hypoxia, and the concentration of ATP was maintained to at least 90% of the normoxic level. Most importantly, the unidirectional rate constant of ATP synthesis from free phosphate decreased less than 25% during hypoxia. This is in contrast to other actively growing tissues such as the maize root tip. gamma-Aminobutyrate was the major nonvolatile fermentation end product after 22 h of hypoxia. Other hypoxia-induced changes included a modest increase in [Ala] and [succinate] as well as a substantial decrease in [malate].

Emergence and recovery response of phosphate metabolites and intracellular pH in intact Mytilus edulis as examined in situ by in vivo 31P-NMR

We employed surface probe-localized 31P-NMR spectroscopy to examine in situ the impact of short-term emergence (hypoxia) and resubmergence on phosphate metabolites and intracellular pH (pHi) in intact mussels. The use of intact organisms ensured that all intrinsic responses remained active while monitoring of individuals minimized uncertainties resulting from stochastic behavior and other individual differences. The use of a photoetched, balanced-match foil probe combined with 1H-NMR images allowed 31P-NMR spectra to be acquired from the posterior adductor muscle with good signal-to-noise. Upon emergence, all mussels exhibited an increase in [Pi], a decline in [phosphoarginine] and pHi, and very little changes in [ATP] with time. The complementary behavior of [phosphoarginine] and [Pi] indicated a precursor-product relationship involved in the maintenance of [ATP] but the similarity between [phosphoarginine] and pHi time-courses cannot be so readily explained. Irregularity in the time-courses of some parameters could have reflected stochastic gaping activity. Resubmergence responses exhibited a reversal of the emergence responses, except that the pHi eventually became supraalkaline with irregular fluctuations. This might be related to the 'oxygen debt' phenomenon and increased oxidative phosphorylation.

Sublethal effects of pentachlorophenol in the abalone (Haliotis rufescens) as measured by in vivo 31P NMR spectroscopy

The sublethal biochemical effects of pentachlorophenol (PCP) were investigated in live, intact red abalones (Haliotis rufescens), using a flow-through exposure system, by in vivo 31P NMR spectroscopy. Based on rangefinding tests (6-hr LC50 = 1.6 mg/L; 6-hr no-observable-effect-level (NOEL) = 0.8 mg/L), three abalones were separately exposed to a sublethal concentration (1.2 mg/L) for 5 hr, followed by a 13 hr recovery period. Effects in foot muscle included both a decrease in phosphoarginine and an increase in inorganic monophosphate concentrations ([PA] and [Pi], respectively); both foot muscle concentrations of adenosine triphosphate [ATP] and intracellular pH (pHi) also declined. Parallel in vitro experiments revealed that concentrations of glycerol 3-phosphate, lactate, citrate, succinate, malate, and alanine (Ala) all increased, while those of glyceraldehyde 3-phosphate and glutamine (Gln) remained stable. Also, these effects were not evident until 2 hr into exposure, possibly the time required for PCP to attain an effective concentration in foot muscle. During recovery, while Pi declined to pre-exposure levels, [PA] completely recovered in only one individual. Also, realkalinization of pHi was similar to recovery of [Pi], and ATP returned to near-initial levels, as did glycerol 3-phosphate, lactate, succinate, malate, and Ala; glyceraldehyde 3-phosphate, citrate, and Gln levels declined. Recovery responses corresponded to the time for PCP clearance from foot muscle. The effects of PCP were similar to those of hypoxia, fatigue, hypersalinity, and arginine kinase inhibitors, and so sublethal PCP concentrations may also inhibit electron transport and arginine kinase as well as uncouple mitochondrial oxidative phosphorylation in intact molluscs. Thus, the effects of pollutants on key biochemical processes may now be measured in intact aquatic organisms as they occur, improving our ability to accurately assess the environmental effects of pollutants in the laboratory.

In vivo 23Na and 31P NMR measurement of a tonoplast Na+/H+ exchange process and its characteristics in two barley cultivars

A Na+ uptake-associated vacuolar alkalinization was observed in roots of two barley cultivars (Arivat and the more salt-tolerant California Mariout) by using 23Na and 31P in vivo NMR spectroscopy. A NaCl uptake-associated broadening was also noted for both vacuolar Pi and intracellular Na NMR peaks, consistent with Na+ uptake into the same compartment as the vacuolar Pi. A close coupling of Na+ with H+ transport (presumably the Na+/H+ antiport) in vivo was evidenced by qualitative and quantitative correlations between Na+ accumulation and vacuolar alkalinization for both cultivars. Prolongation of the low NaCl pretreatment (30 mM) increased the activity of the putative antiport in Arivat but reduced it in California Mariout. This putative antiport also showed a dependence on NaCl concentration for California Mariout but not for Arivat. No cytoplasmic acidification accompanied the antiporter activity for either cultivar. The response of adenosine phosphates indicated that ATP utilization exceeded the capacity for ATP synthesis in Arivat, but the two processes seemed balanced in California Mariout. These comparisons provide clues to the role of the tonoplast Na+/H+ antiport and compensatory cytoplasmic adjustments including pH, osmolytes, and energy phosphates in governing the different salt tolerance of the two cultivars.

Monitoring of metabolic responses of intact Haliotis (abalones) under salinity stress by 31P surface probe localized NMR

Surface probe localized 31P NMR spectroscopy was employed to record the metabolic responses of the foot of intact Haliotis cracherodii and H. rufescens (black and red abalones) under hyper- and hypoosmotic stresses. Use of the surface probe allowed spectral localization on the foot of intact abalones, facilitated monitoring of different sizes of animals, and minimized constraints on aquatic chamber design normally imposed by homogeneous-field probes. Generally, hyperosmotic stress (51%) elicited more rapid changes of phosphate metabolites than hypoosmotic stress (17%). As with the well-studied hypoxic stress in intact mammalian and excised molluscan tissue, both salinity treatments caused drops in the phosphagen and increases in inorganic phosphate levels. However, osmotic stress was distinct from hypoxic stress in that intracellular pH did not change and nucleotide triphosphate (NTP) concentrations dropped immediately. Although these findings are preliminary, they demonstrate the utility of the surface probe approach for studies of environmental stress in intact marine invertebrates.

An in vivo 1H and 31P NMR investigation of the effect of nitrate on hypoxic metabolism in maize roots

The effect of nitrate on the short-term hypoxic response and recovery of flooded mature maize roots has been investigated in vivo by 1H and 31P NMR and in vitro by 1H NMR and gas chromatography-mass spectrometry. Employing 1H NMR in addition to 31P NMR extended the number of identifiable compounds in vivo from 4 to 15, while in vitro two-dimensional NMR and gas chromatography-mass spectrometry aided rigorous in vivo 1H NMR resonance assignments and quantitation of 24 compounds. In the absence of nitrate, the concentrations of key metabolites including alanine, ethanol, gamma-aminobutyrate, lactate, succinate, and sucrose changed during 8 h of hypoxia in a manner consistent with reduced tricarboxylic acid cycle activity and diversion to glycolytic fermentation. The pH drop in the cytoplasm during hypoxia was rapid, about 0.2 unit, and diminished quickly upon recovery. Rapid recovery of ethanol, succinate, and sucrose levels was also observed, which indicates a return to normal aerobic metabolism. Although the hypoxic response itself, including pH, was not greatly affected by the presence of nitrate, nitrate reduced the amount of fermentation end products produced, helped maintain a higher free NTP concentration during hypoxia, and increased the rate of overall recovery from hypoxia. These findings suggest the presence of a nitrate-induced maintenance-level respiration in hypoxic maize roots, which helps explain the protection imparted by nitrate to flooded hypoxic maize plants.

Monitoring of hypoxic metabolism in superfused plant tissues by in vivo 1H NMR

We have used a coaxial superfusion system to obtain physiologically interpretable in vivo 1H NMR spectra at 500 MHz of carrot roots, maize roots, and rice shoots in water (no 2H2O). The superfusion system was constructed from common laboratory parts, required no modification of the probe and sample loading procedure, and was inherently leak resistant. The assignment and quantitation of the in vivo 1H NMR resonances were achieved by performing two-dimensional NMR experiments in vivo, and by in vitro analysis including NMR and gas chromatography-mass spectrometry. The in vivo spectra were dominated by resonances arising from sugars, organic acids, amino acids, and ethanol. In vivo measurements of spin-lattice relaxation times and chemical shifts of beta protons of malate in carrot roots suggested that malate was located in a relatively viscous and acidic compartment. In rice shoots, the hypoxic time courses of 9 metabolites were established in vivo, and 23 in vitro. In both cases, accumulation of lactate, ethanol, Ala, and gamma-aminobutyrate as well as a decrease in Gln and Asn concentrations were observed. These findings are consistent with accelerated glycolysis and decreased tricarboxylic acid cycle activity.

Combined use of 1H-NMR and GC-MS for metabolite monitoring and in vivo 1H-NMR assignments

Thirty-three metabolites were observed in perchloric acid extracts of four different tissues by in vitro 1H-NMR, GC-MS and alcohol dehydrogenase assay, and the information was used to interpret an in vivo two-dimensional nuclear Overhauser effect 1H-NMR spectrum. The metabolite profiles of the different tissues indicate a number of potential tissue-specific markers: N-acetylaspartate and gamma-aminobutyric acid for rat brain, glutamine/glutamic acid ratio for dog heart, arginine and sucrose for carrot, and t-aconitate, sucrose, asparagine/aspartic acid concentration ratios for corn roots. gamma-Aminobutyric acid and malate can be regarded as metabolic indicators for stressed corn roots. Concentrations of threonine and valine in corn roots were constant under hypoxic and salt stress, and can serve as internal standards for both in vivo and in vitro NMR studies. The in vitro information was further used to identify 12 compounds from the in vivo 1H-NMR spectra (including the two-dimensional nuclear Overhauser effect spectrum) of a carrot cylinder by correlating the chemical shift and nuclear Overhauser effect information. Thus, our choice of methods with a capability for structural determination allows the characterization of complex tissue extracts with minimum sample preparation, and supports, as well as complements, in vivo 1H-NMR investigations of metabolism.

Isolation and characterization of two cyanogenic beta-glucosidases from flax seeds

Two cyanogenic beta-glucosidases, linustatinase and linamarase, were isolated and purified from flax seeds (Linum ussitatissimum). They catalyze the sequential hydrolysis of linustatin and neolinustatin to yield acetone and methylethyl ketone cyanohydrins, respectively. The purification procedure for linustatinase involved acetone extraction, precipitation by polyethyleneimine and ammonium sulfate (40-80% saturation), and Red A gel, concanavalin A-Sepharose, and PBE 94 column chromatography; that for linamarase was similar except that polyethyleneimine precipitation was eliminated and DE-52 and Sepharose CL-6B replaced Red A gel column chromatography. The native substrates neolinustatin and linamarin were used for the assay during purification. Both proteins were purified to electrophoretic homogeneity. Linustatinase is an alpha beta dimer (molecular weights of alpha and beta = 39,000 and 19,000, respectively) while linamarase appears to be an alpha 5 beta 5 decamer (molecular weights of alpha and beta = 62,500 and 65,000, respectively). Both enzymes contain mannose or glucose. Linustatinase exists in five different isozymic forms (isoelectric points between 7 and 8) whereas linamarase occurs in one major form (isoelectric point 4 to 5). The kinetic parameters of the two enzymes are similar: acidic pH optima, Km's in the millimolar range, and competitive inhibition by delta-gluconolactone, a transition state analog. The presence of an aglycone structure in the substrates is important for both enzyme activities. In addition, both enzymes are specific towards the beta-glycosidic linkage; linustatinase (a beta-bis-glucosidase) readily hydrolyzes beta-bis-glucosides with 1,6 and 1,3 linkages whereas linamarase (a beta-monoglucosidase) exhibits little activity towards these substrates.