Molecular Basis of Hyperammonemic Encephalopathy in Fibrolamellar Hepatocellular Carcinoma




hyperammonemic encephalopathy is a potentially fatal condition associated with fibrolamellar hepatocellular carcinoma. The mechanism involved in hyperammonemia in patients with fibrolamellar carcinoma was unclear until a possible physiopathological pathway was recently proposed. An ornithine transcarboxylase dysfunction was suggested as a result of increased ornithine decarboxylase activity induced by c-Myc overexpression. This c-Myc overexpression resulted from Aurora Kinase A overexpression derived from the activity of a chimeric kinase that is the final transcript of a deletion in chromosome 19, common to all fibrolamellar carcinomas.


we performed the analysis of the expression of all enzymes involved and tested for the mutation in chromosome 19 in fresh frozen samples of fibrolamellar hepatocellular carcinoma, non-tumor liver and hepatic adenomatosis.


specific DNAJB-PRKACA fusion protein that results from the recurrent mutation on chromosome 19 common to all fibrolamellar carcinoma was detected only in the fibrolamellar carcinoma sample. Fibrolamellar carcinoma and adenomiomatosis samples presented increased expression of Aurora Kinase A, c-MYC and ornithine decarboxylase when compared to normal liver, while ornithine transcarbamylase was decreased.


The proposed physiopathological pathway is correct and that overexpression of c-Myc may also be responsible of hyperammonemia in patients with other types of rapidly growing hepatomas. This gives further evidence to apply new and adequate treatment to this severe complication.


Ammonia is a constituent of body fluids generated in the intestine by bacterial hydrolysis of nitrogen compounds, muscular amino acid transamination, purine nucleotide cycle and metabolic processes mainly in the kidneys and liver [1]. Ammonia and bicarbonate are condensed in the hepatic mitochondria to produce carbamoyl phosphate to initiate urea cycle, the most important mechanism of blood ammonium removal [2]. When the blood level of ammonia increases, it enters the central nervous system (CNS) in excessively and becomes toxic to the brain [3].

Astroglial cells are the only CNS cells that metabolize ammonia [4]. Ammonia is condensed with glutamate to form glutamine. As the level of glutamine increases, it results in astrocyte swelling, cerebral edema and intracranial hypertension [5]. When astrocytes are continuously exposed to ammonia, they may undergo phenotypic transformation into Alzheimer´s type II astrocytes with reduced proliferative activity [6, 7]. Moreover, elevated concentrations of ammonia in CNS promote oxidative stress [89]. Glutamine and ammonia exposure to astrocytes increases reactive oxygen species production [10], another possible cause of astrocyte swelling responsible for neurotoxicity [11].

Liver failure is the cause of 90% of hyperammonemia cases in adults. Those not related to liver failure may be divided in two groups: cases with increased ammonia production and cases with decreased elimination [12].

Increased ammonia production may occur in progressive multiple myeloma [13] and infections by urea-producing bacteria [14]. Rare causes include starvation, total parenteral nutrition, gastrointestinal bleeding and seizures [15]. Reduced elimination occurs mainly in metabolic disorders like urea-cycle disorders, pyruvate metabolism errors, organic acidurias, impaired fatty acid oxidation, dibasic aminoaciduria and congenital portosystemic shunt [1518].

Since 2009, reports have demonstrated the association of fibrolamellar hepatocellular carcinoma (FLHCC) with hyperammonemia [1925]. Nevertheless, none of those articles reached a definite explanation to hyperammonemia in FLHCC patients. Berger et al. theorized that portosystemic shunts were accountable [19]. Alsina et al. suggested that intrahepatic shunting and lack of clearance of nitrogenous compounds by tumor cells were responsible [21].

In 2017, Surjan et al. proposed a new physiopathological pathway to hyperammonemia in patients with FLHCC [26]. According to the theory, all FLHCC present a single and recurrent heterozygous deletion in chromosome 19 that results in a chimeric protein DNAJB1-PRKACA (a catalytic subunit of protein kinase A) [2728]. The DNAJB1-PRKACA kinase is probably both necessary and sufficient to the carcinogenesis of FLHCC [2930], and results in Aurora kinase A (AURKA) overexpression within the tumor, as previously demonstrated [31].

Elevated levels of AURKA upregulates c-Myc transcription affecting cellular proliferation and ATP production, important factors on FLHCC tumorigenesis [32, 33]. c-Myc overexpression leads to increased ornithine decarboxylase (ODC) activity [34]. This results in increased ornithine consumption to polyamines synthesis [35], reducing ornithine bioavailability that results in urea cycle disorder due to ornithine transcarboxylase (OTC) dysfunction and consequent hyperammonemia [26].

The proposal of this physiopathological pathway to HE in a FLHCC patient allowed an innovative treatment with complete neurocognitive recovery. However, the described process was not proved by analysis of involved enzymes activities and RNA expression.

In this study, fresh frozen tissue samples of non-tumor liver parenchyma, FLHCC and one hepatic adenomatosis in a patient that developed HE without liver dysfunction were submitted to analysis of expression of ODC, c-Myc, OTC and AURKA and tested for the chromosome 19 deletion.

Materials And Methods

Three fresh frozen tissue samples were used: a FLHCC in a 33-year-old male patient with multiple hepatic tumors and diffuse peritoneal carcinomatosis that developed severe and refractory hyperammonemic encephlopathy, a non-tumor non-cirrhotic liver and a rapid growing hepatic adenomiomatosis in a 44-year-old female patient that developed hyperammonemia submitted to percutaneous ultrasonography guided diagnostic hepatic lesion bopsy. All tissue samples were obtained by Quick-Core needle biopsies (Cook Group Inc. Bloomington, Indiana. USA). Samples were immediately submitted to cryopreservation with liquid nitrogen.


TRizol (Invitrogen. Carlsbad, California. USA), diethyl pyrocarbonate (DEPC), 2x SYBR Green Reaction Mix (Invitrogen. Carlsbad, California. USA), Super Script III RT/Platinum Taq Mix (Invitrogen. Carlsbad, California. USA), ROX Reference Dye (Invitrogen. Carlsbad, California. USA), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), β-2 microglobulin (B2M), Ethylenediaminetetraacetic acid (EDTA), ethidium bromide solution (EtBr).

Real time PCR

RT-PCR was used to determine messenger RNA (mRNA) levels of proteins of interest. Total RNA was extracted from 100mg of frozen liver with TRIzol reagent following the manufacturer’s instruction. RNA was dissolved in DEPC treated water and quantified spectrophotometrically at 260 nm. One hundred nanograms total RNA were used for each real-time PCR reaction, which were performed in a StepOne equipment (Applied Biosystems Inc. Foster City, CA. USA). RT-PCR was performed in a 15µl reaction mixture containing 7.5µl 2x SYBR Green Reaction Mix, 0.3µl each primer, 0.3µl Super Script III RT/Platinum Taq Mix (10pmol/µl), 0.15µl ROX Reference Dye, and 5µl sample in water. cDNA synthesis was performed at 50ºC for 15 minutes followed by 35 cycles at 95ºC for 15 seconds, annealing temperature for 30 seconds, and 72ºC for 30 seconds. Quantification was performed by 2-DDCT method, using GAPDH and B2M as housekeeping genes[36, 37]. The primers sequences and annealing temperature are listed in Table 1. Primers were designed using GeneRunner Software (Hastings Software Inc. Hastings, NY. USA). The DNAJB1-PRKACA fusion transcript primer sequence was obtained in Graham et al[28]. (Table 1)

Table 1

Sequences and annealing temperature of primers used for real time PCR. (PCR: polymerase chain reaction; AURKA: Aurora Kinase A; ODC ornithine decarboxylase; OTC: ornithine transcarboxylase)


Sense primer (5’ – 3’)

Reverse primer (5’ – 3’)

Annealing temperature

Fragment size (bp)




































Agarose Gel Electrophoresis

PCR amplicons fragments were separated via (1%) agarose gel electrophoresis. The gels were prepared by dissolving the agarose in the TBE buffer (100 mM Tris, 100 mM Boric acid, 2 mM EDTA). To visualize the DNA, 1.5 µl of (10 mg/ml) EtBr was added to the 100 ml (1%) agarose solution. To load the samples, the DNA was mixed in equal volume ratios with the agarose gel loading buffer. Electrophoresis was performed at 100 V. The DNA was detected using UV light and the size of the DNA was determined using standard 100bp DNA ladder.

Compliance with ethical standards

Tissue samples used in this research were obtained from already available biological material and patients signed an informed consent form before the use of the samples. Ethics clearance was obtained from the Ethics Research Committee from the University of São Paulo Medical Faculty and all experiments were performed in accordance with relevant guidelines and regulations.


The DNAJB1-PRKACA fusion protein and mutation on chromosome 19 were detected only in the FLHCC sample (Figure 1). The relative expression versus Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH) of AURKA in FLHCC and adenomiomatosis samples presented increased expression of AURKA, c-Myc and ornithine decarboxylase (Figure 2) when compared to normal liver. On the other hand, ornithine transcarbamylase was decreased in FLHCC and adenomiomatosis when compared to non-tumor liver (Figure 3). There was no difference between FLHCC and adenomiomatosis in the expression of AURKA and c-Myc (Figures 4, and 5). Samples analyses were performed by real time RT-PCR in triplicates. The results are expressed as relative expression compared to GAPDH using the 2-DDCT method. (AURKA: Aurora Kinase A; ODC ornithine decarboxylase; OTC: ornithine transcarboxylase; Fibro: fibrolamellar hepatocellular carincoma; Adeno: adenomiomatosis; GAPDH: Glyceraldehyde-3-Phosphate Dehydrogenase; RT-PCR: real-time polymerase chain reaction, 2-DDCT: 2(-Delta Delta C(T)).


HE is a severe condition that must be suspected in patients that present progressive neurocognitive disorders, seizures and coma even in the absence of liver failure [38]. Rapid onset non-cirrhotic HE in adults can lead to significant brain injury, sequelae and in most of the cases proves to be fatal [39,40].

There are many different etiologies for non-hepatic HE, ranging from infection with urea-producing bacteria to late onset urea cycle disorders or chemotherapy-induction [4,42]. The association between HE and hepatic tumors dates to 1972, when Weber described a urea cycle disorder mimicking an ornithine carbamoyltransferase deficiency [43]. Different types of liver malignancies in non-cirrhotic patients (usually large and rapid growing tumors) have also been accompanied with hyperammonemia [44,45]. However, FLHCC, despite being a rare liver malignancy, is often associated with hyperammonemia and encephalopathy [19-26].

The precise mechanism involved in HE in patients with FLHCC and other hepatic tumors have not been clearly identified in the literature until 2017, when Surjan et al. proposed a new physiopathological pathway to HE theorized when treating a FLHCC patient that developed severe hyperammonemia and coma that showed no signs of liver failure or porto-systemic shunting and that did not present any inborn metabolism error detected in multi-gene panel genetic testing [26,46].

According to the theory, the hyperammonemia would be the result of a urea cycle disorder due to a reduction of the activity of OTC because of ornithine consumption by polyamine synthesis, specially putrescine, spermine and spermidine, caused by an overexpression of ODC [26]. The reduction on the activity of OTC results in lower consumption of aspartate and carbamoyl phosphate that could be spared for biosynthesis of nucleic acids [47]. Moreover, polyamines are ubiquitous small basic molecules that exert important gene regulation functions, being important substrates for DNA stabilization and repair, essential to cellular growth [48]. Those are paramount to carcinogenic steps and represent crucial biological advantages in a malignant microenvironment [35,49].

A proportional overexpression of ODC parallel to OTC activity reduction had been previously described in hepatomas in rats [43]. Nevertheless, the reason to this ODC increased expression had not been understood before.

The proposed explanation would be that, as all FLHCC present a single and recurrent deletion on chromosome 19 that results in a chimeric DNAJB1-PRKACA kinase that augments AURKA expression and, as previously demonstrated AURKA overexpression upregulates c-MYC (oncogene on chromosome 8q24 of cellular origin), the result would be and increased ODC expression secondary to c-Myc signaling [28,33].

This proposed physio pathological pathway would explain why FLHCC patients often develop hyperammonemia and severe encephalopathy. To prove this theory, we performed RT-PCR to determine messenger RNA (mRNA) levels of proteins of AURKA, c-Myc, ODC and OTC in non-tumor non-cirrhotic liver sample and FHLCC sample. Both samples were submitted to DNAJB1-PRKACA fusion protein detection, which was only present in FLHCC. The results corroborated to what the theory suggested.

Moreover, as previous reports demonstrated that non-FLHCC rapidly growing liver tumors could also result in HE due to ODC overexpression for polyamine synthesis and consequent OTC expression reduction, we performed the same analysis to a sample of rapidly growing adenomiomatosis in a patient that developed hyperammonemia and neurocognitive abnormalities. We found a similar gene expression of all proteins.


In conclusion, these findings are paramount to better understand the development of hyperammonemia and its potentially fatal complication HE in patients not only with FLHCC but probably other types of hepatic tumors. Recognizing a different physiopathological pathway than the more common hepatic encephalopathy to this subset of patients allows distinct and probably life-saving treatment options.


Funding: there was no funding for this study.

Conflicts of interest/Competing interests: Rodrigo C. T. Surjan, Thais M. Lima, Elizabeth S. Santos, Sergio P. Silveira, Marcel C. C. Machado, Heraldo P. Souza, Jose C. Ardengh have nothing to disclose.

Availability of data and material: All data from this study can be requested at any time by the reviewers.

Code availability: not applicable.

Authors' contributions: Surjan RCT designed the study. Surjan RCT, and Lima TM wrote the manuscript. Lima TM performed the experiments. Santos ES, Silveira SP, Machado MCC, Souza HP, and Ardengh JC provided critical advice. All authors discussed the results and commented on the manuscript.

Ethics approval: This study obtained ethical approval by the research ethics committee of the 9 de Julho hospital.

Consent for publication not applicable.


  1. Odigwe CC, Khatiwada B, Holbrook C, Ekeh IS, Uzoka C, Ikwu I, Upadhyay B. Noncirrhotic hyperammonemia causing relapsing altered mental status. Proc. (Bayl Univ Med Cent) 2015; 28: 472-474 [PMID: 26424945 DOI: 10.1080/08998280.2015.11929312]
  2. Adeva MM, Souto G, Blanco N, Donapetry C. Ammonium metabolism in humans. Metabolism 2012; 61: 1495-1511 [PMID: 22921946 DOI: 10.1016/j.metabol.2012.07.007]
  3. Lockwood AH, Finn RD, Campbell JA, Richman TB. Factors that affect the uptake of ammonia by the brain: the blood-brain pH gradient. Brain Res 1980; 181:259-266 [PMID: 7350966 DOI: 10.1016/0006-8993(80)90611-3]
  4. Norenberg MD, Rama Rao KV, Jayakumar AR. Signaling factors in the mechanism of ammonia neurotoxicity. Metab. Brain Dis 2009; 24: 103-117 [PMID: 19104923 DOI: 10.1007/s11011-008-9113-6]
  5. Cichoz-Lach H, Michalak A. Current pathogenetic aspects of hepatic encephalopathy and noncirrhotic hyperammonemic encephalopathy. World J Gastroenterol 2013; 19: 26–34 [PMID: 23326159 DOI: 10.3748/wjg.v19.i1.26]
  6. Butterworth RF. Hepatic encephalopathy. Alcohol Res Health 2003: 27: 240-246 [PMID: 15535452]
  7. Bodega G, Segura B, Ciordia S, Mena MDC, López-Fernández LA, García MI, Trabado I, Suárez I. Ammonia Affects Astroglial Proliferation in Culture. PLoS One 2015; 10: e0139619 [PMID: 26421615 DOI: 10.1371/journal.pone.0139619]
  8. Seyan AS, Hughes RD, Shawcross DL. Changing face of hepatic encephalopathy: Role of inflammation and oxidative stress. World J. Gastroenterol 2010; 16: 3347-3357 [PMID: 20632436 DOI: 10.3748/wjg.v16.i27.3347]
  9. Kosenko E, Venediktova N, Kaminski Y, Montoliu C, Felipo V. Sources of oxygen radicals in brain in acute ammonia intoxication in vivo. Brain Res 2003; 981: 193-200 [PMID: 32340177 DOI: 10.3390/medicina56040196]
  10. Bai G, Rao KVR, Panickar KS, Jayakumar AR, Norenberg MD. Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes. J Neuosci Res 2001; 66: 981-991 [PMID: 11746427 DOI: 10.1002/jnr.10056]
  11. Häussinger D. Low grade cerebral edema and the pathogenesis of hepatic encephalopathy in cirrhosis. Hepatology 2006; 43: 1187-1190 [PMID: 16729329 DOI: 10.1002/hep.21235]
  12. Häberle J. Clinical practice: the management of hyperammonemia. Eur J Pediatr 2011; 170: 21-34 [PMID: 21165747 DOI: 10.1007/s00431-010-1369-2]
  13. Kwan L, Wang C, Levitt L. Hyperammonemic encephalopathy in multiple myeloma. N Engl J Med 2002; 346: 1674-1675 [PMID: 12024007 DOI: 10.1056/NEJM200205233462119]
  14. Cordano C, Elisabetta Traverso E, Calabrò V, Borzone C, Stara S, Marchese R, Lucio Marinelli L. Recurring hyperammonemic encephalopathy induced by bacteria usually not producing urease. BMC Res Notes 2014; 7: 324 [PMID: 24884855 DOI: 10.1186/1756-0500-7-324]
  15. Algahtani H, Alameer S, Marzouk Y, Shirah B. Urea cycle disorder misdiagnosed as multiple sclerosis: a case report and review of the literature. Neuroradiol J 2018; 31: 213-217 [PMID: 28635494 DOI: 10.1177/1971400917715880]
  16. Gupta V, Kalra N, Vyas S, Sodhi KS, Thapa BR, Khandelwal N. Embolization of congenital intrahepatic porto-systemic shunt by n-butyl cyanoacrylate. Indian J Pediatr 2009; 76: 1059-1060 [PMID: 19907942 DOI: 10.1007/s12098-009-0202-2]
  17. Lee HH, Poon KH, Lai CK, Au KM, Siu TS, Lai JPS, Mak CM, Yuen YP, Lam CW, Chan AYW. Hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome: a treatable genetic liver disease warranting urgent diagnosis. Hong Kong Med J 2014; 20: 63-66 [PMID: 24473688 DOI: 10.12809/hkmj133826]
  18. Laish I, Ari ZB. Noncirrhotic hyperammonaemic encephalopathy. Liver Int 2011; 31: 1259-1270 [PMID: 21745294 DOI: 10.1111/j.1478-3231.2011.02550.x]
  19. Berger C, Dimant P, Hermida L, Paulin F, Pereyra M, Tejo M. [Hyperammonemic encephalopathy and fibrolamellar hepatocellular carcinoma]. Medicina (B Aires) 2012; 72: 425-427 [PMID: 23089120]
  20. Sulaiman RA, Geberhiwot T. Fibrolamellar hepatocellular carcinoma mimicking ornithine transcarbamylase deficiency. IMD Rep 2014; 16: 4750 [PMID: 24997132 DOI: 10.1007/8904_2014_318]
  21. Alsina AE, Inoue H, Tanaka K, Fujiyoshi J, Matsushita Y, Ochiai M, Koga Y, Matsuura T, Taguchi T, Ohga S. Successful Liver Transplantation for Hyperammonemic Fibrolamellar Hepatocellular Carcinoma. ACG Case Rep J 2016; 3: e106 [PMID: 28558383 DOI: 10.1159/000474930]
  22. Hashash JG, Thudi K, Malik SM. An 18-year-old woman with a 15-cm liver mass and an ammonia level of 342. Gastroenterology 2012; 143: 1401-1402 [PMID: 23000233 DOI: 10.1053/j.gastro.2012.07.002]
  23. Chapuy CI, Sahai I, Sharma R, Zhu AX, Kozyreva ON. Hyperammonemic Encephalopathy Associated with Fibrolamellar Hepatocellular Carcinoma: Case Report, Literature Review, and Proposed Treatment Algorithm. Oncologist 2016; 21: 514-520 [PMID: 26975868 DOI: 10.1634/theoncologist.2015-0267]
  24. Bender HU, Staudigl M, Schmid I, Führer M. Treatment of Paraneoplastic Hyperammonemia in Fibrolamellar Hepatocellular Carcinoma With Oral Sodium Phenylbutyrate. J Pain Symptom Manage 2015; 49: e8-10 [PMID: 25891666 DOI: 10.1016/j.jpainsymman.2015.03.007]
  25. Sethi S, Tageja N, Singh J, Arabi H, Dave M, Badheka A, Revankar S. Hyperammonemic encephalopathy: a rare presentation of fibrolamellar hepatocellular carcinoma. Am J Med Sci 2009; 338: 522-524 [PMID: 20010160 DOI: 10.1097/MAJ.0b013e3181bccfb4]
  26. Surjan RC, dos Santos ES, Basseres T, Makdissi FF, Machado MA. A Proposed Physiopathological Pathway to Hyperammonemic Encephalopathy in a Non-Cirrhotic Patient with Fibrolamellar Hepatocellular Carcinoma without Ornithine Transcarbamylase (OTC) Mutation. Am J Case Rep 2017; 8: 234-241 [PMID: 28270654 DOI: 10.12659/ajcr.901682]
  27. Honeyman JN, Simon EP, Robine N, Chiaroni-Clarke R, Darcy DG, Lim IIP, Gleason CE, Murphy JM, Rosenberg BR, Teegan L, Takacs CN, Botero S, Belote R, Germer S, Emde AK, Vacic V, Bhanot U, LaQuaglia MP, Simon SM. Detection of a recurrent DNAJB1-PRKACA chimeric transcript in fibrolamellar hepatocellular carcinoma. Science 2014; 28: 1010-1014 [PMID: 24578576 DOI: 10.1126/science.1249484]
  28. Graham RP, Jin, L, Knutson DL, Kloft-Nelson SM, Greipp PT, Waldburger N, Roessler S, Longerich T, Roberts LR, Oliveira AM, Halling KC, Schirmacher P, Toberson M. DNAJB1-PRKACA is specific for fibrolamellar carcinoma. Mod Pathol 2015; 28: 822-829 [PMID: 25698061 DOI: 10.1038/modpathol.2015.4]
  29. Darcy DG, Chiaroni-Clarke R, Murphy JM, Honeyman JN, Bhanot U, LaQuaglia MP, Simon SM. The genomic landscape of fibrolamellar hepatocellular carcinoma: whole genome sequencing of ten patients. Oncotarget 2015; 20: 755-70 [PMID: 25605237 DOI: 10.18632/oncotarget.2712]
  30. Kastenhuber ER, Lalazar G, Houlihan SL, Tschaharganeh DF, Baslan T, Chen CC, Requena D, Tian S, Bosbach B, Wilkinson JE, Simon S, Lowe SW. DNAJB1-PRKACA fusion kinase drives tumorigenesis and interacts with β-catenin and the liver regenerative response. Proc Natl Acad Sci U S A 2017; 12: 13076-13084 [PMID: 29162699 DOI: 10.1073/pnas.1716483114]
  31. Simon EP, Catherine A Freije, Benjamin A Farber, Gadi Lalazar, David G Darcy, Joshua N Honeyman, Rachel Chiaroni-Clarke, Brian D Dill, Henrik Molina, Umesh K Bhanot, Michael P La Quaglia, Brad R Rosenberg, Sanford M Simon. Transcriptomic characterization of fibrolamellar hepatocellular carcinoma. Proc Natl Acad Sci U S A 2015; 112: E5916-E5925 [PMID: 26489647 DOI: 10.1073/pnas.1424894112]
  32. Lu L, Han H, Tian Y, Li W, Zhang J, Feng M, Li Y. Aurora kinase A mediates c-Myc's oncogenic effects in hepatocellular carcinoma. Mol Carcinog 2015; 54: 1467-1479 [PMID: 25284017 DOI: 10.1002/mc.22223]
  33. Lim IIP, Greene-Colozzi EA, Murphy JM, Heaton TE, Simon SM, LaQuaglia MP. DNAJB1-PRKACA chimera increases Aurora kinase A expression in fibrolamellar hepatocellular carcinoma. Cancer Res 2015; 75: 214 [DOI: 10.1158/1538-7445.am2015-lb-214]
  34. Nilsson JA, Keller UB, Baudino TA, Yang C, Norton S, Old JA, Nilsson LM, Neale G, Kramer DL, Porter CW, Cleveland JL. Targeting ornithine decarboxylase in Myc-induced lymphomagenesis prevents tumor formation. Cancer Cell 2005; 7: 433-444 [PMID: 15894264 DOI: 10.1016/j.ccr.2005.03.036]
  35. Mohammed A, Janakiram NB, Madka V, Ritchie RL, Brewer M, Biddick L, Patlolla JMR, Sadeghi M, Lightfoot S, Steele VE, Rao CV. Eflornithine (DFMO) Prevents Progression of Pancreatic Cancer by Modulating Ornithine Decarboxylase Signaling. Cancer Prev Res (Phila) 2014; 7: 1198–1209 [PMID: 25248858 DOI: 10.1158/1940-6207.CAPR-14-0176]
  36. Livak KJ, Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods 2001; 25: 402-408 [PMID: 11846609 DOI: 10.1006/meth.2001.1262]
  37. Pfaffl MW. A new mathematical model for relative quantification in real-time RT-PCR. Nucleic Acids Res 2001; 29: e45 [PMCID: PMC55695 DOI: 10.1093/nar/29.9.e45]
  38. Clay AS, Hainline BE. Hyperammonemia in the ICU. Chest 2007; 132: 1368-1378 [PMID: 17934124 DOI: 10.1378/chest.06-2940]
  39. Alameri M, Shakra M, Alsaadi T. Fatal coma in a young adult due to lateonset urea cycle deficiency presenting with a prolonged seizure: a case report. J Med Case Rep 2015; 23: 267 [PMID: 26593089 DOI: 10.1186/s13256-015-0741-2]
  40. Acharya G, Mehra S, Patel R, Frunza-Stefan S, Kaur H. Fatal Nonhepatic Hyperammonemia in ICU Setting: A Rare but Serious Complication following Bariatric Surgery. Case Rep Crit Care 2016; 2016: 8531591 [PMID: 27144037 DOI: 10.1155/2016/8531591]
  41. Upadhyay R, Bleck TP, Busl KM. Hyperammonemia: What Urea-lly Need to Know: Case Report of Severe Noncirrhotic Hyperammonemic Encephalopathy and Review of the Literature. Case Rep Med 2016; 2016; 8512721 [PMID: 27738433 DOI: 10.1155/2016/8512721]
  1. Nott L, Price TJ, Pittman K, Patterson K, Fletcher J. Hyperammonemia encephalopathy:an important cause of neurological deterioration following chemotherapy. Leuk Lymphoma 2007; 48: 1702-1711 [PMID: 17786705 DOI: 10.1080/10428190701509822]
  2. Weber G, Queener SF, Morris HP. Imbalance in ornithine metabolism in hepatomas of different growth rates as expressed in behavior of Lornithine carbamyl transferase activity. Cancer Res 1972; 32: 1933-1940 [PMID: 4345042]
  3. Jeffers LJ, Dubow RA, Zieve L, Reddy KR, Livingstone AS, Neimark S, Viamonte M, Schiff ER. Hepatic encephalopathy and orotic aciduria associated with hepatocellular carcinoma in a noncirrhotic liver. Hepatology 1988; 8: 78-81 [PMID: 2828214 DOI: 10.1002/hep.1840080116]
  4. Turken O, Basekim, C, Haholu A, Karagoz B, Bilgi O, Ozgun A, Kucukardali Y, Narin Y, Yasgan Y, Kandemir EG. Hyperammonemic encephalopathy in a patient with primary hepatic neuroendocrine carcinoma. Med Oncol 2009; 26: 309-313 [PMID: 19031017 DOI: 10.1007/s12032-008-9121-8]
  5. Lazier J, Lupichuk SM, Sosova I, Khan AA. Hyperammonemic encephalopathy in an adenocarcinoma patient managed with carglumic acid. Curr Oncol 2014; 21: e736–e739 [PMID: 25302046 DOI: 10.3747/co.21.2076]
  6. Weber G, Kizaki H, Shiotani T, Tzeng D, Williams JC. The molecular correlation concept of neoplasia: recent advances and new challenges. Adv Exp Med Biol 1977; 92: 89-116 [PMID: 205114 DOI: 10.1007/978-1-4615-8852-8_5]
  7. Pendeville H, Carpino N, Marine JC, Takahashi Y, Muller M, Martial JA, Cleveland JL. The ornithine decarboxylase gene is essential for cell survival during early murine development. Mol Cell Biol 2001; 21: 6549-6558 [PMID: 11533243 DOI: 10.1128/MCB.21.19.6549-6558.2001]
  8. Pegg AE. Mammalian Polyamine Metabolism and Function. IUBMB Life 2009; 61: 880–894 [ PMID: 19603518 DOI: 10.1002/iub.230.