The Mitochondrial Endonuclease M20 Participates in the Down-Regulation of Mitochondrial DNA in Pollen Cells.

Maintaining the appropriate number of mitochondrial DNA (mtDNA) molecules is crucial for supporting mitochondrial metabolism and function in both plant and animal cells. For example, a substantial decrease in mtDNA levels occurs as a key part of pollen development. The molecular mechanisms regulating mtDNA copy number are largely unclear, particularly with regard to those that reduce mtDNA levels. Here, we identified and purified a 20-kD endonuclease, M20, from maize (Zea mays) pollen mitochondria. We found M20 to be an His-Asn-His/Asn (H-N-H/N) nuclease that degrades linear and circular DNA in the presence of Mg2+ or Mn2+ Arabidopsis (Arabidopsis thaliana) AtM20, which shared high sequence similarity with maize M20, localized to the mitochondria, had a similar H-N-H/N structure, and degraded both linear and circular DNA. AtM20 transcript levels increased during pollen development, in parallel with a rapid reduction in mtDNA. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 genome-editing techniques were used to generate knockout lines of AtM20 (atm20), which exhibited a significant delay in the reduction in mtDNA levels in pollen vegetative cells but normal mtDNA levels in somatic cells. The delayed reduction in pollen mtDNA levels was rescued by the transgenic expression of AtM20 in atm20 plants. This study thus uncovers an endonucleolytic DNase in plant mitochondria and its crucial role in reducing mtDNA levels, pointing to the complex mechanism regulating mtDNA levels in plants.

Simultaneous pre-concentration and separation on simple paper-based analytical device for protein analysis.

In this work, fast isoelectric focusing (IEF) was successfully implemented on an open paper fluidic channel for simultaneous concentration and separation of proteins from complex matrix. With this simple device, IEF can be finished in 10 min with a resolution of 0.03 pH units and concentration factor of 10, as estimated by color model proteins by smartphone-based colorimetric detection. Fast detection of albumin from human serum and glycated hemoglobin (HBA1c) from blood cell was demonstrated. In addition, off-line identification of the model proteins from the IEF fractions with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was also shown. This PAD IEF is potentially useful either for point of care test (POCT) or biomarker analysis as a cost-effective sample pretreatment method.

Carrier ampholyte-free isoelectric focusing on a paper-based analytical device for the fractionation of proteins.

Isoelectric focusing plays a critical role in the analysis of complex protein samples. Conventionally, isoelectric focusing is implemented with carrier ampholytes in capillary or immobilized pH gradient gel. In this study, we successfully exhibited a carrier ampholyte-free isoelectric focusing on paper-based analytical device. Proof of the concept was visually demonstrated with color model proteins. Experimental results showed that not only a pH gradient was well established along the open paper fluidic channel as confirmed by pH indicator strip, the pH gradient range could also be tuned by the catholyte or anolyte. Furthermore, the isoelectric focusing fractions from the paper channel can be directly cut and recovered into solutions for post analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. This paper-based isoelectric focusing method is fast, cheap, simple and easy to operate, and could potentially be used as a cost-effective protein sample clean-up method for target protein analysis with mass spectrometry.

Structural and functional insights into lipid-bound nerve growth factors.

Nerve growth factor (NGF) is a dimeric molecule that modulates the survival, proliferation, and differentiation of nervous cells and is also known to act on cells of the immune system and endocrine system. NGFs extracted from mouse submaxillary gland and cobra venom have different immunological behaviors, yet the underlying mechanism remains unclear. Here we report the crystal structure of the NGF purified from Chinese cobra Naja naja atra (cNGF), which unexpectedly reveals a 2-tailed lipid molecule that is embedded between the two protomers of the NGF homodimer. In addition, crystallographic analysis indicated that the purified mouse NGF(mNGF) is free from lipid but can bind lysophosphatidylserine (lyso-PS) in the same pocket as cNGF. Bioassays indicated that the binding of lipid molecules to cNGF and mNGF are essential for their mast cell activation activity and abates their p75(NTR) binding capacity. Taken together, these results suggest a new mechanism for the regulation of the function of NGF.

Protein kinase A-mediated 14-3-3 association impedes human Dapper1 to promote dishevelled degradation.

Wnt signaling regulates embryo development and tissue homeostasis, and its deregulation leads to an array of diseases, including cancer. Dapper1 has been shown to be a key negative regulator of Wnt signaling. However, its function and regulation remain poorly understood. In this study, we report that 14-3-3ß interacts with human Dapper1 (hDpr1). The interaction is dependent on protein kinase A (PKA)-mediated phosphorylation of hDpr1 at Ser-237 and Ser-827. 14-3-3ß binding attenuates the ability of hDpr1 to promote Dishevelled (Dvl) degradation, thus enhancing Wnt signaling. We further provide evidence that PKA-mediated Dpr1 phosphorylation may contribute to growth and tumor formation of colon cancer Caco2 cells. Finally, we show that cyclooxygenase-2 expression and PKA activation are positively correlated with Dvl protein levels in colon cancer samples. Together, our findings establish a novel layer of regulation of Wnt signaling by PKA via the 14-3-3-Dpr1-Dvl axis.

Fibril formation of the rabbit/human/bovine prion proteins.

Prion diseases are infectious fatal neurodegenerative diseases including Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy in cattle. The misfolding and conversion of cellular PrP in such mammals into pathogenic PrP is believed to be the key procedure. Rabbits are among the few mammalian species that exhibit resistance to prion diseases, but little is known about the molecular mechanism underlying such resistance. Here, we report that the crowding agents Ficoll 70 and dextran 70 have different effects on fibrillization of the recombinant full-length PrPs from different species: although these agents dramatically promote fibril formation of the proteins from human and cow, they significantly inhibit fibrillization of the rabbit protein by stabilizing its native state. We also find that fibrils formed by the rabbit protein contain less ß-sheet structure and more α-helix structure than those formed by the proteins from human and cow. In addition, amyloid fibrils formed by the rabbit protein do not generate a proteinase K-resistant fragment of 15-16-kDa, but those formed by the proteins from human and cow generate such proteinase K-resistant fragments. Together, these results suggest that the strong inhibition of fibrillization of the rabbit PrP by the crowded physiological environment and the absence of such a protease-resistant fragment for the rabbit protein could be two of the reasons why rabbits are resistant to prion diseases.

[Differentially expressed urine protein of contrast induced acute kidney injury by two-dimensional differential in-gel electrophoresis and mass spectrometry].

OBJECTIVE: To explore the differentially expressed proteins of contrast-induced nephropathy through a comparison of urinary proteome so as to further elucidate the pathogenesis and discover the disease biomarker. METHODS: The urine samples of 12 patients were collected before and after coronary angiography. Two dimensional electrophoresis was performed after the urine samples were labeled by different dyes. The differences of urine proteome were analyzed by Decyder software and the differentially expressed spots identified by mass spectrometry. RESULTS: A total of 56 differentially expressed spots were detected. Among them, 39 spots were up-regulated and 17 spots down-regulated. And mannose binding lectin and mannose binding lectin associated serine protease 2, key proteins in complement body activation, were both significantly up-regulated. CONCLUSION: Urine proteomic study methods are constructed based on 2D-DIGE and mass spectrometry. The lectin pathway of complement body may be associated with contrast-induced acute kidney injury.

[Detection and identification of specific serum biomarkers in papillary thyroid cancer].

OBJECTIVE: To detect and identify the potential specific serum biomarkers for diagnosis of papillary thyroid cancer. METHODS: Samples of 35 patients with papillary thyroid carcinoma, 40 patients with benign thyroid nodule and 34 healthy individuals were analyzed using the SELDI-TOF ProteinChip System and bioinfomation technology to find the differential peaks which were separated by HPLC and then further analyzed by LC-MS/MS. The protein sequences were analyzed by SEQUEST software and searched in Bioworks database. RESULTS: The top six mass-to-charge ratio (M/Z) peaks with the smallest P value were 6651, 6452, 7653, 7932, 15 106 and 15 848 Da, respectively. The 6651 and 6452 Da proteins were weakly expressed in papillary thyroid carcinoma but highly expressed in benign thyroid nodules and healthy individuals. The differences had statistical significance (P < 0.01). The 7653, 7932, 15 106, 15 848 Da proteins were highly expressed in papillary thyroid carcinoma but weakly expressed in benign thyroid nodules and healthy individuals. The differences were statistically significant (P < 0.01). Combination of these six proteins, using the method of leave-one-out to make crossing detection, the specificity of discriminating papillary thyroid carcinoma and non-cancer was 88.0%, and its sensitivity was 92.5%. The 6651 and 6452 Da proteins were identified as apolipoprotein C-I and apolipoprotein C-III, respectively. The 7653 and 15 106 Da proteins were identified as the same protein-alpha-globin, and the 7932 and 15,848 Da proteins were identified as the same protein-beta-globin. CONCLUSION: The detection of differentially expressed apolipoprotein C-I, apolipoprotein C-III, alpha-globin, and beta-globin may have utility for diagnosis of papillary thyroid carcinoma and are worthy of further investigation.

[Screening and identification analysis of serum protein biomarkers in nephroblastoma].

OBJECTIVE: To screen and characterize the serum protein biomarkers in nephroblastoma so as to establish the proteins as the specific serum biomarkers for diagnosis and prognosis monitoring. METHODS: The differential protein peaks were located by detecting serum samples of preoperative and postoperative patients and normal children using the SELDI-TOF MS technology. After purification, the differential proteins were further analyzed by LC-MS/MS and the protein sequences searched in database. RESULTS: Two peaks with m/z of 6455.5 and 6984.4 were selected as potential biomarkers. They were weakly expressed in nephroblastoma (intensity: 1029 +/- 364, 297 +/- 126) but highly expressed in normal individuals (2108 +/- 837, 753 +/- 226); another peak with m/z of 9190.8 was weakly expressed in preoperative sera (283 +/- 154) but highly expressed in serum samples of postoperative patients and normal children (5974 +/- 657, 6231 +/- 519). The protein at 6455.5 and 9190.8 were identified as apolipoprotein C-III and haptoglobin respectively. CONCLUSION: The detection of differentially expressed apolipoprotein C-III and haptoglobin may have potential utilities for serum diagnosis, malignancy classification and prognosis monitoring of nephroblastoma and is worthy of further studies and applications.

Anterior transversalis fascia approach versus preperitoneal space approach for inguinal hernia repair in residents in northern China: study protocol for a prospective, multicentre, randomised, controlled trial.

INTRODUCTION: Many surgical techniques have been used to repair abdominal wall defects in the inguinal region based on the anatomic characteristics of this region and can be categorised as 'tension' repair or 'tension-free' repair. Tension-free repair is the preferred technique for inguinal hernia repair. Tension-free repair of inguinal hernia can be performed through either the anterior transversalis fascia approach or the preperitoneal space approach. There are few large sample, randomised controlled trials investigating the curative effects of the anterior transversalis fascia approach versus the preperitoneal space approach for inguinal hernia repair in patients in northern China. METHODS AND ANALYSIS: This will be a prospective, large sample, multicentre, randomised, controlled trial. Registration date is 1 December 2016. Actual study start date is 6 February 2017. Estimated study completion date is June 2020. A cohort of over 720 patients with inguinal hernias will be recruited from nine institutions in Liaoning Province, China. Patient randomisation will be stratified by centre to undergo inguinal hernia repair via the anterior transversalis fascia approach or the preperitoneal approach. Primary and secondary outcome assessments will be performed at baseline (prior to surgery), predischarge and at postoperative 1 week, 1 month, 3 months, 1 year and 2 years. The primary outcome is the incidence of postoperative chronic inguinal pain. The secondary outcome is postoperative complications (including rates of wound infection, haematoma, seroma and hernia recurrence). ETHICS AND DISSEMINATION: This trial will be conducted in accordance with the Declaration of Helsinki and supervised by the institutional review board of the Fourth Affiliated Hospital of China Medical University (approval number 2015-027). All patients will receive information about the trial in verbal and written forms and will give informed consent before enrolment. The results will be published in peer-reviewed journals or disseminated through conference presentations. TRIAL REGISTRATION NUMBER: NCT02984917; preresults.

Is delayed gastric emptying so terrible after pylorus-preserving pancreaticoduodenectomy? Prevention and management.

AIM: To explore some operative techniques to prevent the occurrence of delayed gastric emptying (DGE) after pylorus-preserving pancreaticoduodenectomy (PPPD). METHODS: One hundred and eighty-six patients in a single medical center who accepted PPPD were retrospectively studied. The incidence of DGE was investigated and the influence of some operative techniques on the prevention of DGE was analyzed. RESULTS: During the operative process of PPPD, the methods of detached drainage of pancreatic fluid and bile and gastric fistulization were used. Postoperatively, six patients suffered DGE among the 186 cases; the incidence was 3.23% (6/186). One of them was complicated with intraabdominal infection at the same time, and two with pancreatic leakage. CONCLUSION: Appropriate maneuvers during operation are essential to avoid postoperative DGE in PPPD. The occurrence of DGE is avoidable. It should not be used as an argument to advocate hemigastrectomy in PPPD.

COX-2 Promotes Migration and Invasion by the Side Population of Cancer Stem Cell-Like Hepatocellular Carcinoma Cells.

Cancer stem cells (CSCs) are thought to be responsible for tumor relapse and metastasis due to their abilities to self-renew, differentiate, and give rise to new tumors. Cyclooxygenase-2 (COX-2) is highly expressed in several kinds of CSCs, and it helps promote stem cell renewal, proliferation, and radioresistance. Whether and how COX-2 contributes to CSC migration and invasion is unclear. In this study, COX-2 was overexpressed in the CSC-like side population (SP) of the human hepatocellular carcinoma (HCC) cell line HCCLM3. COX-2 overexpression significantly enhanced migration and invasion of SP cells, while reducing expression of metastasis-related proteins PDCD4 and PTEN. Treating SP cells with the selective COX-2 inhibitor celecoxib down-regulated COX-2 and caused a dose-dependent reduction in cell migration and invasion, which was associated with up-regulation of PDCD4 and PTEN. These results suggest that COX-2 exerts pro-metastatic effects on SP cells, and that these effects are mediated at least partly through regulation of PDCD4 and PTEN expression. These results further suggest that celecoxib may be a promising anti-metastatic agent to reduce migration and invasion by hepatic CSCs.

Adjuvant transarterial chemoembolization after curative resection of hepatocellular carcinoma: propensity score analysis.

AIM: To compare survival and recurrence in hepatocellular carcinoma (HCC) patients who did or did not receive adjuvant transarterial chemoembolization (TACE). METHODS: A consecutive sample of 229 patients who underwent curative resection between March 2007 and March 2010 in our hospital was included. Of these 229 patients, 91 (39.7%) underwent curative resection followed by adjuvant TACE and 138 (60.3%) underwent curative resection alone. In order to minimize confounds due to baseline differences between the two patient groups, comparisons were conducted between propensity score-matched patients. Survival data and recurrence rates were compared using the Kaplan-Meier method. Independent predictors of overall survival and recurrence were identified using Cox proportional hazard regression. RESULTS: Among 61 pairs of propensity score-matched patients, the 1-, 2-, and 3-year overall survival rates were 95.1%, 86.7%, and 76.4% in the TACE group and 86.9%, 78.5%, and 73.2% in the control group, respectively. At the same time, the TACE and control groups also showed similar recurrence rates at 1 year (13.4% vs 24.8%), 2 years (30.6% vs 32.1%), and 3 years (40.1% vs 34.0%). Multivariate Cox regression identified serum alpha-fetoprotein level ≥ 400 ng/mL and tumor size > 5 cm as independent risk factors of mortality (P < 0.05). CONCLUSION: As postoperative adjuvant TACE does not improve overall survival or reduce recurrence in HCC patients, further study is needed to clarify its clinical benefit.

Iatrogenic extrahepatic bile duct injury in 182 patients: causes and management.

OBJECTIVE: To describe the causes and treatment of iatrogenic bile duct injury caused by cholecystectomy. METHODS: 182 patients with iatrogenic extrahepatic bile duct injury from 4 university hospitals of China were reviewed. Details of primary cholecystectomy, biliary reconstruction as well as postoperative management were recorded. All patients were followed up for at least 6 months (6 months to 9 years, median 3.5 years). The adequacy of repair was assessed by regular evaluation of the patients' clinical status and liver function variables. Hepatobiliary B-ultrasonography was used routinely in the follow up of patients, and magnetic resonance cholangiopancreatography was applied in the patients suggestive of abnormality. RESULTS: In 152 patients, bile duct injury happened during open cholecystectomy, and in 30 patients during laparoscopic cholecystectomy. All the injuries developed during anterograde cholecystectomy (at the Calot's triangle). All the patients with these injuries underwent choledochocholedochostomy or Roux-en-Y choledochojejunostomy with good results (161 patients), recurrent stricture (11), and death (10). CONCLUSIONS: During cholecystectomy, the Calot's triangle should be identified anatomically, but retrograde cholecystectomy is the optimal choice. Bile duct injury should be discovered as soon as possible and be managed timely. Different operative methods are optional according to the degree of injury and the postoperative period.

Prevention of pancreaticojejunal anastomotic leakage after pancreaticoduodenectomy with separate internal drainage of bile and pancreatic fluid.

OBJECTIVE: To introduce a new reconstructional procedure to decrease the complications after pancreaticoduodenectomy. METHODS: Separate internal drainage of bile and pancreatic fluid in pancreaticoduodenectomy was performed in 256 patients. The digestive tract was reconstructed with Child method, with invaginated pancreaticojejunostomy using a long silastic tube to drain pancreatic fluid internally, an end-to-side choledochojejunostomy and an end-to-side duodenojejunostomy or gastrojejunostomy. Gastrostomy drainage was also performed. RESULTS: No complications of pancreatic leakage were found. CONCLUSION: The separate internal drainage of bile and pancreatic fluid plays an important role in preventing pancreaticojejunal anastomotic leakage.

Angiotensin IV upregulates the activity of protein phosphatase 1α in Neura-2A cells.

The peptide angiotensin IV (Ang IV) is a derivative of angiotensin II. While insulin regulated amino peptidase (IRAP) has been proposed as a potential receptor for Ang IV, the signalling pathways of Ang IV through IRAP remain elusive. We applied high-resolution mass spectrometry to perform a systemic quantitative phosphoproteome of Neura-2A (N2A) cells treated with and without Ang IV using sta ble-isotope labeling by amino acids in cell culture (SILAC), and identified a reduction in the phosphorylation of a major Ser/Thr protein phosphorylase 1 (PP1) upon Ang IV treatment. In addition, spinophilin (spn), a PP1 regulatory protein that plays important functions in the neural system, was expressed at higher levels. Immunoblotting revealed decreased phosphorylation of p70S6 kinase (p70(S6K)) and the major cell cycle modulator retinoblastoma protein (pRB). These changes are consistent with an observed decrease in cell proliferation. Taken together, our study suggests that Ang IV functions via regulating the activity of PP1.

Cupric ions induce the oxidation and trigger the aggregation of human superoxide dismutase 1.

BACKGROUND: Amyotrophic lateral sclerosis (ALS), partly caused by the mutations and aggregation of human copper, zinc superoxide dismutase (SOD1), is a fatal degenerative disease of motor neurons. Because SOD1 is a major copper-binding protein present at relatively high concentration in motor neurons and copper can be a harmful pro-oxidant, we want to know whether aberrant copper biochemistry could underlie ALS pathogenesis. In this study, we have investigated and compared the effects of cupric ions on the aggregation of ALS-associated SOD1 mutant A4V and oxidized wild-type SOD1. METHODOLOGY/PRINCIPAL FINDINGS: As revealed by 90° light scattering, dynamic light scattering, SDS-PAGE, and atomic force microscopy, free cupric ions in solution not only induce the oxidation of either apo A4V or Zn2-A4V and trigger the oligomerization and aggregation of oxidized A4V under copper-mediated oxidative conditions, but also trigger the aggregation of non-oxidized form of such a pathogenic mutant. As evidenced by mass spectrometry and SDS-PAGE, Cys-111 is a primary target for oxidative modification of pathological human SOD1 mutant A4V by either excess Cu(2+) or hydrogen peroxide. The results from isothermal titration calorimetry show that A4V possesses two sets of independent binding sites for Cu(2+): a moderate-affinity site (10(6) M(-1)) and a high-affinity site (10(8) M(-1)). Furthermore, Cu(2+) binds to wild-type SOD1 oxidized by hydrogen peroxide in a way similar to A4V, triggering the aggregation of such an oxidized form. CONCLUSIONS/SIGNIFICANCE: We demonstrate that excess cupric ions induce the oxidation and trigger the aggregation of A4V SOD1, and suggest that Cu(2+) plays a key role in the mechanism of aggregation of both A4V and oxidized wild-type SOD1. A plausible model for how pathological SOD1 mutants aggregate in ALS-affected motor neurons with the disruption of copper homeostasis has been provided.

A new strategy to produce a defensin: stable production of mutated NP-1 in nitrate reductase-deficient Chlorella ellipsoidea.

Defensins are small cationic peptides that could be used as the potential substitute for antibiotics. However, there is no efficient method for producing defensins. In this study, we developed a new strategy to produce defensin in nitrate reductase (NR)-deficient C. ellipsoidea (nrm-4). We constructed a plant expression vector carrying mutated NP-1 gene (mNP-1), a mature α-defensin NP-1 gene from rabbit with an additional initiator codon in the 5'-terminus, in which the selection markers were NptII and NR genes. We transferred mNP-1 into nrm-4 using electroporation and obtained many transgenic lines with high efficiency under selection chemicals G418 and NaNO(3). The mNP-1 was characterized using N-terminal sequencing after being isolated from transgenic lines. Excitingly, mNP-1 was produced at high levels (approximately 11.42 mg/l) even after 15 generations of continuous fermentation. In addition, mNP-1 had strong activity against Escherichia coli at 5 µg/ml. This research developed a new method for producing defensins using genetic engineering.

Identification of a new protein biomarker for colorectal cancer diagnosis.

As one of the most common cancers, colorectal cancer (CRC) is a major public health issue worldwide. Thus, the identification of novel biomarkers to aid in the early diagnosis of CRC is crucial. The aim of the present study was to identify a novel protein biomarker for CRC, and to identify its structure. In this study, a total of 99 serum samples from 73 CRC patients and 26 healthy controls were collected and analyzed by SELDI-TOF-MS. The biomarkers were separated using HPLC and detected with MALDI-TOF-MS. The qualified peaks were ranked by p-value of non-parametric tests and the top 10 peaks displaying significant differences were selected. Among the 10 protein biomarkers, the concentration of a 3.9­kDa protein in the serum of the CRC patients was much lower than that in the healthy controls. Therefore, the 3.9­kDa protein was selected as a biomarker for CRC and its separation and purification were performed. The structure of the 3.9-kDa protein biomarker was determined by LC-MS/MS, and was confirmed to be a fragment of serine/theonine kinase 4 (MST1/STK4). The 3.9­kDa protein biomarker had high sensitivity and specificity for CRC, and its potential clinical application warrants further investigation.

Apoptosis of non-tumor cells contributes to increased serum cytochrome c level in a neuroblastoma xenograft model.

BACKGROUND: Neuroblastoma (NB) is one of the most common malignant solid tumors of childhood. It is still not clear whether the apoptosis of tumor cells or the non-tumor cells contributes to the increase of concentration of cytochrome c (Cyt c) in the serum of the cancer patients. The aim of this research was to identify the source of the Cyt c in the serum when the tumor grows up by subcutaneous inoculation of human NB cells into nude mice. METHODS: We subcutaneously inoculated human NB cells (KP-N-NS) into nude mice and collected the sera of tumor-bearing mice (n = 14) and control mice (n = 25) 4 weeks later in order to screen for and identify differentially expressed proteins in the serum. Differentially expressed proteins in the serum were screened by surface-enhanced laser desorption/ionization-time-of-flight (SELDI-TOF) mass spectrometry. RESULTS: The relative intensity of a protein having a mass-to-charge ratio (m/z) of 11 609 was 3338.37 ± 3410.85 in the tumor group and 59.84 ± 40.74 in the control group, indicating that the expression level of this protein in the tumor group was 55.8 times higher than that in the control group. Serum proteins were separated and purified by high-performance liquid chromatography (HPLC). Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was performed to produce peptide mass fingerprints (PMFs). Spectrum analysis and a database search revealed that the highly expressed protein (m/z = 11 605.4) from the serum of tumor-bearing mice was the mouse Cyt c. CONCLUSIONS: Increased concentration of Cyt c in the serum of tumor-bearing nude mice might be partially attributed to the secretion of this protein by non-tumor cells.