Introduction of BD Vacutainer® Barricor™ tubes in clinical biobanking and application of amino acid and cytokine quality indicators to Barricor plasma.

OBJECTIVES: The use of BD Vacutainer® Barricor™ tubes (BAR) can reduce turnaround time (TAT) and improve separation of plasma from cellular components using a specific mechanical separator. Concentrations of amino acids (AAs) and cytokines, known to be labile during pre-analytical time delays, were compared in heparin (BAR, BD Heparin standard tube [PST]), EDTA and serum gel tubes (SER) to validate previously identified quality indicators (QIs) in BAR. METHODS: Samples of healthy individuals (n=10) were collected in heparin, EDTA and SER tubes and exposed to varying pre- and post-centrifugation delays at room temperature (RT). Cytokines (interleukin [IL]-8, IL-16 and sCD40L) were analyzed by enzyme-linked immunosorbent assay (ELISA) and AAs were characterized by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). RESULTS: All QIs, AAs/AA ratio and cytokines increased during prolonged blood storage in heparin plasma (PST, BAR) and SER tubes. Comparison of 53 h/1 h pre-centrifugation delay resulted in an increase in taurine (Tau) and glutamic acid (Glu) concentrations by more than three times, soluble CD40L increased by 13.6, 9.2 and 4.3 fold in PST, BAR-CTRL and BAR-FAST, and IL-8 increased even more by 112.8 (PST), 266.1 (BAR-CTRL), 268.1 (BAR-FAST) and 70.0 (SER) fold, respectively. Overall, compared to prolonged blood storage, effects of post-centrifugation delays were less pronounced in all tested materials. CONCLUSIONS: BAR tubes are compatible with the use of several established QIs and can therefore be used in clinical biobanking to reduce pre-analytical TAT without compromising QIs and thus pre-analytical sample quality analysis.

IL8 and IL16 levels indicate serum and plasma quality.

BACKGROUND: Longer pre-centrifugation times alter the quality of serum and plasma samples. Markers for such delays in sample processing and hence for the sample quality, have been identified. METHODS: Twenty cytokines in serum, EDTA plasma and citrate plasma samples were screened for changes in concentration induced by extended blood pre-centrifugation delays at room temperature. The two cytokines that showed the largest changes were further validated for their "diagnostic performance" in identifying serum or plasma samples with extended pre-centrifugation times. RESULTS: In this study, using R&D Systems ELISA kits, EDTA plasma samples and serum samples with a pre-centrifugation delay longer than 24 h had an IL16 concentration higher than 313 pg/mL, and an IL8 concentration higher than 125 pg/mL, respectively. EDTA plasma samples with a pre-centrifugation delay longer than 48 h had an IL16 concentration higher than 897 pg/mL, citrate plasma samples had an IL8 concentration higher than 21.5 pg/mL and serum samples had an IL8 concentration higher than 528 pg/mL. CONCLUSIONS: These robust and accurate tools, based on simple and commercially available ELISA assays can greatly facilitate qualification of serum and plasma legacy collections with undocumented pre-analytics.

Implementing routine monitoring for nuclease contamination of equipment and consumables into the quality Management system of a laboratory.

Nucleases are ubiquitous in the environment, present in biospecimens and widely used in many laboratory processes. However, in the wrong context, as contaminants, they have catastrophic potential because of their ability to rapidly degrade nucleic acids whilst retaining high resilience to inactivation. Although laboratories undertake rigorous precautions to prevent nuclease contamination, such measures are not infallible. In 2015, we devised and integrated a novel routine nuclease testing regimen into our Quality Management System that uses cleavable, fluorescent DNA and RNA substrates to detect, monitor and control for nuclease contamination in our laboratory processes, equipment and consumables. The testing regimen enables us to identify higher-risk activities, design our laboratory workflows such that risk is minimized and help fulfil our obligations in respect of ISO 20387:2018 General Requirements for Biobanking and ISO 17025 Testing and Calibrations Laboratory standards, both of which stipulate that environmental conditions in our laboratory must be monitored with defined quality control criteria. In seventeen rounds of testing (30 Test Items per round), 1.1 % of RNase tests and 0.2 % of DNase tests returned elevated nuclease levels (≥2.90 x 10-9 U RNase or 1.67 x 10-3 U DNase) and we were able to take remedial action. In no instance was an elevated nuclease level consequential in terms of an impact on sample quality. We present our protocols, results and observations.

Effect of gemtuzumab ozogamicin on survival of adult patients with de-novo acute myeloid leukaemia (ALFA-0701): a randomised, open-label, phase 3 study.

BACKGROUND: The results of the addition of gemtuzumab ozogamicin, an anti-CD33 antibody conjugate, to the standard treatment for patients with acute myeloid leukaemia in phase 3 trials were contradictory. We investigated whether the addition of low fractionated-dose gemtuzumab ozogamicin to standard front-line chemotherapy would improve the outcome of patients with this leukaemia without causing excessive toxicity. METHODS: In a phase 3, open-label study, undertaken in 26 haematology centres in France, patients aged 50-70 years with previously untreated de novo acute myeloid leukaemia were randomly assigned with a computer-generated sequence in a 1:1 ratio with block sizes of four to standard treatment (control group) with or without five doses of intravenous gemtuzumab ozogamicin (3 mg/m(2) on days 1, 4, and 7 during induction and day 1 of each of the two consolidation chemotherapy courses). The primary endpoint was event-free survival (EFS). Secondary endpoints were relapse-free (RFS), overall survival (OS), and safety. Analysis was by intention to treat. This study is registered with EudraCT, number 2007-002933-36. FINDINGS: 280 patients were randomly assigned to the control (n=140) and gemtuzumab ozogamicin groups (n=140), and 139 patients were analysed in each group. Complete response with or without incomplete platelet recovery to induction was 104 (75%) in the control group and 113 (81%) in the gemtuzumab ozogamicin group (odds ratio 1·46, 95% CI 0·20-2·59; p=0·25). At 2 years, EFS was estimated as 17·1% (10·8-27·1) in the control group versus 40·8% (32·8-50·8) in the gemtuzumab ozogamicin group (hazard ratio 0·58, 0·43-0·78; p=0·0003), OS 41·9% (33·1-53·1) versus 53·2% (44·6-63·5), respectively (0·69, 0·49-0·98; p=0·0368), and RFS 22·7% (14·5-35·7) versus 50·3% (41·0-61·6), respectively (0·52, 0·36-0·75; p=0·0003). Haematological toxicity, particularly persistent thrombocytopenia, was more common in the gemtuzumab ozogamicin group than in the control group (22 [16%] vs 4 [3%]; p<0·0001), without an increase in the risk of death from toxicity. INTERPRETATION: The use of fractionated lower doses of gemtuzumab ozogamicin allows the safe delivery of higher cumulative doses and substantially improves outcomes in patients with acute myeloid leukaemia. The findings warrant reassessment of gemtuzumab ozogamicin as front-line therapy for acute myeloid leukaemia. FUNDING: Wyeth (Pfizer).

Cell cycle arrest in early mitosis and induction of caspase-dependent apoptosis in U937 cells by diallyltetrasulfide (Al2S4).

Naturally occurring organic sulfur compounds (OSCs), such as linear allylsulfides from Allium species, are attracting attention in cancer research, since several OSCs were shown to act beneficially both in chemoprevention and in chemotherapy, while hardly exerting any harmful side effects. Hence, we investigated the possible role of different OSCs in the treatment of leukemia. Thereby, we found that the compounds tested in this study induced apoptosis in U937 cells, with an efficiency depending on the number of sulfides, and selected the most promising candidate, diallyltetrasulfide (Al2S4), for detailed mechanistic studies. Here we show that Al2S4 induced an accumulation of cells in early mitosis (G2/M phase), followed by the activation of caspase-dependent apoptosis. The compound counteracted different anti-apoptotic Bcl-2 family members (Bcl-xL, phospho-Bad and Bcl-2), promoted activation of Bax and Bak and induced the release of cytochrome c into the cytoplasm. Treatment by Al2S4 let to the identification of early apoptotic events including Bcl-xL degradation, Bak activation and release of cytochrome c followed by late events including Bcl-2 proteolysis, Bax activation, Bad dephosphorylation, caspase activation, nuclear fragmentation and phosphatidylserine exposure.

Curcumin regulates signal transducer and activator of transcription (STAT) expression in K562 cells.

Signal transducers and activators of transcription (STATs) play important roles in numerous cellular events as for example differentiation, inflammation or immune response. Furthermore, constitutive STAT activation can be observed in a high number of tumors. In our hands, curcumin treatment induced a decrease of nuclear STAT3, -5a and -5b, without affecting neither STAT1, nor the phosphorylation state of STAT1, -3 or -5 in the K562 cell line. Most interestingly, the decrease of nuclear STAT5a and -5b after curcumin treatment was accompanied by an increase of truncated STAT5 isoforms, indicating that curcumin is able to induce the cleavage of STAT5 into its dominant negative variants lacking the STAT5 C-terminal region. Interferon (IFN)-beta and -gamma treatment induced IFN-stimulated responsive element (ISRE) transcriptional activity, which was efficiently inhibited by curcumin pre-treatment. In parallel, IFN-gamma treatment induced an increase of the amount of nuclear STAT1 and -3, as well as their phosphorylated isoforms. Again, curcumin pre-treatment inhibited these increases. Finally, curcumin treatment inhibited Jak2 mRNA expression as well as cyclin D1 and v-src gene expression in K562 chronic leukaemia cells.

Transcriptional and post-transcriptional regulation of glutathione S-transferase P1 expression during butyric acid-induced differentiation of K562 cells.

Over-expression of glutathione S-transferase P1 is related to chemotherapeutic drug resistance as well as to differentiation of human erythroleukemia cells. In opposition to previously described differentiating inducers which enhance the GST-resistance phenotype, time- and concentration-dependent activation of both erythroid and megakaryocytic differentiation pathways by butyric acid progressively diminished GSTP1 mRNA expression. GSTP1 mRNA expression decreased by 25% (p<0.01) and 64% (p<0.01) in 1mM and 2mM butyric acid-differentiated K562 cells, respectively. These results were associated to both a reduction of GATA-1 binding activity to the GSTP1 promoter and to a posttranscriptional destabilization of GSTP1 mRNA in a concentration dependent manner. Indeed, GSTP1 mRNA half-life decreased from 43.8 to 36.2 h and 12.6 h in 1mM- and 2mM-treated cells, respectively.

Method Validation for Extraction of Nucleic Acids from Peripheral Whole Blood.

BACKGROUND: This article is the fifth in a series of publications providing formal method validation for biospecimen processing. We report the optimization and validation of methodology to obtain nucleic acids of sufficient quantity and quality from blood. METHODS: DNA was extracted using the Chemagic DNA Blood Kit on an MSM I. Extraction was optimized in terms of blood volume, elution buffer volume, and lysis conditions. The optimal protocol was validated for reproducibility, robustness (delay to buffy coat extraction, blood vs. buffy coat, and use of a magnetic rack), and performance (yield, purity, and concentration). RNA was extracted using a PAXgene Blood miRNA kit with a QiaCube. The protocol was validated for reproducibility, robustness (elution buffer, delay, and temperature before extraction), and performance (yield, purity, integrity, and miRNA content). Two platforms (QiaCube, Biorobot Universal) were further compared. RESULTS: For DNA extraction, a 4 mL blood sample, manual lysis, and 300 µL elution buffer were found to be reproducible (CV <10% for DNA yield and A260 nm/A280 nm ratio) and robust (buffy coat vs. whole blood; immediate processing of buffy coat after lysis vs. storage for 1 week at 2-8°C; and magnetic rack use). There was no difference between automated and manual lysis. RNA extracted with the PAXgene Blood miRNA kit on a QiaCube gave high yields and optimal reproducibility (low CV for RNA yield and integrity) with BR5 elution buffer (vs. water and TE). PAXgene tubes could be stored for up to 2 weeks at 2-8°C. The Biorobot Universal System gave similar mean RNA yields with Qiacube and slightly lower but acceptable purity. CONCLUSIONS: We validated automated isolation of DNA with a Chemagic DNA Blood Kit on a magnetic bead-based MSM I, and of RNA with a PAXgene Blood miRNA kit on a silica membrane-based QiaCube or Biorobot (for low and high throughput, respectively).

Chemopreventive and therapeutic effects of curcumin.

Chemoprevention is a promising anti-cancer approach with reduced secondary effects in comparison to classical chemotherapy. Curcumin, one of the most studied chemopreventive agents, is a natural compound extracted from Curcuma longa L. that allows suppression, retardation or inversion of carcinogenesis. Curcumin is also described as an anti-tumoral, anti-oxidant and anti-inflammatory agent capable of inducing apoptosis in numerous cellular systems. In this review, we describe both properties and mode of action of curcumin on carcinogenesis, gene expression mechanisms and drug metabolism.

Method optimization for fecal sample collection and fecal DNA extraction.

BACKGROUND: This is the third in a series of publications presenting formal method validation for biospecimen processing in the context of accreditation in laboratories and biobanks. We report here optimization of a stool processing protocol validated for fitness-for-purpose in terms of downstream DNA-based analyses. METHODS: Stool collection was initially optimized in terms of sample input quantity and supernatant volume using canine stool. Three DNA extraction methods (PerkinElmer MSM I®, Norgen Biotek All-In-One®, MoBio PowerMag®) and six collection container types were evaluated with human stool in terms of DNA quantity and quality, DNA yield, and its reproducibility by spectrophotometry, spectrofluorometry, and quantitative PCR, DNA purity, SPUD assay, and 16S rRNA gene sequence-based taxonomic signatures. RESULTS: The optimal MSM I protocol involves a 0.2 g stool sample and 1000 µL supernatant. The MSM I extraction was superior in terms of DNA quantity and quality when compared to the other two methods tested. Optimal results were obtained with plain Sarstedt tubes (without stabilizer, requiring immediate freezing and storage at -20°C or -80°C) and Genotek tubes (with stabilizer and RT storage) in terms of DNA yields (total, human, bacterial, and double-stranded) according to spectrophotometry and spectrofluorometry, with low yield variability and good DNA purity. No inhibitors were identified at 25 ng/µL. The protocol was reproducible in terms of DNA yield among different stool aliquots. CONCLUSIONS: We validated a stool collection method suitable for downstream DNA metagenomic analysis. DNA extraction with the MSM I method using Genotek tubes was considered optimal, with simple logistics in terms of collection and shipment and offers the possibility of automation. Laboratories and biobanks should ensure protocol conditions are systematically recorded in the scope of accreditation.

Effect of chemopreventive agents on glutathione S-transferase P1-1 gene expression mechanisms via activating protein 1 and nuclear factor kappaB inhibition.

Glutathione S-transferase P1-1 (GSTP1-1) is a phase II drug metabolism enzyme implicated in carcinogenesis and development of resistance to anti-cancer drugs. It was previously shown that both activating protein 1 (AP-1) and nuclear factor kappaB (NF-kappaB) are involved in its regulation. In the present study we examined the inhibitory effect of several chemopreventive agents on the tumor necrosis factor (TNF) alpha- or 12-O-tetradecanoylphorbol 13 acetate (TPA)-induced promoter activity of GSTP1-1, as demonstrated by transient transfection experiments in K562 and U937 leukemia cells. Our results provide evidence for a differential effect of chemopreventive agents such as beta-lapachone, emodin, sanguinarine and capsaicin, which significantly inhibit reporter gene expression as well as TNFalpha- and TPA-induced binding of AP-1 and NF-kappaB, whereas trans-anethole and silymarin do not produce any inhibitory effect. Our results demonstrate the ability of selected chemopreventive agents to decrease GSTP1-1 gene expression mechanisms and could thus contribute to reduce the incidence of glutathione related drug resistance in human leukemia.

Curcumin stability and its effect on glutathione S-transferase P1-1 mRNA expression in K562 cells.

To investigate the stability of curcumin in physiological media, the absorption variation of a curcumin solution was measured in 0.1% and 10% FCS. Under daylight conditions, curcumin degraded very rapidly in 0.1% FCS and was found to be more stable in higher serum concentrations. Under dark conditions, almost no decomposition could be observed after 2 h, whether the measurements were performed in 0.1% or 10% FCS. Furthermore, depending on the medium concentration, differential glutathione S-transferase P1-1 mRNA expression could be observed in K562 cells after incubation with curcumin. Indeed, incubation in 0.1% FCS led to a decrease of mRNA expression, whereas incubation in 10% FCS induced an increase of mRNA production.

5-aza-2'-deoxycytidine-mediated c-myc Down-regulation triggers telomere-dependent senescence by regulating human telomerase reverse transcriptase in chronic myeloid leukemia.

Increased proliferation rates as well as resistance to apoptosis are considered major obstacles for the treatment of patients with chronic myelogenous leukemia (CML), thus highlighting the need for novel therapeutic approaches. Since senescence has been recognized as a physiological barrier against tumorigenesis, senescence-based therapy could represent a new strategy against CML. DNA demethylating agent 5-aza-2'-deoxycytidine (DAC) was reported to induce cellular senescence but underlying mechanisms remain to be elucidated. Here, we report that exposure to DAC triggers senescence in chronic leukemia cell lines as evidenced by increased senescence-associated ß-galactosidase activity and lysosomal mass, accompanied by an up-regulation of cell cycle-related genes. We provide evidence that DAC is able to decrease telomere length, to reduce telomerase activity and to decrease human telomerase reverse transcriptase (hTERT) expression through decreased binding of c-myc to the hTERT promoter. Altogether, our results reveal the role of c-myc in telomere-dependent DAC-induced senescence and therefore provide new clues for improving chronic human leukemia treatments.

Impact of postpartum information about pertussis booster to parents in a university maternity hospital.

Parent-to-infant transmission of pertussis remains an issue in France. Although adult booster vaccination was introduced in 2004 as part of a cocooning strategy targeted primarily to parents of young infants, vaccination coverage in this population has remained low. The aim of this study was to evaluate the impact on vaccination coverage, over two consecutive years, of a protocol in which information about the pertussis booster and a prescription for pertussis vaccine were given to parents upon discharge from a French university maternity hospital. A questionnaire was administered to mothers two months after delivery, during two 3-month periods in 2008 and 2009. Participation rates were 67% (first period) and 76.3% (second period). Information about pertussis was delivered mainly by paediatricians and midwives and was considered clear and pertinent in more than 95% of cases. In 2009, 69% of mothers and 63% of fathers who received a prescription for pertussis vaccine before discharge from the maternity declared being vaccinated, with no difference as compared to 2008. Vaccination was done by a general practitioner (95.9%) and mostly in the first month after birth (81%). Postpartum information about pertussis was successfully implemented and well understood by parents in the maternity hospital and should contribute towards increasing pertussis vaccination coverage in parents of young children.

Anti-proliferative potential of curcumin in androgen-dependent prostate cancer cells occurs through modulation of the Wingless signaling pathway.

Activation of the Wingless (Wnt)/ß-catenin signaling pathway contributes to prostate tumorigenesis and metastasis. Depending of the stage of prostate cancer development, current drug therapies are of limited efficiency, so that prevention with natural compounds appears as an attractive strategy especially due to the slow progressive development of prostate cancer. We report here that the chemopreventive agent curcumin from the rhizome of Curcuma longa was able to affect cell proliferation of androgen-dependent prostate cancer through the induction of cell cycle arrest in G2 and modulation of Wnt signaling. Curcumin decreases the level of Tcf-4, CBP and p300 proteins implicated in the Wnt transcriptional complex that leads to the decrease of ß-catenin/Tcf-4 transcriptional activity and of the expression of ß-catenin target genes (cyclin D1 and c-myc). Subsequent cell death induction is linked to autophagy. Interestingly, in androgen-independent prostate cancer cells, curcumin does not affect Wnt/ß-catenin transcriptional activity. Altogether our results suggest that curcumin is an interesting chemopreventive agent for early stage prostate cancer.

COX-2 inhibitors block chemotherapeutic agent-induced apoptosis prior to commitment in hematopoietic cancer cells.

Enzymatic inhibitors of pro-inflammatory cyclooxygenase-2 (COX-2) possess multiple anti-cancer effects, including chemosensitization. These effects are not always linked to the inhibition of the COX-2 enzyme. Here we analyze the effects of three COX-2 enzyme inhibitors (nimesulide, NS-398 and celecoxib) on apoptosis in different hematopoietic cancer models. Surprisingly, COX-2 inhibitors strongly prevent apoptosis induced by a panel of chemotherapeutic agents. We selected U937 cells as a model of sensitive cells for further studies. Here, we provide evidence that the protective effect is COX-independent. No suppression of the low basal prostaglandin (PG)E(2) production may be observed upon treatment by COX-2 inhibitors. Besides, the non-active celecoxib analog 2,5-dimethyl-celecoxib is able to protect from apoptosis as well. We demonstrate early prevention of the stress-induced apoptotic signaling, prior to Bax/Bak activation. This preventive effect fits with an impairment of the ability of chemotherapeutic agents to trigger apoptogenic stress. Accordingly, etoposide-induced DNA damage is strongly attenuated in the presence of COX-2 inhibitors. In contrast, COX-2 inhibitors do not exert any anti-apoptotic activity when cells are challenged with physiological stimuli (anti-Fas, TNFα or Trail) or with hydrogen peroxide, which do not require internalization and/or are not targeted by chemoresistance proteins. Altogether, our findings show a differential off-target anti-apoptotic effect of COX-2 inhibitors on intrinsic vs. extrinsic apoptosis at the very early steps of intracellular signaling, prior to commitment. The results imply that an exacerbation of the chemoresistance phenomena may be implicated.

Valproic acid perturbs hematopoietic homeostasis by inhibition of erythroid differentiation and activation of the myelo-monocytic pathway.

As a histone deacetylase inhibitor, valproic acid (VPA) is a candidate for anticancer therapy. Besides, VPA exhibits various mechanisms of action and its effects on the molecular basis of hematopoiesis remain unclear. To study the effects of VPA on the hematopoietic system, we performed microarray analysis using K562 cells treated with 1mM VPA over a 72h time course. The association between gene ontology (GO) terms and the lists of differentially expressed genes was tested using the Bioconductor package GOstats. Enrichment analysis for cellular differentiation pathways was performed based on manually curated gene lists. Results from microarray analysis were confirmed by studying cell differentiation features at the molecular and cellular levels using other hematopoietic cell lines as well as hematopoietic stem/progenitor CD34(+) cells. Microarray analysis revealed 3440 modulated genes in the presence of VPA. Genes involved in the granulo-monocytic differentiation pathway were up-regulated while genes of the erythroid pathway were down-regulated. This was confirmed by analyzing erythrocytic and myeloid membrane markers and lineage-related gene expression in HEL, MEG01, HL60 as well as CD34(+) cells. Moreover, GATA-1 and its co-factors (FOG1, SP1) were down-regulated, while myelopoiesis activator PU.1 was up-regulated, in agreement with an inhibition of erythropoiesis. Our functional profiling and cell phenotyping approach demonstrates that VPA is able to alter hematopoietic homeostasis by modifying the cell population balance in the myeloid compartment. This may lead to a potential failure of erythropoiesis in patients with cancer or chronic inflammatory diseases having a well-described propensity to anemia.

UNBS1450, a steroid cardiac glycoside inducing apoptotic cell death in human leukemia cells.

Cardiac steroids are used to treat various diseases including congestive heart failure and cancer. The aim of this study was to investigate the anti-leukemic activity of UNBS1450, a hemi-synthetic cardenolide belonging to the cardiac steroid glycoside family. Here, we report that, at low nanomolar concentrations, UNBS1450 induces apoptotic cell death. Subsequently, we have investigated the molecular mechanisms leading to apoptosis activation. Our results show that UNBS1450 inhibits NF-κB transactivation and triggers apoptosis by cleavage of pro-caspases 8, 9 and 3/7, by decreasing expression of anti-apoptotic Mcl-1 and by recruitment of pro-apoptotic Bak and Bax protein eventually resulting in cell death.

The inhibition of TNF-alpha-induced NF-kappaB activation by marine natural products.

The deregulated activation of NF-kappaB is associated with cancer development and inflammatory diseases. With an aim to find new NF-kappaB inhibitors, we purified and characterized compounds from extracts of the Fijian sponge Rhabdastrella globostellata, the crinoid Comanthus parvicirrus, the soft corals Sarcophyton sp. nov. and Sinularia sp., and the gorgonian Subergorgia sp. after an initial screening of 266 extracts from different marine origins. Results obtained show that selected purified compounds had a cytotoxic effect on the human leukaemia cell line K562, inhibited both TNF-alpha-induced NF-kappaB-DNA binding as well as TNF-alpha-induced IkappaBalpha degradation and nuclear translocation of p50/p65. Furthermore, we observed the inhibition of NF-kappaB activation induced by an overexpression of IKKbeta. Interestingly, natural products inhibited IKKbeta kinase as well as the 26S proteasome proteolytic activity.