Biosynthetic meshes in contaminated fields: where are we now? A systematic review and meta-analysis in humans.

PURPOSE: Selection of an appropriate mesh reinforcement for hernia repair in contaminated fields is a significant problem for surgeons. To date the proper mesh for contaminated fields has not been found. Biosynthetic meshes have emerged as new treatment option in contaminated fields. This study aims to evaluate the postoperative outcomes of biosynthetic meshes in contaminated fields. METHODS: Systematic electronic search (PubMed, Medline, Embase, Scopus), according to PRISMA criteria, was performed. A literature search of scientific papers was performed by two reviewers until April 2021. Articles were chosen based on reference to biosynthetic meshes, their use in infected fields, and in human subjects. GRADE methodology and the modified Newcastle-Ottawa scale were used to assess the quality of studies. According to CDC-Centers for Disease Control classes patients were divided into two subgroups, group 1 (CDC class 2) and group 2 (CDC classes 3-4). RESULTS: The research included 21 articles and 1619 patients were analyzed. Long-term follow-up showed a significant higher recurrence rate than short-term follow-up. P < 0.001. Meta-analysis of these studies showed that the SSI were significantly higher in CDC classes 3-4 than CDC class 2 (P < 0.01). No differences were found in SSO (P = 0.06) and recurrence (P = 0.37) rate among the two groups. Phasix™ was the most common mesh in 15 studies. The mean follow-up was 23.0 months. The surgical site infection (SSI) rate was 17.3%. The surgical site occurrence (SSO) rate was 32.4%. Recurrence rate was 11.5%. CONCLUSION: This is the first systematic review and meta-analysis on the clinical outcomes of abdominal wall repair using biosynthetic mesh in contaminated-infected settings. The results show good results in patients at high risk of postoperative wound complications. The aim of this study is to add to the growing literature on biosynthetic mesh a picture of current literature evidence to help future researchers performing further studies on this topic.

PROPHYlactic Implantation of BIOlogic Mesh in peritonitis (PROPHYBIOM): a prospective multicentric randomized controlled trial.

BACKGROUND: Patients undergoing emergency surgery for peritonitis are at increased risk of abdominal wall-related complications. In patients with peritonitis, the risk of incisional hernia (IH) is extremely elevated. The evaluation of quality of life of patients with incisional hernia showed lower mean scores on physical components of health-related quality of life and body image. Furthermore, the arise of a post-operative abdominal wall complication (i.e., wound dehiscence, evisceration and IH) greatly increases morbidity and mortality rates and prolongs the hospitalization. METHODS: The present study aims to evaluate the efficacy of the use of a swine dermal collagen prosthesis implanted preperitoneally as a prophylactic procedure in urgency/emergency setting against abdominal wall complications in patients operated with contaminated/infected field in peritonitis. The sample size was defined in 90 patients divided in two arms (prosthesis positioning versus normal wall abdominal closure). The follow-up will be performed at 3, 6, and 12 months after surgery. The percentage of incisional hernias, wound infections, and adverse events will be investigated by physical examination and ultrasound. DISCUSSION: The objective is to evaluate the possibility to reduce the incisional hernia rate in patients undergoing urgent/emergent laparotomy in contaminated/infected field with peritonitis by using swine dermal collagen prosthesis preperitoneal positioning as a prophylactic procedure. TRIAL REGISTRATION: ClinicalTrials.gov NCT04681326. Registered (retrospectively after first patient recruited) on 23 December 2020.

Acute supralevator abscess: the little we know.

INTRODUCTION: Acute supralevator abscess (SLA) is an uncommon and complicated form of anorectal sepsis. Its correct management is crucial to avoid complex iatrogenic fistula formation. A comprehensive review of the literature was conducted to determine the incidence of SLA and the surgical outcome with particular reference to the direction of drainage. METHODS: A search of Medline, PubMed and the Cochrane Library was performed to identify all studies reporting surgical drainage of SLA. FINDINGS: A total of 19 studies were identified, including 563 patients. The only two prospective studies reported an incidence of SLA of 10% and 3% in 68 and 100 patients, respectively, with anorectal sepsis. In 17 retrospective studies, the incidence ranged from 0% to 28%. Magnetic resonance imaging (MRI) was performed routinely in only one study. The surgical anatomical classification of the abscess was described in six studies diagnosed at surgery. The direction of surgical drainage whether 'inwards' (into the lumen) or 'outwards' (into the ischioanal fossa) was stated in only six studies. In two of these, the direction of drainage was contradictory to the recommendation made by Parks et al. Recurrent sepsis was reported in eight studies and ranged from 0% to 53%. CONCLUSIONS: Detailed and prospective data on acute SLA are lacking. Its real incidence is unclear and it is not possible to analyse surgical outcomes conclusively according to different direction of drainage. The routine use of MRI in complicated anorectal sepsis would specify the surgical anatomy of SLA before any drainage is carried out.

The impact of transanal local excision of early rectal cancer on completion rectal resection without neoadjuvant chemoradiotherapy: a systematic review.

BACKGROUND: The impact of transanal local excision (TAE) of early rectal cancer (ERC) on subsequent completion rectal resection (CRR) for unfavorable histology or margin involvement is unclear. The aim of this study was to provide a comprehensive review of the literature on the impact of TAE on CRR in patients without neoadjuvant chemoradiotherapy (CRT). METHODS: We performed a systematic review of the literature up to March 2020. Medline and Cochrane libraries were searched for studies reporting outcomes of CRR after TAE for ERC. We excluded patients who had neoadjuvant CRT and endoscopic local excision. Surgical, functional, pathological and oncological outcomes were assessed. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed. RESULTS: Sixteen studies involving 353 patients were included. Pathology following TAE was as follows T0 = 2 (0.5%); T1 = 154 (44.7%); T2 = 142 (41.2%); T3 = 43 (12.5%); Tx = 3 (0.8%); T not reported = 9. Fifty-three percent were > T1. Abdominoperineal resection (APR) was performed in 80 (23.2%) patients. Postoperative major morbidity and mortality occurred in 22 (11.4%) and 3 (1.1%), patients, respectively. An incomplete mesorectal fascia resulting in defects of the mesorectum was reported in 30 (24.6%) cases. Thirteen (12%) patients developed recurrence: 8 (3.1%) local, 19 (7.3%) distant, 4 (1.5%) local and distant. The 5-year cancer-specific survival was 92%. Only 1 study assessed anal function reporting no continence disorders in 11 patients. In the meta-analysis, CRR after TAE showed an increased APR rate (OR 5.25; 95% CI 1.27-21.8; p 0.020) and incomplete mesorectum rate (OR 3.48; 95% CI 1.32-9.19; p 0.010) compared to primary total mesorectal excision (TME). Two case matched studies reported no difference in recurrence rate and disease free survival respectively. CONCLUSIONS: The data are incomplete and of low quality. There was a tendency towards an increased risk of APR and poor specimen quality. It is necessary to improve the accuracy of preoperative staging of malignant rectal tumors in patients scheduled for TAE.

Identification of a caleosin associated with hazelnut (Corylus avellana L.) oil bodies.

Caleosins are involved in several cellular and biological processes that are closely associated with the synthesis, degradation and stability of oil bodies (OB). Because of the importance and the multiple roles of these OB-associated proteins, in silico identification of sequences corresponding to putative caleosins in the hazelnut genome has been performed, and the association with seed OB was verified using a proteomic approach. Five full-length sequences (CavCLO-H1, CavCLO-H2, CavCLO-H3, CavCLO-L1, CavCLO-L2), belonging to the two groups of caleosins (H and L), have been identified in the hazelnut genome. The number of identified caleosins is in agreement with that previously observed in other plant species, confirming that caleosins comprise small gene families in plants. A proteomic approach allowed us to verify only the presence of CavCLO-H1 in hazelnut OB, suggesting that several members inside this family could have different roles during plant growth and development. In silico analysis also suggests that CavCLO-H1 may act as a peroxygenase.

Ventral cervical versus bilateral lateral approach for extirpation of mandibular and medial retropharyngeal lymph nodes in dogs.

OBJECTIVE: To compare ventral cervical and bilateral lateral incisions for extirpation of mandibular and medial retropharyngeal lymph nodes in dogs. STUDY DESIGN: Prospective randomized, crossover controlled cadaver trial. SAMPLE POPULATION: Eight veterinarians with advanced surgical training. METHODS: Study participants were randomized to perform both techniques on paired cadavers. Time to extirpation of the first and last lymph node, length of incisions, and complications were recorded for both techniques. Participants were asked to rate satisfaction with their ability to identify local anatomy and lymph nodes as well as overall preferred technique by using a 10-point numerical rating scale. RESULTS: The total length of skin incised for the bilateral lateral approach exceeded that of the ventral cervical approach by 52.1 mm (mean, P < .001). The surgical time for removal of all 4 lymph nodes did not differ between the 2 approaches. The bilateral lateral approach was preferred by 62.5% (5/8) of participants for visualization of mandibular lymph nodes, and the ventral cervical approach was preferred by 87.5% (7/8) of participants for visualization of local anatomy. Overall, 62.5% (5/8) preferred the ventral cervical approach and 37.5% (3/8) preferred the bilateral lateral approach. CONCLUSION: The ventral cervical approach was preferred by participants for its perceived superior visualization of local anatomy and access to lymph nodes for removal. This approach also resulted in an overall shorter incision length. CLINICAL SIGNIFICANCE: A ventral cervical or bilateral lateral approach allows successful removal of the medial mandibular and retropharyngeal lymph nodes in dogs, and surgical approach may be selected according to individual preference.

Increased Systemic Cytokine/Chemokine Expression in Asthmatic and Non-asthmatic Patients with Bacterial, Viral or Mixed Lung Infection.

This study was aimed to determine the profiles of serum cytokines (IL-1ß, TNF-α, IL-4, IL-5) and chemokines (MCP-1: monocyte chemoattract protein-1 and RANTES: regulated on activation normal T cell expressed and secreted) in individuals with an asthmatic versus a non-asthmatic background with bacterial, viral or mixed acute respiratory infection. Asthmatic (n = 14) and non-asthmatic (n = 29) patients with acute viral, bacterial or mixed (bacterial and viruses) respiratory infection were studied. Patients were also analysed as individuals with pneumonia or bronchitis. Healthy individuals with similar age and sex (n = 10) were used as controls. Cytokine/chemokine content in serum was determined by ELISA. Increased cytokine/chemokine concentration in asthmatic and non-asthmatic patients was observed. However, higher concentrations of chemokines (MCP-1 and RANTES) in asthmatic patients infected by viruses, bacteria or bacteria and viruses (mixed) than in non-asthmatic patients were observed. In general, viral and mixed infections were better cytokine/chemokine inducers than bacterial infection. Cytokine/chemokine expression was similarly increased in both asthmatic and non-asthmatic patients with pneumonia or bronchitis, except that RANTES remained at normal levels in bronchitis. Circulating cytokine profiles induced by acute viral, bacterial or mixed lung infection were not related to asthmatic background, except for chemokines that were increased in asthmatic status.

Efficacy and toxicity of carboplatin and cytarabine chemotherapy for dogs with relapsed or refractory lymphoma (2000-2013).

Medical records of 22 dogs treated with carboplatin (n = 8) or carboplatin and cytarabine (n = 14) chemotherapy for relapsed or refractory lymphoma between 2000 and 2013 were retrospectively reviewed. The clinical response rate was 18.2% (4/22). Median time to progression was 18 days (56 for responders; 12 for non-responders, P = 0.0006). Median overall survival time was 28 days (109 for responders; 21 for non-responders, P = 0.0007). Thrombocytopenia and neutropenia occurred in 84.2% (16/19) and 52.6% (10/19), respectively. Grade IV thrombocytopenia and neutropenia occurred in 56.3% (9/16) and 60.0% (6/10), respectively. Dogs that received both drugs were more likely to become neutropenic (P = 0.022) or thrombocytopenic (P = 0.001) than dogs receiving carboplatin alone. All responders received both drugs giving a 28.6% (4/14) response rate for the combination. Although some dogs responded to the combination, toxicity was high and the responses were not durable. With adequate supportive care, this protocol may be an acceptable rescue option for some dogs.

Use of routine histopathology and factor VIII-related antigen/von Willebrand factor immunohistochemistry to differentiate primary hemangiosarcoma of bone from telangiectatic osteosarcoma in 54 dogs.

Hemangiosarcoma (HSA) of bone and telangiectatic osteosarcoma (tOSA) can appear similar histologically, but differ in histogenesis (malignant endothelial cells versus osteoblasts), and may warrant different treatments. Immunohistochemistry (IHC) for endothelial cell marker factor VIII-related antigen/von Willebrand factor (FVIII-RAg/vWF) is a well-documented ancillary test to confirm HSA diagnoses in soft tissues, but its use in osseous HSA is rarely described. Archived samples of 54 primary appendicular bone tumours previously diagnosed as HSA or tOSA were evaluated using combination routine histopathology (RHP) and IHC. Approximately 20% of tumours were reclassified on the basis of FVIII-RAg/vWF immunoreactivity, typically from an original diagnosis of tOSA to a reclassified diagnosis of HSA. No sample with tumour osteoid clearly identified on RHP was immunopositive for FVIII-RAg/vWF. RHP alone was specific but not sensitive for diagnosis of HSA, compared with combination RHP and IHC. Routine histopathological evaluation in combination with FVIII-RAg/vWF IHC can help differentiate canine primary appendicular HSA from tOSA.

Langmuir monolayers and Differential Scanning Calorimetry for the study of the interactions between camptothecin drugs and biomembrane models.

CPT-11 and SN-38 are camptothecins with strong antitumor activity. Nevertheless, their severe side effects and the chemical instability of their lactone ring have questioned the usual forms for its administration and have focused the current research on the development of new suitable pharmaceutical formulations. This work presents a biophysical study of the interfacial interactions of CPT-11 and SN-38 with membrane mimetic models by using monolayer techniques and Differential Scanning Calorimetry. The aim is to get new insights for the understanding of the bilayer mechanics after drug incorporation and to optimize the design of drug delivery systems based on the formation of stable bilayer structures. Moreover, from our knowledge, the molecular interactions between camptothecins and phospholipids have not been investigated in detail, despite their importance in the context of drug action. The results show that neither CPT-11 nor SN-38 disturbs the structure of the complex liposome bilayers, despite their different solubility, that CPT-11, positively charged in its piperidine group, interacts electrostatically with DOPS, making stable the incorporation of a high percentage of CPT-11 into liposomes and that SN-38 establishes weak repulsive interactions with lipid molecules that modify the compressibility of the bilayer without affecting significantly neither the lipid collapse pressure nor the miscibility pattern of drug-lipid mixed monolayers. The suitability of a binary and a ternary lipid mixture for encapsulating SN-38 and CPT-11, respectively, has been demonstrated.

Quality of life measurement in prospective studies of cancer treatments in dogs and cats.

BACKGROUND: Quality of life (QOL) is an important consideration in healthcare decision-making for pets with cancer. To determine the effect of disease and treatment on pet QOL, this important variable should be objectively measured as an outcome in veterinary cancer studies. OBJECTIVES: To determine the prevalence and methodology of QOL measurement in a sample of recently published reports of prospective studies evaluating cancer treatments in client-owned dogs and cats; to characterize reporting of QOL outcomes and to identify article characteristics associated with QOL measurement. METHODS: English-language reports of prospective studies of cancer treatments in dogs and cats published from 2008 to 2013 were identified using medical research databases combined with a hand-searching strategy. Data pertaining to general article characteristics and QOL measurement were abstracted and summarized. RESULTS: Reports of 144 eligible studies were identified. QOL was measured in 16 (11.1%) studies, with 8 (5.6%) reporting the results. All studies that measured QOL reported using unvalidated instruments, or did not report how QOL was assessed. Only 1 study provided sufficient information for QOL measurements to be replicated. Recently published articles (2011-2013) were significantly more likely to report measuring QOL, compared with earlier articles. CONCLUSIONS: Quality of life of pets undergoing cancer treatment is largely unreported and cannot be meaningfully compared across treatments or disease states using the existing literature. Reliable, validated instruments are needed to facilitate the measurement and comparison of pet QOL in veterinary cancer research. Consistent reporting practices could improve transparency and interpretation of QOL results.

Olive oil adulterated with hazelnut oils: simulation to identify possible risks to allergic consumers.

According to European Union Regulation EC 1531/2001, olive oil labelled as "extra-virgin" should be cold-pressed and contain no refined oil or oil from other oleaginous seeds or nuts. Adulteration of extra virgin olive oil (EVOO) with hazelnut oil (HAO) is a serious concern both for oil suppliers and consumers. The high degree of similarity between the two fats complicates the detection of low percentages of HAO in EVOO. Many analytical approaches have been developed in recent years to trace HAO in EVOO, principally based on chromatographic analyses, differential scanning calorimetry or nuclear magnetic resonance. In addition adulteration of EVOO with HAO may introduce hazelnut-derived allergens. The aim of this work was to analyse the protein and allergen content of EVOO intentionally spiked with raw cold-pressed HAO or solvent-extracted HAO. SDS-PAGE analysis confirmed the presence of hazelnut proteins in solvent-extracted HAO with molecular masses ranging 10-60 kDa. In contrast, cold-pressed HAO showed no traces of protein. In spiked EVOO, solvent-extracted HAO was still detectable at a 1% contamination level. Several bands on SDS-PAGE migrated at apparent molecular masses coinciding with known allergens, such as Cor a 1 (approximately 17 kDa), Cor a 2 (approximately 14 kDa), Cor a 8 (approximately 12 kDa), oleosin (approximately 17 kDa) and Cor a 9 (approximately 60 kDa). MALDI-TOF MS analysis confirmed the presence of two oleosin isoforms and of Cor a 9. Immunoblotting demonstrated that an allergic patient with known reactivity to Cor a 1 and Cor a 2 recognized a 17-kDa band in solvent-extracted HAO. In conclusion, we have shown that adulteration of extra virgin olive oil with solvent-extracted hazelnut oil can be traced by simple SDS-PAGE analysis, and that adulteration introduces a potential risk for hazelnut allergic patients.

Does prolactin induce apoptosis? Evidences in a prostate cancer in vitro model.

BACKGROUND: Prolactin (PRL) regulates prostate growth and differentiation. Some studies have suggested that PRL has a pro-apoptotic effect on a myeloma cell line and in newt spermatogonia. The proliferative effect of PRL on prostate cancer cell lines is, however, a controversial area. AIM: On this account, we evaluated the effects of PRL on the prostate cancer cell lines LNCaP and PC3 apoptosis and proliferation. MATERIALS AND METHODS: LNCaP and PC3 cells were exposed to increasing concentrations of PRL for 24, 48, 72 and 96 hours. Staining with propidium iodide (PI) and TUNEL assay followed by flow cytometry were used to detect apoptosis. LNCaP and PC3 proliferation was assessed by optical microscopy counting. RESULTS: PRL induced a dose-dependent decrease of DNA content and an increase of DNA fragmentation in LNCaP after 96 hours of incubation. These effects were observed with physiological concentrations of PRL and were counteracted by a prolactin receptor antagonist. On the other hand, PRL did not have any effect on DNA content or fragmentation in PC3 cells. No effect of PRL on LNCaP and PC3 proliferation was found. CONCLUSIONS: This study indicates that PRL induces apoptosis in the androgen-responsive cell line LNCaP, whereas no effect was observed in the androgen-insensitive PC3 cell line. These findings suggest that androgen responsiveness may be required for PRL to be effective on prostatic cells.

Central neurocytoma of the fourth ventricle. Case history.

Central neurocytomas are low-grade tumours of neuronal origin, affecting mainly young patients and usually located in the lateral or third ventricle. We report a rare case of central neurocytoma at the fourth ventricle level. Magnetic resonance imaging showed a homogeneously enhancing mass lesion at the fourth ventricle. Gross-total surgical removal was achieved. The histological diagnosis was of central neurocytoma but the lesion showed a fairly elevated Ki-67 index (6%). Given this finding, close neuroimaging monitoring was performed and at the moment the patient is free of recurrence.

Silencing of endogenous IGFBP-5 by micro RNA interference affects proliferation, apoptosis and differentiation of neuroblastoma cells.

Signal transduction through the IGF axis is implicated in proliferation, differentiation and survival during development and adult life. The IGF axis includes the IGF binding proteins (IGFBPs) that bind IGFs with high affinity and modulate their activity. In neuroblastoma (NB), a malignant childhood tumor, we found that IGFBP-5 is frequently expressed. Since NB is an IGF2-sensitive tumor, we investigated the relevance and the function of endogenous IGFBP-5 in LAN-5 and in SY5Y(N) cell lines transfected with micro and small interfering RNAs directed to IGFBP-5 mRNA. Cells in which IGFBP-5 expression was suppressed were growth-inhibited and more prone to apoptosis than the parental cell line and controls. Apoptosis was further enhanced by X-ray irradiation. The ability of these cells to undergo neuronal differentiation was impaired after IGFBP-5 inhibition but the effect was reversed by exposure to recombinant IGFBP-5. Together, these data demonstrate the importance of IGFBP-5 for NB cell functions and suggest that IGFBP-5 might serve as a novel therapeutic target in NB.

Spinal epidural hematoma following coronary thrombolysis. A case report.

A case of cervicothoracic spontaneous spinal epidural hematoma (SSEH) following coronary thrombolysis with r-TPA and intravenous heparin is reported. The clinical picture is discussed, as well as the importance of rapid neuroradiological diagnosis (with spinal MRI being the method of choice) and surgical treatment. Anyway, in these patients, thorough cardiac function evaluation and rapid correction of any clotting disorder is necessary prior to surgery. With the increasing use of fibrinolytic therapy this complication would be more frequent. This underlines the importance of prompt recognition and adequate treatment.

Cyclin D1-dependent regulation of B-myb activity in early stages of neuroblastoma differentiation.

Levels of the transcription factor B-myb must be down-regulated to allow terminal differentiation of neuroectodermal cells and yet its constitutive expression induces early markers of neural differentiation. Thus, we investigated potential mechanisms of enhanced B-myb activity in early stages of neural differentiation. We report here that B-myb expression does not decrease, cyclin A and Sp1 levels remain constant while p21 levels increase continuously upon retinoic acid-induced differentiation of the LAN-5 neuroblastoma cell line. In contrast, cyclin D1 expression is down-regulated at the onset of the differentiative process by protein destabilization. Luciferase assays of promoter activity indicate that B-myb-dependent transactivation is enhanced in LAN-5 cells treated with retinoic acid (RA) for 24 h. The enhancement is independent from cyclin A but is suppressed by a degradation-resistant mutant form of cyclin D1. The importance of cyclin D1 in controlling B-myb activity is further suggested by co-immunoprecipitation experiments, showing that the amount of cyclin D1 co-immunoprecipitated with B-myb decreased after RA treatment. Thus, B-myb may play an active role in the early stages of differentiation when its transactivation activity is enhanced as a consequence of cyclin D1 down-modulation.

Proteolysis of beta-casein as a marker of Grana Padano cheese ripening.

Proteolysis has a critical role in defining the typical organoleptic characteristics of Grana Padano, a well-known Italian cheese. During the ripening process, hydrolysis of beta-casein produces different fragments, the most abundant and widely studied of which are gamma-caseins, three polypeptides containing the HOOC-terminal portion of beta-casein. By sodium dodecyl sulfate-PAGE and a specific anti-beta-casein monoclonal antibody, two beta-casein-derived bands were identified in Grana Padano cheese: betaa and betab. Thanks to the identification of the amino acid sequences, it was shown that: a) betaa contains gamma1-casein [beta-casein (29-209)] and the correlated peptide [beta-casein (30-209)]; b) betab contains gamma2-casein [beta-casein (106-209)] and gamma3-casein [beta-casein (108-209)]. The production of betaa and betab by the three enzymes most involved in cheese proteolysis (pepsin, chymosin, and plasmin) was evaluated by performing in vitro digestions. A significant correlation between abundance of some polypeptides and ripening process was shown.

[Spigelian hernia: 3 case reports]. / Ernia di Spigelio. Descrizione di tre casi clinici.

Spigelian hernia is an uncommon hernia of the abdominal wall, often not easily diagnosed. Three cases of Spigelian hernia are reported. In the first patient it was an incidental discovery, in the second one hernia was complicated by strangulation of the small bowel, in the third patient hernia was symptomatic without complications. In all the patients, in their previous clinical history, an operation for hernia or other abdominal pathologies was observed. These patients were treated surgically, using direct reconstruction of the abdominal wall in two cases, while a non-absorbable mesh was positioned in the preperitoneal space in the third patient. The anatomopathological and clinical features of Spigelian hernia are described and the problems in diagnosis discussed; in addition, the importance of surgical cure in incidental hernia is underlined.

The interferon regulatory factors 1 and 2 bind to a segment of the human c-myb first intron: possible role in the regulation of c-myb expression.

The preferential expression of the protooncogene c-myb in hematopoietic cells is in part regulated by a mechanism of transcriptional block in the first intron. By electrophoresis mobility shift assays using probes corresponding to different segments of the putative human c-myb intron 1 transcription pause region and nuclear extracts from myeloid leukemia HL 60 and fibroblast WI 38 cells, we detected a HL-60-specific DNA-protein complex with a 123-bp fragment containing binding sites for the interferon regulatory factors (IRFs) nuclear proteins. Formation of the DNA-protein complex was abrogated by competition with an oligomer containing the wild-type, but not the mutated, IRF binding site and the complex was specifically supershifted by the anti-IRF-1 or the anti-IRF-2 antibody. Moreover, in vitro translated IRF-1 or IRF-2 protein did interact with the 123-bp c-myb intron 1 fragment. Upon TPA-induced differentiation, c-myb expression was readily down-modulated in parental HL 60 cells, but not in cells transfected with an antisense IRF-1 plasmid. Moreover, chloramphenicol acetyltransferase activity driven by a c-myb promoter containing the entire intron 1 was suppressed upon IRF-1, but not IRF-2 expression. Together, these results are consistent with the existence of a functional relationship between IRF-1 and c-myb in which IRF-1 negatively regulates c-myb expression at the transcriptional level by a mechanism that may depend on the interaction of IRF-1 with a segment of the c-myb gene implicated in transcription pausing.