Expression of p89c-Mybex9b, an alternatively spliced form of c-Myb, is required for proliferation and survival of p210BCR/ABL-expressing cells

The c-Myb gene encodes the p75c-Myb isoform and less-abundant proteins generated by alternatively spliced transcripts. Among these, the best known is pc-Mybex9b, which contains 121 additional amino acids between exon 9 and 10, in a domain involved in protein–protein interactions and negative regulation. In hematopoietic cells, expression of pc-Mybex9b accounts for 10–15% of total c-Myb; these levels may be biologically relevant because modest changes in c-Myb expression affects proliferation and survival of leukemic cells and lineage choice and frequency of normal hematopoietic progenitors. In this study, we assessed biochemical activities of pc-Mybex9b and the consequences of perturbing its expression in K562 and primary chronic myeloid leukemia (CML) progenitor cells. Compared with p75c-Myb, pc-Mybex9b is more stable and more effective in transactivating Myb-regulated promoters. Ectopic expression of pc-Mybex9b enhanced proliferation and colony formation and reduced imatinib (IM) sensitivity of K562 cells; conversely, specific downregulation of pc-Mybex9b reduced proliferation and colony formation, enhanced IM sensitivity of K562 cells and markedly suppressed colony formation of CML CD34+ cells, without affecting the levels of p75c-Myb. Together, these studies indicate that expression of the low-abundance pc-Mybex9b isoform has an important role for the overall biological effects of c-Myb in BCR/ABL-transformed cells

Targeting acute myeloid leukemia by drug-induced c-MYB degradation

Despite advances in our understanding of the molecular basis for particular subtypes of acute myeloid leukemia (AML), effective therapy remains a challenge for many individuals suffering from this disease. A significant proportion of both pediatric and adult AML patients cannot be cured and since the upper limits of chemotherapy intensification have been reached, there is an urgent need for novel therapeutic approaches. The transcription factor c-MYB has been shown to play a central role in the development and progression of AML driven by several different oncogenes, including mixed lineage leukemia (MLL)-fusion genes. Here, we have used a c-MYB gene expression signature from MLL-rearranged AML to probe the Connectivity Map database and identified mebendazole as a c-MYB targeting drug. Mebendazole induces c-MYB degradation via the proteasome by interfering with the heat shock protein 70 (HSP70) chaperone system. Transient exposure to mebendazole is sufficient to inhibit colony formation by AML cells, but not normal cord blood-derived cells. Furthermore, mebendazole is effective at impairing AML progression in vivo in mouse xenotransplantation experiments. In the context of widespread human use of mebendazole, our data indicate that mebendazole-induced c-MYB degradation represents a safe and novel therapeutic approach for AML

Rottura splenica “occulta” in paziente con mononucleosi infettiva

La rottura di milza può essere secondaria a traumi addominali (di solito chiusi) ovvero verificarsi spontaneamente su un organo sano o sede di alterazioni morfologiche secondarie a vari processi patologici. Tra le varie patologie responsabili di rottura occulta, le malattie infettive sono di gran lunga le più frequenti e tra queste un posto preminente ha la mononucleosi infettiva, che si complica con rottura splenica nello 0.5% dei casi, con una mortalità del 30%. Caso clinico. P.M., donna di 16 anni, è ricoverata in urgenza per addome acuto con anemizzazione ingravescente e incipiente instabilità emodinamica, cui si associa un quadro clinico suggestivo di mononucleosi infettiva, successivamente confermata sierologicamente e istologicamente. Confortati dal riscontro strumentale di grossa falda iperdensa pericapsulare splenica in continuità con spandimento peritoneale gravitario pelvico, abbiamo optato per una laparotomia esplorativa. Discussione. La rottura splenica nella mononucleosi si presenta invariabilmente con dolore in ipocondrio sinistro, raramente presente nelle forme non complicate; la sua insorgenza, pertanto, sia in paziente con recente diagnosi certa di mononucleosi sia in paziente con esclusivi reperti clinico-laboratoristici suggestivi di infezione acuta da virus di Epstein-Barr (EBV), obbliga all’esame ultrasonografico e/o alla TC di approfondimento, soprattutto nei casi in cui il dolore si associa a irradiazione alla spalla omolaterale (segno di Kehr), a segni di irritazione peritoneale e a instabilità emodinamica. Il trattamento della complicanza in esame è generalmente rappresentato dalla splenectomia in urgenza

Trattamento degli eventi perforativi post-colangiopancreatografia retrograda con sfinterotomia endoscopica. Esperienza personale

Trattamento degli eventi perforativi post-colangio­pancreatografia retrograda con sfinterotomia endoscopica. Esperienza personale. L.G. Angiò, G. Sfuncia, P. Viggiani, G. Faro, A. Bonsignore, M. Licursi, M. Soliera, M. Galati, A. Putortì Introduzione. La colangiopancreatografia retrograda endoscopica (CPRE) ha apportato reali progressi nella gestione delle patologie bilio-pancreatiche, in virtù della sua ambivalenza diagnostica e terapeutica. Le sue complicanze perforative insorgono in meno dell’1% dei pazienti, ma sono associate a una mortalità del 16%-18%. Casistica personale. Caso 1- F, 89 anni con ittero ostruttivo da calcolosi della via biliare principale (VBP) sottoposta a CPRE con sfinterotomia endoscopica (SE), nel corso della quale si verifica lesione tipo II per cui, vista la parziale bonifica della VBP ottenuta, si opta per un trattamento conservativo, con risoluzione in XII giornata post-CPRE. Caso 2- F, 53 anni con colangiti recidivanti e stenosi post-colecistectomia della VBP già trattata mediante stenting; per il verificarsi di lesione tipo I in corso di CPRE, si sottopone la paziente a intervento chirurgico in urgenza/emergenza con guarigione in XXIII giornata. Caso 3- M, 84 anni con colecistite litiasica, ittero ostruttivo, enfisema polmonare e cardiopatia ischemica; eseguita colecistostomia percutanea in urgenza, si procede successivamente a tentativo di CPRE con evidenza di lesione tipo I e, a causa delle comorbilità, si opta per un trattamento conservativo, non risolutivo, per poi procedere all’intervento chirurgico con exitus per complicanze cardio-respiratorie. Caso 4- M, 89 anni con ittero ostruttivo di ndd; interrotta la CPRE per complicanze respiratorie, si procede a colangiografia transeptica per cutanea (CTP) nel corso della quale si evidenzia una lesione tipo IV, che è trattata conservativamente con dimissione in XII giornata. Caso 5- F, 68 anni con colecistite litiasica e coledocolitiasi; in corso di CPRE con SE si verifica lesione tipo II con segni ingravescenti di addome acuto e, in considerazione del quadro clinico e dell’impossibilità di effettuare bonifica endoscopica della VBP, si dispone l’intervento chirurgico in urgenza/emergenza con exitus per complicanze respiratorie. Discussione. Nella diatriba esistente su quale debba essere il trattamento degli eventi perforativi post-CPRE con SE (intervento chirurgico immediato ovvero terapia conservativa), non possiamo non auspicare un atteggiamento eclettico sulla base delle peculiarità anatomo-cliniche del singolo caso

I tumori stromali gastrointestinali (GIST). Esperienza personale su tre casi a localizzazione nel tenue mesenteriale trattati in urgenza

ummary: Gastrointestinal stromal tumors (GISTs). Personal experience on three cases of the tumors of the small intestine complicated and emergency surgically treated. M. Licursi, A. Bonsignore, F. Fiumara, M. Soliera, G. Grillone, G. Faro, G Pirrone, L.G. Angiò Introduction. GISTs, a new nosological entity recently described, represent a peculiar model of solid tumor: the identification of the molecular mechanism responsible for the oncogenesis led to the development of a new drug (imatinib) active on the specific molecular target, represented by the product of the mutated proto-oncogene c-kit which is a tirosyne kinasi receptor that becomes constitutively active by mutation. Surgical resection, nevertheless, is still the primary treatment and it has to be as complete as possible. These two treatments can be integrated. GISTs are not uniformly kit-positive, and they can be alternatively due to mutations of the PDGFRA gene or, in patients with neurofibromatosis type 1 (NF-1), to generally isolated mutations of the NF-1 gene. Patients and methods. We describe 3 cases of kit-positive GISTs of the small intestine (SISTs), complicated and emergency surgically treated: case 1 - 53 years, female, with small bowel obstruction and concomitant acute intestinal bleeding; case 2 - 71 years, male, with NF-1 and acute intestinal bleeding; case 3 - 47 years, male, with perforation of the Treitz tract. The first two cases have been treated with intestinal resection and immediate mechanical anastomosis; the third one with resection of the pedunculated tumor at its base, where is situated the perforation too. Conclusions. SISTs (20-30%), with little or no symptoms in the initial phases, show notable diagnostic difficulties. Their aspecific and late clinical presentation - typical of this site and of the pathology that we are talking about - and the difficult physical-instrumental approach to small bowel limit the possibility of an accurate diagnosis and expose the patient to potentially fatal acute complications and to risks related to emergency surgery treatment that decreases the possibility of a radical resection

Corpi estranei endorettali introdotti per via anale. Case report

The Authors refer about two cases of retained rectal foreign bodies by trans-anal introduction as consequence of anal eroticism: a deodorant aerosol-can cap and a sizeable phallic object. These reports represent an occasion to talk about the etiology (the wide variety of foreign bodies) and the motivations (eroticism or sadism, clumsy diagnostic and therapeutic procedures, true or presume accidents) responsible for this pathological condition and to consider every therapeutic options employed during the past years, without forgetting that, despite difficulties, non-surgical extraction is to prefer, if possible, because of the negative prognostic implications often related to the surgical treatment. The Authors finally confirm, because of the severity of this pathological condition - with negative outcomes especially in that cases with complete or incomplete perforative complications (produced during introduction through the anus or during several attemps of extraction of the object or caused by its long staying in the rectum because of the patient’s denial of medical care) - the surgeons can’t put aside possible indication for surgical tratmen

Transcriptional repression of c-Myb and GATA-2 is involved in the biologic effects of C/EBPalpha in p210BCR/ABL-expressing cells

Ectopic C/EBPalpha expression in p210(BCR/ABL)-expressing hematopoietic cells induces granulocytic differentiation, inhibits proliferation, and suppresses leukemogenesis. To assess the underlying mechanisms, C/EBPalpha targets were identified by microarray analyses. Upon C/EBPalpha activation, expression of c-Myb and GATA-2 was repressed in 32D-BCR/ABL, K562, and chronic myelogenous leukemia (CML) blast crisis (BC) primary cells but only c-Myb levels decreased slightly in CD34(+) normal progenitors. The role of these 2 genes for the effects of C/EBPalpha was assessed by perturbing their expression in K562 cells. Ectopic c-Myb expression blocked the proliferation inhibition- and differentiation-inducing effects of C/EBPalpha, whereas c-Myb siRNA treatment enhanced C/EBPalpha-mediated proliferation inhibition and induced changes in gene expression indicative of monocytic differentiation. Ectopic GATA-2 expression suppressed the proliferation inhibitory effect of C/EBPalpha but blocked in part the effect on differentiation; GATA-2 siRNA treatment had no effects on C/EBPalpha induction of differentiation but inhibited proliferation of K562 cells, alone or upon C/EBPalpha activation. In summary, the effects of C/EBPalpha in p210(BCR/ABL)-expressing cells depend, in part, on transcriptional repression of c-Myb and GATA-2. Since perturbation of c-Myb and GATA-2 expression has nonidentical consequences for proliferation and differentiation of K562 cells, the effects of C/EBPalpha appear to involve dif-ferent transcription-regulated targets

c-Myb and its target Bmi1 are required for p190BCR/ABL leukemogenesis in mouse and human cells

Expression of c-Myb is required for normal hematopoiesis and for proliferation of myeloid leukemia blasts and a subset of T-cell leukemia, but its role in B-cell leukemogenesis is unknown. We tested the role of c-Myb in p190(BCR/ABL)-dependent B-cell leukemia in mice transplanted with p190(BCR/ABL)-transduced marrow cells with a c-Myb allele (Myb(f/d)) and in double transgenic p190(BCR/ABL)/Myb(w/d) mice. In both models, loss of a c-Myb allele caused a less aggressive B-cell leukemia. In p190(BCR/ABL)-expressing human B-cell leukemia lines, knockdown of c-Myb expression suppressed proliferation and colony formation. Compared with c-Myb(w/f) cells, expression of Bmi1, a regulator of stem cell proliferation and maintenance, was decreased in pre-B cells from Myb(w/d) p190(BCR/ABL) transgenic mice. Ectopic expression of a mutant c-Myb or Bmi1 enhanced the proliferation and colony formation of Myb(w/d) p190(BCR/ABL) B-cells; by contrast, Bmi1 downregulation inhibited colony formation of p190(BCR/ABL)-expressing murine B cells and human B-cell leukemia lines. Moreover, c-Myb interacted with a segment of the human Bmi1 promoter and enhanced its activity. In blasts from 19 Ph(1) adult acute lymphoblastic leukemia patients, levels of c-Myb and Bmi1 showed a positive correlation. Together, these findings support the existence of a c-Myb-Bmi1 transcription-regulatory pathway required for p190(BCR/ABL) leukemogenesis