Distinct biological impact of dephosphorylation vs. downregulation of p210Bcr-Abl: implications for imatinib mesylate response and resistance

Imatinib mesylate suppresses phosphorylation of its kinase target, Bcr-Abl. We hypothesized that loss of p210Bcr-Abl (the kinase target) may lead to imatinib mesylate resistance. We studied K562 cells [chronic myelogenous leukemia (CML) blast crisis line] and MO7E/MBA-1 cells (with MBA-1 cells representing MO7E cells stably transfected with BCR-ABL). Imatinib mesylate resistance developed when p210Bcr-Abl expression was abolished. Furthermore, K562 cells were significantly more growth suppressed after imatinib mesylate exposure than after downregulation of Bcr-Abl expression. Signaling pathways which were functional in the absence of Bcr-Abl expression (NF-kappaB and mitogen-activated protein kinase activation or the growth factor pathway) were disrupted when p210Bcr-Abl was present but dephosphorylated, suggesting that an intact, but enzymatically inactive Bcr-Abl, may interfere with critical growth/signaling pathways. Downregulation of p210Bcr-Abl may be a mechanism by which imatinib mesylate resistance emerges. Samples from three of 15 patients with imatinib mesylate-resistant CML blast crisis had undetectable levels of p210Bcr-Abl. We conclude that retention of a dephosphorylated p210Bcr-Abl has a biologic impact distinct from that of downregulation/loss of p210Bcr-Abl and, in a subset of patients, loss of the target of the kinase inhibitor may lead to imatinib mesylate resistance.     

Small bowel obstruction in an adolescent with pelvic inflammatory disease due to Chlamydia trachomatis

A 19-yr-old adolescent, who was hospitalized because of pelvic inflammatory disease (PID) due to Chlamydia trachomatis, developed bile-stained emesis. A mild amount of free fluid in the pelvis was found on abdominal ultrasound but there was no sonographic evidence of a pelvic mass or of a tubo-ovarian abscess. Plain radiography and computer tomography (with contrast) of the abdomen revealed a high-grade partial small bowel obstruction. Conservative treatment, which included intravenous fluids and antibiotics together with continuous bowel decompression via nasogastric tube, led to resolution of the small bowel obstruction within 2 days and to resumption of oral feeding within 4 days of treatment. Follow-up for 6 months after this episode was uneventful. The present case calls for inclusion of plain radiography of the abdomen in the evaluation of PID associated with emesis. It also suggests that, in a clinically stable patient diagnosed with small bowel obstruction associated with PID, conservative treatment could be attempted before any operative intervention is considered.     

Immune responses elicited against multiple enterotoxigenic Escherichia coli fimbriae and mutant LT expressed in attenuated Shigella vaccine strains

Shigella and enterotoxigenic Escherichia coli (ETEC) continue to be important causes of diarrheal disease in infants and young children in developing countries and are major etiologic agents of traveler's diarrhea. Since attenuated strains of Shigella have been developed as live oral vaccines against shigellosis, we have adapted these attenuated Shigella strains to serve as carriers of ETEC antigens, thereby constituting a hybrid vaccine. Since protective immunity against ETEC is largely directed against fimbrial antigens (of which there are multiple antigenic types), we have individually expressed four different ETEC fimbriae, including CFA/I, CS2, CS3, and CS4, using deltaguaBA attenuated Shigella vaccine strain CVD 1204 as a prototype live vector. Following mucosal (intranasal) immunization of guinea pigs, serum IgG and mucosal IgA responses were elicited against each fimbrial type. An additional strain was constructed expressing a detoxified version of the human ETEC variant of heat labile toxin (LThK63). Following mucosal immunization of guinea pigs with a mixed inoculum containing five Shigella strains each expressing a different ETEC antigen, immune responses were observed against each ETEC antigen plus the Shigella vector.     

Pilot study of pegylated interferon-alpha 2b in patients with essential thrombocythemia

PURPOSE: Interferon-alpha (IFN-alpha) has been shown to control symptoms, reduce platelet counts, and reduce the bone marrow megakaryocyte mass in patients with essential thrombocythemia (ET). A semisynthetic protein-polymer conjugate of IFN-alpha 2b (PEG-IFN2b) increases the serum half-life of IFN-alpha 2b. We conducted a pilot study of Peg-IFN2b in patients with ET. PATIENTS AND METHODS: Patients with a history of persistent (greater than 2 months) platelet counts >600 x 10(9)/l, with hyperplasia of bone marrow megakaryocytes in the absence of an alternate identifiable cause of thrombocytosis were eligible. Patients were required to have either thrombohemorrhagic signs and/or symptoms if previously untreated; persistence of thrombohemorrhagic signs and/or symptoms if receiving anagrelide, IFN-alpha, or hydroxyurea; or intolerance to anagrelide, IFN-alpha, or hydroxyurea. The initial PEG-IFN2b dose was from 1.5 to 4.5 micro g/kg per week subcutaneously with subsequent dose adjustments as indicated by response and adverse events. RESULTS: Eleven patients (nine female, median age 54 years, range 26-69 years) were treated. PEG-IFN2b rapidly controlled platelet counts and resolved symptoms in all patients. The median duration of PEG-IFN2b therapy on-study was 9 months (range 4-17 months). No patient had signs or symptoms of thrombosis or hemorrhage while on study. After 2 months of therapy, 10 patients (91%) were in complete remission, and 11 (100%) after 4 months. One patient discontinued therapy at 4 months because of persistent grade 3 fatigue and a second at 5 months because of anxiety and depression. CONCLUSION: PEG-IFN2b has significant activity in patients with ET. Long-term follow-up of a larger cohort of patients is needed to define its role in this disease.     

Surgical clip found in duodenal ulcer after laparoscopic cholecystectomy

The wide use of surgical clips in laparoscopic surgery has led to a variety of complications. We describe two cases in which a surgical clip was incorporated into a duodenal ulcer after laparoscopic cholecystectomy. The presenting symptom was acute gastrointestinal bleeding. Both patients were treated endoscopically, and the bleeding stopped after the clip was removed from the ulcer base. Although the mechanism by which a surgical clip migrates into the duodenum is unclear, we recommend meticulous Calot's triangle dissection and removal of any wandering or misplaced clips. Endoscopic removal is recommended when a surgical clip is discovered in a bleeding ulcer.     

AMN107, a novel aminopyrimidine inhibitor of p190 Bcr-Abl activation and of in vitro proliferation of Philadelphia-positive acute lymphoblastic leukemia cells

BACKGROUND: Previous studies have shown that patients with Bcr-Abl-positive acute lymphoblastic leukemia (ALL) either have primary disease that is refractory to imatinib mesylate or develop disease recurrence after an initial response. METHODS: The authors investigated the effects of a newly designed Bcr-Abl inhibitor, AMN107, by comparing its in vitro inhibitory potency on p190 Bcr-Abl ALL cell lines with that of imatinib. RESULTS: In two Philadelphia (Ph)-positive ALL cell lines, AMN107 was found to be 30-40 times more potent than imatinib in inhibiting cellular proliferation. AMN107 was also more effective than imatinib in inhibiting phosphorylation of p190 Bcr-Abl tyrosine kinase in cell lines and primary ALL cells. The inhibition of cellular proliferation was associated with the induction of apoptosis in only one of the cell lines. No activity was observed in cell lines lacking the BCR-ABL genotype. CONCLUSIONS: The results of the current study suggest the superior potency of AMN107 compared with imatinib in Ph-positive ALL and support clinical trials of AMN107 in patients with Ph-positive ALL.