Selective inhibition of ADAM metalloproteases as a novel approach for modulating ErbB pathways in cancer.

PURPOSE: ErbB receptor signaling pathways are important regulators of cell fate, and their dysregulation, through (epi)genetic alterations, plays an etiologic role in multiple cancers. ErbB ligands are synthesized as membrane-bound precursors that are cleaved by members of the ADAM family of zinc-dependent metalloproteases. This processing, termed ectodomain shedding, is essential for the functional activation of ErbB ligands. Recent studies suggest that elevated levels of ErbB ligands may circumvent the effectiveness of ErbB-targeted therapeutics. Here, we describe the discovery and preclinical development of potent, selective inhibitors of ErbB ligand shedding. EXPERIMENTAL DESIGN: A series of biochemical and cell-based assays were established to identify selective inhibitors of ErbB ligand shedding. The therapeutic potential of these compounds was assessed in multiple in vivo models of cancer and matrix metalloprotease-related toxicity. RESULTS: INCB3619 was identified as a representative selective, potent, orally bioavailable small-molecule inhibitor of a subset of ADAM proteases that block shedding of ErbB ligands. Administration of INCB3619 to tumor-bearing mice reduced ErbB ligand shedding in vivo and inhibited ErbB pathway signaling (e.g., phosphorylation of Akt), tumor cell proliferation, and survival. Further, INCB3619 synergized with clinically relevant cancer therapeutics and showed no overt or compounding toxicities, including fibroplasia, the dose-limiting toxicity associated with broad-spectrum matrix metalloprotease inhibitors. CONCLUSIONS: Inhibition of ErbB ligand shedding offers a potentially novel and well-tolerated therapeutic strategy for the treatment of human cancers and is currently being evaluated in the clinic.     

Neutrophil inhibitory factor abrogates neutrophil adhesion by blockade of CD11a and CD11b beta(2) integrins.

We studied the basis of inhibition of polymorphonuclear leukocyte (PMN) adhesion induced by neutrophil inhibitory factor (NIF), a 41-kDa CD11/CD18 beta(2) integrin-binding protein isolated from the canine hookworm (Ancylostoma caninum). NIF blocked PMN adhesion in a concentration-dependent manner with complete blockade occurring at approximately 10 nM NIF. Because CD11a and CD11b beta(2) integrins are functionally active on stimulated PMNs, and yet NIF is postulated to inhibit only CD11b integrin by binding to its I domain, we evaluated the contributions of CD11a and CD11b beta(2) integrins in the mechanism of inhibition of PMN adhesion to endothelial cells. We observed an additive inhibitory effect (>90% inhibition) of PMN adhesion to endothelial cells when NIF was used in combination with anti-CD11b monoclonal antibodies, which alone at saturating concentrations reduced PMN adhesion by only 50%. NIF also prevented aggregation of phorbol ester-stimulated JY lymphoblastoid cells that expressed only the functionally active CD11a, suggesting that NIF also can inhibit CD11a-dependent response. We transduced the NIF cDNA into human dermal microvessel endothelial cells in which NIF synthesis and release prevented PMN adhesion to the transduced human dermal microvessel endothelial cells. These data indicated that the potent antiadhesive effect of NIF may be the result of inhibition of CD11a and CD11b beta(2) integrins on PMNs. Moreover, the strategy of NIF release from transduced endothelial cells suggests the feasibility of blocking the CD11a- and CD11b beta(2) integrin-dependent PMN adhesion and PMN migration responses specifically at sites of endothelial cell activation.     

Immunophenotypic analysis of non-Hodgkin's lymphomas in Chinese. A study of 75 cases in Hong Kong

The cell surface markers of 75 cases of non-Hodgkin's lymphoma were studied on cryostat sections using a panel of monoclonal antibodies. Forty-nine cases (65.3%) were found to express a B-cell phenotype, 23 cases (30.7%) a T-cell phenotype, 1 case (1.3%) a histiocytic phenotype and 2 cases (2.7%) no demonstrable surface markers. Follicular lymphoma accounted for only 10.7% of the cases. Most B-cell lymphomas expressed IgM-lambda or IgM-IgD-lambda, but a few failed to express surface immunoglobulin. Among the 23 cases of T-cell lymphoma, 22 were of peripheral T-cell type; most were of helper-cell (T4) phenotype and a significant number expressed J5 (CALLA) and I2 (HLA-DR). The present study shows that the percentage of T-cell lymphoma in Chinese is higher than in Caucasians, but lower than in Japanese. However, when the age-adjusted incidence of non-Hodgkin's lymphoma is considered, the incidence rates of T-cell lymphoma in Hong Kong Chinese and Japanese in areas non-endemic for adult T-cell lymphoma/leukemia are similar; the incidence in Americans is similar or slightly lower. The major difference between the races is that B-cell lymphoma, particularly the follicular type, is much rarer in Asians than Americans.     

Treatment of fungal peritonitis with a combination of intravenous amphotericin B and oral flucytosine, and delayed catheter replacement in continuous ambulatory peritoneal dialysis.

BACKGROUND: Fungal peritonitis (FP) is associated with significant mortality and high risk of peritoneal failure. The optimum treatment for peritoneal dialysis (PD)-associated FP remains unclear. Since January 2000 we have been treating FP with a combination of intravenous amphotericin B and oral flucytosine, together with deferred catheter replacement. We examined the clinical course and outcome of the FP patients treated with this approach (study group). An outcome comparison was also made to an alternatively treated historic cohort (control group). METHODS: This was a single-center retrospective study. The clinical course and outcome of 13 consecutive episodes of FP occurring in 13 patients treated between January 2000 and April 2005 with the study approach were examined. The patients were treated with an incremental dose of intravenous amphotericin B to a target dose of 0.75 - 1 mg/kg body weight/day, and oral flucytosine 1 g/day upon a diagnosis of FP at 3.77 +/- 0.93 days from presentation. Replacement of the peritoneal catheter was intended after complete clearing of effluent, after which, antifungal chemotherapy was continued for another 1 - 2 weeks. Their outcome was compared with 14 historic controls that were treated between April 1995 and December 1999. RESULTS: Mean age of the study group was 58.7 +/- 13.2 years; male-to-female ratio was 2:11; 6 (46.1%) were diabetic. All FP were caused by Candida species (C. albicans, 2; C. parapsilosis, 8; C. glabrata, 3). Two (15.4%) patients died before resolution of the peritonitis. The dialysate effluent cleared in 11 patients (84.6%) after 13.2 +/- 3.3 days of treatment, but 2 patients died of acute myocardial infarction before catheter replacement. Nine patients had their catheters replaced at day 26.7 +/- 7.7 of treatment; all 9 returned to PD after a total of 31 +/- 12.2 days of antifungal chemotherapy. Reversible liver dysfunction was common with this regimen. When compared with the 14 cases in the historic control group (Candida species, 13; Trichosporon, 1), who were treated with amphotericin B, fluconazole, or a combination of the two, and the majority (78.6%) of whose catheters were removed before day 10 of presentation, the study group appeared to have a lower technique failure rate (30.8% vs 78.6%, p = 0.013) and similar all-cause mortality (30.7% vs 28.5%, p = NS), FP-related mortality (15.4% vs 28.5%, p = NS), and length of hospitalization (48.5 +/- 30.2 vs 57.0 +/- 37.7 days, p = NS). However, a significantly earlier commencement of antifungal treatment in the study group (3.8 +/- 0.9 vs 5.8 +/- 2.4 days, p = 0.012) could be an important confounder of outcome. CONCLUSIONS: Combination of intravenous amphotericin B and oral flucytosine with deferred catheter replacement appears to be associated with a relatively low incidence of PD technique failure, without affecting mortality in patients suffering from FP due to yeasts in this preliminary study. Nonetheless, drug-induced hepatic dysfunction was common; close monitoring during treatment is of paramount importance. The reasons accounting for the observed distinctive outcome remain unclear and further study is required to confirm the results and to investigate for the underlying mechanism.     

Aging effects on the secretion of corticosterone in male rats.

BACKGROUND: The effects of aging on zona fasciculatareticularis (ZFR) cell function in male rats were studied. METHODS: Male rats 3, 6, and 22 months of age were divided into three groups, and collagenase-dispersed ZFR cells were isolated and incubated with adrenocorticotropin (ACTH), 8-bromo-adenosine 3':5'-cyclic monophosphate (8-Br-cAMP), ovine prolactin (oPRL), deoxycorticosterone (DOC), or 3-isobutyl-l-methylxanthine (IBMX) at 37 degrees C for 1 hour. Corticosterone concentrations in cell media and cAMP production in ZFR cells were measured by radioimmunoassay. Protein expression of PRL receptor in ZFR cells were analyzed by Western blot. RESULTS: The basal levels of plasma and medium corticosterone were higher in 22-month-old than in 3-month-old rats. In contrast, the release of corticosterone in response to ACTH, 8-Br-cAMP, and DOC was lower in 22-month-old than in 3- and 6-month-old rats. Aging decreased the oPRL-stimulated release of corticosterone but increased the protein expression of PRL receptor in ZFR cells. The basal levels of intracellular cAMP increased with age. However, the ACTH-stimulated production of intracellular cAMP decreased in 22-month-old compared with 3- or 6-month-old rats. The increment of cAMP accumulation in ZFR cells after administration of IBMX was greater in 22-month-old than in 3- or 6-month-old rats. CONCLUSIONS: These results suggest that the aging effects on the production of corticosterone in rat ZFR cells is associated with change of the generation of cAMP, the activity of 11 beta-hydroxylase and the protein expression of PRL receptor.