ALBERT

Description: Chronic inflammation’s tumor-promoting potential is well-recognized; however, the mechanism underlying the development of this immune environment is unknown. Studying the transition from acute, tumor-suppressive to chronic, tumor-promoting allergic contact dermatitis (ACD) revealed how tumor-promoting chronic inflammation develops. Epidermis-derived interleukin (IL)-33 up-regulation and its induction of regulatory T cell (Treg) accumulation in the skin preceded the transition from acute to chronic ACD and triggered the tumor-promoting immune environment in chronic ACD. Mice lacking IL-33 were protected from chronic ACD and its skin cancer sequela compared with wild-type controls (P = 0.0002). IL-33’s direct signaling onto Tregs was required for the development of the tumor-promoting immune environment in the skin. IL-33–Treg signaling was also required for chronic colitis and its associated colorectal cancer development in a colitis model (P 〈 0.0001). Significantly increased IL-33 and Tregs marked the perilesional skin and colon in patients with cancer-prone chronic inflammatory diseases. Our findings elucidate the role of the IL-33/Treg axis in creating a tumor-promoting immune environment in chronic inflammatory diseases and suggest therapeutic targets for cancer prevention and treatment in high-risk patients.

Description: In Ph+ leukemia, the breakpoints within BCR cluster in 3 distinct breakpoint cluster regions (bcr). Rearrangements in the minor (m−), major (M−) and micro (m−) breakpoint cluster region (bcr) give rise to e1a2, e13/14a2 and e19a2 BCR-ABL fusion proteins that are associated with Ph+ ALL, CML and chronic neutrophilic leukemia, respectively. Atypical BCR-ABL fusions have also been reported, mostly in isolated cases. Here, we describe eight patients with an unusual e8a2 BCR-ABL transcript and provide an overview of their common characteristics. The index case (#1) was a 56 year old man diagnosed with CML in 1993. Therapy with busulfan and hydrea induced a complete hematologic remission (CHR) that was maintained until March 2001, when accelerated disease developed. Treatment with imatinib and subsequently AML-type chemotherapy were only transiently effective and the patient died from myeloid blast crisis in March 2003. Cytogenetics demonstrated a standard t(9;22)(q34;q11). Unexpectedly, FISH was consistent with an m-bcr rearrangement and multiplex PCR showed an unusually large band. Sequencing identified a fusion between BCR exon e8 and ABL exon a2, with a 55 bp insert corresponding to an inverted segment of ABL intron Ib (corresponding to nt 29861–29915, Genbank U07561). Immunoblotting of bone marrow mononuclear cells with anti-ABL antibody identified a 200 kDa protein (p200BCR-ABL). Seven additional patients with an e8a2 BCR-ABL fusion have been identified (table 1). These patients tend to have relatively high platelet counts (median 569 x 109/L, range 216 – 1123) and relatively low white counts (median 42 x 109/L, range 4.7 – 146) but no other distinguishing characteristics at diagnosis. With a median follow-up of 36 months (range, 4 –97), two patients had progressed to blast crisis and died, one died from an unrelated cause, and five were alive, one after allogeneic BMT. Remarkably, none of the patients treated with interferon-a achieved even a minor cytogenetic remission, similar to patients with p190-positive CML. Two patients besides case #1 have received imatinib, one has achieved a CHR at four months, and information on the other is not available. Compared to P190 and P210, p200 lacks the pleckstrin homology (PH) domain but retains the Dbl-like and CDC24 homology domains of BCR. Deletion of the PH domain may disrupt the function of the Dbl-like domain to serve as a GTP exchange factor for Rac, Cdc42 and Rho. This may lead to disruption of the actin cytoskeleton and would be expected to cause a disease that is biologically closer to p190 than to p210.

Description: Background: The two common types of BCR-ABL fusion protein, p190 and p210, are associated with Ph-positive ALL and CML, respectively. Compared to p190, p210 retains the Dbl-like, CDC24 homology and PH domains. Dbl-like and CDC24 homology domains are thought to serve as a guanidine exchange factor (GEF) for small G proteins, including Rac, CDC42 and RhoA. It has been suggested that the loss of GEF activity may be responsible for the more aggressive phenotype of p190-positive leukemia (McWhirter and Wang, Oncogene1997; 15(14):1625–34). PH domains bind phosphoinositides and have been implicated in targeting proteins to cellular membranes as well as modulating the activity of the adjacent Dbl-like GEFs. It is not known, however, if the PH domain of BCR plays a role in determining disease features. We therefore decided to study the biology of p200BCR-ABL, a naturally occurring variant identified in several CML patients that lacks the PH domain but retains the Dbl-like and CDC24 homology domains. Materials and methods: p190, p210 and p200BCR-ABL cDNAs were cloned into pSRa and MIGR1 for expression in cell lines and primary murine bone marrow (BM) cells, respectively. The activation of signaling pathways downstream of BCR-ABL was studied in Ba/F3 and 32D cells expressing the various constructs. For colony-forming assays, murine BM cells were infected with p210, p200 or p190 retroviral vectors and seeded in methylcellulose in the presence or absence of cytokines (SCF, IL3 & IL6) and colonies were counted on day 12. For in vivo studies, BM cells isolated from 5-fluorouracil treated 5-6 week-old female Balb/c mice were infected with the various retroviral constructs in the presence of cytokines (SCF, IL3 & IL6), and 4.0 x 105 cells were injected retro-orbitally into lethally irradiated recipient mice. Disease latency was determined by monitoring white blood counts at 48h intervals. Moribund animals were sacrificed and studied by FACS and histopathology. Results: As expected, p200 transformed Ba/F3 and 32D cells to IL-3 independence. Immunoblotting of whole cell lysates with a phosphotyrosine antibody revealed no significant differences in global protein phosphorylation between the three variants, but phosphorylation of BCR-ABL was consistently less sensitive to imatinib inhibition in cells expressing p190 compared to p200 and p210. Analysis of downstream signaling showed approximately 15 fold higher levels of phosphorylated STAT6 in Ba/F3 cells expressing p200 and p190 vs. p210, while STAT5 and AKT phophorylation were similar in all variants. In the absence of cytokines, BM cells from Balb/c mice transduced with p200 and p190 generated significantly more CFU-GM than cells transduced with p210 (p

Description: Background : Systemic mastocytosis (SM) is characterized by infiltration of extracutanous tissues by neoplastic mast cells. Primary target organs are liver, spleen and bone marrow. In some instances, SM progresses to aggressive systemic mastocytosis (ASM) or mast cell leukemia (MCL), which are associated with extensive mast cell infiltration into various organs and their failure. Almost all cases of SM exhibit point mutations at codon 816 of Kit, a receptor tyrosine kinase. These mutations (most commonly D816V) lead to constitutive activation of the kinase and are the causative lesion of SM. Here, we describe a novel murine model of SM/ASM that shares many characteristics with the human disease and may be useful for in vivo drug testing, including targeted therapy of D816 mutant Kit with small molecule inhibitors. Materials and methods : P815 cells, a cell line expressing D814Y Kit (homologous to human D816V kit) that was established in DBA2 mice (Dunn T, Bap M. J Natl Cancer Inst1957;18:587–95) were injected retro-orbitally into two groups (n = 4) of 8–10 week-old syngeneic mice, at a dose of 1x102 and 5x104 cells. Using an automated animal cell counter, the mice were monitored at 48h intervals with full blood counts, including white cell differential and platelets. The presence of mast cells was assessed by FACS for mast cell markers (CD117-PE and CD45-APC) as well as Giemsa staining. The animals were evaluated daily for signs of morbidity. Moribund mice were sacrificed and subjected to autopsy. Liver, spleen and bone marrow were analyzed by histopathology, and the expression and phophorylation status of Kit was assessed by FACS and immunoblotting. Results : Both cell doses induced an aggressive disease, with all animals reaching a moribund stage on day 9 (5x104 cells) and 16 (1x102 cells). A significant (p

Description: Oncogenic mutations of the KIT receptor tyrosine kinase have been identified in several malignancies including gastrointestinal stromal tumors (GIST), systemic mastocytosis (SM), seminomas/dysgerminomas and acute myelogenous leukemia (AML). Mutations in the regulatory juxtamembrane domain are common in GIST, while mutations in the activation loop of the kinase (most commonly D816V) occur predominantly in SM and at low frequency in AML. Several ATP-competitive kinase inhibitors, including imatinib, are effective against juxtamembrane KIT mutants, however, the D816V mutant is largely resistant to inhibition. We analyzed the sensitivities of cell lines expressing wild type KIT, juxtamembrane mutant KIT (V560G) and activation loop mutant KIT (D816V,F,Y and murine D814Y) to a potent Src/Abl kinase inhibitor, AP23464, and analogs. IC50 values for inhibition of cellular KIT phosphorylation by AP23464 were 5–11 nM for activation loop mutants, 70 nM for the juxtamembrane mutant and 85 nM for wild type KIT. Consistent with this, IC50 values in cell proliferation assays were 3–20 nM for activation loop mutants and 100 nM for wild type KIT and the juxtmembrane mutant. In activation loop mutant-expressing cell lines, AP23464, at concentrations ≤50 nM, induced apoptosis, arrested the cell cycle in G0/G1 and down-regulated phosphorylation of Akt and STAT3, signaling pathways critical for the transforming capacity of mutant KIT. In contrast, 500 nM AP23464 was required to induce equivalent effects in wild-type KIT and juxtamembrane mutant-expressing cell lines. These data demonstrate that activation loop KIT mutants are considerably more sensitive to inhibition by AP23464 than wild type or juxtamembrane mutant KIT. Non-specific toxicity in parental cells occurred only at concentrations above 2 μM. Additionally, at concentrations below 100 nM, AP23464 did not inhibit formation of granulocyte/macrophage and erythrocyte colonies from normal bone marrow, suggesting that therapeutic drug levels would not impact normal hematopoiesis. We also examined in vivo target inhibition in a mouse model. Mice were subcutaneously injected with D814Y-expressing (D816V homologous) murine mastocytoma cells. Once tumors were established, compound was administered three-times daily by oral gavage. One hour post treatment we observed 〉90% inhibition of KIT phosphorylation in tumor tissue. Following a three-day treatment regimen, there was a statistically significant difference in tumor size compared to controls. Thus, AP23464 analogs effectively target D816-mutant KIT both in vitro and in vivo and inhibit activation loop KIT mutants more potently than the wild type protein. These data provide evidence that this class of kinase inhibitors may have therapeutic potential for D816V-expressing malignancies such as SM or AML.

Description: Mutations in the kinase domain (KD) of BCR-ABL are the leading cause of acquired imatinib resistance. In some cases, identical mutations were detected at relapse and in pretherapeutic specimens, consistent with selection of resistant clones in the presence of drug. However, the incidence of KD mutations in imatinibnaive patients, irrespective of response to therapy, is unknown. We studied mutation frequency in 66 patients with chronic myelogenous leukemia (CML), using cDNA sequencing and allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR) assays for 8 common mutations. Thirteen patients were positive by ASO-PCR only, 1 by ASO-PCR and sequencing, and 1 by sequencing only (overall frequency, 22.7%). T315I was most frequent (12% of patients). Eleven of the 14 patients with positive ASO-PCR had follow-up samples available for sequencing. Wild-type sequence was detected in 6 of 11, 2 different mutations in 1 of 11, and identical mutations in 4 of 11 patients, 2 of whom had achieved major cytogenetic response. In multivariate analysis mutation detection was associated with clonal cytogenetic evolution, exposure to 6-Thioguanine, and a low platelet count, but not with response to imatinib, event-free survival, and overall survival. KD mutants present at low levels do not invariably lead to relapse, and additional factors are required to induce a fully drug-resistant phenotype. (Blood. 2005; 106:2128-2137)

Description: Oncogenic mutations of the Kit receptor tyrosine kinase occur in several types of malignancy. Juxtamembrane domain mutations are common in gastrointestinal stromal tumors, whereas mutations in the kinase activation loop, most commonly D816V, are seen in systemic mastocytosis and acute myelogenous leukemia. Kit activation-loop mutants are insensitive to imatinib mesylate and have been largely resistant to targeted inhibition. We determined the sensitivities of both Kit mutant classes to the adenosine triphosphate (ATP)–based inhibitors AP23464 and AP23848. In cell lines expressing activation-loop mutants, low-nM concentrations of AP23464 inhibited phosphorylation of Kit and its downstream targets Akt and signal transducer and activator of transcription 3 (STAT3). This was associated with cell-cycle arrest and apoptosis. Wild-type Kit–and juxtamembrane-mutant–expressing cell lines required considerably higher concentrations for equivalent inhibition, suggesting a therapeutic window in which cells harboring D816V Kit could be eliminated without interfering with normal cellular function. Additionally, AP23464 did not disrupt normal hematopoietic progenitor-cell growth at concentrations that inhibited activation-loop mutants of Kit. In a murine model, AP23848 inhibited activation-loop mutant Kit phosphorylation and tumor growth. Thus, AP23464 and AP23848 potently and selectively target activation-loop mutants of Kit in vitro and in vivo and could have therapeutic potential against D816V-expressing malignancies.

Description: Internal tandem duplications (ITDs) of the FMS-like tyrosine kinase 3 (FLT3) receptor tyrosine kinase are found in approximately 30% of patients with acute myelogenous leukemia (AML) and are associated with a poor prognosis. FLT3 ITD mutations result in constitutive kinase activation and are thought to be pathogenetically relevant, implicating FLT3 as a plausible therapeutic target. MLN518 (formerly CT53518) is a small molecule inhibitor of the FLT3, KIT, and platelet-derived growth-factor receptor (PDGFR) tyrosine kinases with significant activity in murine models of FLT3 ITD-positive leukemia. Given the importance of FLT3 and KIT for normal hematopoietic progenitor cells, we analyzed the effect of MLN518 on murine hematopoiesis under steady-state conditions, after chemotherapy-induced myelosuppression, and during bone marrow transplantation. In these assays, we show that MLN518 has mild toxicity toward normal hematopoiesis at concentrations that are effective in treating FLT3 ITD-positive leukemia in mice. We also demonstrate that MLN518 preferentially inhibits the growth of blast colonies from FLT3 ITD-positive compared with ITD-negative patients with AML, at concentrations that do not significantly affect colony formation by normal human progenitor cells. In analogy to imatinib mesylate in BCR-ABL–positive acute leukemia, MLN518-induced remissions may not be durable. Our studies provide the basis for integrating this compound into chemotherapy and transplantation protocols.

Description: Background: Lysophosphatidic acid acyltransferase-β (LPAAT-β) catalyzes the conversion of lysophosphatidic acid (LPA) to phosphatidic acid (PA), an essential component of the Ras pathway. In vascular smooth muscle cells, specific inhibitors of LPAAT-β interfere with the ras and PI3-kinase dependent signaling pathways thereby inducing growth arrest and apoptosis. We have previously shown that CT32228, a specific inhibitor of LPAAT-β, selectively inhibits the growth of CML progenitor cells in cultures without cytokines [ASH 2003, #2415]. Since Bcr-Abl is usually reactivated in cells resistant to the Abl kinase inhibitor imatinib, and Ras and PI3 kinase are downstream targets of Bcr-Abl, we hypothesized that a specific inhibitor of LPAAT-β may have activity against Bcr-Abl-positive CML with resistance to imatinib. Methods: Antiproliferative activity was assessed using the MTS-proliferation assay. Statistical analysis of combination studies (CT32228 + imatinib) was performed by applying the median effect method. Flow cytometry after staining with propidium iodide (PI) was performed to assess the cell cycle, co-staining with annexin allowed the detection of apoptotic cells. Signaling studies were performed by immunoblotting. Results: CT32228 inhibited the proliferation of Bcr-Abl expressing cell lines (AR230-s, K562, KCL22, Baf/BCR-ABL-s, 32DBCR-ABL, MO7p210) with IC50 concentrations between 23 and 105 nM. Similar IC50 values were obtained in lines expressing imatinib resistant BCR-ABL-mutants (Y253F/M351T/T315I/H396R) or amplified wild-type-BCR-ABL (Baf/BCR-ABL-r1, AR230-r), demonstrating the absence of significant cross-resistance. Combination studies with imatinib demonstrated additive to synergistic antiproliferative activity only in cell lines with residual sensitivity towards imatinib. FACS analysis of K562 cells treated with CT32228 showed accumulation of cells in G2/M as early as 6 h after start of treatment. After 24 h, 50% of cells were in G2/M and apoptosis was demonstrable with annexin/PI staining. Consistent with the G2/M arrest, multinucleated cells were evident microscopically at 24 h. Further analysis of apoptotic signalling pathways revealed activation of caspase-3 and PARP cleavage, while activation of caspase-8 and -9 was not demonstrated. In K562 cells treated with CT32228, Erk1/2 phosphorylation was abrogated, consistent with inhibition of mitogen activated kinase signalling as a result of decreased Ras signalling. In contrast phosphorylation of Akt was unaffected suggesting that inhibition of LPAAT-β does not interfere with the PI3K pathway in BCR-ABL-positive cells. Conclusion: CT32228 exerts antileukemic activity in imatinib-resistant cells without cross-resistance to imatinib and is synergistic in combination with imatinib. Cytotoxicity is mediated by cell cycle arrest in G2/M and induction of apoptosis. Interference with the Ras-pathway through MAPK-inhibition may play a key role in the antileukemic effect of CT32228. This data provides the framework for evaluation of CT32228 and related compounds to improve imatinib-based treatment of CML.