Anne-Marie Faussat

Breast cancer resistance protein and P-glycoprotein in 149 adult acute myeloid leukemias.

Purpose: Recently, a new ABC protein, breast cancer resistance protein (BCRP), was described. But its prognosis is not known in acute myeloid leukemia (AML). In addition, the prognosis of P-glycoprotein (Pgp) and BCRP in patients treated homogeneously by the same anthracycline (daunorubicin, idarubicin, or mitoxantrone) during all of the treatment with aracytine is not known. Therefore, we have evaluated the relationship between drug resistance phenotype, in vitro anthracene sensitivity, and the relation to treatment outcome. Experimental Design: We have analyzed 149 AML treated according to protocol of the European Organization for Research and Treatment of Cancer group. The prognostic value of BCRP and Pgp were analyzed in the whole population and according to intercalating agent. Results: BCRP was a prognostic factor, for achievement of complete remission (43% in positive patients and 69% in negative patients, P = 0.005), the 4-year disease-free survival (12% versus 33%, P = 0.03), and the 4-year overall survival (19% versus 38%, P = 0.003). When BCRP expression and Pgp function were categorized in three groups, +/+, +/− or −/+, and −/−, the achievement of complete remission was 45%, 66%, and 90% (P = 0.0003), the 4-year disease-free survival was 8%, 26%, and 40% (P = 0.01), and the 4-year overall survival was 16%, 37%, and 48% (P = 0.001), respectively. Pgp function was a prognostic factor in patients treated by daunorubicin and idarubicin but not by mitoxantrone. In contrast, BCRP expression was a prognostic factor in patients treated by daunorubicin and mitoxantrone but not by idarubicin. Conclusions: BCRP would be implicated in the resistance to chemotherapies in AML. But these are the patients expressing both BCRP and Pgp who have the poorest prognosis.

Semisynthetic homoharringtonine induces apoptosis via inhibition of protein synthesis and triggers rapid myeloid cell leukemia-1 down-regulation in myeloid leukemia cells

Semisynthetic homoharringtonine (ssHHT) is now being evaluated in phase II clinical trials for the treatment of chronic myelogenous leukemia and acute myelogenous leukemia patients. Here, we examined the mechanism of the apoptosis induced by ssHHT in myeloid leukemia cells. First, we have shown that ssHHT induces apoptosis in HL60 and HL60/MRP cell lines in a time- and dose-dependent manner, and independently of the expression of Bax. The decrease of mitochondrial membrane potential and the release of cytochrome c were observed in the apoptotic cells induced by ssHHT. To unveil the relationship between ssHHT and the mitochondrial disruption, we have shown that ssHHT decreased myeloid cell leukemia-1 (Mcl-1) expression and induced Bcl-2 cleavage in HL60 and HL60/MRP cell lines. The Bcl-2 cleavage could be inhibited by the Z-VAD.fmk caspase inhibitor. However, Mcl-1 turnover was very rapid and occurred before caspase activation. The Mcl-1 turnover was only induced by ssHHT and cycloheximide, but not by daunorubicin and cytosine arabinoside, and could be restored by proteasome inhibitors. Second, we confirmed that ssHHT rapidly induced massive apoptosis in acute myelogenous leukemia patient cells. We have also confirmed the release of cytochrome c and a rapid turnover of Mcl-1 in these patient cells, taking place only in apoptotic cells induced by ssHHT but not in cells undergoing spontaneous apoptosis. Finally, we have shown that ssHHT inhibits protein synthesis in both cell line and patient cells. We suggest that the inhibition of protein synthesis and resulting Mcl-1 turnover play a key role in the apoptosis induced by ssHHT. Our results encourage further clinical trials for the use of ssHHT in acute myelogenous leukemia. [Mol Cancer Ther 2006;5(3):723–31]

Oncologic Trogocytosis of an Original Stromal Cells Induces Chemoresistance of Ovarian Tumours

Background The microenvironment plays a major role in the onset and progression of metastasis. Epithelial ovarian cancer (EOC) tends to metastasize to the peritoneal cavity where interactions within the microenvironment might lead to chemoresistance. Mesothelial cells are important actors of the peritoneal homeostasis; we determined their role in the acquisition of chemoresistance of ovarian tumours. Methodology/Principal Findings We isolated an original type of stromal cells, referred to as “Hospicells” from ascitis of patients with ovarian carcinosis using limiting dilution. We studied their ability to confer chemoresistance through heterocellular interactions. These stromal cells displayed a new phenotype with positive immunostaining for CD9, CD10, CD29, CD146, CD166 and Multi drug resistance protein. They preferentially interacted with epithelial ovarian cancer cells. This interaction induced chemoresistance to platin and taxans with the implication of multi-drug resistance proteins. This contact enabled EOC cells to capture patches of the Hospicells membrane through oncologic trogocytosis, therefore acquiring their functional P-gp proteins and thus developing chemoresistance. Presence of Hospicells on ovarian cancer tissue micro-array from patients with neo-adjuvant chemotherapy was also significantly associated to chemoresistance. Conclusions/Significance This is the first report of trogocytosis occurring between a cancer cell and an original type of stromal cell. This interaction induced autonomous acquisition of chemoresistance. The presence of stromal cells within patients tumour might be predictive of chemoresistance. The specific interaction between cancer cells and stromal cells might be targeted during chemotherapy.

The PI3K/Akt and mTOR/P70S6K Signaling Pathways in Human Uveal Melanoma Cells: Interaction with B-Raf/ERK

PURPOSE Activated B-Raf alone cannot induce melanoma but must cooperate with other signaling pathways. The phosphatidylinositol 3-kinase (PI3K)/Akt and mammalian target of rapamycin (mTOR)/p70S6K pathways are critical for tumorigenesis. The authors investigated the role of these pathways in uveal melanoma cells. METHODS The effects of PI3K and mTOR activation and inhibition on the proliferation of human uveal melanoma cell lines expressing either activated (WT)B-Raf or (V600E)B-Raf were investigated. Interactions among PI3K, mTOR, and B-Raf/ERK were studied. RESULTS Inhibition of PI3K deactivated P70S6 kinase, reduced cell proliferation by 71% to 84%, and increased apoptosis by a factor of 5.0 to 8.4 without reducing ERK1/2 activation, indicating that ERK plays no role in mediating PI3K in these processes. In contrast, rapamycin-induced inhibition of mTOR did not significantly affect cell proliferation because it simultaneously stimulated PI3K/Akt activation and cyclin D1 expression. Regardless of B-Raf mutation status, cotreatment with the PI3K inhibitor effectively sensitized all melanoma cell lines to the B-Raf or ERK1/2 inhibition-induced reduction of cell proliferation. B-Raf/ERK and PI3K signaling, but not mTOR signaling, converged to control cyclin D1 expression. Moreover, p70S6K required the activation of ERK1/2. These data demonstrate that PI3K/Akt and mTOR/P70S6K interact with B-Raf/ERK. CONCLUSIONS Activated PI3K/Akt attenuates the inhibitory effects of rapamycin on cell proliferation and thus serves as a negative feedback mechanism. This finding suggests that rapamycin is unlikely to inhibit uveal melanoma growth. In contrast, targeting PI3K while inhibiting B-Raf/ERK may be a promising approach to reduce the proliferation of uveal melanoma cells.

Sequential emergence of MRp- and MDR1-gene over-expression as well as MDR1-gene translocation in homoharringtonine-selected K562 human leukemia cell lines

To investigate the mechanism of resistance to an anti‐neoplastic natural product homoharringtonine (HHT) in leukemic cells, we have established 5 sub‐lines of human myeloid leukemia K562 cells, designated as K‐H30, K‐H100, K‐H200, K‐H300 and K‐H400, which showed progressive resistance to different concentrations of HHT. These sub‐lines were cross‐resistant to daunorubicin, vincristine, etoposide and mitoxantrone, but not to melphalan. Immunofluorescence with monoclonal anti‐Pgp antibody MRK16 and Northern‐blot analysis demonstrated that resistance to HHT is related to the sequential emergence of MRP‐ and MDR1‐gene over‐expression. In the low‐level‐resistant K‐H30 sub‐line, the MDR1 gene was not over‐expressed, but the MRP gene was over‐expressed 2.1‐fold. In the intermediate‐level‐resistant K‐H100 and K‐H200 sublines, both the MRP and the MDR1 genes were over‐expressed. However, in the high‐level‐resistant K‐H300 and K‐H400 sublines, MDR1‐gene over‐expression predominated (20‐ and 21‐fold respectively). On the other hand, GSTπ‐gene expression was decreased in all 5 sub‐lines. Southern‐blot analysis revealed no MRP‐gene amplification in any of the 5 sub‐lines, whereas the MDR1 gene was amplified in the high‐level‐resistant K‐H300 and K‐H400 sub‐lines. The most interesting observation is a homogeneously staining region (HSR) found in chromosome 2 of the K‐H300 and K‐H400 sub‐lines. Chromosome painting and in situ hybridization demonstrated that this HSR was translocated from chromosome 7 and consisted of the amplified MDR1 gene, suggesting that there is a relationship between MDR1‐gene translocation and MDR1‐gene amplification.

The Cellular Prion Protein PrPc Is Involved in the Proliferation of Epithelial Cells and in the Distribution of Junction-Associated Proteins

Background The physiological function of the ubiquitous cellular prion protein, PrPc, is still under debate. It was essentially studied in nervous system, but poorly investigated in epithelial cells. We previously reported that PrPc is targeted to cell–cell junctions of polarized epithelial cells, where it interacts with c-Src. Methodology/Findings We show here that, in cultured human enterocytes and in intestine in vivo, the mature PrPc is differentially targeted either to the nucleus in dividing cells or to cell–cell contacts in polarized/differentiated cells. By proteomic analysis, we demonstrate that the junctional PrPc interacts with cytoskeleton-associated proteins, such as gamma- and beta-actin, alpha-spectrin, annexin A2, and with the desmosome-associated proteins desmoglein, plakoglobin and desmoplakin. In addition, co-immunoprecipitation experiments revealed complexes associating PrPc, desmoglein and c-Src in raft domains. Through siRNA strategy, we show that PrPc is necessary to complete the process of epithelial cell proliferation and for the sub-cellular distribution of proteins involved in cell architecture and junctions. Moreover, analysis of the architecture of the intestinal epithelium of PrPc knock-out mice revealed a net decrease in the size of desmosomal junctions and, without change in the amount of BrdU incorporation, a shortening of the length of intestinal villi. Conclusions/Significance From these results, PrPc could be considered as a new partner involved in the balance between proliferation and polarization/differentiation in epithelial cells.

Prematurely senescent ARPE-19 cells display features of age-related macular degeneration

The etiology of age-related macular degeneration (AMD), the leading cause of blindness in the developed world, remains poorly understood, but may be related to cumulative oxidative stress. The prime target of the disease is the retinal pigmented epithelium (RPE). To study the molecular mechanisms underlying RPE degeneration, we investigated whether repetitive oxidative stress induced premature senescence in RPE cells from the human ARPE-19 cell line. After exposure to 8 mM tert-butylhydroperoxide (tert-BHP) for 1 h daily for 5 days, the cells showed four well-known senescence biomarkers: hypertrophy, senescence-associated beta-galactosidase activity, growth arrest, and cell cycle arrest in G1. A specific low-density array followed by qRT-PCR validation allowed us to identify 36 senescence-associated genes differentially expressed in the prematurely senescent cells. Functional analysis demonstrated that premature senescence induced amyloid beta secretion, resistance to acute stress by tert-BHP and amyloid beta, and defects in adhesion and transepithelial permeability. Coculture assays with choroidal endothelial cells showed the proangiogenic properties of the senescent RPE cells. These results demonstrate that chronic oxidative stress induces premature senescence in RPE cells that modifies the transcriptome and substantially alters cell processes involved in the pathophysiology of AMD. Oxidative stress-induced premature senescence may represent an in vitro model for screening therapeutics against AMD and other retinal degeneration disorders.

Zosuquidar restores drug sensitivity in P-glycoprotein expressing acute myeloid leukemia (AML)

BackgroundChemotherapeutic drug efflux via the P-glycoprotein (P-gp) transporter encoded by the MDR1/ABCB1 gene is a significant cause of drug resistance in numerous malignancies, including acute leukemias, especially in older patients with acute myeloid leukemia (AML). Therefore, the P-gp modulators that block P-gp-mediated drug efflux have been developed, and used in combination with standard chemotherapy. In this paper, the capacity of zosuquidar, a specific P-gp modulator, to reverse chemoresistance was examined in both leukemia cell lines and primary AML blasts.MethodsThe transporter protein expressions were analyzed by flow cytometry using their specific antibodies. The protein functionalities were assessed by the uptake of their fluorescence substrates in presence or absence their specific modulators. The drug cytotoxicity was evaluated by MTT test.ResultsZosuquidar completely or partially restored drug sensitivity in all P-gp-expressing leukemia cell lines tested and enhanced the cytotoxicity of anthracyclines (daunorubicin, idarubicin, mitoxantrone) and gemtuzumab ozogamicin (Mylotarg) in primary AML blasts with active P-gp. In addition, P-gp inhibition by zosuquidar was found to be more potent than cyclosporine A in cells with highly active P-gp.ConclusionThese in vitro studies suggest that zosuquidar may be an effective adjunct to cytotoxic chemotherapy for AML patients whose blasts express P-gp, especially for older patients.

P-gp activity is a critical resistance factor against AVE9633 and DM4 cytotoxicity in leukaemia cell lines, but not a major mechanism of chemoresistance in cells from acute myeloid leukaemia patients

BackgroundAVE9633 is a new immunoconjugate comprising a humanized monoclonal antibody, anti-CD33 antigen, linked through a disulfide bond to the maytansine derivative DM4, a cytotoxic agent and potent tubulin inhibitor. It is undergoing a phase I clinical trial. Chemoresistance to anti-mitotic agents has been shown to be related, in part, to overexpression of ABC proteins. The aim of the present study was to investigate the potential roles of P-gp, MRP1 and BCRP in cytotoxicity in AVE9633-induced acute myeloid leukaemia (AML).MethodsThis study used AML cell lines expressing different levels of P-gp, MRP1 or BCRP proteins and twenty-five samples from AML patients. Expression and functionality of the transporter protein were analyzed by flow cytometry. The cytotoxicity of the drug was evaluated by MTT and apoptosis assays.ResultsP-gp activity, but not MRP1 and BCRP, attenuated AVE9633 and DM4 cytotoxicity in myeloid cell lines. Zosuquidar, a potent specific P-gp inhibitor, restored the sensitivity of cells expressing P-gp to both AVE9633 and DM4. However, the data from AML patients show that 10/25 samples of AML cells (40%) were resistant to AVE9633 or DM4 (IC50 > 500 nM), and this was not related to P-gp activity (p-Value: 0.7). Zosuquidar also failed to re-establish drug sensitivity. Furthermore, this resistance was not correlated with CD33 expression (p-Value: 0.6) in those cells.ConclusionP-gp activity is not a crucial mechanism of chemoresistance to AVE9633. For patients whose resistance to conventional anthracycline AML regimens is related to ABC protein expression, a combination with AVE9633 could be beneficial. Other mechanisms such as microtubule alteration could play an important role in chemoresistance to AVE9633.

Over-expression of cyclin D1 in chronic B-cell malignancies with abnormality of chromosome 11q13

Accurate identification of B‐cell chronic malignancies is sometimes uncertain, despite careful cytologic and immunophenotypic evaluation. Cytogenetics and molecular biology studies may therefore prove useful, because some of these disorders are associated with nonrandom abnormalities, such as the t(11;14)(q13;q32) translocation and bcl‐1 rearrangement mainly observed in mantle‐cell lymphoma (MCL). We studied the expression of cyclin D1 in malignant lymphoid cells from the peripheral blood of 32 patients with various B‐cell chronic lympho‐proliferative disorders, using Northern blot (NB) and RNA in situ hybridization (ISH). Cytogenetic analysis was informative in 18 cases, and most of the missing karyotype data were from typical B‐CLL cases where a t(11;14) is unlikely to be found. Over‐expression of cyclin D1 mRNA was observed by both NB and ISH in four samples (MCL: two cases; lymphoplasmacytic lymphoma: one case, unclassified B‐cell chronic disorder: one case). In each of these cases there was an abnormality of chromosome 11q13, either a t(11;14)(q13;q32) translocation (three cases) or a del(11)(q13) without evidence of chromosome 14 involvement (one case). Cytogenetic and gene rearrangement studies are not available in all institutions and have some technical pitfalls. Because of its close association with bcl‐1 rearrangement and/or t(11;14), the demonstration of cyclin D1 mRNA over‐expression either by NB, or, more conveniently, by ISH, may represent additional information which could be of help for the identification of B‐cell malignancies.