Marion Moos

Structural features of a close homologue of L1 (CHL1) in the mouse: a new member of the L1 family of neural recognition molecules

We have identified a close homologue of L1 (CHL1) in the mouse. CHL1 comprises an N‐terminal signal sequence, six immunoglobulin (Ig)‐like domains, 4.5 fibronectin type III (FN)‐like repeats, a transmembrane domain and a C‐terminal, most likely intracellular domain of ˜100 amino acids. CHL1 is most similar in its extracellular domain to chicken Ng‐CAM (˜40% amino acid identity), followed by mouse L1, chicken neurofascin, chicken Nr‐CAM, Drosophila neuroglian and zebrafish L1.l (37‐28% amino acid identity), and mouse F3, rat TAG‐1 and rat BIG‐1 (˜27% amino acid identity). The similarity with other members of the Ig superfamily [e.g. neural cell adhesion molecule (N‐CAM), DCC, HLAR, rse] is 16‐11%. The intracellular domain is most similar to mouse and chicken Nr‐CAM, mouse and rat neurofascin (˜60% amino acid identity) followed by chicken neurofascin and Ng‐CAM, Drosophila neuroglian and zebrafish L1.l and L1.2 (˜40% amino acid identity). Besides the high overall homology and conserved modular structure among previously recognized members of the L1 family (mouse/human L1/rat NILE; chicken Ng‐CAM; chicken/mouse Nr‐CAM; Drosphila neuroglian; zebrafish L1.l and L1.2; chicken/mouse neurofascin/rat ankyrin‐binding glycoprotein), criteria characteristic of L1 were identified with regard to the number of amino acids between positions of conserved amino acid residues defining distances within and between two adjacent Ig‐like domains and FN‐like repeats. These show a collinearity in the six Ig‐like domains and four adjacent FN‐like repeats that is remarkably conserved between L1 and molecules containing these modules (designated the L1 family cassette), including the GPI‐linked forms of the F3 subgroup (mouse F3/chicken F1l/human CNTN1; rat BIG‐l/mouse PANG; rat TAG‐l/mouse TAX‐l/chicken axonin‐1). The colorectal cancer molecule (DCC), previously introduced as an N‐CAM‐like molecule, conforms to the L1 family cassette. Other structural features of CHL l shared between members of the L1 family are a high degree of N‐glycosidically linked carbohydrates (˜20% of its molecular mass), which include the HNK‐1 carbohydrate structure, and a pattern of protein fragments comprising a major 185 kDa band and smaller fragments of 165 and 125 kDa. As for the other L1 family members, predominant expression of CHL l is observed in the nervous system and at later developmental stages. In the central nervous system CHL l is expressed by neurons, but, in contrast to L1, also by glial cells. Our findings suggest a common ancestral L1‐like molecule which evolved via gene duplication to generate a diversity of structurally and functionally distinct yet similar molecules.

Cancer/Testis Genes in Multiple Myeloma: Expression Patterns and Prognosis Value Determined by Microarray Analysis

Cancer-testis (CT) Ags are expressed in testis and malignant tumors but rarely in nongametogenic tissues. Due to this pattern, they represent attractive targets for cancer vaccination approaches. The aims of the present study are: 1) to assess the expression of CT genes on a pangenomic base in multiple myeloma (MM); 2) to assess the prognosis value of CT gene expression; and 3) to provide selection strategies for CT Ags in clinical vaccination trials. We report the expression pattern of CT genes in purified MM cells (MMC) of 64 patients with newly diagnosed MM and12 patients with monoclonal gammopathy of unknown significance, in normal plasma cell and B cell samples, and in 20 MMC lines. Of the 46 CT genes interrogated by the Affymetrix HG-U133 set arrays, 35 are expressed in the MMC of at least one patient. Of these, 25 are located on chromosome X. The expression of six CT genes is associated with a shorter event-free survival. The MMC of 98% of the patients express at least one CT gene, 86% at least two, and 70% at least three CT genes. By using a set of 10 CT genes including KM-HN-1, MAGE-C1, MAGE-A3/6/12, MAGE-A5, MORC, DDX43, SPACA3, SSX-4, GAGE-1–8, and MAGE-C2, a combination of at least three CT genes—desirable for circumventing tumor escape mechanisms—is obtained in the MMC of 67% of the patients. Provided that the immunogenicity of the products of these 10 CT genes is confirmed, gene expression profiling could be useful in identifying which CT Ags could be used to vaccinate a given patient.

In vivo depletion of B cells using a combination of high‐dose cytosine arabinoside/mitoxantrone and rituximab for autografting in patients with non‐Hodgkin's lymphoma

We performed a pilot study including rituximab (Mabthera; IDEC‐C2B8, Hoffmann‐La Roche) with a sequential high‐dose therapy protocol in 15 patients with follicular and three patients with mantle cell lymphoma and studied the potential of the chemoimmunotherapy to induce depletion of malignant B cells in vivo. Our treatment protocol included induction with three cycles of CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy, followed by peripheral blood stem cell (PBSC) mobilization using high‐dose cytosine arabinoside (2 g/m2 every 12 h, days 1 and 2) and mitoxantrone (10 mg/m2, days 2 and 3) (HAM), preceeded by rituximab (375 mg/m2). The proportion of CD19+ B cells in blood and bone marrow decreased from 1·2 ± 0·4% to 0·13 ± 0·1% (P = 0·01) and from 2·7 ± 0·8% to 0·8 ± 0·5% (P = 0·03) respectively. The number of t(14;18)‐positive cells in blood and bone marrow progressively decreased with treatment, as assessed by the quantitative real‐time PCR assay in four patients. Conversion to PCR‐negativity was achieved in the peripheral blood (PB) of seven informative patients. Leucaphereses were performed during the granulocyte colony‐stimulating factor (G‐CSF)‐supported leucocyte recovery phase. In 17 of 18 patients, a median of 15·1 × 106 CD34+ cells/kg body weight (BW) could be harvested by a single procedure for enrichment by an immunomagnetic method. Leucapheresis products contained 51·3 ± 28·8 × 104 CD19+ B cells/kg BW (mean) and were t(14;18) PCR negative in all seven informative patients. These data compare favourably with results obtained in patients treated with the same regimen without rituximab. The high‐dose therapy (n = 12 patients), including total body irradiation (14·4 Gy) and cyclophosphamide (200 mg/kg BW), was also preceeded by rituximab. Recovery of neutrophils to > 0·5 × 109/l and of platelets to > 20 × 109/l required a median of 13·5 and 11·5 d (range 11–24 and 9–24 d) respectively. In conclusion, the addition of the CD20 antibody to chemotherapy ensured tumour depletion in vivo and allowed the collection of PBSCs devoid of tumour cells and with conserved engraftment capability.

Delineation of distinct subgroups of multiple myeloma and a model for clonal evolution based on interphase cytogenetics.

To delineate multiple myeloma (MM) subgroups and their clonal evolution, we analyzed 81 newly diagnosed patients by interphase fluorescence in situ hybridization using a comprehensive probe set for 10 chromosomes and two IGH rearrangements. A median of 5 probes per patient displayed aberrant signal numbers (range, 1–10). Additional copies most frequently found were for 15q22, 19q13, 9q34, 11q23, and 1q21. Losses commonly observed were of 13q14.3, 17p13, and 22q11. Predominance of gain or loss was quantified by a copy number score (CS) for each patient. Two peaks (CS = +3 and CS = 0) were found by plotting patient copy number scores over CS values corresponding to hyperdiploid and nonhyperdiploid MM. Cluster analysis revealed four major branches: (i) gain of 9q, 15q, 19q, and/or 11q; (ii) deletion of 13q and t(4;14); (iii) t(11;14); and (iv) gain of 1q. Statistical modeling of an oncogenetic tree indicated that early independent events were gain of 15q/9q and/or 11q, t(11;14); deletion of 13q followed by t(4;14); and gain of 1q. Aberrations of 17p13, 22q11, 8p12, and 6q21 were found as subsequent events. MM with gain of 1q was delineated as a subentity with significantly higher beta‐2‐microglobulin and lower hemoglobin levels, indicating a poor prognosis. From our results, we propose a model of MM for clonal evolution.

Expression of EGF-family receptors and amphiregulin in multiple myeloma. Amphiregulin is a growth factor for myeloma cells

A hallmark of plasma cells is the expression of syndecan-1, which has major functions in epithelial cells, in particular as the coreceptor of heparin-binding growth factors. We previously found that heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a growth factor for malignant plasma cells. As amphiregulin (AREG) is another heparin-binding factor of the EGF family, we investigated its role in multiple myeloma (MM). Using Affymetrix DNA microarrays, we show here that the AREG gene was expressed by purified primary myeloma cells from 65 patients and that the expression was higher than in normal bone marrow (BM) plasma cells or plasmablastic cells. AREG stimulated IL-6 production and growth of BM stromal cells. Using real-time reverse transcriptase–polymerase chain reaction, we found that MM cells expressed ErbB receptors and that AREG promoted their growth. Furthermore, PD169540 (a pan-ErbB inhibitor) and IRESSA (an ErbB1-specific inhibitor) induced apoptosis of primary myeloma cells from 10/14 and 4/14 patients, respectively, and there was a synergistic effect with dexamethasone. Altogether, our data provide strong evidence that AREG plays an important role in the biology of MM and emphasize the advantages of using ErbB inhibitors, which might target myeloma cells as well as the tumor environment.

Heparan sulphate proteoglycans are essential for the myeloma cell growth activity of EGF-family ligands in multiple myeloma

The epidermal growth factor (EGF)/EGF-receptor (ErbB1-4) family is involved in the biology of multiple myeloma (MM). In particular, ErbB-specific inhibitors induce strong apoptosis of myeloma cells (MMC) in vitro. To delineate the contribution of the 10 EGF-family ligands to the pathogenesis of MM, we have assessed their expression and biological activity. Comparing Affymetrix DNA-microarray-expression-profiles of CD138-purified plasma-cells from 65 MM-patients and 7 normal individuals to those of plasmablasts and B-cells, we found 5/10 EGF-family genes to be expressed in MMC. Neuregulin-2 and neuregulin-3 were expressed by MMC only, while neuregulin-1, amphiregulin and transforming growth factor-α were expressed by both MMC and normal plasma-cells. Using real-time polymerase chain reaction, we found HB-EGF, amphiregulin, neuregulin-1 and epiregulin to be expressed by cells from the bone marrow-environment. Only the EGF-members able to bind heparan-sulphate proteoglycans (HSPGs) – neuregulin-1, amphiregulin, HB-EGF – promote the growth of MMC. Those ligands strongly bind MMC through HSPGs. The binding and the MMC growth activity was abrogated by heparitinase, heparin or deletion of the HS-binding domain. The number of HS-binding EGF ligand molecules bound to MMC was higher than 105 molecules/cell and paralleled that of syndecan-1. Syndecan-1, the main HSPG present on MM cells, likely concentrates high levels of HS-binding-EGF-ligands at the cell membrane and facilitates ErbB-activation. Altogether, our data further identify EGF-signalling as promising target for MM-therapy.

Evaluation of the cytogenetic aberration pattern in amyloid light chain amyloidosis as compared with monoclonal gammopathy of undetermined significance reveals common pathways of karyotypic instability.

Chromosomal aberrations (CAs) have emerged as important pathogenetic and prognostic factors in plasma cell disorders. Using interphase fluorescence in situ hybridization (FISH) analysis, we evaluated CAs in a series of 75 patients with amyloid light chain amyloidosis (AL) as compared with 127 patients with monoclonal gammopathy of unknown significance (MGUS). We investigated IgH translocations t(11;14), t(4;14), and t(14;16) as well as gains of 1q21, 11q23, and 19q13 and deletions of 8p21, 13q14, and 17p13, detecting at least one CA in 89% of the patients. Translocation t(11;14) was the most frequent aberration in AL, with 47% versus 26% in MGUS (P = .03), and was strongly associated with the lack of an intact immunoglobulin (P < .001), thus contributing to the frequent light chain subtype in AL. Other frequent aberrations in AL included deletion of 13q14 and gain of 1q21, which were shared by MGUS at comparable frequencies. The progression to multiple myeloma (MM) stage I was paralleled by an increased frequency of gain of 1q21 (P = .001) in both groups. Similar branching patterns were observed in an oncogenetic tree model, indicating a common mechanism of underlying karyotypic instability in these plasma cell disorders.

Post‐transplantation tumour load in bone marrow, as assessed by quantitative ASO‐PCR, is a prognostic parameter in multiple myeloma

High‐dose therapy (HDT) and autologous transplantation prolongs remission duration and survival in multiple myeloma (MM), but relapse still occurs at a median of 2 years post‐HDT. In order to investigate whether the number of residual tumour cells in the bone marrow (BM) after transplantation can predict the duration of response, a quantitative allele‐specific oligonucleotide polymerase chain reaction (qASO‐PCR) assay was used to measure tumour load in BM at 3–6 months post‐HDT in 67 patients. The method of maximally selected log‐rank statistics was used to test for the existence of a cut‐off value in the BM tumour load data set. A cut‐off value with respect to progression‐free survival (PFS) was identified (P = 0·001). The estimated threshold for placing patients into a ‘good’ or ‘bad’ prognostic group was 0·015% (n = 22 and 38 respectively) with a median PFS of 64 months vs. 16. Multivariate analysis showed grouping by PCR result to be an independent prognostic factor for PFS (estimated hazard ratio after shrinkage, 3·91). This study identifies for the first time a threshold of the post‐HDT tumour load with prognostic significance for PFS in MM. Quantitative molecular assessment thus may help to identify those patients who are in need of further treatment early after autologous transplantation.

Mobilization of peripheral blood stem cells for autologous transplant in non-Hodgkin's lymphoma and multiple myeloma patients by plerixafor and G-CSF and detection of tumor cell mobilization by PCR in multiple myeloma patients

This report describes the first investigational use of plerixafor in Europe and the determination of tumor cell mobilization by polymerase chain-reaction after plerixafor treatment in a subset of patients with multiple myeloma (MM). Thirty-five patients (31 MM and 4 NHL) received granulocyte colony-stimulating factor (G-CSF) (10 μg/kg) each morning for 4 days. Starting the evening of Day 4, patients recieved plerixafor 0.24 mg/kg. Apheresis was initiated 10–11 h later, in the morning of Day 5. This regimen of G-CSF treatment each morning before apheresis and plerixafor treatment in the evening was repeated for up to 5 consecutive days. Mobilization with plerixafor and G-CSF resulted in a median 2.6-fold increase in peripheral blood (PB) CD34+ cell count compared with before plerixafor treatment. All patients collected ⩾2 × 106 CD34+ cells/kg and 32 of 35 patients collected ⩾5 × 106 CD34+ cells/kg. After plerixafor treatment, 3 of 7 patients had a small increase and 4 of 7 patients had a small decrease in PB tumor cells. No G-CSF was given post transplant. The median number of days to polymorphonuclear leukocyte and platelet engraftment was 14.0 and 11.0, respectively. There were no reports of graft failure. Plerixafor was generally well tolerated. Mobilization of PB CD34+ cells was consistent with previous clinical trials. The addition of plerixafor did not significantly increase the relative number of PB MM tumor cells.

Autografting with CD34+ peripheral blood stem cells: retained engraftment capability and reduced tumour cell content

The efficacy of an immunomagnetic purging method and the Isolex 300 devices were assessed for selecting CD34+ cells from leukapheresis products of 29 patients with non‐Hodgkins lymphoma (NHL), 39 with multiple myeloma and 34 with breast cancer. The mean purity of the CD34+ cell population was 93.6% and the mean recovery was 67.7%. Following enzymatic cleavage by chymopapain the expression of Thy‐1 and Leu‐8 was significantly reduced without affecting haematological recovery. The population of selected CD34+ cells of 4/8 patients with follicular lymphoma became PCR‐negative. A 2.5 log reduction of tumour cells could be achieved in four patients with multiple myeloma as shown by a quantitative PCR assay. There were no tumour cells detectable in any of the 19 CD34+ cell preparations of patients with breast cancer. In 64 patients who received 94 cycles of high‐dose therapy, a mean number of 4.7 × 106 CD34+ cells/kg were autografted. The time needed for platelet reconstitution was different when a comparison was made with 156 patients, who had received unmanipulated leukapheresis products (10 v 12 d, P = 0.006). No significant differences with regard to neutrophil recovery were noted. Five patients had a graft failure. Two of them died (on day 78 and 88 following PBSCT), and three patients were rescued with unmanipulated back‐up transplants. In conclusion, the immunomagnetic selection of CD34+ cells provides autografts with reduced tumour cell content and an engraftment ability similar to that of unmanipulated autografts.