NOTCH1 mutations identify a genetic subgroup of chronic lymphocytic leukemia patients with high risk of transformation and poor outcome.

NOTCH1 has been found recurrently mutated in a subset of patients with chronic lymphocytic leukemia (CLL). To analyze biological features and clinical impact of NOTCH1 mutations in CLL, we sequenced this gene in 565 patients. NOTCH1 mutations, found in 63 patients (11%), were associated with unmutated IGHV, high expression of CD38 and ZAP-70, trisomy 12, advanced stage and elevated lactate dehydrogenase. Sequential analysis in 200 patients demonstrated acquisition of mutation in one case (0.5%) and disappearance after treatment in two. Binet A and B patients with NOTCH1-mutated had a shorter time to treatment. NOTCH1-mutated patients were more frequently refractory to therapy and showed shorter progression-free and overall survival after complete remission. Overall survival was shorter in NOTCH1-mutated patients, although not independently from IGHV. NOTCH1 mutation increased the risk of transformation to diffuse large B-cell lymphoma independently from IGHV, with this being validated in resampling tests of replicability. In summary, NOTCH1 mutational status, that was rarely acquired during the course of the disease, identify a genetic subgroup with high risk of transformation and poor outcome. This recently identified genetic subgroup of CLL patients deserves prospective studies to define their best management.

Extramedullary relapse in acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy.

We analyzed the incidence, presenting features, risk factors of extramedullary (EM) relapse occurring in acute promyelocytic leukemia (APL) treated with all-trans retinoic acid (ATRA) and chemotherapy by using a competing-risk method. In total, 740/ 806 (92%) patients included in three multicenter trials (APL91, APL93 trials and PETHEMA 96) achieved CR, of whom 169 (23%) relapsed, including 10 EM relapses. Nine relapses involved the central nervous system (CNS) and one the skin, of which two were isolated EM relapse. In patients with EM disease, median WBC count was 26950/mm3 (7700-162000). The 3-year cumulative incidence of EM disease at first relapse was 5.0%. Univariate analysis identified age <45 years (P=0.05), bcr3 PML-RARalpha isoform (P= 0.0003) and high WBC counts (> or = 10,000/ mm3) (P<0.0001) as risk factors for EM relapse. In multivariate analysis, only high WBC count remained significant (P= 0.001). Patients with EM relapse had a poorer outcome since median survival from EM relapse was 6.7 months as compared to 26.3 months for isolated BM relapse (P=0.04). In conclusion, EM relapse in APL occurs more frequently in patients with increased WBC counts (> or = 10,000/mm3) and carries a poor prognosis. Whether CNS prophylaxis should be systematically performed in patients with WBC > or = 10,000/mm3 at diagnosis remains to be established.

Outcome of childhood acute promyelocytic leukemia with all-trans-retinoic acid and chemotherapy.

PURPOSE: To determine the results of treatment combining all-trans-retinoic acid (ATRA) and chemotherapy (CT) in childhood acute promyelocytic leukemia (APL). PATIENTS AND METHODS: Children (< 18 years) with newly diagnosed APL were included in the APL93 trial, treated by ATRA followed or combined with daunorubicin-cytarabine, and then randomly assigned between no maintenance, intermittent ATRA, continuous CT, or both. RESULTS: Of the 576 patients included in APL93 trial, 31 (5%) were children, including 22 girls (71%) and nine boys (29%). Thirty of the children (97%) obtained complete remission (CR). ATRA syndrome occurred in four children (13%), who all achieved CR, and headaches occurred in 12 children (39%), with signs of pseudotumor cerebri in five children (16%). Seven patients (23%) relapsed. None of the eight patients who received both ATRA and CT for maintenance relapsed. All relapsing patients achieved a second CR. Twenty-two patients remained in first CR after 43+ to 96+ months, six remained in second CR after 17+ to 66+ months, and three patients had died. The 5-year event-free survival (EFS), relapse, and overall survival rates were 71%, 27%, and 90%, respectively. No difference between adults and children included in the APL93 trial was seen for CR rate, 5-year relapse rate, EFS, and overall survival, but significantly better survival was seen in children after adjustment on WBC counts (P =.02) and incidence of microgranular M3 variant (P =.04). CONCLUSION: ATRA combined with CT for induction and also probably for maintenance provides as favorable results in children with APL as in adults and currently constitutes the reference first-line treatment in both age groups.

Therapy-related acute promyelocytic leukemia.

PURPOSE: To analyze patient cases of therapy-related acute promyelocytic leukemia (tAPL), occurring after chemotherapy (CT), radiotherapy (RT) or both for a prior disorder, diagnosed during the last 20 years in three European countries. PATIENTS AND METHODS: The primary disorder and its treatment, interval from primary disorder to tAPL, characteristics of tAPL, and its outcome were analyzed in 106 patients. RESULTS: Eighty of the 106 cases of tAPL were diagnosed during the last 10 years, indicating an increasing incidence of tAPL. Primary disorders were predominantly breast carcinoma (60 patients), non-Hodgkin's lymphoma (15 patients), and other solid tumors (25 patients). Thirty patients had received CT alone, 27 patients had received RT alone, and 49 patients had received both. CT included at least one alkylating agent in 68 patients and at least one topoisomerase II inhibitor in 61 patients, including anthracyclines (30 patients), mitoxantrone (28 patients), and epipodophyllotoxins (19 patients). Median interval from primary disorder to tAPL diagnosis was 25 months (range, 4 to 276 months). Characteristics of tAPL were generally similar to those of de novo APL. With treatment using anthracycline-cytarabine-based CT or all-trans-retinoic acid combined with CT, actuarial survival was 59% at 8 years. CONCLUSION: tAPL is not exceptional, and develops usually less than 3 years after a primary neoplasm (especially breast carcinoma) treated in particular with topoisomerase II-targeted drugs (anthracyclines or mitoxantrone and less often etoposide). Characteristics and outcome of tAPL seem similar to those of de novo APL.

Allogeneic peripheral blood stem cell transplantation with reduced-intensity conditioning: results of a prospective multicentre study.

Reduced-intensity conditioning (RIC) regimens for allogeneic haematopoietic stem cell transplantation (SCT) have been shown to lead to engraftment of donor stem cells without the severe extra-haematological toxicities of traditional myeloablative transplants. Between December 1998 and December 2000, 76 patients underwent a RIC peripheral blood SCT in a prospective multicentre study. The median age was 53 years, and 57 patients were beyond the early phase of their disease. The conditioning regimens consisted of fludarabine (150 mg/m2) plus melphalan (140 mg/m2) or busulphan (10 mg/kg). Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporin A plus short-course methotrexate. The preparative regimens were well tolerated. All patients experienced severe pancytopenia, but haematological recovery was prompt in all but two cases (early deaths). The 100-d probability of developing grade II-IV acute GVHD was 32% (10% grade III-IV), and the 1-year probability of developing chronic extensive GVHD was 43%. Early complete donor chimaerism was observed in 52/68 patients, and 16 evaluable patients were in complete chimaerism 1 year post transplant. With a median follow-up of 283 d (355 in 48 survivors), the 1-year probability of transplant-related mortality was 20%, and the 1-year overall and progression-free survivals were 60% and 55% respectively. In conclusion, RIC regimens lead to low early toxicity after allografting, with stable donor haematopoietic engraftment, with an apparent low risk of acute GVHD. Chronic GVHD, however, develops in a significant proportion of patients.

Additional cytogenetic changes do not influence the outcome of patients with newly diagnosed acute promyelocytic leukemia treated with an ATRA plus anthracyclin based protocol. A report of the Spanish group PETHEMA.

BACKGROUND AND OBJECTIVES: To analyze in patients with de novo acute promyelocytic leukemia (APL) treated with an ATRA plus anthracyclin-based protocol if the presence of additional cytogenetic aberrations to the t(15;17) influences: 1. clinical and biological presenting features; 2. disease outcome. DESIGN AND METHODS: One hundred and thirteen patients with newly diagnosed APL enrolled in the APL-96 protocol of the Spanish PETHEMA group were studied by conventional karyotyping, FISH and RT-PCR for the PML-RARa fusion. Treatment was homogeneous in all cases and consisted of anthracyclines and ATRA. RESULTS: Additional chromosome aberrations were observed in 30% of cases. The most frequent secondary changes were +8 (14 cases), and abnormalities of chromosomes 9 or 3 (4 patients each), and of chromosomes 1 and 8 (3 cases each). No clinical, biological, morphological, immunophenotypic or molecular differences were observed between the group of APLs with t(15;17) alone and the group of patients with additional changes. Patients with additional changes had a higher rates of complete remission (CR) and 4-year disease-free survival (DFS) (97%, and 97%, respectively) than patients with t(15;17) alone (CR, 70% and DFS, 84%) but these differences were not statistically significant. INTERPRETATION AND CONCLUSIONS: Patients with APL and additional cytogenetic abnormalities do not show different clinical, biological, morphological or molecular features as compared to patients with t(15;17) alone. The prognosis of patients with APL and t(15;17) alone and those with additional changes is similar in both groups. This study indicates that there is no rationale for administering more intensive treatment in APL patients with additional cytogenetic abnormalities receiving ATRA plus anthracycline-based chemotherapy.

Pretreatment characteristics and clinical outcome of acute promyelocytic leukaemia patients according to the PML-RAR alpha isoforms: a study of the PETHEMA group.

Of 167 newly diagnosed acute promyelocytic leukaemia patients, 83 patients were long (L)-form (50%), eight variable (V)-form (5%) and 76 short (S)-form (45%). The V-form and S-form groups presented a significantly higher percentage of patients with white blood cell counts > 10 x 10(9)/l (P < 0.05). The S-form cases displayed a significantly higher number of cases with M3v microgranular features (P = 0.005) and CD34 expression (P < 0.0001). There were no differences between the three isoforms in complete remission (CR) rate (overall CR 90%), but the 3-year disease-free survival was lower for V-form cases than it was for L- and S-form cases (62% vs. 94% and 89%, P = 0.056). We conclude that the V-form and S-form types are associated with some negative prognostic features at diagnosis. However, our data were only able to demonstrate an association with adverse prognosis in the V-form type and, moreover, as the number of cases was limited, needs to be confirmed in large, uniformly treated series.

Additional chromosomal abnormalities in patients with acute promyelocytic leukaemia (APL) do not confer poor prognosis: results of APL 93 trial.

In spite of the recent improvement in the outcome of acute promyelocytic leukaemia (APL) with treatment combining all trans retinoic acid (ATRA) and chemotherapy (CT), some patients with this disease still have a poor outcome. The prognostic significance of chromosomal abnormalities in addition to t(15;17) in APL is uncertain. We examined the prognostic significance of secondary chromosomal changes in 292 patients included in a European trial who were treated with ATRA and CT. The incidence of chromosomal abnormalities in addition to t(15;17) was 26% and trisomy 8 was the most frequent secondary change (46% of the cases with secondary changes). No significant differences were seen with regard to age, sex, initial white blood cell count, % of circulating blasts, platelet count, fibrinogen level and incidence of microgranular variants between patients with or without additional rearrangements. Outcome was also similar between patients with t(15;17) alone and patients with t(15;17) and other clonal abnormalities for complete remission (92% vs. 93% respectively), event-free survival at 2 years (76.1% vs. 78.1% respectively), relapse at 2 years (16.7% vs. 11.6% respectively) and overall survival at 2 years (79.9% vs. 79.5% respectively). Analysis according to the type of induction treatment (ATRA followed by CT or ATRA plus CT) or the type of maintenance treatment (with ATRA, low-dose CT or both) also failed to show any difference between the two groups. Thus, in a large cohort of APL patients treated with ATRA and CT, additional chromosomal abnormalities had no impact on prognosis.

Definition of relapse risk and role of nonanthracycline drugs for consolidation in patients with acute promyelocytic leukemia: a joint study of the PETHEMA and GIMEMA cooperative groups.

Preliminary independent reports of the Italian GIMEMA and the Spanish PETHEMA trials for newly diagnosed acute promyelocytic leukemia (APL) indicated a similarly high antileukemic efficacy in terms of complete remission and disease-free survival rates. To better investigate these studies and the prognostic factors influencing relapse risk, this study analyzed the updated results of 217 patients with PML/RAR alpha-positive APL enrolled in GIMEMA (n = 108) and PETHEMA (n = 109). All patients received identical induction (AIDA schedule) and maintenance. For consolidation, GIMEMA patients received 3 courses including idarubicin/cytarabine, mitoxantrone/etoposide, and idarubicin/cytarabine/thioguanine, whereas PETHEMA patients received the same drugs and dose schedule of idarubicin and mitoxantrone with the omission of nonintercalating agents. Depending on whether molecular relapses were classified as censored or uncensored events, the 3-year Kaplan-Meier estimates of relapse-free survival (RFS) for the combined series were 90 +/- 2% and 86 +/- 2%, respectively. Minor differences observed between the 2 patient cohorts were negligible. Multivariate regression analysis of RFS showed that initial leukocyte (WBC) and platelet counts were the only variables with independent prognostic value. The resulting predictive model for RFS demonstrated its capability of segregating patients into low-risk (WBC count 40 x 10(9)/L), intermediate-risk (WBC count 10 x 10(9)/L) groups, with distinctive RFS curves (P <.0001). The conclusions are that omission of nonanthracycline drugs from the AIDA regimen is not associated with reduced antileukemic efficacy and a simple predictive model may be used for risk-adapted therapy in this disease. (Blood. 2000;96:1247-1253)

Deoxycoformycin in the treatment of patients with hairy cell leukemia: results of a Spanish collaborative study of 80 patients.

BACKGROUND: Deoxycoformycin (DCF) has been reported to produce high response rates in patients with hairy cell leukemia (HCL), but to the authors' knowledge data regarding experience with such therapy in a large HCL series are scarce. METHODS: Between 1988-1997, DCF (4 mg/m(2)/day, every 2 weeks) was administered to 80 HCL patients in 32 Spanish institutions. In 35 of 78 evaluable patients DCF was the first-line therapy; the remaining 43 patients had received other therapies. Pretreatment variables influencing the achievement of complete remission (CR) and event free survival were identified by multivariate analyses. RESULTS: The median number of cycles administered was 7 (range, 1-22 cycles). A CR was obtained in 56 patients (72%) and a partial remission was obtained in 13 patients, for an overall response rate of 88%. In the multivariate analysis previous splenectomy and an Eastern Cooperative Oncology Group (ECOG) performance status > or = 2 were the parameters adversely influencing CR achievement. With a median follow-up of 31.2 months (range, 0.4-126.5 months), disease recurrence was observed in 11 of the CR patients, 5 of whom showed a further response to DCF. An ECOG performance status > or = 2 was the only pretreatment variable associated with a shorter event free survival. Seven patients died, four during the treatment period. The actuarial median event free survival was 46 months (95% confidence interval, 22.5-69.5 months), and 48.7% of the 56 patients who achieved a CR were expected to be alive and disease free at 5 years. Hematologic toxicity (marked neutropenia [22 cases], anemia [6 cases], and thrombocytopenia [1 case]) was the main side effect, followed by nausea and emesis (5 cases); 14 patients required hospitalization. CONCLUSIONS: The results of the current study confirm the effectiveness and acceptable toxicity of DCF in the treatment of patients with HCL.

PROCUSTE1 encodes a cellulose synthase required for normal cell elongation specifically in roots and dark-grown hypocotyls of Arabidopsis.

Mutants at the PROCUSTE1 (PRC1) locus show decreased cell elongation, specifically in roots and dark-grown hypocotyls. Cell elongation defects are correlated with a cellulose deficiency and the presence of gapped walls. Map-based cloning of PRC1 reveals that it encodes a member (CesA6) of the cellulose synthase catalytic subunit family, of which at least nine other members exist in Arabidopsis. Mutations in another family member, RSW1 (CesA1), cause similar cell wall defects in all cell types, including those in hypocotyls and roots, suggesting that cellulose synthesis in these organs requires the coordinated expression of at least two distinct cellulose synthase isoforms.

Beta(1,2)-xylose and alpha(1,3)-fucose residues have a strong contribution in IgE binding to plant glycoallergens.

Primary structures of the N-glycans of two major pollen allergens (Lol p 11 and Ole e 1) and a major peanut allergen (Ara h 1) were determined. Ole e 1 and Ara h 1 carried high mannose and complex N-glycans, whereas Lol p 11 carried only the complex. The complex structures all had a beta(1,2)-xylose linked to the core mannose. Substitution of the proximal N-acetylglucosamine with an alpha(1, 3)-fucose was observed on Lol p 11 and a minor fraction of Ole e 1 but not on Ara h 1. To elucidate the structural basis for IgE recognition of plant N-glycans, radioallergosorbent test analysis with protease digests of the three allergens and a panel of glycoproteins with known N-glycan structures was performed. It was demonstrated that both alpha(1,3)-fucose and beta(1,2)-xylose are involved in IgE binding. Surprisingly, xylose-specific IgE antibodies that bound to Lol p 11 and bromelain did not recognize closely related xylose-containing structures on horseradish peroxidase, phytohemeagglutinin, Ole e 1, and Ara h 1. On Lol p 11 and bromelain, the core beta-mannose is substituted with just an alpha(1,6)-mannose. On the other xylose-containing N-glycans, an additional alpha(1,3)-mannose is present. These observations indicate that IgE binding to xylose is sterically hampered by the presence of an alpha(1,3)-antenna.

Two new 3' PML breakpoints in t(15;17)(q22;q21)-positive acute promyelocytic leukemia.

In the present article, two new types of PML/RARA junctions are described. Both were identified in diagnostic samples from two t(15;17)(q22;q21)-positive acute promyelocytic leukemia (APL) patients who failed to achieve complete remission. By using different sets of primers, reverse transcriptase polymerase chain reaction (RT-PCR) of PML/RARA junctions showed atypical larger bands compared with those generated from the three classical PML breakpoints already described. Sequence analysis of the fusion region of the amplified cDNAs allowed us to determine the specificity of these fragments in both patients. This analysis showed two new hybrid transcripts that were 53 and 306 base pairs (bp) longer than that expressed by the NB4 cell line (PML breakpoint within intron 6), and are the result of the direct joining of RARA exon 3 with PML exon 7a (patient 2) or the 5' portion of PML exon 7b (patient 1), respectively. In patient 1, RT-PCR analysis of the reciprocal RARA/PML junction showed a smaller transcript than that expected in bcr1 cases, while in patient 2 no amplified fragment was obtained. Cytogenetic analysis and/or fluorescence in situ hybridization (FISH) showed that both patients had the t(15;17) translocation. The clinical and hematological profiles expressed by the two patients carrying these unexpected types of PML/RARA rearrangement did not differ significantly from that commonly seen in other APLs with the exception of the poor outcome. Genes Chromosomes Cancer 27:35-43, 2000.

A modified AIDA protocol with anthracycline-based consolidation results in high antileukemic efficacy and reduced toxicity in newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia. PETHEMA group.

The Spanish PETHEMA group designed a protocol for newly diagnosed PML/RARalpha-positive acute promyelocytic leukemia (APL) in which induction and consolidation followed the original AIDA regimen, except for the omission of cytarabine and etoposide from consolidation. Induction consisted of 45 mg/m(2) all-trans retinoic acid (ATRA) daily until complete remission (CR) and 12 mg/m(2) idarubicin on days 2, 4, 6, and 8. Patients in CR received 3 monthly chemotherapy courses: idarubicin 5 mg/m(2)/d x 4 (course no. 1), mitoxantrone 10 mg/m(2)/d x 5 (course no. 2), and idarubicin 12 mg/m(2)/d x 1 (course no. 3). Maintenance therapy consisted of 90 mg/m(2)/d mercaptopurine orally, 15 mg/m(2)/wk methotrexate intramuscularly, and, intermittently, 45 mg/m(2)/d ATRA for 15 days every 3 months. Between November 1996 and December 1998, 123 patients with newly diagnosed PML/RARalpha-positive APL from 39 centers were enrolled. A total of 109 patients achieved CR (89%; 95% confidence interval [CI], 83 to 95), 12 died of early complications, and the remaining 2 were resistant. Consolidation treatment was associated with very low toxicity and no deaths in remission were recorded. Molecular assessment of response by reverse transcriptase-polymerase chain reaction (RT-PCR) showed conversion to PCR-negative in 48 of 99 (51%) and 82 of 88 patients (93%) after induction and consolidation, respectively. The 2-year Kaplan-Meier estimates of overall survival and event-free survival were 82% +/- 4% and 79% +/- 4%, respectively. For patients who achieved CR, the 2-year disease-free survival (DFS) was 92% +/- 3%. These data indicate that a significant reduction in toxicity might be obtained in APL using a less intensive consolidation without apparently compromising the antileukemic effect. These results also suggest a minor role for cytarabine and etoposide in the treatment of newly diagnosed PML/RARalpha-positive APL patients.

A randomized comparison of all transretinoic acid (ATRA) followed by chemotherapy and ATRA plus chemotherapy and the role of maintenance therapy in newly diagnosed acute promyelocytic leukemia. The European APL Group.

All transretinoic acid (ATRA) followed by daunorubicin (DNR)-AraC chemotherapy (CT) has improved the outcome of acute promyelocytic leukemia (APL) by comparison to CT alone. In a randomized trial, (1) we compared 2 induction schedules (ATRA followed by CT [ATRA-->CT] and ATRA plus CT [ATRA+CT, with CT added on day 3 of ATRA treatment]) and (2) we assessed the role of maintenance treatment. Four hundred thirteen patients CT and ATRA+CT (initially randomized patients); patients with a WBC count greater than (high WBC count group, n = 163) and patients 66 to 75 years of age with a WBC count greater than 5,000/microL (elderly group, n = 42) were not initially randomized and received ATRA+CT from day 1 and ATRA -->CT, respectively. All patients achieving CR received 2 additional DNR-AraC courses (only 1 in patients 66 to 75 years of age) and were then randomized for maintenance between no treatment, intermittent ATRA (15 days every 3 months) for 2 years, continuous low-dose CT (6 mercaptopurine + methotrexate) for 2 years, or both, using a 2-by-2 factorial design. Overall, 381 (92%) of the patients achieved complete remission (CR), 31 (7%) suffered an early death, and only 1 patient had leukemic resistance. ATRA syndrome occurred in 64 patients (15%) and was fatal in 5 cases. The CR rate was similar in all induction treatment groups. Event-free survival (EFS) was significantly lower in the high WBC group (P =.0002) and close to significance in the elderly group (P =.086) as compared with initially randomized patients. Relapse at 2 years was estimated at 6% in the ATRA+CT group, versus 16% in the ATRA-->CT group (P =.04, relative risk [RR] =.41). EFS at 2 years was estimated at 84% in the ATRA+CT group, versus 77% in the ATRA-->CT group (P =.1, RR =.62). Two hundred eighty-nine patients were randomized for maintenance. The 2-year relapse rate was 11% in patients randomized to continuous maintenance CT and 27% in patients randomized to no CT (P =.0002) and 13% in patients randomized to intermittent ATRA and 25% in patients randomized to no ATRA (P =.02). An additive effect of continuous maintenance CT and intermittent ATRA was seen, and only 6 of the 74 patients who received both maintenance treatments had relapsed. Overall survival was improved in patients who received maintenance CT (P =.01), and there was a trend for better survival in patients who received maintenance ATRA (P =.22). Our findings strongly suggest that early addition of chemotherapy to ATRA and maintenance therapy combining continuous CT and intermittent ATRA can reduce the incidence of relapse in APL. This effect already translates into significantly better survival for maintenance treatment with continuous CT.

Characterization of N-glycans from Arabidopsis. Application to a fucose-deficient mutant.

The structures of glycans N-linked to Arabidopsis proteins have been fully identified. From immuno- and affinodetections on blots, chromatography, nuclear magnetic resonance, and glycosidase sequencing data, we show that Arabidopsis proteins are N-glycosylated by high-mannose-type N-glycans from Man5GlcNAc2 to Man9GlcNAc2, and by xylose- and fucose (Fuc)-containing oligosaccharides. However, complex biantenary structures containing the terminal Lewis a epitope recently reported in the literature (A. -C. Fitchette-Lainé, V. Gomord, M. Cabanes, J.-C. Michalski, M. Saint Macary, B. Foucher, B. Cavalier, C. Hawes, P. Lerouge, and L. Faye [1997] Plant J 12: 1411-1417) were not detected. A similar study was done on the Arabidopsis mur1 mutant, which is affected in the biosynthesis of L-Fuc. In this mutant, one-third of the Fuc residues of the xyloglucan has been reported to be replaced by L-galactose (Gal) (E. Zablackis, W.S. York, M. Pauly, S. Hantus, W.D. Reiter, C.C.S. Chapple, P. Albersheim, and A. Darvill [1996] Science 272: 1808-1810). N-linked glycans from the mutant were identified and their structures were compared with those isolated from the wild-type plants. In about 95% of all N-linked glycans from the mur1 plant, L-Fuc residues were absent and were not replaced by another monosaccharide. However, in the remaining 5%, L-Fuc was found to be replaced by a hexose residue. From nuclear magnetic resonance and mass spectrometry data of the mur1 N-glycans, and by analogy with data reported on mur1 xyloglucan, this subpopulation of N-linked glycans was proposed to be L-Gal-containing N-glycans resulting from the replacement of L-Fuc by L-Gal.