Clonal rearrangements in childhood and adult precursor B acute lymphoblastic leukemia: a comparative polymerase chain reaction study using multiple sets of primers

Short telomere length is associated with NOTCH1/SF3B1/TP53 aberrations and poor outcome in newly diagnosed chronic lymphocytic leukemia patients

Most previous studies on telomere length (TL) in chronic lymphocytic leukemia (CLL) are based on referral cohorts including a high proportion of aggressive cases. Here, the impact of TL was analyzed in a population-based cohort of newly diagnosed CLL (n = 265) and in relation to other prognostic markers. Short telomeres were particularly associated with high-risk genetic markers, such as NOTCH1, SF3B1, or TP53 aberrations, and predicted a short time to treatment (TTT) and overall survival (OS) (both P < 0.0001). TL was an independent prognostic factor and subdivided patients with otherwise good-prognostic features (e.g., mutated IGHV genes, favorable cytogenetics) into subgroups with different outcome. Furthermore, in follow-up samples (n = 119) taken 5-8 years after diagnosis, TL correlated well with TL at diagnosis and remained unaffected by treatment. Altogether, these novel data indicate that short TL already at diagnosis is associated with poor outcome in CLL and that TL can be measured at later stages of the disease.

LPL is the strongest prognostic factor in a comparative analysis of RNA-based markers in early chronic lymphocytic leukemia

BACKGROUND

The expression levels of LPL, ZAP70, TCL1A, CLLU1 and MCL1 have recently been proposed as prognostic factors in chronic lymphocytic leukemia. However, few studies have systematically compared these different RNA-based markers.

DESIGN AND METHODS

Using real-time quantitative PCR, we measured the mRNA expression levels of these genes in unsorted samples from 252 newly diagnosed chronic lymphocytic leukemia patients and correlated our data with established prognostic markers (for example Binet stage, CD38, IGHV gene mutational status and genomic aberrations) and clinical outcome.

RESULTS

High expression levels of all RNA-based markers, except MCL1, predicted shorter overall survival and time to treatment, with LPL being the most significant. In multivariate analysis including the RNA-based markers, LPL expression was the only independent prognostic marker for overall survival and time to treatment. When studying LPL expression and the established markers, LPL expression retained its independent prognostic strength for overall survival. All of the RNA-based markers, albeit with varying ability, added prognostic information to established markers, with LPL expression giving the most significant results. Notably, high LPL expression predicted a worse outcome in good-prognosis subgroups, such as patients with mutated IGHV genes, Binet stage A, CD38 negativity or favorable cytogenetics. In particular, the combination of LPL expression and CD38 could further stratify Binet stage A patients.

CONCLUSIONS

LPL expression is the strongest RNA-based prognostic marker in chronic lymphocytic leukemia that could potentially be applied to predict outcome in the clinical setting, particularly in the large group of patients with favorable prognosis.

IGHV3-21 gene usage is associated with high TCL1 expression in chronic lymphocytic leukemia

T-cell leukemia/lymphoma protein 1 (TCL1) was recently shown to display an expression pattern in chronic lymphocytic leukemia (CLL) corresponding to molecular subtypes, where poor-risk patients demonstrated higher expression levels. Here, we examined the mRNA expression pattern of TCL1 in 144 patients with CLL, including 67 immunoglobulin heavy-chain variable (IGHV) mutated, 58 IGHV unmutated and 19 patients with IGHV3-21 usage. A higher TCL1 expression level was detected in patients with CLL with unmutated vs. mutated IGHV genes (P < 0.001), whereas no difference was demonstrated within the IGHV3-21 cohort (i.e., mutated vs. unmutated and stereotyped vs. non-stereotyped complementarity determining region 3). The IGHV3-21 subgroup displayed high TCL1 mRNA expression, differing significantly from other IGHV mutated cases (P < 0.001), although 11/19 had mutated IGHV genes. Furthermore, high TCL1 expression levels were associated with significantly shorter overall survival (P < 0.001). Altogether, we show that TCL1 mRNA expression may predict clinical outcome in CLL and that the IGHV3-21 subset, regardless of mutational status, displays high TCL1 expression.

Lipoprotein lipase is differentially expressed in prognostic subsets of chronic lymphocytic leukemia but displays invariably low catalytical activity

Lipoprotein lipase (LPL) expression has been shown to correlate with IGHV mutational status and to predict outcome in chronic lymphocytic leukemia (CLL). We here investigated the prognostic impact of LPL expression in relation to other prognostic markers including IGHV3-21 usage in 140 CLL patients. Additionally, we studied the catalytic activity of LPL in CLL cells. A significant difference in LPL mRNA expression was detected in IGHV unmutated compared to mutated CLL patients (p<0.001). However, the poor-prognostic mutated/stereotyped IGHV3-21 patients did not differ from other mutated CLL cases. Clinical outcome was significantly different in CLL cases with high versus low LPL expression (p<0.001), and LPL expression exceeded mutation status/IGHV3-21 usage as an independent prognostic marker. Finally, LPL protein expression correlated significantly with mRNA expression and was higher in IGHV unmutated versus mutated CLL (p=0.018), although the majority of synthesized protein was catalytically inactive indicating a non-catalytical function in CLL.

In vitro activity of 20 agents in different prognostic subgroups of chronic lymphocytic leukemia--rolipram and prednisolone active in cells from patients with poor prognosis

BACKGROUND

There is a need for development of new drugs for treatment of B-cell chronic lymphocytic leukemia (CLL), especially for poor-prognostic subgroups resistant to conventional therapy.

OBJECTIVE

The in vitro antileukemic activity of 20 different anticancer agents was characterized in tumor cells from CLL, aiming at identifying agents active in poor-prognostic subgroups.

DESIGN AND METHODS

In tumor cells from 40 CLL patients and in peripheral blood mononuclear cells (PBMC) from three healthy controls, the activity of 20 substances was assessed using a non-clonogenic assay. The CLL samples were characterized regarding genomic aberrations by interphase fluorescence in situ hybridization and immunoglobulin heavy-chain variable (IGHV) gene mutational status.

RESULTS

In line with clinical experience, cells from patients with unfavourable genomic aberrations [del(11q)/del(17p)] showed lower drug sensitivity to fludarabine and chlorambucil than cells from patients with favourable cytogenetics [del(13q)/no aberration]. Most investigated drugs demonstrated similar activity in CLL cells from patients with unmutated and mutated IGHV genes as well as in CLL cells vs. PBMC. Interestingly, prednisolone and rolipram displayed high CLL specificity, high activity in CLL cells with unmutated IGHV genes and retained the effect in several cases with 11q/17p deletion. Further studies on prednisolone and rolipram revealed a synergy when these agents were combined in CLL cells, and suggested correlation between drug sensitivity and difference in downstream signaling.

CONCLUSION

Prednisolone and rolipram are interesting for further studies in CLL with inferior prognosis. The study can also be considered a basis for future efforts to find drugs active in subsets of CLL patients that are resistant to conventional therapy.

Quantification of ZAP70 mRNA in B Cells by Real-Time PCR Is a Powerful Prognostic Factor in Chronic Lymphocytic Leukemia

Background: Chronic lymphocytic leukemia (CLL) is heterogeneous with respect to prognosis and clinical outcome. The mutational status of the immunoglobulin variable heavy chain region (IGHV) has been used to classify patients into 2 groups in terms of overall survival (OS) and clinical characteristics, but the labor-intensive nature and the cost of this time-consuming analysis has prompted investigations of surrogate markers.

Methods: We developed a standardized quantitative real-time reverse transcription-PCR (qPCR) method to measure zeta-chain (TCR)-associated protein kinase (ZAP70) mRNA in purified CD19+ cells. We evaluated this and other methods (flow cytometry analyses of ZAP70 and CD38 proteins and qPCR analysis of lipoprotein lipase mRNA) in a cohort of 108 patients (median follow-up, 82 months) to evaluate any associations with IGHV mutational status, OS, and treatment-free survival (TFS).

Results: The association between qPCR-measured ZAP70 and IGHV mutational status was statistically significant [χ2 (1) = 50.95; P &lt;0.0001], and the value of Cramer’s V statistic (0.72) indicated a very strong relation. This method also demonstrated sensitivity, specificity, and positive and negative predictive values of 87.8%, 85.7%, 87.5%, and 86%, respectively. ZAP70 expression was significantly associated with OS (P = 0.0021) and TFS (P &lt;0.0001). ZAP70+ patients had significantly shorter median TFS (24 months) than ZAP70− patients (157 months) (P &lt;0.0001). Moreover, qPCR-measured ZAP70 expression has greater prognostic power than IGHV mutational status and the other prognostic markers tested.

Conclusions: ZAP70 mRNA quantification via qPCR is a strong surrogate marker of IGHV mutational status and a powerful prognostic factor.

Genomic imbalances during transformation from follicular lymphoma to diffuse large B-cell lymphoma

Follicular lymphoma is commonly transformed to a more aggressive diffuse large B-cell lymphoma (DLBCL). In order to provide molecular characterization of this histological and clinical transformation, comparative genomic hybridization was applied to 23 follicular lymphoma and 35 transformed DLBCL tumors from a total of 30 patients. The results were also compared with our published findings in de novo DLBCL. Copy number changes were detected in 70% of follicular lymphoma and in 97% of transformed DLBCL. In follicular lymphoma, the most common alterations were +18q21 (33%), +Xq25-26 (28%), +1q31-32 (23%), and -17p (23%), whereas transformed DLBCL most frequently exhibited +Xq25-26 (36%), +12q15 (29%), +7pter-q22 (25%), +8q21 (21%), and -6q16-21(25%). Transformed DLBCL showed significantly more alterations as compared to follicular lymphoma (P=0.0001), and the alterations -6q16-21 and +7pter-q22 were only found in transformed DLBCL but not in follicular lymphoma (P=0.02). Alterations involving +13q22 were significantly less frequent, whereas -4q13-21 was more common in transformed as compared to de novo DLBCL (P=0.01 and P=0.02, respectively). Clinical progression from follicular lymphoma to transformed DLBCL is on the genetic level associated with acquisition of increasing number of genomic copy number changes, with non-random involvement of specific target regions. The findings support diverse genetic background between transformed and de novo DLBCL.

The G(-248)A polymorphism in the promoter region of the Bax gene does not correlate with prognostic markers or overall survival in chronic lymphocytic leukemia

The G(-248)A polymorphism in the promoter region of the Bax gene was recently associated with low Bax expression, more advanced stage, treatment resistance and short overall survival in B-cell chronic lymphocytic leukemia (CLL), the latter particularly in treated patients. To investigate this further, we analyzed 463 CLL patients regarding the presence or absence of the G(-248)A polymorphism and correlated with overall survival, treatment status and known prognostic factors, for example, Binet stage, VH mutation status and genomic aberrations. In this material, similar allele and genotype frequencies of the Bax polymorphism were demonstrated in CLL patients and controls (n=207), where 19 and 21% carried this polymorphism, respectively, and no skewed distribution of the polymorphism was evident between different Binet stages and VH mutated and unmutated CLLs. Furthermore, no difference in overall survival was shown between patients displaying the G(-248)A polymorphism or not (median survival 85 and 102 months, respectively, P=0.21), and the polymorphism did not influence outcome specifically in treated CLL. Neither did the polymorphism affect outcome in prognostic subsets defined by VH mutation status or genomic aberrations. In conclusion, the pathogenic role and clinical impact of the Bax polymorphism is limited in CLL.

Immunoglobulin mutational status detected through single-round amplification of partial V(H) region represents a good prognostic marker for clinical outcome in chronic lymphocytic leukemia

The immunoglobulin (Ig) mutational status in B-cell chronic lymphocytic leukemia (CLL) distinguishes two subsets of patients with different prognosis. Ig status detection is commonly performed with a panel of V(H) family-specific primers. Although this method detects clonal VDJ rearrangement in virtually all cases, it is technically cumbersome and therefore not widely used clinically. Here, we describe a simple and rapid method to establish the mutational status of IgV(H) in CLL. The method is based on a consensus V(H) FR2 primer, used in both polymerase chain reaction (PCR) and sequencing reactions. Overall, monoclonal B-cell populations were detected in 163 of 189 CLL patients (86%). The prognostic value of IgV(H) mutational status was then evaluated by analyzing survival in 146 CLL cases using different V(H) homology cutoffs. CLL prognostic groups were best separated by the classical 98% cutoff: median survival was 127 and 206 months in unmutated and mutated CLL cases, respectively (P = 0.0023). V(H) FR2 consensus and V(H) family PCR were compared in 41 cases, correctly assigning all cases by both methods. Therefore, we suggest a sequential strategy to detect immunoglobulin mutational status in CLL patients by first using the approach described in this study followed by alternative V(H) family-specific PCRs for negative cases.

Mitogen induced activation, proliferation and surface antigen expression patterns in unmutated and hypermutated chronic lymphocytic leukemia cells

OBJECTIVES

To determine whether the immunoglobulin V(H) gene mutational status has an effect on the activation, proliferation and surface antigen expression of chronic lymphocytic leukemia (CLL) cells when stimulated in vitro.

METHODS

The proliferation and activation responses of CLL cells were studied in 22-immunoglobulin gene V(H) unmutated (UM-CLL) and 12 hypermutated (M-CLL) CLL cases in 4-day cultures. As the mitogen responses have been previously shown to be diverse in CLL, a case-specific strategy based on optimized mitogen combinations (OMCs) of interleukin-2 (IL-2), 12-O-tetradecanoylphorbol 13-acetate (TPA), Staphylococcus aureus Cowan 1 (SAC), and human recombinant tumor necrosis factor alpha (TNF) was applied in cell stimulation. The expression of 23 surface membrane antigens (CD5, CD11c, CD19, CD20, CD21, CD22, CD23, CD25, CD27, CD38, CD40, CD45, CD45RA, CD45RO, CD79b, CD80, CD95, CD124, CD126, CD130, FMC7, IgD, and IgM) was studied by flow cytometry at days 0 and 4.

RESULTS

The proliferation and activation responses were similar in UM-CLL and M-CLL when OMCs contained IL-2, TPA or TNF. SAC induced faster proliferation in UM-CLL than in M-CLL. OMC stimulation induced preferential down-regulation of growth- promoting cell surface receptors CD5, CD21, and CD124 and preferential up-regulation of growth-inhibiting antigen CD80 in M-CLL.

CONCLUSIONS

Difference in immunophenotypic evolution of UM-CLL and M-CLL can be demonstrated if appropriate matrix signals are provided. The pathways for CD5, CD21, CD124 (IL4R), and CD80 (B7-1) regulation should be further explored in relation with somatic hypermutation and outcome of CLL.

Mantle cell lymphomas with clonal immunoglobulin V(H)3-21 gene rearrangements exhibit fewer genomic imbalances than mantle cell lymphomas utilizing other immunoglobulin V(H) genes

A preferential use of one particular immunoglobulin variable heavy chain gene, V(H)3-21, has recently been reported in mantle cell lymphoma, where almost all of these V(H)3-21+ mantle cell lymphomas showed usage of the same light chain Vlambda gene (Vlambda3-19) and also had a tendency towards improved prognosis. These findings suggested that V(H)3-21+ mantle cell lymphomas constitute a distinct subgroup, possibly with antigen stimulation involved in disease pathogenesis. In this study, we applied the comparative genomic hybridization (CGH) method on 37 mantle cell lymphoma tumors in order to investigate if the V(H)3-21+ tumors are different at the genomic level. Interestingly, V(H)3-21+ mantle cell lymphomas (n=14) showed significantly fewer genomic aberrations (mean 2.4) compared to non-V(H)3-21 mantle cell lymphomas (n=23) (mean 4.9). The chromosomal aberrations identified in our study were generally in accordance with previous CGH studies of mantle cell lymphoma; the most frequent aberration was complete or partial loss of chromosome 13, followed by recurrent losses within 6q, 9p, 9q and 11q and frequent gains in 3q, 7p, 8q and 15q. Deletions within 8p and 9p as well as gains in 7p and 15q were found exclusively in the non-V(H)3-21-utilizing tumors. In summary, V(H)3-21+ mantle cell lymphomas demonstrated both a lower number and a different spectrum of genomic aberrations than mantle cell lymphoma in general, thus supporting the hypothesis that V(H)3-21+ mantle cell lymphomas constitute a new subgroup. The findings presented in this report may explain the tendency for a better clinical outcome for patients whose tumors utilize V(H)3-21.

VH gene mutation status and cellular drug resistance in chronic lymphocytic leukaemia

OBJECTIVE

B-cell chronic lymphocytic leukaemia (B-CLL) can be divided into two clinical entities based on the immunoglobulin variable heavy chain (VH) gene mutation status, as cases with unmutated VH genes display a more aggressive disease with shorter survival time than mutated cases. The aim of this study was to investigate whether differences in cellular drug resistance could give an explanation for these divergent clinical courses.

METHODS

The VH gene mutation status was analysed in patients with previously untreated B-CLL using VH gene family-specific PCR amplification and nucleotide sequencing. In vitro sensitivity to cytarabine, fludarabine, cladribine, doxorubicin, idarubicin, vincristine, cyclophosphamide, melphalan and prednisolone was assessed using the non-clonogenic in vitro assay, fluorometric microculture cytotoxicity assay.

RESULTS

The VH genes and in vitro drug resistance were successfully analysed in 46 cases, revealing that 25 (54%) cases showed unmutated and 21 (46%) cases mutated VH genes. Interestingly, the unmutated group generally tended to be more chemosensitive than the mutated group with significant differences for cytarabine and prednisolone (P < or = 0.01).

CONCLUSION

The propensity of inferior drug response in mutated B-CLL may reflect a more differentiated disease than in unmutated B-CLL. We conclude that the difference in prognosis between B-CLL cases with unmutated and mutated VH genes could not be explained by difference in cellular drug resistance.

More extensive genetic alterations in unmutated than in hypermutated cases of chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) is not a uniform disease entity; approximately half of the CLL cases have undergone immunoglobulin V(H) gene hypermutation, whereas the other half display unmutated V(H) genes. We investigated genome changes in 12 hypermutated cases (M-CLL) and 22 unmutated cases (UM-CLL) by use of comparative genomic hybridization, G-banding, and multicolor fluorescence in situ hybridization (m-FISH) after optimal mitogen stimulation and FISH analysis of typical CLL aberrations: 11q deletion, 13q deletion, and trisomy 12. Very high frequencies of aberrations were found in both groups: 82% in UM-CLL and 83% in M-CLL. Deletions of 11q and 13q were equally distributed in M-CLL and UM-CLL. However, larger aberrations detectable by CGH, trisomy 12, and complex aberrations were less frequent in M-CLL than in UM-CLL. These observations led to a hypothesis that unmutated and mutated CLL have different biological Backgrounds, given that large and/or complex chromosomal aberrations and hypermutation of the CLL progenitor cells tend to be mutually exclusive.

Ex vivo drug and irradiation sensitivities in hypermutated and unmutated forms of chronic lymphocytic leukemia cells

Several investigators have now established that chronic lymphocytic leukemia (CLL) is not a uniform disease entity, since approximately half of the cases of CLL have undergone immunoglobulin V region (IgV) hypermutation, whereas the other half display unmutated Ig genes. The median survival time of mutated CLL (M-CLL) cases has been shown to be approximately twice as long as that for unmutated CLL (UM-CLL), but no clear explanation for this difference is currently available. In this work, we have investigated a cohort of previously untreated CLL patients, to see whether the ex vivo sensitivities of leukemic cells of 16 UM-CLL patients differ from those of 8 M-CLL patients, using nine different drugs and two types of irradiation. Our results demonstrated very similar ex vivo sensitivities and tumor cell heterogeneity of sensitivity of UM-CLL and M-CLL cells when tested against chlorambucil, 2-chloro-2'-deoxyadenosine, cyclosporin A, cis-platinum(II)diammine-dichloride, doxorubicin hydrochloride, 2-fluoroadenine-9-beta-D-arabinofuranoside, prednisolone sodium succinate, verapamil, vincristine, gamma-irradiation, and UV-irradiation. This indicates that de novo chemo/radiosensitivity cannot explain the survival difference observed between UM-CLL and M-CLL.

Association between telomere length and V(H) gene mutation status in chronic lymphocytic leukaemia: clinical and biological implications

The immunoglobulin V(H) gene mutation status can divide B-cell chronic lymphocytic leukaemia (CLL) into two entities with a different clinical course. Cases with unmutated V(H) genes, considered to evolve from pregerminal centre (GC) cells, have a worse outcome compared to cases showing mutated V(H) genes, that is, post-GC derived. Also, telomere length has been reported to be of prognostic significance in CLL. Interestingly, telomerase becomes activated during the GC reaction and an elongation of the telomeres occurs in GC B cells. We performed telomere length and V(H) gene analysis in a series of 61 CLL cases, in order to investigate if the unique telomere lengthening shown in GC B cells could reflect the telomere status in the two subsets of mutated and unmutated CLL. A novel association was found between V(H) gene mutation status and telomere length, since significantly shorter telomeres were demonstrated in the unmutated group compared to the mutated group (mean length 4.3 vs 6.3 kbp). Shorter telomeres also constituted a subgroup with a worse prognosis than cases with longer telomeres (median survival 59 vs 159 months). Furthermore, the Ig gene sequence data revealed that samples with high mutations frequency (>6%) had long telomeres ( approximately 8 kbp). Thus, both the telomere and V(H) gene mutation status in CLL appear linked, which may reflect the proliferative history of the clonal cells with regard to the GC reaction.

Surface antigen expression and correlation with variable heavy-chain gene mutation status in chronic lymphocytic leukemia

Recent studies have demonstrated that B-cell chronic lymphocytic leukemia (CLL) consists of two clinical entities with either somatically hypermutated (M-CLL) or unmutated (UM-CLL) immunoglobulin variable heavy-chain (VH) regions. In view of the fact that the cellular biology of these two subsets of disease is currently unexplored, we performed an extensive analysis of the surface antigen expression and correlated this with the VH gene mutation status in a cohort of 32 CLL patients. Using polymerase chain reaction amplification and nucleotide sequencing, the VH genes were shown to be mutated in 10 cases (31%) and unmutated in 22 (69%). The expression of 27 surface membrane antigens in peripheral blood leukemic cells was analyzed by flow cytometry, measuring both the percentage of positive cells as well as the geometric mean fluorescence intensity (GMF). Most of the surface membrane antigens (CD5, CD11c, CD19, CD20, CD21, CD22, CD23, CD25, CD40, CD45, VD79b, CD80, CD95, CD122, CD124, CD126, CD130, CD154, IgM, and IgD) showed a similar expression pattern in both UM-CLL and M-CLL patients. The similarity of M-CLL and UM-CLL, as demonstrated here for the first time with many protein markers, indicates a considerably homogeneous phenotype in both subsets. Furthermore, CD27 was strongly expressed in all cases, which may suggest a memory cell phenotype for both M-CLL and UM-CLL. More positive cells in the UM-CLL group were observed regarding CD38, but CD38 was not a good predictor of VH gene mutation status. Seventy percent of the M-CLL cases, but only 36% of UM-CLL cases, were Ig-lambda+. The most striking differential expression, however, was observed in the two slicing variants of the common leukocyte antigen CD45, namely CD45RO and CD45RA. CD45RO expression was significantly associated with M-CLL, whereas the GMF intensity of CD45RA tended to be associated with UM-CLL. The role of these CD45 splicing variants in the pathogenesis of CLL deserves further investigation.

Polymorphism in the P2X7 receptor gene and survival in chronic lymphocytic leukaemia

BACKGROUND

The P2X7 receptor is a ligand-gated cation channel that mediates ATP-induced apoptotic death in haemopoietic and chronic lymphocytic leukaemia (CLL) cells. We aimed to investigate the clinical effect of a single nucleotide polymorphism in the P2X7 receptor gene (1513A-->C) and correlate findings with the immunoglobulin heavy chain variable (V(H)) gene mutation status, a prognostic marker in CLL.

METHODS

We investigated tumour DNA in 170 patients with CLL using PCR-RFLP analysis with HhaI restriction enzyme cleavage to screen for the polymorphism in the P2X7 receptor gene. The VH gene mutation status was assessed in 165 patients by PCR amplification and nucleotide sequencing. We correlated the findings of the P2X7 receptor genotype with the V(H) gene mutation data and overall survival and screened for the P2X7 receptor polymorphism in 200 healthy controls.

FINDINGS

Of the 170 patients, 35 (21%) were heterozygous and one (1%) homozygous for the 1513C allele; whereas 134 (79%) had the 1513A/A genotype of the P2X7 receptor gene. Overall survival was significantly longer for patients with CLL heterozygous for the 1513C allele than those with the 1513A/A genotype. Median survival for heterozygous patients was 104 months (range 33-467) and 72 months (1-190) for homozygous patients (p=0.009). Of the 165 patients with CLL in whom we assessed the V(H) gene mutation status, the V(H) genes were mutated in 71 (43%) patients and unmutated in 94; 18 (25%) of the 71 patients with mutated genes had 1513C allele compared with 17 (18%) of 94 who had unmutated genes. In patients with mutated VH genes, those with CLL who were 1513C positive had 53 months' longer median survival than did those with the 1513A/A genotype (151 vs 98 months, p=0.011).

INTERPRETATION

The P2X7 polymorphism could affect clinical outcome in CLL, especially in patients with mutated V(H) genes. Studies are necessary to elucidate the biological role of the P2X7 polymorphism in CLL in vivo.

A novel B-cell line (U-2932) established from a patient with diffuse large B-cell lymphoma following Hodgkin lymphoma

Little is known about mechanisms leading to secondary non-Hodgkin lymphomas (NHL) in patients treated for Hodgkin lymphoma (HL). Our aim was to characterise in detail a cell line derived from a diffuse large B-cell lymphoma (DLBCL) that had developed in a patient with relapsing HL. The cell line U-2932 was established from ascites in a patient suffering from DLBCL previously treated for HL with multiple chemotherapy regimens. Characterisation was based on morphology, immunophenotype, Epstein-Barr virus (EBV)-status, IgH gene rearrangement status, tumourigenicity, p53 sequencing, and immunohistochemical expression of p53, BCL-2 and BCL-6. The karyotype was investigated using G-banding, comparative genomic hybridisation (CGH) and spectral karyotype (SKY) analysis. This cell line shows typical morphological features of a DLBCL and grows as colonies in nude mice. It expresses a B-cell phenotype with a somatically hypermutated V(H)4-39 gene and is negative for EBV. The origin of U-2932 was confirmed by demonstrating an identical V(H)4 rearrangement in ascites from the patient. A point mutation of the tumour-suppressor gene p53 was detected in amino acid position 176 and immunohistochemical over-expression of the p53 protein was also demonstrated. U-2932 carries a complex karyotype including high-level amplifications of the chromosomal bands 18q21 and 3q27 and expresses aberrant BCL-2 and BCL-6 immunohistochemically. We were unable to investigate the clonal relationship between the original HL and U-2932. In conclusion, U-2932 is a unique B cell line established from a patient suffering from HL followed by NHL. Overexpression of BCL-2, BCL-6 and p53 may play a role in the tumourigenesis and drug resistance. This cell line may become a useful tool to better understand the mechanisms responsible for development of secondary NHL in patients treated for HL.

Clonal development of a blastoid mantle cell lymphoma studied with comparative genomic hybridization

A molecular cytogenetic study was performed on the diagnostic tumor sample and three relapses from a case with blastoid mantle cell lymphoma. The clonal relatedness of the tumors was demonstrated by identical rearrangements of the immunoglobulin heavy chain gene and was supported by results from comparative genomic hybridization analyses. All samples shared the common alterations of losses of 6q, 9p, and 11q and gains of 3q, 9q, 12p, and 13q, suggesting that they were relatively early events in the tumorigenesis. Relapse 1 also showed a loss of 8p, while relapses 2 and 3 had gained the X chromosome and 7p, in addition, relapse 3 displayed gains of chromosomes 3 and 20. Taken together, the findings suggest that relapses 2 and 3 developed from the diagnostic tumor sample, while relapse 1 represents a separate lineage of tumor progression originating directly from a postulated ancestral tumor cell carrying the common chromosomal alterations identified in all tumors.

Minimal residual disease quantification in childhood acute lymphoblastic leukemia by real-time polymerase chain reaction using the SYBR green dye

OBJECTIVE

Clone specific immunoglobulin (Ig) and T-cell receptor (TCR) gene sequences can be used as molecular targets for detection of minimal residual disease (MRD) in acute lymphoblastic leukemia (ALL). Real-time quantitative PCR (RQ-PCR) with no need for post-PCR processing is an attractive approach for detection and quantification of specific DNA or RNA sequences. In the present study we evaluated a real-time PCR-based technology for MRD quantification in children with precursor-B ALL.

MATERIALS AND METHODS

DNA samples from 36 children with newly diagnosed precursor-B ALL were available for molecular analysis. All patients were uniformly treated according to the Nordic Society of Pediatric Hematology and Oncology (NOPHO) protocols from 1992. A real-time PCR assay was applied for MRD quantification using LightCycler technology and the SYBR green fluorescent dye for detection of clone-specific Ig and TCR gene rearrangements as target sequences. The specificity of the PCR products was verified by melting curve analysis.

RESULTS

Thirty-four of the 36 children with precursor-B ALL (94%) displayed at least one clonal Ig heavy chain (IgH) or TCR gene sequence useful as a molecular target. These clone-specific targets were successfully applied for real-time PCR quantification in all but one patient. Melting curve analysis was important for identifying all specific PCR products. In 32 pediatric precursor-B-ALL patients an MRD level >/=10(-3) at day 29 during induction treatment was significantly correlated with later bone marrow relapse (p = 0.0025).

CONCLUSIONS

Real-time PCR using clone-specific primers and the SYBR green dye for detection is a feasible technique for identifying patients at risk for relapse. This approach provides an easily applicable tool for detection of IgH/TCR gene rearrangements in the routine setting. Melting curve analysis allowed clear distinction between specific rearrangements and unspecific background signals.

Somatic hypermutation and V(H) gene usage in mantle cell lymphoma

Mantle cell lymphoma (MCL) is considered to derive from naïve, pregerminal center (GC) CD5+ B-cells. However, the cell of origin has been questioned in recent studies that showed somatic hypermutations in the immunoglobulin (Ig) variable heavy chain (V(H)) genes in subsets of MCL. To clarify this issue, we analyzed the IgV(H) genes for the presence of somatic hypermutations in 51 MCL cases. Twenty percent of the MCL cases displayed somatically mutated V(H) genes (defined as >2% mutated), whereas 80% showed unmutated V(H) genes. This finding suggests that MCL is a genetically heterogeneous disease, with the majority of cases originating from unmutated pre-GC B-cells and a subset deriving from more mature B-cells which have been exposed to the GC environment and have undergone somatic hypermutation. A biased V(H) gene usage has been demonstrated in several B-cell malignancies; however, this has not yet been investigated in MCL, although V(H)4-34 overusage has been indicated by small studies. Interestingly, we found a restricted usage of three individual V(H) genes in our MCL material; V(H)4-34 (22%), V(H)3-21 (16%) and V(H)5-51 (12%). This novel finding of preferential V(H) gene usage in half of the MCL cases may suggest an antigen driven process occurring in B-cells expressing specific VH genes, thus implicating that Ig specificity could be involved in mantle cell lymphoma development.

Somatically mutated Ig V(H)3-21 genes characterize a new subset of chronic lymphocytic leukemia

Recent studies on the immunoglobulin variable heavy chain (IgV(H)) genes have revealed that B-cell chronic lymphocytic leukemia (B-CLL) consists of at least 2 clinical entities with either somatically mutated or unmutated V(H) genes. We have analyzed the V(H) gene mutation status and V(H) gene usage in 119 B-CLL cases and correlated them to overall survival. A novel finding was the preferential use of the V(H)3-21 gene in mutated cases, whereas biased V(H)1-69 gene usage was found in unmutated cases as previously reported. Interestingly, the subset of mutated cases using the V(H)3-21 gene displayed distinctive genotypic/phenotypic characteristics with shorter average length of the complementarity determining region 3 and clonal expression of lambda light chains. In addition, this mutated subset showed significantly shorter survival than other mutated cases and a similar clinical course to unmutated cases. We therefore suggest that B-CLL cases with mutated V(H)3-21 genes may constitute an additional entity of B-CLL.

Minimal residual disease tests provide an independent predictor of clinical outcome in adult acute lymphoblastic leukemia

PURPOSE

Investigation of minimal residual disease (MRD) in childhood acute lymphoblastic leukemia (ALL) using molecular markers has proven superior to other standard criteria (age, sex, and WBC) in distinguishing patients at high, intermediate, and low risk of relapse. The aim of our study was to determine whether MRD investigation is valuable in predicting outcome in Philadelphia-negative adult patients with ALL.

PATIENTS AND METHODS

MRD was assessed in 85 adult patients with B-lineage ALL by semiquantitative immunoglobulin H gene analysis on bone marrow samples collected during four time bands in the first 24 months of treatment. Fifty patients received chemotherapy only and 35 patients received allogeneic (n = 19) or autologous (n = 16) bone marrow transplantation (BMT) in first clinical remission. The relationship between MRD status and clinical outcome was investigated and compared with age, sex, immunophenotype, and presenting WBC count.

RESULTS

Fisher's exact test established a statistically significant concordance between MRD results and clinical outcome at all times. Disease-free survival (DFS) rates for MRD-positive and -negative patients and log-rank testing established that MRD positivity was associated with increased relapse rates at all times (P <.05) but was most significant at 3 to 5 months after induction and beyond. MRD status after allogeneic BMT rather than before was found to be an important predictor of outcome in 19 adult patients with ALL tested. In patients receiving autologous BMT (n = 16), the MRD status before BMT was more significant (P =.005).

CONCLUSION

The association of MRD test results and DFS was independent of and greater than other standard predictors of outcome and is therefore important in determining treatment for individual patients.

Detailed clonality analysis of relapsing precursor B acute lymphoblastic leukemia: implications for minimal residual disease detection

Genetic instability has important implications for detection of minimal residual disease (MRD) when the target is a clonal genetic marker revealed at diagnosis. A successful MRD detection approach requires a stable marker and for lymphoid leukemias clonal rearrangements of immunoglobulin (Ig) and T cell receptor (TCR) genes are commonly used. In the present study, Ig heavy chain (IgH) and TCR (gamma and delta) genes were studied in 18 consecutive, relapsing precursor-B ALL patients. At least one clonal rearrangement was found in all cases at presentation (IgH 94%, TCRgamma 39% and TCRdelta 28%). An altered rearrangement pattern between diagnosis and relapse was demonstrated in 14 patients (78%). At least one stable molecular target was found in 13 out of 18 cases (72%). Clonal differences between diagnostic and relapse samples were explained by: (1) loss of original rearrangements; (2) V(H) to DJ(H) joining; (3) V(H) gene replacement; (4) appearance of new rearrangements. In two cases with apparently new IgH gene rearrangements at relapse extended sequencing of the diagnostic samples revealed minor clonal rearrangements identical to the relapse clones. Interestingly, one patient displayed instability on both the IgH and TCR gene loci, whereas a stable Igkappa rearrangement was found at presentation and relapse. These data show that clonal diversity is common in precursor-B ALL and strongly suggest that MRD detection should include multiple gene targets to minimize false-negative samples. Even so, five of our 18 relapse cases (28%) lacked stable clonal markers and should have been unsuitable for MRD detection.

Heterogeneity of VH-JH gene rearrangement patterns: an insight into the biology of B cell precursor ALL

Oligoclonal B cell proliferation, as defined by the presence of more than one leukemic clone, has been detected in approximately 20% to 30% of patients with acute lymphoblastic leukemia (ALL) using PCR or Southern blotting. An accurate assessment of these populations is required to avoid false negative measurements of minimal residual disease (MRD) in follow-up bone marrow (BM) samples of ALL patients. In this study, we analysed 29 ALL patients with two or more immunoglobulin heavy (IGH) chain gene rearrangements in the presentation samples using IGH fingerprinting PCR and sequence analysis. Thirty-nine (51%) of 76 sequences (from 15 patients), shared no VNDNJ homology (ie different CDR3 regions). In the remaining 14 patients, at least two related VH sequences were identified in each patient (identical DNJ sequences). Numerical abnormalities of chromosome 14 was detected in 10 patients. Eight patients were analysed at presentation and relapse. In four of them, expansion of a minor presentation-clone was detected at relapse while the major presentation clone disappeared, confirming 'subclonal evolution'. Finally, in our cohort of patients, the presence of related or unrelated IGH clones did not influence overall survival.

Precursor-B-ALL with D(H)-J(H) gene rearrangements have an immature immunogenotype with a high frequency of oligoclonality and hyperdiploidy of chromosome 14

The IGH gene configuration was investigated in 97 childhood precursor-B-ALL patients at initial diagnosis. Rearrangements were found by Southern blotting in all but three patients (97%) and in 30 cases (31%) we observed oligoclonal IGH gene rearrangements. Heteroduplex PCR analysis revealed at least one clonal PCR product in all Southern blot-positive cases. In 89 patients (92%) complete V(D)J rearrangements were found, while incomplete D(H)-J(H) rearrangements occurred in only 21 patients (22%). In 5% of cases the D(H)-J(H) rearrangements were the sole IGH gene rearrangements. Sequence analysis of the 31 identified incomplete rearrangements revealed preferential usage of segments from the D(H)2, D(H)3 and D(H)7 families (78%). While D(H)2 and D(H)3 gene rearrangements occur frequently in normal B cells and B cell precursors, the relatively frequent usage of D(H)7-27 (19%) in precursor-B-ALL patients is suggestive of leukemic transformation during prenatal lymphopoiesis. Among J(H) gene segments in the incomplete D(H)-J(H) rearrangements, the J(H)6 segment was significantly overrepresented (61%). This observation together with the predominant usage of the most upstream D(H) genes indicates that many of the identified clonal D(H)-J(H) gene rearrangements in precursor-B-ALL probably represent secondary recombinations, having deleted pre-existing D(H)-J(H) joinings. The patients with incomplete D(H)-J(H) gene rearrangements were frequently characterized by hyperdiploid karyotype with additional copies of chromosome 14 and/or by IGH oligoclonality. The presence of incomplete D(H)-J(H) joinings was also significantly associated with a less mature immunogenotype: overrepresentation of V(H)6-1 gene segment usage, absence of biallelic TCRD deletions, and low frequency of TCRG gene rearrangements. This immature immunogenotype of precursor-B-ALL with incomplete IGH gene rearrangements was not associated with more aggressive disease.

Improvement of clonality detection rate in multiple myeloma using fluorescent IgH PCR with different sets of primers

The IgH rearrangement provides a useful marker of clonality in B-cell malignancies and amplification of this rearrangement is the method of choice to monitor the residual tumor cells in multiple myeloma (MM). The critical point of this analysis was the false-negative rate observed at diagnosis in patients presenting tumor cells well above the limit of detection. The aim of this study was therefore to increase the clonality detection rate by IgH polymerase chain reaction (PCR). Bone marrow DNA from 37 MM patients were analyzed at diagnosis. IgH PCR with agarose gel detection was performed between framework regions FR3 and FR1, both in combination with 5 different primers in FR4. Fluorescent IgH PCR with highly resolutive capillary electrophoresis was used to improve the detection and to size clonal PCR products. Sixty-two percent of the clonal rearrangements were initially detected with JHD primer specific to the JH segments 1,2,4,5. The use of JH3 and JH6 homologous primers increased the detection rate to 78%, whereas a consensus JH primer only reached 67% of positivity. The lowest detection rates were obtained with JHExt and JH3 with a detection of respectively 43 and 14%. However, three rearrangements were exclusively amplified by JHExt and two additional cases were detected by JH3. The combined use of primers yielded the best score with 89% of positivity. With Genescan analysis, two additional cases showed a monoclonal rearrangement improving the detection rate to 95%. The use of multiple sets of primers along with a highly sensitive genescan analysis makes possible the follow-up of minimal residual disease for most MM patients.