Different mechanisms of cyclin D1 overexpression in multiple myeloma revealed by fluorescence in situ hybridization and quantitative analysis of mRNA levels

Hypermutation in mantle cell lymphoma does not indicate a clinical or biological subentity

Mantle cell lymphoma is a prime example of a well-defined entity based on morphology, phenotype, genetics and also clinical features. Although most patients have an adverse clinical course, some have a better survival than others. The most consistently reported adverse prognostic parameter is a high mitotic rate. Recently, it has been shown that hypermutation in the immunoglobulin heavy-chain gene occurs in a subset of mantle cell lymphomas. It is, however, unclear whether the mutational status is stable over time within a given case, whether hypermutation might be influenced by therapy and how it is related to other relevant biological features of mantle cell lymphoma. In this study, we analyzed 23 typical mantle cell lymphoma cases with respect to mutational status and compared the results with clinicopathological and genetic data to determine whether the presence of mutation indicates a subentity with clinical or pathological relevance. We found somatic hypermutation in 26% of our cases and, interestingly, one case showed ongoing somatic hypermutation. In tumor cells of both mutated and unmutated cases, we found a preferential usage of V(H)3-21 (23%) and V(H)4-34 (19%). No significant correlations were found between mutation status and the other morphological and genetic features analyzed. In conclusion, our results provide additional evidence that mutation status in mantle cell lymphoma is better interpreted as a feature within the spectrum of disease that seems to have little clinical or pathological relevance.

Crystal structure of human CDK4 in complex with a D-type cyclin

The cyclin D1-cyclin-dependent kinase 4 (CDK4) complex is a key regulator of the transition through the G(1) phase of the cell cycle. Among the cyclin/CDKs, CDK4 and cyclin D1 are the most frequently activated by somatic genetic alterations in multiple tumor types. Thus, aberrant regulation of the CDK4/cyclin D1 pathway plays an essential role in oncogenesis; hence, CDK4 is a genetically validated therapeutic target. Although X-ray crystallographic structures have been determined for various CDK/cyclin complexes, CDK4/cyclin D1 has remained highly refractory to structure determination. Here, we report the crystal structure of CDK4 in complex with cyclin D1 at a resolution of 2.3 A. Although CDK4 is bound to cyclin D1 and has a phosphorylated T-loop, CDK4 is in an inactive conformation and the conformation of the heterodimer diverges from the previously known CDK/cyclin binary complexes, which suggests a unique mechanism for the process of CDK4 regulation and activation.

Homoharringtonine inhibits the AKT pathway and induces in vitro and in vivo cytotoxicity in human multiple myeloma cells

Involvement of phosphatidylinositol 3-kinase/Akt-1 in cell survival and proliferation of multiple myeloma (MM) has been well established. In this study, we demonstrate that homoharringtonine (HHT), an antileukemic drug first isolated from the Chinese evergreen Cephalotaxus harringtonia, induces significant cytotoxicity in dexamethasone-sensitive and -resistant and chemotherapy-sensitive MM cell lines in a time and dose-dependent manner. HHT also triggers apoptosis in chemotherapy-resistant patient's myeloma cells. Contrary to dexamethasone, the cytotoxicity of HHT on myeloma is independent of interleukin-6. The mechanism of HHT cytotoxicity is related to down-regulation of Akt phosphorylation/activation and various target genes of Akt including nuclear factor kappa B, XIAP, cIAP and cyclin D1. Moreover, in vivo antitumor activity of HHT is demonstrated in RPMI8226 myeloma xenograft model. Importantly, an additive effect of antitumor is confirmed in the myeloma cells treated with HHT and bortezomib concomitantly with inhibition of phosphorylated Akt. Together, these findings obtained with HHT should give useful insights into a novel antimyeloma chemotherapy.

Efficient shRNA delivery into B and T lymphoma cells using lentiviral vector-mediated transfer

RNA interference is a powerful tool for the functional analysis of proteins by specific gene knockdown. In this study, we devised a rapid and efficient way to screen suitable siRNA sequences and subsequently employ them for specific gene knockdown in usually hard-to-transfect lymphoid cell lines, using a self-inactivating lentiviral vector. Two proteins with different half-lives were chosen, cyclin D1 and STAT3. A specific lacZ reporter fusion assay was used to identify highly effective siRNA sequences. Only siRNA molecules with more than 85% of knockdown efficiency were selected for the generation of lentiviral transfer vectors. Transduction rates of 75-99% were achieved in the lymphoma cell lines Granta 519 (mantle cell lymphoma), Karpas 299, and SUDHL-1 (anaplastic large T cell lymphoma), as demonstrated by green fluorescent protein expression in fluorescence-activated cell sorting analysis. The high level of transduction efficiency allows RNA interference studies to be performed on transduced cells without further manipulation, such as cell sorting or cloning. The LacZ reporter system together with the lentivirus technology is a very important tool in the hematology field, which enables experiments in lymphoid cells that were not possible before.

Specific lentiviral shRNA-mediated knockdown of cyclin D1 in mantle cell lymphoma has minimal effects on cell survival and reveals a regulatory circuit with cyclin D2

Cyclin D1 overexpression is the hallmark of mantle cell lymphoma (MCL). However, the importance of cyclin D1 in the maintenance and progression of the disease remains to be defined. The aim of this study was to elucidate the role of cyclin D1 overexpression using an efficient cyclin D1-shRNA and a lentiviral system in well-characterized MCL cell lines. Surprisingly, the knockdown of cyclin D1 led to a moderate retardation in growth, without induction of apoptosis. The cyclin D1-shRNA-transduced MCL cells showed a 15% shift from S phase to G(1) phase of the cell cycle, a weak induction of p27(Kip1), decreased Rb (Ser807/811) phosphorylation, and a consistent upregulation of cyclin D2 mRNA and protein expression. However, double knockdown of cyclins D1 and D2 did not intensify the effects observed with cyclin D1 knockdown alone. These data suggest that the moderate effects of cyclin D1 downregulation on survival and proliferation are likely the result of compensatory cyclin-independent mechanisms governing proliferation or alternatively, secondary genetic events that make cyclin D1 dispensable. These findings have important implications for MCL therapy, as strategies targeting only cyclin D1 function might be hampered by compensatory regulatory mechanisms, resulting in a low probability of treatment response.

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.

Evaluation of the branched-chain DNA assay for measurement of RNA in formalin-fixed tissues

We evaluated the branched-chain DNA (bDNA) assay QuantiGene Reagent System to measure RNA in formalin-fixed, paraffin-embedded (FFPE) tissues. The QuantiGene Reagent System does not require RNA isolation, avoids enzymatic preamplification, and has a simple workflow. Five selected genes were measured by bDNA assay; quantitative polymerase chain reaction (qPCR) was used as a reference method. Mixed-effect statistical models were used to partition the overall variance into components attributable to xenograft, sample, and assay. For FFPE tissues, the coefficients of reliability were significantly higher for the bDNA assay (93-100%) than for qPCR (82.4-95%). Correlations between qPCR(FROZEN), the gold standard, and bDNA(FFPE) ranged from 0.60 to 0.94, similar to those from qPCR(FROZEN) and qPCR(FFPE). Additionally, the sensitivity of the bDNA assay in tissue homogenates was 10-fold higher than in purified RNA. In 9- to 13-year-old blocks with poor RNA quality, the bDNA assay allowed the correct identification of the overexpression of known cancer genes. In conclusion, the QuantiGene Reagent System is considerably more reliable, reproducible, and sensitive than qPCR, providing an alternative method for the measurement of gene expression in FFPE tissues. It also appears to be well suited for the clinical analysis of FFPE tissues with diagnostic or prognostic gene expression biomarker panels for use in patient treatment and management.

Cyclin D1 positive multiple myeloma: Predominance of the short, 3′UTR-deficient transcript is associated with high cyclin D1 mRNA levels in cases with t(11;14) translocation, but does not correlate with proliferation rate or genomic deletions

Multiple myeloma (MM) frequently shows overexpression of cyclin D1, either due to a t(11;14)(q13;q32) translocation, or in association with polysomy 11. The predominant expression of a cyclin D1 mRNA isoform lacking the 3'-untranslated region (Delta3'UTR) is associated with higher total cyclin D1 mRNA levels, increased proliferation and poor prognosis in mantle cell lymphoma, and can be caused by genetic alterations of the 3'UTR region. The role of this cyclin D1 isoform in MM is unknown. We therefore quantified levels of total and Delta3'UTR cyclin D1 mRNA by real-time RT-PCR in cytogenetically characterized cyclin D1+MM primary cases, and cyclin D1+cell lines. Both long and Delta3'UTR cyclin D1 transcripts were expressed in 35/41 MM cases, but none of the samples showed complete loss of the long transcript or genomic alterations of the 3'UTR. Predominance of the Delta3'UTR mRNA was associated with higher cyclin D1 levels in cases with t(11;14), but did not correlate with the proliferation rate, suggesting a different role of this isoform in MM.

Diagnosis and Classification of Malignant Lymphoma and Related Entities in the Bone Marrow Trephine Biopsy

The trephine bone marrow (BM) biopsy is an important diagnostic tool in patients with malignant lymphoma. BM examination can serve to establish or confirm a primary diagnosis of lymphoma or to determine the extent of disease dissemination for staging purposes. BM histology renders information which cannot be gained equally from aspirate material, such as spacial distribution and extent of infiltrates, BM cellularity and fibrosis. Furthermore, cytology including flow cytometric immunophenotyping can give false-negative results in BM involvement by lymphoma due to intralesional fibrosis. In addition to morphological examination, the availability of a broad panel of antibodies suitable for paraffin-embedded tissues, in conjunction with less damaging decalcification procedures, nowadays enables us to perform complete immunophenotyping on BM trephines and allows for classification of lymphoma infiltrates according to established algorithms. Molecular determination of clonality and interphase fluorescent in situ hybridization can be employed selectively to resolve difficult cases. This review describes important diagnostic features of malignant lymphoma in the BM, relevant differential diagnoses, and the proper use of ancillary techniques.

Chromosomal Translocations t(4;14), t(11;14) and Proliferation Rate Stratify Patients With Mature Plasma Cell Myelomas Into Groups With Different Survival Probabilities—A Molecular Epidemiologic Study on Tissue Microarrays

Plasma cell myelomas (PMs) exhibit clinical and molecular heterogeneity. To date, morphology and immunohistochemistry on bone marrow trephines are of limited value to stratify patients into different prognostic categories. However, some chromosomal translocations are of prognostic and/or of predictive importance in PMs. In this study, the prognostic significance of morphology, CyclinD1 expression, proliferation index (Mib1) and presence of the translocations FGFR3/IgH [t(4;14)] and CCND1/IgH [t(11;14)] are compared in 119 patients with PM. Immunohistochemistry and fluorescence in situ hybridization analysis were carried out on a tissue microarray containing bone marrow trephines. Hundred and one PMs showed a mature morphology whereas 10 were immature. All but one PM carrying a translocation showed a mature morphology. Patients with a t(4;14) (12%) had a statistically significant shorter 1-year survival (P=0.004), whereas those with a t(11;14) (21%) had a trend towards a better clinical outcome. CyclinD1 protein expression was not significantly associated with survival. Besides the t(4;14), an immature morphology (P<0.001) and a proliferation index (Mib1) of more than 10% (P=0.002) were associated with a significantly worse outcome. A high occurrence of strong CyclinD1 protein expression in the tumor cells was predictive of either a t(11;14) or of a low level amplification of the CCND1 gene, suggesting that different molecular mechanisms may have lead to an over-expression of the CyclinD1 protein in PMs. These findings demonstrate that a high proliferation rate and translocations involving the IgH locus can stratify mature PMs into groups with distinct survival probabilities.

Significant impact of survivin on myeloma cell growth

Survivin is a fascinating member of the inhibitor of apoptosis protein (IAP) family with its dual roles in mitosis and apoptosis, and emerges as an attractive target for cancer therapy. Multiple myeloma (MM) is a plasma cell malignancy, characterized by deregulated proliferation, cell-death processes and fatal outcome. We thus investigated survivin expression in myeloma cells and its role in MM biology to evaluate its potential interest as a target in MM treatment. Our results describe the cancer-specific overexpression of survivin in myeloma cells and show a significant correlation between survivin expression at protein level and clinical course of MM. Moreover, survivin knockdown by RNA interference led to growth rate inhibition of myeloma cells related to apoptosis induction and deep cell-cycle disruption. Finally, survivin knockdown sensitized myeloma cells to conventional anti-myeloma agents. Altogether, these data argue for the interest to evaluate survivin antagonists in MM treatment.

Frequency and distribution of trisomy 11 in multiple myeloma patients: relation with overexpression of CCND1 and t(11;14)

Multiple myelomas (MM) recently have been stratified into five groups (TC1-TC5) on the basis of the presence of the recurrent IgH chromosomal translocation and cyclin D expression. Cyclin D1 is detectable in up to one third of MM patients and plays crucial role in the regulation of G1-S transition in cell cycle. To evaluate the mechanisms of cyclin D1 overexpression, fluorescence in situ hybridization analysis with specific probes for the CCND1 gene and t(11;14)(q13;q32) were performed on highly purified plasma cells from bone marrow samples of 30 MM patients at diagnosis. CCND1 gene overexpression was detected in 14/30 cases (46.6%). Patients with evidence of the t(11;14) showed strong nuclear staining for cyclin D1 (TC1 group) and 7/8 demonstrated CCND1 overexpression. The remaining 7/15 cases with increased CCND1 gene copy numbers lacked the t(11;14) and showed low to negative levels of cyclin D1 protein (TC2 group). Trisomy 11 was demonstrated in 2/8 cases carrying the t(11;14) (TC1), 6/7 overexpressing cyclin D1 without the translocation (TC2), and 4/15 negative for both alterations (TC3-TC5). According to our data, trisomy 11 does not appear to directly cause CCND1 gene overexpression because it was present in 4/15 patients without the overexpression of the CCND1 gene and in 2/8 patients carrying the t(11;14). One patient belonging to the TC2 group overexpressed cyclin D1 and lacked both trisomy and translocation, suggesting that cyclin D1 can be dysregulated by additional mechanisms. In the TC2 group, trisomy 11 may probably be considered as a recurrent polisomy of the hyperdiploid status.

Real-time quantitative RT-PCR shows variable, assay-dependent sensitivity to formalin fixation: implications for direct comparison of transcript levels in paraffin-embedded tissues

Real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) is a versatile tool for precise quantification of gene expression. Formalin-fixed and paraffin-embedded (FFPE) tissue is well suited for qRT-PCR, if RNA extraction is optimized and small amplicon sizes are used. However, little is known whether individual assays may show variable sensitivity to fixation. This is of great importance, if a direct comparison of different transcripts is performed within the same sample, such as for mRNA splice variants. We established a cell culture model to test for and quantify differences in performance of individual qRT-PCR assays on FFPE as compared with fresh material, using TaqMan methodology. RNA was isolated from 7 different cell lines either directly or after preparation of a FFPE cell block. RNA from both sources was reverse transcribed and gene expression quantified using 13 different TaqMan assays. All assays allowed highly reproducible target quantification, using both fresh and FFPE-derived cDNA. The 13 assays showed an average Ct difference of 3.2 between fresh and FFPE cells, if identical amounts of cDNA were used as template. However, the Ct shifts varied from 1.8 to 5.1 for individual assays, indicating variable resistance to fixation. These Ct shift differences were statistically highly significant in 27/78 (35%) of all possible combinations of assays. Because the Ct shift remained constant for each assay, they could be used for calculation of correction factors which rendered FFPE-derived expression data highly comparable to those obtained from fresh material, and as a consequence among each other. Thus, a standardized assessment of qRT-PCR assay efficiencies in FFPE allows for precise intraindividual comparison of mRNA species, such as splice variants with different biologic functions, in archival tissues.

Clinical implications of chromosomal abnormalities in multiple myeloma

The adverse prognostic role of cytogenetic abnormalities has recently been established in plasma cell dyscrasias. Modern techniques such as fluorescence in situ hybridization and comparative genomic hybridization have revealed a higher incidence of cytogenetic abnormalities in patients with multiple myeloma (MM) compared to conventional cytogenetics. Hypodiploidy and chromosome 13 abnormalities are found in more than 50% of myeloma patients, representing well known factors with adverse prognosis. Rearrangements involving the switch regions of immunoglobulin heavy chain (IgH) gene at 14q32 with various partner genes represent the most common structural abnormalities, having an incidence of 70% in MM. Structural abnormalities of chromosomes 17 and 8 involving the p53 and c-myc genes are considered to be less frequent events, but carry a poor prognosis. New therapeutic approaches such as non-myeloablative allotransplantation and modern therapeutic agents (thalidomide, lenalidomide, and bortezomib) and their combinations give promise for an improved therapeutic management of patients with MM. The detection of t(4;14), t(14;16), deletion of chromosome 13 on metaphase analysis, or deletion of p53 by FISH will define high-risk prognostic groups that are not generally controlled with high-dose melphalan and autologous stem cell transplantation (ASCT), and should therefore be treated with more investigational therapies. Alternatively, eligible patients who do not have these poor risk factors are more likely to benefit from a high-dose, melphalan-based, regimen followed by ASCT.

Cytogenetics and molecular cytogenetics in multiple myeloma

Multiple myeloma (MM) is characterized by frequent and complex genomic abnormalities that not only essentially contribute to the pathogenesis of this disease but also reflect its prognostic heterogeneity. There is evidence for two more or less mutually exclusive oncogenic pathways in the early development of clonal plasma cell disorders. Approximately half the tumours are non-hyperdiploid and carry translocations of the immunoglobulin heavy-chain (IgH) locus and various oncogenes, for example Cyclin D1, Cyclin D3, and FGFR3. The remaining hyperdiploid tumours exhibit recurrent trisomies - typically of chromosomes 5, 7, 9, 11, 15, 19, and 21 - but infrequently exhibit IgH translocations. While some chromosomal aberrations, such as deletion of chromosome arm 13q, deliver independent prognostic information that is already utilized for risk stratification within clinical trials, the prognostic significance of most other genetic aberrations in MM is undetermined.

Mutually Exclusive Cyclin-Dependent Kinase 4/Cyclin D1 and Cyclin-Dependent Kinase 6/Cyclin D2 Pairing Inactivates Retinoblastoma Protein and Promotes Cell Cycle Dysregulation in Multiple Myeloma

Multiple myeloma, the second most common hematopoietic cancer, ultimately becomes refractory to treatment when self-renewing multiple myeloma cells begin unrestrained proliferation by unknown mechanisms. Here, we show that one, but not more than one, of the three early G(1) D cyclins is elevated in each case of multiple myeloma. Cyclin D1 or D3 expression does not vary in the clinical course, but that alone is insufficient to promote cell cycle progression unless cyclin-dependent kinase 4 (cdk4) is also elevated, in the absence of cdk6, to phosphorylate the retinoblastoma protein (Rb). By contrast, cyclin D2 and cdk6 are coordinately increased, thereby overriding the inhibition by cdk inhibitors p18(INK4c) and p27(Kip1) and phosphorylating Rb in conjunction with the existing cdk4. Thus, cyclin D1 pairs exclusively with cdk4 and cdk6 pairs only with cyclin D2, although cyclin D2 can also pair with cdk4 in multiple myeloma cells. The basis for this novel and specific cdk/D cyclin pairing lies in differential transcriptional activation. In addition, cyclin D1- or cyclin D3-expressing multiple myeloma cells are uniformly distributed in the bone marrow, whereas cdk6-specific phosphorylation of Rb occurs in discrete foci of bone marrow multiple myeloma cells before proliferation early in the clinical course and is then heightened with proliferation and disease progression. Mutually exclusive cdk4/cyclin D1 and cdk6/cyclin D2 pairing, therefore, is likely to be a critical determinant for cell cycle reentry and progression and may play a pivotal role in the expansion of self-renewing multiple myeloma cells.

Ancillary techniques in bone marrow pathology: molecular diagnostics on bone marrow trephine biopsies

Pathologic examination of trephine bone marrow (BM) biopsies plays a central role in the diagnosis and staging of haematological neoplasms and other disorders affecting haematopoiesis. Haematopathology has been profoundly influenced by the advent of molecular genetic techniques suitable for paraffin-embedded tissues, and certain applications, such as the determination of B- and T-cell clonality, belong to its standard diagnostic repertoire. Many of these molecular tests can be performed successfully with nucleic acids extracted from BM trephine biopsies, if some technical aspects specific to this template source such as various fixation and decalcification procedures are taken into consideration. The current indications for molecular BM diagnostics range from the confirmation of lymphoma involvement with gene rearrangement analysis, demonstration of tumor-specific translocations in lymphoid and chronic myeloproliferative disorders along to the detection of microorganisms or marrow involvement by soft tissue sarcomas. The availability of quantitative polymerase chain reaction techniques for the investigation of allelic imbalances and gene expression levels in paraffin-embedded material also open new avenues for research and advanced diagnostics. The molecular detection of minimal residual disease in haematological neoplasms, especially in the context of new treatment strategies, will provide future challenges. This article summarizes the current state of the art in molecular diagnostics applied to paraffin-embedded BM biopsies.

Immunohistochemistry in bone marrow pathology: a useful adjunct for morphologic diagnosis

Pathomorphological examination of trephine biopsies of the bone marrow (BM) represents a standard method for the diagnosis and staging of hematologic neoplasms and other disorders involving the BM. The increasing knowledge about the genetic basis and biology of hematologic neoplasms, as well as the recently proposed WHO classification system, provide the framework for an accurate diagnosis. Although conventional morphology remains the gold standard for paraffin-embedded BM trephines, immunohistochemical stainings have become an integral part of the diagnostic workup. Antibodies suitable for paraffin sections are generally applicable to BM trephines, but modifications of staining protocols may be necessary due to the alternative fixatives and decalcification procedures used for BM biopsies. The indications for immunostainings range from confirmation and classification of lymphoma involvement, subclassification of acute leukemias, and estimating blast counts in myelodysplastic and myeloproliferative syndromes to characterization of BM involvement in nonhematologic neoplasms. Although subtyping of NHL in the BM is more difficult from the point of morphology, classification of the entities that frequently involve the BM, especially the small B-cell lymphomas, can easily be achieved with the help of immunohistochemistry. In this review, we try to summarize the current state of the art in BM immunohistochemistry for the diagnosis of hematologic disorders. Moreover, diagnostic algorithms and useful antibody panels are proposed for a rational and cost-effective approach.

Molecular Classification of Multiple Myeloma: A Distinct Transcriptional Profile Characterizes Patients Expressing CCND1 and Negative for 14q32 Translocations

Purpose

The deregulation of CCND1, CCND2 and CCND3 genes represents a common event in multiple myeloma (MM). A recently proposed classification grouped MM patients into five classes on the basis of their cyclin D expression profiles and the presence of the main translocations involving the immunoglobulin heavy chain locus (IGH) at 14q32. In this study, we provide a molecular characterization of the identified translocations/cyclins (TC) groups.

Materials and Methods

The gene expression profiles of purified plasma cells from 50 MM cases were used to stratify the samples into the five TC classes and identify their transcriptional fingerprints. The cyclin D expression data were validated by means of real-time quantitative polymerase chain reaction analysis; fluorescence in situ hybridization was used to investigate the cyclin D loci arrangements, and to detect the main IGH translocations and the chromosome 13q deletion.

Results

Class-prediction analysis identified 112 probe sets as characterizing the TC1, TC2, TC4 and TC5 groups, whereas the TC3 samples showed heterogeneous phenotypes and no marker genes. The TC2 group, which showed extra copies of the CCND1 locus and no IGH translocations or the chromosome 13q deletion, was characterized by the overexpression of genes involved in protein biosynthesis at the translational level. A meta-analysis of published data sets validated the identified gene expression signatures.

Conclusion

Our data contribute to the understanding of the molecular and biologic features of distinct MM subtypes. The identification of a distinctive gene expression pattern in TC2 patients may improve risk stratification and indicate novel therapeutic targets.

High incidence and intraclonal heterogeneity of chromosome 11 aberrations in patients with newly diagnosed multiple myeloma detected by multiprobe interphase FISH

In multiple myeloma, additional copies of chromosome 11 material, reported to confer an unfavorable prognosis, have been found in 20-45% of patients. To assess the incidence and extent of chromosome 11 aberrations, we performed interphase fluorescence in situ hybridization on CD138+ bone marrow plasma cells of 50 newly diagnosed myeloma patients, using seven locus-specific probes for chromosome 11, one for 13q14.3, and a probe set for translocation t(11;14). In 33 of 50 patients, chromosome 11 aberrations were found. Results indicated a marked intraclonal heterogeneity: in 13 patients, trisomy 11; in 10 patients, subclones with trisomy 11 and partial trisomies 11q coexisted; in 6 patients, only a partial trisomy 11q; and in 6 patients, a tetrasomy or partial tetrasomy 11. The coexistence of subclones with varying extent and copy numbers of chromosome 11 material indicates ongoing structural changes and clonal evolution. Hybridization results delineated 11q23 and 11q25 as the most frequently gained regions, which supports a relevant pathogenetic role of genes on 11q23 and 11q25. To confirm the high incidence of 11q23 gains, a further 50 patients (total n=100) were analyzed for 11q23 and 13q14.3. Myeloma with gains of 11q23 showed a low frequency of deletion 13q14.3 and may prove to be a distinct subgroup of this disease.

Growth inhibition of multiple myeloma cells by a novel IkappaB kinase inhibitor

Involvement of nuclear factor-kappaB (NF-kappaB) in cell survival and proliferation of multiple myeloma has been well established. In this study we observed that NF-kappaB is constitutively activated in all human myeloma cell lines, thus confirming the previous studies. In addition, we found the phosphorylation of p65 subunit of NF-kappaB in addition to the phosphorylation of IkappaBalpha and the activation of NF-kappaB DNA binding and that various target genes of NF-kappaB including bcl-x(L), XIAP, c-IAP1, cyclin D1, and IL-6 are up-regulated. We then examined the effect of a novel IkappaB kinase inhibitor, 2-amino-6-[2-(cyclopropylmethoxy)-6-hydroxyphenyl]-4-piperidin-4-yl nicotinonitrile (ACHP). When myeloma cells were treated with ACHP, the cell growth was efficiently inhibited with IC(50) values ranging from 18 to 35 mumol/L concomitantly with inhibition of the phosphorylation of IkappaBalpha/p65 and NF-kappaB DNA-binding, down-regulation of the NF-kappaB target genes, and induction of apoptosis. In addition, we observed the treatment of ACHP augmented the cytotoxic effects of vincristine and melphalan (l-phenylalanine mustard), conventional antimyeloma drugs. These findings indicate that IkappaB kinase inhibitors such as ACHP can sensitize myeloma cells to the cytotoxic effects of chemotherapeutic agents by blocking the antiapoptotic nature of myeloma cells endowed by the constitutive activation of NF-kappaB.

Simultaneous over-expression of the Her2/neu and PTK6 tyrosine kinases in archival invasive ductal breast carcinomas

Expression of eight tumour-relevant genes was studied in formalin-fixed, paraffin-embedded tissue from 54 invasive ductal breast carcinomas using quantitative reverse transcription PCR (Q-RT-PCR). Seven of the genes map to chromosome 20q and are potential candidates for gene amplification and over-expression. The Her2/neu oncogene, on chromosome 17q, was investigated in the same tumours. Increased expression was most frequent for PTK6, Her2/neu, and ADA. No other 20q candidate gene (AIB1, PTPN1, ZNF217, and PFDN4) was prominent. A significant correlation between the expression of the tyrosine kinases PTK6 and Her2/neu was detected. The frequent elevation of PTK6 expression (in 43/54 tumours), and its correlation with Her2/neu oncogene over-expression, suggests a clinically relevant link between these two over-expressed tyrosine kinases.

Duplication of chromosome arms 9q and 11q: evidence for a novel, 14q32 translocation-independent pathogenetic pathway in multiple myeloma

14q32 translocations [t(14q)] represent critical but not universal events in multiple myeloma (MM). Gains of chromosome arms 1q, 9q, and 11q (+1q, +9q, and +11q) have recently been identified as frequent aberrations in this disease, but their pathogenetic significance remains unclear. We studied a series of 108 MM patients using fluorescence in situ hybridization and DNA probes mapping to chromosome bands 1q21, 9q34, 11q25, 13q14, and 14q32. Three subsets of tumors were defined: (1) MM+/+ (detection of +9q and +11q; 43.5% of cases), (2) MM+/- (+9q or +11q; 21.3%), and (3) MM-/- (neither +9q nor +11q; 35.2%). The incidence of t(14q) was significantly different in these subgroups: 23% in MM+/+, 56% in MM+/-, and 89% in MM-/-. Deletion of 13q (13q-) also was significantly less frequent in MM+/+ (23%) than in MM+/- and MM-/- (36% and 63%, respectively). The nonrandom distribution of chromosomal aberrations in the present series of MM tumors points to a novel, 14q32 translocation-independent pathogenetic pathway in plasma cell neoplasms.

Cyclin D dysregulation: an early and unifying pathogenic event in multiple myeloma

Two oncogenic pathways have been hypothesized for multiple myeloma (MM) and premalignant monoclonal gammopathy of undetermined significance (MGUS) tumors: a nonhyperdiploid pathway associated with a high prevalence of IgH translocations and a hyperdiploid pathway associated with multiple trisomies of 8 chromosomes. Cyclin D1, D2, or D3 expression appears to be increased and/or dysregulated in virtually all MM tumors despite their low proliferative capacity. Translocations can directly dysregulate CCND1 (11q13) or CCND3 (6p21), or MAF (16q23) or MAFB (20q11) transcription factors that target CCND2. Biallelic dysregulation of CCND1 occurs in nearly 40% of tumors, most of which are hyperdiploid. Other tumors express increased CCND2, either with or without a t(4;14) translocation. Using gene expression profiling to identify 5 recurrent translocations, specific trisomies, and expression of cyclin D genes, MM tumors can be divided into 8 TC (translocation/cyclin D) groups (11q13, 6p21, 4p16, maf, D1, D1+D2, D2, and none) that appear to be defined by early, and perhaps initiating, oncogenic events. However, despite subsequent progression events, these groups have differing gene expression profiles and also significant differences in the prevalence of bone disease, frequency at relapse, and progression to extramedullary tumor.

Characterization of oncogene dysregulation in multiple myeloma by combined FISH and DNA microarray analyses

Chromosomal translocations involving the immunoglobulin heavy chain (IGH) locus and various partner loci frequently are associated with multiple myeloma (MM). We investigated the expression profiles of the FGFR3/MMSET, CCND1, CCND3, MAF, and MAFB genes, which are involved in t(4;14)(p16.3;q32), t(11;14)(q13;q32), t(6;14)(p21;q32), t(14;16)(q32;q23), and t(14;20)(q32;q12), respectively, in purified plasma cell populations from 39 MMs and six plasma cell leukemias (PCL) by DNA microarray analysis and compared the results with the presence of translocations as assessed by dual-color FISH or RT-PCR. A t(4;14) was found in 6 MMs, t(11;14) in 9 MMs and 1 PCL, t(6;14) in 1 MM, t(14;16) in 2 MMs and 1 PCL, and t(14;20) in 1 PCL. In all cases, the translocations were associated with the spiked expression of target genes. Furthermore, gene expression profiling enabled the identification of putative translocations causing dysregulation of CCND1 (1 MM and 1 PCL) and MAFB (1 MM and 1 PCL) without any apparent involvement of immunoglobulin loci. Notably, all of the translocations were mutually exclusive. Markedly increased MMSET expression was found in 1 MM showing associated FGFR3 and MMSET signals on an unidentified chromosome. Our data suggest the importance of using combined molecular cytogenetic and gene expression approaches to detect genetic aberrations in MM.

Primary extramedullary plasmacytoma and multiple myeloma: phenotypic differences revealed by immunohistochemical analysis

Primary extramedullary plasmacytomas are infrequent, typically solitary, plasma cell neoplasms that generally pursue an indolent clinical course but may, rarely, convert to multiple myeloma. Phenotypic differences between these two entities are not well defined. Twenty-eight cases of primary extramedullary plasmacytoma and 26 cases of both medullary (n = 17) and extramedullary (n = 9) multiple myeloma were analysed for the expression of proteins known to play a role in the biology of multiple myeloma. Immunohistochemistry was performed on paraffin wax sections using antibodies against cyclin D1, Bcl-2, Bcl-xL, p27, p21, p53, MIB1, CD20, and CD56. Twenty-three extramedullary plasmacytomas were localized in the upper aerodigestive tract, four in the lymph nodes, and one in the testis. There was a strong male predominance (M : F = 6 : 1). None of the patients died from the disease or progressed to multiple myeloma (mean follow-up 50 months). Nine patients developed local relapse and one patient's tumour evolved into a B-cell non-Hodgkin's lymphoma. In contrast to both intra- and extra-medullary multiple myeloma, extramedullary plasmacytoma showed absence of cyclin D1 (p < 0.001) and infrequent expression of CD56 (p < 0.001). Furthermore, extramedullary plasmacytomas were characterized by weaker staining for Bcl-2 protein and rare overexpression of p21 and p53. In comparison to extramedullary multiple myeloma, extramedullary plasmacytoma showed a more mature morphology and lower proliferation indices (p = 0.008). There was no association between the phenotypic parameters investigated and clinical outcome in extramedullary plasmacytoma. In summary, extramedullary plasmacytoma and multiple myeloma show significant immunophenotypic differences, some of which may be of both diagnostic utility and biological relevance.

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.

Genetic heterogeneity in multiple myeloma

In the past decade, many progresses have been made in our knowledge of the genetics of multiple myeloma. The use of molecular cytogenetic techniques has led to the identification of several recurrent (cyto)genetic abnormalities, representing either prognostic markers, or novel therapeutic targets. More global analyses of this genetic heterogeneity using expression array technologies should further extend our understanding of the disease, hopefully enabling some improvements in the treatment of the patients. The goal of this minireview is to summarize these recent advances.

Possible roles for activating RAS mutations in the MGUS to MM transition and in the intramedullary to extramedullary transition in some plasma cell tumors

To assess a possible role in tumor progression, the occurrence and type of K- and N-RAS mutations were determined in purified tumor cells, including samples from patients with premalignant monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM), and extramedullary plasma cell (PC) tumors (ExPCTs). Immunophenotypic aberrant PCs were flow sorted from 20 MGUS, 58 MM, and 13 ExPCT patients. One RAS mutation was identified in 20 MGUS tumors (5%), in contrast to a much higher prevalence of RAS mutations in all stages of MM (about 31%). Further, oncogene analyses showed that RAS mutations are not evenly distributed among different molecular subclasses of MM, with the prevalence being increased in MM-expressing cyclin D1 (P = .015) and decreased in MM with t(4;14) (P = .055). We conclude that RAS mutations often provide a genetic marker if not a causal event in the evolution of MGUS to MM. Surprisingly, RAS mutations were absent in bone marrow tumor cells from all patients with ExPCT, a result significantly different from intramedullary MM (P = .001). From 3 of 6 patients with paired intramedullary and extramedullary PCs and identical immunoglobulin heavy chain gene (IgH) sequences, RAS mutations were identified only in extramedullary PCs, suggesting a role for RAS mutations in the transition from intramedullary to extramedullary tumor.