Clinical significance of telomerase activity in multiple myeloma

Genome Instability in Multiple Myeloma: Facts and Factors

Multiple myeloma (MM) is a malignant neoplasm of terminally differentiated immunoglobulin-producing B lymphocytes called plasma cells. MM is the second most common hematologic malignancy, and it poses a heavy economic and social burden because it remains incurable and confers a profound disability to patients. Despite current progress in MM treatment, the disease invariably recurs, even after the transplantation of autologous hematopoietic stem cells (ASCT). Biological processes leading to a pathological myeloma clone and the mechanisms of further evolution of the disease are far from complete understanding. Genetically, MM is a complex disease that demonstrates a high level of heterogeneity. Myeloma genomes carry numerous genetic changes, including structural genome variations and chromosomal gains and losses, and these changes occur in combinations with point mutations affecting various cellular pathways, including genome maintenance. MM genome instability in its extreme is manifested in mutation kataegis and complex genomic rearrangements: chromothripsis, templated insertions, and chromoplexy. Chemotherapeutic agents used to treat MM add another level of complexity because many of them exacerbate genome instability. Genome abnormalities are driver events and deciphering their mechanisms will help understand the causes of MM and play a pivotal role in developing new therapies.

Prognostic relevance of telomere length and telomerase reverse transcriptase variant (rs2242652) on the multiple myeloma patients

BACKGROUND

The search for enhancement of multiple myeloma prognostic tools is an area of current research. This study aimed to assess the clinicopathological impact of telomere length and telomerase reverse transcriptase (TERT) polymorphic variant, rs2242652, on multiple myeloma (MM) patients.

METHODS

Fifty MM patients and 50 healthy controls were included. Relative telomere length (RTL) and rs2242652 genotype polymorphic variants of TERT were analyzed using real-time polymerase chain reaction (PCR). The MM patients' group was categorized into stage I (n = 16); stage II (n = 12), and stage III (n = 22).

RESULTS

The median telomere length was significantly longer in MM patients' group (0.78) as compared to controls (0.43) (P = .001). Multivariate regression analysis revealed that MM patients with RTL < 0.5 had significant poor response for induction remission therapy with odds ratio 26.45. On the other hand, TERT genotyping analysis of rs2242652 revealed insignificant difference between cases and controls (P = .234), regarding to induction remission response. Survival analysis using Kaplan-Meier curve revealed that patients with shorter telomere length and those with TERT genotype GA had shorter overall survival.

CONCLUSION

Telomere length and TERT rs2242652 genotype polymorphism could be used for refining risk stratification of MM patients.

Distinct Nuclear Organization of Telomeresand Centromeres in Monoclonal Gammopathyof Undetermined Significance and Multiple Myeloma

Both multiple myeloma (MM) and its precursor state of monoclonal gammopathy of undetermined significance (MGUS) are characterized by an infiltration of plasma cells into the bone marrow, but the mechanisms underlying the disease progression remain poorly understood. Previous research has indicated that 3D nuclear telomeric and centromeric organization may represent important structural indicators for numerous malignancies. Here we corroborate with previously noted differences in the 3D telomeric architecture and report that modifications in the nuclear distribution of centromeres may serve as a novel structural marker with potential to distinguish MM from MGUS. Our findings improve the current characterization of the two disease stages, providing two structural indicators that may become altered in the progression of MGUS to MM.

Identifying the biomarker potential of telomerase activity and shelterin complex molecule, telomeric repeat binding factor 2 (TERF2), in multiple myeloma

Telomere length (TL) is maintained by telomere capping protein complex called shelterin complex. We studied the possible involvement and biomarker potential of shelterin complex molecules in naive multiple myeloma (MM) patients and controls. TL, relative telomerase activity (RTA), real-time PCR and Western blotting were performed in bonemarrow sample of 70 study subjects (patients = 50; controls = 20). Significantly lowered mean TL, increased RTA and higher mRNA expression of shelterin molecules were observed in patients, while PIN2/TERF1 interacting telomerase inhibitor 1 (PINX1) showed lower mRNA expression. Significantly increased protein expression of telomeric repeat binding factor 2 (TERF2), protection of telomeres 1, adrenocortical dysplasia homolog, Tankyrase 1 and telomere reverse transcriptase were observed in MM patients. Significant correlation was observed among genes and of genes with clinical parameters. In conclusion, our findings showed alteration of these molecules at mRNA and protein levels suggested their involvement in disease progression. Optimal sensitivity and specificity of TERF2 and RTA on receiver operating characteristics curve analysis and univariate analysis demonstrated their biomarkers potential in better prediction of disease course.

Telomerase and telomere biology in hematological diseases: A new therapeutic target

Telomeres are structures confined at the ends of eukaryotic chromosomes. With each cell division, telomeric repeats are lost because DNA polymerases are incapable to fully duplicate the very ends of linear chromosomes. Loss of repeats causes cell senescence, and apoptosis. Telomerase neutralizes loss of telomeric sequences by adding telomere repeats at the 3' telomeric overhang. Telomere biology is frequently associated with human cancer and dysfunctional telomeres have been proved to participate to genetic instability. This review covers the information on telomerase expression and genetic alterations in the most relevant types of hematological diseases. Telomere erosion hampers the capability of hematopoietic stem cells to effectively replicate, clinically resulting in bone marrow failure. Furthermore, telomerase mutations are genetic risk factors for the occurrence of some hematologic cancers. New discoveries in telomere structure and telomerase functions have led to an increasing interest in targeting telomeres and telomerase in anti-cancer therapy.

HIF-1α and rapamycin act as gerosuppressant in multiple myeloma cells upon genotoxic stress

Multiple myeloma (MM) is still an incurable hematological malignancy. Despite recent progress due to new anti-myeloma agents, the pathology is characterized by a high frequency of de novo or acquired resistance. Delineating the mechanisms of MM resistance is essential for therapeutic advances. We previously showed that long-term genotoxic stress induces the establishment of a senescence-associated secretory phenotype, a pro-inflammatory response that favors the emergence of cells with cancer stem-like properties. Here, we studied the short-term response of MM cells following treatment with various DNA damaging agents such as the energetic C-ion irradiation. MM cells are highly resistant to all treatments and do not enter apoptosis after they arrest cycling at the G2 phase. Although the DNA damage response pathway was activated, DNA breaks remained chronically in damaged MM cells. We found, using a transcriptomic approach that RAD50, a major DNA repair gene was downregulated early after genotoxic stress. In two gerosuppression situations: induction of hypoxia and inhibition of the mammalian target of rapamycin (mTOR) pathway, we observed, after the treatment with a DNA damaging agent, a normalization of RAD50 expression concomitant with the absence of cell cycle arrest. We propose that combining inhibitors of mTOR with genotoxic agents could avoid MM cells to senesce and secrete pro-inflammatory factors responsible for cancer stem-like cell emergence and, in turn, relapse of MM patients.

Expression of Proliferating Cell Nuclear Antigen (PCNA) in Multiple Myeloma: Its Relationship to Bone Marrow Microvessel Density and other Factors of Disease Activity

The expression of the proliferating cell nuclear antigen (PCNA) was studied in plasma cells in bone marrow biopsies from patients with multiple myeloma (MM) using a double immunostaining method. In the same samples, microvessel density (MVD), after staining with anti-CD34 antibodies, was determined before and after chemotherapy. The correlation of PCNA expression and MVD with other myeloma parameters (clinical stage, bone marrow plasma cell infiltration and serum interleukin –6 (IL-6)) was also investigated.

The study population included 51 newly diagnosed MM patients, 12 patients in plateau phase after treatment and 15 normal controls. Pretreatment mean ± SE values of PCNA, MVD, plasma cell infiltration and serum IL-6 were significantly higher than post treatment values and controls. Pretreatment PCNA expression correlated significantly with bone marrow MVD (p<0.05) plasma cell infiltration (p<0.01) and IL-6 (p<0.01).

These findings show that the proliferative activity of plasma cells is related to the angiogenic activity in the bone marrow of multiple myeloma patients. Both PCNA and MVD correlate with markers of disease activity thus may provide additional information when included in the initial evaluation of myeloma bone marrow biopsies.

MUC1-C drives MYC in multiple myeloma

Multiple myeloma (MM) cell lines and primary tumor cells are addicted to the MYC oncoprotein for survival. Little is known, however, about how MYC expression is upregulated in MM cells. The mucin 1 C-terminal subunit (MUC1-C) is an oncogenic transmembrane protein that is aberrantly expressed in MM cell lines and primary tumor samples. The present studies demonstrate that targeting MUC1-C with silencing by clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 editing or with the GO-203 inhibitor is associated with downregulation of MYC messenger RNA and protein. The results show that MUC1-C occupies the MYC promoter and thereby activates the MYC gene by a β-catenin/transcription factor 4 (TCF4)-mediated mechanism. In this way, MUC1-C (1) increases β-catenin occupancy on the MYC promoter, (2) forms a complex with β-catenin and TCF4, and, in turn, (3) drives MYC transcription. Analysis of MM cells using quantitative real-time reverse transcription polymerase chain reaction arrays further demonstrated that silencing MUC1-C is associated with downregulation of MYC target genes, including CCND2, hTERT, and GCLC Analysis of microarray data sets further demonstrated that MUC1 levels positively correlate with MYC expression in MM progression and in primary cells from over 800 MM patients. These findings collectively provide convincing evidence that MUC1-C drives MYC expression in MM.

Differential Expression of Non-Shelterin Genes Associated with High Telomerase Levels and Telomere Shortening in Plasma Cell Disorders

Telomerase, shelterin proteins and various interacting factors, named non-shelterin proteins, are involved in the regulation of telomere length (TL). Altered expression of any of these telomere-associated genes can lead to telomere dysfunction, causing genomic instability and disease development. In this study, we investigated the expression profile of a set of non-shelterin genes involved in essential processes such as replication (RPA1), DNA damage repair pathways (MRE11-RAD50-NBS1) and stabilization of telomerase complex (DKC1), in 35 patients with monoclonal gammopathy of undetermined significance (MGUS) and 40 cases with multiple myeloma (MM). Results were correlated with hTERT expression, TL and clinical parameters. Overall, a significant increase in DKC1, RAD50, MRE11, NBS1 and RPA1 expression along with an upregulation of hTERT in MM compared with MGUS was observed (p≤0.032). Interestingly, in both entities high mRNA levels of non-shelterin genes were associated with short TLs and increased hTERT expression. Significant differences were observed for DKC1 in MM (p ≤0.026), suggesting an important role for this gene in the maintenance of short telomeres by telomerase in myeloma plasma cells. With regard to clinical associations, we observed a significant increase in DKC1, RAD50, MRE11 and RPA1 expression in MM cases with high bone marrow infiltration (p≤0.03) and a tendency towards cases with advanced ISS stage, providing the first evidence of non-shelterin genes associated to risk factors in MM. Taken together, our findings bring new insights into the intricate mechanisms by which telomere-associated proteins collaborate in the maintenance of plasma cells immortalization and suggest a role for the upregulation of these genes in the progression of the disease.

Drug resistance in multiple myeloma: latest findings and new concepts on molecular mechanisms

In the era of new and mostly effective therapeutic protocols, multiple myeloma still tends to be a hard-to-treat hematologic cancer. This hallmark of the disease is in fact a sequel to drug resistant phenotypes persisting initially or emerging in the course of treatment. Furthermore, the heterogeneous nature of multiple myeloma makes treating patients with the same drug challenging because finding a drugable oncogenic process common to all patients is not yet feasible, while our current knowledge of genetic/epigenetic basis of multiple myeloma pathogenesis is outstanding. Nonetheless, bone marrow microenvironment components are well known as playing critical roles in myeloma tumor cell survival and environment-mediated drug resistance happening most possibly in all myeloma patients. Generally speaking, however; real mechanisms underlying drug resistance in multiple myeloma are not completely understood. The present review will discuss the latest findings and concepts in this regard. It reviews the association of important chromosomal translocations, oncogenes (e.g. TP53) mutations and deranged signaling pathways (e.g. NFκB) with drug response in clinical and experimental investigations. It will also highlight how bone marrow microenvironment signals (Wnt, Notch) and myeloma cancer stem cells could contribute to drug resistance in multiple myeloma.

Expression profile of shelterin components in plasma cell disorders. Clinical significance of POT1 overexpression

The core complex of telomere-associated proteins, named the shelterin complex, plays a critical role in telomere protection and telomere length (TL) homeostasis. In this study, we have explored changes in the expression of telomere-associated genes POT1, TIN2, RAP1 and TPP1, in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). A total of 154 patients: 70 with MGUS and 84 with MM were studied. Real-time quantitative PCR was used to quantify gene expression. TL was evaluated by Terminal Restriction Fragments. Our data showed increased expression of POT1, TPP1, TIN2 and RAP1 in MM with respect to MGUS patients, with significant differences for POT1 gene (p=0.002). In MM, the correlation of gene expression profiles with clinical characteristics highlighted POT1 for its significant association with advanced clinical stages, high calcium and β2-microglobulin levels (p=0.02) and bone lesions (p=0.009). In multivariate analysis, POT1 expression (p=0.04) was a significant independent prognostic factor for overall survival as well as the staging system (ISS) (p<0.02). Our findings suggest for the first time the participation of POT1 in the transformation process from MGUS to MM, and provide evidence of this gene as a useful prognostic factor in MM as well as a possible molecular target to design new therapeutic strategies.

Differential downregulation of telomerase activity by bortezomib in multiple myeloma cells-multiple regulatory pathways in vitro and ex vivo

BACKGROUND

The importance of telomerase in multiple myeloma (MM) is well established; however, its response to bortezomib has not been addressed.

METHODS

The effect of bortezomib on telomerase activity and cell proliferation was evaluated in four MM cell lines and in myeloma cells obtained from eight patients. The mechanism of telomerase regulation on epigenetic, transcriptional, and post-translational levels was further assessed in two selected cell lines: ARP-1 and CAG. Clinical data were correlated with the laboratory findings.

RESULTS

Bortezomib downregulated telomerase activity and decreased proliferation in all cell lines and cells obtained from patients, albeit in two different patterns of kinetics. ARP-1 cells demonstrated higher and earlier sensitivity than CAG cells due to differential phosphorylation of hTERT by PKCα. Methylation of hTERT promoter was not affected. Transcription of hTERT was similarly inhibited in both lines by decreased binding of SP-1 and not of C-Myc and NFκB. The ex vivo results confirmed the in vitro findings and suggested existence of clinical relevance.

CONCLUSION

Bortezomib downregulates telomerase activity in MM cells both transcriptionally and post-translationally. MM cells, both in vitro and in patients, exhibit different sensitivity to the drug due to different post-translational response. The effect of bortezomib on telomerase activity may correlate with resistance to bortezomib in patients, suggesting its potential utility as a pre-treatment assessment.

Telomere dysfunction and its role in haematological cancer

Observations in human tumours, as well as mouse models, have indicated that telomere dysfunction may be a key event driving genomic instability and disease progression in many solid tumour types. In this scenario, telomere shortening ultimately results in telomere dysfunction, fusion and genomic instability, creating the large-scale rearrangements that are characteristic of these tumours. It is now becoming apparent that this paradigm may also apply to haematological malignancies; indeed these conditions have provided some of the most convincing evidence of telomere dysfunction in any malignancy. Telomere length has been shown in several malignancies to provide clinically useful prognostic information, implicating telomere dysfunction in disease progression. In these malignancies extreme telomere shortening, telomere dysfunction and fusion have all been documented and correlate with the emergence of increased genomic complexity. Telomeres may therefore represent both a clinically useful prognostic tool and a potential target for therapeutic intervention.

Telomerase inhibition targets clonogenic multiple myeloma cells through telomere length-dependent and independent mechanisms

Background

Plasma cells constitute the majority of tumor cells in multiple myeloma (MM) but lack the potential for sustained clonogenic growth. In contrast, clonotypic B cells can engraft and recapitulate disease in immunodeficient mice suggesting they serve as the MM cancer stem cell (CSC). These tumor initiating B cells also share functional features with normal stem cells such as drug resistance and self-renewal potential. Therefore, the cellular processes that regulate normal stem cells may serve as therapeutic targets in MM. Telomerase activity is required for the maintenance of normal adult stem cells, and we examined the activity of the telomerase inhibitor imetelstat against MM CSC. Moreover, we carried out both long and short-term inhibition studies to examine telomere length-dependent and independent activities.

Methodology/Principal Findings

Human MM CSC were isolated from cell lines and primary clinical specimens and treated with imetelstat, a specific inhibitor of the reverse transcriptase activity of telomerase. Two weeks of exposure to imetelstat resulted in a significant reduction in telomere length and the inhibition of clonogenic MM growth both in vitro and in vivo. In addition to these relatively long-term effects, 72 hours of imetelstat treatment inhibited clonogenic growth that was associated with MM CSC differentiation based on expression of the plasma cell antigen CD138 and the stem cell marker aldehyde dehydrogenase. Short-term treatment of MM CSC also decreased the expression of genes typically expressed by stem cells (OCT3/4, SOX2, NANOG, and BMI1) as revealed by quantitative real-time PCR.

Conclusions

Telomerase activity regulates the clonogenic growth of MM CSC. Moreover, reductions in MM growth following both long and short-term telomerase inhibition suggest that it impacts CSC through telomere length-dependent and independent mechanisms.

Altered mRNA expression of telomere-associated genes in monoclonal gammopathy of undetermined significance and multiple myeloma

In this study, we explored changes in the expression of the telomere maintenance genes, TRF1, TRF2 and TANK1 in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). Results were correlated with human telomerase reverse transcriptase (hTERT ) expression, telomere length (TL) and clinicopathological characteristics. Bone marrow (BM) samples from 132 patients, 64 with MGUS and 68 with MM, were studied. Real-time quantitative reverse transcription-polymerase chain reaction was used to quantify gene expression. TL was evaluated by terminal restriction fragment length analysis. MGUS patients showed increased TRF1 levels (P = 0.006) and lower expression of TRF2 (P = 0.005) and TANK1 (P = 0.003) compared with MM patients. For hTERT analysis, patients were divided into three groups by use of receiver operating characteristics: low (group I [GI]), intermediate (group II [GII]) and high (group III [GIII]) expression. We observed increasing expression of TRF2 and TANK1 from GI to GIII in MGUS and MM, with differences for both genes in MM (P < 0.01) and for TRF2 in MGUS (P < 0.01). GIII patients with the highest telomerase expression had the shortest TL. In both entities, a positive association between TRF2-TANK1, TRF2-hTERT and TANK1-hTERT (P ≤ 0.01) was observed. In MM, the percentage of BM infiltration and Ki-67 index were positively associated with TRF2, TANK1 and hTERT expression (P ≤ 0.03) and negatively with TL (P = 0.02), whereas lactate dehydrogenase was significantly correlated with TRF2 mRNA (P = 0.008). Our findings provide the first evidence of a modification in the expression of telomeric proteins in plasma cell disorders, and suggest that mechanisms other than telomerase activation are involved in TL maintenance in these pathologies.

Flow cytometric detection of human telomerase reverse transcriptase (hTERT) expression in a subpopulation of bone marrow cells

Telomerase activity has been found in most common cancers, thus indicating that telomerase detection may be a useful marker in cancer diagnosis. The telomeric amplification protocol (TRAP) assay and RT-PCR are customarily used to detect telomerase activity and the expression of the associated genes in cells. However, these methods do not provide any information about telomerase activation at an individual cell level. To analyze cells separately, those cells have to be isolated by sometimes complicated method. The immunohistochemical detection of human telomerase reverse transcriptase (hTERT) is useful to detect telomerase positive cells in a background of non-cancerous cells. A method has been developed for the detection of intranuclear hTERT protein, in a subpopulation of hematopoietic cells, using concurrent staining of a cell surface antigen and multicolor flow cytometry. Only mouse monoclonal anti-hTERT antibody demonstrated the specific positivity in immunocytochemistry and immunofluorescent flow cytometry. Human leukemia and myeloma cell lines showed 100% positivity, whereas normal neutrophils showed 0% positivity. hTERT expression was analyzed in hematopoietic precursor cells of bone marrow samples using concurrent staining of surface CD34 antigen and intracellular hTERT protein and multi-parameter flow cytometry. CD34 positive cells demonstrated higher expression of hTERT than CD34 negative cells. A quick, easy and sensitive assay for determining the hTERT protein expression has been developed. Using this method and the multi-parameter nature of flow cytometry and its ability to identify cellular subpopulations will provide a better understanding of the mechanisms regarding the activation of telomerase.

The importance of the telomere and telomerase system in hematological malignancies

Telomeres are specialized chromosomal end structures composed of repeat TTAGGG sequences in humans. They shorten with each cell division and thus serve as the "mitotic clock" of the cell. One of their main functions is the maintenance of chromosomal integrity and their excessive shortening is associated with DNA instability. Telomerase, a unique reverse transcriptase, is inactive in most somatic human cells and is up-regulated in most cancer cells. Recently, the biology of the telomere/telomerase system has attracted much attention because of its possible role in carcinogenesis and aging. In this article we review the biology of this system and its relevance to normal and malignant hematopoietic cells. The biological, diagnostic and prognostic value of telomere/telomerase biology is discussed, as well as its potential future applications in cancer therapeutics.

Telomerase activity and telomere length as prognostic factors of adult T-cell leukemia

For the oncogenesis of many malignancies, it is crucial to prevent the shortening of the telomeres by the action of telomerase. In this study, clinical data and disease outcomes were analyzed in conjunction with the telomerase activity (TA) and telomere length (TL) of peripheral blood mononuclear cells. The study was carried out in 22 patients with adult T-cell leukemia (ATL) (7 chronic and 15 acute types) and in 13 asymptomatic human T-lymphotropic virus type 1 (HTLV-1) carriers. The mean values of TA in acute and chronic type patients were 13.8 and 1.6 total product generated (TPG) units, respectively, as determined by telomeric repeat amplification assays. The mean TA values in HTLV-1 carriers and healthy volunteers were 1.8 and 0.7 TPG, respectively. The mean TA value in acute type patients was significantly higher than in the three other subject groups. The mean TL values in patients with acute and chronic types were 5.39 and 4.38 Kb, respectively, while the mean TL values in HTLV-1 carriers and healthy volunteers were 7.69 and 7.06 Kb, respectively. The mean TL values in all ATL patients and in non-ATL subjects were 5.2 and 7.3 Kb, respectively. The former value is significantly shorter than the latter (p < 0.01). Neither TA nor TL of ATL cells showed any significant association with the number of ATL cells, serum soluble interleukin-2 receptor, or serum lactate dehydrogenase in the peripheral blood of acute type patients. This suggests that the levels of TA and TL did not reflect the ATL tumor load. The median survival period of acute ATL patients with high TA and shortened TL was 0.47 years, however, which was significantly shorter than that of acute ATL patients with low TA and normal TL (4.21 years) (p < 0.002). These data suggest that high TA and shortened TL were associated with poorer prognosis, and that TA and TL may be novel markers for the prognosis of ATL patients.

Telomerase as an independent prognostic factor in head and neck squamous cell carcinoma

BACKGROUND

Telomerase activity has been found to be associated with many cancers, including head and neck squamous cell carcinoma (HNSCC). We examined the association of telomerase activity with the clinical outcome of patients with HNSCC.

METHODS

A PCR-based enzyme immunoassay method was used to measure telomerase activity in 217 matched (grossly normal and cancerous) tissues from patients with HNSCC. Pearson chi-square test was used to analyze the correlation of telomerase activity with clinicopathologic parameters. Kaplan-Meier method and Cox logistic regression model were used for prognostic analysis.

RESULTS

Of the 217 tissues assayed, 4.1% of the normal and 63.3% of the cancer tissues had high levels of telomerase activity. Telomerase activity was shown to be statistically correlated with extracapsule spreading (ECS) of lymph nodes (p =.005) and overall survival (p =.003). On multivariant analysis, overall stage (p =.007), tumor depth (p =.045), and telomerase activity (p =.008) showed independent variables associated with poor survival.

CONCLUSIONS

Telomerase activity has been shown to be an independent prognostic factor for survival in cases of HNSCC. Telomerase may be a potential molecular target for clinical use in prognostication and therapy in cases of the disease.

Telomerase activity and expression of telomerase genes in squamous dysplasia and squamous cell carcinoma of the esophagus

BACKGROUND

Telomerase maintains telomere length and is considered to be necessary for the indefinite proliferation of human cells. Activation of telomerase plays a key role in the malignant transformation process. The aim of this study was to study the regulation of telomerase, and to explore the possibility of telomerase as a biomarker in squamous carcinogenesis of the esophagus.

METHODS

Twenty-nine esophageal squamous cell carcinomas (ESCC) and its corresponding adjacent normal tissues, and 47 epithelial squamous dysplasia tissues were analyzed by the reverse transcriptase-polymerase chain reaction (RT-PCR) technique for the mRNA expression of three major telomerase subunits: human telomerase RNA (hTR), telomerase protein component 1 (TP1), and human telomerase reverse transcriptase (hTERT) and by telomeric repeat amplification protocol assay (TRAP) for telomerase activity.

RESULTS

For the expression of hTR and TP1 mRNA, there were no significant differences among ESCC, dysplasia and normal tissues (P > 0.05). In contrast, hTERT mRNA expression was detected in 28 of 29 ESCC (96.6%), in 23 of 47 dysplasia (48.9%), and only in two of 29 normal tissues (7.5%). Telomerase activity was positive in 25 of 29 ESCC (86.2%), in 21 of 47 (44.7%) epithelial dysplasia tissues, and in none of normal tissue. All together, 95 of 105 cases (90.48%) were concordant for both results, i.e., telomerase activity positive and hTERT positive or telomerase activity negative and hTERT negative tissues, and telomerase activity correlated with hTERT mRNA expression (P < 0.001).

CONCLUSIONS

Higher telomerase activity and hTERT mRNA expression were shown during an early stage in the esophageal carcinogenesis. Activation of telomerase activity was strongly correlated with hTERT mRNA expression, suggesting hTERT is a major regulator of telomerase activity, and telomerase activation may play a critical role in esophageal carcinogenesis. Therefore, telomerase, especially hTERT can be used as a potential molecular biomarker of ESCC.

Telomerase inhibition with an oligonucleotide telomerase template antagonist: in vitro and in vivo studies in multiple myeloma and lymphoma

The effects of telomerase inhibition with an oligonucleotide N3' --> P5' thiophosphoramidate (GRN163) complementary to the telomerase template region were examined on human multiple myeloma (MM) and non-Hodgkin lymphoma (NHL) cell lines, primary MM cells, and tumor xenografts. GRN163 treatment reduced telomerase levels in all cells and induced more rapid telomeric shortening. Continuous GRN163 treatment for 7 to 14 days resulted in proliferative arrest, morphologic changes, and apoptosis characteristic of cell crisis in tumor cell lines with short (1.7-5.4 kb) but not long (9-11 kb) telomeres. Intratumoral administration of GRN163 also inhibited the growth of MM and NHL xenografts established from cell lines with short telomeres (Hs602 lymphoma, 2.7 kb; CAG myeloma, 2.7 kb) and increased tumor apoptosis. However, GRN163 therapy of NHL xenografts established from cells with long telomeres (11.0 kb) had equivocal effects on tumor growth and did not induce apoptosis during this time frame. Systemic daily intraperitoneal administration of GRN163 in myeloma xenografts with short telomere lengths also decreased tumor telomerase levels and reduced tumor volumes. These data demonstrate that telomerase is important for the replication of mature B-cell neoplasia by stabilizing short telomeres, and they suggest that telomerase inhibition represents a novel therapeutic approach to MM and NHL.

Telomere shortening in patients with plasma cell disorders

OBJECTIVES

Telomeres are essential for maintaining chromosomal integrity; their shortening is associated with chromosome instability. The aim of this work was to study telomere length (TL) on bone marrow (BM) cells from patients with multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS).

METHODS

Thirty-one MM patients: 12 at diagnosis (D), 11 at relapse (R) and eight at remission (RE) and two cases with MGUS were studied. TL based on terminal restriction fragment (TRF) assay was evaluated. Cytogenetic and molecular cytogenetic analyses were performed. Telomeric associations (TAs) on BM metaphases were also studied.

RESULTS

TRF analysis in total MM patients showed a mean TRF peak value (5.20 +/- 0.35 kb) shorter than those observed in controls (8.5 +/- 0.5 kb) (P < 0.001). Moreover, TRF at D and R showed a significant telomere shortening (P < 0.001), with TL restored at RE. A strong correlation with the percentage of BM plasma cell infiltration (BMPCI) (rK = -0.540; P = 0.002) was found. Patients with abnormal karyotypes (AK) had significantly shorter TRFs than that observed in MM patients with normal karyotypes (P < 0.05). TRFs in MGUS patients did not differ with respect to controls. TA analysis showed an increased percentage in MM (19.46 +/- 1.98%) with respect to MGUS (6.12 +/- 1.87%) and normal BM cells (2.00 +/- 0.93%) (P < 0.001).

CONCLUSIONS

MM patients showed a significant reduction in TL (> 60% of BMPCI and AK), suggesting a probable association with clinical evolution. Moreover, our findings support the idea that telomere shortening usually leads to increased frequencies of TAs and chromosome instability.

Telomerase and telomere length in multiple myeloma: correlations with disease heterogeneity, cytogenetic status, and overall survival

We have investigated the significance of telomerase activity (TA) and telomere length (TL) in multiple myeloma (MM). The analyses were undertaken on CD138+ MM cells isolated from the marrow of 183 patients either at diagnosis or in relapse. There was heterogeneity in telomerase expression; 36% of the patients had TA levels comparable to those detected in normal plasma cells, and 13% of patients had levels 1- to 4-fold greater than in a neuroblastoma cell line control. The TL of MM cells was significantly shorter than that of the patients' own leukocytes; in 25% of patients, the TL measured less than 4.0 kbp. Analysis of TL distribution indicated selective TA-mediated stabilization of shorter telomeres when mean TL fell below 5.5 kbp. Unusually long (10.8-15.0 kbp) telomeres were observed in 7 patients, and low TA was observed in 5 of 7 patients, suggesting the operation of a TA-independent pathway of telomere stabilization. A strong negative correlation existed between TA and TL or platelet count. TL negatively correlated with age and with interleukin-6 (IL-6) and beta2-microglobulin levels. Various cytogenetic abnormalities, including those associated with poor prognosis, strongly correlated with TA and, to a lesser extent, with short TL. High TA and short TL defined a subgroup of patients with poor prognosis. At 1 year the survival rate in patients with TA levels lower than 25% of neuroblastoma control and TL greater than 5.5 kbp was 82%, whereas in patients with higher TA and shorter TL the survival rate was 63% (P =.004). The 2-year survival rate for patients with TA levels lower than 25% was 81%, and it was 52% in those with higher TA levels (P <.0001).