Time from diagnosis to treatment has no impact on survival in newly diagnosed acute myeloid leukemia treated with venetoclax-based regimens

In newly diagnosed acute myeloid leukemia, immediate initiation of treatment is standard of care. However, deferral of antileukemic therapy may be indicated to assess comorbidities or pre-therapeutic risk factors. We explored the impact of time from diagnosis to treatment on outcomes in newly diagnosed acute myeloid leukemia undergoing venetoclax-based therapy in two distinct cohorts. By querying the Study Alliance Leukemia database and the global health network TriNetX, we identified 138 and 717 patients respectively with an average age of 76 and 72 years who received venetoclax-based firstline therapy. When comparing patients who started treatment earlier or later than 10 days after initial diagnosis, no significant difference in median overall survival was observed - neither in the SAL cohort (7.7 vs. 9.6 months, p=.42) nor in the TriNetX cohort (7.5 vs. 7.2 months, p=.41). Similarly, severe infections, bleeding, and thromboembolic events were equally observed between early and later treatments, both in the overall patient groups and specific subgroups (age ≥75 years or leukocytes ≥20x109/L). This retrospective analysis indicates that delaying the start of venetoclax-based therapy in newly diagnosed acute myeloid leukemia might be a safe option for selected patients, provided that close clinical monitoring is performed.

Tolerability of high dose chemotherapy and autologous stem cell transplantation in elderly patients with multiple myeloma: A single-center retrospective analysis

PURPOSE OF THE STUDY

In the past years, high dose chemotherapy (HDT) with autologous stem cell transplantation (ASCT)has more extensively been performed in elderly patients with multiple myeloma (MM). Several studies found a similar survival benefit compared to younger patients. The objective of our retrospective study is to analyse the tolerability of HDT + ASCT in elderly patients.

PATIENTS AND METHODS

We compared 26 ASCT performed in MM patients ≥65 years to 127 ASCT in patients <65 years by evaluating treatment-tolerability, length of hospital stay and number of transfusions.

RESULTS

There was no significant difference in the duration of hospitalisation (16 days (range 14-47) in the elderly vs. 17 days (range 14-71) days, P =  0.0903), median time of cytopenia (neutrophils<500/μl: 5 days (range 4-24) vs. 6 days (range 3-28) days, P =  0.1091; platelets<30 000/μl: 6 days (range 3-36) vs. 7 days (range 0-53) days, P =  0.274) or incidence of, or degree of complications between the two age-groups. Immediate and day 100 treatment related mortality (TRM) was comparable in both groups (3.85% vs. 1.58%, P =  0.4304).

CONCLUSION

our findings support the concept that HDT + ASCT can be safely administered as first-line option for well-selected patients≥65 years.

Immunological monitoring of newly diagnosed CML patients treated with bosutinib or imatinib first-line

Changes in the immune system induced by tyrosine kinase inhibitors (TKI) have been shown to positively correlate with therapy responses in chronic myeloid leukemia (CML). However, only a few longitudinal studies exist and no randomized comparisons between two TKIs have been reported. Therefore, we prospectively analyzed the immune system of newly diagnosed CML patients treated with imatinib (n = 20) or bosutinib (n = 13), that participated in the randomized BFORE trial (NCT02130557). Comprehensive immunophenotyping, plasma protein profiling, and functional assays to determine activation levels of T and NK cells were performed at diagnosis, 3, and 12 months after therapy start. All results were correlated with clinical parameters such as Sokal risk and BCR-ABL load measured according to IS%. At diagnosis, low Sokal risk CML patients had a higher frequency of cytotoxic cells (CD8 + T and NK cells), increased cytotoxic potential of NK cells and lower frequency of naïve and central memory CD4 + T cells. Further, soluble plasma protein profile divided patients into two distinct clusters with different disease burden at diagnosis. During treatment, BCR-ABL IS% correlated with immunological parameters such as plasma proteins, together with different memory subsets of CD4+ and CD8 + T cells. Interestingly, the proportion and cytotoxic potential of NK cells together with several soluble proteins increased during imatinib treatment. In contrast, no major immunological changes were observed during bosutinib treatment. In conclusion, imatinib and bosutinib were shown to have differential effects on the immune system in this randomized clinical trial. Increased number and function of NK cells were especially observed during imatinib therapy.

γ-Glutamyl Transferase Is an Independent Biomarker of Splanchnic Thrombosis in Patients With Myeloproliferative Neoplasm

Myeloproliferative neoplasms (MPNs) are associated with an increased risk of thrombotic events and constitute the major risk factor of splanchnic venous thrombosis (SVT) in Western countries. Although timely anticoagulation resolves SVT, unrecognized SVT frequently leads to portal hypertension and, potentially, variceal bleeding, which may render anticoagulation difficult. Thus, early identification of SVT development is clinically relevant in MPN patients.In this retrospective analysis, we included 126 patients with MPN and/or SVT referred to our hospital between 2009 and 2014. A total of 86 patients diagnosed with MPN formed the first cohort (PV n = 18, ET n = 16, and MF n = 40), whereas 40 patients who had SVT without adjunct MPN formed a control cohort. Median follow-up period was 960 days. Clinical and laboratory data were collected and analyzed for the identification of potential biomarkers applying descriptive statistics, nonparametric testing, Kaplan-Meier, and logistic regression analysis. The relevance of the identified biomarkers was evaluated in an independent 2nd cohort of 181 patients from the MPN registry of the Study Alliance of Leukemia (SAL-MPN).Thirty-three MPN patients (38%) in the 1st cohort had SVT. Elevated levels of aspartate aminotransferase, alanine aminotransferase, serum bilirubin, or γ-GT were significantly correlated to the presence of SVT. In multivariate testing, CRP and aspartate aminotransferase were predictors for survival and γ-GT remained the only significant variable associated with SVT in MPN patients (P < 0.05). These findings were confirmed in the 2nd cohort comprising 42% of patients with MPN suffering from SVT.Elevated γ-GT levels indicate SVT in MPN patients, whereas CRP levels are independent predictors of patient survival.

Evolution of bosutinib (BOS) toxicity in patients (pts) with Ph+ leukemia after resistance/intolerance to prior therapy

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Background: BOS is an oral dual Src/Abl tyrosine kinase inhibitor (TKI) approved for treatment of Ph+ CML following resistance/intolerance to prior therapy. Prior reports from this phase I/II trial indicated the BOS safety profile was primarily characterized by myelosuppression, gastrointestinal events, and rash. The current analysis compares the incidence of toxicity in Year 1 (Y1) for pts on treatment ≤1 y and within Y1 and Year 2 (Y2) for pts on treatment for >1 y. Methods: BOS 500 mg/d was evaluated in 3 cohorts: chronic phase (CP) CML after imatinib only (CP 2L cohort; n = 286); CP CML after imatinib + dasatinib and/or nilotinib (CP 3L cohort; n = 119); and accelerated/blast phase CML or ALL after prior TKI therapy (ADV cohort; n = 164). Results: The most common treatment-emergent adverse events (TEAEs) in each cohort occurred more frequently within Y1 than Y2 (Table). The incidence for grade 3/4 events followed a similar pattern. AEs were the most common reason for BOS discontinuation in Y1 (CP 2L, 53%; CP 3L, 32%; ADV, 41%). Of the pts whose primary reason for discontinuing BOS was an AE during the first 2 y, most did so during Y1 (CP 2L, n = 51/60 [85%]; CP 3L, n = 22/24 [92%]; ADV, n = 24/25 [96%]); the most common reasons during Y1 were thrombocytopenia (12%; 9%; 4%), increased ALT (6%; 4%; 2%), neutropenia (3%; 6%; 0%), diarrhea (4%; 3%; 0%), and vomiting (3%; 4%; 1%). Serious AEs were more common among pts who discontinued BOS ≤1 y versus on treatment >1 y in the CP 3L and ADV cohorts, but similar in the CP 2L cohort (Table). Conclusions: Discontinuation due to AEs was observed primarily in Y1. For pts on BOS for >1 y, the incidence of common TEAEs decreased substantially after Y1, suggesting BOS tolerability improves after long-term exposure. Clinical trial information: NCT00261846. [Table: see text]

Prognostic role of microRNA polymorphisms in advanced gastric cancer patients

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Background: As little is known about the impact of microRNA (mir) polymorphisms on prognosis of advanced gastric cancer (AGC) we sought to determine their impact on overall survival (OS) in these patients (pts). Methods: Pts were treated with either 5-fluorouracil, leucovorin and oxaliplatin (FLO) or with additional docetaxel (FLOT) in frame of a phase III or 3 phase II trials of the Arbeitsgemeinschaft Internistische Onkologie. All pts consented genetic analyses. DNA was extracted from whole blood samples (n=515) and polymorphisms of mir26a1 (rs7372209), mir27a (rs895819), mir100 (rs1834306), mir125a (rs12975333), mir146a (rs2910164), mir196a2 (rs11614913), mir219-1 (rs107822) and mir423 (rs6505162) were genotyped using PCR-based methods. Hetero- and homozygous variant genotypes were grouped versus homozygous wild type genotypes. Selection of clinical and genetic parameters for the final multivariate model was based on univariate and multivariate Cox-regression analyses with a cut-off value of p < 0.25 and included 498 pts. Results: Median age was 67 (range 23 to 86) years. 42% were treated with FLO and 58% with FLOT with a median OS of 14 months. Multivariate analyses revealed following associations: Genetic factors significantly associated with OS were mir26a1 variant genotypes (HR 1.3 [95%CI (1.01;1.6), p=.025]), mir27a variant genotypes (HR 1.3 [95%CI (1.01;1.6), p=.036]) and mir196a2 variant genotypes (HR 0.8 [95%CI (0.6;0.99), p=.046]). Clinical factors with significant impact on OS were ECOG 2 performance status (HR 1.9 [95%CI (1.3;2.8), p=.002]), curative surgery of advanced disease (HR 0.3 [95%CI (0.1;0.5), p<.001]) and locally advanced disease (HR 0.5 [95%CI (0.3;0.7), p<.001]). Combined analyses of the identified adverse genotypes of mir26a1, mir27a and mir196a2 resulted in a median OS of 9, 13, 14 and 17 months for pts with 0 (n=72), 1 (n=193), 2 (n=171) and 3 (n=54) adverse genotypes (p=.029), respectively. Conclusions: In addition to established clinical factors, mir26a1, mir27a and mir196a2 polymorphisms were significantly associated with OS. Our data suggest a strong impact of these mir polymorphisms on prognosis in AGC and might be of help for a better guidance of treatment decisions.

Clinical and sociodemographic data of cancer patients seeking out-patient based psycho-oncological psychotherapy

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Background: Although there is a defined need for out-patient psychosocial care for cancer patients, data about out-patient psycho-oncological health care services and patients’ usage of ambulatory infrastructure outside certified cancer centres are scarce. Methods: We retrospectively analyzed charts and treatment protocols from 1,369 patients treated between 1998 and 2009 in a psycho-oncology (PO) practice retrieving socio-demographic and cancer-specific data plus data regarding PO intervention. Results: Of 1,180 patients analysed so far, 808 were documented cancer patients and 372 were relatives or friends of cancer patients. Median age of cancer patients was 50 (range 21-81) years, the majority being female (91%). Although PO interventions are not generally covered by most health care insurances in Germany, 87.7% of patients had public health insurance and only 12.7% had private insurance. 62,5% of patients (n=505) were diagnosed with breast cancer, followed by colorectal cancer (n=46), ovarian cancer (n=42), leukemia/lymphoma (n=38) and lung cancer (n=34), although all types of malignancies were represented. 60.1% received curative and 20.3% palliative treatment, while 19.6% could not specify their treatment intention. 503/663 (n=186 not specified) patients had at least one child with 39.5% being less than 18 years of age. 75.9% (176/232) had received high school education, and 37.1% (151/407) were actively working, while 40.3% (164/407) were incapable of work or on retirement pay (22.6%, 92/407). Half of the patients (50.2%) were Aachen residents, while the other half resided within a 50 km radius. Median number of therapy sessions was 12 (range 1-97). Other treatment specific aspects are still being analysed and will be presented at the meeting. Conclusions: Despite the clear demand for all cancer patients, the majority of cancer patients actively seeking out-patient psycho-oncological support are women with breast cancer, while men and other cancer subtypes are clearly underrepresented. Better information, optimized resources, allocation strategies and comprehensive coverage of PO services are needed in order to address more cancer patients with psycho-social distress.

Efficacy and safety of bosutinib (BOS) for Philadelphia chromosome–positive (Ph+) leukemia in older versus younger patients (pts)

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Background: BOS is an oral dual Src/Abl kinase inhibitor with potent activity in Ph+ leukemia. Methods: Efficacy and safety of BOS 500 mg/d was evaluated in older (≥65 y; n = 119) and younger (<65 y; n = 451) pts in 3 cohorts: chronic phase chronic myeloid leukemia (CP CML) after imatinib (IM; CP2L cohort; n = 287); CP CML after IM + dasatinib (DAS) and/or nilotinib (NIL; CP3L cohort; n = 119); and accelerated/blast phase (AP/BP) CML or acute lymphoblastic leukemia after IM ± DAS and/or NIL (ADV cohort; n = 164). Results: Baseline events (≥65 y vs <65 y) included respiratory disorders (35% vs 13%), cardiac disorders (29% vs 9%), and diabetes (4% vs 4%). Median baseline medications were 3 (≥65 y) and 5 (<65 y). Median BOS duration was 11 mo and median follow-up was 31 mo for all pts. 80% of ³65 y and 67% of <65 y pts discontinued BOS, including 32% and 18% due to an adverse event (AE; most commonly thrombocytopenia [6% vs 3%]). Rates of response were similar or lower in older versus younger pts (Table). On-treatment transformation to AP/BP CML was similar between groups. Incidences of nonhematologic treatment-emergent AEs were generally similar between older and younger pts, notably (all grades/grade ≥3 for ≥65 y vs <65 y): diarrhea (85%/9% vs 81%/8%), infection (56%/15% vs 49%/10%), and edema (8%/0% vs 4%/<1%). Common grade ≥3 lab abnormalities (≥65 y vs <65 y) were thrombocytopenia (35% vs 35%), neutropenia (21% vs 25%), and anemia (19% vs 19%). Conclusions: BOS demonstrated similar efficacy and acceptable safety in both older and younger pts across Ph+ leukemia cohorts. [Table: see text]

Cilengitide with cetuximab, cisplatin, and 5-FU in recurrent and/or metastatic squamous cell cancer of the head and neck: The ADVANTAGE phase II trial

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Background: Prognosis for patients with recurrent and/or metastatic squamous cell cancer of the head and neck (R/M-SCCHN) is very poor. αvβ5 integrin is overexpressed in SCCHN and selective integrin blockade is being investigated as a treatment strategy. Methods: ADVANTAGE was a phase I/II study evaluating cilengitide with cetuximab and platinum-based chemotherapy. Eligible patients were ≥18 years with ≥1 measurable lesion, Karnofski performance status ≥70%, and confirmed R/M-SCCHN. The phase II part reported herein was an open-label, randomized, controlled trial investigating progression-free survival (PFS) in patients treated with 2 cilengitide 2000 mg regimens: once weekly (CIL1W) and twice weekly (CIL2W) administration combined with cisplatin, 5-FU, and cetuximab (PFE) as compared with PFE alone (control). Secondary objectives included overall survival (OS) and objective response (OR). Treatment-emergent adverse events (TEAEs) were monitored. Results: 184 eligible patients were enrolled. Overall, patient characteristics were similar across arms. Median duration of treatments was shorter in the CIL2W arm compared with the CIL1W arm (cilengitide: 16.1 vs 23.4 wk, cetuximab: 16.0 vs 22.6 wk, platinum: 16.0 vs 18.0 wk, and 5-FU: 14.6 vs 18.0 wk). Median PFS was 6.4 months in the CIL1W group, 5.6 months in the CIL2W group and 5.7 months in the control group, with CIL1W and CIL2W having HRs of 1.03 (95% CI: 0.67–1.59) and 1.55 (95% CI: 0.99–2.43) vs control. The latter HR was possibly due to less compliance in the CIL2W arm. Median OS was 12.4, 10.6, and 11.6 months in the CIL1W, CIL2W, and control groups, respectively. ORs were observed in 46.8%, 26.7%, and 35.5% of patients in the CIL1W, CIL2W, and control arms, respectively. Most common (≥15%) grade 3/4 TEAEs were neutropenia, hypokalemia, leukopenia, stomatitis, and fatigue. No safety differences were noted between treatment arms. Overall, there were 7 drug-related TEAEs (2 in CIL1W, 2 in CIL2W, and 3 in control) leading to death. Conclusions: In this population, neither of the cilengitide-containing regimens was able to demonstrate a PFS benefit over PFE alone.

Antineoplastic chemotherapy in cancer patients with methicillin-resistant Staphylococcus aureus (MRSA)

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen causing serious morbidity and mortality in immunosuppressed patients. Antineoplastic chemotherapy causes immunosuppression, and thus there is concern whether such patients should proceed to therapy without delay or dose reduction. There are presently no guidelines with appropriate provisions for antineoplastic chemotherapy in cancer patients with MRSA colonization or infection.

PATIENTS AND METHODS

We retrospectively analyzed the clinical outcome of all 27 patients with known MRSA infection or colonization undergoing antineoplastic chemotherapy for solid or hematological malignancies in our institution.

RESULTS

In our patients, MRSA was detected at multiple sites. 11 patients were found to be colonized with MRSA, whereas 16 patients had colonization and/or infection. MRSA sepsis occurred in 12 cases. Interestingly, at the time of MRSA sepsis, neutrophil counts were less than 500/μl in 42% of our patients. However, fatal complications due to MRSA occurred in only 2 patients. Among patients with MRSA sepsis, the mortality rate was 14%.

CONCLUSIONS

Our results with a limited number of patients support the contention that antineoplastic chemotherapy may well be administered to patients with MRSA and should not necessarily lead to dose reduction or treatment delay, especially in cases with curative intent.

Comparative proteome, transcriptome, and genome analysis of a gonadal and an extragonadal germ cell tumor cell line

Whereas clinical differences between testicular and extragonadal germ cell tumors (GCT), like reduced cisplatin sensitivity of extragonadal tumors, are well-established, little is known about underlying tumor biology. A combined approach using global proteome analysis and RT-PCR to assess mRNA levels of selected proteins on the one hand, and array comparative genomic hybridization (array-CGH), on the other hand, was used to compare two germ cell tumor (GCT) cell lines showing embryonal carcinoma histology, one of testicular, and one of extragonadal origin. Overall, the two cell lines show remarkably similar protein profiles. In total, 66 proteins were found to be differentially expressed in an at least 2-fold manner. Of these, 35 proteins (53%) could be positively identified by peptide mass fingerprinting and database search. mRNA levels of 27 differentially expressed proteins were analyzed by RT-PCR. In 17/27 genes (63%), differences in mRNA expression corresponded with differences detected on protein level, suggesting that these proteins are mainly regulated through transcription. Interestingly, no close correlation was found between proteomic and genomic analysis: 13/30 genes (43%) with higher protein levels in one cell line showed higher copy numbers of the respective gene loci in array-CGH analysis. Corresponding differences from proteome, transcriptome, and mRNA analyses were found in 9 of 27 proteins (33%). Several proteins potentially involved in cisplatin resistance were identified in the extragonadal cell line, suggesting that the cisplatin-resistant phenotype of this cell line is multifactorial. Furthermore, our data demonstrate that a combined approach of proteome, transcriptome, and genome analysis is a promising tool to gain information on gene regulation in human tumors.

Blood outgrowth endothelial cells from chronic myeloid leukaemia patients are BCR/ABL1 negative

The existence of adult haemangioblasts with dual haematopoietic and endothelial developmental potential was confirmed after detection of Ph(+) vascular endothelial cells in chronic myeloid leukaemia (CML) patients. Blood outgrowth endothelial cells (OECs) from CML patients were found not to harbour the Philadelphia translocation and were thus not clonally related to BRC/ABL1(+) hematopoietic progenitors, but comprised a distinct subfraction of endothelial cells. Remarkably, the frequency of CML-derived OECs was 9-fold higher as compared to healthy donors (n = 19 and n = 300, respectively; P < 0.0001) and these cells showed increased proliferative potential, possibly reflecting the mobilisation of OEC progenitors by pro-angiogenic cytokines.

Telomere Gap Between Granulocytes and Lymphocytes Is a Determinant for Hematopoetic Progenitor Cell Impairment in Patients With Previous Myocardial Infarction

Objective— We have previously demonstrated that ischemic cardiomyopathy is associated with selective impairment of progenitor cell function in the bone marrow and in the peripheral blood, which may contribute to an unfavorable left ventricular remodeling process.

Methods and Results— With this study, we intended to identify the influence of telomere length on bone marrow functionality in 50 patients with coronary artery disease (CAD) and previous myocardial infarction. Mean telomere length (mTL) was measured simultaneously in peripheral blood leukocytes and mononuclear bone marrow cells (BMC), using the flow-FISH method. Telomere erosion already occurred at the bone marrow level, whereby age (39 bp/yr, P =0.025) and the number of affected vessels (434 bp/vessel, P =0.029) were the only independent predictors. Lymphocytes demonstrated significant TL shortening between BMCs and peripheral blood in CAD patients (−1011±897 bp) as opposed to an increase in a young control group (+235±459 bp, P <0.001). SDF- and VEGF-specific migration of BMCs correlated with mTL of lymphocytes ( r =0.42, P <0.001) and was significantly reduced in CAD patients. Finally, the telomere length difference between granulocytes and lymphocytes was the most determinant for telomere-associated bone marrow impairment ( P <0.001).

Conclusion— In patients with CAD, telomere shortening of BMCs is dependent on both age and the extent of CAD and correlates with bone marrow cell functionality.

Telomere length analysis in monocytes and lymphocytes from patients with systemic lupus erythematosus using multi-color flow-FISH

In order to analyse telomere length in subsets of human peripheral blood lymphocytes and monocytes, we modified a recently developed multicolor flow- fluorescent in situ hybridization (FISH) methodology that combines flow-FISH and antibody staining for cell surface antigens. We analysed telomere length of peripheral blood mononuclear cells in a group of 22 patients with systemic lupus erythematosus (SLE) and 20 age-matched healthy donors. We found that neither CD4+, CD8+, CD19+ cells nor CD14+ monocytes have significantly shorter telomeres compared with their healthy counterparts. On the basis of these findings, we then used monocyte telomere length as internal reference in order to control for intra-individual variability in telomere length. By using this approach, we could demonstrate significant telomere shortening in all three lymphocyte subsets (in all cases P < 0.05) compared with monocytes. However, these differences did not vary significantly between SLE patients and controls. In summary, telomere lengths in subpopulations of hematopoietic cells can be monitored in patients with SLE using multicolor flow-FISH. While confirming data by other groups on telomere length in lymphocyte subpopulations, our data argue against an increased proliferation rate of peripheral blood monocytes reflected by accelerated telomere shortening in patients with SLE.

Targeting telomerase activity by BIBR1532 as a therapeutic approach in germ cell tumors

Germ cell tumors (GCT) possess a high activity of telomerase, a ribonucleoprotein complex compensating the erosion of telomeres during cell division by adding TTAGGG-repeats to the telomeric ends of chromosomes. Cisplatin, the most important drug in the treatment of GCT, preferentially acts on G-rich regions like telomeres. Inhibiting telomerase in tumors can result in telomere shortening and senescence and could increase the efficacy of chemotherapy in refractory patients. The study evaluated the promise of the small molecule telomerase inhibitor BIBR1532 as single agent and assessed a possible synergism with cisplatin in a preclinical model of GCT.GCT-derived cell line 2102EP was cultured with or without 10 microM of BIBR1532. Cell expansion was quantified in population doublings (PD). Telomere length was analyzed by fluorescence in situ hybridization and flow cytometry (flow-FISH). The sensitivity of the cells towards cisplatin was determined by MTT-assay. Telomerase activity was assessed by TRAP assay. After 300 PD, telomere length diminished from 18.5 kb +/- 0.59 kb to 8.9 +/- 0.1 kb in BIBR1532 treated 2102 EP cells as compared to 14.5 +/- 0.0 kb in untreated control cells. Treated cells did not show altered growth kinetics compared to untreated counterparts. Despite effective shortening of telomeres, the sensitivity of the treated cells towards cisplatin did not increase. Concomitant treatment with BIBR1532 and cisplatin did not result in accelerated telomere shortening. Telomere length can be shortened significantly by telomerase inhibition in GCT cell line models. However, possibly in view of their extensive telomere "reserve," telomerase inhibition did neither result in increased sensitivity of 2102 EP cells to cisplatin nor did co-treated cells show accelerated telomere shortening.

Concise review: Telomere biology in normal and leukemic hematopoietic stem cells

The measurement of telomere length can give an insight into the replicative history of the cells in question. Much of the observed telomere loss occurs at the stem and progenitor cell level, even though these populations express the enzyme telomerase. Telomerase-transfected hematopoietic stem cells (HSC), although able to maintain telomere length, are still limited in terms of ability to undergo sequential transplantation, and other factors require to be addressed to achieve optimal levels of stem cell expansion. Unchecked telomere loss by HSC, meanwhile, would appear to play a significant role in the pathogenesis of bone marrow failure, as observed in the condition dyskeratosis congenita. This heterogeneous inherited condition appears to exhibit telomerase dysfunction as a common final pathogenic mechanism. Although less well-established for acquired marrow failure syndromes, mutations in key telomerase components have been described. The identification of the leukemic stem cell (LSC), along with the desire to target this population with anti-leukemia therapy, demands that telomerase biology be fully understood in this cell compartment. Future studies using primary selected LSC-rich samples are required. A better understanding of telomerase regulation in this population may allow effective targeting of the telomerase enzyme complex using small molecule inhibitors or additional novel approaches. Disclosure of potential conflicts of interest is found at the end of this article.

Statins enhance migratory capacity by upregulation of the telomere repeat-binding factor TRF2 in endothelial progenitor cells

BACKGROUND

Cultivation of endothelial progenitor cells (EPCs) leads to premature replicative senescence, limiting ex vivo expansion for potential clinical cell therapy. Recent studies have linked senescence to the dysfunction of telomeres, the "ends" of chromosomes, via the so-called mitotic clock or culture-induced stress. The purpose of this study was to elucidate a possible role of telomere biology in the functional augmentation of EPCs by statins.

METHODS AND RESULTS

Human EPCs were isolated from peripheral blood. Using flow cytometry after fluorescence in situ hybridization with a telomere-specific (C3TA2)3 peptide nucleic acid probe (Flow-FISH), we found mean telomere length in untreated EPCs from healthy subjects to range between 8.5+/-0.2 and 11.1+/-0.5 kb with no change over 6 days of culture, excluding telomere erosion as one cause for premature senescence. Although mean telomere length did not differ between statin-treated and untreated EPCs, atorvastatin (0.1 micromol/L) and mevastatin (1.0 micromol/L) both led to a more than 3-fold increase in the expression of the telomere capping protein TRF2 (telomere repeat-binding factor), as shown by immunoblotting, whereas quantitative reverse transcription-polymerase chain reaction demonstrated no increase in TRF2 mRNA. Telomere dysfunction of EPCs was also paralleled by a 4-fold increase in the DNA damage checkpoint-kinase 2 (Chk2). Conversely, statin cotreatment or overexpression of TRF2 completely suppressed Chk2 induction. Finally, overexpression of a dominant negative mutant of the TRF2 protein abrogated statin-induced enhancement of migratory activity down to baseline values.

CONCLUSIONS

Ex vivo culturing of EPCs leads to "uncapping" of telomeres, indicated by the loss of TRF2. Statin cotreatment of EPCs prevents impairment of their functional capacity by a TRF2-dependent, posttranscriptional mechanism. This is the first time a beneficial effect of statins on telomere biology has been described.

Normalization of previously shortened telomere length under treatment with imatinib argues against a preexisting telomere length deficit in normal hematopoietic stem cells from patients with chronic myeloid leukemia

Telomeres are composed of TTAGGG repeats and associated proteins. In somatic cells, telomere repeats are lost with each cell division, eventually leading to genetic instability and cellular senescence. In previous studies, we described substantial and disease stage-specific telomere shortening in peripheral blood (PB) leukocytes from patients with chronic myeloid leukemia (CML). Here, we sought to determine whether age-adjusted telomere length in PB granulocytes (deltaTEL(gran)) is associated with response to treatment with the selective tyrosine kinase inhibitor imatinib. A total of 517 samples from 206 patients in chronic phase (CP), accelerated phase (AP), and blast crisis (BC) before and up to 706 days after initiation of imatinib therapy (median: 144 days) were analyzed by quantitative fluorescence in situ hybridization of interphase cells in suspension (Flow-FISH); telomere fluorescence was expressed in molecular equivalents of soluble fluorochrome units (MESF). Telomere length in samples from start of treatment up to day 144 was significantly shorter (mean +/- SE; -1.5 +/- 0.3 kMESF) compared to samples from patients treated for more than 144 days (-0.8 +/- 0.3 kMESF, p = 0.035). In patients with repeated measurements, a significant increase in telomere length under treatment was observed. Median telomere length in major remission was found to be significantly longer compared to patients without response to treatment measured either by cytogenetics (n = 246, p < 0.05), interphase FISH (n = 204, p = 0.002), or quantitative RT-PCR (n = 371, p < 0.05). In conclusion, the increase in telomere length under treatment with imatinib reflects a shift from Ph+ to Ph- cells in the PB of patients with CML.

Asymmetric cell divisions sustain long-term hematopoiesis from single-sorted human fetal liver cells

Hematopoietic stem cells (HSCs) in adult marrow are believed to be derived from fetal liver precursors. To study cell kinetics involved in long-term hematopoiesis, we studied single-sorted candidate HSCs from fetal liver that were cultured in the presence of a mixture of stimulatory cytokines. After 8-10 d, the number of cells in primary cultures varied from <100 to >10,000 cells. Single cells in slow growing colonies were recloned upon reaching a 100-200 cell stage. Strikingly, the number of cells in subclones varied widely again. These results are indicative of asymmetric divisions in primitive hematopoietic cells in which proliferative potential and cell cycle properties are unevenly distributed among daughter cells. The continuous generation of functional heterogeneity among the clonal progeny of HSCs is in support of intrinsic control of stem cell fate and provides a model for the long-term maintenance of hematopoiesis in vitro and in vivo.