Reverse Transcription Can Critically Impact the Diagnostic Outcome of BCR::ABL1 Quantitative Real-Time RT-PCR

Reverse transcriptases (RT) are essential tools in BCR::ABL1 fusion transcript monitoring in chronic myeloid leukemia (CML). The RT type and cDNA priming method may impair the stoichiometry of cDNA synthesis, thereby potentially introducing a bias in BCR::ABL1 qRT-PCR data. Using the Acrometrix™ BCR::ABL1 reference panel and 37 clinical specimens, we have comparatively investigated the performance of the RTs MLV and SuperScript IV with random hexamer vs. target-specific priming. Quantitative RT-PCR results identified the priming type and RT type as major factors for diagnostic data variation, mainly due to the different efficacies of processing BCR::ABL1 low-copy-numbers (<50) compared to GUSB or ABL1 high-copy targets. The impairment of SuperScript IV in processing low- and high-copy-number RNA targets equally was not reflected by the diagnostically relevant Log (BCR::ABL1/GUSB%) values. Therefore, the correct representation of housekeeping and BCR::ABL1 target genes should have priority when aiming at as high a number of housekeeping gene copies as possible. Our data suggest that for improving BCR::ABL1 assay sensitivity, increased RNA/cDNA amounts and the use of distinct RT/priming combinations are advantageous. However, for inter-laboratory harmonization, the proper conversion factor according to the CML international standard (IS) has to be reevaluated each time the grade of RT is changed.

Gene Expression Pattern of ESPL1, PTTG1 and PTTG1IP Can Potentially Predict Response to TKI First-Line Treatment of Patients with Newly Diagnosed CML

The achievement of major molecular response (MMR, BCR::ABL1 ≤ 0.1% IS) within the first year of treatment with tyrosine kinase inhibitors (TKI) is a milestone in the therapeutic management of patients with newly diagnosed chronic myeloid leukemia (CML). We analyzed the predictive value of gene expression levels of ESPL1/Separase, PTTG1/Securin and PTTG1IP/Securin interacting protein for MMR achievement within 12 months. Relative expression levels (normalized to GUSB) of ESPL1, PTTG1 and PTTG1IP in white blood cells of patients (responders n = 46, non-responders n = 51) at the time of diagnosis were comparatively analyzed by qRT-PCR. 3D scatter plot analysis combined with a distance analysis performed with respect to a commonly calculated centroid center resulted in a trend to larger distances for non-responders compared to the responder cohort (p = 0.0187). Logistic regression and analysis of maximum likelihood estimates revealed a positive correlation of distance (cut-off) with non-achieving MMR within 12 months (p = 0.0388, odds ratio 1.479, 95%CI: 1.020 to 2.143). Thus, 10% of the tested non-responders (cut-off ≥ 5.9) could have been predicted already at the time of diagnosis. Future scoring of ESPL1, PTTG1 and PTTG1IP transcript levels may be a helpful tool in risk stratification of CML patients before initiation of TKI first = line treatment.

Separase activity distribution can be a marker of major molecular response and proliferation of CD34+ cells in TKI-treated chronic myeloid leukemia patients

Separase, a cysteine endopeptidase, is a key player in mitotic sister chromatid separation, replication fork dynamics, and DNA repair. Aberrant expression and/or altered separase proteolytic activity are associated with aneuploidy, tumorigenesis, and disease progression. Since genomic instability and clonal evolution are hallmarks of progressing chronic myeloid leukemia (CML), we have comparatively examined separase proteolytic activity in TKI-treated chronic phase CML. Separase proteolytic activity was analyzed on single cell level in 88 clinical samples and in 14 healthy controls by a flow cytometric assay. In parallel, BCR-ABL1 gene expression and replication fork velocity were measured by qRT-PCR and DNA fiber assays, respectively. The separase activity distribution (SAD) value indicating the occurrence of MNCs with elevated separase proteolytic activity within samples was found to positively correlate with BCR-ABL1 gene expression levels and loss of MMR (relapse) throughout routine BCR-ABL1 monitoring. Analyses of CD34⁺ cells and MNCs fractionized by flow cytometric cell sorting according to their separase activity levels (H- and L-fractions) revealed that CD34⁺ cells with elevated separase activity levels (H-fractions) displayed enhanced proliferation/viability when compared with cells with regular (L-fraction) separase activity (mean 3.3-fold, p = 0.0011). BCR-ABL1 gene expression positivity prevailed in MNC H-fractions over L-fractions (42% vs. 8%, respectively). Moreover, expanding CD34⁺ cells of H-fractions showed decreased replication fork velocity compared with cells of L-fractions (p < 0.0001). Our data suggests an association between high separase activity, residual BCR-ABL1 gene expression, and enhanced proliferative capacity in hematopoietic cells within the leukemic niche of TKI-treated chronic phase CML.

Increased separase activity and occurrence of centrosome aberrations concur with transformation of MDS

ESPL1/separase, a cysteine endopeptidase, is a key player in centrosome duplication and mitotic sister chromatid separation. Aberrant expression and/or altered separase proteolytic activity are associated with centrosome amplification, aneuploidy, tumorigenesis and disease progression. Since centrosome alterations are a common and early detectable feature in patients with myelodysplastic syndrome (MDS) and cytogenetic aberrations play an important role in disease risk stratification, we examined separase activity on single cell level in 67 bone marrow samples obtained from patients with MDS, secondary acute myeloid leukemia (sAML), de novo acute myeloid leukemia (AML) and healthy controls by a flow cytometric separase activity assay. The separase activity distribution (SAD) value, a calculated measure for the occurrence of cells with prominent separase activity within the analyzed sample, was tested for correlation with the centrosome, karyotype and gene mutation status. We found higher SAD values in bone marrow cells of sAML patients than in corresponding cells of MDS patients. This concurred with an increased incidence of aberrant centrosome phenotypes in sAML vs. MDS samples. No correlation was found between SAD values and the karyotype/gene mutation status. During follow-up of four MDS patients we observed increasing SAD values after transformation to sAML, in two patients SAD values decreased during azacitidine therapy. Cell culture experiments employing MDS-L cells as an in vitro model of MDS revealed that treatment with rigosertib, a PLK1 inhibitor and therapeutic drug known to induce G2/M arrest, results in decreased SAD values. In conclusion, the appearance of cells with unusual high separase activity levels, as indicated by increased SAD values, concurs with the transformation of MDS to sAML and may reflect separase dysregulation potentially contributing to clonal evolution during MDS progression. Separase activity measurement may therefore be useful as a novel additional molecular marker for disease monitoring.

c-MYB is a transcriptional regulator of ESPL1/Separase in BCR-ABL-positive chronic myeloid leukemia

Background

Genomic instability and clonal evolution are hallmarks of progressing chronic myeloid leukemia (CML). Recently, we have shown that clonal evolution and blast crisis correlate with altered expression and activity of Separase, a cysteine endopeptidase that is a mitotic key player in chromosomal segregation and centriole duplication. Hyperactivation of Separase in human hematopoietic cells has been linked to a feedback mechanism that posttranslationally stimulates Separase proteolytic activity after imatinib therapy-induced reduction of Separase protein levels.

Methods and Results

In search for potential therapy-responsive transcriptional mechanisms we have investigated the role of the transcription factor c-MYB for Separase expression in CML cell lines (LAMA-84, K562, BV-173) and in clinical samples. Quantitative RT-PCR and Western blot immunostaining experiments revealed that c-MYB expression levels are decreased in an imatinib-dependent manner and positively correlate with Separase expression levels in cell lines and in clinical CML samples. RNA silencing of c-MYB expression in CML cell lines resulted in reduced Separase protein levels. Gelshift and ChIP assays confirmed that c-MYB binds to a putative c-MYB binding sequence located within the ESPL1 promoter.

Conclusions

Our data suggest that ESPL1/Separase is a regulatory target of c-MYB. Therefore, c-MYB, known to be required for BCR-ABL-dependent transformation of hematopoietic progenitors and leukemogenesis, may also control the Separase-dependent fidelity of mitotic chromosomal segregation and centriole duplication essential for maintenance of genomic stability.

Measurement of separase proteolytic activity in single living cells by a fluorogenic flow cytometry assay

ESPL1/Separase, an endopeptidase, is required for centrosome duplication and separation of sister-chromatides in anaphase of mitosis. Overexpression and deregulated proteolytic activity of Separase as frequently observed in human cancers is associated with the occurrence of supernumerary centrosomes, chromosomal missegregation and aneuploidy. Recently, we have hypothesized that increased Separase proteolytic activity in a small subpopulation of tumor cells may serve as driver of tumor heterogeneity and clonal evolution in chronic myeloid leukemia (CML). Currently, there is no quantitative assay to measure Separase activity levels in single cells. Therefore, we have designed a flow cytometry-based assay that utilizes a Cy5- and rhodamine 110 (Rh110)-biconjugated Rad21 cleavage site peptide ([Cy5-D-R-E-I-M-R]₂-Rh110) as smart probe and intracellular substrate for detection of Separase enzyme activity in living cells. As measured by Cy5 fluorescence the cellular uptake of the fluorogenic peptide was fast and reached saturation after 210 min of incubation in human histiocytic lymphoma U937 cells. Separase activity was recorded as the intensity of Rh110 fluorescence released after intracellular peptide cleavage providing a linear signal gain within a 90–180 min time slot. Compared to conventional cell extract-based methods the flow cytometric assay delivers equivalent results but is more reliable, bypasses the problem of vague loading controls and unspecific proteolysis associated with whole cell extracts. Especially suited for the investigaton of blood- and bone marrow-derived hematopoietic cells the flow cytometric Separase assay allows generation of Separase activity profiles that tell about the number of Separase positive cells within a sample i.e. cells that currently progress through mitosis and about the range of intercellular variation in Separase activity levels within a cell population. The assay was used to quantify Separase proteolytic activity in leukemic cell lines and peripheral blood samples from leukemia patients.

Clonal Evolution and Blast Crisis Correlate with Enhanced Proteolytic Activity of Separase in BCR-ABL b3a2 Fusion Type CML under Imatinib Therapy

Unbalanced (major route) additional cytogenetic aberrations (ACA) at diagnosis of chronic myeloid leukemia (CML) indicate an increased risk of progression and shorter survival. Moreover, newly arising ACA under imatinib treatment and clonal evolution are considered features of acceleration and define failure of therapy according to the European LeukemiaNet (ELN) recommendations. On the basis of 1151 Philadelphia chromosome positive chronic phase patients of the randomized CML-study IV, we examined the incidence of newly arising ACA under imatinib treatment with regard to the p210BCR-ABL breakpoint variants b2a2 and b3a2. We found a preferential acquisition of unbalanced ACA in patients with b3a2 vs. b2a2 fusion type (ratio: 6.3 vs. 1.6, p = 0.0246) concurring with a faster progress to blast crisis for b3a2 patients (p = 0.0124). ESPL1/Separase, a cysteine endopeptidase, is a key player in chromosomal segregation during mitosis. Separase overexpression and/or hyperactivity has been reported from a wide range of cancers and cause defective mitotic spindles, chromosome missegregation and aneuploidy. We investigated the influence of p210BCR-ABL breakpoint variants and imatinib treatment on expression and proteolytic activity of Separase as measured with a specific fluorogenic assay on CML cell lines (b2a2: KCL-22, BV-173; b3a2: K562, LAMA-84). Despite a drop in Separase protein levels an up to 5.4-fold increase of Separase activity under imatinib treatment was observed exclusively in b3a2 but not in b2a2 cell lines. Mimicking the influence of imatinib on BV-173 and LAMA-84 cells by ESPL1 silencing stimulated Separase proteolytic activity in both b3a2 and b2a2 cell lines. Our data suggest the existence of a fusion type-related feedback mechanism that posttranslationally stimulates Separase proteolytic activity after therapy-induced decreases in Separase protein levels. This could render b3a2 CML cells more prone to aneuploidy and clonal evolution than b2a2 progenitors and may therefore explain the cytogenetic results of CML patients.

Evaluation of thymoquinone (TQ) as an antiproliferative, proapoptotic, and immunomodulatory agent in a non-small cell lung cancer cell (NSCLC) line

e14644

Background: NSCLC is the most common cause of cancer death worldwide. We performed in vitro testing of Thymoquinone (TQ), a derivative of black caraway seed against NSCLC cell line NCI-H460 Methods: Cells were grown in RPMI and were plated at a density of 5,000 cells per well in a 96 well plate and cell growth determined in the presence of 80 and 100μM of TQ dissolved in DMSO with appropriate solvent only as control. Cell proliferation was determined at 24, 48 and 72 hrs intervals using 3-(4,5-dimethyltiazol 2-yl)-2,5-diphenyltetraolium bromide (MTT) assay. Factorial analyses of variance (ANOVA) were used to determine the effect of TQ and control with the time. Student-Newman-Keuls test was used to determine statistical significance with P value <0.05 considered significant. Apoptosis was detected using Annexin V-FITC Aptosis Detection Kit analyzing the effects of TQ at 24 hrs after treatment by flow cytometry. The immunomodulatory effects of TQ were tested using RayBio Human Cytokine Antibody Array C series 200. NCI-H460 cells (50,000 cells per well in duplicate 6 well plates) were grown in serum free RPMI media. 24 hrs after treatment with TQ or DMSO media was collected and analyzed for expression of various cytokines. Results: The MTT assay showed that TQ at 80 and 100 μM significantly inhibited cell growth as compared to control and at 24 hrs for example, 100 μM TQ inhibited cell growth by 78%. Apoptosis occurred rapidly after treatment with TQ with 73.5% of cells being positive for expression of Annexin-V as detected by flow cytometry after 24 hrs of exposure to TQ as compared to 2.6% of controls. The cytokine array revealed that TQ significantly decreased expression of ENA-78(Epithelial neutrophil activating peptide), and GRO (Growth related oncogene).ENA-78 is correlated with vascularity and tumor growth in NSCLC tumor, whereas GRO is associated with neoangiogenesis. Conclusions: TQ is shown to be a powerful anti-proliferative, pro-apoptotic and anti- angiogenic agent in a NSCLC cell line.

No significant financial relationships to disclose.

Effect of naturally occurring coumarins on the formation of epidermal DNA adducts and skin tumors induced by benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene in SENCAR mice

Several naturally occurring coumarins previously found to be potent inhibitors of mouse hepatic ethoxyresorufin-O-deethylase (EROD) and/or pentoxyresorufin-O-dealkylase (PROD) were examined for their effects on formation of benzo[a]pyrene (B[a]P) and 7,12-dimethylbenz[a]anthracene (DMBA) DNA adducts in mouse epidermis, as well as, their effects on skin tumor initiation by these polycyclic aromatic hydrocarbons (PAH). Bergamottin, a potent inhibitor of hepatic EROD, given topically 5 min prior to an initiating dose of B[a]P, significantly decreased total covalent binding of B[a]P to DNA in a dose-dependent manner 24 h after treatment. A dose of 400 nmol bergamottin reduced covalent binding of B[a]P by 72%. Coriandrin, at a dose of 400 nmol also significantly reduced total covalent binding of B[a]P by 59%. In addition, formation of the major (+)anti-B[a]P-diol epoxide-N2-dGuo adduct was selectively reduced by both of these coumarins. In contrast, bergamottin and coriandrin did not significantly decrease covalent binding of DMBA to epidermal DNA at doses of either 400 nmol or 800 nmol. Imperatorin and isopimpinellin, which are more potent inhibitors of hepatic PROD activity, significantly reduced overall binding of DMBA to epidermal DNA by 67% and 52%, respectively, when applied at doses of 400 nmol. These two coumarins also inhibited B[a]P-DNA adduct formation at similar doses but to a lesser extent. Imperatorin at a dose of 400 nmol dramatically decreased formation of covalent DNA adducts derived from both the anti and syn diol epoxides of DMBA. Bergamottin was a potent inhibitor of tumor initiation by B[a]P while coriandrin was less effective in this regard. Imperatorin was an effective inhibitor of skin tumor initiation by DMBA and also inhibited complete carcinogenesis by this PAH. At dose levels higher than those effective against DMBA, imperatorin also inhibited tumor initiation by B[a]P. The results demonstrate that several naturally occurring coumarins possess the ability to block DNA adduct formation and tumor initiation by PAHs such as B[a]P and DMBA. The mechanism for reduced DNA adduct formation and tumor initiation appears to involve inhibition of the P450s involved in the metabolic activation of these hydrocarbons. Finally, the differential effects of certain coumarins on B[a]P vs DMBA DNA adduct formation and tumor initiation may be useful for dissecting the role of specific cytochromes P450 in their metabolic activation.

[Epidemiology and prognosis of subungual melanoma]

Among a total of 2038 cases of malignant melanoma, 42 tumours (approximately 2%) were located sub- and periungually. The matrices of thumbs and halluces were primarily affected. Girls and women were more frequently affected than boys and men, and a broad "pyramid of age" was obvious. The mean age for both sexes was 61 years. A mean of 1.5-2 years elapsed between the appearance of the first symptoms and establishment of a definitive diagnosis. Pigmented tumours were recognized earlier than non-pigmented ones. The prognosis in melanoma of the nail has usually been found to be poor. The curves for both survival and recurrences display an initial steep downward course. A flatter course is noted for the survival curve beyond 24 months postoperatively and for the survival curve beyond 48 months after surgery. The 5-year disease-free survival rate following operative removal of the tumour or amputation of the digit is 0.50% for subungual melanoma of the hand and 0.31% for subungual melanoma of the foot. By 10 years after operative removal of the tumour, 43% of the patients with subungual melanoma of the feet are still free of disease. Similar differences are found in the length of survival. The 5-year survival rate is 0.57 for subungual melanoma of the hand and 0.48 for melanoma of the foot. The 10-year survival rates, however, are 0.41 and 0.22, respectively. Significant differences between hand and foot cannot be verified in the rate of subungual melanoma.

Human placental oxytocinase and its relationship to pregnancy plasma oxytocinase

Plasma "oxytocinase of pregnancy" and three placental "oxytocinase" fractions from human placental extracts were compared. On the basis of acrylamide-agarose chromatography, polyacrylamide gel electrophoresis, substrate specificity, heat liability and relative insensitiveness to L-methionine, it is concluded that placental enzyme activities, present in the second acrylamide-agarose peak, are identical with the plasma "pregnancy oxytocinase" and are to be regarded as its source. The hypothesis of a transplacental passage of placental peak II oxytocinase in the blood compartment of the mother seems well supported. Heat treatment of the placental extracts uncovered a minor activity behaving like Oya's microsomal oxytocinase, which is totally unlike the plasma oxytocinase and plays no part in the increased oxytocinase activity of human pregnancy plasma. A hitherto undescribed enzyme activity shares with the pregnancy oxytocinase its specificity towards L-leucyl-beta-naphthylamide and di-S-S-L-cysteinyl-beta-naphthylamide, its heat lability and realtive insensitiveness to L-methionine. However, this activity is carried by a protein of much lower molecular weight as judged by acrylamide-agarose chromatography, which shows only a single activity band on polyacrylamide gel electrophoresis.

[Measurement of plasma oxytocinase. Comparison with urinary excretion of estrogens]

Plasma cystinylaminopeptidase (CAP) activity and 24 h urinary excretion of oestrogens were measured simultaneously in 102 pathological pregnancies. The correlation between the two chemical assays is weak (p = 0,13, to 0,47). Plasma CAP levels were significantly (p less than 0,01) lowered in cases of fetal death; but urinary oestrogen assays were within the normal limits (p greater than 0,1) in this group. Each assay suggested an equal number of correct or incorrect prognoses. Their association resulted in 9 correct prognoses in 12 pregnancies with unfavourable outcome, but led to 12 unduly bad prognoses in a group of 40 normal births. The association of the two assays allows a more adequate diagnosis of high-risk pregnancies, but has the disadvantage of offering an unduly bad prognosis in a greater number of normal cases.

Correlation between date of birth and pollen sensitivity

Attempts by previous investigators have failed to show significant correlation between seasonal pollens and the birth dates of individuals as evidence for the development of tolerance in immunologically immature neonates. Using a large clinic population with adequate controls, significant correlation between ragweed, grass or tree pollen sensitivity and the dates of birth was not obtained.