Gastrointestinal stromal tumors - quantitative detection of the Ki-67, TPX2, TOP2A, and hTERT telomerase subunit mRNA levels to determine proliferation activity and a potential for aggressive biological behavior

Gastrointestinal stromal tumors (GISTs) have an unpredictable biological potential ranging from benign to malignant. Molecular markers involved in the mechanisms of proliferation and cellular senescence may provide additional information about biological behavior of the tumor. The aim of the present study was to investigate Ki-67, TPX2, TOP2A and hTERT mRNA expression levels in specimens from patients with GISTs to define relationships between proliferation activity and biological potential and progression of the disease. We measured Ki-67, TPX2, TOP2A and hTERT mRNA levels using quantitative real-time reverse transcription PCR (RQ RT PCR). The highest Ki-67, TPX2, TOP2A and hTERT mRNA expression levels were found in the highly proliferative BLs (18 specimens), in comparison with GISTs (137 specimens) and LMSs (9 specimens). Patients with GISTs and adequate information about mitotic activity, tumor size and anatomical site (84 specimens) were divided into two groups - GISTs with benign (29 patients) and with malignant (55 patients) potential. We observed association between higher Ki-67, TPX2 and hTERT mRNA levels and the GISTs with malignant potential. Univariate analysis (57 patients with available follow-up information) of survival (Kaplan Meier curves method) revealed a correlation between higher levels of TPX2, Ki-67 and hTERT markers and shorter event-free survival (EFS) or poorer overall survival (OS). The results demonstrate the importance of quantitative assessment of the proliferation activity in GISTs. Proliferation markers of Ki-67, TPX2, TOP2A and hTERT are suitable markers for detection the proliferation activity and telomerase activity of these tumors. Furthermore, the assessment of TPX2, Ki-67 and hTERT expression levels is appropriate for determination of malignant potential of GISTs.

Standardization of WT1 mRNA quantitation for minimal residual disease monitoring in childhood AML and implications of WT1 gene mutations: a European multicenter study

A standardized, sensitive and universal method for minimal residual disease (MRD) detection in acute myeloid leukemia (AML) is still pending. Although hyperexpression of Wilms' tumor (WT1) gene transcript has been frequently proposed as an MRD marker in AML, wide comparability of the various methods used for evaluating WT1 expression has not been given. We established and standardized a multicenter approach for quantifying WT1 expression by quantitative reverse transcriptase PCR (qRT-PCR), on the basis of a primer/probe set combination at exons 6 and 7. In a series of quality-control rounds, we analyzed 69 childhood AML samples and 47 normal bone marrow (BM) samples from 4 participating centers. Differences in the individual WT1 expressions levels ranged within <0.5 log of the mean in 82% of the cases. In AML samples, the median WT1/1E+04 Abelson (ABL) expression was 3.5E+03 compared with that of 2.3E+01 in healthy BM samples. As 11.5% of childhood AML samples in this cohort harbored WT1 mutations in exon 7, the effect of mutations on WT1 expression has been investigated, showing that mutated cases expressed significantly higher WT1 levels than wild-type cases. Hence, our approach showed high reproducibility and applicability, even in patients with WT1 mutations; therefore, it can be widely used for the quantitation of WT1 expression in future clinical trials.

Wilms' tumor gene 1 (WT1) expression in childhood acute lymphoblastic leukemia: a wide range of WT1 expression levels, its impact on prognosis and minimal residual disease monitoring

Wilms' tumor gene 1 (WT1) is overexpressed in the majority (70-90%) of acute leukemias and has been identified as an independent adverse prognostic factor, a convenient minimal residual disease (MRD) marker and potential therapeutic target in acute leukemia. We examined WT1 expression patterns in childhood acute lymphoblastic leukemia (ALL), where its clinical implication remains unclear. Using a real-time quantitative PCR designed according to Europe Against Cancer Program recommendations, we evaluated WT1 expression in 125 consecutively enrolled patients with childhood ALL (106 BCP-ALL, 19 T-ALL) and compared it with physiologic WT1 expression in normal and regenerating bone marrow (BM). In childhood B-cell precursor (BCP)-ALL, we detected a wide range of WT1 levels (5 logs) with a median WT1 expression close to that of normal BM. WT1 expression in childhood T-ALL was significantly higher than in BCP-ALL (P<0.001). Patients with MLL-AF4 translocation showed high WT1 overexpression (P<0.01) compared to patients with other or no chromosomal aberrations. Older children (> or =10 years) expressed higher WT1 levels than children under 10 years of age (P<0.001), while there was no difference in WT1 expression in patients with peripheral blood leukocyte count (WBC) > or =50 x 10(9)/l and lower. Analysis of relapsed cases (14/125) indicated that an abnormal increase or decrease in WT1 expression was associated with a significantly increased risk of relapse (P=0.0006), and this prognostic impact of WT1 was independent of other main risk factors (P=0.0012). In summary, our study suggests that WT1 expression in childhood ALL is very variable and much lower than in AML or adult ALL. WT1, thus, will not be a useful marker for MRD detection in childhood ALL, however, it does represent a potential independent risk factor in childhood ALL. Interestingly, a proportion of childhood ALL patients express WT1 at levels below the normal physiological BM WT1 expression, and this reduced WT1 expression appears to be associated with a higher risk of relapse.

Upregulation of asparagine synthetase fails to avert cell cycle arrest induced by L-asparaginase in TEL/AML1-positive leukaemic cells

L-Asparaginase is a standard component in chemotherapy of childhood acute lymphoblastic leukaemia (ALL). Leukaemic cells carrying TEL/AML1 fusion gene are more sensitive to treatment with L-asparaginase compared to other subtypes of ALL. We demonstrate in vitro the prolonged growth suppression of TEL/AML1[+] cells compared to TEL/AML1[-] leukaemic cells after L-asparaginase treatment simulating treatment protocol. Cell cycle analysis revealed TEL/AML1[+] cells to accumulate in G1/G0 phase (81-98%) compared to TEL/AML1[-] cells (47-60%). Quantitative analysis of asparagine synthetase (AsnS) expression showed the ability of TEL/AML1[+] cells to increase AsnS mRNA levels after L-asparaginase treatment to the same extent as TEL/AML1[-] leukaemic and nonleukaemic lymphoid cells. We hypothesise that TEL/AML1[+] cells are unable to progress into the S phase of cell cycle under nutrition stress caused by L-asparaginase, despite the ability of AsnS upregulation. Significantly higher expression of AsnS was found in untreated leukaemic cells from children with TEL/AML1[+] ALL (n=20) in comparison with the group of age-matched children with ALL bearing no known fusion gene (n=25; P=0.0043). Interestingly, none of the TEL/AML1[+] patients with high AsnS level relapsed, whereas 10/15 patients with AsnS below median relapsed (P=0.00028). Therefore, high AsnS levels in TEL/AML1[+] patients correlate with better prognosis, possibly reflecting the stretched metabolic demand of the lymphoblast.