Ji-chun Ma

U2AF1 Mutations in Chinese Patients with Acute Myeloid Leukemia and Myelodysplastic Syndrome

Somatic mutations of U2AF1 gene have recently been identified in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In this study, we analyzed the frequency and clinical impact of U2AF1 mutations in a cohort of 452 Chinese patients with myeloid neoplasms. Mutations in U2AF1 were found in 2.5% (7/275) of AML and 6.3% (6/96) of MDS patients, but in none of 81 CML. All mutations were heterozygous missense mutations affecting codon S34 or Q157. There was no significant association of U2AF1 mutation with blood parameters, FAB subtypes, karyotypes and other gene mutations in AML. The overall survival (OS) of AML patients with U2AF1 mutation (median 3 months) was shorter than those without mutation (median 7 months) (P = 0.035). No difference in the OS was observed between MDS patients with and without U2AF1 mutations. Our data show that U2AF1 mutation is a recurrent event at a low frequency in AML and MDS.

Overexpression of miR-378 is frequent and may affect treatment outcomes in patients with acute myeloid leukemia

MicroRNA miR-378 plays important roles in tumorigenesis by enhancing cell survival, reducing apoptosis, promoting tumor growth, angiogenesis and promoting cell migration and invasion. Abnormal expression of miR-378 has been observed in various types of cancers. The aim of this study was to investigate the expression status of miR-378 and its clinical significance in patients with acute myeloid leukemia (AML) using real-time quantitative PCR. miR-378 overexpression was identified in 26 of 84 (31%) AML patients. The patients with miR-378 overexpression had lower hemoglobin level than those without miR-378 overexpression (66 versus 78 g/L, respectively, P=0.010). The frequency of miR-378 overexpression in FAB-M2 subtype was higher than other subtypes (44% versus 20%, P=0.032). Moreover, the frequency of miR-378 overexpression was higher in patients with t(8;21) than in others (64% versus 24%, P=0.012). The status of miR-378 expression was not correlated with the mutations of eight genes (FLT3-ITD, NPM1, C-KIT, IDH1/IDH2, DNMT3A, C/EBPA and U2AF1). The difference in relapse-free survival was observed between patients with and without miR-378 overexpression (P=0.049). These findings suggest that miR-378 up-regulation is a common event and might have an adverse impact on prognosis in AML.

The Intermediate Filament Vimentin Mediates MicroRNA miR-378 Function in Cellular Self-renewal by Regulating the Expression of the Sox2 Transcription Factor

Background: We have previously demonstrated that miR-378 expression promotes tumorigenesis and angiogenesis. Results: We show here that miR-378 plays roles in cell self-renewal, survival, and colony formation by enhancing Sox2 expression through repressing vimentin level. Conclusion: Our study demonstrates that miR-378 can trigger a signal cascade. Significance: Our study reveals a novel signaling pathway in modulating cell stemness by miR-378 expression. MicroRNAs are short noncoding RNAs that are implicated in cell self- renewal and cancer development. We show that miR-378 is up-regulated in human cancers and found that tumor cells transfected with miR-378 acquired properties of tumor stem cells, including cell self-renewal. Overexpression of miR-378 enhanced cell survival and colony formation. Isolated from a single-cell colony, the miR-378-expressing cells formed tumors in nude mice at low cell densities. These cells expressed higher levels of miR-378 and formed more and larger spheres and colonies. We found that the miR-378-expressing cells contained a large number of side population cells and could undergo differentiation. Cells transfected with miR-378 expressed increased levels of Sox2. Expression of miR-378 and Sox2 was found correlated significantly in cancer cell lines and in cancer patient specimens. We also observed opposite levels of vimentin in the cancer cell lines and human breast carcinoma specimens. We further demonstrated that vimentin is a target of miR-378, and ectopic transfection of vimentin inhibited Sox2 expression, resulting in decreased cell survival. Silencing vimentin promoted Sox2 expression and cell survival. Our study demonstrates that miR-378 is a regulator of stem cell marker Sox2 by targeting vimentin, which may serve as a new tool in studying the role of stem cells in tumorigenesis.

MiR-378 Promotes the Migration of Liver Cancer Cells by Down-Regulating Fus Expression

Background: miR-378 regulates osteoblast differentiation and participates in tumor cell self-renewal and chemo-resistance. However, the function of miR-378 in liver cancer cell migration has not been reported to date. Methods: miR-378 expression was examined using real-time quantitative PCR. HepG2 cell migration and liver cell invasion were examined using wound-healing and cell invasion assays. Additionally, HepG2 cell metastasis was analyzed in nude mice. Results: miR-378 over-expression enhances HepG2 cell proliferation, migration and liver cell invasion. Typical metastatic lesions were found in the livers of mice injected with miR-378-transfected cells, and high levels of the CMV promoter were detected in the nodules, indicating that miR-378 promoted the metastasis of the tumor cells to the liver. We also demonstrated that miR-378 down-regulated Fus expression. Conclusions: Our results suggested that miR-378 enhanced cell migration and metastasis by down-regulating Fus expression.

Epigenetic dysregulation of ID4 predicts disease progression and treatment outcome in myeloid malignancies

Promoter hypermethylation‐mediated inactivation of ID4 plays a crucial role in the development of solid tumours. This study aimed to investigate ID4 methylation and its clinical relevance in myeloid malignancies. ID4 hypermethylation was associated with higher IPSS scores, but was not an independent prognostic biomarker affecting overall survival (OS) in myelodysplastic syndrome (MDS). However, ID4 hypermethylation correlated with shorter OS and leukaemia‐free survival (LFS) time and acted as an independent risk factor affecting OS in acute myeloid leukaemia (AML). Moreover, ID4 methylation was significantly decreased in the follow‐up paired AML patients who achieved complete remission (CR) after induction therapy. Importantly, ID4 methylation was increased during MDS progression to AML and chronic phase (CP) progression to blast crisis (BC) in chronic myeloid leukaemia (CML). Epigenetic studies showed that ID4 methylation might be one of the mechanisms silencing ID4 expression in myeloid leukaemia. Functional studies in vitro showed that restoration of ID4 expression could inhibit cell proliferation and promote apoptosis in both K562 and HL60 cells. These findings indicate that ID4 acts as a tumour suppressor in myeloid malignancies, and ID4 methylation is a potential biomarker in predicting disease progression and treatment outcome.

Dysregulation of miR-124-1 predicts favorable prognosis in acute myeloid leukemia

OBJECTIVE MicroRNA miR-124 has been suggested as a tumor suppressor for its role in inhibiting cell growth, inducing differentiation and promoting apoptosis. The present study was aimed to investigate the expression status of miR-124-1 and its clinical relevance in patients with acute myeloid leukemia (AML). DESIGNS AND METHODS Real-time quantitative PCR was performed to detect the expression level of miR-124-1 in AML patients. The clinical significance of miR-124-1 expression in AML was investigated. RESULTS miR-124-1 underexpression was identified in 30 (36%) of 83 AML patients. No significant difference could be observed in sex, age and blood parameters between the patients with and without miR-124-1 underexpression. The frequency of miR-124-1 underexpression was higher in the patients with t(15;17) than in others (62% versus 30%, P = 0.040). The status of miR-124-1 expression was not correlated with the mutations of nine genes (FLT3-ITD, NPM1, C-KIT, IDH1/IDH2, DNMT3A, N/K-RAS and C/EBPA). The patients with miR-124-1 underexpression had borderline longer overall survival and relapse-free survival than those without miR-124-1 underexpression (P = 0.052 and 0.045, respectively). CONCLUSIONS These findings suggest that miR-124-1 underexpression is a common event and might have a favorable impact on prognosis in AML.

Detection of SRSF2-P95 mutation by high-resolution melting curve analysis and its effect on prognosis in myelodysplastic syndrome.

Hotspot mutations of serine/arginine-rich splicing factor 2 (SRSF2) gene have been identified in a proportion of hematologic malignancies including myelodysplastic syndrome (MDS). The aim of the present study was to develop a new approach to screen SRSF2 mutation and analyze the clinical relevance of SRSF2 mutations in Chinese MDS. A protocol based on high-resolution melting analysis (HRMA) was established to screen SRSF2-P95 mutation in 108 MDS patients and was compared with Sanger sequencing. The clinical relevance of SRSF2 mutations was further evaluated. HRMA identified five (4.6%) cases with SRSF2 mutation, completely validated by Sanger sequencing without false positive or negative results. The sensitivities of HRMA and Sanger sequencing were 10% and 25% for the detection of SRSF2-P95H mutation, respectively, against the background of wild-type DNA. Patients with SRSF2 mutation had shorter overall survival time than those with wild-type SRSF2 in both the whole cohort of cases and those with normal karyotype (P = 0.069 and 0.023, respectively). Multivariate analysis confirmed SRSF2 mutation as an independent risk factor in both patient populations. We established a fast, high-throughput, and inexpensive HRMA-based method to screen SRSF2 mutation, which could be used in clinical diagnostic laboratories. SRSF2 mutations were significantly associated with mortality rate in the MDS affected Chinese.

Aberrant hypomethylation of SALL4 gene in patients with myelodysplastic syndrome

The abnormalities of SALL4 gene, which encodes a zinc-finger transcription factor and is essential for developmental events, have been found to be involved in tumorigenesis. In this study, we investigated the methylation status of the CpG island of SALL4 promoter region in myelodysplastic syndrome (MDS) using methylation-specific PCR (MSP). Aberrant hypomethylation of SALL4 gene was found in 21.7% (18/83) of the cases analyzed. A significantly positive correlation was identified between the level of SALL4 transcript and the status of SALL4 hypomethylation (R=0.641, P<0.001). No correlation was found between SALL4 hypomethylation and clinical parameters. However, the frequency of SALL4 hypomethylation significantly increased in higher risk MDS (14% in Low/Int-1 versus 39% in Int-2/High, P=0.031). The association between SALL4 hypomethylation and the mutations in three methylation modifiers (IDH1, IDH2 and DNMT3A) was not observed. Although the estimated 50% survival time of the SALL4-hypomethylated group was shorter than that of SALL4-methylated group (11.0 months vs. 20.0 months), the difference was not statistically significant (P=0.430). These findings suggest that hypomethylation of SALL4 promoter is a common event in MDS.

Aberrant hypomethylation of SALL4 gene is associated with intermediate and poor karyotypes in acute myeloid leukemia

OBJECTIVE SALL4 gene has been identified to stimulate the expansion of hematopoietic stem cell (HSCs) and enhance the self-renewal of HSCs. Overexpression of SALL4 has been found in several cancers. The present study was aimed to investigate the methylation status of SALL4 promoter region in acute myeloid leukemia (AML). DESIGNS AND METHODS The methylation status of SALL4 promoter was analyzed in 84 patients with AML using methylation-specific PCR (MSP) and its clinical significance was evaluated. RESULTS Aberrant hypomethylation of SALL4 gene, which was correlated with SALL4 expression, was found in 17.8% (15/84) cases. The patients with SALL4 hypomethylation had significantly older age and higher WBCs than those without SALL4 hypomethylation. The incidence of SALL4 hypomethylation was higher in M1 subtype than in M2 and other subtypes (50%, 26% and 6%, respectively, P=0.001). SALL4 hypomethylation was associated with cytogenetically intermediate and poor groups. Although survival time of the SALL4-hypomethylated AML was shorter than that of SALL4-methylated group (4 months vs 9 months), the difference was not statistically significant (P=0.356). CONCLUSIONS Hypomethylation of SALL4 promoter is a common event and is associated with the intermediate and poor karyotypes in AML.

DLX4 hypermethylation is a prognostically adverse indicator in de novo acute myeloid leukemia.

Hypermethylation of distal-less homeobox 4 (DLX4) has been increasingly identified in several cancers. Our study was aimed to determine the role of DLX4 methylation in regulating DLX4 expression and further analyze its clinical significance in de novo acute myeloid leukemia (AML) patients. DLX4 methylation level was detected by real-time quantitative methylation-specific PCR and bisulfite sequencing PCR. Treatment with 5-aza-2′-deoxycytidine (5-aza-dC) was used for demethylation studies. Clinical significance of DLX4 methylation was obtained by the comparison between the patients with and without DLX4 methylation. DLX4 was significantly methylated in AML patients compared with controls (P < 0.001). DLX4 methylation was negatively associated with DLX7 (the shorter DLX4 isoform) (R = −0.202, P = 0.021) but not BP1 (the longer DLX4 isoform) (R = −0.049, P = 0.582) expression in AML patients. DLX7 and BP1 messenger RNA (mRNA) were significantly increased after 5-aza-dC treatment in leukemic cell lines THP1 and Kasumi-1. DLX4 methylated patients showed significantly higher frequency of U2AF1 mutation compared with DLX4 unmethylated patients (P = 0.043). Both all AML and non-M3 patients with DLX4 methylation presented significantly lower complete remission rate than those with DLX4 unmethylation (P = 0.001 and <0.001, respectively). DLX4 methylated cases had significantly shorter overall survival than DLX4 unmethylated cases among both all AML (P = 0.003), non-M3 AML (P = 0.001), and cytogenetically normal AML (P = 0.032). Multivariate analysis confirmed that DLX4 methylation was independent risk factor in both all AML and non-M3 patients. Our study indicates that DLX4 hypermethylation is negatively associated with DLX7 expression and predicts poor clinical outcome in de novo AML patients.