Chao Xiao

Whole-exome and targeted sequencing identify ROBO1 and ROBO2 mutations as progression-related drivers in myelodysplastic syndromes

The progressive mechanism underlying myelodysplastic syndrome remains unknown. Here we identify ROBO1 and ROBO2 as novel progression-related somatic mutations using whole-exome and targeted sequencing in 6 of 16 (37.5%) paired MDS patients with disease progression. Further deep sequencing detects 20 (10.4%) patients with ROBO mutations in a cohort of 193 MDS patients. In addition, copy number loss and loss of heterogeneity (LOH) of ROBO1 and ROBO2 are frequently observed in patients with progression or carrying ROBO mutations. In in vitro experiments, overexpression of ROBO1 or ROBO2 produces anti-proliferative and pro-apoptotic effects in leukaemia cells. However, this effect was lost in ROBO mutants and ROBO-SLIT2 signalling is impaired. Multivariate analysis shows that ROBO mutations are independent factors for predicting poor survival. These findings demonstrate a novel contribution of ROBO mutations to the pathogenesis of MDS and highlight a key role for ROBO-SLIT2 signalling in MDS disease progression.

High expression of APAF-1 elevates erythroid apoptosis in iron overload myelodysplastic syndrome

Apoptotic protease-activating factor 1 (APAF-1) is a central component of the intrinsic pathway of apoptosis. Our study aims at searching the role of APAF-1 in iron overload myelodysplastic syndrome (MDS). Erythroid apoptosis rate, mRNA expression levels of APAF-1, and caspase-9 activity were determined by flow cytometry, quantitative real-time PCR, and colorimetric assay in MDS patients, respectively. In addition, K562 and MDS-L cell lines were incubated with different concentrations of ferric ammonium citrate (FAC) or ferric ammonium citrate + desferrioxamine (FAC + DFO) in vitro to observe the alteration in erythrocyte apoptosis rate, APAF-1 mRNA, and protein expression levels. Moreover, as control, erythroid apoptosis rate and APAF-1 mRNA expression were detected after silencing APAF-1 expression by endoribonuclease-prepared small interfering RNAs (esiRNAs) in K562 and MDS-L cell lines. Both erythroid apoptosis rate and APAF-1 mRNA expression of the iron overload (IO) group were significantly higher than those of the non-IO group (P < 0.001 and P < 0.001). There is a significant difference of caspase-9 activity between the IO group and the non-IO group (P < 0.001). Erythroid apoptosis rate and APAF-1 mRNA expression of K562 and MDS-L cell lines significantly elevated after FAC incubation in different concentrations (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L), while erythroid apoptosis rate and APAF-1 mRNA expression in the FAC + DFO group declined (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L). After silencing of APAF-1 expression with specific esiRNAs, erythroid apoptosis rate and APAF-1 mRNA expression of K562 and MDS-L cell lines markedly decreased (P < 0.001 and P < 0.001 for K562; P < 0.001 and P < 0.001 for MDS-L). APAF-1 plays an important role in iron-induced erythroid apoptosis increase in MDS.

Increased PD-1/STAT1 ratio may account for the survival benefit in decitabine therapy for lower risk myelodysplastic syndrome

Abstract Decitabine is an effective therapy for patients with lower risk myelodysplastic syndrome (MDS). However, the mechanisms of decitabine’s therapeutic effect are not well established. Forty-four lower risk MDS patients received decitabine therapy. 59.1% patients achieved treatment response, and 53.8% patients who were RBC/platelet-dependent cast off the transfusion burden. The median overall survival (OS) was 19.0 months after decitabine treatment. Moreover, polarization toward type 1 in the CD8 + subset was enhanced, and a significantly increased expression of the PD-1, PD-L1, and PD-1/STAT1 ratio was observed in these lower risk MDS. The patients with amplification of PD-1/STAT1 ratio (2–4) achieved longer OS. Thus, our results suggest that the effect mechanism of decitabine toward lower risk MDS may be the moderate increase of PD-1/STAT1, which contributes to hematopoietic improvement. These findings suggest that a different PD-1-related strategy from those used to treat higher risk patients could be used for lower risk MDS patients.

TP53 mutations predict decitabine-induced complete responses in patients with myelodysplastic syndromes.

To identify the molecular signatures that predict responses to decitabine (DAC), we examined baseline gene mutations (28 target genes) in 109 myelodysplastic syndrome (MDS) patients at diagnosis. We determined that TP53 mutations predicted complete response (CR), as 10 of 15 patients (66·7%) who possessed TP53 mutations achieved a CR. Univariate and multivariate analyses showed that TP53 mutations are the only molecular signatures predictive of a CR to DAC in MDS. Among the ten patients with TP53 mutations who achieved a CR, nine presented with complex karyotypes due to abnormalities involving chromosome 5 and/or chromosome 7, and eight possessed monosomies. Although TP53 mutations were associated with a higher frequency of CRs, they were not associated with improved survival. Poor outcomes were attributed to early relapses and transformation to acute myeloid leukaemia after CR. Post‐DAC therapy patient gene mutation profiles showed that most CR patients exhibited fewer gene mutations after achieving a CR. It seems that suppression of these gene mutations was facilitated by DAC, resulting in a CR. In summary, TP53 mutations might predict decitabine‐induced complete responses in patients with MDS. DAC‐induced responses may result from partial suppression of malignant clones containing mutated TP53 genes.

Iron overload promotes mitochondrial fragmentation in mesenchymal stromal cells from myelodysplastic syndrome patients through activation of the AMPK/MFF/Drp1 pathway

Iron overload (IO) has been reported to contribute to mesenchymal stromal cell (MSC) damage, but the precise mechanism has yet to be clearly elucidated. In this study, we found that IO increased cell apoptosis and lowered cell viability in MSCs, accompanied by extensive mitochondrial fragmentation and autophagy enhancement. All these effects were reactive oxygen species (ROS) dependent. In MSCs with IO, the ATP concentrations were significantly reduced due to high ROS levels and low electron respiratory chain complex (ETC) II/III activity. Reduced ATP phosphorylated AMP-activated protein kinase (AMPK). Activation of AMPK kinase complexes triggered mitochondrial fission. Moreover, gene knockout of AMPK via CRISPR/Cas9 reduced cell apoptosis, enhanced cell viability and attenuated mitochondrial fragmentation and autophagy caused by IO in MSCs. Further, AMPK-induced mitochondrial fragmentation of MSCs with IO was mediated via phosphorylation of mitochondrial fission factor (MFF), a mitochondrial outer-membrane receptor for the GTPase dynamin-related protein 1 (Drp1). Gene knockdown of MFF reversed AMPK-induced mitochondrial fragmentation in MSCs with IO. In addition, MSCs from IO patients with myelodysplastic syndrome (MDS) showed increased cell apoptosis, decreased cell viability, higher ROS levels, lower ATP concentrations and increased mitochondrial fragmentation compared with MSCs from non-IO patients. In addition, iron chelation or antioxidant weakened the activity of the AMPK/MFF/Drp1 pathway in MDS-MSCs with IO from several patients, accompanied by attenuation of mitochondrial fragmentation and autophagy. Taken together, the AMPK/MFF/Drp1 pathway has an important role in the damage to MDS-MSCs caused by IO.

RBBP6 increases radioresistance and serves as a therapeutic target for preoperative radiotherapy in colorectal cancer

Radiotherapy (RT) can be used as preoperative treatment to downstage initially unresectable locally rectal carcinoma, but radioresistance and recurrence remain significant problems. Retinoblastoma binding protein 6 (RBBP6) has been implicated in the regulation of cell cycle, apoptosis and chemoresistance both in vitro and in vivo. The present study investigated whether the inhibition of RBBP6 expression would improve radiosensitivity in human colorectal cancer cells. After SW620 and HT29 cells were exposed to radiation, the levels of RBBP6 mRNA and protein increased over time in both cells. Moreover, a significant reduction in clonogenic survival and a decrease in cell viability in parallel with an obvious increase in cell apoptosis were demonstrated in irradiated RBBP6‐knockdown cells. Transfection with RBBP6 shRNA improved the levels of G2‐M phase arrest, which blocked the cells in a more radiosensitive period of the cell cycle. These observations indicated that cell cycle and apoptosis mechanisms may be connected with tumor cell survival following radiotherapy. In vivo, the tumor growth rate of nude mice in the RBBP6‐knockdown group was significantly slower than that in other groups. These results indicated that RBBP6 overexpression could resist colorectal cancer cells against radiation by regulating cell cycle and apoptosis pathways, and inhibition of RBBP6 could enhance radiosensitivity of human colorectal cancer.

Labile plasma iron, more practical and more sensitive to iron overload in myelodysplastic syndromes

Objectives: In order to gain an insight into labile plasma iron (LPI) in iron metabolism microenvironment in MDS. Methods: We performed ELISA, quantitative real-time polymerase chain reaction, flow cytometry, MRI T2* assays to test LPI, iron biochemical parameters, and liver iron concentration (LIC) among 22 MDS patients. Results: LPI has a statistical difference (P < 0.001 by analysis of variance (ANOVA)), which decreased gradually, among three groups, while no difference was found in adjusted serum ferritin (ASF) (P = 0.086 by ANOVA). After DFO treatment, serum hepcidin expression increased from 301.26 ± 59.78 to 340.33 ± 49.78 µg/l (P = 0.032), while hepcidin/ASF was upregulated gradually from 0.16 ± 0.08 to 0.22 ± 0.03 (P = 0.045). APAF-1 expression (P = 0.047) and erythroid apoptosis rate (P = 0.009) decreased significantly, respectively. No statistical difference was found in EPO (P = 0.247) and GDF15 expression (P = 0.172). LIC dropped from 9.83 ± 4.84 to 6.28 ± 4.01 mg/g dry weight (P < 0.001). No significant difference was found in cardiac T2* (P = 0.594). LPI has a closer connection to LIC than ASF (r = 0.739, P < 0.001 vs. r = 0.321, P = 0.034). Discussion: LPI seems to be a real-time indicator which reflects body iron loading status instantaneously. Despite the limited knowledge available on LPI speciation in different types and degrees of IO, LPI measurements can be and are in fact used for identifying systemic IO and for initiating/adjusting chelation regimens.

High-level expression of P21-Cdc/Rac-activated kinase 7 is closely related to metastatic potential and poor prognosis of colon carcinoma

P21 protein (Cdc42/Rac)-activated kinase 7 (PAK7) can promote neurite outgrowth, induce microtubule stabilization, and activate cell survival signaling pathways. PAK7 expression was found to increase with colon carcinoma progression, but the prognostic value, clinical significance, and underlying mechanisms have not been explored. In my study, the expression of PAK7 was up-related at both the transcriptional and the translational levels in colon tumors compared to that in adjacent normal colon tissue. Patients with PAK7-positive tumors had a lower rate of overall survival (OS) and metastasis-free survival (MFS) (log-rank test, P < 0.001). A Cox proportional hazards model showed that PAK7 expression was an independent prognostic factor for OS (hazard ration [HR], 2.08; 95% confidence interval [CI], 1.16-3.73; P = 0.004) and MFS (HR, 2.88; 95% CI, 1.53-5.42; P < 0.001) in patients with colon cancer. Patients with tumors that were over-expressing PAK7 experienced metastasis, and died within a significantly shorter time after surgery (P < 0.001). Knockdown of PAK7 by a specific short hairpin RNA (shRNA) significantly suppressed the progression of epithelial to mesechymal transition (EMT), migration, and invasion of colon cancer cells in vitro and tumor growth in vivo. However, overexpression of PAK7 significantly promoted these processes. These findings indicate that aberrant PAK7 expression is associated with the occurrence of metastasis and poor clinical outcomes of human colon cancer by promoting the EMT, and the assessment of PAK7 expression might be helpful in predicting metastasis and prognostication for patients with colon cancer.

Association of patatin-like phospholipase domain-containing protein 3 gene polymorphisms with susceptibility of nonalcoholic fatty liver disease in a Han Chinese population.

Abstract Gene polymorphisms had been found to be associated with increased risk of nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to assess the association between rs2896019 and rs3810622 in PNPLA3 with the susceptibility to NAFLD in Han Chinese population. A total of 384 NAFLD patients and 384 controls were enrolled in the study. Blood samples collected from each subject were used for biochemical index analysis and DNA extraction. Genotyping analyses of PNPLA3 rs2896019 and rs3810622 were performed by real-time PCR methods. Results showed that patients with genotype GG of rs2896019 had a higher incidence of NAFLD than patients with genotypes GT and TT (62.4% vs 52.0% and 43.3%, respectively, P = 0.002), and a higher risk of moderate to severe NAFLD than patients with genotypes GT and TT (60.3% vs 46.2% and 40.2%, respectively, P = 0.03). Furthermore, patients with genotype GG of rs2896019 had higher levels of low-density lipoprotein (LDL, P < 0.001), ALT (P = 0.003), and AST (P = 0.002). Patients with genotype TT of rs3810622 had a higher incidence of NAFLD than patients with genotypes CT and CC (56.7% vs 48.4% and 41.5%, respectively, P = 0.013). Likewise, patients with genotype TT of rs3810622 had higher levels of ALT (P = 0.021) and blood glucose (GLU) (P = 0.034). Haplotype association analysis showed that GT haplotype conferred a statistically significant increased risk for NAFLD (OR = 1.49; 95% CI = 1.20–1.84, P < 0.01). These results suggest that PNPLA3 rs2896019 and rs3810622 polymorphisms significantly contribute to increased NAFLD risk in Han Chinese population.