Mutations in the C. elegans Succinate Dehydrogenase Iron-Sulfur Subunit Promote Superoxide Generation and Premature Aging

The mitochondrial succinate dehydrogenase (SDH) is an iron-sulfur flavoenzyme linking the Krebs cycle and the mitochondrial respiratory chain. Mutations in the human SDHB, SDHC and SDHD genes are responsible for the development of paraganglioma and pheochromocytoma, tumors of the head and neck or the adrenal medulla, respectively. In recent years, SDH has become recognized as a source of reactive oxygen species, which may contribute to tumorigenesis. We have developed a Caenorhabditis elegans model to investigate the molecular and catalytic effects of mutations in the sdhb-1 gene, which encodes the SDH iron-sulfur subunit. We created mutations in Pro211; this residue is located near the site of ubiquinone reduction and is conserved in human SDHB (Pro197), where it is associated with tumorigenesis. Mutant phenotypes ranged from relatively benign to lethal and were characterized by hypersensitivity to oxidative stress, a shortened life span, impaired respiration and overproduction of superoxide. Our data suggest that the SDH ubiquinone-binding site can become a source of superoxide and that the pathological consequences of SDH mutations can be mitigated with antioxidants, such as ascorbate and N-acetyl-l-cysteine. Our work leads to a better understanding of the relationship between genotype and phenotype in respiratory chain mutations and of the mechanisms of aging and tumorigenesis.     

Genetic Diversity of the KIR/HLA System and Outcome of Patients with Metastatic Colorectal Cancer Treated with Chemotherapy

Objective

To explore genes of the killer-cell immunoglobulin-like receptor (KIR) and of the HLA ligand and their relationship with the outcome of metastatic colorectal cancer (mCRC) patients treated with first-line 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI).

Methods

A total of 224 mCRC patients were screened for KIR/HLA typing. The determination of the KIR/HLA combinations was based upon the gene content and variants. Genetic associations with complete response (CR), time to progression (TTP) and overall survival (OS) were evaluated by calculating odds and hazard ratios. Multivariate modeling with prognostic covariates was also performed.

Results

For CR, the presence of KIR2DL5A, 2DS5, 2DS1, 3DS1, and KIR3DS1/HLA-Bw4-I80 was associated with increased CR rates, with median ORs ranging from 2.1 to 4.3, while the absence of KIR2DS4 and 3DL1 was associated with increased CR rates (OR 3.1). After univariate analysis, patients that underwent resective surgery of tumor, absence of KIR2DS5, and presence of KIR3DL1/HLA-Bw4-I80 showed a significant better OS (HR 1.5 to 2.8). Multivariate analysis identified as parameters independently related to OS the type of treatment (surgery; HR 2.0) and KIR3DL1/HLA-Bw4-I80 genotype (HR for T-I80 2.7 and for no functional KIR/HLA interaction 1.8). For TTP, no association with KIR/HLA genes was observed.

Conclusion

This study, for the first time, evidences that the genotyping for KIR-HLA pairs are found predictive markers associated with complete response and improves overall survival prediction of FOLFIRI treatment response in metastatic colorectal cancer. These results suggest a role of the KIR/HLA system in patient outcome, and guide new research on the immunogenetics of mCRC through mechanistic studies and clinical validation.     

Mutations in the L-arabinose operon of Escherichia coli B/r with reduced initiator function.

Partial reversion mutants derived from a strain containing a strongly polar initiator-defective mutation (araI1036) in the L-arabinose operon were found to have several characteristics expected of mutants with reduced initiator function. These reversion mutations are cotransduced with the ara region and are probably within the araI region. Furthermore, they permit induction of the L-arabinose operon to a level only one-third of the normal wild-type level. These partially functional initiator regions reduce the expression of structural genes in the cis position only; they function quite independently of wild-type or defective initiator regions in the trans position. These mutants exhibit a two- to threefold increase in the rate of expression of ara operon genes within one-tenth of a generation after a shift of the growth temperature from 28 to 42 degrees C. This suggests that the temperature optimum for initiation of operon expression is higher for the partial revertant strains than it is for strains containing a wild-type initiator region.     

A Genomic Instability Score in Discriminating Nonequivalent Outcomes of BRCA1/2 Mutations and in Predicting Outcomes of Ovarian Cancer Treated with Platinum-Based Chemotherapy

Detecting mutation in BRCA1/2 is a generally accepted strategy for screening ovarian cancers that have impaired homologous recombination (HR) ability and improved sensitivity to PARP inhibitor. However, a substantial subset of BRCA-mutant ovarian cancer patients shows less impaired or unimpaired HR ability, resulting in nonequivalent outcome after ovarian cancer development. We hypothesize that genomic instability provides a lifetime record of DNA repair deficiency and predicts ovarian cancer outcome. Based on the multi-dimensional TCGA ovarian cancer data, we developed a biological rationale-driven genomic instability score integrating somatic mutation and copy number change in a tumor genome. The score successfully divided BRCA-mutant ovarian tumors into cases of significantly improved outcome and cases of unimproved outcome. The score was also capable of discriminating HR-deficiency indicated by BRCA1 epigenetically silencing, EMSY amplification and homozygous deletion of core HR genes. We further found that the score was positively correlated with the complete response rate of chemotherapy and the rate of platinum-sensitivity, and predicted improved outcome of ovarian cancer, regardless of BRCA-mutation status. The score may have important value in outcome prediction and clinical trial design.     

Clinical Analysis of the HBV Infection Status of 135 Patients with Diffuse Large B Cell Lymphoma Treated with R-CHOP or CHOP/CHOP-Like Chemotherapy

Objectives

This study aimed to determine the HBV infection status of 135 patients with DLBCL (diffuse large B cell lymphoma), to analyze the overall survival (OS) and progression-free survival (PFS) of the different HBV infection status groups, and to discuss the relationship between HBV serological test results and the prognosis of DLBCL patients.

Methods

A retrospective analysis was performed of the clinical data, HBV serological test results, and PFS/OS of 135 DLBCL patients who were initially diagnosed and treated with more than 3 cycles of an R-CHOP/CHOP/CHOP-like regimen at our center from January 1, 2008 to December 31, 2012.

Results

The patients in the HBV infection group were older at disease onset (≥60 years old) and were more likely to present with stage 3-4 disease compared with the HBV-free group (P = 0.030 and P = 0.025, respectively). Approximately 50% of the patients with an active HBV infection required a reduction in the chemotherapy dose, and 66.7% of the patients in this group received more than 1 line of therapy; these rates were significantly higher than those in the no infection group (P = 0.003 and P = 0.011, respectively). Although HBV infection had no obvious influence on the outcome of first-line therapy, patients with an inactive infection had a higher relapse/progression rate within 3 months after a CR/PR than patients with an active infection (14/20 vs. 1/12, P = 0.001). The PFS at 1 year, 3 years and OS rates at 1 year, 3 years were significantly lower in the active HBV infection group than in the HBV-free group (P = 0.008, P = 0.002, P = 0.004, and P = 0.002, respectively). The PFS rates at 1 year and 3 year in HBV-free group were higher than those in the HBV infection group (80.5% and 52.9% P = 0.001, 78.1% and 44.4% P = 0.002). The lymphoma-related mortality rates were 2.7% in the no infection group, 19.2% in the HBV infection group (P = 0.004), and 28.6% in the active HBV infection group (P = 0.001). Among the patients treated with MabThera, the PFS in the HBV infection group was 11 months in the HBV infection group and 67 months in the infection-free group (P = 0.000). A Cox regression model of PFS revealed that age ≥60 years and HBV infection were independent prognostic factors (age: P = 0.019, HR = 2.002, 95% CI 1.123-3.567; HBV infection: P = 0.026, HR = 0.494, 95% CI 0.265-0.919).

Conclusion

Compared with the patients in HBV-free group, those in the HBV infection group were older at disease onset, and the active infection patients presented with more advanced disease and had a lower PFS at 1, 3 years as well as a lower OS at 3 years. The patients in the inactive infection group had a higher progression/relapse rate within 3 months after a CR/PR than those in the active infection group. HBV infection was an unfavorable factor for PFS in the MabThera group. An age ≥60 years and HBV infection were independent unfavorable prognostic factors for PFS.     

Associations of pri-miR-34b/c and pre-miR-196a2 Polymorphisms and Their Multiplicative Interactions with Hepatitis B Virus Mutations with Hepatocellular Carcinoma Risk

Background

Genetic polymorphisms of pri-miR-34b/c and pre-miR-196a2 have been reported to be associated with the susceptibility to cancers. However, the effect of these polymorphisms and their interactions with hepatitis B virus (HBV) mutations on the development of hepatocellular carcinoma (HCC) remains largely unknown. We hypothesized that these polymorphisms might interact with the HBV mutations and play a role in hepatocarcinogenesis.

Methods

Pri-miR-34b/c rs4938723 (T>C) and pre-miR-196a2 rs11614913 (T>C) were genotyped in 3,325 subjects including 1,021 HBV-HCC patients using quantitative PCR. HBV mutations were determined by direct sequencing. Contributions of the polymorphisms and their multiplicative interactions with gender or HCC-related HBV mutations to HCC risk were assessed using multivariate regression analyses.

Results

rs4938723 CC genotype was significantly associated with HCC risk compared to HBV natural clearance subjects, adjusted for age and gender (adjusted odds ratio [AOR] = 2.01, 95% confidence interval [CI] = 1.16–3.49). rs4938723 variant genotypes in dominant model significantly increased HCC risk in women, compared to female healthy controls (AOR = 1.85, 95% CI = 1.20–2.84) or female HCC-free subjects (AOR = 1.62, 95% CI = 1.14–2.31). rs4938723 CC genotype and rs11614913 TC genotype were significantly associated with increased frequencies of the HCC-related HBV mutations T1674C/G and G1896A, respectively. rs11614913 was not significantly associated with HCC risk, but its CC genotype significantly enhanced the effect of rs4938723 in women. In multivariate regression analyses, rs4938723 in dominant model increased HCC risk (AOR = 1.62, 95% CI = 1.05–2.49), whereas its multiplicative interaction with C1730G, a HBV mutation inversely associated with HCC risk, reduced HCC risk (AOR = 0.34, 95% CI = 0.15–0.81); rs11614913 strengthened the G1896A effect but attenuated the A3120G/T effect on HCC risk.

Conclusions

rs4938723 might be a genetic risk factor of HCC but its effect on HCC is significantly affected by the HBV mutations. rs11614913 might not be a HCC susceptible factor but it might affect the effects of the HBV mutations or rs4938723 on HCC risk.