Characterisation of renal chloride channel, CLCN5, mutations in hypercalciuric nephrolithiasis (kidney stones) disorders

Mutations of the renal-specific chloride channel (CLCN5) gene, which is located on chromosome Xp11.22, are associated with hypercalciuric nephrolithiasis (kidney stones) in the Northern European and Japanese populations. CLCN5 encodes a 746 amino acid channel (CLC-5) that has approximately 12 transmembrane domains, and heterologous expression of wild-type CLC-5 in Xenopus oocytes has yielded outwardly rectifying chloride currents that were markedly reduced or abolished by these mutations. In order to assess further the structural and functional relationships of this recently cloned chloride channel, additional CLCN5 mutations have been identified in five unrelated families with this disorder. Three of these mutations were missense (G57V, G512R and E527D), one was a nonsense (R648Stop) and one was an insertion (30:H insertion). In addition, two of the mutations (30:H insertion and E527D) were demonstrated to be de novo, and the G57V and E527D mutations were identified in families of Afro-American and Indian origin, respectively. The G57V and 30:H insertion mutations represent the first CLCN5 mutations to be identified in the N-terminus region, and the R648Stop mutation, which has been observed previously in an unrelated family, suggests that this codon may be particularly prone to mutations. Heterologous expression of the mutations resulted in a marked reduction or abolition of the chloride currents, thereby establishing their functional importance. These results help to elucidate further the structure-function relationships of this renal chloride channel.      

Bacterial colonization of infants raised in incubators and under radiant heaters

To assess the effect of open radiant heaters on bacterial colonization of neonates, 24 infants were raised under radiant heaters and 34 in standard incubators. Cultures of the nose, groin, and umbilicus were taken daily for the first 3 days of life. For infants raised in incubators, colonization rates with Staph. aureus ranged up to 47%. Among infants raised under radiant heaters (8 of whom had topical antibiotics applied to the umbilicus), only one was colonized with this organism. Even if the 8 treated infants were excluded, the prevalence of Staph. aureus was significantly greater at the umbilicus and groin in infants raised in incubators.     

Comparison of mutagenesis by O6-methyl- and O6-ethylguanine and O4- methylthymine in Escherichia coli using double-stranded and gapped plasmids

To compare mutagenesis by O6-methylguanine (m6G), O4-methylthymine (m4T) and O6-ethylguanine (e6G), and assess their genotoxicity in Escherichia coli, double-stranded and gapped plasmids were constructed containing a single m6G, e6G or m4T in the initiation codon (ATG) of a lacZ' gene. Modified base induced mutations were scored by the loss of lacZ' activity on X-gal-containing media resulting in formation of white or sectored (mutant) rather than blue (non-mutant) colonies. Genotoxicity experiments with gapped plasmids containing the modified bases indicated that m4T produced a greater number of bacterial colonies than m6G or e6G. m4T was more mutagenic (45% mutant colonies) than m6G (6%) or e6G (11%) in repair competent (w.t.) E. coli when incorporated in double-stranded plasmids. In gapped plasmids, m4T produced 99% mutant colonies (as was observed previously for e6G) in both w.t. E. coli or E. coli deficient in both O6-alkylguanine-DNA alkyltransferases as well as methylation-directed mismatch repair (ada(- )-ogt(-)-mutS[-]). m6G in gapped plasmids produced 62% mutant colonies in w.t. E. coli, but this percentage increased to 94% in the ada(-)- ogt(-)-mutS(-) strain. In double-stranded plasmids both m4T and m6G produced very similar distributions of mutant and non-mutant colonies in the ada(-)-ogt(-)-mutS(-) strain. These observations led to the conclusion that differences in the mutagenicity of m6G and m4T in w.t. E. coli were a result of preferential repair of m6G compared to m4T by alkyltransferase and mismatch repair mechanisms, and did not reflect differences in their respective coding efficiency or their inherent obstructiveness to DNA synthesis as was observed with e6G. The combination of alkyltransferase and mismatch repair was concluded to be primarily responsible for the apparent genotoxicity of m6G compared to m4T in double-stranded plasmids.      

Safety of alectinib for the treatment of metastatic ALK-rearranged non-small cell lung cancer

Introduction: Patients with anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) may derive significant clinical benefit from targeted therapies against this driver mutation, but progression is virtually inevitable. Alectinib is a next-generation ALK inhibitor that provides a novel treatment option for this group of patients.

Areas covered: In this review, we summarize the overall safety and tolerability of alectinib. Specifically, we cover cardiovascular, gastrointestinal, hepatic, musculoskeletal, and respiratory adverse events. The safety profile of alectinib is also described in special populations and in comparison with other ALK inhibitors.

Expert opinion: Alectinib is a well-tolerated tyrosine kinase inhibitor and should be considered for patients with ALK-rearranged NSCLC. The question then arises as to how to choose a next-generation ALK inhibitor in the second-line setting. Understanding acquired resistant mechanisms has become essential. Whether or not to use alectinib in the first-line setting is extremely controversial, but we anticipate its approval for this indication and availability in more countries in the near future.     

贴报-P3系统、器官及分子毒理学

Myeloperoxidase （MPO） is an important metabolizing enzyme involved in oxidative stress response with some environmental carcinogens including benzene which is associated with bone marrow toxicity and leukemia after chronic exposure.     

Management of hepatocellular carcinoma with portal vein tumor thrombosis: Review and update at 2016

Portal vein tumor thrombosis(PVTT) is a common phenomenon in hepatocellular carcinoma(HCC). Compared to HCC without PVTT, HCC with PVTT is characterized by an aggressive disease course, worse hepatic function, a higher chance of complications related to portal hypertension and poorer tolerance to treatment. Conventionally, HCC with PVTT is grouped together with metastatic HCC during the planning of its management, and most patients are offered palliative treatment with sorafenib or other systemic agents. As a result, most data on the management of HCC with PVTT comes from subgroup analyses or retrospective series. In the past few years, there have been several updates on management of HCC with PVTT. First, it is evident that HCC with PVTT consists of heterogeneous subgroups with different prognoses. Different classifications have been proposed to stage the degree of portal vein invasion/thrombosis, suggesting that different treatment modalities may be individualized to patients with different risks. Second, more studies indicate that more aggressive treatment, including surgical resection or locoregional treatment, may benefit select HCC patients with PVTT. In this review, we aim to discussthe recent conceptual changes and summarize the data on the management of HCC with PVTT.     

Expression of the hematopoietic growth factor receptor FLT3 (STK- 1/Flk2) in human leukemias

Normal expression of the hematopoietic growth factor receptor FLT3 (STK- 1@Flk2) is limited to CD34+ stem/progenitor cells. We have evaluated the expression of FLT3 by RNase protection assay and Western blotting in 161 primary bone marrow (BM) samples from patients with leukemia. FLT3 RNA was found to be expressed at a higher level than in normal BM controls in 33 of 33 B-lineage acute leukemias, 11 of 12 acute myeloid leukemias (AMLs), and 3 of 11 T-cell acute leukemias (T-ALLs). Expression of FLT3 RNA was also observed in some cases of blast crisis CML. The FLT3 signal resulted from expression on the leukemic blasts, and was not caused by increased FLT3 expression on normal CD34+ stem/progenitor cells in the leukemic samples. To determine if FLT3 protein was also overexpressed, proteins were extracted from leukemic BM samples and screened by Western blotting with anti-FLT3 antisera. FLT3 protein was not detected in normal BM controls, but was found in 14 of 14 B-lineage ALLs, 36 of 41 AMLs, and 1 of 4 T-ALLs. Stimulation of patient samples with FLT3 ligand resulted in autophosphorylation of the FLT3 receptor, suggesting the receptor is functional in these cells. These data show that FLT3 RNA and protein are aberrantly expressed by AML and ALL cells in that CD34 expression and FLT3 expression are no longer synchronous, and suggest the possibility that overexpression of FLT3 could play a role in the survival and/or proliferation of malignant clones in acute myeloid and lymphoid leukemias.