Introduction Glioblastoma (GBM), the common and aggressive human primary brain tumour (WHO grade IV), is highly resistant to standard radio- and chemotherapy. This is partly due to numerous genetic alterations in oncogenes and DNA damage repair systems. Despite progress in understanding the molecular background of GBM and advances in treatment modalities, survival of GMB patients is only 14 months post-diagnosis. RECQL4 belongs to RecQ family of ATP-dependent DNA helicases and plays an important role in genomic integrity and stability maintenance via involvement in DNA replication, repair, recombination, transcription and telomere maintenance. Mutations in the human RecQ genes are linked with cancer predisposition and/or premature ageing. Of all five human helicases, only RECQL4 is found in mitochondria. We explored if alterations of RECQL4 expression or functions contribute to pathogenesis of human GBM. Material and methods We determined the RECQL4 expression in various tumour specimens (tumour samples, human primary and established glioma cell cultures) by qPCR and Western Blotting. We determined the effect of RECQL4 depletion on cell viability, proliferation and GBM sphere formation using MTT metabolism, BrdU incorporation and tumour sphere forming assays, respectively. Results and discussions We found the upregulated expression of RECQL4 in GBM at mRNA and protein levels when compared to non-transformed human astrocytes. This finding was corroborated by TCGA data analysis. Fractionation of mitochondrial and cytosolic fractions from human glioma cells revealed the presence of RECQL4 in mitochondria. Downregulation (by siRNA) or genetic depletion of RECQL4 (by CRISPRCas9 knockout) in human glioma LN18 and U87-MG cells impaired cell viability and proliferation. We found upregulation of RECQL4 expression in GBM sphere cultures, enriched in glioma stem cells. Transient knock-down of RECQL4 significantly affected tumour sphere formation as evidenced by decreased numbers and sizes of cultured spheres. Conclusion These data indicate that deregulation of RECQL4 expression or function may play an important role in GBM pathobiology. Our results provide a rationale for further studies of RECQL4 role in gliomagenesis. Supported by National Science Centre grants 2015/19/N/NZ3/02374 (SKK) and 2016/22/M/NZ3/00679 (BK) and the Foundation for Polish Science TEAM-TECH Core Facility project „NGS platform for comprehensive diagnostics and personalised therapy in neuro-oncology’ (AK).
Anti-tumour therapies eliminate proliferating tumour cells by induction of DNA damage, but genomic aberrations or transcriptional deregulation may limit responses to therapy. Glioblastoma (GBM) is a malignant brain tumour, which recurs inevitably due to chemo- and radio-resistance. Human RecQ helicases participate in DNA repair, responses to DNA damage and replication stress. We explored if a helicase RECQL4 contributes to gliomagenesis and responses to chemotherapy. We found upregulated RECQL4 expression in GBMs associated with poor survival of GBM patients. Increased levels of nuclear and cytosolic RECQL4 proteins were detected in GBMs on tissue arrays and in six glioma cell lines. RECQL4 was detected both in cytoplasm and mitochondria by Western blotting and immunofluorescence. RECQL4 depletion in glioma cells with siRNAs and CRISPR/Cas9 did not affect basal cell viability, slightly impaired DNA replication, but induced profound transcriptomic changes and increased chemosensitivity of glioma cells. Sphere cultures originated from RECQL4-depleted cells had reduced sphere forming capacity, stronger responded to temozolomide upregulating cell cycle inhibitors and pro-apoptotic proteins. RECQL4 deficiency affected mitochondrial network and reduced mitochondrial membrane polarization in LN18 glioblastoma cells. We demonstrate that targeting RECQL4 overexpressed in glioblastoma could be a new strategy to sensitize glioma cells to chemotherapeutics.
Background/Purpose. The benefit of whole brain radiotherapy (WBRT) for RTOG RPA (Radiation Therapy Oncology Group Recursive Partitioning Analysis) class 3 patients with brain metastases is not well established. The aim of this study was to determine whether WBRT has any benefit in terms of symptoms palliation in such patients. Evaluation of patients’ preferences for WBRT, changes in performance and neurological status were secondary aims. Methods. Ninety-one RTOG RPA class 3 patients were included. All patients received WBRT (20 Gy in 5 fractions) and were asked to complete a questionnaire about their symptoms before and one month after WBRT. The patient's symptom checklist comprised 17 items scored from 0 to 3; a higher score meant a greater symptom intensity. The mean scores at baseline and after treatment were compared. Karnofsky performance status (KPS) and neurological status before and one month after WBRT were also recorded. Patients were asked to express their preference as to the WBRT undergone. Results. Forty-three (47%) patients completed both symptom checklists. The mean scores on the symptom checklist were 18.21 and 21.09 at baseline and one month after WBRT, respectively (p = 0.02). The KPS was estimated after WBRT in 42 patients: 57% of patients improved, 26% worsened, and 17% did not change from the baseline KPS score (p = 0.06). Neurological status did not change from baseline to one month after WBRT (p = 0.44). Only 7% of respondents would not have consented to the WBRT undergone. Conclusion. Our results challenge the palliative value of the WBRT in RPA class 3 patients.
Zinc deficiency is causing malnutrition for nearly one third of world populations. It is especially relevant in cereal-based diets in which low amounts of mineral and protein are present. In biological systems, Zn is mainly associated with protein. Cereal grains contain the highest Zn concentration during early developmental stage. Although hordeins are the major storage proteins in the mature barley grain and suggested to be involved in Zn binding, very little information is available regarding the Zn fertilization effects of hordein transcripts at early developmental stage and possible incorporation of Zn with hordein protein of matured grain. Zinc fertilization experiments were conducted in a greenhouse with barley cv. Golden Promise. Zn concentration of the matured grain was measured and the results showed that the increasing Zn fertilization increased grain Zn concentration. Quantitative real time PCR showed increased level of total hordein transcripts upon increasing level of Zn fertilization at 10 days after pollination. Among the hordein transcripts the amount of B-hordeins was highly correlated with the Zn concentration of matured grain. In addition, protein content of the matured grain was analysed and a positive linear relationship was found between the percentage of B-hordein and total grain Zn concentration while C-hordein level decreased. Zn sensing dithizone assay was applied to localize Zn in the matured grain. The Zn distribution was not limited to the embryo and aleurone layer but was also present in the outer part of the endosperm (sub-aleurone layers) which known to be rich in proteins including B-hordeins. Increased Zn fertilization enriched Zn even in the endosperm. Therefore, the increased amount of B-hordein and decreased C-hordein content suggested that B-hordein upregulation or difference between B and C hordein could be one of the key factors for Zn biofortification of cereal grains due to the Zn fertilization.
Endoglin is a proliferation-associated antigen on endothelial cells and essential for angiogenesis. Soluble endoglin (s‑endoglin), formed by proteolytic cleavage of ectodomain of membrane receptor could be an indicator of tumor‑activated endothelium. The aim of present study was to analyze changes of s‑endoglin level in plasma of lung cancer patients following surgical resection and to estimate the correlation of s‑endoglin with other soluble receptors, sTie2 and sVEGF R1.The study group consisted of 37 patients with stage I of non-small cell lung cancer. Plasma concentrations of s‑endoglin, sTie2 and sVEGF R1 were evaluated by ELISA, three times: before surgical resection and on postoperative day 7 and 30.The median of s‑endoglin concentration decreased significantly on postoperative day 7 when compared with preoperative level and next increased on 30(th) day and it was comparable with that before surgery. s-Endoglin correlated with another soluble receptors, with sTie2 both before surgery (r=0.44) and on postoperative day 7 (r=0.52) and on 30(th) day (r=0.58), with sVEGF R1 - only on postoperative day 7 (r=0.75).The increased level of serum endoglin in lung cancer patients compared to controls and its changes after surgical treatment suggest potential application of soluble form of endoglin as potential tumor marker.
The CENP-W/T complex was previously reported to be required for mitosis. HeLa cells depleted of CENP-W displayed profound mitotic defects, with mitotic timing delay, disorganized prometaphases and multipolar spindles as major phenotypic consequences. In this study, we examined the process of multipolar spindle formation induced by CENP-W depletion. Depletion of CENP-W in HeLa cells labeled with histone H2B and tubulin fluorescent proteins induced rapid fragmentation of originally bipolar spindles in a high proportion of cells. CENP-W depletion was associated with depletion of Hec1 at kinetochores. The possibility of promiscuous centrosomal duplication was ruled out by immunofluorescent examination of centrioles. However, centrioles were frequently observed to be abnormally split. In addition, a large proportion of the supernumerary poles lacked centrioles, but were positively stained with different centrosomal markers. These observations suggested that perturbation in spindle force distribution caused by defective kinetochores could contribute to a mechanical mechanism for spindle pole disruption. 'Spindle free' nocodazole arrested cells did not exhibit pole fragmentation after CENP-W depletion, showing that pole fragmentation is microtubule dependent. Inhibition of centrosome separation by monastrol reduced the incidence of spindle pole fragmentation, indicating that Eg5 plays a role in spindle pole disruption. Surprisingly, CENP-W depletion rescued the monopolar spindle phenotype of monastrol treatment, with an increased frequency of bipolar spindles observed after CENP-W RNAi. We overexpressed the microtubule cross-linking protein TPX2 to create spindle poles stabilized by the microtubule cross-linking activity of TPX2. Spindle pole fragmentation was suppressed in a TPX2-dependent fashion. We propose that CENP-W, by influencing proper kinetochore assembly, particularly microtubule docking sites, can confer spindle pole resistance to traction forces exerted by motor proteins during chromosome congression. Taken together, our findings are consistent with a model in which centrosome integrity is controlled by the pathways regulating kinetochore-microtubule attachment stability.
Translesion synthesis by DNA polymerase eta (poleta) is one mechanism by which cancer cells can tolerate DNA damage by platinum-based anti-cancer drugs. Cells lacking poleta are sensitive to these agents. To help define the consequences of poeta-deficiency, we characterized the effects of equitoxic doses of cisplatin and carboplatin on cell cycle progression and activation of DNA damage response pathways in a human cell line lacking poleta. We show that both cisplatin and carboplatin induce strong S-phase arrest in poleta-deficient XP30RO cells, associated with reduced expression of cyclin E and cyclin B. PIK kinase-mediated phosphorylation of Chk1, H2AX and RPA2 was strongly activated by both cisplatin and carboplatin, but phosphorylation of these proteins was induced earlier by cisplatin than by an equitoxic dose of carboplatin. Compared to Chk1 and H2AX phosphorylation, RPA2 hyperphosphorylation on serine4/serine8 is a late event in response to platinum-induced DNA damage. We directly demonstrate, using dual-labeling flow cytometry, that damage-induced phosphorylation of RPA2 on serine4/serine8 occurs primarily in the S and G(2) phases of the cell cycle, and show that the timing of RPA2 phosphorylation can be modulated by inhibition of the checkpoint kinase Chk1. Furthermore, Chk1 inhibition sensitizes poleta-deficient cells to the cytotoxic effects of carboplatin. Both hyperphosphorylated RPA2 and the homologous recombination protein Rad51 are present in nuclear foci after cisplatin treatment, but these are separable events in individual cells. These results provide insight into the relationship between cell cycle regulation and processing of platinum-induced DNA damage in human cells when poleta-mediated TLS is compromised.
Centromeres are differentiated chromatin domains, present once per chromosome, that direct segregation of the genome in mitosis and meiosis by specifying assembly of the kinetochore. They are distinct genetic loci in that their identity in most organisms is determined not by the DNA sequences they are associated with, but through specific chromatin composition and context. The core nucleosomal protein CENP-A/cenH3 plays a primary role in centromere determination in all species and directs assembly of a large complex of associated proteins in vertebrates. While CENP-A itself is stably transmitted from one generation to the next, the nature of the template for centromere replication and its relationship to kinetochore function are as yet poorly understood. Here, we investigate the assembly and inheritance of a histone fold complex of the centromere, the CENP-T/W complex, which is integrated with centromeric chromatin in association with canonical histone H3 nucleosomes. We have investigated the cell cycle regulation, timing of assembly, generational persistence, and requirement for function of CENPs -T and -W in the cell cycle in human cells. The CENP-T/W complex assembles through a dynamic exchange mechanism in late S-phase and G2, is required for mitosis in each cell cycle and does not persist across cell generations, properties reciprocal to those measured for CENP-A. We propose that the CENP-A and H3-CENP-T/W nucleosome components of the centromere are specialized for centromeric and kinetochore activities, respectively. Segregation of the assembly mechanisms for the two allows the cell to switch between chromatin configurations that reciprocally support the replication of the centromere and its conversion to a mitotic state on postreplicative chromatin.
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