14-3-3ζ negatively regulates mitochondrial biogenesis in GBM residual cells.

Glioblastoma (GBM) is the most lethal primary brain tumour with a median survival of only 15 months. We have previously demonstrated the generation of an in vitro therapy resistance model that captures the residual resistant (RR) disease cells of GBM post-radiation. We also reported the proteomic landscape of parent, residual, and relapse cells using iTRAQ based quantitative proteomics of glioma cells. The proteomics data revealed significant up-regulation (fold change >1.5) of 14-3-3ζ, specifically in GBM RR cells. This was further confirmed by western blots in residual cells generated from GBM cell lines and patient sample-derived short-term primary culture. ShRNA-mediated knockdown of 14-3-3ζ radio-sensitized GBM cells and further stimulated therapy-induced senescence (TIS) and multinucleated giant cells (MNGCs) phenotype in RR cells. Intriguingly, 14-3-3ζ knockdown residual cells also showed a significantly higher number of mitochondria and increased mtDNA content. Indeed, in vitro GST pull-down mass spectrometry analysis of GST tagged 14-3-3ζ from RR cells identified novel interacting partners of 14-3-3ζ involved in cellular metabolism. Taken together, here we identified novel interacting partners of 14-3-3ζ and proposed an unconventional function of 14-3-3ζ as a negative regulator of TIS and mitochondrial biogenesis in residual resistant cells and loss of which also radio-sensitize GBM cells.

Metabolic rewiring in drug resistant cells exhibit higher OXPHOS and fatty acids as preferred major source to cellular energetics.

Alteration in metabolic repertoire is associated with resistance phenotype. Although a common phenotype, not much efforts have been undertaken to design effective strategies to target the metabolic drift in cancerous cells with drug resistant properties. Here, we identified that drug resistant AML cell line HL-60/MX2 did not follow classical Warburg effect, instead these cells exhibited drastically low levels of aerobic glycolysis. Biochemical analysis confirmed reduced glucose consumption and lactic acid production by resistant population with no differences in glutamine consumption. Raman spectroscopy revealed increased lipid and cytochrome content in resistant cells which were also visualized as lipid droplets by Raman mapping, electron microscopy and lipid specific staining. Gene set enrichment analysis data from sensitive and resistant cell lines revealed significant enrichment of lipid metabolic pathways in HL-60/MX2 cells. Further, HL-60/MX2 possessed higher mitochondrial activity and increased OXPHOS suggesting the role of fatty acid metabolism as energy source which was confirmed by increased rate of fatty acid oxidation. Accordingly, OXPHOS inhibitor increased sensitivity of resistant cells to chemotherapeutic drug and fatty acid oxidation inhibitor Etomoxir reduced colony formation ability of resistant cells demonstrating the requirement of fatty acid metabolism and dependency on OXPHOS by resistant leukemic cells for survival and tumorigenicity.

Sustained inhibition of PARP-1 activity delays glioblastoma recurrence by enhancing radiation-induced senescence.

Glioblastoma (GBM) is the most common primary brain tumor and is highly aggressive with a median survival of 15 months. We have previously shown that residual cells of GBM form multinucleated giant cells (MNGCs) showing a senescent phenotype, but eventually escape from therapy induced senescence (TIS), resulting in GBM recurrence. Here we demonstrate the role of PARP-1 in TIS and its recovery. We show that genetic and pharmacological inhibition of PARP-1 has an anti-proliferative effect on GBM cell lines and primary cultures derived from patient samples. Furthermore, the PARP-1 inhibitor olaparib, in combination with radiation increased MNGCs formation and senescence as assessed by ß-galactosidase activity, and macroH2A1 levels in residual cells. Additionally, we found that reduced PARP-1 activity and not protein levels in residual cells was crucial for MNGCs formation and their maintenance in the senescent state. PARP-1 activity was restored to higher levels in recurrent cells that escaped from TIS. Importantly, olaparib + radiation treatment significantly delayed recurrence in vitro as well in vivo in orthotopic GBM mouse models with a significant increase in overall survival of mice. Overall, this study demonstrates that sustained inhibition of PARP-1 activity during radiation treatment significantly delays GBM recurrence.

Inhibition of SETMAR-H3K36me2-NHEJ repair axis in residual disease cells prevents glioblastoma recurrence.

BACKGROUND: Residual disease of glioblastoma (GBM) causes recurrence. However, targeting residual cells has failed, due to their inaccessibility and our lack of understanding of their survival mechanisms to radiation therapy. Here we deciphered a residual cell-specific survival mechanism essential for GBM relapse. METHODS: Therapy resistant residual (RR) cells were captured from primary patient samples and cell line models mimicking clinical scenario of radiation resistance. Molecular signaling of resistance in RR cells was identified using RNA sequencing, genetic and pharmacological perturbations, overexpression systems, and molecular and biochemical assays. Findings were validated in patient samples and an orthotopic mouse model. RESULTS: RR cells form more aggressive tumors than the parental cells in an orthotopic mouse model. Upon radiation-induced damage, RR cells preferentially activated a nonhomologous end joining (NHEJ) repair pathway, upregulating Ku80 and Artemis while downregulating meiotic recombination 11 (Mre11) at protein but not RNA levels. Mechanistically, RR cells upregulate the Su(var)3-9/enhancer-of-zeste/trithorax (SET) domain and mariner transposase fusion gene (SETMAR), mediating high levels of H3K36me2 and global euchromatization. High H3K36me2 leads to efficiently recruiting NHEJ proteins. Conditional knockdown of SETMAR in RR cells induced irreversible senescence partly mediated by reduced H3K36me2. RR cells expressing mutant H3K36A could not retain Ku80 at double-strand breaks, thus compromising NHEJ repair, leading to apoptosis and abrogation of tumorigenicity in vitro and in vivo. Pharmacological inhibition of the NHEJ pathway phenocopied H3K36 mutation effect, confirming dependency of RR cells on the NHEJ pathway for their survival. CONCLUSIONS: We demonstrate that the SETMAR-NHEJ regulatory axis is essential for the survival of clinically relevant radiation RR cells, abrogation of which prevents recurrence in GBM.

Molecular features unique to glioblastoma radiation resistant residual cells may affect patient outcome - a short report.

PURPOSE: Previously we have shown, using a primary glioblastoma (GBM) cell model, that a subpopulation of innately radiation resistant (RR) GBM cells survive radiotherapy and form multinucleated and giant cells (MNGCs) by homotypic fusions. We also showed that MNGCs may cause relapse. Here, we set out to explore whether molecular characteristics of RR cells captured from patient-derived primary GBM cultures bear clinical relevance. METHODS: Primary cultures were derived from 19 naive GBM tumor samples. RR cells generated from these cultures were characterized using various cell biological assays. We also collected clinicopathological data of the 19 patients and assessed associations with RR variables using Spearman's correlation test and with patient survival using Kaplan-Meier analysis. Significance was determined using a log-rank test. RESULTS: We found that SF2 (surviving fraction 2) values (p = 0.029), days of RR cell formation (p = 0.019) and percentage of giant cells (p = 0.034) in the RR population independently correlated with a poor patient survival. We also found that low ATM (Ataxia-telangiectasia mutated) expression levels in RR cells showed a significant (p = 0.002) negative correlation with SF2 values. A low ATM expression level in RR cells along with a high tumor volume was also found to negatively correlate with patient survival (p = 0.011). Finally, we found that the ATM expression levels in RR cells independently correlated with a poor patient survival (p = 0.014). CONCLUSIONS: Our data indicate that molecular features of innately radiation resistant GBM cells independently correlate with clinical outcome. Our study also highlights the relevance of using patient-derived primary GBM cultures for the characterization of RR cells that are otherwise inaccessible for analysis.

PARP-1 depletion in combination with carbon ion exposure significantly reduces MMPs activity and overall increases TIMPs expression in cultured HeLa cells.

BACKGROUND: Hadron therapy is an innovative technique where cancer cells are precisely killed leaving surrounding healthy cells least affected by high linear energy transfer (LET) radiation like carbon ion beam. Anti-metastatic effect of carbon ion exposure attracts investigators into the field of hadron biology, although details remain poor. Poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors are well-known radiosensitizer and several PARP-1 inhibitors are in clinical trial. Our previous studies showed that PARP-1 depletion makes the cells more radiosensitive towards carbon ion than gamma. The purpose of the present study was to investigate combining effects of PARP-1 inhibition with carbon ion exposure to control metastatic properties in HeLa cells. METHODS: Activities of matrix metalloproteinases-2, 9 (MMP-2, MMP-9) were measured using the gelatin zymography after 85 MeV carbon ion exposure or gamma irradiation (0- 4 Gy) to compare metastatic potential between PARP-1 knock down (HsiI) and control cells (H-vector - HeLa transfected with vector without shRNA construct). Expression of MMP-2, MMP-9, tissue inhibitor of MMPs such as TIMP-1, TIMP-2 and TIMP-3 were checked by immunofluorescence and western blot. Cell death by trypan blue, apoptosis and autophagy induction were studied after carbon ion exposure in each cell-type. The data was analyzed using one way ANOVA and 2-tailed paired-samples T-test. RESULTS: PARP-1 silencing significantly reduced MMP-2 and MMP-9 activities and carbon ion exposure further diminished their activities to less than 3 % of control H-vector. On the contrary, gamma radiation enhanced both MMP-2 and MMP-9 activities in H-vector but not in HsiI cells. The expression of MMP-2 and MMP-9 in H-vector and HsiI showed different pattern after carbon ion exposure. All three TIMPs were increased in HsiI, whereas only TIMP-1 was up-regulated in H-vector after irradiation. Notably, the expressions of all TIMPs were significantly higher in HsiI than H-vector at 4 Gy. Apoptosis was the predominant mode of cell death and no autophagic death was observed. CONCLUSIONS: Our study demonstrates for the first time that PARP-1 inhibition in combination with carbon ion synergistically decreases MMPs activity along with overall increase of TIMPs. These data open up the possibilities of improvement of carbon ion therapy with PARP-1 inhibition to control highly metastatic cancers.

Carbon ion beam triggers both caspase-dependent and caspase-independent pathway of apoptosis in HeLa and status of PARP-1 controls intensity of apoptosis.

High linear energy transfer (LET) carbon ion beam (CIB) is becoming very promising tool for various cancer treatments and is more efficient than conventional low LET gamma or X-rays to kill malignant or radio-resistant cells, although detailed mechanism of cell death is still unknown. Poly (ADP-ribose) polymerase-1 (PARP-1) is a key player in DNA repair and its inhibitors are well-known as radio-sensitizer for low LET radiation. The objective of our study was to find mechanism(s) of induction of apoptosis by CIB and role of PARP-1 in CIB-induced apoptosis. We observed overall higher apoptosis in PARP-1 knocked down HeLa cells (HsiI) compared with negative control H-vector cells after irradiation with CIB (0-4 Gy). CIB activated both intrinsic and extrinsic pathways of apoptosis via caspase-9 and caspase-8 activation respectively, followed by caspase-3 activation, apoptotic body, nucleosomal ladder formation and sub-G1 accumulation. Apoptosis inducing factor translocation into nucleus in H-vector but not in HsiI cells after CIB irradiation contributed caspase-independent apoptosis. Higher p53 expression was observed in HsiI cells compared with H-vector after exposure with CIB. Notably, we observed about 37 % fall of mitochondrial membrane potential, activation of caspase-9 and caspase-3 and mild activation of caspase-8 without any detectable apoptotic body formation in un-irradiated HsiI cells. We conclude that reduction of PARP-1 expression activates apoptotic signals via intrinsic and extrinsic pathways in un-irradiated cells. CIB irradiation further intensified both intrinsic and extrinsic pathways of apoptosis synergistically along with up-regulation of p53 in HsiI cells resulting overall higher apoptosis in HsiI than H-vector.

Aqueous reaction quantification after phacoemulsification: Fourier-domain optical coherence tomography versus slitlamp biomicroscopy.

PURPOSE: To compare anterior chamber cell detection after phacoemulsification between Fourier-domain optical coherence tomography (OCT) and slitlamp biomicroscopy. DESIGN: Observational prospective comparative case series. SETTING: Dr. Agarwal's Eye Hospital and Eye Research Centre, Chennai, India. METHODS: Eyes with preoperative nuclear opalescence (NO) grades 1 to 3 that had phacoemulsification with posterior chamber intraocular lens implantation were included. Slitlamp biomicroscopy and Fourier-domain OCT (Cirrus HD) of the anterior chamber were performed 1 day postoperatively. The results were evaluated, and a correlation analysis between the results and preoperative NO, effective phacoemulsification time (EPT), postoperative central corneal thickness (CCT), and intraocular pressure (IOP) was performed. RESULTS: The preoperative NO grade was 1 in 20 eyes, 2 in 55 eyes, and 3 in 42 eyes. Anterior chamber grading was possible by slitlamp biomicroscopy and Fourier-domain OCT in 106 eyes (90.5%) and 117 eyes (100.0%), respectively. A positive correlation between slitlamp biomicroscopy and OCT grading was noted (R(2) = 0.986, P=.000). Slitlamp grading was not possible in 11 eyes (9.4%) with corneal edema (mean CCT 754 µm ± 44.2 [SD]); OCT detected cells in all 11 eyes. There was a difference in slitlamp grading and OCT grading in 7 eyes (6.6%). There was a significant correlation between the OCT cell count and the EPT (P=.000) and NO (P=.000). CONCLUSION: Fourier-domain OCT was as reliable as slitlamp biomicroscopy in assessing postoperative anterior chamber cells.

Green synthesis of gold nanoparticles for staining human cervical cancer cells and DNA binding assay.

Gold nanoparticles have been functionalized by non-ionic surfactants (polysorbates) used in pharmaceutical formulations. This results in the formation of more well-dispersed gold nanoparticles (GNPs) than the GNPs formed in neat water. The synthesized GNPs show good temporal stability. The synthesis conditions are mild and environmentally benign. The GNPs can bind to ct-DNA and displace bound dye molecules. The DNA-binding assay is significant as it preliminarily indicated that DNA-GNP conjugates can be formed. Such conjugates are extremely promising for applications in nanobiotechnology. The GNPs can also stain the human cervical cancer (HeLa) cells over a wide concentration range while remaining non-cytotoxic, thus providing a non invasive cell staining method. This result is very promising as we observe staining of HeLa cells at very low GNP concentrations (1 µM) while the cell viability is retained even at 10-fold higher GNP concentrations.

Radiosensitivity and Induction of Apoptosis by High LET Carbon Ion Beam and Low LET Gamma Radiation: A Comparative Study.

Cancer treatment with high LET heavy ion beam, especially, carbon ion beam ((12)C), is becoming very popular over conventional radiotherapy like low LET gamma or X-ray. Combination of Poly(ADP-ribose) polymerase (PARP) inhibitor with xenotoxic drugs or conventional radiation (gamma or X-ray) is the newer approach for cancer therapy. The aim of our study was to compare the radiosensitivity and induction of apoptosis by high LET (12)C and low LET gamma radiation in HeLa and PARP-1 knocked down cells. We did comet assay to detect DNA breaks, clonogenic survival assay, and cell cycle analysis to measure recovery after DNA damage. We measured apoptotic parameters like nuclear fragmentation and caspase-3 activation. DNA damage, cell killing, and induction of apoptosis were significantly higher for (12)C than gamma radiation in HeLa. Cell killing and apoptosis were further elevated upon knocking down of PARP-1. Both (12)C and gamma induced G2/M arrest although the (12)C had greater effect. Unlike the gamma, (12)C irradiation affects DNA replication as detected by S-phase delay in cell cycle analysis. So, we conclude that high LET (12)C has greater potential over low LET gamma radiation in killing cells and radiosensitization upon PARP-1 inhibition was several folds greater for (12)C than gamma.

miRNA gene counts in chromosomes vary widely in a species and biogenesis of miRNA largely depends on transcription or post-transcriptional processing of coding genes.

MicroRNAs target specific mRNA(s) to silence its expression and thereby regulate various cellular processes. We have investigated miRNA gene counts in chromosomes for 20 different species and observed wide variation. Certain chromosomes have extremely high number of miRNA gene compared with others in all the species. For example, high number of miRNA gene in X chromosome and the least or absence of miRNA gene in Y chromosome was observed in all species. To search the criteria governing such variation of miRNA gene counts in chromosomes, we have selected three parameters- length, number of non-coding and coding genes in a chromosome. We have calculated Pearson's correlation coefficient of miRNA gene counts with length, number of non-coding and coding genes in a chromosome for all 20 species. Major number of species showed that number of miRNA gene was not correlated with chromosome length. Eighty five percent of species under study showed strong positive correlation coefficient (r ≥ 0.5) between the numbers of miRNA gene vs. non-coding gene in chromosomes as expected because miRNA is a sub-set of non-coding genes. 55% species under study showed strong positive correlation coefficient (r ≥ 0.5) between numbers of miRNA gene vs. coding gene. We hypothesize biogenesis of miRNA largely depends on coding genes, an evolutionary conserved process. Chromosomes having higher number of miRNA genes will be most likely playing regulatory roles in several cellular processes including different disorders. In humans, cancer and cardiovascular disease associated miRNAs are mostly intergenic and located in Chromosome 19, X, 14, and 1.

Synthesis, structure, spectroscopic characterization, and protein binding affinity of new water-soluble hetero- and homometallic tetranuclear [Cu(II)2Zn(II)2] and [Cu(II)4] clusters.

Two new water-soluble hetero- and homometallic tetranuclear clusters, Na4[Cu2Zn2(ccdp)2(µ-OH)2]·CH3OH·6H2O (1) and K3[Cu4(ccdp)2(µ-OH)(µ-OH2)]·14H2O (2), have been synthesized in methanol-water at room temperature by exploiting the flexibility, chelating ability, and bridging potential of a carboxylate-rich dinucleating ligand, N,N'-bis(2-carboxybenzomethyl)-N,N'-bis(carboxymethyl)-1,3 diaminopropan-2-ol (H5ccdp). Complex 1 is obtained through the self-assembly of two monoanionic [CuZn(ccdp)](-)fragments, which are, in turn, exclusively bridged by two µ-OH(-)groups. Similarly, complex 2 is formed through the self-assembly of two monoanionic [Cu2(ccdp)](-) species exclusively bridged by one µ-OH(-) and one µ-OH2 groups. Complexes 1 and 2 are fully characterized in the solid state as well as in solution using various analytical techniques including a single-crystal X-ray diffraction study. The X-ray crystal structure of 1 reveals that two Cu(II) centers are in a distorted square-pyramidal geometry, whereas two Zn(II) centers are in a distorted trigonal-bipyramidal geometry. The solid-state structure of 2 contains two dinuclear [Cu2(ccdp)](-) units having one Cu(II) center in a distorted square-pyramidal geometry and another Cu(II) center in a distorted trigonal-bipyramidal geometry within each dinuclear unit. In the powder state, the high-field EPR spectrum of complex 1 indicates that two Cu(II) ions are not spin-coupled, whereas that of complex 2 exhibits at least one noninteracting Cu(II) center coordinated to a nitrogen atom of the ligand. Both complexes are investigated for their binding affinity with the protein bovine serum albumin (BSA) in an aqueous medium at pH ~7.2 using fluorescence spectroscopy. Synchronous fluorescence spectra clearly reveal that complexes 1 and 2 bind to the active sites in the protein, indicating that the effect is more pronounced toward tyrosine than tryptophan. Density functional theory calculations have been carried to find the Fukui functions at the metal sites in complexes 1 and 2 to predict the possible metal centers involved in the binding process with BSA protein.