Radioactive copper (II) (diacetyl-bis N4-methylthiosemicarbazone) (Cu-ATSM) isotopes were originally developed for the imaging of hypoxia in tumors. Because the decay of a 64Cu atom is emitting not ...only positrons but also Auger electrons, this radionuclide has great potential as a theranostic agent. However, the success of 64Cu-ATSM internal radiation therapy would depend on the contribution of Auger electrons to tumor cell killing. Therefore, we designed a cell culture system to define the contributions to cell death from Auger electrons to support or refute our hypothesis that the majority of cell death from 64Cu-ATSM is a result of high-LET Auger electrons and not positrons or other low-LET radiation. Chinese hamster ovary (CHO) wild type and DNA repair–deficient xrs5 cells were exposed to 64Cu-ATSM during hypoxic conditions. Surviving fractions were compared with those surviving gamma-radiation, low-LET hadron radiation, and high-LET heavy ion exposure. The ratio of the D10 values (doses required to achieve 10% cell survival) between CHO wild type and xrs5 cells suggested that 64Cu-ATSM toxicity is similar to that of high-LET Carbon ion radiation (70 keV/μm). γH2AX foci assays confirmed DNA double-strand breaks and cluster damage by high-LET Auger electrons from 64Cu decay, and complex types of chromosomal aberrations typical of high-LET radiation were observed after 64Cu-ATSM exposure. The majority of cell death was caused by high-LET radiation. This work provides strong evidence that 64Cu-ATSM damages DNA via high-LET Auger electrons, supporting further study and consideration of 64Cu-ATSM as a cancer treatment modality for hypoxic tumors.
The present study investigated the effect of targeted mutations in the DNA-dependent protein kinase catalytic subunit and phosphorylation domains on the survival of cells in response to different ...qualities of ionizing radiation. Mutated Chinese hamster ovary V3 cells were exposed to 500 MeV/nucleon initial energy and 200 keV/μm monoenergetic Fe ions; 290 MeV/nucleon initial energy and average 50 keV/μm spread-out Bragg peak C ions; 70 MeV/nucleon initial energy and 1 keV/μm monoenergetic protons; and 0.663 MeV initial energy and 0.3 keV/μm Cs137 γ radiation. The results demonstrated that sensitivity to high linear energy transfer radiation is increased when both S2056 and T2609 clusters each contain a point mutation or multiple mutations are present in either cluster, whereas the phosphoinositide 3 kinase cluster only requires a single mutation to induce the sensitized phenotype of V3 cells. Additionally, the present study demonstrated that sensitivity to DNA cross-linking damage by cisplatin only requires a single mutation in one of the three clusters and that additional point mutations do not increase cell sensitivity.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine immunogenicity varies between individuals, and immune responses correlate with vaccine efficacy. Using data from 1,076 ...participants enrolled in ChAdOx1 nCov-19 vaccine efficacy trials in the United Kingdom, we found that inter-individual variation in normalized antibody responses against SARS-CoV-2 spike and its receptor-binding domain (RBD) at 28 days after first vaccination shows genome-wide significant association with major histocompatibility complex (MHC) class II alleles. The most statistically significant association with higher levels of anti-RBD antibody was HLA-DQB1*06 (P = 3.2 × 10
), which we replicated in 1,677 additional vaccinees. Individuals carrying HLA-DQB1*06 alleles were less likely to experience PCR-confirmed breakthrough infection during the ancestral SARS-CoV-2 virus and subsequent Alpha variant waves compared to non-carriers (hazard ratio = 0.63, 0.42-0.93, P = 0.02). We identified a distinct spike-derived peptide that is predicted to bind differentially to HLA-DQB1*06 compared to other similar alleles, and we found evidence of increased spike-specific memory B cell responses in HLA-DQB1*06 carriers at 84 days after first vaccination. Our results demonstrate association of HLA type with Coronavirus Disease 2019 (COVID-19) vaccine antibody response and risk of breakthrough infection, with implications for future vaccine design and implementation.
In this study we evaluated the effect of linear energy transfer (LET) and chromatin structure on the induction of chromosomal inversion. High LET radiation causes more complex DNA damage than low LET ...radiation; this "dirty" damage is more difficult to repair and may result in an increase in inversion formation. CHO10B2 cells synchronized in either G1 or M phase were exposed 0, 1, or 2 Gy of 5 mm Al and Cu filters at 200 kVp and 20 mA X-rays or 500 MeV/nucleon of initial energy and 200 keV/μ m Fe ion radiation. In order to increase the sensitivity of prior techniques used to study inversions, we modified the more traditional Giemsa plus fluorescence technique so that cells were only allowed to incorporate BrdU for a single cycle verses 2 cycles. The BrdU incorporated DNA strand was labeled using a BrdU antibody and an Alexa Fluor 488 probe. This modified technique allowed us to observe inversions smaller than 0.6 megabases (Mb).
In this study we have shown that high LET radiation induces significantly more inversions in G1 cells than in M phase cells. Additionally, we have shown that the sizes of the induced inversions not only differ between Fe ion and X-rays, but also between G1 and M phase cells exposed to Fe ions.
We have effectively shown that both radiation quality and chromosome structure interact to alter not only the number of inversions induced, but also the size of the inversions.
Potentially lethal damage (PLD) repair has been defined as that property conferring the ability of cells to recover from DNA damage depending on the postirradiation environment. Using a novel cyclin ...dependent kinase 1 inhibitor RO-3306 to arrest cells in the G^sub 2^ phase of the cell cycle, examined PLD repair in G^sub 2^ in cultured Chinese hamster ovary (CHO) cells. Several CHO-derived DNA repair mutant cell lines were used in this study to elucidate the mechanism of DNA double-strand break repair and to examine PLD repair during the G^sub 2^ phase of the cell cycle. While arrested in G^sub 2^ phase, wild-type CHO cells displayed significant PLD repair and improved cell survival compared with cells released immediately from G^sub 2^ after irradiation. Both the radiation-induced chromosomal aberrations and the delayed entry into mitosis were also reduced by G^sub 2^-holding PLD recovery. The PLD repair observed in G^sub 2^ was observed in nonhomologous end-joining (NHEJ) mutant cell lines but absent in homologous recombination mutant cell lines. From the survival curves, G^sub 2^-NHEJ mutant cell lines were found to be very sensitive to gamma-ray exposure when compared to G^sub 2^/homologous recombination mutant cell lines. Our findings suggest that after exposure to ionizing radiation during G^sub 2^, NHEJ is responsible for the majority of non-PLD repair, and conversely, that the homologous recombination is responsible for PLD repair in G^sub 2^.
Potentially lethal damage (PLD) repair has been defined as that property conferring the ability of cells to recover from DNA damage depending on the postirradiation environment. Using a novel cyclin ...dependent kinase 1 inhibitor RO-3306 to arrest cells in the G sub( 2) phase of the cell cycle, examined PLD repair in G sub( 2) in cultured Chinese hamster ovary (CHO) cells. Several CHO-derived DNA repair mutant cell lines were used in this study to elucidate the mechanism of DNA double-strand break repair and to examine PLD repair during the G sub( 2) phase of the cell cycle. While arrested in G sub( 2) phase, wild-type CHO cells displayed significant PLD repair and improved cell survival compared with cells released immediately from G sub( 2) after irradiation. Both the radiation-induced chromosomal aberrations and the delayed entry into mitosis were also reduced by G sub( 2)-holding PLD recovery. The PLD repair observed in G sub( 2) was observed in nonhomologous end-joining (NHEJ) mutant cell lines but absent in homologous recombination mutant cell lines. From the survival curves, G sub( 2)-NHEJ mutant cell lines were found to be very sensitive to gamma-ray exposure when compared to G sub( 2)/homologous recombination mutant cell lines. Our findings suggest that after exposure to ionizing radiation during G sub( 2), NHEJ is responsible for the majority of non-PLD repair, and conversely, that the homologous recombination is responsible for PLD repair in G sub( 2).
Radioactive copper (II) (diacetyl-bis N4-methylthiosemicarbazone) (Cu-ATSM) isotopes were originally developed for the imaging of hypoxia in tumors. Because the decay of a super(64)Cu atom is ...emitting not only positrons but also Auger electrons, this radionuclide has great potential as a theranostic agent. However, the success of super(64)Cu-ATSM internal radiation therapy would depend on the contribution of Auger electrons to tumor cell killing. Therefore, we designed a cell culture system to define the contributions to cell death from Auger electrons to support or refute our hypothesis that the majority of cell death from super(64)Cu-ATSM is a result of high-LET Auger electrons and not positrons or other low-LET radiation. Chinese hamster ovary (CHO) wild type and DNA repair-deficient xrs5 cells were exposed to super(64)Cu-ATSM during hypoxic conditions. Surviving fractions were compared with those surviving gamma-radiation, low-LET hadron radiation, and high-LET heavy ion exposure. The ratio of the D sub(10) values (doses required to achieve 10% cell survival) between CHO wild type and xrs5 cells suggested that super(64)Cu-ATSM toxicity is similar to that of high-LET Carbon ion radiation (70 keV/ mu m). gamma H2AX foci assays confirmed DNA double-strand breaks and cluster damage by high-LET Auger electrons from super(64)Cu decay, and complex types of chromosomal aberrations typical of high-LET radiation were observed after super(64)Cu-ATSM exposure. The majority of cell death was caused by high-LET radiation. This work provides strong evidence that super(64)Cu-ATSM damages DNA via high-LET Auger electrons, supporting further study and consideration of super(64)Cu-ATSM as a cancer treatment modality for hypoxic tumors.
Transcriptome-wide association analysis is a powerful approach to studying the genetic architecture of complex traits. A key component of this approach is to build a model to impute gene expression ...levels from genotypes by using samples with matched genotypes and gene expression data in a given tissue. However, it is challenging to develop robust and accurate imputation models with a limited sample size for any single tissue. Here, we first introduce a multi-task learning method to jointly impute gene expression in 44 human tissues. Compared with single-tissue methods, our approach achieved an average of 39% improvement in imputation accuracy and generated effective imputation models for an average of 120% more genes. We describe a summary-statistic-based testing framework that combines multiple single-tissue associations into a powerful metric to quantify the overall gene-trait association. We applied our method, called UTMOST (unified test for molecular signatures), to multiple genome-wide-association results and demonstrate its advantages over single-tissue strategies.
PDF
