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Combined radiotherapy and chemotherapy
Published in Michael C. Joiner, Albert J. van der Kogel, Basic Clinical Radiobiology, 2018
Vincent Grégoire, Jean-Pascal Machiels, Michael Baumann
As a consequence of this cell-cycle phase selective cytotoxicity of chemotherapeutic agents, the remaining surviving cells could in principle be synchronized. If radiation could be delivered when these ‘synchronized’ cells have reached a more radiosensitive phase of the cell cycle (e.g. G2–mitosis), a tremendous potentiation of the radiation effect could be observed. Such a mechanism of interaction between drugs and ionizing radiation has often been reported in pre-clinical experimental models (e.g. [23]). However, in the clinic, due to much greater intra-tumour heterogeneity and also the difficulty in assessing the appropriate timing between drug administration and radiotherapy delivery, it is unlikely that cell synchronization can be successfully exploited. Furthermore, considering that radiotherapy is typically delivered on a fractionated basis, it is also likely that this effect would be lost after a few fractions.
Cell Biology
Published in C.S. Sureka, C. Armpilia, Radiation Biology for Medical Physicists, 2017
Cell synchronization is a process by which cells at different stages of the cell cycle are brought to the same phase. Thus, a synchronized culture is one in which cells of similar age progress as a group through the division.
Role of Nonhistone Chromosomal Proteins in Selective Gene Expression
Published in Gerald M. Kolodny, Eukaryotic Gene Regulation, 2018
I.R. Phillips, E.A. Shephard, J.L. Stein, G.S. Stein
While taken together these results seem to support control of histone gene readout residing at least in part at the transcriptional level, caution must be exercised in interpreting the in vitro translation and transcription experiments. The limits of detection of histones synthesized in vitro when very small quantities of RNA template are available leave something to be desired. Interpretation of data from in vitro nuclear transcription experiments is complicated by an inability to establish definitively the initiation of RNA chains in vitro and by the presence of endogenous nuclear histone mRNA sequences. Results from in vitro chromatin transcription experiments can be misleading since trancription is carried out with bacterial RNA polymerase, and endogenous chromatin-associated RNA sequences can also interfere with evaluation of nucleic acid hybridization. It must also be pointed out that because, in the experiments just described, hybridization was carried out in RNA excess using unlabeled RNA and a 3H-labeled histone DNA complementary to the mRNAs for the five histones, the presence of rapidly turning over histone mRNA sequences in the nuclear RNA or in the nuclear or chromatin transcripts of G, cells might not have been detected. In fact, Melli et al.521 have detected the presence of histone mRNA sequences in the nucleus throughout the cell cycle of HeLa cells by hybridizing 3H-labeled RNA with excess sea urchin histone DNA. However, there are some reservations concerning the experiments of Melli et al.521 (1) The method utilized for cell synchronization was double thymidine block, a procedure which results in at least 20% of the G1 and G2 cells actually being S phase cells (as measured by 3H-thymidine labeling and autoradiography). This is in contrast to experiments in which the HeLa cDNA probe was used and in which G1, cells were obtained by mitotic selective detachment, a procedure which yields a population of Gi cells containing less than 0.1 % S phase cells. (2) Hybridization analysis of HeLa cell RNAs was carried out with sea urchin DNA and there appears to be only 10 to 15% sequence homology between human and sea urchin histone sequences.556
Identification of novel cis-mutations in the GJA8 gene in a 3-generation Iranian family with autosomal dominant congenital nuclear cataract
Published in Ophthalmic Genetics, 2022
Neda Jabbarpour, Hassan Saei, Mohammad Hossein Jabbarpoor Bonyadi, Mortaza Bonyadi
Congenital cataracts are clinically and genetically diverse. There are more than 300 genes identified to be involved in the development of congenital cataract, including syndromic and non-syndromic cataracts (1). Non-syndromic cataracts are inherited in 8.3 to 25% of cases, of which 76–89% are inherited as autosomal dominant, 7% as autosomal recessive, and 2–10% as X-linked. Congenital cataract, which could lead to blindness or amblyopia in infants, is estimated to have an incidence of 1 to 6 in 10,000 live birth (2). The C × 50 and C × 46‘s N-terminal domains are hotspots for genetic variants related to congenital cataracts (1). Gap junction proteins, encoded by connexin family of genes (abbreviated CX), are frequently identified by their molecular weights, for example, C × 50 (GJA8) is the 50 kDa connexin protein. An alternative nomenclature is the gap junction protein system, which classifies connexins according to their α (GJA) and β (GJB) forms (3). These proteins provide a pathway for the intercellular exchanges of ions, small metabolites, and second messengers which are essential for cell synchronization, growth and development (4). Three connexin isoforms known as C × 43, C × 46, and C × 50 are reported to be expressed in mammalian lens (5). Gap Junction protein alpha-8 (GJA8) gene encodes a transmembrane connexin protein (CX50) essential for the maturation of lens fiber cells and their growth. This protein is a connexin of the ocular lens, which maintains ionic and water balance and transparency and optical properties of the lens (6). Several previous studies have shown the association of this gene with zonular pulverulent cataracts, nuclear progressive cataracts, and cataract-microcornea syndrome with autosomal dominant pattern in the pedigree (7–10).
An Olive Leaf Extract Rich in Polyphenols Promotes Apoptosis in Cervical Cancer Cells by Upregulating p21Cip/WAF1 Gene Expression
Published in Nutrition and Cancer, 2019
Donatella Vizza, Simona Lupinacci, Giuseppina Toteda, Francesco Puoci, Parisi Ortensia I, Anna De Bartolo, Danilo Lofaro, Luca Scrivano, Renzo Bonofiglio, Antonella La Russa, Martina Bonofiglio, Anna Perri
Human cervix cancer cells, HeLa (ATCC), were grown in Minimum Essential Medium (Sigma Aldrich, Milano, Italy) containing 10% Fetal Bovine Serum (FBS, Sigma Aldrich), 1% Glutammine (Sigma Aldrich), 1% non-essential amminoacids (Sigma Aldrich) and 1 mg ml−1 penicillin/streptomycin (P/S), (Sigma Aldrich). All experiments were performed, after 24 h of cell synchronization, in serum free medium. The control was treated with the vehicle [ethanol/water 40/60 (v/v) (untreated, −)].
Parallel comparison of pre-conditioning and post-conditioning effects in human cancers and keratinocytes upon acute gamma irradiation
Published in International Journal of Radiation Biology, 2019
Jason Cohen, Nguyen T. K. Vo, Colin B. Seymour, Carmel E. Mothersill
The noted difference between the ‘0Gy +5h + 2Gy’ and ‘2Gy +5h + 0Gy’ clonogenic survival was a surprising observation. The ‘0Gy +5h + 2Gy’ flasks were at 29 h post seeding prior to irradiation and the ‘2Gy +5h + 0Gy’ clonogenic flask were at 24 h post seeding prior to irradiation. It is possible that there were more cells that doubled at 29 h than those at 24 h. Therefore, we performed two additional experiments to see if this was a possible reason. In the first experiment, we seeded 1 million cells in T25 flasks and counted the total cell numbers in the flasks 24 or 29 h post seeding. We found that the cell numbers at 24 and 29 h were statistically indifferent from each other (Figure S1). As the cell status can be influenced under an extremely low-cell-density environment, in the second experiment we seeded cells at the clonogenic cell density in T25 flasks, stained the flasks with the carbol fuchsin dye 24 or 29 h post seeding, and microscopically scored the number of singlets (single cells) and doublets (cells that already doubled). We found that the singlet percent was the same at 24 and 29 h and the doublet percent was also the same at 24 h and 29 h (Figure S2). Therefore, observed differences in the clonogenic survival cannot be explained by the unmatched percentages of cells that have or have not divided at 24 h and 29 h. It remains possible that the observed differences could be attributable to a cell synchronization effect. However, while the 2 Gy dose could arrest cells, as long as the pre- or post-conditioning flasks are assessed relative to the correct control (24 or 29 h), this should not be an issue. It could, however, provide an explanation for a post-conditioning protective effect if the cell synchronization led to more cells being in a radioresistant cell cycle phase at the time the conditioning dose was applied. Since the conditioning dose is very small it is unlikely to cause the effect seen but the possibility is presented here for consideration. We consider it more likely that parallel processes are induced by small and large doses and that the precise order of administration of the high and low doses are less important than the absolute fact of two-dose administration. On the other hand, differences seen in cells seeded 6 h or 24 h before irradiation could be due to cell cycle arrest, synchronization or ‘lag’ after trypsinization.