Resistance to gemcitabine in a human follicular lymphoma cell line is due to partial deletion of the deoxycytidine kinase gene

BACKGROUND: Gemcitabine is an analogue of deoxycytidine with activity against several solid tumors. In order to elucidate the mechanisms by which tumor cells become resistant to gemcitabine, we developed the resistant subline RL-G from the human follicular lymphoma cell line RL-7 by prolonged exposure of parental cells to increasing concentrations of gemcitabine. RESULTS: In vitro, the IC(50 )increased from 0.015 μM in parental RL-7 cells to 25 μM in the resistant variant, RL-G. Xenografts of both cell lines developed in nude mice were treated with repeated injections of gemcitabine. Under conditions of gemcitabine treatment which totally inhibited the development of RL-7 tumors, RL-G derived tumors grew similarly to those of untreated animals, demonstrating the in vivo resistance of RL-G cells to gemcitabine. HPLC experiments showed that RL-G cells accumulated and incorporated less gemcitabine metabolites into DNA and RNA than RL-7 cells. Gemcitabine induced an S-phase arrest in RL-7 cells but not in RL-G cells. Exposure to gemcitabine induced a higher degree of apoptosis in RL-7 than in RL-G cells, with poly-(ADP-ribose) polymerase cleavage in RL-7 cells. No modifications of Bcl-2 nor of Bax expression were observed in RL-7 or RL-G cells exposed to gemcitabine. These alterations were associated with the absence of the deoxycytidine kinase mRNA expression observed by quantitative RT-PCR in RL-G cells. PCR amplification of désoxycytidine kinase gene exons showed a partial deletion of the dCK gene in RL-G cells. CONCLUSIONS: These results suggest that partial deletion of the dCK gene observed after selection in the presence of gemcitabine is involved with resistance to this agent both in vitro and in vivo

Ethical conference economies? Reimagining the costs of convening academic communities when moving online

Online conferences are widely thought to reduce many of the costs of convening academic communities. From lower carbon emissions, lower fees, less difficulty in attending (particularly for marginalised researchers), and greater accessibility, virtual events promise to address many of the issues that in-person events take for granted. In this article, we draw on a community economies framing from geographers J.K. Gibson-Graham to argue for centring the work of convening within efforts to explore reparative possibilities within the academy. Reflecting on the changing costs arising from moving an originally in-person conference series online, we argue for embracing the opportunities offered. We explore how organising teams might enact alternative values through allocating the material, financial and labour resources traditionally spent for these events differently. We look particularly at how our carbon and financial costs changed, and how, by retaining a fee, we were able to allocate our budgets in ways which redistributed the surplus to participants in need (rather than bolster conference centre profits). We then explore what these changing costs meant in terms of our attendance levels across career stages and geographical locations. Looking at whether our experiment resulted in increased support for online events, we examine the continued ambivalence felt for the virtual. Finally, while we largely explore the benefits of online options, our last section urges caution over assumptions that this move will result in a more sustainable academia, particularly given the intensifications surrounding high quality streaming video, and suggest that we treat current trends as ongoing experiments, rather than solutions

‘What about the coffee break?’: Designing virtual conference spaces for conviviality

Geography, like many other disciplines, is reckoning with the carbon intensity of its practices and rethinking how activities such as annual meetings are held. The Climate Action Task Force of the American Association of Geographers (AAG), for example, was set up in 2019 and seeks to transform the annual conference in light of environmental justice concerns. Mirroring shifts it geographic practice across the globe, these efforts point to a need to understand how new opportunities for knowledge production such as online events can operate effectively. In this article, we offer suggestions for best practice in virtual spaces arising from our Material Life of Time conference held in March 2021, a two day global event that ran synchronously across 15 time zones. Given concerns about lack of opportunities for informal exchanges at virtual conferences, or the “coffee break problem”, we designed the event to focus particularly on opportunities for conviviality. This was accomplished through a focus on three key design issues: the spatial, the temporal and the social. We review previous work on the benefits and drawbacks of synchronous and asynchronous online conference methods and the kinds of geographic communities they might support. We then describe our design approach and reflect on its effectiveness via a variety of feedback materials. We show that our design enabled high delegate satisfaction, a sense of conviviality, and strong connections with new colleagues. However we also discuss the problems with attendance levels and external commitments which hampered shared time together. We thus call for collective efforts to support the ‘event time’ of online meetings, rather than expectations to fit them around everyday tasks. Even so, our results suggest that synchronous online events need not result in geographical exclusions linked to time zone differences, and we outline further recommendations for reworking the spacetimes of the conference

Enhancing the activity of platinum-based drugs by improved inhibitors of ERCC1–XPF-mediated DNA repair

Purpose: The ERCC1–XPF 5′–3′ DNA endonuclease complex is involved in the nucleotide excision repair pathway and in the DNA inter-strand crosslink repair pathway, two key mechanisms modulating the activity of chemotherapeutic alkylating agents in cancer cells. Inhibitors of the interaction between ERCC1 and XPF can be used to sensitize cancer cells to such drugs. Methods: We tested recently synthesized new generation inhibitors of this interaction and evaluated their capacity to sensitize cancer cells to the genotoxic activity of agents in synergy studies, as well as their capacity to inhibit the protein–protein interaction in cancer cells using proximity ligation assay. Results: Compound B9 showed the best activity being synergistic with cisplatin and mitomycin C in both colon and lung cancer cells. Also, B9 abolished the interaction between ERCC1 and XPF in cancer cells as shown by proximity ligation assay. Results of different compounds correlated with values from our previously obtained in silico predictions. Conclusion: Our results confirm the feasibility of the approach of targeting the protein–protein interaction between ERCC1 and XPF to sensitize cancer cells to alkylating agents, thanks to the improved binding affinity of the newly synthesized compounds

Detecting differential allelic expression using high-resolution melting curve analysis: application to the breast cancer susceptibility gene CHEK2

<p>Abstract</p> <p>Background</p> <p>The gene <it>CHEK2 </it>encodes a checkpoint kinase playing a key role in the DNA damage pathway. Though <it>CHEK2 </it>has been identified as an intermediate breast cancer susceptibility gene, only a small proportion of high-risk families have been explained by genetic variants located in its coding region. Alteration in gene expression regulation provides a potential mechanism for generating disease susceptibility. The detection of differential allelic expression (DAE) represents a sensitive assay to direct the search for a functional sequence variant within the transcriptional regulatory elements of a candidate gene. We aimed to assess whether <it>CHEK2 </it>was subject to DAE in lymphoblastoid cell lines (LCLs) from high-risk breast cancer patients for whom no mutation in <it>BRCA1</it> or <it>BRCA2</it> had been identified.</p> <p>Methods</p> <p>We implemented an assay based on high-resolution melting (HRM) curve analysis and developed an analysis tool for DAE assessment.</p> <p>Results</p> <p>We observed allelic expression imbalance in 4 of the 41 LCLs examined. All four were carriers of the truncating mutation 1100delC. We confirmed previous findings that this mutation induces non-sense mediated mRNA decay. In our series, we ruled out the possibility of a functional sequence variant located in the promoter region or in a regulatory element of <it>CHEK2 </it>that would lead to DAE in the transcriptional regulatory milieu of freely proliferating LCLs.</p> <p>Conclusions</p> <p>Our results support that HRM is a sensitive and accurate method for DAE assessment. This approach would be of great interest for high-throughput mutation screening projects aiming to identify genes carrying functional regulatory polymorphisms.</p

Cell-cycle-dependent transcriptional and translational DNA-damage response of 2 ribonucleotide reductase genes in S. cerevisiae

The ribonucleotide reductase (RNR) enzyme catalyzes an essential step in the production of deoxyribonucleotide triphosphates (dNTPs) in cells. Bulk biochemical measurements in synchronized Saccharomyces cerevisiae cells suggest that RNR mRNA production is maximal in late G1 and S phases; however, damaged DNA induces RNR transcription throughout the cell cycle. But such en masse measurements reveal neither cell-to-cell heterogeneity in responses nor direct correlations between transcript and protein expression or localization in single cells which may be central to function. We overcame these limitations by simultaneous detection of single RNR transcripts and also Rnr proteins in the same individual asynchronous S. cerevisiae cells, with and without DNA damage by methyl methanesulfonate (MMS). Surprisingly, RNR subunit mRNA levels were comparably low in both damaged and undamaged G1 cells and highly induced in damaged S/G2 cells. Transcript numbers became correlated with both protein levels and localization only upon DNA damage in a cell cycle-dependent manner. Further, we showed that the differential RNR response to DNA damage correlated with variable Mec1 kinase activity in the cell cycle in single cells. The transcription of RNR genes was found to be noisy and non-Poissonian in nature. Our results provide vital insight into cell cycle-dependent RNR regulation under conditions of genotoxic stress.Massachusetts Institute of Technology. Center for Environmental Health Sciences (deriving from NIH P30-ES002109)National Institutes of Health (U.S.) (grant R01-CA055042)National Institutes of Health (U.S.) (grant DP1-OD006422)Massachusetts Institute of Technology (CSBi Merck-MIT Fellowship

Antiproliferative effects of sapacitabine (CYC682), a novel 2′-deoxycytidine-derivative, in human cancer cells

This study assessed the antiproliferative activity of sapacitabine (CYC682, CS-682) in a panel of 10 human cancer cell lines with varying degrees of resistance or sensitivity to the commonly used nucleoside analogues ara-C and gemcitabine. Growth inhibition studies using sapacitabine and CNDAC were performed in the panel of cell lines and compared with both nucleoside analogues and other anticancer compounds including oxaliplatin, doxorubicin, docetaxel and seliciclib. Sapacitabine displayed antiproliferative activity across a range of concentrations in a variety of cell lines, including those shown to be resistant to several anticancer drugs. Sapacitabine is biotransformed by plasma, gut and liver amidases into CNDAC and causes cell cycle arrest predominantly in the G2/M phase. No clear correlation was observed between sensitivity to sapacitabine and the expression of critical factors involved in resistance to nucleoside analogues such as deoxycytidine kinase (dCK), human equilibrative nucleoside transporter 1, cytosolic 5′-nucleotidase and DNA polymerase-α. However, sapacitabine showed cytotoxic activity against dCK-deficient L1210 cells indicating that in some cells, a dCK-independent mechanism of action may be involved. In addition, sapacitabine showed a synergistic effect when combined with gemcitabine and sequence-specific synergy with doxorubicin and oxaliplatin. Sapacitabine is therefore a good candidate for further evaluation in combination with currently used anticancer agents in tumour types with unmet needs

5&apos;-nucleotidase cN-II emerges as a new predictive biomarker of response to gemcitabine/platinum combination chemotherapy in non-small cell lung cancer

A number of pharmacogenetic studies have been carried out in non-small-cell lung cancer (NSCLC) to identify and characterize genes involved in chemotherapy activity. However, the results obtained so far are controversial and no reliable biomarker is currently used to predict clinical benefit from platinum-based chemotherapy, which represents the cornerstone of treatment of advanced NSCLC. This study investigated the expression levels of ERCC1 and of six genes (RRM1, RRM2, hENT1, dCK, cN-II and CDA) involved in gemcitabine metabolism in locally/advanced NSCLC patients treated with gemcitabine/platinum combination. Gene expression was assessed by quantitative-PCR in laser-microdissected specimens and correlated with tumor response. Frequency distribution of responses above and below the median expression level of biomarkers was compared using a two-sided Fisher's test. 5'-nucleotidase (cN-II) was the only gene differently expressed (p = 0.016) in the responders (complete/partial-response) compared to non-responders (stable/ progressive disease). In the multivariate analysis, overexpression of this catabolic enzyme of gemcitabine remained a significant negative predictive factor. Patients with low cN-II had a modest trend toward increased survival, while both survival and progression-free survival were significantly longer in a more homogenous validation cohort of 40 advanced NSCLC (8.0 vs. 5.1 months, p = 0.026). Moreover, in vitro studies showed that silencing or pharmacological inhibition of cN-II increased the cytotoxicity of gemcitabine. This is the first study demonstrating the role of cN-II as a predictor of response to gemcitabine/platinum combinations in NSCLC. Its validation in prospective studies may improve clinical outcome of selected patients

Inhibition of IGF-1 Signalling Enhances the Apoptotic Effect of AS602868, an IKK2 Inhibitor, in Multiple Myeloma Cell Lines

Multiple myeloma (MM) is a B cell neoplasm characterized by bone marrow infiltration with malignant plasma cells. IGF-1 signalling has been explored as a therapeutic target in this disease. We analyzed the effect of the IKK2 inhibitor AS602868, in combination with a monoclonal antibody targeting IGF-1 receptor (anti-IGF-1R) in human MM cell lines. We found that anti-IGF-1R potentiated the apoptotic effect of AS602868 in LP1 and RPMI8226 MM cell lines which express high levels of IGF-1R. Anti-IGF-1R enhanced the inhibitory effect of AS602868 on NF-κB pathway signalling and potentiated the disruption of mitochondrial membrane potential caused by AS602868. These results support the role of IGF-1 signalling in MM and suggest that inhibition of this pathway could sensitize MM cells to NF-κB inhibitors