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Vault RNA1 regulation of apoptosis in multidrug-resistant GLC4 small cell lung cancer cellsTeye, Emmanuel K. 16 August 2011 (has links)
Small cell lung cancer (SCLC) is an aggressive form of lung cancer that frequently develops multidrug resistance (MDR) during chemotherapy. Vault RNA1 (vRNA1), a non-structural component of the MDR-associated vault organelle, is believed to act as a microRNA (miRNA) and may contribute to MDR by regulating the expression of genes involved in apoptosis, inflammation, and/or drug metabolism. Since vaults function to aid cells in survival, we hypothesized that vRNA1 might be free in the cytoplasm and able to inhibit expression of pro-survival mRNAs when vaults are open in drug-sensitive GLC4/S cells but not in the MDR GLC4/ADR cells where vaults might be closed with the miRNA sequestered within. In order to establish the role of vRNA1 as a regulator of survival in SCLC cells, siRNA-mediated down-regulation of vRNA1 was employed in GLC4/S and GLC4/ADR SCLC cells. Fluorescence microscopy using a green fluorescent 3’ AlexaFluor-488 negative siRNA control was used to estimate transfection efficiency, yielding 56% for GLC4/S and 89% for GLC4/ADR. However, these values and the level of apoptosis before and after transfection, as judged by trypan blue hemacytometer cell counts, were not entirely reliable due to cell clumping. The latter counts indicated a 2-fold decrease in viability in GLC4/S cell following transfection but no decrease in GLC4/ADR cells (p< 0.05). RT-PCR revealed that transfection significantly (p<0.05) decreased vRNA1 expression in GLC4/S cells but not in GLC4/ADR cells, confirming our hypothesis concerning the availability of vRNA1 in the two cell types. Caspase activity measurements showed vRNA1 down-regulation in the GLC4/ADR cells significantly (p≤0.05) increased survival via a 6.1-fold reduction in caspase 3/7 activity, further supporting our hypothesis. However, GLC4/S cells showed a similar loss of apoptosis when transfected with either sivRNA1 or the negative control siRNA. vRNA1 down-regulation did not significantly (p≤0.05) affect the expression of major pro-survival (Bcl-2, Bcl-xL), pro-apoptotic (Bad), or pro-inflammatory (IL-6, NFĸB p65) factors in either GLC4/S or GLC4/ADR cells. However, the drug metabolism protein CYP3A (previously shown by Persson et al., 2009 to be regulated by vRNA1) was significantly (p≤0.05) lowered (~16%) following vRNA1 down-regulation in the GLC4/S cells. In conclusion, we were successful in down-regulating vRNA1 which enhanced cell survival as hypothesized, but we were not able to identify new proteins regulated by vRNA1. / Department of Biology
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A potential role for VPARP in multi-drug resistant GLC4 small cell lung carcinoma cells as determined by immunoprecipitation and mass spectrometry / Potential role for vault poly(ADP) ribose polymerase in multi-drug resistant GLC4 small cell lung carcinoma cells as determined by immunoprecipitation and mass spectrometrySnider, Brandy M. January 2008 (has links)
Only discovered about 20 years ago, the structure of the eukaryotic vault particle has been studied extensively, but the function has yet to be determined. Vault numbers are up regulated in many types of cancer cells that are treated with chemotherapy agents and it is thought that they may act to transport chemotherapy drugs out of such cells, leading to multi-drug resistance (MDR). To determine a possible role of the vault particle in MDR, the goal of this research was to examine one of the functional vault proteins, vault poly(ADP)ribose (VPARP) for interactions with other proteins. Two forms of small cell lung cancer cells were used; GLC4/S which do not exhibit MDR and the MDR cells GLC4/ADR, which are cultured with the chemotherapy drug doxorubicin. Both cell cultures were subjected to a subcellular fractionation followed by gentle immunoprecipitation with an antibody to VPARP. Immunoprecipitated proteins interacting with VPARP were only observed in GLC4/ADR cells, as seen on a PAGE gel. This sample was taken to Monarch Life Sciences and analyzed by mass spectrometry. One interacting protein was found to be NALP1 pyrin domain (PYD), a member of the death domain family of proteins which is involved in inflammation and apoptosis. The interaction of VPARP with NALP1, which only occurred in MDR cells, suggests an exciting, previously unreported possibility – that VPARP binding may inhibit NALP 1-stimulated apoptosis when MDR is occurring. Future studies are needed to examine if levels of NALP1 vary in GLC4 cells with and without treatment with doxorubicin and in normal lung cells. The cellular location (nucleus or cytoplasm) of the interactions should also be identified. Furthermore, immunoprecipitation of proteins interacting with NALP1 should include VPARP and perhaps identify other proteins interacting in the signaling pathways under MDR and normal culture conditions. This information may contribute insight into the function of VPARP and vaults within the cell. / Department of Biology
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The cooperation of the tumor suppressor gene Dlc1 and the oncogene Kras in tumorigenesisBuse, Cordula 25 October 2012 (has links)
This thesis investigated the cooperation of the Kras2 oncogene with the tumor suppressor gene Dlc1 in lung tumor development. Dlc1 is a negative regulator of RhoGTPase proteins, which are mainly involved in the regulation of the actin cytoskeleton and cell migration. We hypothesized that loss of Dlc1 expression leads to more aggressive tumors, which should also result in increased incidence of metastasis.
All experiments were performed in mice containing a heterozygous oncogenic Kras allele and a heterozygous gene trapped Dlc1 allele (KD) and in mice only carrying the oncogenic Kras allele (K+). Throughout all experiments we have consistently found no significant differences between the two groups in terms of tumor burden (tumor numbers, sizes and areas), metastases or methylation patterns.
These results suggest that heterozygous downregulation of Dlc1 is not enough to increase tumor formation and metastasis development in the Kras lung tumors.
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Dömd på förhand : Upplevelser av stigamtisering vid lungcancer / Judged beforehand – experiences of stigma in lung cancerNilsson, Emma, Lorenzson, Jennifer January 2015 (has links)
Lung cancer is a disease which patients experience stigma in society and in care. This is because lung cancer is often seen as a self-inflicted disease. The stigma surrounding lung cancer is due to the strong relationship with smoking and have been shown to have a negative impact on the perceived health. The purpose of this study was to illuminate experiences of stigma for patients with lung cancer. The literature review was based on 11 scientific articles. The analysis resulted in three themes: experiences of being excluded out of context, experienced feelings surrounding stigma and the meeting within healthcare. Ignorance from healthcare and the community lead to patients with lung cancer feeling excluded, therefore it is important that nurses carry with them an awareness and good knowledge of stigma. The experience of stigma in patients with lung cancer was found to be reduced by good treatment and care from medical staff. Further qualitative research should be conducted that focuses on patients' experiences of stigma surrounding lung cancer both in the community and in healthcare. / Lungcancer är en sjukdom där patienter upplever sig stigmatiserade både i samhället och i vården eftersom lungcancer ofta ses som en självförvållad sjukdom. Stigmatiseringen kring lungcancer beror på det starka sambandet till rökning och har visat sig ha en negativ inverkan på den upplevda hälsan. Syftet med denna studie var att belysa upplevelser av stigmatisering av patienter med lungcancer. Litteraturstudien baserades på 11 vetenskapliga artiklar. Resultatet utmynnade i tre teman: upplevelser av att bli utesluten ur sammanhang, upplevda känslor kring stigmatisering och mötet i vården. Okunskap från vården samt från samhället leder till att patienter med lungcancer upplever ett utanförskap, det är därför av stor betydelse att sjuksköterskor bär med sig en medvetenhet och god kunskap kring stigmatisering. Upplevelsen av stigmatisering hos patienter med lungcancer visade sig kunna minska genom ett gott bemötande från vårdpersonalen. Mer kvalitativ forskning bör bedrivas som fokuserar på patienters upplevelser kring stigmatisering vid lungcancer såväl i samhället som i vården.
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Environmental Risk Factors for Lung Cancer Mortality in the Cancer Prevention Study-IITurner, Michelle C 10 January 2012 (has links)
This thesis examined associations between ecological indicators of residential radon and fine particulate matter air pollution (PM2.5) and lung cancer mortality using data from the American Cancer Society Cancer Prevention Study-II (CPS-II) prospective cohort. Nearly 1.2 million CPS-II participants were recruited in 1982. Mean county-level residential radon concentrations were linked to study participants according to ZIP code information at enrollment (mean (SD) = 53.5 (38.0) Bq/m3). Cox proportional hazards regression models were used to obtain adjusted hazard ratios (HRs) and 95% confidence intervals (CI) for lung cancer mortality associated with radon. After necessary exclusions, a total of 811,961 participants in 2,754 counties were retained for analysis. A significant positive linear trend was observed between categories of radon concentrations and lung cancer mortality (p = 0.02). A 15% (95% CI 1 - 31%) increase in the risk of lung cancer mortality was observed per each 100 Bq/m3 radon. Radon was also positively associated with chronic obstructive pulmonary disease mortality (HR per each 100 Bq/m3 = 1.13, 95% CI 1.05 - 1.21). No clear associations were observed between radon and non-respiratory mortality. In lifelong never smokers (n = 188,699), each 10 µg/m3 increase in mean metropolitan statistical area PM2.5 concentrations was associated with a 15-27% increase in the risk of lung cancer death which strengthened among individuals with a history of asthma or any prevalent chronic lung disease at enrollment (p for interaction < 0.05). There was no association between PM2.5 and mortality from non-malignant respiratory disease. In conclusion, this thesis observed significant positive associations between ecological indicators of residential radon and PM2.5 concentrations and lung cancer mortality. These findings further support efforts to reduce radon concentrations in homes to the lowest possible level and strengthens the evidence that ambient concentrations of PM2.5 measured in recent decades are associated with small but measurable increases in lung cancer mortality. Further research is needed to better understand possible complex inter-relationships between environmental risk factors, chronic lung disease, and lung cancer.
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Radiation therapy for metastatic brain tumors from lung cancer : a review to devise individualized treatment plansItoh, Yoshiyuki, Fuwa, Nobukazu, Morita, Kozo 11 1900 (has links)
No description available.
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Importancia clínica de los micrornas de la vía de p53 en cáncer de pulmón no microcítico: miR-34a y miR-16Gallardo Martín, Elena 22 June 2011 (has links)
El cáncer de pulmón no célula pequeña es la neoplasia más frecuente en la actualidad en los países industrializados, siendo la primera causa de mortalidad por cáncer en el varón.
Su incidencia continúa aumentando progresivamente, y su tratamiento, pese a los esfuerzos de investigación de los últimos años, sigue siendo poco efectivo en la mayor parte de los casos, situándose la supervivencia global a los cinco años alrededor del 13%.
La alta tasa de recaída, incluso en estadios iniciales susceptibles de cirugías radicales, justifica el interés de estudiar marcadores pronósticos de supervivencia y recaída. Esto nos ayudaría a distinguir grupos de riesgo, cuyo interés radica en ayudarnos a conocer la necesidad y efecto de los tratamientos adyuvantes, con quimioterapia y radioterapia así como abrir la puerta a posibles nuevas armas terapéuticas.
Dada la alta incidencia de alteraciones en la vía de p53 en el cáncer de pulmón no célula pequeña, y su probable valor pronóstico, nuestra hipótesis es que existen alteraciones en los niveles de expresión de los miRNAs directamente regulados por p53, así como en los reguladores intermedios de la función de p53, con posible valor pronóstico en recaída y supervivencia de pacientes operados de cáncer de pulmón no célula pequeña o no microcítico(CPNCP).
Tratamos pues de identificar el papel que juegan los miRNAs como marcadores útiles en el pronóstico del CPNCP en estadios iniciales, tras cirugía radical. De forma más específica determinar el posible papel pronóstico en recaída y en supervivencia de los miRNAs de la familia de miR-34: miR-34a, miR-34b y miR-34c, cuya transcripción es activada por p53. También definir el posible papel pronóstico en recaída y en supervivencia de los miRNAs miR-16 y miR-143, cuyos niveles finales en la célula, están modulados por p53. Así como, conocer si existen posibles interacciones entre miR-34a, miR-34b, miR-34c, miR-16 y miR-143 a nivel pronóstico.
Para ello, hemos planteado un estudio retrospectivo, con las muestras de tejido tumoral y normal pareado de 70 pacientes, diagnosticados y tratado, de cáncer de pulmón no microcítico estadios I-III, entre Febrero de 1996 y Septiembre de 2002, en el Hospital Clínic de Barcelona. Se realizaron la extracción y cuantificación de RNA. Determinación de los niveles de los microRNAs mencionados. Determinación del estado de metilación de la región promotora del gen MIR34A. Determinación de la presencia de mutaciones de P53 entre los exones 5-8.
Tras estos estudios los resultado obtenidos se han publicado en dos artículos. El primero de ellos en la revista “Carcinogenesis” y el segundo en la revista “Journal of Surgical Oncology”.
En el primer artículo, titulado “miR-34a as a prognostic marker of relapse in surgically resected non-small-cell lung cancer”, relacionamos los niveles de miR-34a con la recaída tumoral, estableciendo tres grupos en función de esta tasa de recaída: el grupo con niveles bajos de miR34a, con un 67% de recaída, los que tenían niveles altos, con un 43% de recaída y los que tenían los niveles más altos con un 0% de recaída. Además, en el análisis univariado para riesgo de recaída, el estado mutacional de P53, los niveles de miR-34a
y el estadio IA vs el resto, se correlacionaron con probabilidad de recaída. Se realizaron dos análisis mutilvariados, incluyendo o no el estado mutacional de P53, permaneciendo en ambos análisis la expresión de miR-34a, como factor independiente para recaída tumoral. Se observó que los pacientes con mutaciones de P53 presentaban una media de expresión de miR-34a más baja. Se observó que el subgrupo de pacientes en el que los niveles de expresión de miR-34a baja coincidían con presencia de mutaciones de P53, presentaban una alta tasa de recaída. En los pacientes sin mutaciones de de P53, existe una diferencia significativa en los niveles de expresión de miR-34a entre los pacientes que presentaban la región promotora de MIR34A metilada vs los que no. Por todo esto, encontramos que miR-34a se demuestra como un nuevo marcador biológico con significación en el pronóstico de la recaída de pacientes sometidos a cirugía del CPNCP, abriendo la posibilidad de una futura herramienta en el algoritmo de decisiones terapéuticas.
En el segundo artículo, titulado “Prognostic Implications of miR-16 Expression Levels in Resected Non-Small-Cell Lung Cancer”, desde la hipótesis de que P53 activa la transcripción de la familia de miRNAs de miR-34 y regula la maduración de miR-16 y miR143, se estudiaron los niveles de expresión de miR-143 y miR-16 en el tejido normal y tumoral pareado de cada paciente de la serie, antes mencionada, de 70 pacientes.
Así los pacientes se clasificaron de acuerdo a los niveles de expresión de miR-16(alto, normal y bajo). Aquellos pacientes con niveles normales tuvieron la mejor evolución, mientras que aquellos con niveles más altos tuvieron la peor. La supervivencia libre de enfermedad (SLE) era de 22,4 meses para los pacientes con niveles altos de miR-16, 71,8 meses para los de niveles normales y de 55,8 meses para los de niveles bajos. La supervivencia global (SG) fue de 23,9 meses para los que tenían niveles altos de miR-16, de 97,6 meses para los que tenían niveles normales y 63,5 meses para aquellos con niveles bajos. No se observó correlación entre los niveles de miR-143 y la evolución clínica de los pacientes. El análisis multivariado mostró a miR-16 como factor pronóstico independiente de SLE Y SG. En un análisis secundario, examinamos la correlación potencial entre la expresión de miR-16 y miR-34a y el estado mutacional de P53.No hubo correlación entre el estado mutacional de P53 y miR-16, pero si se observó una interacción entre miR-16 y miR-34a. En los pacientes con niveles altos de miR-34a, se observaron diferencias entre SLE Y SG, de acuerdo a los niveles de expresión de miR-16, mientras que en los pacientes con niveles bajos de miR-34a presentaban un pobre pronóstico, independientemente de los niveles de expresión de miR-16. Estos resultados nos indican el posible valor pronóstico de miR-16 en pacientes intervenidos de CPNCP, además del posible sinergismo entre miR-34a y miR16. / Non small cell lung cancer is more common today, in industrialized countries and is the leading cause of cancer death in men. Its incidence continues to increase gradually, and their treatment, despite the research efforts of recent years, it remains ineffective in most cases, putting the overall survival at five years about 13%. The high rate of relapse, even in early stages susceptible to radical surgery, justifies the interest in studying prognostic markers of survival and relapse. This would help us distinguish risk groups, whose interest lies in helping to meet the need and effect of adjuvant treatment with chemotherapy and radiotherapy as well as opening the door to possible new therapeutic tools. Given the high incidence of alterations in the p53 pathway in non small cell lung cancer, and likely its prognostic role, our hypothesis is that there are alterations in the expression levels of miRNAs directly regulated by p53, as well as in intermediate regulators of p53 function with potential prognostic value on relapse and survival of patients undergoing non small cell lung cancer (NSCLC). Then, we try to identify the role of miRNAs as useful markers for the prognosis of NSCLC in initial stages, after radical surgery. More specifically determine the possible prognostic role in relapse and survival of the family miRNAs miR-34: miR-34a, miR-34b and miR-34c, whose transcription is activated by p53. Also define the possible prognostic role in relapse and survival of the miRNAs miR-16 and miR-143, whose final levels in the cell are modulated by p53. And, determine whether there are possible interactions between miR-34a, miR-34b, miR-34c, miR-16 and miR-143 as regards prognosis. To do this, we have proposed a retrospective study, with the tumor tissue and paired normal in 70 patients, diagnosed and treated of non small cell lung cancer stages I-III, between February 1996 and September 2002, at the Hospital Clínic, in Barcelona. We performed RNA extraction and quantification. Determining levels of microRNAs mentioned. Determining the status of methylation of the promoter region of the gene MIR34A. Determining the presence of p53 mutations between exons 5-8. Following, the results obtained from these studies have been published in two articles. The first in the journal "Carcinogenesis" and the second in the "Journal of Surgical Oncology." In the first article, entitled "miR-34a as a Prognostic marker of relapse in surgically resected non-small-cell lung cancer", we relate the levels of miR-34a with the tumor relapse, establishing three groups according to the rate of relapse: the group with low levels of miR34a, with 67% relapse, those with high levels, with 43% relapse and those with the highest levels with a 0% relapse. Furthermore, in univariate analysis for risk of relapse, the mutational status of p53, the levels of miR-34a and stage IA vs the rest, were correlated with likelihood of relapse. Two multivariate analyzes were performed, including or not the P53 mutational status, remaining in both analyzes the expression of miR-34a, as an independent factor for tumor relapse. It was observed that patients with p53 mutations had a mean expression of miR-34a lower. It was noted that the subgroup of patients in which the expression levels of miR-34a low coincided with the presence of p53 mutations, had a high rate of relapse. In patients without mutations of p53, there is a significant difference in expression levels of miR-34a between the patients with the methylated promoter region MIR34A vs. those without. For all this, we found that miR-34a is shown as a novel biomarker with prognostic significance in patients relapsed NSCLC undergoing surgery, opening the possibility of a future tool in the therapeutic decision algorithm. In the second article, entitled "Prognostic Implications of miR-16 Expression Levels in Resected Non-Small-Cell Lung Cancer", from the hypothesis that p53 activates transcription of the family of miRNAs miR-34 and regulates the maturation of miR-16 to miR-143, we studied the expression levels of miR-143 and miR-16 in the paired normal and tumor tissue of each patient in the series, mentioned above, in 70 patients. So patients were classified according to the expression levels of miR-16 (high, normal and low). Patients with normal levels had the best clinical course, while those with higher levels had the worst. The disease-free survival (DFS) was 22.4 months for patients with high levels of miR-16, 71.8 months for normal levels of 55.8 months for low levels. Overall survival (OS) was 23.9 months for those with high levels of miR-16, from 97.6 months for those with normal levels and 63.5 months for those with low levels. No correlation was observed between the levels of miR-143 and the clinical course of patients. Multivariate analysis showed miR-16 as an independent prognostic factor for DFS and OS. In a secondary analysis, we examined the potential correlation between the expression of miR-16 and miR-34a and the mutational status of P53. There was no correlation between p53 mutational status and miR-16, but observed an interaction between miR-16 and miR-34a. In patients with high levels of miR-34a, there were differences between DFS and OS, according to the expression levels of miR-16, whereas in patients with low levels of miR-34a had a poor prognosis, regardless of expression levels of miR-16. These results indicate the possible prognostic value of miR-16 in patients operated for NSCLC, as well as possible synergism between miR-34a and miR16
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Breath biomarkers associated with lung cancerTran , Vanessa Hoang, Medical Sciences, Faculty of Medicine, UNSW January 2009 (has links)
Lung cancer (LC) is often diagnosed at advanced stage and as a result, survival rates are low. Recent studies describe exhaled breath and exhaled breath condensate (EBC) as a potential non-invasive method of sampling the airways for assessing inflammation of the respiratory system, and possibly for the early detection of LC. It was hypothesised that higher concentrations of markers and protein will be present in the EBC of LC patients compared to those of normal controls and healthy smokers, and may aid in assessing lung status. Methods: The gaseous phase of breath was investigated for volatile organic compound (VOC) patterns using an electronic nose (eNose) system, in addition to off-line measurements of carbon monoxide (CO) and nitric oxide (NO) levels. The aqueous phase, EBC, was collected during tidal breathing through a glass collection device cooled to 4??C by ice. Nitrite/nitrate (NOx) and pH levels were determined by a fluorescent modification of the Griess method, and silicon chip sensor pH meter, respectively. Protein levels in EBC were examined with a bicinchoninic acid (BCA) assay, silver staining and PAGE techniques, while the levels of tumour markers, CYFRA 21-1 and CEA, were quantified by enzyme-linked immunosorbent assays (ELISA). Results: The eNose machine was not able to produce characteristic VOC profiles from exhaled breath unique to each study group, while no significant difference was observed for mean NOx concentrations in the LC group when compared to other subjects (p=0.8824). Higher protein levels were found in the EBC of LC patient compared to normal controls (p=0.0204), with subsequent measurements of elevated CEA levels observed in the LC group when compared to non-smokers and smokers (p=0.023). Conclusion: This study showed that protein can be detected in the exhaled breath condensate of patients, with a significantly elevated amount in the samples from newly diagnosed LC patients. The mechanism for these differences remains to be determined but may be related to inflammatory changes within the airway, such as vascular protein leakage and release of mediators. Future work may aim to identify the upregulated proteins, and focus on proteomics and tissue microarrays to explore candidate proteins.
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Recovery following pneumonectomy: patients initial 2 year experienceMcLean, Jocelyn Margaret January 2003 (has links)
Little is known about the recovery of patients after pneumonectomy and the impact of the surgery on the lifestyle of young, employed, ex-smokers and their families. This study was conducted to address this knowledge deficit, and gather information that would help health professionals to be able to assist people facing pneumonectomy. A qualitative study using van Manens methodological approach to interpretive phenomenology was chosen, in order to capture a full and rich understanding and meaning of the phenomenon that patients live. The names, age, operation, histological cell type, stage of disease, and disease free status of potential participants were obtained from a Lung Cancer Surgical Database after obtaining ethical approval for the study. Nine participants (three females and six males) met the inclusion criteria and gave informed consent for the study. Data collection comprised of open-ended interviews that were audiotaped, then transcribed verbatim into hard data. Data interpretation was based on the selective reading approach of van Manen from which six thematic statements arose. These are living the discomforts of treatment and recovery, discovering new limitations on myself; functional and emotional, my reliance on support, my financial security is threatened, my survival is at threat, and I wish I had known more. The study found that each participant had a unique experience of recovery and consequently the degree of recovery attained varied between participants. They all had a very strong desire to survive lung cancer and considered the risks of major surgery and loosing a lung to be insignificant compared to the certainty of loosing their life if they did not undergo surgery. This study provided a glimpse of what it was like for a group of patients to live the experience of life after a pneumonectomy and it provides a basis from which nurses can explore further the experiences of patients who are subjected to lung cancer surgery.
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Regrowth resistance in platinum-drug resistant small cell lung cancer cellsStordal, Britta Kristina January 2007 (has links)
Doctor of Philosophy (PhD) / The H69CIS200 cisplatin-resistant and H69OX400 oxaliplatin-resistant cell lines developed as part of this study, are novel models of low-level platinum resistance. These resistant cell lines do not have common mechanisms of platinum resistance such as increased expression of glutathione or decreased platinum accumulation. Rather, these cell lines have alterations in their cell cycle allowing them to proliferate rapidly post drug treatment in a process known as ‘regrowth resistance’. This alteration in cell cycle control has come at the expense of DNA repair capacity. The resistant cell lines show a decrease in nucleotide excision repair and homologous recombination repair, the reverse of what is normally associated with platinum resistance. The alterations in these DNA repair pathways help signal the G1/S checkpoint to allow the cell cycle to progress despite the presence of DNA damage. The decrease in DNA repair capacity has also contributed to the development of chromosomal alterations in the resistant cell lines. Similarities in chromosomal change between the two platinum resistant cell lines have been attributed to inherent vulnerabilities in the parental H69 cells rather than part of the mechanism of resistance. The H69CIS200 and H69OX400 resistant cells are cross-resistant to both cisplatin and oxaliplatin. This demonstrates that oxaliplatin does not have increased activity in low-level cisplatin-resistant cancer. Oxaliplatin resistance also developed more rapidly than cisplatin resistance suggesting that oxaliplatin may be less effective than cisplatin in the treatment of SCLC. The resistant cell lines have also become hypersensitive to taxol but show no alterations in the expression, polymerisation or morphology of tubulin. Rather, the PI3K/Akt/mTOR pathway is involved in both platinum resistance and taxol sensitivity as both are reversed with rapamycin treatment. mTOR is also phosphorylated in the resistant cell lines indicating that platinum resistance is associated with an increase in activity of this pathway. The mechanism of regrowth resistance in the platinum-resistant H69CIS200 and H69OX400 cells is a combination of activation of PI3K/Akt/mTOR signalling and alterations in control of the G1/S cell cycle checkpoint. However, more work remains to determine which factors in these pathways are governing this novel mechanism of platinum resistance.
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