Аллель-специфическая экспрессия генов при канцерогенезе

Recent large-scale genomic studies established the occurrence of multiple DNA sequence variants in genomes of healthy individuals that differ from the reference sequence. Among these variants mostly represented by germline single nucleotide polymorphisms disease-related alleles are detected including alleles which are associated with monogenic disorders, and putative deleterious genetic variants. Apart from functional significance of a particular variant and of a gene harboring it, the penetrance of these allelic variants depends on their expression level and can be determined by preferential expression of a particular allele, or allele-specific expression. It is estimated that 20–30 % of genes present in the human genome display allelic bias in a tissue-specific manner. Allele-specific expression is defined by a range of genetic and epigenetic mechanisms including cis-regulatory polymorphisms, allele-specific binding of transcription factors, allele-specific DNA methylation and regulation through non-coding RNA.Although the data on the issue are scarce, allele-specific expression has been reported to be implicated in several hereditary disorders including benign and malignant tumors of the large intestine. Recent studies that estimate allele-specific expression incidence in tumors and identify wide range of genes displaying allelic imbalance indicate that allele-specific expression might play a significant role in carcinogenesis. Eventually, estimation of transcriptional rate of allelic variants which cause dysfunction of oncogenes and tumor suppressors may prove to be essential for rational choice of antitumor therapeutic strategy. In this review, we outline the main concepts and mechanisms of allele-specific expression and the data on allelic imbalance in tumors.В результате масштабных исследований человеческого генома, проведенных в последние годы, было установлено наличие в геномах здоровых индивидов множества вариантов последовательностей ДНК, отличных от референсной последовательности. Среди этих вариантов, подавляющую часть которых составляют герминативные однонуклеотидные полиморфизмы, обнаруживают аллельные варианты, ассоциированные с развитием заболеваний, в том числе наследственных моногенных болезней, также регистрируются менее изученные потенциально патогенные варианты. Проявление таких вариантов в фенотипе зависит не только от функциональной значимости самой мутации и содержащего ее гена, но и от уровня экспрессии измененного аллеля и может быть обусловлено преобладанием экспрессии одного аллеля гена над другим, или аллель-специфической экспрессией.По современным оценкам аллель-специфическая экспрессия затрагивает 20–30 % генов человека и носит тканеспецифичный характер. Аллель-специфическую экспрессию определяет действие ряда генетических и эпигенетических механизмов, включая цис-регуляторные полиморфизмы, аллель-специфическое связывание транскрипционных факторов, аллель-специфическое метилирование ДНК и регуляцию некодирующими РНК.На сегодняшний день имеются данные о роли аллель-специфической экспрессии в развитии некоторых наследственных заболеваний, в том числе наследственных форм опухолей толстого кишечника. Результаты исследований последних лет, дающие приблизительную оценку распространенности этого явления в опухолях и определяющие широкий спектр проявляющих аллельный дисбаланс генов, указывают на то, что значение аллель-специфической экспрессии для развития опухолей, вероятно, недооценено. В перспективе оценка уровней экспрессии аллельных вариантов, приводящих к нарушению функции онкогенов или опухолевых супрессоров, может оказаться значимым фактором для выбора оптимальных схем противоопухолевой терапии.В обзоре рассматриваются предпосылки к возникновению и механизмы аллель-специфической экспрессии, а также имеющиеся в литературе данные об аллельном дисбалансе в опухолях

Влияние нарушенной экспрессии HNF4α на чувствительность клеток гепатоцеллюлярной карциномы к действию ингибиторов проопухолевых сигнальных каскадов

Introduction. Hepatocellular carcinoma (HCC) is characterized by aggressive course, high lethality rate and resistance to current systemic treatment. Analysis of molecular aberrations associated with HCC pathogenesis that control biological properties of HCC allows to evaluate potential efficacy of inhibiting certain oncogenic cascades. The present study is focused on investigation of the impact of reduced expression of the key hepatocyte differentiation regulator, HNF4α, often downregulated in HCC, that influences sensitivity of HCC cells to inhibitors  of the major oncogenic pathways mTOR, CDK4/6-pRb and ROCK.Materials and methods. Changes in cells proliferation and migration caused by HNF4А gene stable knockdown were tested in human HCC cell cultures HepG2 and Huh7 followed by examination of these cellular properties under mTOR (rapamycin), CDK4/6 (PD0332991, palbociclib) and ROCK 1/2 (Y27632) inhibitors treatment. Gene expression levels were estimated by the real-time polymerase chain reaction method (Real-Time PCR).Results. HNF4А gene knockdown alters HepG2 and Huh7 cell migration associated with E-cadherin and N-cadherin expression changes. The HNF4α repression weakens Y27632-induced blockade of HCC cells migration potential. HNF4А gene knockdown causes resistance  of Huh7 cells and increase of HepG2 cells sensitivity to rapamycin and PD0332991 that block cells migration ability.Conclusions. Expression level of HNF4α renders influence on migration of HCC cells and contributes to their sensitivity to mTOR, CDK4/6 and ROCK1/2 inhibitors’ impact on cell migration activity.Введение. Гепатоцеллюлярная карцинома (ГК) характеризуется агрессивным течением, высокой частотой случаев летальности и устойчивостью к существующим схемам терапии. Исследование ассоциированных с патогенезом ГК молекулярных нарушений, которые влияют на биологические свойства клеток ГК, позволяет оценить потенциальную эффективность ингибирования конкретных проопухолевых сигнальных каскадов. Настоящая работа посвящена изучению действия снижения экспрессии ключевого регулятора гепатоцитарной дифференцировки HNF4α, которое часто происходит в ГК, на чувствительность клеток культур ГК к ингибиторам важных проопухолевых сигнальных путей mTOR, CDK4 / 6-pRb и ROCK.Материалы и методы. В культурах ГК человека HepG2 и Huh7 со стабильным нокдауном гена HNF4A определяли изменение пролиферативного и миграционного потенциалов клеток, а также изменение данных свойств при действии ингибиторов mTOR (рапамицина), CDK4 / 6 (PD0 332 991, палбоциклиба) и ROCK 1 / 2 (Y27 632). Уровни экспрессии генов определяли методом полимеразной цепной реакции в реальном времени.Результаты. Нокдаун гена HNF4А вызывает изменение миграционной способности клеток HepG2 и Huh7, ассоциированное с изменением экспрессии Е-кадгерина и N-кадгерина. Снижение экспрессии HNF4α ослабляет опосредованное Y27632-подавление миграционного потенциала в клетках ГК. Нокдаун гена HNF4А приводит к возникновению устойчивости клеток Huh7 и увеличению чувствительности клеток HepG2 к действию рапамицина и PD0 332 991, блокирующих миграционную способность клеток.Заключение. Уровень экспрессии HNF4α влияет на миграционную способность клеток ГК и их чувствительность к действию ингибиторов mTOR, CDK4 / 6 и ROCK1 / 2 на миграционную активность

Методы детекции специфических для опухолевой ткани однонуклеотидных соматических мутаций в препаратах цДНК из плазмы крови

Introduction. Liquid biopsy is considered as a minimally invasive method of molecular genetic analysis that can be used for early diagnosis, prognosis of disease development, monitoring of residual disease or treatment outcomes, and selection of optimal drug therapy schemes for a patient. Along with the development of tests based on the study of panels of oncologically significant genes or their regions, for various forms of genetically heterogeneous tumors a promising approach could be the use as an object of liquid biopsy of an individual spectrum of somatic mutations of a particular patient that can be detected on the basis of high-throughput sequencing of tumor tissue.Aim. To determine the applicability of different methods for detecting single-nucleotide somatic mutations detected in tumor tissue of a particular patient in cDNA preparations from blood plasma obtained before surgical removal of the tumor and to evaluate the possibility of quantifying the proportion of the alternative variant in the total pool of cDNA. Materials and methods. We used normal and tumor tissue, as well as blood plasma samples from patients with hepatocellular carcinoma, and various methods for detecting single-nucleotide somatic mutations: real-time polymerase chain reaction (PCR) with intercalating dye or with TaqMan probes, droplet digital PCR and high-throughput sequencing of target amplicons.Results. Using the example of a somatic mutation in the TLN1 gene detected in tumor tissue of a patient with hepatocellular carcinoma, methods were developed and tested, each of which allows specific detection of the mutant variant in small amounts (2 ng) of cDNA from the blood plasma of the same patient. The use of droplet PCR and target amplicon sequencing methods allowed us to quantify the proportion of the mutant variant in the total cDNA pool, which was 19.7 and 23.5 %, respectively.Conclusion. Among the methods investigated, droplet digital PCR and targeted amplicon sequencing allow not only reliable detection of mutant variants in small amounts of cDNA, but also adequate quantification, which is particularly important for the development of ways to monitor tumor growth during treatment. The close values of the proportion of mutant variants in cDNA detected by these methods indicate the accuracy of quantitative analysis and the possibility of their use for cross-validation of the results obtained.Введение. Жидкостная биопсия рассматривается как малоинвазивный способ проведения молекулярно-генетического анализа, который может быть использован для ранней диагностики, прогноза течения заболевания, мониторинга остаточной болезни или результатов лечения, а также выбора оптимальных для пациента схем лекарственной терапии. Наряду с разработкой тестов, основанных на исследовании панелей онкологически значимых генов или их участков, для различных форм генетически гетерогенных опухолей перспективным подходом может стать использование в качестве объекта жидкостной биопсии индивидуального спектра соматических мутаций конкретного больного, которые могут быть выявлены с помощью высокопроизводительного секвенирования опухолевой ткани.Цель исследования - определить возможность использования различных методов детекции однонуклеотидных соматических мутаций, выявленных в опухолевой ткани конкретного пациента, в препаратах циркулирующей ДНК (цДНК) из плазмы крови, полученных до хирургического удаления опухоли, и выявить возможность количественной оценки доли альтернативного варианта в общем пуле цДНК.Материалы и методы. В работе использованы препараты нормальной и опухолевой тканей, плазмы крови пациентов с гепатоцеллюлярной карциномой, а также различные методы детекции однонуклеотидных соматических мутаций: полимеразная цепная реакция (ПЦР) в реальном времени с интеркалирующим красителем или с зондами TaqMan, капельная цифровая ПЦР и высокопроизводительное секвенирование таргетных ампликонов.Результаты. На примере соматической мутации в гене TLN1, выявленной в опухолевой ткани пациента с гепатоцеллюлярной карциномой, разработаны и апробированы методы, каждый из которых позволяет специфично детектировать мутантный вариант в малых количествах (2 нг) цДНК из плазмы крови того же пациента. использование капельной ПЦР и секвенирования таргетных ампликонов позволило провести количественную оценку долей мутантного варианта в общем пуле цДНК, которые составили 19,7 и 23,5 % соответственно.Заключение. Капельная цифровая ПЦР и таргетное секвенирование ампликонов позволяют не только надежно детектировать мутантные варианты в малых количествах цДНК, но и адекватно проводить их количественную оценку, что особенно важно для разработки способов мониторинга опухолевого роста в процессе лечения. Близкие значения доли мутантного варианта в цДНК, детектированной этими методами, свидетельствуют о точности количественного анализа и возможности их использования для кросс-валидации получаемых результатов

Epigenetic inactivation of TCF2 in ovarian cancer and various cancer cell lines

Transcription factor 2 gene (TCF2) encodes hepatocyte nuclear factor 1β (HNF1β), a transcription factor associated with development and metabolism. Mutation of TCF2 has been observed in renal cell cancer, and by screening aberrantly methylated genes, we have now identified TCF2 as a target for epigenetic inactivation in ovarian cancer. TCF2 was methylated in 53% of ovarian cancer cell lines and 26% of primary ovarian cancers, resulting in loss of the gene's expression. TCF2 expression was restored by treating cells with a methyltransferase inhibitor, 5-aza-2′deoxycitidine (5-aza-dC). In addition, chromatin immunoprecipitation showed deacetylation of histone H3 in methylated cells and, when combined with 5-aza-dC, the histone deacetylase inhibitor trichostatin A synergistically induced TCF2 expression. Epigenetic inactivation of TCF2 was also seen in colorectal, gastric and pancreatic cell lines, suggesting general involvement of epigenetic inactivation of TCF2 in tumorigenesis. Restoration of TCF2 expression induced expression of HNF4α, a transcriptional target of HNF1β, indicating that epigenetic silencing of TCF2 leads to alteration of the hepatocyte nuclear factor network in tumours. These results suggest that TCF2 is involved in the development of ovarian cancers and may represent a useful target for their detection and treatment

Lancet

BACKGROUND: In 2015, the second cycle of the CONCORD programme established global surveillance of cancer survival as a metric of the effectiveness of health systems and to inform global policy on cancer control. CONCORD-3 updates the worldwide surveillance of cancer survival to 2014. METHODS: CONCORD-3 includes individual records for 37.5 million patients diagnosed with cancer during the 15-year period 2000-14. Data were provided by 322 population-based cancer registries in 71 countries and territories, 47 of which provided data with 100% population coverage. The study includes 18 cancers or groups of cancers: oesophagus, stomach, colon, rectum, liver, pancreas, lung, breast (women), cervix, ovary, prostate, and melanoma of the skin in adults, and brain tumours, leukaemias, and lymphomas in both adults and children. Standardised quality control procedures were applied; errors were rectified by the registry concerned. We estimated 5-year net survival. Estimates were age-standardised with the International Cancer Survival Standard weights. FINDINGS: For most cancers, 5-year net survival remains among the highest in the world in the USA and Canada, in Australia and New Zealand, and in Finland, Iceland, Norway, and Sweden. For many cancers, Denmark is closing the survival gap with the other Nordic countries. Survival trends are generally increasing, even for some of the more lethal cancers: in some countries, survival has increased by up to 5% for cancers of the liver, pancreas, and lung. For women diagnosed during 2010-14, 5-year survival for breast cancer is now 89.5% in Australia and 90.2% in the USA, but international differences remain very wide, with levels as low as 66.1% in India. For gastrointestinal cancers, the highest levels of 5-year survival are seen in southeast Asia: in South Korea for cancers of the stomach (68.9%), colon (71.8%), and rectum (71.1%); in Japan for oesophageal cancer (36.0%); and in Taiwan for liver cancer (27.9%). By contrast, in the same world region, survival is generally lower than elsewhere for melanoma of the skin (59.9% in South Korea, 52.1% in Taiwan, and 49.6% in China), and for both lymphoid malignancies (52.5%, 50.5%, and 38.3%) and myeloid malignancies (45.9%, 33.4%, and 24.8%). For children diagnosed during 2010-14, 5-year survival for acute lymphoblastic leukaemia ranged from 49.8% in Ecuador to 95.2% in Finland. 5-year survival from brain tumours in children is higher than for adults but the global range is very wide (from 28.9% in Brazil to nearly 80% in Sweden and Denmark). INTERPRETATION: The CONCORD programme enables timely comparisons of the overall effectiveness of health systems in providing care for 18 cancers that collectively represent 75% of all cancers diagnosed worldwide every year. It contributes to the evidence base for global policy on cancer control. Since 2017, the Organisation for Economic Co-operation and Development has used findings from the CONCORD programme as the official benchmark of cancer survival, among their indicators of the quality of health care in 48 countries worldwide. Governments must recognise population-based cancer registries as key policy tools that can be used to evaluate both the impact of cancer prevention strategies and the effectiveness of health systems for all patients diagnosed with cancer. FUNDING: American Cancer Society; Centers for Disease Control and Prevention; Swiss Re; Swiss Cancer Research foundation; Swiss Cancer League; Institut National du Cancer; La Ligue Contre le Cancer; Rossy Family Foundation; US National Cancer Institute; and the Susan G Komen Foundation

Worldwide trends in population-based survival for children, adolescents, and young adults diagnosed with leukaemia, by subtype, during 2000–14 (CONCORD-3) : analysis of individual data from 258 cancer registries in 61 countries

Background Leukaemias comprise a heterogenous group of haematological malignancies. In CONCORD-3, we analysed data for children (aged 0–14 years) and adults (aged 15–99 years) diagnosed with a haematological malignancy during 2000–14 in 61 countries. Here, we aimed to examine worldwide trends in survival from leukaemia, by age and morphology, in young patients (aged 0–24 years). Methods We analysed data from 258 population-based cancer registries in 61 countries participating in CONCORD-3 that submitted data on patients diagnosed with leukaemia. We grouped patients by age as children (0–14 years), adolescents (15–19 years), and young adults (20–24 years). We categorised leukaemia subtypes according to the International Classification of Childhood Cancer (ICCC-3), updated with International Classification of Diseases for Oncology, third edition (ICD-O-3) codes. We estimated 5-year net survival by age and morphology, with 95% CIs, using the non-parametric Pohar-Perme estimator. To control for background mortality, we used life tables by country or region, single year of age, single calendar year and sex, and, where possible, by race or ethnicity. All-age survival estimates were standardised to the marginal distribution of young people with leukaemia included in the analysis. Findings 164563 young people were included in this analysis: 121328 (73·7%) children, 22963 (14·0%) adolescents, and 20272 (12·3%) young adults. In 2010–14, the most common subtypes were lymphoid leukaemia (28205 [68·2%] patients) and acute myeloid leukaemia (7863 [19·0%] patients). Age-standardised 5-year net survival in children, adolescents, and young adults for all leukaemias combined during 2010–14 varied widely, ranging from 46% in Mexico to more than 85% in Canada, Cyprus, Belgium, Denmark, Finland, and Australia. Individuals with lymphoid leukaemia had better age-standardised survival (from 43% in Ecuador to ≥80% in parts of Europe, North America, Oceania, and Asia) than those with acute myeloid leukaemia (from 32% in Peru to ≥70% in most high-income countries in Europe, North America, and Oceania). Throughout 2000–14, survival from all leukaemias combined remained consistently higher for children than adolescents and young adults, and minimal improvement was seen for adolescents and young adults in most countries. Interpretation This study offers the first worldwide picture of population-based survival from leukaemia in children, adolescents, and young adults. Adolescents and young adults diagnosed with leukaemia continue to have lower survival than children. Trends in survival from leukaemia for adolescents and young adults are important indicators of the quality of cancer management in this age group.peer-reviewe

Global survival trends for brain tumors, by histology: analysis of individual records for 556,237 adults diagnosed in 59 countries during 2000–2014 (CONCORD-3)

Background: Survival is a key metric of the effectiveness of a health system in managing cancer. We set out to provide a comprehensive examination of worldwide variation and trends in survival from brain tumors in adults, by histology. Methods: We analyzed individual data for adults (15–99 years) diagnosed with a brain tumor (ICD-O-3 topography code C71) during 2000–2014, regardless of tumor behavior. Data underwent a 3-phase quality control as part of CONCORD-3. We estimated net survival for 11 histology groups, using the unbiased nonparametric Pohar Perme estimator. Results: The study included 556,237 adults. In 2010–2014, the global range in age-standardized 5-year net survival for the most common sub-types was broad: in the range 20%–38% for diffuse and anaplastic astrocytoma, from 4% to 17% for glioblastoma, and between 32% and 69% for oligodendroglioma. For patients with glioblastoma, the largest gains in survival occurred between 2000–2004 and 2005–2009. These improvements were more noticeable among adults diagnosed aged 40–70 years than among younger adults. Conclusions: To the best of our knowledge, this study provides the largest account to date of global trends in population-based survival for brain tumors by histology in adults. We have highlighted remarkable gains in 5-year survival from glioblastoma since 2005, providing large-scale empirical evidence on the uptake of chemoradiation at population level. Worldwide, survival improvements have been extensive, but some countries still lag behind. Our findings may help clinicians involved in national and international tumor pathway boards to promote initiatives aimed at more extensive implementation of clinical guidelines

Impact of HNF4α disrupted expression on hepatocellular carcinoma cells sensitivity to oncogenic pathways inhibitors

Introduction. Hepatocellular carcinoma (HCC) is characterized by aggressive course, high lethality rate and resistance to current systemic treatment. Analysis of molecular aberrations associated with HCC pathogenesis that control biological properties of HCC allows to evaluate potential efficacy of inhibiting certain oncogenic cascades. The present study is focused on investigation of the impact of reduced expression of the key hepatocyte differentiation regulator, HNF4α, often downregulated in HCC, that influences sensitivity of HCC cells to inhibitors  of the major oncogenic pathways mTOR, CDK4/6-pRb and ROCK.Materials and methods. Changes in cells proliferation and migration caused by HNF4А gene stable knockdown were tested in human HCC cell cultures HepG2 and Huh7 followed by examination of these cellular properties under mTOR (rapamycin), CDK4/6 (PD0332991, palbociclib) and ROCK 1/2 (Y27632) inhibitors treatment. Gene expression levels were estimated by the real-time polymerase chain reaction method (Real-Time PCR).Results. HNF4А gene knockdown alters HepG2 and Huh7 cell migration associated with E-cadherin and N-cadherin expression changes. The HNF4α repression weakens Y27632-induced blockade of HCC cells migration potential. HNF4А gene knockdown causes resistance  of Huh7 cells and increase of HepG2 cells sensitivity to rapamycin and PD0332991 that block cells migration ability.Conclusions. Expression level of HNF4α renders influence on migration of HCC cells and contributes to their sensitivity to mTOR, CDK4/6 and ROCK1/2 inhibitors’ impact on cell migration activity

Expression of tissue-specific genes with progression of mouse hepatocellular carcinoma

Expression of hepatocyte-specific genes in slow- and fast-growing hepatocellular mouse carcinomas was studied. The fast-growing poorly differentiated passaged hepatocarcinoma (fHC) originated from the well-differentiated slow-growing variant (sHC). In contrast to the parental hepatocarcinoma, in fHC the expression of the hepatocyte nuclear factor 4 (HNF4), in fHC a key factor responsible for hepatocyte differentiation, and several HNF-4-responsive genes, such as those for transferrin, transthyretin, hepatocyte nuclear factor l (HNF1), and serum albumin, was significantly suppressed. The expression of exogenous HNF4 in the fHC cell culture partially restored the expression of hepatocyte marker genes and the appearance of epithelial cell islands in the culture. The described system may serve as a convenient model for further analysis of mechanisms underlying hepatocarcinogenesis and liver tumor progression