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BACKGROUND: Approximately one third of cancer survivors in the United Kingdom face ongoing and debilitating psychological and physical symptoms related to poor quality of life. Very little is known about current post-cancer treatment services. METHODS: Oncology healthcare professionals (HCPs) were invited to take part in a survey, which gathered both quantitative and free text data about the content and delivery of cancer aftercare and patient needs. Analysis involved descriptive statistics and content analysis. RESULTS: There were 163 complete responses from 278 survey participants; 70% of NHS acute trusts provided data. HCPs views on patient post-cancer treatment needs were most frequently: fear of recurrence (95%), fatigue (94%), changes in physical capabilities (89%), anxiety (89%) and depression (88%). A median number of 2 aftercare sessions were provided (interquartile range: 1,4) lasting between 30 and 60 min. Usually these were provided face-to-face and intermittently by a HCP. However, sessions did not necessarily address the issues HCPs asserted as important. Themes from free-text responses highlighted inconsistencies in care, uncertain funding for services and omission of some evidence based approaches. CONCLUSION: Provision of post-cancer treatment follow-up care is neither universal nor consistent in the NHS, nor does it address needs HCPs identified as most important.
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Neoplasias/terapia , Assistência ao Paciente/métodos , Qualidade de Vida/psicologia , Feminino , Pesquisas sobre Atenção à Saúde , Humanos , Masculino , Neoplasias/psicologia , Oncologistas , Reino UnidoRESUMO
BACKGROUND: Approximately 40% of hormone receptor-positive, HER2-negative breast cancers (BCs) are associated with activating mutations of the phosphatidylinositol 3-kinase (PI3K) pathway. Pictilisib, a potent and highly specific class I pan-PI3K inhibitor, demonstrated preclinical activity in BC cell lines and may potentiate the effect of taxanes, benefiting patients with or without aberrant activation of the PI3K pathway. PEGGY (NCT01740336), a randomised, placebo-controlled phase II trial, examined whether pictilisib augments the anti-tumour activity of paclitaxel in patients with hormone receptor-positive, HER2-negative locally recurrent or metastatic BC (mBC). We report results from the protocol-specified interim analysis. PATIENTS AND METHODS: One hundred and eighty-three eligible patients were randomised (1:1) to receive paclitaxel (90 mg/m2 weekly for 3 weeks in every 28-day cycle) with either 260 mg pictilisib or placebo (daily on days 1-5 every week). The primary end point was progression-free survival (PFS) in the intention-to-treat (ITT) population and patients with PIK3CA-mutated tumours. Secondary end points included overall response rate (ORR), duration of response, and safety. RESULTS: In the ITT population, the median PFS was 8.2 months with pictilisib (n = 91) versus 7.8 months with placebo (n = 92) [hazard ratio (HR) for progression or death, 0.95; 95% confidence interval (CI) 0.62-1.46; P = 0.83]. In patients with PIK3CA-mutated tumours, the median PFS was 7.3 months for pictilisib (n = 32) versus 5.8 months with placebo (n = 30) (HR, 1.06; 95% CI 0.52-2.12; P = 0.88). ORR was similar between treatment arms. The safety profile of pictilisib was consistent with previous reports, with no new safety signals. Proportions of patients with grade ≥3 adverse events (AEs), serious AEs, and dose reductions/discontinuations due to AEs were higher with pictilisib. CONCLUSIONS: PEGGY did not meet its primary end point, revealing no significant benefit from adding pictilisib to paclitaxel for patients with hormone receptor-positive, HER2-negative locally recurrent or mBC. CLINICAL TRIAL NUMBER: NCT01740336.
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Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Neoplasias da Mama/tratamento farmacológico , Classe I de Fosfatidilinositol 3-Quinases/genética , Indazóis/administração & dosagem , Recidiva Local de Neoplasia/tratamento farmacológico , Sulfonamidas/administração & dosagem , Adulto , Idoso , Anticorpos Monoclonais Humanizados/administração & dosagem , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Classe I de Fosfatidilinositol 3-Quinases/antagonistas & inibidores , Intervalo Livre de Doença , Feminino , Humanos , Pessoa de Meia-Idade , Metástase Neoplásica , Recidiva Local de Neoplasia/genética , Recidiva Local de Neoplasia/patologia , Paclitaxel/administração & dosagem , Receptor ErbB-2/genéticaRESUMO
BACKGROUND: Chromosomal instability (CIN) has been shown to be associated with drug resistance and poor clinical outcome in several cancer types. However, in oestrogen receptor (ER)-negative breast cancer we have previously demonstrated that extreme CIN is associated with improved clinical outcome, consistent with a negative impact of CIN on tumour fitness and growth. The aim of this current study was to validate this finding using previously defined CIN thresholds in a much larger prospective cohort from a randomised, controlled, clinical trial. PATIENTS AND METHODS: As a surrogate measurement of CIN, dual centromeric fluorescence in situ hybridisation was performed for both chromosomes 2 and 15 on 1173 tumours from the breast cancer TACT trial (CRUK01/001). Each tumour was scored manually and the mean percentage of cells deviating from the modal centromere number was used to define four CIN groups (MCD1-4), where tumours in the MCD4 group were defined as having extreme CIN. RESULTS: In a multivariate analysis of disease-free survival, with a median follow-up of 91 months, increasing CIN was associated with improved outcome in patients with ER-negative cancer (P trend = 0.03). A similar pattern was seen in ER-negative/HER2-negative cancers (Ptrend = 0.007). CONCLUSIONS: This prospective validation cohort study further substantiated the association between extreme CIN and improved outcome in ER-negative breast cancers. Identifying such patients with extreme CIN may help distinguish good from poor prognostic groups, and therefore support treatment and risk stratification in this aggressive breast cancer subtype.
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Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Biomarcadores Tumorais/metabolismo , Neoplasias da Mama/genética , Neoplasias da Mama/mortalidade , Instabilidade Cromossômica , Receptores de Estrogênio/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Antraciclinas/administração & dosagem , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Feminino , Seguimentos , Humanos , Técnicas Imunoenzimáticas , Hibridização in Situ Fluorescente , Pessoa de Meia-Idade , Gradação de Tumores , Estadiamento de Neoplasias , Prognóstico , Estudos Prospectivos , Receptor ErbB-2/metabolismo , Receptores de Progesterona/metabolismo , Taxa de Sobrevida , Taxoides/administração & dosagem , Adulto JovemRESUMO
BACKGROUND: Invasive lobular breast cancer (ILC) and lobular carcinoma in situ (LCIS) are characterised by loss of E-cadherin expression. However germline CDH1 mutations are rare in cases of ILC with no family history of hereditary diffuse gastric cancer (HDGC) and have not been described in women with LCIS. METHODS: We screened the CDH1 gene in 50 cases of bilateral LCIS/ILC using Sanger sequencing and MLPA. RESULTS: Sanger sequencing revealed four pathogenic germline mutations, including a novel splicing mutation (c.48+1G>A). The remaining three (c.1465insC, c.1942G>T, c.2398delC) have been previously described. All four cases had bilateral LCIS +/- ILC and no family history of gastric cancer. CONCLUSION: CDH1 germline mutations have not been previously described in women with LCIS. We have shown that germline CDH1 mutations are associated with early onset of bilateral LCIS with or without ILC in women without a family history of gastric cancer. CDH1 mutation screening should be considered in women with early onset of bilateral LCIS/ILC with no family history of HDGC.
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Neoplasias da Mama/genética , Caderinas/genética , Carcinoma in Situ/genética , Carcinoma Lobular/genética , Antígenos CD , Sequência de Bases , Neoplasias da Mama/patologia , Carcinoma Lobular/patologia , Feminino , Mutação em Linhagem Germinativa/genética , Humanos , Pessoa de Meia-Idade , Análise de Sequência de DNARESUMO
BACKGROUND: Dual anti-human epidermal growth factor receptor 2 (HER2) blockade has improved the outcomes of patients with early and metastatic HER2-positive breast cancer. Here we present the final 10-year analysis of the ALTTO trial. PATIENTS AND METHODS: The ALTTO trial (NCT00490139) is a prospective randomized, phase III, open-label, multicenter study that investigated the role of adjuvant chemotherapy and trastuzumab alone, in combination or sequentially with lapatinib. The primary endpoint was disease-free survival (DFS) and secondary endpoints included overall survival (OS), time to distant recurrence and safety. RESULTS: Overall, 6281 patients with HER2-positive early breast cancer were included in the final efficacy analysis in three treatment groups: trastuzumab (T), lapatinib + trastuzumab (L + T) and trastuzumab followed by lapatinib (TâL). Baseline characteristics were well balanced between groups. At a median follow-up of 9.8 years, the addition of lapatinib to trastuzumab and chemotherapy did not significantly improve DFS nor OS. The 10-year DFS was 77% in T, 79% in L + T and 79% in TâL, and the 10-year OS was 87%, 89% and 89%, respectively. The incidence of any cardiac event was low and similar in the three treatment groups. CONCLUSIONS: With a longer follow-up, no significant improvement was observed in DFS in patients treated with dual anti-HER2 blockade with lapatinib + trastuzumab compared to trastuzumab alone. The 10-year survival rates for the combination group are consistent with other studies that have explored dual anti-HER2 therapy.
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BACKGROUND: There is currently no standardised definition for patients at high risk of recurrence of human epidermal growth factor receptor 2 (HER2)-negative early breast cancer (eBC; stages 1-3) after surgery. This modified Delphi panel aimed to establish expert UK consensus on this definition, separately considering hormone receptor (HR)-positive and triple-negative (TN) patients. METHODS: Over three consecutive rounds, results were collected from 29, 24 and 22 UK senior breast cancer oncologists and surgeons, respectively. The first round aimed to determine key risk factors in each patient subgroup; subsequent rounds aimed to establish appropriate risk thresholds. Consensus was pre-defined as ≥70% of respondents. RESULTS: Expert consensus was achieved on need to assess age, tumour size, tumour grade, number of positive lymph nodes, inflammatory breast cancer and risk prediction tools in all HER2-negative patients. There was additional agreement on use of tumour profiling tests and biomarkers in HR-positive patients, and pathologic complete response (pCR) status in TN patients. Thresholds for high recurrence risk were subsequently agreed. In HR-positive patients, these included age <35 years, tumour size >5 cm (as independent risk factors); tumour grade 3 (independently and combined with other high-risk factors); number of positive nodes ≥4 (independently) and ≥1 (combined). For TN patients, the following thresholds reached consensus, both independently and in combination with other factors: tumour size >2 cm, tumour grade 3, number of positive nodes ≥1. CONCLUSIONS: The results may be a valuable reference point to guide recurrence risk assessment and decision-making after surgery in the HER2-negative eBC population.
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Neoplasias da Mama , Humanos , Adulto , Feminino , Neoplasias da Mama/patologia , Consenso , Receptor ErbB-2/metabolismo , Fatores de Risco , Medição de Risco , Reino UnidoRESUMO
The increasing ubiquity of web-based social networking services is a striking feature of modern human society. The degree to which individuals participate in these networks varies substantially for reasons that are unclear. Here, we show a biological basis for such variability by demonstrating that quantitative variation in the number of friends an individual declares on a web-based social networking service reliably predicted grey matter density in the right superior temporal sulcus, left middle temporal gyrus and entorhinal cortex. Such regions have been previously implicated in social perception and associative memory, respectively. We further show that variability in the size of such online friendship networks was significantly correlated with the size of more intimate real-world social groups. However, the brain regions we identified were specifically associated with online social network size, whereas the grey matter density of the amygdala was correlated both with online and real-world social network sizes. Taken together, our findings demonstrate that the size of an individual's online social network is closely linked to focal brain structure implicated in social cognition.
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Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Rede Social , Adulto , Cognição , Córtex Entorrinal/anatomia & histologia , Córtex Entorrinal/fisiologia , Feminino , Humanos , Internet , Imageamento por Ressonância Magnética , Masculino , Modelos Neurológicos , Modelos Psicológicos , Comportamento Social , Percepção Social , Lobo Temporal/anatomia & histologia , Lobo Temporal/fisiologia , Adulto JovemRESUMO
A small proportion of breast cancers metastasise within the peritoneal cavity. With increasing breast cancer incidence rates, gynaecologists and oncologists will encounter such women more frequently. Most women with intraperitoneal breast cancer are premenopausal. Although data are limited and are likely to be subject to selection bias, the median survival of women undergoing resection appears superior to those not undergoing surgery. Furthermore, survival is broadly similar to that for women undergoing advanced ovarian cancer surgery, particularly when tumour debulking is optimal. Obtaining data via randomised trials is unlikely to be feasible and therefore we recommend prospective data collection via the establishment of an international intraperitoneal breast cancer patient registry. For individual women where survival is anticipated to be more than a few months, we suggest considering referral to a gynaecological oncology team for discussion of surgical options.
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Neoplasias Abdominais/secundário , Neoplasias da Mama/patologia , Neoplasias Pélvicas/secundário , Neoplasias Abdominais/diagnóstico , Neoplasias Abdominais/mortalidade , Neoplasias Abdominais/cirurgia , Neoplasias da Mama/mortalidade , Feminino , Humanos , Neoplasias Pélvicas/diagnóstico , Neoplasias Pélvicas/mortalidade , Neoplasias Pélvicas/cirurgia , Taxa de Sobrevida , Resultado do TratamentoRESUMO
AIMS: Fulvestrant is a selective oestrogen receptor (ER) degrader used in postmenopausal women with hormone receptor-positive advanced breast cancer. The study aim was to analyse demographics and outcomes of UK patients treated with fulvestrant monotherapy at nine representative centres. MATERIALS AND METHODS: Medical records of 459 patients with locally advanced or metastatic ER-positive, HER2-negative breast cancer treated with fulvestrant between August 2011 and November 2018 at nine UK centres were reviewed. Data were collated on demographics, progression-free survival, overall survival and disease response at first radiological assessment following fulvestrant initiation. Patients still alive by December 2018 were censored. RESULTS: Data from 429 of the 459 patients identified were eligible for inclusion in the analysis. The median age was 69 (range 21-95) and 64% (n = 275) had Eastern Cooperative Oncology Group performance status 0-1. Bone was the most commonly involved metastatic site (72%, n = 306). However, 295 (69%) patients had visceral involvement. Patients had received a median 2 (range 0-5) prior lines of endocrine therapy and median 0 (range 0-6) prior chemotherapies. Fulvestrant was first-line therapy in 43 patients (10%). The median duration of treatment was 5 months (range 1-88). The median progression-free survival was 5.5 months. In 51% of 350 patients radiologically assessed, there was evidence of disease response to fulvestrant. Fifteen per cent of these had a complete/partial response. Fulvestrant was discontinued predominantly due to disease progression, with 3% discontinued solely due to adverse events. The median overall survival for the whole cohort was 22.5 months (range 0-88). CONCLUSIONS: This is one of the largest studied cohorts of breast cancer patients treated with fulvestrant. This heavily endocrine-pretreated population reflects real-life use in the UK. Within this context, our retrospective data show that patients can experience maintained disease response when treated with fulvestrant, supporting the importance of equitable availability for all UK patients.
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Neoplasias da Mama , Idoso , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Neoplasias da Mama/patologia , Estradiol/uso terapêutico , Feminino , Fulvestranto/efeitos adversos , Humanos , Receptor ErbB-2 , Receptores de Estrogênio/uso terapêutico , Receptores de Progesterona/uso terapêutico , Estudos RetrospectivosRESUMO
APC is often cited as a prime example of a tumor suppressor gene. Truncating germline and somatic mutations (or, infrequently, allelic loss) occur in tumors in FAP (familial adenomatous polyposis). Most sporadic colorectal cancers also have two APC mutations. Clues from attenuated polyposis, missense germline variants with mild disease and the somatic mutation cluster region (codons 1,250-1,450) indicate, however, that APC mutations might not result in simple loss of protein function. We have found that FAP patients with germline APC mutations within a small region (codons 1,194-1,392 at most) mainly show allelic loss in their colorectal adenomas, in contrast to other FAP patients, whose 'second hits' tend to occur by truncating mutations in the mutation cluster region. Our results indicate that different APC mutations provide cells with different selective advantages, with mutations close to codon 1,300 providing the greatest advantage. Allelic loss is selected strongly in cells with one mutation near codon 1,300. A different germline-somatic APC mutation association exists in FAP desmoids. APC is not, therefore, a classical tumor suppressor. Our findings also indicate a new mechanism for disease severity: if a broader spectrum of mutations is selected in tumors, the somatic mutation rate is effectively higher and more tumors grow.
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Polipose Adenomatosa do Colo/genética , Neoplasias Colorretais/genética , Genes APC/genética , Mutação em Linhagem Germinativa/genética , Modelos Genéticos , Mutação/genética , Adenoma/genética , Adenoma/patologia , Polipose Adenomatosa do Colo/patologia , Alelos , Sequência de Bases , Códon/genética , Neoplasias Colorretais/patologia , Análise Mutacional de DNA , Éxons/genética , Saúde da Família , Fibromatose Agressiva/genética , Fibromatose Agressiva/patologia , Mutação da Fase de Leitura/genética , Deleção de Genes , Frequência do Gene , HumanosRESUMO
We analysed chromosome 16q in 106 breast cancers using tiling-path array-comparative genomic hybridization (aCGH). About 80% of ductal cancers (IDCs) and all lobular cancers (ILCs) lost at least part of 16q. Grade I (GI) IDCs and ILCs often lost the whole chromosome arm. Grade II (GII) and grade III (GIII) IDCs showed less frequent whole-arm loss, but often had complex changes, typically small regions of gain together with larger regions of loss. The boundaries of gains/losses tended to cluster, common sites being 54.5-55.5 Mb and 57.4-58.8 Mb. Overall, the peak frequency of loss (83% cancers) occurred at 61.9-62.9 Mb. We also found several 'minimal' regions of loss/gain. However, no mutations in candidate genes (TRADD, CDH5, CDH8 and CDH11) were detected. Cluster analysis based on copy number changes identified a large group of cancers that had lost most of 16q, and two smaller groups (one with few changes, one with a tendency to show copy number gain). Although all morphological types occurred in each cluster group, IDCs (especially GII/GIII) were relatively overrepresented in the smaller groups. Cluster groups were not independently associated with survival. Use of tiling-path aCGH prompted re-evaluation of the hypothetical pathways of breast carcinogenesis. ILCs have the simplest changes on 16q and probably diverge from the IDC lineage close to the stage of 16q loss. Higher-grade IDCs probably develop from low-grade lesions in most cases, but there remains evidence that some GII/GIII IDCs arise without a GI precursor.
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Neoplasias da Mama/genética , Carcinoma Ductal de Mama/genética , Carcinoma Lobular/genética , Cromossomos Humanos Par 16 , Invasividade Neoplásica/genética , Hibridização de Ácido Nucleico/métodos , Análise Serial de Tecidos/métodos , Aberrações Cromossômicas , Quebra Cromossômica , Análise por Conglomerados , DNA de Neoplasias , Amplificação de Genes , Deleção de Genes , Ligação Genética , Humanos , Perda de Heterozigosidade , Modelos Estatísticos , Estadiamento de NeoplasiasRESUMO
AIMS: Trabectedin (ET-743, Yondelis) is a marine-derived alkaloid that has two actions. It binds in the minor groove of DNA resulting in a conformational change; thus potentially altering interactions with transcription factors and other DNA binding proteins and it also interacts with the transcription-coupled nucleotide excision repair machinery to induce lethal double-stranded DNA breaks. In recent phase II trials it has shown considerable activity in the treatment of sarcomas. Here the use of trabectedin in patients with advanced refractory sarcoma from a single institution is presented. MATERIALS AND METHODS: Twenty-one patients with advanced refractory sarcoma from a single UK centre were treated with trabectedin on a named patient compassionate basis programme. All patients had received prior treatment with an anthracycline, and 95% had received ifosfamide. RESULTS: The patients received a median of four cycles of treatment. Objective partial responses were seen in three patients (14%) and a further eight patients (38%) achieved durable stable disease for a median duration of 4.5 months. The estimated 3- and 6-month progression-free survival was 58.8 and 17.6%, respectively. Six patients experienced early disease progression, and four patients died while on treatment. One death was due to treatment-related toxicity. Overall the drug was relatively well tolerated, with hepatic and haematological toxicities most commonly encountered. Both necessitated delays and/or dose reductions in a proportion of patients. Other significant toxicities were nausea, vomiting and asthenia. CONCLUSION: The disease responses and durable nature of disease stabilisation seen in a proportion of our patients support the continued investigational use of this drug in the treatment of advanced soft tissue sarcomas.
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Antraciclinas/uso terapêutico , Antineoplásicos Alquilantes/uso terapêutico , Dioxóis/uso terapêutico , Ifosfamida/uso terapêutico , Sarcoma/tratamento farmacológico , Tetra-Hidroisoquinolinas/uso terapêutico , Resultado do Tratamento , Adolescente , Adulto , Antineoplásicos Alquilantes/efeitos adversos , Antineoplásicos Alquilantes/farmacologia , Dioxóis/efeitos adversos , Dioxóis/farmacologia , Progressão da Doença , Intervalo Livre de Doença , Feminino , Humanos , Ifosfamida/efeitos adversos , Ifosfamida/farmacologia , Masculino , Pessoa de Meia-Idade , Sarcoma/mortalidade , Sarcoma/fisiopatologia , Tetra-Hidroisoquinolinas/efeitos adversos , Tetra-Hidroisoquinolinas/farmacologia , Fatores de Tempo , Trabectedina , Reino UnidoRESUMO
How does breast cancer progress? There is evidence both to support (S. W. Duffy et al., Br. J. Cancer, 64: 1133-1138, 1991; R. Rajakariar et al., Br. J. Cancer, 71: 150-154, 1995) and refute (M. Hakama et al., Lancet, 345: 221-224, 1995; R. R. Millis et al., Eur. J. Cancer, 34: 548-553, 1998) the hypothesis of dedifferentiation; the theory that as breast cancers grow they evolve from well differentiated (grade I) to poorly differentiated (grade III) tumors. We provide evidence to support the view that the majority of grade I tumors do not progress to grade III tumors. Comparative genomic hybridization was used to screen entire genomes of a large sample (40 grade I and 50 grade III) of invasive ductal breast carcinomas, stratified by grade. We found distinct genetic differences between grade I and grade III tumors. Significantly, we found that 65% of grade I tumors lost the long arm of chromosome 16 compared with only 16% of grade III tumors. This pattern of loss leads us to conclude that the majority of grade I tumors do not progress to grade III tumors. These findings have important implications because they suggest that different breast tumor grades may have distinct molecular origins, pathogenesis, and behavior and, therefore, potentially present distinct molecular targets for research and treatment.
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Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Aberrações Cromossômicas , Cromossomos Humanos Par 16 , Feminino , Humanos , Hibridização de Ácido NucleicoRESUMO
INTRODUCTION AND METHODS: Since the concept of the "two hit hypothesis" was introduced over 20 years ago, a wealth of genetic data has accumulated on the mutations found at tumour suppressor loci. Perhaps surprisingly, these data conceal large gaps in our knowledge which genetic and functional studies are beginning to uncover. The "two hit hypothesis" must be updated to take account of this new information. RESULTS AND DISCUSSION: Here, we discuss both the results of recent studies and some of the questions that they highlight. In particular, how valid are conclusions from inherited Mendelian syndromes when applied to sporadic cancers? Why is allelic loss so common and how does it occur? Are the "two hits" random or interdependent? Is abolition of protein function always optimal for tumorigenesis? Can "third hits" occur and, if so, why? How can mismatch repair deficiency and the methylator phenotype be incorporated into the "two hit" hypothesis? We suggest that the "two hit hypothesis" is not fixed but is evolving as our knowledge expands.
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Mutação , Neoplasias/genética , HumanosRESUMO
Exonuclease 1 (EXO1) is a candidate gene for colorectal tumor susceptibility because it is believed to play a role in mismatch repair. There have been several studies investigating the role of EXO1 in mismatch repair but few investigating its role in causing clinical disease. In one recent study, germline variants of EXO1 were reported to be associated with predisposition to colorectal cancer in families with phenotypes similar to hereditary nonpolyposis colon cancer (HNPCC). We recently identified nine individuals from two British families with multiple cutaneous and uterine leiomyomatosis with independently arising heterozygous germline deletions of 1q42.3 approximately q43 encompassing not only FH, the multiple leiomyomatosis-associated gene, but also several flanking genes, including EXO1. We investigated these families for any indication of predisposition to colorectal cancer or other HNPCC spectrum cancers by means of detailed questionnaires, interviews, and examination of EXO1-null skin leiomyomata for microsatellite instability (MSI). No individual in these families had developed colorectal cancer or known colorectal adenomas, and none had any symptoms warranting gastrointestinal or other investigation. EXO1-null tumors showed no evidence of MSI. This study questions the functional significance of previously reported variants of EXO1 reported in HNPCC-like families and suggests that in humans there may be other as yet undiscovered proteins that have exonuclease function overlapping with that of EXO1 in DNA mismatch repair. Also of interest is the absence of phenotypic abnormality apart from multiple leiomyomatosis in any deletion carrier even though the adjacent genes RGS7, KMO, CHML, and OPN3 were also deleted.
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Neoplasias Colorretais/genética , Exodesoxirribonucleases/genética , Instabilidade Genômica , Repetições de Microssatélites , Deleção de Sequência , Adulto , Idoso , Neoplasias Colorretais/etiologia , Enzimas Reparadoras do DNA , Feminino , Genótipo , Haplótipos , Humanos , Hibridização in Situ Fluorescente , Masculino , Pessoa de Meia-Idade , LinhagemRESUMO
Comparative genomic hybridization (CGH) is a molecular cytogenetic technique used to screen the entire genome for gains and losses of genetic material (1). It is being used increasingly in the study of cancer genetics to identify genes important in the initiation, progression, and, of particular relevance here, metastasis of tumors (2-4).One of the advantages of the technique is that the entire genome is examined in a single experiment, so there is no necessity to know the genetic region of interest prior to investigation. Once regions of gain or loss have been identified, these regions can be defined further using fluorescence in situ hybridization (FISH) (described in Chapter 14 by Goker and Shipley) or molecular genetic techniques. CGH is essentially a modified in situ hybridization. Differentially labeled test or tumor DNA (green) and reference or normal DNA (red) are cohybridized to normal metaphase spreads. Differences in the copy number between test and reference DNA are seen as differences in the ratio of green to red fluorescence intensity on the metaphase chromosomes. Images of the metaphases are captured and quantification of the fluorescence ratios performed using a digital image analysis system. Regions of chromosomal gain are seen as an increased fluorescence ratio whereas regions of loss are seen as a decrease in the fluorescence ratio. Losses are detectable when the region affected exceeds 10 Mb (5), smaller regions of gain are detected if there is high level amplification, for example a 2-Mb region that is amplified five times will be visualized (6). For each tumor, 5/210 metaphases are analyzed and an average fluorescence ratio for each chromosome obtained.
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The seminal 'two-hit hypothesis' implicitly assumes that bi-allelic tumour suppressor gene (TSG) mutations cause loss of protein function. All subsequent events in that tumour therefore take place on an essentially null background for that TSG protein. We have shown that the two-hit model requires modification for the APC TSG, because mutant APC proteins probably retain some function and the two hits are co-selected to produce an optimal level of Wnt activation. We wondered whether the optimal Wnt level might change during tumour progression, leading to selection for more than two hits at the APC locus. Comprehensive screening of a panel of colorectal cancer (CRC) cell lines and primary CRCs showed that some had indeed acquired third hits at APC. These third hits were mostly copy number gains or deletions, but could be protein-truncating mutations. Third hits were significantly less common when the second hit at APC had arisen by copy-neutral loss of heterozygosity. Both polyploid and near-diploid CRCs had third hits, and the third hits did not simply arise as a result of acquiring a polyploid karyotype. The third hits affected mRNA and protein levels, with potential functional consequences for Wnt signalling and tumour growth. Although some third hits were probably secondary to genomic instability, others did appear specifically to target APC. Whilst it is generally believed that tumours develop and progress through stepwise accumulation of mutations in different functional pathways, it also seems that repeated targeting of the same pathway and/or gene is selected in some cancers.