RESUMO
Genetic testing of an Irish kindred identified an exonic nucleotide substitution c.1664T>C (p.Leu555Pro) in the MLH1 mismatch repair (MMR) gene. This previously unreported variant is classified as a "variant of uncertain significance" (VUS). Immunohistochemical (IHC) analysis and microsatellite instability (MSI) studies, genetic testing, a literature and online MMR mutation database review, in silico phenotype prediction tools, and an in vitro MMR activity assay were used to study the clinical significance of this variant. The MLH1 c.1664T>C (p.Leu555Pro) VUS co-segregated with three cases of classic Lynch syndrome-associated malignancies over two generations, with consistent loss of MLH1 and PMS2 protein expression on IHC, and evidence of the MSI-High mutator phenotype. The leucine at position 555 is well conserved across a number of species, and this novel variant has not been reported as a normal polymorphism in the general population. In silico and in vitro analyses suggest that this variant may have a deleterious effect on the MLH1 protein and abrogate MMR activity. Evidence from clinical, histological, immunohistochemical, and molecular genetic data suggests that MLH1 c.1664T>C (p.Leu555Pro) is likely to be the pathogenic cause of Lynch syndrome in this family.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Adenosina Trifosfatases/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo de Erro de Pareamento de DNA/genética , Enzimas Reparadoras do DNA/genética , Proteínas de Ligação a DNA/genética , Mutação/genética , Proteínas Nucleares/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Adenosina Trifosfatases/metabolismo , Adulto , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Enzimas Reparadoras do DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Feminino , Seguimentos , Humanos , Técnicas Imunoenzimáticas , Masculino , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Endonuclease PMS2 de Reparo de Erro de Pareamento , Análise Multivariada , Proteína 1 Homóloga a MutL , Estadiamento de Neoplasias , Proteínas Nucleares/metabolismo , Linhagem , Fenótipo , Prognóstico , Adulto JovemRESUMO
BACKGROUND: Critical to successful execution of mitochondrial-mediated apoptosis is apoptosome formation and subsequent activation of caspases. Defects in this pathway have an important role in colorectal carcinogenesis and chemoresistance; therefore, the expression of apoptosome-associated proteins may be associated with clinical outcome and response to chemotherapy. METHODS: Here we performed a systematic analysis of the immunohistochemical expression of the key proteins involved in apoptosome-dependent caspase activation (APAF1, Pro-caspases 9 and 3, SMAC, and XIAP) in a cohort of Stage II and III colorectal cancer patients from a Phase III trial of adjuvant 5-fluorouracil-based chemotherapy vs postoperative observation alone. RESULTS: Survival analysis indicated that of the apoptosome-associated proteins examined here, Pro-caspase 3 and APAF1 have potential clinical utility as predictive markers in Stage II and III colorectal cancer, respectively. Interestingly, we identified APAF1 staining to be associated with better recurrence-free and overall survival in patients receiving chemotherapy. CONCLUSION: These studies reveal the importance of the apoptosome-dependent caspase activation pathway, specifically Pro-caspase 3 and APAF1 proteins, for predicting both prognosis and response to therapy.
Assuntos
Apoptose , Apoptossomas/metabolismo , Caspases/metabolismo , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Idoso , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Quimioterapia Adjuvante , Ensaios Clínicos Fase III como Assunto , Neoplasias Colorretais/tratamento farmacológico , Ativação Enzimática , Feminino , Fluoruracila/administração & dosagem , Humanos , Técnicas Imunoenzimáticas , Leucovorina/administração & dosagem , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Prognóstico , Análise Serial de TecidosRESUMO
PURPOSE: To investigate the effect of irradiating microcolonies of various sizes on their subsequent ability to form colonies. MATERIALS AND METHODS: The location of individual HPV-G cells in tissue culture flasks was recorded using computerized microscopy. This allowed the cells' positions to be continually revisited, which enabled manual sizing of individual microcolonies both at the time of irradiation (between 0-5 Gy) and following an incubation period during which the microcolonies were assessed for cologenic survival. RESULTS: The experiments indicate that when irradiated as microcolonies, cells have plating efficiencies (PE) that are lower than expected when compared with the prediction from the PE values of cells irradiated individually. CONCLUSION: These data support the conclusions of Mothersill and Seymour (1997b) which challenge the concept of independent survival of certain types of cells following irradiation. The results indicate that interactions between cells can occur even in small aggregates.
