RESUMO
BACKGROUND: To assess the predictive value of early metabolic response (ΔSUV) after short-term treatment with first-line cetuximab in patients (pts) with RAS-wt metastatic colorectal cancer (mCRC). METHODS: In this prospective phase II study, RAS-wt mCRC pts received a single-agent cetuximab run-in therapy of 2 weeks. ΔSUV was assessed with FDG-PET/CT on days 0 and 14. Early clinical response (ECR) was evaluated with CT on day 56 after treatment with FOLFIRI-cetuximab. Primary endpoint was the predictive significance of ΔSUV for ECR. Secondary endpoints were PFS (progression free survival), OS and the influence of ΔSUV on survival. RESULTS: Forty pts were enroled and 33 pts were evaluable for the primary endpoint. The CT response rate was 57.6%. For responders, ΔSUV was significantly higher (p = 0.0092). A significant association of ΔSUV with ECR was found (p = 0.02). Median PFS was 11.7 months and median OS was 33.5 months with a 1-year survival rate of 87.9%. ΔSUV was found to significantly impact the hazard for OS (p = 0.045). CONCLUSIONS: We demonstrate that cetuximab induces metabolic responses in mCRC pts. The study endpoint was met with the ΔSUV discriminating between responders and non-responders. However, these data should be validated in larger patient cohorts.
Assuntos
Cetuximab/administração & dosagem , Neoplasias Colorretais/diagnóstico por imagem , Neoplasias Colorretais/tratamento farmacológico , Adulto , Idoso , Camptotecina/administração & dosagem , Cetuximab/efeitos adversos , Cetuximab/metabolismo , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Feminino , Fluordesoxiglucose F18/administração & dosagem , Fluoruracila/administração & dosagem , Humanos , Leucovorina/administração & dosagem , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Intervalo Livre de Progressão , Estudos ProspectivosRESUMO
Processing of primary transcripts in trypanosomes requires trans splicing and polyadenylation, and at least for the poly(A) polymerase gene, also internal cis splicing. The trypanosome U1 snRNA, which is most likely a cis-splicing specific component, is unusually short and has a relatively simple secondary structure. Here, we report the identification of three specific protein components of the Trypanosoma brucei U1 snRNP, based on mass spectrometry and confirmed by in vivo epitope tagging and in vitro RNA binding. Both T.brucei U1-70K and U1C are only distantly related to known counterparts from other eukaryotes. The T.brucei U1-70K protein represents a minimal version of 70K, recognizing the first loop sequence of U1 snRNA with the same specificity as the mammalian protein. The trypanosome U1C-like protein interacts with 70K directly and binds the 5' terminal sequence of U1 snRNA. Surprisingly, instead of U1A we have identified a novel U1 snRNP-specific protein, TbU1-24K. U1-24K lacks a known RNA-binding motif and integrates in the U1 snRNP via interaction with U1-70K. These data result in a model of the trypanosome U1 snRNP, which deviates substantially from our classical view of the U1 particle and may reflect the special requirements for splicing of a small set of cis-introns in trypanosomes.
Assuntos
Proteínas de Protozoários/química , RNA Nuclear Pequeno/metabolismo , Ribonucleoproteína Nuclear Pequena U1/química , Trypanosoma brucei brucei/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Células Cultivadas , Análise Mutacional de DNA , Espectrometria de Massas , Modelos Genéticos , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , RNA de Protozoário/química , RNA de Protozoário/metabolismo , RNA Nuclear Pequeno/química , Ribonucleoproteína Nuclear Pequena U1/genética , Ribonucleoproteína Nuclear Pequena U1/metabolismoAssuntos
Mieloma Múltiplo , Transplante de Células-Tronco , Idoso , Autoenxertos , Intervalo Livre de Doença , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Mieloma Múltiplo/classificação , Mieloma Múltiplo/mortalidade , Mieloma Múltiplo/terapia , Estudos Retrospectivos , Taxa de SobrevidaAssuntos
Splicing de RNA , RNA Mensageiro/metabolismo , RNA Nuclear Pequeno/genética , Trypanosoma brucei brucei/genética , Animais , Sequência de Bases , Dados de Sequência Molecular , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , RNA Mensageiro/genética , RNA Nuclear Pequeno/químicaRESUMO
Messenger RNA processing in trypanosomes by cis and trans splicing requires spliceosomal small nuclear ribonucleoproteins (snRNPs) U1, U2, U4/U6, and U5, as well as the spliced leader (SL) RNP. As in other eukaryotes, these RNPs share a core structure of seven Sm polypeptides. Here, we report that the identity of the Sm protein constituents varies between spliceosomal snRNPs: specifically, two of the canonical Sm proteins, SmB and SmD3, are replaced in the U2 snRNP by two novel, U2 snRNP-specific Sm proteins, Sm15K and Sm16.5K. We present a model for the variant Sm core in the U2 snRNP, based on tandem affinity purification-tagging and in vitro protein-protein interaction assays. Using in vitro reconstitutions with canonical and U2-specific Sm cores, we show that the exchange of two Sm subunits determines discrimination between individual Sm sites. In sum, we have demonstrated that the heteroheptameric Sm core structure varies between spliceosomal snRNPs, and that modulation of the Sm core composition mediates the recognition of small nuclear RNA-specific Sm sites.
Assuntos
Autoantígenos/metabolismo , Proteínas de Protozoários/metabolismo , Ribonucleoproteína Nuclear Pequena U2/metabolismo , Ribonucleoproteínas Nucleares Pequenas/metabolismo , Spliceossomos/metabolismo , Trypanosoma brucei brucei/metabolismo , Sequência de Aminoácidos , Animais , Autoantígenos/química , Sequência de Bases , Sítios de Ligação , Modelos Biológicos , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Ligação Proteica , Proteínas de Protozoários/química , RNA Nuclear Pequeno/química , RNA Nuclear Pequeno/genética , Ribonucleoproteínas Nucleares Pequenas/química , Alinhamento de Sequência , Especificidade por Substrato , Proteínas Centrais de snRNPRESUMO
Recent structures of the heterodimeric splicing factor U2 snRNP auxiliary factor (U2AF) have revealed two unexpected examples of RNA recognition motif (RRM)-like domains with specialized features for protein recognition. These unusual RRMs, called U2AF homology motifs (UHMs), represent a novel class of protein recognition motifs. Defining a set of rules to distinguish traditional RRMs from UHMs is key to identifying novel UHM family members. Here we review the critical sequence features necessary to mediate protein-UHM interactions, and perform comprehensive database searches to identify new members of the UHM family. The resulting implications for the functional and evolutionary relationships among candidate UHM family members are discussed.