RESUMO
Down-regulation of gelsolin, an actin-binding protein, is frequently found in several types of transformed cells and tumors. The present study demonstrates that gelsolin protein and RNA were absent or markedly reduced in human breast cancer cell lines relative to "normal" mortal human mammary epithelial cells and benign, immortalized cell lines. Moreover, actin filaments were usually attenuated coincident with the reduction in gelsolin. Gelsolin was also missing or greatly decreased in 70% of 30 human sporadic, invasive breast carcinomas examined by immunocytochemistry and in 100% of virally induced mouse and chemically induced rat mammary carcinomas evaluated by Northern analysis. Southern analysis revealed no major mutations in the gelsolin gene of human breast cancer cells. Our results show that partial or total loss of gelsolin expression is common to the majority of breast cancers of diverse etiologies in three animal species and point to gelsolin as a candidate suppressor of breast cancer.
Assuntos
Neoplasias da Mama/química , Gelsolina/análise , Neoplasias Mamárias Experimentais/química , Actinas/análise , Animais , Mama/química , Gelsolina/genética , Humanos , Glândulas Mamárias Animais/química , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Fosfolipase D/metabolismo , RNA Mensageiro/análise , Ratos , Ratos Sprague-Dawley , Transdução de Sinais , Células Tumorais CultivadasRESUMO
A placenta-specific gene, MIPP, is transcriptionally regulated in BALB/c mice by a solo long terminal repeat (LTR) of an intracisternal A-particle (IAP), an endogenous retrotransposon. Expression of IAPs, which is also promoted by LTR sequences, is a frequent aberration in many mouse mammary tumors of BALB/c mice. Given that these retroelements and the placental gene have a common promoter, we hypothesized that the tumors also express the gene. Northern blot analysis and RT-PCR revealed high expression of the placenta-specific gene in BALB/c mouse mammary preneoplasias and carcinomas of diverse etiologies, but not in normal mammary gland from virgin, pregnant and lactating mice. The preneoplasias and tumors expressed two transcripts, one of which is apparently unique to the mammary lesions. The other transcript is the same as one expressed in placenta that is not promoted by the IAP LTR. Despite the parallel expression of the placental gene and IAPs in the mammary tissues, RT-PCR showed that LTR sequences are absent from tumor-associated MIPP transcripts. Southern analysis revealed no gross mutations of the MIPP gene in mammary preneoplasias and tumors. The ectopic expression of the placenta-specific gene in BALB/c mouse mammary preneoplasias and carcinomas raises the possibility that it acts as an oncogene.
Assuntos
Genes de Partícula A Intracisternal , Neoplasias Mamárias Experimentais/genética , Placenta/fisiologia , Proteínas da Gravidez/genética , Animais , Sequência de Bases , Northern Blotting , Feminino , Humanos , Neoplasias Mamárias Experimentais/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Dados de Sequência Molecular , Especificidade de Órgãos , Gravidez , Proteínas da Gravidez/biossíntese , Sequências Repetitivas de Ácido Nucleico , RetroelementosRESUMO
Endogenous murine leukemia virus-related elements (MLVEs) are often overexpressed in primary mammary carcinomas of BALB/c mice. We therefore searched for mutations associated with MLVEs and found amplified sequences of the ecotropic MLVE in hormonally and chemically induced mammary neoplasms. Restriction fragment length polymorphism (RFLP) analysis revealed DNA rearrangements consistent with 1-10 or more new copies of the ecotropic MLVE in the genome of these tumors. This is the first evidence of mutations involving an endogenous retrovirus other than mouse mammary tumor virus in mouse mammary carcinomas.
Assuntos
Vírus da Leucemia Murina/genética , Neoplasias Mamárias Experimentais/virologia , Mutação , 9,10-Dimetil-1,2-benzantraceno , Animais , Carcinógenos , Cocarcinogênese , DNA de Neoplasias/genética , DNA Viral/genética , Feminino , Amplificação de Genes , Glândulas Mamárias Animais/efeitos dos fármacos , Glândulas Mamárias Animais/virologia , Neoplasias Mamárias Experimentais/induzido quimicamente , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Neoplasias Hormônio-Dependentes/virologia , Polimorfismo de Fragmento de Restrição , GravidezRESUMO
Amplified expression of the endogenous retrotransposons, intracisternal A particles (IAPs) and murine leukemia virus-related elements (MLVEs), along with decreased expression of VL30 elements frequently occurs during mouse mammary tumorigenesis. We have now analyzed the expression of these retroelements during the normal developmental and differentiation cycle of the mammary gland as found in virgin, pregnant, lactating, and postlactation adult female BALB/c mice. Retrotransposon expression was either unchanged or decreased during the progressive stages of the cycle compared to virgin tissue. Likewise, growth of mammary epithelial cells in primary culture had little or no effect on expression of IAPs, MLVEs and VL30 sequences. Thus, the dramatic changes involving these retrotransposons in many mouse mammary tumors appear unrelated to any normal state.
