RESUMEN
The genetic events underlying the development of prostate cancer are poorly defined. c-Myc is often activated in tumors that have progressed to metastatic status, so events that promote this process may be important. Bin1 is a nucleocytoplasmic adaptor protein with features of a tumor suppressor that was identified through its ability to interact with and inhibit malignant transformation by c-Myc. We investigated a role for Bin1 loss or inactivation in prostate cancer because the human Bin1 gene is located at chromosome 2q14 within a region that is frequently deleted in metastatic prostate cancer but where no tumor suppressor candidate has been located. A novel polymorphic microsatellite marker located within intron 5 of the human Bin1 gene was used to demonstrate loss of heterozygosity and coding alteration in 40% of informative cases of prostate neoplasia examined. RNA and immunohistochemical analyses indicated that Bin1 was expressed in most primary tumors, even at slightly elevated levels relative to benign tissues, but that it was frequently missing or inactivated by aberrant splicing in metastatic tumors and androgen-independent tumor cell lines. Ectopic expression of Bin1 suppressed the growth of prostate cancer lines in vitro. Our findings support the candidacy of Bin1 as the chromosome 2q prostate tumor suppressor gene.
Asunto(s)
Proteínas Portadoras/genética , Genes Supresores de Tumor , Pérdida de Heterocigocidad , Proteínas Nucleares/genética , Neoplasias de la Próstata/genética , Proteínas Supresoras de Tumor , Proteínas Adaptadoras Transductoras de Señales , Adenocarcinoma/genética , Empalme Alternativo , Northern Blotting , Genes myc , Humanos , Inmunohistoquímica , Intrones , Masculino , Repeticiones de Microsatélite , Neoplasia Intraepitelial Prostática/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales CultivadasRESUMEN
Bin1 is a nucleocytoplasmic adaptor protein and tumor suppressor. A novel protein termed Bau was identified through its ability to interact with a region of Bin1 required to inhibit malignant cell transformation by certain oncogenes. Bau is a splice form of Neurabin-I, one of two related F-actin-binding proteins that are proposed to link cadherin-based cell-cell adhesion sites with the growth regulatory kinase p70S6K. Bau lacks actin- and p70S6K-binding domains found in Neurabin-I but includes coiled-coil domains that are part of its central domain as well as additional sequences not found in Neurabin-I. Interaction with Bin1 requires the presence of the U3 region which is alternately spliced in muscle cells. Bau localizes to the nucleus and cytosol. Like Bin1, Bau can suppress oncogene-mediated transformation and inhibit tumor cell growth. We suggest that Bau may link Bin1 to the Neurabin-I/p70S6K system in muscle and other cells, perhaps providing a mechanism to influence adhesion-dependent signals which affect cell fate.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Empalme Alternativo , Proteínas Portadoras/metabolismo , Transformación Celular Neoplásica , Genes Supresores de Tumor , Proteínas de Microfilamentos/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Supresoras de Tumor , Secuencia de Aminoácidos , Animales , Células COS , División Celular , Núcleo Celular/metabolismo , Citosol/metabolismo , Humanos , Ratones , Proteínas de Microfilamentos/genética , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso/genética , Células Tumorales CultivadasRESUMEN
We cloned and functionally characterized the murine Bin1 gene as a first step to investigate its physiological roles in differentiation, apoptosis, and tumorigenesis. The exon-intron organization of the >/=55-kb gene is similar to that of the human gene. Consistent with a role for Bin1 in apoptosis, the promoter included a functional consensus motif for activation by NF-kappaB, an important regulator of cell death. A muscle regulatory module defined in the human promoter that includes a consensus recognition site for myoD family proteins was not conserved in the mouse promoter. However, Bin1 is upregulated in embryonic development by E10.5 in myotomes, the progenitors of skeletal muscle, supporting a role in myogenesis and suggesting that the mouse and human genes may be controlled somewhat differently during development. In C2C12 myoblasts antisense Bin1 prevents induction of the cell cycle kinase inhibitor p21WAF1, suggesting that it acts at an early time during the muscle differentiation program. Interspecific mouse backcross mapping located the Bin1 locus between Mep1b and Apc on chromosome 18. Since the human gene was mapped previously to chromosome 2q14, the location of Bin1 defines a previously unrecognized region of synteny between human chromosome 2 and mouse chromosome 18.