RESUMO
The mitogenic and anti-apoptotic effects of insulin-like growth factor-I (IGF-I) are regulated by a family of insulin-like growth factor binding proteins (IGFBPs), particularly IGFBP-3. Little is known about the IGF-independent role of IGFBP-3 in breast cancer and the mechanisms regulating its production. The expression of IGFBP-3 in paired malignant and adjacent normal (n=53), and healthy normal (n=17) breast tissue samples was investigated using RT-PCR, immunohistochemistry and ELISA. We compared IGFBP-3 expression with other members of the IGF-I axis, other known tumorigenic genes and clinicopathological parameters. We also developed a novel tissue explant system using fresh normal and malignant breast tissue, with which we examined the in vitro effects of IGFBP-3 alone and in combination with known apoptotic agent, doxorubicin (n=6), on tissue viability and apoptosis. We demonstrated a high level of expression of IGFBP-3 mRNA in all samples. 96% of samples also expressed IGFBP-3 protein. No significant correlation was seen between IGFBP-3 expression and other clinicopathological parameters. The in vitro tissue explant system demonstrated that IGFBP-3 had little effect by itself on apoptosis. However, when used in combination with doxorubicin, increased apoptosis was seen in tumours. In contrast, less apoptosis was seen in normal tissue suggesting a protective effect. These divergent effects suggest a potential novel chemotherapeutic approach in the treatment of breast cancer. These findings suggest that IGFBP-3 may play a role in tumorigenesis, and that IGFBP-3 levels could be used in the future in cancer risk assessment/prevention or as markers of response to cancer treatments.
Assuntos
Neoplasias da Mama/metabolismo , Mama/metabolismo , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/fisiologia , Biomarcadores Tumorais/biossíntese , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/fisiologia , Mama/citologia , Mama/fisiologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Ciclo-Oxigenase 2/biossíntese , Ciclo-Oxigenase 2/genética , Doxorrubicina/farmacologia , Células Epiteliais/metabolismo , Células Epiteliais/fisiologia , Feminino , Humanos , Imuno-Histoquímica , Proteína 3 de Ligação a Fator de Crescimento Semelhante à Insulina , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/biossíntese , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/genética , Fator de Crescimento Insulin-Like I/biossíntese , Fator de Crescimento Insulin-Like I/genética , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Células Estromais/metabolismo , Células Estromais/fisiologia , Técnicas de Cultura de Tecidos , Fator A de Crescimento do Endotélio Vascular/biossíntese , Fator A de Crescimento do Endotélio Vascular/genéticaRESUMO
AIMS: The purpose of this study was to evaluate COX-2 mRNA expression with known clinical prognostic features of breast cancer, oestrogen/progesterone receptor status, tumour size and grade. METHODS: Total RNA was extracted from 45 frozen breast tumour (invasive) and 22 normal breast tissue samples. COX-2 mRNA transcription was quantified using a real time RT-PCR assay and expressed as copy number/microg total RNA. All specimens were assessed for tumour grade, size, nodal status and presence of vascular invasion and oestrogen and progesterone receptor status. RESULTS: COX-2 mRNA was detected in all samples with a median copy number of 1.15 x 10(7) for tumours and 6.5 x 10(6) for normal samples. Expression was significantly higher in oestrogen receptor negative tumours compared to the receptor positive group. There was no correlation between COX-2 mRNA levels and tumour size, grade, nodal status and presence of vascular invasion. CONCLUSIONS: COX-2 mRNA expression is increased in oestrogen and progesterone receptor negative breast cancers.
