Biomedical subjects

Namrata Bose

Publications and source records attributed to Namrata Bose.

3 recordsLinked to original sources

PubMed2006

The Akt pathway in human breast cancer: a tissue-array-based analysis.

The Akt pathway, an important regulator of cell proliferation and survival, is deregulated in many cancers. The pathway has achieved considerable importance due to the development of kinase inhibitors that are able to successfully reduce tumor growth. This study was conducted to determine the status of the Akt pathway in human breast cancers and to study the relationship between the different component proteins. Expression levels of PTEN, phosphorylated forms of the constituent proteins (Akt, FKHR, mTOR, and S6) and cyclin D1 were evaluated by immunohistochemistry, on consecutive sections from a tissue microarray containing 145 invasive breast cancers and 140 pure ductal carcinomas in-situ. Aberrant expression was correlated statistically with tumor characteristics and disease outcome. The Akt pathway was found to be activated early in breast cancer, in the in-situ stage. In all, 33, 15, 32, and 60% of ductal carcinoma in-situ showed overexpression of Akt, FKHR, mTOR, and cyclin D1. PTEN loss did not correlate statistically with expression of AKT or any of the other proteins with the exception of S6, indicating that Akt activation was not a result of PTEN loss. Expression levels of PTEN and S6 were significantly different in in-situ and invasive cancers, indicating association with disease progression. Loss of PTEN was noted in 11% of in-situ as compared to 26% of invasive cancers, while S6 overexpression was seen in 47% in-situ and in 72% invasive cancers. High-grade carcinomas were associated with PTEN loss, while low-grade carcinomas with good prognostic features showed cyclin D1 overexpression and were associated with longer disease free survival. Additionally, cancers with mTOR overexpression showed a three times greater risk for disease recurrence. Overall, a large proportion of in-situ and invasive breast cancers overexpressed cyclinD1 and S6. Our results may have significant implications in the development and application of targeted therapy.

Breast Neoplasms↗

PubMed2005

Down-regulation and growth inhibitory role of C/EBPalpha in breast cancer.

PURPOSE: CCAAT/enhancer binding proteins (C/EBP) are a family of transcription factors that regulate proliferation and differentiation in a variety of tissues. The purpose of this study was to explore the possibility that C/EBPalpha is involved in breast cancer. EXPERIMENTAL DESIGN: We quantified C/EBPalpha mRNA expression levels in 24 primary breast tumors, 16 normal breast samples, and 8 breast cancer cell lines using quantitative real-time reverse transcription-PCR assay. C/EBPalpha protein levels were further determined by immunohistochemical analysis. To examine the consequence of C/EPBalpha expression in breast cancer, we stably transfected an inducible C/EPBalpha expression vector into three breast cancer cell lines. RESULTS: Low expression of C/EBPalpha mRNA was found in 83% of primary breast cancer samples. Immunohistochemical study further showed either a markedly reduced or undetectable expression of C/EBPalpha protein in 30% of breast cancer specimens. The other 70% of breast cancers had C/EBPalpha expression in both the cytoplasm and nucleus; in control, C/EBPalpha was localized to the nucleus in the normal ductal cells. C/EBPalpha expression was associated with estrogen- and progesterone receptor-negative status. Induction of C/EBPalpha expression in these cell lines resulted in growth inhibition accompanied by G0-G1 cell cycle arrest and reduced anchorage-independent cell growth. C/EBPalpha expression was associated with down-regulation of c-myc and up-regulation of p21, PPARgamma, and the breast epithelial differentiation marker, maspin. CONCLUSIONS: These results suggest that reduced expression of C/EBPalpha may play a role in the development and/or progression of breast cancer.

Blotting, Western↗

PubMed2004

PTEN promoter is methylated in a proportion of invasive breast cancers.

The PTEN protein is a negative regulator of the Akt pathway, leading to suppression of apoptosis and increased cell survival. Its role as a tumor-suppressor gene has been adequately substantiated, and homozygous mutations have been demonstrated in familial and sporadic cancers. In breast cancers, expression of PTEN protein is lost/reduced in 38% of cases. Somatic mutations are, however, rarely found. Our study was therefore designed to determine if differential methylation of the PTEN promoter region has a role in the transcriptional inactivation of the gene in invasive breast carcinomas. A total of 44 samples of invasive human breast cancer, 5 breast cancer cell lines and 16 samples of normal human breast tissue from young and elderly women were studied for methylation of the PTEN promoter by methylation-specific PCR and PTEN protein expression by immunohistochemistry. PTEN methylation occurred in 34% of breast cancers, and 60% of these samples were associated with loss of PTEN protein. Analyzed from a different perspective, 34% of breast cancers had reduced expression of PTEN and 60% had a methylated PTEN promoter. None of the breast cancer cell lines and normal breast tissues showed methylation. In summary, methylation of the PTEN promoter leads to PTEN inactivation in a subset of human breast cancers.

Adult↗