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Characterisation of a messenger RNA selectively expressed in human breast cancer
R A Skilton1, Y A Luqmani, R A McClelland
1Ludwig Institute for Cancer Research, St George's Hospital Medical School, London, UK.
Abstract:
A complementary DNA library from MCF-7 cells was screened using 32P-cDNA derived from a breast carcinoma and from normal breast tissue. From 10(5) plaques (20% of library) we obtained a clone (Md2) which was differentially expressed in the carcinoma. The distribution of its corresponding transcript of 6-700 nucleotides was examined in normal and neoplastic cells, by filter and in situ hybridisation. We observed localisation of 35S-Md2 to the tumour cells of breast cancers with no significant reaction over stromal or vascular elements or on normal ductal epithelia. M13 sequencing showed Md2 to be 250 nucleotides in length, of which 197 were homologous to the 3'-untranslated region and a short open reading frame of the pS2 gene (Masiakowski et al., 1982). Md2 mRNA was found principally in breast carcinoma cell lines and tumours, with low levels in benign breast disease and no expression in non-breast squamous cell lines. Approximately 43% (23/54) of carcinomas contained this mRNA (varying from + to + + + + level); it was present in 20/38 (53%) of ER positive carcinomas compared to 3/16 (19%) of ER negative carcinomas. In 21 patients who had undergone primary endocrine therapy for recurrent disease expression of Md2 in the primary tumour correlated with the subsequent response to treatment (P = 0.041) and was of similar predictive value as ER status. Both tests correctly predicted outcome in about 76% of cases.
Insights
A novel breast cancer marker, Md2, is highly expressed in tumors and predicts response to endocrine therapy. Md2 mRNA levels correlate with estrogen receptor status and treatment outcomes.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Breast cancer diagnosis and treatment rely on markers like estrogen receptor (ER) status.
- Identifying novel biomarkers for breast cancer is crucial for improving patient outcomes.
- The pS2 gene is known to be involved in breast cancer, but its specific role and related markers require further investigation.
Purpose of the Study:
- To identify and characterize novel genes differentially expressed in breast carcinoma.
- To investigate the expression pattern and diagnostic potential of the identified clone (Md2) in breast tissues.
- To evaluate the correlation between Md2 expression and response to endocrine therapy in breast cancer patients.
Main Methods:
- Screening of a complementary DNA (cDNA) library from MCF-7 cells using labeled cDNA from breast carcinoma and normal breast tissue.
- Differential screening to identify clone Md2, followed by Northern hybridization and in situ hybridization to analyze transcript distribution.
- M13 sequencing to determine the nucleotide sequence and homology of Md2.
- Analysis of Md2 mRNA expression in various breast cell lines, tumors, and benign breast disease samples.
- Correlation analysis of Md2 expression with ER status and response to endocrine therapy in patients with recurrent breast cancer.
Main Results:
- A differentially expressed clone, Md2, was identified and found to be homologous to the 3'-untranslated region and a short open reading frame of the pS2 gene.
- Md2 mRNA was predominantly localized to tumor cells in breast cancers, with minimal expression in normal breast tissue, stromal, or vascular elements.
- Md2 mRNA was frequently detected in breast carcinoma cell lines and tumors (43%), with higher prevalence in ER-positive (53%) compared to ER-negative (19%) carcinomas.
- Expression of Md2 in primary tumors significantly correlated with patient response to endocrine therapy for recurrent disease (P = 0.041).
- Md2 expression demonstrated a predictive value for treatment response similar to ER status, with both correctly predicting outcomes in approximately 76% of cases.
Conclusions:
- Md2 represents a novel biomarker for breast cancer, showing specific expression in tumor cells.
- Md2 mRNA levels are associated with ER status and can serve as a predictive marker for response to endocrine therapy.
- The findings suggest that Md2 could be a valuable addition to existing prognostic and predictive tools in breast cancer management.