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Gene expression in oestrogen-dependent human breast cancer xenograft tumours
A M Thompson1, C M Steel, M E Foster
1Department of Surgery, Royal Infirmary of Edinburgh, UK.
Abstract:
Xenograft tumours from an oestrogen-dependent human breast cancer cell line MCF-7 have been established and characterised in thymectomised, irradiated female CBA strain mice. There was evidence for selection in xenografts of a subpopulation of MCF-7 cells with an altered pattern of gene expression as measured by mRNA levels compared with the original cells in vitro. Tumorigenicity increased significantly on repeated animal passage but oestrogen dependence was retained. Following injection of the mice with oestrogen, mitosis was induced in the tumour cells with associated increases in thymidine uptake and percentage of cells in S-phase. In accord with these changes, c-myc and p53 expression were increased and TGF-beta was suppressed. Thereafter the expression of the c-myc and p53 genes fell whilst that of the TGF-beta gene was induced as the oestrogenic-stimulus declined. The oestrogen-regulated mRNA pS2 showed a biphasic response to oestrogen and levels declined as the serum oestrogen fell to undetectable levels. This xenograft system demonstrates that changes in transcription of oncogenes, growth factor and oestrogen-regulated genes can be detected in vivo in response to oestrogen. It thus provides an in vivo model for studies of the biochemical and molecular basis for therapeutic manipulation of hormone-sensitive human breast cancer.
Insights
This study establishes a novel xenograft model for human breast cancer (MCF-7 cells) in mice. The model effectively demonstrates in vivo gene expression changes in response to estrogen, aiding hormone-sensitive breast cancer research.
Area of Science:
- Oncology
- Molecular Biology
- Endocrinology
Background:
- Estrogen plays a crucial role in the growth and progression of hormone-sensitive breast cancers.
- Understanding the molecular mechanisms underlying estrogen's effects is vital for developing effective therapies.
- MCF-7 cells, an estrogen-dependent human breast cancer cell line, are widely used in research.
Purpose of the Study:
- To establish and characterize an in vivo xenograft model using MCF-7 cells in mice.
- To investigate the dynamic changes in gene expression in response to estrogen stimulation and withdrawal.
- To provide a platform for studying the molecular basis of hormone-sensitive breast cancer therapy.
Main Methods:
- Establishment and characterization of MCF-7 xenografts in thymectomized, irradiated female CBA mice.
- Monitoring tumor growth, estrogen dependence, and cell cycle progression (thymidine uptake, S-phase percentage).
- Quantification of mRNA levels for key genes including c-myc, p53, TGF-beta, and pS2 using molecular techniques.
Main Results:
- Xenografts showed increased tumorigenicity with passage but retained estrogen dependence.
- Estrogen administration induced mitosis, increased thymidine uptake, and S-phase percentage.
- Dynamic changes in gene expression were observed: c-myc and p53 increased with estrogen, while TGF-beta was suppressed; these reversed upon estrogen withdrawal. The estrogen-regulated gene pS2 exhibited a biphasic response.
Conclusions:
- The developed xenograft model accurately reflects in vivo transcriptional responses to estrogen in human breast cancer cells.
- This model allows for the detection of dynamic changes in oncogenes, growth factors, and estrogen-regulated genes.
- It serves as a valuable in vivo tool for investigating the molecular underpinnings of hormone-sensitive breast cancer and its therapeutic manipulation.