The combined immunodetection of AP-2α and YY1 transcription factors is associated with ERBB2 gene overexpression in primary breast tumors

INTRODUCTION: Overexpression of the ERBB2 oncogene is observed in about 20% of human breast tumors and is the consequence of increased transcription rates frequently associated with gene amplification. Several studies have shown a link between activator protein 2 (AP-2) transcription factors and ERBB2 gene expression in breast cancer cell lines. Moreover, the Yin Yang 1 (YY1) transcription factor has been shown to stimulate AP-2 transcriptional activity on the ERBB2 promoter in vitro. In this report, we examined the relationships between ERBB2, AP-2alpha, and YY1 both in breast cancer tissue specimens and in a mammary cancer cell line. METHODS: ERBB2, AP-2alpha, and YY1 protein levels were analyzed by immunohistochemistry in a panel of 55 primary breast tumors. ERBB2 gene amplification status was determined by fluorescent in situ hybridization. Correlations were evaluated by a chi2 test at a p value of less than 0.05. The functional role of AP-2alpha and YY1 on ERBB2 gene expression was analyzed by small interfering RNA (siRNA) transfection in the BT-474 mammary cancer cell line followed by real-time reverse transcription-polymerase chain reaction and Western blotting. RESULTS: We observed a statistically significant correlation between ERBB2 and AP-2alpha levels in the tumors (p < 0.01). Moreover, associations were found between ERBB2 protein level and the combined high expression of AP-2alpha and YY1 (p < 0.02) as well as between the expression of AP-2alpha and YY1 (p < 0.001). Furthermore, the levels of both AP-2alpha and YY1 proteins were inversely correlated to ERBB2 gene amplification status in the tumors (p < 0.01). Transfection of siRNAs targeting AP-2alpha and AP-2gamma mRNAs in the BT-474 breast cancer cell line repressed the expression of the endogenous ERBB2 gene at both the mRNA and protein levels. Moreover, the additional transfection of an siRNA directed against the YY1 transcript further reduced the ERBB2 protein level, suggesting that AP-2 and YY1 transcription factors cooperate to stimulate the transcription of the ERBB2 gene. CONCLUSION: This study highlights the role of both AP-2alpha and YY1 transcription factors in ERBB2 oncogene overexpression in breast tumors. Our results also suggest that high ERBB2 expression may result either from gene amplification or from increased transcription factor levels

Different mechanisms are implicated in ERBB2 gene overexpression in breast and in other cancers

The ERBB2 gene is overexpressed in 30% of breast cancers and this has been correlated with poor prognosis. ERBB2 is upregulated in other cancers such as prostate, pancreas, colon and ovary. In breast cancer cells, the mechanisms leading to ERBB2 gene overexpression are increased transcription and gene amplification. In these cancers, AP-2 transcription factors are involved in ERBB2 overexpression, and AP-2 levels are correlated with p185(c-erbB-2) levels. In this work, we wanted to know if the same molecular mechanisms are responsible for the ERBB2 upregulation in non-breast cancers. We compared ERBB2 gene copy number, p185(c-erbB-2) and mRNA levels with AP-2 levels in several ovary, prostate, colon and pancreas cancer cells. A moderate expression of erbB-2 mRNA and protein were observed in some cells without gene amplification. In contrast to breast cancer cells, AP-2 factors were absent or low in some non-breast cells which did express ERBB2. It is thus likely that AP-2 is not a major player in the increased levels of erbB-2 transcripts in non-breast cancer cells. The transcriptional activity of the ERBB2 promoter in colon and ovary cancer cells was estimated using reporter vectors. The results showed that the promoter regions involved in ERBB2 gene overexpression in breast cancer cells are different from those that lead to the gene upregulation in colon and ovary cancers. In conclusion, our results indicate that different transcriptional and post-transcriptional mechanisms are responsible for the increased levels of erbB-2 transcript and protein in breast and non-breast cancer cells

Expression of the bovine growth hormone gene in cultured rodent cells.

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Expression of the bovine growth hormone in cultured rodent cells.

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Growth hormone gene expression in eucaryotic cells directed by the Rous aSrcoma viral long terminal repeat or cytomegalovirus immediate early promoter-regulator

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A comparison of bovine growth hormone expression directed by bGH genomic or intronless DNA in transiently transfected eukaryotic cells.

Two recombinant DNA plasmids were constructed with identical transcriptional and translational regulatory elements controlling expression of the bovine growth hormone (bGH) gene or the bGH gene lacking introns. Transient expression of these plasmids in cultured eukaryotic cells, monitored by assaying secretion of bGH into the culture medium, was employed to examine the relative importance of introns in the expression of this gene. The bGH gene lacking introns is expressed more efficiently than the bGH gene in avian and mammalian cells

Growth hormone gene expression in eukaryotic cells directed by the Rous sarcoma virus long terminal repeat or cytomegalovirus immediate-early promoter.

The cytomegalovirus (CMV) immediate-early (IE) gene-regulatory region was found to be three- to fourfold more efficient than the Rous sarcoma retroviral long terminal repeat (LTR) in promoting expression of the bovine growth hormone (bGH) gene by rat GH3 cells

Extragenital Endometriosis

Parietal, appendiceal, pleuropulmonary and diaphragmatic endometriosis represent 5% of endometriosis cases. Diagnosis and management of these extra-genital localisations are described according to the literature. Parietal endometriosis usually requires large resection of the tumor. Appendiceal endometriosis is frequently observed in cases of digestive endometriosis. Induration or rigidity of the appendix due to the presence of deep infiltrating endometriosis justifies appendicectomy. Thoracic and diaphragmatic endometriosis is characterized by the presence of typical symptoms during the perimenstrual periode. Medical treatment obtaining therapeutic amenorrhea is firstly administered and surgery is indicated in cases of symptoms recurrence

Expression of a synthetic gene encoding human insulin-like growth factor I in cultured mouse fibroblasts.

A synthetic gene encoding human insulin-like growth factor I (hIGF-I) was assembled and inserted into an expression vector containing the cytomegalovirus immediate early (CMV-IE) transcriptional regulatory region and portions of the bovine growth hormone gene. The recombinant plasmid encodes a 97 amino acid fusion protein containing the first 27 amino acids of the bovine growth hormone precursor and the 70 amino acids of hIGF-I. This plasmid, when transiently introduced into cultured mouse fibroblasts, directs synthesis of the fusion protein, subsequent proteolytic removal of the bovine growth hormone signal peptide, and secretion of hIGF-I into the culture medium. Conditioned medium from transfected cells inhibits binding of 125I-labeled IGF-I to type I IGF receptors on human placental membranes and to acid-stable human serum carrier proteins. The recombinant hIGF-I produced is biologically active, as monitored by the stimulation of DNA synthesis in vascular smooth muscle cells