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E Leygue

Publications and source records attributed to E Leygue.

36 records · Page 2Linked to original sources
PubMed1999

Oestrogen receptor-alpha variant mRNA expression in primary human breast tumours and matched lymph node metastases.

We have shown previously that the relative expression of a truncated oestrogen receptor-alpha variant mRNA (ER clone 4) is significantly increased in axillary node-positive primary breast tumours compared with node-negative tumours. In this study, we have examined the relative expression of clone 4-truncated, exon 5-deleted and exon 7-deleted oestrogen receptor-alpha variant mRNAs in 15 primary breast tumour samples and in synchronous axillary lymph node metastases. Overall, there were no significant differences between the primary tumours and the matched metastases in the relative expression of these three specific variant mRNAs. Furthermore, the pattern of all deleted oestrogen receptor-alpha variant mRNAs appeared conserved between any primary and its matched secondary tumour.

Breast Neoplasms↗
PubMed1999

Altered expression of exon 6 deleted progesterone receptor variant mRNA between normal human breast and breast tumour tissues.

The progesterone receptor (PR) is an important prognostic marker in breast cancer as well as a marker of responsiveness to endocrine therapies. The presence of several exon-deleted PR variant mRNAs in both normal and neoplastic breast samples has recently been reported. Amongst them, a variant mRNA deleted in exon 6 (D6-PR mRNA) that if translated would encode a truncated PR-like protein missing the hormone binding domain and one of the transactivating domains of the wild-type PR protein. In order to determine whether changes in D6-PR variant expression could occur during tumorigenesis, its expression was investigated by reverse transcription and polymerase chain reaction in ten normal reduction mammoplasty samples, nine breast tumours with high PR levels (> 100 fmol mg(-1) protein) and eight breast tumours with low PR levels (< 15 fmol mg(-1) protein), as determined by ligand binding assay. The relative expression of D6-PR to wild-type PR mRNA was lower (P< 0.01 ) in normal than in all tumour breast samples. Moreover, a trend to lower (P < 0.1) relative D6-PR expression was observed in high PR tumours, compared to low PR tumours. These data suggest that increased expression of D6-PR occurs during tumorigenesis.

Adult↗
PubMed1999

Variant estrogen receptor-alpha messenger RNA expression in hormone-independent human breast cancer cells.

T5-PRF cells are insensitive to the growth-stimulatory effects of estrogen while still retaining expression of estrogen receptor-alpha (ER-alpha). In the apparent absence of ligand, T5-PRF cells have a 3. 6+/-0.5 (s.e.m.)-fold increased basal ER-alpha activity and elevated basal progesterone receptor levels compared with the parent, estrogen-sensitive, T5 cells. Long-range ER-alpha reverse transcription-PCR was performed to characterize variant ER-alpha mRNA expression in the two cell lines. An increased relative expression of an exon 3/4-deleted ER-alpha mRNA variant was found in T5-PRF. Recombinant expression of this ER-alpha variant resulted in significantly increased estrogen responsiveness, as well as a trend to increased basal ligand-independent activity when expressed with wild-type ER-alpha in ER-negative cell lines, as well as significantly increasing both ligand-independent and estrogen-induced ER-alpha transcriptional activity when expressed in parental T5 cells. These results suggest a role for altered variant ER-alpha in ligand-independent activation of ER-alpha which may contribute to hormone independence in breast tumors.

Breast Neoplasms↗
PubMed1999

The human orphan receptor PXR messenger RNA is expressed in both normal and neoplastic breast tissue.

The expression of PXR mRNA and a variant PXR mRNA, deleted in 111 nucleotides in the ligand-binding domain, was detected by reverse transcription-PCR amplification in both normal and neoplastic human breast tissues. The level of PXR mRNA did not differ between breast tumors and their adjacent matched normal breast tissues. However, the expression of PXR mRNA did vary among breast tumors. A statistically significant inverse relationship was found between the level of PXR mRNA expression and estrogen receptor (ER) status, as defined by ligand binding analysis. The level of PXR mRNA expression in ER+ tumors (median = 22.4, n = 15) was significantly lower (P = 0.04) than the level of PXR mRNA expression in ER-tumors (median = 46.7, n = 15). No relationship with progesterone receptor status was found. These data raise the possibility that PXR has a role in human breast tissues.

Alternative Splicing↗
PubMed1998

Altered estrogen receptor alpha and beta messenger RNA expression during human breast tumorigenesis.

Using a multiplex reverse transcription-PCR assay, we compared the relative expression of estrogen receptor (ER) alpha and ER-beta mRNA between adjacent samples of normal breast tissue and matched primary breast tumors obtained from 18 different patients. Within this cohort, 7 tumors were ER negative, and 11 tumors were ER positive, as determined by the ligand binding assay. No differences in the ratio of ER-alpha:ER-beta expression were observed in the ER-negative cohort. However, in the ER-positive cohort, a significantly (P < 0.02) higher ER-alpha:ER-beta ratio was observed in the tumor compared with that of the normal tissue component. Our data revealed that the increase in the ER-alpha:ER-beta ratio was due primarily to a significant (P < 0.05) increase in ER-alpha mRNA expression in conjunction with a lower ER-beta mRNA expression in the tumor compared with that of the normal compartment in some, but not all, ER-positive cases. These results suggest that the role of ER-alpha- and ER-beta-driven pathways and/or their interaction change during breast tumorigenesis.

Breast↗
PubMed1998

Expression of lumican in human breast carcinoma.

Lumican mRNA has been identified as being differentially expressed between different regions of the same human breast tumor. In situ hybridization study of 26 independent breast tumors confirmed the presence of lumican mRNA in fibroblast-like cells within stroma and showed a significant increase of its expression in tumor compared to adjacent normal stroma (P < 0.001). Higher lumican expression was associated with higher tumor grade, lower estrogen receptor levels in the tumor, and younger age of the patients (P < 0.05). Reverse transcription-PCR analysis of total RNA extracted from 19 independent breast tissues exhibiting lesions that are thought to parallel tumor progression also suggests that this proteoglycan is differentially expressed during tumor progression.

Adult↗
PubMed1998

Estrogen receptor-beta mRNA variants in human and murine tissues.

Estrogen receptor (ER)-beta mRNA splice variants have been identified in human breast tumors as well as normal human and mouse ovarian, uterine and mammary tissues. In both species transcripts deleted in exons 5 or 6, or 5 + 6 have been characterized by RT-PCR followed by cloning and sequencing. In mouse tissues an ER-beta transcript containing 54 nucleotides inserted in frame between exons 5 and 6 was identified. Interestingly, no equivalent of the mouse inserted transcript was detected in any of the four human tissues analyzed.

Amino Acid Sequence↗
PubMed1998

The pathophysiological role of estrogen receptor variants in human breast cancer.

The accumulated evidence supports the expression of estrogen receptor variants at both the mRNA and protein levels. The relative level of expression of some estrogen receptor variant mRNAs and possibly progesterone receptor variant mRNAs is altered during breast tumorigenesis and breast cancer progression. The altered expression of estrogen receptor variants may effect estrogen signal transduction as well as the interpretation of assays where the estimation of estrogen receptor levels is used as a guide to treatment strategies and prognosis.

Breast Neoplasms↗
PubMed1997

Estrogen receptor variants and mutations.

There is a large and increasing body of experimental and clinical data supporting the existence or variant estrogen receptor (ER) proteins in both normal and neoplastic estrogen target tissues including human breast. Therefore, future examination of ER signal transduction and/or measurement of ER protein must take into account variant ER expression. The functions of variant ER proteins, either physiological or pathological, remain unclear, although a role(s) for some ER variants in breast tumorigenesis and breast cancer progression would be consistent with the accumulated data. Possible tissue specific expression leads to the speculation that ER variants may have a role in tissue specific estrogen action. The following review focuses on the current knowledge available in the scientific literature with respect to the type and characteristics of estrogen receptor variants and mutations that have been identified to occur naturally in tissues and cell lines.

Animals↗
PubMed1997

Expression of estrogen receptor-beta in human breast tumors.

The expression of a recently described novel estrogen receptor, ER-beta, was detected in several human breast tumor biopsy samples and several human breast epithelial cell lines using reverse transcription and polymerase chain reaction (RT-PCR) analysis. Cloning and sequencing of the PCR product from a breast tumor confirmed the identity of the sequence with that of the ER-beta mRNA previously reported in human testis. The expression of ER-beta was not correlated with that of ER-alpha, and both ER-alpha positive and ER-alpha negative cell lines expressed ER-beta mRNA. However, some breast tumors and some cell lines coexpress ER-beta and ER-alpha mRNA. Our data support a possible role for ER-beta in human breast cancer.

Biopsy↗
PubMed1997

Oestrogen receptor variants and mutations in human breast cancer.

Several oestrogen receptor variant and mutated mRNA species have been identified in human breast samples and cell lines. Over-expression and altered expression of some of these mRNAs have been correlated with breast tumourigenesis and progression. The following review focuses on the current knowledge available in the scientific literature with respect to the type and characteristics of oestrogen receptor variants and mutations that have been identified as occurring naturally in human breast tissues and cell lines.

Animals↗
PubMed1996

Identification of novel exon-deleted progesterone receptor variant mRNAs in human breast tissue.

Using an approach based on the co-amplification of wild-type and exon deleted progesterone receptor (PR) variant cDNAs, we identified exon-deleted PR variant mRNAs in both normal and neoplastic human breast tissues. Several naturally occurring variants, whose sequences revealed precise whole exon deletions, may encode putative PR-like proteins which lack some functional domains of the wild-type PR molecule. We suggest that these PR variant proteins could have a pathophysiological role in progestin action, as suggested for estrogen receptor variant proteins.

Breast↗
PubMed1996

Differential expression of psoriasin messenger RNA between in situ and invasive human breast carcinoma.

The mRNA encoding the calcium-binding protein psoriasin was identified as being more highly expressed in the in situ versus the invasive component of the same breast tumor. Reverse transcription-PCR analysis of total RNA extracted from three independent cases of ductal carcinoma in situ of the comedo type and three cases of high-grade invasive ductal carcinoma revealed a detectable level of psoriasin mRNA expression in the in situ lesions only. Similar analysis performed on total RNA extracted from frozen sections of 32 independent breast samples, representing a continuum from normal to invasive tumor, confirmed high psoriasin expression in ductal carcinoma in situ of the comedo type only. The possible functional role of the psoriasin protein in breast tumor cells remains to be determined.

Breast Neoplasms↗
PubMed1996

Prevalence of estrogen receptor variant messenger RNAs in human breast cancer.

A new approach, based on the competitive amplification of wild-type and exon-deleted estrogen receptor (ER) variant cDNAs, was used to screen 100 human breast tumors for the presence of ER variants. Already described exon 4-deleted ER mRNA was preferentially detected in tumors with lower grades (P < 0.05) or higher progesterone receptor levels (P < 0.01), whereas new ER variants, deleted in exons 2-4 or in regions within exons 3-7 were associated with higher grades (P < 0.025) and higher ERs (P < 0.001). This approach allows investigation of the expression of multiple ER variant mRNAs and may implicate them as new prognostic markers and as possible contributors to tumor progression.

Breast Neoplasms↗
PubMed1996

Epidermal growth factor receptor and c-erbB-2 expression in normal breast tissue during the menstrual cycle.

EGF receptor (EGF-R) and c-erbB-2 are homologous tyrosine kinase transmembrane receptors. They are involved in controlling proliferation, and probably differentiation, of normal breast epithelial cells, and their expression has been linked to the prognosis of breast cancer. Their physiological roles in normal breast tissue remain to be elucidated, as most studies to date have involved breast cancer cell lines. We studied the location of EGF-R and c-erbB-2 in 100 samples of normal breast with standard immunohistochemical methods and double-labelling techniques. EGF-R was mainly expressed on the stroma and myoepithelial cells, whereas c-erbB-2 expression was exclusively epithelial. An image analyser was used to quantitate variations in their expression during the menstrual cycle. EGF-R and c-erbB-2 expression on epithelial cells was stronger during the luteal phase than the follicular phase (p < 0.01 for EGF-R). The pattern of expression was also compared with that in 28 breast cancers and 7 fibroadenomas.

Breast↗
PubMed1996

Triple primer polymerase chain reaction. A new way to quantify truncated mRNA expression.

The most practical method to quantify mRNA expression within small tumor samples is reverse transcription (RT) followed by quantitative polymerase chain reaction (PCR). One approach, known as "competitive RT-PCR" allows absolute quantitation by reference to synthetic RNA standards but is time-consuming and requires multiple manipulations that limit its usefulness as a screening assay. We describe here a new approach to quantify truncated type mRNAs relative to the wild-type transcripts in small amounts of tissue. This technique, called RT-triple primer-PCR, consists of coamplification of wild-type and truncated cDNAs using three primers in the PCR. To validate this approach, a truncated estrogen receptor variant (clone 4) was quantified relative to the wild-type estrogen receptor using plasmid preparations. The ratio of triple primer-PCR products obtained was directly related to the initial ratio of input cDNAs. RT-triple primer-PCR was then used to compare the relative expression of clone 4 mRNA in frozen sections of normal human breast tissue and human breast tumors with characteristics of good prognosis. The statistically significant difference (P = 0.03) observed between normal and tumor tissues suggests that elevated expression of the clone 4 variant may be associated with early steps of tumorigenesis. This technique provides a useful alternative to already described quantitative RT-PCR techniques for the quantification of truncated mRNA within small amounts of biological material.

Base Sequence↗
PubMed1995

Estradiol stimulates c-myc proto-oncogene expression in normal human breast epithelial cells in culture.

The proto-oncogene c-myc is involved in the stimulation of cell proliferation, and its expression is known to be stimulated by estradiol (E2) in human breast cancer cell lines and various non-cancerous E2-dependent tissues. However, little information is currently available concerning its expression and regulation in normal human breast tissue. We therefore studied c-myc expression and hormone modulation in normal human breast epithelial (HBE) cells in culture, routinely obtained in our laboratory and which remain hormone-dependent. On these normal HBE cells, E2 induced a biphasic increase in c-myc mRNA level, with a first peak as early as 30 min, and a secondary increase after 2 h of treatment; this stimulation was dose-dependent, with an optimal concentration of 10 nM E2. Its primary action is probably at the transcriptional level since the half-life of c-myc mRNA measured in the presence of actinomycin D (12 +/- 3 min) was not modified by E2 treatment. In addition, E2 stimulation of c-myc mRNA does not require protein synthesis since it was not suppressed by cycloheximide treatment. Western blot studies of c-myc protein in HBE cells revealed the same biphasic pattern of stimulation, with a first peak after 60 min and a second one after 2 h of E2 treatment. In conclusion, the c-myc proto-oncogene is expressed in normal HBE cells, as in breast cancer cells. Moreover, E2 stimulates c-myc expression which, therefore, may partly mediate the growth-promoting effect of E2.

Breast↗