Cell lines:
- High GSTp mRNA level in MCF-7/Adr, MDA-MB-231, Hs578T; low level in MCF-7, T-47D, ZR-75B (inverse association between GSTp expression and estrogen receptor (ER) -alpha content).
- It appears that methylation status of the GSTp promoter contributes significantly to the levels of GSTP expressed in ER- and ER+ breast cancer cell lines (Jhaveri M.S. and Morrow C.S., 1998a).
- The role of proximal promoter elements in GSTP1 gene expression was investigated in MCF-7 (
ER+, GST P1-) and HS578T (
ER-, GST P1+) BCC. Transient transfection of GST P1 promoter-CAT reporter genes confirmed that the GST P1 TPA-responsive element (TRE) (-69 to -60) and the adjacent distal GC box (-56 to -51) are required for basal promoter activity in both cell lines. Other studies identified differences in the GST P1 promoter activity and DNA-protein interactions between the two BCC lines. Electrophoretic mobility shift assay revealed a protein-TRE interaction that is unique to nuclear proteins derived from GST P1 expressing HS578T cells. Furthermore, a putative silencer region contained within sequences -130 to -70 selectively reduced GST P1 promoter-CAT reporter gene expression in MCF-7 but not HS578T cells. While this cell-line specific silencer contributed to the level of GST P1 promoter activity observed in the two cell lines, analysis of cells stably transfected with a novel genomic GST P1 minigene vector established that the silencer is insufficient to completely repress GST P1 transcription in
ER+, MCF-7 cells that do not normally express endogenous GST P1 (Jhaveri M.S. and Morrow C.S., 1998b).
- It was found that the MCF-7/ADR BCC line was 30-65-fold more resistant to doxorubicin than the MCF-7/WT (wild-type) BCC. Total cytosolic GST catalytic activity was elevated 23-fold in the MCF-7/ADR cells as compared with the MCF-7/WT cells. MCF-7/ADR cells showed pronounced overexpression of GST P1 mRNA in comparison with the wild-type cell line (Wang K. et al., 1999).
Tumors:
- GST pi was found to be variably expressed in human tumors, with the lowest relative levels occurring in lymphoma and breast cancer and the highest levels found in lung cancer and head and neck tumors. In addition, comparison of paired specimens from the same patient indicated that GST pi expression was increased in many tumors relative to matched normal tissue (Moscow J.A. et al., 1989).
- Detectable levels of
mdr1 mRNA was observed in 25 out of 49 breast tumours, with up to a 100-fold range in expression. A narrower range of GST-pi expression was also observed in these tumours (Keith W.N. et al., 1990).
- Expression of GSTP by intraduct breast carcinoma was evaluated by immunohistochemistry. Thirty-seven of 92 carcinomas (40%) were GSTP positive. GSTP staining did not correlate with histological variables,
c-erbB-2 overexpression or with clinical outcome. The GSTP status of recurrences did not correlate with that of the index lesion (Bellamy C.O. and Harrison B.J., 1994).
- More than 300 primary human tumors were studied for aberrant methylation of GSTP1 using methylation-specific PCR. GSTP1 hypermethylation was most frequent in breast and renal carcinoma, showing aberrant methylation in 30 and 20% of the cases, respectively. Other tumor types showed promoter methylation only rarely or not at all. Hypermethylation of GSTP1 was associated with loss of expression demonstrated by immunohistochemistry (Esteller M. et al., 1998).
- Formalin-fixed paraffin-embedded tissue specimens obtained from 21 invasive breast cancers and 16 adjacent (benign) tissues were immunohistochemically stained using polyclonal anti-human GST-pi antibody. There was positive (defined as >10% immunoreactive tumor cells) but variable expression of GST-pi in 10 (48%) cases. Nuclear morphometry in these 10 tumors revealed immunoreactive malignant cells to be larger (mean area 41.7+/-1.0 microm2) and more rounded in form when compared with non-staining cancer cells (mean area 28.7+/-0.7 microm2). It was also observed that GST-pi immunonegative tumor cells in GST-pi expressing tumors had different morphologies from malignant cells in the remaining 11 (52%) cancers that were regarded as GST-pi negative. Increased GST-pi expression determined by the percentage of positively staining tumor cells, was found to be significantly correlated with increased variability in nuclear area and perimeter in the subset of node-positive tumors. These findings suggest that there exists two sub-populations of cancer cells with distinct nuclear morphologies in GST-pi positive tumors; factors other than GST-pi expression are likely to have a phenotypic effect on breast cancer cells; and there may be a special significance of this enzyme in axillary node-positive breast tumors (Huang J. et al., 2000).
Bellamy C.O. and Harrison B.J. (1994) Evaluation of glutathione S-transferase Pi in non-invasive ductal carcinoma of breast. Br. J. Cancer 69, 183-185.
Esteller M. et al. (1998) Inactivation of glutathione S-transferase P1 gene by promoter hypermethylation in human neoplasia. Cancer Res. 58, 4515-4518.
Huang J. et al. (2000) Nuclear morphometry and glutathione S-transferase pi expression in breast cancer. Oncol. Rep. 7, 609-613.
Jhaveri M.S. and Morrow C.S. (1998a) Methylation-mediated regulation of the glutathione S-transferase P1 gene in human breast cancer cells. Gene 210, 1-7.
Jhaveri M.S. and Morrow C.S. (1998b) Contribution of proximal promoter elements to the regulation of basal and differential glutathione S-transferase P1 gene expression in human breast cancer cells. Biochim. Biophys. Acta 1396, 179-190.
Keith W.N. et al. (1990) Expression of
mdr1 and gst-pi in human breast tumours: comparison to in vitro chemosensitivity. Br. J. Cancer 61, 712-716.
Lacave R. et al.(1998) Comparative evaluation by semiquantitative reverse transcriptase polymerase chain reaction of
MDR1,
MRP and GSTp gene expression in breast carcinomas. Br. J. Cancer 77, 694-702.
Moscow J.A. et al.(1988) Isolation of the human anionic glutathione S-transferase cDNA and the relation of its gene expression to estrogen-receptor content in primary breast cancer. Proc. Natl. Acad. Sci. USA 85, 6518-6522.
Moscow J.A. et al. (1989) Expression of anionic glutathione-S-transferase and
P-glycoprotein genes in human tissues and tumors. Cancer Res. 49, 1422-1428.
Wang K. et al. (1999) Glutathione S-transferases in wild-type and doxorubicin-resistant MCF-7 human breast cancer cell lines. Xenobiotica 29, 155-170.
