Comparative effects of 17 beta-estradiol, progestin R5020, tamoxifen and RU38486 on lactate dehydrogenase activity in MCF-7 human breast cancer cells

Progesterone Receptor-Mediated Regulation of Cellular Glucose and 18F-Fluorodeoxyglucose Uptake in Breast Cancer

Context

Positron emission tomography imaging with 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG) is used clinically for initial staging, restaging, and assessing therapy response in breast cancer. Tumor FDG uptake in steroid hormone receptor-positive breast cancer and physiologic FDG uptake in normal breast tissue can be affected by hormonal factors such as menstrual cycle phase, menopausal status, and hormone replacement therapy.

Objective

The purpose of this study was to determine the role of the progesterone receptor (PR) in regulating glucose and FDG uptake in breast cancer cells.

Methods and Results

PR-positive T47D breast cancer cells treated with PR agonists had increased FDG uptake compared with ethanol control. There was no significant change in FDG uptake in response to PR agonists in PR-negative MDA-MB-231 cells, MDA-MB-468 cells, or T47D PR knockout cells. Treatment of T47D cells with PR antagonists inhibited the effect of R5020 on FDG uptake. Using T47D cell lines that only express either the PR-A or the PR-B isoform, PR agonists increased FDG uptake in both cell types. Experiments using actinomycin D and cycloheximide demonstrated the requirement for both transcription and translation in PR regulation of FDG uptake. GLUT1 and PFKFB3 mRNA expression and the enzymatic activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were increased after progestin treatment of T47D cells.

Conclusion

Thus, progesterone and progestins increase FDG uptake in T47D breast cancer cells through the classical action of PR as a ligand-activated transcription factor. Ligand-activated PR ultimately increases expression and activity of proteins involved in glucose uptake, glycolysis, and the pentose phosphate pathway.

The Biochemical and Clinical Perspectives of Lactate Dehydrogenase: An Enzyme of Active Metabolism

BACKGROUND

Lactate dehydrogenase (LDH) is a group of oxidoreductase isoenzymes catalyzing the reversible reaction between pyruvate and lactate. The five isoforms of this enzyme, formed from two subunits, vary in isoelectric points and these isoforms have different substrate affinity, inhibition constants and electrophoretic mobility. These diverse biochemical properties play a key role in its cellular, tissue and organ specificity. Though LDH is predominantly present in the cytoplasm, it has a multi-organellar location as well.

OBJECTIVE

The primary objective of this review article is to provide an update in parallel, the previous and recent biochemical views and its clinical significance in different diseases.

METHODS

With the help of certain inhibitors, its active site three-dimensional view, reactions mechanisms and metabolic pathways have been sorted out to a greater extent. Overexpression of LDH in different cancers plays a principal role in anaerobic cellular metabolism, hence several inhibitors have been designed to employ as novel anticancer agents.

DISCUSSION

LDH performs a very important role in overall body metabolism and some signals can induce isoenzyme switching under certain circumstances, ensuring that the tissues consistently maintain adequate ATP supply. This enzyme also experiences some posttranslational modifications, to have diversified metabolic roles. Different toxicological and pathological complications damage various organs, which ultimately result in leakage of this enzyme in serum. Hence, unusual LDH isoform level in serum serves as a significant biomarker of different diseases.

CONCLUSION

LDH is an important diagnostic biomarker for some common diseases like cancer, thyroid disorders, tuberculosis, etc. In general, LDH plays a key role in the clinical diagnosis of various common and rare diseases, as this enzyme has a prominent role in active metabolism.

Monitoring mammary tumor progression and effect of tamoxifen treatment in MMTV-PymT using MRI and magnetic resonance spectroscopy with hyperpolarized [1-13C]pyruvate

PURPOSE

To use dynamic magnetic resonance spectroscopy (MRS) of hyperpolarized (13)C-pyruvate to follow the progress over time in vivo of breast cancer metabolism in the MMTV-PymT model, and to follow the response to the anti-estrogen drug tamoxifen.

METHODS

Tumor growth was monitored by anatomical MRI by measuring tumor volumes. Dynamic MRS of hyperpolarized (13)C was used to measure an "apparent" pyruvate-to-lactate rate constant (kp) of lactate dehydrogenase (LDH) in vivo. Further, ex vivo pathology and in vitro LDH initial reaction velocity were evaluated.

RESULTS

Tamoxifen significantly halted the tumor growth measured as tumor volume by MRI. In the untreated animals, kp correlated with tumor growth. The kP was somewhat but not significantly lower in the treated group. Studies in vitro confirmed the effects of tamoxifen on tumor growth, and here the LDH reaction velocity was reduced significantly in the treated group.

CONCLUSION

These hyperpolarized (13)C MRS findings indicate that tumor metabolic changes affects kP. The measured kp did not relate to treatment response to the same extent as did tumor growth, histological evaluation, and in vitro determination of LDH activity.

Temporal proteomic analysis of IGF-1R signalling in MCF-7 breast adenocarcinoma cells

Dysregulation of the insulin-like growth factor 1 receptor signalling network is implicated in tumour growth and resistance to chemotherapy. We explored proteomic changes resulting from insulin-like growth factor 1 stimulation of MCF-7 adenocarcinoma cells as a function of time. Quantitative analysis using iTRAQ reagents and 2-D LC-MS/MS analysis of three biological replicates resulted in the identification of 899 proteins (p<or=0.05) with an estimated mean false-positive rate of 2.6%. Quantitative protein expression was obtained from 681 proteins. Further analysis by supervised k-means clustering identified five temporal clusters, which were submitted to the FuncAssociate server to assign overrepresented gene ontology terms. Proteins associated with vesicle transport were significantly overrepresented. We further analyzed our data set for proteins showing temporal significance using the software, extraction and analysis of differential gene expression, resulting in 20 significantly and temporally changing proteins (p<or=0.1). These significant proteins play roles in, among others, altered glucose metabolism (lactate dehydrogenase A and pyruvate kinase M1/M2) and cellular stress (nascent polypeptide-associated complex subunit alpha and heat shock (HSC70) proteins). We used multiple reaction monitoring to validate these interesting proteins and have revealed several differences in relative peptide expression corresponding to protein isoforms and variants.

Hormonal regulation of lactate dehydrogenase-A through activation of protein kinase C pathways in MCF-7 breast cancer cells

Lactate dehydrogenase A (LDH-A) is hormonally regulated in rodents, and increased expression of LDH-A is observed during mammary gland tumorigenesis. The mechanisms of hormonal regulation of LDH-A were investigated using a series of deletion and mutant constructs derived from the rat LDH-A gene promoter. Results of these studies show that constructs containing the -92 to -37 region of the LDH-A promoter are important for basal and E2-induced transactivation, and mutation of the consensus CRE motif within this region results in significant loss of basal activity and hormone-responsiveness. Gel mobility shift assays using nuclear extracts from MCF-7 cells show that both CREB and ATF-1 interact with the CRE. Studies with kinase inhibitors show that E2-induced activation of this CRE is dependent on protein kinase C, and these data indicate that LDH-A is induced through a non-genomic pathway of estrogen action.

Effects of neonatal exposure to the antiprogestin mifepristone, RU 486, on the sexual development of the rat

RU 38486 (RU 486, mifepristone) is a potent progesterone receptor antagonist that has been used in humans in the pharmacologic induction of abortion. The effects of exposure to RU 486 during the neonatal period of the rat has not been previously reported. We examined the consequences of such exposure in the context of sexual development. Long-Evans rat pups were subcutaneously injected with either 100 micrograms RU 486, 300 micrograms RU 486, 500 micrograms progesterone (P), or 50 micrograms testosterone propionate (TP) in 0.05 ml sesame oil, or oil vehicle alone within 8 hours of birth, and 24 and 48 hours later. Treatment with either dose of RU 486 significantly advanced the onset of vaginal opening in females and attenuated defeminization of the lordosis response measured in males castrated as adults. As expected, TP-treated subjects were masculinized and defeminized, with females displaying fused vaginas and neither males nor females demonstrating lordosis behavior. Treatment with P caused no significant alterations in either the timing of vaginal opening or sexual behavior. These results indicate that RU 486 has clear developmental effects in the rat. Since this may well be a result of progesterone receptor blockade, further research is needed to clarify the processes involved.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on cell growth and the secretion of the estrogen-induced 34-, 52- and 160-kDa proteins in human breast cancer cells

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the growth of estrogen-responsive MCF-7 human breast cancer cells in the presence of 17 beta-estradiol was determined. After treatment with 17 beta-estradiol (1 nM), TCDD (10 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) the cells were monitored daily for cell growth and DNA content for 7 days. The results showed that TCDD inhibited cell proliferation and DNA content of untreated cells and inhibited the 17 beta-estradiol-stimulated cell proliferation and increase in cellular DNA content. In contrast, TCDD did not effect the growth of estrogen non-responsive MDA-MB-231 human breast cancer cells. TCDD (0.1-10 nM) also caused a concentration-dependent decrease in the 17 beta-estradiol-induced proliferation in MCF-7 cells. The effects of TCDD on the 17 beta-estradiol-induced secretion of the 52-kDa protein (i.e. procathepsin D), the 34-kDa (cathepsin D) and 160-kDa proteins were also determined in the MCF-7 and MDA-MB-231 human breast cancer cell lines. The levels of the proteins were determined by autoradiographic analysis of the incorporation of [35S]methionine into the secreted proteins which were separated by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of MCF-7 cells with 17 beta-estradiol (1 nM), TCDD (10 and 100 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) resulted in levels of the 52-kDa protein which were 497, 63.6, 98.1 and 66.3%, respectively, of the corresponding levels observed in control (untreated) cells. Using the same concentrations, the levels of the 34-kDa protein secreted into the media were 372, 42.3, 64.0 and 43.8% of control values, respectively, and the corresponding levels of the 160-kDa protein were 381, 52.9, 71.2 and 76.6% of the control values, respectively. In contrast, treatment of MDA-MB-231 cells with 17 beta-estradiol (1 nM), TCDD (10 and 100 nM) and 17 beta-estradiol (1 nM) plus TCDD (10 nM) resulted in a 31-39% reduction in the secretion of the 52-kDa protein however these effects were not statistically different from the control values. In addition, the treatments did not cause any significant effects on the secretion of the 34- and 160-kDa proteins by MDA-MB-231 cells. These results clearly confirm and extend the range of antiestrogenic effects caused by TCDD in estrogen-responsive MCF-7 cells and indicate that the MDA-MB-231 cells are not responsive to the antiestrogenic effects of TCDD.

Action of antiestrogens on the (Ca2+ + Mg2+)-ATPase and Na+/Ca2+ exchange of brain cortex membranes

The effect of tamoxifen (TAM) and other antiestrogens on the Ca2+ transport activity of synaptic plasma membranes (SPM) and microsomal membranes isolated from sheep brain cortex was investigated. The maximal (Ca2+ + Mg2+)-ATPase activity of SPM, which is reached at a pCa of about 6.0-6.5, is decreased by about 30% in the presence of 50 microM TAM, whereas the (Ca2+ + Mg2+)-ATPase activity of microsomes, which is maximal at a pCa of about 5.0, is decreased by about 90% by 50 microM TAM. In parallel experiments, we observed that the ATP-dependent Ca2+ uptake is also affected differently by TAM in the two membrane preparations. We found that 50 microM TAM inhibits SPM Ca2+ uptake by about 25-30%, whereas the ATP-dependent Ca2+ uptake by the microsomal fraction is inhibited by about 60%. No significant effect of TAM was observed on the Na+/Ca2+ exchange of either membrane system. The results indicate that TAM is a more potent inhibitor of the active, calmodulin-independent Ca2+ transport system of the intracellular membranes than of that of the plasma membranes, which is calmodulin-dependent. It appears that TAM inhibits calmodulin-mediated reactions, probably through its binding to calmodulin, as we showed previously. However, the Ca2+ transport system of microsomes, which does not depend on calmodulin, is also particularly sensitive to TAM.