ICI182,780 induces p21Waf1 gene transcription through releasing histone deacetylase 1 and estrogen receptor alpha from Sp1 sites to induce cell cycle arrest in MCF-7 breast cancer cell line

We used the estrogen-responsive MCF-7 breast cancer cell line as a relevant model to study the anti-proliferative effects of ICI182,780 and identified the negative cell cycle regulator p21Waf1 as a specific target of ICI182,780. Furthermore, silencing of the p21Waf1 expression by small interfering RNA overcame the G0/G1 cell cycle arrest induced by ICI182,780, suggesting that the induction of p21Waf1 expression has a direct role in mediating the ICI182,780-induced G0/G1 arrest. We further demonstrated that the induction of p21Waf1 by ICI182,780 is mediated at transcriptional and gene promoter levels through the proximal Sp1 sites located near the transcription start site. Co-immunoprecipitation, DNA "pull-down," and chromatin immunoprecipitation experiments together showed that in cycling cells, estrogen receptor alpha and histone deacetylase 1 (HDAC1) are recruited to the proximal Sp1 sites of the promoter to repress p21Waf1 expression. In the presence of ICI182,780, estrogen receptor alpha and HDACs are dissociated from Sp1, resulting in increased histone acetylation and de-repression of the p21Waf1 promoter and induction of p21Waf1 expression. The fact that p21Waf1 expression is normally repressed by HDAC activity in cycling cells is further demonstrated by the finding that p21Waf1 transcription can be induced by the silencing of HDACs with small interfering RNA or treatment with HDAC inhibitors.

Breast cancer oestrogen independence mediated by BCAR1 or BCAR3 genes is transmitted through mechanisms distinct from the oestrogen receptor signalling pathway or the epidermal growth factor receptor signalling pathway

Introduction

Tamoxifen is effective for endocrine treatment of oestrogen receptor-positive breast cancers but ultimately fails due to the development of resistance. A functional screen in human breast cancer cells identified two BCAR genes causing oestrogen-independent proliferation. The BCAR1 and BCAR3 genes both encode components of intracellular signal transduction, but their direct effect on breast cancer cell proliferation is not known. The aim of this study was to investigate the growth control mediated by these BCAR genes by gene expression profiling.

Methods

We have measured the expression changes induced by overexpression of the BCAR1 or BCAR3 gene in ZR-75-1 cells and have made direct comparisons with the expression changes after cell stimulation with oestrogen or epidermal growth factor (EGF). A comparison with published gene expression data of cell models and breast tumours is made.

Results

Relatively few changes in gene expression were detected in the BCAR-transfected cells, in comparison with the extensive and distinct differences in gene expression induced by oestrogen or EGF. Both BCAR1 and BCAR3 regulate discrete sets of genes in these ZR-75-1-derived cells, indicating that the proliferation signalling proceeds along distinct pathways. Oestrogen-regulated genes in our cell model showed general concordance with reported data of cell models and gene expression association with oestrogen receptor status of breast tumours.

Conclusions

The direct comparison of the expression profiles of BCAR transfectants and oestrogen or EGF-stimulated cells strongly suggests that anti-oestrogen-resistant cell proliferation is not caused by alternative activation of the oestrogen receptor or by the epidermal growth factor receptor signalling pathway.

The Src kinase pathway promotes tamoxifen agonist action in Ishikawa endometrial cells through phosphorylation-dependent stabilization of estrogen receptor (alpha) promoter interaction and elevated steroid receptor coactivator 1 activity

Tamoxifen is the most widely used selective estrogen receptor modulator for breast cancer in clinical use today. However, tamoxifen agonist action in endometrium remains a major hurdle for tamoxifen therapy. Activation of the nonreceptor tyrosine kinase src promotes tamoxifen agonist action, although the mechanisms remain unclear. To examine these mechanisms, the effect of src kinase on estrogen and tamoxifen signaling in tamoxifen-resistant Ishikawa endometrial adenocarcinoma cells was assessed. A novel connection was identified between src kinase and serine 167 phosphorylation in estrogen receptor (ER)-alpha via activation of AKT kinase. Serine 167 phosphorylation stabilized ER interaction with endogenous ER-dependent promoters. Src kinase exhibited the additional function of potentiating the transcriptional activity of Gal-steroid receptor coactivator 1 (SRC-1) and Gal-cAMP response element binding protein-binding protein in endometrial cancer cells while having no effect on Gal-p300-associated factor and Gal fusions of the other p160 coactivators glucocorticoid-interacting protein 1 (transcriptional intermediary factor 2/nuclear coactivator-2/SRC-2) and amplified in breast cancer 1 (receptor-associated coactivator 3/activator of transcription of nuclear receptor/SRC-3). Src effects on ER phosphorylation and SRC-1 activity both contributed to tamoxifen agonist action on ER-dependent gene expression in Ishikawa cells. Taken together, these data demonstrate that src kinase potentiates tamoxifen agonist action through serine 167-dependent stabilization of ER promoter interaction and through elevation of SRC-1 and cAMP response element binding protein-binding protein coactivation of ER.

Ligand- and cell-specific effects of signal transduction pathway inhibitors on progestin-induced vascular endothelial growth factor levels in human breast cancer cells

We evaluated the signaling pathways involved in regulating vascular endothelial growth factor (VEGF), a potent angiogenic growth factor, in response to natural and synthetic progestins in breast cancer cells. Inhibition of the phosphoinositide-3'-kinase (PI3-kinase) signaling pathway or the specificity protein-1 (SP-1) transcription factor abolished both progesterone- and medroxyprogesterone acetate (MPA)-induced VEGF secretion from BT-474 and T47-DCO)cells. Inhibitors of the MAPK kinase 1/2/MAPK and N-terminal jun kinase/MAPK signaling pathways blocked both progesterone- and MPA-induced VEGF secretion in BT-474 cells. However, these inhibitors blocked only progesterone-, but not MPA-induced VEGF secretion in T47-DCO cells. Inhibitors of PI3-kinase or SP-1 blocked both progesterone- and MPA-induced increases in VEGF mRNA levels in T47-DCO cells. The proximal SP-1 sites within the VEGF promoter were critical for progestin-dependent induction of VEGF. In contrast, MAPK inhibitors did not block the progesterone- or MPA-induced increases in VEGF mRNA in T47-DCO cells, suggesting that MAPK inhibitors decreased progesterone-induced VEGF secretion in T47-DCO cells by blocking posttranscriptional mechanisms. The MAPK kinase/ERK/MAPK-independent induction of VEGF mediated by MPA was associated with the PRB [progesterone receptor (PR) B] isoform of the PR in T47-DCO cells. None of the inhibitors tested reduced basal PR levels or abrogated PR-dependent gene expression from a reporter plasmid, indicating that loss of PR function cannot explain any of the observed effects. Because the PI3-kinase signaling pathway and SP-1 transcription factor play critical roles in progestin-dependent VEGF induction, these may be useful targets for developing antiangiogenic therapies to prevent progression of progestin-dependent human breast cancers.

Tamoxifen--what next?

Most patients with advanced breast cancer (ABC) ultimately die due to disease progression. Consequently, treatments for ABC are predominantly palliative in nature and, therefore, the tolerability profile of a given treatment is particularly relevant in these patients. While cytotoxic chemotherapy and endocrine therapy exhibit efficacy in hormone-sensitive, advanced disease, it is endocrine therapy that combines efficacy with minimal acute toxicity. Tamoxifen has been the chosen endocrine therapy for postmenopausal, hormone-sensitive, ABC for over 20 years. More recently, new endocrine agents with different mechanisms of action from tamoxifen have been introduced. Evidence indicates that the aromatase inhibitors anastrozole (Arimidex; AstraZeneca; Wilmington, DE), letrozole (Femara; Novartis Pharmaceuticals Corp.; East Hanover, NJ) and exemestane (Aromasin; Pharmacia Corp.; Peapack, NJ) offer superior efficacy and tolerability to tamoxifen in the first-line treatment of postmenopausal, hormone-sensitive ABC. Similarly, after tamoxifen failure, fulvestrant (Faslodex; AstraZeneca), a new estrogen receptor (ER) antagonist that downregulates the ER, is at least as effective as anastrozole, is well tolerated, and is not cross-resistant with tamoxifen. Unlike tamoxifen, fulvestrant has no known agonist effects. The sequential use of such agents may prolong the time during which endocrine therapies can be used, thereby avoiding the more acute toxicities associated with cytotoxic chemotherapy. Indeed, a series of studies has shown that this sequential use is a relevant, active, and well-tolerated option. Establishing the comparative efficacies and optimal sequences that incorporate the newer endocrine agents will be central in determining the future role of hormonal therapy in ABC; the results of this work will determine the relative place of tamoxifen in what is a rapidly changing therapeutic environment.

Endocrine approaches for the treatment of early and advanced breast cancer in postmenopausal women

Preventing clinical progression is the major treatment goal for both early and advanced breast cancer. For hormone-responsive cases (about 70% of the total), this can necessitate the use of sequential hormone therapies at various points during the patient's life. Newer hormonal therapies, such as the third-generation aromatase inhibitor anastrozole, are now competing with tamoxifen as first choice endocrine therapy in breast cancer. In addition, a further non-steroidal aromatase inhibitor letrozole has been shown to be beneficial when given at completion of 5 years adjuvant tamoxifen. In light of these new data, current treatment paradigms need to be reviewed. Already well established as second-line treatments for advanced breast cancer, the improved risk:benefit profiles of anastrozole and letrozole compared with tamoxifen mean that these agents are now also recognised alternative treatments in the first-line relapse setting. More recent studies demonstrate that anastrozole may also have an improved risk:benefit profile compared with tamoxifen when used as initial adjuvant therapy in early breast cancer. Anastrozole is also being evaluated as a preventative treatment in women at high risk of developing breast cancer. A new addition to the endocrine treatment armamentarium is the oestrogen receptor antagonist fulvestrant, which, unlike tamoxifen, has no agonist effects. Fulvestrant is at least as effective as anastrozole in the second-line treatment of advanced breast cancer, and provides similar benefits to tamoxifen when used as first-line therapy in patients with advanced, hormone receptor-positive tumours.

2-Methoxyestradiol induces cell cycle arrest and apoptosis of nasopharyngeal carcinoma cells

AIM

To investigate 2-methoxyestradiol induced apoptosis and its mechanism of action in CNE2 cell lines.

METHODS

CNE2 cells were cultured in RPMI-1640 medium and treated with 2-methoxyestradiol in different concentrations. MTT assay was used to detect growth inhibition. Flow cytometry and DNA ladders were used to detect apoptosis. Western blotting was used to observe the expression of p53, p21(WAF1), Bax, and Bcl-2 protein.

RESULTS

2-methoxyestradiol inhibited proliferation of nasopharyngeal carcinoma CNE2 cells with IC(50) value of 2.82 micromol/L. The results of flow cytometry showed an accumulation of CNE2 cells in G2/M phase in response to 2-methoxyestradiol. Treatment of CNE2 cells with 2-methoxyestradiol resulted in DNA fragmentation. The expression levels of protein p53 and Bcl-2 decreased following 2-methoxyestradiol treatment in CNE2 cells, whereas Bax and p21(WAF1) protein expression were unaffected after treatment with 2-methoxyestradiol.

CONCLUSION

These results suggest that 2-methoxyestradiol induced cell cycle arrest at G2/M phase and apoptosis of CNE2 cells which was associated to Bcl-2 down-regulation.

Effects of 17beta-estradiol, tamoxifen and raloxifene on the protein and mRNA expression of interleukin-6, transforming growth factor-beta1 and insulin-like growth factor-1 in primary human osteoblast cultures

We investigated the effects of 17betaestradiol and two selective estrogen receptor modulators, tamoxifen and raloxifene, on the expression and release of constitutive and interleukin-1-stimulated interleukin (IL)-6, transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor-1 by osteoblasts in primary culture from trabecular bone of healthy post-menopausal women. After 24 h incubation with 10(-8) M concentration of these compounds, there was no decrease in: a) the constitutive or IL-1beta-induced levels of IL-6 protein released to culture medium; b) the constitutive IL-6 mRNA expression after incubation of osteoblasts with 10(-8) M 17betaestradiol or 10(-8) M tamoxifen for 1, 3, 6, 24 or 30 h. Although a decrease after 30 h of treatment with 10(-8) M, raloxifene was found in mRNA IL-6 expression, and this fact was not reflected by a decrease in the release of IL-6 protein to the culture medium after 48 h of incubation with 10(-8) M or 10(-7) M raloxifene. Tumoral growth factorTGF-betal expression was not influenced by incubation with these compounds. Gene expression of IGF-I increased following 24 or 30 h incubation with 10(-8) M 17beta-estradiol and 30 h incubation with raloxifene. Tamoxifen did not affect IGF-I expression. In conclusion, the effects of estradiol or tamoxifen on bone metabolism do not appear to be mediated through the regulation of osteoblast IL-6 release or synthesis, but raloxifene produces a decrease in mRNA IL-6 expression. The actions of estradiol, tamoxifen and raloxifene do not appear to be mediated by tumoral growth factor TGF-beta1. On the other hand, an increase in IGF-I synthesis induced by raloxifene and estradiol could mediate, in part, the effects of these compounds on bone.

Bcl-2 antisense therapy in multiple myeloma

Most malignant plasma cells overexpress Bcl-2, which contributes to resistance against apoptosis induced by dexamethasone and other anticancer agents. Oblimersen sodium (Genasense, previously known as G3139), an antisense oligonucleotide that specifically binds to bcl-2 messenger RNA, decreases production of Bcl-2 protein in both human myeloma cell lines, as well as in ex vivo purified myeloma cells, and enhances the cytotoxicity of dexamethasone and doxorubicin. Combining oblimersen with other anticancer agents represents a therapy-enhancing strategy to reverse the multidrug resistance seen in multiple myeloma (MM). Phase II trials are evaluating the potential role of oblimersen in reversing resistance to standard therapies. Preliminary results from these trials in patients with refractory or relapsed MM indicate that the combination of oblimersen with dexamethasone/thalidomide (Thalomid) or vincristine/doxorubicin/dexamethasone is active and well tolerated and that oblimersen may help overcome chemotherapy resistance and restore sensitivity to MM cells. A randomized phase III clinical trial comparing dexamethasone plus oblimersen with dexamethasone alone in patients with relapsed or refractory myeloma has completed enrollment, with results expected to be available in 2004. Future studies will focus on the role of oblimersen in combination with novel biologic agents such as bortezomib (Velcade).

Gonadotropin-releasing hormone (GnRH) agonist triptorelin inhibits estradiol-induced serum response element (SRE) activation and c-fos expression in human endometrial, ovarian and breast cancer cells

BACKGROUND AND METHODS

The majority of human endometrial (>80%), ovarian (>80%) and breast (>50%) cancers express GnRH receptors. Their spontaneous and epidermal growth-factor-induced proliferation is dose- and time-dependently reduced by treatment with GnRH and its agonists. In this study, we demonstrate that the GnRH agonist triptorelin inhibits estradiol (E2)-induced cancer cell proliferation.

RESULTS

The proliferation of quiescent estrogen receptor alpha (ER alpha)-/ER beta-positive, but not of ER alpha-negative/ER beta-positive endometrial, ovarian and breast cancer cell lines, was significantly stimulated (P<0.001) (ANOVA) after treatment with E2 (10(-8) M). This effect was time- and dose-dependently antagonized by simultaneous treatment with triptorelin. The inhibitory effect was maximal at 10(-5) M concentration of triptorelin (P<0.001). In addition, we could show that, in ER alpha-/ER beta-positive cell lines, E2 induces activation of serum response element (SRE) and expression of the immediate early-response gene c-fos. These effects were blocked by triptorelin (P<0.001). E2-induced activation of estrogen-response element (ERE) was not affected by triptorelin.

CONCLUSIONS

The transcriptional activation of SRE by E2 is due to ER alpha activation of the mitogen-activated protein kinase (MAPK) pathway. This pathway is impeded by GnRH, resulting in a reduction of E2-induced SRE activation and, in consequence, a reduction of E2-induced c-fos expression. This causes downregulation of E2-induced cancer cell proliferation.

Trastuzumab plus tamoxifen: anti-proliferative and molecular interactions in breast carcinoma

HER2 overexpression has been associated with anti-estrogen resistance in human breast cancer, and it has been suggested that the combined treatment of an anti-HER2 antibody plus tamoxifen has enhanced anti-cancer efficacy in breast cancer. The detailed anti-proliferative interactions between trastuzumab and tamoxifen were analyzed with the isobologram and Chou and Talalay methods, which assess the presence of synergy, addition or antagonism. We used the breast cancer cell lines that are estrogen receptor (ER)-positive and HER2-positive. We also analyzed the molecular changes on the HER2 and (ER) signaling pathways that are induced by trastuzumab plus tamoxifen. In terms of cancer cell proliferation, the simultaneous combination of trastuzumab and tamoxifen on BT-474 cells was more growth inhibitory (44%) than the treatment with trastuzumab (24%) or tamoxifen (31%) alone. Isobologram analysis of simultaneous trastuzumab plus tamoxifen exposure showed, however, that there were antagonistic interactions at an effect level of 30% (IC30). Using Chou and Talalay analysis we also observed antagonistic interactions at lower levels of cell kill, although there were additive effects at highest levels of cell kill. Trastuzumab followed by tamoxifen showed antagonism at all effects levels. Tamoxifen followed by trastuzumab showed antagonism at lower levels of cell kill, and additivity at higher levels of cell kill. Similar interactions were observed using T47D cells. The molecular effects of the combined treatment with trastuzumab plus tamoxifen on the levels of HER2 and ER signaling showed that, with respect to HER2 protein levels, trastuzumab downregulated HER2 by 27%, tamoxifen upregulated HER2 by 40%, and the combination of trastuzumab plus tamoxifen did not induce changes in HER2 respect to control. With respect to HER2 mRNA, trastuzumab upregulated HER2 mRNA to 367%, tamoxifen to 166%, and the combination to 401%. With respect to HER2 phosphorylation, trastuzumab upregulated HER2 phosphorylation to 352%, tamoxifen to 202% and the combination to 633%. Epidermal growth factor receptor levels were not changed by trastuzumab or tamoxifen alone, and were upregulated to 138% by the combination. The protein levels and activity of extracellular recptor kinase were not modified by trastuzumab, tamoxifen or the combination. Finally, estrogen receptor protein and mRNA levels were downregulated to about 50% by trastuzumab, tamoxifen or the combination. Taken together, our results show that in ER-positive breast cancer cells overexpressing HER2, trastuzumab plus tamoxifen have antagonistic interactions when used in combination, and that this antagonism may be related with an increase in HER2 signaling pathways that occurs when tamoxifen is added to trastuzumab.

The tamoxifen-induced suppression of telomerase activity in the human hepatoblastoma cell line HepG2: a result of post-translational regulation

PURPOSE

Patients with advanced hepatocellular carcinoma (HCC) have shown to benefit from tamoxifen treatment. The mechanisms of tamoxifen action in HCC, however, are not yet clearly understood. Results from studies on the human hepatoblastoma cell line HepG2 provide evidence that estrogen-receptor-alpha-independent antiproliferative actions of tamoxifen in HCC are mediated by the suppression of telomerase activity [5].

MATERIALS AND METHODS

We investigate the pathway of the tamoxifen-induced down-regulation of telomerase activity, using HepG2 cells incubated over 24 h or 48 h in the presence of 20 microM tamoxifen.

RESULTS

The transcriptional levels of the three telomerase core components-human telomerase RNA (hTR), human telomerase reverse transcriptase (hTERT) (all variants), and telomerase-associated protein (TP1)-did not change during tamoxifen treatment, as revealed by RT-PCR analysis. Furthermore, the hTERT splice pattern was not shifted from the active full-length variant (+alpha/+beta) to the inactive deletion variants (-alpha; -beta; -alpha/-beta) and the level of the 120 kDa hTERT full-length protein remained constant, as shown by Western blot analysis. Protein kinase C (PKC) activity has been suggested to be crucial for post-translational up-regulation of telomerase activity. In HepG2 cells, we observed a tamoxifen-induced suppression of the total protein kinase C (PKC) activity (cytosolic and membrane-bound). Inhibition of PKC with bisindolylmaleimide I resulted in a reduction of telomerase activity, as revealed by TRAP-assay. Alpha-tocopherol (vitamin E) diminished the effects of tamoxifen on PKC-activity as well as on telomerase activity.

CONCLUSIONS

We conclude that the tamoxifen-induced decrease of telomerase activity in HepG2 cells is mediated post-translationally via suppression of PKC-activity.

Bone mineral density among premenopausal women with early breast cancer in a randomized trial of adjuvant endocrine therapy

PURPOSE

To examine the effects on bone mineral density of 2 years of treatment with a luteinizing hormone-releasing hormone (LHRH) agonist alone or in combination with tamoxifen or tamoxifen alone in premenopausal breast cancer.

PATIENTS AND METHODS

We recruited 89 women from two centers in Stockholm participating in a randomized multicenter trial of three different endocrine approaches in the adjuvant setting (Zoladex in Premenopausal Patients Trial). The women were assigned to receive the LHRH agonist goserelin with or without tamoxifen, tamoxifen alone, or no endocrine therapy. The treatment was given for 2 years. We measured total-body bone density before start of treatment and at 12, 24, and 36 months.

RESULTS

After 2 years of treatment, there was a significant loss of bone mineral density (mean change, -5%; P <.001) in the women receiving goserelin alone. The combined goserelin and tamoxifen treatment, as well as tamoxifen alone, resulted in a lesser but statistically significant decline in bone mineral density (mean change, -1.4%; P =.02; and -1.5%; P <.001). One year after cessation of treatment, the goserelin group alone showed a partial recovery from bone loss (mean change, 1.5%; P =.02).

CONCLUSION

Two years of ovarian ablation from goserelin treatment caused a significant reduction in bone mineral density but there was a partial recovery from the bone loss 1 year after cessation of treatment. The addition of tamoxifen seems to partially counteract the demineralizing effects of goserelin.

Endocrinology and hormone therapy in breast cancer: aromatase inhibitors versus antioestrogens

Endocrine therapies act by either blocking or downregulating the oestrogen receptor or by reducing oestrogen concentrations around and within the cancer cell. In postmenopausal women, oestrogen suppression is achieved by inhibition of the enzyme aromatase by aromatase inhibitors (AIs). Modern AIs (anastrozole, letrozole and exemestane) are more potent than earlier ones and suppress oestradiol levels in plasma to virtually undetectable concentrations. Recent comparisons of AIs with the most widely used oestrogen receptor blocking drug tamoxifen indicate that, in general, AIs result in increased response rates and greater durations of response. Here, we summarize data supporting the difference between the two types of treatment and attempt to account for the underlying mechanisms that favour AIs.

NF-kappa B inhibition markedly enhances sensitivity of resistant breast cancer tumor cells to tamoxifen

Studies show that high Akt activity in breast carcinoma is associated with endocrine therapy resistance. Breast cancer cell lines expressing a constitutively active Akt are able to proliferate under reduced estrogen conditions, and are resistant to the growth inhibitory effects of tamoxifen. Understanding the targets of Akt signaling mediating tamoxifen resistance is of clinical significance. One possible target is nuclear factor kappa B (NF-kappa B), a transcription factor that plays a critical role in resistance to apoptosis and the induction of angiogenesis and invasion. In the present study, we found that Akt activity correlated with phosphorylation of I kappa B (the negative regulator of NF-kappa B), NF-kappa B DNA binding and tamoxifen resistance in vivo. Importantly, we found that co-treatment with the NF-kappa B inhibitor, parthenolide, or overexpression of I kappa B superrepressor restored tamoxifen sensitivity to our refractory Akt MCF-7 cells. These data suggest that activation of NF-kappa B via the PI3K/Akt signaling pathway may be a significant mechanism for development of endocrine therapy resistance in breast cancer, and that inhibition of NF-kappa B may be an effective treatment strategy to limit the progression of this disease.

Unexpected response of hormone-refractory prostate cancer to treatment with an antileukemic chemotherapy regimen

Our patient was a 61-year-old man with hormone-refractory prostate cancer and a rapidly rising serum prostate-specific antigen level. During the course of therapy for prostate cancer, abnormal blood counts and subsequent bone marrow biopsy led to a diagnosis of acute lymphoblastic leukemia. He was treated with a chemotherapeutic regimen in standard use for lymphoblastic leukemia, which resulted in an unusual response of his prostate cancer, with declining serum prostate-specific antigen levels that had reached undetectable levels at the time of the patient's death from acute sepsis and leukemic relapse. Autopsy showed minimal evidence of prostate cancer, localized to the prostate.

[Additional effect of SERM: mammary gland]

One of selective estrogen receptor modulators (SERMs), tamoxifen, has been widely used for prevention of breast cancer, postoperative adjuvant therapy and treatment of advanced breast cancer. The relation of a long-term administration of tamoxifen and its adverse effects have been extensively investigated. Favorable effects of tamoxifen are:the reduction in the risk of contralateral breast cancer, gain in bone density in postmenopausal women and decrease in serum low-density lipoprotein cholesterol. Unfavorable effects are: gynecologic problems and the increase in the risk of endometrial cancer and thromboembolism. In contrast, another SERM, raloxifene, has reported to have similar favorable adverse effects but no unfavorable effect on endometrium.

Octreotide inhibits proliferation and induces apoptosis of hepatocellular carcinoma cells

AIM

To study the effect of octreotide on cell proliferation and apoptosis in different hepatocellular carcinoma (HCC) cells and hepatocytes.

METHODS

The proliferation of HCC cells (HepG2, SMMC-7721) and hepatocytes (L-02) was determined by MTT assay. Apoptosis was detected either by fluorescent staining, transmission electron microscopy or flow cytometry. The content of AFP in the supernatant of cultured HCC cells was determined by electrochemiluminescence immunoassay. The expression of SSTR subtypes was identified by RT-PCR.

RESULTS

The proliferation of HCC cells and L-02 cells was inhibited significantly by octreotide (0.25, 0.5, 1.0, 2.0 and 4.0 mg/L). However, the apoptosis of HCC cells markedly increased in a concentration-dependent manner. Both the apoptosis index and the percentage of apoptotic cells in L-02 cells were significantly lower than those of HepG2 and SMMC-7721 cells. The content of AFP in the supernatant of cultured HepG2 cells treated with octreotide was also statistically reduced. Furthermore, SSTR2 and SSTR4 were positive in both the hepatocellular carcinoma cells and in the L-02 cells. SSTR3 was only expressed in the two heptatocellular carcinoma cells, and SSTR5 was found in the SMMC-7721 cells. No SSTR1 was detected either in HCC cells or L-02 cells.

CONCLUSIONS

Apoptosis induction is a major mechanism of octreotide inhibition on hepatocellular cells. SSTR3 is expressed in the HCC cells, but not in the L-02 cells, which suggests a molecular basis for the HCC-selective effects of octreotide.

Induction of the DNA repair gene O6-methylguanine—DNA methyltransferase by dexamethasone in glioblastomas

Object. The DNA repair enzyme O6-methylguanine—DNA methyltransferase (MGMT) inhibits the cytotoxic effect of alkylating agents on tumor cells. The presence of two nonconsensus glucocorticoid-responsive elements in the human MGMT promoter region indicates the potential regulation of MGMT expression by glucocorticoid agents. This study was performed to elucidate whether dexamethasone affects the expression of MGMT in glioblastoma multiforme (GBM) cells, thereby limiting the benefit of chemotherapeutic alkylating agents.

Methods. Four GBM cell lines (A172, T98G, U138MG, and U87MG) were exposed to the alkylating agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) with or without dexamethasone. The expression levels of MGMT were correlated with the cytotoxic effects of ACNU in GBM cells. In the presence of ACNU alone, dexamethasone alone, and the combination of both agents, messenger RNA expression of MGMT was induced to varying degrees with the highest increases seen in the later conditions. This dexamethasone-dependent induction of the MGMT gene was even observed in U87MG cells in which the promoter is methylated, although the absolute expression of MGMT mRNA was the lowest in that cell line. The induction of MGMT by dexamethasone was associated with an increased resistance of these cells to ACNU.

Conclusions. These results indicate that dexamethasone-mediated upregulation of MGMT limits the efficiency of alkylating agents in the treatment of malignant gliomas.

A high serum matrix metalloproteinase-2 level is associated with an adverse prognosis in node-positive breast carcinoma

PURPOSE

The aim of this study was to determine whether serum matrix metalloproteinase (MMP) -2 and MMP-9 levels could predict overall and disease-free survival in primary node-positive breast cancer.

EXPERIMENTAL DESIGN

MMP-2 and MMP-9 levels were quantitatively measured in serum after surgery from 133 patients with primary node-positive breast cancer using enzyme-linked immunoassays. All of the patients received adjuvant therapy, postmenopausal endocrine treatment (tamoxifen or toremifen for 3 years) and premenopausal six cycles of CMF chemotherapy. The follow-up time for all of the patients was 5 years.

RESULTS

Overall survival (OS) and disease-free survival (DFS) rates were better among patients with low MMP-2 levels than in patients with high levels (OS, 91% versus 75%, P = 0.020; DFS, 82% versus 58%, P = 0.005). The appearance of bone and visceral metastases was also significantly lower in patients with low serum MMP-2 levels (bone metastases, 10% versus 23%, P = 0.050; visceral metastases, 12% versus 34%, P = 0.018). The prognostic value of MMP-2 levels was most pronounced among a subgroup of estrogen receptor-positive patients (OS, 96% versus 78%, P = 0.052; DFS, 85% versus 58%, P = 0.014), whereas no significant difference was found among estrogen receptor-negative patients (OS, 73% versus 69%, P = 0.25; DFS, 73% versus 63%, P = 0.32). In multivariate analysis, MMP-2 level together with nodal status (NS), progesterone receptor (PgR), and tumor size (T) remained independent predictors for DFS (NS, P = 0.002; PgR, P = 0.004; T, P = 0.023; MMP2, P = 0.039) and OS (NS, P = 0.0002; PgR, P = 0.004; T, P = 0.004; MMP2, P = 0.032). MMP-9 levels did not correlate with survival.

CONCLUSIONS

The results suggest that serum postoperative MMP-2 level is a predictor of DFS and OS, and could help to stratify breast cancer patients with primary node-positive disease into low- and high-risk groups.

Bicalutamide monotherapy versus leuprolide monotherapy for prostate cancer: effects on bone mineral density and body composition

PURPOSE

Gonadotropin-releasing hormone agonists decrease bone mineral density, lean mass, and muscle size and increase fat mass in men with prostate cancer. Less is known about the effects of bicalutamide monotherapy on bone mineral density and body composition.

PATIENTS AND METHODS

In a 12-month, open-label study, we randomly assigned 52 men with prostate cancer and no bone metastases to receive either leuprolide or bicalutamide (150 mg by mouth daily). Bone mineral density and body composition were measured by dual energy x-ray absorptiometry and quantitative computed tomography.

RESULTS

Mean (+/- standard error) bone mineral density of the posterior-anterior lumbar spine decreased by 2.5% +/- 0.5% in the leuprolide group and increased by 2.5 +/- 0.5 in the bicalutamide group from baseline to 12 months (P <.001). Mean changes in bone mineral density of the total body, total hip, femoral neck, and trabecular bone of the lumbar spine also differed significantly between groups (P < or =.003 for each comparison). Fat mass increased by 11.1% +/- 1.3% in the leuprolide group and by 6.4% +/- 1.1% in the bicalutamide group (P =.01). Changes in lean mass, muscle size, and muscle strength were similar between the groups. Breast tenderness and enlargement were more common in the bicalutamide group than in the leuprolide group. Fatigue, loss of sexual interest, and vasomotor flushing were less common in the bicalutamide group than in the leuprolide group.

CONCLUSION

In men with prostate cancer, bicalutamide monotherapy increases bone mineral density, lessens fat accumulation, and has fewer bothersome side effects than treatment with a gonadotropin-releasing hormone agonist.

Comparison of the antiproliferative properties of antiestrogenic drugs (nafoxidine and clomiphene) on glioma cells in vitro

The antitumoral activity of nonsteroidal antiestrogens on C6 and low passage of human glioma cells was investigated. Tamoxifen and its metabolite, 4-hydroxytamoxifen, did not influence viability of the human cells, but tamoxifen had a limited antiproliferative effect on C6 cells (IC50: 49 micromol/l). The derivatives of tamoxifen, nafoxidine and clomiphene, caused reduction of living cell number in a dose-dependent manner. These two drugs showed differences in their potency following 24-hour incubation in a humidified atmosphere with 37 degrees C and 5% CO2. Obtained from a tetrazolium-formazan growth rate assay, IC50 of nafoxidine for C6 cells was calculated as 44 micromol/l and for the human cells as 16.5 micromol/l. The calculated IC50 dose of clomiphene for C6 is 16 micromol/l and for the human cells 13 micromol/l. Compared to the other drugs we used, it is clear that clomiphene is the most efficient inhibitor of C6 and the human glioma cells. These preliminary results suggest that nafoxidine and clomiphene possess antiproliferative effect on two different sources of glioma cells and therefore, instead of tamoxifen, multiple activities of these drugs may enable their use in combination therapy of glioblastoma malignancies.

Effects of dexamethasone, all-trans retinoic acid, vitamin D(3) and interferon-alpha on FO myeloma cells

BACKGROUND

Since multiple myeloma responds poorly to conventional chemotherapy or radiotherapy, new therapeutic approaches are needed. This study investigated the effects of dexamethasone, all-trans retinoic acid (ATRA), the active metabolite of vitamin D(3) [1,25(OH)(2)D(3)] and interferon-alpha on FO mouse myeloma cells (non-immunoglobulin-secreting myeloma cell line) in single drug or drug combination groups in vitro.

METHODS

Apoptosis ratio and change in cell counts in 4 single drug groups (dexamethasone, ATRA, vitamin D(3) and interferon-alpha) and 6 combination drug groups (dexamethasone + vitamin D(3,) dexamethasone + ATRA, dexamethasone + interferon-alpha, vitamin D(3) + ATRA, vitamin D(3) + interferon-alpha, interferon-alpha + ATRA) were compared with the control group.

RESULTS

When treatment groups were compared with the control group, there was a significant increase in apoptosis in all, but this was most prominent in the group treated with dexamethasone alone. The apoptosis ratios were 0.10 and 6.82% in the control and dexamethasone-only groups, respectively. We also found that there was a significant decrease in cell count, particularly in the dexamethasone-only, ATRA-only, and ATRA-vitamin D(3) combination groups.

CONCLUSION

ATRA, interferon-alpha, vitaminD(3) and particularly dexamethasone have significant effects on FO mouse myeloma cells resulting in a decreased cell count and an increased apoptosis ratio. This study should be repeated with human myeloma cell lines for further information.