Tamoxifen induces apoptosis in Fas+ tumor cells by upregulating the expression of Fas ligand

Claudin 1 promotes migration and increases sensitivity to tamoxifen and anticancer drugs in luminal-like human breast cancer cells MCF7

Downregulation of claudin 1, a critical tight junction protein, has been correlated with increased invasiveness in breast cancer. However, recent studies suggest that claudin 1 contributes to the progression of some molecular subtypes of breast cancer. In this study, claudin 1 promotes migration in luminal-like MCF7 human breast cancer cells and increases their sensitivity to tamoxifen, etoposide, and cisplatin. We also observed an inverse relationship between upregulation of claudin 1 and TGFβ. Collectively, our results suggest that claudin 1 has the potential to be used as a predictive marker for treatment efficacy for specific breast cancer patient subgroups.

Prognostic value of the Fas/Fas ligand system in breast cancer

Fas and its ligand (FasL) are known to play a crucial role in the genetically controlled mechanism of cell death, and their deregulation in cancer cells is involved in the immune escape of the tumor. The aim of this review is to analyze the current knowledge on the prognostic value of Fas/FasL in breast cancer patients. Both the results of other authors and our own experiences indicate that the lack of Fas ligand, and particularly Fas, is related to a significantly worse prognosis. It probably results from the resistance of Fas-deficient breast tumors to the mechanisms of apoptosis. On the other hand, some results suggest that the Fas/FasL-dependent mechanisms of tumor spread may be different for various target tissues. The expression of the Fas/Fas-ligand system has potential prognostic application in view of current knowledge, and consequently should be considered as an additional prognostic factor in breast cancer patients.

Tamoxifen non-estrogen receptor mediated molecular targets

Recent experimental studies revealing new biological effects of tamoxifen on tumor cells both expressing and not expressing different types of estrogen receptors (ERα and ERβ) show new aspects of a seemingly well known agent. This review describes tamoxifen targets, the blocking of which leads to inhibition of tumor cell growth and angiogenesis, stimulation of programmed cell death (apoptosis, autophagia and necrosis), inhibition of multidrug resistance, invasion and metastasis. Since outcomes of tamoxifen action on cells are prognostically good from the point of view of both tumor growth/metastasis inhibition and tumor response to drug therapy, the authors believe this is an extremely important addition to tamoxifen antiestrogenic effect. Arguments are provided to consider the strategy of long-term tamoxifen treatment proposed by Professor Craig V. Jordan in the 1970s that is also applicable to the treatment of other tumors. This is, first of all, the fact that expression of estrogen receptor-beta that can also be targeted by tamoxifen therapy in solid tumors of practically all known sites and histologies. The authors believe that molecular biological screening of patients with respect to expression of tamoxifen cellular targets other than ERα and ERβ is needed to use to the full all tamoxifen biological activities other than modulation of estrogen receptors during long-term adjuvant therapy for cancers of various sites.

Apoptogenic activity of 2α,3α-dihydroxyurs-12-ene-28-oic acid from Prunella vulgaris var. lilacina is mediated via mitochondria-dependent activation of caspase cascade regulated by Bcl-2 in human acute leukemia Jurkat T cells

ETHNOPHARMACOLOGICAL RELEVANCE

The dried spikes of Prunella vulgaris var. lilacina (Labiatae) have been used for traditional herbal medicine to treat fever, inflammation, dropsy, gonorrhea and cancer in Korea, Japan and China. The present study evaluated the apoptotic effect of 2α,3α-dihydroxyurs-12-en-28-oic acid (DHURS), purified from the dried spikes on human acute leukemia Jurkat T cells.

MATERIALS AND METHODS

Cell viability was assessed by MTT assay. Mitochondrial membrane potential (Δψm) loss, apoptotic change of the cell cycle, and apoptotic cells were measured by flow cytometric analysis. Mitochondrial cytochrome c release and activation of caspase cascade were determined by Western blot analysis. Caspase-12 activity and caspase-3 activity were assayed using the Fluorometric Assay Kit and the Colorimetric Assay Kit, respectively.

RESULTS

Treatment of Jurkat T cells with DHURS (20-25 μg/ml) caused cytotoxicity and apoptotic DNA fragmentation along with Δψm loss, mitochondrial cytochrome c release, activation of caspase-9, -7, -3, and -8, and PARP degradation. However, these apoptotic events were abrogated by overexpression of Bcl-2. Pretreatment of the cells with the pan-caspase inhibitor (z-VAD-fmk), the caspase-9 inhibitor (z-LEHD-fmk) or the caspase-3 inhibitor (z-DEVD-fmk) to prevent DHURS-induced apoptosis could block the activation of caspase-7 and -8, and PARP degradation, but not the Δψm loss, activation of caspase-9 and -3. Both FADD- and caspase-8-positive wild-type Jurkat clone A3, FADD-deficient Jurkat clone I2.1, and caspase-8-deficient Jurkat clone I9.2 exhibited similar susceptibilities to the cytotoxicity of DHURS, excluding an involvement of Fas/FasL system in triggering the apoptosis. The IC(50) value for Jurkat T cells was ∼22 μg/ml, whereas that for human peripheral T cells was 25 μg/ml.

CONCLUSIONS

These results indicate that DHURS-induced apoptogenic activity in Jurkat T cells, which was less potent in normal peripheral T cells, was mediated by Δψm loss, mitochondrial cytochrome c release, and subsequent activation of caspase-9 and -3, leading to activation of caspase-7 and -8, which could be regulated by Bcl-2.

Circulating apoptotic proteins are increased in long-term disease-free breast cancer survivors

Circulating apoptotic proteins are increased in patients with heart failure. We evaluated whether circulating soluble (s) apoptosis-related proteins and inflammation markers are increased in long-term disease free breast cancer survivors and associated with cardiotoxicity, and if subgroups could be identified based on the applied treatments. Circulating tumour necrosis factor (TNF) alpha, sTNF-receptor (sTNF-R) 1 and 2, sFas, sFas ligand, sTNF-related apoptosis inducing ligand (sTRAIL) and serum HER2 were measured with immunoassay. High-sensitivity C-reactive protein (HS-CRP), fibrinogen, plasma B-type and N-terminal atrial natriuretic peptide (NT-ANP and BNP) were also determined. Thirty-four patients with median 6.0 years follow-up and 12 healthy age-matched women were enrolled. Chemotherapy, consisting of five cycles fluorouracil, epirubicin (90 mg/m(2)), cyclophosphamide (FEC) (n=14) or four cycles FEC followed by myeloablation with high-dose carboplatin, cyclophosphamide, thiotepa (n=20), preceded irradiation and tamoxifen. Circulating apoptosis markers were higher in patients than in controls. No associations with cardiac dysfunction were observed. sFas ligand and sTRAIL were higher in the high-dose than in the standard-dose group. In conclusion, we observed increased circulating apoptotic protein levels in long-term disease-free breast cancer survivors, treated with adjuvant chemoradiotherapy, particularly after myeloablative chemotherapy. The potential relation with late cardiotoxicity of antineoplastic therapy deserves further study.

Fas expression in primary breast cancer is related to neoplastic infiltration of perilymphatic fat

PURPOSE

Various studies have revealed that both Fas and its ligand play an important role in cancer biology. The aim of our study was to determine if there is a relationship between the expression of Fas or Fas-ligand in breast cancer and the presence of malignant cells in perilymphatic fat.

MATERIAL/METHODS

Tumor samples from 147 consecutive breast cancer patients, aged 35-81 (median, 59), were subjected to analysis. The expressions of Fas and Fas-ligand were determined immunohistochemically.

RESULTS

The expression of Fas, but not Fas-ligand, was significantly less frequent in breast cancer patients in whom malignant cells infiltrated through the perilymphatic fat (p=0.042). The infiltration of paranodal fatty tissue occurred more often in cases of ductal carcinomas (p=0.008), larger primary tumors (pT>or=2, p=0.030) and regional lymph node involvement (pN>or=1, p=0.021). Univariate analysis revealed that perilymphatic fat infiltration shortened overall survivals in breast cancer patients (p=0.05), similarly to postmenopausal status (p=0.034), age >60 years (p=0.05) and regional lymph node involvement (p=0.05). None of the aforementioned factors, however, was revealed as an independent predictor of survival in multivariate analysis.

CONCLUSIONS

The study showed that lack of Fas in primary breast cancer is associated with perilymphatic fat infiltration. Consequently, both the absence of Fas in the primary tumor and the occurrence of neoplatic cells in paranodal fatty tissue should be considered in the prognosis, complementing existing conventional factors.

Effects of prolonged tamoxifen treatment on receptor expression and apoptosis of ovarian cancer cells

OBJECTIVE

Tamoxifen, which is widely used in the treatment of breast cancer, also has a beneficial effect on cisplatin-refractory ovarian cancer. In this study, we investigated the long-term effects of this drug on estrogen-receptor-positive ovarian cancer cells.

METHODS

We performed an in vitro selection process by long-term treatment of BG-1 ovarian cancer cells with 4-hydroxy tamoxifen (4-OH TAM). Drug effects on cell growth were determined by measurement of relative cell numbers (MTS assay), the apoptotic effects of 4-OH TAM were determined by analysis of poly (ADP-ribose) polymerase (PARP) cleavage and by ELISA measurement of DNA-histone complexes in cytoplasm.

RESULTS

Analysis of BG-1(LT) ovarian cancer cells isolated after 5 months of long-term treatment with 4-OH TAM revealed both a significantly reduced apoptotic and antiproliferative effect of this drug. Further experiments to examine expression changes of the receptor tyrosine kinases EGFR, HER2 and estrogen receptor alpha did not reveal any alterations in BG-1(LT) if compared to wild-type cells. In contrast, in this cell line, a significant alteration in the expression of estrogen receptor beta was observed.

CONCLUSION

Our findings indicate that long-term treatment with 4-OH TAM is able to diminish both the antiproliferative and apoptotic action of this drug on BG-1 ovarian cancer cells. Our data suggest that the responsiveness of ovarian cancer cells to 4-OH TAM decreases after long-term treatment with this drug in vitro like previously observed after long-term treatment of breast cancer cells.

Antiestrogens, aromatase inhibitors, and apoptosis in breast cancer

Antiestrogens have been the therapeutic agents of choice for breast cancer patients whose tumors express estrogen receptors, regardless of menopausal status. Unfortunately, many patients will eventually develop resistance to these drugs. Antiestrogens primarily act by preventing endogenous estrogen from activating estrogen receptors and promoting cell growth, which can ultimately lead to tumor cell death. Understanding the mechanisms by which antiestrogens cause cell death or apoptosis is critical to our efforts to develop ways to circumvent resistance. This article focuses on antiestrogen-induced apoptosis both in vitro and in vivo. We review the clinical utility of both antiestrogens and aromatase inhibitors and their apoptogenic mechanisms in cell culture models. Among the key signaling components discussed are the roles of Bcl-2 family members, several cytokines, and their receptors, p53, nuclear factor kappa B (NFkappaB), IRF-1, phosphatidylinositol 3-kinase (PI3K)/Akt, and specific caspases. Finally, we discuss the evidence supporting a role for apoptotic defects in acquired and de novo antiestrogen resistance.

Tamoxifen long-term treatment in vitro alters the apoptotic response of MCF-7 breast cancer cells

In this study, we examined alterations in the apoptotic response of tamoxifen (TAM)-resistant breast cancer cells. We used an in vitro selection approach for TAM resistance by means of long-term culture of MCF-7 breast cancer cells with increasing concentrations of TAM. The apoptotic response to TAM was determined by means of ELISA measurement of apoptotic DNA-histone complexes in cytoplasm and by Annexin-V staining. MCF-7(LT) cells isolated after 5 months of long-term treatment with TAM exhibited a significantly reduced apoptotic response to this drug, even if administered in high concentrations up to 20 microM. This reduced apoptotic response was also observed after treatment with the topoisomerase II inhibitor etoposide, a pro-apoptotic antineoplastic drug. Microarray experiments comparing the transcriptome of MCF-7(LT) and wild-type cells revealed both the down-regulated expression of several genes coding for pro-apoptotic proteins and the up-regulation of genes coding for apoptosis inhibitors. Further experiments to determine expression changes of the receptor tyrosine kinases HER2 and epidermal growth factor receptor did not reveal any alterations in MCF-7(LT) if compared to wild-type cells. Our findings suggest that long-term treatment with TAM in vitro does not necessarily change the expression of receptor tyrosine kinases, but can modulate the expression of apoptotic key genes impairing the apoptotic response of MCF-7 breast cancer cells.

Mechanism underlying cytotoxicity of thialysine, lysine analog, toward human acute leukemia Jurkat T cells

We first report the mechanism for the inhibitory effect of the lysine analog, thialysine on human acute leukemia Jurkat T cells. When Jurkat T cells were treated with thialysine (0.32-2.5 mM), apoptotic cell death along with several biochemical events such as mitochondrial cytochrome c release, caspase-9 activation, caspase-3 activation, degradation of poly (ADP-ribose) polymerase, and DNA fragmentation was induced in a dose- and time-dependent manner. However, these thialysine-induced apoptotic events were significantly abrogated by an ectopic expression of Bcl-xL, which is known to block mitochondrial cytochrome c release. Decylubiquinone, a mitochondrial permeability transition pore inhibitor, also suppressed thialysine-induced apoptotic events. Comparison of the thialysine-induced alterations in the cell cycle distribution between Jurkat T cells transfected with Bcl-xL gene (J/Bcl-xL) and Jurkat T cells transfected with vector (J/Neo) revealed that the apoptotic cells were mainly derived from the cells accumulated in S and G2/M phases following thialysine treatment. The interruption of cell cycle progression in the presence of thialysine was accompanied by a significant decline in the protein level of cdk4, cdk6, cdc2, cyclin A, cyclin B1, and cyclin E. These results demonstrate that the cytotoxic activity of thialysine toward Jurkat T cells is attributable to not only apoptotic cell death mediated by a mitochondria-dependent death signaling pathway, but also interruption of cell cycle progression by a massive down-regulation in the level of cdks and cyclins.

The B.M.R. of your association

Recent studies have shown the involvement of the Fas system (Fas receptor and its ligand FasL) in cancerous processes. The absence or downregulation of Fas, reported in the majority of human tumors, conflicts with its presence in cancerous cells from the same tumors but maintained in vitro. Recently, the eventual role of environmental factors in the loss of Fas expression, or in the in vivo selection of a Fas-negative cell population has been suggested. We determined the Fas expression and function in the Capan-1 human cancerous pancreatic duct cells over 2 successive passages in vivo separated by a period of 10-20 passages in vitro. We showed that Capan-1 cells express Fas and are sensitive to Fas-mediated apoptosis when maintained in vitro. When these cells were xenografted into nude mice the expression of Fas was lost in the majority of the tumors. Culture of tumor-derived cells exhibited that they became Fas-positive and sensitive to Fas-mediated apoptosis after a short period in vitro. The loss/gain of Fas was reproduced after re-explantation and re-culture of these Fas-expressing cells. Furthermore, RT-PCR evidenced a strong inhibition of Fas, FLICE and FADD mRNAs expression in the xenografts. Our observations indicate that the expression of Fas and its function could depend to factors in the tumoral environment. The in vivo loss of Fas may thus play an important role in the tumor formation and in the evasion of tumor cells from immune surveillance.