Growth arrest associated changes of mRNA levels in breast cancer cells measured by semi-quantitative RT-PCR: potential early indicators of treatment response

Organophosphate flame retardants induce oxidative stress and Chop/Caspase 3-related apoptosis via Sod1/p53/Map3k6/Fkbp5 in NCI-1975 cells

Organophosphate flame retardants (OPFRs) have been ubiquitously detected in dust and air which could cause damage to human health through inhalation. Currently the understanding of their adverse effects and potential mechanisms on the lung are still limited. In this study, human non-small cell lung cancer cell line NCI-H1975 was used to investigate the cytotoxicity, oxidative stress, cellular apoptosis of 9 typical OPFRs with concentrations varied from 0 to 200 μM, and their toxic mechanism associated with molecular structure was compared. After 72 h, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) displayed the highest cytotoxicity, followed by 2-ethylhexyl diphenyl phosphate (EHDPP), tris(2-butoxyethyl) phosphate (TBOEP) and tris(2-chloroisopropyl) phosphate (TCIPP), while tris(2-chloroethyl) phosphate (TCEP) and tris(2-ethylhexyl) phosphate (TEHP) exhibited the least suppression on cell viability. These results indicated that the variation of cytotoxicity on OPFRs could only be partially explained by their ester linkage. Moreover, the overexpression of intracellular reactive oxygen species (ROS), free Ca²⁺ and cellular apoptosis suggested that exposure to OPFRs can lead to apoptosis related to oxidative stress. Six genes associated with oxidative stress and apoptosis were upregulated dramatically compared with the control, demonstrating OPFRs induced Chop/Caspase 3-related apoptosis by activating Sod1/p53/Map3k6/Fkbp5 expression in NCI-H1975 cells. This is the first study to investigate cytotoxicity and related mechanism on commonly-used OPFRs in NCI-H1975 cells.

Identification of MAGEA antigens as causal players in the development of tamoxifen-resistant breast cancer

The antiestrogen tamoxifen is a well-tolerated, effective treatment for estrogen receptor-α-positive (ER+) breast cancer, but development of resistance eventually limits its use. Here we show that expression of MAGEA2, and related members of this cancer-testis antigen family, is upregulated in tamoxifen-resistant tumor cells. Expression of MAGEA2 in tumor lines grown in vitro or as xenografts led to continued proliferation in the presence of tamoxifen. At the molecular level, we demonstrate that MAGEA2 protein localizes to the nucleus and forms complexes with p53 and ERα, resulting in repression of the p53 pathway but increased ER-dependent signaling. In a series of ER+, tamoxifen-treated breast cancer patients, we show a highly significant (P=0.006) association between MAGEA (melanoma-associated antigen) expression and reduced overall survival, confirming the clinical significance of our observations.

Graphene as a nanocarrier for tamoxifen induces apoptosis in transformed cancer cell lines of different origins

A cationic amphiphile, cholest-5en-3β-oxyethyl pyridinium bromide (PY(+) -Chol), is able to efficiently disperse exfoliated graphene (GR) in water by the physical adsorption of PY(+) -Chol on the surface of GR to form stable, dark aqueous suspensions at room temperature. The GR-PY(+) -Chol suspension can then be used to solubilize Tamoxifen Citrate (TmC), a breast cancer drug, in water. The resulting TmC-GR-PY(+) -Chol is stable for a long time without any precipitation. Fluorescence emission and UV absorption spectra indicate the existence of noncovalent interactions between TmC, GR, and PY(+) -Chol in these suspensions. Electron microscopy shows the existence of segregated GR sheets and TmC 'ribbons' in the composite suspensions. Atomic force microscopy indicates the presence of 'extended' structures of GR-PY(+) -Chol, which grows wider in the presence of TmC. The slow time-dependent release of TmC is noticed in a reconstituted cell culture medium, a property useful as a drug carrier. TmC-GR-PY(+) -Chol selectively enhanced the cell death (apoptosis) of the transformed cancer cells compared to normal cells. This potency is found to be true for a wide range of transformed cancer cells viz. HeLa, A549, ras oncogene-transformed NIH3T3, HepG2, MDA-MB231, MCF-7, and HEK293T compared to the normal cell HEK293 in vitro. Confocal microscopy confirmed the high efficiency of TmC-GR-PY(+) -Chol in delivering the drug to the cells, compared to the suspensions devoid of GR.

Association of Over-Expressed Estrogen Receptor Alpha with Development of Tamoxifen Resistant Hyperplasia and Adenocarcinomas in Genetically Engineered Mice

BACKGROUND

Estrogen receptor alpha (ERα) and cyclin D1 are frequently co-expressed in human breast cancer. Some, but not all, studies link tamoxifen resistance to co-expression of cyclin D1 and ERα. In mice over-expression of either cyclin D1 or ERα in mammary epithelial cells is sufficient to induce mammary hyperplasia. Cyclin D1 over-expression in mice leads to mammary adenocarcinoma associated with activated estrogen signaling pathways. ERα over-expression in mice leads to mammary hyperplasia and cancer. Significantly, disease development in these mice is abrogated by loss of cyclin D1.

METHODS

Genetically engineered mouse models were used to determine whether or not ERα over-expression demonstrated cooperativity with cyclin D1 over-expression in cancer development, reaction to the chemical carcinogen DMBA, or tamoxifen response.

RESULTS

Adding ERα over-expression to cyclin D1 over-expression increased the prevalence of hyperplasia but not cancer. Single dose DMBA exposure did not increase cancer prevalence in any of the genotypes although cyclin D1 over-expressing mice demonstrated a significant increase in hyperplasia. Tamoxifen treatment was initiated at both young and older ages to test for genotype-specific differences in response. Although normal ductal structures regressed in all genotypes at both younger and older ages, tamoxifen did not significantly reduce the prevalence of either hyperplasia or cancer in any of the genotypes. All of the cancers that developed were hormone receptor positive, including those that developed on tamoxifen, and all showed expression of nuclear-localized cyclin D1. In summary, development of tamoxifen resistant hyperplasia and cancer was associated with expression of ERα and cyclin D1.

CONCLUSION

These preclinical models will be useful to test strategies for overcoming tamoxifen resistance, perhaps by simultaneously targeting cell cycle regulatory pathways associated with cyclin D1.

The efficacy of tamoxifen in estrogen receptor-positive breast cancer cells is enhanced by a medical nutriment

Avemar, a fermented wheat germ extract, has been applied in the supplementary therapy of human cancers. Because tamoxifen is commonly used in the therapy of ER+ breast cancer, in this study the combined effect of tamoxifen and Avemar treatment was investigated on MCF-7 breast cancer cells, in order to detect a possible agonistic or antagonistic action. Cytotoxicity was measured by MTT assay, the percentage of mitoses and apoptotic cells was determined morphologically, apoptosis and S-phase was measured by flow cytometry, and estrogen-receptor activity was determined by semiquantitative measurement of the estrogen-responsive pS2 gene mRNA production. Tamoxifen (1 nM) alone had no effect on the percentage of the apoptotic cell fraction and significantly reduced the percentage of the S-phase, compared to untreated cells. Avemar (625 microg/mL) significantly increased apoptosis after 48 hours of treatment. Tamoxifen together with Avemar significantly increased apoptosis already 24 hours after starting treatment but had only a slight (not significant) effect on mitosis and S-phase. Estrogen-receptor activity of MCF-7 cells was enhanced by Avemar, decreased by tamoxifen, and was further decreased by combined tamoxifen and Avemar treatment. As apoptosis increased when Avemar was added to tamoxifen treatment, the use of supplementary therapy with Avemar in the case of ER+ breast tumors may enhance the therapeutic effects of tamoxifen.

H3 mRNA level as a new proliferative marker in astrocytomas

Replication-dependent H3.1 and H3.2 histones are encoded by 11 genes. The H3 mRNA levels in brain astrocytomas using real-time RT-PCR assay was examined. The sequence of primers and probe used in amplification was designed basing on the reference sequence GenBank accession no. The H3 mRNA levels correlated with tumor grade (R=0.56, P=0.0012), Ki-67 proliferative antigen labeling index (R=0.58, P=0.0008) and patient survival time (R=-0.50, P=0.005), discriminating low-grade and high-grade tumors. Quantification of H3 mRNA with real-time RT-PCR using the proposed pair of primers may supplement classic proliferative tests and predictive factors in brain astrocytomas.

Tamoxifen increases apoptosis but does not influence markers of proliferation in an MCF-7 xenograft model of breast cancer

Twenty-four nude mice bearing MCF-7 breast cancer cells grown as xenografts and treated with tamoxifen (2.5 mg slow-release pellet) were studied for up to 35 days. Tumour size was measured in 2 dimensions at regular time-intervals and tumours were harvested on each of days 2, 4, 7, 14, 28 and 35 after the start of treatment. Control animals (8) received no treatment and the tumours were harvested after 0 or 35 days. Tumour sections were assessed for prevalence of apoptosis and mitosis and examined immunocytochemically for Ki(67)(MIB-1) and bcl-2 expression. Tumours increased in size during tamoxifen-treatment, but at a significantly slower rate (max. 2.6-fold) than in the untreated control animals; thus tumours not actually regressing may, nevertheless, be responding significantly to tamoxifen. MIB-1 and bcl-2 immunostaining and mitosis failed to show any consistent change over the period of study. Apoptosis, however, increased progressively and significantly to day-28 in tamoxifen-treated tumours, reaching approximately a 5-fold increase over day-0 values, then decreasing again to nearly 3-fold by day-35 (P= 0.0002). The apoptosis: mitosis ratio in treated tumours also increased to approximately 10-fold on day-28 over day-0 values, decreasing to nearly 4-fold by day-35 (P= 0.037). Within the treated group, apoptosis was significantly inversely correlated with both mitosis (R = -0.38, P= 0.03) and expression of bcl-2 (R = -0.48, P= 0.0056) and strongly positively correlated with both time on tamoxifen (R = +0.63, P= 0.0003) and the % inhibition of growth by tamoxifen (R = +0.58,P = 0.0012) in the 28 individual, treated tumours (estimated relative to the mean growth rate in the controls). The apoptosis: mitosis ratio was also inversely correlated with bcl-2 expression (R = -0.56, P= 0.0021) and positively correlated with both time on tamoxifen (R = +0.50, P= 0.0068) and % inhibition of growth (R = +0.56, P= 0.0019). In this hormone-sensitive tumour model for breast cancer, in which tamoxifen caused inhibition rather than regression, it was not possible to detect significant changes in the marker proteins Ki(67)and bcl-2, or in the prevalence of mitosis in relation to treatment; these factors may therefore not be accurate indices of response to tamoxifen in all situations. By contrast, however, tamoxifen induced a significant, early increase in the prevalence of apoptosis associated with inhibition of tumour growth and an inverse relationship in both mitosis and bcl-2 expression, suggesting that apoptosis may be an accurate and sensitive early marker of even a moderate response to tamoxifen.

Additive effects of tamoxifen and the farnesyl transferase inhibitor FTI-277 on inhibition of MCF-7 breast cancer cell-cycle progression

The efficacy of tamoxifen in the hormonal therapy of breast cancer is well established, but therapeutic resistance is inevitable. FTIs are a new class of anticancer drugs that are in phase III clinical evaluation. Since the mechanisms of action of these 2 classes of drugs are different, we tested the combination of tamoxifen and FTI-277 on inhibiting proliferation of hormone-dependent MCF-7 human breast cancer cells. An additive effect on cell proliferation was demonstrated, accompanied by an additive G(0)/G(1) arrest. The major effect of the combination of the 2 drugs was to maintain p21(waf/cip1) at an intermediate level, higher than that observed in the presence of tamoxifen alone. This was associated with an additive effect on inactivation of cyclin E-Cdk2 complexes and decreased phosphorylation of pRb and p130 pocket proteins. These effects were accompanied by increased association of 2 CDIs, p27(kip1) and p21(waf/cip1), with cyclin E-Cdk2 complexes. These data demonstrate that the additive effect is likely predominantly due to the recruitment of p27(kip1) and, to a lesser extent, p21(waf/cip1) into the cyclin E-Cdk2 complexes. Together, these results suggest that the combination of FTI and tamoxifen may increase the antitumor effect of either drug alone in breast cancer.

The Ca(2+) channel antagonists mibefradil and pimozide inhibit cell growth via different cytotoxic mechanisms

We show that mitogenic cells expressing T-type Ca(2+) channels (T-channels) are more sensitive to the antiproliferative effects of the drugs pimozide and mibefradil than cells without significant T-channel expression. The growth of Y79 and WERI-Rb1 retinoblastoma cells, as well as MCF7 breast cancer epithelial cells, all of which express T-channel current and mRNA for T-channel subunits, is inhibited by pimozide and mibefradil with IC(50) values between 0.6 and 1.5 microM. Proliferation of glioma C6 cells, which show little T-channel expression, is less sensitive to these drugs (IC(50) = 8 and 5 microM for pimozide and mibefradil, respectively). Neither drug seems to alter cell cycle or the expression of cyclins. Although this strong correlation between T-channel expression and growth inhibition exists, the following results suggest that the drugs inhibit cell growth via different cytotoxic pathways: 1) pimozide and mibefradil have additive effects on T-channel current inhibition, whereas the antiproliferative activity of the drugs together is synergistic; 2) an increase in the number of apoptotic Y79 and MCF7 cells and a decrease in the mRNA for the antiapoptotic gene Bcl-2 is detected only in pimozide-treated cells, whereas in mibefradil-treated cells, the toxicity is primarily necrotic; and 3) growth inhibition by mibefradil is reduced in Y79 cells transfected with T-channel antisense and in differentiated Y79 cells (which have decreased T-channel expression), but growth inhibition by pimozide is affected to a lesser extent. These results suggest that pimozide and mibefradil inhibit cell proliferation via different cytotoxic pathways and that in the case of pimozide, it is unlikely that this effect is mediated solely by T-channel inhibition.

The modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase is a negative regulator of estrogen receptor-mediated transcription upon alkylation DNA damage

Cell proliferation requires precise control to prevent mutations from replication of (unrepaired) damaged DNA in cells exposed spontaneously to mutagens. Here we show that the modified human DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (R-MGMT), formed from the suicidal repair of the mutagenic O(6)-alkylguanine (6RG) lesions by MGMT in the cells exposed to alkylating carcinogens, functions in such control by preventing the estrogen receptor (ER) from transcription activation that mediates cell proliferation. This function is in contrast to the phosphotriester repair domain of bacterial ADA protein, which acts merely as a transcription activator for its own synthesis upon repair of phosphotriester lesions. First, MGMT, which is constitutively present at active transcription sites, coprecipitates with the transcription integrator CREB-binding protein CBP/p300 but not R-MGMT. Second, R-MGMT, which adopts an altered conformation, utilizes its exposed VLWKLLKVV peptide domain (codons 98 to 106) to bind ER. This binding blocks ER from association with the LXXLL motif of its coactivator, steroid receptor coactivator-1, and thus represses ER effectively from carrying out transcription that regulates cell growth. Thus, through a change in conformation upon repair of the 6RG lesion, MGMT switches from a DNA repair factor to a transcription regulator (R-MGMT), enabling the cell to sense as well as respond to mutagens. These results have implications in chemotherapy and provide insights into the mechanisms for linking transcription suppression with transcription-coupled DNA repair.

Amplification of c-myc gene and overexpression of c-Myc protein in breast cancer and adjacent non-neoplastic tissue

BACKGROUND

Deregulated c-Myc expression and alterations of c-myc oncogene have been reported to play an important role in breast cancer tumorigenesis. We examined the relationship between c-Myc protein level, amplification of c-myc oncogene and commonly used clinical and pathologic factors.

METHODS

The studies were conducted on 94 ductal and lobular cancers. Amplification of c-Myc was assessed by the semiquantitative multiplex PCR assay. The amount of c-Myc protein was estimated by the densitometry analysis of Western blots.

RESULTS

Amplification of c-Myc was found in 21% of examined cancers. There was no association of c-myc amplification with established risk factors. Overexpression of c-Myc protein without c-myc amplification was associated with negative status of axillary lymph node. The size of lobular carcinoma displaying overexpression of c-Myc and the normal copy number of c-myc gene was significantly smaller than the size of tumor with elevated c-Myc and amplification of c-myc gene (p < 0.01). Within tumors displaying overexpression of c-Myc protein and c-myc gene amplification the size of ductal carcinoma was smaller than the size of lobular carcinoma (p < 0.007).

CONCLUSION

Data presented in this study suggest that alterations of c-myc gene and c-Myc protein level might be related to breast cancer progression. The prognostic utility of elevated level of c-Myc protein associated with normal status of c-myc gene for patients with lobular carcinoma requires further studies.

The ER repeat protein YT521-B localizes to a novel subnuclear compartment

The characterization of distinct subnuclear domains suggests a dynamic nuclear framework supporting gene expression and DNA replication. Here, we show that the glutamic acid/arginine-rich domain protein YT521-B localizes to a novel subnuclear structure, the YT bodies. YT bodies are dynamic compartments, which first appear at the beginning of S-phase in the cell cycle and disperse during mitosis. Furthermore, in untreated cells of the human cell line MCF7 they were undetectable and appeared only after drug- induced differentiation. YT bodies contain transcriptionally active sites and are in close contact to other subnuclear structures such as speckles and coiled bodies. YT bodies disperse upon actinomycin D treatment, whereas other transcriptional inhibitors such as alpha-amanitin or DRB have little effect. On the basis of our experiments, we propose that YT521-B may participate in the assembly of genes into transcription centers, thereby allowing efficient regulation of gene expression.

Selective activation in the MAPK pathway by Hg(II) in precision-cut rabbit renal cortical slices

The kidneys are the primary organ for the accumulation and toxicity of inorganic mercury. In these studies the molecular response of precision-cut rabbit renal cortical slices to low levels of inorganic mercury was examined. Cortical slices (275 microm) were obtained from 1.0 kg NZW rabbits and exposed to mercuric chloride [Hg(II)] at concentrations of 0.01-10 microM for 2-8 h. Overt cytotoxicity, as assessed by intracellular K(+) levels, was not observed following exposure to these concentrations of Hg(II). However, an induction of heme-oxygenase-1 (Hsp32) was seen following a 2-h challenge to Hg(II). A dose-dependent induction of the DNA binding activity of the AP-1 transcription factor after 4 h of Hg(II) exposure correlated with a dose-dependent enhancement of c-jun gene expression following 2 h of Hg(II) exposure. Additionally, an increase in phosphorylated c-Jun NH(2)-terminal protein kinase (JNK) was observed following 2 h of Hg(II) exposure. These results suggest activation of the mitogen-activated protein (MAP) signal transduction pathway, specifically the c-Jun NH(2)-terminal protein kinase (JNK) pathway. No changes were observed, however, in the DNA binding activity of ATF2 and Elk-1, transcription factors involved in both the JNK and p38 pathways of MAP signal transduction, nor in the gene expression of c-myc. This selectivity of alterations in molecular signaling suggests an acute response in signal transduction, specifically activation of the JNK pathway in renal tissue following exposure to nanomolar concentrations of Hg(II).

p53 may mediate the mdr-1 expression via the WT1 gene in human vincristine-resistant leukemia/lymphoma cell lines

To investigate the regulatory mechanism of the expression of the multidrug resistance gene (mdr-1) and the multidrug resistance-associated protein gene (mrp), we investigated if p53, WT1, RB, C-myc, N-myc, cyclin D1, p16INK4 (p16) are involved in the acquirement of multidrug resistance phenotype (MDR) in human vincristine (VCR)-resistant cells of leukemia/lymphoma cell lines. By using RT-PCR, we observed that MDR in VCR-resistant cell lines was mediated by either mdr-1 or mrp genes. In cells that acquired the overexpression of mdr-1, downregulation of p53 and upregulation of WT-1 were observed. In contrast, no constant change of genes was observed in cells that overexpressed mrp. Although the change in the expression level of cyclin D1 and p-16 accompanied the development of VCR resistance, the mRNA of RB, C-myc and N-myc showed no correlation with the degree of VCR resistance or the level of mdr-1 expression. These results may provide a plausible diagnostic marker for determination of drug sensitivity in cancer patients and suggest that p53 may mediate directly or indirectly the expression of mdr-1 via WT1 in VCR-resistant hematologic cell lines.

Estrogen-induced c-fos protooncogene expression in MCF-7 human breast cancer cells: role of estrogen receptor Sp1 complex formation

17Beta-estradiol (E2) induces c-fos protooncogene expression in MCF-7 human breast cancer cells, and previous studies in HeLa cells identified an imperfect palindromic estrogen-responsive element (-1212 to -1200) that was required for trans-activation. In contrast, the estrogen-responsive element was not required for E2 responsiveness in MCF-7 cells, and using a series of constructs containing wild-type (pF1) and mutant 5'-flanking sequences (-1220 to -1155) from the c-fos protooncogene promoter in transient transfection assays, it was shown that a GC-rich motif (5'-GGGGCGTGG) containing an imperfect Sp1-binding site was required for hormone-induced activity. This sequence also bound Sp1 protein in gel mobility shift assays, and coincubation with the estrogen receptor (ER) enhanced Sp1-DNA binding. E2 and 4'-hydroxytamoxifen, but not ICI 164,384, induced reporter gene activity in cells transiently transfected with pF1. E2 induced reporter gene activity in MDA-MB-231 breast cancer cells transiently cotransfected with pF1 and wild-type ER or variant ER in which the DNA-binding domain was deleted (HE11); plasmids expressing N-terminal or C-terminal domains of the ER containing activator function-1 or -2, respectively, were inactive in these assays. In contrast, only wild-type ER mediated 4'-hydroxytamoxifen-induced activity. Induction of c-fos protooncogene expression by E2 in MCF-7 cells is dependent on the formation of a transcriptionally active ER/Sp1 complex that binds to a GC-rich enhancer element.

Breast cancer cell response to calcitonin: modulation by growth-regulating agents

Calcitonin may induce cyclic AMP production by breast cancer cells and inhibit their growth. The molecular complex leading to cyclic AMP production in response to calcitonin is made of the calcitonin receptor coupled to the adenylate cyclase by at least one guanine nucleotide-binding protein (G-protein, of the Gs type). Our aim was to determine whether and how the responses of cells to calcitonin were modulated by growth-regulating agents not directly acting through the cyclic AMP pathway. We found that the cyclic AMP response to calcitonin was reduced after preincubation of cells with the mitogens 17beta-estradiol and epidermal growth factor (EGF), while it was enhanced after preincubation with the growth inhibitors tamoxifen and 1,25(OH)2D3, as well as with an antisense oligonucleotide to the proto-oncogene c-myc. Scatchard-plots revealed no significant change in the calcitonin receptor number or affinity. On the other hand, the cyclic AMP production of cells in response to activators unrelated to calcitonin, such as forskolin, a direct adenylate cyclase effector, and isoproterenol, a beta-adrenergic receptor agonist, was modulated only weakly or not at all by the growth-regulating agents. This suggested that the effects observed were essentially calcitonin-specific and associated with events located between the calcitonin receptor and the adenylate cyclase. Since a Go- or Gi-protein has been previously implicated in the calcitonin signal transduction, we tested the action of pertussis toxin, a specific inhibitor of these G-proteins. Pertussis toxin produced a general increase in the cyclic AMP response of cells to calcitonin; moreover, the toxin almost abolished the effect of mitogens and antimitogens on that parameter. We conclude that in breast cancer cells, the calcitonin receptor and the adenylate cyclase are coupled by at least one Go/Gi-protein sensitive to growth-regulating agents; this results in a modulation of the cyclic AMP response to calcitonin by these agents. On the other hand, the growth-inhibitory effect of calcitonin on breast cancer cells was reduced by 17beta-estradiol and enhanced by tamoxifen. We suggest that this could be a consequence of changes in cyclic AMP levels and deserves further investigation.

A method to monitor mRNA levels in human breast tumor cells obtained by fine-needle aspiration

A method based on the reverse transcriptase-polymerase chain reaction (RT-PCR) was developed that allows the determination of relative mRNA expression levels in fine-needle aspirates from human tumors. The method was developed for the c-erbB-2 gene, using the porphobilinogen deaminase (PBGD) gene as an internal standard. It was validated for mRNA isolated from cell lines and for material obtained by fine-needle aspiration from human breast cancer. Gene expression levels were determined by measuring the activity of radiolabeled RT-PCR-amplified gene-specific bands with a phosphor imager. At least four points are measured on the log-linear part of the amplification cycle versus signal intensity curves, and subsequently the distance between the curves of the gene of interest and that of an internal standard gene is used to calculate the relative expression levels. The method worked equally well with the BRCA1 gene, illustrating that it can be generalized to other genes. The method is suitable to measure or monitor semiquantitively gene expression levels in accessible human tumors in situ.