Silencing of the glycerophosphocholine phosphodiesterase GDPD5 alters the phospholipid metabolite profile in a breast cancer model in vivo as monitored by 31P MRS

Abnormal choline phospholipid metabolism is an emerging hallmark of cancer, which is implicated in carcinogenesis and tumor progression. The malignant metabolic phenotype is characterized by high levels of phosphocholine (PC) and relatively low levels of glycerophosphocholine (GPC) in aggressive breast cancer cells. Phosphorus (³¹P) MRS is able to non‐invasively detect these water‐soluble metabolites of choline as well as ethanolamine phospholipid metabolism. Here we have investigated the effects of stably silencing glycerophosphoester diesterase domain containing 5 (GDPD5), which is an enzyme with glycerophosphocholine phosphodiesterase activity, in MDA‐MB‐231 breast cancer cells and orthotopic tumor xenografts. Tumors in which GDPD5 was stably silenced with GDPD5‐specific shRNA contained increased levels of GPC and phosphoethanolamine (PE) compared with control tumors. Copyright © 2014 John Wiley & Sons, Ltd.     

Targeting choline phospholipid metabolism: GDPD5 and GDPD6 silencing decrease breast cancer cell proliferation,migration, and invasion

Abnormal choline phospholipid metabolism is associated with oncogenesis and tumor progression. We have investigated the effects of targeting choline phospholipid metabolism by silencing two glycerophosphodiesterase genes, GDPD5 and GDPD6, using small interfering RNA (siRNA) in two breast cancer cell lines, MCF‐7 and MDA‐MB‐231. Treatment with GDPD5 and GDPD6 siRNA resulted in significant increases in glycerophosphocholine (GPC) levels, and no change in the levels of phosphocholine or free choline, which further supports their role as GPC‐specific regulators in breast cancer. The GPC levels were increased more than twofold during GDPD6 silencing, and marginally increased during GDPD5 silencing. DNA laddering was negative in both cell lines treated with GDPD5 and GDPD6 siRNA, indicating absence of apoptosis. Treatment with GDPD5 siRNA caused a decrease in cell viability in MCF‐7 cells, while GDPD6 siRNA treatment had no effect on cell viability in either cell line. Decreased cell migration and invasion were observed in MDA‐MB‐231 cells treated with GDPD5 or GDPD6 siRNA, where a more pronounced reduction in cell migration and invasion was observed under GDPD5 siRNA treatment as compared with GDPD6 siRNA treatment. In conclusion, GDPD6 silencing increased the GPC levels in breast cancer cells more profoundly than GDPD5 silencing, while the effects of GDPD5 silencing on cell viability/proliferation, migration, and invasion were more severe than those of GDPD6 silencing. Our results suggest that silencing GDPD5 and GDPD6 alone or in combination may have potential as a new molecular targeting strategy for breast cancer treatment. Copyright © 2016 John Wiley & Sons, Ltd.     

Choline kinase‐α protein and phosphatidylcholine but not phosphocholine are required for breast cancer cell survival

High levels of total choline and phosphocholine (PC) are consistently observed in aggressive cancers. Choline kinase (Chk) catalyzes choline phosphorylation to produce PC in phosphatidylcholine (PtdCho) biosynthesis. PtdCho is the most abundant phospholipid in eukaryotic cell membranes and plays a dual role as the structural component of membranes and as a substrate to produce lipid second messengers such as phosphatidic acid and diacylglycerol. Chk‐α, but not Chk‐β, is overexpressed in various cancers, and is closely associated with tumor progression and invasiveness. We have previously shown that downregulation of mRNA using small interfering RNA (siRNA) against Chk‐α (siRNA‐Chk) or Chk short hairpin RNA, and the resultant decrease of Chk‐α protein levels, significantly reduced proliferation in breast cancer cells and tumors. A novel potent and selective small‐molecule Chk‐α inhibitor, V‐11‐0711, that inhibits the catalytic activity of Chk has recently been developed. Here, we used triple negative MDA‐MB‐231 and SUM149 breast cancer cells to further investigate the role of Chk‐α in cancer, by examining Chk‐α protein levels, cell viability/proliferation, choline phospholipid and lipid metabolism, lipid droplet formation, and apoptosis, following treatment with V‐11‐0711. Under the conditions used in this study, treatment with V‐11‐0711 significantly decreased PC levels but did not reduce cell viability as long as Chk‐α protein and PtdCho levels were not reduced, suggesting that Chk‐α protein and PtdCho, but not PC, may be crucial for breast cancer cell survival. These data also support the approach of antitumor strategies that destabilize Chk‐α protein or downregulate PtdCho in breast cancer treatment. Copyright © 2015 John Wiley & Sons, Ltd.     

Choline kinase overexpression increases invasiveness and drug resistance of human breast cancer cells

A direct correlation exists between increased choline kinase (Chk) expression, and the resulting increase of phosphocholine levels, and histological tumor grade. To better understand the function of Chk and choline phospholipid metabolism in breast cancer we have stably overexpressed one of the two isoforms of Chk‐α known to be upregulated in malignant cells, in non‐invasive MCF‐7 human breast cancer cells. Dynamic tracking of cell invasion and cell metabolism were studied with a magnetic resonance (MR) compatible cell perfusion assay. The MR based invasion assay demonstrated that MCF‐7 cells overexpressing Chk‐α (MCF‐7‐Chk) exhibited an increase of invasion relative to control MCF‐7 cells (0.84 vs 0.3). Proton MR spectroscopy studies showed significantly higher phosphocholine and elevated triglyceride signals in Chk overexpressing clones compared to control cells. A test of drug resistance in MCF‐7‐Chk cells revealed that these cells had an increased resistance to 5‐fluorouracil and higher expression of thymidylate synthase compared to control MCF‐7 cells. To further characterize increased drug resistance in these cells, we performed rhodamine‐123 efflux studies to evaluate drug efflux pumps. MCF‐7‐Chk cells effluxed twice as much rhodamine‐123 compared to MCF‐7 cells. Chk‐α overexpression resulted in MCF‐7 human breast cancer cells acquiring an increasingly aggressive phenotype, supporting the role of Chk‐α in mediating invasion and drug resistance, and the use of phosphocholine as a biomarker of aggressive breast cancers. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of breast cancers and therapy response by MRS and quantitative gene expression profiling in the choline pathway

Tumor choline metabolites have potential for use as diagnostic indicators of breast cancer phenotype and can be non‐invasively monitored in vivo by MRS. Extract studies have determined that the principle diagnostic component of these peaks is phosphocholine (PCho), the biosynthetic precursor to the membrane phospholipid, phosphatidylcholine (PtdCho). The ability to resolve and quantify PCho in vivo would improve the accuracy of this putative diagnostic tool. In addition, determining the biochemical mechanisms underlying these metabolic perturbations will improve the understanding of breast cancer and may suggest potential molecular targets for drug development. Reported herein is the in vivo resolution and quantification of PCho and glycerophosphocholine (GPC) in breast cancer xenografts in SCID mice via image‐guided ³¹P MRS, localized to a single voxel. Tumor metabolites are also detected using ex vivo extracts and high‐resolution NMR spectroscopy and are quantified in the metastatic tumor line, MDA‐mb‐231. Also reported is the quantification of cytosolic and lipid metabolites in breast cells of differing cancer phenotype, and the identification of metabolites that differ among these cell lines. In cell extracts, PCho and the PtdCho breakdown products, lysophosphatidylcholine, GPC and glycerol 3‐phosphate, are all raised in breast cancer lines relative to an immortalized non‐malignant line. These metabolic differences are in direct agreement with differences in expression of genes encoding enzymes in the choline metabolic pathway. Results of this study are consistent with previous studies, which have concluded that increased choline uptake, increased choline kinase activity, and increased phosholipase‐mediated turnover of PtdCho contribute to the observed increase in PCho in breast cancer. In addition, this study presents evidence suggesting a specific role for phospholipase A₂‐mediated PtdCho catabolism. Gene expression changes following taxane therapy are also reported and are consistent with previously reported changes in choline metabolites after the same therapy in the same tumor model. Copyright © 2008 John Wiley & Sons, Ltd.     

Correlation of phospholipid metabolites with prostate cancer pathologic grade, proliferative status and surgical stage - impact of tissue environment

This study investigates the relationship between phospholipid metabolite concentrations, Gleason score, rate of cellular proliferation and surgical stage in malignant prostatectomy samples by performing one- and two-dimensional, high-resolution magic angle spinning, total correlation spectroscopy, pathology and Ki-67 staining on the same surgical samples. At radical prostatectomy, surgical samples were obtained from 49 patients [41 with localized TNM stage T1 and T2, and eight with local cancer spread (TNM stage T3)]. Thirteen of the tissue samples were high-grade prostate cancer [Gleason score: 4?+?3 (n?=?7); 4?+?4 (n?=?6)], 22 low-grade prostate cancer [Gleason score: 3?+?3 (n?=?17); 3?+?4 (n?=?5)] and 14 benign prostate tissues. This study demonstrates that high-grade prostate cancer shows significantly higher Ki-67 staining and concentrations of phosphocholine (PC) and glycerophosphocholine (GPC) than does low-grade prostate cancer (2.4?±?2.8% versus 7.6?±?3.5%, p?相似文献   

Clinical characteristics and biomarkers of breast cancer associated with choline concentration measured by 1H MRS

This study investigated the association between the total choline (tCho) concentration and the clinical characteristics and biomarker status of breast cancer. Sixty‐two patients with breast cancer, 1.5 cm or larger in size on MR images, were studied. The tCho concentration was correlated with the MRI features, contrast enhancement kinetics, clinical variables and biomarkers. Pairwise two‐tailed Spearman's nonparametric test was used for statistical analysis. The tCho concentration was higher in high‐grade than moderate‐/low‐grade tumors (p = 0.04) and in tumors with higher K_trans and k_ep (p < 0.001 for both). The association of tCho concentration with age (p = 0.05) and triple negative biomarker (p = 0.09) approached significance. tCho was not detected in 17 patients, including 15 with invasive ductal cancer and two with infiltrating lobular cancer. Fifteen of the 17 patients had moderate‐ to low‐grade cancers, and 11 had human epidermal growth factor‐2‐negative cancer, suggesting that these two factors might lead to false‐negative choline. Higher tCho concentration in high‐grade tumors and tumors with higher K_trans and k_ep indicates that choline is associated with cell proliferation and tumor angiogenesis. The higher choline level in younger women may be caused by their more aggressive tumor type. The results presented here may aid in the better interpretation of ¹H MRS for the diagnosis of breast lesions. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantification of phosphocholine and glycerophosphocholine with 31P edited 1H NMR spectroscopy

Choline and the related compounds phosphocholine (PC) and glycerophosphocholine (GPC) are considered to be important metabolites in oncology. Past studies have demonstrated correlations linking the relative ratios and concentrations of these metabolites with the development and progression of cancer. Currently, in vivo and tissue ex vivo magnetic resonance spectroscopy methods have mostly centered on measuring the total concentration of these metabolites and have difficulty in differentiating between them. Here, a new scheme that uses (31)P edited (1)H spectroscopy to quantify the concentrations of choline, PC and GPC in biological samples is reported and its applicability is demonstrated using samples of human brain tumor extracts. This method is particularly well-suited for analytical situations where the PC and GPC resonances are not sufficiently resolved and/or are obscured by other metabolites. Consequently, this scheme has the potential to be used for the analysis of choline compounds in ex vivo tissue samples.     

Estrogen receptor β– an independent prognostic marker in estrogen receptor α and progesterone receptor‐positive breast cancer?

Both subtypes of estrogen receptor (ER), ERα and ERβ, are normally present in the mammary gland. The role of ERα as a prognostic marker in breast cancer is well established due to the beneficial effect of providing tamoxifen as adjuvant therapy. The role of ERβ, however, is less clear. To gain insight into the importance of ERβ in breast cancer, 145 primary breast cancers were examined by immunohistochemistry for ERβ, and the expression level was compared with ERα and progesterone receptor (PR) status. Especially, we wanted to examine the significance of ERβ in the contrasting ERα+/PR+ and ERα?/PR? subgroups. In the ERα+/PR+ subgroup (dual positive), the survival difference between patients with low, medium and high ER β level was statistically significant (p = 0.004), with more than 70% of patients with medium and high ERβ levels surviving 100 months, compared with less than 30% in the group with low ERβ level. Further, for ERα+/PR+ patients there was a reduced risk of fatal outcome by multivariate analysis with increasing ERβ levels (p(trend) < 0.01 [univariate analysis]; p(trend) = 0.05 [multivariate analysis]). The risk was 31% and 27% for medium and high ERβ levels, respectively, compared with low ERβ level, adjusting for standard prognostic factors such as tumor diameter, nuclear tumor grade (quantified by mean nuclear area), lymph node status, and patient age at operation. For patients with ERα?/PR? tumors (dual negative), however, there was no association between ERβ levels and patient outcome. Our findings indicate that ERβ expression provides independent prognostic information for breast cancers with ERα/PR‐positive status, a feature typical among screen‐detected breast cancers. The role of ERβ needs to be further evaluated especially in this group of breast cancers.     

Investigation of immunohistochemical ERα, ERβ and ERβcx expressions in normal and neoplastic breast tissues

Estrogen receptor alpha (ERα) is a well-established prognostic marker in breast cancer. The role of estrogen receptor beta (ERβ) in breast cancers is still under investigation. We aimed to investigate the clinicopathological significance and immunohistochemical expression patterns of ERα, total ERβ (ERβ) and its spliced variant ERβcx in normal breast, ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC). Our study population comprised 10 normal breasts, 26 DCISs and 44 IDCs. Immunohistochemical expression of these markers was investigated in sections of formalin-fixed, paraffin-embedded blocks by 2 observers. In invasive ductal carcinomas, ERβ expression had a significant positive correlation with ERα expression (p=0.013), while ERβcx expression was significantly associated with the presence of lymphovascular invasion (p=0.046). There was a significant relationship between ERα expression and low histological grade (p<0.0001). Similarly, ERα+/ERβ+ tumors (p=0.004) and ERα+/ERβcx+ tumors (p=0.008) were significantly associated with low histological grade, too. ERα expression (p=0.009), ERβcx expression (p=0.048) and ERα+/ERβ+ coexpression (p=0.002) increased significantly in progression from normal breast to invasive ductal carcinoma. Expression of ERα correlates with less aggressive phenotypic features, and ERβ expression is positively correlated with ERα expression in breast cancer. ERβcx is associated with aggressive features and can take part in the progression of invasive carcinoma. Increase in ERα+/ERβ+ coexpression, ERα expression and ERβcx expression in breast cancer progression indicates an enhancement in ER expressions or an alteration in expression patterns of different ER variants during mammary carcinogenesis.     

Relationship between p53 pathway and estrogen receptor status in endometrioid-type endometrial cancer

We analyzed the mechanism of estrogen receptor (ER) loss and status of the p53 pathway in 64 cases of endometrial cancer. 26.6% (17 of 64) of endometrial cancers lost ER. Methylation of the ER CpG island was significantly related to ER status (P = 0.0074). However, the methylation site of the ER CpG island differed between breast and endometrial cancers. The abnormal expression rate of p14ARF, MDM2, p53, and the p53 pathway were 7.8% (5 of 64), 32.8% (21 of 64), 25.0% (16 of 64) and 53.1% (34 of 64), respectively. There was no significant difference in the overexpression of MDM2 between p53-positive cases (43.8%: 7 of 16) and p53-negative cases (29.2%; 14 of 48) (P = 0.3595). Abnormal p53 was higher in grade 3 tumors (55.6%; 5 of 9) than in grade 1 and 2 tumors (20.0%; 11 of 55) (P = 0.0364). The abnormality of the p53 pathway was higher in grade 3 tumors (88.9%; 8 of 9) than in grade 1 and 2 tumors (47.3%; 26 of 55) (P = 0.0294). However, there was no significant difference in abnormal p53 pathway between ER-negative and ER-positive cases. In endometrial cancer, ER CpG island methylation was the important mechanism of ER loss. However, there was no significant relationship between the p53 pathway and ER status.     

1H HR‐MAS and genomic analysis of human tumor biopsies discriminate between high and low grade astrocytomas

We investigate the profile of choline metabolites and the expression of the genes of the Kennedy pathway in biopsies of human gliomas (n = 23) using ¹H High Resolution Magic Angle Spinning (HR‐MAS, 11.7 Tesla, 277 K, 4000 Hz) and individual genetic assays. ¹H HR‐MAS spectra allowed the resolution and relative quantification by the LCModel of the resonances from choline (Cho), phosphocholine (PC) and glycerophosphorylcholine (GPC), the three main components of the combined tCho peak observed in gliomas by in vivo ¹H NMR spectroscopy. All glioma biopsies depicted a prominent tCho peak. However, the relative contributions of Cho, PC, and GPC to tCho were different for low and high grade gliomas. Whereas GPC is the main component in low grade gliomas, the high grade gliomas show a dominant contribution of PC. This circumstance allowed the discrimination of high and low grade gliomas by ¹H HR‐MAS, a result that could not be obtained using the tCho/Cr ratio commonly used by in vivo ¹H NMR spectroscopy. The expression of the genes involved in choline metabolism has been investigated in the same biopsies. High grade gliomas depict an upregulation of the β gene of choline kinase and phospholipase C, as well as a downregulation of the cytidyltransferase B gene, the balance of these being consistent with the accumulation of PC. In the low grade gliomas, phospholipase A₁ and lysophospholypase are upregulated and phospholipase D is downregulated, supporting the accumulation of GPC. The present findings offer a promising procedure that will potentially help to accurately grade glioma tumors using ¹H HR‐MAS, providing in addition the genetic background for the alterations of choline metabolism observed in high and low grade gliomas. Copyright © 2009 John Wiley & Sons, Ltd.     

Associations of common variants at 1p11.2 and 14q24.1 (RAD51L1) with breast cancer risk and heterogeneity by tumor subtype: findings from the Breast Cancer Association Consortium

A genome-wide association study (GWAS) identified single-nucleotide polymorphisms (SNPs) at 1p11.2 and 14q24.1 (RAD51L1) as breast cancer susceptibility loci. The initial GWAS suggested stronger effects for both loci for estrogen receptor (ER)-positive tumors. Using data from the Breast Cancer Association Consortium (BCAC), we sought to determine whether risks differ by ER, progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), grade, node status, tumor size, and ductal or lobular morphology. We genotyped rs11249433 at 1p.11.2, and two highly correlated SNPs rs999737 and rs10483813 (r(2)= 0.98) at 14q24.1 (RAD51L1), for up to 46 036 invasive breast cancer cases and 46 930 controls from 39 studies. Analyses by tumor characteristics focused on subjects reporting to be white women of European ancestry and were based on 25 458 cases, of which 87% had ER data. The SNP at 1p11.2 showed significantly stronger associations with ER-positive tumors [per-allele odds ratio (OR) for ER-positive tumors was 1.13, 95% CI = 1.10-1.16 and, for ER-negative tumors, OR was 1.03, 95% CI = 0.98-1.07, case-only P-heterogeneity = 7.6 × 10(-5)]. The association with ER-positive tumors was stronger for tumors of lower grade (case-only P= 6.7 × 10(-3)) and lobular histology (case-only P= 0.01). SNPs at 14q24.1 were associated with risk for most tumor subtypes evaluated, including triple-negative breast cancers, which has not been described previously. Our results underscore the need for large pooling efforts with tumor pathology data to help refine risk estimates for SNP associations with susceptibility to different subtypes of breast cancer.     

A methyl-deviator epigenotype of estrogen receptor-positive breast carcinoma is associated with malignant biology

We broadly profiled DNA methylation in breast cancers (n = 351) and benign parenchyma (n = 47) for correspondence with disease phenotype, using FFPE diagnostic surgical pathology specimens. Exploratory analysis revealed a distinctive primary invasive carcinoma subclass featuring extreme global methylation deviation. Subsequently, we tested the correlation between methylation remodeling pervasiveness and malignant biological features. A methyl deviation index (MDI) was calculated for each lesion relative to terminal ductal-lobular unit baseline, and group comparisons revealed that high-grade and short-survival estrogen receptor-positive (ER(+)) cancers manifest a significantly higher MDI than low-grade and long-survival ER(+) cancers. In contrast, ER(-) cancers display a significantly lower MDI, revealing a striking epigenomic distinction between cancer hormone receptor subtypes. Kaplan-Meier survival curves of MDI-based risk classes showed significant divergence between low- and high-risk groups. MDI showed superior prognostic performance to crude methylation levels, and MDI retained prognostic significance (P < 0.01) in Cox multivariate analysis, including clinical stage and pathological grade. Most MDI targets individually are significant markers of ER(+) cancer survival. Lymphoid and mesenchymal indexes were not substantially different between ER(+) and ER(-) groups and do not explain MDI dichotomy. However, the mesenchymal index was associated with ER(+) cancer survival, and a high lymphoid index was associated with medullary carcinoma. Finally, a comparison between metastases and primary tumors suggests methylation patterns are established early and maintained through disease progression for both ER(+) and ER(-) tumors.     

Noninvasive imaging identifies new roles for cyclooxygenase-2 in choline and lipid metabolism of human breast cancer cells

The expression of cyclooxygenase-2 (COX-2) is observed in approximately 40% of breast cancers. A major product of the COX-2-catalyzed reaction, prostaglandin E(2), is an inflammatory mediator that participates in several biological processes, and influences invasion, vascularization and metastasis. Using noninvasive MRI and MRS, we determined the effect of COX-2 downregulation on the metabolism and invasion of intact poorly differentiated MDA-MB-231 human breast cancer cells stably expressing COX-2 short hairpin RNA. Dynamic tracking of invasion, extracellular matrix degradation and metabolism was performed with an MRI- and MRS-compatible cell perfusion assay under controlled conditions of pH, temperature and oxygenation over the course of 48 h. COX-2-silenced cells exhibited a significant decrease in invasion relative to parental cells that was consistent with the reduced expression of invasion-associated matrix metalloproteinase genes and an increased level of the tissue inhibitor of metalloproteinase-1. We identified, for the first time, a role for COX-2 in mediating changes in choline phospholipid metabolism, and established that choline kinase expression is partly dependent on COX-2 function. COX-2 silencing resulted in a significant decrease in phosphocholine and total choline that was detected by MRS. In addition, a significant increase in lipids, as well as lipid droplet formation, was observed. COX-2 silencing transformed parental cell metabolite patterns to those characteristic of less aggressive cancer cells. These new functional roles of COX-2 may identify new biomarkers and new targets for use in combination with COX-2 targeting to prevent invasion and metastasis.     

Prognostic predictors in breast cancer patients with postoperative 5-fluorouracil-based chemotherapy

Thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) are enzymes involved in the metabolism of 5-fluorouracil (FU). To investigate the relationship of these activities with clinicopathological factors and survival, we measured TS (88 patients) and DPD (122 patients) activities in resected specimens of breast cancer by enzyme assay. Significant difference was found only in TS activity between tumors > or = 20 mm in diameter and those < 20 mm (p = 0.015). There were no significant differences in TS or DPD activity among any other factors. When patients were grouped based on the cut-off levels of TS and DPD activities, 5-year recurrence-free survival rate was 68.8% in the low TS group and 39.7% in the high TS group (p = 0.0081), and 50.8% in the low DPD group and 66.5% in the high DPD group (p = 0.1627). The Cox proportional hazard model demonstrated that in patients in whom we measured TS activity, significant prognostic factors were nodal status and estrogen receptor (ER) status by univariate analysis, and ER status was also significant by multivariate analysis. In patients in whom DPD activity was measured, the significant prognostic factor was ER status by univariate analysis, and ER and Progesterone receptor (PgR) status by multivariate analysis. These results suggested that TS activity, nodal status and hormone receptors may be possible predictors of clinical outcome in breast cancer, but further investigation on prognostic predictors in 5-FU-based chemotherapy is required.     

Molecular causes of elevated phosphoethanolamine in breast and pancreatic cancer cells

Elevated phosphoethanolamine (PE) is frequently observed in MRS studies of human cancers and xenografts. The role of PE in cell survival and the molecular causes underlying this increase are, however, relatively underexplored. In this study, we investigated the roles of ethanolamine kinases (Etnk‐1 and 2) and choline kinases (Chk‐α and β) in contributing to increased PE in human breast and pancreatic cancer cells. We investigated the effect of silencing Etnk‐1 and Etnk‐2 on cell viability as a potential therapeutic strategy. Both breast and pancreatic cancer cells showed higher PE compared with their nonmalignant counterparts. We identified Etnk‐1 as a major cause of the elevated PE levels in these cancer cells, with little or no contribution from Chk‐α, Chk‐β, or Etnk‐2. The increase of PE observed in pancreatic cancer cells in culture was replicated in the corresponding tumor xenografts. Downregulation of Etnk‐1 with siRNA resulted in cell cytotoxicity that correlated with PE levels in breast and pancreatic cancer cells. Etnk‐1 may provide a potential therapeutic target in breast and pancreatic cancers.     

Comparison of HR MAS MR spectroscopic profiles of breast cancer tissue with clinical parameters

Breast cancer is the most frequent form of cancer in women and improved diagnostic methods are desirable. Malignant cells have altered metabolism and metabolic mapping might become a tool in cancer diagnostics. High-resolution magic angle spinning (HR MAS) MR spectroscopy of tissue biopsies provides detailed information on metabolic composition. The 600 MHz 1H HR MAS spectra were acquired of breast cancer tissue from 85 patients and adjacent non-involved tissue from 18 of these patients. Tissue specimens were investigated by microscopy after MR analysis. The resulting spectra were examined by three different approaches. Relative intensities of glycerophosphocholine (GPC), phosphocholine (PC) and choline were compared for cancerous and non-involved specimens. Eight metabolites, choline, creatine, beta-glucose, GPC, glycine, myo-inositol, PC and taurine, were quantified from the recorded spectra and compared with tumor histological type and size, patient's lymph node status and tissue composition of sample. The spectra were also compared with tumor histological type and size, lymph node status and tissue composition of samples using principal component analysis (PCA). Tumor samples could be distinguished from non-involved samples (82% sensitivity, 100% specificity) based on relative intensities of signals from GPC, PC and choline in 1H HR MAS spectra. Tissue concentrations of metabolites showed few differences between groups of samples, which can be caused by limitations in the quantification procedure. Choline and glycine concentrations were found to be significantly higher in tumors larger than 2 cm compared with smaller tumors. PCA of MAS spectra from patients with invasive ductal carcinomas indicated a possible prediction of spread to axillary lymph nodes. Metabolite estimates and PCA of MAS spectra were influenced by the percentage of tumor cells in the investigated specimens.     

31P MRSI and 1H MRS at 7 T: initial results in human breast cancer

This study demonstrates the feasibility of the noninvasive determination of important biomarkers of human (breast) tumor metabolism using high‐field (7‐T) MRI and MRS. ³¹P MRSI at this field strength was used to provide a direct method for the in vivo detection and quantification of endogenous biomarkers. These encompass phospholipid metabolism, phosphate energy metabolism and intracellular pH. A double‐tuned, dual‐element transceiver was designed with focused radiofrequency fields for unilateral breast imaging and spectroscopy tuned for optimized sensitivity at 7 T. T₁‐weighted three‐dimensional MRI and ¹H MRS were applied for the localization and quantification of total choline compounds. ³¹P MRSI was obtained within 20 min per subject and mapped in three dimensions over the breast with pixel volumes of 10 mL. The feasibility of monitoring in vivo metabolism was demonstrated in two patients with breast cancer during neoadjuvant chemotherapy, validated by ex vivo high‐resolution magic angle spinning NMR and compared with data from an age‐matched healthy volunteer. Concentrations of total choline down to 0.4 mM could be detected in the human breast in vivo. Levels of adenosine and other nucleoside triphosphates, inorganic phosphate, phosphocholine, phosphoethanolamine and their glycerol diesters detected in glandular tissue, as well as in tumor, were mapped over the entire breast. Altered levels of these compounds were observed in patients compared with an age‐matched healthy volunteer; modulation of these levels occurred in breast tumors during neoadjuvant chemotherapy. To our knowledge, this is the first comprehensive MRI and MRS study in patients with breast cancer, which reveals detailed information on the morphology and phospholipid metabolism from volumes as small as 10 mL. This endogenous metabolic information may provide a new method for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment. Copyright © 2011 John Wiley & Sons, Ltd.