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.     

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.     

Metabolite quantification and high-field MRS in breast cancer

In vivo 1H MRS is rapidly developing as a clinical tool for diagnosing and characterizing breast cancers. Many in vivo and in vitro experiments have demonstrated that alterations in concentrations of choline-containing metabolites are associated with malignant transformation. In recent years, considerable efforts have been made to evaluate the role of 1H MRS measurements of total choline-containing compounds in the management of patients with breast cancer. Current technological developments, including the use of high-field MR scanners and quantitative spectroscopic analysis methods, promise to increase the sensitivity and accuracy of breast MRS. This article reviews the literature describing in vivo MRS in breast cancer, with an emphasis on the development of high-field MR scanning and quantitative methods. Potential applications of these technologies for diagnosing suspicious lesions and monitoring response to chemotherapy are discussed.     

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.     

Routine testing for PALB2 mutations in familial pancreatic cancer families and breast cancer families with pancreatic cancer is not indicated

PALB2-mutation carriers not only have an increased risk for breast cancer (BC) but also for pancreatic cancer (PC). Thus far, PALB2 mutations have been mainly found in PC patients from families affected by both PC and BC. As it is well known that the prevalence of gene mutations varies between different populations, we studied the prevalence of PALB2 mutations in a Dutch cohort of non-BRCA1/2 familial PC (FPC) families and in non-BRCA1/2 familial BC (FBC) families with at least one PC case. Mutation analysis included direct sequencing and multiplex ligation-dependent probe amplification (MLPA) and was performed in a total of 64 patients from 56 distinct families (28 FPC families, 28 FBC families). In total, 31 patients (48%) originated from FPC families; 24 were FPC patients (77%), 6 had a personal history of BC (19%) and 1 was a suspected carrier (3.2%). The remaining 33 patients (52%) were all female BC patients of whom 31 (94%) had a family history of PC and 2 (6.1%) had a personal history of PC. In none of these 64 patients a PALB2 mutation was found. Therefore, PALB2 does not have a major causal role in familial clustering of PC and BC in non-BRCA1/2 families in the Dutch population.     

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.     

Characterization of choline kinase in human endothelial cells

High choline kinase‐α (Chk‐α) expression is frequently observed in cancer cells, making it a novel target for pharmacological and molecular inhibition. As inhibiting agents are delivered systemically, it is important to determine Chk‐α expression levels in endothelial cells that line both normal and tumor vasculature, and the effect of Chk‐α downregulation on these cells. Here, we characterized Chk‐α expression and the effect of its downregulation in human umbilical vein endothelial cells (HUVECs) relative to MDA‐MB‐231 human breast cancer cells. We used small interfering RNA (siRNA) to downregulate Chk‐α expression. Basal mRNA levels of Chk‐α were approximately three‐fold lower in HUVECs relative to MDA‐MB‐231 breast cancer cells. Consistent with the differences in Chk‐α protein levels, phosphocholine levels were approximately 10‐fold lower in HUVECs relative to MDA‐MB‐231 cells. Transient transfection with siRNA‐Chk resulted in comparable levels of mRNA and protein in MDA‐MB‐231 breast cancer cells and HUVECs. However, there was a significant reduction in proliferation in MDA‐MB‐231 cells, but not in HUVECs. No significant difference in CD31 immunostaining was observed in tumor sections obtained from mice injected with control luciferase‐short hairpin (sh)RNA or Chk‐shRNA lentivirus. These data suggest that systemically delivered agents that downregulate Chk‐α in tumors will not affect endothelial cell proliferation during delivery, and further support the development of Chk‐α downregulation as a cancer‐specific treatment. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of in vivo MR methods in the study of breast cancer metabolism

In the last two decades, various in vivo MR methodologies have been evaluated for their potential in the study of cancer metabolism. During malignant transformation, metabolic alterations occur, leading to morphological and functional changes. Among various MR methods, in vivo MRS has been extensively used in breast cancer to study the metabolism of cells, tissues or whole organs. It provides biochemical information at the metabolite level. Altered choline, phospholipid and energy metabolism has been documented using proton (¹H), phosphorus (³¹P) and carbon (¹³C) isotopes. Increased levels of choline‐containing compounds, phosphomonoesters and phosphodiesters in breast cancer, which are indicative of altered choline and phospholipid metabolism, have been reported using in vivo, in vitro and ex vivo NMR studies. These changes are reversed on successful therapy, which depends on the treatment regimen given. Monitoring the various tumor intermediary metabolic pathways using nuclear spin hyperpolarization of ¹³C‐labeled substrates by dynamic nuclear polarization has also been recently reported. Furthermore, the utility of various methods such as diffusion, dynamic contrast and perfusion MRI have also been evaluated to study breast tumor metabolism. Parameters such as tumor volume, apparent diffusion coefficient, volume transfer coefficient and extracellular volume ratio are estimated. These parameters provide information on the changes in tumor microstructure, microenvironment, abnormal vasculature, permeability and grade of the tumor. Such changes seen during cancer progression are due to alterations in the tumor metabolism, leading to changes in cell architecture. Due to architectural changes, the tissue mechanical properties are altered; this can be studied using magnetic resonance elastography, which measures the elastic properties of tissues. Moreover, these structural MRI methods can be used to investigate the effect of therapy‐induced changes in tumor characteristics. This review discusses the potential of various in vivo MR methodologies in the study of breast cancer metabolism.     

Stem cells and breast cancer

Proliferation in continuously renewing tissues, including the mammary gland, is hierarchically organized with a small number of slowly dividing stem cells and a greater number of more rapidly proliferating 'transit amplifying' cells. Mammary stem cells have been recently identified and purified based on their surface antigen expression. The recognition of mammary epithelial stem cells had led to the hypothesis that these may be at the root of breast cancer. In support of this, a highly tumorigenic subpopulation of cancer cells – cancer stem cells – has recently been identified in primary and metastatic breast cancer samples and in a number of established breast cancer cell lines. The existence of cancer stem cells would explain why only a small minority of cancer cells is capable of extensive proliferation and transferral of the tumour. In this article we aim to review the evidence in support of the existence of both normal mammary stem cells and breast cancer stem cells, and provide further insight into how taking this subpopulation of cells into account may affect the way we treat epithelial cancers in the future.     

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.     

吉西他滨抑制胰腺癌细胞糖酵解

目的研究吉西他滨对miR-1208在胰腺癌细胞中表达的影响及其抑制胰腺癌细胞糖酵解的分子机制。方法用real-time PCR法检测胰腺癌组织及细胞系中miR-1208以及糖酵解关键基因的表达;在胰腺癌细胞系Bx PC-3与PANC-1分别转染miR-1208模拟物与阴性对照,利用CCK-8试剂盒、乳酸以及葡萄糖检测试剂盒,研究细胞增殖、乳酸分泌以及葡萄糖利用情况;设计拯救实验研究吉西他滨、miR-1208与胰腺癌细胞代谢的关系。结果 miR-1208在胰腺癌组织中表达下调(60%,12/20)(P0.05);miR-1208过表达明显抑制胰腺癌细胞增殖、乳酸分泌以及葡萄糖的消耗(P0.05),miR-1208导致LDH-A与LDH-D的内源性表达水平下调;经吉西他滨处理的胰腺癌细胞系Bx PC-3与PANC-1,其内源性miR-1208表达水平明显上调(P0.01),而其LDH-A、LDH-D的表达水平明显下调(P0.01)。在胰腺癌细胞中,敲低miR-1208表达抑制吉西他滨诱导的细胞代谢方式转换。LDH-A是miR-1208在胰腺癌细胞中的功能靶基因。结论吉西他滨通过调控miR-1208介导的LDH-A通路发挥抑制胰腺癌细胞糖酵解的功能。     

ILK在胰腺癌中的表达及临床病理意义

目的研究整合素连接激酶(ILK)在胰腺癌中的表达情况及其与临床病理特征的关系。方法利用免疫组织化学方法和Western Blot方法检测61例胰腺癌标本,26例癌旁组织,4例正常胰腺组织中ILK蛋白的表达情况,并统计分析其表达率与临床病理学特征的相关性。结果免疫组织化学染色示ILK蛋白定位于细胞浆,其表达率为65.6%,其中7例Ⅲ期胰腺癌中有6例ILK染色强度均呈(+++);26例癌旁组织中有3例阳性表达,表达率11.5%;4例正常胰腺组织未见ILK的表达,胰腺癌组织的ILK表达明显高于可配对癌旁组织(P0.05)及正常胰腺组织(P0.01)。Western Blot检测发现胰腺癌组织ILK蛋白的表达水平明显高于癌旁组织(P0.01)。结论 ILK高表达与胰腺癌患者病理类型中的分化程度无关,而与肿瘤的淋巴结转移、临床分期密切相关。     

Molecular detection of minimal residual disease in colorectal and breast cancer

Recent developments in the field of molecular biology enable us to detect tumour cells at a submicroscopical level. In colorectal and breast cancer the most important prognostic factor is dissemination of malignant cells to locoregional lymph nodes. An important issue is whether molecular 'super'-staging augments the accuracy by which the prognosis of individual patients can be assessed. Over the past few years numerous studies have reported the use of different PCR-based techniques in various types of cancer. The reported incidence of micrometastases and specificity of different assays varies tremendously. This clearly indicates the need for uniformity in protocols. For colorectal cancer the use of molecular techniques may improve staging and guide clinical decisions. For breast cancer there is still need to prove the clinical implication of finding occult metastatic disease. Nevertheless, PCR-based techniques are a powerful tool in the staging of common solid tumours and are likely to find their way into the daily practice of diagnostic histopathologists in the near future.     

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.     

Molecular pathology of pancreatic cancer

By genomic and epigenomic screening techniques, substantial progress has been made in our understanding of pancreatic cancer. The comprehensive studies of the pancreatic cancer genome have revealed that most genetic alterations are identified to be associated with specific core signaling pathways including high‐frequency mutated genes such as KRAS, CDKN2A, TP53, and SMAD4 along with several low‐frequency mutated genes. Three types of histological precursors of pancreatic cancer: pancreatic intraepithelial neoplasia, mucinous cystic neoplasm, and intraductal papillary mucinous neoplasm, had been recognized by morphological studies and the recent genomic screening techniques revealed that each of these precursor lesions were associated with specific molecular alterations. In the familial pancreatic cancer cases, several responsible genes were discovered. Epigenetic changes also play an important role in the progression of pancreatic cancer. Several tumor suppressor genes were silenced due to aberrant promoter CpG island hypermethylation. Several genetically engineered mouse models, based on the Kras mutation, were created, and provided reliable tools to identify the key molecules responsible for the development or progression of pancreatic cancer.     

Investigation of breast cancer using two‐dimensional MRS

Proton (¹H) MRS enables non‐invasive biochemical assay with the potential to characterize malignant, benign and healthy breast tissues. In vitro studies using perchloric acid extracts and ex vivo magic angle spinning spectroscopy of intact biopsy tissues have been used to identify detectable metabolic alterations in breast cancer. The challenges of ¹H MRS in vivo include low sensitivity and significant overlap of resonances due to limited chemical shift dispersion and significant inhomogeneous broadening at most clinical magnetic field strengths. Improvement in spectral resolution can be achieved in vivo and in vitro by recording the MR spectra spread over more than one dimension, thus facilitating unambiguous assignment of metabolite and lipid resonances in breast cancer. This article reviews the recent progress with two‐dimensional MRS of breast cancer in vitro, ex vivo and in vivo. The discussion includes unambiguous detection of saturated and unsaturated fatty acids, as well as choline‐containing groups such as free choline, phosphocholine, glycerophosphocholine and ethanolamines using two‐dimensional MRS. In addition, characterization of invasive ductal carcinomas and healthy fatty/glandular breast tissues non‐invasively using the classification and regression tree (CART) analysis of two‐dimensional MRS data is reviewed. Copyright © 2008 John Wiley & Sons, Ltd.     

Breast cancer resistance protein expression is associated with early recurrence and decreased survival in resectable pancreatic cancer patients

The prognosis of pancreatic ductal adenocarcinoma (PDAC) remains dismal even after complete resection, with most recurrences occurring within 1–2 years postoperatively. Adenosine triphosphate (ATP)‐binding cassette (ABC) transporters have been demonstrated to play major roles in multidrug resistance (MDR) of cancers. In this study, we evaluated the expression statuses and the clinical significance of MDR1 (ABCB1), MDR‐associated proteins (MRPs/ABCC) 1, 2 and 3, and breast cancer resistance protein (BCRP/ABCG2) in 67 surgically resected PDACs by immunohistochemistry. MDR1, MRP1, MRP2, MRP3 and BCRP were expressed in 35 (52.2%), 56 (83.6%), 61 (91.0%), 49 (73.1%) and 49 (73.1%) out of 67 cases, respectively. The expression statuses of the MDR‐related proteins were positively correlated with each other (P < 0.05). Tumors expressing MRP1 (P= 0.015), MRP2 (P= 0.022) and MRP3 (P < 0.001) demonstrated more frequent perineural invasion. MDR1 expression was significantly correlated with lymphatic invasion (P= 0.047). High BCRP expression in PDAC was a significant prognostic factor for early tumor recurrence (HR = 2.43, P= 0.003) and poor survival (HR = 2.63, P= 0.001). MDR‐related proteins are frequently expressed in PDAC, and high BCRP expression is a significant independent predictor for early recurrence and poor survival. Immunohistochemical analysis for BCRP expression in PDAC may be a useful test in identifying a subgroup of patients with a poor prognosis.     

Normal breast stem cells, malignant breast stem cells, and the perinatal origin of breast cancer

Both experimental and epidemiological evidence support the concept that the in utero environment can influence an individual's risk of breast cancer in adult life. Recently identified breast stem cells may be the key to understanding the mechanism underlying this phenomenon. It has been theorized that breast cancers arise from breast stem cells. Our emerging view of the characteristics of normal breast stem cells and their link to malignant breast stem cells is reviewed here. It has also been postulated that factors that expand the normal breast stem cell pool in utero would increase the probability that one such cell might undergo an oncogenic mutation or epigenetic change. We dicuss how a number of proposed perinatal determinants of adult breast cancer risk, including (1) in utero estrogen and IGF-1 levels, (2) birthweight, (3) breast density, and (4) early-life mutagen exposure, can be tied together by this “breast stem cell burden” hypothesis.