Cathepsin D in breast cancer: mechanisms and clinical applications, a 1999 overview

Short-Term Exposure to Foodborne Xenoestrogens Affects Breast Cancer Cell Morphology and Motility Relevant for Metastatic Behavior In Vitro

Breast cancer is highly susceptible to metastasis formation. During the time of disease progression, tumor pathophysiology can be impacted by endogenous factors, like hormonal status, as well as by environmental exposures, such as those related to diet and lifestyle. New lines of evidence point toward a potential role for foodborne endocrine disruptive chemicals in this respect; however, mechanistic understanding remains limited. At the molecular level, crucial steps toward metastasis formation include cell structural changes, alteration of adhesion, and reorganization of cytoskeletal proteins involved in motility. Hence, this study investigates the potential of dietary xenoestrogens to impact selected aspects of breast cancer cell mechanotransduction. Taking the onset of the metastatic cascade as a model, experiments focused on cell-matrix adhesion, single-cell migration, and adaptation of cell morphology. Dietary mycoestrogens alternariol (AOH, 1 μM) and α-zearalenol (α-ZEL, 10 nM), soy isoflavone genistein (GEN, 1 μM), and food packaging plasticizer bisphenol A (BPA, 10 nM) were applied as single compounds or in mixtures. Pursuing the hypothesis that endocrine active molecules could affect cell functions beyond the estrogen receptor-dependent cascade, experiments were performed comparing the MCF-7 cell line to the triple negative breast cancer cells MDA MB-231. Indeed, the four compounds functionally affected the motility and the adhesion of both cell types. These responses were coherent with rearrangements of the actin cytoskeleton and with the modulation of the expression of integrin β1 and cathepsin D. Mechanistically, molecular dynamics simulations confirmed a potential interaction with fragments of the α1 and β1 integrin subunits. In sum, dietary xenoestrogens proved effective in modifying the motility and adhesion of breast cancer cells, as predictive end points for metastatic behavior in vitro. These effects were measurable after short incubation times (1 or 8 h) and contribute to shed novel light on the activity of compounds with hormonal mimicry potential in breast cancer progression.

Role of cathepsin D induced by Porphyromonas gingivalis lipopolysaccharide in periodontitis

Periodontitis is an inflammatory disease of tooth-supporting tissues caused by oral bacteria. Periodontal ligament loss and alveolar bone destruction occur in progressive periodontitis. Since gingival crevicular fluids (GCF) reflects the inflammatory environment of the periodontal pocket, it is a very important specimen for developing targets for periodontitis diagnosis. An antibody array was performed using GCF collected from healthy participants and patients with periodontitis to identify the proteolytic enzymes involved in periodontitis. Of 21 targets on the antibody array membrane, kallikrein 6 (KLK6), kallikrein 10 (KLK10), cathepsin A (CathA), and cathepsin D (CathD) showed higher levels in periodontitis GCF than in GCF from healthy participants. Lipopolysaccharide stimulation of Porphyromonas gingivalis (PG-LPS) in immortalized gingival fibroblasts only increased CathD protein levels among the four targets. The substrate cleavage activity of CathD was increased in PG-LPS-treated immortalized gingival fibroblast extract. The PG-LPS-induced substrate cleavage effect was abolished by the CathD inhibitor pepstatin A. Osteoclast formation was promoted by treatment with conditioned media from PG-LPS- treated immortalized gingival fibroblasts but inhibited by the CathD inhibitor pepstatin A. These results suggest that PG-LPS affected the osteoclast formation process by increasing CathD expression in cells around the alveolar bone, thereby participating in periodontitis progression.

Enhanced lysosomal function is critical for paclitaxel resistance in cancer cells: reversed by artesunate

The mechanism underlying the resistance of cancer cells to chemotherapeutic drug varies with different cancer cells. Recent evidence shows that lysosomal function is associated with drug resistance of cancer cells. Artesunate, a derivative of artemisinin, displays broad antitumor activity and direct cytotoxicity on various tumor cells. Our previous study shows that artesunate increases autophagosome accumulation, while significantly decreases autolysosome number in cancer cells, suggesting that artesunate might impair the lysosomal function. In this study, we investigated the effects of artesunate on lysosomal function and its relationship with chemotherapeutic drug resistance in cancer cells. We found that the lysosomal function was significantly enhanced in two drug-resistant (A549/TAX and A549/DDP) cells. Furthermore, we showed that the enhanced lysosomal function by overexpression of transcription factor EB (TFEB) significantly increased MCF-7 cells resistance to doxorubicin (DOX), whereas the decreased lysosomal function by TFEB-knockdown or lysosome inhibitor chloroquine increased MCF-7 cells sensitivity to DOX. Treatment of A549/TAX cells with artesunate (2.5-50 μM) dose-dependently inhibited lysosomal function and the clearance of dysfunctional mitochondria, and induced cell apoptosis. Moreover, we demonstrated that artesunate exerted more potent inhibition on the resistant (A549/TAX and MCF-7/ADR) cells with higher activity of lysosomal function. Our results suggest that artesunate or other inhibitors of lysosomal function would be potential in the treatment of cancer cells with drug resistance caused by the enhanced lysosomal function.

Plasma Cathepsin D Activity Rather Than Levels Correlates With Metabolic Parameters of Type 2 Diabetes in Male Individuals

Objective

Type 2 diabetes mellitus is a metabolic disorder characterized by insulin resistance. Previous studies in patients demonstrated that plasma levels of cathepsin D (CTSD), which is optimally active in the acidic environment of lysosomes, correlate with insulin resistance. As plasma pH is slightly reduced in type 2 diabetic patients and we have previously shown that plasma CTSD activity is causally linked to insulin levels in vivo, it is likely that the activity of CTSD in plasma will be increased in type 2 diabetes compared to healthy individuals. However, so far the interaction between CTSD activity and levels to postprandial metabolic derangements in type 2 diabetes is not known.

Methods

Eighteen type 2 diabetes and 16 age-matched healthy males were given 2 consecutive standardized mixed meals, after which blood samples were collected. Plasma metabolic parameters as well as CTSD levels and activity were measured, and changes in plasma pH was assessed.

Results

In line with the elevation of plasma free fatty acids (FFA) levels in male type 2 diabetics patients, plasma pH in type 2 diabetic individuals was decreased compared to male healthy individuals. While plasma CTSD levels were similar, plasma CTSD activity was increased in male type 2 diabetic compared to male healthy individuals. Besides, plasma CTSD activity rather than levels significantly correlated with indicators of type 2 diabetes (HbA1c, HOMA-IR and glucose). Furthermore, FFA was also independently associated with plasma CTSD activity (standardized β = 0.493, p = 0.007).

Conclusions

Despite similar plasma CTSD levels, type 2 diabetic male individuals showed increased plasma CTSD activity compared to healthy males, which was independently linked to plasma FFA levels. Our data therefore point toward plasma CTSD as a metabolic regulator in male type 2 diabetes.

Characterizing the Relapse Potential in Different Luminal Subtypes of Breast Cancers with Functional Proteomics

Poor prognosis due to the high relapse and metastasis rates of breast cancer has been particularly linked to the luminal B subtype. The current study utilized MCF-7 and ZR-75-1 to investigate various luminal subtypes of breast cancers that have discrepant expressions in the estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2). Understanding of the differential protein profiles and the associated pathways could help alleviate the malignance and promote the long-term survival rate of breast cancer patients. Functional proteome tools were applied to comprehensively delineate the global protein alterations that reflect the varieties of biological features between the two subtypes. In this study, a total of 11 proteins with significant and meaningful changes were identified. These protein targets including PRX2, CK19, nucleophosmin and cathepsin D were mostly involved in cell differentiation or proliferation. Particularly, cathepsin D was highly expressed in the luminal B subtype. Moreover, the level of cathepsin-D was also upregulated in the clinical metastatic tissues. Accordingly, the RNA interference-mediated silencing of cathepsin D stimulated ER expression but suppressed the level of HER2. The knockdown of cathepsin D enhanced the level of ZO-1 and a remarkable decrease in N-cadherin was also detected. Again, the matrix metalloproteinases (MMP) activity was impaired under the cathepsin D abolishment. Collectively, this study represented a modality to explore novel relationships in a proteome complex and highlighted the functional roles of cathepsin D in treatment options for different subtypes of breast cancer.

Cathepsin D in the Tumor Microenvironment of Breast and Ovarian Cancers

Cancer remains a major and leading health problem worldwide. Lack of early diagnosis, chemoresistance, and recurrence of cancer means vast research and development are required in this area. The complexity of the tumor microenvironment in the biological milieu poses greater challenges in having safer, selective, and targeted therapies. Existing strategies such as chemotherapy, radiotherapy, and antiangiogenic therapies moderately improve progression-free survival; however, they come with side effects that reduce quality of life. Thus, targeting potential candidates in the microenvironment, such as extracellular cathepsin D (CathD) which has been known to play major pro-tumorigenic roles in breast and ovarian cancers, could be a breakthrough in cancer treatment, specially using novel treatment modalities such as immunotherapy and nanotechnology-based therapy. This chapter discusses CathD as a pro-cancerous, more specifically a proangiogenic factor, that acts bi-functionally in the tumor microenvironment, and possible ways of targeting the protein therapeutically.

Effects of extracellular acidity on resistance to chemotherapy treatment: a systematic review

Metabolic alterations in the tumor microenvironment have a complex effect on cancer progression. Extracellular acidity is a consequence of metabolic switch in cancer and results in cell phenotypes with higher resistance to chemotherapeutics. However, mechanisms underlying the relationship between the extracellular acidity and chemoresistance are not clearly understood. This systematic review was carried out by searching the databases PubMed and EMBASE using the keywords "cancer" and "acidosis" or "acidic" and "chemoresistance" or "drug resistance." In vitro and in vivo studies that evaluated the effects of acidification of the tumor microenvironment on chemotherapeutic treatments were included. Literature reviews, letters to the editor, and articles that were not published in English were excluded. The search resulted in a total of 352 articles. After discarding 75 duplicate references, 277 articles were analyzed by sequentially reading through their titles, abstracts, and finally full-text. A total of 14 articles was selected. Acidification of the tumor microenvironment can trigger resistance through different mechanisms, such as increase in drug efflux transporters, inhibition of proton pumps, induction of the unfolded protein response (UPR), and cellular autophagy.

Functional Relationship and Gene Ontology Classification of Breast Cancer Biomarkers

Breast cancer is a complex disease that still imposes a significant healthcare burden on women worldwide. The etiology of breast cancer is not known but significant advances have been made in the area of early detection and treatment. The advent of advanced molecular biology techniques, mapping of the human genome and availability of high throughput genomic and proteomic strategies opens up new opportunities and will potentially lead to the discovery of novel biomarkers for early detection and prognostication of breast cancer. Currently, many biomarkers, particularly the hormonal and epidermal growth factor receptors, are being utilized for breast cancer prognosis. Unfortunately, none of the biomarkers in use have sufficient diagnostic, prognostic and/or predictive power across all categories and stages of breast cancer. It is recognized that more useful information can be generated if tumors are interrogated with multiple markers. But choosing the right combination of biomarkers is challenging, because 1) multiple pathways are involved, 2) up to 62 genes and their protein products are potentially involved in breast cancer-related mechanisms and 3) the more markers evaluated, the more the time and cost involved. This review summarizes the current literature on selected biomarkers for breast cancer, discusses the functional relationships, and groups the selected genes based on a Gene Ontology™ classification.

Host Cell Proteases: Cathepsins

Cathepsins are proteolytic enzymes with a broad spectrum of substrates. They are known to reside within endo-lysosomes where they acquire optimal conditions for proteolytic activity and substrate cleavage. However, cathepsins have been detected in locations other than the canonical compartments of the endocytotic pathway. They are often secreted from cells in either proteolytically inactive proform or as mature and active enzyme; this may happen in both physiological and pathological conditions. Moreover, cytosolic and nuclear forms of cathepsins have been described and are currently an emerging field of research aiming at understanding their functions in such unexpected cellular locations. This chapter summarizes the canonical pathways of biosynthesis and transport of cathepsins in healthy cells. We further describe how cathepsins can reach unexpected locations such as the extracellular space or the cytosol and the nuclear matrix. No matter where viruses and cathepsins encounter, several outcomes can be perceived. Thus, scenarios are discussed on how cathepsins may support virus entry into host cells, involve in viral fusion factor and polyprotein processing in different host cell compartments, or help in packaging of viral particles during maturation. It is of note to mention that this review is not meant to comprehensively cover the present literature on viruses encountering cathepsins but rather illustrates, on some representative examples, the possible roles of cathepsins in replication of viruses and in the course of disease.

Cathepsin D non-proteolytically induces proliferation and migration in human omental microvascular endothelial cells via activation of the ERK1/2 and PI3K/AKT pathways

Epithelial ovarian cancer (EOC) frequently metastasises to the omentum, a process that requires pro-angiogenic activation of human omental microvascular endothelial cells (HOMECs) by tumour-secreted factors. We have previously shown that ovarian cancer cells secrete a range of factors that induce pro-angiogenic responses e.g. migration, in HOMECs including the lysosomal protease cathepsin D (CathD). However, the cellular mechanism by which CathD induces these cellular responses is not understood. The aim of this study was to further examine the pro-angiogenic effects of CathD in HOMECs i.e. proliferation and migration, to investigate whether these effects are dependent on CathD catalytic activity and to delineate the intracellular signalling kinases activated by CathD. We report, for the first time, that CathD significantly increases HOMEC proliferation and migration via a non-proteolytic mechanism resulting in activation of ERK1/2 and AKT. These data suggest that EOC cancer secreted CathD acts as an extracellular ligand and may play an important pro-angiogenic, and thus pro-metastatic, role by activating the omental microvasculature during EOC metastasis to the omentum.

Expression profile of cathepsins indicates the potential of cathepsins B and D as prognostic factors in breast cancer patients

Breast cancer is one of the most prevalent types of cancer in women and contributes to 32% of all female cancer cases. Cathepsins, a family of proteins, are known to have a critical role in human cancers. However, previous studies on the systematic analysis of the role of cathepsin family members in breast cancer are limited. The aim of the present study was to identify biological markers to predict prognosis and treatment response of breast cancer patients, as well as to elucidate novel therapeutic targets. The present study analyzed the expression of six members of cathepsin family, including cathepsins B, G, D, K, L and V in 188 breast cancer tissue specimens using immunohistochemistry. The data showed that all members of the tested cathepsin families featured cytoplasmic staining. Notably, expression of cathepsin L was associated with advanced tumor stages, while cathepsins B and K expression levels were associated with positive estrogen receptor expression; in addition, cathepsin K expression was also demonstrated to be associated with progesterone receptor expression. Cathepsins V and D expression levels were found to be associated with breast cancer metastasis, while the expression levels of cathepsins B and D were associated with poor disease-free survival in breast cancer patients. In addition, univariate analysis demonstrated that breast cancer metastasis to the bone and the expression of cathepsin B protein were associated with poor disease-free survival. In conclusion, the results of the present study indicated that the altered expression of cathepsins, in particular cathepsins B and D, contributed to the progression of breast cancer and poor disease-free survival in breast cancer patients.

The Potential Role of the Proteases Cathepsin D and Cathepsin L in the Progression and Metastasis of Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the leading cause of death from gynecologic malignancies and has a poor prognosis due to relatively unspecific early symptoms, and thus often advanced stage, metastasized cancer at presentation. Metastasis of EOC occurs primarily through the transcoelomic route whereby exfoliated tumor cells disseminate within the abdominal cavity, particularly to the omentum. Primary and metastatic tumor growth requires a pool of proangiogenic factors in the microenvironment which propagate new vasculature in the growing cancer. Recent evidence suggests that proangiogenic factors other than the widely known, potent angiogenic factor vascular endothelial growth factor may mediate growth and metastasis of ovarian cancer. In this review we examine the role of some of these alternative factors, specifically cathepsin D and cathepsin L.

Treatment with kaempferol suppresses breast cancer cell growth caused by estrogen and triclosan in cellular and xenograft breast cancer models

As a phytoestrogen, kaempferol (Kaem) is one of bioflavonoids, which are found in a variety of vegetables including broccoli, tea and tomato. In this study, the antiproliferative effects of Kaem in triclosn (TCS)-induced cell growth were examined in MCF-7 breast cancer cells. TCS promoted the cell viability of MCF-7 cells via estrogen receptor α (ERα) as did 17β-estradiol (E2), a positive control. On the other hand, Kaem significantly suppressed E2 or TCS-induced cell growth. To elucidate the molecular mechanisms of TCS and Kaem, alterations in the expressions of cell cycle, apoptosis and metastasis-related genes were identified using western blot assay. The treatment of the cells with TCS up-regulated the protein expressions of cyclin D1, cyclin E and cathepsin D, while down-regulated p21 and bax expressions. Kaem reversed TCS-induced gene expressions in an opposite manner. The phosphorylation of IRS-1, AKT, MEK1/2 and ERK was increased by TCS, indicating that TCS induced MCF-7 cell proliferation via nongenomic ER signaling pathway associated with IGF-1R. Kaem presented an antagonistic activity on this signaling by down-regulating the protein expression of pIRS-1, pAkt and pMEK1/2 promoted by E2 or TCS. In an in vivo xenografted mouse model, tumor growth was induced by treatment with E2 or TCS, which was identified in the measurement of tumor volume, hematoxylin and eosin staining, bromodeoxyuridine and immunohistochemistry assay. On the contrary, E2 or TCS-induced breast tumor growth was inhibited by co-treatment with Kaem, which is consistent with in vitro results. Taken together, these results revealed that Kaem has an anticancer effect against procancer activity of E2 or TCS, a xenoestrogen, in breast cancer and may be suggested as a prominent agent to neutralize breast cancer risk caused by TCS.

Cathepsin D stimulates the activities of secreted plasminogen activators in the breast cancer acidic environment

Two proteases cathepsin D (cath D) and urokinase plasminogen activator (uPA) are tissue markers associated with an increased risk of metastasis in breast cancer. We investigated whether cath D, the major aspartyl protease overexpressed by breast cancer cells can trigger a proteolytic cascade via activation of plasminogens at the extracellular pH measured in hypoxic tumors. The effects of the aspartyl protease inhibitor pepstatin on the plasminogen activator (PA) system were analysed by conditioning media of human MDA-MB231 breast cancer cells at pH 6.6 and pH 7.4. Zymography analysis of culture media showed that pepstatin inhibited the secreted activity of tissue-type plasminogen activator (tPA) but not that of uPA. tPA was identified on the basis of the molecular weight, the immunoreactivity with relevant antibodies and the resistance to amiloride, a specific uPA inhibitor. The secreted tPA activity measured by a chromogenic assay in the presence of amiloride was also inhibited by pepstatin at pH 6.6. Surprisingly, pepstatin did not affect secreted tPA protein concentration but markedly increased the amount of the secreted plasminogen activator inhibitor-1 (PAI-1). We conclude that cath D overexpressed by these cells, stimulates at pH 6.6, but not at neutral pH, the extracellular PA proteolytic activity indirectly via PAI-1 proteolysis. This suggests that cath D at acidic pH close to the hypoxic regions of solid tumors, contributes to trigger a proteolytic cascade facilitating cancer cell invasion and metastasis.

Dipeptide mimic oligomer transporter mediates intracellular delivery of Cathepsin D inhibitors: a potential target for cancer therapy

Implication of the intracellular proteolytic activity of Cathepsin D (CathD), a lysosomal aspartyl-protease overexpressed in numerous solid tumors, has been evidenced on tumor growth. Its intracellular inhibition by potent inhibitors such as pepstatin constitutes a relevant but challenging molecular target. Indeed the potential of pepstatin as a therapeutic molecule is hampered by its too low intracellular penetration. We addressed this limitation by designing and developing a bioconjugate combining a pepstatin derivative with a new vector of cell penetration (CPNP) specifically targeting the endolysosomal compartment. We showed that this pepstatin conjugate (JMV4463) exhibited high anti-proliferative effect on tumor cell cultures via intracellular CathD inhibition and altered cell cycle associated with apoptotic events in vitro. When tested in mice xenografted with breast cancer cells, JMV4463 delayed tumor emergence and growth.

Cathepsin D acts as an essential mediator to promote malignancy of benign prostatic epithelium

BACKGROUND

Stromal-epithelial interactions are important in both development and prostate cancer. Stromal changes have been shown to be powerful prognostic indicators of prostate cancer progression and of patient death helping to define lethal versus indolent phenotypes. The specific molecular underpinnings of these interactions are incompletely understood. We investigated whether stromal cathepsin D (CathD) overexpression affects prostate tumorigenesis through a paracrine mechanism.

METHODS

Normal prostate fibroblasts (NPF) were retrovirally transduced to overexpress cyclin D1 (CD1) and were designated NPF(CD1) . Cathepsin D expression was knocked down using shRNA in cancer associated fibroblasts (CAF) and NPF(CD1) . We analyzed these stromal cell lines using immunohistochemistry, Western blot, and tissue recombination.

RESULTS

An examination of human prostate tissue revealed significantly increased stromal staining of CathD in malignant prostate tissue. Overexpression of CD1 in normal prostate fibroblasts (NPF(CD1) ) produced a phenotype similar to, but more moderate than, CAF in a tissue recombination model. Knockdown studies revealed that CathD is required for NPF(CD1) motility and invasive growth in vitro. BPH-1 cell proliferation was found to be induced when cultured with NPF(CD1) conditioned medium, this effect was inhibited when CathD was knocked down in NPF(CD1) cells. Overexpression of CathD in prostate stromal cells induced malignancy in adjacent epithelium, and this transformation was inhibited when stromal CathD expression was knocked down in CAF.

CONCLUSIONS

The study presented here demonstrates increased CathD expression is seen in human CAF. The upregulation of CD1 results in concomitant increases in CathD expression. Elevated CathD expression in the stroma contributes to tumor promotion.

Recent development of highly sensitive protease assay methods: Signal amplification through enzyme cascades

Proteases are involved in almost all biological processes, and therefore, aberrant activity of many of these enzymes is an important indicator of disease. Various methods have been developed to analyze protease activity, among which, protease assays based on resonance energy transfer are currently used most widely. However, quantitative methods with relatively higher sensitivity are needed, especially for disease diagnosis at early stages. One of the strategies to achieve higher sensitivity is to implement signal amplification of the protease activity. In this review, we briefly summarize the protease assay methods based on resonance energy transfer, and then elaborate the efforts to develop sensitive protease assays through signal amplification by using enzyme cascades.

Clinical and Biological Significance of Cathepsin D Levels in Breast Cancer Cytosol in Women Over 70 years

Objective

To study cytosolic cathepsin D behavior and possible relationship with other clinical and biological parameters in women affected by breast invasive ductal carcinomas and older than 70 years (range: 71–88).

Material and methods

cytosolic levels of cathepsin D were determined by an Immunoradiometric Assay (IRMA-CIS France). Clinical and biological factors analyzed were: size, axillary lymph node involvement, distant metastasis, histological grade, ploidy, S phase cell, cytosolic estrogen receptor, progesterone receptor and pS2, and concentrations of epidermal growth factor receptor (EGFR) in cell membranes.

Results

Cathepsin D concentrations ranged between 13 and 1228 pmol/mg prot.. Median value of 41 was considered as threshold of positivity. Cathepsin D positive tumors showed higher S-phase values (P = 0.046) and were most often histological grade III (P = 0.047). However, the most important finding was the existence of a positive correlation (r = 0.51786) and statistically significant (P < 0.05) between S-phase values and cathepsin D in the overall group of tumors, and those ER+, but not in ER−. We determined cathepsin D concentrations in 131 women with invasive ductal breast carcinomas, but aged between 50 and 70 years (median 61) and we did not find differences based on those values in women >70 years. In addition, we found no correlation between S-phase values and Cathepsin D, both overall and in relation with hormone dependence (ER).

Conclusions

Those results led us to the following conclusions: (1) cytosolic concentrations of cathepsin D in invasive infiltrating breast carcinomas in women over 70 are similar to those seen in women with the same type of tumor, but aged 50 to 70 years and are associated with increased cell proliferation measured by S phase, and histological grade III; (2) in women older than 70 years, cathepsin D concentrations are statistically significantly correlated with phase synthesis values in hormone-dependent tumors, but not in hormone-independent, fact not observed in infiltrating ductal breast carcinomas of women aged between 50 and 70. This could reflect a different mitogenic role of the aspartyl protease enzyme linked to hormone dependence as age function parameter.

Clinicopathological significance of cathepsin D expression in non-small cell lung cancer is conditional on apoptosis-associated protein phenotype: an immunohistochemistry study

Cathepsin D is a well-known peptidase which belongs to the family of aspartic peptidases. It has been found to be overexpressed in many malignant tumors and associated with cancer metastasis and clinical outcome. However, its function in cancers remains controversial. Recently, increasing evidence shows that cathepsin D may play important roles in cell apoptosis. In the current study, we examined the expression of cathepsin D and a group of apoptosis-associated proteins including bcl-2, caspase 3, fas, fasL, p53, and survivin in nonsmall cell lung cancer (NSCLC) tissues to investigate the possible association between cathepsin D and these apoptosis-associated proteins and the clinicopathological features using immunohistochemistry. Cathepsin D expression was detected in cancer tissues including cancer cells (positive rate 64.5%(49/76)) and stromal parts including leukocytes, fibroblasts, capillary endothelial cells, and the matrix. No significant difference was found between the expression of cathepsin D in cancer cells and the corresponding non-tumor portions including bronchial epithelia and submucosal glands (positive rate 53.3% (8/15)) (p>0.05). Immunofluorescence study on formalin-fixed, paraffin-embedded specimens confirmed the cytoplasmic expression of cathepsin D in cancer cells and non-tumor portions. Western blot study detected both mature and immature forms of cathepsin D in lung and NSCLC tissues, while the expression level of neither form showed a significant difference between these tissues (p>0.05). Positive association was found between cathepsin D expression and fas status (p<0.01) but not with the other apoptosis-associated proteins (p>0.05) in cancer cells. Cathepsin D expression alone was not associated with any of the clinicopathological features (p>0.05), while multiplemarker analysis revealed that two immunostaining phenotypes based on the expression of cathepsin D and one of the apoptosis-associated proteins, namely, cathepsin D+/caspase 3- and cathepsin D+/p53+ showed clinicopathological significance. The cathepsin D+/caspase 3- group was associated with advanced tumor node metastasis stages (III and IV) (p<0.05), while the cathepsin D+/p53+ group was associated with lymph node metastasis (p<0.05). The present findings indicate that the expression of cathepsin D in non-small cell lung cancer may have possible contributions to cancer development which is conditional on apoptosis-associated protein phenotype.

Reduction of metastasis using a non-volatile buffer

The tumor microenvironment is acidic as a consequence of upregulated glycolysis and poor perfusion and this acidity, in turn, promotes invasion and metastasis. We have recently demonstrated that chronic consumption of sodium bicarbonate increased tumor pH and reduced spontaneous and experimental metastases. This occurred without affecting systemic pH, which was compensated. Additionally, these prior data did not rule out the possibility that bicarbonate was working though effects on carbonic anhydrase, and not as a buffer per se. Here, we present evidence that chronic ingestion of a non-volatile buffer, 2-imidazole-1-yl-3-ethoxycarbonylpropionic acid (IEPA) with a pK_a of 6.9 also reduced metastasis in an experimental PC3M prostate cancer mouse model. Animals (n = 30) were injected with luciferase expressing PC3M prostate cancer cells either subcutaneously (s.c., n = 10) or intravenously (i.v., n = 20). Four days prior to inoculations, half of the animals for each experiment were provided drinking water containing 200 mM IEPA buffer. Animals were imaged weekly to follow metastasis, and these data showed that animals treated with IEPA had significantly fewer experimental lung metastasis compared to control groups (P < 0.04). Consistent with prior work, the pH of treated tumors was elevated compared to controls. IEPA is observable by in vivo magnetic resonance spectroscopy and this was used to measure the presence of IEPA in the bladder, confirming that it was orally available. The results of this study indicate that metastasis can be reduced by non-volatile buffers as well as bicarbonate and thus the effect appears to be due to pH buffering per se.

Protease sensing with nanoparticle based platforms

Nanoparticulate systems in various unique configurations are highly effective at detecting protease activity both in vivo and in vitro. In this article, we have summarised the conventional modern methods for monitoring protease activity, and critically appraised recent advances in protease-responsive nanosensors.

Synthesis and preclinical evaluations of 2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one monosodium phosphate (CHM-1-P-Na) as a potent antitumor agent

CHM-1 [2-(2-fluorophenyl)-6,7-methylenedioxyquinolin-4-one] (1) has a unique antitumor mechanism of action. However, because 1 has relatively low hydrophilicity, it was evaluated only via ip administration, which is not clinically acceptable. In this study, we synthesized the monosodium phosphate salt (CHM-1-P-Na, 4) of 1 as a hydrophilic prodrug. Compound 4 was rapidly converted into 1 following iv and po administration and also possessed excellent antitumor activity in a SKOV-3 xenograft nude mice model. Compound 4 also had clear-cut pharmacological effects on enzymes related with tumor cells. Neither 4 nor 1 significantly affected normal biological function in a safety pharmacology profiling study. Compound 1 caused apoptotic effects in breast carcinoma cells via accumulation of cyclin B1, and importantly, the endogenous levels of the mitotic spindle checkpoint proteins BubR1 directly correlated with cellular response to microtubule disruption. With excellent antitumor activity profiles, 4 is highly promising for development as an anticancer clinical trials candidate.

In vitro testing of a protease-sensitive contrast agent for optoacoustic imaging

We have designed a protease-sensitive imaging probe for optoacoustic imaging whose absorption spectrum changes upon cleavage by a protease of interest. The probe comprises an active site, a derivative of chlorophyll or natural photosynthetic bacteriochlorophyll that absorbs in the near infrared, conjugated to a peptide backbone specific to the protease being imaged. The uncleaved molecules tend to aggregate in dimers and trimers, causing a change in the absorption spectrum relative to that of the monomer. Upon cleavage, the probe molecules deaggregate, giving rise to a spectrum characteristic of monomers. We show using photospectrometry that the two forms of the probe have markedly different absorption spectra, which could allow for in vivo optoacoustic identification using a multiwavelength imaging strategy. Optoacoustic measurements using a narrow-band dye laser find spectral peaks in the two forms of the probe at the expected location. The optoacoustic signal from the uncleaved probe is found to be considerably weaker than that of the cleaved probe, perhaps due to poor optical-acoustic coupling in the aggregated molecules. However, ultimately, it is detection of the cleaved probe that is of the greatest import, since it reports on the protease activity of interest.

Cathepsin D is the primary protease for the generation of adenohypophyseal vasoinhibins: cleavage occurs within the prolactin secretory granules

Vasoinhibins are a family of N-terminal prolactin (PRL) fragments that inhibit blood vessel growth, dilation, permeability, and survival. The aspartyl endoprotease cathepsin D is active at acidic pH and can cleave rat PRL to generate vasoinhibins. We investigated whether and where vasoinhibins could be generated by cathepsin D in the adenohypophysis of rats and mice and whether their production could be gender dependent. Vasoinhibins were detected in primary cultures of rat adenohypophyseal cells by Western blot with antibodies directed against the N terminus of PRL but not the C terminus. Ovariectomized, estrogen-treated females show greater levels of adenohypophyseal vasoinhibins than males. Peptide sequencing analysis revealed that the cleaved form of PRL in rat adenohypophyseal extracts contains the PRL N terminus and a second N terminus starting at Ser(149), the reported cleavage site of cathepsin D in rat PRL. In addition, cathepsin D inhibition by pepstatin A reduced vasoinhibin levels in rat adenohypophyseal cell cultures. Confocal and electron microscopy showed the colocalization of cathepsin D and PRL within rat adenohypophyseal cells and secretory granules, and a subcellular fraction of rat adenohypophysis enriched in secretory granules contained cathepsin D activity able to generate vasoinhibins from PRL. Of note, vasoinhibins were absent in the adenohypophysis of mice lacking the cathepsin D gene but not in wild-type mice. These findings show that cathepsin D is the main protease responsible for the generation of adenohypophyseal vasoinhibins and that its action can take place within the secretory granules of lactotrophs.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Up-regulation of cathepsin B expression and enhanced secretion in mitochondrial DNA-depleted osteosarcoma cells

BACKGROUND INFORMATION

mtDNA (mitochondrial DNA) mutations that impair oxidative phosphorylation can contribute to carcinogenesis through the increased production of reactive oxygen species and through the release of proteins involved in cell motility and invasion. On the other hand, many human cancers are associated with both the up-regulation and the increased secretion of several proteases and heparanase. In the present study, we tried to determine whether the depletion in mtDNA could modulate the expression and/or the secretion of some lysosomal hydrolases in the 143B osteosarcoma cells, as these mtDNA-depleted cells are characterized by a higher degree of invasiveness than the parental cells.

RESULTS

In comparison with the parental cells, we measured a higher amount of procathepsin B in the conditioned culture medium of the 143B cells lacking mtDNA (rho(0) 143B cells), as well as a rise in the specific activity of intracellular cathepsin B. In addition, we observed an activation of the transcription factor NF-kappaB (nuclear factor kappaB) in the cells devoid of functional mitochondria. Finally, we demonstrated that the down-regulation of the NF-kappaB p65 subunit by RNA interference led to a reduction in cathepsin B expression in rho(0) 143B cells.

CONCLUSIONS

The up-regulation of cathepsin B by NF-kappaB, followed by its secretion into the extracellular environment, might be partly responsible for the previously reported invasiveness of the mtDNA-depleted 143B osteosarcoma cells.

Expression of the putative tumor suppressor gene PTPN13/PTPL1 is an independent prognostic marker for overall survival in breast cancer

Although it is well established that some protein tyrosine kinases have a prognostic value in breast cancer, the involvement of protein tyrosine phosphatases (PTPs) is poorly substantiated for breast tumors. Three of these enzymes (PTP-gamma, LAR, and PTPL1) are already known to be regulated by estrogens or their antagonists in human breast cancer cells. We used a real-time reverse transcriptase polymerase chain reaction method to test the expression levels of PTP-gamma, LAR and its neuronal isoform, and PTPL1 in a training set of RNA from 59 breast tumors. We sought correlations between levels of these molecular markers, current tumor markers, and survival. We then quantified the expression level of the selected phosphatase in 232 additional samples, resulting in a testing set of 291 breast tumor RNAs from patients with a median follow-up of 6.4 years. The Spearman nonparametric test revealed correlations between PTPL1 expression and differentiation markers. Cox univariate analysis of the overall survival studies demonstrated that PTPL1 is a prognostic factor [risk ratio (RR)=0.45], together with the progesterone receptor (PR) (RR=0.52) and node involvement (RR=1.58). In multivariate analyses, PTPL1 and PR retained their prognostic value (RRs of 0.48 and 0.55, respectively). This study demonstrates for the first time that PTPL1 expression level is an independent prognostic indicator of favorable outcome for patients with breast cancer. In conjunction with our mechanistic studies, this finding identifies PTPL1 as an important regulatory element of human breast tumor aggressiveness and sensitivity to treatments such as antiestrogens and antiaromatase.

Lysosomal involvement in cell death and cancer

Lysosomes, with their arsenal of degradative enzymes are increasingly becoming an area of interest in the field of oncology. The changes induced in this compartment upon transformation are numerous and whereas most are viewed as pro-oncogenic the same processes also render cancer cells susceptible to lysosomal death pathways. This review will provide an overview of the pro- and anti-oncogenic potential of this compartment and how these might be exploited for cancer therapy, with special focus on lysosomal death pathways.

Causes and consequences of increased glucose metabolism of cancers

In this review we examine the mechanisms (causes) underlying the increased glucose consumption observed in tumors within a teleological context (consequences). In other words, we will ask not only "How do cancers have high glycolysis?" but also, "Why?" We believe that the insights gained from answering the latter question support the conclusion that elevated glucose consumption is a necessary component of carcinogenesis. Specifically we propose that glycolysis is elevated because it produces acid, which provides an evolutionary advantage to cancer cells vis-à-vis normal parenchyma into which they invade.

Proteomic screening of a cell line model of esophageal carcinogenesis identifies cathepsin D and aldo-keto reductase 1C2 and 1B10 dysregulation in Barrett's esophagus and esophageal adenocarcinoma

Esophageal adenocarcinoma (EA) incidence is increasing rapidly and is associated with a poor prognosis. Identifying biomarkers of disease development and progression would be invaluable tools to inform clinical practice. Two-dimensional polyacrylamide gel electrophoresis was used to screen 10 esophageal cell lines representing distinct stages in the development of esophageal cancer. Thirty-three proteins were identified by MALDI-TOF-MS which demonstrated differences in expression across the cell lines. Western blotting and qRT-PCR confirmed increased cathepsin D and aldo-keto reductases 1C2 and 1B10 expression in metaplastic and dysplastic cell lines. Expression of these proteins was further assessed in esophageal epithelium from patients with nonerosive (NERD) and erosive gastro-esophageal reflux disease, Barrett's esophagus (BE) and EA. When compared with normal epithelium of NERD patients, (i) cathepsin D mRNA levels demonstrated a stepwise increase in expression (p<0.05) in erosive, metaplastic and EA tissue; (ii) AKR1B10 expression increased (p<0.05) 3- and 9-fold in erosive and Barrett's epithelium, respectively; and (iii) AKR1C2 levels increased (p<0.05) in erosive and Barrett's epithelium, but were reduced (p<0.05) in EA. These proteins may contribute to disease development via effects on apoptosis, transport of bile acids and retinoid metabolism and should be considered as candidates for further mechanistic and clinical investigations.

The aspartic protease napsin A suppresses tumor growth independent of its catalytic activity

Members of the aspartic protease family have been implicated in cancer progression. The aspartic protease napsin A is expressed in type II cells of the lung, where it is involved in the processing of surfactant protein B (SP-B). Napsin A is also expressed in kidney, where its function is unknown. Here, we examined napsin A mRNA expression in human kidney tissues using in situ hybridization. Whereas strong napsin A mRNA expression was observed in kidney proximal tubules, expression was detected in only one of 29 renal cell carcinomas. This result is consistent with previous observations of loss of napsin A expression in high-grade lung adenocarcinomas. We re-expressed napsin A in the tumorigenic HEK293 kidney cell line and examined the phenotype of stably transfected cells. Napsin A-expressing HEK293 cells showed an altered phenotype characterized by formation of cyst-like structures in three-dimensional collagen cultures. Napsin A-expressing cells also showed reduced capacity for anchorage-independent growth and formed tumors in SCID mice with a lower efficiency and slower onset compared to vector-transfected control cells. Mutation of one of the aspartic acid residues in the napsin A catalytic site inactivated enzymatic activity, but did not influence the ability to suppress colony formation in soft agar and tumor formation. The mutation of the catalytic site did not affect processing, glycosylation or intracellular localization of napsin A. These data show that napsin A inhibits tumor growth of HEK293 cells by a mechanism independent of its catalytic activity.

Role of prolactin and vasoinhibins in the regulation of vascular function in mammary gland

The formation of new blood vessels has become a major focus of mammary gland research stimulated by the therapeutic opportunities of controlling angiogenesis in breast cancer. Normal growth and involution of the mammary gland are profoundly affected by the expansion and regression of blood vessels, whereas dysregulation of angiogenesis is characteristic of breast cancer growth and metastasis. Prolactin stimulates the growth and differentiation of the mammary gland under normal conditions, but its role in breast cancer is controversial. Its action is complicated by the fact that prolactin itself is angiogenic, but proteases cleave prolactin to generate vasoinhibins, a family of peptides that act on endothelial cells to suppress angiogenesis and vasodilation and to promote apoptosis-mediated vascular regression. This review summarizes our current knowledge about the vascular effects of prolactin and the generation and action of vasoinhibins, and discusses their possible contribution to the regulation of blood vessels in the normal and malignant mammary gland.

Procathepsin D secreted by HaCaT keratinocyte cells - A novel regulator of keratinocyte growth

Procathepsin D (pCD), the precursor form of lysosomal aspartic protease, is overexpressed and secreted by various carcinomas. The fact that secreted pCD plays an essential role in progression of cancer has been established. In this study, we describe substantial secretion of pCD by the human keratinocyte cell line HaCaT, under serum-free conditions. Moreover, exogenous addition of purified pCD enhanced the proliferation of HaCaT cells. The proliferative effect of pCD was inhibited by a monoclonal antibody against the activation peptide (AP) of pCD. Treatment of HaCaT cells with pCD or AP led to the secretion of a set of cytokines that might promote the growth of cells in a paracrine manner. The role of secreted pCD and its mechanism of action were studied in a scratch wound model and the presence of pCD and AP enhanced regeneration, while this effect was reversed by the addition of anti-AP antibody. Expression and secretion of pCD was upregulated in HaCaT cells exposed to various stress conditions. Taken together, our results strongly suggest that the secretion of pCD is not only linked to cancer cells but also plays a role in normal physiological conditions like wound healing and tissue remodeling.

Deciphering the molecular basis of breast cancer metastasis with mouse models

Breast cancer begins as a localized disease, but has the potential to spread to distant sites within the body. This process--known as metastasis--is the leading cause of death from breast cancer. Whether the ability of cancer cells to metastasize is an intrinsic or acquired feature is currently a topic of considerable debate. Nevertheless, the key cellular events required for metastasis are generally accepted. These include invasion of the surrounding stromal tissue, intravasation, evasion of programmed cell death, arrest within the vasculature at a distant site, extravasation, and establishment and growth within a new microenvironment. The development of mouse models that faithfully mimic critical aspects of human neoplasia has been instrumental in framing our current understanding of multistage carcinogenesis. This review examines the advantages and limitations of existing murine models for mammary carcinogenesis for probing the molecular mechanisms that contribute to metastasis, as well as non-invasive tumor imaging approaches to facilitate these investigations.

Loss of tumourigenicity of stably ERbeta-transfected MCF-7 breast cancer cells

Proliferation of breast cancer cells is mediated by estrogen receptors (ER)-ERalpha and ERbeta. At present, contradictory observations complicate the understanding of involvement of ERbeta in breast cancer and functional definition of ERbeta as a prognostic marker. A stable expression of full length ERbeta was established in the ERalpha-positive MCF-7 breast carcinoma cell line to evaluate the role for ERbeta in maintenance of cell viability and estrogenic response, as well as proliferation, morphology and cell cycle progression. In order to verify in vivo tumourigenicity of ERbeta transfectants were transplanted into nude mice. Transfection of ERbeta in MCF-7 resulted in a marginal increase of gelsolin protein expression. Constitutive expression of ERbeta resulted in a significant 30% inhibition of cellular growth compared with transfection of the mock vector alone (p=0.043). This reduction in growth was associated a retardation of transition into S-phase of the cell cycle. The in vitro response to 17beta-estradiol was reversed in cells over-expressing ERbeta (p=0.016). However, no difference in response to the antiestrogens tamoxifen and ICI 182,780 was observed in the presence of ERbeta. Importantly, over-expression of ERbeta prevented establishment and growth of tumours as subcutaneous xenografts in immunodeficient mice in vivo. These observations support the notion that ERbeta is a tumour suppressor and is exploitable in terms of cancer prevention, improving therapeutic response or predicting disease progression.

COUP-TFI modulates estrogen signaling and influences proliferation, survival and migration of breast cancer cells

We previously showed that COUP-TFI interacts with the Estrogen Receptor alpha (ER alpha) to recruit Extracellular signal Regulated Kinases (ERKs) in an Estradiol (E2)-independent manner, resulting in an enhancement of ER alpha transcriptional activity. However, the involvement of COUP-TFI in physiologically relevant functions of ER alpha, such as the mitogenic activity that E2 has on breast cancer cells, remains poorly understood. Here, we first showed that the amounts of COUP-TFI protein are higher in dedifferentiated mammary cell lines (MDA-MB-231) and tumor breast cells as compared to the differentiated MCF-7 cell line and normal breast cells. To evaluate the functional relevance of the COUP-TFI/ER alpha interplay in mammary cells, we generated MCF-7 cells that stably over-express COUP-TFI. We found that the over-expression of COUP-TFI enhances motility and invasiveness of MCF-7 cells. COUP-TFI also promotes the proliferation of MCF-7 cells through ER alpha-dependent mechanisms that target cell cycle progression and cell survival. To further investigate the mechanisms underlying these effects of COUP-TFI, we evaluated the expression of known E2-target genes in breast cancer, and found that COUP-TFI differentially regulated genes involved in cell proliferation, apoptosis, and migration/invasion. Notably, Cathepsin D (CTSD) transcript and protein levels were significantly higher in presence and absence of E2 in MCF-7 over-expressing COUP-TFI. Chromatin Immunoprecipitation assays showed that ER alpha, phospho-RNA Polymerase II, as well as p68 RNA Helicase, a phospho-Serine 118 dependent co-activator of ER alpha, were preferentially recruited onto the CTSD gene proximal promoter in COUP-TFI over-expressing cells. These results suggest that COUP-TFI selectively regulates the expression of endogenous E2-target genes and consequently modifies ER alpha positive mammary cells response to E2.

Secretion of Cytokines in Breast Cancer Cells: The Molecular Mechanism of Procathepsin D Proliferative Effects

Procathepsin D (pCD) is a major secreted protein in estrogen receptor-positive (ER+) breast cancer cell lines. Several independent studies have documented pronounced mitogenic effect of secreted pCD on cancer tissue-derived cell lines, including those from breast, lung, and prostate cancer. It has also been shown that the proliferative effect of pCD involves both autocrine and paracrine modes of action. Recent studies have suggested that pCD could act as a key paracrine communicator between cancer and stromal cells. We have shown earlier that the proliferative activity of pCD depends on the activation peptide sequence of pCD. The present study casts light on the mechanism by which pCD influences the proliferation of cancer cells expressing the ER. Results described in the current paper clearly show that pCD initiates secretion of cytokines interleukin-4 (IL-4), IL-8, IL-10, IL-13, macrophage inflammatory protein-1beta and (MIP-1beta) from such tumor cells. Secreted cytokines take part in the proliferation of the cancer cells, as proven by selective inhibition using antibodies. In addition, expression of cytokine receptors on tested cell lines corresponded to the effects of individual cytokines. An analogous pattern was also observed for fibroblasts, which, under physiologic conditions, are the cells in closest contact with the tumor tissue and play a role in tumor growth and invasion. Our observations were further supported by coculture experiments that are in agreement. Although very similar in response to addition of pCD, the invasive ER- cells do not secrete cytokines. Together with previous in vivo results, these data point to pCD as one of key molecules for therapeutic attack in breast cancer.

Cathepsin D Is Secreted from M-BE Cells: Its Potential Role as a Biomarker of Lung Cancer

The early diagnosis of lung cancer is an effective approach to reduce the mortality caused by malignancy. To explore serum biomarkers of lung cancer at early stage, M-BE, a SV40T-transformed human bronchial epithelial cell line with the phenotypic features of early tumorigenesis at high passage, was cultured in the conditioned media to collect its secretory proteins. The proteins secreted from different passage M-BE cells were extracted and then separated by two-dimensional electrophoresis (2-DE). MALDI-TOF/TOF mass spectrometry was adopted to identify the passage-dependent 2-DE spots. Totally, 47 proteins were identified, including 23 that were up-regulated and 24 that were down-regulated. Of these proteins, cathepsin D was a typical secretory protein that exhibited the increased abundance either in culture media or in cells during passaging. Furthermore, the proteomic conclusions were validated in the clinical samples of lung cancer patients. When sandwich ELISA was used, the concentrations of cathepsin D in plasma showed significant differences between lung squamous cell carcinomas (SCC, 104 cases) and normal donors (36 cases, p <or= 0.015). When tissue microarray (TMA) was used, cathepsin D expression levels in SCC tissues (178 cases) were significantly higher than those in normal donors (40 cases, p < 0.001). The present study has revealed that M-BE cells at different passages could secrete or release some proteins into the living environment, which might serve as the potential resource for exploring the biomarkers of lung cancer.

Radiation-induced posttranscriptional control of M6P/IGF2r expression in breast cancer cell lines

The mannose 6-phosphate/insulin-like growth factor 2 receptor (M6P/IGF2r), a member of the IGF axis of growth factors, is a negative regulator of cell growth and a putative tumor suppressor gene. Regulation of M6P/IGF2r levels is critical in breast physiology; low expression is associated with various aspects of breast cancer. We have found that ionizing radiation induces the rapid expression of M6P/IGF2r in a dose-dependent manner in MCF7 human breast cancer cells. We show that this increase is mediated, at least in part, by a stabilization of M6P/IGF2r transcripts by radiation in both ER positive (MCF7 and T47D) and ER negative (MDA-MB-231) breast cancer cell lines. It is probable, therefore, that posttranscriptional dysregulation of M6P/IGF2r is a contributing mechanism in breast cancer development and breast cancer response to therapy. This is a novel find that underscores the importance of posttranscriptional control of radiation-induced gene expression-a phenomenon that has often been paradigmatically attributed to transcriptional control.