Cathepsin D in normal and neoplastic thyroid tissues

Shotgun proteomics of thyroid carcinoma exosomes - Insight into the role of exosomal proteins in carcinogenesis and thyroid homeostasis

BACKGROUND

Transport of molecules via exosomes is one of the factors involved in thyroid cancer development, and transported molecules may serve as cancer biomarkers. The aim of the study was to characterize protein content of thyroid-derived exosomes and their functional effect exerted on recipient cells.

METHODS

LC-MS/MS proteomics of exosomes released by FTC and 8305C thyroid carcinoma cell lines, and Nthy-ori 3-1 normal thyroid follicular cells was performed, followed by bioinformatic analysis and functional tests (wound healing and Alamar Blue assays).

RESULTS

Exosomes from Nthy-ori 3-1 cells had the highest number of 1504 proteins, while in exosomes from thyroid carcinoma FTC and 8305C cells 730 and 1304 proteins were identified, respectively. For proteins uniquely found in FTC- and 8305C-derived exosomes, enriched cancer-related gene ontology categories included cell adhesion, positive regulation of cell migration, N-glycosylation, drug resistance, and response to NK/T cell cytotoxicity. Furthermore, through label-free quantification (that identified differentially expressed proteins) and comparison with The Human Protein Atlas database several potential diagnostic and/or prognostic biomarkers were indicated. Finally, exosomes from FTC and 8305C cells displayed ability to stimulate migratory properties of recipient Nthy-ori 3-1 cells. Additionally, 8305C-derived exosomes increased recipient cell viability.

CONCLUSIONS

Multiple proteins identified in thyroid cancer-derived exosomes have a direct link to thyroid cancer progression. Also, in functional tests exosomes enhanced growth and dissemination of non-transformed thyroid cells.

GENERAL SIGNIFICANCE

The obtained results expands the knowledge concerning the role of exosomal proteins in thyroid cancer and indicate potential biomarkers for further evaluation in clinical settings.

Phormidepistatin from the Cyanobacterium UIC 10484: Assessing the Phylogenetic Distribution of the Statine Pharmacophore

A new linear lipopeptide, phormidepistatin (1), containing an epi-statine amino acid was isolated from cf. Phormidium sp. strain UIC 10484. The planar structure was elucidated by 1D and 2D NMR experimentation. The relative configuration was determined by J-based configurational analysis and the absolute configuration by advanced Marfey's analysis. Given that the statine moiety is an established pharmacophore known to inhibit aspartic proteases, phormidepistatin was evaluated against cathepsin D and displayed limited activity. With 1 containing a statine-like moiety, we sought to assess the distribution of this γ-amino acid within the phylum Cyanobacteria. In-depth MS/MS analysis identified the presence of phormidepistatin in cf. Phormidium sp. UIC 10045 and cf. Trichormus sp. UIC 10039. A structure database search identified 33 known cyanobacterial metabolites containing a statine or statine-like amino acid and, along with phormidepistatin, were grouped into 10 distinct compound classes. A phylogenetic tree was built comprising all cyanobacteria with established 16S rRNA sequences known to produce statine or statine-like-containing compound classes. This analysis suggests the incorporation of the γ-amino acid into secondary metabolites is taxonomically widespread within the phylum. Overall, it is our assessment that cyanobacteria are a potential source for statine or statine-like-containing compounds.

Significance of nuclear cathepsin V in normal thyroid epithelial and carcinoma cells

Altered expression and/or localization of cysteine cathepsins is believed to involve in thyroid diseases including cancer. Here, we examined the localization of cathepsins B and V in human thyroid tissue sections of different pathological conditions by immunolabeling and morphometry. Cathepsin B was mostly found within endo-lysosomes as expected. In contrast, cathepsin V was detected within nuclei, predominantly in cells of cold nodules, follicular and papillary thyroid carcinoma tissue, while it was less often detected in this unusual localization in hot nodules and goiter tissue. To understand the significance of nuclear cathepsin V in thyroid cells, this study aimed to establish a cellular model of stable nuclear cathepsin V expression. As representative of a specific form lacking the signal peptide and part of the propeptide, N-terminally truncated cathepsin V fused to eGFP recapitulated the nuclear localization of endogenous cathepsin V throughout the cell cycle in Nthy-ori 3-1 cells. Interestingly, the N-terminally truncated cathepsin V-eGFP was more abundant in the nuclei during S phase. These findings suggested a possible contribution of nuclear cathepsin V forms to cell cycle progression. Indeed, we found that N-terminally truncated cathepsin V-eGFP expressing cells were more proliferative than those expressing full-length cathepsin V-eGFP or wild type controls. We conclude that a specific molecular form of cathepsin V localizes to the nucleus of thyroid epithelial and carcinoma cells, where it might involve in deregulated pathways leading to hyperproliferation. These findings highlight the necessity to better understand cathepsin trafficking in health and disease. In particular, cell type specificity of mislocalization of cysteine cathepsins, which otherwise act in a functionally redundant manner, seems to be important to understand their non-canonical roles in cell cycle progression.

Immunohistochemical Expression of Cathepsin D in Primary and Recurrent Squamous Cell Carcinoma

AIM

The aim of this study is to analyze and compare the immunohistochemical expression of cathepsin B in primary oral squamous cell carcinoma (OSCC) and recurrent OSCC.

MATERIALS AND METHODS

A total of 50 cases were studied immunohistochemically for rabbit polyclonal antihuman cathepsin D expression. A total of 10 cases of breast carcinoma were taken as positive controls. Immunohistochemical staining was performed using labeled streptavidin-biotin technique.

RESULTS

All the 45 cases of OSCC, both primary and recurrent cases included, showed varying grades of cathepsin D immu-noreactivity. Statistical significance at 5% level was observed in cathepsin D expression between the different grades of well, moderate, and poorly differentiated primary squamous cell carcinomas. In the comparison of cathepsin D staining intensity among primary squamous cell carcinomas with and without recurrence, a statistical significance between the groups was observed when the p-value was at 10%, but the same comparison was not significant when the p-value was at 5%.

CONCLUSION

Cathepsin D expression in primary squamous cell carcinomas with recurrences was very variable as compared with primary squamous cell carcinomas without recurrences. Comparison of cathepsin D expression in primary with their recurrent counterparts showed mostly similar intensity of expression in recurrent carcinomas, thus suggesting its limited usefulness in predicting recurrence.

CLINICAL SIGNIFICANCE

Although cathepsin D might have shown limited usefulness in predicting cancer recurrence, it, however, is a proven valuable tool to detect the aggressiveness of various other tumors, and if corroborated with a larger sample may hold the key to early, more effective, and more specific treatment modalities for cases of oral cancer also.

Unveiling a novel biomarker panel for diagnosis and classification of well-differentiated thyroid carcinomas

Thyroid cancer is the most common human endocrine malignancy with increasing global incidence. Papillary thyroid carcinomas (PTC) and follicular thyroid carcinomas (FTC) are well-differentiated thyroid cancers (WDTC) accounting for 95% of all thyroid cancer cases, with survival rates of almost 100% when diagnosed early. Since PTC and FTC have different modes of metastasis, they require different treatment strategies. Standard diagnosis by fine needle aspiration with cytopathological examination can be inaccurate in approximately 10-30% of all cases and difficult to definitively classify as WDTC. Currently, there is no single or panel of biomarkers available for thyroid cancer diagnosis and classification. This study identified novel biomarkers for thyroid cancer diagnosis and classification using proteomics, which may be translated into a biomarker panel for clinical application. Two-dimensional SDS-PAGE and mass spectrometry were used to identify potential biomarkers in papillary and follicular thyroid carcinoma cell lines, and the biomarkers were validated in five PTC and five FTC tissues, with their adjacent normal tissues from Thai patients. Eight biomarkers could distinguish PTC from normal tissues, namely enolase 1, triose phosphate isomerase, cathepsin D, annexin A2, cofilin 1, proliferating cell nuclear antigen (PCNA), copine 1 and heat shock protein 27 kDa (HSP27). These biomarkers can also discriminate FTC from normal tissues, except for annexin A2. On the contrary, annexin A2, cofilin 1, PCNA and HSP27 can be used to classify the types of WDTC. These findings have potential for use as a novel multi-marker panel for more accurate diagnosis and classification to better guide physicians on thyroid cancer treatment. Moreover, our results suggest the involvement of proteins in cell growth and proliferation, and the p53 pathway in the carcinogenesis of WDTC, which may lead to targeted therapy for thyroid cancer.

Alteration of cathepsin D trafficking induced by hypoxia and extracellular acidification in MCF-7 breast cancer cells

The microenvironment that surrounds tumor cells is characterized by hypoxic conditions and extracellular acidity. These hostile conditions induce crucial changes in cell behavior and can promote the secretion of many soluble factors such as growth factors, cytokines and enzymes. The lysosomal aspartyl-endopeptidase cathepsin D (CD) is a marker of poor prognosis in breast cancer and is associated with a metastatic risk. In this study, the transport of CD was investigated in a model of breast cancer cells line (MCF-7) cultivated under hypoxia and acidification of media. CD secretion was assessed using Western blot analysis and protease activity was measured in conditioned culture media. We demonstrate that cultured MCF-7 cells secrete an active 52 kDa pCD precursor and report that under hypoxia there was an increased amount of pCD secreted. More surprisingly, extracellular acidification (pH 6 and 5.6) induced the secretion of the fully-mature and active (34 kDa + 14 kDa) double chain CD. Our findings reflect the fact that chemical anomalies influence the secretion path of CD in a breast cancer cell model, resulting in altered trafficking of the mature form. This important result may provide new arguments in favor of the role of extracellular CD in the degradation of the matrix proteins that constitute the breast tumor microenvironment.

Cathepsin D activity and selectivity in the acidic conditions of a tumor microenvironment: Utilization in the development of a novel Cathepsin D substrate for simultaneous cancer diagnosis and therapy

Pro-Cathepsin D (pCD) is an aspartyl endopeptidase which is over expressed in many cancers. This over expression generally led to its secretion into the extracellular culture medium of cancer cells. Moreover, pCD can auto activate and cleave its substrates at an acidic pH compatible with that found in tumor microenvironments (TME). Thus, exploiting these two pathological characteristics of TME offers the opportunity to develop new protease-activated vector on the basis of their specific substrate structures. The aim of this study was to validate new pCD substrates in the extracellular pH conditions of TME. As a first step, we investigated the effect of pH on the catalytic activity and selectivity of mature Cathepsin D (CD). It was found that the increase in the pH of the media led to a decrease in the reaction rate. However, the specificity of mature CD was not affected by a variation in pH. In the second step, the effect of the substrate structure was studied. We demonstrated that the substrate structure had a significant effect on the catalytic activity of CD. In fact, some modifications in peptide structure induced a change in the catalytic behavior that involved a substrate activation phenomenon. We suggest that this activation may be related to the amphiphilic nature of the modified peptide that may induce an interfacial activation mechanism. Finally, pCD, which is the major form found in the extracellular culture medium of cancer cells, was used. We demonstrated that the proform of CD cleave the modified peptide 5 at pH 6.5 with the same cleavage selectivity obtained with the mature form of the protease. These data provide a better understanding of CD behavior in tumor microenvironment conditions and this knowledge can be used to develop more specific tools for diagnosis and drug delivery.

Lysosomal acid hydrolases of the cathepsin family are novel targets of INSL3 in human thyroid carcinoma cells

Insulin-like peptide 3 (INSL3) is present in hyperactive and neoplastic thyrocytes, but the functional role of this relaxin-like peptide hormone during carcinogenesis in the thyroid gland is currently unknown. We generated new cell models of stable transfectants of the human follicular thyroid carcinoma cell line FTC-133 expressing and secreting bioactive human INSL3. These transfectants displayed higher intracellular ATP levels, but INSL3 failed to act as a promoter of growth. The acquisition of an invasive tumor cell phenotype with local tissue invasion represents the beginning of a number of events leading to metastasis, the major cause of fatal outcome in cancer patients. Here we demonstrate a function of INSL3 in elastin degradation, which is considered an early step during basal membrane penetration and tissue invasion by tumor cells. INSL3 markedly increased the production of the lysosomal enzymes cathepsin-L and cathepsin-D. Enhanced secretion of the elastinolytic cathepsin-L was associated with increased elastinolytic activity of FTC-133-INSL3 transfectants. Thus, we provide the first evidence that the INSL3 peptide can promote early tumor cell invasiveness in human thyroid carcinoma cells by enhancing their metabolic activity and elastin-degrading potential.

Relaxin enhances the oncogenic potential of human thyroid carcinoma cells

The role of members of the insulin-like superfamily in human thyroid carcinoma is primarily unknown. Here we demonstrate the presence of RLN2 relaxin and relaxin receptor LGR7 in human papillary, follicular, and undifferentiated anaplastic thyroid carcinoma suggesting a specific involvement of relaxin-LGR7 signaling in thyroid carcinoma. Stable transfectants of the LGR7-positive human follicular thyroid carcinoma cell lines FTC-133 and FTC-238 that secrete bioactive proRLN2 revealed this hormone to act as a multifunctional endocrine factor in thyroid carcinoma cells. Although RLN2 did not act as a mitogen, it acted as an autocrine/paracrine factor and significantly increased anchorage-independent growth and thyroid carcinoma cell motility and invasiveness through elastin matrices. Suppression of LGR7 expression by LGR7-siRNA abolished the RLN2-mediated accelerated tumor cell motility. The increased elastinolytic activity correlated with enhanced production and secretion of the lysosomal proteinases cathepsin-D (cath-D) and cath-L forms hereby identified as new RLN2 target molecules in human neoplastic thyrocytes. We found the intracellular distribution of procath-L specifically altered in RLN2 transfectants, providing first evidence for selective actions of relaxin on the powerful elastinolytic cath-L production, storage, and secretion in thyroid carcinoma cells. Thus, relaxin enhances the oncogenic potential and acts as novel endocrine modulator of invasiveness in human thyroid carcinoma cells.

CD26 (Dipeptidyl Aminopeptidase IV) Expression in Normal and Diseased Human Thyroid Glands

The objective of the present study was to investigate CD26 (dipeptidyl aminopeptidase IV) expression in normal and diseased thyroids and its relation to differentiation and cell proliferation. CD 26 was also evaluated as a possible marker of malignancy in thyroid neoplasias. A total of 38 normal thyroids and 117 diseased thyroids (neoplastic and non-neoplastic) were evaluated. CD26 and thyroglobulin (Tg) expression was determined by analyzing at least 200 cells/specimen. A minimum of 500 cells/specimen were counted to calculate the MIB-1-positive cell rate expressed as a percentage of total nucleated epithelial cells. CD26 expression was absent in all thyroids from fetuses and children. Among the adults, 7.1 % had CD26 expression only in oncocytic metaplastic areas. In 3 of the 7 elderly subjects, CD26 expression was present in 0.2-90% of epithelial cells. CD26 expression was observed in all diseased thyroids. Since this enzyme is also expressed in benign conditions, it is not useful as a marker of malignancy. There was no relationship between CD26 and Tg expression. The MIB-1-positive cell rate was found to be low for all kinds of thyroid tissues, and when the cell proliferation rate was analyzed according to CD26 expression, a greater cell proliferation rate was found in CD26-positive differentiated (follicular and papillary) carcinomas than in CD26-negative carcinomas. These results demonstrate that expression of this enzyme is related to the proliferative activity of follicular cells.