Keratin expression and its significance in five cultured melanoma cell lines derived from primary, recurrent and metastasized melanomas

Transcript levels of keratin 1/5/6/14/15/16/17 as potential prognostic indicators in melanoma patients

Keratins (KRTs), the intermediate filament-forming proteins of epithelial cells, are extensively used as diagnostic biomarkers in cancers and associated with tumorigenesis and metastasis in multiple cancers. However, the diverse expression patterns and prognostic values of KRTs in melanoma have yet to be elucidated. In the current study, we examined the transcriptional and clinical data of KRTs in patients with melanoma from GEO, TCGA, ONCOMINE, GEPIA, cBioPortal, TIMER and TISIDB databases. We found that the mRNA levels of KRT1/2/5/6/8/10/14/15/16/17 were significantly differential expressed between primary melanoma and metastatic melanoma. The expression levels of KRT1/2/5/6/10/14/15/16/17 were correlated with advanced tumor stage. Survival analysis revealed that the high transcription levels of KRT1/5/6/14/15/16/17 were associated with low overall survival in melanoma patients. GSEA analysis indicated that the most involved hallmarks pathways were P53 pathway, KRAS signaling, estrogen response early and estrogen response late. Furthermore, we found some correlations among the expression of KRTs and the infiltration of immune cells. Our study may provide novel insights for the selection of prognostic biomarkers for melanoma.

ATP Synthase Subunit Epsilon Overexpression Promotes Metastasis by Modulating AMPK Signaling to Induce Epithelial-to-Mesenchymal Transition and Is a Poor Prognostic Marker in Colorectal Cancer Patients

Metastasis remains the major cause of death from colon cancer. We intend to identify differentially expressed genes that are associated with the metastatic process and prognosis in colon cancer. ATP synthase epsilon subunit (ATP5E) gene was found to encode the mitochondrial F₀F₁ ATP synthase subunit epsilon that was overexpressed in tumor cells compared to their normal counterparts, while other genes encoding the ATP synthase subunit were repressed in public microarray datasets. CRC cells in which ATP5E was silenced showed markedly reduced invasive and migratory abilities. ATP5E inhibition significantly reduced the incidence of distant metastasis in a mouse xenograft model. Mechanistically, increased ATP5E expression resulted in a prominent reduction in E-cadherin and an increase in Snail expression. Our data also showed that an elevated ATP5E level in metastatic colon cancer samples was significantly associated with the AMPK-AKT-hypoxia-inducible factor-1α (HIF1α) signaling axis; silencing ATP5E led to the degradation of HIF1α under hypoxia through AMPK-AKT signaling. Our findings suggest that elevated ATP5E expression could serve as a marker of distant metastasis and a poor prognosis in colon cancer, and ATP5E functions via modulating AMPK-AKT-HIF1α signaling.

Immunohistochemical expression of keratins 6, 7, 8, 14, 16, 18, 19, and MNF-116 pancytokeratin in primary and metastatic melanoma of the head and neck

OBJECTIVE

To investigate the immunohistochemical expression (IHCE) of selected keratins in primary cutaneous and mucosal melanoma (pM), and metastatic melanoma (metsM) of the head and neck and to compare their expression to a group of undifferentiated/poorly differentiated tumors of the same anatomic region.

STUDY DESIGN

IHCE of K6, K7, K8, K14, K16, K18, and K19 were studied in 29 melanomas and 70 cases of non-melanoma tumors of the same anatomic region (neuroendocrine carcinoma, neuroblastoma, olfactory neuroblastoma, sinonasal undifferentiated carcinoma, undifferentiated nasopharyngeal carcinoma, anaplastic large cell lymphoma, poorly differentiated squamous cell carcinoma (PDSCC), and Ewing sarcoma). MNF-116 pancytokeratin was investigated in melanoma.

RESULTS

All studied keratins, except K6, were expressed in melanoma. IHCE of MNF-116, K8, and K18 was higher in metsM compared with pM. K14 and K16 expression was highest in PDSCC.

CONCLUSIONS

metsM expresses keratins more than pM, specifically K8, K18, and MNF-116. Keratin positivity in an undifferentiated or poorly differentiated neoplasm does not necessarily exclude the diagnosis of melanoma.

Pathologic and gene expression features of metastatic melanomas to the brain

BACKGROUND

The prognosis of metastatic melanomas to the brain (MBM) is variable with prolonged survival in a subset. It is unclear whether MBM differ from extracranial metastases (EcM) and primary melanomas (PrM).

METHODS

To study the biology of MBM, histopathologic analysis of tumor blocks from patients' craniotomy samples and whole-genome expression profiling (WGEP) with confirmatory immunohistochemistry were performed.

RESULTS

High mononuclear infiltrate and low intratumoral hemorrhage were associated with prolonged overall survival (OS). Pathway analysis of WGEP data from 29 such craniotomy tumor blocks demonstrated that several immune-related BioCarta gene sets were associated with prolonged OS. WGEP analysis of MBM in comparison with same-patient EcM and PrM showed that MBM and EcM were similar, but both differ significantly from PrM. Immunohistochemical analysis revealed that peritumoral CD3⁺ and CD8⁺ cells were associated with prolonged OS.

CONCLUSIONS

MBMs are more similar to EcM compared with PrM. Immune infiltrate is a favorable prognostic factor for MBM.

Downregulation of keratins 8, 18 and 19 influences invasiveness of human cultured squamous cell carcinoma and adenocarcinoma cells

Keratin (K) expression index has been reported to be related to cell invasion activity in adenocarcinoma. In a previous study, we observed a negative correlation between K expression and cell invasion activity; i.e., when many Ks are expressed in the cells, the cell activity is low. To further elucidate the correlation between Ks and invasion activity, RNA interference experiments of K8, K18 and K19 were carried out to clarify the essential role of Ks using T24 and HEC-1 as typical squamous cell carcinoma and adenocarcinoma cells, respectively. K8 small interfering RNA (siRNA) was most effective against K18 and K19 expression and demonstrated the strongest effect on relative invasion activity among the siRNAs used. These results suggest that K8/K18 or K8/K19 filaments may play roles in internal cell structure and invasion activity. Moreover, K18 and K19 were capable of substituting for each other, and K18 or K19 formed filaments with K8. In addition, cells treated with K8 siRNA demonstrated high invasion activity, which was approximately double that observed with control siRNA in HEC-1 cells. The order of effects was K8>K19>K18 in the two cell lines. The above results suggest that K8 may play a signifiant role in invasive functions in epithelial and metastatic cells.

Cytokeratin expression in malignant melanoma: potential application of in-situ hybridization analysis of mRNA

Occasional reports indicated cytokeratin (CK) protein expression (mainly by immunohistochemistry) in malignant melanoma (MM) and suggested an association with unfavorable clinical parameters. However, the mRNA expression of CK and its clinicopathologic significance in MM has not been specifically evaluated. We investigated the mRNA and protein expression of nine CKs in melanoma cell lines and tissues, in particular the prognostic significance of CK18 mRNA expression. Reverse transcription (RT)-PCR (CK6-10, 14 and 18-20), in-situ hybridization (ISH) (CK18), and western blotting (CK18 and pan-cytokeratin AE1/AE3) were performed on MM cell lines A375, A875, M14, and SK-MEL-1. Eighty MM tissue samples were analyzed by ISH and immunohistochemistry for CK18 expression. The mRNA of CK6-8, 10, 14, 18, and 19 (but not CK9 and 20) was detected in one to four of the melanoma cell lines by RT-PCR. CK18 was detected in all four cell lines by RT-PCR, ISH, and western blotting. CK18 mRNA ISH was positive in three of 30 (10.0%), 10 of 25 (40.0%), and 12 of 25 (48.0%) of primary cutaneous, primary mucosal, and metastatic melanomas, respectively (overall positivity: 25 of 80, 31.3%). CK18 immunostaining was only observed focally in eight of 80 (10.0%) of MM tissue samples, and AE1/AE3 immunostaining was altogether negative. Significantly, CK18 mRNA ISH positivity (but not protein immunohistochemistry) was associated with poorer prognosis by both univariate analysis (P<0.001) and multivariate analysis (relative risk=5.430, 95% confidence interval 2.246-13.128, P<0.001). CK18 mRNA could be identified in one-third of melanoma tissue samples and is an adverse prognostic factor. ISH is superior to immunohistochemistry for analyzing CK18 expression in MM.

Proteomic comparison of nasopharyngeal cancer cell lines C666-1 and NP69 identifies down-regulation of annexin II and beta2-tubulin for nasopharyngeal carcinoma

CONTEXT

Nasopharyngeal carcinoma (NPC), common in southern China and North Africa, has a complex etiology involving interplay between viral, environmental, and hereditary factors and is almost constantly associated with the Epstein-Barr virus. Since the prognosis of locally advanced and metastatic diseases is poor, increased understanding of the pathogenesis of NPC would be important for discovering novel markers for patients' management.

OBJECTIVES

To compare the proteomic expression profile between an Epstein-Barr virus-associated NPC cell line (C666-1) and a normal NP cell line (NP69). The proteins with differential expression were analyzed in 40 undifferentiated NPC paraffin-embedded specimens.

DESIGN

Differentially expressed proteins discovered between the two cell lines were identified by mass spectrometry. After confirmation by immunocytochemical staining, their expression in patient samples was measured using 40 pairs of undifferentiated NPCs together with their adjacent normal epithelia.

RESULTS

Proteomic findings indicated that adenosine triphosphate synthase alpha chain was up-regulated, whereas annexin II, annexin V, beta(2)-tubulin, and profilin 1 were down-regulated. After confirming the results in agar-processed cell lines, annexin II and beta(2)-tubulin expression were found to be lower in tumor cells than in adjacent normal epithelial cells in 100% and 90% of the patients' specimens, respectively. Finally, annexin II down-regulation was positively associated with lymph node metastasis, suggesting that it may be a prognostic factor in NPC.

CONCLUSIONS

The results suggest that annexin II and beta(2)-tubulin down-regulation is important in NPC formation and may represent potential targets for further investigations.

Unexpected expression of Hsp47, a replacement of one amino acid (Val 7 Leu) in the amino terminal region, in cultured human tumorigenic cell lines

BACKGROUND

In general, it has been stated that keratin (K) molecules are glycosylated. During biochemical studies of K subunits, we encountered a glycoprotein that does not judge K subunits.

OBJECTIVE

This study was intended to elucidate how the above glycoprotein co-exists in the K fraction prepared from ISO-HAS (cultured angiosarcoma cell line).

METHODS

We analyzed and sequenced a remarkable spot, which was shown as a glycoprotein by periodic acid Sciff's (PAS) staining, in the K fraction prepared from ISO-HAS.

RESULTS

The glycoprotein was identified as an N-terminal amino acid sequence covering 10 residues of the spot. A homology search showed that it was identical to that of Hsp47 (matured type), except for one amino acid (seventh amino acid: Val 7 Leu). Similar results were confirmed for four other tumorigenic cell line types. Subsequent PAS staining using the same samples after 2D-PAGE revealed no glycosylated Ks.

CONCLUSION

No glycosylated Ks were found by PAS staining in the K fraction prepared from four tumorigenic cell line types. During K preparation from cultured human tumor cell lines, Hsps might be associated with K expression in tumor cells.

Identification and functional characterization of ASK/Dbf4, a novel cell survival gene in cutaneous melanoma with prognostic relevance

Malignant melanoma is one of the most aggressive and invasive metastatic tumors derived from melanocytes that have undergone malignant transformation by acquisition of genetic and epigenetic alterations. Oligonucleotide microarray-based screening of distinct stages in the tumor progression model of cutaneous melanoma identified ASK/Dbf4, as a novel determinant for melanoma development. Quantitative real-time polymerase chain reaction-based confirmation of ASK/Dbf4 on a series of benign nevi, dysplastic nevi, primary cutaneous melanomas and cutaneous melanoma metastases; and a number of other controls using normal human melanocytes as calibrator not only revealed a melanoma-specific over-expression but also revealed that higher ASK/Dbf4-expressing melanomas were associated with lower relapse-free survival. Additionally, we also confirmed the observed over-expression of ASK/Dbf4 in melanoma using western blot analysis and immunohistochemistry. As ASK/Dbf4 is known to be a cyclin-like regulatory subunit of mammalian Cdc7 from the studies in yeast, the present study investigated its role in melanoma cells. In keeping with its expected role, our data suggest that up-regulated ASK/Dbf4 is localized in the nucleus and binds to human Cdc7 to form Cdc7-ASK/Dbf4 complexes in several analyzed melanoma cell lines. Further, we demonstrate that small interfering RNA-mediated depletion of ASK/Dbf4 retarded melanoma cell survival and proliferation. In summary, we report the differential regulation of a novel gene, namely ASK/Dbf4, in melanoma and suggest that up-regulation of ASK/Dbf4 is a novel molecular determinant with prognostic relevance that confers a proliferative advantage in cutaneous melanoma.

Identification of mitochondrial FoF1-ATP synthase involved in liver metastasis of colorectal cancer

Liver metastasis is a major cause of poor survival of colorectal cancer patients. In order to identify the proteins associated with liver metastasis in colorectal cancer, we carried out two-dimensional gel electrophoresis-based comparative proteomic analysis of normal colon mucosa, primary colon cancer tissue and corresponding metastatic tumor tissue in liver. The proteins identified were further validated by immunohistochemical analysis of 67 quadruplet samples of normal colon primary colorectal cancer and normal liver-synchronous liver metastasis, and 251 colorectal cancers as well as in vitro invasion assay of the human colon cancer cell line, SNU-81. From proteomic assessment, the mitochondrial FoF1-ATP synthase (ATP synthase) alpha-subunit was identified as a protein that is upregulated in liver metastasis compared with the primary tumor. Immunohistochemical analyses confirmed a significant increase in the expression of ATP synthase alpha- and d-subunits in synchronous liver metastasis compared with primary tumor and normal mucosa, respectively. ATP synthase alpha- and d-subunits were overexpressed in 197 (78.5%) and 190 (75.7%), respectively, of the 251 colorectal cancers. The alpha- and d-subunits were significantly associated with liver metastasis (P < 0.05) as well as low histological grade (P < 0.0001). The d-subunit also correlated with venous invasion (P = 0.026) and distant metastasis (P = 0.032). In stage III cancers, d-subunit expression was independently associated with poor survival (P = 0.017). Furthermore, transfection of small interfering RNA targeted to ATP synthase alpha- and d-subunits resulted in decreased in vitro invasiveness of the human colon cancer cell line. Our overall findings demonstrate that increased ATP synthase is associated with liver metastasis of colorectal cancer.

Keratin 16 Expression in Epidermal Melanocytes of Normal Human Skin

Although the prevailing dogma states that keratin filaments are the hallmark of keratinocytes and other epithelial cells, recent publications suggest that they may be expressed by a variety of normal and malignant cells of different embryonic origin. Keratin expression has been reported in fibroblasts and endothelial cells as well as in various sarcomas. Also, some human melanomas express keratins in addition to the traditional diagnostic markers of differentiation, such as S-100 and melanocyte-specific antigens. Many studies have shown that cultured cells obtained from various melanomas express keratin. Most recently, keratin expression has also been shown in cultured melanocytes of normal skin. We now report that normal human melanocytes in vivo express keratin 16 (K16) but not keratins 1, 5, 8, 10, 14, or even keratin 6, the type II partner that is normally expressed with K16 in keratinocytes. Similarly, melanocytes in vitro express K16 but not K6. Keratin 16 expression in vivo was present in basal melanocytes in specimens derived from donors (0-77 years) and from different anatomic locations, suggesting that keratin 16 is constitutively expressed by all melanocytes. It appears that keratin expression may be more prevalent than previously assumed, and that these cytoskeletal filaments may play important roles in tissues and cells other than epithelia.

Lineage infidelity of MDA-MB-435 cells: expression of melanocyte proteins in a breast cancer cell line

The origin of cell lines is critical in defining cell type-specific biological functions. Several reports suggested that the MDA-MB-435 cell line, a cell line extensively used for studying breast cancer biology, has a gene expression pattern most compatible with melanocyte origin. However, we demonstrate that MDA-MB-435 cells express breast-specific or epithelial-specific markers. Also, MDA-MB-435 cells were induced to express breast differentiation-specific proteins and secrete milk lipids as observed in other well-established breast cancer cell lines. Notably, MDA-MB-435 cells also expressed melanocyte-specific proteins as did another highly aggressive breast cancer cell line. MDA-MB-435 xenograft tissue sections stained entirely positive for epithelium-specific markers but only partially positive for melanocyte-specific markers. Thus, MDA-MB-435 is most likely a breast epithelial cell line that has undergone lineage infidelity.

Occurrence and comparison of the expressed keratins in cultured human fibroblasts, endothelial cells and their sarcomas

We investigated keratin (K) expression in cultured fibroblasts, endothelial cells and their sarcomas by using two-dimensional gel electrophoresis and electron microscopy techniques. Although the fibroblast and endothelial cell lines were derived from mesenchyme, we confirmed Ks in both cell lines. The K in two cultured cell lines consisted of K14 and K16, together with vimentin. In addition to the above Ks, K5 and K8/K17 were comprised in each cell line, respectively. On the other hand, the cultured fibrosarcomas contained K8 and K18 in addition to the Ks present in the cultured fibroblasts, except K17. Moreover, cultured angiosarcomas showed the same Ks expression as those of the cultured fibrosarcomas, except vimentin. However, electron microscopy showed that the extremely thin fiber-like substances existed or at least did not form filamentous structures in four cultured cell types.

Identification of 12-lipoxygenase interaction with cellular proteins by yeast two-hybrid screening

The platelet isoform of 12-lipoxygenase (12-LOX) is expressed in a variety of human tumors. 12-LOX metabolizes arachidonic acid to 12(S)-hydroxyeicosateraenoic acid (12(S)-HETE), which induces a number of cellular responses associated with tumor progression and metastasis. Little is known about 12-LOX regulation and no direct regulators of 12-LOX activity have been identified. To identify potential regulators of 12-LOX, we isolated cDNAs encoding 12-LOX interacting proteins using the yeast two-hybrid system. We screened a yeast two-hybrid interaction library from human epidermoid carcinoma A431 cells and identified four cellular proteins that interact specifically with 12-LOX. We identified type II keratin 5, lamin A, the cytoplasmic domain of integrin beta4 subunit and a phosphoprotein C8FW as 12-LOX interacting proteins. Here, we demonstrated that keratin 5, a 58 kD protein required for formation of 8 nm intermediate filaments, binds to 12-LOX in human tumor cells and may contribute to the regulated trafficking of 12-LOX. We also showed that lamin A binds 12-LOX in human tumor cells. These proteins provide the first candidate regulators of 12-LOX.

The cytoskeleton of digestive epithelia in health and disease

The mammalian cell cytoskeleton consists of a diverse group of fibrillar elements that play a pivotal role in mediating a number of digestive and nondigestive cell functions, including secretion, absorption, motility, mechanical integrity, and mitosis. The cytoskeleton of higher-eukaryotic cells consists of three highly abundant major protein families: microfilaments (MF), microtubules (MT), and intermediate filaments (IF), as well as a growing number of associated proteins. Within digestive epithelia, the prototype members of these three protein families are actins, tubulins, and keratins, respectively. This review highlights the important structural, regulatory, functional, and unique features of the three major cytoskeletal protein groups in digestive epithelia. The emerging exciting biological aspects of these protein groups are their involvement in cell signaling via direct or indirect interaction with a growing list of associated proteins (MF, MT, IF), the identification of several disease-causing mutations (IF, MF), the functional role that they play in protection from environmental stresses (IF), and their functional integration via several linker proteins that bridge two or potentially all three of these groups together. The use of agents that target specific cytoskeletal elements as therapeutic modalities for digestive diseases offers potential unique areas of intervention that remain to be fully explored.

The correlation of the metastatic ability with keratin expression in cultured murine melanoma cell lines, B16-F1 and-F10

Keratin is an intermediate filament that is a major structural protein of epithelial cells. Until now, the expression of keratin in melanoma cells has not been well understood. Recently, it has been reported that keratin expression is correlated with invasive and metastatic behavior in a variety of cell types. We report keratin expression in cultured murine melanoma cell lines B16-F1 (low incidence of lung colonization) and F10 (high incidence of lung colonization) using an aqueous solution (10 mM Tris-HCl (pH 7.4)/10 mM EDTA/phenylmethyl sulphonyl fluoride (PMSF, 10 micrograms/ml). By comparing these two cell lines, we investigated whether differences in keratin expression can influence the metastatic ability of tumor cell lines in vitro. However, no remarkable differences in keratin expression were found in these cell lines.

Detecting expression of keratins 8/18 in human HaCaT keratinocytes

Differences in treatment solution affect the efficiency of keratin extraction in cultured human squamous cell carcinomas, malignant melanomas, and melanocytes. Using an aqueous solution that is excellent for cultured cells, we focused this study on the expression of keratin subunits in the spontaneously immortalized human keratinocyte cell line HaCaT. We extracted several keratin (K) subunits, namely K4, K7, K8, K15, K17, and K18, and ATP synthase alpha-chain, in addition to those previously reported by Boukamp et al. (J Cell Biol 1988;106:761-771) in human HaCaT keratinocytes. In particular, K8 and K18 subunits, which are related to tumorigenesis, may be very important subunits within the specificities of immortalized HaCaT cells. Vimentin, which is frequently co-expressed in cultured epithelial cell lines, was not expressed.