Occurrence of differentiated keratin peptide(K1) in cultured human squamous cell carcinomas

In vitro amyloidogenic peptides of galectin-7: possible mechanism of amyloidogenesis of primary localized cutaneous amyloidosis

Pathogenesis of primary localized cutaneous amyloidosis (PLCA) is unclear, but pathogenic relationship to keratinocyte apoptosis has been implicated. We have previously identified galectin-7, actin, and cytokeratins as the major constituents of PLCA. Determination of the amyloidogenetic potential of these proteins by thioflavin T (ThT) method demonstrated that galectin-7 molecule incubated at pH 2.0 was capable of binding to the dye, but failed to form amyloid fibrils. When a series of galectin-7 fragments containing β-strand peptides were prepared to compare their amyloidogenesis, Ser(31)-Gln(67) and Arg(120)-Phe(136) were aggregated to form amyloid fibrils at pH 2.0. The rates of aggregation of Ser(31)-Gln(67) and Arg(120)-Phe(136) were dose-dependent with maximal ThT levels after 3 and 48 h, respectively. Their synthetic analogs, Phe(33)-Lys(65) and Leu(121)-Arg(134), which are both putative tryptic peptides, showed comparable amyloidogenesis. The addition of sonicated fibrous form of Ser(31)-Gln(67) or Phe(33)-Lys(65) to monomeric Ser(31)-Gln(67) or Phe(33)-Lys(65) solution, respectively, resulted in an increased rate of aggregation and extension of amyloid fibrils. Amyloidogenic potentials of Ser(31)-Gln(67) and Phe(33)-Lys(65) were inhibited by actin and cytokeratin fragments, whereas those of Arg(120)-Phe(136) and Leu(121)-Arg(134) were enhanced in the presence of Gly(84)-Arg(113), a putative tryptic peptide of galectin-7. Degraded fragments of the galectin-7 molecule produced by limited trypsin digestion, formed amyloid fibrils after incubation at pH 2.0. These results suggest that the tryptic peptides of galectin-7 released at neutral pH, may lead to amyloid fibril formation of PLCA in the intracellular acidified conditions during keratinocyte apoptosis via regulation by the galectin-7 peptide as well as actin and cytokeratins.

Squamous metaplasia induced by transfection of human papillomavirus DNA into cultured adenocarcinoma cells

BACKGROUND/AIM

It has been reported previously in cases of adenosquamous carcinoma of the lung in Okinawa, a subtropical island 2000 km south of mainland Japan, that the squamous cell carcinoma components were positive for human papillomavirus (HPV) by non-isotopic in situ hybridisation (NISH). The adenocarcinoma cells adjacent to the squamous cell carcinoma components were enlarged and also positive for HPV. This is thought to indicate that after adenocarcinoma cells are infected with HPV, they undergo morphological changes, and that "squamous metaplasia" follows. In this present study, the effects of HPV transfection into adenocarcinoma cells were examined. The relation between the region expressing the HPV gene and squamous metaplasia was also studied.

METHODS

Plasmid pBR322 containing HPV type 16 (HPV-16) was transfected into cultured colonic adenocarcinoma (DLD-1) and lung adenocarcinoma (PC-14) cells using the calcium phosphate method. Neomycin was used as a selection marker. The presence of HPV E1, E2, E4, E5, E6, E7, L1, and L2 mRNAs and also transglutaminase 1, involucrin, cyclin dependent kinases (CDKs), cyclins, caspases, apoptosis inducing factor, DNase gamma, Fas, and Fas ligand mRNAs in HPV transfected cells was investigated by means of reverse transcription polymerase chain reaction (RT-PCR). The G0-G1 cell population was analysed by flow cytometry. Morphological examination under light and electron microscopes was also carried out.

RESULTS

The virus transfected cells showed squamous metaplasia when they were injected into severe combined immunodeficient mice, expressing the high molecular weight keratin (Moll's number 1 keratin) and involucrin molecules immunohistochemically, and involucrin and transglutaminase I mRNAs by RT-PCR. The squamous metaplasia was most conspicuous in the HPV transfected DLD-1 cell when compared with HPV transfected PC-14 cells. Squamous metaplasia was most clearly demonstrated in one HPV transfected DLD-1 cell clone, which expressed not only E2 but also E6-E7 fusion gene mRNA. Viral L1 mRNA expression was absent in HPV transfected cell clones, and was not related to squamous metaplasia. The growth rate of HPV transfected cells was reduced. Transfection of the virus into the cultured adenocarcinoma cells increased the G0-G1 cell population greatly, as assessed by flow cytometer analysis. Furthermore, in the virus transfected cells, apoptosis was also observed by means of the terminal deoxynucleotidyl transferase mediated dUTP biotin nick end labelling method.

CONCLUSION

HPV transfection into adenocarcinoma cells induced clear squamous metaplasia. One of the HPV transfected cell clones that expressed E2 and E6-E7 fusion gene mRNA showed the squamous metaplasia particularly clearly, and apoptosis was also demonstrated.

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.

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.

Carcinoma of the lung in Okinawa, Japan: with special reference to squamous cell carcinoma and squamous metaplasia

In Okinawa, a subtropical island in southern Japan, squamous cell carcinoma (SCC), especially the well-differentiated form, is prevalent, while this form is relatively rare in both the mainland and other countries (e.g. United States of America). More patients with SCC from Okinawa, moreover, were positive for human papillomavirus (HPV) DNA by polymerase chain reaction (PCR) (79%), and harbored HPV types 6, 16 and 18, in combination. On the other hand, less than 30% of the mainland patients were positive for HPV DNA by PCR. Those patients who were positive all harbored only one HPV type. Furthermore, in Okinawa, there were a significant number of cases with adenosquamous carcinoma, and they too were positive for HPV DNA. The SCC and the adenocarcinoma cells adjacent to the SCC component in these cases were also positive for HPV DNA, and such adenocarcinoma cells were enlarged in size with relatively wide cytoplasm. The authors postulate that HPV infects adenocarcinoma cells and changes them to enlarged cells, followed by squamous metaplasia. In this report, HPV DNA was transfected to adenocarcinoma cells (cultured cell lines) and this showed that HPV causes squamous metaplasia. In addition, aberrant expression of p53 was demonstrated in a large number of the SCC cases in Okinawa. The enlarged adenocarcinoma cells adjacent to the SCC components in adenosquamous carcinomas also showed aberrant expression of p53. The recent advances in the studies of anti-oncogenes, p53, etc. and oncogenes are outlined. It is to be noted that the molecular mechanisms of carcinogenesis in the lung have been studied in general, classifying lung tumors into two groups, namely, small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC). However, because human lung cancer is represented by a wide variety of histologic types, molecular genetic studies according to a more detailed histological subclassification is needed.

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

With the exception of two cases, keratin is not expressed in cultured human melanoma cells. Using 2D-PAGE, immunological and electron microscopic analyses, we found keratin subunits in five established cultured cell lines derived from primary, recurrent and metastasized melanomas. The keratin subunits were composed of K1, K5, K10, K14, K15 and K18 in all cell lines examined, together with vimentin. In addition, K8, K16 and K18 expression were demonstrated in recurrent and metastasized cell lines. The results of the present and our previous study [Katagata Y, et al. J Dermatol Sci 1996;13:219-227] indicate that expression of keratin in melanoma cells may be a universal phenomenon. A specific increase in the proportion of K5 among the keratin subunits was suggestive of the nature of melanoma cells. Moreover, we detected two polypeptides that migrated on 2D-PAGE at positions which did not correspond to those of any keratin subunit. The amino acid sequences of these two polypeptides were determined; one was the human ATP synthase alpha-chain but the other did not match any known polypeptide in our homology search.

Identification of K1/K10 and K5/K14 keratin pairs in human melanoma cell lines

Keratin expression in cultured malignant melanoma cells has been studied only rarely. Moreover, no studies have reported of universality of keratin expression in human malignant melanoma cells. In this study, therefore, we analyzed keratin expression in eight cell lines. Using a low-salt aqueous solution without high salt and Triton X-100, as a washing buffer for keratin extraction, followed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and immunological analysis, we demonstrated keratin expression in all eight human malignant melanoma cell lines. The keratin polypeptide expressions common to all melanoma cells were K1, K5, K10 and K14. In addition, K8, K13, K17 and K18, respectively, were detected in individual cells. A measure of keratin expression universality in malignant melanoma cells may have implications regarding their invasive and metastatic behaviors, co-expressed with vimentin.

Confirmation and an unusual quality of the differentiated keratin peptide (K1) in cultured human squamous cell carcinomas

Recently K1 keratin peptide (K1, 68 kDa) was found to be present in two kinds of cultured human squamous cell carcinomas (HSCs) using a low-salt aqueous solution, rather than the high-salt solution containing Triton X-100 employed by many researchers up until now. To confirm whether this phenomenon is universal in cultured HSCs we analyzed K1 peptide in four other kinds of HSCs using the same procedures. Moreover, the K1 peptide detected was a little unusual with respect to solubility versus urea concentration. Epidermal K1 peptide is usually solubilized by 6-8 M urea and reductant; however, the K1 peptide in cultured HSCs was about 80-90% extracted by 1-2 M urea in a stepwise extraction procedure. This finding may have important implications regarding evaluation of keratin extracted from normal epidermal and cultured keratinocytes.

Evidence of differentiated keratin peptide (K1) in cultured human squamous cell carcinomas: demonstration of generality by three different approaches

The largest keratin peptide (K1, 68KD) has not been detectable in cultured human squamous cell carcinomas. However, quite recently, the K1 peptide was clarified to be present in two kinds of cultured HSC by using a low salt aqueous solution, rather than the high salt and Triton X-100 employed by many previous researchers (Biochem. Biophys. Res. Commun., 182, 1440-1445, 1992). To determine whether this phenomenon is common or not in cultured HSCs, I further demonstrated the K1 peptide by extracting it with two different buffers and by 2D-PAGE, immunological techniques, and Northern blot analysis, using another kind of HSC. Until now, keratin extraction has been done using high salt/Triton X-100 solution, during which K1 peptide may be removed because it has developed an affinity with the buffer. Many investigators may have therefore overlooked it.