Differences of expression of cytokeratin polypeptides in various epithelial skin tumors

CD271 activation prevents low to high-risk progression of cutaneous squamous cell carcinoma and improves therapy outcomes

BACKGROUND

Cutaneous squamous cell carcinoma (cSCC) is the second most prevalent form of skin cancer, showing a rapid increasing incidence worldwide. Although most cSCC can be cured by surgery, a sizeable number of cases are diagnosed at advanced stages, with local invasion and distant metastatic lesions. In the skin, neurotrophins (NTs) and their receptors (CD271 and Trk) form a complex network regulating epidermal homeostasis. Recently, several works suggested a significant implication of NT receptors in cancer. However, CD271 functions in epithelial tumors are controversial and its precise role in cSCC is still to be defined.

METHODS

Spheroids from cSCC patients with low-risk (In situ or Well-Differentiated cSCC) or high-risk tumors (Moderately/Poorly Differentiated cSCC), were established to explore histological features, proliferation, invasion abilities, and molecular pathways modulated in response to CD271 overexpression or activation in vitro. The effect of CD271 activities on the response to therapeutics was also investigated. The impact on the metastatic process and inflammation was explored in vivo and in vitro, by using zebrafish xenograft and 2D/3D models.

RESULTS

Our data proved that CD271 is upregulated in Well-Differentiated tumors as compared to the more aggressive Moderately/Poorly Differentiated cSCC, both in vivo and in vitro. We demonstrated that CD271 activities reduce proliferation and malignancy marker expression in patient-derived cSCC spheroids at each tumor grade, by increasing neoplastic cell differentiation. CD271 overexpression significantly increases cSCC spheroid mass density, while it reduces their weight and diameter, and promotes a major fold-enrichment in differentiation and keratinization genes. Moreover, both CD271 overexpression and activation decrease cSCC cell invasiveness in vitro. A significant inhibition of the metastatic process by CD271 was observed in a newly established zebrafish cSCC model. We found that the recruitment of leucocytes by CD271-overexpressing cells directly correlates with tumor killing and this finding was further highlighted by monocyte infiltration in a THP-1-SCC13 3D model. Finally, CD271 activity synergizes with Trk receptor inhibition, by reducing spheroid viability, and significantly improves the outcome of photodynamic therapy (PTD) or chemotherapy in spheroids and zebrafish.

CONCLUSION

Our study provides evidence that CD271 could prevent the switch between low to high-risk cSCC tumors. Because CD271 contributes to maintaining active differentiative paths and favors the response to therapies, it might be a promising target for future pharmaceutical development.

Cytokeratin 10 (CK10) expression in cancer: A tissue microarray study on 11,021 tumors

Cytokeratin 10 (CK10) is a type I acidic low molecular weight cytokeratin which is mainly expressed in keratinizing squamous epithelium of the skin. Variable levels of CK10 protein have been described in squamous carcinomas of different sites and in some other epithelial neoplasms. To comprehensively determine the prevalence of CK10 expression in normal and neoplastic tissues, a tissue microarray containing 11,021 samples from 131 different tumor types and subtypes was analyzed by immunohistochemistry. CK10 immunostaining was detectable in 41 (31.3 %) of 131 tumor categories, including 18 (13.7 %) tumor types with at least one strongly positive case. The highest rate of positive staining was found in squamous cell carcinomas from various sites of origin (positive in 18.6 %-66.1 %) and in Warthin tumors of salivary glands (47.8 %), followed by various tumor entities known to potentially exhibit areas with squamous cell differentiation such as teratomas (33.3 %), basal cell carcinomas of the skin (14.3 %), adenosquamous carcinomas of the cervix (11.1 %), and several categories of urothelial neoplasms (3.1 %-16.8 %). In a combined analysis of 956 squamous cell carcinomas from 11 different sites of origin, reduced CK10 staining was linked to high grade (p < 0.0001) and advanced stage (p = 0.0015) but unrelated to HPV infection. However, CK10 staining was not statistically related to grade (p = 0.1509) and recurrence-free (p = 0.5247) or overall survival (p = 0.5082) in 176 cervical squamous cell carcinomas. In the urinary bladder, CK10 staining occurred more commonly in muscle-invasive (17.7 %) than in non-invasive urothelial carcinomas (4.0 %-6.0 %; p < 0.0001). In summary, our data corroborate a role of CK10 as a suitable marker for mature, keratinizing squamous cell differentiation in epithelial tissues. CK10 immunohistochemistry may thus be instrumental for a more objective evaluation of the clinical significance of focal squamous differentiation in cancer.

Staphylococcus aureus inhibits terminal differentiation of normal human keratinocytes by stimulating interleukin-6 secretion

BACKGROUND

Staphylococcus aureus (S. aureus) is found on the skin of approximately 90% of patients with atopic dermatitis and approximately 20% of apparently healthy subjects. S. aureus induces keratinocytes and immune cells to secrete immunoregulatory factors that cause epidermal barrier dysfunction in atopic skin.

OBJECTIVE

This study examined factors that cause epidermal permeability barrier dysfunction in skin colonized by S. aureus.

METHODS

We examined the effect of S. aureus on keratinocyte differentiation in the stratum corneum (SC) of in vivo skin, normal human keratinocytes (NHKs) and a reconstructed human epidermis (RHE) model. The fold change in expression of the terminal differentiation markers and the level of secreted cytokines were investigated.

RESULTS

The SC displayed decreased expression of keratin 10 (KRT 10). NHKs treated with S. aureus extracts increased expression of interleukin (IL)-6 and significantly reduced expression of the terminal differentiation markers KRT 1, KRT 10, loricrin (LOR), and filaggrin (FLG); however, the expression of basal layer markers (KRT 5, KRT 14) remained unchanged. Treatment of NHKs with an anti-IL-6 antibody in combination with IL-6 or the S. aureus extracts inhibited the decrease in KRT 10 mRNA or protein expression. After the RHEs were exposed to the S. aureus extracts, KRT 1 and KRT 10 protein levels decreased.

CONCLUSIONS

These findings suggest that S. aureus inhibits the terminal differentiation of keratinocytes by stimulating IL-6 secretion.

PD-1 blockage delays murine squamous cell carcinoma development

Engagement of programmed death-1 (PD-1) with its two ligands [programmed death ligand-1 (PD-L1) and PD-L2] has been associated with the suppression of tumor-reactive T cells; however, the underlying mechanism for this T-cell dysfunction is not clear. We hypothesized that PD-1 and PD-L1 signals are, in part, responsible for squamous cell carcinoma (SCC) escape from immune antitumor regulation by modulation of the tumor environment. In the present study, we used a multistage model of SCC to examine the role of PD-1/PD-L1 activation during tumor development. Tumor sites presented an increased percentage of CD4(+) and CD8(+) T cells expressing PD-1 when compared with non-tumorigenic control mice, whereas the expression of PD-L1 was particularly increased in F4/80(+) macrophages in tumor sites. Further, the systemic immune neutralization of PD-1 resulted in a decreased number and delayed incidence rate of papillomas followed by a differential expression of cytokeratins, suggesting that the PD-1-PD-L1 interaction contributes to the progression of SCC by downregulation of antitumor responses. In fact, blocking PD-1 increased the percentage of CD8(+) and CD4(+) T cells, and the levels of interferon-γ in the tumor sites. Our results indicated involvement of PD-1(+) T cells in SCC development and in the modulation of the inflammatory immune response.

Epithelial keratin and filaggrin expression in seborrheic keratosis: evaluation based on histopathological classification

OBJECTIVES

Seborrheic keratosis (SK) is classified into six types: hyperkeratotic; acanthotic; irritated; clonal; reticulated; and adenoid. However, the origins of the respective types of SK remain unclear.

METHODS

To clarify the histogenetic origins of SK, we performed immunohistochemical studies of keratin (K) and filaggrin expression, taking into account the histopathological classifications of SK.

RESULTS

Hyperkeratotic SK mainly expressed K1, K10, and filaggrin. Acanthotic SK mainly expressed K14 with some K15. Irritated SK mainly expressed K14 and K17 in squamous eddies. Clonal SK, reticulated SK, and adenoid SK mainly expressed K14. The results show that hyperkeratotic SK differentiated towards squamoid terminal keratinization, whereas acanthotic, irritated, clonal, reticulated, and adenoid SK mainly differentiated towards basaloid undifferentiated cells. In addition, acanthotic SK differentiated towards the hair bulge, and irritated SK differentiated towards the follicular infrainfundibulum.

CONCLUSIONS

Based on the patterns of keratin and filaggrin expression demonstrated by the histopathological types, SK demonstrated diverse differentiation towards epidermal keratinization, basaloid cells, the infrainfundibulum and hair follicle bulges, which suggests that SK is in an undifferentiated and hyperproliferative state with heterogeneous differentiation. The immunohistochemical method of investigating patterns of keratin expression is useful in the differential diagnosis of cutaneous epithelial tumors.

Cytokeratin 10-negative nested pattern enables sure distinction of clonal seborrheic keratosis from pagetoid Bowen's disease

BACKGROUND

The histopathologic pattern of clonal seborrheic keratosis (SK) is quite similar to the nested pattern of pagetoid Bowen's disease [squamous cell carcinoma in situ (SCCIS)], and differentiation between the two can be challenging, especially when only small pieces are available for interpretation.

METHODS

Eleven examples of clonal SK and 13 examples of pagetoid SCCIS were examined histopathologically (tabulating necrotic keratinocytes, suprabasal mitoses, infiltrate, parakeratosis housing plump nuclei, crowding of nuclei) and immunohistochemically (using Ki-67, bcl-2, cytokeratin 7 and cytokeratin 10). Sensitivity, specificity, p-values (Fisher's exact test, two-tailed) and positive/negative likelihood ratios (+LR/-LR) were calculated.

RESULTS

Significant differences were seen with regard to crowding (p = 0.0009) and mitoses (p = 0.0006); however, only complete absence of necrotic keratinocytes or of crowding appeared to be diagnostically convincing for a diagnosis of clonal SK (-LR < 0.01). Significant differences were also seen with bcl-2 (p = 0.0005) and cytokeratin 10 antibodies (p < 0.00001). Both markers displayed a typical nested pattern in clonal SK, nests being bcl-2-positive and cytokeratin 10-negative. Cytokeratin 10-negative nests were the most convincing criterion for differentiation between clonal SK and pagetoid SCCIS (+LR > 10, -LR < 0.01).

CONCLUSIONS

The most reliable marker to distinguish clonal SK from pagetoid SCCIS is cytokeratin 10 when it spares nests. Other criteria that assist in the differential diagnosis are bcl-2 expression, absence of crowding and of mitoses.

Emergence of keratin 17 vs. loss of keratin 13: their reciprocal immunohistochemical profiles in oral carcinoma in situ

To evaluate differential expressions for keratin (K) subtypes 13 and 17 in oral borderline malignancies, we examined 67 surgical specimens of the oral mucosa for their immunohistochemical profiles. From those specimens, 173 foci of epithelial dysplasia, 152 foci of carcinoma in situ (CIS), and 82 foci of squamous cell carcinoma (SCC) were selected according to our diagnostic criteria, along with 20 areas of normal epithelia. In normal epithelia, there was no K17 positivity (0%), whereas definite K13 positivity (100%) was observed. The same tendencies were obtained in mild (undefined) and moderate (true) epithelial dysplasias (K17: 0%; K13: 100%). In contrast, all CIS (100%) had K17 positivities, while K13 positivities were lost in many of them (7%). Similar tendencies were confirmed in invasive SCC (K17: 100%, K13: 4%). Simultaneous immunopositivities for K17 and K13 were found only in SCC (7%) and CIS (4%) foci with distinct keratinization. These foci also showed K10 positivities, though K10 positive areas were not identical to K13 positive areas. The results indicate that expressions of K17 and K13 are reciprocal in oral epithelial lesions and that the K17 emergence is related to malignancies.

Basal cell carcinoma: cell of origin, cancer stem cell hypothesis and stem cell markers

Cancer stem cells have recently been described in several high-grade neoplasms. It is still unclear if they also occur in cutaneous malignancies. Cancer stem cells are not identical with somatic stem cells. The presence of tumour stem cells in a neoplasm does not in itself equal that the tumour derives from a somatic stem cell. A cell originally lacking stem cell characteristics could also acquire those features during the course of carcinogenesis and then becomes the clonal founder cell of a tumour. Basal cell carcinoma (BCC) is the most common cutaneous malignancy. A plethora of various stem cell markers has been applied to study its cellular origin. Intriguingly, the anatomical origin of BCC is still uncertain. This review will discuss the various stem cell markers used in BCC and the cellular origin of this tumour, and touches briefly on the possibility of cancer stem cells in BCC. If BCC or other skin cancers harbour tumour stem cells, these cells could be specifically targeted, making use of specific cell surface molecules such as receptor proteins. Novel drugs directed against those receptor proteins could replace currently available shotgun approaches including imiquimod.

Immunostaining in Mohs micrographic surgery: a review

BACKGROUND

With the advent of incorporating the immunoperoxidase staining technique into the processing of frozen tissue, the use of Mohs micrographic surgery (MMS) has been expanded to include several high-risk tumors such as lentigo maligna, malignant melanoma, and dermatofibrosarcoma protuberans.

OBJECTIVES

To thoroughly review the English medical literature pertaining to the use of immunohistochemical staining techniques on frozen sections during MMS and to summarize the basic relevant outcomes from the different relevant studies.

MATERIALS AND METHODS

Medline search was conducted, with the following words used in the search criteria: "Mohs surgery,""staining,""immunostaining," and "immunoperoxidase." RESULTS Generally, all immunostains showed advantage over the traditional hematoxylin and eosin approach. Studies of MART-1 in melanoma chemosurgery indicated that it is typically crisp and has less background staining than MEL-5 and better staining consistency than HMB-45. In cases of desmoplastic melanomas, S100 is the stain of choice.

CONCLUSION

Immunostaining offers an advantage in MMS. Large, randomized, prospective studies comparing the different immunostains are still lacking in the literature. The authors have indicated no significant interest with commercial supporters.

Insights into the role of the calcium sensing receptor in epidermal differentiation in vivo

While the important role of calcium (Ca(++)) signaling is fundamental in epidermal cell physiology, a detailed knowledge of precisely how epidermal cells respond to Ca(++) levels is not clear. Using peptide-specific antibodies that we generated, we set out to evaluate the temporal and spatial distribution pattern of the Ca(++)-sensing receptor (CaSR) during epidermogenesis and to assess its involvement in the mature epidermis (e.g., in acute injury and tumorigenesis). Our data indicate a developmentally regulated expression of CaSR: up-regulation occurs in specific epidermal cells and cell layers in normal development or in response to injury when epidermal cells are induced to undergo commitment and early differentiation events, and down-regulation occurs in terminal differentiation stages. These results provide a new perspective on the role of the CaSR in these processes and describe a novel tool for evaluating Ca(++)-mediated epidermal differentiation.

Comparative proteomics analysis of cytokeratin and involucrin expression in lesions from patients with systemic lupus erythematosus

To get a better understanding of the abnormal differentiation or maturation of keratinocytes, we studied the expression and distribution of cytokeratin and involucrin in lesions from systemic lupus erythematosus patients. Two groups of 10 specimens each from systemic lupus erythematosus and normal controls were analyzed by two-dimensional gel electrophoresis, mass spectrometric protein identification, Western blotting and immunohistochemistry. Our results showed that keratin 1 (K1)/K10 together with the new synthesis of K6/K16 were down-regulated and that K5/K14, K2e and involucrin were up-regulated. We found that involucrin was strongly stained in lower epidermal cell layers while K1/10 was weakly stained, particularly when compared with staining in normal epidermis. Additionally, we found that the expression of involucrin was increased. These results imply an aberrant early and terminal differentiation stage in the epidermis of systemic lupus erythematosus, which may be associated with inflammatory cytokines released during the wound healing response of lesion.

K16 expression in uninvolved psoriatic skin: a possible marker of pre-clinical psoriasis

BACKGROUND

K16, a type I keratin, is upregulated in hyperproliferative states including psoriasis. It has been used as a marker of psoriasis and its expression is upregulated in relapsing psoriasis and downregulating in resolving. We evaluated non-lesional psoriatic skin for K16 expression.

METHODS

Sixty-seven non-lesional and lesional skin samples from patients with psoriasis and normal skin from 19 non-psoriatic patients were studied by immunohistochemistry on frozen sections with K16.

RESULTS

Seventeen of 19 normal skin samples showed staining of basal cells in the deeper part of the rete ridges. Sixty-two non-lesional psoriatic skin samples showed intense basal staining of K16. Of the remaining five non-lesional samples, diffuse intense suprabasal staining in one, pan-epidermal staining in two, and no staining was seen in two samples. Suprabasal (37), diffuse (14), sandwich (12), and basal (3) pattern staining were seen in psoriatic skin. One psoriatic skin sample did not show any expression.

CONCLUSION

Our results demonstrate that K16 expression is also observed in non-lesional psoriatic skin and may serve as a marker of preclinical psoriasis.

Impaired sphingomyelinase activity and epidermal differentiation in atopic dermatitis

A defective permeability barrier leads to the penetration of environmental allergens into the skin and initiates immunological reactions and inflammation crucially involved in the pathogenesis of atopic dermatitis (AD). Decreased stratum corneum ceramide content may cause the defect in permeability barrier function consistently found in AD. Acid and neutral sphingomyelinase (A- and N-SMase) generate ceramides with structural and signal transduction functions in epidermal proliferation and differentiation. We determined epidermal SMase activities, DNA synthesis, involucrin, loricrin, filaggrin, and keratin expression in lesional and non-lesional skin of AD patients. We found decreased epidermal A-SMase activity in lesional and non-lesional skin, correlating with reduced stratum corneum ceramide content and disturbed barrier function. N-SMase activity was reduced in non-lesional skin and more significantly reduced in lesional skin, correlating with impaired expression of cornified envelope proteins and keratins, important for skin barrier function. Changes in involucrin, loricrin, filaggrin, keratin K 5 (basal) and K 16 (proliferation associated) were noticed in non-lesional and lesional skin, whereas changes in K 10 (suprabasal), K 6 (proliferation associated), and K 17 (inflammation associated) were found only in lesional skin. In summary, reduction in SMase-generating ceramides and impaired differentiation are involved in the defective barrier function found in AD.

Keratins and the keratinocyte activation cycle

In wound healing and many pathologic conditions, keratinocytes become activated: they turn into migratory, hyperproliferative cells that produce and secrete extracellular matrix components and signaling polypeptides. At the same time, their cytoskeleton is also altered by the production of specific keratin proteins. These changes are orchestrated by growth factors, chemokines, and cytokines produced by keratinocytes and other cutaneous cell types. The responding intracellular signaling pathways activate transcription factors that regulate expression of keratin genes. Analysis of these processes led us to propose the existence of a keratinocyte activation cycle, in which the cells first become activated by the release of IL-1. Subsequently, they maintain the activated state by autocrine production of proinflammatory and proliferative signals. Keratins K6 and K16 are markers of the active state. Signals from the lymphocytes, in the form of Interferon-gamma, induce the expression of K17 and make keratinocytes contractile. This enables the keratinocytes to shrink the provisional fibronectin-rich basement membrane. Signals from the fibroblasts, in the form of TGF-beta, induce the expression of K5 and K14, revert the keratinocytes to the healthy basal phenotype, and thus complete the activation cycle.

Transgenic expression of cyclin-dependent kinase 4 results in epidermal hyperplasia, hypertrophy, and severe dermal fibrosis

In a previous report we have described the effects of expression of D-type cyclins in epithelial tissues of transgenic mice. To study the involvement of the D-type cyclin partner cyclin-dependent kinase 4 (CDK4) in epithelial growth and differentiation, transgenic mice were generated carrying the CDK4 gene under the control of a keratin 5 promoter. As expected, transgenic mice showed expression of CDK4 in the epidermal basal-cell layer. Epidermal proliferation increased dramatically and basal cell hyperplasia and hypertrophy were observed. The hyperproliferative phenotype of these transgenic mice was independent of D-type cyclin expression because no overexpression of these proteins was detected. CDK4 and CDK2 kinase activities increased in transgenic animals and were associated with elevated binding of p27(Kip1) to CDK4. Expression of CDK4 in the epidermis results in an increased spinous layer compared with normal epidermis, and a mild hyperkeratosis in the cornified layer. In addition to epidermal changes, severe dermal fibrosis was observed and part of the subcutaneous adipose tissue was replaced by connective tissue. Also, abnormal expression of keratin 6 associated with the hyperproliferative phenotype was observed in transgenic epidermis. This model provides in vivo evidence for the role of CDK4 as a mediator of proliferation in epithelial cells independent of D-type cyclin expression.

K15 expression implies lateral differentiation within stratified epithelial basal cells

Keratins are intermediate filament proteins whose expression in epithelial tissues is closely linked to their differentiated state. The greatest complexity of this expression is seen in the epidermis and associated structures. The critical basal (proliferative) cell layer expresses the major keratin pair, K5 and K14, but it also expresses an additional type I keratin, K15, about which far less is known. We have compared the expression of K15 with K14 in normal, pathological, and tissue culture contexts; distinct differences in their expression patterns have been observed that imply different regulation and function for these two genes. K15 appears to be preferentially expressed in stable or slowly turning over basal cells. In steady-state epidermis, K15 is present in higher amounts in basal cells of thin skin but in lower amounts in the rapidly turning over thick plantar skin. Although remaining high in basal cell carcinomas (noninvasive) it is suppressed in squamous cell carcinomas (which frequently metastasize). Wounding-stimulated epidermis loses K15 expression, whereas K14 is unchanged. In cultured keratinocytes, K15 levels are suppressed until the culture stratifies, whereas K14 is constitutively expressed throughout. Therefore, unlike K14, which appears to be a fundamental component of all keratinocytes, K15 expression appears to be more tightly coupled to a mature basal keratinocyte phenotype.

Keratin 4 upregulation by retinoic acid in vivo: a sensitive marker for retinoid bioactivity in human epidermis

Retinoids affect keratinocyte differentiation and modulate the expression of many epidermal proteins, among them cellular retinoic acid-binding protein II and the family of cytokeratins. The upregulation of the former protein is a well-known phenomenon, whereas the retinoid-induced regulation of epidermal keratin expression is more complex and only partially understood. We studied the effect of topical retinoids on the expression in healthy skin of cellular retinoic acid-binding protein II, tazarotene-induced genes 1 and 2, several epidermal keratins (K1, K2e, and K10), and two mucous keratins (K4 and K13) known to appear in epidermis under certain abnormal conditions. Reverse transcription-polymerase chain reaction experiments showed that the K4 expression was the one most overtly induced by 2 wk of open treatment with 0.05% of retinoic acid and tazarotene. Using real-time quantitative polymerase chain reaction (TaqMan) and normalization of the mRNA values to beta-actin, the increase in K4 was found to be 100-1000-fold. In comparison, the expression of K13 and cellular retinoic acid-binding protein II was increased 10-50-fold, the K1 and K10 mRNA levels remained unchanged, and the K2e level decreased by a factor of 100-1000. In parallel biopsies, immunohistochemistry showed no change in K1, K2e, or K10 staining, but a strong de novo appearance of K4 in the granular layer after retinoid treatment. In a separate study, occlusive application of 0.025% retinoic acid in four healthy subjects produced a maximal K4 mRNA signal after 48 h and strong K4 staining after 80 h. Finally, a dose-response study showed that the de novo appearance of K4 can be utilized as a sensitive test for retinoid bioactivity in epidermis in vivo.

An immunohistochemical study of abnormal keratinocyte differentiation in molluscum contagiosum

To investigate abnormalities in the keratinization process in lesional epidermis of molluscum contagiosum, production of filaggrin, loricrin, Ted-H-1 antigen, involucrin, cystatin A and CD95 ligand (CD95L) was investigated using specific antibodies. Anti-filaggrin monoclonal antibody (MoAb) did not react with keratohyalin granules (KHG), but with the substance around virus particles in the stratum corneum. KHG reacted with anti-loricrin polyclonal antibody (PoAb) and anti-Ted-H-1 MoAb. Anti-involucrin PoAb and anti-cystatin A PoAb reacted with materials in the cytoplasm of the middle stratum spinosum to the stratum granulosum. CD95L was expressed in the cell membrane region of the living cell layers in lesional epidermis. These observations suggest that the keratinization process may be altered in molluscum contagiosum.

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.

Cytokeratin expression in trichoblastic fibroma (small nodular type trichoblastoma), trichoepithelioma and basal cell carcinoma

Classical trichoblastic fibroma or small nodular type trichoblastoma (Ackerman) is a rare tumour. This tumour, trichoepithelioma and basal cell carcinoma (BCC) have some overlapping histopathological features. There are only a few reports on immunohistochemical studies in large series of these three neoplasms. We investigated immunostaining patterns of 10 different anticytokeratin (CK) antibodies and several other markers in these neoplasms, comparing them with the patterns in normal adult and fetal skin. In trichoblastic fibroma (three cases), CK1/5/10/14, CK7, CK8/18, CK10/11, CK14, CK17 and CK19 were expressed in the basaloid nests, and CK6 and involucrin were detected in the inner layers of keratinous cysts. Trichoepithelioma (seven cases) expressed CK1/5/10/14, CK8/18, CK14, CK17 and CK19 in the basaloid nests, and CK6, CK10, CK10/11 and involucrin were positive in the keratinous cysts. However, no CK7 expression was observed. Solid and keratotic types of BCC (29 cases) expressed CK1/5/10/14, CK7, CK8/18, CK14, CK17 and CK19 in the basaloid nests. The keratinous cysts in BCC were stained with anti-CK6, CK10, CK10/11 and involucrin antibodies. Coupled with the expression of CK8/18, CK17 and CK19 in the outer root sheath of the adult hair follicle, these three neoplasms shared a keratin phenotype characteristic of the outer root sheath. Judging from our immunohistochemical results, trichoblastic fibroma and BCC cannot be differentiated by their patterns of CK expression. The expression of CK7, which is noted in fetal hair follicles, trichoblastic fibroma and BCC, suggests the presence of subpopulations that retain fetal phenotypic characteristics in these two neoplasms. Although the current concept regards trichoepithelioma and trichoblastic fibroma as a single tumour group, the lack of CK7 expression in trichoepithelioma supports the notion that the two are different.

cDNA cloning, expression, and assembly characteristics of mouse keratin 16

There has been speculation as to the existence of the mouse equivalent of human type I keratin 16 (K16). The function of this keratin is particularly intriguing because, in normal epidermis, it is usually confined to hair follicles and only becomes expressed in the suprabasal intrafollicular regions when the epidermis is traumatized. Previous studies suggested that K16 is highly expressed in the skin of mice carrying a truncated K10 gene. We therefore used the skin of heterozygous and homozygous mice to create a cDNA library, and we report here the successful cloning and sequencing of mouse K16. Recent in vitro studies suggested that filaments formed by human K16 are shorter than those formed by other type I keratins. One hypothesis put forward was that a proline residue in the 1B subdomain of the helical domain was responsible. The data presented here demonstrate that this proline is not conserved between mouse and human, casting doubt on the proposed function of this proline residue in filament assembly. In vitro assembly studies showed that mouse K16 produced long filaments in vitro. Also, in contrast to previous observations, transfection studies of PtK2 cells showed that mouse K16 (without the proline) and also human K16 (with the proline) can incorporate into the endogenous K8/K18 network without detrimental effect. In addition, K16 from both species can form filaments de novo when transfected with human K5 into immortalized human lens epithelial cells, which do not express keratins. These results suggest that reduced assembly capabilities due to unusual sequence characteristics in helix 1B are not the key to the unique function of K16. Rather, these data implicate the tail domain of K16 as the more likely protein domain that determines the unique functions.

Differentiation and cathepsin D expression in human oral tumors

OBJECTIVES/HYPOTHESIS

This study aimed to ascertain whether cathepsin D expression could be related to the stage of differentiation of oral tumors.

STUDY DESIGN

Human oral biopsies of 10 squamous cell carcinomas and of the corresponding perilesional normal tissues were used. The tumors had all been clinically graded as advanced stage but nonmetastatic; five were classified histopathologically as poorly differentiated.

METHODS

The gene expression of cathepsin D and keratin K13 in the biopsies was measured by reverse transcription polymerase chain reaction. Ratios of tumor-to-control readings helped compensate for sample variability.

RESULTS

Keratin K13, as a suprabasal cell marker, tended to confirm the histological grading of the tumors (but was not otherwise useful in distinguishing tumors from normal tissue). Substantial overexpression of cathepsin D was found in the poorly differentiated tumors.

CONCLUSIONS

Cathepsin D overexpression is considered a prognostic indicator of metastasis. In this sample, it was also associated with dedifferentiation. Cathepsin D might serve as a valuable gauge in clinical exploration of the connection between dedifferentiation and metastasis.

Epidermal signal transduction and transcription factor activation in activated keratinocytes

In the area of biology, many laboratories around the world are dissecting and characterizing signal transduction mechanisms and transcription factors responsive to various growth factors and cytokines, in various cell types. However, because of the differences in systems used, it is not clear whether these systems coexist, whether they interact meaningfully, and what their relative roles are. Epidermal keratinocytes are the perfect cell type in which to integrate this knowledge, because in these cells these mechanisms are known to be relevant. Keratinocytes both produce and respond to growth factors and cytokines, especially in pathological conditions and during wound healing, when the physiology of keratinocytes is altered in a way specified by the presence of a subset growth factors and cytokines. In fact, growth factors and cytokines cause the major changes in gene expression and keratinocyte behavior in various cutaneous diseases. In some cases, such as in wound healing, these responses are highly beneficial; in others, such as in psoriasis, they are pathological. It is not clear at present which are operating in which conditions, which are important for the healing process and which are harmful. Growth factors and cytokines affect keratinocytes sometimes simultaneously, at other times individually. In this manuscript we describe the signal transduction pathways responsible for the effects of interferons, the EGF/TGF alpha family and the TNF alpha/IL-1 family of signaling molecules. We also describe the important transcription factors known to be functional in epidermis, with particular emphasis on those factors that are activated by growth factors and cytokines. Finally, we describe what is known about transcriptional regulation of keratin genes, especially those specifically expressed in pathological processes in the epidermis. We expect that the enhanced understanding of the pathways regulating gene expression in keratinocytes will identify the pharmacological targets, the signal transducing proteins and the corresponding transcription factors, used by growth factors and cytokines. This research will led to development of compounds precisely aimed at those targets, allowing us to isolate and inhibit the harmful side effects of growth factors and cytokines. Such compounds should lead to highly specific and therefore more effective treatments of the cutaneous disorders in which these pathways play significant roles.

In situ hybridization study of cytokeratin 4, 13, 16 and 19 mRNAs in human developing junctional epithelium

Cytokeratins (CKs) are now considered to be reliable markers for following the development and differentiation of epithelial tissue. We have investigated the pathway of differentiation in human developing junctional epithelium using monoclonal antibodies and two-dimensional gel electrophoresis of microdissected tissue to identify CK 19, CK 16, CK 14, CK 13, CK 6, CK 5, CK 4 in the junctional epithelium (JE) over partially erupted human teeth. The CK profile was similar to that of developing oral epithelia, suggesting that the junctional epithelium in teeth during eruption is of odontogenic origin. The present study used in situ hybridization to determine the distribution of the mRNAs of CKs 19, 16, 13 and 4 in human developing junctional epithelium and to examine the correlation between mRNAs and their encoded proteins. CK 19 mRNA was abundant in the basal cell layers of the primary junctional epithelium (PJE) but less concentrated in the suprabasal layers. CK16, 13 and 4 mRNAs were abundant in the basal cell layers of the PJE. The parabasal cell layers reacted intensely to the cRNA probe complementary to CK16 mRNA, as were the reactions in the suprabasal cell layers of the PJE for the CK 13 and 4 probes. Our results demonstrate that the PJE express the genes encoding for CKs 16 and 4 that have been revealed previously only by electrophoresis. They therefore confirm that the PJE is a well-differentiated stratified epithelium with a complex unique phenotype that produces CKs specific for basal cells (CK 19), CKs associated with hyperproliferation (CK 16), and finally those associated with stratification (CKs 4 and 13). Only synthesis of CK 19 protein and mRNA are strictly parallel. CKs 4 and 13 mRNAs are present in basal and suprasal cells, while their encoded proteins were not, except for CK 13 in suprabasal cell layers of PJE, where the amount of its mRNAs was coincident with the expression of the protein.

A case of pseudovascular adenoid squamous cell carcinoma of the skin with spindle cell pattern

We report a case of pseudovascular adenoid squamous cell carcinoma which was in the form of a dome-shaped, cherry red tumor on the right cheek of an 86-year-old Japanese woman. Histologically, two types of atypical cells were identified; round cells in the upper part and spindle cells in the lower part. In the upper part, inter-anastomosing sinusoid-like pseudolumina were observed between the cords of the tumor cells. Immunohistochemically, the tumor cells did not express Factor VIII-related and CD34 antigens or bind Ulex europaes I agglutinin, except for only one anti-cytokeratin antibody. Ultrastructurally, the tumor cells contained tonofilaments and desmosomes and represented acantholysis. From the electron microscopy, possible role of capillary hyperpermeability on the acantholytic process of the neoplastic cells was suggested.

Delays in malignant tumor development in transgenic mice by forced epidermal keratin 10 expression in mouse skin carcinomas

The keratin cytoskeleton is formed in different epidermal compartments by distinct polypeptides. Basal, proliferative keratinocytes express keratin (K) 5 and K14, whereas, suprabasal, post-mitotic keratinocytes express K1 and K10. Changes in this keratin pattern have been found to occur in hyperproliferative skin disorders and, in particular, throughout mouse epidermal carcinogenesis. Whereas some keratins not found in normal epidermis (K6, K16, K13, and K8) are induced at different stages of tumor development, K1 and K10 expression is lost. To determine whether K1 and K10 loss is just a consequence of the altered differentiation program or an event required for tumor progression, we generated transgenic mice carrying the human keratin 10 gene (hK10) under the control of a bovine keratin 6 gene regulatory region, which is silent in normal skin but is induced and drives transgene expression in hyperproliferative skin keratinocytes and, therefore, in skin tumors. Transgenic animals subjected to a complete carcinogenesis protocol developed tumors that contained various amounts of transgenic hK10. Although no significant difference was found in tumor number or malignancy, tumor onset was significantly delayed in transgenic mice, indicating that the presence of K10 actually impairs tumor development.

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.

The distribution of the desmosomal protein, plakophilin 1, in human skin and skin tumors

Desmosomes are predominant among the types of plaque-bearing adhering junctions found in human skin. These structures contain a set of desmosomal cadherins and cytoplasmic plaque proteins, the synthesis of which is differentiation dependent. As plakophilin 1, a member of the armadillo gene family, is an important accessory desmosomal plaque protein, we raised several monoclonal antibodies specific for this protein and applied immunohistochemical and immunoblotting procedures to study the distribution of plakophilin 1 in desmosomes in adult and fetal skin, psoriatic epidermis, various epithelial skin tumors, and keratinocyte sheets grown in culture. In epidermis, the spinous layers were prominently immunostained by plakophilin 1 antibodies, whereas the basal cell layer was only weakly stained and the stratum corneum was entirely unstained. The staining observed in psoriatic epidermis was somewhat heterogeneous. In hair follicles, the outer root sheath (ORS) was delineated in its suprabasal cell layers, with variable staining in its upper and lower parts. All basal cells of the ORS remained unstained, as did upper inner root sheath (IRS) and matrix cells of lower bulb. In eccrine sweat glands, the reaction was confined to inner dermal ductal cells, with the acini remaining unstained. The desmosomal immunostaining observed in basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) was very heterogeneous: In general, junctions in well-differentiated stratified tumor regions were more intensely stained than sections of poorly differentiated and invasively growing BCCs and SCCs. Plakophilin 1 was also prominent in the desmosomes of keratinocyte sheets grown in culture. The cell type-specific, i.e., differentiation-dependent, distribution of desmosomal plakophilin 1 is discussed in relation both to the stratification of the cutaneous epithelia and to tumor differentiation and growth.

Response to interferon treatment decreases with epidermal dedifferentiation in condylomas

After interferon (IFN) treatment of patients with condyloma acuminatum, groups clinically proven to be responders or nonresponders were selected, and cellular parameters that might influence the clinical response were studied in pretreatment biopsies by reverse transcription polymerase chain reaction (RT-PCR). The nonresponders were found to express higher amounts of cellular proliferative markers, such as proliferating cell nuclear antigen (PCNA), cyclin A, and cdc 2 kinase, but lower levels of growth suppressor genes (TGF-beta 1, TGF-beta 2 and p53) before IFN treatment. The responders retained the epidermal keratinization, except for some signs of hyperproliferation (K6, K16 cytokeratins). In addition, the nonresponders showed a shift in the keratinization pattern to a mucosal or fetal type, as evidenced by high expression of the K18, K6, K16 and K13 cytokeratins but decreased K5, K14 and K10 levels before treatment. The expression of the human papillomavirus (HPV) genes is consistent with these differentiation patterns. The crucial conclusion to be drawn from this study is that those condylomas whose pretreatment phenotype most closely resembles that of normal epidermis respond to IFN treatment, whereas those more akin to nonkeratinizing epithelia fail to respond, i.e. the resistance of condylomas to IFN treatment is correlated with dedifferentiation.

Immunohistochemical study of primary and recurrent basal cell and metatypical carcinomas of the skin

We investigated cell proliferation and expression of cytoskeletal proteins in 32 cases of primary basal cell carcinomas (BCC), 10 cases of recurrent BCC, and 10 cases of metatypical carcinomas (MTC). Paraffin-embedded biopsies were evaluated immunohistochemically with a battery of antibodies. Antibodies to proliferating cell nuclear antigen (PCNA) demonstrated comparatively low numbers of proliferating cells in 25 of 32 cases of primary BCC. In contrast, both recurrent BCC and MTC exhibited three to four times higher levels of proliferating cells than primary BCC. PCNA-positive cells were usually distributed uniformly throughout the lobules; at times, however, they were localized to the outer areas of those neoplasms, with a comparatively low level of proliferation index. Antibodies to keratin 17 strongly stained cells of all BCC cases, and antibodies to keratin 8 reacted with most of them. In contrast, the staining intensity of both types of keratin in MTC was decreased six to eight times as compared with all BCC. In addition, cells of eight BCC and three MTC reacted with antibodies to smooth muscle alpha-actin and myosin, neoplasms that did not differ by the number of PCNA-positive nuclei from carcinomas without contractile proteins. The differences in cell proliferation and keratin expression between BCC and MTC may be useful criteria for further distinguishing these carcinomas. The appearance of contractile proteins in some BCC and MTC may be the result of, or implies, myoepithelial differentiation.

Characterization of nuclear protein binding sites in the promoter of keratin K17 gene

Keratin K17, while not present in healthy skin, is expressed under various pathological conditions, including psoriasis and cutaneous allergic reactions. The regulatory circuits involved in transcription of the human keratin K17 gene are poorly understood. To begin an analysis of the molecular mechanisms that regulate K17 gene transcription, we have studied the interactions between the nuclear proteins and the promoter region of the human K17 gene. That promoter region comprised 450 bp upstream from the translation initiation site. For these studies, we used electrophoretic mobility-shift assays, computer analysis, site-directed mutagenesis, and DNA-mediated cell transfection. In addition to the previously characterized interferon-gamma-responsive elements, we identified eight protein binding sites in the promoter. Five of them bind the known transcription factors NF1, AP2, and Sp1 and three others bind still unidentified proteins. Using site-directed mutagenesis, we have demonstrated the importance of the protein binding sites for the promoter function involved in both constitutive and interferon-induced expression of the K17 keratin gene.

Epithelial markers and differentiation in adnexal neoplasms of the skin: an immunohistochemical study including individual cytokeratins

Applying immunohistochemical procedures for the detection of eight different cytokeratin (CK) polypeptides and other differentiation markers, we compared the staining patterns of normal cutaneous structures with those of benign adnexal tumors (n = 65). Syringomas exhibited a marker pattern highly reminiscent of that seen in normal dermal eccrine ducts (EMA in peripheral cells, CK 10 in intermediate cells, and CK 6, CK 19, and CEA in luminal cells). Nodular hidradenomas exhibited complex patterns suggesting relationship between tumor cells, including clear cells, and normal secretory coil cells (CK 7, CK 8, CK 19, and EMA); however, dermal-duct and epidermoid differentiation were also detectable. In both cylindromas and spiradenomas, zonal staining patterns were apparent: modified myoepithelial cells were positive for smooth-muscle-type actin, while the luminal cells mainly expressed ductal markers (CK 6 and CK 19) and, less prominently, secretory-coil markers including CK 7. Eccrine poromas exhibited a widespread reaction for CK 5/6 and EMA, analogous to peripheral dermal duct cells, but focal maturation toward inner-ductal and secretory-coil cells was also demonstrable. The staining pattern observed in trichoepitheliomas resembled that of the outer but not the inner root sheath. In conclusion, the detailed marker profiles obtained in the present study have broadened our understanding of the differentiation and nature of these highly singular tumor types.

Maintenance of cell-type-specific cytoskeletal character in epithelial cells out of epithelial context: cytokeratins and other cytoskeletal proteins in the rests of Malassez of the periodontal ligament

We have determined the patterns of synthesis of cytokeratins and other epithelial marker proteins in the "rests of Malassez" of the periodontium of rabbits and humans, by immunofluorescence microscopy of cryosections prepared from fixed and decalcified rabbit teeth with attached ligament or from manually isolated human periodontal ligaments. Proteins of the major cell structures characterizing epithelial differentiation are present in Malassez cells: a complex set of cytokeratins as well as desmosomal, hemidesmosomal and basal lamina proteins. In addition, we have shown these cytoskeletal and extracellular matrix structures by electron microscopy. The cytokeratin complement of Malassez cells was found to be highly complex, as 8 of the total of 20 known epithelial cytokeratins were detected (nos. 5, 7, 8, 14, 15, 17, 18, 19). This pattern, together with the presence of the desmosomal cadherins Dsg2 and Dsc2 and the cytoplasmic desmosome plaque-associated protein plakophilin 1, indicates that the cells of the rests of Malassez are derived from the basal cell layer of a stratified squamous epithelium rather than from simple epithelial or neuroendocrine epithelial cells. Our observations show that Malassez cells retain the major characteristics of epithelial cells throughout their differentiation from the root sheath epithelium into the rests of Malassez, even though the surface location and the polar tissue architecture that typify epithelial are lost during this process. From this study we further conclude that the specific cytoskeletal complement of the Malassez cells represents an intrinsic gene expression program that neither depends on nor causes the formation of a stratified epithelium. We also compare the specific cytoskeletal features of Malassez cells with those of other persisting epithelial residues and discuss the potential value of these findings in relation to the histogenesis and diagnostic classification of dental and periodontal cysts and tumors.

Changes of cytokeratin and involucrin expression in squamous cell carcinomas of the skin during progression to malignancy

The detection of cytokeratins in neoplastic tissues by immunohistochemical methods has numerous diagnostic and investigative applications, because cytokeratins are usually conserved in tumour cells during malignant transformation. Recently, however, it has been reported that progression to malignancy is associated with commencement of expression of low-molecular-weight cytokeratins. In the present study, 42 specimens from 35 cases of squamous cell carcinoma (SCC) of the skin were analysed by immunohistochemical techniques, using polyclonal anti-involucrin antibody and a panel of monoclonal antikeratin antibodies, in order to investigate the nature and differentiation of SCCs. The expression of cytokeratins and involucrin in well-differentiated SCCs was similar to that in normal epidermis. In contrast with well-differentiated SCCs, the expression of differentiation-specific cytokeratins and involucrin was diminished in the immature tumour cells in proportion to the malignancy of the SCCs. Some antibodies, however, stained all tumour cells, irrespective of the degree of malignancy. Furthermore, expression of simple epithelial and non-cornifying stratified squamous epithelial cytokeratins was observed in atypical tumour cells of poorly differentiated SCCs. It is of interest that similar expression was noted in many tumour cells in the lymph node metastases and in some tumour cells in the primary cutaneous lesions. Cytokeratin expression similar to that in normal epidermal keratinocytes was conserved in well-differentiated SCCs, but the expression of cytokeratins changed during progression to malignant transformation. The expression of simple epithelial or non-cornifying stratified squamous epithelial cytokeratins in cutaneous SCCs may be a marker for their capability of invasion and metastatic potential.

Relative amounts of keratin 17 are higher than those of keratin 16 in hair-follicle-derived tumors in comparison with nonfollicular epithelial skin tumors

Specimens of trichilemmal cyst, malignant trichilemmoma, keratoacanthoma, and epidermal cyst were examined to characterize keratin peptides in hair-follicle-derived tumors. Keratins were extracted from the specimens and analyzed by two-dimensional gel electrophoresis and densitometry; the results were then compared with those for normal epidermis, the outer root sheath of hair follicles, psoriatic epidermis, and various nonfollicular cutaneous epithelial tumors. The specific nonfollicular tumors examined were squamous cell carcinoma, Bowen disease, actinic keratosis, eccrine porocarcinoma, and sebaceous carcinoma. Immunohistochemistry also was performed with a few anti-keratin monoclonal antibodies. As a general rule, K6 and K16 were expressed in hyperproliferative conditions, such as epidermal tumors, and K17 was coexpressed in the same lesions. The ratio of K16 to K17 in many epithelial skin tumors has been unclear until now. K17 content exceeded K16 content in most follicular tumors, whereas in almost all the nonfollicular tumors and the psoriatic epidermis, K17 levels were less than or about equal to K16 levels. There was a significant difference in the ratio of K16 to K17 between follicular and nonfollicular skin tumors. These results indicate that alterations in the content of these keratins may be associated with follicular differentiation.

Differentiation and tumor progression

Clinical and experimental experience indicate that differentiation and malignancy are inversely correlated. However, more recent experimental studies using mouse and human keratinocyte systems have demonstrated that complete or even substantial loss in overall epithelial differentiation is not a prerequisite for malignant growth of cancer cells. Major defects in differentiation are also not a prerequisite for premalignant stages, in particular for cell immortalization, which is considered an early and essential step in the transformation process. Moreover, progressive dedifferentiation, often associated with advanced tumor stages, is also found in immortalized cell lines which are, however, nontumorigenic. On the other hand, malignant cell lines may have maintained a high degree of their normal differentiation program and sensitivity to differentiation modulators. However, to date no transformed keratinocyte cell lines with completely normal differentiation have been observed. Since epidermal keratinization is a very complex process involving many different parameters and is fully expressed only under in vivo conditions, an exact and quantitative comparison of such ill-defined phenomena (differentiation and malignancy) is still problematic. Obviously, both phenomena are under separate control and not causally linked. Nevertheless, a better understanding of factors and mechanisms regulating differentiation and of their disturbance in carcinogenesis would offer new possibilities to design novel tumor therapeutic strategies in the field of differentiation therapy.

Immunohistochemical techniques in Mohs micrographic surgery: their potential use in the detection of neoplastic cells masked by inflammation

BACKGROUND

Histopathologic evaluation of tissue obtained from Mohs micrographic surgery is the key step in obtaining complete tumor removal. Residual undetected tumor may result in recurrence.

OBJECTIVE

In circumstances in which the histopathologic interpretation is difficult, we assessed the potential use of immunohistochemical techniques to detect tumor in Mohs micrographic surgical specimens.

METHODS

A rapid immunoperoxidase technique with monoclonal anticytokeratin antibodies was performed on Mohs frozen sections. Cases selected included morpheaform basal cell carcinomas, perineural tumors, and sections with dense inflammation without apparent tumor.

RESULTS

Four cases are described as examples that highlight the potential usefulness of immunostaining of Mohs tissue sections. Anticytokeratin antibodies helped to confirm free tumor margins, thus avoiding the unnecessary sacrifice of normal tissue, and to delineate tumor not identified in hematoxylin and eosin frozen sections.

CONCLUSION

Immunohistochemical staining of Mohs micrographic surgical specimens with anticytokeratin antibodies is particularly useful when dense inflammatory infiltrate is present, because the latter may obscure any residual tumor. Application of this technique to difficult cases may prevent tumor recurrences or unnecessary excision of normal tissue.

Expression of the homeobox gene HOXC4 in keratinocytes of normal skin and epithelial skin tumors is correlated with differentiation

Homeobox (HOX) genes share a highly conserved 183-bp sequence. The encoded proteins are capable of binding to specific DNA sequences and functioning as transcription factors. HOX genes play a critical role in the temporal and spatial differentiation of cells during embryogenesis. In several adult tissues, HOX genes are expressed in a constant, tissue-specific pattern, whereas in malignant tumors of these tissues an altered expression pattern was found. We investigated the expression of HOXC4 in adult normal skin by reverse-transcription polymerase chain reaction and non-radioactive RNA in situ hybridization. Moreover, HOXC4 expression was studied in various epidermal neoplasms (solar keratosis, six specimens; Bowen's disease, four; squamous cell carcinoma, nine; basal cell carcinoma, three) by RNA in situ hybridization. HOXC4 was found to be expressed in the suprabasal layers of the epidermis in normal skin specimens and the adjacent non-lesional epidermis of all other specimens. Atypical keratinocytes of solar keratoses and Bowen's disease as well as basaloid cells of basal cell carcinomas were negative. In squamous cell carcinoma, well differentiated areas with keratinization showed HOXC4 expression, whereas poorly differentiated areas were negative. Immunostaining with an antibody against cytokeratin 10, a marker of epidermal differentiation, was performed. A good correlation between the distribution pattern of HOXC4 and cytokeratin 10 in the lesions examined was found. These results suggest that HOXC4 is expressed mainly in differentiated keratinocytes. Lack of differentiation (as in neoplastic cells) is accompanied by downregulation of HOXC4 expression.

Cytokeratin profile of the junctional epithelium in partially erupted teeth

This study uses cytokeratins (CK) as markers to investigate the phenotype of the junctional epithelium (JE) in partially erupted human teeth. The gingival samples, which were clinically healthy, were carefully dissected from the teeth. Cryostat sections were cut for histological staining, immunofluorescence microscopy and gel electrophoresis. Cytokeratins were extracted after microdissection. The basal and suprabasal epithelial cell markers, cytokeratins 4, 5, 13, 14 and 19 were detected with specific monoclonal antibodies. They showed that the junctional epithelium in erupting teeth has a complex topography. The cytokeratin immunohistochemical profile distinguished between the primary junctional epithelium (CK 5, 14 and 19 in basal and suprabasal cells and CK 13 faintly stained throughout the suprabasal layers) and the adjacent epithelium that had the same cytokeratin profile as the sulcular epithelium (CK 5, 14 and 19 in basal cells and CK 4 and 13 intensively stained in the suprabasal cells). Extraction, two-dimensional electrophoresis and western blotting showed that this transitional JE during eruption also contained CK 6, 16 and perhaps CK 4. Thus, the JE in erupting teeth shows patterns of CK distribution that are very similar to that of developing oral epithelia.

Intermediate filaments in oral neoplasia. I. Oral cancer and epithelial dysplasia

The major value of intermediate filaments (IFs) in biological and applied research lies in their high order of cell and tissue specificity. This is particularly well illustrated in keratin (K) expression in various oral epithelia. Although the original class of IF is usually conserved in tissues after neoplastic transformation, epithelia show a tendency to shift their pattern of keratin expression in a manner which, while not predictable with precision, may sometimes be of diagnostic or prognostic significance. This review compares the keratins in normal oral epithelia, which show a mainly site-dependent expression, with those in squamous cell carcinoma. Key changes in the latter are the presence of simple epithelial keratins, K8 and K18 (occasional K7), reduced expression of differentiation-linked keratins (K1, K10, K4 and K13) and a tendency for down-regulation of primary keratins, K5 and K14. Moderate and severe dysplasias also tend to exhibit K8 and K18 with concomitant disordered expression of differentiation-linked keratins. There are reports of similar changes after neoplastic transformation in other mucosal sites and skin. Before this information can be applied diagnostically in immunocytochemical studies, the anti-keratin antibodies must be fully characterised and their interaction with the relevant tissue, both frozen and conventionally processed, should be evaluated.

FB1, a monoclonal antibody reacting with a keratin 14 epitope, stains only a small subset of psoriatic basal keratinocytes

A murine monoclonal antibody, FB1, reacted with the basal keratinocytes of human stratified epithelia. One-dimensional and two-dimensional immunoblotting assays, performed on keratins extracted from HaCat cells and normal human keratinocytes, showed that FB1 recognizes K14. When LL002, another K14 monoclonal antibody is added, the FB1 stained area in the 2D-immunoblot seems to cover a fraction of the LL002 spot. Immunohistochemical data obtained from studies on normal human tissues supported the K14 specificity of FB1, but when compared with two other monoclonal antibodies, LL002 and RCK107 reacting with K14, some differences appeared. These differences were mainly seen in sweat glands, hair follicles, psoriatic epidermis and salivary glands. In psoriatic epidermis, FB1 showed a heterogeneous pattern of staining of the basal cell compartment. Intense reactivity was only observed at the bottom of the rete ridges. Staining diminished and finally disappeared in the basal cells above the dermal papillae. This observation supports the view that an increased germinative cell population in psoriasis involves a partially differentiated amplifying compartment in which the number of cell divisions is increased.