Distribution of CD44 variant isoforms in human skin: differential expression in components of benign and malignant epithelia

Expression of cell adhesion molecules regulates epithelial cell differentiation and organization of complex tissues such as skin. The CD44 family of adhesion molecules is generated by alternative splicing of up to 10 variant exons encoding inserts into the extracellular domain. Expression of CD44 variant exons has been correlated with metastatic potential of some epithelial malignancies. We studied the distribution of total and variant CD44 isoforms containing exons v4, v6, and v9 in normal skin, basal cell carcinoma, and in control tissues using immunohistologic assays. While normal epidermis and other stratified squamous epithelia reacted strongly with antibodies specific for standard CD44 (CD44S) and CD44 isoforms containing exons v4, v6, and v9, the epithelium of eccrine glands was reactive, often in a polarized distribution, only with antibodies specific for CD44S and isoforms containing exon v9. These studies suggest that differential expression of CD44 variant exons may be important in development and organization of epithelial structures within skin. Malignant cells in basal carcinoma tissues were found to have low reactivity with antibodies specific for CD44S or variant CD44 molecules. The low expression of CD44 molecules in basal cell carcinomas may play a role in the relatively low probability of metastasis of these neoplasms.     

Changes in CD44 isoform expression during inflammatory skin disease

The CD44 family of cell surface glycoproteins is widely-expressed in epithelial, mesothelial and haemopoietic tissues and is thought to function primarily as adhesion molecules. The molecule has an intracellular, a trans-membrane and an extracellular domain. The membrane proximal region of the extracellular domain is of variable structure depending on which of 10 variable exons are involved in coding for this region. Both in vitro stimulated T cells and cytokine stimulated keratinocytes are known to express certain isoforms. In this study we have investigated whether specific isoforms of the CD44 molecule are expressed on epithelial cells and lymphocytes in the course of two inflammatory skin diseases, namely lupus erythematosus and lichen planus. Monoclonal antibodies, specific to the epitopes of the CD44 molecule encoded by v3, v4/5, v6 and v8/9 variable exons and a pan CD44 marker, were used on 10 lupus and 8 lichen planus frozen skin samples and compared with normal skin from 9 different body sites. Results failed to show detectable levels of variant isoforms of CD44 on lymphocytes in either inflammatory skin disease, despite evidence of T cell activation. All CD44 variant isoforms were reduced on the keratinocytes in some sections of lupus and lichen planus. The results are discussed in the context of the current models for the role of CD44 in the immune response.     

CD44 and melanocytic tumors: a possible role for standard CD44 in the epidermotropic spread of melanoma

CD44 is a polymorphic family of cell membrane glycoproteins that mediate cell-matrix and cell-cell interactions involved in the mechanisms of tumor invasion and metastasis, and are subject to differential regulation during normal and malignant cell growth. We have investigated immunohistochemically the expression of CD44S and the variant isoforms CD44v3 and CD44v6 in paraffin-embedded tissue from 5 Spitz nevi, 3 compound melanocytic nevi, 2 blue nevi, 6 primary melanomas, 15 cutaneous metastases (three epidermotropic, nine dermal and three ulcerated) and 10 lymph node metastases of melanoma. Melanocytes were extensively positive for CD44S in primary melanomas and benign melanocytic proliferations. Among 15 cases of cutaneous metastases of melanoma, the three epidermotropic metastases, as well as one of the three ulcerated ones were positive for CD44S. CD44S expression was diminished or totally absent in six of the nine dermal metastases, in two of the ulcerated metastases and in seven of the ten lymph node metastases. CD44v3 and CD44v6 melanocytic expression was absent in all the lesions studied.
According to our results, selective retention of CD44S expression by melanocytes in epidermotropic metastases of melanoma seems to indicate that preservation of CD44S may contribute to the intraepidermal spread of melanoma.     

Atypical Response of Xeroderma Pigmentosum to 5‐Fluorouracil: A Histopathological Image Analysis Study Reveals New Insight into Etiopathogenesis

The histological distinction between dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) may be difficult. CD34 and Factor XIIIa have been used to differentiate DF from DFSP, but there is a lack of specificity. CD44 is a membrane glycoprotein which has multiple isoforms generated by alternative splicing of variant exons. CD44 is the principal cell surface receptor for hyaluronate (HA). In this study we explored the expression of standard CD44 (CD44s) and its isoforms (CD44v3, CD44v4, CD44v5, CD44v6, CD44v7, CD44v7v8, and CD44v10), and HA in DF and DFSP. Immunohistochemistry was performed on the biopsy specimens of 15 cases of DF and 4 cases of DFSP, using antibodies for the CD44s and its isoforms, and hyaluronate binding protein (HABP). Tumor cells displayed a strong CD44s immunoreactivity in all cases of DF whereas a faint HA positivity was observed in the tumor stroma. DF cells were negative for CD44v3, CD44v4, CD44v6, CD44v7 and CD44v7v8 but they showed a strong reactivity for CD44v5 and CD44v10. CD44s expression was significantly reduced or absent in all DFSP lesions and the tumor stroma displayed a strong staining for HA. Our results indicate that CD44 and HA can be used as additional diagnostic markers to distinguish DF from DFSP.     

Expression of CD44 isoforms and β1,6-branched oligosaccharides in human malignant melanoma is correlated with tumor progression but not with mettastatisc potential

CD44, a family of closely related glycoproteins generated by alternative splicing, as well as the increased β1,6-branching of Asn-linked oligosaccharides (β1,6-branches), have been implicated in tumor progression and metastasis. We have investigated the expression of CD44 standard (CD44s), various CD44 splice variants (CD44v3,- v4,- v5,- v6 and- v9), and of β1,6-branches in a total of 37 paraffin-embedded human primary melanomas and metastases.
Out of the 28 studied primary melanomas, 27 were positive for CD44s, 21 for CD44v5 (cytoplasmic staining) and 26 for β1,6 branches. Furthermore, superficial spreading melanomas showed a significant (p=0.004) stronger staining for CD44s than the thick (> 1.5 mm) nodular melanomas, whereas no significant difference was found with regard to staining for CD44v5 and β1,6-branches. Eight of the 9 studied melanoma metastases were positive for CD44s, 6 for CD44v5 (cytoplasmic staining) and 7 for β1,6-branches. No CD44v3, -v4, -v6 and -v9 could be detected in any of the tumors. On average, metastases as compared to primary tumors, exhibited a significant (p=0.002) weaker staining for CD44s. However, metastasizing melanomas could not be distinguished from non-metastasizing ones based on CD44 immunostaining.     

CD44 and hyaluronate in the differential diagnosis of dermatofibroma and dermatofibrosarcoma protuberans

The histological distinction between dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) may be extremely difficult. CD34 and Factor XIIIa have been used to differentiate DF from DFSP. However, there is an overlap and relative lack of specificity of their expressions. CD44 is a widely distributed integral membrane glycoprotein, which is expressed as a multitude of isoforms generated by alternative splicing of at least 10 different variant exons and post-translational modifications. CD44 is currently thought to be the principal cell surface receptor for hyaluronate (HA), the major component of the extracellular matrix. In this study we aimed to assess the expression of standard CD44 (CD44s) and its isoforms (CD44v3, CD44v4, CD44v5, CD44v6, CD44v7, CD44v7v8, and CD44v10), and HA in DF and DFSP. Immunohistochemical staining was performed on the biopsy specimens of 15 cases of DF and four cases of DFSP, using antibodies that recognize the CD44s, different CD44 isoforms and the hyaluronate binding protein (HABP). Tumor cells displayed a strong CD44s immunoreactivity in all cases of DF whereas a faint HA positivity was observed in the tumor stroma. The DF cells were negative for CD44v3, CD44v4, CD44v6, CD44v7 and CD44v7v8 but showed a strong reactivity for CD44v5 and CD44v10. In contrast, CD44s' expression was significantly reduced or absent in all DFSP lesions and the tumor stroma displayed strong staining for HA. Our results indicate that CD44 and HA can be used as additional diagnostic markers to distinguish DF from DFSP.     

The expression of CD44 glycoprotein adhesion molecules in basal cell carcinomas is related to growth pattern and invasiveness

Basal cell carcinomas (BCCs) of the skin exhibit a wide range of histological growth patterns as well as a highly variable rate of invasiveness. A large body of experimental and clinical studies supports a role for the CD44 glycoprotein family in the latter process. In the present study, we explored the distribution and the level of expression of pan-CD44, CD44v3, CD44v5 and CD44v6 in BCCs. The use of paraffin sections, combined with an antigen retrieval procedure, yielded far more detailed data than would have been possible with frozen sections. On average, the level of expression of the four CD44 isoforms studied appeared to differ relatively little. However, tumours or tumour areas consisting of thin tumour cell strands showed a significantly stronger expression of all four isoforms than those consisting of solid tumour cell groups. Furthermore, the highest CD44 expression was frequently observed in the smallest tumour cell strands in the tumour periphery. In these strands, the label seemed to be located not only at the tumour cell-tumour cell interface, as in other tumour areas, but also on the tumour cell surfaces facing the stroma. We are presently assessing the exact localization of CD44 at the cellular level by immunoelectron microscopy. In most cases, different growth patterns with significantly different levels of CD44 expression were found side by side within individual tumours. CD44 expression is therefore not a static tumour cell characteristic but is correlated with tumour architecture and tumour-stroma interaction.     

Tyrosinase immunoreactivity in formalin-fixed, paraffin-embedded primary and metastatic melanoma: frequency and distribution

Monoclonal antibody T311 specifically detects tyrosinase protein expression. Tyrosinase-derived peptides are recognized by CD8+ T-celis and applied in immunotherapy. We examined formalin-fixed paraffin-embedded tissue of 50 melanoma (primary n=31, metastatic n=19) and 41 control cases (junctional, dermal, compound, Spitz, Reed, balloon-cell nevi) by immunochemistry using the alkaline phosphatase-anti-alkaline phosphatase method after antigen retrieval. Staining with mAb T311 showed a sensitivity of 94% for melanoma with a very high specificity for melanocytic cells. Immunopositivity (94% of melanomas overall) correlated inversely with clinical stage: clinical stage I and stage II showed 100%, stage III and stage IV 86% immunoreactivity each. Staining changed from an exclusively homogeneous pattern in early stages to a more heterogeneous pattern in later stages. Melanocytic control tissue like nevi of different subtypes all showed weak to moderate, homogeneous immunoreactivity with polarity towards the epidermis. RT-PCR ELISA analysis of short-term melanoma cell cultures displayed mRNA expression in only half of the originally immunopositive tumors only, suggesting rapid mRNA expression loss in culture. mAb T311 allows detection of melanoma-associated tyrosinase protein expression and thus profiling of melanomas using routine archival tissue suited for immunotherapy approaches involving tyrosinase derived epitopes.     

The universal detection of antigens from one skin biopsy specimen

Background: Immunohistochemistry is an important tool in dermatology but is limited. Certain antigens can only be preserved in formalin-fixed paraffin-embedded sections, while others can only be detected on frozen sections, resulting in situations where two biopsies are needed. We aimed to develop a technique for universal detection of different antigens out of just one biopsy specimen.
Methods: Single biopsies were obtained from lesional skin of patients with psoriasis. Standard sample procedures for frozen and paraffin-embedded sections were used. To convert frozen tissue into paraffin-embedded sections, the biopsy specimen was disposed of the embedding medium and subsequently fixed in 10% neutral buffered formalin. We applied various antigen retrieval techniques with alkaline solutions. The differential expression of keratin 10, keratin 15, CD3, CD26 and human beta defensin-2 (HBD-2) was examined using immunohistochemical staining.
Results: We showed that keratin 10 and 15 can be stained on both frozen and paraffin-embedded sections. Staining of paraffin-embedded sections required unmasking with trypsin and Tris-buffered saline Tween solution, respectively. CD3 and CD26 can only be detected on frozen sections, while HBD-2 can only be detected on paraffin-embedded sections.
Conclusion: We have described a straightforward technique that gives us the opportunity to use just one biopsy specimen to obtain frozen sections as well as paraffin-embedded sections.     

A comparative immunohistochemical study of lichen planus and discoid lupus erythematosus

A comparative immunohistochemical study was performed on skin biopsies from 10 patients with lichen planus and 10 patients with discoid lupus erythematosus (DLE). A panel of antibodies against T lymphocytes (UCHL-1, OPD-4, CD8, CD45), B lymphocytes (L-26), granulocytes (Leu-M1), activation markers (Ki-1, LN-3), macrophages, fibroblasts and dendritic cells (FXIIIa, S-100, Mac-387, K.P-1, vimentin), endothelial cells (CD34), and epithelial cells (epithelial membrane antigen) was employed using a peroxidase-anti-peroxidase technique. The recently released CD8 antiserum required microwave antigen retrieval of formalin-fixed, paraffin-embedded tissue to label lymphocytes. The results showed many similarities in the lymphocyte subsets and macrophages between lichen planus and discoid lupus erythematosus. The most important differences between the two conditions were statistically significant increases in the number of S-100⁺ cells in the epidermis and dermis, FXIIIa⁺ cells in the dermis and CD34⁺ vessels within the inflammatory infiltrate in lichen planus.     

CD44v6 is a marker for systemic spread in cutaneous T-cell lymphomas

Adhesion molecules are involved in leukocyte recruitment, lymphocyte recirculation, and in several aspects of tumour biology. Recent discoveries of surface proteins on tumour cells involved in tumour metastasis may explain the invasive behaviour, the migration involving reversible adhesive contacts, the release into the circulation and the extravasation of tumour cells.
CD44 is a family of glycoproteins involved in cell-cell and cell-matrix interactions. The v6 (variant exon v6) form of CD44 confers a metastatic potential onto some carcinoma cells. In the present study, the expression of CD44v6 on skin biopsies of 10 inflammatory skin diseases, 30 cutaneous lymphomas (CL), 11 reactive lymph nodes, 10 primary nodal non-Hodgkin's lymphomas (NHL) and 5 secondary nodal NHL was investigated immunohistochemically.
None of the 10 nodal NHL were CD44v6 positive for the neo-plastic B- or T-cells, whereas 11/12 CL with systemic spread showed a distinct CD44vG expression in the skin. CD44v6 was not expressed on the tumour cells of skin biopsies of patients without systemic spread (18 cases of CL). In conclusion, CD44v6 expression is connected to an aggressive behaviour of CL.     

CD44 variant isoform v10 is expressed on tumor-infiltrating lymphocytes and mediates hyaluronan-independent heterotypic cell-cell adhesion to melanoma cells

CD44 is a family of cell-surface receptors on human lymphocytes that act as co-stimulatory molecules leading to the induction of effector functions in T cells. We have analyzed primary cutaneous malignant melanomas with clinical and histologic signs of tumor regression using immunohistochemistry and observed the predominant expression of the CD44 variant isoform v10 on CD3 CD4/CD8 co-expressing tumor-infiltrating lymphocytes (TIL). We further analyzed the role of CD44v10 in adhesion of lymphocytes to human melanoma cells. In contrast to CD44- lymphatic cells, CD44v10+ lymphatic cells strongly bound to cultured human melanoma cells and to frozen tissue samples of melanomas. Antibody blocking studies revealed a hyaluronan-, integrin-, and selectin-independent pathway of adhesion. Furthermore, CD44v10+ lymphatic cells exhibited significantly higher invasiveness in three-dimensional collagen matrices as compared with CD44H+ and CD44-negative lymphocytes. These results indicate that expression of CD44v10 on TIL may mediate adhesion to melanoma cells and result in gain of novel invasive properties.     

CD44 and variants in melanocytic skin neoplasms

Expression of cell surface molecules that mediate cell-matrix and cell-cell interactions largely contributes to the ability of melanoma cells to migrate and spread beyond the primary site of the tumor. CD44, the principal cell-surface receptor for hyaluronate, and its numerous splice variants have been reported to play a crucial role in invasion and the metastatic process of different human neoplasms, including primary malignant melanoma (PMM). The aim of this study was to clarify which isoforms of CD44 (standard CD44 and CD44 variants) are distributed in PMM with a vertical tumor thickness of >1.4 mm. Staining of CD44 standard (CD44s) and splice variants was further examined for diagnostic and prognostic relevance in a panel of melanocytic skin lesions. Ten cases of PMM with Breslow >1.4 mm were analysed by immunohistochemistry using monoclonal antibodies specific for CD44s and the splice variants v3, v5, v6, v7, v7-8, and v10. In addition, using anti-CD44s, v5, and v6 antibodies, 55 meianocytic lesions, including dermal nevi (n=12), Clark nevi (dysplastic nevi) (CN; n=11), melanoma in situ (Mis; n=8), PMM (n=18), and cutaneous metastasis of malignant melanoma (cM-MM; n=6) were assessed. Staining intensities were scored visually and evaluated by means of a staining index. In ten cases of PMM with a Breslow index >1.4 mm positive staining was ascertained for CD44s, v5 and for v6 in three cases. No staining was found for v3, v7, v7-8, and v10. Examination of CD44s, v5, and v6 in 55 melanocytic skin lesions revealed a high index for CD44s in all specimens and a weak staining of v5 in Mis; dermal nevi and CN did not stain for v5. However, in PMM and cMMM we found v5 to be strongly positive. The isoform v6 showed a variable index only in PMM, but without connection to established prognostic criteria. We conclude that CD44s and splice variants can not be regarded as indicators for tumor progression in malignant melanomas. However, v5 may potentially serve as a diagnostic marker for meianocytic skin lesions.     

CD44 expression in melanocytic lesions: a marker of malignant progression?

CD44 is the major human cell surface receptor for hyaluronate and functions in a diverse range of physiological processes. Alternative splicing of a single gene generates a lamily of splice variants (CD44v1-10) in addition to the standard isoform. CD44H. Expression of CD44. particularly CD44v6. has heen descrihcd to correlate with metastasis formation in various tumours, although evidence in malignant melanoma is inconclusive. In this study, we explored the immunohisto-chemical pattern of CD44 expression in a range of melanocytic lesions using a panel of monoclonal antibodies raised to CD44H and the variants v 3, v4/5. v6and v8/9. Skin biopsies of 106 lesions from 100 patients were assessed and included benign and dysplastic naevi. melanoma in situ, malignant melanomas in horizontal and vertical growth phase, and cutaneous and lymph node metastases. CD44H was highly expressed in benign and dysplastic naevi and in melanoma in situ. However, expression within melanomas diminished with increasing invasiveness. and the pattern of expres-sion observed correlated significantly with the growth phase of the lesion rather than its Brcslow thickness. CD44 splice variants were not detected in any lesions. These results suggest a possible role for downregulation of CD44H in modulating the biological behaviour of malignant melanoma.     

Expression of CD44 isoforms in basal cell carcinomas

The expression of CD44 isoforms (CD44std, CD44v6, CD44v10) was investigated by an immuno-histochemical technique in 42 basal cell carcinomas (BCC) of the superficial and nodular variety. All BCCs studied displayed very low amounts of CD44std, a receptor for hyaluronic acid. Except for single CD44std-positive cells located preferentially in the central parts of the BCC nests, the bulk of the tumour formations were CD44std-negative. CD44v6 showed a heterogeneous distribution pattern accentuated in the peripheral palisading tumour cells. In superficial BCCs, the labelling intensity for CD44v6) increased with the size of the tumour nests. CD44v10 was not detectable in BCCs Our findings support the notion that CD44v6 is not linked to the metastatic proclivity of tumours originating from keratinocytes. We suggest that the very low expression of the receptor for hyaluronic acid (CD44std) may be one of the factors which block the formation of metastases from BCCs.     

Desmoplastic and spindle cell melanomas express protein markers of the neural crest but not of later committed stages of Schwann cell differentiation

BACKGROUND: The rare desmoplastic and spindle cell variants of malignant melanoma exhibit histological and biochemical features suggestive of early Schwann cell differentiation. These features include a spindle-shaped morphology, neurotropism, and the expression of the low affinity nerve growth factor receptor (p75NGFR). METHODS: We evaluated by immunohistochemistry (using formalin-fixed, paraffin-embedded tissues) nine desmoplastic and three spindle cell melanomas for the expression of peripherin, p75NGFR, neural cell adhesion molecule (CD56/N-CAM), and growth-associated phosphoprotein-43 (GAP-43). Peripherin is expressed in the neural crest and in neurons, but not in cells committed to the Schwann cell lineage. p75NGFR and CD56/N-CAM also are expressed in early neural crest cells, but persist in unmyelinated and early premyelinating Schwann cells. GAP-43 is expressed in unmyelinated Schwann cells, but is downregulated in the later premyelinating to promyelinating stages of cells committed to the Schwann cell lineage. RESULTS: Peripherin was expressed in 7/12 (58%), p75NGFR in 4/12 (33%), and CD56/N-CAM in 6/12 (50%) of the desmoplastic and spindle cell melanomas. GAP-43 was not expressed (0%) in any of the 12 melanomas (chi2, p = 0.05). CONCLUSIONS: Desmoplastic and spindle cell melanomas express protein markers common to cells of the neural crest and to neurons similar to the immunophenotype previously reported for epithelioid cell melanomas. The expression of peripherin and the lack of expression of GAP-43 further define that these rare subtypes of melanoma do not recapitulate the later committed stages of Schwann cell differentiation.     

Immunohistochemical Detection of Ki-67 in Epithelial Skin Tumors in Formalin-fixed Paraffin-embedded Tissue Sections Using a New Monoclonal Antibody (MIB-1)

The expression of the Ki-67 antigen was investigated in 44 epithelial skin tumors using an immunohistochemical technique on formalin-fixed, paraffin-embedded tissue sections. Microwave oven heating was employed for retrieval of the antigen in these tissue sections. The staining patterns varied among the epithelial skin tumors. The assessment of immunohistochemical staining was based upon the growth fraction (GF), defined as the number of Ki-67 positive cells divided by the total number of tumor cells counted and expressed as a percentage. GF was 9.7 ± 3.1% in seborrheic keratosis, 19.5 ± 2.9% in keratoacanthoma, 23.1 ± 4.9% in basal cell carcinoma, 18.5 ± 6.3% in actinic keratosis, 37.1 ± 6.0% in Bowen's disease, and 32.9 ± 10.5% in squamous cell carcinoma. There was a significant difference in GF between the keratoacanthoma and squamous cell carcinoma (p<0.01). Actinic keratosis showed a relatively low GF, whereas Bowen's disease showed a high one. Furthermore, the GF tended to increase with tumor cell differentiation in squamous cell carcinoma: 23.7% (±5.0) in well-differentiated, 35.0% (±6.2) in moderately-differentiated, and 47.6% (±4.5) in poorly-differentiated squamous cell carcinomas. Immunohistochemistry with MIB-1 may give useful additional information in the differential diagnosis of KA and SCC.     

骨桥蛋白和CD44v6在乳房外Paget病中的表达及其生物学意义

目的探讨骨桥蛋白(OPN)和CD44v6在乳房外Paget病中的表达特点及其生物学意义。方法应用免疫组化二步法分别检测34例乳房外Paget病患者皮损及20例正常对照皮肤中OPN和CD44v6的表达情况。结果 OPN和CD44v6在乳房外Paget病中阳性表达分别为70.59%和82.35%,显著高于正常皮肤组织的40%和0,差异有统计学意义(P0.05)。乳房外Paget病中OPN和CD44v6阳性表达与淋巴结转移有关(P0.05),OPN和CD44v6的表达呈正相关(P0.05)。结论 OPN和CD44v6高表达在乳房外Paget病的发生发展中起着重要的协同作用,两者的高表达与乳房外Paget病的淋巴结转移有关。     

Gottron's papules exhibit dermal accumulation of CD44 variant 7 (CD44v7) and its binding partner osteopontin: a unique molecular signature

The accumulated mucin in non-Gottron's dermatomyositis (DM) lesions is primarily chondroitin-4-sulfate (C4S), which is immunomodulatory in vitro. Gottron's papules are a particularly resistant manifestation of DM that often persist after other lesions have resolved with therapy. We examined non-Gottron's DM lesions and Gottron's papule skin biopsies for C4S, CD44 variant 7 (CD44v7), a chondroitin sulfate-binding isoform causally implicated in autoimmunity, and osteopontin (OPN), a CD44v7 ligand implicated in chronic inflammation. Gottron's papule dermis contained more C4S and CD44v7 than non-Gottron's lesions. Normal skin showed less CD44v7 over joints relative to Gottron's lesions. All DM dermis had increased OPN compared with healthy skin. Mechanically stretching cultured fibroblasts for 6?hours induced CD44v7 mRNA and protein, whereas IFN-γ treatment induced OPN mRNA and protein. OPN alone did not induce CD44v7, but stretching dermal fibroblasts in the presence of OPN increased human acute monocytic leukemia cell line (THP-1) monocyte binding, which is blunted by anti-CD44v7 blocking antibody. C4S, CD44v7, and OPN are three molecules uniquely present in Gottron's papules that contribute to inflammation individually and in association with one another. We propose that stretch-induced CD44v7 over joints, in concert with dysregulated OPN levels in the skin of DM patients, increases local inflammatory cell recruitment and contributes to the pathogenesis and resistance of Gottron's papules.