Epithelial hyaluronic acid and CD44v6 are mutually involved in invasion of colorectal adenocarcinomas and linked to patient prognosis

Desmoplastic stroma of colorectal adenocarcinomas contains a variety of extracellular matrix molecules, including hyaluronic acid (HA). Overexpression of the HA receptor CD44 and, in particular, its splicing variant CD44v6 has been described as a prognostic factor for patients with colorectal adenocarcinomas in some studies, but converse reports also exist. Our hypothesis is that these divergent results may be related to the fact that the function of CD44v6 depends on the HA content of cell-surrounding matrix. Therefore, we studied the expression of HA and CD44v6 in tissue samples of 145 patients suffering from colorectal adenocarcinomas using immunohistochemistry. Expression of HA was separately evaluated in tumor epithelium and stroma. We additionally examined the influence of HA on invasion and adhesion of colorectal adenocarcinoma cells in vitro. The results show that epithelial HA expression was not correlated with tumor stage but with lymph-node or distant metastasis. Patients with tumors expressing epithelial HA had a decreased overall survival (P=0.017) as well as tumors with coexpression of epithelial HA and CD44v6 (P=0.011). The latter issue remained an independent prognostic factor in multivariate analysis (relative risk 5.06; 95% confidence interval, 1.18–21.57; P=0.028). HA exclusively stimulated in vitro invasion of CD44v6-expressing cells. This stimulation was partly reversed by an anti-CD44v6 antibody. Our findings suggest that the adverse prognostic effect of CD44v6 in colorectal adenocarcinoma might be restricted to those tumors that have pericellular HA.     

CD44和CD44v6基因在胃腺癌组织中的表达及其意义

目的： 研究胃腺癌组织中ＣＤ４４ 的表达及其与淋巴结转移和预后的关系。方法： 应用免疫组化方法, 对１０５ 例胃腺癌组织中ＣＤ４４ 的表达进行了观察, 并对其中６２ 例患者做了随访。结果： ＣＤ４４ 和ＣＤ４４ｖ６ 基因的表达率分别为５４－３ ％ 和４８－６ ％ 。ＣＤ４４ｖ６ 在胃腺癌组织中的表达与癌细胞的分化、浸润深度, 以及临床分期和预后有关（Ｐ＜ ０－０５）, 而ＣＤ４４ 的表达则与上述临床病理指标无关。另外, 抗ＣＤ４４ 和抗ＣＤ４４ｖ６ 抗体的阳性反应, 与癌细胞的淋巴结转移有关（ＣＤ４４ｖ６, Ｐ＜ ０－０１ ; ＣＤ４４ , Ｐ＜ ０－０５） 。结论： ＣＤ４４ 的表达可用于胃癌患者的病情监测, 其中ＣＤ４４ｖ６ 有望作为判断预后的一个指标。     

Standard and variant CD44 isoforms are commonly expressed in lung cancer of the non-small cell type but not of the small cell type

Cluster of differentiation 44 (CD44) encompasses a polymorphic family of cell membrane glycoproteins involved in the mechanism of tumour invasion and metastasis. Since non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) display very different rates of progression, a significant discrepancy in their CD44 expression profiles is to be expected. An immunohistochemical study was undertaken on the expression of standard CD44 (CD44s) and the variant isoforms containing the domains encoded by variant exon 3 (CD44v3) or variant exon 6 (CD44v6) in paraffin-embedded bronchial biopsy specimens from 32 NSCLC cases and 11 SCLC cases. An absolute lack of immunoreactivity for CD44s, CD44v3, and CD44v6 was obtained in every case of SCLC, whereas 28 of the 32 NSCLC cases showed a positive immunoreaction for at least one of the three epitopes investigated. In conclusion, the occurrence of standard and variant CD44 isoforms in NSCLC and their absence in SCLC suggest the possibility that CD44 is in some way instrumental in conditioning the biological behaviour of NSCLC, but not of SCLC, whose metastatic cascade would be set in motion by the activation of hitherto unidentified, CD44-independent pathways.     

CD44 expression in soft tissue sarcomas

Recent studies have shown that expression of alternatively splicing variants of CD44 is correlated with prognosis for several kinds of malignant tumors. However, little is known about the expression of CD44 standard and variant isoforms in soft tissue sarcomas. In this study 47 cases of soft tissue sarcoma [18 malignant fibrous histiocytomas (MFHs), 13 synovial sarcomas (SSs), 7 malignant schwannomas (MSs), and 9 liposarcomas (LSs)] were examined immunohistochemically. The monoclonal antibodies to the standard form of CD44 (CD44H) and variant exons of CD44v3, 4, 5, 6, 7, 9, and v10 were used. We analyzed the membranous expression pattern of CD44H and CD44 variant exons and assessed the relation between expression of CD44s and metastasis-free survival rates (MFSR) of patients with soft tissue sarcoma. A few sarcomas expressed CD44v3 (2/47) and v7 (2/47), but none of the sarcomas expressed CD44v10. CD44v4 (5/47), v5 (4/47), v6 (10/47), and v9 (9/47) are relatively common types of variant isoforms in soft tissue sarcomas. Expression of CD44v6 is more frequently detected in high-grade than in low-grade tumors. CD44v6 or CD44v9 expression was correlated with metastasis-free survival of patients with soft tissue sarcomas. Received: 22 Juni 1999 / Accepted: 19 November 1999     

Short-term treatment with anti-CD44v7 antibody, but not CD44v4, restores the gut mucosa in established chronic dextran sulphate sodium (DSS)-induced colitis in mice

Increased expression of CD44 variant isoforms have been shown on the inflammatory infiltrates in human and mouse colitis and blockade or deletion of CD44 isoforms inhibit experimental colitis. The objective of this study was to find out if short-term treatment of CD44 antibodies specific to CD44v7, but not to other variant isoforms, suppresses leucocyte-endothelial interaction in chronic dextran sodium sulphate (DSS)-induced colitis in mice. Chronic colitis was induced by oral administration of four cycles of 5% DSS in BALB/c mice. Expression of CD44 was investigated on isolated mononuclear cells of the gut immune system. In established colitis, mice were treated with antibodies against CD44v7 or CD44v4 three times in 7 days. Intravital microscopy was used to study leucocyte-endothelial interactions and leucocyte extravasation. As a marker of inflammatory infiltrates myeloperoxidase was quantified in gut tissue. CD44-induced apoptosis was determined by fluorescence staining of hypodiploidic cell nuclei. In chronic DSS-induced colitis both CD44 variant isoforms, v4 and v7 were significantly up-regulated on mononuclear cells. However, whereas anti-CD44v7 antibody treatment induced a marked restoration of the gut mucosa and significantly reduced endothelial sticking and extravasation of circulating leucocyte in vivo (P < 0.01), application of anti-CD44v4 or an isotype control antibody had no anti-inflammatory effect. A significant reduction of myeloperoxidase activity was detected after blockade of CD44v7, but not v4. Short-term treatment with anti-CD44v7 antibody blocks T cell extravasation and recruitment to the intestinal mucosa and cures established experimental colitis.     

Importance of different CD44v6 expression in human gastric intestinal and diffuse type cancers for metastatic lymphogenic spreading

In 42 human gastric adenocarcinomas of intestinal (n=25) and diffuse types (n=17) the expression of CD44v6 splice variants was investigated immunohistochemically and compared with the pattern of lymphogenic tumor spreading. Distinct differences were observed between the two cancer types: 92% of intestinal-type tumors expressed CD44v6 as in the intestinal metaplasia in chronic atrophic gastritis, while v6 expression occurred in only 17% of diffuse-type cancers. The analysis of RNA expression confirmed the immunohistochemical data. Intestinal-type cancers yielded a much more complex pattern of amplification products hybridizing to exon v6 than did normal mucosa, whereas diffuse-type tumors did not express exon v6. Also the pattern of lymphogenic spreading was quite different between the two cancer types: in diffuse-type tumors only a sinus carcinosis without CD44v6 expression was observed in a significantly higher number of lymph nodes than in intestinal-type cancers, which showed in particular infiltrative lymph node metastases always with CD44v6 expression as in the primary tumors. When infiltrative lymph node invasion occurred in v6-negative diffuse-type cancers, v6 neoexpression was also demonstrable in the lymph node metastases. Additionally, the number of infiltrative lymphogenic metastases increased with more extensive v6 expression in primary gastric cancers of both types. These data suggest that the expression of CD44v6 isoform is important for the infiltrative spreading of tumor cells into lymph nodes. Addtionally, the phenotypic similarities in v6 expression between intestinal metaplasia and intestinal-type cancers, but not of tumors of diffuse type, may support the Correa hypothesis.Abbreviations AC Adenocarcinoma - mAb Monoclonal Antibody - PCR Polymerase chain reaction     

Differential expression of CD44v6 in metastases of intestinal and diffuse types of gastric carcinoma.

AIMS: To assess whether standard and variant isoforms of CD44 (CD44s, CD44v5, and CD44v6) have a differential expression profile in early versus advanced gastric adenocarcinoma of the diffuse and intestinal types and their metastases. METHODS: Immunohistochemical expression of CD44s, CD44v5, and CD44v6 was evaluated in 14 early gastric cancers (nine intestinal and five diffuse) and 37 advanced adenocarcinomas (21 intestinal and 16 diffuse) as well as in 18 cases of perigastric lymph node metastasis. Ten normal and five metaplastic gastric mucosa samples were also included in the study. RESULTS: Although no significant association was found between the degree of invasion and the CD44 expression profile, CD44v6 positivity was detected more frequently in metastases of intestinal-type carcinomas (66%) than in metastases of diffuse-type neoplasms (11%) (p < 0.05). Weak CD44s, CD44v5, and CD44v6 expression was observed focally in both normal and metaplastic gastric mucosa samples. CONCLUSIONS: These data suggest that CD44v6 expression may be involved in the production of lymph node metastases in intestinal-type gastric carcinoma but not in the diffuse-type disease, the metastatic potential of which is most likely unrelated to the CD44 family of adhesion molecules.     

Complex CD44 splicing combinations in synovial fibroblasts from arthritic joints

CD44 is a broadly expressed cell surface glycoprotein which is the major cell surface receptor for the glycosaminoglycan, hyaluronan. In humans, alternative splicing of up to 9 variant exons (v2–v10) into CD44 mRNA, together with post-translational modification via glycosylation and chondroitin sulfate attachment has the potential of generating a large number of CD44 isoforms. Insertion of these various exons has the potential to change the functional capacities of the molecule and has implications in disease. We have analyzed CD44 splice variant expression in cultured VCAM-1-positive synovial fibroblasts isolated from patients with osteo- or rheumatoid arthritis and from normal synovium. Rheumatoid and osteoarthritic tissue express CD44 splice variants at the cell surface level. At the mRNA level exons v3, v6, v7, v8, v9 and v10 were detected in different splicing combinations. Rheumatoid tissue showed high expression, osteoarthritic tissues showed great variation. In contrast, non-inflamed tissue showed no splicing events. Our results indicate that the nature of CD44 splice variant expression may be linked to the inflammatory state of the synovial joint.     

CD44 isoform expression in synovial sarcoma correlates with epitheliogenesis but not prognosis

AIMS : We immunohistochemically determined the expression of CD44 standard and splice variant isoforms in a series of synovial sarcomas and sought correlations with histological subtype and clinical parameters including outcome. METHODS AND RESULTS: From 39 patients, a total of 56 formalin-fixed and paraffin-embedded tumour samples (including initial, recurrent and metastatic tumours) were used to immunohistochemically evaluate the expression of epitopes encoded by CD44s and the CD44 splice variants CD44v3-v10. Significance of proposed prognostic indicators was evaluated in relation to the survival, time to local recurrence and time to metastases using log-rank analysis. Sixty-four percent of synovial sarcomas expressed CD44s and 46% expressed CD44v3-v10 (var). Synovial sarcomas with epithelial or epithelioid areas preferentially expressed CD44s in these areas when compared with the spindle cell element. There were no correlations with clinical parameters or outcome. CONCLUSION: The expression of CD44 was not found to correlate with survival, local recurrence or metastatic ability. In synovial sarcoma, CD44 and variant isoform expression appears to be associated with the degree of epithelial differentiation. CD44 expression in synovial sarcoma shows interesting similarities to CD44 expression in embryological epitheliogenesis.     

Motility of colon cancer cells: modulation by CD44 isoform expression

The invasion of cancer cells at primary tumor sites and their migration during metastatic spread require the expression of cell adhesion and motility proteins. Whether accelerated cell motility is necessary in these two processes is not universally accepted. In this study we took advantage that CD44, a cell adhesion protein, has different metastatic potentials depending on its splicing isoforms to examine how they affect cell motility. We established stable transfectants of standard and variant isoforms of CD44 in SW620 cells, a human colon carcinoma cell line that does not express CD44. The morphology of the cells varied according to the CD44 isoform expressed, but actin filament distribution remained unchanged. Using the wound assay in a two-dimensional in vitro cell motility system, we found that the expression of standard CD44 increases cell motility, whereas CD44 isoforms containing an exon sequence associated with metastatic dissemination has a slowing effect. Cell proliferation was also decreased by the expression of variant CD44 isoforms. Overall, colon cancer cells expressing variant CD44 isoforms had slower cell motility, possibly due to alterations in their cell adhesion properties. In conclusion, this study suggests that, contrary to common models, the metastatic phenotype is associated with a slow rate of cell migration when tested in vitro.     

Editorial

The family of CD44 glycoproteins has diverse functions in cell–cell and cell–matrix interactions. The standard form of CD44 is of importance in the dissemination of lymphoma, whereas the clinical significance of the variant exon v6-containing forms of CD44 (CD44v6) is not known. The expression of different forms of CD44 was investigated by using antibodies against the constant part of CD44 (CD44c) and CD44v6 in 56 primary and 17 recurrent non-Hodgkin's lymphomas and correlated with several clinicopathological parameters and with prognosis. Fifty-seven per cent of the primary non-Hodgkin's lymphomas expressed CD44v6 and 73 per cent expressed the constant epitope. Expression of both CD44c and CD44v6 was associated with low histological grade of malignancy. CD44c expression was associated with a low cellular proliferation rate as assessed by DNA flow cytometry. Of several factors tested, high expression of the variant from v6 was the only factor that was associated with unfavourable recurrence-free survival (P=0·04). We conclude that CD44v6 is associated with a low histological grade, but, on the other hand, with an unfavourable outcome, which suggests that the combination of CD44v6 and histological grading may form a particularly strong prognostic parameter in non-Hodgkin's lymphoma.     

CD44 and the adhesion of neoplastic cells.

CD44 is a family of transmembrane glycoproteins that act mainly as a receptor for hyaluronan. It can also bind some other extracellular matrix ligands (chondroitin sulphate, heparan sulphate, fibronectin, serglycin, osteopontin) with lower affinity. CD44 is encoded by a single gene containing 20 exons, 10 of which (v1-v10) are variant exons inserted by alternative splicing. The standard, ubiquitously expressed isoform of CD44, does not contain sequences encoded by these variant exons. Numerous variant isoforms of CD44 containing different combinations of exons v1-v10 inserted into the extracellular domain can be expressed in proliferating epithelial cells and activated lymphocytes. CD44 plays a significant role in lymphocyte homing. Both alternative splicing and glycosylation influence receptor function of the molecule, usually reducing its affinity to hyaluronan. The cytoplasmic domain of CD44 communicates with the cytoskeleton via ankyrin and proteins belonging to the ezrin-moesin-radixin family. Relatively little is known about the intracellular events following interactions of CD44 with its ligands. Some variant isoforms, especially those containing sequences encoded by v6-v10, are overexpressed in both human and animal neoplasms. In a rat pancreatic adenocarcinoma model one of the variant CD44 isoforms was proved to be determinant in the metastatic process. For some human neoplasms (carcinomas of the digestive tract, non-Hodgkin's lymphomas, thyroid carcinomas, and others) correlations have been made between the particular pattern of CD44 variants produced by neoplastic cells and clinicopathological parameters of tumours, such as grade, stage, presence of metastases, and survival. In vitro studies indicate that modifications of CD44 expression result in different ligand recognition and influence cell motility, invasive properties, and metastatic potential of experimental tumours. Investigation of CD44 neoexpression can be useful both in early cancer diagnosis and in predicting tumour behaviour. It can also contribute to better understanding of molecular mechanisms leading to neoplastic transformation.     

人CD44新剪接变异体克隆及分析

目的：应用逆转录多聚酶链式反应（RT-PCR）分析CD44在鼻咽癌组织和鼻咽癌细胞株中表达，来寻找新的人CD44剪接变异体。方法：在CD44基因起始和终止密码子两端及变异剪接外显子v10中和剪接位点处设计特异性引物，以鼻咽癌组织、细胞株5-8F和HNE1 cDNA为模板进行RT-PCR扩增，产物测序。然后，应用生物信息学对克隆序列进行分析。结果：新克隆的CD44剪接变异体有1634bp，包含一个完整的阅读框，起始密码子在序列的12位，终止密码子在序列的1301位，可变剪接区只有变异型剪接外显子10，预测编码429氨基酸。GenBank登陆号：EF581837。结论：一个新的、预测编码429个氨基酸的CD44剪接变异体存在于研究的人鼻咽癌组织和细胞株中，它的功能有待于进一步研究。     

ANALYSIS OF HUMAN ARTICULAR CHONDROCYTE CD44 ISOFORM EXPRESSION AND FUNCTION IN HEALTH AND DISEASE

Interactions between articular chondrocytes and components of the extracellular matrix are of potential importance in the normal function of cartilage and in the pathophysiology of arthritis. Little is known of the basis of these interactions, but cell adhesive molecules such as CD44 are likely to be involved. Immunohistology using six well-characterized anti-CD44 monoclonal antibodies demonstrated standard CD44 isoform (CD44H) expression by all chondrocytes in normal and osteoarthrotic (OA) cartilage but absence of the CD44E variant. Polymerase chain reaction (PCR) of reverse transcribed mRNA from monolayer cultures of normal and OA chondrocytes using primer sequences which span the region containing variably spliced exons produced a predominant band representing the standard form of CD44, which lacks the variable exons 6–15 (v1–v10). No product was seen at the expected size of the epithelial variant of CD44 (CD44v8–10). Use of exon-specific primers, however, showed expression of variant exons resulting in multiple minor isoforms. Standard CD44 was also shown to be the predominantly expressed isoform identified by immunoprecipitation, but human articular chondrocytes did not adhere to hyaluronan in vitro . Chondrocyte CD44 may function as an adhesion receptor for other matrix molecules such as fibronectin or collagen.     

CD44 promotes resistance to apoptosis in human colon cancer cells

Overexpression of CD44, especially its variant isoforms, occurs consistently in colon cancer, as compared to autologous normal colon, and this change occurs also in most other types of cancer. One of the basic features of malignant transformation is the acquisition of resistance to apoptosis. In this study, we asked whether the expression of CD44 and some of its variant isoforms commonly found in colon cancer participate in resistance to apoptosis and what are the mechanisms involved. A human colon cancer cell line, SW620, which does not express CD44 was stably transfected with standard, v3-10, and v8-10 containing isoforms of CD44. Mock-transfected and CD44-transfected cells were exposed to etoposide to induce apoptosis. Apoptotic and concomitant changes relevant to the mechanisms of apoptosis were monitored by flow cytometry, DNA fragmentation, and immunoblot analyses. It was observed that resistance to apoptosis induced by etoposide is promoted by CD44 expression in SW620, and this resistance is better sustained by the full variant isoform, v3-10. Concomitant alterations in caspase 9, caspase 3, Bcl-xl, and Bak indicated that the resistance to apoptosis in this model involved the mitochondrial pathway. The differential response of CD44 transfectants was associated with a downregulation of pRb and phosphorylated AKT. The results of this study are consistent with the conclusion that expression of variant CD44 isoforms which is characteristic of colon cancer, and most other types of cancer, confers a selective advantage to resist apoptosis, thereby promoting cell transformation into a malignant phenotype, in conjunction with other anti-apoptotic factors.     

Expression of hyaluronic acid and its receptors, CD44s and CD44v6, in normal, hyperplastic, and neoplastic endometrium

The interaction between epithelial tumor cells and their surrounding stroma is important in tumor progression and metastasis. This is accomplished through a number of transmembrane receptors that interact with stromal extracellular matrix molecules. One of these receptors, CD44, binds to extracellular matrix component hyaluronic acid (HA). The purpose of this study was to evaluate the significance of HA, CD44s, and CD44v6 in benign, hyperplastic, atypical, and malignant endometrial epithelia. Archival paraffin-embedded cell blocks from proliferative endometrium (n = 11), secretory endometrium (n = 12), simple hyperplasia (n = 13), complex hyperplasia without atypia (n = 9), complex hyperplasia with atypia (n = 17), and adenocarcinoma (n = 21) were stained for HA, CD44s, and CD44v6. HA was detected throughout the normal menstrual cycle but was more intense during the secretory phase. Only during the secretory phase was CD44s expressed in the stromal cells in 11 cases (92%), whereas CD44v6 was detected in glandular epithelium in 9 (75%). CD44s was expressed in the glandular epithelium in 2 (15%) cases of simple hyperplasia, 4 (44%) of complex hyperplasia without atypia, 14 (82%) of complex hyperplasia with atypia, and in 16 (76%) of adenocarcinoma. CD44v6 was expressed in the glandular epithelium in 1 (11%) case of complex hyperplasia without atypia, 17 (100%) cases of complex hyperplasia with atypia, and in 18 (86%) cases of adenocarcinoma, but in none of the cases of simple hyperplasia. The endometrial stromal cells expressed CD44v6 in 1 (8%) case of simple hyperplasia, 6 (67%) of complex hyperplasia without atypia, 8 (47%) of complex hyperplasia with atypia, and in 3 (14%) of adenocarcinoma. We concluded that in the normal menstrual cycle, the timing of peak staining of HA and CD44s in the stroma and the up-regulation of CD44v6 in secretory glands are coincident with the period in which the endometrium is most receptive to embryo implantation. HA is more abundant in the stroma adjacent to the tumor, suggesting that interactions between tumor cells and stromal HA promote tumorigenesis. With progression from hyperplasia and with increasing atypia to adenocarcinoma, levels of stromal HA, glandular CD44v6, and glandular and stromal CD44s all increase. Thus, HA and CD44 are both involved in the development and progression of endometrial cancer.