Lymphocyte homing and clinical behavior of non-Hodgkin's lymphoma

CD44 variant expression in cutaneous T-cell lymphoma

Expression of the lymphocyte homing receptor CD44 and its splice variants have been linked to tumour dissemination and poor prognosis in non-Hodgkin's lymphoma. Specifically, the in vitro expression of variant exon V6 confers metastatic potential in rat pancreatic carcinoma cell lines. In this study, we investigated the expression of CD44 splice variants in cutaneous T-cell lymphomas, including patients with mycosis fungoides (MF), Sezary syndrome (SS), large-cell anaplastic lymphoma (LCAL) and HTLV1-associated cutaneous lymphoma. In addition, 4 involved lymph nodes from 2 patients with MF and 1 patient with SS were examined. Inflammatory dermatoses, lichen planus and psoriasis, and normal skin were also studied. Immunohistochemistry was performed using a panel of monoclonal antibodies, including those with specificity for CD44H (standard isoform) and variant exons V3, V6 and V8-9. Normal epidermal keratinocytes were consistently CD44H and CD44 V3, V6 and V8-9 positive. In all the different clinicopathological subtypes and stages of cutaneous T-cell lymphomas, including involved lymph nodes, tumour cells consistently expressed CD44H, but were CD44 V3 and V6 negative. CD44 V8-9 was expressed on a majority of tumour cells in 2/5 LCAL and on occasional tumour cells in 2/5 LCAL. Occasional V8-9 positive tumour cells were also identified in 6/13 MF, 1/4 SS and 3/4 HTLV1. In 2/3 lymph node samples from 2 patients with tumour-stage MF, CD44 V8-9 expression was found on a small percentage of atypical mononuclear cells. Scattered V8-9 positive dermal mononuclear cells were present in sections of lichen planus and psoriasis. We have found no evidence to suggest that the metastasis-associated CD44 variant exon (V6) is expressed in cutaneous T-cell lymphoma, or that CD44H expression is associated with an adverse prognostic group. It is not clear whether the strong expression of CD44 V8-9 in 2 patients with CD30 positive LCAL reflects activation status or metastatic potential.

Expression of CD44 standard form and variant isoforms in non-small cell lung carcinomas

CD44, a cell adhesion molecule, has been implicated in tumor invasion and metastasis in certain malignancies. We studied the expression of CD44 standard (CD44s) and variant isoforms (CD44v) in 98 non-small cell lung carcinomas (NSCLCs) by immunohistochemistry and correlated the observations with clinical outcome. Formalin-fixed, paraffin-embedded archival tissues from 49 squamous cell carcinomas (SCCs) and 49 adenocarcinomas (ACs) were immunostained after microwave irradiation with monoclonal antibodies against CD44s and CD44v3, v4/5, v6, v7/8, and v10, and the results were correlated with histological tumor type, tumor stage, recurrence, and survival rates. SCCs of the lung showed strong membranous expression of each of the CD44s, v3, v4/5, v6, and v10 proteins in comparison with ACs (P < .0001). Staining for CD44 v4/5 was overwhelmingly positive in SCCs (72%) as compared with ACs (2.2%). Intense immunoreactivity for CD44v6 was present in 19 of 20 (95%) metastatic lung carcinomas. The bronchiolar basal cells and alveolar pneumocytes were positive for CD44s, v3, and v6. CD44s and variant isoform expression did not correlate with tumor stage, recurrence, and survival rates. In conclusion, there is significant immunopositivity of CD44s and variant isoforms in SCCs over ACs of the lung. Expression of CD44v6 may suggest an increased risk for local lymph node metastasis in NSCLCs. CD44v4/5 reactivity may be useful to discriminate squamoid differentiation in poorly differentiated NSCLCs.

High CD44 surface expression on primary tumours of malignant melanoma correlates with increased metastatic risk and reduced survival

The cell surface glycoprotein CD44 has been implicated in the progression and metastasis of certain human tumours including malignant melanoma (MM). In animal models, certain MM cell lines, expressing high levels of CD44, displayed an augmented capacity for haematogenous metastasis, compared to those with low CD44 levels. To determine whether, in vivo, the level of CD44 expressed by primary tumours of MM (PMM) is related to their metastatic potential, CD44 expression on PMM was studied in 92 patients, classified by their metastatic risk based on histological measurement of vertical tumour thickness (VT): in situ PMM, low-risk PMM (VT < or = 0.7 mm), intermediate risk PMM (VT = 0.71-1.4 mm) and high-risk PMM (VT > 1.4 mm). Paraffin-embedded sections were stained immunohistochemically with a panCD44 MAb. The level of CD44 expression on PMM was analysed semiquantitatively with epidermal CD44 staining set as an internal standard. High levels of CD44 were detected in 58.3% of high-risk PMM, 40.6% of intermediate-risk PMM, 36.7% of low-risk PMM and 16.7% of in situ PMM. Seventy-four per cent (17/23) of patients who developed and/or died of MM metastasis were CD44 high, and importantly, among these were 5 patients, whose metastatic risk had been estimated low, based on the measurement of VT. Finally, Kaplan-Meier analysis revealed patients whose PMM were CD44 high to have a significantly reduced 5-year survival rate compared to those that were CD44 low (P < 0.05). We conclude that in our patient population, a high level expression of CD44 on PMM is associated with increased metastatic risk and reduced survival.

Expression of CD44 splice variants in colorectal cancer

BACKGROUND

The CD44 gene codes for a family of heavily glycosylated cell surface proteins that have been linked with tumour metastasis. The aim of the study was to analyse the expression of CD44 messenger RNA in colorectal cancer.

METHODS

The expression of CD44 variants 2 and 7 in colorectal tumour samples was compared with that in normal colon and lymphocytes from 59 patients using reverse transcription-polymerase chain reaction followed by blot hybridization with exon-specific probes, and a nested polymerase chain reaction.

RESULTS

All samples of tumour and metastatic tissue showed complex overexpression of many alternatively spliced products of the CD44 gene. Normal colon, liver and lymphocytes predominantly expressed the standard form of the CD44 molecule (CD44S) with low levels of two or three variants hybridizing to exons v2 and v7.

CONCLUSION

Deranged CD44 gene activity in colorectal cancer cells is confirmed. The analysis of CD44 gene expression may provide a promising marker for the early detection of colonic tumours.

CD44 is an independent prognostic factor in early-stage cervical cancer

The expression of specific cell-adhesion molecule CD44 isoforms (splice variants) is associated with metastatic spread and poor prognosis in human malignancies. The aim of this study was to evaluate whether CD44 isoform expression is a prognostic factor in early-stage cervical cancer. We used 4 different variant exon sequence-specific murine monoclonal antibodies to the CD44 isoforms CD44v3, CD44v5, CD44v6 and CD44v7-8 to study the prognostic value of CD44 splice variants in 200 cases of International Federation of Gynecology and Obstetrics (FIGO) stage-IB cervical cancer by immunohistochemistry. In the univariate analysis, the expression of CD44v3 (log-rank test, p = 0.03) and CD44v6 (log-rank test, p = 0.03) was correlated with poor overall survival. In the subgroup of patients without metastatic disease in the pelvic lymph nodes, expression of CD44v6 was correlated with poor disease-free and overall survival (log-rank test, p = 0.04 and p = 0.01, respectively). Multivariate analysis, correcting for the confounding variables pelvic lymph-node involvement, depth of invasion and histologic grading, revealed CD44v6 to be an independent prognostic factor for overall survival of patients with early-stage cervical cancer. The results of this study indicate that CD44v6 is an additional prognostic marker in surgically treated cervical cancer. The assessment of CD44 isoform expression could be of clinical value in deciding upon adjuvant therapy, resulting in a more individualized management of therapy.

Expression of cell adhesion molecule CD44 in primary tumors of the liver: an immunohistochemical study

CD44, a widely distributed integral membrane protein, has been implicated in tumor invasion and metastatic spread in some human carcinomas and lymphomas. In this study, 35 cases of hepatocellular carcinoma from 32 patients (11 cholangiocarcinomas, 9 hepatic adenomas, and 5 cases of focal nodular hyperplasia, a non-neoplastic lesion) were examined by immunohistochemical methods for expression of CD44. The mouse monoclonal antibody A3D8 was used on formalin-fixed, paraffin-embedded tissue; this antibody does not distinguish between standard CD44 and splice variants. Positive membrane staining was seen in 13 of 35 cases of hepatocellular carcinoma (12 of 32 patients), 8 of 11 cases of cholangiocarcinoma, and 1 of 9 cases of hepatic adenoma. The strongest staining for CD44 was seen in two cases of fibrolamellar carcinoma, but CD44 expression was otherwise not related to degree of tumor differentiation. All five cases of focal nodular hyperplasia were negative for CD44. In non-neoplastic liver, hepatocytes were negative; sinusoidal lining cells and portal lymphocytes were positive; bile ducts and proliferating bile ductules were focally positive in some cases. Anatomic stage at time of presentation was similar in both groups of patients, with most patients presenting with stage III or IV disease. A trend towards slightly longer survival in patients whose hepatocellular carcinomas were CD44 negative was noted. These results show that aberrant CD44 expression is present in a subset of hepatocellular carcinomas and in most cholangio-carcinomas. The relationship between CD44 expression and tumor spread is unclear in this group of tumors, but is unlikely to be a simple association between CD44 expression and metastatic potential.

Decreased levels of CD44 protein and mRNA in prostate carcinoma. Correlation with tumor grade and ploidy

BACKGROUND

CD44, a transmembrane protein, is associated with cell-cell and cell-matrix interaction and with tumor growth and metastasis. Expression of both standard form and variant isoforms of CD44 protein has been associated with aggressive behavior and metastasis in various tumors, but has not been characterized in prostate adenocarcinoma (PAC).

METHODS

The expression of CD44 standard (CD44s) and splice variant v3, v4/5, v6, v7/8, and v10 proteins were studied in 109 PACs and correlated with tumor grade, DNA ploidy, and mRNA levels. Monoclonal antibodies against the various CD44 proteins were applied to microwave irradiated, formalin fixed, paraffin embedded sections. The DNA content of the tumors was evaluated by the Feulgen method with the CAS200 Image Analyzer. Total RNA exhibiting 18s and 28s bands was derived from two benign prostatic tissues and 5 PACs exhibiting decreased levels of CD44 protein by immunohistochemistry. The RNA was analyzed with reverse transcriptase polymerase chain reaction using CD44 specific primers.

RESULTS

The basal cells of the benign prostatic acini revealed uniform membranous staining for CD44s, v3, and v6 in 95-97% of cases. Similar staining was observed for v4/5, v7/8, and v10 in 40%, 30%, and 2% of cases, respectively. Secretory epithelial cells of the benign prostatic acini showed predominant expression of CD44s (97% of cases). Staining for CD44 variant proteins (v3, v4/5, v6, v7/8, and v10) in this location ranged from 9-22% of cases. Approximately 70% of the PACs showed significant loss of CD44s expression, which correlated with high tumor grade (Gleason > or = 7) (P = 0.01) and aneuploid status (P = 0.002). In 93-98% of the PACS, there was a complete lack of membranous expression for all CD44 variant isoforms. The metastatic PACS did not show preferential expression of either the standard form or any variant isoform. The cDNA from the normal prostates yielded a prominent CD44 standard form polymerase chain reaction product at 482 base pair (bp) and variant isoforms at approximately 650 and 850 bp. No CD44 products could be amplified from the subset of five PAC cDNAs, even when present at four-fold excess.

CONCLUSIONS

PACS exhibit down-regulation of CD44 protein expression, which correlates with high tumor grade and aneuploidy. v6 and v3 isoforms were preferentially expressed in the basal cells of benign prostatic acini. Based on a subset of cases, loss of CD44 protein expression is associated with decreased abundance of CD44 mRNA.

Expression of CD44 variant isoforms in peripheral blood leukocytes in malignant lymphoma and leukemia: inverse correlation between expression and tumor progression

In a variety of human tumors, including high grade Non-Hodgkin's lymphoma (hgNHL), a linkage between expression of CD44 variant isoforms (CD44v) and tumor progression has been described. In search of an easily accessible diagnostic parameter, expression of CD44 standard (CD44s) and CD44 variant isoforms (exons v5, v6, v7 and v10) in peripheral blood lymphocytes (PBLs) of patients with hematological malignancies was evaluated by fluorescence activated cell scanning. The analysis of 30 blood samples of healthy donors and patients with non-malignant diseases and of 183 blood samples of patients with malignant hematological disorders revealed that only in patients with malignant disorders did a measurable proportion of PBLs express CD44 variant isoforms, mostly exons v5, v6, v7 and, less frequently, exon v10. Elevated levels of CD44v expression were noted in PBLs of patients with acute and chronic myeloid leukemia (AML: 16%, CML: 25%), Hodgkin's disease (HD: 17%), multiple myeloma (MM: 22%), polycythemia vera (PV: 33%), acute lymphoid leukemia (ALL: 23%) and, most frequently, in PBLs of patients with non-Hodgkin's lymphoma (NHL:54%). CD44v expression was not restricted to the malignant phenotype, but instead was also noted in T cells, B cells and monocytes, preferentially in a subpopulation of large cells. Furthermore, expression of CD44v in PBLs was not linked to the histological grading or clinical staging. There was, however, an inverse correlation with tumor progression, whereas response to therapy was frequently accompanied by upregulation of CD44v. Thus, expression of CD44v in the PBLs of patients with NHL mainly reflected immune responsiveness. Since NHL manifests itself primarily in lymphoid organs, its progression is difficult to follow. Monitoring of CD44v in PBLs could be used as an additional and convenient parameter for surveying the course of disease.

Prognostic value of immunohistochemically detected CD44 isoforms CD44v5, CD44v6 and CD44v7-8 in human breast cancer

We investigated the expression of CD44 isoforms containing variant exons v5, v6 and v7-8 in 115 human breast cancer specimens by means of immunohistochemistry. CD44 isoforms CD44v5, CD44v6 and CD44v7-8 were detected in 56% (n = 64), 24% (n = 28) and 15% (n = 17), respectively. In 36 specimens of axillary lymph node metastasis, expression of CD44v5, CD44v6 and CD44v7-8 was found in 94% (n = 34), 92% (n = 33) and 89% (n = 32), respectively. Five year survival rates with or without CD44v5 and CD44v6 expression were 71% versus 86% (log-rank test, P = 0.02) and 62% versus 81% (log-rank test, P = 0.001), respectively. For disease-free survival, expression of CD44v5, CD44v6 and CD44v7-8 showed a prognostic impact (log-rank test, P = 0.004, P = 0.0001 and P = 0.0001, respectively). However, multivariate analysis revealed that all investigated CD44 isoforms failed to be independent predictors of the patient's outcome.

Metastatic potential of lymphoma/leukemia cell lines in SCID mice is closely related to expression of CD44

To investigate whether the lymphocyte homing receptors, adhesion molecules regulating normal lymphocyte traffic, influence the dissemination of lymphoma cells, 24 lymphoma/leukemia cell lines were inoculated into SCID mice subcutaneously, and the correlation between the expression of the adhesion molecules and the metastatic potential of the cell lines was examined. Among the six adhesion molecules examined (LFA-1, ICAM-1, CLA, VLA-4, L-selectin and CD44), L-selectin increased the incidence of lymph node metastasis, and CD44 expression was related to both lymph node and organ (hematogenous) metastasis. A monoclonal antibody to the standard form of CD44 (CD44s), Hermes-3, inhibited the local growth and remote metastasis of CD44+ cell lines. Thus, it is concluded that at least CD44s expression is important in both lymphatic and hematogenous metastasis.

Alternatively spliced variants of the cell adhesion molecule CD44 and tumour progression in colorectal cancer

Increased expression of alternatively spliced variants of the CD44 family of cell adhesion molecules has been associated with tumour metastasis. In the present study, expression of alternatively spliced variants of CD44 and their cellular distribution have been investigated in human colonic tumours and in the corresponding normal mucosa, in addition to benign adenomatous polyps. The expression of CD44 alternatively spliced variants has been correlated with tumour progression according to Dukes' histological stage. CD44 variant expression was determined by immunohistochemisty using monoclonal antibodies directed against specific CD44 variant domains together with RT-PCR analysis of CD44 variant mRNA expression in the same tissue specimens. We demonstrate that as well as being expressed in colonic tumour cells, the full range of CD44 variants, CD44v2-v10, are widely expressed in normal colonic crypt epithelium, predominantly in the crypt base. CD44v6, the epitope which is most commonly associated with tumour progression and metastasis, was not only expressed by many benign colonic tumours, but was expressed as frequently in normal basal crypt epithelium as in malignant colonic tumour cells, and surprisingly, was even absent from some metastatic colorectal tumours. Expression of none of the CD44 variant epitopes was found to be positively correlated with tumour progression or with colorectal tumour metastasis to the liver, results which are inconsistent with a role for CD44 variants as indicators of colonic cancer progression.

Expression of the CD44 variant isoforms 6 and 4/5 in breast cancer. Correlation with established prognostic parameters

Eighty one invasive breast cancers were analysed immunohistochemically to detect if they expressed the adhesion molecules CD44 v6 and v4/5, and the results were evaluated using the semiquantitative IR-score. The results were further divided into four groups: negative, weak positive, moderate positive and strong positive. Fifteen benign breast tumors were also analysed. Sixty eight breast cancers were CD44v6 and v4/5 positive. T3 and T4 cancers showed statistically significant higher positive CD44 rates than T1 and T2 cancers (P < 0.05). We also found a statistically significant correlation between the estrogen receptor and the CD44 status and between the CD44 status and the cathepsin-D status, whereas no correlation between CD44 and the lymph node status, the M status, the grading of the tumors, the progesterone receptor and the menopausal status could be found. Eleven benign tumors were CD44v6 and v4/5 positive. We could not establish any correlation between the expression of CD44 and the metastasizing capacity of breast cancer.

Signaling through CD44 is mediated by tyrosine kinases. Association with p56lck in T lymphocytes

Evidence from a large body of studies indicates that CD44 is involved in a number of important biological processes, including lymphocyte activation and homing, hematopoiesis, and tumor progression and metastasis. A proper understanding of the role of CD44 in these processes has been severely hampered by a lack of insight into the mode in which CD44 communicates with intracellular signal transduction pathways. In this report, we have addressed this aspect of CD44 functioning by studying CD44 signaling in T lymphocytes. We show that ligation of CD44 by monoclonal antibodies (mAbs) transduces signals to T cells which lead to tyrosine phosphorylation of ZAP-70 and other intracellular proteins. In vitro kinase assays demonstrate that cross-linking of CD44 induces an increase in the intrinsic activity of p56lck. Furthermore, immunoprecipitations show that CD44 is physically associated with p56lck. Our findings suggest that tyrosine kinases, particularly p56lck, play a central role in CD44 mediated signaling.

Targeted disruption of CD44 in MDAY-D2 lymphosarcoma cells has no effect on subcutaneous growth or metastatic capacity

CD44 splice variants have been shown to be involved in metastasis of carcinomas. In addition, the standard form of CD44 has been implicated in metastasis, particularly of melanomas and lymphomas. To investigate this, we have generated a CD44-negative mutant of the highly metastatic murine MDAY-D2 lymphosarcoma. The two CD44 alleles of this diploid cell line were sequentially disrupted by homologous recombination, using isogenic CD44 genomic constructs interrupted by a neomycin or hygromycin resistance-conferring gene. The resulting double knockout (DKO) cells had completely lost the capacity to bind to immobilized hyaluronic acid, but did not differ from MDAY-D2 cells in integrin expression or in vitro growth. Subcutaneous (s.c.) growth potential and metastatic capacity of MDAY-D2 and DKO cells were assessed by s.c. and i.v. injection of the lowest cell dose (10(3) or 10(4), respectively) that gave rise to tumor formation by MDAY-D2 cells in approximately 100% of the mice. Quite unexpectedly, we observed no difference at all in either s.c. growth rate or local invasion into surrounding tissues between MDAY-D2 cells and the CD44-negative DKO cells. Also hematogenous metastasis formation upon i.v. injection was similar: both parental and DKO cells metastasized extensively to the spleen, liver, and bone marrow. We conclude that, at least for these MDAY-D2 lymphosarcoma cells, the standard form of CD44 is dispensable for tumor growth and metastasis. Our results show that targeted disruption of genes in tumor cells is a feasible approach to study their role in tumorigenesis and metastasis.

Involvement of CD44 and its variant isoforms in membrane-cytoskeleton interaction, cell adhesion and tumor metastasis

CD44s (standard form of CD44) is a transmembrane glycoprotein whose external domain displays extracellular matrix adhesion properties by binding both hyaluronic acid (HA) and collagen. The cytoplasmic domain of CD44s interacts with the cytoskeleton by binding directly to ankyrin. It has been shown that post-translational modifications, such as phosphorylation (by protein kinase C), acylation (by acyl-transferase) and GTP-binding enhanced CD44's interaction with cytoskeletal proteins. Most importantly, the interaction between CD44s and the cytoskeletal protein, ankyrin, is required for the modulation of CD44s cell surface expression and its adhesion function. Recently, a number of tumor cells and tissues have been shown to express CD44 variant (CD44v) isoforms. Using RT-PCR and DNA sequence analyses, we have found that unique CD44 splice variant isoforms are expressed in both prostate and breast cancer cell lines and carcinomas. Most importantly intracellular ankyrin is preferentially accumulated underneath the patched/capped structures of CD44 variant isoform in both breast and prostate cancer cells attached to HA-coated plates. We propose that selective expression of CD44v isoforms unique for certain metastatic carcinomas and their interaction with the cytoskeleton may play a pivotal role in regulating tumor cell behavior during tumor development and metastasis.

Adhesion or anti-adhesion in cancer: what matters more?

The regulation of adhesion processes between normal epithelial cells is an essential condition for the maintenance of appropriate tissular architecture and differentiation. Quantitative and qualitative alterations in these homotypic adhesions occur during the transformation of normal into malignant epithelium. How these complex alterations in various homotypic adhesions modify the ability of tumor cells to detach from the original neoplastic site, to grow and move as single or clumped cells, and to invade the stroma are current issues in tumor biology. This review contrasts tumor cell adhesion mediated by E-cadherin which is consistently decreased in carcinomas, with adhesion mediated by CD44 and CEA which are increased in the tumors. A model proposing to resolve the apparent paradox of simultaneous adhesion and anti-adhesion mediated by the same protein is proposed.

CD44v6 is a marker for systemic spread in cutaneous T-cell lymphomas. A comparative study between nodal and cutaneous 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 neoplastic B- or T-cells, whereas 11/12 CL with systemic spread showed a distinct CD44v6 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.

Restoration of CD44H expression in colon carcinomas reduces tumorigenicity

OBJECTIVE

The functional consequences of reintroduction of the CD44H cell adhesion molecule into colon carcinomas were investigated.

BACKGROUND

CD44 is a cell surface adhesion molecule that is normally present in numerous isoforms as a result of messenger RNA alternative splicing. Individual CD44 isoforms differ in their ability to enhance tumorigenic or metastatic potential when overexpressed on tumor cells. Reverse transcriptase-polymerase chain reaction analysis demonstrates that CD44H is down-regulated during transformation of normal colon mucosa to carcinoma. The functional consequences of CD44H down-regulation in colon carcinomas has not been clarified.

METHODS

Tumor cell lines and fresh tissue specimens were examined for CD44 expression by Western blot analysis. CD44H cDNA and site-directed mutants of CD44H cDNA were transfected into colon carcinoma cells. Stable transfectants were examined for adhesion to hyaluronate, in vitro growth, and in vivo growth.

RESULTS

CD44H expression was nearly undetectable in primary colon carcinomas and colon carcinoma cell lines. In contrast, normal mucosa expressed high levels of CD44H. When CD44H was reintroduced into colon carcinoma cells, their in vitro and in vivo growth was significantly reduced. This CD44H-mediated growth rate reduction required an intact cytoplasmic domain.

CONCLUSIONS

Transformation of normal mucosa to colon carcinoma is associated with a down-regulation of CD44H, which consequently may enhance the growth rate and tumorigenicity.

CD44: physiological expression of distinct isoforms as evidence for organ-specific metastasis formation

Continuous progress has been achieved during recent decades in the therapy of metastasizing malignancies by improving chemotherapeutic strategies and new approaches in radiation therapy. Genetic manipulation of tumor cells and of the tumor fighting immune system is hoped to add significant contributions to curative interventions in disseminated tumors. That we are still far from eradicating death by malignant growth is due ultimately to our limited understanding of the cascade of events resulting in metastasis formation, which until recently was believed to rely on multiple rounds of mutation and selection processes. This implies an individually specific history of each metastatic tumor, which would rule out uniform diagnostic and therapeutic concepts. When it was noted in a rat tumor model that the transfer of cDNA of a single gene, a CD44 variant isoform (CD44v) covering the exons v4-v7, sufficed to initiate metastasis formation of a locally growing tumor, hope was created that a "metastogene" may have been identified. Although the idea of CD44v expression as a unifying concept for tumor progression was not sustained, the discovery of CD44v-initiated metastatic spread allowed a conceptually new hypothesis on tumor progression as a consequence of the reactivation of genetic programs of ontogeny, stem cell differentiation, and/or lymphocyte activation. Since distinct CD44 isoforms play an important role in these processes, unraveling the functions of this family of molecules can indeed provide a cornerstone in the understanding of tumor progression. This article summarizes briefly the present knowledge on known functions of CD44 isoforms with particular focus on parallels between physiological programs and tumor progression.

CD44 isoforms containing exons V6 and V7 are differentially expressed on mitogenically stimulated normal and Epstein-Barr virus-transformed human B cells

CD44, a cell adhesion molecule, exists in multiple isoforms that are generated by RNA alternative splicing. CD44 isoforms containing exon V6 (CD44 V6) have been associated with tumorigenesis and metastasis. We investigated the association between human B-cell activation and CD44 V6 isoform expression by analysing its expression in resting and mitogenically stimulated B cells. Results showed that resting B cells expressed the CD44 H (no variable exon) isoform alone. Activation of B cells [phorbol myristate acetate (PMA), surface immunoglobulin cross-linking alone or in the presence of interleukin-2 (IL-2)] induced CD44E (variable exon V8-10), R2 (VIO) and CD44 isoforms containing exons V6 and/or V7 (CD44 V6/V7). Epstein-Barr virus (EBV) infection of B cells, an alternative method of B-cell activation, induced the expression of CD44 E and R2 but not CD44 V6/V7. These results indicate that CD44 V6/V7 expression depends on the mode of activation. CD44 isoform expression was also investigated in a panel of EBV-negative and EBV-positive Burkitt's lymphoma (BL) B-cell lines. EBV-negative BL cells did not express CD44. In contrast, EBV-positive BL cells expressed CD44 H, R2 and E but not CD44 V6/V7 isoforms, suggesting an association between EBV infection and CD44 isoform induction. To determine directly the role of EBV in CD44 isoform induction, an EBV-negative BL cell line, BL30 (negative for all isoforms of CD44), BL30 infected in vitro with the EBNA-2-defective P3HR1 (BL30/P3HR1), and the wild-type B95-8 strain of EBV (BL30/B95-8) were examined. The parental BL30 cells infected with the wild-type EBV strain, but not with the P3HR-1 strain, expressed CD44 H, R2 and E isoforms, as seen in EBV-immortalized B cells. These studies suggest that (1) alternative splicing of CD44 isoforms is differentially regulated depending on the mode and state of cell activation, and that (2) the CD44 V6/V7 isoforms may represent B-cell activation antigens that are induced by mitogenic stimulation but not following EBV infection.

CD44v6 expression in non-Hodgkin's lymphoma: an association with low histological grade and poor prognosis

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.

Evaluation of CD44 prognostic value in neuroblastoma: comparison with the other prognostic factors

CD44 gene products are potential markers of aggressiveness in different tumour models, a result which prompted us to study clinical neuroblastoma (NB) specimens. CD44 expression was determined by immunostaining of 52 tumour samples from newly diagnosed NB with a monoclonal antibody (J173) directed against an epitope common to all CD44 isoforms. CD44 immunoreactivity was detected in 37 of the tumours (71%). CD44 was expressed in all 22 NBs with favourable prognoses (stages 1, 2 or 4S), but only 50% (15/30) of advanced NB (stages 3 and 4) (P < 10(-4)), suggesting that the absence, rather than the overexpression, of CD44 is a signal of tumour aggressiveness. The cumulative progression-free survival was significantly longer in patients with CD44 positive tumours compared with patients with CD44 negative tumours (P < 10(-5)). More importantly, progression-free survival was also significantly higher in CD44 positive patients within the high-risk group (P < 0.01). In univariate analysis, we tested the prognostic value of tumour expression of CD44 in comparison with tumour stage, age, tumour histology, and presence or absence of amplification of the MYCN protooncogene. All five measures had significant prognostic value. The expression of CD44 and the absence of MYCN amplification were the most powerful predictors of a favourable outcome. In a multivariate analysis of these measures, CD44 expression and tumour stage were the only independent prognostic factors for the prediction of patient survival. NB is the first clinical model described in which tumour aggressiveness correlates with repression rather than stimulation of CD44 expression. We recommend the use of CD44 as an additional biological marker in the initial staging of NB.

Blood group antigens as tumor markers, parasitic/bacterial/viral receptors, and their association with immunologically important proteins

Blood group antigens (BGAs) are chemical moieties on the red blood cell (RBC) membrane. Some BGAs (e.g., A, B, H, Lewis, P, I) are widely distributed throughout the body and may not be primarily erythroid antigens. Statistical correlations with ABO blood groups and disease have been made for years and have been highly controversial. It is not known if BGAs have a biological function. There are increasing reports of BGAs [e.g., Le(x) (an isomer of Le(a)), Le(y) (an isomer of Le(b)), T, Tn, "A-like"] appearing as "new" antigens on malignant tissue. Their presence and membrane density appears to correlate with the metastatic potential of the tumor. This often parallels loss of normal BGAs (e.g., ABH) from the tissue. Some of these antigens have been shown to influence the humoral and cellular response and have been used in assays to determine preclinical cancer, and in tumor immunotherapy. Interactions of some parasites and bacteria with human cells have been shown to depend on the presence of certain BGAs. P. vivax malarial parasites only enter human RBCs when the Fy6 Duffy blood group protein is present on the RBCs. Certain E. coli will only attach to the epithelial cells of the urinary tract if P or Dr BGAs are present in the epithelial cells. The P antigen is also the RBC receptor for Parvovirus B19. Leb has recently been found to be the receptor for H. pylori in the gastric tissue. The high frequency BGA, AnWj, is the RBC receptor for H. influenzae. BGAs have been shown to be associated closely with some important complement proteins. Ch/Rg BGAs have been found not to be true BGAs but are RBC-bound C4 (C4d). Knops/McCoy/York BGAs have been located on the C3b/C4b receptor (CR1). The high frequency BGAs of the Cromer (Cr) system are located on decay accelerating factor (DAF or CD55). Cartwright (Yt) BGAs are located on RBC acetylcholinesterase molecules. DAF and acetylcholinesterase are on phosphatidylinositol-glycan (PIG) linked proteins. When the PIG anchor is missing from RBCs, as in paroxysmal nocturnal hemoglobinuria, the affected RBCs lack all Cr, Yt, JMH, Hy/Gy, Do and Emm BGAs. The most important ligand for P, E and L selectins is sialyl-Le(x). This interaction is the tethering stage that start the leukocytes' journey from the circulation into the tissue. It appears that malignant cells may move through tissue in a similar way and may explain the close association of Le(x) with metastasis. Thus, there are increasing data suggesting a biological role for BGAs unrelated to the RBC.

New CD44 splice variants associated with human breast cancers

Changes in the CD44 variant (CD44v) isoforms on the cell surface have been correlated with tumor metastasis. In this study we have examined the expression of CD44 variant isoforms in human breast carcinoma samples by a variety of techniques including immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR), and nucleotide sequencing. Using RT-PCR, we have determined that normal human breast tissue contains primarily the CD44 epithelial (CD44E) form and very little CD44 standard (CD44s) form. However, metastatic breast carcinomas appear to overexpress both the CD44E and CD44s forms and also display multiple new species of CD44 variant isoforms. Histocytochemical staining using anti-CD44 antibody (recognizing a common determinant of the CD44 class of glycoproteins) confirms that the CD44 molecules are overexpressed and preferentially located in metastatic breast cancer tissues. Nucleotide sequencing analyses indicate that at least four new CD44 variant isoforms (i.e., displaying unique splicing via the insertion or the deletion of exons 7, 10, 11, and 14) may be closely associated with human metastatic breast cancers. These newly described CD44 variant isoforms may be useful for monitoring the progression of human breast cancer metastasis.

The binding of acute myeloid leukemia blast cells to human endothelium

AML blast cell adhesion to endothelium is in all likelihood a prerequisite for blast cell migration across the vascular wall in the periphery and the subsequent establishment of leukemic extravascular disease. A general feature of malignant cells is their acquisition of altered or aberrant adhesive capabilities which appear to be associated with their ability to metastasize. Aberrant expression of integrin adhesion molecules and of membrane oligosaccharide structures is found in AML and various solid tumors. With respect to AML, these alterations in adhesive phenotype may confer a proliferative advantage on the malignant cells in the marrow, may facilitate egress from the bone marrow into the peripheral vasculature and may enable AML blast cells to traverse the vessel wall and so establish extravascular disease. Oncogenes may be directly involved in the acquisition of such aberrant adhesive phenotypes. Neutrophil extravasation is described as a model for leukocyte migration across the vessel wall and brief summaries of experimental work involving aspects of AML blast cell and normal CD34+ bone marrow cell adhesion to endothelium in vitro are described.

Expression of the cell adhesion molecule CD44 in gastric adenocarcinomas

CD44, an integral membrane glycoprotein expressed by many cell types, serves as the principal transmembrane hyaluronate receptor and may be a determinant of metastatic and invasive behavior in carcinomas. The expression of CD44 in 23 gastric adenocarcinoma and 12 peptic ulcer disease (PUD) resection specimens and gastric carcinoma cell lines HS746t and KATO III was examined by immunohistochemistry using the murine monoclonal antibody A3D8 on formalin-fixed, paraffin-embedded tissue or cells. Western blot analysis of whole cell lysates of KATO III and HS746t cells showed protein bands at 85 to 90 kd with KATO III cells expressing an additional band at 145 kd. In normal stomach gastric epithelium was negative. In PUD foveolar epithelium was focally positive, but staining did not correlate with the extent of gastritis. In carcinoma cases intensity of staining was progressively stronger comparing intestinal metaplasia with dysplasia with intramucosal carcinoma. Invasive carcinoma was invariably more strongly positive than dysplasia or intramucosal carcinoma. Twelve adenocarcinomas were weakly positive and 11 were strongly positive. The staining intensity of metastases (12 cases) was the same or weaker than the primary tumor. For the 12 patients whose carcinomas were weakly positive, mean length of survival for the six who died was 23.3 months. Five of the 11 patients whose carcinomas strongly expressed CD44 died within the study period with a mean length of survival of 11.0 months. A key consequence of CD44 overexpression in gastric carcinomas may be development of the invasive phenotype and strong expression may indicate a poorer prognosis.

Expression of integrins and CD44 isoforms in non-Hodgkin's lymphomas: CD44 variant isoforms are preferentially expressed in high-grade malignant lymphomas

Low- and high-grade malignant non-Hodgkin's lymphomas have been investigated by immunohistochemistry for their expression of various integrins and CD44 isoforms. Comparison with the expression patterns obtained in non-malignant adult lymph nodes revealed the following differences: alpha 6 and beta 4 integrins were expressed in several high-grade malignant lymphomas to a lower degree than in both the low-grade malignant lymphomas and the normal lymph nodes; all other integrins (alpha 2, alpha 4, alpha 5, alpha v, beta 1, beta 2, beta 3, and beta 7) did not exhibit significant differences in the expression levels between malignant and non-malignant tissues. The standard isoform of CD44 (CD44s) was highly expressed in all lymphoid tissues. Using CD44 exons-specific monoclonal antibodies, CD44 variant isoforms were not detected in non-malignant lymph nodes and were detected only rarely in low-grade malignant lymphomas. In contrast, high-grade malignant lymphomas expressed several CD44 variant isoforms, which included the products from the variant exons 3v, 6v, and 9v, but not 4v. Specifically, detection of exon 3v and 6v products indicates a more aggressive phenotype.

Adhesion molecules: novel molecular tools in tumor pathology

Cell adhesion is a key process, elementary in the establishment of tissue architecture and differentiation. In neoplasia, in which there is a disruption of tissue architecture and a derangement in differentiation, it has been postulated that changes in cell-cell and cell-matrix interactions account for the ability of cancer cells to transgress normal tissue boundaries and disperse to distant sites. Complex and coordinated reductions and increases in adhesion have been proposed to be necessary for tumor invasion and metastasis. This hypothesis has fueled the interest of cancer research teams to evaluate the expression of various adhesion molecules in a wide range of human malignancies in the hope of pinpointing some of the cell adhesion alterations underlying tumor behavior. To date, a multitude of transmembrane glycoproteins, including cell-cell adhesion molecules (CAMs) and cell-matrix or substratum adhesion molecules (SAMs), have been identified; their structure, molecular genetics, and biochemistry have been elucidated, and we are beginning to understand their normal function. A few of these, on the basis of current evidence, seem to be promising candidate molecules for a role in neoplasia. This article aims to summarize recent developments in this field of adhesion research as well as the clinical applications in diagnostic pathology arising from it. First, by way of introduction, a summary of the biochemical and functional characterization of each family of adhesion receptors will be presented, followed by a presentation of the experimental data implicating them in the control of invasion, metastasis, and differentiation.

Cell surface expression and functional significance of adhesion molecules on human myeloma-derived cell lines

Multiple myeloma is characterized by the presence of malignant plasma cells predominantly localized in bone marrow. Our prior studies have suggested that human myeloma derived-cell lines adhere specifically to fibronectin and to bone marrow stromal cells (BMSCs) via beta 1 and beta 2 integrins as well as RGD peptide, and that tumour cell to BMSC contact triggers interleukin-6 (IL-6) secretion from BMSCs. Since IL-6 is a growth factor for myeloma, adhesion may be important in paracrine IL-6 mediated tumour cell growth. We therefore examined phenotypic expression of adhesion molecules on the U266 and IM-9 human myeloma-derived cell lines using the panel of monoclonal antibodies (MoAbs) directed at adhesion molecules submitted to the Vth International Conference on Human Leukocyte Differentiation Antigens. U266 and IM-9 myeloma cell lines express mainly CD29, CD49d, VLA-1, CD18, CD54, ICAM-2 and ICAM-3. In contrast, CD49b, VLA-3, CD49f, CD11b, VCAM-1, selectins and selectin-ligands were not expressed on these cell lines. Specific adherence of IM-9 cells to BMSC line LP101 was demonstrated which could be partially blocked by pre-incubation and culture of tumour cells with anti-beta 1 integrin, anti-beta 2 integrin, anti-CD49d, anti-VLA-5, anti-CD11a, anti-CD44 and anti-CD54 MoAbs. The combination of these MoAbs (anti-CD29, CD18, CD11a, CD49d, VLA-5, CD44, CD54, ICAM-2, ICAM-3 MoAbs) decreased but did not completely abrogate binding of IM-9 to BMSCs. Moreover, increases in IL-6 secretion from BMSCs after adherence of IM-9 cells were also partially blocked by these MoAbs. These findings suggest that multiple adhesion pathways may mediate adherence of myeloma cell lines to BMSCs, localizing tumour cells in the marrow microenvironment and triggering IL-6 secretion by BMSCs which may augment tumour cell growth.

Primary cutaneous B-cell lymphomas in Japan. A report of three cases and a comparison of Japanese and white patients

BACKGROUND

In contrast to cutaneous T-cell lymphoma, primary cutaneous B-cell lymphomas (pCBCL) are rare in Japan. Thus there have been no reports in the English literature that analyze Japanese pCBCL cases in detail.

OBJECTIVE

We describe three additional Japanese cases of pCBCL and review the Japanese literature to compare their clinical features and prognoses with those in cases that involve white persons.

METHODS

In our three cases, we performed immunohistochemical and flow cytometric analyses to determine the phenotypes of tumor cells. Genotypic analysis was also conducted by Southern blotting. In addition, we reviewed 43 cases of pCBCL reported in Japan.

RESULTS

In our three cases of pCBCL, the lack of systemic involvement indicated that they were primary cutaneous tumors. One of our cases, which had a poor prognosis, lacked both HLA-DR and CD44 phenotypes, which are usually observed in the diffuse large-cell type of pCBCL. We found three major differences between the reported Japanese cases including ours and the cases that involved white persons: (1) histologically, the diffuse type was presented in 79% of lesions of less than 12 months' duration in the Japanese cases but in only 9% of lesions in white persons; (2) chemotherapy was more frequently selected in the Japanese cases (51%), whereas radiotherapy was used more frequently in white cases (71%); and (3) the death rate from pCBCL was much higher in Japanese (16%) than in white (2%) persons.

CONCLUSION

pCBCL in Japanese persons seems to be different from that in white persons in frequency, in histoarchitectural growth pattern, and in prognosis.

Expression of CD44 splice variants during lymphocyte activation and tumor progression

Recently, splice variants of CD44 have been described that confer metastatic potential to non-metastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies against variant CD44 (CD44v) sequences, we have examined the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and in colorectal neoplasia. Lymphohematopoietic cells express low levels of CD44v glycoproteins. During the process of lymphocyte activation in vitro and in vivo, expression of CD44v glycoproteins is transiently upregulated. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that confers metastatic capability. In human colorectal neoplasia we observed overexpression of CD44 splice variants in all invasive carcinomas. Already at early stages of colorectal tumor progression exon v5 epitopes were overexpressed. Tumor progression was strongly related to expression of CD44 isoforms containing exon v6 encoded domains. The findings establish CD44 variants as tumor progression markers in colorectal cancer.

CD44 expression in Merkel cell carcinoma may correlate with risk of metastasis

We retrospectively studied 25 cases of cutaneous primary, locally recurrent or metastatic Merkel cell carcinoma to see if expression of the cell surface marker CD44 correlated with metastatic potential. In 3 of 6 cases in which metastasis was documented, CD44 was found on membranes of tumor cells. Three cutaneous lesions associated with local metastasis did not express CD44. Three primary tumors expressed CD44 but had not disseminated at the time of this report; follow-up after excision of the primary lesion in these cases was less than 6 months. None of the primary or locally recurrent Merkel cell carcinomas followed longer than 6 months (14 of 19 cases) expressed CD44. We conclude that expression of CD44 in Merkel cell carcinoma may eventually be of some value in the assessment of prognosis of cutaneous Merkel cell carcinoma.

Expression of alternatively spliced forms of the CD44 extracellular-matrix receptor on human lung carcinomas

Expression of isoforms of the CD44 hyaluronan receptor/lymph-node endothelial receptor by human tumour cells is thought to play a role in tumour growth and metastasis. These isoforms which vary in the length of the extracellular domain are generated by differential RNA splicing that involves the 10 alternative exons (v1 to v10) encoding the membrane proximal region of the molecule. Several tumours have been shown to over-express CD44 containing the v6 exon, and this, together with other evidence, has led to the suggestion that v6 may play a causative role in tumour metastasis. In this report we have compared the expression of CD44 isoforms between different lung tumour lines, including SCLC, squamous-cell carcinoma, adenocarcinoma and mesothelioma, using both RT-PCR and fluorescent antibody staining with a panel of CD44 exon-specific monoclonal antibodies (MAbs). Our results show large differences in vCD44 expression between individual tumour lines. Little or no vCD44 containing the metastasis-associated v6 exon was detected in most tumours, including the highly metastatic SCLC lines. Indeed, the SCLC lines and some squamous-cell carcinomas contained only very low levels of either vCD44 or CD44H, indicating that CD44 expression may not always correlate with tumour development or dissemination. One of the squamous-cell carcinomas studied (HOTZ) was found to express a complex mixture of CD44 splice variants similar to the immortalized normal bronchial epithelial line BEAS-2B. Cloning and sequencing of vCD44 from the HOTZ cell line yielded several splice variants that have also been identified on leukaemic cells, normal keratinocytes and activated peripheral-blood lymphocytes.

Glycoprotein CD44 expression and its association with survival in breast cancer

To investigate the clinical significance of CD44 expression (lymphocyte-homing receptor) in adenocarcinoma, deparaffinized sections from 198 female breast carcinomas were stained with Hermes-3 MoAb for CD44 glycoprotein. In 16% of the cancers most (> or = 90%) of the cancer cells stained positively for CD44, whereas the rest of the cancers were either heterogenous (46%) or negative (38%) in CD44 staining. Cancers with > 50% CD44 positive cells were more often poorly differentiated (grade 3) than those with < or = 50% positive cells (38 vs. 19%, P = 0.006), they had higher mitotic counts (P = 0.04), and were more often estrogen receptor negative (52 vs. 31%, P = 0.01). Among ductal not otherwise specified cancers and node-positive cancers strong CD44 expression was associated with poor outcome (P = 0.05 and 0.02, respectively). However, CD44 expression was not an independent prognostic factor in these subgroups in a multivariate analysis. Unlike in lymphomas the unfavorable prognosis associated with CD44 expression may not be explained by the greater metastatic potential of CD44-positive cells, because the difference in mortality between the groups appeared to diminish with time, and CD44 positivity was associated with aggressive histological features.

Lymphocyte homing receptor (CD44) expression is associated with poor prognosis in gastrointestinal lymphoma

Lymphocyte homing receptor (CD44) is involved in lymphocyte adhesion to endothelial cells of high endothelial venules (HEVs) and lymphocyte exit from the blood circulation, and it may be involved also in hematogenous dissemination of malignant lymphoma. Prognostic significance of lymphocyte homing receptor expression defined by Hermes-3 antibody was studied among 27 gastrointestinal lymphomas followed up for 8 to 20 years after the diagnosis. Lymphomas lacking or with very weak homing receptor expression (n = 14, 52%) were associated with 57% 10-year survival rate as compared with only 15% among lymphomas that expressed CD44 more strongly (P = 0.02). We conclude that lack of lymphocyte homing receptor expression is common in gastrointestinal lymphoma, and that CD44 expression is associated with unfavourable prognosis.

Regulated expression of exon v6 containing isoforms of CD44 in man: downregulation during malignant transformation of tumors of squamocellular origin

CD44 is a family of glycoproteins involved in cell-cell and cell-matrix interactions. In addition to the major 90-kD form present on most hematopoietic cells, larger 140-230 kD forms are found on keratinocytes and carcinoma cell lines. These bigger isoforms of CD44 arise by alternative splicing that results in insertion of one or more of the "variant" exons into the extracellular part of the 90-kD constant form of the molecule. In rat, v6 (variant exon v6) containing form of CD44 confers metastatic potential to carcinoma cells, and therefore, it is of interest to study the distribution of this isoform in humans. We raised antibodies against a synthetic peptide containing a sequence encoded by the exon v6. A mAb thus obtained (designated Var3.1) strongly reacted with the plasma membranes of squamous cells in upper layers of skin and tonsil surface epithelia. Weaker staining was seen in germinal centers, vascular endothelia and enterocytes. Exon v6 containing forms of CD44 (CD44v6) were absent from tissue leukocytes and connective tissue components. In comparison, Hermes-3 epitope (on the constant part) containing forms of CD44 were preferentially localized in basal layers of epithelia, present on the surface on most leukocytes and connective tissue cells, and undetectable on the luminal surface of high endothelial venules. In benign neoplasms, epithelial cells stained with mAb Var3.1 like in normal tissues. In contrast, immunostaining of 30 squamous carcinoma specimens (both primary and metastatic lesions) revealed that malignant transformation resulted in downregulation or disappearance of Var3.1 epitope, but in majority of cases, not in diminished synthesis of the Hermes-3 epitope. Biochemical analyses showed that mAb Var3.1 recognized two major forms of CD44 (220 and 300 kD). In conclusion, epitopes on exon v6 and constant part of CD44 are differentially synthesized and regulated during normal and malignant growth of cells in man.