Non-invasive detection of bladder cancer by identification of abnormal CD44 proteins in exfoliated cancer cells in urine

Comprehensive characterization of cell-free tumor DNA in plasma and urine of patients with renal tumors

BACKGROUND

Cell-free tumor-derived DNA (ctDNA) allows non-invasive monitoring of cancers, but its utility in renal cell cancer (RCC) has not been established.

METHODS

Here, a combination of untargeted and targeted sequencing methods, applied to two independent cohorts of patients (n = 91) with various renal tumor subtypes, were used to determine ctDNA content in plasma and urine.

RESULTS

Our data revealed lower plasma ctDNA levels in RCC relative to other cancers of similar size and stage, with untargeted detection in 27.5% of patients from both cohorts. A sensitive personalized approach, applied to plasma and urine from select patients (n = 22) improved detection to ~ 50%, including in patients with early-stage disease and even benign lesions. Detection in plasma, but not urine, was more frequent amongst patients with larger tumors and in those patients with venous tumor thrombus. With data from one extensively characterized patient, we observed that plasma and, for the first time, urine ctDNA may better represent tumor heterogeneity than a single tissue biopsy. Furthermore, in a subset of patients (n = 16), longitudinal sampling revealed that ctDNA can track disease course and may pre-empt radiological identification of minimal residual disease or disease progression on systemic therapy. Additional datasets will be required to validate these findings.

CONCLUSIONS

These data highlight RCC as a ctDNA-low malignancy. The biological reasons for this are yet to be determined. Nonetheless, our findings indicate potential clinical utility in the management of patients with renal tumors, provided improvement in isolation and detection approaches.

Impact of CD44 expression on radiation response for bladder cancer

Background Identification of potential factors that can stratify tumors' response to specific therapies will aid in the selection of cancer therapy. Radioresistance is the major obstacles to positive outcomes in bladder cancer patients after definite chemotherapy. CD44, a cancer stem cell surface marker, is relevant in treatment resistance. In the present study, we examined the role of CD44 in bladder cancer.

Methods We retrospectively analyzed the clinical outcomes of 85 bladder cancer patients treated with definite chemoradiotherapy, and correlated the expressions of CD44 with IL-6 and treatment response. Furthermore, the bladder cancer cell lines HT1197 and MB49 were selected for cellular and animal experiments to investigate the links between the CD44, IL-6 and radiation response.

Results Analyzing the clinical specimen, the staining of CD44 was significantly linked with higher clinical stage, lower complete response rates, higher loco-regional failure rate and lower survival rate with intact bladder for patients treated with definite CCRT. In addition, the frequency of CD44 immunoreactivity was significantly higher in IL-6-positive bladder cancer specimens. By cellular experiments, the expression of CD44 was stimulated by IL-6 and linked with the cancer stem cell-like property. As demonstrated through in vitro and animal experiments using immunocompromised and immunocompetent hosts, CD44+ bladder cancer cells appeared more resistant to irradiation, associated with less RT-induced cell death.

Conclusions Our findings suggested that CD44 is important in predicting the radiation response of bladder tumor cells. If overexpressed CD44 and/or IL-6 were noted in pre-surgical specimens, radical cystectomy is more likely to be preferred.

Evaluation of RNA and DNA extraction from liquid-based cytology specimens

Molecular diagnosis using DNA and RNA derived from malignant tumors and molecular biological tools such as the quantitative polymerase-chain-reaction (qPCR) is a commonly used technique in clinical pathology. In this report, we compared the qualitative extraction of RNA and DNA from cancer cells fixed using several liquid-based cytology (LBC) kits. Ten to 1,000 cells from the T24 urinary bladder cancer cell line and SKG-II cervical cancer cell line were fixed with 55% methanol and three different methanol-based LBC solutions. The mRNA levels of CD44 in T24 cells and E7 in SKG-II cells and DNA levels of p53 in T24 cells and E7 in SKG-II cells were analyzed by qPCR. mRNA and DNA extracted from T24 and/or SKG-II cells fixed with methanol-based LBC solutions were efficiently detected, but to differing degrees, by qPCR. mRNA, and DNA from cells fixed with a formaldehyde-containing fixative liquid were detected at significantly low copy numbers by qPCR. Our results demonstrate that LBC systems are powerful tools for cytopathology and immunocytochemistry applications. However, the appropriate fixative must be selected for cell preservation when a small number of LBC samples is used for molecular testing, particularly in RNA-based molecular analyses. Diagn. Cytopathol. 2016;44:833-840. © 2016 Wiley Periodicals, Inc.

Recent developments in hyaluronic acid-based nanomedicine for targeted cancer treatment

INTRODUCTION

Hyaluronic acid (HA) has emerged as a promising applicant for the tumor-targeted delivery of various therapeutic agents. Because of its biocompatibility, biodegradability and receptor-binding properties, HA has been extensively investigated as the drug delivery carrier. In this review, recent advances in HA-based nanomedicines are discussed.

AREAS COVERED

This review focuses on HA-based nanomedicines for the diagnosis and treatment of cancer. In particular, recent advances in HA-drug conjugates and HA-based nanoparticles for small molecular drug delivery are discussed. The bioreducible HA conjugates for small interfering ribonucleic acid delivery have been also discussed.

EXPERT OPINION

To develop a successful HA-based nanomedicine, it has to be prepared without significant deterioration of intrinsic property of HA. The chemical modification of HA with drugs or hydrophobic moieties may reduce the binding affinity of HA to the receptors. In addition, since the HA-based nanomedicines tend to accumulate in the liver after their systemic administration, new strategies to overcome this issue have to be developed.

MicroRNA-34a functions as an anti-metastatic microRNA and suppresses angiogenesis in bladder cancer by directly targeting CD44

BACKGROUND

Metastasis have considered as an important clinical obstacle in the treatment of human cancer including bladder cancer. Post-transcriptional regulation has emerged as robust effectors of metastasis. MiRNAs are involved in cancer development and progression, acting as tumor suppressors or oncogenes. In this study, we focus on it that microRNA-34a functions as an anti-metastatic microRNA and suppress angiogenesis in bladder cancer by directly targeting CD44.

METHODS

The expression of mir-34a was detected by quantitative real-time PCR. Oligonucleotide and lentivirus were used to overexpress miR-34a. Tube formation assay and transwell assay were used to examine the effect on bladder cancer tube formation, migration and invasion in vitro. Animal models were used to examine the effect on metastasis and angiogenesis in vivo. Luciferase assay was carried out to verify the precise target of miR-34a.

RESULTS

We not only proved that mir-34a was significantly downregulated in bladder cancer tissues and cell lines but also that circulating miR-34a levels are reduced in bladder cancer, and their levels were positively relevance. Gain-of-function experiments investigated that increased mir-34a expression suppressed tube formation and reduced cell migration and invasion. In vivo metastasis, assays also demonstrated that overexpression of mir34a markedly inhibited bladder cancer metastasis. CD31, an endothelial cell-specific marker which stained in T24 tumors to evaluate for blood vessel density, the immunohistochemistry results showed that blood vessel quantification reduced dramatically in the T24 tumors over-expressing mir-34a. Combining with our previous studies and bioinformatics analysis, we expected that CD44 gene was a direct target of mir-34a, siRNA-mediated knockdown of CD44 partially phenocopied mir-34a overexpression suggesting that the pro-apoptotic role of mir-34a may be mediated primarily through CD44 regulation, whereas restoring the expression of CD44 attenuated the function of mir-34a in bladder cancer cells. Additionally, we identified that EMT (epithelial-mesenchymal transition) related proteins could be regulated by mir-34a which indicated that mir-34a could partially reserve EMT.

CONCLUSION

Our study defines a major metastasis and angiogenesis suppressive role for mir-34a, a microRNA functions as a tumor suppressor in bladder cancer by directly targeting CD44, which would be helpful as a therapeutic approach to block bladder cancer metastasis.

Noninvasive approaches for detecting and monitoring bladder cancer

Bladder cancer is the second most common cancer of the urinary tract. Despite existing multiapproach treatment strategies, including radical cystectomy, bladder-sparing therapy with transurethral resection, chemotherapy and radiotherapy, patients with deeply invasive bladder cancers display poor prognosis, with a survival rate of only 30-50%. This can be avoided through proper surveillance and monitoring. Several genetic factors contribute to the progression of bladder cancer, and these molecules serve as cancer biomarkers. Blood, plasma, serum and urine are commonly analyzed for the presence of biomarkers, which can be both nuclear as well as mitochondrial in nature. This review discusses the efficacy of such biomarkers as well as highlights some potential prognostic markers in the field of noninvasive bladder cancer detection.

DNA damage in inflammation-related carcinogenesis and cancer stem cells

Infection and chronic inflammation have been recognized as important factors for carcinogenesis. Under inflammatory conditions, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from inflammatory and epithelial cells and result in oxidative and nitrative DNA damage, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-nitroguanine. The DNA damage can cause mutations and has been implicated in the initiation and/or promotion of inflammation-mediated carcinogenesis. It has been estimated that various infectious agents are carcinogenic to humans (IARC group 1), including parasites (Schistosoma haematobium (SH) and Opisthorchis viverrini (OV)), viruses (hepatitis C virus (HCV), human papillomavirus (HPV), and Epstein-Barr virus (EBV)), and bacterium Helicobacter pylori (HP). SH, OV, HCV, HPV, EBV, and HP are important risk factors for bladder cancer, cholangiocarcinoma, hepatocellular carcinoma, cervical cancer, nasopharyngeal carcinoma, and gastric cancer, respectively. We demonstrated that 8-nitroguanine was strongly formed via inducible nitric oxide synthase (iNOS) expression at these cancer sites of patients. Moreover, 8-nitroguanine was formed in Oct3/4-positive stem cells in SH-associated bladder cancer tissues and in Oct3/4- and CD133-positive stem cells in OV-associated cholangiocarcinoma tissues. Therefore, it is considered that oxidative and nitrative DNA damage in stem cells may play a key role in inflammation-related carcinogenesis.

Role of CD44 in tumour progression and strategies for targeting

CD44 or hyaluronan receptor is a transmembrane receptor associated with aggressive tumour growth, proliferation, and metastasis. In normal physiology, this receptor has a crucial role in cell adhesion, inflammation, and repair processes. However, many tumour cells over-express this receptor and abuse it to become progressive and perpetual units. The article comments from common functioning of the CD44 receptor, to its diabolic multi-dimensional effects in promotion of malignant cells. It also illuminates the relations of CD44 endorsed processes with other biomolecular events in cancer progression. In an end, the review focuses comprehensively at ongoing researches to exploit the CD44 over-expression as a probable target in treatment, management, and diagnosis of malignancy.

Nuclear localization of COX-2 in relation to the expression of stemness markers in urinary bladder cancer

Inflammation may activate stem cells via prostaglandin E2 (PGE2) production mediated by cyclooxygenase-2 (COX-2) expression. We performed an immunohistochemical analysis of the expression of stemness markers (Oct3/4 and CD44v6) and COX-2 in urinary bladder tissues obtained from cystitis and cancer patients with and without Schistosoma haematobium infections. Immunoreactivity to Oct3/4 was significantly higher in S. haematobium-associated cystitis and cancer tissues than in normal tissues. CD44v6 expression was significantly higher in bladder cancer without S. haematobium than in normal tissues. COX-2 was located in the cytoplasmic membrane, cytoplasm, and nucleus of the cancer cells. Interestingly, the nuclear localization of COX-2, which was reported to function as a transcription factor, was significantly associated with the upregulation of Oct3/4 and CD44v6 in bladder cancer tissues with and without S. haematobium infection, respectively. COX-2 activation may be involved in inflammation-mediated stem cell proliferation/differentiation in urinary bladder carcinogenesis.

Isolation and characterisation of antibodies which specifically recognise the peptide encoded by exon 7 (v2) of the human CD44 gene

Aims-Exon 7 of the human CD44 gene is overexpressed in many commonly occurring carcinomas. The aim of the study was to explore the diagnostic and therapeutic potential of this frequent abnormality.Methods-A new monoclonal antibody (mAb, M-23.6.1) and a polyclonal antibody (pAb,S-6127) to the corresponding antigen were raised by immunising mice and sheep, respectively, with a specially constructed fusion protein HIV2 (gp32)-CD44 exon 7.Results-Characterisation of mAb, M-23.6.1 by ELISA, western blotting, immunocytochemistry, and FACS analysis confirmed that it specifically recognises an epitope in the region between amino acids 19 and 33 of the peptide encoded by this exon. Western blotting experiments with two cell lines, RT112 and ZR75-1, known from RT-PCR data to be overtranscribing the exon, yielded a monospecific band of approximately 220 kDa, and immunocytochemistry showed discrete membrane staining on the same cell lines. Fluorescent antibody cell sorting (FACS) revealed binding to greater than 90% of the cells of each of these lines. Specificity of recognition of the antigen was shown by inhibition of the precise immunoreactivity typically seen in ELISA and Western blots, by pre-incubation with synthetic exon 7 peptide or fragments of it.Conclusions-The new antibodies will be useful tools for the further analysis of abnormal CD44 isoforms and their clinical implications.

Comparison of CD44 and cytokeratin 20 mRNA in voided urine samples as diagnostic tools for bladder cancer

OBJECTIVES

We evaluated the diagnostic efficacy of urinary CD44 and cytokeratin 20 (CK20) mRNA in comparison with voided urine cytology (VUC) for the detection of bladder cancer.

DESIGN AND METHODS

A total of 136 Egyptian patients provided a single voided urine sample for CD44, CK20 mRNA and VUC before cystoscopy. Of the 136 cases, 111 were histologically diagnosed as bladder cancer whereas the remaining 25 had benign urological disorders. A group of 20 healthy volunteers was also included in this study. Voided urine was centrifuged and the urine sediment was used for cytology, estimation of CD44 by ELISA and RNA extraction. CK20 mRNA was detected by conventional RT-PCR and quantitative real-time RT-PCR.

RESULTS

The best cutoff values for CD44 and relative CK20 mRNA detected by real-time RT-PCR were calculated by receiver operating characteristic curve. The positivity rates and the mean ranks for CD44 and CK20 mRNA showed significant difference among the three investigated groups (p=0.001). Quantitative real-time RT-PCR results were comparable to conventional RT-PCR for the detection of CK20 mRNA. The positivity rate of CD44 was significantly associated with schistosomiasis and urine cytology. The overall sensitivity and specificity were 52.3% and 88.9% for VUC, 63.1% and 88.9% for CD44, and 82.0% and 97.8% for CK20 mRNA. Combined sensitivity of VUC with CD44 and CK20 mRNA together (95.5%) was higher than either the combined sensitivity of VUC with CD44 (78.4%) or with CK20 mRNA (91.0%) or than that of the biomarker alone.

CONCLUSION

Urinary CD44 and CK20 mRNA had higher sensitivities compared to VUC. However, when the diagnostic efficacy was considered, CK20 mRNA by either conventional RT-PCR or real-time RT-PCR had the highest sensitivity and specificity compared to CD44 and VUC.

Alternatives to cytology in the management of non-muscle invasive bladder cancer

The natural history of non-muscle invasive bladder cancer is characterized by a high probability of recurrence and in the case of high-grade tumors, progression to muscle invasive cancer. This mandates a follow-up strategy designed to identify recurrences in the bladder early in their evolution in order to facilitate early intervention and ablation. Urine cytology is considered the gold standard urine biomarker. Although specificity exceeds 90% to 95%, its overall sensitivity ranges from 40% to 60% in expert hands and is both tumor grade and operator dependent. While cytology is an excellent test for detection of high-grade disease, the sensitivity is particularly weak for the detection of low grade tumors. This has spawned an entire field of research of in vitro diagnostic tests and cell-based assays in order to improve the diagnostic accuracy for detection of incident or recurrent disease. To date, the US Food and Drug Administration approved dipstick and immunoassays marketed as point-of-care tests. The point-of-care tests are intended for use as an adjunct to cystoscopy and cytology, and may have a role in the office evaluation of hematuria patients. Monoclonal antibody-based tests combined with cytology may improve the diagnostic accuracy and are superior to cytology alone. A recently approved cell-based assay, utilizing fluorescent in situ hybridization technology, may help resolve suspicious cytologies, and provide early and additional information about the biology of the bladder urothelium beyond that provided by cytology, a marker of disease relatively late in evolution. Novel promising markers are in various stages of clinical testing, and a panel of biomarkers may serve in the future as a feasible alternative to urine cytology and cystoscopy for the screening, detection, and follow-up of non-muscle invasive bladder cancer.

CD44 in cancer

CD44 is a multistructural and multifunctional cell surface molecule involved in cell proliferation, cell differentiation, cell migration, angiogenesis, presentation of cytokines, chemokines, and growth factors to the corresponding receptors, and docking of proteases at the cell membrane, as well as in signaling for cell survival. All these biological properties are essential to the physiological activities of normal cells, but they are also associated with the pathologic activities of cancer cells. Experiments in animals have shown that targeting of CD44 by antibodies, antisense,and CD44-soluble proteins markedly reduces the malignant activities of various neoplasms, stressing the therapeutic potential of anti-CD44 agents. Furthermore, because alternative splicing and posttranslational modifications generate many different CD44 sequences, including, perhaps, tumor-specific sequences, the production of anti-CD44 tumor-specific agents may be a realistic therapeutic approach. However, in many cancers (renal cancer and non-Hodgkin's lymphomas are exceptions), a high level of CD44 expression is not always associated with an unfavorable outcome. On the contrary, in some neoplams CD44 upregulation is associated with a favorable outcome. Even worse, in many cases different research grows analyzing the same neoplastic disease reached contradictory conclusions regarding the correlation between CD44 expression and disease prognosis, possibly due to differences in methodology. These problems must be resolved before applying anti-CD44 therapy to human cancers.

[Molecular biology in bladder cancer]

Progress of molecular biology with regard to etiopathogeny of tumours in general, and cancer of the bladder in particular, is taking place at such a vertiginous pace that practising urologists find themselves overwhelmed in terms of their ability to learn and keep updated in so complex a subject. The understanding of certain molecular factors with critical influence on the formation, growth and progression of a tumour of the bladder, is forcing us to make unbiased assessments on the role they will play in the evolution and survival of this neoplasia. It is anticipate they will be much more reliable than traditionally established morphological factors such as grade and stage. We also include a literature review with an analysis and elucidation of the role played by oncogenes, tumor suppressor genes, vascular density markers, telomerase etc., in the formation and growth of cancer of the bladder and their likely relationships with already established clinico-pathological factors.

Abnormal expression of CD44 variants in the exfoliated cells in the feces of patients with colorectal cancer

BACKGROUND & AIMS

Recent investigations have shown that CD44 variant exons are frequently overexpressed in human colorectal adenocarcinoma. The aim of this study was to investigate abnormal expression of the CD44 gene in exfoliated cells from patients with colorectal cancer.

METHODS

Exfoliated cells in feces from 25 patients with colorectal cancer before and after surgery and from 15 healthy volunteers were analyzed. CD44 standard, variant 6, and variant 10 messenger RNA (mRNA) expressions were examined in the exfoliated cells in feces by using reverse-transcription polymerase chain reaction followed by Southern hybridization with exon-specific probes.

RESULTS

CD44 standard mRNA was detected in all samples before and after surgery and in all healthy volunteers. CD44 variant 6 and variant 10 mRNA were detected in 17 of 25 patients (68%) and 15 of 25 patients (60%), respectively, in individual feces obtained before surgery. CD44 variant 6 mRNA and variant 10 mRNA were detected in postoperative samples in 3 of 25 patients (12%) and 7 of 25 patients (28%), respectively. Fifteen of 17 patients who were positive for CD44v6 based on preoperative fecal samples became negative after surgery (88.2%). Similarly, 12 of 15 patients who were CD44v10 positive in preoperative fecal samples were negative postoperatively (80%).

CONCLUSIONS

These results suggest that analysis of CD44 variant expression in the exfoliated cells in feces can provide a noninvasive diagnostic test for colorectal cancer.

Up-regulation of CD44 variant exon expression in endometrial carcinomas: analysis of mRNA and protein isoforms, and relation to clinicopathological factors

In order to clarify the relation between expression of individual CD44 variant exons and tumor progression, 34 endometrial carcinomas (endometrioid type) were investigated, as well as 27 samples of normal endometrium, using a combination of reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot hybridization (SBH). Western blotting was also performed for comparison of protein levels with the results of the RT-PCR/SBH methods. Analysis of gross CD44 splicing patterns demonstrated high-level expression of variant isoforms in endometrial carcinomas as compared with normal endometrium. Exon-specific RT-PCR/SBH assays revealed large, abundant transcripts of individual variant exons in particular v3, v4, and v5, in tumors, but these isoforms were also expressed in normal endometria, suggesting a lack of tumor-specificity. No individual CD44 variant transcripts were associated with any of the prognostic factors investigated. Parallel observations showed variant CD44 transcripts to be more readily detectable than protein isoforms in the same samples. These findings indicate that in endometrial carcinomas, expression of individual variant CD44 exons is markedly up-regulated, but this molecule may not be useful as a consistent indicator of tumor progression.

CD44 variant isoform expression and breast cancer prognosis

We examined the expression of CD44 isoforms in samples of breast cancer tissues from 95 patients by reverse transcription-polymerase chain reaction and immunohistochemistry, and tried to correlate the results with survival period. At the RNA level, expression of exon v2 was observed in 33 (35%) and that of v6 in 69 (73%) of the 95 specimens. Patients with CD44v2 mRNA expression had significantly shorter survival times than those with v2-negative tumors (P = 0.05), but there was only a weak correlation, if any, between v6 mRNA expression and overall survival (P = 0.06). Tumor tissue from 22 (23%) and 72 (76%) patients showed positive immunoreactivity with monoclonal antibody (mAb) M23.6.1. (CD44v2) and mAb 2F10 (CD44v6), respectively. Immunohistochemical evidence of CD44v2 peptide expression correlated with overall survival (P = 0.02), but there was no such association with CD44v6 expression in these tumors (P = 0.67). There were significant correlations between v2 immunoreactivity and higher histological grade and lower levels of estrogen and progesterone receptor. There was no significant correlation between v6 immunoreactivity and such clinicopathological characteristics. Although the expression of v2 was significantly associated with reduced overall survival, it was not an independent prognostic factor because it also correlated with progesterone receptor status. These findings suggest that v2 isoform expression might have more value than v6 expression for clinical use.

CD44 in inflammation and metastasis

CD44 is a major cell surface receptor for the glycosaminoglycan, hyaluronan (HA). CD44 binds HA specifically, although certain chondroitin-sulfate containing proteoglycans may also be recognized. CD44 binding of HA is regulated by the cells in which it is expressed. Thus, CD44 expression alone does not correlate with HA binding activity. CD44 is subject to a wide array of post-translational carbohydrate modifications, including N-linked, O-linked and glycosaminoglycan side chain additions. These modifications, which differ in different cell types and cell activation states, can have profound effects on HA binding function and are the main mechanism of regulating CD44 function that has been described to date. Some glycosaminoglycan modifications also affect ligand binding specificity, allowing CD44 to interact with proteins of the extracellular matrix, such as fibronectin and collagen, and to sequester heparin binding growth factors. It is not yet established whether the HA binding function of CD44 is responsible for its proposed involvement in inflammation. It has been shown, however, that CD44/HA interactions can mediate leukocyte rolling on endothelial and tissue substrates and that CD44-mediated recognition of HA can contribute to leukocyte activation. Changes in CD44 expression (mainly up-regulation, occasionally down-regulation, and frequently alteration in the pattern of isoforms expressed) are associated with a wide variety of cancers and the degree to which they spread; however, in other cancers, the CD44 pattern remains unchanged. Increased expression of CD44 is associated with increased binding to HA and increased metastatic potential in some experimental tumor systems; however, in other systems increased HA binding and metastatic potential are not correlated. CD44 may contribute to malignancy through changes in the regulation of HA recognition, the recognition of new ligands and/or other new biological functions of CD44 that remain to be discovered.

Analysis of anomalous CD44 gene expression in human breast, bladder, and colon cancer and correlation of observed mRNA and protein isoforms

Many studies have now demonstrated disorganized overexpression of the CD44 gene in various types of human malignant tumors, and this abnormality has emerged as an interesting candidate marker for early cancer diagnosis. The purpose of this work was to analyze and compare the patterns of transcription and translation of this gene in human breast (ZR75-1; MDAMB-435 clone 4A4) and colon (HT29) tumor cell lines and in tumors of the breast, bladder, and colon, with the aim of identifying the most suitable analyte for diagnostic purposes. Transcription was studied by reverse transcription-polymerase chain reaction using CD44-specific primers and probes complementary to exons in the standard (exons 3 to 5 and 16 to 18) and variably expressed regions of this gene (exons 7, 8, 10, 11, and 15). Translation was investigated by Western blot analysis and immunohistochemistry using monoclonal antibodies specific to the standard form of CD44 and to the products of the same variant exons. Southern blot hybridization analysis of the reverse transcription-polymerase chain reaction products showed a large number of CD44 transcripts in tumor cells. Direct comparison of these Southern blots with Western blots on matched tumor-cell-line extracts indicated that most of the diverse mRNA isoforms did not detectably translate into proteins. However, immunohistochemistry of normal and malignant breast (n = 17 and 23, respectively), bladder (n = 5 and 19), and colon (n = 19 and 19) tissue specimens showed increased staining of CD44 standard and CD44 variant proteins in the carcinoma cells. Combination of this information with the data from reverse transcription-polymerase chain reaction and Western blot analysis indicates that the overexpression at the protein level involves only a minority of the aberrant RNA transcripts. We conclude that the development of methods for the accurate quantitation of over-abundant CD44 RNA species in clinical samples offers the most promising approach to improved early diagnosis of malignancy using this new marker.