Expression of CD44 variant exons 8-10 in colorectal cancer and its relationship to metastasis

Evaluation of CD44s, CD44v6, CXCR2, CXCL1, and IL-1β in Benign and Malignant Tumors of Salivary Glands

BACKGROUND

Several studies have reported an association between high expression of CD44 in different types of cancer. However, no study has reported a link among CD44 expression, other biomarkers, and the aggressiveness of salivary gland tumors.

METHODS

A total of 38 specimens were obtained from non-tumorous salivary glands, benign and malignant tumors in salivary glands. Immunohistochemical analyses of CD44s, CD44v6, IL-1β, CXCL1, and CXCR2 were performed, and the area of positive cells was assessed.

RESULTS

We found that both CD44s and CXCR2 expression were increased in the benign and malignant groups. CD44v6 was also increased in both groups, but it had the highest level in the malignant group. IL-1β was the only biomarker that increased significantly in the malignant group in comparison to the other two groups.

CONCLUSIONS

CD44s, CD44v6, CXCR2, and IL-1β expressions were found to be higher in salivary gland tumors. However, IL-1β alone may play a crucial role in the aggressiveness of salivary gland tumors as this cytokine was expressed only in the malignant group with high expression associated with high-grade malignancy.

Identification of novel alternative splicing isoform biomarkers and their association with overall survival in colorectal cancer

BACKGROUND

Alternative splicing (AS) is an important mechanism of regulating eukaryotic gene expression. Understanding the most common AS events in colorectal cancer (CRC) will help developing diagnostic, prognostic or therapeutic tools in CRC.

METHODS

Publicly available RNA-seq data of 28 pairs of CRC and normal tissues and 18 pairs of metastatic and normal tissues were used to identify AS events using PSI and DEXSeq methods.

RESULT

The highly significant splicing events were used to search a database of The Cancer Genome Atlas (TCGA). We identified AS events in 9 genes in CRC (more inclusion of CLK1-E4, COL6A3-E6, CD44v8-10, alternative first exon regulation of ARHGEF9, CHEK1, HKDC1 and HNF4A) or metastasis (decrease of SERPINA1-E1a, CALD-E5b, E6). Except for CHEK1, all other 8 splicing events were confirmed by TCGA data with 382 CRC tumors and 51 normal controls. The combination of three splicing events was used to build a logistic regression model that can predict sample type (CRC or normal) with near perfect performance (AUC = 1). Two splicing events (COL6A3 and HKDC1) were found to be significantly associated with patient overall survival. The AS features of the 9 genes are highly consistent with previous reports and/or relevant to cancer biology.

CONCLUSIONS

The significant association of higher expression of the COL6A3 E5-E6 junction and HKDC1 E1-E2 with better overall survival was firstly reported. This study might be of significant value in the future biomarker, prognosis marker and therapeutics development of CRC.

Modulation of CD44, EGFR and RAC Pathway Genes (WAVE Complex) in Epithelial Cancers

Cancer hallmarks help in understanding the diversity of various neoplasms. Epithelial cancers play an immense role in the tumor biology through Epithelial-Mesenchymal Transition (EMT) process. Receptor tyrosine kinase, as well as phosphatidyl ionositol-3 kinase pathways, play an important role in the regulation of cell proliferation, survival, and differentiation during EMT. Till date, numerous studies have shown modulation in the expression profile of potential targets like CD44, EGFR, and Rac in epithelial cancers. CD44 interacts with EGFR and recruits other molecules which further activate the Rac pathway intermediates. This review mainly focused on modulation of genes like CD44, EGFR, and Rac pathway intermediates which play a crucial role in the tumor progression, metastasis, proliferation, and invasion characteristics in epithelial cancers with EMT properties. Hence, targeting Rac pathway might be a more strategically relevant approach in treating epithelial cancers.

Phase I study of salazosulfapyridine in combination with cisplatin and pemetrexed for advanced non-small-cell lung cancer

Spliced variant isoforms of CD44 (CD44v) are a marker of cancer stem cells in solid tumors. They stabilize the xCT subunit of the transporter system xc(–) and thereby promote synthesis of the antioxidant glutathione. Salazosulfapyridine (SASP) is an inhibitor of xCT and suppresses the proliferation of CD44v‐positive cancer cells. Chemotherapy‐naïve patients with advanced non‐squamous non‐small‐cell lung cancer were enrolled in a dose‐escalation study (standard 3 + 3 design) of SASP in combination with cisplatin and pemetrexed. The primary end‐point was the percentage of patients who experience dose‐limiting toxicity. Fifteen patients were enrolled in the study. Dose‐limiting toxicity was observed in one of six patients at a SASP dose of 1.5 g/day (elevation of aspartate and alanine aminotransferase levels, each of grade 3), two of five patients at 3 g/day (hypotension or pneumonitis, each of grade 3), and two of three patients at 4.5 g/day (anorexia of grade 3). The maximum tolerated dose was thus 3 g/day, and the recommended dose was 1.5 g/day. The overall response rate was 26.7% and median progression‐free survival was 11.7 months, much longer than that for cisplatin–pemetrexed alone in previous studies. Exposure to SASP varied markedly among individuals according to ABCG2 and NAT2 genotypes. The serum concentration of free CD44v protein was increased after the first cycle of treatment, possibly reflecting death of cancer stem cells. Salazosulfapyridine was thus given safely in combination with cisplatin–pemetrexed, with the addition of SASP tending to prolong progression‐free survival. This trial is registered in the UMIN Clinical Trials Registry as UMIN000017854.

Development of high-affinity monoclonal antibody using CD44 overexpressed cells as a candidate for targeted immunotherapy and diagnosis of acute myeloid leukemia

AIM

CD44s antigens have been suggested as an efficient biomarker for cancer stem cells. Current study aimed to develop a hybridoma that producing a high affinity murine anti-human CD44 monoclonal antibody for early diagnostic laboratory tests of some cancer.

MATERIALS AND METHODS

To make hybridoma against CD44, mice were immunized with MDA-MB-468 cells. Resulted hybridomas using three culture media were screened by indirect ELISA, then cloned by limiting dilution, and isotype was determined after obtaining ascitic fluid and antibody purification.

RESULTS

We obtained a stable secreting clone, capable of secreting a high-affinity monoclonal antibody against CD44 protein, IgG2a kappa, with the affinity of 5.4 × 10-8 M without cross-reactivity.

CONCLUSION

We could establish a hybridoma in a native form. This stable and high-affinity anti-CD44 mAb has a potential for diagnostic procedures and laboratory research. Thus, it could be exploited as a suitable tool for target-specific diagnosis and even treatment in several cancers.

Rapid and reliable detection of CD44 variants in gastric carcinoma using a nested reverse transcription-polymerase chain reaction

The present study aimed to establish a rapid and reliable method for detecting the expression of cluster of differentiation 44 variant (CD44v) in gastric carcinoma, and to investigate the significance of CD44v in gastric carcinoma. Using a nested reverse transcription-polymerase chain reaction (RT-PCR) technique, the expression of CD44v and CD44v8-10 was analyzed in gastric cancer tissues (128 cases), precancerous lesions (19 cases of atypical hyperplasia and 6 cases of intestinal metaplasia) and corresponding adjacent non-cancerous tissues (153 cases). The tumor and non-cancerous biopsy samples of 153 patients were analyzed using nested RT-PCR. All the PCR products included bands at 482 bp, demonstrating positive CD44 expression. By contrast, the CD44v band (>600 bp) was observed in 132/153 total tumor samples (86.3%), including 114/128 gastric cancer samples (89.1%), 16/19 atypical hyperplasia samples (84.2%) and 2/6 intestinal metaplasia samples (33.3%). However, 18/153 non-cancerous tissues samples (11.8%) exhibited a CD44v band. Thus, CD44v expression was significantly higher in gastric cancer tissues and precancerous lesions compared with that of adjacent non-cancerous tissues (P<0.05). Furthermore, there was a significant difference in CD44v8-10 expression detected between gastric cancer and adjacent non-cancerous tissue samples (P<0.05). Among the 25 patients with precancerous lesions, 8/19 atypical hyperplasia cases and 1/6 intestinal metaplasia cases were positive for CD44v8-10 expression. The difference in the CD44v8-10 expression rate among the various pathological types of gastric cancer (n=128) cases was not significant (P>0.05). Additionally, immunohistochemical analysis identified CD44v positivity (++) in 59/76 (77.6%) cases of gastric cancer and 5/12 (41.1%) cases of atypical hyperplasia. The CD44v and CD44v8-10 PCR products were confirmed by sequencing analysis. The results of the present study indicated that nested RT-PCR technology may be exploited as a method for gastric carcinoma diagnosis.

Regulation of CD44E by DARPP-32-dependent activation of SRp20 splicing factor in gastric tumorigenesis

Objective

CD44E is a frequently overexpressed variant of CD44 in gastric cancer. Mechanisms that regulate CD44 splicing and expression in gastric cancer remain unknown. Herein, we investigated the role of DARPP-32 (dopamine and cAMP-regulated phosphoprotein, Mr 32000) in promoting tumor growth through regulation of CD44 splicing.

Design

Quantitative luciferase reporter, quantitative real-time RT-PCR (qRT-PCR), Western blot, co-immunoprecipitation, ubiquitination, and tumor xenograft experiments were performed.

Results

Western blot and qRT-PCR results indicated that knockdown of endogenous DARPP-32 markedly reduces expression of CD44 V8-V10 (CD44E). Using a quantitative splicing luciferase reporter system, we detected a significant increase in the reporter activity following DARPP-32 overexpression (p < 0.001). Conversely, knocking down endogenous DARPP-32 significantly attenuated the splicing activity (p < 0.001). Further experiments showed that DARPP-32 regulates the expression of SRp20 splicing factor and co-exists with it in the same protein complex. Inhibition of alternative splicing with digitoxin followed by immunoprecipitation and immunoblotting indicated that DARPP-32 plays an important role in regulating SRp20 protein stability. The knockdown of endogenous DARPP-32 confirmed that DARPP-32 regulates the SRp20-dependent CD44E splicing. Using tumor xenograft mouse model, knocking down endogenous DARPP-32 markedly reduced SRp20 and CD44E protein levels with a decreased tumor growth. The reconstitution of SRp20 expression in these cells rescued tumor growth. In addition, we also demonstrated frequent co-overexpression and positive correlation of DARPP-32, SRp20 and CD44E expression levels in human gastric primary tumors.

Conclusion

Our novel findings establish for the first time the role of DARPP-32 in regulating splicing factors in gastric cancer cells. The DARPP-32–SRp20 axis plays a key role in regulating the CD44E splice variant that promotes gastric tumorigenesis.

Colon cancer stem cells: implications in carcinogenesis

The cancer stem cell model was described for hematologic malignancies in 1997 and since then evidence has emerged to support it for many solid tumors as well, including colon cancer. This model proposes that certain cells within the tumor mass are pluripotent and capable of self-renewal and have an enhanced ability to initiate distant metastasis. The cancer stem cell model has important implications for cancer treatment, since most current therapies target actively proliferating cells and may not be effective against the cancer stem cells that are responsible for recurrence. In recent years great progress has been made in identifying markers of both normal and malignant colon stem cells. Proteins proposed as colon cancer stem cell markers include CD133, CD44, CD166, ALDH1A1, Lgr5, and several others. In this review we consider the evidence for these proteins as colon cancer stem cell markers and as prognostic indicators of colon cancer survival. Additionally, we discuss potential functions of these proteins and the implications this may have for development of therapies that target colon cancer stem cells.

The beta-catenin/TCF4 pathway modifies alternative splicing through modulation of SRp20 expression

Gene expression programs can become activated in response to extracellular signals. One evolutionarily conserved example is binding of Wnt glycoproteins to their receptor, which triggers a signal transduction cascade that stabilizes cytoplasmic beta-catenin protein, allowing it to translocate into the nucleus. There, beta-catenin binds to TCF/Lef family transcription factors and promotes the expression of target genes. Mutations in either the beta-catenin gene itself or its partner protein APC are responsible for the oncogenic activation of this pathway in colorectal tumors. Here we report the splicing factor SRp20 as a novel target gene of beta-catenin/TCF4 signaling. Transfection of activated beta-catenin mutants into colorectal cells increased expression of endogenous SRp20 transcript and protein and also stimulated a luciferase reporter construct containing the SRp20 gene promoter. In contrast, inhibition of endogenous beta-catenin signaling by a dominant-negative TCF4 construct down-regulated both luciferase reporter and SRp20 expression. We further demonstrate that the beta-catenin/TCF4-mediated increase in SRp20 protein levels is sufficient to modulate alternative splicing decisions in the cells. In particular, we observed a change in the alternative splicing pattern in a control minigene reporter as well as in the endogenous SRp20-regulated CD44 cell adhesion protein. These results demonstrate that the beta-catenin/TCF4 pathway not only stimulates gene transcription, but also promotes the generation of transcript variants through alternative splicing. Our data support the recent notion that transcription and alternative splicing represent two different layers of gene expression and that signaling pathways act upon a coordinated network of transcripts in each layer.

Comparative analysis of immunohistochemical markers with invasiveness and histologic differentiation in squamous cell carcinoma and basal cell carcinoma of the skin

BACKGROUND

This study evaluates several tumor-related markers to examine the expression pattern of markers according to the invasiveness and histopathologic differentiation of squamous cell carcinoma and basal cell carcinoma.

METHODS

Ninety-four cases of squamous cell carcinoma and 108 cases of basal cell carcinoma using tissue array in order to determine correlations between the expression of Ki-67, p53, EGFR, CD44v6, MMP-1 and MMP-3, invasiveness and histologic differentiation. In order to determine invasiveness, we measured the depth of invasion in resected tissues.

RESULTS

The depth of invasion showed a correlation with CD44v6 expression of tumor cell in both squamous cell carcinoma and basal cell carcinoma (P = 0.009, P = 0.036, respectively) and with the MMP-1 expression of stromal cell in squamous cell carcinoma (P = 0.010). The differentiation of squamous cell carcinoma was correlated with Ki-67 index. The loss of palisading arrangement in basal cell carcinoma was correlated with the MMP-1 expression of stromal cells (P = 0.045).

CONCLUSIONS

CD44v6 and MMP-1, expressed in tumor cells and stromal cells respectively, are significant markers associated with the invasiveness of tumors in squamous cell carcinoma and basal cell carcinoma of the skin and that it will be helpful to evaluate the invasiveness by measuring the expression of these markers.

Biology of colorectal liver metastases: A review

Metastatic growth is a selective, non-random process, which in the case of colorectal cancer, frequently occurs in the liver and is the major cause of cancer related death in these patients. This review summarises attempts to find biological and molecular markers of metastasis and their role in establishment of secondary tumours. Recent evidence suggests that liver metastases are phenotypically different to the primary from which they were derived and thus represent a separate disease entity.

Colorectal cancer: genetics of development and metastasis

It has been well documented that there are two major pathways in colorectal carcinogenesis. One is the chromosomal instability pathway (adenoma-carcinoma sequence), which is characterized by allelic losses on chromosome 5q (APC), 17p (p53), and 18q (DCC/SMAD4), and the other is a pathway that involves microsatellite instability. Recent progress in molecular biology, however, has shown that colorectal carcinogenesis is not necessarily clearly divided into these two pathways, but is in fact more complicated. Other routes, including the transforming growth factor-beta/SMAD pathway, the serrated pathway, and the epigenetic pathway, have been reported. Cross talk among these pathways has also been reported. In the invasion and metastasis steps of colorectal cancers, many more genes have now been identified as being involved in proteolysis, adhesion, angiogenesis, and cell growth. Recently accumulated evidence indicates that colorectal cancer is a genetically heterogeneous and complicated disease.

Accuracy of two-dimensional electrophoresis for target discovery in human colorectal cancer

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is increasingly used for target discovery in human disease to complement genomic studies. We have assessed the possibilities and limits of 2-D PAGE applied to human colorectal cancer. Up to 10(8) epithelial cells were purified from paired normal and pathological biopsies using Ber-EP4 coated magnetic beads, allowing the elimination of cellular and fluid contaminations. The mean coefficient of variation (CVAR) of repeated 2-D PAGE analysis with silver staining was lying between 20 and 28%. However, only 47% (interrun) to 76% (intrarun) of spots could be matched within a triplicate experiment. Interindividual phenotypic variability was high. Intratumoral phenotypic variability was not found to be significant. When method and tumor variability were added, 90% of CVAR were inferior to 48%. Thus, two-fold up- or down-regulation of protein expression reveals biological significance. Serial paired comparison of 923 proteins in 10 patients showed highly reproducible differences between normal and cancer tissues. Under well defined experimental conditions and after the high variability of the technique has been considered, 2-D PAGE parallel analysis of paired colorectal samples allows patient-specific tumor profiling.

Cross-talk between human monocytes and cancer cells during reactive oxygen intermediates generation: the essential role of hyaluronan

Human monocytes exhibit considerable cytocidal activity against tumor (but not normal cells) associated, at least partly, with the generation of reactive oxygen intermediates (ROIs). The present study examined the role of surface determinants and hyaluronan (HA) in the induction of ROI production by human monocytes stimulated with cancer cells, as measured by luminol-enhanced chemiluminescence (CL). The inhibitory effect of monoclonal antibodies (MAbs) indicated the engagement of CD18, CD29 and CD44 adhesion molecules. Preincubation of monocytes and tumor cells, expressing CD44 determinants, with either anti-CD44 MAb or HA inhibited CL generation. Addition of HA to monocytes decreased the expression of CD44 and induced CL response. Supernatants from the cultures of tumor cells stimulated CL response of monocytes, an effect that was abolished by treatment of the supernatants with hyaluronidase (HAase) or by preincubation of monocytes with an anti-CD44 MAb. These results indicate that several surface molecules of monocytes, including CD44, are required to trigger the generation of ROI after their contact with tumor cells, whereas HA overexpressed on some cancer cells may allow monocytes (via CD44) to distinguish between transformed and normal cells. However, blocking of CD44 on monocytes by free HA dampens their response to tumor cells. Taken together, these observations suggest that the presence of HA in the tumor stroma may modulate effector functions of infiltrating macrophages and their interactions with cancer cells in situ.

Decreased CD44 standard form expression correlates with prognostic variables in ovarian carcinomas

Expression of CD44 standard form (CD44s) was evaluated by automated immunohistochemical analysis using the anti-CD44 A3D8 clone in 101 ovarian epithelial neoplasms including 82 primary tumors (64 carcinomas and 18 tumors of low malignant potential [LMP]), 9 lymph node metastases, 8 malignant ascites, and 2 peritoneal implants. Immunostaining was scored semiquantitatively. Tumors were graded according to the FIGO (International Federation of Gynecology and Obstetrics) classification system. Tumor stage and patient survival were determined from the patient records. While 9 of 18 LMP tumors expressed CD44s, only 15 of 64 carcinomas expressed it. In the carcinomas, univariate analysis revealed that decreased CD44s expression correlated with high tumor grade, advanced stage, and shortened survival. Loss of CD44s expression also was noted in the tumor cells in 8 of 9 lymph node metastases, 7 of 8 malignant ascites, and 1 of 2 implants. Multivariate analysis revealed that only tumor stage independently correlated with patient survival. Loss of CD44s expression determined by immunohistochemical analysis is more common in ovarian carcinomas than in LMP tumors; correlates with prognostic variables including tumor grade, stage, and survival; and may have an important role in the dissemination of ovarian cancer.

A novel orthotopic implantation model of human esophageal carcinoma in nude rats: CD44H mediates cancer cell invasion in vitro and in vivo

A new orthotopic esophageal cancer model was developed by implanting fragments of xenografts of T.T human esophageal squamous carcinoma cells into the cervical esophagus of athymic rats. The rats had symptoms analogous to the human clinical course such as respiratory distress, dysphagia, vomiting of blood, or Horner syndrome, followed by death resulting from suffocation. Microscopic metastases of lymph node were observed around the tumor in 3 of 18 rats. A new cell line (T.T-1) was established from these metastases. Flow cytometry showed that T.T-1 and T.T parental cells had nearly the same surface levels of beta1-integrin, alpha2-integrin, alpha3-integrin and E-cadherin, and no expression of CD44v3, CD44v6 and alpha5-integrin. T.T-1 cells had a higher level of CD44H, however, and a greater binding efficiency to the extracellular matrix components; laminin, type IV collagen, hyaluronic acid, and fibronectin than T.T cells. Anti-CD44H antibody significantly decreased the binding efficiency of T.T-1 cells. T.T-1 cells were also significantly more invasive than T.T cells through all the extracellular matrix components except hyaluronic acid. After orthotopic implantation histological examination showed that T.T-1 tumors invaded beyond the esophageal mucosa and tracheal muscle layer and obstructed the esophagus and trachea. No invasion was observed with T.T tumors. Rats with T.T-1 or T.T tumors survived an average of 32.0 and 50.7 days, respectively (p < 0.01). In addition T.T-1 tumors expressed higher levels of CD44H mRNA than T.T tumors. In summary, our newly developed orthotopic implantation model is a valid model of esophageal cancer because it followed the same clinical course experienced by humans. Moreover, using cells derived from this model, we were able to demonstrate that CD44H is involved in esophageal cancer cell invasion.

Expression of CD44 variants in lung cancer and its relationship to hyaluronan binding

We examined the expression of CD44 variant forms and their binding to hyaluronan (HA) in lung cancer cell lines. There was no relationship between the level of expression of CD44 variants and HA binding in different lung cancer cell lines. The expression of CD44v6 and CD44E in some cell lines was not always associated with HA binding. There was no relationship between the tissue pathological type and CD44 expression or HA binding. Deglycosylation by neuraminidase induced CD44-HA binding in human lung cancer cell lines. Our findings suggest that the HA binding ability of CD44, which is negatively regulated by glycosylation, might be a more important factor in tumorigenesis or metastasis than the expression of CD44 variant forms.

Establishment and characterization of human pancreatic carcinoma lines with a high metastatic potential in the liver of nude mice

To investigate of human pancreatic cancer metastasis to the liver, a pancreatic carcinoma line, HPC-3, was injected into the spleens of nude mice. The cells from a few liver metastatic foci of the mice injected with HPC-3 were expanded in vitro and subsequently injected into the spleens of nude mice. By repeating these procedures, we were able to obtain a cell line, designated HPC-3H4. The mice were observed to have liver metastasis in 6 of 6 (100%) cases injected with HPC-3H4, whereas the rate was 0% at 3 weeks after the intrasplenic injection of HPC-3. The tumorigenicity of HPC-3H4 was more rapid than that of HPC-3. The motile activity of HPC-3H4 was also stronger than that of HPC-3, and the adhesion to the extracellular matrix of HPC-3H4 was stronger than that of HPC-3. We also analyzed the cell surface expression of the metastasis-related adhesion molecules. As a result, no substantial changes were observed in the expression level of adhesion molecules. These results suggest that HPC-3H4 is useful for studies aimed at the prevention of liver metastasis.

Alternatively spliced CD44 isoforms containing exon v10 promote cellular adhesion through the recognition of chondroitin sulfate-modified CD44

Correlations have been noted between the expression of certain alternatively spliced CD44 isoforms and the metastatic propensity of various histologically distinct tumor cell types. The precise mechanism by which particular CD44 isoforms contribute to the metastatic process is, however, unclear. In the present study we demonstrate that CD44R2, a CD44 isoform highly expressed on activated and transformed hemopoietic cells, can recognize and bind a common determinant present on CD44H and CD44R1. Importantly, CD44H lacked this activity. Pretreatment of TIL1 cells expressing CD44H or CD44R1 with chondroitinase ABC inhibited adhesion to CD44R2, suggesting that the unique inserted region present within the CD44R2 molecule, encoded by exon v10, mediates cell adhesion by potentiating the recognition of chondroitin sulfate moieties presented in association with other CD44 molecules. These data help explain the differential involvement of v10-containing CD44 isoforms in tumor metastasis.

Cytosol concentrations of CD44 isoforms in breast cancer tissue

The role of the adhesion molecule CD44 in the natural history of breast cancer is controversial. We investigated the CD44 isoform CD44v5 and CD44v6 concentrations in the cytosol of 90 breast cancer specimens, 9 fibroadenomas and 22 normal breast tissue specimens by means of ELISA. CD44v5 and CD44v6 cytosol concentrations were statistically significantly higher in breast cancer compared with fibroadenoma and normal breast tissue (Mann-Whitney U-test, p = 0.009 and p < 0.001, respectively). When CD44 isoforms were correlated with lymph node involvement, histological grading, histological type, tumor stage and age at diagnosis, we found no statistically significant correlation with any of the investigated clinico-pathological parameters. In univariate and multivariate analyses, CD44v5 and CD44v6 were of no prognostic relevance regarding disease-free survival in breast cancer patients (log-rank test, p = 0.16 and p = 0.08, respectively). Our results indicate that CD44 isoforms are increased in samples from tumors relative to normal tissue. Our data show that CD44v5 and CD44v6 isoform expression, although up-regulated by malignant transformation, is not required to acquire a metastatic phenotype in breast cancer. Furthermore, our data support the assumption that cytosolic CD44 isoforms are of no prognostic relevance for disease-free survival of breast cancer patients.

Ratio of CD44 epithelial variant to CD44 hematopoietic variant is a useful prognostic indicator in gastric and colorectal carcinoma

BACKGROUND

The CD44 is a cell adhesion molecule that is present as numerous isoforms created by mRNA alternative splicing. Expression of variant isoforms of CD44 is associated with tumor growth and metastasis. The aim of this study was to evaluate whether CD44 isoform expression is a prognostic factor in gastric and colorectal cancer.

METHODS

We performed a polymerase chain reaction analysis following reverse transcriptase treatment for CD44 expression in fresh surgical specimens obtained from 25 colon carcinomas and 30 gastric carcinomas and matched adjacent normal mucosa. We determined the epithelial variant/hematopoietic variant (E/H) ratio (the amount of the CD44 epithelial variant transcript relative to the CD44 hematopoietic variant transcript) in cancer tissues and examined it for correlations with clinicopathological parameters and survival rate.

RESULTS

The E/H ratio in tumor tissue was significantly higher than that in adjacent non-cancerous mucosa. In gastric and colorectal cancer tissues, there was no significant relationship between E/H ratio and clinicopathological parameters. However, patients who died due to tumor recurrence had a higher E/H ratio than surviving patients with colorectal cancer. In gastric cancer, patients with high E/H tumors had a shorter survival time than those with low E/H tumors.

CONCLUSIONS

Our results suggest that the E/H ratio is a useful indicator of prognosis in gastric and colorectal carcinoma.

Alterative expression of the collagenase and adhesion molecules in the highly metastatic clones of human colonic cancer cell lines

Human colonic carcinoma cell lines, KM12C, KM12SM and KM12L4, were previously established and their in vivo metastatic potentials have been well evaluated. The highly metastatic cell lines KM12SM and KM12L4 were derived from the parental low metastatic cell line KM12C in vivo. To evaluate the metastatic behavior of these cell lines in vitro, we examined colony formation on monolayers of the pulmonary arterial endothelial (CPAE) cells. On day 4, the highly metastatic cell lines showed an approximately 2-fold increase in number of colonies on CPAE cell monolayers relative to the parental KM12C cell line. To investigate what evidence is correlated with their metastatic and invasive abilities, Northern blot analysis and flow cytometry were performed in all cell lines. According to the results of Northern blot analysis, the levels of matrix metalloproteinase (MMP)-2 and c-met mRNA expression were increased in highly metastatic cell lines as compared with the parental cell line. We also examined the cell-surface expression of several adhesion molecules by flow cytometry. The levels of expression of sialyl Lewisa antigen (sLe(a)) in KM12SM and KM12L4 were twice higher than that in KM12C. However, the levels of expression of E-cadherin in KM12SM and KM12L4 were decreased to half that in KM12C. The alterative expression of the collagenase and adhesion molecules might contribute to their metastatic/invasive abilities of these cell lines both in vivo and in vitro.

Down-regulated expression of CD44 variant 6 in oral squamous cell carcinomas and its relationship to regional lymph node metastasis

The expression of the adhesion molecule CD44 variant 6 (CD44v6) was studied immunohistochemically on 38 oral squamous cell carcinomas (SCCs) and 10 biopsies of healthy oral mucosa. The relationship between the expression of CD44v6 and regional lymph node metastasis was also investigated. The expression of CD44v6 was apparently down-regulated in oral SCC, but not in normal oral mucosa. Carcinomas expressing lower levels of CD44v6 exhibited more frequent regional lymph node metastasis. The expression of CD44v6 showed no statistically significant relationship to the degree of differentiation, but tended to be down-regulated in poorly differentiated carcinoma. No significant relation was found between the expression of CD44v6 in primary and metastatic lesions.

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.

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.

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.

The calcium-binding protein calretinin-22k, an alternative splicing product of the calretinin gene is expressed in several colon adeno carcinoma cell lines

An alternatively spliced mRNA for the calcium-binding protein calretinin (CR) is present in the colon adenocarcinoma cell line WiDr. As a consequence of a frame shift, the resulting protein, calretinin-22k (CR-22k), consists of the first 178 amino acids of calretinin followed by a carboxy-terminal peptide of 14 amino acids that is not present in full-length calretinin. Antibodies specific for this C-terminal region have been generated by 2 different methods. A peptide corresponding to the specific C-terminal region of CR-22k was either chemically synthesized and coupled to a carrier protein or was expressed in Escherichia coli as a carboxyterminal fusion to a carrier protein applying recombinant techniques. Both antisera produced in rabbits were tested in Western blots and immuno-histochemical experiments. The antisera recognized human recombinant CR-22k overexpressed in E. coli, but not fulllength calretinin and stained fixed WiDr cells. The presence of CR-22k was also confirmed in the colon cell lines CO115/3 in which mRNA coding for CR-22k mRNA coding for CR-22k mRNA is present as well as in the lines COLO205 and LS-180, all of which also express full-length calretinin. Although the intracellular distribution of CR-22k and CR are similar as evidenced by immunohistochemical stainings, CR-22k is preferentially localized in the nucleus in the cell lines LS-180 and Co115/3 suggesting potentially different roles for the two proteins.

Expression of CD44 variant exons 8-10 in gastric cancer

The expression of CD44 variant containing variant exons 8-10 product (CD44v8-10) was studied by western blot analysis and immunohistochemistry in gastric cancers using a monoclonal antibody, 44-1V. On western blots, a single band of 130 kD was recognized in stomach cancer cell lines. CD44v8-10 expression, with reactivity localized in the cell membrane, was found in 65 (33.5%) of the 194 advanced gastric cancers. There was no correlation between CD44v8-10 immunoreactivity and serosal, lymphatic, or lymph node invasion. However, there was significant correlation with CD44v8-10 immunoreactivity and venous invasion. CD44v8-10-positive cancers were more frequently associated with hematogenous metastasis than those which were immunonegative. There was an inverse association between CD44v8-10 immunoreactivity and peritoneal dissemination, especially in diffuse type adenocarcinomas. These observations indicate that CD44v8-10 may play a role in the metastasis of gastric cancer.