The aim of this study was to evaluate CD44v6 protein expression and its prognostic value of CD44v6 in ovarian carcinoma. The expression of CD44v6 was analyzed in 62 patients with ovarian carcinoma by immunohistochemical method. The data obtained were analyzed by univariate and multivariate analyses. The present study clearly demonstrates that tumor tissues from 41 (66.1%) patients showed positive expression with CD44v6. The expression of CD44v6 was significantly correlated with histological type, FIGO stage and histological grade of ovarian carcinomas. Concerning the prognosis, the survival period of patients with CD44v6 positive was shorter than that of patients with CD44v6 negative (36.6% versus 66.7%, 5-year survival,
Ovarian carcinoma is one of the leading causes of cancer-related deaths from gynecological cancer and the seventh most common cancer worldwide [
Adhesion processes are involved in all levels of the metastatic cascade. Most of the adhesion receptor families so far reported, including integrins, cadherins, selectins, immunoglobulins, and proteoglycans, have played a great role in various stages of tumor progression and metastasis [
CD44 family is one kind of important cell adhesion molecules. The CD44 gene is 50–60 kDa in size, resides on chromosome 11p13, and is known to be composed of at least 20 exons. CD44v6 is an important isoform of CD44 family [
To date, however, the reports concerning the relationship between the expression of CD44v6 and prognosis of ovarian carcinoma are scare.
Therefore, the present study was designed to clarify possible role of adhesion molecule CD44v6 in ovarian carcinomas. In this study, we examined the immunohistochemical expression of CD44v6 in 62 cases of ovarian carcinoma and define the relationship between the expression of CD44v6 and clinicopathological parameters in ovarian carcinoma. Importantly, we investigated adhesion molecule CD44v6 expression for its prognostic value in ovarian carcinomas by univariate and multivariate analysis.
Women with a diagnosis of epithelial ovarian carcinoma were randomized and recruited to this cohort study. The exclusion criterion was inadequate follow-up data and chemotherapy or radiotherapy before operation. Finally, 62 patients were eligible and selected for the study. Formalin-fixed, paraffin-embedded blocks were retrieved from the pathologic archives of the Department of Pathology at the Affiliate Hospital of Xi’an Jiaotong University.
The slides were evaluated by at least two pathologists. All discordant cases were reevaluated, and the result was defined by consensus. Tumors were surgically staged according to the International Federation of Gynecology and Obstetrics (FIGO) Staging Systems. Ovarian carcinomas were graded according to the histological degree of differentiated as well-differentiated (G1), moderately differentiated (G2), or as poorly differentiated (G3) carcinomas.
Of the 62 tumors, 45 were serous, 5 were mucinous, 8 were endometrioid, and 4 were undifferentiated. The clinicopathological parameters including age, menopausal status, nulliparous status, FIGO staging, and histological type and grade were evaluated.
Immunolocalization was performed using a streptavidin-biotin immunoperoxidase method according to the suppler’s protocol (SP kit, Zhongshan, Beijing, China). Briefly, paraffin-embedded sections of formalin-fixed tissue sample were deparaffinized in xylene and rehydrated in graded concentrations of ethanol. After quenching the endogenous peroxidase acitivity with 0.3% H2O2, the sections were microwaved in 10 mmol/L sodium citrate (pH 6.0) for 15 min for antigen retrieval. After antigen retrieval, the 10% normal goat serum was applied to slides to eliminate nonspecific staining (endogenous background staining). The sections were then incubated with primary antibodies (Anti-CD44v6, Santa Cluz, CA, USA) for 90 min at 37°C, and after three successive rinsings with washing buffer (PBS), they were further incubated with biotinylated goat antimouse antibodies for 30 min at 37°C; after rinsing, the tissue sections were incubated with the horseradish peroxidase- (HRP-) conjugated streptavidin for 20 min at room temperature. The slides were washed and stained with 3, 3′-diaminobenzidine (DAB) and then counter-stained with hematoxylin, dehydrated, and mounted with balsam for examination. Negative controls were obtained by omitting the primary antibody, substituted by PBS.
Positivity was scored semiquantitatively as CD44v6-negative (−), weakly (+), moderately (
For statistics, all the samples that expressed CD44v6 form (+) to (
All statistical comparisons were performed using SPSS version 13.0 software (SPSS Inc., Chicago, USA). For statistical analysis, the correlation between antigen expression and other clinicopathologic parameters was assessed by
62 cases ovary carcinomas were successfully analyzed. Table
Correlation of the clinicopathologic features and 5-year survival rates.
Clinicopathologic parameters | Number of cases | 5-years survival | ||
---|---|---|---|---|
Age |
21 |
10 (47.6) | > 0.05 | |
Menopausal status |
17 |
7 (41.2) | > 0.05 | |
Nulliparous status |
9 |
3 (33.3) | > 0.05 | |
Histological type |
5 |
1 (20) | < 0.05 | |
FIGO stage |
16 |
14 (87.5) | < 0.05 | |
Grade |
19 |
15 (78.9) | < 0.05 |
CD44v6 protein was preferentially expressed along the membrane of tumor cells. See Figure
Correlation between CD44v6 protein expression and various clinicopathologic parameters.
Clinicopathologic parameters | Number of cases | CD44v6-positive cases (%) | ||
---|---|---|---|---|
Age |
21 |
13 (61.9) | > 0.05 | |
Menopausal status |
17 |
11 (64.7) | > 0.05 | |
Nulliparous status |
9 |
6 (66.7) | > 0.05 | |
Histological type |
5 |
2 (40) | > 0.05 | |
FIGO stage |
16 |
5 (31.2) | < 0.05 | |
Grade |
19 |
6 (52.6) | < 0.05 | |
Survival period |
33 |
26 (78.8) | < 0.05 |
Immunohistochemical staining for CD44v6 protein in ovarian carcinomas, DAB
The 5-year survival rate of the women in this study was 46.7% (29/62). A significance difference was found between CD44v6 expression and 5-year survival rate; see Table
Overall survival curves of patients with CD44v6 positive (Blue line) and negative (Green line) ovarian carcinoma (
Our results suggested that CD44v6 might be a useful factor for evaluating the prognosis of the women with ovarian carcinoma. Cox proportional hazards regression models were used to evaluate the hazard ratio and indicated that FIGO stage, histological grade, nulliparous, and CD44v6 were significant among the seven prognostic factors (
Multivariate analyses of prognostic for survival of women with ovarian carcinomas.
Factors | Regression coefficient | Relative risk | |
---|---|---|---|
Age | 0.778 | 2.177 | > 0.05 |
Menopause status | 0.504 | 1.655 | > 0.05 |
Nulliparous | 1.207 | 3.343 | < 0.05 |
Histological type | 0.375 | 1.455 | > 0.05 |
FIGO stage | 0.465 | 1.592 | < 0.05 |
Grade | 0.685 | 1.984 | < 0.05 |
CD44v6 | 1.926 | 6.849 | < 0.05 |
CD44, a transmembrane glycoprotein, is the prominent cell surface receptor for hyaluronan [
However, there have been few reports on the correlation between clinicopathological indices and CD44v6 expression in ovarian carcinoma [
In the present study, CD44v6 was expressed in 66.1% of ovarian carcinomas. This result was similar to that of the previous study in other tumors such as breast cancer [
Although there is a similarity in expression pattern between different ovarian carcinomas, there are some differences; a possible explanation for the difference may be that ovarian carcinomas are heterogeneous entities, some derived from borderline tumors and others arising de novo.
Concerning prognosis, we found that the expression of the CD44v6 was significantly associated with increased mortality. The patient with CD44v6 positive tumors had a shorter survival than those with CD44 negative tumors. The 5-year survival rate of CD44v6 positive was 36.6% but that of negative was 66.7%. These results suggested that downregulation of CD44v6 was associated with a good prognosis in patient with ovarian carcinoma. These indicated that CD44v6 might be an important and useful marker for indicating a poor prognosis in women with ovarian carcinoma.
Differing methods were used in previous studies in which the relationship between CD44v6 expression and prognosis was investigated. For example, Yamada et al. [
In conclusion, CD44v6 is considered to be correlated with histological grade, FIGO stage, and survival period of ovarian carcinomas and to play an important role in predicating the prognosis of patients with ovarian carcinomas. CD44v6 may become an important prognostic factor in ovarian carcinoma. However, further studies are needed to fully elucidate the regulatory mechanisms of CD44 variant expression, and further studies using a large sample and longer follow-up are necessary to verify these results.
This paper was supported by Grants from the National Natural Science Foundation (no. 30700654) and the Scientific Technology Planning of Shaanxi Province, China (2005K15-G2), Traditional Medicine project of Shaanxi Province (2005024), and The Fundamental Research Funds for the Central University (XJJ 2011024).