Improving strategies for diagnosing ovarian cancer: a summary of the International Ovarian Tumor Analysis (IOTA) studies

In order to ensure that ovarian cancer patients access appropriate treatment to improve the outcome of this disease, accurate characterization before any surgery on ovarian pathology is essential. The International Ovarian Tumor Analysis (IOTA) collaboration has standardized the approach to the ultrasound description of adnexal pathology. A prospectively collected large database enabled previously developed prediction models like the risk of malignancy index (RMI) to be tested and novel prediction models to be developed and externally validated in order to determine the optimal approach to characterize adnexal pathology preoperatively. The main IOTA prediction models (logistic regression model 1 (LR1) and logistic regression model 2 (LR2)) have both shown excellent diagnostic performance (area under the curve (AUC) values of 0.96 and 0.95, respectively) and outperform previous diagnostic algorithms. Their test performance almost matches subjective assessment by experienced examiners, which is accepted to be the best way to classify adnexal masses before surgery. A two-step strategy using the IOTA simple rules supplemented with subjective assessment of ultrasound findings when the rules do not apply, also reached excellent diagnostic performance (sensitivity 90%, specificity 93%) and misclassified fewer malignancies than did the RMI. An evidence-based approach to the preoperative characterization of ovarian and other adnexal masses should include the use of LR1, LR2 or IOTA simple rules and subjective assessment by an experienced examiner.

Integration of cell phone imaging with microchip ELISA to detect ovarian cancer HE4 biomarker in urine at the point-of-care

Ovarian cancer is asymptomatic in the early stages and most patients present with advanced levels of disease. The lack of cost-effective methods that can achieve frequent, simple and non-invasive testing hinders early detection and causes high mortality in ovarian cancer patients. Here, we report a simple and inexpensive microchip ELISA-based detection module that employs a portable detection system, i.e., a cell phone/charge-coupled device (CCD) to quantify an ovarian cancer biomarker, HE4, in urine. Integration of a mobile application with a cell phone enabled immediate processing of microchip ELISA results, which eliminated the need for a bulky, expensive spectrophotometer. The HE4 level detected by a cell phone or a lensless CCD system was significantly elevated in urine samples from cancer patients (n = 19) than healthy controls (n = 20) (p < 0.001). Receiver operating characteristic (ROC) analyses showed that the microchip ELISA coupled with a cell phone running an automated analysis mobile application had a sensitivity of 89.5% at a specificity of 90%. Under the same specificity, the microchip ELISA coupled with a CCD had a sensitivity of 84.2%. In conclusion, integration of microchip ELISA with cell phone/CCD-based colorimetric measurement technology can be used to detect HE4 biomarker at the point-of-care (POC), paving the way to create bedside technologies for diagnostics and treatment monitoring.

Effect of human epididymis protein 4 gene silencing on the malignant phenotype in ovarian cancer

BACKGROUND

Human epididymis secretory protein 4 (HE4) has been proved to be a promising novel biomarker for the detection of epithelial ovarian carcinomas. Compared with CA125, HE4 assay demonstrated an improved ability to discriminate between pelvic mass with malignant and benign disease. Though it is well known that HE4 is overexpressed in ovarian cancer, however, the role of HE4 in the carcinogenesis and progression of ovarian cancer remains unkown.

METHODS

In this study, we explored the role of HE4 in the carcinogenesis and progression of ovarian cancer. We screened nine ovarian cancer cell lines for HE4 expression, and using RNA interference (RNAi), we silenced HE4 gene expression in CaoV3 and SKOV3.ip1 ovarian cancer cell lines. We assessed the effect of HE4 gene silencing on the transformed phenotype by examining the cell cycle, apoptosis, proliferation and transwell migration/invasion in vitro.

RESULTS

HE4 gene silencing induces G0/G1 arrest and blocks the progression from the G1 to S phase in CaoV3 and SKOV3.ip1 cells. HE4 knockdown also inhibited cell proliferation, migration and invasion in SKOV3.ip1 cells in vitro.

CONCLUSION

HE4 may be involved in the regulation of the cell cycle and promote ovarian cancer migration and invasion.

The diagnostic accuracy of two human epididymis protein 4 (HE4) testing systems in combination with CA125 in the differential diagnosis of ovarian masses

BACKGROUND

Cancer antigen 125 (CA125) is the best known single tumor marker for ovarian cancer (OC). We investigated whether the additional information of the human epididymis protein 4 (HE4) improves diagnostic accuracy.

METHODS

We retrospectively analyzed preoperative sera of 109 healthy women, 285 patients with benign ovarian masses (cystadenoma: n=78, leimyoma: n=66, endometriosis: n=52, functional ovarian cysts: n=79, other: n=10), 16 low malignant potential (LMP) ovarian tumors and 125 OC (stage I: 22, II: 15, III: 78, IV: 10). CA125 was analyzed using the ARCHITECT system, HE4 using the ARCHITECT(a) system and EIA(e) technology additionally.

RESULTS

The lowest concentrations of CA125 and HE4 were observed in healthy individuals, followed by patients with benign adnexal masses and patients with LMP tumors and OC. The area under the curve (AUC) for the differential diagnosis of adnexal masses of CA125 alone was not significantly different to HE4 alone in premenopausal (CA125: 86.7, HE4(a): 82.6, HE4(e): 81.6% p>0.05) but significantly different in postmenopausal [CA125: 93.4 vs. HE4(a): 88.3 p=0.023 and vs. HE4(e): 87.8% p=0.012] patients. For stage I OC, HE4 as a single marker was superior to CA125, which was the best single marker in stage II-IV. The combination of CA125 and HE4 using risk of malignancy algorithm (ROMA) gained the highest sensitivity at 95% specificity for the differential diagnosis of adnexal masses [CA125: 70.9, HE4(a): 67.4, HE4(e): 66.0, ROMA(a): 76.6 and ROMA(e): 74.5%], especially in stage I OC [CA125: 27.3, HE4(a): 40.9, HE4(e): 40.9, ROMA(a): 45.5 and ROMA(e): 45.5%].

CONCLUSIONS

CA125 is still the best single marker in the diagnosis of OC. HE4 alone and even more the combined analysis of CA125 and HE4 using ROMA improve the diagnostic accuracy of adnexal masses, especially in early OC.

Evaluation of the accuracy of serum human epididymis protein 4 in combination with CA125 for detecting ovarian cancer: a prospective case-control study in a Korean population

BACKGROUND

This study aimed to determine the serum concentrations of CA125 and human epididymis protein 4 (HE4) in patients with ovarian cancer, and to evaluate the sensitivity and specificity of these biomarkers for differentiating between patients with benign gynecological disease and those with ovarian cancer, when used alone and in combination in a Korean population.

METHODS

We consecutively recruited 159 women with an adnexal mass, including 78 women with ovarian cancer. A total of 224 healthy women served as controls. The serum concentrations of HE4 and CA125 were analyzed using immunochemiluminescence assays. The concentrations of the markers were compared among the different subgroups, and the diagnostic accuracy of each marker and the combination of the two markers was assessed by plotting receiver operating characteristic (ROC) curves. In addition, the Risk of Ovarian Malignancy Algorithm (ROMA) was utilized to categorize patients into low- and high-risk groups for epithelial ovarian cancer.

RESULTS

Serum HE4 and CA125 concentrations were significantly higher in the ovarian cancer patients compared with those seen in patients with benign disease or in the healthy controls (p<0.0001 in both). In patients with an adnexal mass, the area under the ROC curve was higher when the combination of the markers was used compared with use of CA125 only. Using ROMA, patients could be successfully classified into high- and low-risk group, with 87.5% sensitivity at a specificity of 93.8%.

CONCLUSIONS

These findings suggest that measuring serum HE4 concentrations along with CA125 concentrations may provide higher accuracy for detecting ovarian cancer.

HE4 in ovarian cancer: from discovery to clinical application

Despite the relatively low prevalence, ovarian cancer is the fifth leading cause of death from cancer among women. As such, an early diagnosis for establishing a timely surgical and/or chemotherapeutic treatment is essential for improving the outcome. The most reliable, but not always straightforward, approach to diagnose ovarian cancer relies on multiple, time-consuming and expensive investigative tools. These typically include clinical presentation (i.e., pelvic or abdominal pain, urinary frequency or urgency, increased abdominal size or bloating) with pelvic examination, transvaginal ultrasonography (US), and measurement of carbohydrate antigen 125 (CA125). Although the conventional pathway to develop and market a clinically useful biomarker is challenging, recent advances in genomic and proteomic technologies have led to the identification of previously unknown candidate markers of ovarian cancer. Some of these are currently under clinical validation. The human epididymis protein 4 (HE4) has recently been approved by the Food and Drug Administration for monitoring recurrence or progression of epithelial ovarian cancer. Nevertheless, reliable clinical evidence demonstrates that HE4, used alone or in combination with CA125, substantially improves the accuracy of screening and/or disease monitoring. This chapter will review the current knowledge on biologic and clinical applications of ovarian cancer biomarkers, with particular emphasis on the newly proposed marker, HE4.

Comparison of different ovarian cancer detection algorithms

The objective of the study was to evaluate the accuracy of a combined-two step ovarian cancer screening tool consisting of the ovarian cancer symptom index combined with either a risk of ovarian malignancy algorithm (ROMA) or a risk of malignancy index.

MATERIAL AND METHODS

The case-control study consisted of 31 patients with ovarian cancer, 30 patients with benign ovarian diseases and 27 age-matched healthy controls.

RESULTS

Sensitivity and specificity of the ovarian cancer symptom index among menopausal women were 84.6% and 52.9%, respectively. ROMA revealed the highest discriminative value when compared to others (AUC 98.4%). When the cutoff level of 28 was applied for menopausal women, ROMA revealed sensitivity and specificity of 95.8% and 93.1%, respectively.

CONCLUSIONS

The ovarian cancer symptom index could be used as the first step in ovarian cancer screening with subsequent application of ROMA as a second step screening tool. A larger sample size in both control and patient groups should be evaluated to reach clear conclusions.

Comparison of a novel multiple marker assay vs the Risk of Malignancy Index for the prediction of epithelial ovarian cancer in patients with a pelvic mass

OBJECTIVE

We sought to compare the Risk of Malignancy Index (RMI) to the Risk of Ovarian Malignancy Algorithm (ROMA) to predict epithelial ovarian cancer (EOC) in women with a pelvic mass.

STUDY DESIGN

In all, 457 women with imaging results from ultrasound, computed tomography, magnetic resonance imaging, and serum HE4 and CA125 determined prior to surgery for pelvic mass were evaluable. RMI values were determined using CA125, imaging score, and menopausal status. ROMA values were determined using HE4, CA125, and menopausal status.

RESULTS

At a set specificity of 75%, ROMA had a sensitivity of 94.3% and RMI had a sensitivity of 84.6% for distinguishing benign status from EOC (P = .0029). In patients with stage I and II disease, ROMA achieved a sensitivity of 85.3% compared with 64.7% for RMI (P < .0001).

CONCLUSION

The dual marker algorithm utilizing HE4 and CA125 to calculate a ROMA value achieves a significantly higher sensitivity for identifying women with EOC than does RMI.

[Measurement of serum human epididymis secretory protein 4 combined with CA125 assay in differential diagnosis of endometriosis cyst and ovarian benign and malignant tumors]

OBJECTIVE

To investigate the value of human epididymis secretory protein 4(HE4) combined with CA125 assay in differential diagnosis of endometriosis cyst and ovarian malignant tumor.

METHODS

The level of HE4 and CA125 were measured by enzyme-linked immunosorbent assay (ELISA) in the serum specimens of 46 cases in endometriosis cyst group, 36 cases in malignant ovarian tumor group, 60 cases in benign ovarian diseases and 50 women in healthy women group. Those results were shown with median level. The normal range were 0-150 pmol/L in HE4 and 0-35 kU/L, which either one was more than the threshold value defined as positive index. The sensitivity of assay was evaluated by receiver operating characteristic (ROC) curve, the relation and value of HE4 or CA125 alone and combination assay in diagnosis of endometriosis was analyzed by Mann-Whitney U test and correlation analysis.

RESULTS

(1) HE4: the median levels of HE4 were 52.4, 51.0, 50.0 pmol/L in group of endometriosis, normal control and benign ovarian tumor, which didn't show statistical difference. However, HE4 was 507.5 pmol/L in ovarian cancer group, which was significantly higher than those of 3 groups (P<0.05). (2) CA125: there were significant different in median level of CA125 was observed as 743.0 kU/L in ovarian cancer, 84.9 kU/L in endoemtriosis, 15.4 kU/L in benign ovarian disease, and 11.5 kU/L in healthy women (P<0.05). (3) The single assay: when compared with that in endometriosis group, receiver operating characteristic area under the curve (ROC-AUC) were 0.933 in HE4 alone and 0.821 in CA125 alone assay in ovarian cancer group. The specificity was 95% and the sensitivity was 79.6% and 49.0%. (4) The combination assay: when compared with those in endometriosis group, the ROC-AUC was 0.936, the specificity was 95% and the sensitivity was 81.0% in ovarian cancer.

CONCLUSIONS

Measurement of HE4 could be used in differential diagnosis of endometriosis cyst. And the combination of HE4 and CA(125) assay could discriminate ovarian endometriosis cysts from ovarian malignant tumors effectively.

[The values of serum human epididymis secretory protein 4 and CA(125) assay in the diagnosis of ovarian malignancy]

OBJECTIVE

To evaluate the value of human epididymis secretory protein 4 (HE4) and CA(125) in the diagnosis of ovarian malignancy.

METHODS

HE4 and CA(125) in the serum specimens of malignant ovarian tumor group (30 cases), benign ovarian diseases (110 cases; 45 benign ovarian tumor, 57 endometriotic diseases and 8 pelvic inflammation were included) and healthy women group (137 cases) were assayed double blindly. The levels and the diagnosis efficiency of the HE4 and CA(125) were analyzed.

RESULTS

(1) The median levels of HE4 and CA(125) were significantly higher in malignant ovarian tumor group (244 pmol/L and 601 kU/L respectively) than those of the benign ovarian diseases group (32 pmol/L and 22 kU/L respectively) and healthy women group (32 pmol/L and 11 kU/L respectively) (P = 0.000 - 0.029). The median levels of CA(125) were also higher in endometriotic diseases and pelvic inflammation groups (53 and 41 kU/L respectively) than those of benign ovarian tumor group and healthy women group (12 and 11 kU/L respectively; P = 0.000 - 0.031). (2) The positive rate of HE4 was lower than that of CA(125) in malignant ovarian tumor group (P = 0.036). HE4 was negative in benign diseases and healthy women groups. But the positive rates of CA(125) were 56.1% and 5/8 respectively in endometriotic diseases and pelvic inflammation groups and there were significant differences compared with HE4 (P = 0.000). (3) The HE4 assay had advantage over the CA(125) assay in receiver operating characteristic-area under the curve (ROC-AUC) and sensitivity with a specificity of 100% when ovarian malignancy was compared with controls having benign diseases and healthy women, benign tumor or benign diseases groups respectively. The CA(125) assay had advantage over the HE4 assay in ROC-AUC and sensitivity with the same specificity when ovarian cancers were compared with controls having healthy women group. (4) Combined assay of HE4 and CA(125) was better than CA(125) alone when ovarian malignancy was compared with controls having any group. (5) Combined assay was better than HE4 alone in ROC-AUC and sensitivity with the same specificity when ovarian cancers were compared with controls having benign diseases and healthy women or healthy women groups. And combined assay was lower in the ROC-AUC and the sensitivity with specificity of 100% than HE4 when ovarian cancers were compared with controls having benign tumors or benign diseases groups respectively. (6) The diagnosis efficiency of the HE4 assay at the level 86 pmol/L determined in ROC curve with controls having benign diseases and healthy women group and at the 95% reference level 50 pmol/L of healthy women or 150 pmol/L recommended by the kit respectively was compared. The sensitivity of 50 pmol/L was 73% higher than 150 pmol/L and 86 pmol/L, while the specificity and positive predictive value were lower (P = 0.002, P = 0.000). The specificity, accuracy and positive predictive value of HE4 assay at the set point of 150 pmol/L and 86 pmol/L were 100%, 96% and 96%. The set point of 86 pmol/L had advantage over 150 pmol/L at the sensitivity of diagnosis, 70% and 63% respectively. But the positive predictive value was 95% lower than 150 pmol/L, being 100%. There was no significant difference (P = 0.883, P = 0.883).

CONCLUSIONS

The specificity of HE4 assay is higher than CA(125) assay in the diagnosis of ovarian cancer and HE4 combined with CA(125) assay can improve the diagnoses. The set point of 150 pmol/L is advantageous for the accurate diagnosis, while the set point of 86 pmol/L is advantageous for the screening of malignant ovarian cancer.

SMRP and HE4 as biomarkers for ovarian carcinoma when used alone and in combination with CA125 and/or each other

Assays measuring SMRP (mesothelin) and HE4 (a secreted protease) in serum and other body fluids (including urine for SMRP) are likely to be clinically useful for patients with ovarian cancer, as data indicate that they complement CA125 for diagnosis and monitoring of patients. Both markers have temporal stability, as does CA125, which may be utilized to facilitate earlier diagnosis by performing longitudinal studies on high risk subjects. Preliminary data show autoantibodies to native mesothelin in some patients with ovarian carcinoma and in some healthy women. We are presently studying their relationship to the patients' clinical state to learn whether measurements of antibody levels provide information that can aid diagnosis and monitoring of treated patients. Prospective studies are needed to establish the clinical relevance of our findings.

Comparing adaptive and non-adaptive algorithms for cancer early detection with novel biomarkers

It may be possible to reduce cancer mortality by monitoring the concentrations of serum biomarkers over time in men and women to detect their cancer early, when it is most curable. The simplest approach to using a biomarker for screening is to sequentially use fixed thresholds as a means to determine an abnormal test (e.g., PSA exceeding 4 mg/ml, CA 125 exceeding 30 U/ml). Alternatives to the simplest single threshold (ST) rules include more sophisticated algorithms that make use of screening history that accumulates over time and determines abnormal tests using individualized reference ranges. Although in principle longitudinal algorithms should out perform fixed threshold rules, the actual benefit gained will depend on behavior of the biomarker, the screening algorithm, and the screening frequency. Little information has been available to help predict when conditions should compel the adoption of the more sophisticated algorithms and when conditions suggest the simpler algorithms should suffice, or indeed be preferred. In this manuscript we evaluate the conditions under which one should expect great benefit, and when one should not expect benefit, by comparing the ability of simple and complex algorithms to detect cancer early under a variety of biomarker behaviors and screening frequencies.

Serum S100B protein is increased in fasting rats

BACKGROUND

S100B is a calcium-binding protein expressed and secreted by astrocytes; serum and cerebrospinal fluid (CSF) S100B elevation has been proposed as an index of brain damage. However, other tissues are shown to produce this protein and the clinical significance of serum S100B elevation has been discussed.

METHODS

We investigated the levels of serum and CSF S100B in fasting Wistar rats. Animals were divided into two groups, control and fasting for 48 h, and S100B levels in serum and CSF were determined by ELISA. S100B secretion in dissociated epididymal fat cells was investigated in the presence of epinephrine.

RESULTS

We observed a significant >2-fold increase of S100B levels in serum of fasting rats, without changes in its CSF content. Moreover, we demonstrated in vitro epinephrine stimulated S100B release from fat cells.

CONCLUSIONS

Present results reinforce that extracerebral sources of S100B, particularly adipocytes, contribute to its serum levels and support the idea that caution is needed when interpreting serum S100B increase as a clinical marker of brain damage.

Bead-based ELISA for validation of ovarian cancer early detection markers

PURPOSE

Efforts to validate ovarian cancer early detection biomarkers with immunoassays are challenged by the limited specimen volumes available. We sought to develop a specimen-efficient assay to measure CA125 in serum, assess its reproducibility, validity, and performance, and test its potential for multiplexing and combining with human epididymis protein 4 (HE4), a promising novel ovarian cancer marker.

EXPERIMENTAL DESIGN

Four pairs of commercially available anti-CA125 antibodies and one pair of anti-HE4 antibodies were evaluated for accuracy in measuring known concentrations of antigen on a bead-based platform. The two best pairs were further assessed for reproducibility, validity, and the ability to discriminate between blinded serum samples obtained from ovarian cancer cases (n = 66) and women without ovarian cancer (n = 125).

RESULTS

Suitability for use in a bead-based assay varied across CA125 antibody pairs. Two CA125 bead-based assays were highly reproducible (overall correlations between replicates >/= 0.95; coefficients of variation < 0.2) and strongly correlated with the research standard CA125II RIA (correlations >/= 0.9). Their ability to distinguish ovarian cancer cases from non-cases based on receiver operating characteristic analyses (area under the curve, AUC, of 0.85 and 0.84) was close to that of the CA125II RIA (AUC, 0.87). The HE4 bead-based assay showed lower reproducibility but yielded an AUC of 0.89 in receiver operating characteristics analysis. Multiplexing was not possible but a composite marker including CA125 and HE4 achieved an AUC of 0.91.

CONCLUSION

Optimization procedures yielded two bead-based assays for CA125 that perform comparably to the standard CA125II RIA, which could be combined with an HE4 bead-based assay to improve diagnostic performance, and requires only 15 muL of sample each.

Proteins with whey-acidic-protein motifs and cancer

The importance of early diagnosis to reduce the morbidity and mortality from cancer has led to a search for new sensitive and specific tumour markers. Molecular techniques developed over the past few years allow simultaneous screening of thousands of genes, and have been applied to different cancers to identify many genes that are modulated in various cancers. Of these, attention has focused on genes coding for a family of proteins with whey-acidic-protein (WAP) motifs. Most notably, the genes coding for elafin, antileukoproteinase 1 (previously called secretory leucocyte proteinase inhibitor, SLPI), WAP four disulphide core domain protein 1 (previously called prostate stromal protein 20 kDa, PS20), and WAP four disulphide core domain protein 2 (previously called major human epididymis-specific protein E4, HE4), have been identified as candidate molecular markers for several cancers. In this review, we assess data for an association between cancer and human WAP proteins, and discuss their potential role in tumour progression. We also propose a new mechanism by which WAP proteins might have a role in carcinogenesis.

The Carbohydrate Structure of DEFB126, the Major Component of the Cynomolgus Macaque Sperm Plasma Membrane Glycocalyx

Based on the amino-acid sequence of the macaque epididymal secretory protein, ESP 13.2 (Q9BEE3/AJ236909), it has now been classified as beta-defensin DEFB126. DEFB126 is one of the five beta-defensins with genes that are clustered along chromosome 20pl3, and all five proteins have an extended carboxy terminus that continues beyond the 6-cysteine beta-defensin core region. This 60-amino acid carboxyl tail extension of the DEFB126 molecule is extraordinarily rich in threonine and serine (40%), many of which appear to be likely candidates for having O-glycosylation. DEFB126 has been shown to coat the entire surface of cynomolgus macaque sperm as they move through the corpus/caudal region of the epididymis. It is a major glycocalyx barrier to the external environment and is retained until the completion of capacitation. Sperm exposed to fluorescein-conjugated poly-L-lysine or Alexa488-histone showed a very uniform fluorescent labeling pattern over the entire sperm surface, almost identical to that observed with anti-DEFB126 Ig label. Sperm surface components that were released following treatment with caffeine/cAMP (in vitro capacitation) were blotted and probed with three different lectins which are known to recognize terminal sialic acid residues, and all three recognized the 35 kDa DEFB126 band. Neuraminidase treatment of sperm shifted the molecular weight of DEFB126 from 34-36 kDa to approximately 38-40 kDa and removed or greatly inhibited sialic acid-specific lectin recognition. O-Glycanase treatment alone was ineffective at removal of the oligosaccharides, but prior treatment with neuraminidase was sufficient to enable the O-glycanase treatment to effectively change the apparent molecular weight to 10 kDa, confirming that a major portion of the molecular mass is associated with the carbohydrate portion. Western blots of neuraminidase-treated DEFB126 showed strong recognition with a number of lectins that identify beta-galactose and also lectins that recognize the N-acetylgalactosamine-serine/threonine, the proposed connection site of O-glycosylation. All of the lectins that recognized DEFB126 on Western blots were used to fluorescently probe sperm. The fluorescent patterns that were observed with poly-L-lysine, Alexa488-histone, sialic acid-specific lectins, and galactose-specific lectins showed even distributions over the entire sperm surface and the patterns were identical to sperm labeled with anti-DEFB126 Ig, and all but the antibody did not recognize neuraminidase-treated sperm.

Profiling and imaging proteins in the mouse epididymis by imaging mass spectrometry

Different aspects of matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) have been used as discovery tools to obtain global and time-correlated information on the local proteomic composition of the sexually mature mouse epididymis from both qualitative and semiquantitative points of view. Tissue sections and laser captured microdissected cells and secretory products were analyzed by MALDI-MS and from the recovered protein profiles, over 400 different proteins were monitored. Over 50 of these, some of which have been identified, displayed regionalized behavior from caput to cauda within the epididymis. Combining the information obtained from high-resolution imaging mass spectrometry and laser captured microdissection experiments, numerous proteins were localized within the epididymis at the cellular level. Furthermore, from the signal intensities observed in the different protein profiles organized in space, semiquantitative information for each protein was obtained.

Postnatal development and testosterone dependence of a rat epididymal protein identified by neonatal tolerization

A rat epididymal protein of 27 kDa was identified using neonatal tolerization. This study reports the production and characterization of a polyclonal antiserum to this protein. ELISA was used to demonstrate that this antiserum reacts strongly with epididymal sperm proteins, but has little or no reactivity with testicular proteins. Western blot analysis revealed that this polyclonal antiserum recognized a 27 kDa protein extracted from the corpus epididymidis as well as from spermatozoa from the corpus and cauda epididymides, and immunostaining revealed the presence of the protein in the corpus to cauda epididymides. Stronger reactivity was observed in the supranuclear region and stereocilla of principal cells of the corpus epididymidis and in the luminal content of the corpus and cauda epididymides. The testicular section showed no reactivity. Treatment with the antiserum resulted in time- and dose-dependent agglutination of rat spermatozoa. By indirect immunofluorescence, the antiserum localized proteins in the mid-piece region of rat spermatozoa. Studies were carried out to determine the age at which the protein first became apparent during postnatal development. The protein was expressed from day 40 onwards, as demonstrated by western blot analysis. The androgen regulation of this protein was ascertained by castration and supplementation studies. Expression of this protein showed a decline starting at day 14 after castration and by day 21 the protein was absent; however, androgen replacement resulted in the reappearance of the protein. The results of these studies indicate that the protein identified is specific to the epididymis, and is regulated by development and androgens. The importance of epididymis-specific proteins that are regulated by androgens in sperm maturation is discussed, and the need to ascertain the sequence of the protein and clone the cognate gene is indicated.