Use of specific ELISA for the detection of antibodies directed against p53 protein in patients with hepatocellular carcinoma

Value of anti-p53 antibody as a biomarker for hepatocellular carcinoma: Evidence from a meta-analysis

INTRODUCTION

The incidence of hepatocellular carcinoma (HCC) ranks sixth in the world, but its mortality is the third highest due to the lack of early diagnostic markers. Nowadays, the increase of autoantibody levels has been found in many cancers, and many studies have begun to pay attention to the detection of anti-p53 antibodies in HCC. The purpose of this study is to quantitatively and comprehensively analyze the potential diagnostic value of anti-p53 autoantibodies in HCC METHODS:: English articles up to November 2019 were collected. The overall sensitivity and specificity were calculated. Besides, the positive likelihood ratio, negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic curves of the overall diagnostic accuracy of anti-p53 antibody were calculated by STATA software. Finally, according to the heterogeneity of the results, the subgroup analysis, and the publication bias were performed.

RESULTS

A total of 16 eligible studies were incorporated into this meta-analysis, including 1323 patients with HCC and 1896 control. The pooled sensitivity was 0.28(0.17-0.41) and specificity was 0.98 (0.95-0.99). The pooled DOR was 10.44 (6.31-17.29) and the pooled NLR was 0.74 (0.63-0.86). The area under ROC curve of symmetrical ROC was 0.840.

CONCLUSIONS

The anti-p53 antibody has a high specificity for HCC, but the low sensitivity is not perfect and would limit the clinical application. The anti-p53 antibody would help rule out HCC but not help rule in HCC for early diagnosis. Whether combined as a diagnostic panel with other biomarkers or laboratory tests may prove useful requires further study.

Immunohistochemical Determination of p53 Protein Overexpression for Predicting p53 Gene Mutations in Hepatocellular Carcinoma: A Meta-Analysis

BACKGROUND

Whether increased expression of the tumor suppressor protein p53 indicates a p53 gene mutation in hepatocellular carcinoma (HCC) remains unclear. We conducted a meta-analysis to determine whether p53 protein overexpression detected by immunohistochemistry (IHC) offers a diagnostic prediction for p53 gene mutations in HCC patients.

METHODS

Systematic literature searches were conducted with an end date of December 2015. A meta-analysis was performed to estimate the diagnostic accuracy of IHC-determined p53 protein overexpression in the prediction of p53 gene mutations in HCC. Sensitivity, subgroup, and publication bias analyses were also conducted.

RESULTS

Thirty-six studies were included in the meta-analysis. The results showed that the overall sensitivity and specificity for IHC-determined p53 overexpression in the diagnostic prediction of p53 mutations in HCC were 0.83 (95% CI: 0.80-0.86) and 0.74 (95% CI: 0.71-0.76), respectively. The summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 2.65 (95% CI: 2.21-3.18) and 0.36 (95% CI: 0.26-0.50), respectively. The diagnostic odds ratio (DOR) of IHC-determined p53 overexpression in predicting p53 mutations ranged from 0.56 to 105.00 (pooled, 9.77; 95% CI: 6.35-15.02), with significant heterogeneity between the included studies (I2 = 40.7%, P = 0.0067). Moreover, subgroup and sensitivity analyses did not alter the results of the meta-analysis. However, potential publication bias was present in the current meta-analysis.

CONCLUSION

The upregulation of the tumor suppressor protein p53 was indeed linked to p53 gene mutations. IHC determination of p53 overexpression can predict p53 gene mutations in HCC patients.

Autoantibodies against tumor-associated antigens for detection of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common tumors worldwide. The survival rate after the onset of symptoms is generally less than one year for the late presentation of HCC, and reliable tools for early diagnosis are lacking. Therefore, novel biomarkers for the early detection of HCC are urgently required. Recent studies show that the abnormal release of proteins by tumor cells can elicit humoral immune responses to self-antigens called tumor-associated antigens (TAAs). The corresponding autoantibodies can be detected before the clinical diagnosis of cancer. Therefore, there is growing interest in using serum autoantibodies as cancer biomarkers. In this review, we focus on the advances in research on autoantibodies against TAAs as serum biomarker for detection of HCC, the mechanism of the production of TAAs, and the association of autoantibodies with patients' clinical characteristics.

Aptamer--nanoparticle-based chemiluminescence for p53 protein

A simple colorimetric biosensing technique based on the interaction of gold nanoparticles (AuNPs) with the aptamer was developed for detection of p53, a tumor suppressor protein, in the current study. Aggregation of AuNPs was induced by desorption of the p53 binding RNA aptamer from the surface of AuNPs as a result of the aptamer target interaction leading to the color change of AuNPs from red to purple. The detection limit of p53 protein by the colorimetric approach was 0.1 ng/ml after successful optimization of the amount of aptamer, AuNPs, salts, and incubation time. Furthermore, the catalytic activity of the aggregated AuNPs was greatly enhanced by chemiluminescence (CL) reaction, where the detection limit was enhanced to 10 pg/ml with a regression coefficient of R2 = 0.9907. Here the sensitivity was increased by 10-fold compared with the AuNP-based colorimetric method. Hence, the sensitivity of detection was increased by employing CL, by using the catalytic activity of aggregated AuNPs, on the luminol-hydrogen peroxide reaction. Thus, the combination of colorimetric and CL-based aptasensor can be of great advantage in increasing the sensitivity of detection for any target analyte.

Autoantibodies to tumor-associated antigens combined with abnormal alpha-fetoprotein enhance immunodiagnosis of hepatocellular carcinoma

The identification and characterization of tumor-associated antigens (TAAs) and their use in antigen mini-arrays for cancer immunodiagnosis has been of interest recently as an approach to cancer detection. In this study, autoantibodies in sera from a patient with HCC were used as probes to immunoscreen a HepG2 cDNA expression library for the identification of TAAs involved in malignant liver transformation. Recombinant proteins from two genes identified in this manner, Sui1 and RalA were expressed, purified and used as antigens in immunoassays to detect the presence of antibodies in sera from 77 patients with HCC, 30 with chronic hepatitis (CH), 30 with liver cirrhosis (LC) and 82 normal human sera (NHS). The prevalence of antibody to Sui1 and RalA in HCC were 11.7% (9/77) and 19.5% (15/77), respectively, which were significantly higher than prevalence in liver cirrhosis (3.3% and 3.3%), chronic hepatitis (0% and 0%) and normal human sera (0% and 0%). When Sui1 and RalA were added to a panel of eight other TAAs used in a previous study, the final cumulative prevalence of anti-TAA antibodies in HCC to the 10 TAA array was raised to 66.2% (51/77). The specificity for HCC compared with LC, CH and NHS, was 66.7%, 80.0%, and 87.8%, respectively. When anti-TAA was added to abnormal serum AFP as combined diagnostic markers, it raised the diagnostic sensitivity from 66.2% to 88.7%. AFP and anti-TAA were independent markers and the simultaneous use of these two markers significantly resulted in the increased sensitivity of HCC detection.

The clinical significance of autoantibodies in gastrointestinal malignancies: an overview

Autoimmunity can be associated with cancer and one of the forms of its expression is the development of antibodies to autologous cellular antigens. The types of cellular proteins which induce autoantibody responses in gastrointestinal malignancies are quite varied and include cellular proteins encoded by mutated normal genes (p53), cellular proteins that are overexpressed and/or aberrantly expressed in malignant tissues (carcinoembryonic antigen), inhibitors of apoptosis (survivin and livin), major components of mucus (mucins), surface receptors of apoptosis (Fas) and nuclear-restricted proteins (double-stranded DNA, single-stranded DNA and Sm family proteins). In the past few years, due to the great clinical interest and the advancement in detection techniques, the above list has grown significantly and a large number of cancer-related antigens, which trigger a specific humoral immune response to the host, have also been identified. The authors review the autoantibodies associated with gastrointestinal malignancies and their clinical implications.

Serological markers of liver cancer

Serological markers for hepatocellular carcinoma (HCC) are important for early diagnosis, as well as monitoring of tumour aggressiveness, treatment responsiveness, recurrence and survival. The three most common markers are total alpha-fetoprotein (AFP), Lens culinaris agglutinin-reactive AFP (AFP-L3) and protein induced by vitamin K absence or antagonist-II (PIVKA-II). Total AFP has the sensitivity of 60% and specificity of 90% for the detection of HCC. Increase in the percentage of AFP-L3 over the total AFP (>10%) is very specific for small HCC. PIVKA-II is also more specific than total AFP in detecting HCC. AFP-L3 and PIVKA-II levels correlate with tumour aggressiveness and prognosis. All three markers are useful for monitoring treatment responsiveness and tumour recurrence. Since the levels of the three markers are independent of each other, combination of measurement of two or three markers will increase the sensitivity and diagnostic accuracy. Some novel markers including glypican-3 are being extensively studied.

Rapid and sensitive immunomagnetic-electrochemiluminescent detection of p53 antibodies in human serum

The mutation of tumor suppressor p53 gene is common in malignant tumor. p53 antibodies are products of immunoresponse against abnormal p53 protein. It has been found that p53 antibodies are of importance in tumor's diagnosis, prognosis and relapse monitoring. However, current method for detecting p53 antibodies, i.e. enzyme-linked immunosorbent assay (ELISA), requires a long time with multiple steps, and the assay is only semi-quantitative. In this work, a protocol for quantitative detection of p53 antibodies in human serum using immunomagnetic electrochemiluminescence (IM-ECL) was devoloped. The immunoassay format consisted of a three antibody sandwich in which a biotinylated capture antibody, was banded with the commercial p53 protein. A detector antibody was added to bind the p53 protein at another site. Then, secondary antibody, labeled with ruthenium(II) tris-bipyridal, was added and, when bound to the bead immunocompiex, generated light in the presence of an excess of tripropylamine. The light was detected and measured by the analyzer made by us. Our experimental results indicate that the sensitivity of this assay was 10 pg of p53 antibodies per ml of reference serum (normal human serum). A stable calibration curve with a wide dynamic range was established. The calibration curve was linear from 0.01 to 1000 ng/ml, thus, making quantitation possible. An immunologic prozone effect was observed above 1000 ng p53 antibodies per milliliter of serum. Serum samples from lung and nasopharyngeal carcinoma patients were tested using the IM-ECL assay. The positive rate of p53 antibodies were 28.6% in lung carcinoma and 8.33% in nasopharyngeal carcinoma, respectively. p53 antibody concentration in the carcerous human sera were quantified from the calibration curve. In the case of lung carcinoma, a trend was found that a higher p53 antibody concentration in the serum was likely linked to a higher stage of the cancer. This trend was not found in nasopharyngeal carcinoma. The assay uses only 50 microl of sample per test and requires a 30-min incubation period in addition to a 50 s acquisition time. This assay has several advantages over the commonly used ELISA method in terms of sensitivity, linear range, and assay time. Results of the study suggest that IM-ECL is a feasible method for rapid and sensitive detection of p53 antibodies in human serum.

Anti-p53 in breast cancer: concordance of different assay procedures and association with p53 antigen expression

OBJECTIVE

Anti-p53 levels detected by different methods were compared in a predefined group of patients with breast cancer and correlated with p53 antigen expression in the corresponding tumors.

METHODS

P53 autoantibodies were investigated in 165 patients with primary breast cancer using ELISAs with recombinant or native p53. Immunoblot and indirect immunofluorescence (Huh7) were used for confirmation, p53 antigen expression in the tumor was determined immunohistochemically.

RESULTS

Using ELISA, overall 18/165 positives (11%) were detected, with only partly concordant results between the assays. Five positive sera were confirmed by immunoblot, and three also by indirect immunofluorescence. Anti-p53-positive patients detected by more than two assays showed accumulated p53 in the tumor (6/6) and mostly suffered from recurrent tumors (4/6; p = 0.02). In these cases, a trend towards a shortened disease-free interval was found (26 vs. 49 months; n.s.). In patients with a positive or borderline result in only one of the serological methods, there was no increased rate of p53 accumulation compared to anti-p53-negative patients (4/19 versus 35/126).

CONCLUSIONS

Lack of assay standardization may partly explain the divergence in reports on anti-p53 and its clinicopathological associations. We speculate that, in different groups of patients, anti-p53 might be induced by different mechanisms.

Detection of the anti-P53 antibodies in dogs with tumors

To detect the anti-P53 antibodies of dogs with tumors, a GST-recombinant canine (rc) P53 fusion protein was expressed and purified. Immunoblot analysis was performed using this GST-rcP53 fusion protein as an antigen and serum samples from dogs suffering from tumors as primary antibodies. Out of 16 serum samples obtained from various tumor cases, four samples showed reaction with GST-rcP53. In contrast, serum from other 12 dogs with tumors, four dogs with non-neoplastic diseases and two control healthy dogs (as controls) did not show any reaction with GST-rcP53 in immunoblotting. The p53 gene mutation and the P53 protein expression were examined, using the tumor tissues to explore the relationship between the existence of the GST-rcP53 bands, gene mutations of p53 and the accumulation of P53 protein. One case, which showed a clear GST-rcP53 band, had a point mutation of the p53 cDNA and showed nuclear accumulation of P53 protein. These results suggest that the anti-P53 antibodies are also produced in tumor dogs with p53 gene mutations.

p53 and anti-p53 antibodies as possible markers of a switch towards a neoplastic phenotype in patients infected by Helicobacter pylori

Helicobacter pylori is a definite carcinogen whose mechanism of action is still unknown. The aim of this work was (1) to determine the presence of p53 protein and related antibodies in patients affected by various gastric pathologies and chronically infected with H. pylori, and (2) to try to discover a test to be used as a marker of a possible switch towards a neoplastic phenotype.

Clinical significance of circulating anti-p53 antibodies in European patients with hepatocellular carcinoma

p53 alterations are considered to be predictive of poor prognosis in hepatocellular carcinoma (HCC) and may induce a humoral response. Anti-p53 serum antibodies were assessed by enzyme-linked immunosorbent assay (ELISA) using purified recombinant human p53 on 130 European HCC patients before treatment and during the clinical course of the disease. p53 immunohistochemistry was performed on tumours from the 52 patients who underwent surgery, and DNA sequencing analysis was initiated when circulating anti-p53 antibodies were detected. Nine (7%) HCC patients had anti-p53 serum antibodies before treatment. During a mean period of 30 months of follow-up, all the negative patients remained negative, even when recurrence was observed. Of the nine positive patients, eight were still positive 12-30 months after surgery. The presence of anti-p53 serum antibodies was correlated neither with mutation of the p53 gene nor the serum alpha-fetoprotein levels and clinicopathological characteristics of the tumours. However, a greater incidence of vascular invasion and accumulation of p53 protein were observed in the tumours of these patients (P<0.03 and P<0.01 respectively) as well as a better survival rate without recurrence (P = 0.05). In conclusion, as was recently shown in pancreatic cancer, anti-p53 serum antibodies may constitute a marker of relative 'good prognosis' in a subgroup of patients exhibiting one or several markers traditionally thought to be of bad prognosis.

Serum antibodies against p53 in relation to cancer risk and prognosis in breast cancer: a population-based epidemiological study

To perform an epidemiological evaluation of the predictive value of p53 autoantibodies in breast cancer, we measured antibodies against p53 in serum samples from 165 breast cancer patients in comparison with serum samples from 330 healthy controls, selected from the same population as the cases and matched for age, sex and specimen storage time. Median age of patients was 51 years (range 25-64 years). Presence of serum p53 autoantibodies was analysed by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blotting. The lower ELISA reactivities were similar for cases and controls, but presence of high-level reactivity was more common among cases than among controls [odds ratio (OR) 9.03, 95% confidence interval (CI) 2.40-50.43]. Presence of Western blot-detected p53 autoantibodies had a very similar association (OR 10.8, CI 3.0-59.4). Among the cases, we also studied whether there was any correlation between level of anti-p53 antibodies and stage of the disease or survival. There was no significant correlation between presence of antibodies and stage of the disease. There was a significant negative correlation between presence of p53 antibodies and survival (P = 0.003). A stepwise multivariate Cox regression analysis showed that T-stage, age and presence of anti-p53 antibodies were significant independent prognostic variables, with a dose-dependent negative effect on survival for all three variables. We conclude that presence of anti-p53 antibodies are of significance both for the risk of having breast cancer and the risk of dying from breast cancer.

Humoral immune response to p53 in malignant glioma

p53 immunoreactivity and humoral immune response to p53 were examined in 14 patients with malignant glioma, including 4 patients with leptomeningeal glioma cell dissemination. Twelve patients expressed p53 protein within the tumour tissue. p53 antibodies were detected in the serum in 2 of 14 patients but never in the cerebrospinal fluid (CSF). Soluble p53 protein was detected neither in serum nor in CSF of the glioma patients. CSF levels of the immunosuppressive cytokine, transforming growth factor (TGF)-beta, were elevated in the glioma patients, including those with a humoral response to p53. These preliminary findings raise the possibility of systemic humoral immune responses to antigens, including mutant p53, expressed by glioma cells in the central nervous system.

Molecular markers of carcinogenesis

The protein products of oncogenes and tumor suppressor genes play critical roles in the development of many cancers. The expression of a number of these proteins can be detected in extracellular fluids such as blood. This article reviews the literature on the application of methods for the detection of the proteins of oncogenes and tumor suppressor genes in the blood of humans with cancer or at risk for the development of cancer. The detection of these proteins in blood may be useful molecular markers of carcinogenesis that could play an important part in cancer diagnosis, prognosis, and prevention.