The Combination of the Selective Cyclooxygenase-2 Inhibitor Celecoxib with Weekly Paclitaxel Is a Safe and Active Second-Line Therapy for Non-Small Cell Lung Cancer

PURPOSE

The selection of effective schedules of treatment for metastatic non-small cell lung cancer still remains a challenge for the oncologist. The present multicentric phase II study was designed in order to investigate the activity and safety of the combination of weekly paclitaxel and celecoxib as second-line treatment for non-small cell lung cancer. As a secondary endpoint, the possible correlation of biomarkers with objective response was investigated in a subset of patients.

PATIENTS AND METHODS

Patients with platinum-refractory non-small cell lung cancer and Eastern Cooperative Oncology Group performance status 0-2 entered the present phase II study. Paclitaxel was administered at the dose of 80 mg/m(2) i.v. weekly for 6 weeks, followed by a 2-week rest, and celecoxib, 400 mg p.o. b.i.d. administered continuously. A cycle consisted of 8 weeks of treatment. Determination of circulating vascular endothelial growth factor and interleukin 6 was performed at baseline and every two cycles.

RESULTS

Fifty-eight patients were enrolled: median age, 60 years (range, 30-77 years); male/female ratio = 44/14; performance status, 0, 31 patients; 1, 25 patients; and 2, two patients. Predominant histotype was adenocarcinoma (34 cases), and most patients had at least two sites of disease. According to the intent-to-treat analysis, 14/58 objective responses (24.1%) and 24/58 (41.3%) stabilizations of disease were observed, with a median duration of 4 months (range, 2-22+ months) and 5 months (range, 1-13 months), respectively. Median time to progression and median overall survival were 5 and 11 months, respectively. One-year survival was 42.5%. The main toxicity was neuropathy (4% of grade 3). Preliminary results suggest that decrease in serum vascular endothelial growth factor level is significantly associated with clinical response.

DISCUSSION

Combination of celecoxib and weekly paclitaxel is safe and active new regimen in pretreated non-small cell lung cancer. Toxicity appears not to be worsened by the addition of celecoxib. According to preliminary results, serum vascular endothelial growth factor level seems to be predictive of response, suggesting that it should be further investigated as a surrogate marker of response.

Modification of nucleic acid levels per mitochondrion induced by thyroidectomy or triiodothyronine administration

The authors have determined the liver mitochondrial population (number of mitochondria/nucleus) in young rats, which has been thyroidectomized (T) or thyroidectomized and subsequently treated with triiodothyronine (T3). They have observed that thyroidectomy decreased such a population to 72.3% with respect to the normal one, while the T3 administration (at the dose of 10 mug/100 g body weight every second day, from day 50 to day 60 of age) restored the mitochondria number to 81.8% of normal ones. The average levels of proteins per mitochondrion were 8.90 X 10(-13) g in the liver of normal 60-day-old rats. This content was doubled in T rats of the same age while the levels of nucleic acids or the nucleic acid polymerase activities per mitochondrion were enhanced, notwithstanding that the specific values (referred to mg mitochondrial protein) decreased. The T3 administration severely lowered the content of protein per mitochondrion, and this may indicate that thyroid hormones control the normal assemblage of mitochondrial protein.

Urinary reference ranges and exposure profile for lithium among an Italian paediatric population

The aims of the present study were to establish reference values useful in monitoring Lithium (Li) treatment and to trace environmental Li exposure profiles in paediatric age. A cross-sectional study was conducted on a group of healthy Italian children aged 5-11. Data on possible predictors were assessed through a questionnaire, and Li levels in morning and evening urinary samples were determined by ICP-MS technique. The reference intervals for the evening and morning samples were respectively 3.8-51.9μgL^-1 or 5.6-60.6μgg^-1 creatinine and 4.8-71.7μgL^-1 or 4.8-73.2μgg^-1 creatinine. Urinary Li levels showed a significantly inverse correlation with age and a positive correlation with urinary creatinine in both the evening and morning samples. No other studied variables influenced Li urinary excretion. These results, obtained using a readily available matrix as urine, can be useful for both environmental research and Li treatment monitoring.

Quantitative measurement of soluble cytokeratin fragments in tissue cytosol of 599 node negative breast cancer patients: a prognostic marker possibly associated with apoptosis

Apoptosis is associated with caspase-mediated proteolysis of Type I (K18 and K19) cytokeratins. We previously showed a positive association between the levels of tissue polypeptide antigen (TPA), that recognizes cytokeratins K8, K18, and K19 fragments, and induced apoptosis in breast cancer cell lines. The aim of the present study was to evaluate the interrelationships between TPA, steroid receptors, and p53, and their joint prognostic role in node-negative breast cancer patients not treated with adjuvant therapies. Age and pT were also considered since they are known prognostic factors. Five hundred and ninety-nine cases with N- breast cancer were evaluated (median follow-up: 60 months). TPA was measured by an immunoradiometric assay and p53 by an immunochemiluminescent assay in tumor cytosol. Multiple correspondence analysis was used to study the associations among variables. Their prognostic role (univariate analysis) and their joint effect (multivariate analysis) on RFS were investigated with Cox regression models. TPA showed a direct association with ER and PgR. Higher p53 values were weakly associated to low values of ER, PgR, and TPA. Younger age was related to low and intermediate values of ER and PgR and to low p53 values, while older age was related to high values of ER. Multivariate analysis showed a significant prognostic impact for pT, age, ER, and TPA. Among the interactions considered clinically relevant, only that between ER and age was found. RFS estimated values were poorer in cases with lower than in those with higher TPA values, both in patients expected to have a poor (pT2, young age, low ER) and a better prognosis (pT1, older age, high ER). From the findings of the present study we can draw the following conclusions: The relationship of TPA with prognosis gives an additional contribution to pT, age, and steroid receptors in N- breast cancer; TPA may be considered the first marker of apoptosis measured with a fully standardized quantitative method in tumor cytosol and could be evaluated in prognostic indexes including markers related to different biological mechanisms.

The Prognostic Value of Vascular Endothelial Growth Factor, Urokinase Plasminogen Activator and Plasminogen Activator Inhibitor-1 in Node-Negative Breast Cancer

The vascular endothelial growth factor (VEGF) and the plasminogen activator system play an essential role in solid tumor angiogenesis and in tumor invasion and metastasis. In the present study we investigated the relationship between patient outcome and levels of VEGF, urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) in tumor cytosols of 196 node-negative primary invasive breast cancer patients who did not receive any adjuvant therapy. The median follow-up was 65 months. VEGF, uPA and PAI-1 were measured by commercially available enzyme-linked immunosorbent assays. Cox's univariate analysis showed that pT (p=0.0007), uPA (p=0.0156) and PAI-1 (p=0.0015) had a significant impact on relapse-free survival, whereas VEGF did not have any prognostic value (p=0.18). Bivariate analysis showed significant interactions between uPA and PAI-1 (p=0.0035) and between VEGF and PAI-1 (p=0.006). Our study confirms that uPA and PAI-1 cytosol levels can be considered as prognostic factors for relapse-free survival in node-negative breast cancer. Moreover, the interaction between VEGF and PAI-1 warrants further investigation into the relationship between the biomarkers of angiogenesis and those of the protease cascade.

Experimental validation of specificity of the squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) assay in patients with cirrhosis

BACKGROUND

Squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) is a useful biomarker for the risk of development of hepatocellular carcinoma (HCC) in patients with cirrhosis due to its progressive increase associated to HCC evolution. In patients with cirrhosis, other assays have been affected by interfering reactivities of IgM. In this study, the analytical specificity of the SCCA-IgM assay was assessed by evaluating SCCA-IgM measurement dependence on different capture phases, and by measuring the recovery of SCCA-IgM reactivity following serum fractionation.

METHODS

Serum samples from 82 patients with cirrhosis were analyzed. SCCA-IgM was measured using the reference test (Hepa-IC, Xeptagen, Italy) that is based on rabbit oligoclonal anti-squamous cell carcinoma antigen (SCCA) and a dedicated ELISA with a mouse monoclonal anti-SCCA as the capture antibody.

RESULTS

SCCA-IgM concentrations measured with the reference assay (median value=87 AU/mL) were higher than those measured with the mouse monoclonal test (median value=78 AU/mL). However, the differences in the SCCA-IgM distribution were not statistically significant (p>0.05). When SCCA-IgM concentrations measured with both tests were compared, a linear correlation was found (r=0.77, p<0.05). Fractionation of the most reactive sera by gel-filtration chromatography showed that total recovery of SCCA-IgM reactivity was seen only in the fractions corresponding to components with a molecular weight higher than IgM and SCCA (>2000 kDa) with both tests.

CONCLUSIONS

The equivalence of both SCCA-IgM assays and the absence of reactivity not related to immune complexes support the analytical specificity of SCCA-IgM measurements. The results validate the assessment of SCCA-IgM for prognostic purposes in patients with cirrhosis.

Evaluation of Critical Differences of CEA and CA15.3 Levels in Serial Samples from Patients Operated for Breast Cancer

In the present investigation we evaluated the variability of tumor marker levels in the follow-up of patients without evidence of disease after resection of primary breast cancer. CEA and CA15.3 were measured using commercially available methods in serial blood samples collected from 170 patients. The coefficient of variation among all samples from each patient, which accounts for the total variability (analytical variability + biological variability), was widely scattered (from 4 to 99% for CEA; from 4 to 52% for CA15.3). The critical difference was calculated using the formula designed by Eraser [CD = 2.77. (CVa2 + CVb2)1/2]. It ranged from 11 to 276 for CEA and from 11 to 144 for CA15.3. From the present findings we conclude that:

1) it is possible to identify individually tailored decision criteria to evaluate tumor marker variations in the follow-up of breast cancer patients;

2) in a considerable number of cases the non-tumor-related variability is too high to allow the early identification of minor tumor marker variations that are of clinical relevance.

Serum CA549 in primary breast cancer: comparison with CA15.3 and MCA

We carried out a comparison of three commonly used mucin markers, CA549, CA15.3 and MCA. Serum samples from 184 healthy women and 237 patients with primary breast cancer were evaluated. The markers were measured using commercially available immunometric assays. Like CA15.3 and MCA, CA549 was significantly associated with tumour size and lymph node status, being an effective indicator of tumour bulk. CA549 was significantly correlated with both CA15.3 and MCA. Positive/negative concordance rate was very good (93.7%) between CA549 and MCA. Conversely, CA15.3 was positive and CA549 negative in 20.4% of cases. Axillary status was not significantly different in the latter group of patients and in cases in which CA15.3 and CA549 showed concordant results. From the present findings we draw the following major conclusions: 1. CA549 and MCA are highly correlated and their association should not provide additional information; however, they should not be considered interchangeable since they may behave differently in individual cases. 2. CA549 and CA15.3, although well correlated, are discordant in a significant number of cases. Longitudinal studies are needed to verify the usefulness of the association between the two markers. 3. The three evaluated mucin markers are not interchangeable in individual patients; if a patient is monitored with a marker, she should be followed up with the same marker.

The Usefulness of the Combination of Free CA 15.3 and CA 15.3-IGM Complexes for Breast Cancer Diagnosis

Background

Several studies have shown that the main circulating biomarkers of liver and colorectal cancer can be detected in the bloodstream and are also associated with immunoglobulin M to form stable complexes. These immune complexes show increased capacity of discrimination between cancer patients and healthy controls if combined with the free biomarker form. Within the context of the Project FIRB 2003 - Nanosized Cancer Polymarker Biochip - we wanted to investigate if IgM complexes have importance also in breast cancer. We focused our study on the immune complexes between IgM and CA 15.3 because free CA 15.3 is the most commonly used breast cancer biomarker in clinical practice. However, this biomarker alone lacks satisfactory sensitivity especially in early cancer detection.

Aim

The aim of our study was to assess the occurrence of immune complexes between CA 15.3 and IgM in sera from patients with primary breast cancer and in sera from healthy controls to evaluate its putative diagnostic value compared with the diagnostic value of free CA 15.3.

Methods

A total of 130 serum samples were obtained from 56 healthy women (mean age±SD, 45±8.23 years) and 74 women with stage l and II breast cancer (mean age±SD, 59±13.6 years) before any treatment, either surgical or chemo-therapeutic. Serum samples were collected, aliquoted and stored at-80°C in the centralized biobank of the project according to very stringent standard operating procedures (SOPs) distributed by the coordinating unit. To evaluate the presence of CA 15.3-lgM immune complexes, we developed and validated a novel enzyme-linked immunosorbent assay (ELISA) with a polyclonal rabbit anti-human CA 15.3 antibody (Abcam) as the catcher antibody. CA 15.3-lgM was detected with peroxidase-conjugated anti-human IgM and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydrogen peroxide as substrate (Sigma Aldrich, Italy). The levels of CA 15.3-lgM were expressed in arbitrary units per mL (AU/mL) by interpolation on a calibration curve obtained by serial dilution of a reference calibrator purified by gel filtration chromatography from a pool of serum samples with high levels of CA 15.3-lgM. Serum levels of free CA 15.3 were assessed in parallel on each sample using an automated immunoassay system (ADVIA Centaur-Siemens Diagnostics) and expressed in U/mL.

Results

To discriminate between cancer patients and healthy controls, we used as cutoff values 31.5 U/mL for free CA 15.3 (corresponding to the cutoff used in the clinical routine) and 794 AU/mL for CA 15.3-lgM (representing the 95th percentile of the distribution of serum levels of CA 15.3-lgM in healthy controls). By using these cutoff values, we obtained a sensitivity of 1 0% (7/74 cases) and a specificity of 95% (53/56 controls) for CA 15.3-lgM. The sensitivity and specificity of free CA15.3 were 7% (5/74 cases) and 1 00% (56/56 controls), respectively. Interestingly, the serum levels of the two biomarkers did not overlap, so their combination at 95% specificity identified 12/74 cases (16.2%). When we took a cutoff of 22 U/ mL for free CA15.3 (the 95th percentile of its distribution in healthy controls), we calculated a sensitivity of 26% (1 9/74 cases) and a specificity of 95% (53/56 controls); its combination with CA 15.3-lgM had a sensitivity of 34% (25/74 cases) and a specificity of 90% (50/56 controls).

Conclusions

These results demonstrate for the first time the presence of CA 15.3-lgM in the bloodstream of patients with breast cancer. In addition, our data suggest that CA 15.3-lgM is a complementary serological marker to free CA 15.3 and the combination of these biomarkers could improve the diagnosis of breast cancer.

Biochemical parameters for prognostic evaluation in patients with breast cancer

We evaluated the prognostic value of tissue polypeptide antigen (TPA), cathepsin D and pS2 in 267 patients operated for primary breast cancer. Cathepsin D, pS2 and cytosol TPA were independent of each other and of N, T, estrogen (ER) and progesterone (PgR) receptors. Cathepsin D was the best prognostic indicator for disease-free survival and pS2 for overall survival. The simultaneous evaluation of the three parameters was an effective discriminator between high and low risk patients in both N- and N+. Considering that cathepsin D, pS2 and cytosol TPA can be easily measured with reliable methods in small amounts of tissue, we conclude that they are a promising panel of biochemical parameters suitable for the assessment of the risk of relapse in patients with breast cancer.

Osteopontin-Igm as a Marker for the Diagnosis of Hepatocellular Carcinoma

Introduction

Biomarkers for early hepatocellular carcinoma (HCC) detection are still a clinical need. Recent data indicate that cancer-associated antigens lead to the formation of circulating IgM-linked immune complexes as the result of natural IgM production by the innate immune response. The SCCA-IgM immune complex has already been described for primary liver cancer detection. Osteopontin (OPN) is a member of the SIBLING family of proteins recently shown to be related to tumorigenesis, progression and metastasis in various cancer types.

Aim

To evaluate the serum levels of the OPN-IgM complex in comparison to the SCCA-IgM complex in patients with HCC.

Patients

A total of 256 patients were analyzed including 151 patients with HCC (M/F 115/36; mean age ± SD: 67 ± 12 years) and 106 patients with cirrhosis (M/F 68/38; mean age ± SD: 62 ± 12 years). HCC, tested before any therapeutic approach, was mainly of viral etiology (58% HCV, 11% HBV), while alcohol abuse (22%) was the main risk factor for the remaining cases. A similar distribution was found in patients with cirrhosis (46% HCV, 15% HBV, 38% alcohol).

Methods

Serum levels of OPN-IgM were measured using a homemade ELISA assay with a polyclonal anti-human OPN antibody (Biodesign Int, USA). SCCA-IgM was detected in serum using an ELISA assay kit (Hepa-IC, Xeptagen).

Results

OPN-IgM was positive in 64/151 (42%) patients with HCC and in 45/106 (42%) patients with cirrhosis (specificity 58%), while the reference biomarker SCCA-IgM showed 35% sensitivity (49/139) and 71 % specificity. When patients were stratified on the basis of etiology, the sensitivity values for OPN-IgM and SCCA-IgM were 51% vs 44% in HCV patients, and 36% vs 23% in the other patients, while the specificity was lower for OPN-IgM (55% vs 69% in HCV patients; 62% vs 72% in the other patients). Combination of the two biomarkers resulted in an increase in sensitivity to 63% for viral etiology and to 40% for nonviral etiology.

Conclusion

Different IgM-linked biomarkers are detectable in primary liver cancer. OPN-IgM and SCCA-IgM showed a similar behavior, while the combination of these biomarkers increased the diagnostic performance for primary liver cancer.

Epidermal growth-factor receptors and erbb2 protein expression in esophageal cancer and normal mucosa

The epidermal growth factor receptor (EGFr) and the erbB2 protein (p185) concentrations were assessed in 31 esophageal cancer specimens and in the corresponding normal mucosa, in order to investigate the possible links with the main clinical and pathological parameters. Detectable and high affinity EGFr was found in 27/31 cancer and in 18/31 normal tissue samples. EGFr concentrations were not significantly different between cancer and normal tissue, although a trend toward higher levels in cancer was found. No relationships were found with histologic type, tumor bulk, lymph node status, pathologic stage, ploidy and type of surgical resection. A significant negative correlation between EGFr levels and overall survival was found. Detectable levels of p185 were found in all the tissues examined, but the expression was higher in adenocarcinoma than in squamous cell carcinoma samples. The EGFr role in malignant transformation still has to be established, but the determination could be of clinical use. As for p185, its role in the onset of esophageal cancer could be confined to the subgroup of the adenocarcinomas.

Detection of different estrogen receptor forms in breast cancer cytosol by enzyme immunoassay

Estrogen receptors (ER) are routinely measured in tissue extracts from breast cancer using a radioligand binding assay (RBA) and an enzyme immunoassay (EIA). Although good correlation was found between the two methods, they are expected to measure, at least in part, different ER amounts in individual samples, because the RBA should detect unfilled ER only, whereas EIA should recognize both unfilled receptors and those filled by endogenous estrogens. The purpose of the present investigation was to evaluate if ER-EIA mainly detects ER filled by endogenous estrogens when using an estrogen-free buffer to dilute cytosol samples. Indeed, the commercially available EIA assay kit (ER-EIA; Abbott) is equipped with a sample dilution buffer containing a high concentration of 17beta-estradiol which should allow for the saturation of all the ERs. ER was measured in 57 cytosol samples from primary breast cancer with RBA and ER-EIA. In the latter case, samples were diluted using both the estradiol-rich dilution buffer of the kit and an estrogen-free low salt phosphate buffer. RBA and ER-EIA showed tightly correlated results. However, ER-EIA detected higher ER levels than RBA in the majority of cases. Results obtained by low salt ER-EIA were also correlated to both RBA and ER-EIA, showing, however, lower ER concentrations. ER levels measured by ER-EIA were not significantly different from the sum of ER concentrations found by RBA and low salt ER-EIA. These findings suggest that ER-EIA detects ER only in the conformational status that is achieved after saturation by estrogens. These findings were confirmed by sedimentation shift experiments, which showed that the monoclonal antibody D547 used in the kit binds ER in the occupied form only. This leads to the conclusion that ER-EIA detects functioning (in terms of binding with estradiol) ERs. From the present investigation, we suggest that it is possible and probably worthwhile to optimize the EIA method by using different buffers to measure: (a) the total number of ERs capable of binding estradiol; (b) the ER filled by endogenous estrogens; and (c) by difference, the unfilled ER concentrations.

[Use of radioisotope technics for determination of thyroid hormones. Research on blood and urine]

At first the AA. present the recent progresses reached in the Endocrinology diagnostic with the aid of the radioisotopic techniques; successively they refer about the principles regulating the chemical reactions used in the dosage of the single hormones and about the use of index interesting the clinical practice. The AA. compare the methods of dosage used in the kits of various firms outlining the problems concerning the technological times, the operations number, the contamination risk. They performed several control tests on the T3 RIA, recently introduced into the clinical diagnostic, on the calibration curve, on the repeatibility of the results, on the recovery tests, on the sensitivity of the tarature curve, showing the normal and abnormal values obtained in their hospital. They refer moreover on the results obtained dosing together on the same samples T4, TBC, ETR, T3, RIA, TSH and on the clinical utility of the single tests. Several dosages of T3 and of T4 were effected on urine to have informations on the urinary excretion levels of the thyroid hormones in normal and abnormal subjects. At last they hypothesize the use of the hormonal urinary values and the plasmatic ones for calculating an ormonal thyroid clearance.

Validation of blood collection procedures for the determination of circulating vascular endothelial growth factor (VEGF) in different blood compartments

AIMS OF THE STUDY

Studies on circulating VEGF have reported mixed results, possibly due to a lack of standardization of the pre-analytical phase. The aim of our investigation was to standardize the sampling procedure for the determination of VEGF in different blood fractions.

BASIC PROCEDURES

We evaluated various clotting times for obtaining serum in 30 subjects, as well as different procedures for the preparation of plasma Edinburgh anticoagulant mixture (EDTA, PGE1, theophylline) and CTAD. VEGF was also assayed in lysed whole blood. In vitro platelet activation was monitored by measuring the levels of PF4. VEGF and PF4 were measured using commercially available enzyme-linked immunoassays.

MAIN FINDINGS

Clotting time increased the release of VEGF, which reached a plateau between 2 and 4 hours. The percent increase of VEGF at 2 hours ranged from 118% to 4,515% (median 327%) compared to samples centrifuged within 10 min from withdrawal. VEGF was not different and PF4 was very low or undetectable in Edinburgh plasma and CTAD plasma, while it was significantly higher in sodium citrate plasma. VEGF in CTAD plasma was not correlated with platelet count or leukocytes. Serum VEGF did not correlate with the leukocyte number, but it correlated significantly with the platelet count.

PRINCIPAL CONCLUSIONS

The procedures for sample collection described above are highly standardized and easy to perform in a routine setting. We therefore suggest systematic evaluation of VEGF in CTAD plasma, in serum (clotting for 2 hours at room temperature) and in whole blood, until prospective controlled clinical studies will have clarified in which blood compartment(s) VEGF provides clinically relevant information.

Evaluation of the Analytical Specificity of SCCA-IGM Assay for Monitoring Patients with Cirrhosis

Background and aim

An increasing number of clinical data suggests the importance of the assessment of serum levels of the squamous cell carcinoma antigen (SCCA)-lgM immune complex for the diagnosis of hepatocellular carcinoma (HCC). In addition, monitoring of SCCA-IgM immune complexes has been described as a useful prognostic approach in patients with cirrhosis since the progressive increase of SCCA-IgM over time is associated with a higher risk of HCC development. Because other assays in patients with cirrhosis have been affected by interfering IgMs, the aim of the present study was to assess the specificity of SCCA-IgM reactivity in cirrhotic patients by evaluating SCCA-IgM detection dependence on different capturing phases and by measuring the recovery of SCCA-IgM reactivity after serum fractionation.

Patients and methods

Serum samples from 82 patients with cirrhosis (M/F ratio 3/1; mean age ± SD: 56 ± 9 years) were collected at the Liver Unit of the Department of Clinical and Experimental Medicine, University of Padua, according to the approved institutional procedures. Serum levels of SCCA-IgM were measured using two different ELISA tests: the reference assay based on a rabbit oligoclonal anti-human SCCA antibody (Hepa IC, Xeptagen, Italy) and a dedicated ELISA with a mouse monoclonal anti-SCCA as capture antibody.

Results

Serum levels of SCCA-IgM measured with the reference assay (median value 87 AU/mL) were higher than levels measured with the mouse monoclonal test (median value 78 AU/mL), but the differences were not statistically significant (Mann-Whitney U test, p>0.05). When SCCA-IgM levels measured with both tests were compared, a linear correlation was found (r = 0.77, p < 0.001). An in silico analysis using available structural data of SCCA showed the presence of up to three putative antigenic sites localized on the SCCA surface, thus providing evidence that the test with the mouse monoclonal anti-SCCA antibody could underestimate the total circulating immune complexes due to the steric hindrance of the enormous mass of IgM (900 kDa) that could mask on the SCCA (45 kDa) surface the binding site recognized by the monoclonal antibody. To show that the SCCA-IgM assay was not affected by interfering IgMs, we measured the recovery of SCCA-IgM reactivity after serum fractionation of ten of the most reactive samples in both assays. Total recovery of SCCA-IgM reactivity was obtained with both assays in the fractions corresponding to components with higher molecular weight than IgM and SCCA (>2000 kDa).

Conclusions

The results of this study indicate that the reactivity measured in cirrhotic patients is related only to SCCA-IgM immune complexes and is not affected by other serum components, supporting the analytical specificity of the SCCA-IgM assay and validating the importance of SCCA-IgM as a risk biomarker for HCC development.