'Low' faecal immunochemical test (FIT) colorectal cancer: a 4-year comparison of the Nottingham '4F' protocol with FIT10 in symptomatic patients

AIM

The aim of this work was to evaluate colorectal cancer (CRC) outcomes after 'low' (sub-threshold) faecal immunochemical test (FIT) results in symptomatic patients tested in primary care.

METHOD

This work comprised a retrospective audit of 35 289 patients with FIT results who had consulted their general practitioner with lower gastrointestinal symptoms and had subsequent CRC diagnoses. The Rapid Colorectal Cancer Diagnosis pathway was introduced in November 2017 to allow incorporation of FIT into clinical practice. The local '4F' protocol combined FIT results with blood tests and digital rectal examination (DRE): FIT, full blood count, ferritin and finger [DRE]. The outcome used was detection rates of CRC, missed CRC and time to diagnosis in local 4F protocols for patients with a subthreshold faecal haemoglobin (fHb) result compared with thresholds of 10 and 20 μg Hb/g faeces.

RESULTS

A single threshold of 10 μg Hb/g faeces identifies a population in whom the risk of CRC is 0.2%, but this would have missed 63 (10.5%) of 599 CRCs in this population. The Nottingham 4F protocol would have missed fewer CRCs [42 of 599 (7%)] despite using a threshold of 20 μg Hb/g faeces for patients with normal blood tests. Subthreshold FIT results in patients subsequently diagnosed with a palpable rectal tumour yielded the longest delays in diagnosis.

CONCLUSION

A combination of FIT with blood results and DRE (the 4F protocol) reduced the risk of missed or delayed diagnosis. Further studies on the impact of such protocols on the diagnostic accuracy of FIT are expected. The value of adding blood tests to FIT may be restricted to specific parts of the fHb results spectrum.

Sociodemographic variations in the uptake of faecal immunochemical tests in primary care: a retrospective study

BACKGROUND

Faecal immunochemical test (FIT) usage for symptomatic patients is increasing, but variations in use caused by sociodemographic factors are unknown. A clinical pathway for colorectal cancer (CRC) was introduced in primary care for symptomatic patients in November 2017. The pathway was commissioned to provide GPs with direct access to FITs.

AIM

To identify whether sociodemographic factors affect FIT return in symptomatic patients.

DESIGN AND SETTING

A retrospective study was undertaken in Nottingham, UK, following the introduction of FIT as triage tool in primary care. It was mandated for all colorectal referrals (except rectal bleeding or mass) to secondary care. FIT was used, alongside full blood count and ferritin, to stratify CRC risk.

METHOD

All referrals from November 2017 to December 2021 were retrospectively reviewed. Sociodemographic factors affecting FIT return were analysed by multivariate logistic regression.

RESULTS

A total of 35 289 (90.7%) patients returned their index FIT, while 3631 (9.3%) did not. On multivariate analysis, males were less likely to return an FIT (odds ratio [OR] 1.11, 95% confidence interval [CI] = 1.03 to 1.19). Patients aged ≥65 years were more likely to return an FIT (OR 0.78 for non-return, 95% CI = 0.72 to 0.83). Unreturned FIT more than doubled in the most compared with the least deprived quintile (OR 2.20, 95% CI = 1.99 to 2.43). Patients from Asian (OR 1.82, 95% CI = 1.58 to 2.10), Black (OR 1.21, 95% CI = 0.98 to 1.49), and mixed or other ethnic groups (OR 1.29, 95% CI = 1.05 to 1.59) were more likely to not return an FIT compared with patients from a White ethnic group. A total of 599 (1.5%) CRCs were detected; 561 in those who returned a first FIT request.

CONCLUSION

FIT return in those suspected of having CRC varied by sex, age, ethnic group, and socioeconomic deprivation. Strategies to mitigate effects on FIT return and CRC detection should be considered as FIT usage expands.

Faecal immunochemical testing reduces demand and improves yield of Leicester's 2-week pathway for change in bowel habit

AIM

We look at the effect of introducing the faecal immunochemical test (FIT) in the straight-to-test 2-week pathway for change in bowel habit (CIBH).

METHOD

The FIT in primary care triages 2-week wait (2WW) colorectal referrals for patients aged 60 years and above for straight-to-test CT colonography (CTC). We compare the impact of the FIT on numbers of 2WW CTCs, in the year before and after FIT, in both colorectal cancer (CRC) detection and cost-effectiveness at both 4 μg Hb/g faeces and 10 μg Hb/g faeces.

RESULTS

At a threshold of 4 μg Hb/g faeces, the positive predictive value of the FIT for diagnosis of CRC is 5.0% with a negative predictive value of 99.8% and a polyp detection rate of 25.5%. The introduction of the FIT resulted in a reduction in the number of CTCs performed through the CIBH pathway from a mean of 143.9 per month prior to the FIT to 66.8 CTCs per month once the FIT was well established. Given a FIT threshold of 10 μg Hb/g the number of CTCs would be predicted to fall by 70.4% to 42.6 CTCs per month resulting in higher CRC and polyp detection rate, and an estimated annual cost saving of £238 258 in our institution.

CONCLUSION

The FIT use in primary care improves the yield of 2WW referrals for CIBH alone and reduces the burden and cost of investigations to exclude CRC. Improvements may be possible by increasing the cut-off employed, without adversely affecting the risk of missing a cancer.

A Poisson scaling approach to backward wave propagation in a tube

A mathematical analysis of wave propagation along an elastic cylindrical tube is presented, with the aim of determining the range of Poisson's ratio for which backward wave propagation (i.e. at negative group velocity) can occur near the ring frequency. This range includes zero Poisson's ratio and a surrounding interval of positive and negative values, whose width depends on the thickness of the tube. The whole range of Poisson's ratio is considered, so that the work applies to modern materials, e.g. composites. All results are presented in simple analytic form by means of a dominant balance in parameter space. The identification of this balance, which is unique, is a main new result in the paper, which makes possible a new type of shell theory based on 'Poisson scaling'. The mathematical approach is deductive from the equations of motion, rather than being based on kinematic hypotheses. A key finding, accessible via the Poisson scaling, is that the regime of negative group velocities extends to high wavenumbers, while being confined to a narrow band of frequencies. Thus responses localized in space are possible for near-monochromatic forcing, an important fact for nonlinear theories of tube dynamics near the ring frequency. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 1)'.

Abstract 5405: Expression of cathepsin D in early-stage breast cancer and its prognostic and predictive value

Purpose: Cathepsin D is a proteolytic enzyme that is normally localized in the lysosomes and is involved in the malignant progression of breast cancer. The expression of Cathepsin D is regulated by steroid hormones including oestrogen and growth factors. There are conflicting results between different studies regarding Cathepsin D significance as prognostic and predictor marker in breast cancer. Furthermore, Cathepsin D has not been recommended for clinical use by the American Society of Clinical Oncology because of insufficient evidence. This study was aimed to fill the gap in the lack of recent and large studies on prognostic significance of Cathepsin D expression by studying a large well-characterized series of primary breast cancer for cathepsin D expression using immunohistochemistry.

Methods: Expression of Cathepsin D was assessed by immunohistochemical staining of tissue microarrays, in a large well-characterized series of early-stage operable breast cancer (n=954) from Nottingham Primary Breast Carcinoma Series between the period of 1988 and 1998 who underwent primary surgery. Correlation of cathepsin D expression with clinicopathological parameters and prognosis was evaluated.

Results: Cathepsin D expression was positive in 28.8% (275/954) of breast cancer tumors. Positive expression of cathepsin D was significantly associated with high histological grade (p=0.007), pleomorphism (p=0.002), poor Nottingham Prognostic Index score (NPI) (p<0.002), recurrence (p=0.005) and distant metastasis (p<0.0001). Kaplan-Meier analysis showed that Cathepsin D expression was significantly associated with shorter breast cancer specific survival (BCSS) (p=0.001), higher risk of recurrence (p=0.001) and distant metastasis (p<0.0001). Cathepsin D positive tumors with ER positive staining who were treated with tamoxifen were associated with lower BCSS and higher risk of developing distant metastasis (p=0.001).

Conclusion: This study shows Cathepsin D expression as a promising prognostic biomarker for early operable invasive breast cancer. Our results indicate that Cathepsin D expressing tumors are associated with shorter breast cancer specific survival and higher risk of recurrence and metastasis. Cathepsin D could be clinically useful to predict response to tamoxifen treatment. Targeting Cathepsin D either through inhibition of action or interference with the proteolytic pathway could be used to treat metastatic breast cancers expressing Cathepsin D.

Citation Format: Inas M. Alhudiri, Christopher C. Nolan, Ian O. Ellis, Emad A. Rakha, Adam Elzagheid, Andrew R. Green, Caroline J. Chapman. Expression of cathepsin D in early-stage breast cancer and its prognostic and predictive value [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5405.

Faecal immunochemical testing and blood tests for prioritization of urgent colorectal cancer referrals in symptomatic patients: a 2-year evaluation

BACKGROUND

A novel pathway incorporating faecal immunochemical testing (FIT) for rapid colorectal cancer diagnosis (RCCD) was introduced in 2017. This paper reports on the service evaluation after 2 years of pathway implementation.

METHODS

The RCCD protocol was based on FIT, blood results and symptoms to stratify adult patients in primary care. Two-week-wait (2WW) investigation was indicated for patients with rectal bleeding, rectal mass and faecal haemoglobin (fHb) level of 10 µg Hb/g faeces or above or 4 µg Hb/g faeces or more in the presence of anaemia, low ferritin or thrombocytosis, in all other symptom groups. Patients with 100 µg Hb/g faeces or above had expedited investigation . A retrospective audit of colorectal cancer detected between 2017 and 2019 was conducted, fHb thresholds were reviewed and critically assessed for cancer diagnoses.

RESULTS

In 2 years, 14788 FIT tests were dispatched with 13361 (90.4 per cent) completed returns. Overall, fHb was less than 4 µg Hb/g faeces in 9208 results (68.9 per cent), 4-9.9 µg Hb/g in 1583 (11.8 per cent), 10-99.9 µg Hb/g in 1850 (13.8 per cent) and 100 µg Hb/g faeces or above in 720 (5.4 per cent). During follow-up (median 10.4 months), 227 colorectal cancers were diagnosed. The cancer detection rate was 0.1 per cent in patients with fHb below 4 µg Hb/g faeces, 0.6 per cent in those with fHb 4-9.9 µg Hb/g faeces, 3.3 per cent for fHb 10-99.9 µg Hb/g faeces and 20.7 per cent for fHb 100 µg Hb/g faeces or above. The detection rate in the cohort with 10-19.9 µg Hb/g faeces was 1.4 per cent, below the National Institute for Health and Care Excellence threshold for urgent referral. The colorectal cancer rate in patients with fHb below 20 µg Hb/g faeces was less than 0.3 per cent.

CONCLUSION

Use of FIT to "rule out" urgent referral from primary care misses a small number of cases. The threshold for referral may be adjusted with blood results to improve stratification .

Quantitative FIT stratification is superior to NICE referral criteria NG12 in a high-risk colorectal cancer population

BACKGROUND

Guidelines for urgent investigation of colorectal cancer (CRC) are based on age and symptom-based criteria. This study aims to compare the diagnostic value of clinical features and faecal immunochemical test (FIT) results to identify those at a higher risk of CRC, thereby facilitating effective triage of patients.

METHODS

We undertook a review of all patients referred for investigation of CRC at our centre between September 2016 and June 2018. Patients were identified using a prospectively recorded local database. We performed a logistic regression analysis of factors associated with a diagnosis of CRC.

RESULTS

One-thousand-and-seven-hundred-eighty-four patients with FIT results were included in the study. Change in bowel habit (CIBH) was the most common referring clinical feature (38.3%). Patients diagnosed with CRC were significantly older than those without malignancy (74.0 years vs 68.9 years, p = 0.0007). Male patients were more likely to be diagnosed with CRC than females (6.5% vs 2.5%, Chi-squared 16.93, p < 0.0001). CRC was diagnosed in 3.5% (24/684) with CIBH compared to 8.1% (6/74) with both CIBH and iron deficiency anaemia. No individual or combination of referring clinical features was associated with an increased diagnosis of CRC (Chi-squared, 8.03, p = 0.155). Three patients with negative FIT results (< 4 µg Hb/g faeces) were diagnosed with CRC (3/1027, 0.3%). The highest proportion of cancers detected was in the ≥ 100 µg Hb/g faeces group (55/181, 30.4%).

CONCLUSION

In a multivariate model, FIT outperforms age, sex and all symptoms prompting referral. FIT has greater stratification value than any referral symptoms. FIT does have value in patients with iron deficiency anaemia.

Choice of faecal immunochemical test matters: comparison of OC-Sensor and HM-JACKarc, in the assessment of patients at high risk of colorectal cancer

Objectives

Currently, NICE recommends the use of faecal immunochemical test (FIT) at faecal haemoglobin concentrations (f-Hb) of 10 μg Hb/g faeces to stratify for colorectal cancer (CRC) risk in symptomatic populations. This f-Hb cut-off is advised across all analysers, despite the fact that a direct comparison of analyser performance, in a clinical setting, has not been performed.

Methods

Two specimen collection devices (OC-Sensor, OC-S; HM-JACKarc, HM-J) were sent to 914 consecutive individuals referred for follow up due to their increased risk of CRC. Agreement of f-Hb around cut-offs of 4, 10 and 150 µg Hb/g faeces and CRC detection rates were assessed. Two OC-S devices were sent to a further 114 individuals, for within test comparisons.

Results

A total of 732 (80.1%) individuals correctly completed and returned two different FIT devices, with 38 (5.2%) CRCs detected. Median f-Hb for individuals diagnosed with and without CRC were 258.5 and 1.8 µg Hb/g faeces for OC-S and 318.1 and 1.0 µg Hb/g faeces for HM-J respectively. Correlation of f-Hb results between OC-S/HM-J over the full range was rho=0.74, p<0.001. Using a f-Hb of 4 µg Hb/g faeces for both tests found an agreement of 88.1%, at 10 µg Hb/g faeces 91.7% and at 150 µg Hb/g faeces 96.3%. A total of 114 individuals completed and returned two OC-S devices; correlation across the full range was rho=0.98, p<0.001.

Conclusions

We found large variations in f-Hb when different FIT devices were used, but a smaller variation when the same FIT device was used. Our data suggest that analyser-specific f-Hb cut-offs are applied with regard to clinical decision making, especially at lower f-Hb.

Neuronal antibody detection and improved lung cancer prediction in Lambert-Eaton myasthenic syndrome

Since approximately 50% of patients with Lambert-Eaton myasthenic syndrome (LEMS) subsequently develop small-cell lung cancer (SCLC), it is important to be able to predict cancer occurrence in these patients at neurological presentation. We aimed to determine whether circulating biomarkers were effective and objective predictors of cancer development in LEMS. We found that the presence of either SOX2, N-type voltage gated calcium channel or GABAb antibodies at LEMS diagnosis was highly sensitive (84%) and specific (87%) for the detection of SCLC. Screening for SOX2 and neuronal antibodies is a useful adjunct to clinical predictive scoring tools in predicting SCLC in LEMS.

Could stool collection devices help increase uptake in bowel cancer screening programmes?

Objective

To understand the usage and acceptability of a faecal collection device amongst participants in the National Health Service Bowel Cancer Screening Programme, with the aim of influencing future uptake.

Setting

Participants completing faecal occult blood test retests as part of the routine Bowel Cancer Screening Programme in Eastern England.

Methods

A faecal collection device and questionnaire were sent to all potential retest participants during a one-month period to collect information on prior stool collection methods and ease of use and usefulness of the enclosed faecal collection device.

Results

Out of 1087 participants invited, 679 (62.5%) returned their questionnaire. Of these, 429 (63.2%) trialled the faecal collection device at least once, 163 (38.4%) found the device made collecting their sample easier than previously, 189 (44.6%) found it made collection more difficult and 72 (17.0%) said it made no difference. Similar numbers reported finding that the faecal collection device made collecting the sample more pleasant (130, 31.5%), less pleasant (103, 25.0%) and no different (179, 43.4%) compared with previous collection without a faecal collection device.

Conclusion

Although a small proportion of participants found the faecal collection device helpful, a considerable majority did not or did not use it at all. Offering faecal collection devices is unlikely to produce a substantial increase in bowel cancer screening uptake.

Autoantibodies: Opportunities for Early Cancer Detection

Cancer cells can induce an immunological response resulting in the production of tumor-associated (TA) autoantibodies. These serum immunobiomarkers have been detected for a range of cancers at an early stage before the development of clinical symptoms. Their measurement is minimally invasive and cost effective using established technologies. TA autoantibodies are present in a clinically significant number of individuals and could supplement current screening modalities to aid early diagnosis of high-risk populations and assist the clinical management of patients. Here we review their production, discovery, and validation as biomarkers for cancer and their current and future potential as clinical tools.

Qualitative research in healthcare: an introduction to grounded theory using thematic analysis

In today's NHS, qualitative research is increasingly important as a method of assessing and improving quality of care. Grounded theory has developed as an analytical approach to qualitative data over the last 40 years. It is primarily an inductive process whereby theoretical insights are generated from data, in contrast to deductive research where theoretical hypotheses are tested via data collection. Grounded theory has been one of the main contributors to the acceptance of qualitative methods in a wide range of applied social sciences. The influence of grounded theory as an approach is, in part, based on its provision of an explicit framework for analysis and theory generation. Furthermore the stress upon grounding research in the reality of participants has also given it credence in healthcare research. As with all analytical approaches, grounded theory has drawbacks and limitations. It is important to have an understanding of these in order to assess the applicability of this approach to healthcare research. In this review we outline the principles of grounded theory, and focus on thematic analysis as the analytical approach used most frequently in grounded theory studies, with the aim of providing clinicians with the skills to critically review studies using this methodology.

A class of reduced-order models in the theory of waves and stability

This paper presents a class of approximations to a type of wave field for which the dispersion relation is transcendental. The approximations have two defining characteristics: (i) they give the field shape exactly when the frequency and wavenumber lie on a grid of points in the (frequency, wavenumber) plane and (ii) the approximate dispersion relations are polynomials that pass exactly through points on this grid. Thus, the method is interpolatory in nature, but the interpolation takes place in (frequency, wavenumber) space, rather than in physical space. Full details are presented for a non-trivial example, that of antisymmetric elastic waves in a layer. The method is related to partial fraction expansions and barycentric representations of functions. An asymptotic analysis is presented, involving Stirling's approximation to the psi function, and a logarithmic correction to the polynomial dispersion relation.

Serum autoantibody measurement for the detection of hepatocellular carcinoma

Background

Individuals with liver disease, and especially those with Hepatitis B or C, are at an increased risk of developing hepatocellular carcinoma (HCC) which is the third most common cause of cancer-related death worldwide. Inadequate screening tests largely account for presentation of advanced tumours and high mortality rates. Early detection of HCC amongst high-risk groups is paramount in improving prognosis. This research aimed to further characterise the previously described humoral immune response raised to tumour-associated antigens (TAAs) in the serum of patients with HCC.

Methods

Serum from 96 patients with confirmed HCC, 96 healthy controls matched for age and sex, 78 patients with confirmed liver cirrhosis and 91 patients with confirmed chronic liver disease were analysed for the presence of IgG autoantibodies raised to 41 recombinant TAAs/antigen fragments by ELISA.

Results

Varying autoantibody specificities (97–100%) and sensitivities (0–10%) were observed to individual TAAs. A 21-antigen panel achieved a specificity of 92% and sensitivity of 45% for the detection of HCC. This same panel identified 21% of 169 high-risk controls as having elevated autoantibody levels. A reproducible panel of 10 antigens achieved a specificity of 91% and sensitivity of 41% in HCC. 15% of 152 high-risk controls gave positive results with this panel.

Conclusions

This minimally invasive blood test has the potential to offer advantages over currently available tools for the identification of HCC amongst pre-disposed patients. Results are comparable to current gold standards in HCC (Ultrasonography) and to similar tests in other cancers (EarlyCDT-Lung).

Application of a high throughput method of biomarker discovery to improvement of the EarlyCDT(®)-Lung Test

BACKGROUND

The National Lung Screening Trial showed that CT screening for lung cancer led to a 20% reduction in mortality. However, CT screening has a number of disadvantages including low specificity. A validated autoantibody assay is available commercially (EarlyCDT®-Lung) to aid in the early detection of lung cancer and risk stratification in patients with pulmonary nodules detected by CT. Recent advances in high throughput (HTP) cloning and expression methods have been developed into a discovery pipeline to identify biomarkers that detect autoantibodies. The aim of this study was to demonstrate the successful clinical application of this strategy to add to the EarlyCDT-Lung panel in order to improve its sensitivity and specificity (and hence positive predictive value, (PPV)).

METHODS AND FINDINGS

Serum from two matched independent cohorts of lung cancer patients were used (n = 100 and n = 165). Sixty nine proteins were initially screened on an abridged HTP version of the autoantibody ELISA using protein prepared on small scale by a HTP expression and purification screen. Promising leads were produced in shake flask culture and tested on the full assay. These results were analyzed in combination with those from the EarlyCDT-Lung panel in order to provide a set of re-optimized cut-offs. Five proteins that still displayed cancer/normal differentiation were tested for reproducibility and validation on a second batch of protein and a separate patient cohort. Addition of these proteins resulted in an improvement in the sensitivity and specificity of the test from 38% and 86% to 49% and 93% respectively (PPV improvement from 1 in 16 to 1 in 7).

CONCLUSION

This is a practical example of the value of investing resources to develop a HTP technology. Such technology may lead to improvement in the clinical utility of the EarlyCDT--Lung test, and so further aid the early detection of lung cancer.

P4-08-03: Serum Autoantibodies to Breast Cancer Associated Antigens Reflect Tumor Biology: An Opportunity for Early Detection & Prevention?

Autoantibodies (AABs) are produced as an immune response to abnormal ('non-self') cancer antigens. Previous studies have reported that AABs can be measured in the blood long before cancers are presently diagnosed, e.g., up to 4 years before screening mammography identified breast cancers and up to 5 years before screening CT detected lung cancers. EarlyCDT™-Lung is currently available as an aid to early detection of lung cancer in high risk patients and measures a panel of seven AABs to general cancer antigens and also lung cancer (LC) specific antigens. These AABs have previously been reported to be associated with the two main types of LC i.e., non-small cell and small cell LC. This study looked at AABs to 4 general cancer antigens to evaluate whether their levels reflected different biology in primary breast tumors.

Methods

770 patients presented with primary breast cancer to three centers (Nottingham, UK n=323; Munich, Germany n=320; Oklahoma, USA n=127); the median ages and ranges were 61 (26-82), 61 (20-88) & 65 (54-84) years, respectively. All had serum samples taken post-diagnosis and pre-treatment. The tumors were well characterized for histological grade, estrogen receptor (ER), progesterone receptor (PgR) and HER2 status. Serum samples were tested for AABs to four generic cancer antigens(Ags) (p53, SOX2, NY-ESO-1 and Annexin1) originally included as part of Oncimmune's EarlyCDT™-Lung assay. The AABs were measured by ELISA on the Oncimmune platform, and the EarlyCDT™-Lung cutoffs were used to determine positivity.

Results

131/770 (17%) of primary breast cancers showed elevated AAB levels to one or more of the limited panel of four generic antigens. Positivity for each AAB was correlated with histological grade, ER, PgR and HER2 status. The results, which were similar for each of the three centres, were combined, and the results are shown in Table 1 below.

EarlyCDT-Lung: an immunobiomarker test as an aid to early detection of lung cancer

Recent publications have reported the technical and clinical validation of EarlyCDT-Lung, an autoantibody test which detected elevated autoantibodies in 40% of lung cancers at diagnosis. This manuscript reports the results of EarlyCDT-Lung run on four new (postvalidation) data sets. The following four cohorts of patients (n = 574) with newly diagnosed lung cancer were identified: group 1 (n = 122), 100% small cell lung cancer (SCLC); group 2 (n = 249), 97% non-small cell lung cancer (NSCLC); group 3 (n = 122), 100% NSCLC; group 4 (n = 81), 62% NSCLC. Serum samples were obtained after diagnosis, prior to any anticancer treatment. Autoantibody levels were measured against a panel of six tumor-related antigens (p53, NY-ESO-1, CAGE, GBU4-5, Annexin 1, and SOX2) in the EarlyCDT-Lung panel and previously established cutoffs applied. In groups 2, 3, and 4, patients were individually matched by gender, age, and smoking history to a control individual with no history of malignant disease. Assay sensitivity was tested in relation to cancer type and stage, and in the matched normals to demographic variables. The autoantibody panel showed sensitivity/specificity of 57%/n.d (not done) for SCLC in group 1, 34%/87% for NSCLC in group 2, 31% and 84% for NSCLC in group 3, and 35%/89% for NSCLC and 43%/89% for SCLC in group 4. There was no significant difference in positivity of EarlyCDT-Lung and different lung cancer stages. These studies confirm the value of an autoantibody assay, EarlyCDT-Lung, as an aid to detecting lung cancer in patients at high risk of the disease.

Immunobiomarkers in small cell lung cancer: potential early cancer signals

PURPOSE

We investigated the presence of autoantibodies as immunobiomarkers to a panel of tumor-associated antigens in a group of individuals with small cell lung cancer (SCLC), a disease group that has a poor overall cancer prognosis and therefore may benefit most from early diagnosis.

EXPERIMENTAL DESIGN

Sera from 243 patients with confirmed SCLC and normal controls matched for age, sex, and smoking history were analyzed for the presence of these early immunobiomarkers (i.e., autoantibodies to p53, CAGE, NY-ESO-1, GBU4-5, Annexin I, SOX2, and Hu-D) by ELISA.

RESULTS

Autoantibodies were seen to at least 1 of 6 antigens in 55% of all the SCLC patients' sera tested, with a specificity of 90% compared with controls. Using a higher assay cutoff to achieve a specificity of 99%, autoantibodies were still detectable in 42% of SCLC patients (receiver operator characteristic area under the curve = 0.76). There was no significant difference in sensitivity when analyzed by stage of the cancer or by patient age or gender. The frequency of autoantibodies to individual antigens varied, ranging from 4% for GBU4-5 to 35% for SOX2. Levels of Annexin I autoantibodies were not elevated in patients with SCLC. Antibodies were also detected in 4 separate patients whose sera were taken up to 3 months before tumor diagnosis.

CONCLUSION

The presence of an autoantibody to one or more cancer-associated antigens may provide an important addition to the armamentarium available to the clinician to aid early detection of SCLC in high-risk individuals.

Clinical validation of an autoantibody test for lung cancer

Background: Autoantibodies may be present in a variety of underlying cancers several years before tumours can be detected and testing for their presence may allow earlier diagnosis. We report the clinical validation of an autoantibody panel in newly diagnosed patients with lung cancer (LC).

Patients and methods: Three cohorts of patients with newly diagnosed LC were identified: group 1 (n = 145), group 2 (n = 241) and group 3 (n = 269). Patients were individually matched by gender, age and smoking history to a control individual with no history of malignant disease. Serum samples were obtained after diagnosis but before any anticancer treatment. Autoantibody levels were measured against a panel of six tumour-related antigens (p53, NY-ESO-1, CAGE, GBU4-5, Annexin 1 and SOX2). Assay sensitivity was tested in relation to demographic variables and cancer type/stage.

Results: The autoantibody panel demonstrated a sensitivity/specificity of 36%/91%, 39%/89% and 37%/90% in groups 1, 2 and 3, respectively, with good reproducibility. There was no significant difference between different LC stages, indicating that the antigens included covered the different types of LC well.

Conclusion: This assay confirms the value of an autoantibody panel as a diagnostic tool and offers a potential system for monitoring patients at high risk of LC.

Sequence analysis of immunoglobulin variable region genes that encode autoantibodies expressed by lymphomas of mucosa associated lymphoid tissue

Aim-To determine whether the immunoglobulin genes used by three gastric mucosa associated lymphoid tissue type lymphomas with known autoreactivity are mutated from germline as mutation from germline is an indicator of exposure to a mutational mechanism which characteristically acts on B cells as they undergo a follicle centre response.Methods-Cell lines established from two cases of MALT type lymphoma secrete autoantibodies recognising follicular dendritic cells (one case) and basement membrane (one case). The immunoglobulin heavy chain variable region genes (IgV(H)) and light chain variable region genes (IgV(L)) used by these cell lines, and the IgV(H) genes from a third case recognising human IgG were sequenced.Results-All three cases studied had mutated IgV(H) genes, while the IgV(L) genes were unmutated.Conclusion-The presence of mutations in IgV(H) genes is consistent with the origin of gastric MALT type lymphomas from B cells which have traversed the lymphoid follicle.

Technical validation of an autoantibody test for lung cancer

Background: Publications on autoantibodies to tumour-associated antigens (TAAs) have failed to show either calibration or reproducibility data. The validation of a panel of six TAAs to which autoantibodies have been described is reported here.

Materials and methods: Three separate groups of patients with newly diagnosed lung cancer were identified, along with control individuals, and their samples used to validate an enzyme-linked immunosorbant assay. Precision, linearity, assay reproducibility and antigen batch reproducibility were all assessed.

Results: For between-replicate error, samples with higher signals gave coefficients of variation (CVs) in the range 7%–15%. CVs for between-plate variation were only 1%–2% higher. For between-run error, CVs were in the range 15%–28%. In linearity studies, the slope was close to 1.0 and correlation coefficient values were generally >0.8. The sensitivity and specificity of individual batches of antigen varied slightly between groups of patients; however, the sensitivity and specificity of the panel of antigens as a whole remained constant. The validity of the calibration system was demonstrated.

Conclusions: A calibrated six-panel assay of TAAs has been validated for identifying nearly 40% of primary lung cancers via a peripheral blood test. Levels of reproducibility, precision and linearity would be acceptable for an assay used in a regulated clinical setting.

A strategy to reveal potential glycan markers from serum glycoproteins associated with breast cancer progression

Aberrant glycosylation on glycoproteins that are either presented on the surface or secreted by cancer cells is a potential source of disease biomarkers and provides insights into disease pathogenesis. N-Glycans of the total serum glycoproteins from advanced breast cancer patients and healthy individuals were sequenced by HPLC with fluorescence detection coupled with exoglycosidase digestions and mass spectrometry. We observed a significant increase in a trisialylated triantennary glycan containing alpha1,3-linked fucose which forms part of the sialyl Lewis x epitope. Following digestion of the total glycan pool with a combination of sialidase and beta-galactosidase, we segregated and quantified a digestion product, a monogalactosylated triantennary structure containing alpha1,3-linked fucose. We compared breast cancer patients and controls and detected a 2-fold increase in this glycan marker in patients. In 10 patients monitored longitudinally, we showed a positive correlation between this glycan marker and disease progression and also demonstrated its potential as a better indicator of metastasis compared to the currently used biomarkers, CA 15-3 and carcinoembryonic antigen (CEA). A pilot glycoproteomic study of advanced breast cancer serum highlighted acute-phase proteins alpha1-acid glycoprotein, alpha1-antichymotrypsin, and haptoglobin beta-chain as contributors to the increase in the glycan marker which, when quantified from each of these proteins, marked the onset of metastasis in advance of the CA 15-3 marker. These preliminary findings suggest that specific glycans and glycoforms of proteins may be candidates for improved markers in the monitoring of breast cancer progression.

The O-linked glycosylation of secretory/shed MUC1 from an advanced breast cancer patient's serum

MUC1 is a high molecular weight glycoprotein that is overexpressed in breast cancer. Aberrant O-linked glycosylation of MUC1 in cancer has been implicated in disease progression. We investigated the O-linked glycosylation of MUC1 purified from the serum of an advanced breast cancer patient. O-Glycans were released by hydrazinolysis and analyzed by liquid chromatography-electrospray ionization-mass spectrometry and by high performance liquid chromatography coupled with sequential exoglycosidase digestions. Core 1 type glycans (83%) dominated the profile which also confirmed high levels of sialylation: 80% of the glycans were mono-, di- or trisialylated. Core 2 type structures contributed approximately 17% of the assigned glycans and the oncofoetal Thomsen-Friedenreich (TF) antigen (Galbeta1-3GalNAc) accounted for 14% of the total glycans. Interestingly, two core 1 type glycans were identified that had sialic acid alpha2-8 linked to sialylated core 1 type structures (9% of the total glycan pool). This is the first O-glycan analysis of MUC1 from the serum of a breast cancer patient; the results suggest that amongst the cell lines commonly used to express recombinant MUC1 the T47D cell line processes glycans that are most similar to patient-derived material.

Autoantibodies in lung cancer: possibilities for early detection and subsequent cure

BACKGROUND

People with lung cancer usually present at a late stage in the course of their disease when their chances of long-term survival are low. At present there is little to offer for early diagnosis, even in those at high risk of developing the disease. Autoantibodies have been shown to be present in the circulation of people with various forms of solid tumour before cancer-associated antigens can be detected, and these molecules can be measured up to 5 years before symptomatic disease.

OBJECTIVE

To assess the potential of a panel of tumour-associated autoantibody profiles as an aid to other lung cancer screening modalities.

METHODS

Plasma from normal controls (n = 50), patients with non-small cell lung cancer (n = 82) and patients with small cell lung cancer (n = 22) were investigated for the presence of autoantibodies to p53, c-myc, HER2, NY-ESO-1, CAGE, MUC1 and GBU4-5 by enzyme-linked immunosorbent assay.

RESULTS

Raised levels of autoantibodies were seen to at least 1/7 antigens in 76% of all the patients with lung cancer plasma tested, and 89% of node-negative patients, with a specificity of 92%. There was no significant difference between the detection rates in the lung cancer subgroups, although more patients with squamous cell carcinomas (92%) could be identified.

CONCLUSION

Measurement of an autoantibody response to one or more tumour-associated antigens in an optimised panel assay may provide a sensitive and specific blood test to aid the early detection of lung cancer.

Two-step method to isolate target recombinant protein from co-purified bacterial contaminant SlyD after immobilised metal affinity chromatography

As part of a study to purify the internal domain of HER2 (ICD) from recombinant expression, through metal immobilised affinity chromatography (IMAC), we encountered a contaminant, SlyD, a 29 kDa native E. coli protein. SlyD is a recurrent contaminant, with a histidine rich domain enabling binding to IMAC columns and thus co-elution with the target protein. Research has been carried out on this protein and its purification, however, no work mentions how to treat it as a true contaminant or describe procedures to isolate it from target proteins. In this report, we described a two-step chromatographic method for the purification of ICD, including IMAC as a capture step and size exclusion chromatography (SEC) as a polishing step. IMAC allowed us to purify ICD from bacterial crude with SlyD co-eluting. SEC then allowed us to resolve ICD from SlyD and achieve a purity greater than 95% for ICD. However, this method has been developed to accommodate any protein whose molecular weight is different enough from SlyD to be separated by SEC.

Use of autoantibodies in breast cancer screening and diagnosis

Breast cancer is the most common cancer among women and accounts for 6% of all cancer deaths. Current screening modalities for breast cancer diagnosis include mammography, digital mammography and magnetic resonance imaging; however, there is still an urgent need to develop an alternative modality of screening for earlier diagnosis. Autoantibodies to tumor-associated autoantigens can be elicited in breast cancer patients. Tumor-associated antigens vary between cancers and can be the result of a number of different events, including mutation, overexpression or altered expression patterns. The inherent amplification of signals provided by the host's own immune system to low levels of tumor-associated antigens in early disease provides a potential route to the early diagnosis of cancer. In addition, autoantibody responses in breast cancer have been correlated with patient survival and their response to treatment.

Malignancy-induced autoimmunity to MUC1: initial antibody characterization

Numerous reports document the existence of autoantibodies to MUC1 in the circulation of individuals with breast and other solid malignancies, with the majority of researchers utilizing MUC1 peptides in their detection. This report documents the purification, using peptide and whole molecule, and characterization of such autoantibodies from an individual with an unusual, highly MUC1-positive, myosarcoma. Purification of autoantibodies from serum was performed using affinity chromatography against either MUC1 peptide or whole molecule MUC1 [derived both from the patient (Pt-MUC1) and from a pool of sera from patients with advanced breast cancer (ABC-MUC1)]. Enzyme-linked immunosorbent assays (ELISAs) were used to compare specificity of purified autoantibodies. Peptide epitopes were determined by Ptifcan system against 7-mer peptides covering the 20 amino acid repeat of the MUC1 extracellular domain. Substantially higher amounts of autoantibodies were isolated when purifying against Pt-MUC1 rather than either ABC-MUC1 or peptide. Whole molecule purified autoantibodies demonstrated an increased specificity for tumour-derived MUC1. Pt-MUC1 autoantibodies were of both the immunoglobulin (Ig)G and IgM class, whilst autoantibodies purified against ABC-MUC1 and MUC1 peptide were IgG only. A greater range of peptide epitopes was defined by those autoantibodies purified against whole molecule. This report presents data indicating the presence of autoantibodies to MUC1 in an individual diagnosed with a MUC1 over-expressing myosarcoma. Confirmation of these autoantibodies as being specific for tumour-associated MUC1 is given. Further, it suggests that, although autoantibodies are present that recognize core protein determinants, the initial, and dominant, immunizing epitope is not purely pretentious in nature.

Transport properties of the calcium ionophore ETH-129

The transport mechanism and specificities of ionophore ETH-29 have been investigated in a highly defined phospholipid vesicle system, with the goal of facilitating the application of this compound to biological problems. ETH-129 transports Ca(2+) via an electrogenic mechanism, in contrast to A23187 and ionomycin, which function in a charge neutral manner. The rate of transport is a function of membrane potential, increasing by 3.9-fold per 59 mV over a broad range of that parameter. Rate is independent of the transmembrane pH gradient and strongly stimulated by the uncoupler carbonyl cyanide m-chlorophenylhydrazone when no external potential has been applied. The effect of uncoupler reflects the collapse of an opposing potential arising during Ca(2+) transport, but also reflects the formation of a mixed complex between the uncoupler, ETH-129, and Ca(2+) that readily permeates the vesicle membrane. Oleate does not substitute for the uncoupler in either regard. ETH-129 transports polyvalent cations according to the selectivity sequence La(3+) > Ca(2+) > Zn(2+) approximately equal to Sr(2+) > Co(2+) approximately equal to Ni(2+) approximately equal to Mn(2+), with the magnitude of the selectivity coefficients reflecting the cation concentration range considered. There is little or no activity for the transport of Na(+), K(+), and Mg(2+). These properties suggest that ETH-129 will be useful for investigating the consequences of a mitochondrial Ca(2+) overload in mammalian cells, which is difficult to pursue through the application of electroneutral ionophores.

Autosomal recessive cerebellar ataxia with oculomotor apraxia (ataxia-telangiectasia-like syndrome) is linked to chromosome 9q34

Ataxia with oculomotor apraxia (ataxia-telangiectasia-like syndrome [AOA]; MIM 208920) is an autosomal recessive disorder characterized by ataxia, oculomotor apraxia, and choreoathetosis. These neurological features resemble those of ataxia-telangiectasia (AT), but in AOA there are none of the extraneurological features of AT, such as immunodeficiency, neoplasia, chromosomal instability, or sensitivity to ionizing radiation. It is unclear whether these patients have a true disorder of chromosomal instability or a primary neurodegenerative syndrome, and it has not been possible to identify the defective gene in AOA, since the families have been too small for linkage analysis. We have identified a new family with AOA, and we show that the patients have no evidence of chromosomal instability or sensitivity to ionizing radiation, suggesting that AOA in this family is a true primary cerebellar ataxia. We have localized the disease gene, by linkage analysis and homozygosity mapping, to a 15.9-cM interval on chromosome 9q34. This work will ultimately allow the disease gene to be identified and its relevance to other types of autosomal recessive cerebellar ataxias to be determined.

Ionomycin, a carboxylic acid ionophore, transports Pb(2+) with high selectivity

Studies utilizing phospholipid vesicle loaded with chelator/indicators for polyvalent cations show that ionomycin transports divalent cations with the selectivity sequence Pb(2+) > Cd(2+) > Zn(2+) > Mn(2+) > Ca(2+) > Cu(2+) > Co(2+) > Ni(2+) > Sr(2+). The selectivity of this ionophore for Pb(2+) is in contrast to that observed for A23178 and 4-BrA23187, which transport Pb(2+) at efficiencies that are intermediate between those of other cations. When the selectivity difference of ionomycin for Pb(2+) versus Ca(2+) was calculated from relative rates of transport, with either cation present individually and all other conditions held constant, a value of approximately 450 was obtained. This rose to approximately 3200 when both cations were present and transported simultaneously. 1 microM Pb(2+) inhibited the transport of 1 mM Ca(2+) by approximately 50%, whereas the rate of Pb(2+) transport approached a maximum at a concentration of 10 microM Pb(2+) when 1 mM Ca(2+) was also present. Plots of log rate versus log ionomycin or log Pb(2+) concentration indicated that the transporting species is of 1:1 stoichiometry, ionophore to Pb(2+), but that complexes containing an additional Pb(2+) may occur. The species transporting Pb(2+) may include H.IPb.OH, wherein ionomycin is ionized once and the presence of OH(-) maintains charge neutrality. Ionomycin retained a high efficiency for Pb(2+) transport in A20 B lymphoma cells loaded with Indo-1. Both Pb(2+) entry and efflux were observed. Ionomycin should be considered primarily as an ionophore for Pb(2+), rather than Ca(2+), of possible value for the investigation and treatment of Pb(2+) intoxication.

A human monoclonal antibody encoded by the V4-34 gene segment recognises melanoma-associated ganglioside via CDR3 and FWR1

A heterohybridoma cell line producing the human monoclonal antibody (MoAb) MDT.1 has been established. The heavy chain of MoAb MDT.1 is encoded by the VH gene segment V4-34 (previously designated VH4-21), and the light chain is encoded by the V kappa 1-L12a gene segment, both in germline configuration. MDT.1 has reactivity against lipid A, double- and single-stranded DNA, red blood cell associated i antigen, and ganglioside antigens. In a panel of tumour cell lines, MDT.1 reacted specifically with melanoma cells and other tumour cells of neuroectodermal origin. Cellular recognition appears to be via tumour-associated ganglioside antigens, and may involve the minimal essential epitope NeuNac alpha 2-->3Gal beta 1-->-4Glc-. Binding to ganglioside antigen is inhibited by the monoclonal anti-idiotypic antibody 9G4. Since the 9G4 idiotope is located in framework region 1 (FWR1) of V4-34-encoded antibodies, this region is likely to be involved, either directly or indirectly, in ganglioside binding. The complementarity-determining region 3 (CDR3) of MDT.1 is arginine rich, with five out of 12 residues being arginine and these residues are candidates for interaction with the negatively charged ganglioside. The ability of MoAb MDT.1 to recognise ganglioside antigens is associated with potentially useful anti-tumour activity.

V(H) gene analysis of Burkitt's lymphoma in children from north-western Iran

Cases of Burkitt's lymphoma (BL) from north-western Iran were investigated for the usage and somatic mutational pattern of their immunoglobulin variable region genes. Potentially functional V(H) genes were amplified from 6/12 of the tumour masses and all of these were derived from the V(H)3 family, with 4/6 being derived from the most commonly used V(H)3 family member, V3-23. All of the tumour sequences were mutated from their germline counterparts, to varying degrees, with a mean level of 5.8%, indicating that the cell of origin had encountered the germinal centre. Intraclonal sequence heterogeneity was also evident in 4/6 of the lymphomas, showing that the tumour cells had undergone further somatic mutation following neoplastic transformation. Analysis of the five potentially functional mutated V(H) sequences showed a significant clustering of replacement mutations in the complementarity-determining region 2, consistent with a role for antigen in selection of tumour cell sequences. The pattern of extensive somatic mutation, and intraclonal variation, in these mainly EBV+ve tumours, was similar to that previously reported in V(H) sequences of EBV+ve endemic BL (eBL) and EBV-ve sporadic BL (sBL), with the mean level of somatic mutation lying between those reported for eBL (7.7%) and sBL (4.0%). However, VH gene bias and the distribution of mutations in the Iranian cases showed features which differed from those reported for endemic or sporadic BL.

Sequence analysis of V(4-34)-encoded antibodies from single B cells of two patients with systemic lupus erythematosus (SLE)

SLE is an autoimmune disease characterized by the presence of autoantibodies against double-stranded (ds)DNA. A large proportion (approx. 40%) of patients with lupus also have increased levels of serum immunoglobulin encoded by the V(4-34) heavy chain gene, which often fluctuate with disease activity, and this gene is utilized by a subset of anti-dsDNA antibodies. In order to probe the nature of the V(4-34)-encoded immunoglobulin, B cells were isolated from the blood of two patients with active disease, using the 9G4 MoAb specific for the immunoglobulin gene product. Following cell picking, single-cell polymerase chain reaction (PCR) amplification of cDNA was used to investigate both V(H) and V(L) genes. Sequences were obtained from B cells synthesizing IgM (n = 10), IgG (n = 4) and IgA (n = 1). For V(H), all were derived from V(4-34) as expected, and the isotype-switched sequences and 2/6 IgM sequences were somatically mutated. In contrast, V(L) (12 kappa and 3 lambda) showed a low level of mutation, possibly indicating secondary rearrangements. The three most highly mutated V(H) sequences were associated with unmutated V(L) sequences. Analysis of the distribution of mutations revealed only minor clustering in complementarity-determining regions (CDRs) characteristic of antigen selection. The CDR3 lengths of V(H) ranged from five to 19 amino acids, and in 3/15 there was evidence of an excess of positively charged amino acids, compared with the normal expressed repertoire. Basic amino acids were also found at the V(L)-J(L) junctions in 4/15. These findings provide insight into the V(4-34)-V(L) gene combinations used by B cells in patients with SLE which might have clinical relevance.

Clonally related IgE and IgG4 transcripts in blood lymphocytes of patients with asthma reveal differing patterns of somatic mutation

Isotype switching to IgE contributes to atopic asthma, therefore strategies to divert this process to alternative isotypes could have therapeutic relevance. It is known that patients with allergic disease have serum IgE and IgG4 antibodies with similar specificities, and that cytokines such as IL-4 mediate switching to both of these isotypes. Availability of variable region gene analysis has allowed us to probe isotype variants at the single-cell level. An earlier report described identification in a single atopic patient of short transcripts with a common complementarity-determining region "clonal signature" in combination with C mu, C gamma4 and C epsilon. We have extended this analysis, and have identified V(H)-Cgamma4 transcripts with clear clonal relationship to IgE-derived sequences in blood lymphocytes from three of four patients with atopic asthma. No other IgG subclasses were detected, confirming the link between IgE and IgG4. Full sequences were obtained from each clonally related isotype in all patients, and showed extensive somatic mutation. As previously found for IgE, the IgG4 isotypes had evident intraclonal variation. There were shared mutations between isotypes, but also many differences, indicative of separate cell populations with divergent mutational histories. These findings indicate that, in atopic patients, an individual B cell commonly switches to either IgE or IgG4. Cells producing each isotype then co-exist in the recirculating pool, and the balance between them may influence the disease process.

Insight into Burkitt's lymphoma from immunoglobulin variable region gene analysis

Analysis of usage of V(H) and V(L) genes, and the degree and pattern of somatic mutation, has been used to investigate the cell of origin and clonal history in cases of Burkitt's lymphoma (BL). Tumor cell lines and biopsy material from patients with endemic, sporadic and AIDS-associated BL have been compared. V(H) genes were most commonly derived from the V(H)3 (52%) and V(H)4 (39%) families. This shows a similar gene usage of the V(H)3 family to that seen in the normal peripheral blood repertoire (55%), but a biased usage of the V(H)4 family (22% in normal). There was no restriction in V(L) gene usage. This overall distribution was similar in all subsets of BL. In all categories, there was significant somatic mutation in both V(H) and V(L) sequences. There was no evidence for accumulation of mutations in cell lines cultured in vitro indicating that all mutations in BL-derived cell lines have accumulated in vivo. The mean percentage level of mutation +/- standard deviation was greater in endemic BL (V(H) = 7.7 +/- 4.0, V(L) = 5.3 +/- 2.2) and AIDS-associated BL (V(H) = 7.5 +/- 3.6, V(L) = 3.9 +/- 1.9) than in sporadic BL (V(H) = 4.0 +/- 2.5, V(L) = 2.2 +/- 1.2). The pattern of somatic hypermutation was similar in V(H) and V(L) sequences of the different types of BL although the light chain genes were less mutated. Mutational patterns in the V(H) genes did not reveal a conventional role for antigen in selection of tumor cell sequences in 23/25 V(H) genes analysed. In contrast, patterns in V(L) sequences were consistent with a role for antigen in 8/13 sBL +/- eBL cases and 8/17 cases overall. The presence of EBV did not seem to influence the quantity or pattern of somatic mutations. Evidence for intraclonal variation was seen in uncloned cell lines from cases of eBL and AIDS-associated BL and confirmed in biopsy material in some, but not all cases of eBL, sBL and AIDS-associated BL examined. These common features indicate that the B-cells involved in all types of BL are derived from cells that have traversed the germinal centre, and that the somatic mutation mechanism may still be operative following neoplastic transformation. Overall, in 10/30 cases, there was evidence of significant clustering of replacement amino acids, in CDRs, particularly in V(L), indicating that the B-cell of origin is likely to have been selected by antigen.

Immunogenetic analysis of a panel of monoclonal IgG and IgM anti-PDC-E2/X antibodies derived from patients with primary biliary cirrhosis

BACKGROUND/AIMS

Autoantibodies with specificity for the E2 component of the pyruvate dehydrogenase complex (PDC-E2) are commonly present in primary biliary cirrhosis. The aim of this study was to generate and characterise human anti-PDC-E2 monoclonal antibodies and analyse immunoglobulin gene usage and mutation for clues to pathogenesis.

METHODS

Peripheral B-lymphocytes from two patients with primary biliary cirrhosis were used to generate heterohybridomas secreting PDC-E2 specific monoclonal antibodies. The antibodies were characterised by ELISA, immunoblotting, indirect immunofluorescence and enzyme inhibition techniques, and their encoding immunoglobulin genes were amplified, cloned and sequenced.

RESULTS

Four IgGlambda and one IgMlambda monoclonal antibodies specific for PDC-E2 were generated: all gave bands at 74 kD and 52 kD on PDC immunoblots, two clones were specific for the lipoylated inner lipoyl domain, and all inhibited target enzyme function. Sequence analysis suggested unrestricted VH gene usage, but a strong preference for lambda light chains. The extent of somatic mutation was high (3-20%), with evidence for antigen selection in 3/5 VH sequences.

CONCLUSIONS

These monoclonal antibodies closely resemble the hallmark autoantibodies of primary biliary cirrhosis. Their specificities demonstrate true cross reactivity between an epitope on PDC-E2 and Protein X, and the existence of a subset of B cells that recognise only the lipoylated form of the antigen. The pattern of immunoglobulin gene mutations suggests an antigen-driven selection of high affinity IgG autoantibodies, supporting a possible role for exogenous antigen in the pathogenesis of primary biliary cirrhosis.

Immunogenetic analysis of the heavy chain variable regions of IgE from patients allergic to peanuts

Peanuts are one of the most allergenic of the foods, and hypersensitivity responses to peanut allergens can be fatal. Although the nature of the antigenic components of peanuts is being defined at the molecular level, there is little information on the induced IgE antibodies, which are central to the allergic reaction. Recognition sites of IgE antibody molecules arise from the variable regions of heavy and light chains (VH and VL). By using nested polymerase chain reactions with specific primers for the available repertoire of VH genes, together with primers in the constant epsilon region, we have amplified VH sequences of IgE from blood lymphocytes of two patients with peanut allergy. After cloning and sequencing the products, we found a predominance of VH1 family use in both patients, which was not found in control IgM-specific primers. The IgE VH sequences were highly somatically mutated, but in only six of 17 cases was there clear evidence for clustering of amino acids indicative of antigen selection. Previous results from patients with allergy to house dust mites have indicated predominance of VH5 use and little evidence for antigen selection. Although results from two patients allergic to peanuts must be regarded as preliminary, they do suggest that the IgE response to peanuts may have a different VH bias, with a similar mutational pattern.

Phage surface expression for analysis of recognition sites of human autoantibodies: comparison of single chain Fv and Fab

Human autoantibodies can mediate the pathology of autoimmune disease. To plan therapeutic intervention based on inhibition of binding to autoantigen, it is desirable to map the amino acid residues involved in recognition. Bacterial expression provides a simple and rapid system for production and mutagenesis of recombinant antibody fragments, but there are problems with reproducible folding and dispersity of soluble products. Expression at the surface of phage particles avoids both these problems, and allows variable region gene sequences to be expressed as functional monomers. To apply this technology, we have expressed a human anti-DNA monoclonal antibody, derived from a hybridoma, at the surface of the phage. The presence of the phage particle allowed highly sensitive detection of antibody activity by ELISA, so that minimal levels of expression were required. By measuring the amount of expressed antibody protein, it was possible to analyze the antibody activity/microgram. We expressed the antibody as FAB or single chain (sc) Fv, and found binding activities to be closely similar. The parental anti-DNA antibody utilizes the human V4-34 gene and displays the associated conformation-dependent 9G4 idiotope. Both the Fab and scFv expressed the idiotope, confirming similar molecular folding. This technology can be applied rapidly and efficiently to investigations of human autoantibody structure, with the option for expression as either Fab or scFv, and the only requirement being knowledge of VH and VL sequences.

Rapid cytotoxicity of human B lymphocytes induced by VH4-34 (VH4.21) gene-encoded monoclonal antibodies, II

We have previously described complement-independent killing of human B lymphocytes by two IgM MoAbs derived from the VH4-34 (VH4.21) gene. Analysis of 17 independently derived VH4-34-encoded MoAbs shows that B cell toxicity is not limited to the two described MoAbs, but is a general property shared by a subset of MoAbs derived from the VH4-34 gene. As observed by two independent microscopy techniques, giant membrane pores were formed on target B cells within 10-15 min of exposure to cytotoxic VH4-34-derived MoAbs. Toxicity by individual MoAb correlated directly to its B cell binding intensity measured by FACS, i.e. stronger the binding greater the killing. Sequence analysis showed that V(H) region in germ-line or in near germ-line configuration was necessary but not sufficient for B cell binding. In addition, a particular sequence motif enriched in basic amino acids in the CDR3 may be required to supplement the reactivity mediated by the V(H) region of the MoAb molecule. VH4-34-encoded antibodies that fulfil the above sequence requirements have cold agglutinin activity towards the i antigen of cord erythrocytes. In vivo, such anti-i/anti-B cell antibodies are rarely detected in healthy adults, but serum levels are dramatically elevated in selective pathological conditions, such as systemic lupus erythematosus and infectious mononucleosis. This strict regulation may be related to the novel and rapid mechanism of human B cell toxicity demonstrated by antibodies encoded by a single human V(H) gene.

Pattern of usage and somatic hypermutation in the V(H)5 gene segments of a patient with asthma: implications for IgE

The V(H)5 family contains two functional genes, V5-51 and V(H)32, and appears to be over-represented in IgE antibodies from patients with allergic disease. Previous sequence analysis of V(H)5 gene segments in IgE has revealed a substantial level of somatic hypermutation, with evidence for hotspots. To assess characteristics of V(H)5 gene behavior, V(H)5 gene segments in combination with C mu, C gamma, C alpha, and C epsilon have been amplified from blood B lymphocytes of a patient with atopic asthma. Sequence analysis revealed strong preferential usage of one of the two V(H)5 gene segments (V5-51) by IgM, IgG, and IgA. In contrast, IgE used both genes equally. Levels of somatic mutation were higher following all isotype switches, particularly to IgA. Mutational hotspots were identifiable in all isotypes, leading to several common replacement amino acids. The dominant mutational site in IgM was a common hotspot at Ser31. IgG, IgA, and IgE-derived sequences had mainly common hotspots, with few distinct sites. The results indicate that mutational hotspots are a feature of the V(H)5 gene, are identifiable at an early stage of somatic hypermutation, and are not a unique feature of IgE. Generation of IgE antibodies appears to involve three processes: the preferential use of V(H)5 genes, consistent with superantigen stimulation; the accumulation of somatic mutations in common hotspots, some of which are in complementarity-determining regions (CDR); and the acquisition of non-hotspot mutations in CDR, accounting for approximately 50% of replacement amino acids in these sites, and presumably contributing to affinity maturation.

Cancer families: what risks are they given and do the risks affect management?

The numbers of referrals to genetics clinics for people with a family history of cancer is increasing rapidly. Although it is likely that presymptomatic testing will soon be available for some families, for the majority of people with a family history of malignancy, risk can only be assessed by examining their pedigrees and referring to standard texts. In order to find out if clinical geneticists are providing consistent risks and suggestions for management we surveyed consultant clinical geneticists with a questionnaire about four people with a family history of malignancy. The clinical geneticists replying to our questionnaire gave consistent advice for the person with a family history of colon cancer, but there was wide variation in suggested risks and management for those with family histories of breast and multisite cancers. This survey shows that deciding on appropriate management for cancer families can be difficult and that there is uncertainty about the most effective methods of screening young people at high risk of developing cancers. However, it is important to provide consistent advice in order to evaluate screening protocols and lack of consistency in advice given to different family members can cause anxiety and distress. Consistency may be achieved by the use of one model for risk calculation, and by representatives from several specialties, such as surgery, radiology, genetics, and public health working together in order to coordinate local and national screening policies.

VH and VL gene analysis in sporadic Burkitt's lymphoma shows somatic hypermutation, intraclonal heterogeneity, and a role for antigen selection

Tumor cell lines and one tumor biopsy from seven cases of Epstein-Barr virus (EBV) genome-negative sporadic Burkitt's lymphoma (BL) have been investigated for usage and mutational pattern of Ig variable region genes. The VH genes were derived from the VH 3 (one) and VH4 (six) families and both the IgM-positive (six) and the IgA-positive (one) were all mutated from their germline counterparts. The VL genes were derived from V kappa 1 (one), V kappa 3 (one), V lambda 1 (four), and V lambda 2 (one) families and were also somatically hypermutated. Biopsy material from one of the IgM-positive cases showed VH and VL sequences that matched the derived cell line, with additional intraclonal sequence heterogeneity, indicating that the tumor cells had undergone posttranformation somatic mutation. Mutational patterns in V(H) genes did not show a conventional role for antigen in selecting tumor cell sequences. In contrast, patterns in VL sequences were consistent with a role for antigen in five of seven cases. The pattern of extensive scattered somatic hypermutation and intraclonal variation is similar to that in VH sequences of EBV genome-positive endemic BL, although the degree of mutational activity is less. These common features indicate that B cells involved in the two variants of BL may share a common clonal history.

Ionophore 4-BrA23187 transports Zn2+ and Mn2+ with high selectivity over Ca2+

The cation transport selectivities of the Ca2+ ionophores A23187, Ionomycin, and 4-BrA23187 have been determined using a model system comprised of phospholipid vesicles loaded with the chelator/indicator Quin-2. At pH 7.00 and a 100 microM concentration of the cations, A23187 displays the transport selectivity sequence Zn2+ > Mn2+ > Ca2+ > Co2+ > Ni2+ > Sr2+, with the absolute rates of transport spanning approximately 3 orders of magnitude. Similar data are obtained with Ionomycin, although the relative transport rates of Zn2+ and Mn2+ are equivalent, and the range of absolute rates is decreased by a factor of approximately 3. When values are normalized to those of Ca2+, transport selectivity is seen to be only weakly related to complexation or extraction selectivity. It is also seen that, when used to manipulate Ca2+ (or Mg2+), both ionophores can be expected to alter the distribution of additional divalent cations which have known biological activities. 4-BrA23187 is a low-activity ionophore for Ca2+, compared to A23187 and Ionomycin, while retaining comparable activities as an ionophore for the other cations. As a consequence, 4-BrA23187 is highly selective for the transport of Zn2+ and Mn2+, compared to Ca2+, with selectivity ratios approaching that of valinomycin for K+ over Na+ when conditions are optimal. Plots of the log of the rate of cation transport vs the log of the ionophore concentration indicate that Ca2+ is transported primarily as a 2:1 complex by A23187 and 4-BrA23187, but Zn2+ and Mn2+ are transported, in part, as 1:1 complexes. These findings, together with a postulated low stability of 2:1, compared to 1:1 complexes between 4-BrA23187 and divalent cations, partially explain the novel transport selectivity of this compound. Unlike A23187 or Ionomycin, 4-BrA23187 may be useful for investigating cell regulation by Zn2+ and Mn2+, without interference by regulatory mechanisms which respond to Ca2+.

Use of phage surface expression to analyze regions of human V4-34(VH4-21)-encoded IgG autoantibody required for recognition of DNA: no involvement of the 9G4 idiotope

The V4-34 gene encodes the majority of autoanti-red cell Abs of I/i specificity. It also encodes a proportion of autoanti-DNA Abs found in patients with systemic lupus erythematosus. Nucleotide sequence analysis of mAbs that use this gene has indicated a role for CDR3 in discrimination between these autoantigens. Specifically, anti-DNA activity may require basic amino acids, such as arginine, found in this region. To investigate this requirement, we have expressed VH and VL sequences from a patient's IgG anti-DNA mAb, as Fab molecules at the surface of phage. Expressed Fab bound strongly to DNA, whereas control VH and VL pairs from an anti-red cell mAb did not. Replacement of the homologous mutated V4-34 sequence by germ-line sequence did not affect binding, indicating that somatic mutations in VH did not contribute significantly. In contrast, replacement of the basic CDR3 by an anti-red cell CDR3 abrogated anti-DNA activity, confirming its major role. However, an influence of VL was revealed by replacing homologous mutated V kappa IIIb by an unmutated V kappa IIIb sequence, reducing binding by approximately 50%. This influence was apparent only with homologous VH since the mutated V kappa was unable to generate anti-DNA activity when combined with anti-red cell VH. The 9G4 idiotope, which arises from FWR1, was expressed by all constructs. Substitution of Trp by Ser at position 7 in FWR11 caused complete loss of idiotope expression, with no effect on recognition of DNA, indicating no influence of idiotope expression on anti-DNA activity. Phage surface expression provides a powerful and rapid technique for assessing sequences relevant for Ab specificity or idiotope expression.

Use of phage surface expression to analyze regions of human V4-34(VH4-21)-encoded IgG autoantibody required for recognition of DNA: no involvement of the 9G4 idiotope

The V4-34 gene encodes the majority of autoanti-red cell Abs of I/i specificity. It also encodes a proportion of autoanti-DNA Abs found in patients with systemic lupus erythematosus. Nucleotide sequence analysis of mAbs that use this gene has indicated a role for CDR3 in discrimination between these autoantigens. Specifically, anti-DNA activity may require basic amino acids, such as arginine, found in this region. To investigate this requirement, we have expressed VH and VL sequences from a patient's IgG anti-DNA mAb, as Fab molecules at the surface of phage. Expressed Fab bound strongly to DNA, whereas control VH and VL pairs from an anti-red cell mAb did not. Replacement of the homologous mutated V4-34 sequence by germ-line sequence did not affect binding, indicating that somatic mutations in VH did not contribute significantly. In contrast, replacement of the basic CDR3 by an anti-red cell CDR3 abrogated anti-DNA activity, confirming its major role. However, an influence of VL was revealed by replacing homologous mutated V kappa IIIb by an unmutated V kappa IIIb sequence, reducing binding by approximately 50%. This influence was apparent only with homologous VH since the mutated V kappa was unable to generate anti-DNA activity when combined with anti-red cell VH. The 9G4 idiotope, which arises from FWR1, was expressed by all constructs. Substitution of Trp by Ser at position 7 in FWR11 caused complete loss of idiotope expression, with no effect on recognition of DNA, indicating no influence of idiotope expression on anti-DNA activity. Phage surface expression provides a powerful and rapid technique for assessing sequences relevant for Ab specificity or idiotope expression.