Image-based multiplex immune profiling of cancer tissues: translational implications. A report of the International Immuno-oncology Biomarker Working Group on Breast Cancer

Recent advances in the field of immuno-oncology have brought transformative changes in the management of cancer patients. The immune profile of tumours has been found to have key value in predicting disease prognosis and treatment response in various cancers. Multiplex immunohistochemistry and immunofluorescence have emerged as potent tools for the simultaneous detection of multiple protein biomarkers in a single tissue section, thereby expanding opportunities for molecular and immune profiling while preserving tissue samples. By establishing the phenotype of individual tumour cells when distributed within a mixed cell population, the identification of clinically relevant biomarkers with high-throughput multiplex immunophenotyping of tumour samples has great potential to guide appropriate treatment choices. Moreover, the emergence of novel multi-marker imaging approaches can now provide unprecedented insights into the tumour microenvironment, including the potential interplay between various cell types. However, there are significant challenges to widespread integration of these technologies in daily research and clinical practice. This review addresses the challenges and potential solutions within a structured framework of action from a regulatory and clinical trial perspective. New developments within the field of immunophenotyping using multiplexed tissue imaging platforms and associated digital pathology are also described, with a specific focus on translational implications across different subtypes of cancer. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Spatial analyses of immune cell infiltration in cancer: current methods and future directions: A report of the International Immuno-Oncology Biomarker Working Group on Breast Cancer

Modern histologic imaging platforms coupled with machine learning methods have provided new opportunities to map the spatial distribution of immune cells in the tumor microenvironment. However, there exists no standardized method for describing or analyzing spatial immune cell data, and most reported spatial analyses are rudimentary. In this review, we provide an overview of two approaches for reporting and analyzing spatial data (raster versus vector-based). We then provide a compendium of spatial immune cell metrics that have been reported in the literature, summarizing prognostic associations in the context of a variety of cancers. We conclude by discussing two well-described clinical biomarkers, the breast cancer stromal tumor infiltrating lymphocytes score and the colon cancer Immunoscore, and describe investigative opportunities to improve clinical utility of these spatial biomarkers. © 2023 The Pathological Society of Great Britain and Ireland.

Quantitative measurement of duplicated DNA as a diagnostic test for Charcot-Marie-Tooth disease type 1a

Charcot-Marie-Tooth disease type 1 (CMT1) is a hereditary motor and sensory neuropathy. The autosomal dominant subtype is often linked with a large duplication on chromosome 17p11.2. The gene encoding the peripheral myelin protein PMP 22 (the critical gene in this subtype of CMT1) is located within this duplication. To detect this duplication in chromosomal DNA from individuals thought to have CMT1, we compared the hybridization signals of two DNA probes within this duplication (VAW412R3a and VAW409R3a) with the signal of a reference probe (E3.9). When duplication was present, the signals from the first two probes increased from 100% (for nonduplicated samples) to 145% and 142%, respectively. The day-to-day variance was 3.7% and 5.1%, respectively. We demonstrated this DNA duplication in 49 of 95 DNA samples from unrelated individuals thought to have CMT1. Moreover, because hereditary neuropathy with liability to pressure palsies (HNPP) is based on a DNA deletion in the same area of chromosome 17, this quantitative test may be useful in establishing the presence of HNPP. In a preliminary investigation, four unrelated patients with HNPP yielded test values of 63% and 54%, respectively, of those for nonduplicated samples (CV 19% and 18%, respectively; n = 4), suggesting a deletion in 17p11.2.

Abstract P5-18-02: A quantitative centrosomal amplification score (CAS) predicts local recurrence in ductal carcinoma in situ

Background: About 60-80% of ductal carcinoma in situ (DCIS) cases are high-grade (HG) DCIS with an elevated risk of local recurrence (LR) even after a lumpectomy. Patients are often under or over treated due to the lack of accurate recurrence risk prediction models. Current prognostic models such as OncotypeDX and Van Nuys Prognostic Index (VNPI) lack consistency and are limited to a specific subset of patients. Here in this study, we show that the extent of centrosome amplification (CA) in a DCIS lesion can predict the risk of LR after lumpectomy. CA refers to presence of supernumerary or large centrosomes and is a characteristic of pre-invasive lesions, and breast tumors, and promotes erroneous mitoses and chromosomal instability.

Methods: We have pioneered a semi-automated pipeline that integrates immunofluorescence confocal microscopy with digital image analysis and yields a quantitative Centrosomal Amplification Score (CAS) for each patients' tumor sample by evaluating severity and frequency of centrosomal aberrations therein. To this end, we first immunofluorescently stained centrosomes in formalin fixed paraffin embedded resection samples from DCIS patients (discovery cohort n=133 and a validation cohort n=119) using an antibody against γ-tubulin, and co-stained nuclei with DAPI. Next, we imaged the slides and processed the raw 3D image data using IMARIS Biplane 8.2 3D volume rendering software. Finally, we calculated centrosome numbers and volume in ˜250 cells from each patient sample. Using a mathematical algorithm, we generated a composite CAS score for each patient sample by integrating the numerical (CASi) and structural (CASm) aberrations.

Results: We found that DCIS patients with recurrence exhibited higher CAS. Intriguingly, higher CAS was also associated with greater risk of developing ipsilateral breast events [Hazard ratio (HR) =7.58 for discovery cohort and HR=5.8 for validation cohort, p<0.0001] which remained significant (HR=8.5 for discovery and HR=3.39, p<0.0001) after accounting for the confounding factors like age, tumor size, comedo necrosis and radiotherapy. Kaplan Meir survival analysis indicated that high CAS was associated with poor recurrence-free survival (RFS) (p<0.001). For the high and low CAS groups, the 5-year risk of recurrence was 87.5% and 12.5% respectively (p<0.001). In our discovery cohort, a head-to-head comparison of the ability of VNPI and CAS to predict recurrence illuminated that CAS was able to stratify the DCIS group in recurrence and recurrence-free group with much higher significance (p<0.0001) than the Van Nuys Prognostic Index (VNPI) (HRs for CAS- 8.8 vs. VNPI 0.959). Finally, the Harrell's concordance index using SAS PROC PHREG tests yielded that the probability of a patient with poorer/lower RFS to be in the high CAS group is 76.2%.

Conclusion: Our data compellingly show that CAS quantifies the risk of recurrence in DCIS patients with the highest concordance and provides a novel and innovative tool to tailor their treatment based on their risk profile.

Citation Format: Mittal K, Kaur J, Wei G, Toss MS, Osan RM, Janssen EA, Søiland H, Rakha EA, Rida PC, Aneja R. A quantitative centrosomal amplification score (CAS) predicts local recurrence in ductal carcinoma in situ [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-18-02.

Abstract P4-14-08: Serum concentrations of tamoxifen and Z-endoxifen may predict sexual dysfunction in the 2nd year of adjuvant endocrine treatment

Background and rationale: Side effects of adjuvant treatment with tamoxifen (tam) may impair Quality of Life (QoL) and have been suggested as an independent variable for discontinuation of tam1. There are large inter-patient variabilities in prevalence and severance of side effects among tam users. Therefore, there is a need for biological markers that can predict side effects. A potential biological predictor is the serum concentrations of tam and/or its metabolites. In this prospective observational study we have analyzed serum concentrations of tam and 9 metabolites over 3 years. Patients Reported Outcome Measures (PROM) were obtained to elucidate possible associations between side effects, adherence and tam metabolism.

Methods: Breast cancer patients using adjuvant tam (20mg/d) were recruited through the Prospective Breast Cancer Biobank project between 2011 and 2016. Inclusion criteria were ER positive status, ≥ 6 months tam use, tumor size of ≥0.1 cm and being able to read and write Norwegian. Concentration levels of tam and metabolites in serum were analyzed by LC-MS/MS2 and adherence data were collected through the Norwegian prescription database. PROM-data comprised of validated questioners reporting side effects of endocrine treatment and QoL. Statistical analyses comprised non-parametric tests, logistic regression, chi square tests and the Benjamin-Hochberg procedure to correct for multiple testing.

Results: Associations between metabolite concentrations and side effects were run as a cross sectional analysis (N=149) and separate analysis of each year of follow-up with 85, 77 and 65 patients at the 1st, 2nd and 3rd year respectively. We found that 78 % of patients reported side effects, 66 % reported mood swings, 21 % reported severe hot flushes and 71 % reported decreased libido. When analyzing years separately, we found that on the 2nd year patients experiencing vaginal dryness had significantly higher levels of tamoxifen (P=0.032, after correction for multiple testing and adjustment for clinical relevant variables) compared to patients not experiencing vaginal dryness. Also, on year 2 the patients in the lower quartile of Z-endoxifen (≤17.9 nM) had significantly lower libido (p=0.015) compared to patients with Z-endoxifen levels >17.9 nM after adjustment for clinical relevant variables and correction for multiple testing. Analyses regarding adherence are not complete and more results will be presented in the poster.

Discussion: Our data indicates that high serum concentrations of tam and low concentrations of Z-endoxifen are associated with vaginal dryness and sexual dysfunction. Patients reporting “very low libido” had the highest levels of tam, suggesting that slow metabolic conversion and accumulation of tam may contribute to sexual dysfunction. Our results were only significant in the second year of follow-up, possibly because patients wait to resume sexual activity after diagnosis, chemo and surgery. After receiving advice (i.e. lubricants), the symptoms are often reduced in the subsequent follow-up (3rd year). In conclusion, our results indicate that monitoring tam serum concentrations may be used to predict side effects.

1 Owusu C. et al. JCO. 2008

2 Helland T. et al. BCR. 2017

Citation Format: Helland T, Haugstøyl ME, Hagen KB, Kvaløy JT, Lunde S, Lode K, Lind RA, Gripsrud BH, Bifulco E, Gebreslase NS, Jonassen J, Hustad SS, Aas T, Lende TH, Lien EA, Janssen EA, Mellgren G, Søiland H. Serum concentrations of tamoxifen and Z-endoxifen may predict sexual dysfunction in the 2nd year of adjuvant endocrine treatment [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-14-08.

Abstract P3-12-05: Serum levels of the active tamoxifen metabolite Z-4OHtam is predictive of long-term survival in luminal B subtype of breast cancer patients

Background

Tamoxifen (tam) is the main adjuvant endocrine treatment option in premenopausal breast cancer (BC) patients comprising luminal-like tumors. However, a significant proportion of tam-users will experience a relapse within 15 years of primary surgery. We postulate that some patients do not achieve the full clinical benefit of tam due to inter-individual differences in the metabolism of the drug and that the clinical relevance of this may be different between molecular subtypes of BC. Here, we have compared the prognostic value of threshold levels of active tam metabolites in PAM50 luminal (lum) A and B molecular subtypes.

Material and Methods

A number of 64 lum-like BC patients who were relapse-free 3 years after surgery, were retrospectively analyzed in the observational Oslo1 study. All patients received 20 mg tamoxifen daily for 5 years. Serum was obtained at the time of the 3 years follow-up. A sensitive and accurate LC-MS/MS method was developed and validated for the detection and quantification of tam and 9 metabolites in human serum. The median follow-up time from serum sampling to BC death or last follow-up was 13.9 years (0.6-16.5). Recurrence score and molecular subtype of the patients were determined on FFPE-tumor samples using the PAM50 classification algorithm.

Results

A linear trend was identified for the correlation between active metabolite Z-4OHtam and BCSS (p=0.021, HR=0.64, CI95=0.43–0.93). There was no linear association between the remaining metabolites and BC outcome. We further explored the possible association between survival and concentration thresholds for the active metabolites Z-4OHtam and Z-endoxifen and identified supervised cut off values representing low concentrations for Z-4OHtam (≤3.26 nM) and Z-endoxifen (≤9.00 nM). BC patients with low Z-4OHtam had a BCSS of 33.3% compared to 82.8% in patients with Z-4OHtam >3.26 nM (p<0.001, logrank; HR=6.83, CI 95=2.09-22.36). Lum status (A vs B; HR=5.50, CI95= 1.66-18.25) and Z-4OHtam concentration status (high vs low; HR=6.05, CI95=1.74-21.06) were the only factors left in the final multivariable model. A log-linear relationship between the ROR score and BCSS (p=0.002, HR=1.09, CI95=1.03–1.15) was identified after adjustment of clinically relevant variables and lum status was highly prognostic, (Lum A vs B; p=0.001, HR=5.2, CI=1.72-15.46). Therefore, we wanted to compare the prognostic value of the Z-4OHtam threshold in patients subgroups stratified by lum status. Low concentrations of Z-4OHtam were associated with poorer survival for patients in the lum B group only (HR=4.94, CI 95=1.16-21-02). For the lum A patients no significant association was found.

Discussion

Low levels (≤ 3.26 nM) of the active tam metabolite Z-4OHtam was associated with a poorer long-term outcome in tam-treated BC patients. However, when grouping patients according to the PAM50-based molecular subtype, this was only significant in patients belonging to the lum B subtype. Our results suggest that higher levels of active tam metabolites and thus better ER blockage are more important in the more aggressive lum B subtype.

Citation Format: Helland T, Søiland H, Hustad S, Lash TL, Kvaløy JT, Renolen A, Borgen E, Bifulco E, Henne N, Lien EA, Mellgren G, Naume B, Janssen EA. Serum levels of the active tamoxifen metabolite Z-4OHtam is predictive of long-term survival in luminal B subtype of breast cancer patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-12-05.

Novel immunohistochemistry-based signatures to predict metastatic site of triple-negative breast cancers

BACKGROUND

Although distant metastasis (DM) in breast cancer (BC) is the most lethal form of recurrence and the most common underlying cause of cancer related deaths, the outcome following the development of DM is related to the site of metastasis. Triple negative BC (TNBC) is an aggressive form of BC characterised by early recurrences and high mortality. Athough multiple variables can be used to predict the risk of metastasis, few markers can predict the specific site of metastasis. This study aimed at identifying a biomarker signature to predict particular sites of DM in TNBC.

METHODS

A clinically annotated series of 322 TNBC were immunohistochemically stained with 133 biomarkers relevant to BC, to develop multibiomarker models for predicting metastasis to the bone, liver, lung and brain. Patients who experienced metastasis to each site were compared with those who did not, by gradually filtering the biomarker set via a two-tailed t-test and Cox univariate analyses. Biomarker combinations were finally ranked based on statistical significance, and evaluated in multivariable analyses.

RESULTS

Our final models were able to stratify TNBC patients into high risk groups that showed over 5, 6, 7 and 8 times higher risk of developing metastasis to the bone, liver, lung and brain, respectively, than low-risk subgroups. These models for predicting site-specific metastasis retained significance following adjustment for tumour size, patient age and chemotherapy status.

CONCLUSIONS

Our novel IHC-based biomarkers signatures, when assessed in primary TNBC tumours, enable prediction of specific sites of metastasis, and potentially unravel biomarkers previously unknown in site tropism.

Consistent condom use increases spontaneous regression in high-risk non-HPV16 but not in HPV16 CIN2-3 lesions, a prospective population-based cohort study

Background

The major cause of cervical intraepithelial neoplasia (CIN) is persistent infection with human papillomavirus (HPV). Most CIN grade 2 and 3 lesions are treated with cone excision, although a substantial proportion (6-50%) of CIN2-3 lesions will regresses spontaneously. Predictors for regression of CIN2-3 are desirable in order to reduce this overtreatment.

Methods

In this prospective cohort study, 145 consecutive women with first-time onset CIN2-3 in colposcopy-directed biopsies and standardized biopsy-cone excision interval were included. The genotype of the high-risk human papillomaviruses (=hrHPV) and clinical factors including sexual behaviour, parity, contraception and smoking were assessed. Patients were divided into two groups according to lesions containing HPV16 (hrHPV16+) and high-risk non-HPV16 (hrHPV16-) genotypes.

Results

Women whose partners consistently used condoms showed a significantly higher regression rate than women using other types of contraception (53% versus 13%, p<0.0001). However, this effect was only seen in hrHPV16- patients (73% regression rate versus 13%, p<0.0001). HrHPV16+ patients had a significantly higher number of sexual partners and more current smokers compared to hrHPV16- patients. The regression rate was not significantly different in CIN2-3 lesions containing HPV16 (hrHPV16+) versus hrHPV16- genotypes.

Conclusions

Heterogeneity among hrHPV genotypes excists. HPV-genotype analyses can identify women who significantly increase their chance of regression by consistent condom use.

Discrimination of grade 2 and 3 cervical intraepithelial neoplasia by means of analysis of water soluble proteins recovered from cervical biopsies

Background

Cervical intraepithelial neoplasia (CIN) grades 2 and 3 are usually grouped and treated in the same way as "high grade", in spite of their different risk to cancer progression and spontaneous regression rates. CIN2-3 is usually diagnosed in formaldehyde-fixed paraffin embedded (FFPE) punch biopsies. This procedure virtually eliminates the availability of water-soluble proteins which could have diagnostic and prognostic value.

Aim

To investigate whether a water-soluble protein-saving biopsy processing method followed by a proteomic analysis of supernatant samples using LC-MS/MS (LTQ Orbitrap) can be used to distinguish between CIN2 and CIN3.

Methods

Fresh cervical punch biopsies from 20 women were incubated in RPMI1640 medium for 24 hours at 4°C for protein extraction and subsequently subjected to standard FFPE processing. P16 and Ki67-supported histologic consensus review CIN grade (CIN2, n = 10, CIN3, n = 10) was assessed by independent gynecological pathologists. The biopsy supernatants were depleted of 7 high abundance proteins prior to uni-dimensional LC-MS/MS analysis for protein identifications.

Results

The age of the patients ranged from 25-40 years (median 29.7), and mean protein concentration was 0.81 mg/ml (range 0.55 - 1.14). After application of multistep identification criteria, 114 proteins were identified, including proteins like vimentin, actin, transthyretin, apolipoprotein A-1, Heat Shock protein beta 1, vitamin D binding protein and different cytokeratins. The identified proteins are annotated to metabolic processes (36%), signal transduction (27%), cell cycle processes (15%) and trafficking/transport (9%). Using binary logistic regression, Cytokeratin 2 was found to have the strongest independent discriminatory power resulting in 90% overall correct classification.

Conclusions

114 proteins were identified in supernatants from fresh cervical biopsies and many differed between CIN2 and 3. Cytokeratin 2 is the strongest discriminator with 90% overall correct classifications.

Trypsin in colorectal cancer: molecular biological mechanisms of proliferation, invasion, and metastasis

Trypsin is involved in colorectal carcinogenesis and promotes proliferation, invasion, and metastasis. Although a well-known pancreatic digestive enzyme, trypsin has also been found in other tissues and various cancers, most importantly of the colorectum. Moreover, colorectal cancers with trypsin expression have a poor prognosis and shorter disease-free survival. Biological understanding of how trypsin causes cancer progression is emerging. It seems to act both directly and indirectly through a 'proteinase-antiproteinase-system', and by activation of other proteinase cascades. Invasion of the basal membrane by cancer cells may be promoted directly by trypsin digestion of type I collagen. Trypsin activates, and is co-expressed with matrix metalloproteinases (MMPs), which are known to facilitate invasion and metastasis. MMP-2, MMP-7, and MMP-9 are co-expressed together with trypsin and seem to be of particular importance in proliferation, progression, and invasion. MMPs may play a role in both conversion from adenoma to carcinoma, and in the initiation of invasion and metastasis. Co-segregation of trypsin and MMPs within the tumour environment is important for the activation of MMPs, and may explain the deleterious effect of trypsin on prognosis in colorectal cancer. Trypsin and proteinase-activated receptor 2 (PAR-2) act together in an autocrine loop that promotes proliferation, invasion, and metastasis through various mechanisms, of which prostaglandin synthesis is important. Stimulated by trypsin, both MMP and PAR-2 may activate the mitogenic MAPK-ERK pathway through activation of the epidermal growth factor receptor. Experimental trypsin inhibition is feasible but not very effective, and trypsin as a target for clinical therapy is unlikely to be successful owing to its universal distribution. However, as the pathways of trypsin and co-activated protein cascades emerge, biological understanding of colorectal carcinogenesis will be further illuminated and may pave the way for prognosticators, predictors, and novel targets of therapy.

X-linked cardioskeletal myopathy and neutropenia (Barth syndrome) (MIM 302060)

X-linked cardioskeletal myopathy, neutropenia and abnormal mitochondria (MIM 302060) (synonyms: Barth syndrome, 3-methylglutaconic acid-uria type II, endocardial fibroelastosis type 2) has been reported in patients and families from Europe, North America and Australia. Previous studies characterized the main components of the disease: dilated cardiomyopathy, skeletal myopathy, neutropenia, 3-methylglutaconic aciduria and diminished statural growth. Respiratory chain impairments have been found in several studies, without pinpointing a single enzyme complex. 3-Methylglutaconic aciduria is shared with several other disorders that affect the respiratory chain. Previous studies excluded a block in the major pathway of leucine catabolism. We performed leucine loading, accompanied by fasting, in patients and observed a significant rise of 3-methylglutaconic acid and 3-methylglutaric acid. Taken together with the absence of an enzymatic block in the major leucine catabolic route, the possibility remains that the increased basal excretion of 3-methylglutaconic acid and other products of branched-chain amino acids is the result of overload of this pathway or--more likely--mitochondrial leakage. Linkage studies have localized the gene to the Xq28 region. The associated tafazzin gene (TAZ), has been fully characterized recently, and mutations located in conserved regions have been reported. Carrier detection and prenatal diagnosis have now become possible through mutation analysis. Sequence homology of the TAZ gene to a highly conserved superclass of acyltransferases (Neuwald's hypothesis) predicts a glycerophospholipid as the missing end product. This points to the (lipid) structure of the inner mitochondrial membrane as a promising new area of research.

The X-linked gene G4.5 is responsible for different infantile dilated cardiomyopathies

Barth syndrome (BTHS) is an X-linked disorder characterized clinically by the associated features of cardiac and skeletal myopathy, short stature, and neutropenia. The clinical manifestations of the disease are, in general, quite variable, but cardiac failure as a consequence of cardiac dilatation and hypertrophy is a constant finding and is the most common cause of death in the first months of life. X-linked cardiomyopathies with clinical manifestations similar to BTHS have been reported, and it has been proposed that they may be allelic. We have recently identified the gene responsible for BTHS, in one of the Xq28 genes, G4.5. In this paper we report the sequence analysis of 11 additional familial cases: 8 were diagnosed as possibly affected with BTHS, and 3 were affected with X-linked dilated cardiomyopathies. Mutations in the G4.5 gene were found in nine of the patients analyzed. The molecular studies have linked together what were formerly considered different conditions and have shown that the G4.5 gene is responsible for BTHS (OMIM 302060), X-linked endocardial fibroelastosis (OMIM 305300), and severe X-linked cardiomyopathy (OMIM 300069). Our results also suggest that very severe phenotypes may be associated with null mutations in the gene, whereas mutations in alternative portions or missense mutations may give a "less severe" phenotype.

Connexin32 gene mutations in X-linked dominant Charcot-Marie-Tooth disease (CMTX1)

Single-strand conformational polymorphisms (SSCP) of the connexin32 gene were analyzed in 121 patients possibly affected by Charcot-Marie-Tooth (CMT) disease. The 121 patients were selected from 443 possible CMT/HNPP (hereditary neuropathy with liability to pressure palsies) patients based on genetic linkage to Xq13.1, absence of the 17p12 duplication and deletion, and absence of point mutations in PMP22 and P0. We found five new mutations at nucleotides 105 (C-T), 316 (C-G), 321 (C-T), 328 (T-C), and 657 (G-C), and three mutations at nucleotide 126 (C-T), 249 (G-A), and 477 (G-A) previously described in other unrelated families. The nucleotide changes resulted in seven amino-acid substitutions and one premature stop codon.

Deletions in Xq28 in two boys with myotubular myopathy and abnormal genital development define a new contiguous gene syndrome in a 430 kb region

We have recently described a female patient with myotubular myopathy (MTM1) and an interstitial deletion at Xq28. Characterisation of the deletion allowed us to position the MTM1 gene to a 600 kb region between DXS304 and DXS497. In order to further restrict the region we screened for deletions in a set of 38 patients. We found two overlapping deletions in boys that in addition to MTM1 showed an unexpected abnormal genital development. As the latter phenotype is not found in the other non-deleted MTM1 patients, our observations are best explained by a contiguous gene syndrome. The deletions define a 430 kb region that contains the MTM1 gene and most likely a gene implicated in male sexual development. A high resolution physical map of this region is presented.

Transepidermal water vapour loss is not increased during and following dithranol irritation

Dithranol is established as a very successful treatment for psoriasis. Its main disadvantages are irritation and staining at sites of application. The aim of the present study was to elucidate further the mechanism of dithranol-induced irritation, in particular to what extent this is related to an impairment of the skin barrier. Dithranol 3% in cream, paste and petrolatum was applied to the forearm skin of 20 volunteers and left in situ for 1 h. Transepidermal water loss (TEWL) was measured during a period of 2 weeks following dithranol application. In addition, a visual scoring system and colorimetry were used to assess erythema. The study showed conclusively that TEWL was not affected by the application of dithranol, even though pronounced erythema occurred.

The gene for X-linked myotubular myopathy is located in an 8 Mb region at the border of Xq27.3 and Xq28

X-linked recessive myotubular myopathy (XLMTM) is a rare and severe neonatal neuromuscular disease characterized by muscle weakness, hypotonia, and respiratory problems. Here we report an extensive linkage analysis in two families with XLMTM. Using 18 markers in the Xq27-Xqter region we found a maximum two-point lod score of Z = 4.00 at theta = 0.00 for the marker II-10 (DXS466). Three recombinations were detected between markers and the disease locus. At the distal side of Xq27.3 a recombination was present in between RNI (DXS369) and VK23b (DXS297), another in between VK23b (DXS297) and II-10 (DXS466), and at the proximal side of Xq28 a recombination in between U6.2 (DXS304) and Cpx67 (DXS134). Combining the results of both families we conclude that XLMTM is located in the 8 Mb(11 cM) region between VK23b (DXS297) and Cpx67 (DXS134).

Quantitative measurement of duplicated DNA as a diagnostic test for Charcot-Marie-Tooth disease type 1a

Charcot-Marie-Tooth disease type 1 (CMT1) is a hereditary motor and sensory neuropathy. The autosomal dominant subtype is often linked with a large duplication on chromosome 17p11.2. The gene encoding the peripheral myelin protein PMP 22 (the critical gene in this subtype of CMT1) is located within this duplication. To detect this duplication in chromosomal DNA from individuals thought to have CMT1, we compared the hybridization signals of two DNA probes within this duplication (VAW412R3a and VAW409R3a) with the signal of a reference probe (E3.9). When duplication was present, the signals from the first two probes increased from 100% (for nonduplicated samples) to 145% and 142%, respectively. The day-to-day variance was 3.7% and 5.1%, respectively. We demonstrated this DNA duplication in 49 of 95 DNA samples from unrelated individuals thought to have CMT1. Moreover, because hereditary neuropathy with liability to pressure palsies (HNPP) is based on a DNA deletion in the same area of chromosome 17, this quantitative test may be useful in establishing the presence of HNPP. In a preliminary investigation, four unrelated patients with HNPP yielded test values of 63% and 54%, respectively, of those for nonduplicated samples (CV 19% and 18%, respectively; n = 4), suggesting a deletion in 17p11.2.

Allelic heterogeneity in hereditary motor and sensory neuropathy type Ia (Charcot-Marie-Tooth disease type 1a)

The most frequently found mutation in autosomal dominant hereditary motor and sensory neuropathy type I (HMSN I) is a large duplication on chromosome 17p11.2 containing probes VAW409R3, VAW412R3, and EW401. We investigated a family with severe features of HMSN I, and demonstrated the absence of this duplication by a quantitative analysis of the hybridization signals of VAW409R3 and VAW412R3. Linkage analysis, however, revealed linkage with probe VAW409R3a (lod score, 3.22), which demonstrates the existence of allelic heterogeneity within the HMSN Ia locus. These findings have implications for clinical practice and for investigating the identity of the HMSN Ia gene.

The masked threshold to noise ratio in brainstem electric response audiometry: assessment of the conductive loss component by bone-conducted masking

The aim of this study was to assess the conductive loss component (CLC) by brainstem electric response audiometry. A bone-conducted noise was used to mask out the response to a conventional air-conducted click stimulus. The difference between the levels of the click and the noise is defined as the masked threshold to noise ratio (MTNR). This MTNR was determined for 21 normal ears (MTNR = -13 +/- 5 dB). The increase in MTNR compared to this normative value is a measure of the CLC. For 10 ears with an artificially induced purely conductive loss, the increase in MTNR is in good agreement with the results of conventional pure-tone and brainstem electric response audiometry.

De-novo mutation in hereditary motor and sensory neuropathy type I

Isolated cases of hereditary motor and sensory neuropathy type I (HMSN I, Charcot-Marie-Tooth disease type 1) have been thought to be most frequently autosomal recessive. We have found that a recently discovered duplication in chromosome 17, responsible for most cases of autosomal dominant HMSN I, is present as a de-novo mutation in 9 out of 10 sporadic patients. This finding has important implications for genetic counselling of isolated patients with HMSN I.

The duplication in Charcot-Marie-Tooth disease type 1a spans at least 1100 kb on chromosome 17p11.2

Recently, it has been shown that Charcot-Marie-Tooth disease type 1a (CMT1a) is linked with a duplication of a DNA segment that is detected by probe VAW409R3, and that is located on chromosome 17p11.2. Here, we show that this duplication also contains VAW412R3a, but not A10-41 and EW503. Accounting for the duplication in recombination analysis, we found recombinants between CMT1a and EW301 and EW502, but not with A10-41, VAW409R3, and VAW412R3. Using pulsed-field gel electrophoresis analysis, we estimated the minimal size of the duplicated region in CMT1a patients to be 1100 kb.