Genomic characterization and detection of potential therapeutic targets for peritoneal mesothelioma in current practice

Peritoneal mesothelioma (PeM) is an aggressive tumor with limited treatment options. The current study aimed to evaluate the value of next generation sequencing (NGS) of PeM samples in current practice. Foundation Medicine F1CDx NGS was performed on 20 tumor samples. This platform assesses 360 commonly somatically mutated genes in solid tumors and provides a genomic signature. Based on the detected mutations, potentially effective targeted therapies were identified. NGS was successful in 19 cases. Tumor mutational burden (TMB) was low in 10 cases, and 11 cases were microsatellite stable. In the other cases, TMB and microsatellite status could not be determined. BRCA1 associated protein 1 (BAP1) mutations were found in 32% of cases, cyclin dependent kinase inhibitor 2A/B (CDKN2A/B) and neurofibromin 2 (NF2) mutations in 16%, and ataxia-telangiectasia mutated serine/threonine kinase (ATM) in 11%. Based on mutations in the latter two genes, potential targeted therapies are available for approximately a quarter of cases (i.e., protein kinase inhibitors for three NF2 mutated tumors, and polyADP-ribose polymerase inhibitors for two ATM mutated tumors). Extensive NGS analysis of PeM samples resulted in the identification of potentially effective targeted therapies for about one in four patients. Although these therapies are currently not available for patients with PeM, ongoing developments might result in new treatment options in the future.

Quantitative modeling of tumor dynamics and development of drug resistance in non-small cell lung cancer patients treated with erlotinib

Insight into the development of treatment resistance can support the optimization of anticancer treatments. This study aims to characterize the tumor dynamics and development of drug resistance in patients with non-small cell lung cancer treated with erlotinib, and investigate the relationship between baseline circulating tumor DNA (ctDNA) data and tumor dynamics. Data obtained for the analysis included (1) intensively sampled erlotinib concentrations from 29 patients from two previous pharmacokinetic (PK) studies, and (2) tumor sizes, ctDNA measurements, and sparsely sampled erlotinib concentrations from 18 patients from the START-TKI study. A two-compartment population PK model was first developed which well-described the PK data. The PK model was subsequently applied to investigate the exposure-tumor dynamics relationship. To characterize the tumor dynamics, models accounting for intra-tumor heterogeneity and acquired resistance with or without primary resistance were investigated. Eventually, the model assumed acquired resistance only resulted in an adequate fit. Additionally, models with or without exposure-dependent treatment effect were explored, and no significant exposure-response relationship for erlotinib was identified within the observed exposure range. Subsequently, the correlation of baseline ctDNA data on EGFR and TP53 variants with tumor dynamics' parameters was explored. The analysis indicated that higher baseline plasma EGFR mutation levels correlated with increased tumor growth rates, and the inclusion of ctDNA measurements improved model fit. This result suggests that quantitative ctDNA measurements at baseline have the potential to be a predictor of anticancer treatment response. The developed model can potentially be applied to design optimal treatment regimens that better overcome resistance.

Concurrent Langerhans Cell Histiocytosis and Acute Myeloid Leukemia Without Clonal Relationship

This case report describes a woman in her 30s who had been treated with chemotherapy and presented with Langerhans cell histiocytosis and acute myeloid leukemia (AML).

Molecular alterations and potential actionable mutations in peritoneal mesothelioma: a scoping review of high-throughput sequencing studies

BACKGROUND

Peritoneal mesothelioma (PeM) is a rare malignancy with a poor prognosis. Currently there is a lack of effective systemic therapies. Due to the rarity of PeM, it is challenging to study new treatment options. Off-label use of targeted drugs could be an effective approach. This scoping review aims to explore the genomic landscape of PeM to identify potential therapeutic targets.

MATERIALS AND METHODS

A systematic literature search of Embase, Medline, Web of Science, the Cochrane Library, and Google Scholar was carried out up to 1 November 2022. Studies that reported on molecular alterations in PeM detected by high-throughput sequencing techniques were included. Genes that were altered in ≥1% of PeMs were selected for the identification of potential targeted therapies.

RESULTS

Thirteen articles were included, comprising 824 PeM patients. In total, 142 genes were altered in ≥1% of patients, of which 7 genes were altered in ≥10%. BAP1 was the most commonly altered gene (50%). Other commonly altered genes were NF2 (25%), CDKN2A (23%), CDKN2B (17%), PBRM1 (15%), TP53 (14%), and SETD2 (13%). In total, 17% of PeM patients were carriers of a germline mutation, mainly in BAP1 (7%).

CONCLUSIONS

This scoping review provides an overview of the mutational landscape of PeM. Germline mutations might be a larger contributor to the incidence of PeM than previously thought. Currently available targeted therapy options are limited, but several targeted agents [such as poly (ADP-ribose) polymerase (PARP), enhancer of zeste homolog 2 (EZH2), and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors] were identified that might provide new targeted therapy options in the future.

Medulloblastoma in adults: evaluation of the Dutch society for neuro-oncology treatment protocol

PURPOSE

Medulloblastoma is a rare tumor in adults. The objective of this nationwide, multicenter study was to evaluate the toxicity and efficacy of the Dutch treatment protocol for adult medulloblastoma patients.

METHODS

Adult medulloblastoma patients diagnosed between 2010 and 2018 were identified in the Dutch rare tumors registry or nationwide pathology database. Patients with intention to treat according to the national treatment protocol were included. Risk stratification was performed based on residual disease, histological subtype and extent of disease. All patients received postoperative radiotherapy [craniospinal axis 36 Gy/fossa posterior boost 19.8 Gy (14.4 Gy in case of metastases)]. High-risk patients received additional neoadjuvant (carboplatin-etoposide), concomitant (vincristine) and adjuvant chemotherapy (carboplatin-vincristine-cyclophosphamide) as far as feasible by toxicity. Methylation profiling, and additional next-generation sequencing in case of SHH-activated medulloblastomas, were performed.

RESULTS

Forty-seven medulloblastoma patients were identified, of whom 32 were treated according to the protocol. Clinical information and tumor material was available for 28 and 20 patients, respectively. The histological variants were mainly classic (43%) and desmoplastic medulloblastoma (36%). Sixteen patients (57%) were considered standard-risk and 60% were SHH-activated medulloblastomas. Considerable treatment reductions and delays in treatment occurred due to especially hematological and neurotoxicity. Only one high-risk patient could complete all chemotherapy courses. 5-years progression-free survival (PFS) and overall survival (OS) for standard-risk patients appeared worse than for high-risk patients (PFS 69% vs. 90%, OS 81% vs. 90% respectively), although this wasn't statistically significant.

CONCLUSION

Combined chemo-radiotherapy is a toxic regimen for adult medulloblastoma patients that may result in improved survival.

P11.69.B IDH1/2wildtype gliomas grade 2 and 3 with molecular glioblastoma-like profile have a distinct course of epilepsy compared toIDH1/2wildtype glioblastomas

Background

IDH1/2 wildtype (IDHwt) glioma WHO grade 2 and 3 patients with pTERT mutation and/or EGFR amplification and/or +7/−10 chromosome gain/loss have a similar overall survival time as IDHwt glioblastoma patients, and are both considered glioblastoma IDHwt according to the WHO 2021 classification. However, differences in seizure onset have been observed. This study aimed to compare the course of epilepsy in the two glioblastoma subtypes.

Material and Methods

We analyzed epilepsy data of an existing cohort including IDHwt histologically lower-grade glioma WHO grade 2 and 3 with molecular glioblastoma-like profile (IDHwt hLGG) and IDHwt glioblastoma patients. Primary outcome was the incidence proportion of epilepsy during the disease course. Major secondary outcomes included onset of epilepsy, number of seizure days and antiepileptic drug (AED) polytherapy.

Results

Out of 254 patients, 78% (50/64) IDHwt hLGG and 68% (129/190) IDHwt glioblastoma patients developed epilepsy during the disease course (p=0.121). Epilepsy onset before histopathological diagnosis occurred more frequently in IDHwt hLGG compared to IDHwt glioblastoma patients (90% versus 60%, p<0.001), with a significantly longer median time to diagnosis (3.5 versus 1.3 months, p<0.001). Median total seizure days was also longer for IDHwt hLGG patients (7.0 versus 3.0, p=0.005), and they received more often AED polytherapy (32% versus 17%, p=0.028).

Conclusion

Although the incidence proportion of epilepsy during the entire disease course is similar, IDHwt hLGG patients show a significantly higher incidence of epilepsy before diagnosis and a significantly longer median time between first seizure and diagnosis compared to IDHwt glioblastoma patients, indicating a distinct clinical course.

Adjuvant and concurrent temozolomide for 1p/19q non-co-deleted anaplastic glioma (CATNON; EORTC study 26053-22054): second interim analysis of a randomised, open-label, phase 3 study

BACKGROUND

The CATNON trial investigated the addition of concurrent, adjuvant, and both current and adjuvant temozolomide to radiotherapy in adults with newly diagnosed 1p/19q non-co-deleted anaplastic gliomas. The benefit of concurrent temozolomide chemotherapy and relevance of mutations in the IDH1 and IDH2 genes remain unclear.

METHODS

This randomised, open-label, phase 3 study done in 137 institutions across Australia, Europe, and North America included patients aged 18 years or older with newly diagnosed 1p/19q non-co-deleted anaplastic gliomas and a WHO performance status of 0-2. Patients were randomly assigned (1:1:1:1) centrally using a minimisation technique to radiotherapy alone (59·4 Gy in 33 fractions; three-dimensional conformal radiotherapy or intensity-modulated radiotherapy), radiotherapy with concurrent oral temozolomide (75 mg/m2 per day), radiotherapy with adjuvant oral temozolomide (12 4-week cycles of 150-200 mg/m2 temozolomide given on days 1-5), or radiotherapy with both concurrent and adjuvant temozolomide. Patients were stratified by institution, WHO performance status score, age, 1p loss of heterozygosity, the presence of oligodendroglial elements on microscopy, and MGMT promoter methylation status. The primary endpoint was overall survival adjusted by stratification factors at randomisation in the intention-to-treat population. A second interim analysis requested by the independent data monitoring committee was planned when two-thirds of total required events were observed to test superiority or futility of concurrent temozolomide. This study is registered with ClinicalTrials.gov, NCT00626990.

FINDINGS

Between Dec 4, 2007, and Sept 11, 2015, 751 patients were randomly assigned (189 to radiotherapy alone, 188 to radiotherapy with concurrent temozolomide, 186 to radiotherapy and adjuvant temozolomide, and 188 to radiotherapy with concurrent and adjuvant temozolomide). Median follow-up was 55·7 months (IQR 41·0-77·3). The second interim analysis declared futility of concurrent temozolomide (median overall survival was 66·9 months [95% CI 45·7-82·3] with concurrent temozolomide vs 60·4 months [45·7-71·5] without concurrent temozolomide; hazard ratio [HR] 0·97 [99·1% CI 0·73-1·28], p=0·76). By contrast, adjuvant temozolomide improved overall survival compared with no adjuvant temozolomide (median overall survival 82·3 months [95% CI 67·2-116·6] vs 46·9 months [37·9-56·9]; HR 0·64 [95% CI 0·52-0·79], p<0·0001). The most frequent grade 3 and 4 toxicities were haematological, occurring in no patients in the radiotherapy only group, 16 (9%) of 185 patients in the concurrent temozolomide group, and 55 (15%) of 368 patients in both groups with adjuvant temozolomide. No treatment-related deaths were reported.

INTERPRETATION

Adjuvant temozolomide chemotherapy, but not concurrent temozolomide chemotherapy, was associated with a survival benefit in patients with 1p/19q non-co-deleted anaplastic glioma. Clinical benefit was dependent on IDH1 and IDH2 mutational status.

FUNDING

Merck Sharpe & Dohme.

Prognostic significance of genome-wide DNA methylation profiles within the randomised, phase 3, EORTC CATNON trial on non-1p/19q deleted anaplastic glioma

Background

Survival in patients with IDH1/2-mutant (mt) anaplastic astrocytomas is highly variable. We have used the prospective phase 3 CATNON trial to identify molecular factors related to outcome in IDH1/2mt anaplastic astrocytoma patients.

Methods

The CATNON trial randomized 751 adult patients with newly diagnosed 1p/19q non-codeleted anaplastic glioma to 59.4 Gy radiotherapy +/− concurrent and/or adjuvant temozolomide. The presence of necrosis and/or microvascular proliferation was scored at central pathology review. Infinium MethylationEPIC BeadChip arrays were used for genome-wide DNA methylation analysis and the determination of copy number variations (CNV). Two DNA methylation-based tumor classifiers were used for risk stratification. Next-generation sequencing (NGS) was performed using 1 of the 2 glioma-tailored NGS panels. The primary endpoint was overall survival measured from the date of randomization.

Results

Full analysis (genome-wide DNA methylation and NGS) was successfully performed on 654 tumors. Of these, 432 tumors were IDH1/2mt anaplastic astrocytomas. Both epigenetic classifiers identified poor prognosis patients that partially overlapped. A predictive prognostic Cox proportional hazard model identified that independent prognostic factors for IDH1/2mt anaplastic astrocytoma patients included; age, mini-mental state examination score, treatment with concurrent and/or adjuvant temozolomide, the epigenetic classifiers, PDGFRA amplification, CDKN2A/B homozygous deletion, PI3K mutations, and total CNV load. Independent recursive partitioning analysis highlights the importance of these factors for patient prognostication.

Conclusion

Both clinical and molecular factors identify IDH1/2mt anaplastic astrocytoma patients with worse outcome. These results will further refine the current WHO criteria for glioma classification.

INTELLANCE 2/EORTC 1410 randomized phase II study of Depatux-M alone and with temozolomide vs temozolomide or lomustine in recurrent EGFR amplified glioblastoma

Background

Depatuxizumab mafodotin (Depatux-M) is a tumor-specific antibody–drug conjugate consisting of an antibody (ABT-806) directed against activated epidermal growth factor receptor (EGFR) and the toxin monomethylauristatin-F. We investigated Depatux-M in combination with temozolomide or as a single agent in a randomized controlled phase II trial in recurrent EGFR amplified glioblastoma.

Methods

Eligible were patients with centrally confirmed EGFR amplified glioblastoma at first recurrence after chemo-irradiation with temozolomide. Patients were randomized to either Depatux-M 1.25 mg/kg every 2 weeks intravenously, or this treatment combined with temozolomide 150–200 mg/m² day 1–5 every 4 weeks, or either lomustine or temozolomide. The primary endpoint of the study was overall survival.

Results

Two hundred sixty patients were randomized. In the primary efficacy analysis with 199 events (median follow-up 15.0 mo), the hazard ratio (HR) for the combination arm compared with the control arm was 0.71 (95% CI = 0.50, 1.02; P = 0.062). The efficacy of Depatux-M monotherapy was comparable to that of the control arm (HR = 1.04, 95% CI = 0.73, 1.48; P = 0.83). The most frequent toxicity in Depatux-M treated patients was a reversible corneal epitheliopathy, occurring as grades 3–4 adverse events in 25–30% of patients. In the long-term follow-up analysis with median follow-up of 28.7 months, the HR for the comparison of the combination arm versus the control arm was 0.66 (95% CI = 0.48, 0.93).

Conclusion

This trial suggests a possible role for the use of Depatux-M in combination with temozolomide in EGFR amplified recurrent glioblastoma, especially in patients relapsing well after the end of first-line adjuvant temozolomide treatment. (NCT02343406)

RET Fluorescence In Situ Hybridization Analysis Is a Sensitive but Highly Unspecific Screening Method for RET Fusions in Lung Cancer

INTRODUCTION

RET gene fusions are established oncogenic drivers in 1% of NSCLC. Accurate detection of advanced patients with RET fusions is essential to ensure optimal therapy choice. We investigated the performance of fluorescence in situ hybridization (FISH) as a diagnostic test for detecting functional RET fusions.

METHODS

Between January 2016 and November 2019, a total of 4873 patients with NSCLC were routinely screened for RET fusions using either FISH (n = 2858) or targeted RNA next-generation sequencing (NGS) (n = 2015). If sufficient material was available, positive cases were analyzed by both methods (n = 39) and multiple FISH assays (n = 17). In an independent cohort of 520 patients with NSCLC, whole-genome sequencing data were investigated for disruptive structural variations and functional fusions in the RET and compared with ALK and ROS1 loci.

RESULTS

FISH analysis revealed RET rearrangement in 48 of 2858 cases; of 30 rearranged cases double tested with NGS, only nine had a functional RET fusion. RNA NGS yielded RET fusions in 14 of 2015 cases; all nine cases double tested by FISH had RET locus rearrangement. Of these 18 verified RET fusion cases, 16 had a split signal and two a complex rearrangement by FISH. By whole-genome sequencing, the prevalence of functional fusions compared with all disruptive events was lower in the RET (4 of 9, 44%) than the ALK (27 of 34, 79%) and ROS1 (9 of 12, 75%) loci.

CONCLUSIONS

FISH is a sensitive but unspecific technique for RET screening, always requiring a confirmation using an orthogonal technique, owing to frequently occurring RET rearrangements not resulting in functional fusions in NSCLC.

Prognostic value of TERT promoter mutations in conjunctival melanomas in addition to clinicopathological features

AIMS

To evaluate the prognostic value of clinical, histopathological and molecular features and to relate different treatment modalities to clinical outcome in conjunctival melanomas (CM).

METHODS

Retrospective review of clinical, histopathological and BRAF V600E and telomerase reverse transcriptase (TERT) promoter mutation status and treatment modalities, correlated to recurrence and metastasis in 79 patients with CM, diagnosed between 1987 and 2015 in three tertiary referral centres in the Netherlands and Belgium.

RESULTS

Out of 78 evaluable patients, recurrences occurred in 16 patients and metastasis in 12 patients (median follow-up time 35 months (0-260 months)). Tumour thickness >2 mm, pT status, the presence of epithelioid cells, ulceration and mitoses was significantly correlated with metastasis (p value 0.046, 0.01, 0.02, 0.001 and 0.003, respectively). Furthermore, CM frequently harbour BRAF V600E and TERT promoter mutations (29% and 43%, respectively). TERT promoter mutations were correlated to shorter metastasis-free survival (p value 0.002). No significant correlation was found for clinical parameters and metastatic disease. Palpebral, forniceal and caruncular melanomas were more prone to develop recurrences (p value: 0.03). Most CM were treated with excision with adjuvant therapy.

CONCLUSION

In line with the recommendations in the Eighth Edition of the American Joint Committee on Cancer Staging for CM, the pathology report should include information about pT status, tumour thickness, presence of epithelioid cells, ulceration and mitoses. Furthermore, information about the presence of a TERT promoter mutation and BRAF V600E mutation is of interest for therapeutic decision making. The presence of a TERT promoter mutation is correlated to metastatic disease.

Plasma Predictive Features in Treating EGFR-Mutated Non-Small Cell Lung Cancer

Although epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) are the preferred treatment for patients with EGFR-mutated non-small cell lung cancer (NSCLC), not all patients benefit. We therefore explored the impact of the presence of mutations found in cell-free DNA (cfDNA) and TKI plasma concentrations during treatment on progression-free survival (PFS). In the prospective START-TKI study blood samples from 41 patients with EGFR-mutated NSCLC treated with EGFR-TKIs were available. Next generation sequencing (NGS) on cfDNA was performed, and plasma TKI concentrations were measured. Patients without complete plasma conversion of EGFR mutation at week 6 had a significantly shorter PFS (5.5 vs. 17.0 months, p = 0.002) and OS (14.0 vs. 25.5 months, p = 0.003) compared to patients with plasma conversion. In thirteen (second line) osimertinib-treated patients with a (plasma or tissue) concomitant TP53 mutation at baseline, PFS was significantly shorter compared to six wild-type cases; 8.8 vs. 18.8 months, p = 0.017. Erlotinib Cmean decrease of ≥10% in the second tertile of treatment was also associated with a significantly shorter PFS; 8.9 vs. 23.6 months, p = 0.037. We obtained evidence that absence of plasma loss of the primary EGFR mutation, isolated plasma p.T790M loss after six weeks, baseline concomitant TP53 mutations, and erlotinib Cmean decrease during treatment are probably related to worse outcome.

TP53 Mutations in Serum Circulating Cell-Free Tumor DNA As Longitudinal Biomarker for High-Grade Serous Ovarian Cancer

The aim of this study was to determine an optimal workflow to detect TP53 mutations in baseline and longitudinal serum cell free DNA (cfDNA) from high-grade serous ovarian carcinomas (HGSOC) patients and to define whether TP53 mutations are suitable as biomarker for disease. TP53 was investigated in tissue and archived serum from 20 HGSOC patients by a next-generation sequencing (NGS) workflow alone or combined with digital PCR (dPCR). AmpliSeq™-focused NGS panels and customized dPCR assays were used for tissue DNA and longitudinal cfDNAs, and Oncomine NGS panel with molecular barcoding was used for baseline cfDNAs. TP53 missense mutations were observed in 17 tissue specimens and in baseline cfDNA for 4/8 patients by AmpliSeq, 6/9 patients by Oncomine, and 4/6 patients by dPCR. Mutations in cfDNA were detected in 4/6 patients with residual disease and 3/4 patients with disease progression within six months, compared to 5/11 patients with no residual disease and 6/13 patients with progression after six months. Finally, mutations were detected at progression in 5/6 patients, but not during chemotherapy. NGS with molecular barcoding and dPCR were most optimal workflows to detect TP53 mutations in baseline and longitudinal serum cfDNA, respectively. TP53 mutations were undetectable in cfDNA during treatment but re-appeared at disease progression, illustrating its promise as a biomarker for disease monitoring.

Plasma Cell-Free DNA Testing of Patients With EGFR Mutant Non–Small-Cell Lung Cancer: Droplet Digital PCR Versus Next-Generation Sequencing Compared With Tissue-Based Results

PURPOSE

To compare the results of plasma cell-free DNA (cfDNA) droplet digital PCR (ddPCR) and next-generation sequencing (NGS) on detection of epidermal growth factor receptor ( EGFR) primary activating mutations and p.T790M with results of tissue analysis in patients with EGFR mutated non–small-cell lung cancer.

METHODS

All patients with EGFR mutated non–small cell lung cancer for which a pathology and a plasma specimen were available upon progression between November 2016 and July 2018 were selected. Concordance, Cohen’s κ, and intraclass correlation coefficients were calculated.

RESULTS

Plasma cfDNA and pathology specimens of 36 patients were analyzed. Agreement between ddPCR and NGS was 86% (κ = 0.63) for the primary activating mutation and 94% (κ = 0.89) for the p.T790M detection. Allele ratios were comparable, with an intraclass correlation coefficient of 0.992 and 0.997, respectively. Discrepancies of some degree were found in 15 patients (41.7%). In six patients (16.7%), no mutations were detected in cfDNA. In three patients (8.3%), p.T790M was detected in plasma but not in the pathology specimen, whereas in three other patients (8.3%), p.T790M was demonstrated in the pathology specimen but not in plasma. Concordance of cfDNA and pathology for the primary activating mutation was 69% for ddPCR and 83% for NGS. For the detection of p.T790M, this was 75% (κ = 0.49) for ddPCR as well as for NGS.

CONCLUSION

Mutual agreement is high between NGS and ddPCR in cfDNA on the level of a specific mutation, with comparable ratio results. Plasma testing of EGFR primary activating mutations and p.T790M shows high concordance with pathology results, for NGS as well as for ddPCR, depending on the extent of the panel used. In NGS, more genetic aberrations can be investigated at once.

Abstract B136: Highly accurate DNA-based detection of MET exon 14 skipping mutations in non-small cell lung cancer and clinical response upon targeted treatment

Background: Approximately 1.6%-5.7% of non-small cell lung cancers (NSCLC) are described to be driven by oncogenic MET exon 14 skipping mutations (METex14del). Although currently no therapy is registered specifically against METex14del, Phase I/II clinical trials and named patient based programs with cMET inhibitors show promising results. RNA-based analysis seems most optimal for METex14del detection, because theoretically, it would capture all MET exon 13-exon 15 fusions, regardless of the underlying DNA changes. However, acquiring sufficient RNA is often problematic. An alternative is DNA-based analysis, but commercially available DNA-based panels only detect up to 63% of known METex14del alterations. The goal of this study is to describe an optimized DNA-based diagnostic test for METex14del, and to report the histologic and clinical features of a real world METex14del non-squamous NSCLC patient cohort, including follow-up of patients treated with cMET-targeted therapy and consequent resistance mechanisms to cMET inhibition. Methods: Routine diagnostic pathology NSCLC FFPE specimens were investigated by a custom-made DNA-based targeted amplicon-based next generation sequencing (NGS) panel which includes 4 amplicons for METex14del detection. Retrospectively, histopathological characteristics and clinical follow up were investigated for advanced NSCLC with METex14del. We only present data of patients receiving crizotinib in a named patient based program (Pfizer Oncology). Results: In silico analysis showed that our custom-made NGS panel can detect 96% of reported METex14 alterations. From Jan 2016 - May 2018, METex14del was found in 2% of patients with NSCLC tested for therapeutic purposes (31/1496). Outside above mentioned timeframe and tested for other purposes, an additional 15 patients were detected, making a total of 46 NSCLC patients with METex14del, since introduction of our panel in May 2015. Adenocarcinoma was the most common histological type (31/46, 68.9%), followed by sarcomatoid carcinoma (8/46, 17.8%). Thirty-six patients had advanced NSCLC, they were predominantly male (69% vs 31%) and mostly (ex) smokers (64% vs 31%), with a median age of 76.5 years at disease onset [range 53-90]. Eleven patients were treated with targeted therapy, either with crizotinib in named patient based program or in clinical trials. With crizotinib, disease control was achieved for 4 out of 5 patients (3 PR [PFS 4 -12 mo], 1 SD [14 mo]). Biopsy at progression revealed a resistance mechanism (MET c.3682G&gt;A; p.D1228N) to crizotinib in two patients, respectively, 6 and 12 months after start of crizotinib treatment. Conclusions: In this study, we show that we can detect 96% of the known MET exon 14 skipping mutations using our custom-made DNA based NGS approach for DNA isolated from FFPE tissue. In this large consecutive series, METex14del was found in 2% of NSCLC, mostly elderly patients, in a good condition and with a smoking history. Although a small cohort, patients responded well to targeted treatment, underlining the need for routine testing of METex14del in advanced non-squamous NSCLC to guarantee optimal personalized treatment.

Citation Format: Melinda Pruis, WRR Geurts, JH von der Thüsen, IC Meijssen, WNM Dinjens, JGJV Aerts, MP Lolkema, HJ Dubbink, MS Paats. Highly accurate DNA-based detection of MET exon 14 skipping mutations in non-small cell lung cancer and clinical response upon targeted treatment [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B136. doi:10.1158/1535-7163.TARG-19-B136

Highly accurate DNA-based detection and treatment results of MET exon 14 skipping mutations in lung cancer

OBJECTIVES

The oncogenic MET exon 14 skipping mutation (METex14del) is described to drive 1.3 %-5.7 % of non-small-cell lung cancer (NSCLC) and multiple studies with cMET inhibitors show promising clinical responses. RNA-based analysis seems most optimal for METex14del detection, however, acquiring sufficient RNA material is often problematic. An alternative is DNA-based analysis, but commercially available DNA-based panels only detect up to 63 % of known METex14del alterations. The goal of this study is to describe an optimized DNA-based diagnostic test for METex14del in NSCLC, including clinical features and follow-up of patients treated with cMET-targeted therapy and consequent resistance mechanisms.

MATERIAL AND METHODS

Routinely processed diagnostic pathology non-squamous NSCLC specimens were investigated by a custom-made DNA-based targeted amplicon-based next generation sequencing (NGS) panel, which includes 4 amplicons for METex14del detection. Retrospectively, histopathological characteristics and clinical follow up were investigated for advanced non-squamous NSCLC with METex14del.

RESULTS

In silico analysis showed that our NGS panel is able to detect 96 % of reported METex14 alterations. METex14del was found in 2 % of patients with non-squamous NSCLC tested for therapeutic purposes. In total, from May 2015 - Sep 2018, METex14del was found in 46 patients. Thirty-six of these patients had advanced non-squamous NSCLC, they were predominantly elderly (76.5 years [53-90]), male (25/36) and (ex)-smokers (23/36). Five patients received treatment with crizotinib (Pfizer Oncology), in a named patient based program, disease control was achieved for 4/5 patients (3 partial responses, 1 stable disease) and one patient had a mixed response. Two patients developed a MET D1228N mutation during crizotinib treatment, inducing a resistance mechanism to crizotinib.

CONCLUSIONS

This study shows that METex14del can be reliably detected by routine DNA NGS analysis. Although a small cohort, patients responded well to targeted treatment, underlining the need for routine testing of METex14del in advanced non-squamous NSCLC to guarantee optimal personalized treatment.

OS10.1 Survival analysis of IDH wildtype astrocytomas with molecular features of glioblastoma, WHO grade IV

BACKGROUND

Recently, isocitrate dehydrogenase wildtype (IDHwt) lower grade gliomas (LGGs) that have a telomerase reverse transcriptase (TERT) promoter mutation and/or gain of chromosome 7 combined with loss of chromosome 10 and/or epidermal growth factor receptor amplification have been reclassified as IDHwt astrocytomas with molecular features of glioblastoma, WHO grade IV (‘astrocytomas IDHwt, WHO IV’). Survival of these tumors meeting the criteria of these tumors is less well studied. The objective of this study is to compare the overall survival (OS) between the IDHwt astrocytomas, WHO IV and histological glioblastomas (GBMs).

MATERIAL AND METHODS

In this retrospective multicenter cohort study, all adult patients with a newly diagnosed IDHwt LGG (histologically WHO grade II or III) and with molecular data available were selected from the Erasmus MC and the LUMC from October 2002 to April 2019. LGG patients showing contrast enhancement with necrosis on the MRI at the time of histological diagnosis were excluded. Molecular data were determined using a diagnostic NGS panel. A historical cohort of 195 patients with IDHwt GBMs with molecular data available was used to compare OS. OS was measured from the date of the first diagnostic MR scan.

RESULTS

79 IDHwt LGG patients were identified of which 62 patients had molecular features of glioblastoma (‘astrocytomas IDHwt, WHO IV’), 11 patients did not have these molecular features (‘astrocytomas IDHwt, WHO II & III’). In the remaining 6 patients the molecular data were not conclusive (astrocytomas IDHwt, WHO NOS). Patients with astrocytomas IDHwt, WHO IV were slightly older at diagnosis (median age = 57 years) than patients with GBMs IDHwt in the reference cohort or astrocytomas IDHwt, WHO II & III (respectively: median age 55 years, p=0.032 and 47 years, p=0.035). The relatively young age of our GBM IDHwt cohort reflects more extensive molecular testing in younger patients and histologically lower grade tumors. The median OS of astrocytomas IDHwt, WHO IV (23.8 months) was similar to the median OS of GBMs (19.2 months, log-rank test p=0.37). The median OS in 19 patients with only TERT promoter mutations was 16.8 months, similar to GBMs (p=0.94).

CONCLUSION

There is no statistically significant difference between the OS of IDHwt astrocytomas with molecular features of glioblastoma and the OS of true glioblastomas. Grade II and III IDHwt astrocytoma with molecular features of glioblastoma should be designated WHO grade IV. The presence of TERT promoter mutations alone in this histological context also qualifies for this designation.

Granular dot-like staining with MLH1 immunohistochemistry is a clone-dependent artefact

Immunohistochemistry (IHC) for DNA mismatch repair proteins MLH1, PMS2, MSH2, and MSH6 is used for microsatellite instability (MSI) screening in colorectal carcinoma (CRC) and endometrial carcinoma (EC). Loss of PMS2, with retained MLH1 staining occurs in germline mutations of PMS2 gene, and is an indication for genetic testing. We report a pitfall of immunohistochemical interpretation in an EC, initially regarded as MLH1-positive and PMS2-negative. Review of the MLH1-IHC (M1-clone) revealed a granular, dot-like, nuclear staining. On repeating the MLH1-IHC with a different clone (ES05-clone), complete negativity was noted, and on molecular testing, MLH1 promotor methylation was detected. The dot-like pattern was therefore adjudged a clone-dependent artefact. On reviewing the archived MLH1-IHC slides, we observed the same dot-like pattern in two CRCs; in both cases the M1-clone had been used. Awareness of this artefact may prevent reporting errors, and unnecessary referrals for germline mutation testing.

Abstract P1-06-06: Direct ex vivo observation of homologous recombination defect reversal after DNA damaging chemotherapy in metastatic breast cancer patients

Introduction

Better predictive biomarkers for response to Poly ADP-Ribose inhibitors (PARPi) are required, since on the one hand evidence is emerging that PARPi are also effective beyond germline BRCA mutated (gBRCAm) cancers and on the other hand gBRCAm cancers can become resistant to PARPi. Therefore, we previously developed a functional homologous recombination (HR) assay exploiting the formation of RAD51 foci in proliferating cells after ex vivo irradiation of fresh primary breast cancer (BrC) tissue (n=148): the REpair CAPacity (RECAP) test. The aim of the current study is to molecularly characterize real-time HR deficient (HRD) tumors and explore the utility of RECAP as a predictive biomarker for PARPi treatment in metastatic BrCs.

Material and method

Patients with advanced or recurrent BrC with easily accessible metastases were eligible. Fresh tissue biopsies from metastatic BrC lesions were collected in customized medium, irradiated with 5 Gy and cultured for 2 hours. Molecular characterization of functional HRD biopsies as well as platinum/PARP resistant biopsies was performed by targeted sequencing (BRCA1/2, TP53, CHEK2, PALB2), BRCA1 promoter methylation analysis and multiplex ligation-dependent probe amplification (MLPA) analysis of BRCA1 and BRCA2 to identify large rearrangements.

Results

41 biopsies were derived from 38 patients with recurrent or metastatic BrC. The RECAP test had a high success rate (93%) when performed on core needle or punch biopsies, and test results were available within 1 week. HRD was detected in 13 out of 41 biopsies (32%), among which 5 were gBRCAm, indicating that the RECAP test identifies more patients who may benefit from PARPi treatment than gBRCA analysis only. Among the 8 non-gBRCAm HRD tumors was one tumor with a germline PALB2 mutation, one with BRCA1 promoter hypermethylation and two with somatic variants of unkown significance (VUSes) in BRCA2. In three gBRCAm patients BRCA reversion was detected, as the HRD tumors became HR proficient (HRP) after showing in vivo progressive disease (PD) on cisplatin/PARPi treatment. One of these patients obtained a secondary BRCA1 mutation that restored the open reading frame and led to production of full-length BRCA1 protein, while the causative molecular event in the other patients is still elusive.

Conclusion

The RECAP test is a robust and reproducible HRD test which identifies approximately 60% more potential candidates for PARPi treatment, as 40% of HRD tumors were caused by gBRCAm. Due to its functional character, the RECAP test reflects the real-time HR status regardless of BRCA mutational status and therefore detects HR reversal upon therapy resistance. Thus, RECAP shows great potential as a predictive biomarker for PARPi treatment of metastatic BrC.

Citation Format: Meijer TG, Verkaik NS, Van Deurzen CH, Dubbink HJ, Den Toom TD, Dinjens WN, Kanaar R, Van Gent DC, Jager A. Direct ex vivo observation of homologous recombination defect reversal after DNA damaging chemotherapy in metastatic breast cancer patients [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 P1-06-06.

Interim results from the CATNON trial (EORTC study 26053-22054) of treatment with concurrent and adjuvant temozolomide for 1p/19q non-co-deleted anaplastic glioma: a phase 3, randomised, open-label intergroup study

BACKGROUND

The role of temozolomide chemotherapy in newly diagnosed 1p/19q non-co-deleted anaplastic gliomas, which are associated with lower sensitivity to chemotherapy and worse prognosis than 1p/19q co-deleted tumours, is unclear. We assessed the use of radiotherapy with concurrent and adjuvant temozolomide in adults with non-co-deleted anaplastic gliomas.

METHODS

This was a phase 3, randomised, open-label study with a 2 × 2 factorial design. Eligible patients were aged 18 years or older and had newly diagnosed non-co-deleted anaplastic glioma with WHO performance status scores of 0-2. The randomisation schedule was generated with the electronic EORTC web-based ORTA system. Patients were assigned in equal numbers (1:1:1:1), using the minimisation technique, to receive radiotherapy (59·4 Gy in 33 fractions of 1·8 Gy) alone or with adjuvant temozolomide (12 4-week cycles of 150-200 mg/m² temozolomide given on days 1-5); or to receive radiotherapy with concurrent temozolomide 75 mg/m² per day, with or without adjuvant temozolomide. The primary endpoint was overall survival adjusted for performance status score, age, 1p loss of heterozygosity, presence of oligodendroglial elements, and MGMT promoter methylation status, analysed by intention to treat. We did a planned interim analysis after 219 (41%) deaths had occurred to test the null hypothesis of no efficacy (threshold for rejection p<0·0084). This trial is registered with ClinicalTrials.gov, number NCT00626990.

FINDINGS

At the time of the interim analysis, 745 (99%) of the planned 748 patients had been enrolled. The hazard ratio for overall survival with use of adjuvant temozolomide was 0·65 (99·145% CI 0·45-0·93). Overall survival at 5 years was 55·9% (95% CI 47·2-63·8) with and 44·1% (36·3-51·6) without adjuvant temozolomide. Grade 3-4 adverse events were seen in 8-12% of 549 patients assigned temozolomide, and were mainly haematological and reversible.

INTERPRETATION

Adjuvant temozolomide chemotherapy was associated with a significant survival benefit in patients with newly diagnosed non-co-deleted anaplastic glioma. Further analysis of the role of concurrent temozolomide treatment and molecular factors is needed.

FUNDING

Schering Plough and MSD.

Functional analysis of MSH2 unclassified variants found in suspected Lynch syndrome patients reveals pathogenicity due to attenuated mismatch repair

BACKGROUND

Lynch syndrome, an autosomal-dominant disorder characterised by high colorectal and endometrial cancer risks, is caused by inherited mutations in DNA mismatch repair (MMR) genes. Mutations fully abrogating gene function are unambiguously disease causing. However, missense mutations often have unknown functional implications, hampering genetic counselling. We have applied a novel approach to study three MSH2 unclassified variants (UVs) found in Dutch families with suspected Lynch syndrome.

METHODS

The three mutations were recreated in the endogenous Msh2 gene in mouse embryonic stem cells by oligonucleotide-directed gene modification. The effect of the UVs on MMR activity was then tested using a set of functional assays interrogating the main MMR functions.

RESULTS

We recreated and functionally tested three MSH2 UVs: MSH2-Y165D (c.493T>G), MSH2-Q690E (c.2068C>G) and MSH2-M813V (c.2437A>G). We observed reduced levels of MSH2-Y165D and MSH2-Q690E but not MSH2-M813V proteins. MSH2-M813V was able to support all MMR functions similar to wild-type MSH2, whereas MSH2-Y165D and MSH2-Q690E showed partial defects.

CONCLUSIONS

Based on the results from our functional assays, we conclude that the MSH2-M813V variant is not disease causing. The MSH2-Y165D and MSH2-Q690E variants affect MMR function and are therefore likely the underlying cause of familial cancer predisposition. Since the MMR defect is partial, these variants may represent low penetrance alleles.

Androgen receptor coregulators: recruitment via the coactivator binding groove

Androgens are key regulators of male sexual differentiation and essential for development and maintenance of male reproductive tissues. The androgens testosterone and dihydrotestosterone mediate their effect by binding to, and activation of the androgen receptor (AR). Upon activation, the AR is able to recognize specific DNA sequences in gene promoters and enhancers from where it recruits coregulators to orchestrate chromatin remodeling and transcription regulation. The number of proteins that bind to the AR has surpassed 200 and many of them enhance (coactivator) or repress (corepressor) its transactivating capacity. For most of these coregulators, their AR binding interface and their exact mode of action still needs to be elucidated, but for some of the more classical coactivators and corepressors, we gained insight in their working mechanisms. Of particular interest are specific sequences (LxxLL and FxxLF-like motifs) in a subset of coactivators that interact with the AR via a coactivator binding groove in the ligand-binding domain. As compared to other steroid receptors, the conformation of the AR coactivator binding pocket is unique and preferentially binds FxxLF-like motifs. This predisposition is expected to contribute to the regulation of specific sets of target genes via recruitment of selected coregulators. This review provides an overview of these (inter)actions with a focus on the unique characteristics of the AR coactivator binding groove.

Donor-transmitted metastasis of colorectal carcinoma in a transplanted liver

A 62-year-old man with alcoholic liver cirrhosis underwent liver transplantation. The transplantation went uneventful and the ultrasound imaging of the liver performed after transplantation did not show any abnormalities. Eighteen months later, an intra-hepatic focal lesion was found on ultrasound. A contrast-enhanced ultrasound revealed a lesion with a malignant pattern of contrast uptake. The histo-pathological and subsequent molecular-pathological analysis concluded a colorectal metastasis of donor origin. The donor had no history of malignancy but no complete autopsy had been performed which illustrates the importance of the meticulous donors` screening. Transplanted patients carry a high risk of developing malignancy in general but donor related-tumors are very rare. The therapeutic considerations differ substantially between recipient- and donor-related malignancies. Therefore, considering the possibility of donor-related tumor by raising suspicion of malignant lesion with appropriate imaging and distinction from recipient-related malignancy by molecular analysis are crucial for proper therapeutic decision.

PTEN in colorectal cancer: a report on two Cowden syndrome patients

Heterozygous germline PTEN mutations cause Cowden syndrome. The risk of colorectal cancer in Cowden patients, however, remains a matter of debate. We describe two patients presenting with colorectal cancer at a young age (28 and 39 years) and dysmorphisms fitting the Cowden spectrum. Heterozygous germline mutations in PTEN were found in both patients. Moreover, analysis of the resected colorectal cancer specimens revealed loss of heterozygosity at the PTEN locus with retention of the mutated alleles, and greatly reduced or absent PTEN expression. Histologically and molecularly, the tumours showed resemblance with sporadic colorectal cancers, although they had prominent fibrotic stroma. Our data indicate that PTEN loss was involved in carcinogenesis in the two patients, supporting that colorectal cancer is part of the Cowden syndrome-spectrum. This is in line with data on sporadic colorectal cancer, mice studies and emerging epidemiological data on Cowden syndrome. Although the exact role of germline PTEN mutations in the carcinogenesis of colorectal cancer remains unclear, we think that Cowden syndrome should be in the differential diagnosis of colorectal cancer certainly in view of the possible prognostic and therapeutic consequences. Prospective follow-up and surveillance of PTEN mutation carriers from the age of 25 to 30 years in a study setting should clarify this issue.

Segregation of non-p.R132H mutations in IDH1 in distinct molecular subtypes of glioma

Mutations in the gene encoding the isocitrate dehydrogenase 1 gene (IDH1) occur at a high frequency (up to 80%) in many different subtypes of glioma. In this study, we have screened for IDH1 mutations in a cohort of 496 gliomas. IDH1 mutations were most frequently observed in low grade gliomas with c.395G>A (p.R132H) representing >90% of all IDH1 mutations. Interestingly, non-p.R132H mutations segregate in distinct histological and molecular subtypes of glioma. Histologically, they occur sporadically in classic oligodendrogliomas and at significantly higher frequency in other grade II and III gliomas. Genetically, non-p.R132H mutations occur in tumors with TP53 mutation, are virtually absent in tumors with loss of heterozygosity on 1p and 19q and accumulate in distinct (gene-expression profiling based) intrinsic molecular subtypes. The IDH1 mutation type does not affect patient survival. Our results were validated on an independent sample cohort, indicating that the IDH1 mutation spectrum may aid glioma subtype classification. Functional differences between p.R132H and non-p.R132H mutated IDH1 may explain the segregation in distinct glioma subtypes.

IDH1 mutations in low-grade astrocytomas predict survival but not response to temozolomide

BACKGROUND

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) have been implicated in tumorigenesis of gliomas. Patients with high-grade astrocytomas with IDH1 or IDH2 mutations were reported to have a better survival, but it is unknown if this improved survival also holds for low-grade astrocytoma and whether these mutations predict outcome to specific treatment.

METHODS

We retrospectively investigated the correlation of IDH1 and IDH2 mutations with overall survival and response to temozolomide in a cohort of patients with dedifferentiated low-grade astrocytomas treated with temozolomide at the time of progression after radiotherapy.

RESULTS

IDH1 mutations were present in 86% of the 49 progressive astrocytomas. No mutations in IDH2 were found. Presence of IDH1 mutations were early events and significantly improved overall survival (median survival 48 vs 98 months), but did not affect outcome of temozolomide treatment.

CONCLUSION

These results indicate that IDH1 mutations identify a subgroup of gliomas with an improved survival, but are unrelated to the temozolomide response.

A review on the molecular diagnostics of Lynch syndrome: a central role for the pathology laboratory

Lynch syndrome (LS) is caused by mutations in mismatch repair genes and is characterized by a high cumulative risk for the development of mainly colorectal carcinoma and endometrial carcinoma. Early detection of LS is important since surveillance can reduce morbidity and mortality. However, the diagnosis of LS is complicated by the absence of a pre-morbid phenotype and germline mutation analysis is expensive and time consuming. Therefore it is standard practice to precede germline mutation analysis by a molecular diagnostic work-up of tumours, guided by clinical and pathological criteria, to select patients for germline mutation analysis. In this review we address these molecular analyses, the central role for the pathologist in the selection of patients for germline diagnostics of LS, as well as the molecular basis of LS.

A novel mutation F826L in the human androgen receptor in partial androgen insensitivity syndrome; increased NH2-/COOH-terminal domain interaction and TIF2 co-activation

A novel mutation F826L located within the ligand binding domain (LBD) of the human androgen receptor (AR) was investigated. This mutation was found in a boy with severe penoscrotal hypospadias (classified as 46,XY DSD). The AR mutant F826L appeared to be indistinguishable from the wild-type AR, with respect to ligand binding affinity, transcriptional activation of MMTV-luciferase and ARE2-TATA-luciferase reporter genes, protein level in genital skin fibroblasts (GSFs), and sub-cellular distribution in transfected cells. However, an at least two-fold higher NH2-/COOH-terminal domain interaction was found in luciferase and GST pull-down assays. A two-fold increase was also observed for TIF2 (transcription intermediary factor 2) co-activation of the AR F826L COOH-terminal domain. This increase could not be explained by a higher stability of the mutant protein, which was within wild-type range. Repression of transactivation by the nuclear receptor co-repressor (N-CoR) was not affected by the AR F826L mutation. The observed properties of AR F826L would be in agreement with an increased activity rather than with a partial defective AR transcriptional activation. It is concluded that the penoscrotal hypospadias in the present case is caused by an as yet unknown mechanism, which still may involve the mutant AR.

The role of cofactors in sex steroid action

Sex steroid signalling determines female and male sexual development and maintains the female and male phenotype in adults. Steroids carry out their function by activation of their cognate intracellular receptor, which is a ligand-dependent transcription factor. Steroid receptors function by binding to specific structural elements in the regulatory regions of target genes and by recruitment of cofactors by protein-protein interaction. Cofactors might display enzymatic activities that modify histones and other proteins. Cofactors also include proteins that modulate the chromatin structure and protein complexes that function as bridging factors between the multi-protein complexes. This review focuses mainly on the function of the androgen receptor and its cofactors and their role in androgen insensitivity syndrome.

An Sp1 binding site is essential for basal activity of the human prostate-specific transglutaminase gene (TGM4) promoter

Human prostate-specific transglutaminase (hTG(P)) is a cross-linking enzyme encoded by the TGM4 gene. The TGM4 gene promoter was characterized by deletion mapping and mutational analysis. Promoter constructs, containing the minimal promoter requirements, could efficiently drive transcription in the prostate cancer cell lines PC346C and LNCaP and the hepatic cancer cell line Hep3B. The region between positions -113 and -61 was demonstrated to be essential for core promoter activity. Further analysis revealed the functional importance of an Sp1 binding motif, 5'-ACCCCGCCCC-3', at positions -96 to -87. This sequence is a binding site of the ubiquitous transcription factors Sp1 and Sp3.

Human prostate-specific transglutaminase: a new prostatic marker with a unique distribution pattern

Human prostate-specific transglutaminase (hTGp) is a cross-linking enzyme, the physiologic function of which has not been established unequivocally yet. To gain insight into its distribution, we raised antisera against hTGp. By using Western blotting analysis, we found that these antisera specifically recognize a 77-kDa protein in prostatic fluids, seminal plasmas, and prostatic tissues. The concentrations of hTGp in these fluids and tissues were found to be highly variable among individuals. Immunohistochemical examination of several formalin-fixed paraffin-embedded human tissues revealed an exclusive expression in the prostate. The histologic localization and distribution of hTGp within the prostate was assessed by studying multiple sections from tumor-containing prostatectomy specimens and needle biopsies. hTGp expression was entirely restricted to luminal epithelial cells. No basal epithelial cells or stromal cells were stained. Within the prostate, large areas without any hTGp-positive cells were seen. Immunopositive cells were present either in a scattered pattern or concentrated in single or multiple glands in which all luminal epithelial cells expressed hTGp. The latter staining pattern occurred frequently, but not exclusively, in the peripheral zone, whereas scattered expression was most often observed in the transitional zone. Expression of the hTGp protein could occasionally be observed in high-grade prostatic intraepithelial neoplasia, but was not detected in prostate carcinoma cells. The expression pattern as observed for hTGp has not been found thus far for any other prostate-specific marker.

The human prostate-specific transglutaminase gene (TGM4): genomic organization, tissue-specific expression, and promoter characterization

Human prostate-specific transglutaminase (hTGP) is a cross-linking enzyme secreted by the prostate. In this study, we performed dot blot analysis of 50 normal human tissues to demonstrate unambiguously the prostate-specific expression of hTGP. Furthermore, we elucidated the genomic organization of the TGM4 gene, the gene encoding hTGP. The structure of this gene displays striking similarity to that of other transglutaminase (TGase) genes. The TGM4 gene spans approximately 35 kb of genomic DNA and consists of 13 exons and 12 introns. The main transcription initiation site is located 52 bp upstream of the translational start codon. A hTGP splice variant of intron 1 was detected. This splice variant contains an in-frame antisense Alu element insertion. The TGM4 promoter was analyzed by sequencing and transfection experiments. At positions -1276 to -563, the promoter harbors a cyclophilin pseudogene with 94% similarity to the cyclophilin A cDNA. Deletion mapping of the TGM4 promoter in the transiently transfected human prostate cancer cell line PC346C showed comparable activity of 2.1-, 1.5-, and 0.5-kb promoter fragments.

Expression of prostatic factors measured by reverse transcription polymerase chain reaction in human papillomavirus type 18 deoxyribonucleic acid immortalized prostate cell lines

OBJECTIVES

To investigate expression of the prostatic markers prostate-specific antigen (PSA), prostate-specific membrane antigen (PSM), and the androgen receptor (AR) after human papillomavirus (HPV) type 18 deoxyribonucleic acid (DNA) transfection and subsequent immortalization of human prostate epithelial cells.

METHODS

Recently, two human prostate epithelial cell lines were established by HPV transformation: PZ-HPV-7, derived from normal peripheral zone (PZ) tissue, and CA-HPV-10, derived from high Gleason grade adenocarcinoma. Expression of PSA was studied by the reverse transcription polymerase chain reaction (RT-PCR), because in preliminary studies using immunocytochemistry and Northern blotting, no PSA expression was found. PSM was analyzed by RT-PCR and nested RT-PCR. These analyses included primary human prostate cell strains. Furthermore, androgen-supplemented methylthiazol tetrazolium (MTT) growth assays were performed and expression of AR was studied by immunocytochemistry. Prostate carcinoma cell lines LNCaP and PC-346C were included as positive controls and breast carcinoma cell line MCF-7 as a negative control.

RESULTS

Both cell lines exhibited low levels of RNA for PSA and PSM in comparison with cell lines LNCaP and PC-346C. AR expression by immunocytochemistry was negative using monoclonal antibody F39.4 and polyclonal antibody SP-197. In an androgen-supplemented environment, growth rates of both HPV immortalized cell lines were not stimulated in contrast to LNCaP.

CONCLUSIONS

RNA transcripts of PSA and PSM were detected by RT-PCR in HPV immortalized prostate epithelial cell lines PZ-HPV-7 and CA-HPV-10. The expression of prostate-specific markers may further validate the utility of this stepwise transformation model of human prostate carcinogenesis.

The aroA gene of Campylobacter jejuni

The gene for 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase (aroA) cloned from Campylobacter jejuni (Cj) strain 81116 was identified by complementation of an Escherichia coli (Ec) auxotrophic aroA mutant. The Cj aroA gene has been sequenced. It encodes an enzyme of 428 amino acids (aa), that is homologous to other bacterial EPSP synthases, especially that of Bacillus subtilis with which it has a 39% aa identity. The transcriptional start point was mapped. It is present in an upstream open reading frame (ORF) that has a strong homology to the gene encoding phenylalanine tRNA synthetase (pheS). Downstream from aroA another ORF is present which is homologous to the lytB gene of Ec. The stop codon of the aroA gene overlaps the start codon of lytB.

Tissue specific and androgen-regulated expression of human prostate-specific transglutaminase

Transglutaminases (TGases) are calcium-dependent enzymes catalysing the post-translational cross-linking of proteins. In the prostate at least two TGases are present, the ubiquitously expressed tissue-type TGase (TGC), and a prostate-restricted TGase (TGP). This paper deals with the molecular cloning and characterization of the cDNA encoding the human prostate TGase (hTGP). For this purpose we have screened a human prostate cDNA library with a probe from the active-site region of TGC. The largest isolated cDNA contained an open reading frame encoding a protein of 684 amino acids with a predicted molecular mass of 77 kDa as confirmed by in vitro transcription-translation and subsequent SDS/PAGE. The hTGP gene was tissue-specifically expressed in the prostate, yielding an mRNA of approx. 3.5 kb. Furthermore, a 3-fold androgen-induced upregulation of hTGP mRNA expression has been demonstrated in the recently developed human prostate cancer cell line, PC346C. Other well established human prostate cancer cell lines, LNCaP and PC-3, showed no detectable hTGP mRNA expression on a Northern bolt. The gene coding for prostate TGase was assigned to chromosome 3.

Single point mutations in domain II of the yeast mitochondrial release factor mRF-1 affect ribosome binding

We have recently described two yeast strains that are mutated in the MRF1 gene encoding the mitochondrial release factor mRF-1. Both mutants provoke gene-specific defects in mitochondrial translational termination. In the present study we report the cloning, sequencing, as well as an analysis of residual activities of both mutant mrf1 alleles. Each allele specifies a different single amino acid substitution located one amino acid apart. The amino acid changes do not affect the level or cellular localization of the mutant proteins, since equal amounts of wild type and mutant mRF-1 were detected in the mitochondrial compartment. Over-expression of the mutant alleles in wild type and mrf1 mutant yeast strains produces a phenotype consistent with a reduced affinity of the mutant release factors for the ribosome, indicating that the mutations map in a release factor domain involved in ribosome binding. We also demonstrate that nonsense suppression caused by a mutation in the mitochondrial homolog of the E. coli small ribosomal protein S4 can be reversed by a slight over-expression of the MRF1 gene.