Impact of Pre-Analytical Factors on MSI Test Accuracy in Mucinous Colorectal Adenocarcinoma: A Multi-Assay Concordance Study

Immunohistochemistry (IHC) and polymerase chain reaction (PCR) and fragment separation by capillary electrophoresis represent the current clinical laboratory standard for the evaluation of microsatellite instability (MSI) status. The importance of reporting MSI status in colorectal cancer is based on its potential for guiding treatment and as a prognostic indicator. It is also used to identify patients for Lynch syndrome testing. Our aim was to evaluate pre-analytical factors, such as age of formalin-fixed and paraffin-embedded (FFPE) block, neoplastic cell percentage, mucinous component, and DNA integrity, that may influence the accuracy of MSI testing and assess the concordance between three different MSI evaluation approaches. We selected the mucinous colorectal cancer (CRC) histotype for this study as it may possibly represent an intrinsic diagnostic issue due to its low tumor cellularity. Seventy-five cases of mucinous CRC and corresponding normal colon tissue samples were retrospectively selected. MMR proteins were evaluated by IHC. After DNA quality and quantity evaluation, the Idylla™ and TapeStation 4200 platforms were adopted for the evaluation of MSI status. Seventy-three (97.3%) cases were successfully analyzed by the three methodologies. Overall, the Idylla™ platform showed a concordance rate with IHC of 98.0% for microsatellite stable (MSS)/proficient MMR (pMMR) cases and 81.8% for MSI/deficient MMR (dMMR) cases. The TapeStation 4200 system showed a concordance rate with IHC of 96.0% for MSS/pMMR cases and 45.4% for MSI/dMMR cases. The concordance rates of the TapeStation 4200 system with respect to the Idylla™ platform were 98.1% for MSS profile and 57.8% for MSI profile. Discordant cases were analyzed using the Titano MSI kit. Considering pre-analytical factors, no significant variation in concordance rate among IHC analyses and molecular systems was observed by considering the presence of an acellular mucus cut-off >50% of the tumor area, FFPE year preparation, and DNA concentration. Conversely, the Idylla™ platform showed a significant variation in concordance rate with the IHC approach by considering a neoplastic cell percentage >50% (p-value = 0.002), and the TapeStation 4200 system showed a significant variation in concordance rate with the IHC approach by considering a DNA integrity number (DIN) ≥4 as cut-off (p-value = 0.009). Our data pinpoint a central role of the pre-analytical phase in the diagnostic outcome of MSI testing in CRC.

Abstract 2582: Investigating the origin and function of circulating miRNA in lung cancer

MicroRNAs (miRNAs) are small, highly conserved noncoding RNA molecules involved in the regulation of gene expression. MicroRNAs are resistant to harsh conditions and stably exist in body fluids (e.g. saliva, urine, breast milk, blood). Circulating cell-free miRNAs (cf-miRNA) were shown to be effective biomarkers for the early diagnosis of cancer. Furthermore, cf-miRNA were also found in exosomes that are nano-sized extracellular vesicles which exchange molecular information among cells. However, the understanding of origin of cf-miRNAs and of biological function still remains elusive. We recently identified a signature of cf-miRNAs diagnostic for lung cancer which we now hypothesize being released by lung cancer cells (EP-cf-miRNA) and by tumor microenvironment (TME-cf-miRNA). In particular, two cf-miRNAs, miR-29a and 223-3p, were selected as prototypes of EP- and TME-cf-miRNAs for further investigations.We found that the expression of miR-223-3p was higher in TME than in cancer cells of a cohort of 19 lung adenocarcinoma. In contrast, miR-29a-3p was frequently overexpressed (≥2 fold) in cancer cells. Interestingly, the serum concentration of cf-miR-29a was lower than miR-223-3p and this also in exosomes.We next investigated the expression profile of miR-29a/223-3p in a panel of lung normal and adenocarcinoma cell lines (N=14). miR-29a/223-3p were both expressed intracellularly and in exosomes. Of note, the miR-29a expression level resembles that observed in lung cancer cells from FFPE samples. Conversely, miR-223-3p expression was lower in the adenocarcinoma cell lines which further confirm a more TME origin. We are now expanding our analysis by screening the whole set of cf-miRNAs by high-throughput qPCR profile (OpenArray technology) and by applying laser capture microdissection to investigate single cancer epithelial cells and TME. Our work provides proof of principle demonstration of an effective approach to investigate cf-miRNA origin to unravel the role of cf-miRNA in lung adenocarcinoma.

Citation Format: Tommaso Colangelo, Francesco Mazzarelli, Roberto Cuttano, Elisa Dama, Valentina Melocchi, Paolo Graziano, Fabiola Fiordelisi, Fabrizio Bianchi. Investigating the origin and function of circulating miRNA in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2582.

Frequent NRG1 fusions in Caucasian pulmonary mucinous adenocarcinoma predicted by Phospho-ErbB3 expression

NRG1 fusions were recently reported as a new molecular feature of Invasive Mucinous Adenocarcinoma (IMA) of the lung. The NRG1 chimeric ligand acts as a strong inductor of phosphorylation and tyrosine kinase activity of the ErbB2/ErbB3 heterodimer, thus enhancing the PI3K–AKT/MAPK pathways. The NRG1 fusions were widely investigated in Asian IMA cohorts, whereas just anecdotal information are available about the occurrence of NRG1 fusions in IMA Caucasian population.

Here we firstly explored a large Caucasian cohort of 51 IMAs and 34 non-IMA cases for the occurrence of NRG1 rearrangements by fluorescent in situ hybridization (FISH) and RNA target sequencing. FISH results were correlated to the immunohistochemical expression of phosphorylated-ErbB3 (pErbB3) receptor and the mutational status of KRAS, EGFR and ALK genes.

The NRG1 rearrangements were detected in 31% IMAs and 3% non-IMAs and the CD74-NRG1 fusion transcript variant was characterized in 4 NRG1-positive IMAs. Moreover, pErbB3 expression was found to be strictly associated to the mucinous pattern (p = 0.012, Chi-square test) and all IMA cases showing aberrant expression of pErbB3 demonstrated NRG1 rearrangements. No significant correlation between NRG1 rearrangements and EGFR, KRAS or ALK mutations respectively, was observed.

We report for the first time that NRG1 fusions are driver alterations clearly associated with mucinous lung adenocarcinoma subtype of Caucasian patients and not exclusive of Asiatic population. pErbB3 immunostaining may represent a strong predictor of NRG1 fusions, pointing out the detection of pErbB3 by IHC as a rapid and effective pre-screening method to select the NRG1-positive patients.

Subcutaneous Ewing sarcoma/PNET as a second cancer in a previously irradiated young patient. an uncommon type of post-irradiation soft tissue sarcoma

Soft tissue sarcomas account for a small proportion of second cancers, with an estimated frequency of < 10%. The most common histologic type of soft tissue sarcomas as second cancers include mostly high-grade sarcomas, such as rhabdomyosarcoma, malignant peripheral nerve sheath tumour, fibrosarcoma, leiomyosarcoma, synovial sarcoma, alveolar soft part sarcoma and Ewing sarcoma/primitive neuroectodermal tumour (PNET). We report a case of superficial soft tissue Ewing sarcoma/PNET as a second cancer in a young patient previously treated for Hodgkin's disease (HD). To the best of our knowledge and based on a literature search, this is the first reported case of post-irradiation soft tissue Ewing sarcoma/PNET as a second cancer arising in the same area irradiated for cure of HD.

Soluble intercellular adhesion molecule-1 (sICAM-1) concentrations in Graves' disease patients followed up for development of ophthalmopathy

It is commonly recognized that a few patients with Graves' disease (GD) develop an overt ophthalmopathy, although most of them show subclinical extraocular muscle enlargement by appropriate imaging techniques. At present, it is not possible to identify the subgroup of GD patients with subclinical retroorbital connective involvement. Recently, it has been shown that increase of soluble intercellular adhesion molecule-1 (sICAM-1) serum levels is correlated to clinical activity score in active Graves' ophthalmopathy (GO) patients with or without hyperthyroidism, suggesting that sICAM-1 serum values could reflect the degree of ocular inflammatory activity. The aim of this longitudinal study was to evaluate sICAM-1 serum levels in GD patients without clinical ophthalmopathy and to assess their possible relationship with occurrence of GO. We measured sICAM-1 serum levels in 103 initially hyperthyroid GD patients without clinical ophthalmopathy and in 100 healthy subjects. All patients were treated with methimazole for 2 yr. Sera were collected from all patients before treatment and then monthly for the first 6 months of therapy, every 2 months in the following 6 months, and finally at the end of the follow-up study. Patients developing GO were excluded from the follow-up at the onset of ophthalmopathy. During the follow-up 17 GD patients (16.5%, group 1) developed overt eye involvement (14 as active inflammatory ophthalmopathy and 3 as ophthalmopathy without clinical retroorbital connective inflammation) and 86 (83.5%, group 2) did not. At start of the study, the mean of sICAM-1 serum concentrations did not differ significantly between the 2 groups, but it was significantly higher than in controls in both groups. No significant correlation between serum sICAM-1 concentrations and free thyroid hormone levels was found in the 2 groups of patients. During the follow-up study, a further increase of sICAM-1 serum levels was observed in 12 of the 14 patients (85.7%) of group 1 who developed active inflammatory ophthalmopathy not only at the onset but also before clinical GO appearance. On the contrary, the 3 patients of group 1 that developed ophthalmopathy without clinical retroorbital inflammation did not show any further increase of sICAM-1 levels at every time of follow-up in comparison with the starting values, even if their sICAM-1 levels were always higher than in normal controls. Finally, group 2 patients showed significantly decreased sICAM-1 levels throughout the follow-up period when compared with the starting values, although they were still significantly higher than in controls. These results indicate that a further increase of sICAM-1 serum levels before the onset of clinical ophthalmopathy may be a marker of subclinical retroorbital connective inflammation in GD patients. Therefore, our study suggests that serial determinations of sICAM-1 serum levels could help to identify and trace at the right time those GD patients prone to developing active inflammatory ophthalmopathy.

[Autoimmune Addison's disease. Current knowledge and prospects]

Idiopathic Addison's disease (IAD) is a chronic organ-specific autoimmune disease sometimes associated with other autoimmune endocrine diseases. The prevalence is 50-100/million with an incidence of 5-6 cases/million/year. A genetic predisposition to this disease has been reported in subjects with phenotype HLA-DR3, -DR4, -A1, -B8 or HLA-A28, -B8; a phenotype HLA-B8 has been described in subjects with adrenal autoantibodies (AA) not progressing toward an overt disease. There is strong evidence that AA can play a pathogenic role or at least can be considered good immunological markers in IAD. AA may damage adrenal function by a cytotoxic process directed at adrenal cell surface or other intracellular antigens. An antigenic activity has been recently attributed to P450c enzymes and in particular to P450c21. Clinical manifestations of IAD can be preceded by a long period of subclinical adrenocortical impairment, characterized only by the presence of AA with or without adrenocortical function findings. In our experience, where AA titers were 1:8 or higher, progression of adrenal disease was likely with time. A spontaneous remission can indeed occur with lower titers, especially in early stages of subclinical adrenal insufficiency. Finally, a reversal of previously significant AA positive titers in patients in more advanced stages of subclinical adrenal insufficiency seems to be induced by corticosteroid therapy.