Detection of effusion tumor cells under different storage and processing conditions

BACKGROUND

Circulating tumor cells (CTCs) shed into blood provide prognostic and/or predictive information. Previously, the authors established an assay to detect carcinoma cells from pleural fluid, termed effusion tumor cells (ETCs), by employing an immunofluorescence-based CTC-identification platform (RareCyte) on air-dried unstained ThinPrep (TP) slides. To facilitate clinical integration, they evaluated different slide processing and storage conditions, hypothesizing that alternative comparable conditions for ETC detection exist.

METHODS

The authors enumerated ETCs on RareCyte, using morphology and mean fluorescence intensity (MFI) cutoffs of >100 arbitrary units (a.u.) for epithelial cellular adhesion molecule (EpCAM) and <100 a.u. for CD45. They analyzed malignant pleural fluid from three patients under seven processing and/or staining conditions, three patients after short-term storage under three conditions, and seven samples following long-term storage at -80°C. MFI values of 4',6-diamidino-2-phenylindol, cytokeratin, CD45, and EpCAM were compared.

RESULTS

ETCs were detected in all conditions. Among the different processing conditions tested, the ethanol-fixed, unstained TP was most similar to the previously established air-dried, unstained TP protocol. All smears and Pap-stained TPs had significantly different marker MFIs from the established condition. After short-term storage, the established condition showed comparable results, but ethanol-fixed and Pap-stained slides showed significant differences. ETCs were detectable after long-term storage at -80°C in comparable numbers to freshly prepared slides, but most marker MFIs were significantly different.

CONCLUSIONS

It is possible to detect ETCs under different processing and storage conditions, lending promise to the application of this method in broader settings. Because of decreased immunofluorescence-signature distinctions between cells, morphology may need to play a larger role.

Solid-Basaloid Adenoid Cystic Carcinoma of the Breast: An Aggressive Subtype Enriched for Notch Pathway and Chromatin Modifier Mutations With MYB Overexpression

Adenoid cystic carcinoma (AdCC) is a rare triple-negative breast cancer analogous to its extramammary counterparts. Diagnosis of the more aggressive solid-basaloid variant of AdCC (SB-AdCC) can be challenging due to poorly defined histopathologic and molecular features. We characterized 22 invasive and in situ basaloid carcinomas by morphology, immunohistochemistry, genetics, and MYB status using multiple platforms and assessed clinical behavior and neoadjuvant chemotherapy responses. After consensus review, 16/22 cases were classified as SB-AdCC. All SB-AdCC had predominantly solid growth and at least focal myxohyaline stroma and were immune-poor. Eosinophilic squamoid cells (69%, 11/16) and basement membrane-like secretions (69%, 11/16) were common, and intercalated ducts (31%, 5/16) were less frequent. SB-AdCC typically expressed SOX10 (100%, 16/16) and luminal markers (100%, 16/16 CK7; 88%, 14/16 CD117; 93%, 13/14 CAM5.2). SMA (40%, 6/15) expression was less common, and SMM (27%, 3/11), GATA3 (20%, 3/15), and p63 (25%, 4/16) were mostly negative. MYB protein and/or MYB RNA overexpression was universal in evaluable cases (13/13), with RNA in situ hybridization (10/10) more reliable than immunohistochemistry (10/11, plus 4 excisions inconclusive). Fluorescence in situ hybridization and/or next-generation sequencing identified MYB rearrangements (20%, 3/15) and amplifications/copy gains (60%, 9/15) but no MYB::NFIB fusions. SB-AdCC often had aberrations in Notch pathway (60%, including 40% NOTCH1 and 20% NOTCH2) and/or chromatin modifier (60%, including 33% CREBBP) genes, with relatively infrequent TP53 mutations (27%). Unclassified invasive basaloid carcinomas lacking described histologic features of SB-AdCC (n = 4) and basaloid ductal carcinoma in situ (n = 2) showed similar immunoprofiles and genetics as SB-AdCC, including Notch aberrations and MYB overexpression with MYB rearrangements/amplifications. Overall, nodal (22%) and distant (33%) metastases were common, and 23% of patients died of disease (mean follow-up, 35 months; n = 22). Responses were poor in all 7 neoadjuvant chemotherapy-treated patients, without any achieving pathologic complete response. The data highlight the histopathologic spectrum of basaloid carcinomas including SB-AdCC and reveal shared genetics and MYB activation, which can be diagnostically useful. Aggressive behavior and poor treatment responses emphasize a need for additional treatment approaches.

Comprehensive epithelial biomarker analysis of malignant mesothelioma: EpCAM positivity is a potential diagnostic pitfall

BACKGROUND

Epithelial cell adhesion molecule (EpCAM) is frequently used to distinguish carcinoma from background mesothelial cells during cytologic examination of body cavity fluids. Previously, the authors identified one malignant mesothelioma case with strong and diffuse membranous EpCAM staining, making it indistinguishable from carcinoma.

METHODS

In this study, the authors evaluated all available effusion specimens from patients with malignant mesothelioma, including the above-mentioned index case, obtained at Stanford Health Care, from 2011 to 2021 (N = 17) as well as control cases (N = 5). Analyses included an immunohistochemistry (IHC) assay for EpCAM and claudin-4, a multiplexed immunofluorescent (IF) assay for EpCAM, and an RNA in situ hybridization assay targeting EpCAM.

RESULTS

The authors detected EpCAM positivity of variable intensity and percentage in four malignant mesothelioma cases (23.5%; although only two showed positivity for the epithelial-specific IHC marker MOC31 in ≥40% of cells) and claudin-4 negativity in all cases, with two cases displaying focal and weak claudin-4 staining in <1% of cells. Multiplexed IF staining on the cases with EpCAM IHC positivity showed strong, membranous EpCAM staining in one of four cases. RNA in situ hybridization also was used to assess the correlation between EpCAM positivity by IHC/IF and RNA expression levels. Strong EpCAM RNA expression was detected in the three malignant mesothelioma cases.

CONCLUSIONS

The current findings revealed that a subset of epithelioid malignant mesothelioma cases mimic or exhibit the immunophenotypic features of carcinoma when evaluating for EpCAM only. Additional biomarker testing, such as claudin-4, may help avoid this potential pitfall to yield accurate diagnoses.

The Interaction of SWI/SNF with the Ribosome Regulates Translation and Confers Sensitivity to Translation Pathway Inhibitors in Cancers with Complex Perturbations

Subunits from the chromatin remodelers mammalian SWItch/Sucrose Non-Fermentable (mSWI/SNF) are mutated, deleted, or amplified in more than 40% of cancers. Understanding their functions in normal cells and the consequences of cancerous alterations will provide insight into developing new targeted therapies. Here we examined whether mSWI/SNF mutations increase cellular sensitivity to specific drugs. Taking advantage of the DepMap studies, we demonstrate that cancer cells harboring mutations of specific mSWI/SNF subunits exhibit a genetic dependency on translation factors and are sensitive to translation pathway inhibitors. Furthermore, mSWI/SNF subunits were present in the cytoplasm and interacted with the translation initiation machinery, and short-term inhibition and depletion of specific subunits decreased global translation, implicating a direct role for these factors in translation. Depletion of specific mSWI/SNF subunits also increased sensitivity to mTOR-PI3K inhibitors. In patient-derived breast cancer samples, mSWI/SNF subunits expression in both the nucleus and the cytoplasm was substantially altered. In conclusion, an unexpected cytoplasmic role for mSWI/SNF complexes in translation suggests potential new therapeutic opportunities for patients afflicted by cancers demonstrating alterations in their subunits.

SIGNIFICANCE

This work establishes direct functions for mSWI/SNF in translation and demonstrates that alterations in mSWI/SNF confer a therapeutic vulnerability to translation pathway inhibitors in cancer cells.

Immunofluorescent and molecular characterization of effusion tumor cells reveal cancer site-of-origin and disease-driving mutations

BACKGROUND

Effective cancer treatment relies on precision diagnostics. In cytology, an accurate diagnosis facilitates the determination of proper therapeutics for patients with cancer. Previously, the authors developed a multiplexed immunofluorescent panel to detect epithelial malignancies from pleural effusion specimens. Their assay reliably distinguished effusion tumor cells (ETCs) from nonmalignant cells; however, it lacked the capacity to reveal specific cancer origin information. Furthermore, DNA profiling of ETCs revealed some, but not all, cancer-driver mutations.

METHODS

The authors developed a new multiplex immunofluorescent panel that detected both malignancy and pulmonary origin by incorporating the thyroid transcription factor-1 (TTF-1) biomarker. Evaluation for TTF-1-positive ETCs (T-ETCs) was performed on 12 patient samples. T-ETCs and parallel ETCs from selected patients were collected and subjected to DNA profiling to identify pathogenic mutations. All samples were obtained with Institutional Review Board approval.

RESULTS

Malignancy was detected in all samples. T-ETCs were identified in 9 of 10 patients who had clinically reported TTF-1 positivity (90% sensitivity and 100% specificity). Furthermore, DNA profiling of as few as five T-ETCs identified pathogenic mutations with equal or greater sensitivity compared with profiling of ETCs, both of which showed high concordance with clinical findings.

CONCLUSIONS

The findings suggest that the immunofluorescent and molecular characterization of tumor cells from pleural effusion specimens can provide reliable diagnostic information, even with very few cells. The integration of site-specific biomarkers like TTF-1 into ETC analysis may facilitate better refined diagnosis and improve patient care.

High-grade serous ovarian tumor cells modulate NK cell function to create an immune-tolerant microenvironment

Tubo-ovarian high-grade serous carcinoma (HGSC) is unresponsive to immune checkpoint blockade despite significant frequencies of exhausted T cells. Here we apply mass cytometry and uncover decidual-like natural killer (dl-NK) cell subpopulations (CD56+CD9+CXCR3+KIR+CD3-CD16-) in newly diagnosed HGSC samples that correlate with both tumor and transitioning epithelial-mesenchymal cell abundance. We show different combinatorial expression patterns of ligands for activating and inhibitory NK receptors within three HGSC tumor compartments: epithelial (E), transitioning epithelial-mesenchymal (EV), and mesenchymal (vimentin expressing [V]), with a more inhibitory ligand phenotype in V cells. In cocultures, NK-92 natural killer cells acquire CD9 from HGSC tumor cells by trogocytosis, resulting in reduced anti-tumor cytokine production and cytotoxicity. Cytotoxicity in these cocultures is restored with a CD9-blocking antibody or CD9 CRISPR knockout, thereby identifying mechanisms of immune suppression in HGSC. CD9 is widely expressed in HGSC tumors and so represents an important new therapeutic target with immediate relevance for NK immunotherapy.

Identification and characterization of effusion tumor cells (ETCs) from remnant pleural effusion specimens

BACKGROUND

Cancer is a leading cause of death worldwide, and patients may have advanced disease when diagnosed. Targeted therapies guided by molecular subtyping of cancer can benefit patients significantly. Pleural effusions are frequently observed in patients with metastatic cancer and are routinely removed for therapeutic purposes; however, effusion specimens have not been recognized as typical substrates for clinical molecular testing because of frequent low tumor cellularity.

METHODS

Excess remnant pleural effusion samples (N = 25) from 21 patients with and without suspected malignancy were collected at Stanford Health Care between December 2019 and November 2020. Samples were processed into ThinPrep slides and underwent novel effusion tumor cell (ETC) analysis. The ETC results were compared with the original clinical diagnoses for accuracy. A subset of confirmed ETCs was further isolated and processed for molecular profiling to identify cancer driver mutations. All samples were obtained with Institutional Review Board approval.

RESULTS

The authors established novel quantitative standards to identify ETCs and detected epithelial malignancy with 89.5% sensitivity and 100% specificity in the pleural effusion samples. Molecular profiling of confirmed ETCs (pools of 5 cells evaluated) revealed key pathogenic mutations consistent with clinical molecular findings.

CONCLUSIONS

In this study, the authors developed a novel ETC-testing assay that detected epithelial malignancies in pleural effusions with high sensitivity and specificity. Molecular profiling of 5 ETCs showed promising concordance with the clinical molecular findings. To promote cancer subtyping and guide treatment, this ETC-testing assay will need to be validated in larger patient cohorts to facilitate integration into cytologic workflow.