Development of a 23-color flow cytometry panel for the characterization of myelomonocytic differentiation with applications for MRD testing

It is well agreed that measurable residual disease (MRD) testing in acute leukemia patients following induction chemotherapy has profound prognostic implications. Flow cytometry is well suited to be the mainstay for MRD testing due to the heterogenous immunophenotypic and molecular natures of leukemia. Current flow cytometry MRD testing involves examination of more than 15 antigens, requiring multiple tubes to be run for each patient as current clinical flow cytometers are limited to examining 12 parameters per tube. Because multiple tubes are required, hematopathologists must infer antigen expression between tubes, which can be difficult. As MRD testing has such prognostic implications and defines treatment stratifications and outcomes, MRD testing requires very high sensitivity. While several groups have improved sensitivity by increasing the number of cells analyzed, we propose that increasing the antigenic targets in a single immunophenotyping assay will improve sensitivity by enhancing our ability to differentiate normal from abnormal hematopoietic cells. To test this, we utilized spectral flow cytometry, which allows for targeting more parameters with the same number of lasers for a single instrument. We developed a 23-color flow cytometry panel which was designed to thoroughly examine myelomonocytic differentiation and included multiple other antigenic targets which are known to be aberrantly expressed on leukemia cells. The panel also included a live-dead stain to exclude dead cells from analysis. All data was collected with a 3-laser Cytek Northern Lights spectral flow cytometer, which can analyze 10 million events in ~10 minutes. We tested this panel on more than 50 bone marrow aspirate samples, including normal samples, multiple myeloid leukemias, myelodysplastic samples, as well as more than 20 aspirate samples which also had MRD testing completed at a reference laboratory. Our results for MRD testing had excellent concordance with results from the gold-standard reference laboratory method. As our method only required one tube to be run per sample, we were routinely able to analyze at least 10 million cells per sample. Using in silico modelling from our data, we determined the sensitivity of our assay to be an average of 0.005% (range 0.002 – 0.015%) depending on the specific immunophenotype, when analyzing 10 million cells. As we examined all marker expression in a single tube, we were able to model sensitivity as if only 10-parameters were collected per tube and inference was required between tubes for analysis as is the current standard practice. We found that our 23-color assay was significantly more sensitive (p =0.02) compared to running multiple 10-color tubes and inferring between samples. Overall, higher parameter flow cytometric assays (>20 markers) allow for a more sensitive and robust MRD analysis than current gold-standard methods and should be explored for utilization in the clinical setting.

Analysis of Genomic Characteristics and Transmission Routes of Patients With Confirmed SARS-CoV-2 in Southern California During the Early Stage of the US COVID-19 Pandemic

Importance

In late December 2019, an outbreak of a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China. Data on the routes of transmission to Los Angeles, California, the US West Coast epicenter for coronavirus disease 2019 (COVID-19), and subsequent community spread are limited.

Objective

To determine the transmission routes of SARS-CoV-2 to Southern California and elucidate local community spread within the Los Angeles metropolitan area.

Design, Setting, and Participants

This case series included 192 consecutive patients with reverse transcription-polymerase chain reaction (RT-PCR) test results positive for SARS-CoV-2 who were evaluated at Cedars-Sinai Medical Center in Los Angeles, California, from March 22 to April 15, 2020. Data analysis was performed from April to May 2020.

Main Outcomes and Measures

SARS-CoV-2 viral genomes were sequenced. Los Angeles isolates were compared with genomes from global subsampling and from New York, New York; Washington state; and China to determine potential sources of viral dissemination. Demographic data and outcomes were collected.

Results

The cohort included 192 patients (median [interquartile range] age, 59.5 [43-75] years; 110 [57.3%] men). The genetic characterization of SARS-CoV-2 isolates in the Los Angeles population pinpointed community transmission of 13 patients within a 3.81 km2 radius. Variation landscapes of this case series also revealed a cluster of 10 patients that contained 5 residents at a skilled nursing facility, 1 resident of a nearby skilled nursing facility, 3 health care workers, and a family member of a resident of one of the skilled nursing facilities. Person-to-person transmission was detected in a cluster of 5 patients who shared the same single-nucleotide variation in their SARS-CoV-2 genomes. High viral genomic diversity was identified: 20 Los Angeles isolates (15.0%) resembled SARS-CoV-2 genomes from Asia, while 109 Los Angeles isolates (82.0%) were similar to isolates originating from Europe. Analysis of other common respiratory viral pathogens did not reveal coinfection in the cohort.

Conclusions and Relevance

These findings highlight the precision of detecting person-to-person transmission and accurate contact tracing directly through SARS-CoV-2 genome isolation and sequencing. Development and application of phylogenetic analyses from the Los Angeles population established connections between COVID-19 clusters locally and throughout the US.

Improved Recognition of Hematogones From Precursor B-Lymphoblastic Leukemia by a Single Tube Flow Cytometric Analysis

OBJECTIVES

To improve diagnostic accuracy in differentiating hematogones from leukemic blasts in cases of precursor B-lymphoblastic leukemia/lymphoma (B-ALL), particularly those that are posttreatment or after bone marrow transplant, and to provide an algorithmic approach to this diagnostic challenge.

METHODS

A seven-color antibody panel including CD10, CD19, CD45, CD38, CD34, CD58, and CD81 was generated to assess the feasibility of a single tube panel and provide an algorithmic approach to distinguish hematogones from B-ALL. Fifty-three cases were analyzed, and results were correlated with histology and ancillary studies.

RESULTS

There was a significant difference in mean fluorescent intensity (MFI) for CD81 and CD58 when comparing hematogones and B-ALL populations (P < .001). B-ALL cases had a mean (SD) MFI of 24.6 (27.5; range, 2-125) for CD81 and 135.6 (72.6; range, 48-328) for CD58. Hematogones cases had a mean (SD) MFI of 70.2 (19.2; range, 42-123) for CD81 and 38.8 (9.4; range, 23-58) for CD58.

CONCLUSIONS

The flow cytometry panel with the above markers and utilization of the proposed algorithmic approach provide differentiation of hematogones from B-ALL. This includes rare cases of hematogones and B-ALL overlap where additional ancillary studies are necessary.

Next-Generation Sequencing: A Novel Approach to Distinguish Multifocal Primary Lung Adenocarcinomas from Intrapulmonary Metastases

Distinguishing between multiple lung primary tumors and intrapulmonary metastases is imperative for accurate staging. The American Joint Committee on Cancer (AJCC) criteria are routinely used for this purpose but can yield equivocal conclusions. This study evaluated whether next-generation sequencing (NGS) using the 50-gene AmpliSeq Cancer Hotspot Panel version 2 can help facilitate this distinction. NGS was performed on known primary-metastatic pairs (8 patients) and multiple lung adenocarcinomas (11 patients). Primary-metastatic pairs had high mutational concordance. Seven pairs shared mutations, and 1 was concordant for having no mutations. Driver mutations in KRAS (n = 4), EGFR (n = 2), and BRAF (n = 1) were always concordant. Multiple lung tumors from 3 patients were completely concordant and predicted by NGS to be intrapulmonary metastases, whereas 8 had completely discordant mutations and were predicted to be independent primary tumors. The NGS prediction correlated with the AJCC (eighth edition) prediction in all patients for whom the latter was unequivocal (8 of 11). Furthermore, it separated patients by overall survival. Patients with predicted multiple independent primary tumors by NGS had better survival than those with distant metastases (P = 0.016, log-rank test), whereas those with predicted intrapulmonary metastases had no difference (P = 0.527). With further validation, the 50-gene panel has the potential to serve as an adjunct to the AJCC criteria.

Abstract B12: Co-targeting of MYC and BCL2 signaling is a promising treatment strategy for double hit and triple hit B-cell lymphomas

Background: Overexpression of MYC and BCL2 or/and BCL6 due to genomic rearrangements is the key molecular feature of double hit lymphoma (DHL) or triple hit lymphoma (THL). Patients with DHL and THL show very aggressive disease course and poor survival because there is no effective treatment modality. The objective of this study is to assess the impact of MYC and BCL2 inhibition on established DHL and patient derived THL cells in vitro.

Methods: Primary THL cell line named as CS-THL1 was established from an 85 year-old lymphoma patient. Immunohistochemistry (IHC) was conducted to determine the levels of MYC, BCL2, BCL6, or Ki-67 expression in formalin-fixed, paraffin-embedded tissues. MTS assays were employed to evaluate the anti-growth efficacy of MYC inhibitor 10058-F4 or JQ-1, and BCL-2 inhibitor ABT-199, a BH3 mimetic, in CS-THL1 and DoGKiT cells alone or together and with or without vincristine or doxorubicin. Apoptosis, cytochrome c release and intracellular expression of BCL2, BCL-xL, BIM, and MCL-1 protein in response to drugs were analyzed by flow cytometry.

Results: Expression of MYC, BCL2, BCL6 and proliferation factor Ki-67 protein was increased in THL, as shown by IHC. Analysis of cell viability demonstrated that inhibition of MYC by 10058-F4 or JQ-1 or BCL2 by ABT-199 as a single agent significantly attenuated the growth of CS-THL1 and DoGKiT cells in dose- and time-dependent manners. Combination of 10058-F4 or JQ-1 and ABT-199 or together with vincristine or doxorubicin synergistically suppressed CS-THL1 and DoGKiT cell growth compared with single agent treatment. As demonstrated by multiple approaches, apoptosis due to inhibition of BCL2 by ABT-199 or inhibition of MYC with 10058-F4 or JQ-1 exposure was the underlying cause of the observed growth retardation in CS-THL1 and DoGKiT cells.

Conclusion: These observations suggest that concurrent inhibition of MYC and BCL2 pathway signaling is a potential treatment modality for patients with aggressive DH and TH B-cell lymphomas.

Citation Format: Munevver Cinar, Fred Rosenfelt, Sepehr Rokshar, Raju Pillai, Jean Lopategui, Melissa Cervania, Bekir Cinar, Serhan Alkan. Co-targeting of MYC and BCL2 signaling is a promising treatment strategy for double hit and triple hit B-cell lymphomas. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B12.

Large-cell transformation of a composite lymphoma

Composite lymphoma is a rarely reported entity, defined as two or more morphologically distinct types of lymphoma at the same anatomic site, occurring either synchronously or metachronously. Since 1978, about 100 case reports of composite lymphoma have been cited, many involving combinations of low-grade B-cell lymphomas. To our knowledge, no cases of large-cell transformation of composite lymphoma have yet been described. We report the case of a patient who presented with diffuse large B-cell lymphoma (DLBCL) fifteen years after successful treatment for a mature B-cell lymphoma. Reassessment of the patient's lymph node from 1995, using techniques not previously available, resulted in a revised diagnosis of composite lymphoma, comprising both follicular lymphoma (FL) and small lymphocytic lymphoma (SLL). Analysis of B-cell gene rearrangement studies using BIOMED-2-based PCR, and of t(14;18) rearrangements by both FISH and PCR, provided evidence that the DLBCL evolved from transformation of the composite lymphoma, specifically from its FL component. B-cell gene rearrangement studies also supported a clonal relationship between the FL and SLL components of the composite lymphoma.