Spatially Resolved Tumor Microenvironment Predicts Treatment Outcomes in Relapsed/Refractory Hodgkin Lymphoma

PURPOSE

About a third of patients with relapsed or refractory classic Hodgkin lymphoma (r/r CHL) succumb to their disease after high-dose chemotherapy followed by autologous stem-cell transplantation (HDC/ASCT). Here, we aimed to describe spatially resolved tumor microenvironment (TME) ecosystems to establish novel biomarkers associated with treatment failure in r/r CHL.

PATIENTS AND METHODS

We performed imaging mass cytometry (IMC) on 71 paired primary diagnostic and relapse biopsies using a marker panel specific to CHL biology. For each cell type in the TME, we calculated a spatial score measuring the distance of nearest neighbor cells to the malignant Hodgkin Reed Sternberg cells within the close interaction range. Spatial scores were used as features in prognostic model development for post-ASCT outcomes.

RESULTS

Highly multiplexed IMC data revealed shared TME patterns in paired diagnostic and early r/r CHL samples, whereas TME patterns were more divergent in pairs of diagnostic and late relapse samples. Integrated analysis of IMC and single-cell RNA sequencing data identified unique architecture defined by CXCR5+ Hodgkin and Reed Sternberg (HRS) cells and their strong spatial relationship with CXCL13+ macrophages in the TME. We developed a prognostic assay (RHL4S) using four spatially resolved parameters, CXCR5+ HRS cells, PD1+CD4+ T cells, CD68+ tumor-associated macrophages, and CXCR5+ B cells, which effectively separated patients into high-risk versus low-risk groups with significantly different post-ASCT outcomes. The RHL4S assay was validated in an independent r/r CHL cohort using a multicolor immunofluorescence assay.

CONCLUSION

We identified the interaction of CXCR5+ HRS cells with ligand-expressing CXCL13+ macrophages as a prominent crosstalk axis in relapsed CHL. Harnessing this TME biology, we developed a novel prognostic model applicable to r/r CHL biopsies, RHL4S, opening new avenues for spatial biomarker development.

52 Characterization of the tumor microenvironment in melanoma using Multiplexed Ion Beam Imaging (MIBI)

Background

The complexity of the tumor microenvironment (TME) necessitates the application of high-dimensional methods that can spatially resolve the phenotypic heterogeneity that exists within tumors. MIBI, which combines time-of-flight secondary ion mass spectrometry (ToF-SIMS) with metal labeled antibodies to simultaneously image 40+ proteins at subcellular spatial resolution, was used to classify cell populations and their expression of immunoregulatory proteins within 54 melanoma samples.

Methods

A tissue microarray (TMA) comprised of 0.6 mm FFPE melanoma cores was stained with a panel of 30 metal labeled antibodies. The tissue was imaged using MIBI and multi-step processing was performed to create images of the samples. Single cell segmentation enabled enumeration of 32 cell populations and quantitative analyses were performed of both immune checkpoint expression and the spatial relationships between cells of different types.

Results

Tumor cells and immune cells represented 62% (1.4% - 92.2%) and 24% (2.0% - 92.1%), respectively, of the segmented cells from the melanoma samples. Fibroblasts, lymphatics, and blood vessels were also present at varying densities. Within the immune compartment, M2 macrophages, M2 monocytes, and monocyte-derived dendritic cells (mDCs) were most abundant, representing 36.3% (4.9% - 79.3%), 7.0% (0.0% - 30.6%), and 9.8% (0.0% - 34.6%), respectively, of the total immune cell infiltrate. Rare populations such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells were at greater than 100 cells/mm2 in six samples and four samples, respectively. The presence of immune checkpoint markers (IDO-1, LAG3, PD-1, PD-L1, TIM-3) varied between populations and between samples. A minority of the samples showed expression of IDO-1 and PD-L1 on myeloid populations. Interestingly, among the myeloid subsets, M2 macrophages and monocyte-derived dendritic cells showed the most abundant PD-L1 expression. Although many samples had few T cell infiltrates, those that did showed expression of PD-1, LAG-3, and TIM-3 on T cell populations.

Conclusions

MIBI offers high-parameter tissue imaging, at sensitivity and resolution suited to understanding the complex tumor immune landscape, including the spatial relationships of immune and tumor cells and the expression of immunoregulatory proteins. Datasets that quantify population densities and immune checkpoint expression levels across tumor samples, such as the present one, can be used to test for associations to clinical variables and further understand the TME at the cellular level.

48 Advances in multiplexed ion beam imaging (MIBI) for immune profiling of the tumor microenvironment

Background

Multiplexed ion beam imaging (MIBI) combines time-of-flight secondary ion mass spectrometry (ToF-SIMS) with metal labeled antibodies to image 40+ proteins in a single scan at subcellular spatial resolution. Here, we show that the recently released MIBIscope provides improved sensitivity for detecting immune checkpoint markers and offers greater throughput at higher resolution than the alpha instrument.

Methods

Serial sections from three FFPE NSCLC samples, in addition to a control slide consisting of various unremarkable tissues, were stained with a panel of 25 metal labeled antibodies. The tissue was imaged at subcellular resolution using the MIBIscope and the alpha instrument. Masses of detected species were assigned to target biomolecules given the unique label of each antibody and multi-step processing was used to create images. Cell classification was performed using two complementary methods that differed in the need for cell segmentation to phenotypically characterize the tissue environments and quantify marker expression.

Results

Replicate regions of interest (ROIs) were collected on both instruments with similarly sized ROIs acquired in 17 minutes with the MIBIscope compared to 280 minutes with the alpha instrument. Fourier Ring Correlation (FRC) showed the resolution to be greater on the MIBIscope as compared to the alpha instrument with FRC also demonstrating uniform resolution across an ROI 2.5X greater in size. Even with the 16X greater speed of the MIBIscope, the signal of the 25 markers across replicate ROIs was increased (y=x^1.07) and showed similar expression patterns to those observed on the alpha instrument (figure 1). This resulted in greater sensitivity to markers with low expression, such as checkpoint markers. Eleven cell populations were classified across the ROIs utilizing two methods, with both methods showing a similar frequency of tumor cells and B, T, and myeloid cell subsets between instruments. Segmentation enabled the number of cells within a population to be calculated but defining boundaries is laborious and signal from neighboring cells can result in misclassification. Performing classification at the pixel level, without segmentation, enabled the fraction of the tissue that is tumor or any other cell type to be rapidly determined.

Abstract 48 Figure 1

Comparison of images acquired between instrumentsThe signal intensity is greater on the MIBIscope and shows a similar staining pattern as achieved by the alpha instrument. Shown are 3 overlays from a single scan from replicate ROIs of an NSCLC sample displayed with the same contrast settings.

Conclusions

The MIBIscope enables the phenotypic characterization of tumor and non-tumor microenvironments. Co-expression of markers can be used to classify tumor and immune populations and to quantify the expression of markers associated with immune suppression. The increased sensitivity and throughput of the MIBIscope, in combination with the 40-parameter capability and subcellular resolution, provides a platform uniquely suited to understanding the complex tumor immune landscape.

Single-Cell Transcriptome Analysis Reveals Disease-Defining T-cell Subsets in the Tumor Microenvironment of Classic Hodgkin Lymphoma

Hodgkin lymphoma is characterized by an extensively dominant tumor microenvironment (TME) composed of different types of noncancerous immune cells with rare malignant cells. Characterization of the cellular components and their spatial relationship is crucial to understanding cross-talk and therapeutic targeting in the TME. We performed single-cell RNA sequencing of more than 127,000 cells from 22 Hodgkin lymphoma tissue specimens and 5 reactive lymph nodes, profiling for the first time the phenotype of the Hodgkin lymphoma-specific immune microenvironment at single-cell resolution. Single-cell expression profiling identified a novel Hodgkin lymphoma-associated subset of T cells with prominent expression of the inhibitory receptor LAG3, and functional analyses established this LAG3⁺ T-cell population as a mediator of immunosuppression. Multiplexed spatial assessment of immune cells in the microenvironment also revealed increased LAG3⁺ T cells in the direct vicinity of MHC class II-deficient tumor cells. Our findings provide novel insights into TME biology and suggest new approaches to immune-checkpoint targeting in Hodgkin lymphoma. SIGNIFICANCE: We provide detailed functional and spatial characteristics of immune cells in classic Hodgkin lymphoma at single-cell resolution. Specifically, we identified a regulatory T-cell-like immunosuppressive subset of LAG3⁺ T cells contributing to the immune-escape phenotype. Our insights aid in the development of novel biomarkers and combination treatment strategies targeting immune checkpoints.See related commentary by Fisher and Oh, p. 342.This article is highlighted in the In This Issue feature, p. 327.

Abstract 2789: Highly multiplexed imaging mass cytometry reveals immune cell composition and spatial heterogeneity in diffuse large B cell lymphoma associated with treatment outcome

Diffuse large B cell lymphoma (DLBCL) is an aggressive and heterogenous entity characterized by its variable clinical and biological behaviour, and approximately 30% of patients experience relapsed or refractory disease after first-line therapy. We hypothesize that a better characterization of the tumor microenvironment (TME) might help identify patients who may benefit from individualized immunotherapies. Similar studies in this area have been limited by technical challenges - conventional highly multiplexed techniques require tissue disruptions that lose spatial information, while those that retain tissue architecture can only examine 6-8 markers simultaneously. We and others have previously reported that PD-L1 expression is correlated with decreased survival in a cohort of 85 DLBCL patients. In the present study, we characterized TME components, including their types, frequency and spatial interaction, in DLBCL using imaging mass cytometry (IMC), which allows high-dimensional, single-cell and spatial analysis of FFPE tissues at sub-cellular resolution. Using a panel of 32 antibodies, IMC was performed on a subset of our previously studied cohort. We examined 41 cores from 33 DLBCL cases, 17 GCB and 16 non-GCB, by Hans criteria. Clinical outcome data were available for 29 patients, 22 of whom had complete response (CR) to R-CHOP therapy while 7 had primary refractory disease. Using both supervised gating and unsupervised clustering algorithm, IMC data were analyzed for relevant immunophenotypes and compared across clinical outcome groups. The TME was mainly composed of 13.1% ± 1.9% (mean ± SE) CD4+ T-helper cells, 10.8% ± 1.1% CD8+ cytotoxic T cells, 6.3% ± 0.9% CD68+ macrophages, 2.7% ± 0.5% FoxP3+ regulatory T cells, and 58.1% ± 3.4% tumor cells. In non-GCB group, higher ratio of regulatory T cells was associated with refractory disease. In contrast, activated granzyme-B+/CD8+ cytotoxic T cells were more frequent in CR group, while markers of exhaustion (Tim3, Lag3) were found in patients with refractory disease. To gain functional insight into the various immune subsets, we performed spatial analysis of the immune cells and their relation to blood vessels and tumor cells. Nearest distance analysis showed that CD4+ cells were most tightly clustered around blood vessels in patients with CR, while in those with refractory diseases, CD4+ cells were further away from the vessels (p=0.03). On the contrary, distances between cytotoxic T cells and regulatory T cells showed no difference between CR and refractory patients. Together, these results show variable composition of the different immune cells and their spatial heterogeneity to be associated with the clinical outcome of DLBCL patients and that spatial analysis of immune cells should be explored as a potential biomarker for patients treated with immunotherapies.

Citation Format: Monirath Hav, Erik Gerdtsson, Mohan Singh, Anthony Colombo, James Hicks, Peter Kuhn, Imran Siddiqi, Akil Merchant. Highly multiplexed imaging mass cytometry reveals immune cell composition and spatial heterogeneity in diffuse large B cell lymphoma associated with treatment outcome [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 2789.

Abstract 1189: Revisiting immune exhaustion in Hodgkin’s lymphoma

Clinical successes with immune check-point blockers have demonstrated the potency of the immune system in controlling cancers, most strikingly in Hodgkin lymphoma (HL), where overall response rates to PD1/L1 inhibitors approach 90%. Complete or durable responses, however, are uncommon, therefore targeting the PD1/L1 axis alone is not sufficient. Recent work analyzing the spatial arrangement of PD1 and PDL1 expressing cells has given us new insight into the mechanism of action of PD1/L1 inhibitors, however this work limited itself to studying a single check point marker on a subset of cells. We hypothesize that comprehensive profiling of the frequency and spatial arrangement of immune cells in the Hodgkin lymphoma tumor immune microenvironment (TME) will provide new insights into the mechanism of checkpoint blockers and identify novel targets for immune therapy. Until now, multiparameter spatial analysis of the immune microenvironment was limited by technical challenges. Flow and mass cytometry are able to identify immune subsets of interest but spatial information is lost. Multiplex tissue imaging methods are limited to 6-8 simultaneous markers and cannot capture the full complexity of the immune phenotypes. The Fluidigm Hyperion imaging mass cytometry (IMC) system combines a CyTOF mass cytometer with a laser ablation system allowing for 40+ parameter simultaneous immunophenotyping on a single slide of FFPE tissue, with sub-cellular resolution. We have developed a panel of 34 antibodies that allow for comprehensive characterization of CD4, CD8 and myeloid cells components in the TME of Hodgkin lymphoma using IMC. Here we report on our spatial analysis of TIM3 and LAG3 expressing CD4+ lymphocytes. Our data suggests LAG3+CD4+ and TIM3+CD4+ lymphocytes had shorter mean nearest distance to PDL1+Hodgkin Reed-Sternberg (HRS) cells upon comparison to PDL1- HRS cells (t-test, p=1.703e-08,p=1.126e-14). Future studies should explore multiple exhausted marker models that seeks to further understand the presence of simultaneous exhaustion signals in the niche environment. These data suggest that therapies that target TIM3 and/or LAG3 should be tested in Hodgkin Lymphoma and that spatial analysis of immune subsets by IMC should be explored as selective and pharmacodynamic biomarkers.

Citation Format: Anthony R. Colombo, Monirath Hav, Erik Gerdtsson, Jose Bisnesto-Villasboas, Stephen Ansell, James Hicks, Peter Kuhn, Akil Merchant. Revisiting immune exhaustion in Hodgkin’s lymphoma [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 1189.

Prevalence of Abnormal Cervical Cytology in HIVNegative Women Participating in a Cervical Cancer Screening Program in Calmette Hospital, Cambodia

Prevalence of Abnormal Cervical Cytology in HIVNegative Women Participating in a Cervical Cancer Screening Program in Calmette Hospital, Cambodia.

Pathologic Assessment of Rectal Carcinoma after Neoadjuvant Radio(chemo)therapy: Prognostic Implications

Neoadjuvant radio(chemo)therapy is increasingly used in rectal cancer and induces a number of morphologic changes that affect prognostication after curative surgery, thereby creating new challenges for surgical pathologists, particularly in evaluating morphologic changes and tumour response to preoperative treatment. Surgical pathologists play an important role in determining the many facets of rectal carcinoma patient care after neoadjuvant treatment. These range from proper handling of macroscopic specimens to accurate microscopic evaluation of pathological features associated with patients' prognosis. This review presents the well-established pathological prognostic indicators and discusses challenging features in order to provide both surgical pathologists and treating physicians with a checklist that is useful in a neoadjuvant setting.

Prognostic value of tumor shrinkage versus fragmentation following radiochemotherapy and surgery for rectal cancer

Most patients with rectal cancer receive neoadjuvant radiochemotherapy (RCT), causing a variable decrease in tumor mass. We evaluated the prognostic impact of pathologic parameters reflecting tumor response to RCT, either directly or indirectly. Seventy-six rectal cancer patients receiving neoadjuvant RCT between 2006 and 2009 were included. We studied the association between disease-free survival (DFS) and the "classical" clinicopathologic features as well as tumor deposits, circumferential resection margin (CRM), Dworak regression grade, and tumor and nodal downstaging. Patients with tumor downstaging had a longer DFS (p = 0.05), indicating a more favorable prognosis when regression was accompanied by a decrease in tumor infiltrative depth, referred to as tumor shrinkage. Moreover, tumor downstaging was significantly associated with larger CRM and nodal downstaging (p = 0.02), suggesting that shrinkage of the primary tumor was associated with a decreased nodal tumor load. Higher Dworak grade did not correlate with tumor downstaging, nor with higher CRM or prolonged DFS. This implies that tumor mass decrease was sometimes due to fragmentation rather than shrinkage of the primary tumor. Lastly, the presence of tumor deposits was clearly associated with reduced DFS (p = 0.01). Assessment of tumor shrinkage after RCT via tumor downstaging and CRM is a good way of predicting DFS in rectal cancer, and shrinkage of the primary tumor is associated with a decreased nodal tumor load. Assessing regression based on the amount of tumor in relation to stromal fibrosis does not accurately discern tumor fragmentation from tumor shrinkage, which is most likely the reason why Dworak grade had less prognostic relevance.

Colorectal cancer in young Cambodians

AIM

Colorectal cancer (CRC) is a common disease in the older population, but it has become increasingly evident that it is also not infrequent in the young. The aim of this study was to describe the epidemiological, clinical and pathological characteristics of CRC in young Cambodians.

METHODS

We examined clinical and pathological data from all CRC cases registered in the two reference centres for gastrointestinal tumours in Cambodia between 2005-2010. Age-specific CRC incidence rates were computed using the national population census 2008 data from the National Institute of Statistics. We compared differences in distribution of tumour location, histology, differentiation and UICC/TNM stage in two age groups, namely < 40 and ≥ 40.

RESULTS

During this period, there were 356 new CRC cases, of which 29.8% affected patients younger than 40. This proportion is the second highest in the world, with a higher proportion only reported in Egyptian population. The crude incidence was 2.82 and 2.36 per 100,000 in females and males, respectively. Adenocarcinoma was the most common histologic type, and >50% of all tumours occurred in the colon, with no appreciable variation between the two age groups. Mucin-producing and advanced-grade tumours were twice more frequent in the young.

CONCLUSION

The unusually high CRC proportion in the young in our study could be due to referral bias. Nevertheless, together with the continuous exposure to hazardous environmental agents and the prevalent consanguinity in Cambodia, this question warrants further research to advance our understanding of CRC risk factors and perhaps genetic-environmental interactions in CRC epidemiology in young adults.

MDM2 gene amplification and protein expressions in colon carcinoma: is targeting MDM2 a new therapeutic option?

The aim of this study was to investigate murine double minute-2 (MDM2) gene copy number changes in colon carcinoma and to correlate these findings with an immunohistochemical analysis of MDM2 protein expression and histopathologic prognostic indicators of the tumors. The study included 80 cases of sporadic colon carcinomas. MDM2 protein expression was assessed by immunohistochemistry, and MDM2 gene status by fluorescence in situ hybridization. MDM2 gene amplification was detected in 18% of the 80 cases examined. A strong correlation was found between MDM2 gene amplification and the presence, intensity, and staining proportion of cytoplasmic MDM2 protein expression (p = 0.01). No correlation was found between MDM2 gene amplification and the well-established histopathologic prognostic factors. Given the correlation with gene amplification, we clearly demonstrated that cytoplasmic expression of MDM2 protein is true and relevant and that this finding has to be taken into account when immunohistochemistry would be used as a screening for MDM2 gene amplification in the near future. Targeting MDM2 could be a new approach in colon cancer therapy. The amplification status could be a predictive factor of the response to MDM2-targeted therapy.

Clear-cell variant of solid-pseudopapillary neoplasm of the pancreas: a case report and review of the literature

Solid-pseudopapillary neoplasm (SPN) of the pancreas is a rare neoplasm reported to have a favourable prognosis because of its slow-growing behaviour. Ignored and misdiagnosed in the past, SPN has recently been increasingly studied. Its clear cell variant creates challenges in distinction from other clear cell tumours in the pancreas. We report a 31-year-old Cambodian woman who presented with abdominal pain and a palpable epigastric mass. Exploratory laparotomy revealed a 5.2 cm well-demarcated tumour in the head of the pancreas, which was treated with Whipple procedure. Microscopically, the tumour showed an extensive solid growth pattern consisting of cells with abundant clear cytoplasm, and papillary areas containing cells with eosinophilic cytoplasm, indicating a clear-cell solid-papillary neoplasm. Perineural and duodenal wall invasion was present. The tumour cells were immunonegative for chromogranin-A and synaptophysin but positive for CD56, cyclin D1, CD10, vimentin, and progesterone receptor. They showed strong nuclear and cytoplasmic expression and reduced membranous expression of beta-catenin protein. In the pseudopapillary area, they showed nuclear E-cadherin localization and absence of membranous staining. The patient was well without local recurrence or metastasis at one year follow-up. Difficulties are recognized in differentiating clear-cell SPN from "sugar" tumours, metastatic renal cell carcinoma, clear-cell variant of pancreatic endocrine neoplasm and ductal adenocarcinoma. When facing such difficulties, nuclear and cytoplamic beta-catenin, nuclear E-cadherin expressions and absence of membranous E-cadherin staining are useful in differentiating clear-cell SPN from other clear cell tumours in the pancreas. Although a rare neoplasm, it is important to recognize this entity for appropriate management.