TIGIT is Frequently Expressed in the Tumor Microenvironment of Select Lymphomas: Implications for Targeted Therapy

Immune checkpoint inhibitors against Programmed Cell Death Protein 1/Programmed Cell (PD-1/PD-L1) and CTLA-4/B7 axes have had limited success in hematologic malignancies, requiring the need to explore alternative targets such as T-cell immunoreceptor with Ig and ITIM domains (TIGIT)/CD155 to improve durable clinical responses. We undertook this study to investigate the expression profile of TIGIT such that the potential efficacy of TIGIT blockade could be mapped among lymphoma subtypes. We validated an immunohistochemical assay for TIGIT and evaluated its expression in lymphoma and tumor microenvironment (TME) cells in 661 lymphoma/leukemia biopsies. Multiplex immunofluorescence was used for correlation with normal TME cell subsets. Tumor or TME TIGIT-positivity was defined as moderate to strong membrane staining in at least 10% of tumor or TME cells, respectively. TME TIGIT expression was correlated with overall survival and progression-free survival and comparison with PD-L1 expression. In most cases, lymphoma cells were TIGIT-negative except for angioimmunoblastic and peripheral T-cell lymphomas, which showed 91% and 47% positivity, respectively. A high proportion of small B-cell lymphoma and anaplastic large cell lymphoma cases had TIGIT-positive TME cells. Chronic lymphocytic leukemia/small lymphocytic lymphoma patients with TIGIT-negative TME cells showed significantly shorter overall survival ( P =0.04). No other statistically significant differences were found. When TIGIT was expressed in TME cells, there were a comparable number of TIGIT-positive only and dual TIGIT/PD-L1 positive cases except for more TIGIT-positive only cases in CLL/SLL. TIGIT expression shows distinctive profiles among lymphoma subtypes. Chronic lymphocytic leukemia/small lymphocytic lymphoma and anaplastic large cell lymphoma demonstrated high TME TIGIT expression compared with PD-L1, with a high proportion of dual TIGIT and PD-L1-positivity. Our results are likely to contribute to the design and correlative study of therapeutic response in clinical trials targeting TIGIT alone or in combination with PD1/PDL1.

Detection of Aberrant CD58 Expression in a Wide Spectrum of Lymphoma Subtypes: Implications for Treatment Resistance

CD58 or lymphocyte function-associated antigen-3, is a ligand for CD2 receptors on T and NK cells and is required for their activation and target cell killing. We recently showed a trend toward higher frequency of CD58 aberrations in patients with diffuse large B-cell lymphoma (DLBCL) who progressed on chimeric antigen receptor-T-cell treatment compared with those who responded. Given that CD58 status may be an important measure of T-cell-mediated therapy failure, we developed a CD58 immunohistochemical assay and evaluated CD58 status in 748 lymphomas. Our results show that CD58 protein expression is downregulated in a significant proportion of all subtypes of B-, T-, and NK-cell lymphomas. CD58 loss is significantly related to poor prognostic indicators in DLBCL and to ALK and DUSP22 rearrangements in anaplastic large-cell lymphoma. However, it is not associated with overall or progression-free survival in any of the lymphoma subtypes. As eligibility for chimeric antigen receptor-T-cell therapy is being extended to a broader spectrum of lymphomas, mechanisms of resistance, such as target downregulation and CD58 loss, may limit therapeutic success. CD58 status is therefore an important biomarker in lymphoma patients who may benefit from next-generation T-cell-mediated therapies or other novel approaches that mitigate immune escape.

Effusion tumor cell (ETC) detection from cytology samples following long-term storage

Introduction/Objective

Circulating tumor cells (CTCs) are shed from solid tumors into blood. The RareCyte CTC system involves multiplexed fluorescence whole-slide imaging of blood for antibody-based identification of EpCAM/cytokeratin-positive and CD45-negative CTCs. We have previously established an assay to detect carcinoma effusion tumor cells (ETCs) from remnant pleural fluid samples employing RareCyte, providing a potential avenue for tumor cell detection from any cytology sample. To facilitate this, our aim is to evaluate slide storage conditions. We hypothesize that long-term storage of pleural fluid ThinPrep slides at -20°C prior to RareCyte analysis will yield similar ETC numbers and characteristics to freshly-prepared slides.

Methods/Case Report

ETCs were identified and counted via RareCyte according to our previously established criteria (EpCAM mean fluorescence intensity (MFI) > 100 arbitrary unit (a.u.), CD45 MFI < 100 a.u., and cellular morphology). We analyzed 7 paired fresh-stored pleural fluid samples. Stored samples were maintained at -20°C for 154 or 385 days. ETCs counts between the fresh and stored conditions were compared using a Wilcoxon signed-rank test. Marker intensities from the 35 EpCAM-brightest cells across one paired fresh-stored sample were compared using a two-tailed independent t-test. The cutoff for significance is p<0.05.

Results (if a Case Study enter NA)

The median (25%, 75%) number of cells detected in the 7 fresh and stored samples was 36 (14, 129) and 13 (5, 22), respectively, and was not significantly different (p=0.08). Although the MFIs for DAPI nuclear staining (p=0.12) and CD45 (p=0.82) were not significantly different between the fresh and stored 35 EpCAM-brightest cells, cytokeratin (p=0.02) and EpCAM (p<0.00001) MFIs were significantly less in stored samples.

Conclusion

Detecting ETCs is possible after long-term storage at -20°C despite a significant decrease in EpCAM and cytokeratin MFIs in stored samples. In this small sample, paired ETC counts were not significantly different. These preliminary results provide a foundation for larger studies to define storage conditions.

Abstract 1440: Evolution of CD19 expression in pediatric B-cell malignancies in the era of targeted therapy

Introduction: Ubiquitous expression of CD19 renders it an ideal target for immunotherapy in B-cell neoplasms. As such, loss or decrease in CD19 is emerging as a means of cancer resistance. As a referral center for CD22-based approaches, an alternative target in B-cells, we had the opportunity to serially evaluate CD19 changes following targeted therapy.

Methods: In this retrospective chart review, we assessed for evolution of CD19 expression in patients referred for CD22 immunotherapies. Data collection included demographics, prior therapies, and serial CD19 expression as assessed by flow cytometry (% positivity and site density), response to prior CD19 targeted therapy, and change from baseline.

Results: 56 unique patients were analyzed. The median age was 19 years (range 4-30). At the time of referral (baseline), 23 (41%) subjects were CD19 negative, all following > 1 forms of CD19-targeted therapy. 8 (14%) were CD19 partial positive including 2 patients who were 28% and 81% CD19 positive but CD19-immunotherapy naïve. 25 (43%) were CD19 positive, 2 were CD19 dim following blinatumomab, and 7 were CD19-immunotherapy naïve. In 40 of 56 subjects (71%), there was no change in CD19 expression. 16 (29%) patients had either gain or loss of CD19. In those with CD19 re-expression, the median time for this occurrence was 91 days from baseline.

Conclusions: In this heterogenous population, we document evolution in CD19 expression following CD19-immunotherapy and identified unique patients with inherent CD19 alterations. Some patients retain or regain CD19 expression, conferring new susceptibility to CD19 targeting, while others permanently lose CD19, rendering further CD19-targeted approaches futile. The development of this latter population raises the concern for the outgrowth of subclinical CD19 negative clones. Pairing these findings with genomics will be important to understand the mechanism behind these changes in expression in the search to optimize treatment for B-cell cancers.

Table 1Baseline DemographicsFirst Change from Baselinen=56 (%)# with CR to prior therapyChangen (%)Days to ↑ CD19 expression (Median, IQR)Age (median, range in years)19 (4-30)Male38 (68%)At study baseline*CD19 negative23 (41%)Baseline CD19 Negative (n=23)Remains CD19 neg17 (74%)NAPrior CD19 CAR1614Prior blinatumomab32Becomes CD19 Partial4 (17%)133 (351)Both33**Other CD19 targeted (SGN19a)10Becomes CD19 Positive2 (9%)416 (39)No prior targeted therapy0–CD19 partial#8 (14%)Baseline CD19 Partial (n=8)Becomes CD19 neg0NAPrior CD19 CAR10Prior blinatumomab62Remains CD19 partial4 (50%)NABoth00Becomes CD19 positive4 (50%)53 (66)No prior targeted therapy2–CD19 positive23 (41%)Baseline CD19 positive (n=25)Becomes CD19 neg##2 (8%)NAPrior CD19 CAR55Prior blinatumomab74Becomes CD19 partial3 (12%)NABoth42**No prior targeted therapy7–CD19 dim^ (uniformly positive)2 (4%)CD19 dim to positive1 (4%)21 (NA)Prior CD19 CAR00Prior blinatumomab21Remains CD19 positive19 (76%)NABoth00No prior targeted therapy00CR: Complete remissionIQR: interquartile range*Baseline represents first sample that subject had at the time of referral to the NIH with detectable disease^Indicates CD19 expression < 2000 sites/cells#Partial positivity defined by < 95% antigen positive**Complete response to CD19 CAR, no response to blinatumomab##Following interval CD19 targeted-therapy

Citation Format: Diane Libert, Constance M. Yuan, Haneen Shalabi, Dalia Salem, Bonnie Yates, Cindy Delbrook, Terry Fry, John Shern, Maryalice Stetler-Stevenson, Nirali Shah. Evolution of CD19 expression in pediatric B-cell malignancies in the era of targeted therapy [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 1440.

Histoplasma Urinary Antigen Testing Obviates the Need for Coincident Serum Antigen Testing

OBJECTIVES

Serum and urine antigen (SAg, UAg) detection are common tests for Histoplasma capsulatum. UAg detection is more widely used and reportedly has a higher sensitivity. We investigated whether SAg detection contributes meaningfully to the initial evaluation of patients with suspected histoplasmosis.

METHODS

We reviewed 20,285 UAg and 1,426 SAg tests ordered from 1997 to 2016 and analyzed paired UAg and SAg tests completed on the same patient within 1 week. We determined the positivity rate for each test.

RESULTS

Of 601 paired specimens, 542 were concurrent negatives and 48 were concurrent positives (98% agreement). Medical records were available for eight of 11 pairs with discrepant results. UAg was falsely positive in six instances, truly positive once, and falsely negative once.

CONCLUSIONS

These findings support using a single antigen detection test, rather than both UAg and SAg, as an initial screen for suspected histoplasmosis. This aligns with the current practice of most physicians.

Modulation of basal cell fate during productive and transforming HPV-16 infection is mediated by progressive E6-driven depletion of Notch

In stratified epithelia such as the epidermis, homeostasis is maintained by the proliferation of cells in the lower epithelial layers and the concomitant loss of differentiated cells from the epithelial surface. These differentiating keratinocytes progressively stratify and form a self‐regenerating multi‐layered barrier that protects the underlying dermis. In such tissue, the continual loss and replacement of differentiated cells also limits the accumulation of oncogenic mutations within the tissue. Inactivating mutations in key driver genes, such as TP53 and NOTCH1, reduce the proportion of differentiating cells allowing for the long‐term persistence of expanding mutant clones in the tissue. Here we show that through the expression of E6, HPV‐16 prevents the early fate commitment of human keratinocytes towards differentiation and confers a strong growth advantage to human keratinocytes. When E6 is expressed either alone or with E7, it promotes keratinocyte proliferation at high cell densities, through the combined inactivation of p53 and Notch1. In organotypic raft culture, the activity of E6 is restricted to the basal layer of the epithelium and is enhanced during the progression from productive to abortive or transforming HPV‐16 infection. Consistent with this, the expression of p53 and cleaved Notch1 becomes progressively more disrupted, and is associated with increased basal cell density and reduced commitment to differentiation. The expression of cleaved Notch1 is similarly disrupted also in HPV‐16‐positive cervical lesions, depending on neoplastic grade. When taken together, these data depict an important role of high‐risk E6 in promoting the persistence of infected keratinocytes in the basal and parabasal layers through the inactivation of gene products that are commonly mutated in non‐HPV‐associated neoplastic squamous epithelia. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.