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Objectives Recent genomic studies suggest the biological significance of the cylindromatosis (CYLD) gene in thymic epithelial tumors (TETs). CYLD is a crucial regulator of immune response, and we previously reported that CYLD mutation is associated with high PD-L1 expression in thymic carcinoma. Therefore, we wanted to explore the role and mechanism of CYLD in regulating PD-L1 expression in TETs. Materials and methods The role of CYLD in PD-L1 expression was assessed by knockdown of CYLD in TET cells upon stimulation with interferon gamma (IFN-γ), tumor necrosis factor-α (TNF-α) or polyinosinic-polycytidylic acid (poly I:C). The molecular mechanism was investigated through analysis of downstream molecules in the STAT1/IRF1 pathway. Moreover, the clinical correlation between low CYLD and high PD-L1 expression, and the clinical impact of CYLD expression were evaluated in tissue microarrays of 105 TET cases. Results CYLD knockdown significantly enhanced the expression of PD-L1 in presence of IFN-γ stimulation in most TET cell lines. However, this phenomenon was not observed in presence of TNF-α stimulation. CYLD knockdown upregulated IFN-γ mediated activation of the STAT1/IRF1 axis, which in turn induced PD-L1 expression. Interestingly, we found a significant association between low CYLD expression and ≥ 50 % PD-L1 expression (p = 0.001). In addition, the average proportion of tumor cells exhibiting PD-L1 staining was significantly higher in the low CYLD expression group (24.7 %) than in the high CYLD expression group (5.2 %) (p = 0.005). There was no correlation between CYLD expression and the frequency of pre-existing paraneoplastic auto-immune diseases. In advanced stages (III/IV), the low CYLD expressing group had numerically worse survival than the high CYLD group (log-rank p = 0.089). Conclusions Our findings provide insight into the mechanism of regulation of PD-L1 expression by CYLD in TET cells. Tumors with low CYLD expression could be potential targets for PD-1/PD-L1 inhibitors.

BACKGROUND: Cellular senescence and the senescence-associated secretory phenotype (SASP) may contribute to the development of radiation therapy–associated side effects in the lung and blood vessels by promoting chronic inflammation. In the brain, inflammation contributes to the development of neurologic disease, including Alzheimer’s disease. In this study, we investigated the roles of cellular senescence and Δ133p53, an inhibitory isoform of p53, in radiation-induced brain injury. METHODS: Senescent cell types in irradiated human brain were identified with immunohistochemical labeling of senescence-associated proteins p16(INK4A) and heterochromatin protein Hp1γ in 13 patient cases, including 7 irradiated samples. To investigate the impact of radiation on astrocytes specifically, primary human astrocytes were irradiated and examined for expression of Δ133p53 and induction of SASP. Lentiviral expression of ∆133p53 was performed to investigate its role in regulating radiation-induced cellular senescence and astrocyte-mediated neuroinflammation. RESULTS: Astrocytes expressing p16(INK4A) and Hp1γ were identified in all irradiated tissues, were increased in number in irradiated compared with untreated cancer patient tissues, and had higher labeling intensity in irradiated tissues compared with age-matched controls. Human astrocytes irradiated in vitro also experience induction of cellular senescence, have diminished Δ133p53, and adopt a neurotoxic phenotype as demonstrated by increased senescence-associated beta-galactosidase activity, p16(INK4A), and interleukin (IL)-6. In human astrocytes, Δ133p53 inhibits radiation-induced senescence, promotes DNA double-strand break repair, and prevents astrocyte-mediated neuroinflammation and neurotoxicity. CONCLUSIONS: Restoring expression of the endogenous p53 isoform, ∆133p53, protects astrocytes from radiation-induced senescence, promotes DNA repair, and inhibits astrocyte-mediated neuroinflammation.

Background The prognostic value of arginase expression in hepatocellular carcinoma (HCC) has been evaluated previously. However, no clear distinction exists yet on the role of arginase-1 as a predictor of recurrence in HCC. Cytokeratin 19 (CK19), a cholangiocytic marker, is occasionally expressed in HCC, but the combination of arginase-1 and CK19 expression has never been evaluated. The aim of the study was to investigate the usefulness of arginase-1 and CK19 expression alone and in combination for prognosticating HCC tumor recurrence after surgical resection. Methods Tissue sections from 112 HCCs were immunostained using an automated method and the mouse monoclonal arginase-1 and mouse monoclonal CK19 antibodies. The clinicopathologic variables, including alpha-fetoprotein levels, viral hepatitis, cirrhosis, tumor size, grade and number, vascular invasion, tumor-node-metastasis (TNM) stage, and tumor recurrence and survival, were obtained from each patient's medical records. The variables were assessed for correlation with the immunochemical results. Comparisons of recurrence-free and overall survival were performed using univariate and multivariate regression analyses. A P-value of ≤ 0.05 was considered statistically significant. Results High arginase-1 expression was detected in the HCCs of 93 patients (83%), whereas CK19 was positive in the HCCs of only 19 patients (17%). In the univariate analyses, CK19 positivity in HCC was associated with decreased recurrence-free survival compared with CK19-negative HCC (P = 0.0002). Arginase-1 expression was associated with decreased recurrence-free survival when patients were stratified over advanced TNM stage and presence of vascular invasion. The combination of arginase-1 and CK19 expression was a better predictor of decreased recurrence-free survival (P = 0.00008). Arginase-1/CK19 expressions when combined with multiple tumors, TNM stage and vascular invasion were also associated with decreased recurrence-free survival. In the multivariate analysis, tumor grade, CK19 and arginase-1/CK19 expressions were identified as independent prognostic indicators for decreased recurrence-free survival. Conclusion Arginase-1 and CK19 combination immunoreactivity is a potential biomarker of adverse prognosis in HCC, correlating with the presence of multiple tumors, vascular invasion and advanced stage.

Miz-1 (Myc-interacting zinc finger) activates target genes through transcription factors that are regulated by specific antimitogenic signals. Association with Myc converts Miz-1 from being a transcriptional activator to a repressor. This binding and the formation of Myc/Miz-1 complex induces a change in the biophysical properties of the Miz-1 protein, rendering the complex insoluble and causing to relocalize inside the nucleus. In addition, this association stabilizes Myc and as a result represses transcription. With uncontrolled tumor progress, metastatic tumor expansion can occur through epithelial-to-mesenchymal transition (EMT) and the induction of ZEB-1 (Zinc Finger E-Box Binding Homeobox-1). Zeb-1 expression is highly associated with aggressive behavior tumor types. A cohort of 98 human cholangiocarcinoma carcinoma (CC) including 14 with mixed (CC)/(HCC) resected cases whose formalin fixed paraffin embedded (FFPE) tissue sections containing adjacent benign and malignant tumor lesions were examined by immunohistochemistry (IHC) using Miz-1 (ZBTB17), ZEB-1 (OT13G6), c-Myc (Y69), and Ki-67 (Mib-1) monoclonal antibodies. The clinicopathologic variables, including viral hepatitis, cirrhosis, tumor size, grade and number, vascular invasion, tumor-node-metastasis (TNM) stage, were obtained from each patient’s medical records. The variables were assessed for correlation with the immunohistochemical results. Compared to the adjacent benign liver section, reduction of Miz-1 expression was observed in 98/98 (100%) (P 5%), and ZEB-1 was observed in 18/98 (18.36%) (P5%), ZEB-1, and nuclear Miz-1 expression in 12/20 (60%) (P=0.12) cases (4 CC and 8 mixed (CC)/(HCC) cases). All 12 cases with positive ZEB-1 had confirmed positive lymph node involvement. These results support the role of Miz-1 as one of the intermediary checkpoints required for the induction of cell cycle arrest and apoptosis. Positive c-Myc/ZEB-1 coupled with Miz-1 reduced cytoplasmic and its re-localization to a nuclear expression confirms the transcriptional repressor role of the Myc/Miz-1 complex and the activation of the ZEB-1 gene as a predictor of increased metastatic expansion, therapy resistance, and poor survival in high grade CC, and CC/HCC cases. These findings correlate with a cohort of an adequate number of differently graded lesions from 147 HCC cases that showed similar expression pattern of Miz-1, c-Myc and Zeb-1 to better confirm our hypothesis in epithelial derived human malignancies with frequently amplified 8q24 chromosome. Citation Format: Joeffrey J. Chahine, Sumeyye Culfaci, DongHyang Kwon, Pamela Tuma, Bhaskar V.S. Kallakury. c-Myc expression coupled with loss of cytoplasmic Miz-1 expression and its re-localization to a nuclear expression in high grade cholangio and hepatocholangio carcinomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5721.

Background Key regulators of antitumor immunity such as arginase-1 and the adenosine pathway may have an important role in modulating the effect of immunotherapy. Here, we investigated the expression profile of these immune-related biomarkers in thymic epithelial tumors (TETs) and small cell lung cancer (SCLC), 2 solid tumors where immune checkpoint inhibitors have activity. Materials and Methods Immunohistochemical staining was performed using tissue microarrays of 123 TET (110 thymoma and 13 thymic carcinoma) and 125 SCLC cases. The expression profile of the following immune-related biomarkers was assessed: arginase-1, CD39, CD73, A2AR, PD-L2, and CD15. The expression profile was also correlated with clinical data. Results No sample was positive for arginase-1. In the adenosine pathway, the prevalence of positive staining for CD39, CD73, and A2AR was 4.9%, 2.5%, and 69.2%, in TETs and 0%, 1.7%, and 50.8%, in SCLC. The multivariate analysis showed that CD39 expression was significantly associated with worse disease related survival (hazard ratio [HR], 10.36; 95% confidence interval [CI]: 2.01-53.47; P= .005) and a shorter time-to progression (HR, 11.35; 95% CI, 2.11-61.23; P = .005) in TETs. Other biomarkers were not associated with disease related survival or time to progression in TETs. No biomarker was associated with survival in SCLC. Conclusion Arginase-1 was not detectable in TETs and SCLC. Expression of markers in the adenosine pathway were present in both TETs and SCLC. CD39 expression in tumor cells may identify subsets of patients with TETs with an unfavorable prognosis.

Uncomplicated Delivery in a Patient with Covid-19 The peripartum care of a woman with Covid-19 at 39 weeks of gestation is described. The woman and the neonate were discharged home on hospital day ...

Background This study sought to evaluate the effect of tumor-infiltrating lymphocyte (TIL) density and programmed death ligand 1 (PD-L1) expression on the prognosis of esophageal cancer. Methods Banked tissue specimens from 53 patients who underwent esophagectomies for malignancy at a single institution over a 6-year period were stained for cluster of differentiation 3 (CD3), CD8, and PD-L1. Tumors were characterized as staining high or low density for CD3 and CD8, as well as positive or negative for PD-L1. TIL density and PD-L1 expression were analyzed in the context of survival, recurrence, and perioperative characteristics. Results Median follow-up was 823 days, with 92.5% survival and 26.8% recurrence rates. All tumors were adenocarcinomas. Neoadjuvant chemotherapy was given in 56.6% of cases, and neoadjuvant radiotherapy was given in 37.7%. High CD3 density was found in 83%, whereas high CD8 density was found in 56.6%. A total of 18.9% of the tumors stained positive for PD-L1. Survival was significantly shorter in Kaplan-Meier analysis for patients with primary tumors staining positive for PD-L1 (log rank: p = 0.05). Multivariable analysis controlling for neoadjuvant therapy, TIL markers, PD-L1, age, and sex found no significant difference in recurrence or survival. Conclusions Positive staining for PD-L1 may be a prognostic marker for decreased survival in esophageal adenocarcinoma. Additional TIL cell types should be investigated for creation of an esophageal cancer Immunoscore. PD-L1 has potential as a therapeutic target.

Background: The diagnosis of hepatocellular carcinoma (HCC) is dependent on the histologic and immunohistochemical analysis of biopsy and resection specimens. The distinction of HCC from metastatic neoplasms is pertinent for treatment and prognostic purposes. Arginase-1 (Arg-1), a marker of hepatocellular differentiation, has shown superior sensitivity and specificity when compared to other immunohistochemical markers of detection of HCC such as hepatocyte paraffin antigen (HepPar-1). Studies have shown that poorly differentiated HCC can lose arginase expression, however well differentiated HCC are rarely ever arginase negative. Methods: In this study Arg-1 expression was detected using immunohistochemical staining on tissue specimens from 40 confirmed cases of well differentiated HCC specimens using a highly specific monoclonal antibody for Arg-1. Specificity of the Arg-1 antibody was evaluated by immunostaining of 24 non-HCC tumors in the liver and 200 non-liver neoplasms using paraffin block and tissue micro-array (TMA) based immunohistochemistry. Results: Four well differentiated HCC cases were found to be completely negative for Arg-1 and similarly all 224 non-HCC tumors did not express Arg-1. The arginase negative well differentiated tumors were positive for other hepatocellular markers such as HepPar-1 and polyclonal carcinoembryonic antigen (pCEA). Of the four tumors, only one recurred at 28 months. All patients are currently stable with a mean survival of 43 months. Conclusions: Arg-1 negative well differentiated HCC can be a clinical dilemma which can lead to misdiagnosis. Confirmation with other hepatocellular markers such as HepPar1 and pCEA is essential in making the correct diagnosis. The clinicopathologic outcomes of arginase negative well differentiated HCC has been poorly characterized, thus our findings are of utmost importance in understanding the clinical behavior of these tumors. This may have a potential role in understanding the mechanism of the use of targeted therapy in HCC tumors.

Keratin 19 (K19) belongs to the keratin family of proteins, which maintains structural integrity of epithelia. In cancer, K19 is highly expressed in several types where it serves as a diagnostic marker. Despite the positive correlation between higher expression of K19 in tumor and worse patient survival, the role of K19 in breast cancer remains unclear. Therefore, we ablated K19 expression in MCF7 breast cancer cells and found that K19 was required for cell proliferation. Transcriptome analyses of KRT19 knockout cells identified defects in cell cycle progression and levels of target genes of E2F1, a key transcriptional factor for the transition into S phase. Furthermore, proper levels of cyclin dependent kinases (CDKs) and cyclins, including D-type cyclins critical for E2F1 activation, were dependent on K19 expression, and K19-cyclin D co-expression was observed in human breast cancer tissues. Importantly, K19 interacts with cyclin D3, and a loss of K19 resulted in decreased protein stability of cyclin D3 and sensitivity of cells towards CDK inhibitor-induced cell death. Overall, these findings reveal a novel function of K19 in the regulation of cell cycle program and suggest that K19 may be used to predict the efficacy of CDK inhibitors for treatments of breast cancer.

Although Epithelial-Mesenchymal Transition (EMT) in cancers remains controversial, its relevance in tumor progression is a subject of investigation. The presence of cellular changes associated with EMT in bladder tumor progression have been well investigated, unlike other human carcinomas with very little data available to date. ZEB-1 which targets E-Cadherin repression is a transcriptional regulator that has been implicated in EMT, and its nuclear expression in tumor cells has been associated with aggressive malignancies in some types of cancer. Recently, it was also reported that ZEB-1 inhibits the expression of proapoptotic factor B-cell lymphoma (Bcl)-2 interacting mediator of cell death (BIM) by binding directly to the BIM promoter and repressing its transcription. We tested this hypothesis with a human cohort of 24 Cholangiocarcinoma (CC), 18 Hepatocellular (HCC) and 31 Renal Cell (RCC) human carcinomas. Formalin fixed paraffin embedded tissue sections containing benign and tumor lesions were immunostained using the Dako Autostainers Link 48 along with ZEB-1 monoclonal OT13G6 (ABCAM), Bcl-2 monoclonal 124 (Agilent, Dako), and E-Cadherin monoclonal NCH-38 (Agilent, Dako) antibodies. Nuclear, membraneous and/or cytoplasmic immunoreactivity was scored based on the intensity and percentage of positive cells in both the benign epithelium and adjacent tumor in each case. E-Cadherin was highly expressed in both the adjacent benign and malignant components with no significant variability in all three carcinomas, with ZEB-1 and Bcl-2 evaluated for the any positivity staining in both components for all cases. Results are detailed in the table below.All positive ZEB-1 cases in HCC were in high grade cases unlike the positive ZEB-1 in RCC which were in low grade cases. But more noticeably, 8/10 (80%) positive ZEB-1 were also positive for Bcl-2 in all three carcinoma types. Despite the small number of cases analyzed in this cohort a trend in the expression of ZEB-1 and its co-expression with BCL-2 may have some prognostic implications. We are currently extending this analysis to a larger number of CC, HCC, and RCC to closely examine the significance of ZEB-1, and Bcl-2 expression across differently graded lesions to further test our hypothesis. Citation Format: Joeffrey J. Chahine, Kyungmin Ko, Bhaskar VS Kallakury, Pamela L. Tuma. Variable expression of ZEB-1, Bcl-2, and E-cadherin in human hepatocholangio and renal cell carcinomas [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6471.

Recent studies report that the polarity gene myelin and lymphocyte protein 2 (MAL2), is overexpressed in multiple human carcinomas largely at the transcript level. Because chromosome 8q24 amplification (where MAL2 resides) is associated with hepatocellular- and cholangio-carcinomas, we examined MAL2 protein expression in these human carcinoma lesions and adjacent benign tissue using immunohistochemistry. For comparison, we analyzed renal cell carcinomas that are not associated with chromosome 8q24 amplification. Surprisingly, we found that MAL2 protein levels were decreased in the malignant tissues compared to benign in all three carcinomas, suggesting MAL2 expression may be anti-oncogenic. Consistent with this conclusion, we determined that endogenously overexpressed MAL2 in HCC-derived Hep3B cells or exogenously expressed MAL2 in hepatoma-derived Clone 9 cells (that lack endogenous MAL2) promoted actin-based protrusion formation with a reciprocal decrease in invadopodia. MAL2 overexpression also led to decreased cell migration, invasion and proliferation (to a more modest extent) while loss of MAL2 expression reversed the phenotypes. Mutational analysis revealed that a putative Ena/VASP homology 1 recognition site confers the MAL2-phenotype suggesting its role in tumor suppression involves actin remodeling. To reconcile decreased MAL2 protein expression in human carcinomas and its anti-oncogenic phenotypes with increased transcript levels, we propose a transcriptional regulatory model for MAL2 transient overexpression.

Background SCLC accounts for 15% and 20% of all lung cancers, with combined SCLC (CSCLC) comprising 2% to 5%. Little is known about the clinical characteristics and molecular changes associated with the various histologic components. Methods A total of 205 SCLC cases were resected between 2005 and 2015. Clinical and pathologic features were analyzed. All CSCLC cases were confirmed by histologic examination and immunohistochemistry. The individual components were microdissected using a novel automated dissection system, and DNA was extracted and subjected to targeted exome sequencing. Results A total of 10 cases of CSCLC were identified out of 170 cases with adequate histologic material; squamous cell carcinoma comprised the second component in half of these (n = 5). There were no significant differences between CSCLC and pure SCLC with respect to clinical features. The median follow-up time was 36 months. The median survival times of patients with pure SCLC and CSCLC were 58 months and 26 months, respectively ( p = 0.030). The different components of three cases of CSCLC were deemed adequate for microdissection and sequencing. Approximately 75% of the identified somatic mutations were present in both components. There were also 15 gene mutations or six amplifications unique to only one of the components. Conclusions We identified no significant clinical or pathologic differences between pure SCLC and CSCLC; CSCLC was associated with decreased overall survival compared with pure SCLC. The histologic components of CSCLC had high genetic concordance but also showed divergent genotypes. These findings may suggest a common precursor with subsequent acquisition of oncogenic changes in CSCLC.

Recent work has found that Myelin and Lymphocyte Protein 2 (MAL2), a protein that functions in polarized protein sorting, is frequently overexpressed in many epithelial-derived human cancers, and has been linked to poor prognosis in patients with colorectal and pancreatic cancers. Yet, its role in tumorigenesis is unknown. Our recent overexpression/knockdown studies in polarized hepatic WIF-B cells, Hep3B hepatocellular carcinoma cells and hepatoma-derived Clone9 cells all indicate that MAL2 is a tumor suppressor. How can MAL2’s function as a tumor suppressor be reconciled with its upregulated expression and link to bad prognosis in human cancers? MAL2 resides on chromosome region 8q24, a region frequently amplified in multiple epithelial-derived human cancers along with c-Myc, a well-known oncogenic driver whose overexpression dysregulates gene expression leading to downstream decreased expression of MAL2 via inactivation of the Miz1 transcription factor. Our prediction is that lower grade lesions from human epithelial-derived cancers display high MAL2 expression that will diminish as cancers progress into higher grade lesions and metastases with a concomitant increase in c-Myc expression. We tested this hypothesis with a cohort, of 23 cholangiocarcinoma (CC), 18 hepatocellular (HCC) and 20 renal cell (RCC) human carcinoma cases whose formalin fixed paraffin embedded tissue sections containing benign and later-stage tumor lesions were immunostained using the Dako Autostainers Link 48 along with Mal2 rabbit polyclonal (ABCAM), Miz-1 monoclonal ZBTB17(NOVUS), c-Myc monoclonal Y69 (ABCAM) and Ki-67 monoclonal Mib-1(Dako) antibodies. Nuclear and/or cytoplasmic immunoreactivity was scored based on the intensity and percentage of positive cells in both the benign epithelium and adjacent tumor component in each case. In all three carcinoma types, both MAL2 and Miz-1 expression was high in the benign tissue. In the tumor component MAL2 and Miz-1 expression was respectively lost in 15/23(65%) and 22/23(96%) CC, 13/18(72%) and 17/18(94%) HCC, 13/20(65%) and 16/20(80%) RCC cases. In contrast only 2/20 (10%) and 1/20(5%) RCC cases showed an upregulated expression of MAL2 and Miz-1 respectively compared to the benign component, with all three remaining carcinoma cases showing no up-or-down regulation in protein expression. However, no enhanced c-Myc expression was detected in the tumor lesions despite the higher proliferative index as indicated by Ki-67 labeling. These results indicate a concordant down-regulation of both MAL2 and Miz-1 in CC, HCC, and RCC supporting a tumor suppressor role in these cancers. We are currently extending these studies to other epithelial-derived cancer tissue types and also are more closely examining MAL2, Miz1 and c-Myc expression across graded lesions to better test our hypothesis. Note: This abstract was not presented at the meeting. Citation Format: Alfonso Lopez-Coral, Joeffrey J. Chahine, Bhaskar V. Kallakury, Pamela L. Tuma. A paradox: Expression of the myelin and lymphocyte protein 2 (MAL2) is down-regulated in human hepatocholangio and renal carcinomas in contrast to its up-regulation in other cancers [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 5246.

e24279Background: Epithelial cancers express various tumor-associated carbohydrate antigens. Diagnostic and prognostic utility of expression of these antigens has been studied in cancers of thyroid...

Background: The success of anti PD–1 therapy in Hodgkin lymphoma has led to clinical trials in other types of lymphomas. However, there is limited data on PD–L1 expression in acute leukemias. In this study, we analyzed PD–L1 protein expression and tumor mutational burden in various hematologic malignancies including leukemias, lymphomas and myelomas. Methods: In the IHC cohort, formalin fixed paraffin embedded sections from 92 hematologic malignancies including acute myeloid and lymphoblastic leukemia (AML, ALL), Hodgkin lymphoma (HL), diffuse large B-cell lymphoma (DLBCL), low-grade non-Hodgkin lymphoma (LGNHL) and myeloma were immunostained using the FDA approved PD-L1 IHC 22C3 pharmDx assay [monoclonal mouse anti-PD–L1 antibody (DAKO clone 22C3)]. Any perceptible partial or complete membrane staining in all viable tumor cells was scored as follows: 50%-high level PD-L1 expression. In the second cohort of 2064 cases, comprehensive genomic profiling (CGP) was performed using a hybrid–capture, adaptor ligation assay to a mean depth of >672X. Tumor mutation burden (TMB) was calculated from a minimum of 1.11MB of sequenced DNA as previously described and reported as mutations/MB. High PD–L1 expression was noted in 100% of HL. DLBCL showed significantly higher PD–L1 positivity compared to LGNHL (p=0.01). No correlation for PD–L1 expression was noted between AML and ALL (p = 0.2). On CGP analysis of the second cohort, TMB was significantly higher in DLBCL as compared to LGNHL (p Conclusion: The high PD-L1 expression in both HL and DLBCL and high TMB in DLBCL may be linked to enhanced responsiveness to check point inhibitor therapy in these cancers. PD-L1 expression and TMB are relatively infrequent and at low levels in acute leukemias. Additionally, novel anti PD–1/PD–L1 therapeutic strategies are worthy of consideration for both advanced stage refractory/relapsed acute myeloid and lymphoblastic leukemias. Results: PD-L1 expression and TMB are tabulated below.PD-L1 IHCTMB (mutations/MB)Tumor typenLow PositiveHigh PositiveTotal Positive (%)n>=10.0>=20.0AML21505/21 (24%)50%0%ALL3212012/32 (38%)10%0%HL1001010/10 (100%)368%8%DLBCL10448/10 (80%)25344%15%LGNHL10202/10 (20%)930%0%Myeloma9202/9 (22%)NANANA Citation Format: Lina Abdul Karim, Peng Wang, Jose de Guzman, Brandi Higgins, Joeffrey Chahine, Christine Sheehan, Bhaskar Kallakury, Jeffrey S. Ross. PDL1 protein expression and tumor mutation burden in hematologic malignancies: correlation with Hodgkin and high grade lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3724. doi:10.1158/1538-7445.AM2017-3724

e20009 Background: SCLC accounts for 15%-20% of all lung cancer, 2%-5% of them are combined SCLC. The objectives of this study were to evaluate the prognostic factors in a large series of resected SCLC patients, and to perform genetic analysis of combined forms. Methods: 205 SCLC cases were resected at Tianjin Cancer Hospital between 1/2005 and 12/2015. We analyzed: gender, age, type of resection, cigarette index (CI), tumor markers (CEA, SCC, NSE, Cyfra21-1), R resection type, number of resected lymph nodes (LNs), ratio of metastatic LNs, and pathological stage. All combined SCLC cases were identified by H&E staining and confirmed by immunohistochemistry. The different components were microdissected using an automated dissection system (MillisectTM, Roche Diagnostics) and DNA was extracted and subjected to targeted exome sequencing. Results: The median follow-up time was 24 (2-121) months. Median survival time of all the patients was 24 months; 5-year survival rates were 51.4% overall, and 69.5%, 66.5%, 34.4%, and 0% for pathological stage I, II, III, and IV, respectively. Multivariate analysis indicated age, CI, complete resection, number of resected LNs and the ratio of metastatic LNs as independent prognostic factors. Twelve cases of combined SCLC were identified out of 170 with adequate histological material: 6/12 were combined with squamous cell carcinoma. 1-, 3-, 5-year survival rates were 73.3%, 0% and 0%. There were no significant differences between combined SCLC and pure SCLC with respect to gender, age, pathological stage, LN status and tumor markers. Three cases were successfully sequenced. Around 50% gene mutations were present in both components (10/24; 14/27; 4/5 respectively). TP53 mutations were present in all three cases. One case displayed amplification of 2 genes in both components. Interestingly, there were also gene mutations and amplifications that are unique to one of the components. Conclusions: In this large resected SCLC series we identified CI, complete resection, resected number of LNs and ratio of metastatic LNs to be prognostic. Combined SCLC had worse survival than pure SCLC. The histologically different components had a significant number of common as well as unique genetic alterations.

8573 Background: There are few treatment options for thymic carcinoma after chemotherapy. We completed a single institution phase II study of pembrolizumab (P) in patients with recurrent thymic carcinomas. Methods: Main eligibility criteria included: progression after ≥ 1 chemotherapy line, ECOG PS 0-2, no history of autoimmune disease, and adequate organ function. P was given at 200mg IV every 3 weeks. The primary objective of the study was response rate (RR) by RECIST v1.1 criteria; secondary objectives were PFS and OS, and safety. Results: From 3/2015 to 12/2016 we accrued 41 patients. Of 40 eligible patients, 29 were male, 19 Caucasians, median age was 57 years (range 25-80), 14 had squamous carcinoma histology, and 19 ECOG PS 0. Median number of cycles delivered was 6 (range 1-31). The most common side effects were mild fatigue (10), diarrhea (4) and rhinorrhea (4). Six patients developed multiple grade 3-4 immune-relates AEs (irAEs): myocarditis/myositis (1), myositis/myocarditis/hepatitis/myasthenia gravis (1), myositis/hepatitis (1), bullous pemphigoid (1), hepatitis (1), hepatitis/pancreatitis/diabetes mellitus type 1 (1). There were no treatment related deaths. The 2 patients who developed myocarditis required a pacemaker. Three patients interrupted treatment because of irAEs (all responders) and 3 because of progression around the time of the irAE. irAEs were more frequent in females (4/6; p = .026). Five patients developed hypothyroidism and 1 hyperthyroidism. RR assessed in all 40 eligible patients was 22.5%: 1 complete response, 8 partial responses (plus 1 unconfirmed), 20 stable disease and with 11 progressions. Two partial responses show minimal residual disease with no PET uptake. Two responders have progressed and 5 responses are beyond 12 months duration. Of 29 cases tested for PD-L1 staining (Dako 22C3), high PD-L1 (≥50% tumor cells positive) was seen in 8 (28%); 6/9 responders had high PD-L1 expression. Targeted NGS in 15 cases did not show correlation between mutational burden and response. Conclusions: P has activity in patients with thymic carcinoma. irAEs are more frequent than in other tumors. Further analysis of NGS, Nanostring and PD-L1 expression and updated survival will be presented. Clinical trial information: NCT02364076.

e17094 Background: While the vast majority of patients with locally advanced HPV+ HNC are cured by combined modality treatment, more than 1 in 4 pts will suffer recurrence. Understanding the genomi...

e17097 Background: The cause for the rising incidence of HPV+ HNC remains unexplained. Research in cervical cancer has identified genetic variants of HPV16 that define subtypes -- European (E) vs N...