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Background: Gut microbiome has been associated with the efficacy of immune checkpoint inhibitors (ICI) in patients with various types of cancers but not yet in hepatocellular carcinoma (HCC). Aims: To investigate the association between gut microbiome and efficacy of ICI in patients with HCC. Methods: Patients with HCC who were scheduled to receive ICI were prospectively enrolled. Fecal samples were collected within 7 days before initiation of ICI (baseline) and 8 weeks later. Gut microbiome was assessed using 16S rRNA sequencing and shotgun whole-genome sequencing and correlated with objective response (complete or partial response), disease control (objective response or stable disease for ≥16 weeks), and overall survival. Results: Thirty-six patients with HCC were enrolled, and 20 of them provided both baseline and 8-week feces. Alpha diversity, richness, and compositions of baseline gut microbiome indicated no difference between responders and nonresponders or between disease control and nondisease control groups. For the 20 paired feces, immunotherapy did not change any of the major microbiome features. No specific taxa were enriched in patients with objective response. Three taxa-Bifidobacterium, Coprococcus, and Acidaminococcus-were enriched in patients with disease control. However, the baseline abundance of these three taxa did not predict overall survival benefit. Conclusions: In this exploratory study, we failed to disclose any overt association of gut microbiome with the efficacy of ICI in patients with HCC. A larger prospective study is warranted for definite conclusion.

e14596 Background: Immune-related adverse events (irAEs) are major hurdle to immune checkpoint blockade (ICB). Corticosteroid (CS) is effective in controlling the majority of irAEs. Although recent studies suggested CS use does not jeopardize the anti-tumor efficacy of ICB, prophylactic use of CS remains prohibited with the concerns of attenuating efficacy of ICB. This study aimed to investigate the effects of CS premedication on the efficacy of ICB in murine hepatocellular carcinoma models. Methods: Anti-mCTLA-4 (9D9C, BMS) and anti-mPD-1 antibodies (4H2, ONO) were intraperitoneally (ip) administered to tumor-bearing mice (subcutaneous Hepa 1-6 model and orthotopic BNL 1MEA.7R.1 model) with or without dexamethasone (DEXA) premedication (10 and 200 μg, equivalent to minimal anti-inflammatory dosage and pulse therapy in human, respectively). Efficacy of ICB was evaluated as tumor shrinkage. Tumor-infiltrating lymphocytes (TILs) were isolated for single cell RNA-sequencing and effector function analysis through flow cytometry. Results: In the subcutaneous model, all tumors treated with ICB alone (N=7) or ICB plus DEXA 10 μg (N=5) completely regressed, but 1 out of 7 tumors treated with ICB plus DEXA 200 μg escaped. However, the tumor growth was not significantly different between groups ( P-value >0.05, multiple Mann-Whitney test). In the orthotopic model (N=5/group), the mean (± standard error) tumor weights on day 21 after tumor implantation for isotype control, ICB, ICB plus DEXA 10 μg and ICB plus DEXA 200 μg were 2.45 (± 0.54), 0.73 (± 0.18), 0.98 (± 0.65), and 0.69 (± 0.17) grams, respectively ( P-value >0.05, comparing ICB plus DEXA 10 or 200 μg with ICB). At transcriptomic level, premedication with either dosage of DEXA significantly reduced the percentage of effector memory cells and increased the percentage of exhausted effector cells in the CD8 TIL population, which appeared to counterbalance the effects of ICB. However, at protein level, premedication of DEXA 10 or 200 μg did not reduce the interferon-γ or granzyme B production of CD8 TILs in both models (Table). Conclusions: CS premedication did not attenuate the efficacy of ICB. Our study provides the scientific basis to evaluate the potential of prophylactic CS in preventing ICB-induced irAEs in clinical studies.[Table: see text]

Purpose: Tumor-infiltrating tissue-resident memory CD8 T cells (CD8 TRM; CD103+ CD8+) are considered tumor-specific and may correlate better with the tumor response to immune checkpoint blockade (ICB). This study evaluated the association of tumor-infiltrating CD8 TRM and their subsets with the efficacy of immunotherapy in patients with advanced hepatocellular carcinoma (HCC). Experimental Design: Consecutive HCC patients who received ICB in prospective trials were analyzed. Formalin-fixed paraffin-embedded tumor sections were stained for DAPI, CD8, CD103, CD39, programmed cell death-1 (PD-1), and programmed cell death ligand 1 (PD-L1) using a multiplex immunohistochemical method. The densities of CD8 T cells, CD8 TRM, and CD39+ or PD-L1+ subsets of CD8 TRM were correlated with tumor response and overall survival (OS). Results: A total of 73 patients were identified, and 48 patients with adequate pretreatment tumor specimens and complete follow-up were analyzed. A median of 32.7% (range: 0–92.6%) of tumor-infiltrating CD8 T cells were TRM. In subset analyses, 66.6% ± 34.2%, 69.8% ± 33.4%, and 0% of CD8 TRM cells coexpressed CD39, PD-L1, and PD-1, respectively. The objective response rates for CD8 T cell-high, CD8 TRM-high, CD39+ CD8 TRM-high, and PD-L1+ CD8 TRM-high groups were 41.7%, 37.5%, 37.5%, and 29.2%, respectively. Patients with CD8 T cell-high, but not those with CD8 TRM-high, CD39+ CD8 TRM-high, or PD-L1+ CD8 TRM-high, tumors, had significantly prolonged OS (p = 0.0429). Conclusions: Compared with total tumor-infiltrating CD8 T cells, tumor-infiltrating CD8 TRM or their subsets failed to provide additional advantages in predicting the efficacy of immunotherapy for HCC.

Ineffectiveness of immune checkpoint inhibitors in patients with castration- resistant prostate cancer (CRPC) suggests that CRPC may harbor a profound immunosuppressive tumor microenvironment. However, immune tumor microenvironment of CRPC has never been well investigated due to limited availability of castration-resistant tumor tissue. To characterize the changes in immune tumor microenvironment during CRPC progression and identify disease stage which is potentially favorable for immunotherapy, we studied the densities of tumor-infiltrating immune cells by using the immunohistochemical method and manual counting in paired castration-naive (CN) and castration-resistant (CR) tumors. We identified 11 metastatic prostate cancer patients who had received palliative transurethral resection of prostate both before androgen deprivation therapy (ADT) and at the time when castration resistance emerged from the hospital database during 2006.1~2017.3. We also used prostatic tissue from 5 patients with benign prostate hyperplasia as the normal prostate control. The median age at diagnosis of PC patients was 74.7 (range: 62-85) year-old. The numbers of tumors with Gleason score 7, 8, 9 and 10 were 1, 1, 6, and 2, respectively. The median PSA level at diagnosis was 96.6 (range: 3.3-847.7) ng/ml. The median overall survival after initiation of ADT was 48.8 months. The median density of CD4+ T cells (no./mm2) was 182.3 (45.0-363.5) for normal prostate, 160.9 (range: 12.6-240.6) for CNPC and 69.4 (range: 31-499.6) for CRPC (non-statistically significant; n.s.). The median density of CD8+ T cells (no./mm2) was 12.5 (range: 32.5-220.7) for normal prostate, 65.7 (range: 3.7-195.6) for CNPC and 53.8 (range: 4.4-190.4) for CRPC (n.s.). The median density of CD20+ B cells (no./mm2) was 132.1 (range: 54.6-514.4) for normal prostate, 112.2 (range: 3.7-298.9) for CNPC and 47.6 (range: 7.0-137.3) for CRPC (n.s.). The median density of CD68+ macrophages (no./mm2) was 31 (range: 0.4-248.7) for normal prostate, 77.5 (range: 3.7-403.7) for CNPC and 31.7 (range: 2.2-180.8) for CRPC (n.s.). The tumor-infiltrating immune cell densities in CNPC did not correlate with PSA level, Gleason score or ADT response. Only high B cell density in CNPC was prognostic for overall survival (median: 23.9 months for patients with high tumor-infiltrating B cell density vs. 64 months for patients with low tumor-infiltrating B cell density; P=0.0463). In conclusion, immune tumor microenvironment of CNPC and CRPC is very similar and is not different from normal prostate. It suggests that immune checkpoint inhibitors may not be effective against CNPC unless combining with other treatment, such as ADT or radiotherapy, which can reprogram the tumor microenvironment toward more immunosupportive. Citation Format: Ying-Chun Shen, Chia-Tung Shun, Ching-Ping Yeh, Jhe-Cyuang Kuo, Yu-Chieh Tsai, Chung-Hsin Chen, Chao-Yuan Huang, Yeong-Shiau Pu. Immune cell infiltration and its clinical correlations in paired castration-naive and castration-resistant prostate cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4697.