Selective targeting of the functionally exhausted malignant T cells in cutaneous T-cell lymphoma (CTCL) and distinct cells within the tumor microenvironment (TME) via PD1/PD-L1 blockade (durvalumab) may restore an anti-tumor immune response. The oral immunomodulator lenalidomide, which has activity in CTCL, may enhance durvalumab immune checkpoint blockade. Our phase 1/2 clinical trial of durvalumab and lenalidomide in patients with refractory/advanced CTCL (NCT03011814) sought to assess safety and tolerability and identify the maximum tolerated dose/recommended phase 2 dose (RP2D) of lenalidomide plus fixed-dose durvalumab. Secondary and tertiary objectives were to investigate efficacy and effects on the TME. Thirteen patients were evaluable for toxicities and 12 for dose decisions and response. No serious adverse events (SAEs) or dose-limiting toxicities (DLTs) were observed during cycles 1-3 (DLT evaluation period), and dose level 3 is the RP2D. The most frequent AEs were tumor flare, fatigue, neutropenia, and leukopenia. Three patients developed grade 1/2 autoimmune thyroiditis that resolved with treatment. Best overall and skin response rates were 58.3% (95% CI: 27.7% - 84.8%) and 75% (95% CI: 42.8% - 94.5%) respectively. Median cycles of treatment were 11 (range, 3-42+). Median duration of response was 25.5 (range 8-36.5) months. The combination showed clinical activity with 7 partial responses, and 4 stable disease. Potentially predictive immune signatures were downregulation of TNF-alpha signaling via NFκB, IFN-gamma, and PI3-AKT-mTOR signaling pathways in responders vs up-regulation of MYC targets and pro-inflammatory pathways in non-responders. Profiling of immune cell compositions revealed changes in individual immune cell clusters based on treatment response.

Abstract Large cell transformation of mycosis fungoides (LCT-MF) occurs in 20-50% of advanced MF and is associated with an aggressive clinical course and poor survival not to overcome by any standard treatment regimen. We have previously identified a distinct miRNA expression profile in LCT-MF from that of non-transformed MF with significant upregulation of miR-21 and miR-146a. Our analyses demonstrated the involvement of genes for immune checkpoint pathways such as ICOS-ICOSL and PD1-PDL1 signaling (Di Raimondo C et al. Cancers 2021). Here, we aimed to investigate the efficacy of antagomiR-146a and -21 (amiR-146a, and -21) on the tumor growth and CD8+ tumor infiltrating lymphocyte exhaustion in LCT-MF. The amiR-146a, and -21 were synthesized in our DNA/RNA Synthesis Core by linking CpG-D19. In vitro, CTCL cell lines (Myla and HH) were treated with amiR-146a and -21, the cell viability was assessed by the 2,5-diphenyl-2H-tetrazolium bromide assay and cell apoptosis was evaluated using apoptosis assay. We found that amiR-146a, and -21 synergistically inhibited the proliferation of MyLa and HH cells due to the activation of apoptosis through Caspase3/7 pathways and inducing cell cycle arrest by blocking STAT3/CDK1/Cyclin B1 pathway. Our RNA-seq data indicated that the exhausted CD8+ T cells express elevated amounts of STAT3, IRF4, and BATF in LCT-MF compared with non-LCT MF. To evaluate the functional importance of amiR-146a, and -21 on CD8+ T cell exhaustion, we induced an exhausted state of CD8+ T cells with high level of immune checkpoints and dysfunctional cytokine production by continues anti-CD3/DC28 beads and culture supernatant (MyLa or HH cell) exposure. Our data revealed that amiR-146a and -21 attenuated the CD8+ T cell exhaustion by blockade of immune checkpoints and STAT3/IRF4/BATF pathway to trigger the cytotoxic immune response. Collectively, the findings of our study suggest that targeting miR-146a and -21 is a promising and novel therapeutic strategy for LCT-MF. Citation Format: Zhen Han, Piotr Swiderski, Xiwei Wu, Yate-Ching Yuan, Jun Wu, Chingyu Su, Hanjun Qin, Steven Rosen, Christiane Querfeld. Therapeutic targeting miR-146a and miR-21 induce malignant cell death and regulate CD8+ T-cell function in mycosis fungoides with large-cell transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2907.

Introduction: Mycosis fungoides (MF) and the leukemic variant Sézary syndrome (SS), commonly referred to as cutaneous T cell lymphoma (CTCL), are disfiguring and incurable malignancies with a poor prognosis for those with refractory/advanced-stage (R/A) disease. The dysregulated/exhausted immunophenotype is a hallmark of CTCL and a key feature in disease pathogenesis, influencing patients' response and resistance to therapy. Here we present the randomized Phase 2 portion of our phase 1/2 trial to compare single agent durvalumab to durvalumab + lenalidomide in relapsed/advanced CTCL (NCT03011814). The primary end point was objective response rate (ORR) using the global composite response (based on skin, blood, nodes, and viscera) according to consensus guidelines. Secondary end points included duration of response, progression-free survival, and toxicity. Exploratory endpoints were the relationships between gene expression profile, tumor microenvironment (TME), and antitumor activity. Methods: Adult patients with histologically confirmed MF/SS, who had failed ≥2 systemic therapies were enrolled and randomized 1:1 to single agent durvalumab (1500 mg (day 1 of 28-day cycle) or durvalumab (same dose) & lenalidomide (10 mg for cycle 1, 15 mg for cycle 2, then 20 mg for subsequent cycles daily for 21 days of each 28-day cycle). The gene expression profile, tumor microenvironment (TME), and antitumor activity was analyzed on matched pre- and on-treatment skin and blood samples. Results: A total of 25 pts were randomized (intent-to-treat population: 12 durvalumab alone vs. 13 durvalumab + lenalidomide) with the following characteristics at the time of enrollment: median age 56 years (26-79) vs. 65 years (32-88); stage IB, 2 (17%) vs 4 (31%); stage IIB, 5 (42%) vs 3 (23%); stage III/IV, 5 (42%) vs 6 (46%); large cell transformation 3 (25%) vs 5 (38%). The median number of prior systemic treatments for both single and combo arm was 3. Global best ORR 42% (5/12) for single agent durva and 75% (9/12, 1 patient inevaluable for response). Median follow up time was 14.5 (range, 0.5-29.7) months. Median PFS was 6.2 months for durva arm, and not reached (2.8-NA) for durva/len arm. 12-month PFS was 36% (95% CI: 11%-63%) for durva arm and 73% (95% CI: 38%-91%) for durva/len arm. No serious AEs were observed. The most common treatment-emergent adverse events (shown below for combo arm) that were more frequent in the durvalumab/lenalidomide arm vs durvalumab arm and included fatigue (n=10), diarrhea (n=6), anemia (5), decreased platelets (n=5), leukopenia & neutropenia (n=4), constipation (n=4), and leg edema (n=4). The majority of AEs with both treatment arms were mild to moderate in severity (grade I/II, 92%; grade III, 8 %). One grade IV neutropenia on combo arm was observed. Median cycles of treatment were 4.5 (range, 2-26+) and 8 (range 1-29+) for single and combo arms.) One death occurred on each arm at 2.2 months (durva) and 6.6 months (durva/len) after discontinuation of study drug. 2 pts remain on treatment on each arm arm. Molecular profiling using CIBERSORT and single cell analysis revealed distinct changes of daptive and innate immune cell signatures and cellular signaling interactions within the TME that occurred in each treatment arm when compared to baseline. Multiplex cytokine analysis highlights that durva/len promotes a Th1 cytokine microenvironment. Conclusions: This randomized phase 2 trial of anti-PD-L1 (durvalumab) +/- lenalidomide evaluating anti-tumor activity demonstrated superior clinical activity of combinatorial durvalumab/lenalidomide vs single-agent durvalumab in refractory/advanced CTCL. Responses were durable and ongoing, and treatment was well tolerated. Correlative studies provided evidence for predictive adaptive and innate immune signatures and signaling pathways within the CTCL TME associated with clinical response.

Cutaneous T cell lymphoma (CTCL) is a disfiguring and incurable disease characterized by skin-homing malignant T cells surrounded by immune cells that promote CTCL growth through an immunosuppressive tumor microenvironment (TME). Preliminary data from our phase I clinical trial of anti–programmed cell death ligand 1 (anti–PD-L1) combined with lenalidomide in patients with relapsed/refractory CTCL demonstrated promising clinical efficacy. In the current study, we analyzed the CTCL TME, which revealed a predominant PD-1+ M2-like tumor-associated macrophage (TAM) subtype with upregulated NF-κB and JAK/STAT signaling pathways and an aberrant cytokine and chemokine profile. Our in vitro studies investigated the effects of anti–PD-L1 and lenalidomide on PD-1+ M2-like TAMs. The combinatorial treatment synergistically induced functional transformation of PD-1+ M2-like TAMs toward a proinflammatory M1-like phenotype that gained phagocytic activity upon NF-κB and JAK/STAT inhibition, altered their migration through chemokine receptor alterations, and stimulated effector T cell proliferation. Lenalidomide was more effective than anti–PD-L1 in downregulation of the immunosuppressive IL-10, leading to decreased expression of both PD-1 and PD-L1. Overall, PD-1+ M2-like TAMs play an immunosuppressive role in CTCL. Anti–PD-L1 combined with lenalidomide provides a therapeutic strategy to enhance antitumor immunity by targeting PD-1+ M2-like TAMs in the CTCL TME.

Introduction: Mycosis fungoides (MF) and the leukemic variant Sézary syndrome (SS), commonly referred to as cutaneous T cell lymphoma (CTCL), are characterized by clonal expansion of malignant T cells in the skin within a background of chronic inflammation. Advanced stages have an unfavorable prognosis. The skin microenvironment plays an important role in the development and progression of MF and SS. We have shown that the malignant T cells escape immune surveillance via immune checkpoint signaling such as the PD-1/PD-L1 axis. In our phase I dose-escalating study anti-PD-L1 (durvalumab) & lenalidomide demonstrated a tolerable safety profile with significant clinical activity in refractory/advanced CTCL. We initiated the randomized Phase 2 portion to compare single agent durvalumab to durvalumab combined with lenalidomide in relapsed/advanced CTCL (NCT03011814). The primary end point was objective response rate (ORR) using the global composite response (based on skin, blood, nodes, and viscera) according to consensus guidelines. Secondary end points included duration of response, progression-free survival, and toxicity. Relationships between gene expression profile, tumor-microenvironment, and antitumor activity were exploratory end points. Methods:Adult patients with histologically confirmed MF or SS, who had failed ≥2 systemic therapies were enrolled and randomized 1:1 to single agent durvalumab (1500 mg (day 1 of 28-day cycle) or durvalumab (same dose) & lenalidomide (10 mg for cycle 1, 15 mg for cycle 2, then 20 mg for subsequent cycles daily for 21 days of each 28-day cycle). The study used a “pick a winner” design based on ORR. Serial skin and blood samples were collected to assess the impact on the tumor microenvironment (TME) and anti-tumor activity. Results:A total of 23 patients were randomized and had the following characteristics (11 durvalumab vs 12 durvalumab/lenalidomide): median age 57 yrs (35-79) vs 63 yrs (32-88); stage IB, 2 (18%) vs 4 (33%); stage IIB, 4 (36%) vs 3 (25%); stage III/IV, 5 (45%) vs 5 (42%); MF, 8 (73%) vs 8 (67%); e-MF/SS, 4 (36%) vs 2 (17%); large cell transformation 3 (27%) vs 5 (42%). The median number of prior systemic treatments for both single and combo arm was 3. Global best ORR was 58% for durvalumab/ lenalidomide vs 36% for durvalumab alone.Median follow up time was 7.9 (range, 0.9-27.6) months. Analysis is ongoing. One patient died one month after discontinuation from study due to PD. No serious AEs were observed. The most common treatment-emergent adverse events (shown below for combo arm) were more frequent in the durvalumab/lenalidomide arm vs durvalumab arm and included fatigue (n=9), diarrhea (n=4), decreased platelets (n=4), leg edema (n=3), constipation (n=3), hyperglycemia (n=3), anemia (n=3), and leukopenia & neutropenia (n=3). The majority of AEs with both treatment arms were mild to moderate in severity (grade I/II, 91%; grade III, 8 %). No grade IV event except 1 neutropenia on combo arm was observed. Median cycles of treatment were 4 (range, 1-12) and 5 (range 1-7) for single and combo arms.) Five pts remain on treatment on single agent durvalumab vs 3 pts on combo arm. Molecular profiling using CIBERSORT and single cell analysis revealed distinct changes of immune cell signatures and cellular signaling interactions within the TME that occurred in each treatment arm when compared to baseline. Conclusions: This randomized phase 2 trial of durvalumab (anti-PD-L1) +/- lenalidomide evaluating anti-tumor activity demonstrated superior clinical activity of combinatorial durvalumab/lenalidomide vs single-agent durvalumab in refractory/advanced CTCL. Responses were durable and ongoing, and treatment was well tolerated. Our correlative results from sequential skin biopsies demonstrated immune signatures for enhanced anti-tumor responses on skin biopsies at baseline may be predictive of response to checkpoint blockade and yield insights into mechanisms of therapeutic resistance.

Abstract Immune checkpoint (IC) blockade for programmed cell death 1 (PD1) and PD-Ligand 1 (PD-L1) has shown promising and durable therapeutic outcomes in cutaneous T-cell lymphoma (CTCL), but resistance and/or relapses are common. While research focused on improving adaptive immune functions in CTCL, we investigated the role of 1) the “do not eat me signal” (CD47), and PD-L1, as a dual (innate and adaptive IC)-targeting strategy in CTCL. RNA sequencing and flow cytometric analysis showed that CTCL tumor cells and CTCL cell lines (MyLa, Hut78, HH, and H9 cells) overexpressed CD47 and PD-L1 compared with healthy control, and CD47 positively correlated with PD-L1 in CTCL patients. Overexpression of CD47 and PD-L1 was induced by high MYC expression in CTCL tumor cells lines. In addition, the signal-regulatory protein (SIRP)α receptor for CD47 and PD-L1 were significantly more abundant on macrophages, dendritic cells and natural killer cells in CTCL patients than healthy control by flow cytometric analysis. Furthermore, the RNA sequencing data indicated that the M2 macrophages, immature dendritic cells, and inhibitory receptors expressed natural killer cells in CTCL patients were higher than in healthy control. Notably, TTI-621 (SIRPαFc) treatment decreased M2 macrophage, immature dendritic cells, and inhibitory receptors expressed natural killer cells in CTCL patients at the end of the treatment, compared to baseline. In vitro, TTI-621 treatment increased the macrophage phagocytic activity compared to untreated control. Moreover, TTI-621 synergized with an anti-PD-L1 antibody (durvalumab) to reprogram M2-like TAMs, induced by MyLa supernatant, to M1-like phenotypes. The simultaneous blockade of both CD47 and PD-L1 inhibited growth of CTCL cell lines more potently than each single antibody alone or blank control in vitro. Enhanced CD8+ T cell mediated killing was detected using a chromium-release assay following dual blockade of in CTCL cell lines, suggesting anti-CD47 and anti-PD-L1 may synergistically facilitate elimination of CTCL tumor cells through specific pathways. RNA-sequencing analysis indicated that these effects were mediated by cell death related pathways such as apoptosis, autophagy, and necroptosis. Collectively, our findings demonstrated that CD47 and PD-L1 are critical regulators of innate and adaptive immune surveillance in CTCL and that dual targeting of CD47 and PD-L1 will provide insight into tumor immunotherapy to improve tumor control in CTCL. Citation Format: Zhen Han, Mingye Feng, Xiwei Wu, Chingyu Su, Yate-Ching Yuan, Hanjun Qin, James F. Sanchez, Jasmine Zain, Steven T. Rosen, Christiane Querfeld. CD47 Blockade potentiates immunotherapy of durvalumab against cutaneous T cell lymphoma [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 5196.

Large cell transformation of mycosis fungoides (LCT-MF) occurs in 20–50% of advanced MF and is generally associated with poor response and dismal prognosis. Although different mechanisms have been proposed to explain the pathogenesis, little is known about the role of microRNAs (miRs) in transcriptional regulation of LCT-MF. Here, we investigated the miR and mRNA expression profile in lesional skin samples of patients with LCT-MF and non-LCT MF using RNA-seq analysis. We found miR-146a and miR-21 to be significantly upregulated, and miR-708 the most significantly downregulated miR in LCT-MF. Integration of miR and mRNA expression profiles revealed the miR-regulated networks in LCT-MF. Ingenuity pathway analysis (IPA) demonstrated the involvement of genes for ICOS-ICOSL, PD1-PDL1, NF-κB, E2F transcription, and molecular mechanisms of cancer signaling pathways. Quantitative real time (qRT)-PCR results of target genes were consistent with the RNA-seq data. We further identified the immunosuppressive tumor microenvironment (TME) in LCT-MF. Moreover, our data indicated that miR-146a, -21 and -708 are associated with the immunosuppressive TME in LCT-MF. Collectively, our results suggest that the key LCT-MF associated miRs and their regulated networks may provide insights into its pathogenesis and identify promising targets for novel therapeutic strategies.

Abstract M2-like tumor-associated macrophages (TAMs) are abundant and influence cutaneous T cell lymphoma (CTCL) development by inducing immunosuppression. Although it is well established that depletion of M2-like TAMs delays CTCL development, little is known about the underlying mechanisms that shape programmed cell death 1+ (PD1+) M2-like TAMs phenotype in CTCL. Here we identified PD1+ M2-like TAMs accumulated in CTCL lesional skin. Moreover, RNA-seq analysis of human CTCL tissues revealed an up-regulation of the TLR/NF-κB and JAK/STAT signaling pathways. In vitro, PD1+ TAMs exhibited an M2-like profile, with a significant increase in the expression of CD163, CD206, and IL-10, and a clear decrease in the expression of CD80, IL-1β, CXCL-10, and CXCL-11, and the activation of TLR/NF-κB and JAK/STAT signaling pathways. To determine whether PD1+ M2-like TAMs could be reprogrammed, anti-PD-L1 (durvalumab) and lenalidomide were used for treatment of MyLa-conditioned media induced human peripheral blood monocyte-derived PD1+ M2-like TAMs. The results show that anti-PD-L1 and lenalidomide synergistically reshaped M2-like TAMs to M1-like TAMs in vitro through ablation of the TLR/NF-κB and JAK/STAT signaling pathways, which was linked with functional changes in phagocytic activity and cell migration. In conclusion, TLR/NF-κB and JAK/STAT signaling pathways may drive PD1+ M2-like TAMs programming in the CTCL tumor microenvironment, anti-PD-L1 and lenalidomide may reshape PD1+ M2-like TAMs and induce functional changes through ablation of these specific pathways in CTCL. Corresponding author: Christiane Querfeld, MD, PhD. Div. of Dermatology and Beckman Research Institute, City of Hope. 1500 E. Duarte Road, Duarte, CA 91010. Email: cquerfeld@coh.org Phone: 626-634-4436 Fax: 626-218-6190 Citation Format: Zhen Han1,5, Chingyu Su1,5, Xiwei Wu2,5, Hanjun Qin2,5, Steven T. Rosen3,5, Christiane Querfeld1,3,4,5. Reprogramming of PD1+ M2-like tumor-associated macrophages with anti-PD-L1 and Lenalidomide in cutaneous T cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2759.

Background: M2-like tumor-associated macrophages (TAMs) are the most abundant phenotype that promote the growth of cutaneous T cell lymphoma (CTCL) by inducing immunosuppression. Although PD1/PD-L1blockade has demonstrated efficacy in CTCL, little is known about the effects on tumor-associated macrophages. Here, we report that anti–PD-L1 treatment favorably impacts the phenotype and function of tumor macrophages by polarizing the macrophage compartment toward a more pro-inflammatory phenotype. Understanding the mechanisms of macrophage reprogramming will identify novel therapeutic targets to reverse impaired immunity. Methods and results: We used multiplex immunofluorescence staining of lesional skin samples of CTCL patients demonstrating co-localization of PD1 on CD163+ M2 macrophages. Moreover, RNA-seq analysis performed on tissue sections from same CTCL specimens revealed an up-regulation of the TLR, NF-κB and JAK/STAT signaling pathways. To further confirm PD1 expression on M2 TAMs in CTCL, we cultured CD14+ cells from healthy donor-derived peripheral blood in conditioned media (CM) from MyLa cells. We observed macrophage differentiation towards an PD1+ M2 phenotype, with significant CD163, CD206 and PD1 upregulation but not CD80 expression. The TRIF-stimulated NF-κB and JAK/STAT signaling pathways, downstream of both TLR3 and TLR4 were activated in PD1+ M2-like TAMs. Furthermore, our RT-PCR results show significantly elevated IL-10 levels, but decreased IL-1β, CXCL-10 and CXCL-11 compared to control. To determine whether PD1+ M2-like TAMs could be reprogrammed, anti-PD-L1 (durvalumab) and lenalidomide were used for treatment of MyLa-conditioned media induced human peripheral blood monocyte-derived PD1+ M2-like TAMs. The results show that anti-PD-L1 and lenalidomide synergistically increased IL-1β, CXCL-10, and CXCL-11 expression, but significantly decreased IL-10 level compared with the untreated control in vitro through ablation of TLR3, TLR4 and the downstream signaling pathways, which was linked with functional changes in phagocytic activity and cell migration. M2-like tumor-associated macrophages (TAMs) are the most abundant phenotype that promote the growth of cutaneous T cell lymphoma (CTCL) by inducing immunosuppression. Although PD1/PD-L1blockade has demonstrated efficacy in CTCL, little is known about the effects on tumor-associated macrophages. Here, we report that anti–PD-L1 treatment favorably impacts the phenotype and function of tumor macrophages by polarizing the macrophage compartment toward a more pro-inflammatory phenotype. Understanding the mechanisms of macrophage reprogramming will identify novel therapeutic targets to reverse impaired immunity. We used multiplex immunofluorescence staining of lesional skin samples of CTCL patients demonstrating co-localization of PD1 on CD163+ M2 macrophages. Moreover, RNA-seq analysis performed on tissue sections from same CTCL specimens revealed an up-regulation of the TLR, NF-κB and JAK/STAT signaling pathways. To further confirm PD1 expression on M2 TAMs in CTCL, we cultured CD14+ cells from healthy donor-derived peripheral blood in conditioned media (CM) from MyLa cells. We observed macrophage differentiation towards an PD1+ M2 phenotype, with significant CD163, CD206 and PD1 upregulation but not CD80 expression. The TRIF-stimulated NF-κB and JAK/STAT signaling pathways, downstream of both TLR3 and TLR4 were activated in PD1+ M2-like TAMs. Furthermore, our RT-PCR results show significantly elevated IL-10 levels, but decreased IL-1β, CXCL-10 and CXCL-11 compared to control. To determine whether PD1+ M2-like TAMs could be reprogrammed, anti-PD-L1 (durvalumab) and lenalidomide were used for treatment of MyLa-conditioned media induced human peripheral blood monocyte-derived PD1+ M2-like TAMs. The results show that anti-PD-L1 and lenalidomide synergistically increased IL-1β, CXCL-10, and CXCL-11 expression, but significantly decreased IL-10 level compared with the untreated control in vitro through ablation of TLR3, TLR4 and the downstream signaling pathways, which was linked with functional changes in phagocytic activity and cell migration.

M2-like tumor-associated macrophages (TAMs) are abundant and influence cutaneous T cell lymphoma (CTCL) development by inducing immunosuppression. Although it is well established that depletion of M2-like TAMs delays CTCL development, little is known about the underlying mechanisms that shape programmed cell death 1+ (PD1+) M2-like TAMs phenotype in CTCL. Here we identified PD1+ M2-like TAMs accumulated in CTCL lesional skin. Moreover, RNA-seq analysis of human CTCL tissues revealed an up-regulation of the TLR/NF-κB and JAK/STAT signaling pathways. In vitro, PD1+ TAMs exhibited an M2-like profile, with a significant increase in the expression of CD163, CD206, and IL-10, and a clear decrease in the expression of CD80, IL-1β, CXCL-10, and CXCL-11, and the activation of TLR/NF-κB and JAK/STAT signaling pathways. To determine whether PD1+ M2-like TAMs could be reprogrammed, anti-PD-L1 (durvalumab) and lenalidomide were used for treatment of MyLa-conditioned media induced human peripheral blood monocyte-derived PD1+ M2-like TAMs. The results show that anti-PD-L1 and lenalidomide synergistically reshaped M2-like TAMs to M1-like TAMs in vitro through ablation of the TLR/NF-κB and JAK/STAT signaling pathways, which was linked with functional changes in phagocytic activity and cell migration. In conclusion, TLR/NF-κB and JAK/STAT signaling pathways may drive PD1+ M2-like TAMs programming in the CTCL tumor microenvironment, anti-PD-L1 and lenalidomide may reshape PD1+ M2-like TAMs and induce functional changes through ablation of these specific pathways in CTCL. Corresponding author: Christiane Querfeld, MD, PhD. Div. of Dermatology and Beckman Research Institute, City of Hope. 1500 E. Duarte Road, Duarte, CA 91010. Email: cquerfeld@coh.org Phone: 626-634-4436 Fax: 626-218-6190 Citation Format: Zhen Han1,5, Chingyu Su1,5, Xiwei Wu2,5, Hanjun Qin2,5, Steven T. Rosen3,5, Christiane Querfeld1,3,4,5. Reprogramming of PD1+ M2-like tumor-associated macrophages with anti-PD-L1 and Lenalidomide in cutaneous T cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2759.

Background: Tumor-associated macrophages (TAMs) play a key role in cutaneous T cell lymphoma (CTCL) growth and neoplastic T cells escape immune surveillance via PD1-PD-L1 axis (Querfeld, C., et al., Blood 2019; Khodadoust, M.S., et al., J Clin Oncol, 2020). There remains a lack of knowledge about how cytokines regulate the mechanisms controlling tumor-growth and polarize the tumor microenvironment (TME). Methods and Results: To investigate PD-L1 and PD1 expression on TAMs and T cells in mycosis fungoides (MF) and the leukemic variant Sézary syndrome (SS) patients, we performed multiplex immunofluorescence (IF) staining of lesional skin samples of MF patients that demonstrated co-localization of PD-L1 on CD163+ M2 macrophages and PD1 expression on CD4+ and CD8+ T cells. In addition, significant enrichment of CD14+ and CD16+/CD14dim CD163+ M2-like monocytes/macrophages with upregulated PD-L1 expression in SS patients compared to healthy donors (HDs) was found via FACS analysis. We also performed 30-plex Luminex cytokine assay on plasma samples, which showed significantly increased IL-6, IL-10, IFNγ and TNFα levels in plasma of MF/SS compared to HDs. To investigate whether polarization towards an M2-like macrophage phenotype with increased PD-L1 expression correlated with the cytokine expression from CTCL-TME, we cultured total PBMCs from HDs with conditioned media (CM) from well established CTCL cell lines MyLa and HuT78 and analyzed PD-L1 mRNA, total PD-L1 protein and PD-L1 surface expression on M2-like macrophages. Significantly increased expression of PD-L1 protein in total PBMCs, especially on CD14+ and CD16+/CD14dim M2-like macrophages was seen. To understand whether distinct cytokines are associated with PD-L1 upregulation on CD163+ M2-like populations, total PBMCs from HDs were stimulated with human recombinant IL-6, IL-10, IFNγ or TNFα. Antibody blocking studies were conducted by adding anti human IL-6, IL-10, IFNγ or TNFα to the cultures with CM. TNFα stimulation significantly increased the CD14+ M2-like subset, but did not affect CD16+/CD14dim M2-like subset. We observed increased PD-L1 expression on both M2-like populations with TNFα compared to other cytokines. In contrast, blockade of TNFα significantly decreased the CD14+ M2-like subset with reduced PD-L1 expression and increased CD16+/CD14dim M2-like cells with upregulated PD-L1 expression. To explore whether the STAT pathway regulates PD-L1 expression through cytokines from CTCL TME, we incubated total PBMCs from HDs in CM of MyLa and HuT78 cells with/without a pan-STAT inhibitor, and in media alone. Inhibition of STAT signaling decreased CD14+ M2-like macrophage population, but did not alter the CD16+/CD14dim M2-like population. In addition, pan-STAT inhibition significantly reduced surface expression of PD-L1 on both CD14+ and CD16+/CD14dim M2-like macrophages. The effects of cytokines on STAT signaling components in regulating PD-L1 expression were also investigated by FACS and immunoblots. TNFα blockade significantly downregulated PD-L1, but also pSTAT1, pSTAT3 and pNF-κB levels, illustrating the role of TNFα on STAT1, STAT3 and NF-κB pathways in conjunction with PD-L1 expression. Stimulation with TNFα increased pSTAT3 level in CD14+ M2-like macrophages, while it did not significantly change pSTAT3 in CD16+/CD14dim M2-like macrophages. Anti-TNFα reduced pSTAT3 levels in CD14+ M2-like macrophages, but profoundly increased PD-L1 in CD16+/CD14dim M2-like macrophages, which aligns with our data of increased PD-L1 expression on CD16+/CD14dim M2-like macrophages following TNFα blockade. Conclusion: We profiled immune alterations of monocyte/macrophages populations and PD-L1 expression in CTCL regulated by selected cytokines. Our results support the dominant role of TNFα in the CTCL microenvironment. Here we show that TNFα potentiates the immunosuppressive TME through macrophage polarization and STAT-mediated PD-L1 regulation. Our results identify potential targets for combination immunotherapy. Disclosures Zain: Seattle Genetics: Research Funding; Mundai Pharma: Research Funding; Kyowa Kirlin: Research Funding. Abdulla:Johnson Johnson: Research Funding; Mallinckrodt: Consultancy, Speakers Bureau. Rosen:Seattle Genetics: Consultancy; NeoGenomics: Consultancy; Aileron Therapeutics: Consultancy; Novartis: Consultancy; Pebromene: Consultancy; Celgene: Speakers Bureau; Abbvie: Speakers Bureau; paradigm Medical Communications: Speakers Bureau. Querfeld:Trillium: Consultancy; Stemline: Consultancy; Bioniz: Consultancy; Helsinn: Consultancy; Celgene: Research Funding; Kyowa Kirin: Consultancy; MiRagen: Consultancy.

Background: Cutaneous T-cell lymphoma (CTCL), collectively known as mycosis fungoides (MF) and Sézary syndrome (SS) arises from CD4+ T cells in a background of chronic inflammation. The chronic inflammation fosters the growth of CTCL cells and may facilitate T-cells exhaustion that is characterized by deprived effector function and sustained expression of inhibitory receptors. As a result, malignant CTCL cells escape immune surveillance and are not eliminated. At present, the roles of miRNAs or signaling pathways involved in the expression of immune checkpoints in CTCL has yet to be elucidated. Therefore, this project is aimed to elucidate how immune checkpoints are regulated by miRNAs, and how this regulation contributes to T-cell exhaustion and the development of CTCL. Methods: We first conducted miRNAseq analysis to assess the miRNA profile of 50 CTCL patient tumor samples. The sequencing data analysis was performed at the City of Hope Integrative Genomics Core. Next, we verified the expression of 3 highly upregulated miRNAs (miR-155, -21 and -130) from the miRNAseq analysis in 5 CTCL cell lines and tumor samples using qRT-PCR and in situ hybridization (ISH). Finally, we transfected the CTCL cell line Myla 2059 and HuT 78 with anti-miR-155, -21, -130 or Scramble (Scr) control using the Lonza nucleofection kit and nucleofector machine. Cell lysates were prepared 72 hours after transfection and then subjected to Western Blot analysis. We probed the blot with antibodies against SOCS, PTEN, pSTAT3 and GAPDH as a loading control. Results: The data analysis revealed that miR-155 had the highest correlation with CTLA-4 (r = 0.59, P < 0.0001), PD1 (r = 0.42, P = 0.0021), PD-L1 (r = 0.42, P = 0.0025), TIM3 (r = 0.63, P < 0.0001), LAG3 (r = 0.57, P < 0.0001), and ICOS (r = 0.74, P < 0.0001) mRNA; -21 had the highest correlation with PD-L1 (r = 0.44, P = 0.0012), TIM3 (r = 0.52, P < 0.0001), and ICOS (r = 0.37, P < 0.0073) mRNA; and -130 had the highest correlation with CTLA-4 (r = 0.5, P = 0.0002), PD-L1 (r = 0.54, P < 0.0001), TIM3 (r = 0.69, P < 0.0001), LAG3 (r = 0.49, P = 0.0003), and ICOS (r = 0.68, P < 0.0001) mRNA. qRT-PCR and ISH revealed that miRs-155, -21 and -130 were upregulated in all 5 CTCL cell lines and primary tumor samples. There was a dramatic increase in SOCS proteins and significant decrease in pSTAT3 expression in Myla 2059 and HuT 78 cells transfected with anti-miRs-155, -21 or -130, compared to cells transfected with Scr. Conclusions: Immune checkpoints and ligands like PD-L1 expression in CTCL are regulated by miRs-155, -21 and -130. The SOCS family of proteins, negative regulators of STAT signaling, are involved in miRs-155, -21 and -130-induced immune checkpoints expression in CTCL. Taken together, these results demonstrate the mechanisms of miRNA-induced T cell exhaustion and pave the way for the development of miRNA therapeutics in CTCL. Disclosures Rosen: Seattle Genetics: Consultancy; Celgene: Speakers Bureau; paradigm Medical Communications: Speakers Bureau; Abbvie: Speakers Bureau; NeoGenomics: Consultancy; Aileron Therapeutics: Consultancy; Novartis: Consultancy; Pebromene: Consultancy. Querfeld:Celgene: Research Funding; Stemline: Consultancy; Trillium: Consultancy; MiRagen: Consultancy; Kyowa Kirin: Consultancy; Bioniz: Consultancy; Helsinn: Consultancy.

Introduction: T cell exhaustion is a hallmark of CTCL and alterations in mRNA profiles correlate with immune checkpoint expression, with potential clinical relevance (Querfeld et al. 2018). There is no immunophenotypic marker that can distinguish malignant CD4+ T cells from benign CD4+ T cells in the infiltrate and intratumoral heterogeneity poses a major challenge to treatments and long-term remissions. The microenvironment in CTCL harbors multiple immune cells that may contribute to the development of resistance to drug treatments; however, the genomic and molecular determinants of response to therapeutic agents remain incompletely understood. The aim of our study was to distinguish malignant from non-malignant T cells based on TCR α/β repertoires and to understand the transcriptional landscapes of malignant and non-malignant cells in the TME while on anti-PD-L1 therapy. Methods: Migrated cells from skin explants were harvested and subsequently analyzed by our paired single-cell RNA and T cell receptor (TCR; alpha/beta) sequencing on ~3000-4000 cells from skin lesions of 6 patients with mycosis fungoides at baseline and cycle 1 day 15 with anti-PD-L1 + lenalidomide. Results: We identified 14 gene clusters. Differential expression (DE) of genes in each of the unique clusters were identified by comparing gene expression from cells in each cluster to that of all other cells in the dataset, using a cut-off of P < 0.05 and further requiring expression of the gene in >25% of cells in the cluster. Thus, DE-identified genes are expressed either uniquely or by a large proportion of cells within each cluster compared to all other clusters. TCR clones in these cells were also characterized. Through this combined analysis, we demonstrated differences in the diversity, clonal expansion and T cell phenotypes that differentiated expanded malignant T cell populations (cluster 0-3) from non-malignant T cells including tumor infiltrating lymphocytes (TILs), regulatory T cells (Tregs), NK/T cells, and from immune cells such as B cells, antigen presenting cells (dendritic cells, macrophages) and other cells (stromal, epithelial cells) (cluster 4-13). Comparing baseline to C1D15 we were able to identify microenvironmental changes that occurred during treatment, specifically characterized the expression and significance of PD1, LAG3, CTLA4, TIM3 and ICOS in malignant and non-malignant T cell clusters, which demonstrated differential expression of these targets in malignant T cells (clusters 0-4). Non-malignant T cell phenotyping revealed an enriched tumor-infiltrating CD8+ T cell population at baseline with upregulation of LAG3 gene expression, and FOXP3+ CD4+ regulatory T cell population with high expression of CTLA4 and ICOS consistent with inducible Tregs (iTregs) in all, but one baseline sample that did not resolve during treatment (C1D15). Conclusions: Paired scRNA and TCRseq revealed distinctive functional composition of T cells and other immune cells. Combined scRNA expression and scTCR analysis identified malignant from non-malignant T cell subsets. Malignant T cell clones diminished in responders during treatment, while shifted or emerged in non-responders. Clonal enrichment of iTregs and exhausted CD4 and CD8 T cells were identified that did not resolve during treatment. suggesting that potential targeting of ICOS, CTLA4 and/or LAG3 will reverse T cell dysfunction in TILS and iTregs, respectively and increase clinical benefit of anti-PD-L1 blockade. Disclosures Querfeld: Stemline: Consultancy; MiRagen: Consultancy; Kyowa Kirin: Consultancy; Bioniz: Consultancy; Helsinn: Consultancy; Trillium: Consultancy; Celgene: Research Funding. Rosen:Novartis: Consultancy; Pebromene: Consultancy; Aileron Therapeutics: Consultancy; Celgene: Speakers Bureau; paradigm Medical Communications: Speakers Bureau; Abbvie: Speakers Bureau; Seattle Genetics: Consultancy; NeoGenomics: Consultancy.