No. and functions as a tumor suppressor (1). SWI/SNF complexes are multi-subunit complexes that remodel chromatin in an ATP-dependent manner (1). In addition to core subunits such as SNF5 that are present in all SWI/SNF complexes, other subunits are only present in certain complexes. For example, the mutually unique ARID1A and ARID1B subunits are only associated with BRG1-associated factor (BAF) complexes, while ARID2, PBRM1 and FLI-06 BRD7 subunits are specific for polybromo BAF (PBAF) complexes (1). The ARID1A made up of SWI/SNF complex epigenetically activates or represses gene expression via controlling gene accessibility (1,2). is amongst the most frequently mutated genes in human cancer (3). In addition to inactivating mutations, shows deletions in many tumor types in the cBioPortal datasets. Notably, inactivating mutations in occur frequently in ovarian clear cell carcinomas (OCCC; 50%) (4). Over 90% of mutation in OCCCs are either frameshift or nonsense FLI-06 that led to loss of ARID1A protein expression (4). FLI-06 There is an unmet need for effective treatment modalities for subunit of the PBAF complex (7). Likewise, inactivation of the PBAF subunits BRD7, ARID2, and PBRM1 confers susceptibility to T cell-mediated killing in melanoma (8). Finally, mutation correlates with an increase of PD-L1 expression (9). However, the mechanism by which ARID1A regulates PD-L1 expression remains not fully comprehended. Notably, published literature show that anti-PD-L1 treatment only has a modest effect on improving the survival of mice FLI-06 bearing ARID1A-inactivated tumors (9). This suggests that checkpoint blockade-based combination therapeutic strategies are necessary for treating (encoding PD-L1) gene and HDAC6 inhibition synergizes with anti-PD-L1 in ARID1A-inactivated ovarian cancer. The combination depends on cytotoxic T cell activity to limit tumor progression cancer cells were cultured in RPMI 1640 (Corning Life Sciences) supplemented with 10% fetal bovine serum (FBS; Sigma-Aldrich) and 1% penicillin/streptomycin. The ovarian clear cell carcinoma cell line RMG1 was cultured in 1:1 Dulbeccos altered Eagles medium (DMEM)/F12 (Corning Life Sciences) supplemented with 10% FBS and 1% penicillin/streptomycin. RMG1 cells were obtained from the Japanese Collection of Research Bioresources in 2015. OVCA429 cells were obtained from I.M. Shih in 2015. ID8-cells were obtained from J. R. Conejo-Garcia in 2015. All cells were used within 10 passages. The viral packaging Phoenix and 293FT cells were cultured in DMEM (Corning Life Sciences) supplemented with 10% FBS and 1% penicillin/streptomycin. All cells were incubated at 37C in humidified atmosphere made up of 5% CO2. Cell lines were authenticated at the Wistar Institute Genomics Facility using short tandem repeat profiling using AmpFLSTR Identifiler PCR Amplification kit (Life Technologies) right before experiments. Mycoplasma contamination was monthly tested with LookOut Mycoplasma PCR detection (Sigma-Aldrich) right before experiments. Quantitative reverse-transcriptase PCR (qRT-PCR) Total RNA was extracted using TRIzol (Invitrogen), and then purified with DNase treatment (Qiagen). RNA expression was decided using the QuantStudio 3 Real-Time PCR System (Thermo Fisher) and iTaq Universal SYBR Green One-step kit (Bio-Rad Laboratories). The primers sequences are as following: human (forward, 5-ATGGTGGTGCCGACTACAA-3; reverse, 5-TCCAGATGACTTCGGCCTT-3), mouse (forward, 5-GCCACTTCTGAGCATGAACTA-3; reverse, 5-GACACTTCTCTTCCCACTCAC-3). The expression was normalized using human (forward, 5-AACTTTCGATGGTAGTCGCCG-3; reverse, 5-CCTTGGATGTGGTAGCCGTTT-3) expression, or mouse (forward, 5-GGGTTCCTCCTTTCACAGAA-3; reverse, 5-GATGCCAGGACCTGTATGCT-3). Reagents and antibodies ACY1215 (Cat. No: S8001) was purchased from Selleckchem. Anti-PD-L1 (Cat. No: BE0101, clone: 10F.9G2) and anti-mouse CD8 (Cat. No: BE0117, clone: YTS 169.4) antibodies were purchased from Bio X Cell. Interferon-gamma was purchased from Thermo Fisher (Cat. No: PHC4031) or from ProSpec (Cat. No: CYT-358). The following antibodies were purchased from the indicated suppliers: rabbit anti-ARID1A (Cell Signaling, Cat. No: 12354, 1:1000), rabbit AF-6 anti-ARID1B (Cell Signaling, Cat. No: 92964, 1:1000), mouse anti-ARID1B (Santa Cruz, Cat. No: sc-32762, 1:1000), mouse anti–actin (Sigma-Aldrich, Cat. No: A5441, 1:10,000), mouse anti-FLAG (Sigma-Aldrick, Cat. No: F1804), rabbit anti-PD-L1 (Cell Signaling, Cat. No: 13684S, 1:1000, Abcam, Cat. No: ab213480, 1:1000). For flow cytometric analysis, APC/CY7 anti-CD69 (Cat. No: 104525), BV711 anti-CD3 (Cat. No: 100349), APC anti-CD4 (Cat. No: 100516), PE anti-CD8 (Cat. No: 100708), FITC anti-Granzyme B (Cat. No: 372206), PE/Cy7 anti-interferon-gamma (Cat. No: 505825) antibodies were purchased from.