RITA selectively inhibits proliferation of BAP1-deficient cutaneous melanoma cells in vitro / 南方医科大学学报

OBJECTIVE@#To screen for small molecular compounds with selective inhibitory activity against cutaneous melanoma cells with BAP1 deletion.@*METHODS@#Cutaneous melanoma cells expressing wild-type BAP1 were selected to construct a BAP1 knockout cell model using CRISPR-Cas9 system, and small molecules with selective inhibitory activity against BAP1 knockout cells were screened from a compound library using MTT assay. Rescue experiment was carried out to determine whether the sensitivity of BAP1 knockout cells to the candidate compounds was directly related to BAP1 deletion. The effects of the candidate compounds on cell cycle and apoptosis were detected with flow cytometry, and the protein expressions in the cells were analyzed with Western blotting.@*RESULTS@#The p53 activator RITA from the compound library was shown to selectively inhibit the viability of BAP1 knockout cells. Overexpression of wild-type BAP1 reversed the sensitivity of BAP1 knockout cells to RITA, while overexpression of the mutant BAP1 (C91S) with inactivated ubiquitinase did not produce any rescue effect. Compared with the control cells expressing wild-type BAP1, BAP1 knockout cells were more sensitive to RITA-induced cell cycle arrest and apoptosis (P < 0.0001) and showed an increased expression of p53 protein, which was further increased by RITA treatment (P < 0.0001).@*CONCLUSION@#Loss of BAP1 results in the sensitivity of cutaneous melanoma cells to p53 activator RITA. In melanoma cells, the activity of ubiquitinase in BAP1 is directly related to their sensitivity to RITA. An increased expression of p53 protein induced by BAP1 knockout is probably a key reason for RITA sensitivity of melanoma cells, suggesting the potential of RITA as a targeted therapeutic agent for cutaneous melanoma carrying BAP1-inactivating mutations.

Pharmacological inhibition of BAP1 recruits HERC2 to competitively dissociate BRCA1-BARD1, suppresses DNA repair and sensitizes CRC to radiotherapy

Radiotherapy is widely used in the management of advanced colorectal cancer (CRC). However, the clinical efficacy is limited by the safe irradiated dose. Sensitizing tumor cells to radiotherapy via interrupting DNA repair is a promising approach to conquering the limitation. The BRCA1-BARD1 complex has been demonstrated to play a critical role in homologous recombination (HR) DSB repair, and its functions may be affected by HERC2 or BAP1. Accumulated evidence illustrates that the ubiquitination-deubiquitination balance is involved in these processes; however, the precise mechanism for the cross-talk among these proteins in HR repair following radiation hasn't been defined. Through activity-based profiling, we identified PT33 as an active entity for HR repair suppression. Subsequently, we revealed that BAP1 serves as a novel molecular target of PT33 via a CRISPR-based deubiquitinase screen. Mechanistically, pharmacological covalent inhibition of BAP1 with PT33 recruits HERC2 to compete with BARD1 for BRCA1 interaction, interrupting HR repair. Consequently, PT33 treatment can substantially enhance the sensitivity of CRC cells to radiotherapy in vitro and in vivo. Overall, these findings provide a mechanistic basis for PT33-induced HR suppression and may guide an effective strategy to improve therapeutic gain.

Gene mutation profiling and clinical significances in patients with renal cell carcinoma

Abstract Objectives The pathological mechanisms of patients with Renal Cell Carcinoma (RCC) remain defined. This study aimed to evaluate relationships between the landscape of gene mutations and their clinical significance in RCC patients. Methods Tissue and peripheral blood samples of 42 patients with RCC were collected and performed for the Next Generation Sequencing (NGS) with Geneseeq PrimeTM 425-gene panel probes. Their landscapes of gene mutation were analyzed. We also carried out an evaluation of Tumor-Node-Metastasis (TNM) staging, RENAL nephelometry score, surgery, and targeted drug treatment of patients. Then we compared the correlations of landscape in gene mutations and the prognosis. Results The most common gene alternations, including BAP1, PBRM1, SETD2, CSF1R, NPM1, EGFR, POLE, RB1, and VHL genes, were identified in tissue and blood samples of 75% of patients. EGFR, POLE, and RB1 gene mutations frequently occurred in relapsed and metastatic patients. BAP1, CCND2, KRAS, PTPN11, ERBB2/3, JAK2, and POLE were presented in the patients with > 9 RENAL nephelometry score. Univariable analysis indicated that SETD2, BAP1, and PBRM1 genes were key factors for Disease-Free Survival (DFS). Multivariable analysis confirmed that mutated SETD1, NPM1, and CSF1R were critical factors for the Progression Free Survival (PFS) of RCC patients with target therapy. Conclusions Wild-type PBRM1 and mutated BAP1 in patients with RCC were strongly associated with the outcomes of the patient. The PFS of the patients with SETD2, NPM1, and CSF1R mutations were significantly shorter than those patients without variants.

Alterations of DNA damage response pathway: Biomarker and therapeutic strategy for cancer immunotherapy

Genomic instability remains an enabling feature of cancer and promotes malignant transformation. Alterations of DNA damage response (DDR) pathways allow genomic instability, generate neoantigens, upregulate the expression of programmed death ligand 1 (PD-L1) and interact with signaling such as cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling. Here, we review the basic knowledge of DDR pathways, mechanisms of genomic instability induced by DDR alterations, impacts of DDR alterations on immune system, and the potential applications of DDR alterations as biomarkers and therapeutic targets in cancer immunotherapy.

Tumor-derived neomorphic mutations in ASXL1 impairs the BAP1-ASXL1-FOXK1/K2 transcription network

Additional sex combs-like 1 (ASXL1) interacts with BRCA1-associated protein 1 (BAP1) deubiquitinase to oppose the polycomb repressive complex 1 (PRC1)-mediated histone H2A ubiquitylation. Germline BAP1 mutations are found in a spectrum of human malignancies, while ASXL1 mutations recurrently occur in myeloid neoplasm and are associated with poor prognosis. Nearly all ASXL1 mutations are heterozygous frameshift or nonsense mutations in the middle or to a less extent the C-terminal region, resulting in the production of C-terminally truncated mutant ASXL1 proteins. How ASXL1 regulates specific target genes and how the C-terminal truncation of ASXL1 promotes leukemogenesis are unclear. Here, we report that ASXL1 interacts with forkhead transcription factors FOXK1 and FOXK2 to regulate a subset of FOXK1/K2 target genes. We show that the C-terminally truncated mutant ASXL1 proteins are expressed at much higher levels than the wild-type protein in ASXL1 heterozygous leukemia cells, and lose the ability to interact with FOXK1/K2. Specific deletion of the mutant allele eliminates the expression of C-terminally truncated ASXL1 and increases the association of wild-type ASXL1 with BAP1, thereby restoring the expression of BAP1-ASXL1-FOXK1/K2 target genes, particularly those involved in glucose metabolism, oxygen sensing, and JAK-STAT3 signaling pathways. In addition to FOXK1/K2, we also identify other DNA-binding transcription regulators including transcription factors (TFs) which interact with wild-type ASXL1, but not C-terminally truncated mutant. Our results suggest that ASXL1 mutations result in neomorphic alleles that contribute to leukemogenesis at least in part through dominantly inhibiting the wild-type ASXL1 from interacting with BAP1 and thereby impairing the function of ASXL1-BAP1-TF in regulating target genes and leukemia cell growth.

Benign multicystic peritoneal mesothelioma: literature review and update

Benign multicystic peritoneal mesothelioma (BMPM) is a rare peritoneal tumor diagnosed predominantly in pre-menopausal women. Associated risk factors include endometriosis and pelvic inflammatory disease in women, and prior abdominal surgery in both genders. To date, the pathogenesis of this disease remains controversial with possible etiologies, including a neoplastic versus a reactive process. Given the risk factors, some authors believe that this disease is secondary to a reactive process. However, because some studies describe cases where there is no prior surgical history or inflammatory milieu present, and because of this entity's predilection for recurrence, some authors believe the origin to be neoplastic. Some genetic and familial associations have also been reported. Malignant transformation is extremely rare, with only two cases reported in the literature, despite the recurrence potential. Like the etiology, the name of this entity is also controversial. Some authors prefer the term "peritoneal inclusion cyst (PCM)" instead of "benign cystic mesothelioma" and argue that the term mesothelioma should only be used when there is evidence of atypia. Most cases of BMPM are discovered incidentally. Others reflect sequela of tumor mass effect. It appears intra-operatively as large, multi-focal, cystic lesions in the peritoneal and pelvic cavity. Diagnosis is achieved through surgical sampling with histopathological examination. Immunobiologically, BMPM exhibits multiple small cystic spaces with flattened lining containing calretinin positive cells without atypical features, mitotic figures, or tissue invasion. Treatment includes cytoreductive surgery. Here we present a case of BMPM in a 60-year-old male - a rare disease in an uncommon patient population.

Expressions of BAP1 and TET2 proteins in bone marrow of patients with chronic myelomonocytic leukemia and their significances / 白血病·淋巴瘤

Objective To investigate the expressions of BAP1 and TET2 proteins in bone marrow of patients with chronic myelomonocytic leukemia (CMML) and their relationship with the prognosis of CMML. Methods The bone marrow paraffin specimens of 41 cases from 41 adult CMML patients diagnosed by Shanghai Sino-US Joint Leukemia Coordination Group from September 2003 to May 2007 were collected. The immunohistochemistry was used to detect the expressions of BAP1 and TET2 proteins in 41 CMML patients. The expressions of TET2 and BAP1 proteins were also detected by the same method in 40 adult patients with acute myelomonocytic leukemia (AMML) and 20 patients with iron deficiency anemia (IDA) diagnosed at the same time as the comparison. The clinical data of 41 CMML patients were analyzed by using retrospective cohort study. The count data were compared by using chi-square test. The correlation between expressions of BAP1 and TET2 proteins was analyzed by using Pearson correlation analysis. Kaplan-Meier method was used to calculate the survival time, and Log-rank test was used for single factor analysis. Results In 41 CMML patients, the positive expression rate of BAP1 was 31.7％ (13/41), including 28.6％ (8/28) in CMML-1 patients and 38.5％ (5/13) in CMML-2 patients; the positive expression rate of TET2 was 41.5％ (17/41), including 39.3％ (11/28) in CMML-1 patients and 46.2％ (6/13) in CMML-2 patients. In 40 AMML patients, the positive expression rate of BAP1 was 32.5％ (13/40), and the positive expression rate of TET2 was 35.0％ (14/40). In 20 IDA patients, the positive expression rate of BAP1 was 5.0％ (1/20), and TET2 had no positive expression. There was no significant difference in the expressions of BAP1 and TET2 proteins between CMML-1 and CMML-2 patients (χ 2 = 0.40, P = 0.53; χ 2 = 0.17, P = 0.68). There was no significant difference in the expressions of BAP1 and TET2 proteins between CMML and AMML patients (χ 2 = 0.01, P = 0.94; χ 2 = 0.36, P = 0.64). There were significant differences in the positive expression rate of BAP1 and TET2 proteins between hematological neoplastic disease (CMML+AMML) and hematological non-neoplastic disease (IDA) (χ 2 = 6.01, P < 0.05; χ 2 = 11.04, P < 0.01). Pearson correlation analysis showed that there was no correlation between expressions of BAP1 and TET2 proteins (r = 0.35, P = 0.27). Univariate analysis showed that anemia (Hb < 60 g/L), mature monocyte count ≥ 2.0×109/L, neutrophil count (1.5×109/L), abnormal karyotype were associated with poor prognosis for CMML. Protein expressions of BAP1 and TET2 were not related with the prognosis of CMML (χ 2 = 0.28, P = 0.600; χ 2 = 0.53, P = 0.460). Conclusion Both BAP1 and TET2 proteins have high positive expression rates in CMML patients, but the expressions of them are not related to the prognosis.

Loss of Nuclear BAP1 Expression Is Associated with High WHO/ISUP Grade in Clear Cell Renal Cell Carcinoma

BACKGROUND: BRCA1-associated protein 1 (BAP1) mutations are frequently reported in clear cell renal cell carcinoma (ccRCC); however, very few studies have evaluated the role of these mutations in other renal cell carcinoma (RCC) subtypes. Therefore, we analyzed BAP1 protein expression using immunohistochemistry in several RCC subtypes and assessed its relationship with clinicopathological characteristics of patients. METHODS: BAP1 expression was immunohistochemically evaluated in tissue microarray blocks constructed from 371 samples of RCC collected from two medical institutions. BAP1 expression was evaluated based on the extent of nuclear staining in tumor cells, and no expression or expression in < 10% of tumor cells was defined as negative. RESULTS: Loss of BAP1 expression was observed in ccRCC (56/300, 18.7%), chromophobe RCC (6/26, 23.1%), and clear cell papillary RCC (1/4, 25%), while we failed to detect BAP1 expression loss in papillary RCC, acquired cystic disease-associated RCC, or collecting duct carcinoma. In ccRCC, loss of BAP1 expression was significantly associated with high World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grade (p = .002); however, no significant correlation was observed between loss of BAP1 expression and survival in ccRCC. Loss of BAP1 expression showed no association with prognostic factors in chromophobe RCC. CONCLUSIONS: Loss of BAP1 nuclear expression was observed in both ccRCC and chromophobe RCC. In addition, BAP1 expression loss was associated with poor prognostic factors such as high WHO/ISUP grade in ccRCC.

Prognoses and Clinical Outcomes of Primary and Recurrent Uveal Melanoma / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Uveal melanoma has a very poor prognosis despite successful local primary tumor treatment. In this study, we investigated prognostic factors that more accurately reflected the likelihood of recurrence and survival and delineated a prognostic model that could effectively identify different risk groups based on initial clinical parameters. MATERIALS AND METHODS: Prognostic factors associated with distant recurrence, recurrence-free survival (RFS), progression-free survival, and overall survival from distant recurrence to death (OS2) were analyzed in 226 patients with stage I-III uveal melanoma who underwent primary local therapy. RESULTS: Forty-nine patients (21.7%) had distant recurrences, which occurred most frequently in the liver (87.7%). In a multivariate analysis, local radiotherapy improved RFS among patients with multiple recurrence risk factors relative to excision (not reached vs. 19.0 months, p=0.004). Patients with BRCA1-associated protein-1 (BAP1)–negative primary tumors showed a longer RFS duration after primary treatments, while those with BAP1-negative metastatic tissues had a shorter OS2 compared to those with BAP1-positive tumors, both not statistically insignificance (RFS: not reached vs. 82.0 months, p=0.258; OS2: 15.7 vs. 24.4 months, p=0.216). Male sex (hazard ratio [HR], 3.79; p=0.012), a short RFS (HR, 4.89; p=0.014), and a largest metastatic tumor linear diameter ≥ 45 mm (HR, 5.48; p=0.017) were found to correlate with worse post-recurrence survival. CONCLUSION: Risk factors could be used to classify uveal melanoma cases and subsequently direct individual treatment strategies. Furthermore, metastasectomy appears to contribute to improved survival outcomes.

Research advance on BAP1 and its function in tumor suppression / 上海交通大学学报（医学版）

BAP1 is a member of the ubiquitin C-terminal hydrolases (UCH) subfamily of deubiquitylases with basic function of removing monoubiquitin or ubiquitin chains from the specific substrate proteins. As well, it is a key factor in regulating gene expression, cell cycle, cell differentiation,cell apoptosis and DNA damage response, dependent or independent of its deubiquitination function. Evidences haverevealed that mutation or downregulation of BAP1 can prominently increase the occurrence of cancers, including uveal melanoma, mesothelioma, renal cell carcinoma, breast cancer and lung cancer. Currently, the tumor spectrum and the pathogenic mechanism on BAP1 have not been illustrated clearly, and need to be further researched,which might bring a new opportunity in treatment of cancers.

Bap1 y neoplasias melanocíticas / Bap1 and melanocytic neoplasms

El melanoma maligno cutáneo (MMC) es un cáncer genéticamente heterogéneo, en cuya patogénesis participarían varios genes. Algunos de estos activan la vía MAP kinasa (BRAF, NRAS, KIT, NF1), mientras que otros confieren una mayor susceptibilidad a melanoma familiar, como CDKN2A, CDK4, MITF y BAP1. BAP1 (BRCA1-associated-protein 1) ha sido descrito como una proteína que se une a BRCA1 para inhibir el crecimiento celular. Actualmente se sabe que es producto de un gen supresor de tumores (denominado BAP1) y que actúa como una enzima con actividad deubiquitinasa, la cual se asocia a varios complejos de proteínas, regulando diversas vías celulares relacionadas con el ciclo celular, diferenciación y muerte celular, así como también gluconeogénesis y respuesta a daño del ADN. Tanto su actividad deubiquitinasa como su localización nuclear son relevantes para su función en la supresión de tumores.

Malignant cutaneous melanoma (MMC) is a genetically heterogeneous cancer and various genes participate in its pathogenesis. Some of these genes activate the MAP kinase pathway (BRAF, NRAS, KIT, NF1) and others are related to a higher susceptibility to familial melanoma like CDKN2A, CDK4, MITF y BAP1. BAP1 (BRCA1-associated –protein 1) has been described as a BRCA1-binding protein inhibiting cell growth. This protein is a product of a gene with tumor suppressor activity, the protein being a deubiquitinase associated to multiple protein complexes regulating various cellular pathways, including the cell cycle, differentiation and cell death, as well as gluconeogenesis and DNA damage response. Both deubiquitinase activity and location to the nucleus are relevant to its tumor suppressor function.