Integrative genomic and transcriptomic analysis reveals prognostic markers and immune subtype in Chinese ovarian clear cell carcinoma.
Authors: Yang Huijuan , Ye Shuang , Li Qin , Wu Yutuan , Jiang Wei , Zhou Shuling , Yang Wentao , Chen Chunxiang , Zhou Yuxi , Yang Yuchen , Shan Boer , Huang Shenglin 
Published: June 2021

e17529 Background: Ovarian clear cell carcinoma (OCCC) is a subtype of ovarian cancer characterized by chemo-resistance and poor survival. Herein, we performed comprehensive genomic and transcriptomic profiling of OCCC tissues to identify prognostic markers and immune subtype in Chinese patients. Methods: A total of 61 patients were included, comprising 41 early-stage and 19 late-stage tumors. Tissue samples were collected before chemotherapy and subjected to capture-based targeted sequencing using a panel consisting of 520 cancer related genes and whole transcriptomic sequencing. Genetic alterations, tumor mutation burden (TMB), microsatellite instability (MSI), and gene expression were evaluated. Association analysis was performed to evaluate clinical and genetic factors with platinum-sensitivity and treatment effects. A nomogram was constructed to predict survival outcomes. Single sample Gene Set Enrichment analysis (ssGSEA) was performed with gene expression profile and immune gene sets. Results: Genetic alterations were mainly identified in ARID1A (49%), PIK3CA (48%), TP53 (18%), ATM (15%), SMARCA4 (13%) and PRKDC (13%). Co-occurrence of mutations in ARID1A with PIK3CA and PRKDC were observed (p < 0.05). Meanwhile, no alterations were identified in BRCA1/2. Patients harboring ATM mutations tended to be platinum sensitive compared to those wildtype counterparts (p < 0.05). In patients with stage IV OCCC, mutations of ARID1A, PIK3CA, SMARCA4 and the HRR pathway were also related to higher percentage of platinum-sensitivity, though significance was not achieved. Mutations of FGFR2, NOTCH1 and the BER pathway were more frequently identified in patients with stage II to IV than stage I (p < 0.05). Patients harboring alterations at chromosome 8q covering genes such as PRKDC showed better overall survival (OS) (p < 0.05). Both clinical factors and frequently mutated genes were used to construct a nomogram for progression-free survival (PFS) prediction. The clinical factors (stage, platinum response and residual disease) in combination with genetic mutations ( ATM and SMARCA4) showed better performance in predicting PFS than clinical factors alone (concordance index 0.85 vs. 0.74, p < 0.01). Transcriptomic analysis with ssGSEA of immune pathway revealed an immune subtype with enrichment of PD-1 signaling. OCCC patients with this immune subtype showed poor PFS and OS. Integration of genomic and transcriptomic analysis showed that the immune subtype patients had higher mutation rate of PIK3CA. Conclusions: The mutational profiles of OCCC were varied in patients with different platinum response and tumor stages. An immune subtype of OCCC with poor survival and enrichment of PD-1 signaling was identified. Our study identified several potential prognostic markers of OCCC at genetic level and revealed an immune subtype for potential immunotherapy.