Concurrent RB1 Loss and BRCA Deficiency Predicts Enhanced Immunologic Response and Long-term Survival in Tubo-ovarian High-grade Serous Carcinoma
Authors: Saner Flurina A.M. , Takahashi Kazuaki , Budden Timothy , Pandey Ahwan , Ariyaratne Dinuka , Zwimpfer Tibor A. , Meagher Nicola S. , Fereday Sian , Twomey Laura , Pishas Kathleen I. , Hoang Therese , Bolithon Adelyn , Traficante Nadia ,   for the Australian Ovarian Cancer Study Group, Alsop Kathryn , Christie Elizabeth L. , Kang Eun-Young , Nelson Gregg S. , Ghatage Prafull , Lee Cheng-Han , Riggan Marjorie J. , Alsop Jennifer , Beckmann Matthias W. , Boros Jessica , Brand Alison H. , Brooks-Wilson Angela , Carney Michael E. , Coulson Penny , Courtney-Brooks Madeleine , Cushing-Haugen Kara L. , Cybulski Cezary , El-Bahrawy Mona A. , Elishaev Esther , Erber Ramona , Gayther Simon A. , Gentry-Maharaj Aleksandra , Gilks C. Blake , Harnett Paul R. , Harris Holly R. , Hartmann Arndt , Hein Alexander , Hendley Joy , Hernandez Brenda Y. , Jakubowska Anna , Jimenez-Linan Mercedes , Jones Michael E. , Kaufmann Scott H. , Kennedy Catherine J. , Kluz Tomasz , Koziak Jennifer M. , Kristjansdottir Björg , Le Nhu D. , Lener Marcin , Lester Jenny , Lubiński Jan , Mateoiu Constantina , Orsulic Sandra , Ruebner Matthias , Schoemaker Minouk J. , Shah Mitul , Sharma Raghwa , Sherman Mark E. , Shvetsov Yurii B. , Soong T. Rinda , Steed Helen , Sukumvanich Paniti , Talhouk Aline , Taylor Sarah E. , Vierkant Robert A. , Wang Chen , Widschwendter Martin , Wilkens Lynne R. , Winham Stacey J. , Anglesio Michael S. , Berchuck Andrew , Brenton James D. , Campbell Ian , Cook Linda S. , Doherty Jennifer A. , Fasching Peter A. , Fortner Renée T. , Goodman Marc T. , Gronwald Jacek , Huntsman David G. , Karlan Beth Y. , Kelemen Linda E. , Menon Usha , Modugno Francesmary , Pharoah Paul D.P. , Schildkraut Joellen M. , Sundfeldt Karin , Swerdlow Anthony J. , Goode Ellen L. , DeFazio Anna , Köbel Martin , Ramus Susan J. , Bowtell David D.L. , Garsed Dale W. 
Published: June 2024

Abstract

Purpose:
The purpose of this study was to evaluate RB1 expression and survival across ovarian carcinoma histotypes and how co-occurrence of BRCA1 or BRCA2 (BRCA) alterations and RB1 loss influences survival in tubo-ovarian high-grade serous carcinoma (HGSC).

Experimental Design:
RB1 protein expression was classified by immunohistochemistry in ovarian carcinomas of 7,436 patients from the Ovarian Tumor Tissue Analysis consortium. We examined RB1 expression and germline BRCA status in a subset of 1,134 HGSC, and related genotype to overall survival (OS), tumor-infiltrating CD8+ lymphocytes, and transcriptomic subtypes. Using CRISPR-Cas9, we deleted RB1 in HGSC cells with and without BRCA1 alterations to model co-loss with treatment response. We performed whole-genome and transcriptome data analyses on 126 patients with primary HGSC to characterize tumors with concurrent BRCA deficiency and RB1 loss.

Results:
RB1 loss was associated with longer OS in HGSC but with poorer prognosis in endometrioid ovarian carcinoma. Patients with HGSC harboring both RB1 loss and pathogenic germline BRCA variants had superior OS compared with patients with either alteration alone, and their median OS was three times longer than those without pathogenic BRCA variants and retained RB1 expression (9.3 vs. 3.1 years). Enhanced sensitivity to cisplatin and paclitaxel was seen in BRCA1-altered cells with RB1 knockout. Combined RB1 loss and BRCA deficiency correlated with transcriptional markers of enhanced IFN response, cell-cycle deregulation, and reduced epithelial–mesenchymal transition. CD8+ lymphocytes were most prevalent in BRCA-deficient HGSC with co-loss of RB1.

Conclusions:
Co-occurrence of RB1 loss and BRCA deficiency was associated with exceptionally long survival in patients with HGSC, potentially due to better treatment response and immune stimulation.