Combinations of anti-cancer drugs can overcome resistance and provide new treatments1,2. The number of possible drug combinations vastly exceeds what could be tested clinically. Efforts to systematically identify active combinations and the tissues and molecular contexts in which they are most effective could accelerate the development of combination treatments. Here we evaluate the potency and efficacy of 2,025 clinically relevant two-drug combinations, generating a dataset encompassing 125 molecularly characterized breast, colorectal and pancreatic cancer cell lines. We show that synergy between drugs is rare and highly context-dependent, and that combinations of targeted agents are most likely to be synergistic. We incorporate multi-omic molecular features to identify combination biomarkers and specify synergistic drug combinations and their active contexts, including in basal-like breast cancer, and microsatellite-stable or KRAS-mutant colon cancer. Our results show that irinotecan and CHEK1 inhibition have synergistic effects in microsatellite-stable or KRAS–TP53 double-mutant colon cancer cells, leading to apoptosis and suppression of tumour xenograft growth. This study identifies clinically relevant effective drug combinations in distinct molecular subpopulations and is a resource to guide rational efforts to develop combinatorial drug treatments.

CRISPR genetic screens in cancer cell models are a powerful tool to elucidate oncogenic mechanisms and to identify promising therapeutic targets. The Project Score database (https://score.depmap.sanger.ac.uk/) uses genome-wide CRISPR–Cas9 dropout screening data in hundreds of highly annotated cancer cell models to identify genes required for cell fitness and prioritize novel oncology targets. The Project Score database currently allows users to investigate the fitness effect of 18 009 genes tested across 323 cancer cell models. Through interactive interfaces, users can investigate data by selecting a specific gene, cancer cell model or tissue type, as well as browsing all gene fitness scores. Additionally, users can identify and rank candidate drug targets based on an established oncology target prioritization pipeline, incorporating genetic biomarkers and clinical datasets for each target, and including suitability for drug development based on pharmaceutical tractability. Data are freely available and downloadable. To enhance analyses, links to other key resources including Open Targets, COSMIC, the Cell Model Passports, UniProt and the Genomics of Drug Sensitivity in Cancer are provided. The Project Score database is a valuable new tool for investigating genetic dependencies in cancer cells and the identification of candidate oncology targets.

Edited by Luke O'NeillThe addition of ubiquitin to a target protein has long been implicated in the process of degradation and is the primary mediator of protein turnover in the cell. Recently, however, many non-proteolytic functions of ubiquitination have emerged as key regulators of cellular homeostasis. In this review, we will describe the various non-traditional functions of ubiquitination, with particular focus on how they can be used as signaling entities in cancer formation and progression. Elaboration of this topic can lead to a better understanding of oncogenic mechanisms, as well as the discovery of novel druggable proteins within the ubiquitin pathway.

Approximately 70% of breast cancers express estrogen receptor α (ERα) and depend on this key transcriptional regulator for proliferation and differentiation. While patients with this disease can be treated with targeted anti-endocrine agents, drug resistance remains a significant issue, with almost half of patients ultimately relapsing. Elucidating the mechanisms that control ERα function may further our understanding of breast carcinogenesis and reveal new therapeutic opportunities.Here we investigated the role of deubiquitinases (DUB) in regulating ERα in breast cancer. An RNAi loss-of-function screen in breast cancer cells targeting all DUB identified USP11 as a regulator of ERα transcriptional activity, which was further validated by assessment of direct transcriptional targets of ERα. USP11 expression was induced by estradiol (E2), an effect that was blocked by tamoxifen and not observed in ERα-negative cells. Mass spectrometry revealed a significant change to the proteome and ubiquitinome in USP11 knockdown cells in the presence of E2.RNA sequencing in LCC1 USP11 knockdown cells revealed significant suppression of cell cycle-associated and ERα target genes, phenotypes that were not observed in LCC9 USP11 knockdown, anti-endocrine resistant cells. In a breast cancer patient cohort coupled with in silico analysis of publicly available cohorts, high expression of USP11 was significantly associated with poor survival in ERα-positive patients.Overall, this study highlights a novel role for USP11 in the regulation of ERα activity, where USP11 may represent a prognostic marker in ERα-positive breast cancer. SignificanceA newly identified role for USP11 in ERα transcriptional activity represents a novel mechanism of ERα regulation and a pathway to be exploited for the management of ER-positive breast cancer.Research.

Approximately 70% of breast cancers overexpress the estrogen receptor α (ERα) and depend on this key transcriptional regulator for growth and differentiation. The discovery of novel mechanisms controlling ERα function represent major advances in our understanding of breast cancer progression and potentially offer attractive new therapeutic opportunities. Here, we investigated the role of deubiquitinating enzymes (DUBs), which act to remove ubiquitin moieties from proteins, in regulating transcriptional activity of ERα in breast cancer. To identify DUBs involved in the regulation of ERα transcriptional activity, we performed an RNAi loss-of-function screen using a library of shRNA vectors targeting all human DUB genes. The DUB library consisted of pools of four non-overlapping shRNAs targeting all 108 known or putative DUBs (432 shRNAs in total). We found that suppression of a number of DUBs markedly repressed or enhanced the activity of an estrogen-response-element (ERE) luciferase reporter following estradiol (E2) stimulation. Of particular interest, suppression of the BRCA2-associated DUB, USP11, was found to down-regulate ERα transcriptional activity. Subsequent validation using two individual siRNAs targeted to USP11 revealed a notable reduction in expression of endogenous ERα target genes in the ZR-75-1 cell line, as quantified using qRT-PCR. Immunoprecipitation of ERα revealed no physical interaction with USP11, however E2 stimulation resulted in translocation of USP11 to the nucleus, suggesting a potential role in E2-induced transcription. Furthermore, USP11 expression was found to be upregulated in the estrogen-independent cell line LCC1 when compared to their parental MCF7 cells. Knockdown of USP11 in LCC1 cells resulted in decreased mRNA expression of a panel of ERα target genes, suggesting a role for USP11 in an estrogen independent setting. To support the prognostic relevance of USP11, immunohistochemical staining of a breast cancer tissue microarray (n=144) was performed. Kaplan-Meier analysis of this cohort revealed a highly significant association between poor overall survival (OS) (p=0.030) and breast cancer-specific survival (BCSS) (p=0.041). In silico analysis of publically available breast cancer gene expression datasets further supported an association between high USP11 mRNA levels and poor prognosis. We observed a significant correlation between high expression of USP11 mRNA in ER-positive patients and poor distant metastasis-free survival (DMFS) (HR 2, CI 1.37-2.91, p=0.00023). This correlation was also significant in ER-positive patients who had received endocrine therapy only (HR 2.9, CI 1.63-5.15, p=0.00015). These results suggest a role for USP11 in driving cellular growth and identify USP11 as novel therapeutic target in breast cancer. Citation Format: Lisa Dwane, Aisling E. O'Connor, Laoighse Mulrane, Annette M. Dirac, Karin Jirstrom, John P. Crown, Rene Bernards, William M. Gallagher, Tríona Ní Chonghaile, Darran P. O'Connor. Functional genomic screening identifies USP11 as a novel regulator of ERα transcription in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3040. doi:10.1158/1538-7445.AM2017-3040