Peter Black

Bladder cancer is the 5th most common cancer in Canada and an estimated 9,000 Canadians are diagnosed with bladder cancer each year. Cisplatin-based Neoadjuvant chemotherapy (NAC) followed by radical cystectomy in patients with muscle-invasive bladder cancer (MIBC) has been shown to improve five-year survival, and is therefore currently the first-line standard of care in patients. However, 60% of patients are inherently resistant to NAC at the time of cystectomy. Several mechanisms of cellular resistance to cisplatin have been proposed, however, the mechanisms presented thus far still do not offer and effective patient response prediction in the context of MIBC. As such, in order to elucidate mechanisms of resistant to cisplatin, the study presented in this thesis takes advantage of a pooled genome‐wide CRISPR knock‐out library targeting 19,114 protein coding genes with 76,441 synthetic guide RNAs (sgRNAs) which allows for an unbiased screen.We first established the capacity to carry out a pooled genome-wide CRISPR screen by optimizing screening conditions. A full-scale screen revealed that several genes involved in the pro-apoptotic pathway (such as CASP8, BAX, and TNFSFR10A) and cell cycle regulation have the potential to confer resistance to cisplatin when knocked out. For this study, we validated the top hit from our screen, SLFN11, and established that the loss of SLFN11 confers a cisplatin resistant phenotype in MIBC. Overall, the study presented here offers SLFN11 as a potential biomarker to aid in clinical decision making and to anticipate resistance to cisplatin-based NAC in MIBC. Further, targeting SLFN11 associated pathways could allow for the development of combination therapies to be used in conjunction with cisplatin in the future.

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