Targeting Wnt/β-cateinin epigenomics for colorectal cancer treatment

Background: Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer-related death in the world. Australia leads the incidence rates of CRC worldwide that the lifetime risk of developing CRC is 1 in 13 among Australians. What’s worse, CRC was ranked the second most common (cause of cancer death in Australia, with an estimated death of 5,500 people annually. Unfortunately, due to lack of effective targeted therapy, the 5-year overall survival rate of CRC is limited to roughly 69%, lagging well behind other common cancers such as breast, melanoma and prostate (over 90% survival rate). Hence, there is a critical unmet need to develop new targeted therapies for colorectal cancer. Over 90% of CRCs arise from genetic mutations that activate a tumour-initiating pathway called Wnt/β-catenin pathway. Abrogating β-catenin function results in the loss of tumorigenic potential of Wnt-active CRC cells. This makes β-catenin a most prominent treatment target in CRC. However, targeting β-catenin so far eludes clinical success, as pharmacologically blocking β-catenin remains technically infeasible. β-catenin mainly promotes the transformation of normal cells into cancer cells through activating the expression of various tumour-initiating genes. This process requires the recruitment of assorted transcriptional co-activators, especially epigenetic enzymes, and these epigenetic enzymes are ideal drug targets. Epigenetic enzymes are responsible for the reading of genetic code via introducing chemical modifications on DNA and its associated proteins, whose reprograming is indispensable for the initiation and progression of virtually all colorectal tumours. The recruitment of epigenetic enzymes is essential for β-catenin to initiate the expression of tumour-promoting genes and CRC development. Thus, targeting epigenetic enzymes that are essential for β-catenin function is a promising therapeutic strategy against CRC. However, the epigenetic enzymes that are selectively required for β-catenin function remain largely unknown. Methods and preliminary results: We employed a state-of-the-art gene editing tool (CRISPR-Cas9) to systemically investigate β-catenin-related therapeutic targets on a whole genome scale and validate the results using a confirmatory screen that specifically targeting epigenetic modifiers. Secondary validation of epigenetic regulators of Wnt/β-catenin signalling will be conducted using arrayed CRISPR screening and functional experiments. Wnt/β-catenin signaling activity will be assessed using RNA-seq, chromatin-immunoprecipitation sequencing (CHIP-seq) or Cut&Run, and real-time PCR (RT-PCR) analysis. Organoid and xenograft models will be employed to examine the effects of genetic and pharmaceutic targeting of epigenetic regulators in blocking oncogenic β-catenin activity and CRC malignancy. Expected outcomes: 1. The regulatory mechanisms underlying oncogenic Wnt/β-catenin epigenomics. 2. The effects of targeting epigenetic regulators in blocking oncogenic Wnt/β-catenin signaling. 3. The potential of targeting epigenetics as a therapeutic strategy for CRC treatment.