Investigating the intracellular response to replication stress and mitotic stress for novel immunotherapies

Chromosomal instability (CIN) is a hallmark of solid tumors, contributing to cancer progression, therapeutic resistance, and tumor heterogeneity. In this PhD project we explored the impact of deregulation of the spindle assembly checkpoint (SAC), as an example of mitotic stress (MS), and replication stress (RS) on colorectal cancer (CRC) spheroids and organoids, by investigating their roles in CIN and immune modulation. We first developed innovative methodologies for assessing the functionality of the SAC and measuring constitutive RS levels. SAC and RS profiles were analysed in correlation with treatment responses, including resistance to conventional chemotherapeutics. This revealed a high prevalence of weakened SAC and elevated constitutive RS in CRC cells with stemness potential. This finding highlights the unique ability of cancer stem cells (CSCs) to tolerate genomic instability through weakened SAC and elevated RS. Cell stratification based on SAC and RS parameters enabled the identification of SACLOW and RSLOW subtypes exhibiting resistance to various compounds, highlighting the potential for patient stratification. Targeting specific vulnerabilities in these subtypes, such as RPS6KB1 and PARP-1, may offer new avenues for precision therapy. Additionally, this study demonstrates that boost RS and modulate SAC are two valid strategies to enhances immune visibility, suggesting a promising way to induce an immune response directed against cancer cells. Further investigations are required to elucidate the intricate interplay between RS, mitotic defects, and immune responses, particularly against CSCs, paving the way for innovative cancer therapies.