Intestinal Apc-inactivation induces HSP25 dependency.

The majority of colorectal cancers (CRCs) present with early mutations in tumor suppressor gene APC. APC mutations result in oncogenic activation of the Wnt pathway, which is associated with hyperproliferation, cytoskeletal remodeling, and a global increase in mRNA translation. To compensate for the increased biosynthetic demand, cancer cells critically depend on protein chaperones to maintain proteostasis, although their function in CRC remains largely unexplored. In order to investigate the role of molecular chaperones in driving CRC initiation, we captured the transcriptomic profiles of murine wild type and Apc-mutant organoids during active transformation. We discovered a strong transcriptional upregulation of Hspb1, which encodes small heat shock protein 25 (HSP25). We reveal an indispensable role for HSP25 in facilitating Apc-driven transformation, using both in vitro organoid cultures and mouse models, and demonstrate that chemical inhibition of HSP25 using brivudine reduces the development of premalignant adenomas. These findings uncover a hitherto unknown vulnerability in intestinal transformation that could be exploited for the development of chemopreventive strategies in high-risk individuals.

Intestinal stem cell dynamics in homeostasis and cancer.

The relationship between intestinal stem cells (ISCs) and colorectal cancer (CRC) has been a topic of intense study. Uncovering stem cell dynamics in homeostasis and following acquisition of oncogenic mutations has provided unprecedented insights into CRC initiation, and it is increasingly evident that the microenvironment plays a key role in regulating stem cell fate and functionality. Consequently, imbalances in the signaling between the niche and ISCs perturb homeostasis and promote cancer development. Furthermore, stem cell-like cells drive growth and progression of established CRCs and these cells also critically rely on microenvironmental input. Here, we highlight the importance of stem cell/niche interactions in developing and established CRC and discuss how these can be modulated to develop novel preventive and therapeutic interventions.

Intestinal organoid co-culture protocol to study cell competition in vitro.

Intestinal organoid cultures are a powerful tool to study epithelial cells in vitro, as they are able to proliferate and differentiate into all cell lineages observed in vivo. Co-culturing organoids with distinct genetic backgrounds provides an excellent approach to study contact dependent and independent interactions between healthy and mutant epithelial intestinal cells. Here, we provide 2D and 3D approaches to mouse organoid co-cultures using fluorescently labeled organoids and demonstrate the analysis of these co-cultures using flow cytometry and microscopy-based approaches. For complete details on the use and execution of this profile, please refer to van Neerven et al., 2021.

High-Fat Diet Impacts on Tumor Development in the Gut.

A high-fat diet (HFD) directly acts on intestinal stem cells by increasing their numbers and proliferation, resulting in an elevated risk of developing colorectal cancer (CRC). In a recent study, Mana et al. revealed that HFD-mediated intestinal tumor formation can be reduced by inhibiting fatty acid oxidation.

Apc-mutant cells act as supercompetitors in intestinal tumour initiation.

A delicate equilibrium of WNT agonists and antagonists in the intestinal stem cell (ISC) niche is critical to maintaining the ISC compartment, as it accommodates the rapid renewal of the gut lining. Disruption of this balance by mutations in the tumour suppressor gene APC, which are found in approximately 80% of all human colon cancers, leads to unrestrained activation of the WNT pathway1,2. It has previously been established that Apc-mutant cells have a competitive advantage over wild-type ISCs3. Consequently, Apc-mutant ISCs frequently outcompete all wild-type stem cells within a crypt, thereby reaching clonal fixation in the tissue and initiating cancer formation. However, whether the increased relative fitness of Apc-mutant ISCs involves only cell-intrinsic features or whether Apc mutants are actively involved in the elimination of their wild-type neighbours remains unresolved. Here we show that Apc-mutant ISCs function as bona fide supercompetitors by secreting WNT antagonists, thereby inducing differentiation of neighbouring wild-type ISCs. Lithium chloride prevented the expansion of Apc-mutant clones and the formation of adenomas by rendering wild-type ISCs insensitive to WNT antagonists through downstream activation of WNT by inhibition of GSK3ß. Our work suggests that boosting the fitness of healthy cells to limit the expansion of pre-malignant clones may be a powerful strategy to limit the formation of cancers in high-risk individuals.